In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source ...In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source UAV transmits data to a relay UAV using the FSO technique.In the second hop,the relay UAV forwards data to a destination Mobile Station(MS)via an RF channel,with the RIS enhancing coverage and performance.The relay UAV operates in a Decode-and-Forward(DF)mode.As the main contribution,we provide a mathematical performance analysis of the RIS-assisted FSO-RF mixed dual-hop UAV system,evaluating outage probability,Bit-Error Rate(BER),and average capacity.The analysis accounts for factors such as atmospheric attenuation,turbulence,geometric losses,and link interruptions caused by UAV hovering behaviors.To the best of our knowledge,this is the first theoretical investigation of RIS-assisted FSO-RF mixed dual-hop UAV communication systems.Our analytical results show strong agreement with Monte Carlo simulation outcomes.Furthermore,simulation results demonstrate that RIS significantly enhances the performance of UAV-aided mixed RF/FSO systems,although performance saturation is observed due to uncertainties stemming from UAV hovering behavior.展开更多
For contingencies occurring in a complex marine environment, Unmanned Surface Vehicle (USV) has to recognize the situation and decide behaviors,?and?plan the following actions through the Integrated Mission Planning P...For contingencies occurring in a complex marine environment, Unmanned Surface Vehicle (USV) has to recognize the situation and decide behaviors,?and?plan the following actions through the Integrated Mission Planning Process. Therefore, researches are actively being carried out about it. However, since it is difficult to test the actual USV with the mission planning process, it is necessary to develop a virtual experimental environment based on Modeling?&?Simulation (M&S). In this study, we developed an integrated simulation environment capable of simulating and analyzing the overall mission of USV. In Part?I, we modelled the USV Integrated Mission Planning Process and in Part?II, we developed an experimental framework and interface for loading them. In addition, we verified the suitability of this model through scenarios and defined the Mission of Effectiveness (MOE) concept for USV mission analysis.展开更多
In recent years, the weapon systems have been changing drastically because of the advancement of science technology and the change of military concept of combat. There is an unmanned system at the center of all those ...In recent years, the weapon systems have been changing drastically because of the advancement of science technology and the change of military concept of combat. There is an unmanned system at the center of all those changes. Especially, in case of maritime environment, as the center stage of combat has changed from ocean to coastal areas, it is difficult for the existing naval forces to effectively operate in shallow waters. Therefore, unmanned underwater vehicles (UUVs) are being required at an increasing pace. In this paper, we analyze the characteristics of already developed UUVs, which are the key unmanned system of the marine battlefield environment in the future. Through the analysis of development cases and the investigation of the essential technologies, the critical design issues of UUVs are elaborated. We also suggest the future directions of the UUV technologies based on the case analysis.展开更多
In this paper,an integrated guidance and control approach is presented to improve the performance of the missile interception.The approach includes damping augmented system with attitude rate feedback to decrease the ...In this paper,an integrated guidance and control approach is presented to improve the performance of the missile interception.The approach includes damping augmented system with attitude rate feedback to decrease the oscillation during the homing phase for missiles with low damping.In addition,physical constraints,which can affect the performance of the missile interception,such as acceleration limit,seeker’s look angle,and look angle rate constraints are considered.The integrated guidance and control problem is formulated as a convex quadratic optimization problem with equality and inequality constraints,and the solution is obtained by a primal–dual interior point method.The performance of the proposed method is verified through several numerical examples.展开更多
In recent years, because of the development of marine military science technology, there is a growing interest in the unmanned systems throughout the world. Also, the demand of Unmanned Surface Vehicles (USVs) which c...In recent years, because of the development of marine military science technology, there is a growing interest in the unmanned systems throughout the world. Also, the demand of Unmanned Surface Vehicles (USVs) which can be autonomously operated without the operator intervention is increasing dramatically. The growing interests lie in the facts that those USVs can be manufactured at much lower costs, and can be operated without the human fatigue, while can be sent to the hostile or quite dangerous areas that are inherently unhealthy for human operators. The utilization and the deployment of such vessels will continue to grow in the future. In this paper, along with the technological development of unmanned surface vehicles, we investigate and analyze the cases of already developed platforms and identify the trends of the technological advances. Additionally, we suggest the future directions of development.展开更多
