UAV Formation Trajectory Planning Algorithms: A Review
Round 1
Reviewer 1 Report
This manuscript presents an interesting review of UAV Formation Trajectory Planning Algorithms. Moreover, the authors present a classification framework of UAV formation trajectory planning algorithms.
First of all, the topic is interesting and the article contains a good overview of essential algorithms related to UAV path planning. However, the article presents several flaws that must be corrected before its publication.
After reading the title and the abstract, the reader expects to find a “general” UAV article, not specific to military UAVs. The authors cannot generalize if they only focus the article on one sector. The article should include a broader view of drones. There are other very important fields for UAV path planning, such as agriculture, energy, and civil sectors, and the authors systematically ignore them. In addition, there are several points in the article that conflict with this point. For example, the title is “UAV Formation Trajectory Planning Algorithms”, which is a title that includes all types of drones and sectors, not just military drones. In addition, the authors indicate in the abstract phrases such as “because of its remarkable functions and flexibility to accomplish complex and changeable tasks, such as search and rescue, resource exploration, reconnaissance and surveillance”, that cover all kinds of tasks for drones. However, the article is only focused on the military field. I consider that all sectors (not only the military) should be addressed throughout the manuscript, mainly in the introduction. However, if the authors want to focus only on the military, at least the title, the abstract and the conclusions must be modified accordingly. Authors should decide and rewrite the manuscript accordingly.
All figure and table captions must be improved. The caption should explain what is shown in each figure. Besides, the paper needs a revision of its structure because it contains a lot of errors and mistakes, for example, there are figures without captions, captions without figures, figures with low quality, unfinished sentences, and so on.
Finally, the article should be written more formally and the English must be revised, as several parts are difficult to understand. This is especially critical in a review article, as in this case. Therefore I suggest a complete revision of the English language by a professional.
Specific comments:
Line 2
Since the article is already a review, I suggest changing the order of the words in the title to “UAV Formation Trajectory Planning Algorithms: a review”
Line28
UAVs, not Uavs
Line 28
“such as the 1991 Gulf War, the Afghanistan War, the Iraq War, the fight against ISIS, the 2011 decapitation operation code-named Neptune Spear approved by U.S. President Barack Obama, and the Russia-Ukraine conflict in 2022”
these examples are clearly biased since drones have been used in other conflicts in which the USA is not involved (e.g. the Syrian war in which Russia is involved). This is a scientific article, therefore this information should be removed.
Line 35
It is not clear to this reviewer what is the meaning of “seduction” in this context.
Line 37
“Angle”
Why is “A” in capital letters?
Line 37
“Angle may be limited, and the target area cannot be observed from multiple different directions; When faced with a large-scale search task, the entire reconnaissance area cannot be effectively covered.”
This sentence is hard to understand, please rephrase.
Line 38
“When”
Why is “W” in capital letters?
Line 39-43
Please, add references.
Line 55
“The formation flight of UAVs can improve the aerodynamic efficiency of UAVs, thus reducing the overall flight resistance and saving fuel.”
How? In a straight-line formation? What about wind turbulence and other issues? Please elaborate further on this statement and add references.
Line 60
“It can be seen that UAV formation flight has incomparable advantages over single UAV”
Incomparable? In what sense? Please, provide examples and add references.
Line 66
“by domestic and foreign scholars”
Who are domestic? And who are foreign? Which data support this statement?
Moreover, is this information really necessary in a scientific article?
Line 66
“shows a rapid growth trend.”
Add references.
Line 74
“UAV formation trajectory planning is to plan the flyable trajectory”
Please, rephrase
Line 85
“The planning space is large and complex,”
Always? And what if the “battlefield” is a single neighborhood or even a house?
Line 92
“a large number of literatures have put forward solutions from different angles”
It is not clear what the meaning of this sentence is, especially with “a large number of literatures”, please rephrase it.
Line 92-96
This paragraph is hard to understand, rephrase it.
Line 97
“Compared with many literatures on UAV formation trajectory planning [2] [3] [4] [5],”
Authors must add a brief resume about each citation, not a single phrase for everything.
Line 99-104
The authors indicate in line 17 “a simple framework of UAV formation trajectory planning algorithm is proposed”, but this statement is not included in this paragraph. Why?
Line 116-122
This paragraph is hard to understand, rephrase it.
Line 124
The quality of Figures 3 and 4 is very low, please improve it.
Line 128
“which is that the long plane collects”
Please, rephrase
line 131
“is shown in Figure 4.”
