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The paper presents an application of reassigned wavelet scalogram for rotor system fault diagnosis. It is a topic of interest to the researchers in the related areas but the paper needs very significant improvement before acceptance for publication. My detailed comments are as follows:
1. The wavelet method (reassigned wavelet scalogram) used in the paper works very well for the underlying fault diagnosis problem. On the other hand, this wavelet method is a
well-established method, and the present research is a direct application of this method without new contribution in methodological research.
2. For the above reason, the presentation should be focused on the results. Unfortunately, the presentation is far from acceptable for publication. The material was not properly organized and it is strongly suggested that the authors check carefully the English writing and use standard terminologies in the technical area.
3. The title of the paper should be more specific since numerous studies have been done on the fault diagnosis of rotor systems using wavelets and time-frequency methods. Also, remove the word "research".
4. On Section 1:
· This section listed many references that are mainly related to rotor dynamics and are not directly related to rotor system diagnosis. If the authors would like to keep these references, some discussions on the relevance of these refs to the present research are needed.
· Review on the directly relevant refs will be more helpful for the reader. Also, time-frequency and wavelets are mainly for non-stationary and transient analysis. The author may discuss in more detail what types of transients and non-stationary components would appear in rotor system vibration.
· A few sentences on the organization of the paper will be helpful.
5. On Section 2:
· Since the major method used in the application is reassigned wavelet scalogram, it is not needed to give the details of three other methods (only give a few words and give the refs). Instead, the authors may discuss more on the relationship between traditional wavelet
scalogram and the reassigned wavelet scalogram, and explain why the latter is better than the former.
· Eq (2): the right-hand-side is wrong and "2" is missed.
· The description after Eq (2) is not clear. See Cohen's book for details about the cross-terms.
6. On Sections 3 and 4:
The description needs to be improved. The material in Section 3 should be organized in several paragraphs.
7. On Section 5:
· The authors did a good experiment and some of the phenomena presented in the
time-frequency planes are also very interesting. However, the observations should be
described concisely, and the authors should focus more on: 1) whether these phenomena are general characteristics, and 2) if possible, explain the reason of the phenomena and the advantages of reassigned wavelet scalogram over other time-frequency methods.
· In fact, it is possible to interpret most of the phenomena in the time-frequency planes using
rotor dynamics. For example, shaft rub causes broadband vibration and will result in nearly horizontal lines in the phase planes.
· Some of the paragraphs are too long.
8. The conclusion should be concise and only summarize the most important contribution of the research.
Reviewer #2: This paper presents the results of time-frequency analysis applied to a table top rotating machinery test rig under a set of fault conditions. The title of the paper is very
misleading because no automated methods for either fault detection or diagnosis/isolation are discussed in the paper. Rather, under different fault scenarios, several time-frequency methods available in the literature are evaluated for their ability to generate visually
discriminating features associated with the fault conditions. Hence, this paper provides a characterization of time-frequency features associated with rotating machinery faults as opposed to the development of any type of fault diagnosis methodology. Hence, the paper must be judged solely on the quality of the experimentation, the presentation of the results, and how the time-frequency features identified in the various fault cases relates to the dynamical operating conditions of the rig.
The main problem with the paper is that it is very poorly written, and this makes the evaluation and interpretation of the main contributions of the paper obscure. The paper requires a complete rewrite to improve the grammar, style and readability. Also consider:
In equation (1) on page 2, what does it mean that h(t) is centered at t=0 and f=0? h(t) is a windowing function in the time domain!
What is the point of the simulation experiments, what do they add to what is already known about the time-frequency techniques from the literature?
Since the only contribution of the paper is the time-frequency analysis, the results of these computations need to be explained in detail in the text and the graphical results need to be properly annotated so that readers can comprehend and understand which distinguishing features are associated with the faults. Currently, the graphical results are poorly displayed and it is difficult to correlate the figures with the text.以下是从一个朋友转载来的，关于英文投稿过程中编辑给出的意见。与大家一起分享。
以下12点无轻重主次之分。每一点内容由总结性标题和代表性审稿人意见构成。
1、目标和结果不清晰。
It is noted that your manuscript needs careful editing by someone with expertise in technical English editing paying particular attention to English grammar, spelling, and sentence structure so that the goals and results of the study are clear to the reader.
2、未解释研究方法或解释不充分。
◆ In general, there is a lack of explanation of replicates and statistical me
thods used in the study.
◆ Furthermore, an explanation of why the authors did these various experiments should be provided.
3、对于研究设计的rationale:
Also, there are few explanations of the rationale for the study design.
4、夸张地陈述结论/夸大成果/不严谨：
The conclusions are overstated. For example, the study did not show
if the side effects from initial copper burst can be avoid with the polymer formulation.
5、对hypothesis的清晰界定：
A hypothesis needs to be presented。
6、对某个概念或工具使用的rationale/定义概念：
What was the rationale for the film/SBF volume ratio?
7、对研究问题的定义：
Try to set the problem discussed in this paper in more clear,
write one section to define the problem
8、如何凸现原创性以及如何充分地写literature review:
The topic is novel but the application proposed is not so novel.
9、对claim,如A＞B的证明，verification:
There is no experimental comparison of the algorithm with previously known work, so it is impossible to judge whether the algorithm is an improvement on previous work.
10、严谨度问题：
MNQ is easier than the primitive PNQS, how to prove that.
11、格式（重视程度）：
◆ In addition, the list of references is not in our style. It is close but not completely correct. I have attached a pdf file with "Instructions for Authors" which shows examples.
◆ Before submitting a revision be sure that your material is properly prepared and
formatted. If you are unsure, please consult the formatting nstructions to authors that are given under the "Instructions and Forms" button in he upper right-hand corner of the screen.
12、语言问题（出现最多的问题）：
有关语言的审稿人意见：
◆ It is noted that your manuscript needs careful editing by someone with expertise in technical English editing paying particular attention to English grammar, spelling, and sentence structure so that the goals and results of the study are clear to the reader. ◆ The authors must have their work reviewed by a proper translation/reviewing service before submission; only then can a proper review be performed. Most sentences contain grammatical and/or spelling mistakes or are not complete sentences.
◆ As presented, the writing is not acceptable for the journal. There are pro
blems with sentence structure, verb tense, and clause construction.
◆ The English of your manuscript must be improved before resubmission. We str ongly suggest that you obtain assistance from a colleague who is well-versed i
n English or whose native language is English.
◆ Please have someone competent in the English language and the subject matte r of your paper go over the paper and correct it. ?
◆ the quality of English needs improving.
来自编辑的鼓励：
Encouragement from reviewers:
◆ I would be very glad to re-review the paper in greater depth once it has be
en edited because the subject is interesting.
◆ There is continued interest in your manuscript titled "……" which you subm itted to the Journal of Biomedical Materials Research: Part B - Applied Biomat erials.
◆ The Submission has been greatly improved and is worthy of publication.