Recently,reactive materials have been developed for penetrative projectiles to improve impact resistance and energy capacity.However,the design of a reactive material structure,involving shape and size,is challenging ...Recently,reactive materials have been developed for penetrative projectiles to improve impact resistance and energy capacity.However,the design of a reactive material structure,involving shape and size,is challenging because of difficulties such as high non-linearity of impact resistance,manufacturing limitations of reactive materials and high expenses of penetration experiments.In this study,a design optimization methodology for the reactive material structure is developed based on the finite element analysis.A finite element model for penetration analysis is introduced to save the expenses of the experiments.Impact resistance is assessed through the analysis,and result is calibrated by comparing with experimental results.Based on the model,topology optimization is introduced to determine shape of the structure.The design variables and constraints of the optimization are proposed considering the manufacturing limitations,and the optimal shape that can be manufactured by cold spraying is determined.Based on the optimal shape,size optimization is introduced to determine the geometric dimensions of the structure.As a result,optimal design of the reactive material structure and steel case of the penetrative projectile,which maximizes the impact resistance,is determined.Using the design process proposed in this study,reactive material structures can be designed considering not only mechanical performances but also manufacturing limitations,with reasonable time and cost.展开更多
Laser-structuring is an effective method to promote ion diffusion and improve the performance of lithium-ion battery(LIB)electrodes.In this work,the effects of laser structuring parameters(groove pitch and depth)on th...Laser-structuring is an effective method to promote ion diffusion and improve the performance of lithium-ion battery(LIB)electrodes.In this work,the effects of laser structuring parameters(groove pitch and depth)on the fundamental characteristics of LIB electrode,such as interfacial area,internal resistances,material loss and electrochemical performance,are investigated,LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2) cathodes were structured by a femtosecond laser by varying groove depth and pitch,which resulted in a material loss of 5%-14%and an increase of 140%-260%in the in terfacial area between electrode surface and electrolyte.It is shown that the importance of groove depth and pitch on the electrochemical performance(specific capacity and areal discharge capacity)of laser-structured electrode varies with current rates.Groove pitch is more im porta nt at low current rate but groove depth is at high curre nt rate.From the mapping of lithium concentration within the electrodes of varying groove depth and pitch by laser-induced breakdown spectroscopy,it is verified that the groove functions as a diffusion path for lithium ions.The ionic,electronic,and charge transfer resistances measured with symmetric and half cells showed that these internal resistances are differently affected by laser structuring parameters and the changes in porosity,ionic diffusion and electronic pathways.It is demonstrated that the laser structuring parameters for maximum electrode performance and minimum capacity loss should be determined in consideration of the main operating conditions of LIBs.展开更多
In this study, the bending formability of an extruded Mg–9Al–1Zn–0.3Mn–0.9Ca–0.6Y–0.5 MM(AZXWMM91100, wt%) alloy at room temperature is significantly improved through application of a combined precompression and...In this study, the bending formability of an extruded Mg–9Al–1Zn–0.3Mn–0.9Ca–0.6Y–0.5 MM(AZXWMM91100, wt%) alloy at room temperature is significantly improved through application of a combined precompression and subsequent annealing(PCA) treatment. As the amount of precompression applied along the extrusion direction(ED)(i.e., the total strain) increases from 4% to 6%, the area fraction of ED-oriented grains of the PCA-treated alloy increases, which consequently causes an improvement in its bending formability because these grains accommodate larger tensile strain along the ED during bending. As the temperature of the subsequent annealing treatment increases from 350 ℃ to 450 ℃, both the area fraction of the ED-oriented grains and the average grain size increase, and the residual dislocation density decreases owing to the promotion of boundary migration and occurrence of the recovery process at higher temperatures.Consequently, the bending formability of both the 4%-precompressed and the 6%-precompressed samples increases with an increase in the annealing temperature. However, when the precompressed samples are annealed at 300 ℃, their bending formability is lower than that of the extruded alloy because the dislocations formed by precompression remain even after the subsequent annealing at this temperature.展开更多
This study is a preparation phase for integrated visualization of battlefield situation. To develop the ground control station for unmanned systems, many factors have to be considered from the design stages, such as l...This study is a preparation phase for integrated visualization of battlefield situation. To develop the ground control station for unmanned systems, many factors have to be considered from the design stages, such as layout, information component, representation scheme, and human operation methods. Considering such many factors can be very difficult, hence we conducted an in-depth investigation of design factors from major UAV stations around the world. We analyzed the design characteristics and the specifics. In conclusion, we were able to derive some common aspects of design characteristics, which lead to the successful design approach.展开更多