Figures should appear after the citation in the text, not before.
Line 184
Where is the caption of the figure?
Line 186
“Fig. 6”
The authors use sometimes “figure” and others “fig.”. Please, unify.
Line 187
Isolated caption.
Lin 199-203
This paragraph is hard to understand, please rephrase.
Line 243
The authors use sometimes “figure” and others “fig.”. Please, unify.
Line 244
“gram”
Line 276
The authors use sometimes “figure” and others “fig.”. Please, unify.
Line 292
The authors use sometimes “figure” and others “fig.”. Please, unify.
Line 318
Where is table 1?
Line 328
“Heuristic algorithms are mostly optimization algorithms that search for the approximate optimal solution at an acceptable computational cost.”
This is a very vague definition. Please, expand it and add references.
Line 428
Where is table 2?
Line 443
The authors use sometimes “figure” and others “fig.”. Please, unify.
Line 585
Line of text between the caption and the table.
Line 586
Line of text between the caption and the figure.
Line 841
“Fig. 19 is a trajectory diagram of an ant colony optimization algorithm (ACO).”
Please explain what is shown in the figure. What are the cells, the numbers…
Line 842
The caption should explain what is shown in the figure. What are the cells, the numbers…
Line 966
Please improve the quality of the figure.
Line 1046
Please improve the quality of the figure.
Line 1071
“Table 7 summarizes the contents of UAV formation trajectory planning using machine learning algorithm in our investigation.”
This sentence, as currently worded, implies that the authors of the manuscript used machine learning to develop their research. Since this is a "review" article, I assume the sentence is incorrect. Please rewrite it correctly.
Linen 1083-1095
This paragraph is hard to understand, please rephrase.
Line 1089
“By”
Why capital letters?
Line 1270
“or it is a rolling time window method.”
This sentence makes no sense here.
Line 1317
“With the advancement of low airspace reform”
What does this mean? A legislative reform? where? What are the implications? Please, add references.
Line 1371
I would also add that it is necessary to find methods/develop algorithms to reduce computing requirements in order not only to save time, allowing real-time planning, but also to be more efficient in terms of energy.
Line 1421
Why the conclusions are so general and there is nothing related to the military sector? All the introduction and, in general, the paper, is based on UAV military tasks. The authors cannot generalize if they are only focused on one area. Therefore, I suggest changing the conclusions accordingly or, on the contrary, adding information about other areas, such as agriculture or civil engineering, in the rest of the article, especially in the introduction.
Author Response
I can see from your valuable opinions that you are a professional and careful person. Please accept my thanks to you. The uploaded attachment is the document that I got after gradual modification according to your suggestions and those of another reviewer.
Point 1: Since the article is already a review, I suggest changing the order of the words in the title to “UAV Formation Trajectory Planning Algorithms: a review”.
Response 1: According to your opinion, the word order in the title has been changed to " UAV Formation Trajectory Planning Algorithms: a review".
Point 2: UAVs, not Uavs.
Response 2: I'm sorry, this kind of mistake shouldn't happen. Thank you for your criticism and correction. "Uavs" has been changed to "UAVs".
Point 3: “such as the 1991 Gulf War, the Afghanistan War, the Iraq War, the fight against ISIS, the 2011 decapitation operation code-named Neptune Spear approved by U.S. President Barack Obama, and the Russia-Ukraine conflict in 2022”.
these examples are clearly biased since drones have been used in other conflicts in which the USA is not involved (e.g. the Syrian war in which Russia is involved). This is a scientific article, therefore this information should be removed.
Response 3: What I want to express here is the application of drones in these places. There are no biased examples, nor does it say that the United States has participated in all conflicts. I am very sorry for the misunderstanding caused by my inappropriate expression. I have changed my expression, and thank you for your valuable suggestions.
Point 4: It is not clear to this reviewer what is the meaning of “seduction” in this context.
Response 4: " seduction " means to trick the enemy. I'm very sorry for the misunderstanding caused by my inappropriate expression. I've replaced it with other words. If it's inappropriate, I hope to get your criticism and correction.
Point 5: “Angle”
Why is “A” in capital letters?
Response 5: I'm sorry, this kind of mistake shouldn't happen. Thank you for your criticism and correction. "Angle" has been changed to "angle".
Point 6: “Angle may be limited, and the target area cannot be observed from multiple different directions; When faced with a large-scale search task, the entire reconnaissance area cannot be effectively covered.”
This sentence is hard to understand, please rephrase.
