• Journal of the Korea Society for Simulation
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• v.28 no.3
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• pp.57-63
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• 2019

This study suggests the level of guaranteed reserves that should be accumulated in order to provide guaranteed interest contracts to pension members. To calculate the guaranteed reserve, this study employs the method using variable insurance contracts with guaranteed interest options. The average return of three major pensions (national pension, private teacher's pension, civil servants pension) funds, from 2010 to 2018, is set as the target rate of return and then we establish 0%, 1.0%, 1.5% and 2.0% each as our minimum guaranteed returns for their respective guaranteed reserves. Our results firstly show that gaps between each guaranteed reserves are increasing as times goes on. Second, the probability of shortfall reserve is on the decrease as the pension fund is mature. Conclusively, a long-term conservative balance between risk and return is one of the best investing strategies in pension funds providing the guaranteed interest.

• Journal of the Korea Society for Simulation
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• v.19 no.3
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• pp.109-117
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• 2010

In this study, we consider stationary waiting times in a simple fork-and-join type queue which consists of three single-server machines, Machine 1, Machine 2, and Assembly Machine. We assume that the queue has a renewal arrival process and that independent service times at each node are either deterministic or non-overlapping. We also assume that the Machines 1 and 2 have an infinite buffer capacity whereas the Assembly Machine has two finite buffers, one for each machine. Services at each machine are given by FIFO service discipline and a communication blocking policy. We derive the explicit expressions for stationary waiting times at all nodes as a function of finite buffer capacities by using (max,+)-algebra. Various characteristics of stationary waiting times such as mean, higher moments, and tail probability can be computed from these expressions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.1
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• pp.63-68
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• 2011

Many countries all over the world have been doing lunar exploration projects. Korea has also been doing basic research on lunar exploration. The development of communication systems for lunar exploration projects is one of the most important aspects of performing a successful lunar mission. In this paper, we design a DSP (Digital Signal Processor) prototype based on the requirement analysis of a communication link for lunar exploration and implement its core module considering the international standards for deep space communications to perform a basic research on baseband processor development. It is verified by comparing the bit error rate of the DSP prototype with that of a computer simulation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.149-153
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• 2012

We propose a traffic information service for which traffic data are collected over ad-hoc networks from neighbor vehicles, processed to minimize the data size, and eventually provided to its destination. The proposed scheme simply relies on the existing navigtion systems in vehicles and wireless communication devices for vehicle-to-vehicle communication, rather than on a separately established server. It allows collecting and analyzing traffic status of large areas without incorporating separated monitoring systems, e.g., probe cars and enables to provide accurate traffic information to drivers in timely manner. We also evaluate its performance by ns-3 simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.654-659
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• 2010

In this paper, we propose a new frequency allocation method for improvement of edge and low 5% user throughputs. Although many kinds of inter cell interference mitigation methods have been proposed, those have still high complexity of implementation. The proposed algorithm has lower complexity and higher edge user throughput than conventional algorithms since the same frequency allocation method is applied in all cell. Finally, we analyze and compare the edge and low 5% user throughputs using a system level simulation (SLS).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10C
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• pp.1042-1050
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• 2007

This paper describes the system which automatically generates power-minimized embedded cores from MDL descriptions. An automatic generation system is constructed which generated embedded cores which consumes less power for application programs. From the usage information on pipeline stages for each instruction, the proposed system generates embedded cores with the capability of detecting/resolving pipeline hazards. The generated cores are configured such that the power consumption is minimized. The proposed system has been tested by generating HDL codes for ARM9, MIPS R3000 architectures. Experimental results show functional accuracy of the generated cores, and show that power reduction of $20%{\sim}40%$ has been observed for benchmark programs.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.10
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• pp.687-696
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• 2010

In this study, FDD algorithm was developed using the normalized distance method and general pattern classifier method that can be applied to constant air volume air handling unit(CAV AHU) system. The simulation model using TRNSYS and EES was developed in order to obtain characteristic data of CAV AHU system under the normal and the faulty operation. Sensitivity analysis of fault detection was carried out with respect to fault progress. When differential pressure of mixed air filter increased by more than about 105 pascal, FDD algorithm was able to detect the fault. The return air temperature is very important measurement parameter controlling cooling capacity. Therefore, it is important to detect measurement error of the return air temperature. Measurement error of the return air temperature sensor can be detected at below $1.2^{\circ}C$ by FDD algorithm. FDD algorithm developed in this study was found to indicate each failure modes accurately.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.100-106
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• 2013

This paper presents design and control of an 'Omni-directional Cleaning Robot (OdCR)' which employs omni-wheels at three edges of its triangular configuration. Those omni-wheels enable the OdCR to move in any directions so that lateral movement is possible. For OdCR to be localized, a StarGazer sensor is used to provide accurate position and heading angle based on landmarks on the ceiling. In addition to that, ultrasonic sensors are installed to detect obstacles around OdCR's way. Experimental studies are conducted to test the functionality of the system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7A
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• pp.662-668
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• 2011

This paper analyzes the performance of the Ad hoc On-demand Distance Vector (AODV) routing protocol and Optimized Link State Routing (OLSR) for Mobile Ad hoc Networks (MANETs) using node mobility models. Mobility affects the performance of a routing protocol as it causes changes to network topology. Thus, evaluating the performance of a MANET routing protocol requires mobility models that can accurately represent the movements of mobile nodes. Therefore, this paper evaluates the performance of the AODV and OLSR routing protocols using the random way point model and the Levy walk model by the ns-2 simulations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.10
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• pp.669-678
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• 2008

When operating a complex facility, Fault Detection and Diagnosis (FDD) system is beneficial in equipment management by providing the operator with tools which can help find out a failure of the system. In this research, FDD algorithm was developed using the general pattern classifier method that can be applied to centrifugal chiller system. The simulation model for a centrifugal chiller system was developed in order to obtain characteristic data of turbo chiller system under normal and faulty operation. We tested FDD algorithm of a centrifugal chiller using data from simulation model at full load performance and 60% part load performance. In this research, we presented fault detection method using a normalized distance. Sensitivity analysis of fault detection was carried out with respect to fault progress. FDD algorithm developed in this study was found to indicate each failure modes accurately.