This study is a preparation phase for visualization of utilized information using ergonomic user interface and standardization of elements for GCS (Ground Control System). Therefore, we investigated the instances of G...This study is a preparation phase for visualization of utilized information using ergonomic user interface and standardization of elements for GCS (Ground Control System). Therefore, we investigated the instances of GCS (such as hawk and patriot missile’s GCS) for defense system. Based on the collected data, we compared and analyzed the GCS screen design. In this paper, we conduct case study for ergonomically development of GCS. It is expected that this research improves the situational awareness and reduces the user’s task load.展开更多
This study presents a simplified blast load prediction method on structures behind a protective barrier.The proposed method is basically an empirical approach based on Kingery-Bulamsh(K-B)chart and finite element(FE)a...This study presents a simplified blast load prediction method on structures behind a protective barrier.The proposed method is basically an empirical approach based on Kingery-Bulamsh(K-B)chart and finite element(FE)analysis results.To this end,this study divides the structure into three regions by three critical points.Blast loads at each critical point can be calculated based on K-B chart and an approximation according to FE analysis results.Finally,peak reflected overpressure and impulse distributed on the structure can be approximately estimated by linearly connecting blast loads at each critical point.In order to confirm a feasibility of the proposed method,a series of numerical simulations were carried out.The simulation results were compared with FE analysis results which are presented in the open literature.From such comparisons,it was found that the proposed method is applicable to predict blast loads on structures behind a protective barrier.展开更多
High-strength bainitic steels have created a lot of interest in recent times because of their excellent combination of strength,ductility,toughness,and high ballistic mass efficiency.Bainitic steels have great potenti...High-strength bainitic steels have created a lot of interest in recent times because of their excellent combination of strength,ductility,toughness,and high ballistic mass efficiency.Bainitic steels have great potential in the fabrication of steel armor plates.Although various approaches and methods have been conducted to utilize the retained austenite(RA)in the bainitic matrix to control mechanical properties,very few attempts have been conducted to improve ballistic performance utilizing transformationinduced plasticity(TRIP)mechanism.In this study,high-strength bainitic steels were designed by controlling the time of austempering process to have various volume fractions and stability of RA while maintaining high hardness.The dynamic compressive and ballistic impact tests were conducted,and the relation between the effects of TRIP on ballistic performance and the adiabatic shear band(ASB)formation was analyzed.Our results show for the first time that an active TRIP mechanism achieved from a large quantity of metastable RA can significantly enhance the ballistic performance of high-strength bainitic steels because of the improved resistance to ASB formation.Thus,the ballistic performance can be effectively improved by a very short austempering time,which suggests that the utilization of active TRIP behavior via tuning RA acts as a primary mechanism for significantly enhancing the ballistic performance of high-strength bainitic steels.展开更多
An important requirement in a military domain is a highly reliable mobility management method,especially when components of the networks aremoving in tactical network environments.To increase reliability,themobility m...An important requirement in a military domain is a highly reliable mobility management method,especially when components of the networks aremoving in tactical network environments.To increase reliability,themobility management technology of the tactical network should be able to reflect the characteristics of the tactical network,such as a limited environment,failure,and hierarchical unit structure.In this paper,we propose a proxy-based hierarchical distributedmobilitymanagement scheme,which is highly focused on tactical networks.Considering the characteristics of tactical networks,the proposed scheme is composed of the following:1)a proxy-based method,2)a distributed mobility management method that synchronizes a mobility database between entities,and 3)a method of managing mobility by dividing the tactical network into upper and lower layers.Mathematical analysis and modeling and simulation results demonstrate that the method outperforms the existing state-of-the-art method in overcoming entity failure,handover cost,and delay in tactical environments.展开更多
A rapid and simple organic extraction method for the determination of the chemical warfare agent, isopropyl methylphosphonofluoridate (sarin, GB) in human plasma has been developed using gas chromatography-tandem mass...A rapid and simple organic extraction method for the determination of the chemical warfare agent, isopropyl methylphosphonofluoridate (sarin, GB) in human plasma has been developed using gas chromatography-tandem mass spectrometry (GC-MS/MS). In the course of method development, several organic solvents have been screened and chloroform show a low background and increase signal to noise ratio of GB among other organic solvents. Especially, the organic extraction method of reactivated GB from the human plasma has a 30% greater recovery yield than solid-phase ex-traction (SPE). This simple extraction method was successfully applied to the trace analysis of nerve agents in human plasma in the 3rd Organisation for the Prohibition of Chemical Weapons (OPCW) confidence building exercise on biomedical sample analysis.展开更多
