Friday, February 15, 2008

Dissertations and These Sites

Here is a list of dissertation and theses search sites I have found. Feel free

Free Dissertations/Theses Sites

Abes: Agence Bibliographique de l'Enseignement Superieur
http://www.abes.fr/abes/DesktopDefault.aspx?Loupe=Moin Citations to French
dissertations.

Australian Digital Theses Program http://adt.caul.edu.au This site provides both
published in Australia.

The British Library http://www.bl.uk/services/bsds/dsc/theses.html The British
doctoral theses from the early 1970s onward), from the United States (475,000
doctoral theses), and from Canada (several hundred doctoral theses from 1980
forward).

Center for Research Libraries http://www.crl.edu Twenty thousand doctoral
dissertations from outside of the United States and Canada are searchable from
this site. Items can be ordered through ILL by students, faculty, and staff.

Cybertheses http://www.cybertheses.org/cybertheses/cybertheses.html Cybertheses
allows access to citations of French dissertations from 1972 to the present.

Digital Library and Archives http://scholar.lib.vt.edu/theses Digital Library
and Archives allows searching for citations and abstracts of over 6,700 theses
and dissertations. Free full-text access is provided for over 4,500 of these
items.

Directory of Dissertations in Progress
http://www.historians.org/pubs/dissertations/index.cfm "The Directory contains
3,804 dissertations in progress at 170 academic departments in Canada and the
U.S." This is a citation database of dissertations in progress in the area of
history.

Dissertation.com http://www.dissertation.com Dissertation.com has just a few
hundred dissertations and theses in its collection, but the site allows free,

Doctoral Dissertations in Musicology http://www.music.indiana.edu/ddm This is an
international database of citations for dissertations in musicology that
contains over 12,000 records. Dissertations are from approximately 1950 to the
present.

NDLTD - Networked Digital Library of Theses and Dissertations
digital dissertations and theses that are in PDF format. A significant number
of these resources are freely available in full-text and can be viewed online.

PhdData: The Universal Index of Dissertations in Progress http://www.phddata.org
PhdData has citations from several thousand dissertations in progress from
various parts of the world.

Proquest Digital Dissertations http://wwwlib.umi.com/dissertations Proquest
provides the past two years of citations and abstracts in their Digital
Dissertations database at no cost.

available for all items published between January 1, 1998 to August 31, 2002.

Theses Link Collection http://www.mkengel.de/thesis/thesis.htm This site gives
links to dissertation/theses search sites in many different countries, including
Austria, Germany, The Netherlands, Sweden, and Norway.

TREN: Theological Research Exchange Network http://www.tren.com TREN provides
citations to 6,800 theological theses/dissertations and conference papers.
Items can then be purchased through this site. The opening page actually states
that they have 10,000 theses/dissertations, but the search page allows searching
of 6,800 items.

How to Write a PhD Thesis

Joe Wolfe
School of Physics
The University of New South Wales, Sydney

This guide to thesis writing gives simple and practical advice on the problems of getting started, getting organised, dividing the huge task into less formidable pieces and working on those pieces. It also explains the practicalities of surviving the ordeal. It includes a suggested structure and a guide to what should go in each section. It was originally written for graduate students in physics, and most of the specific examples given are taken from that discipline. Nevertheless, the feedback from users indicates that it has been widely used and appreciated by graduate students in diverse fields in the sciences and humanities.

• Getting started
• What is a thesis? For whom is it written? How should it be written?
• Thesis Structure

• How to survive a thesis defence

Getting Started

When you are about to begin, writing a thesis seems a long, difficult task. That is because it is a long, difficult task. Fortunately, it will seem less daunting once you have a couple of chapters done. Towards the end, you will even find yourself enjoying it---an enjoyment based on satisfaction in the achievement, pleasure in the improvement in your technical writing, and of course the approaching end. Like many tasks, thesis writing usually seems worst before you begin, so let us look at how you should make a start.

An outline

How do you make an outline of a chapter? For most of them, you might try the method that I use for writing papers, and which I learned from my thesis adviser (Stjepan Marcelja): Assemble all the figures that you will use in it and put them in the order that you would use if you were going to explain to someone what they all meant. You might as well rehearse explaining it to someone else---after all you will probably give several talks based on your thesis work. Once you have found the most logical order, note down the key words of your explanation. These key words provide a skeleton for much of your chapter outline.

Once you have an outline, discuss it with your adviser. This step is important: s/he will have useful suggestions, but it also serves notice that s/he can expect a steady flow of chapter drafts that will make high priority demands on his/her time. Once you and your adviser have agreed on a logical structure, s/he will need a copy of this outline for reference when reading the chapters which you will probably present out of order. If you have a co-adviser, discuss the outline with him/her as well, and present all chapters to both advisers for comments.

Organisation

It is encouraging and helpful to start a filing system. Open a word-processor file for each chapter and one for the references. You can put notes in these files, as well as text. While doing something for Chapter n, you will think "Oh I must refer back to/discuss this in Chapter m" and so you put a note to do so in the file for Chapter m. Or you may think of something interesting or relevant for that chapter. When you come to work on Chapter m, the more such notes you have accumulated, the easier it will be to write.

Make a back-up of these files and do so every day at least (depending on the reliability of your computer and the age of your disk drive). Do not keep back-up disks close to the computer in case the hypothetical thief who fancies your computer decides that s/he could use some disks as well.

A simple way of making a remote back-up is to send it as an email attachment to a consenting email correspondent, preferably one in a different location. You could also send it to yourself. In either case, be careful to dispose of superseded versions so that you don't waste disk space, especially if you have bitmap images or other large files.

You should also have a physical filing system: a collection of folders with chapter numbers on them. This will make you feel good about getting started and also help clean up your desk. Your files will contain not just the plots of results and pages of calculations, but all sorts of old notes, references, calibration curves, suppliers' addresses, specifications, speculations, letters from colleagues etc., which will suddenly strike you as relevant to one chapter or other. Stick them in that folder. Then put all the folders in a box or a filing cabinet. As you write bits and pieces of text, place the hard copy, the figures etc in these folders as well. Touch them and feel their thickness from time to time---ah, the thesis is taking shape.

If any of your data exist only on paper, copy them and keep the copy in a different location. Consider making a copy of your lab book. This has another purpose beyond security: usually the lab book stays in the lab, but you may want a copy for your own future use. Further, scientific ethics require you to keep lab books and original data for at least ten years, and a copy is more likely to be found if two copies exist.

