An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing lit...An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.展开更多
In this paper,we establish the integration by parts formula for the solution of fractional noise driven stochastic heat equations using the method of coupling.As an application,we also obtain the shift Harnack inequal...In this paper,we establish the integration by parts formula for the solution of fractional noise driven stochastic heat equations using the method of coupling.As an application,we also obtain the shift Harnack inequalities.展开更多
In order to optimize the spares configuration project at different stages during the life cycle, the factor of time is considered to relax the assumption of the spares steady demand in multi-echelon technique for reco...In order to optimize the spares configuration project at different stages during the life cycle, the factor of time is considered to relax the assumption of the spares steady demand in multi-echelon technique for recoverable item control(METRIC)theory. According to the method of systems analysis, the dynamic palm theorem is introduced to establish the prediction model of the spares demand rate, and its main influence factors are analyzed,based on which, the spares support effectiveness evaluation index system is studied, and the system optimization-oriented spares dynamic configuration method for multi-echelon multi-indenture system is proposed. Through the analysis of the optimization algorithm, the layered marginal algorithm is designed to improve the model calculation efficiency. In a given example, the multi-stage spares configuration project during its life cycle is gotten, the research result conforms to the actual status, and it can provide a new way for the spares dynamic optimization.展开更多
In many fields of high-tech industry the ultra-t hi n wall parts are employed. In this paper the experiments were carried out to dis cuss the surface microstructure of the camera’s guided drawtube by applying ult ras...In many fields of high-tech industry the ultra-t hi n wall parts are employed. In this paper the experiments were carried out to dis cuss the surface microstructure of the camera’s guided drawtube by applying ult rasonic vibration cutting device to the traditional lathe. The influence rule of the cutting condition on the surface roughness was put forward, which was drawn by comparing the ultrasonic cutting with the common cutting by use of the cemen ted carbide tool and the polycrystalline diamond (PCD) tool. The test results sh owed that the ultrasonic cutting performs better than the common cutting in the same condition. According to the test results analyzing, the surface characteriz ation is influenced clearly by the rigidity of the acoustic system and the machi ne tool, as well the setting height of the tool tip. Otherwise, the dense regula r low frequency vibration ripples will be scraped on the machined surface. When the tool tip is set higher than the rotating center of the work piece by three t imes of the amplitude of ultrasonic vibration, the vibration ripples behave alig ht; they turn light and shade alternatively when the tool tip is lower than the rotating center of the work piece by three times of the amplitude of ultrasonic vibration. According to the test result analyzing, the following conclusions are put forward: 1) The surface roughness in ultrasonic cutting is better than that in common cutting. Under a one third critical cutting velocity, the value of th e surface roughness in ultrasonic cutting rise slightly along with the cutting v elocity, while in common cutting it decreases contrast to the cutting velocity; the curves of the surface roughness in ultrasonic cutting and common cutting see m to be alike, both increase along with the feed rate and the cutting depth, but the value in ultrasonic cutting is smaller in the same condition.2) The influen ce of the coolant on the surface roughness cannot be ignored. The kerosene can b e employed to improve the surface roughness in ultrasonic machining.3) In ultras onic cutting process of aluminum alloy ultra-thin wall work piece, the PCD tool performs better than the cemented carbide tools.4) The vibration ripples result from the not enough rigidity of the acoustic system and the improper setting he ight of the tool tip. The departure of the tool tip from the rotating center of the work piece to some extent causes the vibration ripples on the machined surfa ce.展开更多
The inner hole parts played an oriented or supporting role in engineering machinery and equipment,which are prone to appear surface damages such as wear,strain and corrosion. The precise pulse plasma arc powder weldin...The inner hole parts played an oriented or supporting role in engineering machinery and equipment,which are prone to appear surface damages such as wear,strain and corrosion. The precise pulse plasma arc powder welding method is used for surface damage repairing of inner hole parts in this paper. The working principle and process of the technology are illustrated,and the microstructure and property of repairing layer by precise pulse plasma powder welding and CO2 gas shielded welding are tested and observed by microscope,micro hardness tester and X-ray residual stress tester etc. Results showed that the substrate deformation of thin-walled inner hole parts samples by precise pulse plasma powder welding is relatively small. The repair layer and substrate is metallurgical bonding,the transition zones( including fusion zone and heat affected zone) are relatively narrow and the welding quality is good. It showed that the thin-walled inner hole parts can be repaired by this technology and equipment.展开更多