Recently,multipath transmission control protocol(MPTCP)was standardized so that data can be transmitted through multiple paths to utilize all available path bandwidths.However,when high-speed long-distance networks ar...Recently,multipath transmission control protocol(MPTCP)was standardized so that data can be transmitted through multiple paths to utilize all available path bandwidths.However,when high-speed long-distance networks are included in MPTCP paths,the traffic transmission performance of MPTCP is severely deteriorated,especially in case the multiple paths’characteristics are heavily asymmetric.In order to alleviate this problem,we propose a“Coupled CUBIC congestion control”that adopts TCP CUBIC on a large bandwidth-delay product(BDP)path in a linked increase manner for maintaining fairness with an ordinary TCP traversing the same bottleneck path.To verify the performance excellence of the proposed algorithm,we implemented the Coupled CUBIC Congestion Control into Linux kernels by modifying the legacy MPTCP linked-increases algorithm(LIA)congestion control source code.We constructed asymmetric heterogeneous network testbeds mixed with large and small BDP paths and compared the performances of LIA and Coupled CUBIC by experiments.Experimental results show that the proposed Coupled CUBIC utilizes almost over 80%of the bandwidth resource in the high BDP path,while the LIA utilizes only less than 20%of the bandwidth for the same path.It was confirmed that the resource utilization and traffic transmission performance have been greatly improved by using the proposed Coupled CUBIC in high-speed multipath networks,as well as maintaining MPTCP fairness with competing single-path CUBIC or Reno TCP flows.展开更多
The integrated Mission Planning System?(MPS) of Unmanned Surface Vehicle?(USV) refers to the process which can recognize, decide, plan situations and carry out missions, such as human beings, for all incidental or com...The integrated Mission Planning System?(MPS) of Unmanned Surface Vehicle?(USV) refers to the process which can recognize, decide, plan situations and carry out missions, such as human beings, for all incidental or complex events occurring at sea. In the actual operating environment, it is necessary to develop a simulation software environment and analyze, verify it in advance so as to make an appropriate mission plan considering equipment, sensor, fuel, and other available resources. The existing USV mission planning process methodology has several limitations in the analysis of USV missions because the scenario to be tested is limited and autonomy of USV is not considered sufficiently. To overcome these problems, we constructed a process that considers various missions and is more autonomous, and an integrated environment in which to experiment. In this study, we designed a multi-agent based USV Integrated Mission Planning System and modeled each component. In addition, we constructed the USV remote operation S/W based on M&S that user can experiment with the modeled process and verified the usefulness of the developed system through simulations.展开更多
The importance of the aircraft is increasing gradually;among them it may be called Ground Control Station (GCS) receiving the highest expectations. In aspect of operation, operator’s workload and working speed are on...The importance of the aircraft is increasing gradually;among them it may be called Ground Control Station (GCS) receiving the highest expectations. In aspect of operation, operator’s workload and working speed are one of the most important factors. Thus, we need to compare Touch mode and Non Touch mode in order to improve workload and working speed. In this paper, we analyzed the differences of Touch mode and Non Touch mode about workload, working speed in operation of aircraft. Through NASA-TLX and Measured working time, quantified data were collected and an analysis of variance (ANOVA) was performed. According to experimental result, working speed and workload according to input mode showed significant difference. In ground operation, Touch mode is better than Non Touch mode about working speed and workload. In the Touch mode, the optimal value of lower display angle was selected as 60。 angle.展开更多
Advanced countries around the world are spurring the development of Unmanned Surface Vehicles (USVs) that can operate autonomously at marine environment. The key enabling technology for such USVs is the mission planni...Advanced countries around the world are spurring the development of Unmanned Surface Vehicles (USVs) that can operate autonomously at marine environment. The key enabling technology for such USVs is the mission planning system (MPS) that can autonomously navigate through the harsh waters. The MPS not only has the functions for the navigation, but also has the capabilities, such as obstacle avoidance, malfunction corrections, dealing with unexpected events, return home functions, and many other eventualities that cannot be programmed in advance. The autonomy levels are increasingly moving higher and it is foreseeable that the trend will continue in the future. The main purpose of this paper is the analysis of the MPS onboard the USVs, in terms of the categories, functions, and technological details. Also, we analyze the case study of autonomous mission planning control systems in various fields and introduce the features that constitute the critical functionalities of the mission planning systems.展开更多
In Side-by-Side helicopter system, pilots and co-pilot occupy same place and make a community about instruments. So both pilots have a great interaction and communication compared with tandem helicopter. In our previo...In Side-by-Side helicopter system, pilots and co-pilot occupy same place and make a community about instruments. So both pilots have a great interaction and communication compared with tandem helicopter. In our previous research, we found the TSD information is effected on mission conduction greatly. We also realized the new task assignment is required. To compensate for our previous research and find the optimal task assignment in side-by-side helicopter system, we set up the second experiment. We established the scenario and did some experiment. Measuring data is performance total time, killing rate, and pilot & gunner workload data similar to before experiment 1, and this project has a purpose about finding optimal task assignment and researching strong point than Tandem system using 1 & 2 experiment totally.展开更多