If you haven't already done so, you should archive your electronic data, in an appropriate format. Spreadsheet and word processor files are not suitable for long term storage. Archiving data by Joseph Slater is a good guide.

While you are getting organised, you should deal with any university paperwork. Examiners have to be nominated and they have to agree to serve. Various forms are required by your department and by the university administration. Make sure that the rate limiting step is your production of the thesis, and not some minor bureaucratic problem.

One of the big FAQs for scientists: is there a word processor, ideally one compatible with MS Word, but which allows you to type mathematical symbols and equations conveniently? One solution is LaTeX, which is powerful, elegant, reliable, fast and free from http://www.latex-project.org/ or http://www.miktex.org/. As far as I know, the only equation editor for MS Word is slow and awkward. (If anyone knows a way of writing equations in this software without using the mouse, many people including this author would like to hear from you!) Another solution is to use old versions of commercial software. Word 5.1 allows equations to be typed comfortably: it is faster in this respect than LaTeX, with the added advantage of 'what you see is what you get' (WYSIWYG). (If anyone knows how to run Word 5.1 on OSX, please let me know!) A search will find sites that provide discontinued software, but, not knowing whether this is legal or not, I shan't link to them. (I am told that LyX, available free at http://www.lyx.org/, is a convenient front-end to LaTeX that has WYSIWYG. )

Commercial word processors have gradually become bigger, slower, less reliable and more awkward to use as they acquire more features. This is a general feature of commercial software and an important input to the computing industry. If software and operating system performance did not deteriorate, people would not need to buy new computers and profits would fall for makers of both hard- and soft-ware. Software vendors want it to look fancy and obvious in the demo, and they don't really care about its ease, speed and reliability to an expert user because the expert user has already bought it. In our example, it is much faster to type equations and to do formatting with embedded commands because you use your fingers independently rather than your hand and because your fingers don't leave the keyboard. However, click-on menus, although they are slow and cumbersome when typing, look easy to use in the shop.

A timetable

I strongly recommend sitting down with the adviser and making up a timetable for writing it: a list of dates for when you will give the first and second drafts of each chapter to your adviser(s). This structures your time and provides intermediate targets. If you merely aim "to have the whole thing done by [some distant date]", you can deceive yourself and procrastinate more easily. If you have told your adviser that you will deliver a first draft of chapter 3 on Wednesday, it focuses your attention.

You may want to make your timetable into a chart with items that you can check off as you have finished them. This is particularly useful towards the end of the thesis when you find there will be quite a few loose ends here and there.

Iterative solution

Whenever you sit down to write, it is very important to write something. So write something, even if it is just a set of notes or a few paragraphs of text that you would never show to anyone else. It would be nice if clear, precise prose leapt easily from the keyboard, but it usually does not. Most of us find it easier, however, to improve something that is already written than to produce text from nothing. So put down a draft (as rough as you like) for your own purposes, then clean it up for your adviser to read. Word-processors are wonderful in this regard: in the first draft you do not have to start at the beginning, you can leave gaps, you can put in little notes to yourself, and then you can clean it all up later.

As you write your thesis, your scientific writing is almost certain to improve. Even for native speakers of English who write very well in other styles, one notices an enormous improvement in the first drafts from the first to the last chapter written. The process of writing the thesis is like a course in scientific writing, and in that sense each chapter is like an assignment in which you are taught, but not assessed. Remember, only the final draft is assessed: the more comments your adviser adds to first or second draft, the better.

Before you submit a draft to your adviser, run a spell check so that s/he does not waste time on those. If you have any characteristic grammatical failings, check for them.

What is a thesis? For whom is it written? How should it be written?

Obviously your examiners will read the thesis. They will be experts in the general field of your thesis but, on the exact topic of your thesis, you are the world expert. Keep this in mind: you should write to make the topic clear to a reader who has not spent most of the last three years thinking about it.

Your thesis will also be used as a scientific report and consulted by future workers in your laboratory who will want to know, in detail, what you did. Theses are occasionally consulted by people from other institutions, and the library sends microfilm versions if requested (yes, still). More commonly theses are now stored in an entirely digital form. These may be stored as .pdf files on a server at your university. The advantage is that your thesis can be consulted much more easily by researchers around the world. (See e.g. Australian digital thesis project for the digital availability of research theses.) Write with these possibilities in mind.

It is often helpful to have someone other than your adviser(s) read some sections of the thesis, particularly the introduction and conclusion chapters. It may also be appropriate to ask other members of staff to read some sections of the thesis which they may find relevant or of interest, as they may be able to make valuable contributions. In either case, only give them revised versions, so that they do not waste time correcting your grammar, spelling, poor construction or presentation.

How much detail?

The short answer is: rather more than for a scientific paper. Once your thesis has been assessed and your friends have read the first three pages, the only further readers are likely to be people who are seriously doing research in just that area. For example, a future research student might be pursuing the same research and be interested to find out exactly what you did. ("Why doesn't the widget that Bloggs built for her project work any more? Where's the circuit diagram? I'll look up her thesis." "Blow's subroutine doesn't converge in my parameter space! I'll have to look up his thesis." "How did that group in Sydney manage to get that technique to work? I'll order a microfilm of that thesis they cited in their paper.") For important parts of apparatus, you should include workshop drawings, circuit diagrams and computer programs, usually as appendices. (By the way, the intelligible annotation of programs is about as frequent as porcine aviation, but it is far more desirable. You wrote that line of code for a reason: at the end of the line explain what the reason is.) You have probably read the theses of previous students in the lab where you are now working, so you probably know the advantages of a clearly explained, explicit thesis and/or the disadvantages of a vague one.

Make it clear what is yours

If you are writing in the passive voice, you must be more careful about attribution than if you are writing in the active voice. "The sample was prepared by heating yttrium..." does not make it clear whether you did this or whether Acme Yttrium did it. "I prepared the sample..." is clear.

Style

The text must be clear. Good grammar and thoughtful writing will make the thesis easier to read. Scientific writing has to be a little formal---more formal than this text. Native English speakers should remember that scientific English is an international language. Slang and informal writing will be harder for a non-native speaker to understand.