Response 6: It has been rewritten as " when a single UAV performs a reconnaissance mission, it may be restricted by the observation angle, and it cannot observe the target area from many different directions; when faced with a large-scale search task, a single UAV cannot effectively cover the entire reconnaissance area;; " Please correct me if there is something that is not very difficult to understand.
Point 7: “When”
Why is “W” in capital letters?
Response 7: I'm sorry, this kind of mistake shouldn't happen. Thank you for your criticism and correction. "When" has been changed to "when".
Point 8: Please, add references.
Response 8: References have been added according to your comments.
Point 9: “The formation flight of UAVs can improve the aerodynamic efficiency of UAVs, thus reducing the overall flight resistance and saving fuel.”
How? In a straight-line formation? What about wind turbulence and other issues? Please elaborate further on this statement and add references.
Response 9: Your question is very good. I added the qualification to this part, and changed this part to "When the UAV formation is not in extreme weather, keeping different formations can improve the aerodynamic efficiency of the UAV to varying degrees, and then reduce the overall flight resistance, achieving the effect of saving fuel. ",at the same time added references, if you have any good suggestions, please correct me in time.
Point 10: “It can be seen that UAV formation flight has incomparable advantages over single UAV”
Incomparable? In what sense? Please, provide examples and add references.
Response 10: This sentence is equivalent to a summary of the previous sentence, and at the same time connects the following. In order to avoid misunderstanding, I modified this sentence to the previous one. Thanks to your advice.
Point 11 and point 12: “by domestic and foreign scholars”
Who are domestic? And who are foreign? Which data support this statement?
Moreover, is this information really necessary in a scientific article?
Response 11 and response 12: After careful consideration of your suggestion, I think it is really unnecessary to add this part of information to the article, so I choose to delete this part. Thank you for your valuable suggestion.
Point 13 : “UAV formation trajectory planning is to plan the flyable trajectory”
Please, rephrase
Response 13: According to your suggestion, I have changed the complete sentence to "The purpose of UAV formation trajectory planning is to make each UAV safely reach the target point from the starting point according to the specific task, terrain, weather and other environmental factors of each UAV, as well as its own flight performance, on the premise of satisfying multiple constraints, so as to achieve the best or better specified performance index.”
Point 14: “The planning space is large and complex,”
Always? And what if the “battlefield” is a single neighborhood or even a house?
Response 14: According to your suggestion, in order to make the content of the article more rigorous, I rewrote this sentence into: "In many cases, the planning space is large and complex, for example, there are various space obstacles and dynamic threats in the modern battlefield environment.". If the "battlefield" is a community or even a house, these environments are also relatively narrow for UAV formation, so it can be considered as a complex environment, but its space scope is relatively small, which should be a special case.
Point 15: “a large number of literatures have put forward solutions from different angles”
It is not clear what the meaning of this sentence is, especially with “a large number of literatures”, please rephrase it.
Response 15: According to your suggestion, I have modified this part of the complete sentence into: " For the trajectory planning of UAV formation, many papers have proposed solutions from different perspectives, but there are still many unsolved problems and many limitations, resulting in numerous and complex papers without a comprehensive and systematic classification, which is not conducive to research and reading."
Point 16: This paragraph is hard to understand, rephrase it.
Response 16: According to your suggestion, I reorganized this paragraph and changed it to "For the trajectory planning of UAV formation, many papers have proposed solu-tions from different perspectives, but there are still many unsolved problems and many limitations, resulting in numerous and complex papers without a comprehensive and systematic classification, which is not conducive to research and reading."
Point 17: “Compared with many literatures on UAV formation trajectory planning [2] [3] [4] [5],”
Authors must add a brief resume about each citation, not a single phrase for everything.
Response 17: Based on your suggestions, I added the descriptions of those articles and added the following 4 paragraphs:
The first paragraph: Reference [9] classifies and statistically analyzes various UAV formation coopera-tive trajectory planning problems from three elements of UAV system (task, unmanned crew and environment) and three elements of UAV formation cooperative trajectory planning problems (UAV trajectory, target and constraint), but this article does not discuss the UAV formation trajectory planning algorithm.
The second paragraph: Stochastic Heuristic Algorithms (SHA) are reviewed in reference [10], and the characteristics, improvements, applications, advantages and disadvantages of some of them are discussed. However, non-SHA algorithms in UAV formation flight trajectory are not discussed in this paper.
