• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.788-794
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• 2007

The policy of US DoD is moving towards implementation of Network Centric Warfare(NCW) concepts. NCW is commonly described as the integration and synchronization of four key interdependent elements such as command and control, sensor system, engagement systems and the network. Therefore the military policy of Korea military is needed to access and examine the policy of NCW communication environment and crypto communication, which is able to apply it. In this case study, We are reviewed the security framework of the concept of network centric warfare in the centering around the US. It is introduced the core technology in the network centric warfare, and it is reviewed the security framework such as, the requirements of security, the characteristics security of global information grid, joint tactical radion system, net centric enterprise services, transformational communication satellite, in the basis of core technology, and analysis the effect of crypto communication relay between command node and surbornate node in NCW environment. This report support the assistance, which is considered the elements of surrounding effects in the varied crypto communication research area of NCW.

• Journal of KIISE:Software and Applications
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• v.27 no.1
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• pp.1-12
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• 2000

Model checking is a formal verification technique which checks the consistency between a requirement specification and a behavior model of the system by explorating the state space of the model. We apply model checking to the formal verification of the concurrent object-oriented system, using an existing model checker SPIN which has been successful in verifying concurrent systems. First, we propose an Actor-based modeling language, called APromela, by extending the modeling language Promela which is a modeling language supported in SPIN. APromela supports not only all the primitives of Promela, but additional primitives needed to model concurrent object-oriented systems, such as class definition, object instantiation, message send, and synchronization.Second, we provide translation rules for mapping APromela's such modeling primitives to Promela's. As an application of APromela, we suggest a verification method for UML models. By giving an example of specification, translation, and verification, we also demonstrate the applicability of our proposed approach, and discuss the limitations and further research issues.

• Journal of Power Electronics
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• v.18 no.1
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• pp.70-80
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• 2018

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.2
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• pp.64-70
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• 2021

Nowadays, there are significant interests in real-time remote control using wireless networks. In implementing real-time remote control, one important factor is delay performance of real-time control message. Especially, the technique to reduce jitter of delay is necessary in transmitting periodically real-time control message. In this paper, we proposed synchronized transmission to reduce jitter of delay, when real-time control message was transmitted through wireless networks. The proposed transmission kept synchronization between source node and wireless transmitter and controlled transmission instance to transmit real-tie control message with fixed delay in wireless networks. According to results of experiment in military unmanned vehicle system, the proposed transmission reduced jitter of delay as 32% as that of a non-employing case.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.12
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• pp.997-1004
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• 2020

A synchropter is a type of rotorcraft in which a pair of blades inclined with each other rotates in synchronization. Removing the tail rotor enables an efficient and compact configuration similar to a coaxial-rotor helicopter. This paper describes the design and flight test results of a small synchropter to examine the suitability of a drone system for the army. The synchropter in this paper is a small vehicle with a rotor diameter of 1.4m and a weight of 7kg and was assembled based on commercial parts to examine flight characteristics effectively. The flight control system adopted Pixhawk, which is designed based on an open-architecture. The model-based design technique is applied to develop the control law of the synchropter and a new firmware embedded on the Pixhawk. Through qualitative flight tests, we analyzed the flight characteristics. As a result of the analysis, we confirmed the possibility of application as a drone system of the synchropter.

• Smart Structures and Systems
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• v.31 no.3
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• pp.259-273
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• 2023

Real-time hybrid simulation (RTHS) is an effective experimental technique for structural dynamic assessment. However, time delay causes displacement de-synchronization at the interface between the numerical and physical substructures, negatively affecting the accuracy and stability of RTHS. To this end, the authors have proposed a model-based adaptive control strategy with a Kalman filter (MAC-KF). In the proposed method, the time delay is mainly mitigated by a parameterized feedforward controller, which is designed using the discrete inverse model of the control plant and adjusted using the KF based on the displacement command and measurement. A feedback controller is employed to improve the robustness of the controller. The objective of this study is to further validate the power of dealing with a nonlinear control plant and to investigate the potential challenges of the proposed method through actual experiments. In particular, the effect of the order of the feedforward controller on tracking performance was numerically investigated using a nonlinear control plant; a series of actual RTHS of a frame structure equipped with a magnetorheological damper was performed using the proposed method. The findings reveal significant improvement in tracking accuracy, demonstrating that the proposed method effectively suppresses the time delay in RTHS. In addition, the parameters of the control plant are timely updated, indicating that it is feasible to estimate the control plant parameter by KF. The order of the feedforward controller has a limited effect on the control performance of the MAC-KF method, and the feedback controller is beneficial to promote the accuracy of RTHS.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.3
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• pp.245-255
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• 2023

Time comparison techniques are necessary for generating and keeping Coordinated Universal Time (UTC) and distributing standard time clocks. Global Navigation Satellite System (GNSS) Common View, GNSS All-in-View, Two-Way Satellite Time and Frequency Transfer (TWSTFT), Very Long Baseline Interferometry (VLBI), optical fiber, and Network Time Protocol (NTP) based methods have been used for time comparison. In these methods, GNSS based time comparison techniques are widely used for time synchronization in critical national infrastructures and in common areas of application such as finance, military, and wireless communication. However, GNSS-based time comparison techniques are vulnerable to jamming or interference environments and it is difficult to respond to GNSS signal disconnection according to the international situation. In response, in this paper, Code-Division Multiple Access (CDMA) based All-to-All TWSTFT operation method is proposed. A software-based simulation platform also was designed for performance analysis in multi-TWSTFT signal environments. Furthermore, code and carrier measurement jitters were calculated in multi-signal environments using the designed simulation platform. By using the technique proposed in this paper, it is anticipated that the TWSTFT-based time comparison method will be used in various fields and satisfy high-performance requirements such as those of a GNSS master station and power plant network reference station.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.485-489
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• 2002

The concepts from OOP have been integrated in a concurrency, leading to the emergence of concurrent OOP. Concurrency of concurrent OOP and various model technique of OOP language are integrated had been proposed. Concurrent programming and OOP technique unite that can gain various kinds advantage to develop concurrency application program. There have been a number of models proposed for integrating concurrency and OOP However, concurrency and inheritance are two paradigms which are difficult to combine in a suitable manner. The inheritance anomaly is the conclicted phenomena, which occurs only when concurrency is integrated with inheritance. The inheritance anoay is referred to as the serious difficulty in integrating inheritance and concurrency in a simple and efficient manner within a concurrent OOP. Concurrency and inheritance with integrated that Drop reusability of object remarkably and require re-justice of code that is inherited in subclass. So concurrency and inheritance with integrated Collision that happen between two special qualitys or Interference phenomenon is inheritance anomaly. Effect of inheritance anomaly minimum Much study findings announced about access method to improve code reusability. Wish to approach in paper that is division by synchronization code and method code to solve interference problem between and concurrency.