Short, simple phrases and words are often better than long ones. Some politicians use "at this point in time" instead of "now" precisely because it takes longer to convey the same meaning. They do not care about elegance or efficient communication. You should. On the other hand, there will be times when you need a complicated sentence because the idea is complicated. If your primary statement requires several qualifications, each of these may need a subordinate clause: "When [qualification], and where [proviso], and if [condition] then [statement]". Some lengthy technical words will also be necessary in many theses, particularly in fields like biochemistry. Do not sacrifice accuracy for the sake of brevity. "Black is white" is simple and catchy. An advertising copy writer would love it. "Objects of very different albedo may be illuminated differently so as to produce similar reflected spectra" is longer and uses less common words, but, compared to the former example, it has the advantage of being true. The longer example would be fine in a physics thesis because English speaking physicists will not have trouble with the words. (A physicist who did not know all of those words would probably be glad to remedy the lacuna either from the context or by consulting a dictionary.)

Sometimes it is easier to present information and arguments as a series of numbered points, rather than as one or more long and awkward paragraphs. A list of points is usually easier to write. You should be careful not to use this presentation too much: your thesis must be a connected, convincing argument, not just a list of facts and observations.

One important stylistic choice is between the active voice and passive voice. The active voice ("I measured the frequency...") is simpler, and it makes clear what you did and what was done by others. The passive voice ("The frequency was measured...") makes it easier to write ungrammatical or awkward sentences. If you use the passive voice, be especially wary of dangling participles. For example, the sentence "After considering all of these possible materials, plutonium was selected" implicitly attributes consciousness to plutonium. This choice is a question of taste: I prefer the active because it is clearer, more logical and makes attribution simple. The only arguments I have ever heard for avoiding the active voice in a thesis are (i) many theses are written in the passive voice, and (ii) some very polite people find the use of "I" immodest. Use the first person singular, not plural, when reporting work that you did yourself: the editorial 'we' may suggest that you had help beyond that listed in your acknowledgments, or it may suggest that you are trying to share any blame. On the other hand, retain plural verbs for "data": "data" is the plural of "datum", and lots of scientists like to preserve the distinction. Just say to yourself "one datum is ..", "these data are.." several times. An excellent and widely used reference for English grammar and style is A Dictionary of Modern English Usage by H.W. Fowler.

Presentation

There is no need for a thesis to be a masterpiece of desk-top publishing. Your time can be more productively spent improving the content than the appearance.

In many cases, a reasonably neat diagram can be drawn by hand faster than with a graphics package, and you can scan it if you want an electronic version. Either is usually satisfactory. A one bit (i.e. black and white), moderate resolution scan of a hand-drawn sketch will be bigger than a line drawing generated on a graphics package, but not huge. While talking about the size of files, we should mention that photographs look pretty but take up a lot of memory. There's another important difference, too. The photographer thought about the camera angle and the focus etc. The person who drew the schematic diagram thought about what components ought to be depicted and the way in which the components of the system interacted with each other. So the numerically small information content of the line drawing may be much more useful information than that in a photograph.

Another note about figures and photographs. In the digital version of your thesis, do not save ordinary photographs or other illustrations as bitmaps, because these take up a lot of memory and are therefore very slow to transfer. Nearly all graphics packages allow you to save in compressed format as .jpg or .gif files. Further, you can save space/speed things up by reducing the number of colours. In vector graphics (as used for drawings), shades or grey are often produced by black and white pixels, so one-bit colour is adequate.

In general, students spend too much time on diagrams---time that could have been spent on examining the arguments, making the explanations clearer, thinking more about the significance and checking for errors in the algebra. The reason, of course, is that drawing is easier than thinking.

I do not think that there is a strong correlation (either way) between length and quality. There is no need to leave big gaps to make the thesis thicker. Readers will not appreciate large amounts of vague or unnecessary text.

Approaching the end

A deadline is very useful in some ways. You must hand in the thesis, even if you think that you need one more draft of that chapter, or someone else's comments on this section, or some other refinement. If you do not have a deadline, or if you are thinking about postponing it, please take note of this: A thesis is a very large work. It cannot be made perfect in a finite time. There will inevitably be things in it that you could have done better. There will be inevitably be some typos. Indeed, by some law related to Murphy's, you will discover one when you first flip open the bound copy. No matter how much you reflect and how many times you proof read it, there will be some things that could be improved. There is no point hoping that the examiners will not notice: many examiners feel obliged to find some examples of improvements (if not outright errors) just to show how thoroughly they have read it. So set yourself a deadline and stick to it. Make it as good as you can in that time, and then hand it in! (In retrospect, there was an advantage in writing a thesis in the days before word processors, spelling checkers and typing programs. Students often paid a typist to produce the final draft and could only afford to do that once.)

How many copies?

Talk to your adviser about this. As well as those for the examiners, the university libraries and yourself, you should make some distribution copies. These copies should be sent to other researchers who are working in your field so that:
• they can discover what marvellous work you have been doing before it appears in journals;
• they can look up the fine details of methods and results that will or have been published more briefly elsewhere;
• they can realise what an excellent researcher you are. This realisation could be useful if a post- doctoral position were available in their labs. soon after your submission, or if they were reviewers of your research/post-doctoral proposal. Even having your name in their bookcases might be an advantage.

Whatever the University's policy on single or double-sided copies, the distribution copies could be double-sided paper, or digital, so that forests and postage accounts are not excessively depleted by the exercise. Your adviser could help you to make up a list of interested and/or potentially useful people for such a mailing list. Your adviser might also help by funding the copies and postage if they are not covered by your scholarship. A CD with your thesis will be cheaper than a paper copy. You don't have to burn them all yourself: companies make multiple copies for several dollars a copy.

The following comment comes from Marilyn Ball of the Australian National University in Canberra: "When I finished writing my thesis, a postdoc wisely told me to give a copy to my parents. I would never have thought of doing that as I just couldn't imagine what they would do with it. I'm very glad to have taken that advice as my parents really appreciated receiving a copy and proudly displayed it for years. (My mother never finished high school and my father worked with trucks - he fixed 'em, built 'em, drove 'em, sold 'em and junked 'em. Nevertheless, they enjoyed having a copy of my thesis.)"

Personal

In the ideal situation, you will be able to spend a large part---perhaps a majority---of your time writing your thesis. This may be bad for your physical and mental health.

Typing
Set up your chair and computer properly. The Health Service, professional keyboard users or perhaps even the school safety officer will be able to supply charts showing recommended relative heights, healthy postures and also exercises that you should do if you spend a lot of time at the keyboard. These last are worthwhile insurance: you do not want the extra hassle of back or neck pain. Try to intersperse long sessions of typing with other tasks, such as reading, drawing, calculating, thinking or doing research.