In equipment integrated logistics support(ILS), the supply capability of spare parts is a significant factor. There are lots of depots in the traditional support system, which makes too many redundant spare parts and ...In equipment integrated logistics support(ILS), the supply capability of spare parts is a significant factor. There are lots of depots in the traditional support system, which makes too many redundant spare parts and causes high cost of support. Meanwhile,the inconsistency among depots makes it difficult to manage spare parts. With the development of information technology and transportation, the supply network has become more efficient. In order to further improve the efficiency of supply-support work and the availability of the equipment system, building a system of one centralized depot with multiple depots becomes an appropriate way.In this case, location selection of the depots including centralized depots and multiple depots becomes a top priority in the support system. This paper will focus on the location selection problem of centralized depots considering ILS factors. Unlike the common location selection problem, depots in ILS require a higher service level. Therefore, it becomes desperately necessary to take the high requirement of the mission into account while determining location of depots. Based on this, we raise an optimal depot location model. First, the expected transportation cost is calculated.Next, factors in ILS such as response time, availability and fill rate are analyzed for evaluating positions of open depots. Then, an optimization model of depot location is developed with the minimum expected cost of transportation as objective and ILS factors as constraints. Finally, a numerical case is studied to prove the validity of the model by using the genetic algorithm. Results show that depot location obtained by this model can guarantee the effectiveness and capability of ILS well.展开更多
Taking high speed rotating shaft parts as the research object,the general fault mode of the parts is analyzed.The analysis process of shaft parts is expounded by means of finite element analysis method.A variety of fa...Taking high speed rotating shaft parts as the research object,the general fault mode of the parts is analyzed.The analysis process of shaft parts is expounded by means of finite element analysis method.A variety of fatigue life prediction methods for mechanical equipment parts are reviewed in this paper.And the selection and calculation method of parameters in the life prediction model of shaft parts are summarized.Finally,taking a gear shaft of a reducer as an example,the Morrow linear correction of the elastic stress model,Manson-Halford(M-H)correction model and Smith Watson Topper(SWT)correction model are applied to fatigue life assessments.The prediction results of the SWT correction model are relatively conservative.The prediction results of the Morrow linear correction of the elastic stress model and the M-H model are similar,and they are larger than the SWT correction model.展开更多
In this paper, a new bulge-forming technology is described to manufacture a polycarbonate semisphere shell. Some experiments have been done, and the experimental results show that this technique is feasible to form po...In this paper, a new bulge-forming technology is described to manufacture a polycarbonate semisphere shell. Some experiments have been done, and the experimental results show that this technique is feasible to form polycarbonate part. But the wall thickness distribution of the bulged specimen by this method is not so even.展开更多
[Objectives] This study was conducted to analyze the composition of volatile oil in different parts of fennel(Foenicuzu vulgare Mill.) and to compare the differences in the composition of volatile oil in different par...[Objectives] This study was conducted to analyze the composition of volatile oil in different parts of fennel(Foenicuzu vulgare Mill.) and to compare the differences in the composition of volatile oil in different parts of fennel.[Methods]The steam distillation method was applied to extract volatile oil from different parts of fennel,and the components of volatile oil from different parts of fennel were separated and identified by GC-MS.The relative content of each component was determined by the peak area normalization method.[Results]37,33,18,and 44 chemical components were separated from the volatile oil of fennel roots,stems,young leaves and fruit,respectively,accounting for 98.64%,99.34%,99.59% and 95.99% of the total volatile oil of corresponding parts.A total of 77 chemical components were identified in the four parts,of which 5 were common components.The main component of the volatile oil in the stems and young leaves was trans-anethole.The main components of the volatile oil in fruit were estragole and trans-anethole.And the main component of the volatile oil in the roots was dill apiol.The components in the volatile oil of fennel roots,stems,young leaves and fruit were different in type and content.[Conclusions]This study provides a theoretical reference for the further effective development and utilization of fennel resources.展开更多
The optimal material removal strategy can improve a geometric accuracy and surface quality of thin-walled parts such as turbine blades and blisks in high-speed ball end milling.The dominant conception in the material ...The optimal material removal strategy can improve a geometric accuracy and surface quality of thin-walled parts such as turbine blades and blisks in high-speed ball end milling.The dominant conception in the material removal represents the persistence of the workpiece cutting stiffness in operation to advance the machining accuracy and machining efficiency.On the basis of theoretical models of cutting stiffness and deformation,finite element method (FEM) is applied to calculate the virtual displacements of the thin-walled part under given virtual loads at the nodes of the discrete surface.With the reference of deformation distribution of the thin-walled part,the milling material removal strategy is optimized to make the best of bracing ability of still uncut material.This material removal method is summarized as the lower stiffness region removed firstly and the higher stiffness region removed next.Analytical and experimental results show the availability,which has been verified by the blade machining test in this work,for thin-walled parts to reduce cutting deformation and meliorate machining quality.展开更多
