• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.194-202
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• 2019

Reliability analysis of the components frequently starts with the data that manufacturer provides. If enough failure data are collected from the field operations, the reliability should be recomputed and updated on the basis of the field failure data. However, when the failure time record for a component contains only a few observations, all statistical methodologies are limited. In this case, where the failure records for multiple number of identical components are available, a valid alternative is combining all the data from each component into one data set with enough sample size and utilizing the useful information in the censored data. The ROK Navy has been operating multiple Patrol Killer Guided missiles (PKGs) for several years. The Korea Multi-Function Control Console (KMFCC) is one of key components in PKG combat system. The maintenance record for the KMFCC contains less than ten failure observations and a censored datum. This paper proposes a Bayesian approach with a Dirichlet mixture model to estimate failure time density for KMFCC. Trends test for each component record indicated that null hypothesis, that failure occurrence is renewal process, is not rejected. Since the KMFCCs have been functioning under different operating environment, the failure time distribution may be a composition of a number of unknown distributions, i.e. a mixture distribution, rather than a single distribution. The Dirichlet mixture model was coded as probabilistic programming in Python using PyMC3. Then Markov Chain Monte Carlo (MCMC) sampling technique employed in PyMC3 probabilistically estimated the parameters' posterior distribution through the Dirichlet mixture model. The simulation results revealed that the mixture models provide superior fits to the combined data set over single models.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.979-987
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• 2012

This paper implements and integrates algorithms for terrain following of UCAVs (Unmanned Combat Aerial Vehicles): trajectory generation, guidance, and navigation. Terrain following is very important for UCAVs because they perform very dangerous missions such as Suppression of Enemy Air Defences while the terrain following can improve the survivability of UCAVs against from the air defence systems of the enemy. To deal with the GPS jamming, terrain referenced navigation based on nonlinear filter is chosen. For the trajectory generation, Voronoi diagram is adopted to generate horizontal plane path to avoid the air defense system. Cubic spline method is used to generate vertical plane path to prevent collisions with ground while flying sufficiently close to surface. Follow-the-Carrot and pure pursuit tracking methods, which are look-ahead point based guidance algorithms, are applied for the guidance. Numerical simulation is performed to verify the performance of the integrated terrain following algorithm.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.2
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• pp.95-103
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• 2002

We know that the all of warfare system has been becoming complex and variety in warfield thru the Gulf-War. The all of warfare electronic systems is designed to inter-operate by networks in recently. Especially Warfare Equipment systems of Men-of-War(War ship) as like KDX(Korea Destroyer, Experimental), FF(Frigate), PCC(Costal Patrol Craft), Submarine are connected by Combat System Databus to the Command system(C2 System), so C2 system can control all of equipments in ship. In this view, the status of network(Combat System Databus) is very critical parameter in war field. So In this paper, we propose the method of Network Management System construction for War ship, and especially propose the architectural design of network management system for DX(Destroyer, Experimental) equipments using SNMP(Simple Network Management Protocol). And Link Utilization is monitored by simulation. 

• Korean Journal of Computational Design and Engineering
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• v.22 no.2
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• pp.141-149
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• 2017

Vulnerability assesses the loss of major performance functions of GCV (Ground Combat Vehicles) when it is hit by enemy's shell. To decide the loss of major functions, it is determined what effects are on the performance of GCV when some components of GCV are failed. M&S (Modeling and Simulation) technology is used to vulnerability assessment. The hydro-pneumatic suspension is used as a sample part. The procedures of vulnerability assessment of the hydro-pneumatic suspension are shown as follows: 1) The components of the suspension are defined, and shot lines are generated evenly around the part. 2) The penetrated components are checked by using the penetration equation. 3) The function model of the suspension is designed by using IDEF0. 4) When the failure of the critical components of the suspension happens, its effect on the function of the suspension can be estimated using DMEA (Damage Mode and Effects Analysis). 5) The diagram of FTA (Fault Tree Analysis) is designed by exploiting DMEA. 6) The damage probability of the suspension is calculated by using FTA and vulnerable area method. In this paper, SLAP (Shot Line Analysis Program) which was developed based on COVART methodology. SLAP calculates the damage probability and visualizes the vulnerable areas of the suspension.