If you do not touch type, you should learn to do so for the sake of your neck as well as for productivity. There are several good software packages that teach touch typing interactively. If you use one for say 30 minutes a day for a couple of weeks, you will be able to touch type. By the time you finish the thesis, you will be able to touch type quickly and accurately and your six hour investment will have paid for itself. Be careful not to use the typing exercises as a displacement activity.

Exercise
Do not give up exercise for the interim. Lack of exercise makes you feel bad, and you do not need anything else making you feel bad while writing a thesis. 30-60 minutes of exercise per day is probably not time lost from your thesis: I find that if I do not get regular exercise, I sleep less soundly and longer. How about walking to work and home again? (Walk part of the way if your home is distant.) Many people opine that a walk helps them think, or clears the head. You may find that an occasional stroll improves your productivity.

Food
Do not forget to eat, and make an effort to eat healthy food. You should not lose fitness or risk illness at this critical time. Exercise is good for keeping you appetite at a healthy level. I know that you have little time for cooking, but keep a supply of fresh fruit, vegetables and bread. It takes less time to make a sandwich than to go to the local fast food outlet, and you will feel better afterwards.

Drugs
Thesis writers have a long tradition of using coffee as a stimulant and alcohol or marijuana as relaxants. (Use of alcohol and coffee is legal, use of marijuana is not.) Used in moderation, they do not seem to have ill effects on the quality of thesis produced. Excesses, however, are obviously counter-productive: several espressi and you will be buzzing too much to sit down and work; several drinks at night will slow you down next day.

Others
Other people will be sympathetic, but do not take them for granted. Spouses, lovers, family and friends should not be undervalued. Spend some time with them and, when you do, have a good time. Do not spend your time together complaining about your thesis: they already resent the thesis because it is keeping you away from them. If you can find another student writing a thesis, then you may find it therapeutic to complain to each other about advisers and difficulties. S/he need not be in the same discipline as you are.

Coda

Keep going---you're nearly there! Most PhDs will admit that there were times when we thought about reasons for not finishing. But it would be crazy to give up at the writing stage, after years of work on the research, and it would be something to regret for a long time.

Writing a thesis is tough work. One anonymous post doctoral researcher told me: "You should tell everyone that it's going to be unpleasant, that it will mess up their lives, that they will have to give up their friends and their social lives for a while. It's a tough period for almost every student." She's right: it is certainly hard work, it will probably be stressful and you will have to adapt your rhythm to it. It is also an important rite of passage and the satisfaction you will feel afterwards is wonderful. On behalf of scholars everywhere, I wish you good luck!

A suggested thesis structure

The list of contents and chapter headings below is appropriate for some theses. In some cases, one or two of them may be irrelevant. Results and Discussion are usually combined in several chapters of a thesis. Think about the plan of chapters and decide what is best to report your work. Then make a list, in point form, of what will go in each chapter. Try to make this rather detailed, so that you end up with a list of points that corresponds to subsections or even to the paragraphs of your thesis. At this stage, think hard about the logic of the presentation: within chapters, it is often possible to present the ideas in different order, and not all arrangements will be equally easy to follow. If you make a plan of each chapter and section before you sit down to write, the result will probably be clearer and easier to read. It will also be easier to write.

Your institution may have a form for this (UNSW does). In any case, this standard page gives the university library the right to publish the work, possibly by microfilm or some other medium. (At UNSW, the Postgraduate Student Office will give you a thesis pack with various guide-lines and rules about thesis format. Make sure that you consult that for its formal requirements, as well as this rather informal guide.)

Declaration
Check the wording required by your institution, and whether there is a standard form. Many universities require something like: "I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the award of any other degree or diploma of the university or other institute of higher learning, except where due acknowledgment has been made in the text. (signature/name/date)"

Title page
This may vary among institutions, but as an example: Title/author/"A thesis submitted for the degree of Doctor of Philosophy in the Faculty of Science/The University of New South Wales"/date.

Abstract
Of all your thesis, this part will be the most widely published and most read because it will be published in Dissertation Abstracts International. It is best written towards the end, but not at the very last minute because you will probably need several drafts. It should be a distillation of the thesis: a concise description of the problem(s) addressed, your method of solving it/them, your results and conclusions. An abstract must be self-contained. Usually they do not contain references. When a reference is necessary, its details should be included in the text of the abstract. Check the word limit.

Acknowledgments
Most thesis authors put in a page of thanks to those who have helped them in matters scientific, and also indirectly by providing such essentials as food, education, genes, money, help, advice, friendship etc. If any of your work is collaborative, you should make it quite clear who did which sections.

The introduction starts on page 1, the earlier pages should have roman numerals. It helps to have the subheadings of each chapter, as well as the chapter titles. Remember that the thesis may be used as a reference in the lab, so it helps to be able to find things easily.

Introduction
What is the topic and why is it important? State the problem(s) as simply as you can. Remember that you have been working on this project for a few years, so you will be very close to it. Try to step back mentally and take a broader view of the problem. How does it fit into the broader world of your discipline?

Especially in the introduction, do not overestimate the reader's familiarity with your topic. You are writing for researchers in the general area, but not all of them need be specialists in your particular topic. It may help to imagine such a person---think of some researcher whom you might have met at a conference for your subject, but who was working in a different area. S/he is intelligent, has the same general background, but knows little of the literature or tricks that apply to your particular topic.

The introduction should be interesting. If you bore the reader here, then you are unlikely to revive his/her interest in the materials and methods section. For the first paragraph or two, tradition permits prose that is less dry than the scientific norm. If want to wax lyrical about your topic, here is the place to do it. Try to make the reader want to read the kilogram of A4 that has arrived uninvited on his/her desk. Go to the library and read several thesis introductions. Did any make you want to read on? Which ones were boring?

This section might go through several drafts to make it read well and logically, while keeping it short. For this section, I think that it is a good idea to ask someone who is not a specialist to read it and to comment. Is it an adequate introduction? Is it easy to follow? There is an argument for writing this section---or least making a major revision of it---towards the end of the thesis writing. Your introduction should tell where the thesis is going, and this may become clearer during the writing.

Literature review

Ideally, you will already have much of the hard work done, if you have been keeping up with the literature as you vowed to do three years ago, and if you have made notes about important papers over the years. If you have summarised those papers, then you have some good starting points for the review.