Paragraph 3: In reference [11], the flight trajectory planning algorithm of UAV formation is di-vided into five categories, including optimal algorithm, graph theoretic-based plan-ning method, heuristic information-based planning algorithm, swarm intelligence al-gorithm and neural network algorithm, and a simple description is given. However, this paper does not discuss specific algorithms.
Paragraph 4: Reference [12] reviews swarm intelligence algorithms from four aspects, such as collision avoidance processing, task allocation, trajectory planning and formation re-combination, and discusses classical algorithms among them. However, this paper does not discuss non-swarm intelligence algorithms, which has certain limitations.
Point 18: The authors indicate in line 17 “a simple framework of UAV formation trajectory planning algorithm is proposed”, but this statement is not included in this paragraph. Why?
Response 18: Here I say that I have made a detailed classification, which is actually another meaning expressed in line 17. I just use relatively short words to express it. I hope there is no misunderstanding.
Point 19: This paragraph is hard to understand, rephrase it.
Response 19: According to your suggestion, I have reorganized the language of lines 116-122. The revised paragraph reads "Global trajectory planning algorithm belongs to static programming algorithm, which carries out trajectory planning based on existing map information and seeks an optimal trajectory from the starting point to the target point. In this paper, global trajectory planning algorithms are divided into traditional algorithms and intelligent algorithms according to whether they are inspired by natural organisms. Based on the imitation of human behavior or other animal behavior, intelligent algorithms are divided into machine learning algorithms and heuristic algorithms. The global trajectory planning algorithm framework is shown in Figure 3."
Point 20: The quality of Figures 3 and 4 is very low, please improve it.
Response 20: I'm sorry for the low quality of the picture you said. In fact, the quality of this picture is not low. It should have been much bigger than it is now. So I'm going to zoom in a little bit here.
Figure 3
Figure 4
Point 21: “which is that the long plane collects”
Please, rephrase
Response 21: According to your suggestion, This paragraph has been rewritten as “which means that the pilot aircraft collects the current position infor-mation and local obstacle information in real time according to the UAV sensor in formation, so as to obtain the optimal trajectory from the starting point to the target point. The local trajectory planning algorithm framework is shown in Figure 4. ".
Point 22: “is shown in Figure 4.”
Figures should appear after the citation in the text, not before.
Response 22: The error has been corrected.
Point 23: Where is the caption of the figure?
Response 23: In this section, the title of the graphic was originally: "Figure 6. A Kind of Dubins Trajectory Diagram." I modified it, and the revised title was: "Figure 6. An LRL Trajectory Diagram of Dubins Curve."
Point 24: “Fig. 6”
The authors use sometimes “figure” and others “fig.”. Please, unify.
Response 24: All "Fig." have been changed to "Figure".
Point 25: Isolated caption.
Response 25: Here's the title of Figure 6, and the format may be misplaced when uploading.
Point 26: This paragraph is hard to understand, please rephrase.
Response 26: According to your opinion, I revised the original text. The specific changes are as follows:
Before modification: "however, the difference is that Floyd algorithm is to find the distance between any two points, which is the shortest route with multiple sources and can be calculated with negative weight, while Dijkstra algorithm is to find the shortest route from one vertex to all other vertices, which is the shortest route with single source and cannot calculate the negative weight loop."
After modification: "different from Dijkstra's algorithm, Floyd's algorithm is to find the distance between any two points, which is the shortest path from multiple sources, and can be calculated with negative weights, while Dijkstra's algorithm is to find the shortest path from one vertex to all other vertices, which is the shortest path from one source, and cannot be calculated with negative weights."
Point 27: The authors use sometimes “figure” and others “fig.”. Please, unify.
Response 27: All "Fig." have been changed to "Figure".
Point 28: “gram”
Response 28: The picture title has been modified as follows:
Before modification: "Figure 8. A Voronoi diagram trajectory diagram."
After modification: "Figure 8. A Voronoi diagram method of trajectory diagram."
Point 29 and point 30: The authors use sometimes “figure” and others “fig.”. Please, unify.
Response 29 and point 30: All "Fig." have been changed to "Figure".
Point 31: Where is table 1?
Response 31: Table 1 May have been misformatted when it was uploaded. I have corrected this mistake. Thank you for your advice.
Point 32: “Heuristic algorithms are mostly optimization algorithms that search for the approximate optimal solution at an acceptable computational cost.”
This is a very vague definition. Please, expand it and add references.
Response 32: According to your opinion, I revised the original text. The specific changes are as follows:
Before modification: "Heuristic algorithms are mostly optimization algorithms that search for the approximate optimal solution at an acceptable computational cost."