Spare parts are very essential in most industrial companies. They are characterized by their large number and their high impact on the companies’ operations whenever needed. Therefore companies tend to analyze their ...Spare parts are very essential in most industrial companies. They are characterized by their large number and their high impact on the companies’ operations whenever needed. Therefore companies tend to analyze their spare parts demand and try to estimate their future consumption. Nevertheless, they face difficulties in figuring out an optimal forecasting method that deals with the lumpy and intermittent demand of spare parts. In this paper, we performed a comparison between five forecasting methods based on three statistical tools;Mean squared error (MSE), mean absolute deviation (MAD) and mean error (ME), where the results showed close performance for all the methods associated with their optimal parameters and the frequency of the spare part demand. Therefore, we proposed to compare all the methods based on the tracking signal with the objective of minimizing the average number of out of controls. This approach was tested in a comparative study at a local paper mill company. Our findings showed that the application of the tracking signal approach helps companies to better select the optimal forecasting method and reduce forecast errors.展开更多
[Objectives] To analyze and compare the difference in volatile components of different cultivars and different parts of Artemisia argyi by using headspace solid phase microextraction( HS-SPME) and provide scientific b...[Objectives] To analyze and compare the difference in volatile components of different cultivars and different parts of Artemisia argyi by using headspace solid phase microextraction( HS-SPME) and provide scientific basis for comprehensive development and rational utilization of Artemisia argyi. [Methods]Firstly,HS-SPME was used to extract the volatile components from the leaves,seeds,and stems of seven-tip Artemisia argyi,five-tip Artemisia argyi,and golden Artemisia argyi. Their chemical composition was analyzed by gas chromatographymass spectrometry( GC-MS),and the relative mass fraction of each component was determined by area normalization method. [Results] For the same variety of Artemisia argyi,the content of volatile components in leaves was higher than in seeds and stems except camphor,and the content of volatile components in seven-tip Artemisia argyi leaves was higher than in five-tip Artemisia argyi and golden Artemisia argyi leaves.HS-SPME-GC-MS analysis showed that eucalyptol,camphor,thujone,α-pinene,1-caryophyllene and caryophyllene oxide with higher content were detected in different parts of the different cultivars of Artemisia argyi. [Conclusions]Seven-tip Artemisia argyi leaves were the best medicinal parts of the three cultivars,followed by seven-tip Artemisia argyi seeds.展开更多
Parts of speech conversion refers to transforming the certain words of the source language into another category words of the target language, which is one of the common methods and techniques used in the translation ...Parts of speech conversion refers to transforming the certain words of the source language into another category words of the target language, which is one of the common methods and techniques used in the translation of English and Chinese languages. This paper starts from a relatively significant difference in English and Chinese language— the tendency of static words in English in contrast to that of dynamic words in Chinese, to explore the theoretical basis of transference in parts of speech in English and Chinese language translation. Combining with a large number of examples, the author puts forward some skills on transformation of parts of speech in English-Chinese translation to guide translation practice. The study found that the theoretical basis of the conversion in English and Chinese mostly including:1) there is a boundary ambiguity between lexical category;2)English SV/SVO structure is rigorous, which leads to expressing the dynamic meaning by means of using other lexical category; 3) the development of social culture not only makes new words continue to increase rapidly, but also gives many used words with new meanings; 4)it is acknowledged in Lexical morphology that English words which come from derivation are in larger number and derivations can make the word class of the corresponding original words either the same or different. The dynamic and specific features of Chinese make it more use of verbs in language use. Thus, in the process of translation, appropriate parts of speech conversion can make the translation more in line with their own habits of expression.展开更多
It is a new method of surveying leg spuds of self-elevating drilling platforms to lift them out of water with the help of additional middle guide blocks. Its main advantages in comparison with other methods normally u...It is a new method of surveying leg spuds of self-elevating drilling platforms to lift them out of water with the help of additional middle guide blocks. Its main advantages in comparison with other methods normally used up to now are: less expensive, time saving, no need for specially designated water area, direct visual observation, good reliability and safety. The working principle has been presented with the example of two platforms "Bohai No. 8" and "Bohai No. 10", to which the method was used. Also a comprehensive comparison with other methods in technological and economical aspects is given in the paper.展开更多