How many papers? How relevant do they have to be before you include them? Well, that is a matter of judgement. On the order of a hundred is reasonable, but it will depend on the field. You are the world expert on the (narrow) topic of your thesis: you must demonstrate this.

A political point: make sure that you do not omit relevant papers by researchers who are like to be your examiners, or by potential employers to whom you might be sending the thesis in the next year or two.

Middle chapters

In some theses, the middle chapters are the journal articles of which the student was major author. There are several disadvantages to this format.

One is that a thesis is both allowed and expected to have more detail than a journal article. For journal articles, one usually has to reduce the number of figures. In many cases, all of the interesting and relevant data can go in the thesis, and not just those which appeared in the journal. The degree of experimental detail is usually greater in a thesis. Relatively often a researcher requests a thesis in order to obtain more detail about how a study was performed.

Another disadvantage is that your journal articles may have some common material in the introduction and the "Materials and Methods" sections.

The exact structure in the middle chapters will vary among theses. In some theses, it is necessary to establish some theory, to describe the experimental techniques, then to report what was done on several different problems or different stages of the problem, and then finally to present a model or a new theory based on the new work. For such a thesis, the chapter headings might be: Theory, Materials and Methods, {first problem}, {second problem}, {third problem}, {proposed theory/model} and then the conclusion chapter. For other theses, it might be appropriate to discuss different techniques in different chapters, rather than to have a single Materials and Methods chapter.

Here follow some comments on the elements Materials and Methods, Theory, Results and discussion which may or may not correspond to thesis chapters.

Materials and Methods
This varies enormously from thesis to thesis, and may be absent in theoretical theses. It should be possible for a competent researcher to reproduce exactly what you have done by following your description. There is a good chance that this test will be applied: sometime after you have left, another researcher will want to do a similar experiment either with your gear, or on a new set-up in a foreign country. Please write for the benefit of that researcher.

In some theses, particularly multi-disciplinary or developmental ones, there may be more than one such chapter. In this case, the different disciplines should be indicated in the chapter titles.

Theory
When you are reporting theoretical work that is not original, you will usually need to include sufficient material to allow the reader to understand the arguments used and their physical bases. Sometimes you will be able to present the theory ab initio, but you should not reproduce two pages of algebra that the reader could find in a standard text. Do not include theory that you are not going to relate to the work you have done.

When writing this section, concentrate at least as much on the physical arguments as on the equations. What do the equations mean? What are the important cases?

When you are reporting your own theoretical work, you must include rather more detail, but you should consider moving lengthy derivations to appendices. Think too about the order and style of presentation: the order in which you did the work may not be the clearest presentation.

Suspense is not necessary in reporting science: you should tell the reader where you are going before you start.

Results and discussion
The results and discussion are very often combined in theses. This is sensible because of the length of a thesis: you may have several chapters of results and, if you wait till they are all presented before you begin discussion, the reader may have difficulty remembering what you are talking about. The division of Results and Discussion material into chapters is usually best done according to subject matter.

Make sure that you have described the conditions which obtained for each set of results. What was held constant? What were the other relevant parameters? Make sure too that you have used appropriate statistical analyses. Where applicable, show measurement errors and standard errors on the graphs. Use appropriate statistical tests.

Take care plotting graphs. The origin and intercepts are often important so, unless the ranges of your data make it impractical, the zeros of one or both scales should usually appear on the graph. You should show error bars on the data, unless the errors are very small. For single measurements, the bars should be your best estimate of the experimental errors in each coordinate. For multiple measurements these should include the standard error in the data. The errors in different data are often different, so, where this is the case, regressions and fits should be weighted (i.e. they should minimize the sum of squares of the differences weighted inversely as the size of the errors.) (A common failing in many simple software packages that draw graphs and do regressions is that they do not treat errors adequately. UNSW student Mike Johnston has written a plotting routine that plots data with error bars and performs weighted least square regressions. It is at http://www.phys.unsw.edu.au/3rdyearlab/graphing/graph.html). You can just 'paste' your data into the input and it generates a .ps file of the graph.

In most cases, your results need discussion. What do they mean? How do they fit into the existing body of knowledge? Are they consistent with current theories? Do they give new insights? Do they suggest new theories or mechanisms?

Try to distance yourself from your usual perspective and look at your work. Do not just ask yourself what it means in terms of the orthodoxy of your own research group, but also how other people in the field might see it. Does it have any implications that do not relate to the questions that you set out to answer?

Final chapter, references and appendices

Conclusions and suggestions for further work
Your abstract should include your conclusions in very brief form, because it must also include some other material. A summary of conclusions is usually longer than the final section of the abstract, and you have the space to be more explicit and more careful with qualifications. You might find it helpful to put your conclusions in point form.

It is often the case with scientific investigations that more questions than answers are produced. Does your work suggest any interesting further avenues? Are there ways in which your work could be improved by future workers? What are the practical implications of your work?

This chapter should usually be reasonably short---a few pages perhaps. As with the introduction, I think that it is a good idea to ask someone who is not a specialist to read this section and to comment.

It is tempting to omit the titles of the articles cited, and the university allows this, but think of all the times when you have seen a reference in a paper and gone to look it up only to find that it was not helpful after all.

Should you reference web sites and, if so, how? If you cite a journal article or book, the reader can go to a library and check that the cited document and check whether or not it says what you say it did. A web site may disappear, and it may have been updated or changed completely. So references to the web are usually less satisfactory. Nevertheless, there are some very useful and authoritative sources. So, if the rules of your institution permit it, it may be appropriate to cite web sites. (Be cautious, and don't overuse such citations. In particular, don't use a web citation where you could reasonably use a "hard" citation. Remember that your examiners are likely to be older and more conservative.) You should give the URL and also the date you downloaded it. If there is a date on the site itself (last updated on .....) you should included that, too.

Appendices
If there is material that should be in the thesis but which would break up the flow or bore the reader unbearably, include it as an appendix. Some things which are typically included in appendices are: important and original computer programs, data files that are too large to be represented simply in the results chapters, pictures or diagrams of results which are not important enough to keep in the main text.