After modification: "Heuristic algorithms are mostly optimization algorithms that search for the approximate optimal solution based on empirical rules at an acceptable computational cost to find the solution to the problem. Instead of systematically searching for answers, it uses past experience to choose effective methods, but it cannot guarantee the speed of solutions and the degree of optimization of feasible solutions [31]."
Here I expand the heuristic algorithm and add references [31].
Point 33: Where is table 2?
Response 33: Table 2 May have been misformatted when it was uploaded. I have corrected this mistake. Thank you for your advice.
Point 34: The authors use sometimes “figure” and others “fig.”. Please, unify.
Response 34: All "Fig." have been changed to "Figure".
Point 35 and point 36: Line of text between the caption and the table.
Response 35 and response 36: It may be the format error caused by uploading. I have made the modification. Thank you for your suggestion.
Point 37 and point 38: “Fig. 19 is a trajectory diagram of an ant colony optimization algorithm (ACO).”
Please explain what is shown in the figure. What are the cells, the numbers…
Response 37 and response 38: According to your suggestion, I have added a description to the picture. The description is as follows:
"Cell" is the map block after rasterizing the map, "number" is the number of the map block, and the black part represents obstacles.
Point 39: Please improve the quality of the figure.
Response 39: First of all, thank you for your advice, but here I want to say sorry, please allow me to give you an explanation, the explanation is as follows:
This figure is quoted from one of the references in this article, which has been attributed. This is a top view of matlab. Due to color superposition caused by Angle, you may think it is very fuzzy. In fact, it is a high-quality picture that can clearly observe the track, so I can't improve its quality. Hope to get your understanding.
Point 40: Please improve the quality of the figure.
Response 40: First of all, thank you for your advice, but here I want to say sorry, please allow me to give you an explanation, the explanation is as follows:
This figure is a PNG image that I drew with Viso and generated directly. It is actually a high-quality image, which may be blurred due to the shrinking of the image. I have enlarged the image in the article. Hope to get your understanding.
Point 41: “Table 7 summarizes the contents of UAV formation trajectory planning using machine learning algorithm in our investigation.”
This sentence, as currently worded, implies that the authors of the manuscript used machine learning to develop their research. Since this is a "review" article, I assume the sentence is incorrect. Please rewrite it correctly.
Response 41: According to your suggestion, I have made the modification as follows:
Before modification: Table 7 summarizes the contents of UAV formation trajectory planning using machine learning algorithm in our investigation.
Modified: Table 7 summarizes the content of machine learning algorithms in the survey.
Point 42: This paragraph is hard to understand, please rephrase.
Response 42: According to your suggestion, I have made the modification as follows:
Before modification: The Artificial Potential Field (APF) was first proposed by Khatib as a virtual force method. The artificial potential field method designed the movement of each UAV in the flight environment to be in a hypothetical artificial field. For each UAV, the target point generated an attractive field, while the obstacle generated a repulsive force field. Un-der the superposition of the attractive field and repulsive force field, each UAV generated a feasible trajectory in the direction of potential field decline. Generally, in order to simplify the calculation, by calculating the negative gradient of the gravitational potential function and the repulsive potential function, the gravitational force and re-pulsive force of each UAV in the potential field can be obtained, and the resultant force of each UAV can be obtained. According to the resultant force, the control quantity required by each UAV to make attitude adjustment can be calculated, so as to guide the formation UAV to avoid obstacles and complete the trajectory planning. Fig. 25 is a schematic diagram of artificial potential field.
Modified: Artificial Potential Field method (APF) is a virtual force method proposed by Khatib. Artificial potential field method assumes that each UAV moves in a new artificial field. For each UAV, the attraction field is generated by the target point, and the repulsion field is generated by the obstacle. Under the action of the attraction field and repulsion field, each UAV generates a feasible trajectory along the downward direction of the potential field. In general, in order to simplify the calculation, the gravity of the UAV in the potential field can be obtained by calculating the negative gradient of the gravitational potential function. By calculating the negative gradient of the repulsive potential function, the repulsive force of UAV in the potential field can be obtained. And that gives you the resultant force on the UAV. According to the resultant force, the control quantity required for UAV attitude adjustment is calculated, and then the UAV formation is guided to avoid obstacles to complete trajectory planning.
Point 43: “By”
Why capital letters?
Response 43: I'm sorry, this kind of mistake shouldn't happen. Thank you for your criticism and correction. "By" has been changed to "by".