Every electrical conductive medium placed in a time varying magnetic field is the seat of eddy currents that dissipate power through Joule effect. The induction hardening process takes advantage of this effect. The po...Every electrical conductive medium placed in a time varying magnetic field is the seat of eddy currents that dissipate power through Joule effect. The induction hardening process takes advantage of this effect. The power concentrates in the surface of the piece (skin effect), the thickness of which depends on the electromagnetic properties and the frequency of the currents. The numerical simulation of such a process is of major interest to control and estimate the thickness of the treated layer, the superficial hardness, the residual stresses (often compressive in the surface) or the residual distortions. In this paper we focus on the interactions between electromagnetism and heat transfer for the simulation of the heating stage. The method used to couple both phenomena is detailed. A magnetic vector potential formulation is used for the electromagnetic analysis and an approach coupling finite elements with boundary elements is presented. Such a method is especially useful when moving parts are involved as it is generally the case for induction hardening processes. The air is represented by a boundary element that enables to consider independent meshes for all the conductive media within the device (piece and coils). Moreover, meshes are now the same for the electromagnetic and thermal analyses. This considerably facilitates the analysis that is performed step by step, each step corresponding to a position of the moving media. At each step, the matrices associated with the boundary element are calculated and the magneto-dynamic and thermal analyses are performed. Finally, an application is presented.展开更多
Thin-walled parts are typically difficult-to-cut components due to the complex dynamics in cutting process.The dynamics is variant for part during machining,but invariant for machine tool.The variation of the relative...Thin-walled parts are typically difficult-to-cut components due to the complex dynamics in cutting process.The dynamics is variant for part during machining,but invariant for machine tool.The variation of the relative dynamics results in the difference of cutting stage division and cutting parameter selection.This paper develops a novel method for whole cutting process optimization based on the relative varying dynamic characteristic of machining system.A new strategy to distinguish cutting stages depending on the dominated dynamics during machining process is proposed,and a thickness-dependent model to predict the dynamics of part is developed.Optimal cutting parameters change with stages,which can be divided by the critical thickness of part.Based on the dynamics comparison between machine tool and thickness-varying part,the critical thicknesses are predicted by an iterative algorithm.The proposed method is validated by the machining of three benchmarks.Good agreements have been obtained between prediction and experimental results in terms of stages identification,meanwhile,the optimized parameters perform well during the whole cutting process.展开更多
By adopting the parameterized designing method of f ea ture assembled and feature unit, for the feature of non-conventional type parts , such as welding box and bearer, by use of Visual C++ and AutoCAD a s soft tools,...By adopting the parameterized designing method of f ea ture assembled and feature unit, for the feature of non-conventional type parts , such as welding box and bearer, by use of Visual C++ and AutoCAD a s soft tools, the system can successfully carry out the basic function of featur e assembled, the processing of two-dimensional figure, the building of three-d imensional feature, the automatic producing of technical papers, and so on. The thoughts and design methods of this system can be served as the preference to CA D/CAPP integrated for othernon-conventional type parts. For non-conventional parts, its feature is too much, so the parameter is much. By adopting interactive entry for graphic parameter, under the control of main c ontrol module, through inputting the feature parameter and calling the feature g raphic unit, the function for modeling is completed. To reduce input of feature parameter, the description of position feature is adopted in the feature descrip tion of non-conventional parts, that is, fix position is constraint through str ucture and dimension of non-conventional parts. In such a manner, the assembled process has been transformed the coordinate conversion process, and this is ver y important in the production of three-dimensional graphics. In the one hand, b y calling the feature of parts in the library of feature-graphic unit, the two -dimensional DXF file and three-dimensional SCR file are automatically produce d in AutoCAD. On the other hand, by calling the rules and standard operational s equences in the technologic knowledge base, through inferring of inference engin e, the assembled sequence of non-conventional parts and welding sequences are a utomatically produced. The two aspects constitute overall design philosophy for system. So the CAD/CAPP integration of feature-assembled for non-conventio nal parts are completed. The principle of dividing feature is based on the thought of group technology, t hat is, according to the function feature of parts. The feature-assembled p arameterized design method is to divide the parts into many feature-units, acco rding to the structure, function, and secondary feature, and the each unit is in teractively produced, so the whole part is assembled gradually. At the same time , to display the sequences which deviser chooses varied features, hidden feature code is adopted. The feature-unit parameterized design method is to assemble dimension, margin tolerance and fitting-in, and surface roughness into one unit that it becomes a fixed structure. However big it is, it could be added to or taken off like a ba sic feature-unit.By adopting above-mentioned methods, the module of parts is e stablished. Under the integrated environment, according to basic construct of expert system, CAPP system is made up of three sectionsdynamic database (document-view ), knowledge library and inference engine. Dynamic database is served as storing initialized and middle information as well as ultimate design result. The knowl edge library is composed of static database, rule set, and standard welding proc ess library.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.52005371)Shanghai Municipal Natural Science Foundation of China(Grant No.22ZR1463900)+1 种基金Fundamental Research Funds for the Central Universities of China(Grant No.22120220649)State Key Laboratory of Mechanical System and Vibration of China(Grant No.MSV202318).