Some sites with related material

How to survive a thesis defence
Research resources and links supplied by Deakin University
"Final year projects": a guide from Mike Hart at King Alfred's College, Winchester, UK
Postgraduate Student Resources supplied by University of Canberra
A useful aid to surviving meetings with management
The National Association of Graduate - Professional Students (USA)

Some relevant texts

Stevens, K. and Asmar, C (1999) 'Doing postgraduate research in Australia'. Melbourne University Press, Melbourne ISBN 0 522 84880 X.
Phillips, E.M and Pugh, D.S. (1994) 'How to get a PhD : a handbook for students and their supervisors'. Open University Press, Buckingham, England
Tufte, E.R. (1983) 'The visual display of quantitative information'. Graphics Press, Cheshire, Conn.
Tufte, E.R. (1990) 'Envisioning information' Graphics Press, Cheshire, Conn.

How to Write a Ph.D. Dissertation

Charlottesville, Virginia
Abstract
In this paper we demonstrate that writing a Ph.D. dissertation can have
many benefits. Not only do you obtain extensive typesetting experience,

Chapter I: Introduction

Ph.D. dissertations (e.g., Schulman 1995a; Cox 1995) are commonly believed to be comprehensive compendiums of the original research done by a graduate student in partial fulfillment of the requirements for the degree of Doctor of Philosophy.² In reality, the Ph.D. thesis is usually a number of disparate chapters whose most important feature is not the thoroughness of the experimental description but rather the width of the margins. In this paper, the second article in a series on scientific writing that began with Schulman (1996a), we will discuss the phenomenon of the Ph.D. thesis.

Chapter II: Preparing to Write

There comes a time in the life of every graduate student when she or he realizes that another two years of graduate school cannot be endured. Even though a year spent writing your thesis will be filled with frustration and angst, it will end up being worth it in order to escape school forever.
Remember the following phrase: "No one will ever read your thesis.'' You'll hear this phrase a number of times as you finish up, and it's vitally important that you believe it to be true. The phrase is important because without it you would be tempted to work on your thesis until everything is perfect, and you would never finish.
Say "It's good enough for the thesis" to yourself several times a day. Tell yourself that you'll correct all the mistakes when you turn the various chapters into independent scientific papers, even though this won't happen (see Schulman 1996a and references therein).

Your thesis committee should consist of between four and nine researchers in and outside of your field. Each committee member has a specific duty.
Your thesis advisor has the most important job: to reassure you that you don't have to do many of the things you're positive you should do. She or he will likely say, It's good enough for the thesis'' fairly often.
You also need one committee member who will insist on more mathematical rigor, one who will demand that the thesis be made more concise by getting rid of all that irrelevant math, and two or three to say that you should do all the things your thesis advisor told you didn't need to be done.
There should also be at least one committee member who will never read the thesis, and who will therefore ask only general questions at your thesis defense. The other graduate students who attend your defense will often bet on which professors read your thesis. Be prepared to determine the winner (note that it is not considered sporting to participate in this game yourself).
Try to set a defense date early so as to give your committee ample time to schedule conferences, vacations, and/or elective surgery for that day.

Chapter IV: Producing the Thesis

Legend has it that doctoral students in ancient times used to produce their dissertations using a device called a "typewriter." While there is some archeological evidence for typewriter use in the past, many researchers doubt the plausibility of such claims (e.g. Schulman 1995a).
These days, dissertations are produced using word processing programs such as Word or Word Perfect, or computer typesetting systems such as TeX or LaTeX. The former will give you practice in drawing by hand all the symbols that aren't supported, while with the latter you have the opportunity to craft new typesetting definitions to satisfy your university's dissertation policies. For example,
\long\def\printfrontnonchapter{\vfil\eject \rightpage\null\vskip 1in \centerline{{\bf \Uppercase{\frontnonchapterheader}}}\vskip 22pt plus 73pt \relax\bigskip\setwidespacing \frontnonchaptertext\par} (Jerius 1992).
Be sure not to choose the wrong method of producing your thesis.

Chapter V: Writing the Thesis

The Ph.D. thesis usually begins with a pithy quote, after which there will sometimes be a dedication to one's parents, life partner, and/or pet tapir.
Following this is probably the most important part of the dissertation: the acknowledgments section. This is the only section that everyone who picks up your thesis will read. They will happen upon your dissertation in the library and flip through the first few pages, looking for a juicy acknowledgments section. This is your chance to make obscure references to secret loves, damn various faculty members with faint praise, or be very mysterious by having no acknowledgments section at all so that everyone wonders what you're hiding.
After the awknowledments should be the various tables of contents, denoting the page numbers on which the reader may find every section, subsection, subsubsection, figure, table, appendix, footnote, and semicolon in the thesis.
Next comes the first thesis chapter, the introduction, which is judged on the basis of how far back in the past you start. Although the introduction is supposed to enable someone with no knowledge of your field to read and understand your thesis, this is an impossible goal. Instead, simply reference sources such as Rontgen (1896), Galileo (1610), Aristotle (-350), or other similarly ancient researchers. The idea to get across is that your work, being based on the work of great scientists of the past, must be truly worthwhile. Even though these works have little to do with your research, your committee isn't going to look up the references.
After the introduction come chapters that describe what you did, where you did it, when you did it, why you did it, and how much more work has to be done before you can obtain definitive results. This last point is usually discussed in the concluding chapter.

Chapter VI: The Thesis Defense

Remember those dreams you used to have about going to class and finding out that there was a big test that day for which you hadn't studied? The thesis defense is worse, because you find out that although you studied very hard, you didn't study the right things.
The fun part is that at most universities the first part of your defense is open to the public, so that your parents will probably want to come and videotape the event.

Chapter VII: Rewriting

Your thesis defense was tough, but you survived. Your committee members have signed a piece of paper saying that they are satisfied with your dissertation as long as your thesis advisor is happy with the revisions you make. Don't fall into the trap of trying to make everything perfect! Remember the phrase from Chapter II, "No one will ever read your thesis."
Once your advisor is happy with the revisions, take one unbound, unperforated, paginated copy of your dissertation, two copies of your abstract, one extra copy of your title page, the signed evaluation forms from your committee members in a sealed, notarized envelope, the receipt proving your payment of the Thesis Publication Fee, your diploma application, and proof of your doctoral candidacy enrollment to the Bureaucratic Office of Records, Education, and Dissertations (your requirements may vary; void where prohibited).
The folks at BORED will take a ruler to every page in your thesis, making sure that all the margins are correct and insisting that you go back and redo them if even one page is wrong.