The aim of this research was to investigate the impacts of changing environmental factors on pilots by implementing the effective flight procedure that we found from the previous research. During the experiments, camc...The aim of this research was to investigate the impacts of changing environmental factors on pilots by implementing the effective flight procedure that we found from the previous research. During the experiments, camcorders were used to monitor and analyze the tasks and physical exhaustion of the pilot. NASA-TLX was also used to collect the data of the workload. Through this experiment, we were able to approach the experiment from a different angle regarding the optimal assigned work of the pilot, unlike the previous studies. Also, we were able to find out the impacts of environmental factors on the pilot’s workload.展开更多
基金supported in part by the National Research Foundation of Korea(NRF)funded by the Korea government(MSIT)under Grant NRF-2022R1I1A3073740in part by the MSIT(Ministry of Science and ICT),Korea,under the ITRC(Information Technology Research Center)support program(IITP-2024-RS-2024-00436406)supervised by the IITP(Institute for Information&Communications Technology Planning&Evaluation)+1 种基金in part by the Institute for Information and Communications Technology Promotion(IITP)Grant funded by the Korea Government(MSIP,Development of Cube Satellites Based on Core Technologies in Low Earth Orbit Satellite Communications)under Grant RS-2024-00396992in part by the Korea Research Institute for Defense Technology planning and advancement(KRIT)grant,funded by the Korea government(DAPA(Defense Acquisition Program Administration))(21-106-A00-007,Space-Layer Intelligent Communication Network Laboratory,2022).
文摘In this paper,we investigate a Recofigurable Intelligent Surface(RIS)-assisted Free-Space Optics-Radio Frequency(FSO-RF)mixed dual-hop communication system for Unmanned Aerial Vehicles(UAVs).In the first hop,a source UAV transmits data to a relay UAV using the FSO technique.In the second hop,the relay UAV forwards data to a destination Mobile Station(MS)via an RF channel,with the RIS enhancing coverage and performance.The relay UAV operates in a Decode-and-Forward(DF)mode.As the main contribution,we provide a mathematical performance analysis of the RIS-assisted FSO-RF mixed dual-hop UAV system,evaluating outage probability,Bit-Error Rate(BER),and average capacity.The analysis accounts for factors such as atmospheric attenuation,turbulence,geometric losses,and link interruptions caused by UAV hovering behaviors.To the best of our knowledge,this is the first theoretical investigation of RIS-assisted FSO-RF mixed dual-hop UAV communication systems.Our analytical results show strong agreement with Monte Carlo simulation outcomes.Furthermore,simulation results demonstrate that RIS significantly enhances the performance of UAV-aided mixed RF/FSO systems,although performance saturation is observed due to uncertainties stemming from UAV hovering behavior.
文摘For contingencies occurring in a complex marine environment, Unmanned Surface Vehicle (USV) has to recognize the situation and decide behaviors,?and?plan the following actions through the Integrated Mission Planning Process. Therefore, researches are actively being carried out about it. However, since it is difficult to test the actual USV with the mission planning process, it is necessary to develop a virtual experimental environment based on Modeling?&?Simulation (M&S). In this study, we developed an integrated simulation environment capable of simulating and analyzing the overall mission of USV. In Part?I, we modelled the USV Integrated Mission Planning Process and in Part?II, we developed an experimental framework and interface for loading them. In addition, we verified the suitability of this model through scenarios and defined the Mission of Effectiveness (MOE) concept for USV mission analysis.
文摘In recent years, the weapon systems have been changing drastically because of the advancement of science technology and the change of military concept of combat. There is an unmanned system at the center of all those changes. Especially, in case of maritime environment, as the center stage of combat has changed from ocean to coastal areas, it is difficult for the existing naval forces to effectively operate in shallow waters. Therefore, unmanned underwater vehicles (UUVs) are being required at an increasing pace. In this paper, we analyze the characteristics of already developed UUVs, which are the key unmanned system of the marine battlefield environment in the future. Through the analysis of development cases and the investigation of the essential technologies, the critical design issues of UUVs are elaborated. We also suggest the future directions of the UUV technologies based on the case analysis.
文摘In this paper,an integrated guidance and control approach is presented to improve the performance of the missile interception.The approach includes damping augmented system with attitude rate feedback to decrease the oscillation during the homing phase for missiles with low damping.In addition,physical constraints,which can affect the performance of the missile interception,such as acceleration limit,seeker’s look angle,and look angle rate constraints are considered.The integrated guidance and control problem is formulated as a convex quadratic optimization problem with equality and inequality constraints,and the solution is obtained by a primal–dual interior point method.The performance of the proposed method is verified through several numerical examples.