文摘An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.
基金supported by the Natural Science Foundation of China(11901005,12071003)the Natural Science Foundation of Anhui Province(2008085QA20)。
文摘In this paper,we establish the integration by parts formula for the solution of fractional noise driven stochastic heat equations using the method of coupling.As an application,we also obtain the shift Harnack inequalities.
基金supported by the National Defense Pre-research Project in 13th Five-Year(41404050502)the National Defense Science and Technology Fund of the Central Military Commission(2101140)
文摘In order to optimize the spares configuration project at different stages during the life cycle, the factor of time is considered to relax the assumption of the spares steady demand in multi-echelon technique for recoverable item control(METRIC)theory. According to the method of systems analysis, the dynamic palm theorem is introduced to establish the prediction model of the spares demand rate, and its main influence factors are analyzed,based on which, the spares support effectiveness evaluation index system is studied, and the system optimization-oriented spares dynamic configuration method for multi-echelon multi-indenture system is proposed. Through the analysis of the optimization algorithm, the layered marginal algorithm is designed to improve the model calculation efficiency. In a given example, the multi-stage spares configuration project during its life cycle is gotten, the research result conforms to the actual status, and it can provide a new way for the spares dynamic optimization.
文摘In many fields of high-tech industry the ultra-t hi n wall parts are employed. In this paper the experiments were carried out to dis cuss the surface microstructure of the camera’s guided drawtube by applying ult rasonic vibration cutting device to the traditional lathe. The influence rule of the cutting condition on the surface roughness was put forward, which was drawn by comparing the ultrasonic cutting with the common cutting by use of the cemen ted carbide tool and the polycrystalline diamond (PCD) tool. The test results sh owed that the ultrasonic cutting performs better than the common cutting in the same condition. According to the test results analyzing, the surface characteriz ation is influenced clearly by the rigidity of the acoustic system and the machi ne tool, as well the setting height of the tool tip. Otherwise, the dense regula r low frequency vibration ripples will be scraped on the machined surface. When the tool tip is set higher than the rotating center of the work piece by three t imes of the amplitude of ultrasonic vibration, the vibration ripples behave alig ht; they turn light and shade alternatively when the tool tip is lower than the rotating center of the work piece by three times of the amplitude of ultrasonic vibration. According to the test result analyzing, the following conclusions are put forward: 1) The surface roughness in ultrasonic cutting is better than that in common cutting. Under a one third critical cutting velocity, the value of th e surface roughness in ultrasonic cutting rise slightly along with the cutting v elocity, while in common cutting it decreases contrast to the cutting velocity; the curves of the surface roughness in ultrasonic cutting and common cutting see m to be alike, both increase along with the feed rate and the cutting depth, but the value in ultrasonic cutting is smaller in the same condition.2) The influen ce of the coolant on the surface roughness cannot be ignored. The kerosene can b e employed to improve the surface roughness in ultrasonic machining.3) In ultras onic cutting process of aluminum alloy ultra-thin wall work piece, the PCD tool performs better than the cemented carbide tools.4) The vibration ripples result from the not enough rigidity of the acoustic system and the improper setting he ight of the tool tip. The departure of the tool tip from the rotating center of the work piece to some extent causes the vibration ripples on the machined surfa ce.