You've passed the format check, and it's time to make a hundred copies of your thesis and distribute them to departmental libraries all over the world so that everyone in your field can read it. Your advisor should pay for the photocopying and postage (see Schulman & Cox 1997 for a detailed justification).
Try not to think of all the errors lurking in your thesis as you address the envelopes to Professor Famous or Doctor Influential. You want to publicize your dissertation as much as possible so that prospective employers will at least have heard your name.
Some journals will publish brief summaries of your dissertation (e.g. Schulman 1995b; Schulman 1996b), but be warned that these journals may want you to format your summary quite specifically. The requirements for the mini-Annals of Improbable Research are particularly restrictive; it can be difficult to summarize five years of work in five lines of text.

Chapter IX: Conclusion

Congratulations, Doctor! You've escaped from graduate school and can now have your frequent-flyer literature addressed to Dr. Your Name, complain when forms only list Mr/Ms/Mrs, and smirk when surgeons whine about all the people with academic doctorates who are making the title meaningless for medical doctors. Go out and make the world a better place.

Bibliography

Wenn Drachen Schiffe schleppen

13. Februar 2008 Normalerweise sind Reeder eher konservative Menschen: Läuft eine Sache gut, wird nichts daran geändert. Doch seit die Preise für Treibstoff auf mehr als 600 Dollar je Tonne gestiegen sind, denken die Reeder darüber nach, wie sie diese Kosten senken können. Was ihnen die Globalisierung an lukrativen Aufträgen mit satten Gewinnen verspricht, machen die Ölpreise sonst im Handumdrehen zunichte.

An Ideen mangelt es nicht. Die einfachste lautet: langsamer fahren. Noch vor wenigen Jahren wollten Schiffsingenieure Containerfachter mit 28 Knoten (knapp 52 km/h) Höchstgeschwindigkeit bauen. Doch man kommt auch langsamer ans Ziel, dazu billiger und mit geringeren Emissionen. Jeder Knoten an der Spitze wird mit wesentlich höherem Treibstoffverbrauch erkauft als bei langsamer Fahrt.

Ein Zugdrachen für ein Schiff

Eine andere Idee: Die Schiffe werden mit einem Hilfssegel ausgestattet, genaugenommen mit einem Zugdrachen. Die Idee ist eigentlich alt. Bereits die Chinesen ließen Drachen steigen, auf dass der Wind ihre Dschunken schleppen möge. Doch im Gegensatz zu den Segeln aus dem Reich der Mitte ist das heutige Drachensegel ein Hightech-Gerät. Vor Jahren machte der Hamburger Ingenieur Stephan Wrage Urlaub auf Spiekeroog. Er war begeisterter Drachensegler. In seinen Händen konnte er spüren, welch starken Zug ein Drachen entfalten kann, wenn der Wind kräftig bläst und das Fluggerät rasend schnell Schleifen ziehen lässt.

Damit war die Idee geboren: ein Zugdrachen für ein Schiff. Der Ingenieur entwickelte seine Idee weiter und gründete das Unternehmen SkySails GmbH mit Sitz in Hamburg. Vor wenigen Jahren trat er mit seiner Idee an die Öffentlichkeit. Er erntete Spott und müdes Lächeln aus den Kreisen der Schifffahrt. Heute spottet niemand mehr, im Gegenteil. Er habe mehrere Aufträge, noch mehr Reservierungen und erhalte zahlreiche Anfragen von Interessenten aus aller Welt, berichtet der Unternehmer. Im vergangenen Dezember war in Hamburg Taufe des Schwergutfrachters „Beluga SkySails“ der Bremer Beluga Shipping GmbH. Die 1995 von Niels Stolberg gegründete Reederei hat sich als eine der ersten entschlossen, das „SkySails-System“ - so die geschützte Bezeichnung - auf ihren Schiffen einzusetzen. „Ich kann Ihnen nichts garantieren“, sagte Stolberg damals seinen Gästen. „Es kann sein, dass uns das Segel im Atlantik um die Ohren fliegt.“

Jungfernfahrt im Januar

Im Januar war das erste mit einem Zugdrachen ausgestattete Schiff der Reederei, jene 132 Meter lange Beluga SkySails, mit einer Fabrikausrüstung an Bord auf Jungfernfahrt nach Venezuela aufgebrochen. Zurzeit steuert der Frachter durch die Karibik den Hafen Davant bei New Orleans an, Anfang März wird er in einem norwegischen Hafen anlegen. Wann immer die Winde günstig stehen, setzt die Crew das Segel. Noch ist es ihr nicht um die Ohren geflogen.

Bevor der Schwergutfrachter Mitte Januar in Bremen ablegte, lud die Reederei zu einer Probefahrt in der Wesermündung ein. Da die Mannschaft den Zugdrachen auf dem werftneuen Schiff noch nicht ganz in Betrieb hatte nehmen können, war die Probefahrt spannend. Erschwerend kam hinzu, dass am frühen Nachmittag der Wind nachließ. Ohne Wind kein Segel, ohne Segel kein Hilfsantrieb. Nach einer Stunde kam endlich eine kräftige Brise auf und blies die Luftkammern des schlaff am Mast hängenden Zugdrachens auf, so dass er seine elegante Bogenform annahm und am Zugseil aufsteigen konnte. Vorschriftsgemäß stand er dann über dem Vorschiff, am straffen Seil.

„Letzten Endes hat die Neugier gesiegt“

Das SkySails-System ist nicht einfach ein Segel, das im starren Flug über dem Vorschiff steht und mittels einer Leine das Schiff schleppt. Die Kraft, die sich auf diese Weise selbst bei starkem Wind entfalten würde, wäre viel zu gering. Der Zugdrachen muss große Achten fliegen, die von einer unter dem Segel hängenden Gondel gesteuert werden. Da der Querschnitt des Drachensegels wie die Tragfläche eines Flugzeugs beschaffen ist, entsteht bei dem Flug an der Vorderseite ein Unterdruck, der das Segel vorwärts zieht. Im Gegensatz zum starren Flug lassen sich nur im dynamischen Flug sehr hohe Anströmgeschwindigkeiten erzielen. Die Kraft wächst im Quadrat: Eine Verdoppelung der Anströmgeschwindigkeit des Drachens ergibt die vierfache Zugkraft.

