Kyung-Min Seo

High optical responsivity of InAlAs-InGaAs metamorphic high-electron mobility transistor on GaAs substrate with composite channels

The high optical responsivity of the InAlAs-InGaAs metamorphic high-electron mobility transistor on GaAs substrate with composite channels is reported. Experimental results verify that the photovoltaic effect causing the effective decrease of threshold voltage is responsible for the photoresponse to a 1.55-/spl mu/m optical illumination.

Measurement of Effectiveness for an Anti-torpedo Combat System Using a Discrete Event Systems Specification-based Underwater Warfare Simulator

Modeling and simulation (M&S) has long played an important role in developing tactics and evaluating the measure of effectiveness (MOE) for the underwater warfare system. In simulation-based acquisition, M&S technology facilitates decisions about future equipment procurements, such as a mobile decoy or a torpedo. In addition, assessment of submarine tactical development, during an engagement against a torpedo, can be conducted using M&S techniques. This paper presents a case study that applies discrete event systems specification-based M&S technology to develop a simulation of an underwater warfare system, specifically, an anti-torpedo combat system, to analyze the MOE of the system. The entity models required for M&S are divided into three sub-models: controller, maneuver, and sensor model. The developed simulation allows us to conduct a statistical evaluation of the overall underwater warfare system under consideration, an assessment of the anti-torpedo countermeasure’s effectiveness, and an assessment of tactics development of the underwater vehicle. Moreover, it can be utilized to support the decision-making process for future equipment procurements. In order to analyze the system effectiveness, we performed extensive combat experiments by varying parameters, such as various tactics and weapon performance. The experimental results show how the factors influence the MOEs of the underwater warfare system.

DEVS-based combat modeling for engagement-level simulation

This paper presents a modeling method to demonstrate engagement-level military simulation which includes few combat objects, or entities. To this end, the paper, on the basis of the discrete event system specification (DEVS) formalism, centers on two ideas: (1) a combat entity’s model structure at the composition level; and (2) behavioral delineation of the entity’s elementary component. In detail, we classify the combat entity model into platform and weapon models and create six groups of the model categorized by two dimensions: three activities and two abstractions. And the elementary component in the group interprets an engagement scenario as a flow of executable tasks, which are expressed by DEVS semantics. The stated structures and semantics provide intuitive appeal, reducing the effort required to read and understand the model’s behavior. From the combat experiments, we can gain interesting experimental results regarding engagement situations employing underwater weapons and their tactical operations. Finally, we expect that this work will serve an immediate application suited to various engagement situations.

Simulation-based optimization for design parameter exploration in hybrid system: a defense system example

This paper presents a method for solving the optimization problems that arise in hybrid systems. These systems are characterized by a combination of continuous and discrete event systems. The proposed method aims to find optimal design configurations that satisfy a goal performance. For exploring design parameter space, the proposed method integrates a metamodel and a metaheuristic method. The role of the metamodel is to give good initial candidates and reduced search space to the metaheuristic optimizer. On the other hand, the metaheuristic method improves the quality of the given candidates. This proposal also demonstrates a defense system that illustrates the practical application of the presented method. The optimization objective of the case study is to find the required operational capability configurations of a decoy that meet the desired measure of effectiveness. Through a comparison with a full search method, two metamodeling methods without the aid of metaheuristics and a metaheuristic method without the support of metamodels, we confirmed that the proposed method provides same high-quality solutions as those of the full search method at a small computational cost.

DEXSim: an experimental environment for distributed execution of replicated simulators using a concept of single simulation multiple scenarios

This paper presents an efficient and scalable experimental environment for distributed execution of replicated simulators. By taking a performance-centered approach, the proposed technique makes the best use of distributed hardware resources for faster data collection. Accordingly, the primary contribution of this work is to describe how the environment improves scalability and utilizes distributed hardware resources efficiently. To do this, we suggest a new concept of single simulation multiple scenarios and propose a distributed execution simulation framework regarding the following three aspects: (1) layered architecture model design; (2) protocol definitions interacting with them; and (3) framework implementation. The proposed model architecture and protocol definitions guarantee a straightforward structural scalability and an efficient load-balanced utilization between hardware resources. Moreover, the framework operates simulation execution automatically without users’ extra work. In order to prove the efficiency of the proposed framework, we performed three extensive experiments with different models, that is, different systems. The experimental results show that simulation performance increases proportionally with the number of hardware resources, minimizing the overhead of the proposed framework’s utilization.