文摘In recent years, because of the development of marine military science technology, there is a growing interest in the unmanned systems throughout the world. Also, the demand of Unmanned Surface Vehicles (USVs) which can be autonomously operated without the operator intervention is increasing dramatically. The growing interests lie in the facts that those USVs can be manufactured at much lower costs, and can be operated without the human fatigue, while can be sent to the hostile or quite dangerous areas that are inherently unhealthy for human operators. The utilization and the deployment of such vessels will continue to grow in the future. In this paper, along with the technological development of unmanned surface vehicles, we investigate and analyze the cases of already developed platforms and identify the trends of the technological advances. Additionally, we suggest the future directions of development.
基金the Agency for Defense Development,Republic of Korea[grant number UD170110GD].
文摘Recently,reactive materials have been developed for penetrative projectiles to improve impact resistance and energy capacity.However,the design of a reactive material structure,involving shape and size,is challenging because of difficulties such as high non-linearity of impact resistance,manufacturing limitations of reactive materials and high expenses of penetration experiments.In this study,a design optimization methodology for the reactive material structure is developed based on the finite element analysis.A finite element model for penetration analysis is introduced to save the expenses of the experiments.Impact resistance is assessed through the analysis,and result is calibrated by comparing with experimental results.Based on the model,topology optimization is introduced to determine shape of the structure.The design variables and constraints of the optimization are proposed considering the manufacturing limitations,and the optimal shape that can be manufactured by cold spraying is determined.Based on the optimal shape,size optimization is introduced to determine the geometric dimensions of the structure.As a result,optimal design of the reactive material structure and steel case of the penetrative projectile,which maximizes the impact resistance,is determined.Using the design process proposed in this study,reactive material structures can be designed considering not only mechanical performances but also manufacturing limitations,with reasonable time and cost.
基金supported by a GIST Research Institute(GRI)grant funded by the GIST in 2021supported by the Korea In stitute for Advancement of Tech no logy(KIAT)grant funded by the Korea Government(MOTIE).(P0008763,The Competency Development Program for Industry Specialist.)。
文摘Laser-structuring is an effective method to promote ion diffusion and improve the performance of lithium-ion battery(LIB)electrodes.In this work,the effects of laser structuring parameters(groove pitch and depth)on the fundamental characteristics of LIB electrode,such as interfacial area,internal resistances,material loss and electrochemical performance,are investigated,LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2) cathodes were structured by a femtosecond laser by varying groove depth and pitch,which resulted in a material loss of 5%-14%and an increase of 140%-260%in the in terfacial area between electrode surface and electrolyte.It is shown that the importance of groove depth and pitch on the electrochemical performance(specific capacity and areal discharge capacity)of laser-structured electrode varies with current rates.Groove pitch is more im porta nt at low current rate but groove depth is at high curre nt rate.From the mapping of lithium concentration within the electrodes of varying groove depth and pitch by laser-induced breakdown spectroscopy,it is verified that the groove functions as a diffusion path for lithium ions.The ionic,electronic,and charge transfer resistances measured with symmetric and half cells showed that these internal resistances are differently affected by laser structuring parameters and the changes in porosity,ionic diffusion and electronic pathways.It is demonstrated that the laser structuring parameters for maximum electrode performance and minimum capacity loss should be determined in consideration of the main operating conditions of LIBs.
基金supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government(MSIP, South Korea,No. 2019R1A2C1085272)。
文摘In this study, the bending formability of an extruded Mg–9Al–1Zn–0.3Mn–0.9Ca–0.6Y–0.5 MM(AZXWMM91100, wt%) alloy at room temperature is significantly improved through application of a combined precompression and subsequent annealing(PCA) treatment. As the amount of precompression applied along the extrusion direction(ED)(i.e., the total strain) increases from 4% to 6%, the area fraction of ED-oriented grains of the PCA-treated alloy increases, which consequently causes an improvement in its bending formability because these grains accommodate larger tensile strain along the ED during bending. As the temperature of the subsequent annealing treatment increases from 350 ℃ to 450 ℃, both the area fraction of the ED-oriented grains and the average grain size increase, and the residual dislocation density decreases owing to the promotion of boundary migration and occurrence of the recovery process at higher temperatures.Consequently, the bending formability of both the 4%-precompressed and the 6%-precompressed samples increases with an increase in the annealing temperature. However, when the precompressed samples are annealed at 300 ℃, their bending formability is lower than that of the extruded alloy because the dislocations formed by precompression remain even after the subsequent annealing at this temperature.