Point 44: “or it is a rolling time window method.”
This sentence makes no sense here.
Response 44: I am sorry that there are some problems in the expression here, so I make the following modifications:
Before modification: Model Predictive Control (MPC) is a typical online planning method with edge planning and execution, or it is a rolling time window method.
After modification: Model Predictive Control (MPC) is a typical online planning method with con-current planning and concurrent execution. In other words, it is a rolling time window method.
Point 45: “With the advancement of low airspace reform”
What does this mean? A legislative reform? where? What are the implications? Please, add references.
Response 45: I'm glad to explain it to you. Low-altitude airspace is an important strategic resource of every country and the main activity area of military aviation and general aviation. Like land resources and marine resources, it contains great economic, national defense and social values. However, most UAVs, especially light and small civil UAVs, have been operating in low-altitude airspace, and a conflict may exist between increasing the number of UAVs and the limited low airspace. To promote low-altitude airspace resource development and to standardize the operation and management of UAVs in urban regions, some global laws and regulations and key technologies for urban low-altitude applications of UAVs have been implemented. Finally, I added the reference [164] according to your request.
Point 46: I would also add that it is necessary to find methods/develop algorithms to reduce computing requirements in order not only to save time, allowing real-time planning, but also to be more efficient in terms of energy.
Response 46: I actually thought about this before and forgot to include it in this article. I have added the section 7.4 in the article. The following is the content of section 7.4:
7.4. New algorithm
At present, the existing flight trajectory planning algorithms of UAV formation are more or less flawed. Therefore, developing an algorithm that can reduce compu-ting requirements, save time, allow real-time planning, and be more energy efficient is also a very worthwhile direction to explore.
Thank you very much for your advice.
Point 47: Why the conclusions are so general and there is nothing related to the military sector? All the introduction and, in general, the paper, is based on UAV military tasks. The authors cannot generalize if they are only focused on one area. Therefore, I suggest changing the conclusions accordingly or, on the contrary, adding information about other areas, such as agriculture or civil engineering, in the rest of the article, especially in the introduction.
Response 47: Thank you for your criticism. According to your suggestions, I have added information on agriculture, energy and civil fields in the introduction, and corresponding references [2][3][4].
Finally, I wish you every success in your work.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
UAV's trajectory planning algorithm is the. most important feature which will influence both scale and applications of this technology in real-world. The authors have done a commendable job in studying and categorizing the review. The review is very comprehensive and can understand the challenges overwhelming the authors in preparation of manuscript. My suggestions are on two fronts.
First, add more supplementary data points about the companies and their profiles using various kinds of algorithms. This will assist and augment your arguments made through Figure 1 and 2.
Second, improve the English language of the article and try to reduce the repetitions of texts across different sections.
Author Response
As you can see from your valuable opinion, you are a professional and attentive person. Please accept my thanks to you. The uploaded attachment is the document I got after step-by-step revisions based on your suggestions and the suggestions of another reviewer.
Point 1: First, add more supplementary data points about the companies and their profiles using various kinds of algorithms. This will assist and augment your arguments made through Figure 1 and 2.
Response 1: According to your suggestion, I have added data sources to Figure 1 and Figure 2.
Point 2: Second, improve the English language of the article and try to reduce the repetitions of texts across different sections.
Response 2: According to your comments and those of another reviewer, I have revised many parts of the article, and all the newly uploaded pdf documents have been marked in red.
Finally, I wish you every success in your work.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors improved the manuscript accordingly to the specific comments.
However, they did not consider the general comments indicated in the first review, and there are still two main points that should be improved:
1. All figure and table captions must be improved. The caption should explain what is shown in each figure (what the cells represent, the lines, and so on).
2. English should be improved and revised throughout the article.
Author Response
Dear reviewer, I am very glad to receive your suggestion. In response to your suggestions, I have made modifications according to the points. Specific modifications are as follows:
Point 1: All figure and table captions must be improved. The caption should explain what is shown in each figure (what the cells represent, the lines, and so on).
Response 1: According to your requirements, I have modified the titles of all the figures and tables. The specific modifications are as follows: First, most of the pictures in the article are explained in the title (except for the parts that have already been annotated in the picture); Secondly, I made further changes to all the table headings.
Point 2: English should be improved and revised throughout the article.
Response 2: According to your request, every sentence in the article has been improved and modified.
Finally, I wish you every success in your work.
Author Response File: Author Response.pdf