• Journal of the Korea Society for Simulation
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• v.23 no.1
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• pp.33-42
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• 2014

In this paper we analyzed the search patterns for the anti-submarine warfare (ASW) surface ships cooperating with ASW helicopters. For this purpose, we modeled evasive motion of a submarine with a probabilistic method. And maneuvers and search actions of ships and helicopters participating in the anti-submarine search mission are designed. And for each simulation scenario, the case where a ship and a helicopter searches a submarine independently according to its optimized search pattern is compared with the case where the search platforms participate in the ASW mission cooperatively. Based on the simulation results, we proposed the reconfigured search patterns that help cooperative ASW surface ships increase the total cumulative detection probability (CDP).

• Proceedings of the Korea Information Processing Society Conference
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• 2017.04a
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• pp.97-100
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• 2017

As part of overseas defense program of the US's Trump administration, the military allies were asked to cover partial operation costs for the weaponry deployed at the US bases in their countries. This raised the Korean government's, as well as defense industry's interest in constructing a tactical/strategic communication network and investments are being made actively. Thus, in this study, the performances of WiMAX and WLAN have been compared and a tactical/strategic communication network has been constructed for simulation by using OPNET. As a result, the simulation for the network using combat tanks was successful. An average communication distance that can be achieved by WLAN in open terrain is about 200m as it has been designed on the premise of short-range wireless communications. When the distance was increased to 1km, the tanks could not receive data. By contrast, it was able to confirm that the WiMAX-based network has allowed smooth communications at the same distance. Based on this result, it can be concluded that using WiMAX for tactical operations will have much more merit than adopting WLAN as far as the distance is concerned.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.3
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• pp.380-387
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• 2011

In this paper, we considered the authoritative representation of Command and Fire Control System(CFCS) for the surface ship that was the engineering level model to develop system specifications and to analyze operational concepts on the concept design phase and to analyze military requirements, effectiveness and performance for the system. The engineering level model of CFCS can be used in simulation independently of the surface ship's type, and also it takes reuse, interoperability, and extension into consideration. The detailed sub-models, internal and external data interface, data flow among each sub-model, sensor and weapon models about the engineering level model of CFCS was defined. It was verified via engineering level simulations according to the V&V process.

• ETRI Journal
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• v.27 no.1
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• pp.53-63
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• 2005

A compressed video bitstream is sensitive to errors that may severely degrade the reconstructed images even when the bit error rate is small. One approach to combat the impact of such errors is the use of error concealment at the decoder without increasing the bit rate or changing the encoder. For spatial-error concealment, we propose a method featuring edge continuity and texture preservation as well as low computation to reconstruct more visually acceptable images. Aiming at temporal error concealment, we propose a two-step algorithm based on block matching principles in which the assumption of smooth and uniform motion for some adjacent blocks is adopted. As simulation results show, the proposed spatial and temporal methods provide better reconstruction quality for damaged images than other methods.

• ETRI Journal
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• v.29 no.2
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• pp.231-233
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• 2007

One of the drawbacks in an OFDM system is the high peak-to-average power ratio (PAPR). Among a number of techniques to reduce the high PAPR, simple amplitude predistortion (SAP), a form of active constellation extension, has been proposed to effectively achieve the desired PAPR. In this letter, a novel scheme, simple amplitude and phase predistortion (SAPP), is proposed. In SAP the carriers' amplitude is utilized to combat the peak signal. Each amplitude is amplified according to its degree of contribution as a metric. In addition to amplitude, SAPP also utilizes the phase. Simulation results indicate that the proposed scheme provides better PAPR reduction than SAP.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1982-1985
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• 2003

Future cellular networks will mainly be driven by, high quality channels, high band with utilization, low power consumption and efficient network management. For a given channel allocation, the capacity and quality of communication of cellular radio systems using CDMA(Code Division Multiple Access) can be increased by using a transmitter power control scheme to combat the near-far problem. Centralized power control schemes or distributed ones to maximize the minimum signal-to-interference in each user of CDMA wireless network have been investigated. This paper has proposed a distributed power control algorithm, which employs an adaptive search scheme, in order to solve quickly the linear systems of equations for power update in CDMA cellular radio systems. The simulation results show that the proposed scheme has faster convergence rate than the typical bang-bang type of distributed power control algorithm, which has been much used as a reference algorithm in IS-95A and W-CDMA communication network.