文摘This study is a preparation phase for integrated visualization of battlefield situation. To develop the ground control station for unmanned systems, many factors have to be considered from the design stages, such as layout, information component, representation scheme, and human operation methods. Considering such many factors can be very difficult, hence we conducted an in-depth investigation of design factors from major UAV stations around the world. We analyzed the design characteristics and the specifics. In conclusion, we were able to derive some common aspects of design characteristics, which lead to the successful design approach.
文摘This study is a preparation phase for visualization of utilized information using ergonomic user interface and standardization of elements for GCS (Ground Control System). Therefore, we investigated the instances of GCS (such as hawk and patriot missile’s GCS) for defense system. Based on the collected data, we compared and analyzed the GCS screen design. In this paper, we conduct case study for ergonomically development of GCS. It is expected that this research improves the situational awareness and reduces the user’s task load.
基金supported by the Agency for Defense DevelopmentAgency for Defense Development。
文摘This study presents a simplified blast load prediction method on structures behind a protective barrier.The proposed method is basically an empirical approach based on Kingery-Bulamsh(K-B)chart and finite element(FE)analysis results.To this end,this study divides the structure into three regions by three critical points.Blast loads at each critical point can be calculated based on K-B chart and an approximation according to FE analysis results.Finally,peak reflected overpressure and impulse distributed on the structure can be approximately estimated by linearly connecting blast loads at each critical point.In order to confirm a feasibility of the proposed method,a series of numerical simulations were carried out.The simulation results were compared with FE analysis results which are presented in the open literature.From such comparisons,it was found that the proposed method is applicable to predict blast loads on structures behind a protective barrier.
基金supported by the Agency for Defense Development(grant No.UE161030GD)the Korea University Grant for Dr.S.S.Sohnthe BK21 Plus Project for Center for Creative Industrial Materials。
文摘High-strength bainitic steels have created a lot of interest in recent times because of their excellent combination of strength,ductility,toughness,and high ballistic mass efficiency.Bainitic steels have great potential in the fabrication of steel armor plates.Although various approaches and methods have been conducted to utilize the retained austenite(RA)in the bainitic matrix to control mechanical properties,very few attempts have been conducted to improve ballistic performance utilizing transformationinduced plasticity(TRIP)mechanism.In this study,high-strength bainitic steels were designed by controlling the time of austempering process to have various volume fractions and stability of RA while maintaining high hardness.The dynamic compressive and ballistic impact tests were conducted,and the relation between the effects of TRIP on ballistic performance and the adiabatic shear band(ASB)formation was analyzed.Our results show for the first time that an active TRIP mechanism achieved from a large quantity of metastable RA can significantly enhance the ballistic performance of high-strength bainitic steels because of the improved resistance to ASB formation.Thus,the ballistic performance can be effectively improved by a very short austempering time,which suggests that the utilization of active TRIP behavior via tuning RA acts as a primary mechanism for significantly enhancing the ballistic performance of high-strength bainitic steels.
基金This work was supported by the Agency for Defense Development.
文摘An important requirement in a military domain is a highly reliable mobility management method,especially when components of the networks aremoving in tactical network environments.To increase reliability,themobility management technology of the tactical network should be able to reflect the characteristics of the tactical network,such as a limited environment,failure,and hierarchical unit structure.In this paper,we propose a proxy-based hierarchical distributedmobilitymanagement scheme,which is highly focused on tactical networks.Considering the characteristics of tactical networks,the proposed scheme is composed of the following:1)a proxy-based method,2)a distributed mobility management method that synchronizes a mobility database between entities,and 3)a method of managing mobility by dividing the tactical network into upper and lower layers.Mathematical analysis and modeling and simulation results demonstrate that the method outperforms the existing state-of-the-art method in overcoming entity failure,handover cost,and delay in tactical environments.
文摘A rapid and simple organic extraction method for the determination of the chemical warfare agent, isopropyl methylphosphonofluoridate (sarin, GB) in human plasma has been developed using gas chromatography-tandem mass spectrometry (GC-MS/MS). In the course of method development, several organic solvents have been screened and chloroform show a low background and increase signal to noise ratio of GB among other organic solvents. Especially, the organic extraction method of reactivated GB from the human plasma has a 30% greater recovery yield than solid-phase ex-traction (SPE). This simple extraction method was successfully applied to the trace analysis of nerve agents in human plasma in the 3rd Organisation for the Prohibition of Chemical Weapons (OPCW) confidence building exercise on biomedical sample analysis.
基金This result was supported by“Regional Innovation Strategy(RIS)”through the National Research Foundation of Korea(NRF)funded by Ministry of Education(MOE)(2021RIS-004).