文摘The inner hole parts played an oriented or supporting role in engineering machinery and equipment,which are prone to appear surface damages such as wear,strain and corrosion. The precise pulse plasma arc powder welding method is used for surface damage repairing of inner hole parts in this paper. The working principle and process of the technology are illustrated,and the microstructure and property of repairing layer by precise pulse plasma powder welding and CO2 gas shielded welding are tested and observed by microscope,micro hardness tester and X-ray residual stress tester etc. Results showed that the substrate deformation of thin-walled inner hole parts samples by precise pulse plasma powder welding is relatively small. The repair layer and substrate is metallurgical bonding,the transition zones( including fusion zone and heat affected zone) are relatively narrow and the welding quality is good. It showed that the thin-walled inner hole parts can be repaired by this technology and equipment.
基金supported by the Science Challenge Project(TZ2018007)the National Natural Science Foundation of China(71671009+2 种基金 61871013 61573041 61573043)
文摘In equipment integrated logistics support(ILS), the supply capability of spare parts is a significant factor. There are lots of depots in the traditional support system, which makes too many redundant spare parts and causes high cost of support. Meanwhile,the inconsistency among depots makes it difficult to manage spare parts. With the development of information technology and transportation, the supply network has become more efficient. In order to further improve the efficiency of supply-support work and the availability of the equipment system, building a system of one centralized depot with multiple depots becomes an appropriate way.In this case, location selection of the depots including centralized depots and multiple depots becomes a top priority in the support system. This paper will focus on the location selection problem of centralized depots considering ILS factors. Unlike the common location selection problem, depots in ILS require a higher service level. Therefore, it becomes desperately necessary to take the high requirement of the mission into account while determining location of depots. Based on this, we raise an optimal depot location model. First, the expected transportation cost is calculated.Next, factors in ILS such as response time, availability and fill rate are analyzed for evaluating positions of open depots. Then, an optimization model of depot location is developed with the minimum expected cost of transportation as objective and ILS factors as constraints. Finally, a numerical case is studied to prove the validity of the model by using the genetic algorithm. Results show that depot location obtained by this model can guarantee the effectiveness and capability of ILS well.
基金National Natural Science Foundation of China(No.71761030)
文摘Taking high speed rotating shaft parts as the research object,the general fault mode of the parts is analyzed.The analysis process of shaft parts is expounded by means of finite element analysis method.A variety of fatigue life prediction methods for mechanical equipment parts are reviewed in this paper.And the selection and calculation method of parameters in the life prediction model of shaft parts are summarized.Finally,taking a gear shaft of a reducer as an example,the Morrow linear correction of the elastic stress model,Manson-Halford(M-H)correction model and Smith Watson Topper(SWT)correction model are applied to fatigue life assessments.The prediction results of the SWT correction model are relatively conservative.The prediction results of the Morrow linear correction of the elastic stress model and the M-H model are similar,and they are larger than the SWT correction model.
文摘In this paper, a new bulge-forming technology is described to manufacture a polycarbonate semisphere shell. Some experiments have been done, and the experimental results show that this technique is feasible to form polycarbonate part. But the wall thickness distribution of the bulged specimen by this method is not so even.
基金Supported by Anshun Science and Technology Innovation Platform Construction Project(ASKP[2017]03)。
文摘[Objectives] This study was conducted to analyze the composition of volatile oil in different parts of fennel(Foenicuzu vulgare Mill.) and to compare the differences in the composition of volatile oil in different parts of fennel.[Methods]The steam distillation method was applied to extract volatile oil from different parts of fennel,and the components of volatile oil from different parts of fennel were separated and identified by GC-MS.The relative content of each component was determined by the peak area normalization method.[Results]37,33,18,and 44 chemical components were separated from the volatile oil of fennel roots,stems,young leaves and fruit,respectively,accounting for 98.64%,99.34%,99.59% and 95.99% of the total volatile oil of corresponding parts.A total of 77 chemical components were identified in the four parts,of which 5 were common components.The main component of the volatile oil in the stems and young leaves was trans-anethole.The main components of the volatile oil in fruit were estragole and trans-anethole.And the main component of the volatile oil in the roots was dill apiol.The components in the volatile oil of fennel roots,stems,young leaves and fruit were different in type and content.[Conclusions]This study provides a theoretical reference for the further effective development and utilization of fennel resources.