Effectiveness Analysis of Anti-torpedo Warfare Simulation for Evaluating Mix Strategies of Decoys and Jammers

Modeling and Simulation (M&S) engineering has been widely used for design and evaluation of underwater warfare systems. M&S engineering enables more efficient procurement of military equipment by analyzing these systems with simulations. This paper extends previous work, which used an anti-torpedo simulator with only decoys. To facilitate more diverse simulations of anti-torpedo combat, we design and add a simple jammer model, because the jammer is one of the most effective counter-measures against torpedo attacks. Utilizing this proposed model, we collect experimental data about the survivability of surface-ships that use anti-torpedo strategies and analyze the proper parameter values of jammers that satisfy the required Measure of Effectiveness (MOE). The experimental results show both the required performance of jammers and the efficiency of jammers with decoys. The results can be utilized to support the decision-making process for future equipment procurement.

Enhancing model composability and reusability for entity-level combat simulation: A conceptual modeling approach:

This paper presents a conceptual model design for entity-level combat simulation to enhance model composability and reusability. For conceptual modeling, we first describe the following three problem situations: (1) joint design of logical/physical modeling; (2) flexible model modification during scenario extension; and (3) cooperative modeling with different domain experts. To this end, we propose a two-dimensional model partition method for a combat entity, which partitions the combat entity depending on the functional aspect horizontally and the abstract level vertically. Thus, the proposed method guarantees transparent simplification of the combat entity and facilitates flexible model composition when simulating in the integration and the interoperation environments. Based on the proposed conceptual modeling, empirical measurements demonstrate the enhancement of model composability and reusability during scenario extension for anti-submarine warfare from static decoy to mobile decoy and from pattern-running torpedo to wire-guided torpedo simulations.

Data Management and Time Synchronization in PlugSim: A DEVS-Based Framework for Interoperation of Simulations

As modern systems are increasing in complexity, modeling and simulating them are also becoming difficult. In particular, modeling and simulation (M&S) with one modeling method reveals the limitations of many simulation purposes. In order to tackle this limitation, the interoperation concept has been developed. For the interoperation of simulations, data management and time synchronization are indispensable. In this paper, we explain how the data management and time synchronization are performed in PlugSim environment. PlugSim is the DEVS-based framework for interoperation of simulations and its theoretical basis depends on the DEVS-BUS. PlugSim helps developers create an environment of interoperation of simulations. For better understanding, we provide an example and show the result of simulation in the case study.

Communication Analysis of Network-Centric Warfare via Transformation of System of Systems Model into Integrated System Model Using Neural Network

Communication system in the network-centric warfare (NCW) has been analyzed from the perspective of the system of systems (SoS), which consists of a combat system and a network system so that the two reflect each other’s effects. However, this paradoxically causes a prolonged execution time. To solve this problem, this paper proposes an advanced integrated modeling method for the communication analysis in the NCW via the transformation of the SoS, which reduces the simulation execution time while ensuring the accuracy of the communication effects. The proposed models mainly cover interentity traffic and intraentity mobility developed in the form of feed-forward neural networks to guarantee two-way interactions between the combat system and the network system. Because they are characterized as discrete events, the proposed models are designed with the discrete-event system specification (DEVS) formalism. The experimental results show that the proposed transformation reduced an error by 6.40% compared to the existing method and reduced the execution time 3.78-fold compared to the SoS-based NCW simulation.

Achieving Data Interoperability of Communication Interfaces for Combat System Engineering

System of systems (SoS) engineering ensures that subsystems successfully interoperate with one another via a physical network along with the designed interface specifications. The twofold challenge that motivated the authors is regarding the achievement of the interoperability for an SoS-based combat system as follows: 1) the validation of the interface specifications against the specified requirements at the system-design phase and 2) the verification of the subsystems against the interface specifications at the system-integration phase. To this end, an interoperability validation and verification toolset (IVVT) consisting of the following three components was developed: signal distributor, message collector, and message analyzer. The signal distributor captures the signal data in the middle of the existing communication interfaces, the message collector stores the signals in the form of distinguishable messages, and the message analyzer evaluates the messages by comparing the designed interface specifications that cover the communication syntax and semantics. For the experimentations, the developed IVVT was utilized for the combat systems of real submarines that have been domestically targeted for a renovation project. The objective of the experiments is the validation of the overall designed interface specifications before the development of the subsystems. The empirical results show that 12 fault cases were found in the specifications, some of which are extremely critical; therefore, a preferential validation of the specifications could prevent the incompatibilities between the subsystems during the combat system integration. In a future work, the authors will employ the IVVT for a verification of the developed subsystems to be integrated depending on the validity of the interface specifications.