文摘Recently,multipath transmission control protocol(MPTCP)was standardized so that data can be transmitted through multiple paths to utilize all available path bandwidths.However,when high-speed long-distance networks are included in MPTCP paths,the traffic transmission performance of MPTCP is severely deteriorated,especially in case the multiple paths’characteristics are heavily asymmetric.In order to alleviate this problem,we propose a“Coupled CUBIC congestion control”that adopts TCP CUBIC on a large bandwidth-delay product(BDP)path in a linked increase manner for maintaining fairness with an ordinary TCP traversing the same bottleneck path.To verify the performance excellence of the proposed algorithm,we implemented the Coupled CUBIC Congestion Control into Linux kernels by modifying the legacy MPTCP linked-increases algorithm(LIA)congestion control source code.We constructed asymmetric heterogeneous network testbeds mixed with large and small BDP paths and compared the performances of LIA and Coupled CUBIC by experiments.Experimental results show that the proposed Coupled CUBIC utilizes almost over 80%of the bandwidth resource in the high BDP path,while the LIA utilizes only less than 20%of the bandwidth for the same path.It was confirmed that the resource utilization and traffic transmission performance have been greatly improved by using the proposed Coupled CUBIC in high-speed multipath networks,as well as maintaining MPTCP fairness with competing single-path CUBIC or Reno TCP flows.
文摘The integrated Mission Planning System?(MPS) of Unmanned Surface Vehicle?(USV) refers to the process which can recognize, decide, plan situations and carry out missions, such as human beings, for all incidental or complex events occurring at sea. In the actual operating environment, it is necessary to develop a simulation software environment and analyze, verify it in advance so as to make an appropriate mission plan considering equipment, sensor, fuel, and other available resources. The existing USV mission planning process methodology has several limitations in the analysis of USV missions because the scenario to be tested is limited and autonomy of USV is not considered sufficiently. To overcome these problems, we constructed a process that considers various missions and is more autonomous, and an integrated environment in which to experiment. In this study, we designed a multi-agent based USV Integrated Mission Planning System and modeled each component. In addition, we constructed the USV remote operation S/W based on M&S that user can experiment with the modeled process and verified the usefulness of the developed system through simulations.
文摘The importance of the aircraft is increasing gradually;among them it may be called Ground Control Station (GCS) receiving the highest expectations. In aspect of operation, operator’s workload and working speed are one of the most important factors. Thus, we need to compare Touch mode and Non Touch mode in order to improve workload and working speed. In this paper, we analyzed the differences of Touch mode and Non Touch mode about workload, working speed in operation of aircraft. Through NASA-TLX and Measured working time, quantified data were collected and an analysis of variance (ANOVA) was performed. According to experimental result, working speed and workload according to input mode showed significant difference. In ground operation, Touch mode is better than Non Touch mode about working speed and workload. In the Touch mode, the optimal value of lower display angle was selected as 60。 angle.
文摘Advanced countries around the world are spurring the development of Unmanned Surface Vehicles (USVs) that can operate autonomously at marine environment. The key enabling technology for such USVs is the mission planning system (MPS) that can autonomously navigate through the harsh waters. The MPS not only has the functions for the navigation, but also has the capabilities, such as obstacle avoidance, malfunction corrections, dealing with unexpected events, return home functions, and many other eventualities that cannot be programmed in advance. The autonomy levels are increasingly moving higher and it is foreseeable that the trend will continue in the future. The main purpose of this paper is the analysis of the MPS onboard the USVs, in terms of the categories, functions, and technological details. Also, we analyze the case study of autonomous mission planning control systems in various fields and introduce the features that constitute the critical functionalities of the mission planning systems.
文摘In Side-by-Side helicopter system, pilots and co-pilot occupy same place and make a community about instruments. So both pilots have a great interaction and communication compared with tandem helicopter. In our previous research, we found the TSD information is effected on mission conduction greatly. We also realized the new task assignment is required. To compensate for our previous research and find the optimal task assignment in side-by-side helicopter system, we set up the second experiment. We established the scenario and did some experiment. Measuring data is performance total time, killing rate, and pilot & gunner workload data similar to before experiment 1, and this project has a purpose about finding optimal task assignment and researching strong point than Tandem system using 1 & 2 experiment totally.
文摘The aim of this research was to investigate the impacts of changing environmental factors on pilots by implementing the effective flight procedure that we found from the previous research. During the experiments, camcorders were used to monitor and analyze the tasks and physical exhaustion of the pilot. NASA-TLX was also used to collect the data of the workload. Through this experiment, we were able to approach the experiment from a different angle regarding the optimal assigned work of the pilot, unlike the previous studies. Also, we were able to find out the impacts of environmental factors on the pilot’s workload.