SkySails besteht aus mehreren Komponenten, die sich nachträglich auf fast jedem Frachter einbauen lassen. Das Drachensegel wird im Vorschiff unter der Back in einem Stauraum aufbewahrt, zusammen mit der koffergroßen Steuergondel. Durch eine Luke wird es auf die Back gezogen und an einem Teleskopmast eingehängt, der sich auf 15 Meter Länge ausfahren lässt. Durch zwei Öffnungen im Segel bläst der Wind das Drachensegel auf, so dass es bereits am Mast seine durch zahlreiche dünne Schnüre vorgegebene Bogenform annimmt. Die Schnüre laufen in der gelben Steuergondel zusammen. Bei Windstärke drei ist der Moment gekommen: Das Segel schwebt zügig empor, nur gehalten von einer gelben Leine, welche die Zugkraft auf das Schiff überträgt. In knapp 300 Meter Höhe beginnt der Zugdrachen seine großen Achten zu fliegen, die von der Gondel durch Steuerseile vorgegeben werden. Auf der Brücke sieht die Crew auf einem Bildschirm, in welchem Bereich das Segel seine Kraft entfalten kann und wie das Schiff zu steuern ist. Verlässt das Schiff den günstigen Sektor oder dreht der Wind, können Bereiche erreicht werden, in denen das Segel zwar noch Achten fliegt, aber kaum noch echte Zugkraft entfaltet. Ein Schiffsführer kann also nicht einfach drauflosfahren, er muss das System kennen und mitdenken. Im Extremfall kann ein Zugdrachen in die See stürzen. Gerät das Zugseil in den Propeller, wäre der Schaden unabsehbar.

Kapitän Heldt sieht die möglichen Gefahren gelassen: „Wir müssen uns nur an paar Regeln halten: Wir dürfen nicht über 300 Meter fliegen, nicht im Verkehrstrennungsgebiet segeln und nicht nah an der Küste“, erläutert er. An das neue System musste er sich erst gewöhnen: „Am Anfang hatte ich gemischte Gefühle dabei, aber letzten Endes hat die Neugier gesiegt.“ Auf einem Segelschiff hat Heldt, der seit 42 Jahren zur See fährt, noch nie gearbeitet, die notwendigen Kenntnisse für SkySails hat er sich in einem Spezialkursus erworben. „Wenn etwas schiefläuft, genügt ein Druck auf den Notknopf, und die Leine zum Segel wird gekappt.“

Automatisch den Bogen raus

Das Innovative am SkySails-System steckt in der koffergroßen gelben Gondel, in der mehrere Rechner über Leinen den Flug des Drachens steuern. Das System arbeitet vollautomatisch: Die Mannschaft muss sich also nicht überlegen, ob der Drachen im optimalen Bogensegment schwebt, wo er sicher fliegt und genügend Zug entwickeln kann. Der Wind muss im übrigen nicht unbedingt von achtern kommen. Er kann auch seitlich eintreffen, wobei die erzielte Zugkraft abnimmt. Steht das Segel querab zur Fahrtrichtung, ergibt sich in der Summe der Kräfte kein Vortrieb.

Das 8 mal 20 Meter große Segel entfaltet im Durchschnitt etwa acht Tonnen Schub. Da die Zugleine schräg am Himmel steht, kommen nur etwa vier Tonnen echte Zugkraft am Schiff an. Bei 20 Tonnen Schubkraft, die für die Reisegeschwindigkeit von 12 Knoten (22,2 km/h) der 10 000 Tonnen verdrängenden Beluga SkySails erforderlich sind, macht das 20 Prozent der gesamten Schubkraft aus. Der Kapitän kann nun die Hauptmaschine drosseln. Von diesem Zeitpunkt an sinkt der Treibstoffverbrauch des Frachters. Da das Segel voraussichtlich auf 30 bis 40 Prozent der Fahrtstrecke eingesetzt werden kann, ergibt sich rechnerisch eine Ersparnis von sechs bis acht Prozent.

Bonus für die Mannschaft

Vorerst gibt es nur Schätzungen, wie viel Treibstoff eingespart werden kann. „Erst wenn die Beluga SkySails in einigen Wochen von ihrer ersten großen Fahrt zurückkommt, werden genaue Zahlen vorliegen“, sagt Stephan Brabeck, einer der Geschäftsführer von SkySails. Von dieser Pilotphase hängt viel für das Unternehmen ab. Mit rund 500.000 Euro gibt Stolberg die Investition für ein Schiff von der Größe der Beluga SkySails an, inklusive der notwendigen Verstärkungen auf dem Vorschiff. Das Segel und die Leine unterliegen hohem Verschleiß, bedingt durch die salzhaltige Luft, vor allem aber durch die Sonneneinstrahlung, die der Beschichtung des Segels zusetzt. Brabeck rechnet im Dauerbetrieb mit zwei Drachen im Jahr: „Wir testen besser geeignete Beschichtungen, so dass das Segel dem Sonnenlicht länger widerstehen kann.“

Diesmal genügt ein Knopfdruck, und die Leine des Drachensegels wird eingeholt. Keine zwei Minuten, und das Segel hängt wieder am Teleskopmast auf dem Vorschiff. Der Mast fährt herunter, Segel samt Gondel werden geborgen, Luke zu. Wäre der Zugdrachen feucht geworden, würde im Stauraum ein Gebläse Luft hindurchpusten, um ihn zu trocknen. Damit das System nach Kräften genutzt wird, erhält die Mannschaft 20 Prozent der Treibstoffersparnis als Bonus ausbezahlt, vom Kapitän bis zum Schiffsjungen. Selbst der Koch wird über seinen Töpfen jede Minute segnen, die der Drachen seine Achten über dem Schiff ziehen wird.

Große Pläne liegen in der Schublade

SkySails hat längst Pläne für größere Systeme in der Schublade. Nach dem 160 Quadratmeter großen Segel der Beluga SkySails sind Zugdrachen von doppelter und vierfacher Fläche geplant. „Bei 1250 Quadratmeter ist Schluss, da wiegt die Gondel allein 130 Kilogramm“, sagt Brabeck. Eine weitere Grenze ist die Größe der Schiffe: 180 bis 200 Meter Länge, etwa 100.000 Tonnen Verdrängung, gelten als Obergrenzen.

Am besten eigne sich das SkySails-System für Tanker, Massengutschiffe und kleine Containerfrachter mit 12 bis 15 Knoten Fahrtgeschwindigkeit (22 bis 27 km/h). Containerschiffe der Postpanamax-Klasse mit einem Riesen-Zugdrachen unter der Sonne wird es also nicht geben. Insofern bleibt den Reedereien großer Containerschiffe vorerst nur die langsamere Fahrt, um die Treibstoffkosten zu senken.