基金Sponsored by the Major National Science and Technology Special Project of China (Grant No.2009ZX04014-053)the National Natural Science Foundation of China (Grant No.51005183)
文摘The optimal material removal strategy can improve a geometric accuracy and surface quality of thin-walled parts such as turbine blades and blisks in high-speed ball end milling.The dominant conception in the material removal represents the persistence of the workpiece cutting stiffness in operation to advance the machining accuracy and machining efficiency.On the basis of theoretical models of cutting stiffness and deformation,finite element method (FEM) is applied to calculate the virtual displacements of the thin-walled part under given virtual loads at the nodes of the discrete surface.With the reference of deformation distribution of the thin-walled part,the milling material removal strategy is optimized to make the best of bracing ability of still uncut material.This material removal method is summarized as the lower stiffness region removed firstly and the higher stiffness region removed next.Analytical and experimental results show the availability,which has been verified by the blade machining test in this work,for thin-walled parts to reduce cutting deformation and meliorate machining quality.
文摘Spare parts are very essential in most industrial companies. They are characterized by their large number and their high impact on the companies’ operations whenever needed. Therefore companies tend to analyze their spare parts demand and try to estimate their future consumption. Nevertheless, they face difficulties in figuring out an optimal forecasting method that deals with the lumpy and intermittent demand of spare parts. In this paper, we performed a comparison between five forecasting methods based on three statistical tools;Mean squared error (MSE), mean absolute deviation (MAD) and mean error (ME), where the results showed close performance for all the methods associated with their optimal parameters and the frequency of the spare part demand. Therefore, we proposed to compare all the methods based on the tracking signal with the objective of minimizing the average number of out of controls. This approach was tested in a comparative study at a local paper mill company. Our findings showed that the application of the tracking signal approach helps companies to better select the optimal forecasting method and reduce forecast errors.
基金Supported by Natural Science Foundation of Hubei Province(2004AB242)
文摘[Objectives] To analyze and compare the difference in volatile components of different cultivars and different parts of Artemisia argyi by using headspace solid phase microextraction( HS-SPME) and provide scientific basis for comprehensive development and rational utilization of Artemisia argyi. [Methods]Firstly,HS-SPME was used to extract the volatile components from the leaves,seeds,and stems of seven-tip Artemisia argyi,five-tip Artemisia argyi,and golden Artemisia argyi. Their chemical composition was analyzed by gas chromatographymass spectrometry( GC-MS),and the relative mass fraction of each component was determined by area normalization method. [Results] For the same variety of Artemisia argyi,the content of volatile components in leaves was higher than in seeds and stems except camphor,and the content of volatile components in seven-tip Artemisia argyi leaves was higher than in five-tip Artemisia argyi and golden Artemisia argyi leaves.HS-SPME-GC-MS analysis showed that eucalyptol,camphor,thujone,α-pinene,1-caryophyllene and caryophyllene oxide with higher content were detected in different parts of the different cultivars of Artemisia argyi. [Conclusions]Seven-tip Artemisia argyi leaves were the best medicinal parts of the three cultivars,followed by seven-tip Artemisia argyi seeds.
文摘Parts of speech conversion refers to transforming the certain words of the source language into another category words of the target language, which is one of the common methods and techniques used in the translation of English and Chinese languages. This paper starts from a relatively significant difference in English and Chinese language— the tendency of static words in English in contrast to that of dynamic words in Chinese, to explore the theoretical basis of transference in parts of speech in English and Chinese language translation. Combining with a large number of examples, the author puts forward some skills on transformation of parts of speech in English-Chinese translation to guide translation practice. The study found that the theoretical basis of the conversion in English and Chinese mostly including:1) there is a boundary ambiguity between lexical category;2)English SV/SVO structure is rigorous, which leads to expressing the dynamic meaning by means of using other lexical category; 3) the development of social culture not only makes new words continue to increase rapidly, but also gives many used words with new meanings; 4)it is acknowledged in Lexical morphology that English words which come from derivation are in larger number and derivations can make the word class of the corresponding original words either the same or different. The dynamic and specific features of Chinese make it more use of verbs in language use. Thus, in the process of translation, appropriate parts of speech conversion can make the translation more in line with their own habits of expression.
文摘It is a new method of surveying leg spuds of self-elevating drilling platforms to lift them out of water with the help of additional middle guide blocks. Its main advantages in comparison with other methods normally used up to now are: less expensive, time saving, no need for specially designated water area, direct visual observation, good reliability and safety. The working principle has been presented with the example of two platforms "Bohai No. 8" and "Bohai No. 10", to which the method was used. Also a comprehensive comparison with other methods in technological and economical aspects is given in the paper.
文摘Every electrical conductive medium placed in a time varying magnetic field is the seat of eddy currents that dissipate power through Joule effect. The induction hardening process takes advantage of this effect. The power concentrates in the surface of the piece (skin effect), the thickness of which depends on the electromagnetic properties and the frequency of the currents. The numerical simulation of such a process is of major interest to control and estimate the thickness of the treated layer, the superficial hardness, the residual stresses (often compressive in the surface) or the residual distortions. In this paper we focus on the interactions between electromagnetism and heat transfer for the simulation of the heating stage. The method used to couple both phenomena is detailed. A magnetic vector potential formulation is used for the electromagnetic analysis and an approach coupling finite elements with boundary elements is presented. Such a method is especially useful when moving parts are involved as it is generally the case for induction hardening processes. The air is represented by a boundary element that enables to consider independent meshes for all the conductive media within the device (piece and coils). Moreover, meshes are now the same for the electromagnetic and thermal analyses. This considerably facilitates the analysis that is performed step by step, each step corresponding to a position of the moving media. At each step, the matrices associated with the boundary element are calculated and the magneto-dynamic and thermal analyses are performed. Finally, an application is presented.
基金National Key R&D Program of China(Grant No.2018YFB1701901)Guangdong Provincial Key-Area Research and Development Program(Grant No.2020B090927002).
文摘Thin-walled parts are typically difficult-to-cut components due to the complex dynamics in cutting process.The dynamics is variant for part during machining,but invariant for machine tool.The variation of the relative dynamics results in the difference of cutting stage division and cutting parameter selection.This paper develops a novel method for whole cutting process optimization based on the relative varying dynamic characteristic of machining system.A new strategy to distinguish cutting stages depending on the dominated dynamics during machining process is proposed,and a thickness-dependent model to predict the dynamics of part is developed.Optimal cutting parameters change with stages,which can be divided by the critical thickness of part.Based on the dynamics comparison between machine tool and thickness-varying part,the critical thicknesses are predicted by an iterative algorithm.The proposed method is validated by the machining of three benchmarks.Good agreements have been obtained between prediction and experimental results in terms of stages identification,meanwhile,the optimized parameters perform well during the whole cutting process.
文摘By adopting the parameterized designing method of f ea ture assembled and feature unit, for the feature of non-conventional type parts , such as welding box and bearer, by use of Visual C++ and AutoCAD a s soft tools, the system can successfully carry out the basic function of featur e assembled, the processing of two-dimensional figure, the building of three-d imensional feature, the automatic producing of technical papers, and so on. The thoughts and design methods of this system can be served as the preference to CA D/CAPP integrated for othernon-conventional type parts. For non-conventional parts, its feature is too much, so the parameter is much. By adopting interactive entry for graphic parameter, under the control of main c ontrol module, through inputting the feature parameter and calling the feature g raphic unit, the function for modeling is completed. To reduce input of feature parameter, the description of position feature is adopted in the feature descrip tion of non-conventional parts, that is, fix position is constraint through str ucture and dimension of non-conventional parts. In such a manner, the assembled process has been transformed the coordinate conversion process, and this is ver y important in the production of three-dimensional graphics. In the one hand, b y calling the feature of parts in the library of feature-graphic unit, the two -dimensional DXF file and three-dimensional SCR file are automatically produce d in AutoCAD. On the other hand, by calling the rules and standard operational s equences in the technologic knowledge base, through inferring of inference engin e, the assembled sequence of non-conventional parts and welding sequences are a utomatically produced. The two aspects constitute overall design philosophy for system. So the CAD/CAPP integration of feature-assembled for non-conventio nal parts are completed. The principle of dividing feature is based on the thought of group technology, t hat is, according to the function feature of parts. The feature-assembled p arameterized design method is to divide the parts into many feature-units, acco rding to the structure, function, and secondary feature, and the each unit is in teractively produced, so the whole part is assembled gradually. At the same time , to display the sequences which deviser chooses varied features, hidden feature code is adopted. The feature-unit parameterized design method is to assemble dimension, margin tolerance and fitting-in, and surface roughness into one unit that it becomes a fixed structure. However big it is, it could be added to or taken off like a ba sic feature-unit.By adopting above-mentioned methods, the module of parts is e stablished. Under the integrated environment, according to basic construct of expert system, CAPP system is made up of three sectionsdynamic database (document-view ), knowledge library and inference engine. Dynamic database is served as storing initialized and middle information as well as ultimate design result. The knowl edge library is composed of static database, rule set, and standard welding proc ess library.
