• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.2
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• pp.1-7
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• 2005

For the reliability evaluation of the track drive unit(TDU), firstly, we analyzed the major failure modes through FMEA(failure mode & effects analysis), FTA(failure tree analysis), and 2-stage QFD(quality function deployment), and then quantitatively determined the priority order of test items. The Minitab analysis was also performed for prediction of life distribution and parameters of TDU by use of field failure data collected from 430 excavators for two years. In addition, we converted the fluctuation load in field conditions into the equivalent load, and for evaluation of the accelerated lift by the cumulative fatigues, the equivalent load is again divided into the fluctuation load by reference of test time. And then, by use of the test method in this paper, the acceleration factor(AF) of needle bearing inside planetary gear which is the most weakly designed part of TDU is achieved as 5.3. This paper presents the quantitative selection method of test items for reliability evaluation, the determination method of the accelerated life test time, and the method of non-failure test time based on a few of samples. And, we proved the propriety of the proposed methods by experiments using a TDU for a 30 ton excavator.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.102-107
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• 2006

In this study, the dynamic environment of satellite consists of excessive vibration at low frequency and irregular acceleration transferred by launch vehicle structure. Excessive vibration at low frequency is generally approximated by a sinusoidal wave from 100Hz to 200Hz and primarily used to preliminary design The random vibration is created by structural vibration due to the combustion of launch vehicle, separation stage and external aerodynamic noise. these are transferred to the adapter structure between satellite and launch vehicle through the structure of launch vehicle. random vibration is being specified for acceptance tests, screening tests, and qualification tests, because it has been shown that random vibration more closely represents the true environments in which the electronic equipment must operate.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.6
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• pp.82-92
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• 2001

This paper describes implementation of an embedded 32-Bit RISC core for portable communication/information equipment, such as cellular phones, PDA(Personal Digital Assistants), notebook, etc. The RISC core implements the ARM$\circled$V 4 instruction set, operates with typical 5-stage pipeline. It supports Thumb code to improve the code density, and uses the dynamic power management method of pipeline registers. It was modeled and simulated in RTL level using VHDL, and verified with ARMulator of ADS (Arm Developer Suite) and had average CPI of 1.44. The core is synthesized automatically using the cell library based on $0.6{\mu}m$ CMOS 1-poly 3-metal CMOS technology. It consists of about 41,000 gates and the clock frequency is expected to be above 45 MHz.

• IEMEK Journal of Embedded Systems and Applications
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• v.3 no.1
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• pp.19-24
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• 2008

To reduce time-to-market, more and more embedded system developers and system-on-chip designers rely on microprocessor-based design methodology. ARM processor has been a major player in this industry over the last 10 years. However, there are many restrictions on developing embedded software using ARM processor in the early design stage. For those who are not familiar with embedded software development environment or who cannot afford to have an expensive embedded hardware equipment, testing their software on a real ARM hardware platform is a challenging job. To overcome such a problem, we have designed VMA (Virtual ARM Machine), which offers easier testing and debugging environment to ARM based embedded system developers. Major benefits that can be achieved by utilizing a virtual ARM platform are (1) reducing development cost, (2) lowering the entrance barrier for embedded system novices, and (3) making it easier to test and debug embedded software designs. Unlike many other purely software-oriented ARM simulators which are independent of real hardware platforms, VMA is specifically targeted on SYS-Lab 5000 ARM hardware platform, (designed by Libertron, Inc.), which means that VMA imitates behaviors of embedded software as if the software is running on the target embedded hardware as closely as possible. This paper will describe how VMA is designed and how VMA can be used to reduce design time and cost.

• Steel and Composite Structures
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• v.3 no.3
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• pp.185-198
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• 2003

The concept of performance based seismic design has been gradually accepted by the earthquake engineering profession recently, in which the cost-effectiveness criterion is one of the most important principles and more attention is paid to the structural performance at the inelastic stage. Since there are many uncertainties in seismic design, reliability analysis is a major task in performance based seismic design. However, structural reliability analysis may be very costly and time consuming because the limit state function is usually a highly nonlinear implicit function with respect to the basic design variables, especially for the complex large-scale structures for dynamic and nonlinear analysis. Understanding statistical properties of the structural inelastic deformation, which is the aim of the present paper, is helpful to develop an efficient approximate approach of reliability analysis. The present paper studies the statistical properties of the maximum elastoplastic story drift of steel frames subjected to earthquake load. The randomness of earthquake load, dead load, live load, steel elastic modulus, yield strength and structural member dimensions are considered. Possible probability distributions for the maximum story are evaluated using K-S test. The results show that the choice of the probability distribution for the maximum elastoplastic story drift of steel frames is related to the mean value of the maximum elastoplastic story drift. When the mean drift is small (less than 0.3%), an extreme value type I distribution is the best choice. However, for large drifts (more than 0.35%), an extreme value type II distribution is best.

• Journal of the Korea Institute of Building Construction
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• v.8 no.5
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• pp.67-73
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• 2008

Recent trends in construction towards larger scale and taller buildings are causing problems by ineffective existing management approach in construction industry have emerged. Delivering necessary materials and mobilizing the human resources and equipment In a timely manner to keep labor on schedule have become a critical issue to be addressed. In particular, many specialty contractors carrying out multiple projects have been experiencing difficulties mobilizing the manpower on time and in right places due to poor communication at each stage of labor supply, resulting in waste of valuable resources. Hence, it's imperative for the specialty contractors to obtain specific information on labor demand so as to set up a communication and labor management system to ensure the right human resources will be mobilized in the right place at the right time. The study therefore is aimed at developing an optimal human resources management system for specialty contractors performing multiple projects. To that end, the study is focused on rebar and concrete work. The outcome of the study is expected to help allocate the right human resources to the right place in a timely fashion, thereby achieving an effective workflow at construction sites.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.6
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• pp.91-98
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• 2014

For the purpose of designing and applying the optimum surge protection scheme, multi-stage coordinated surge protective device(SPD) system is suitable to successfully fulfill its tasks; first, to divert a large amount of the transient energy, second, to clamp the overvoltage to the level below the withstand impulse voltage of the equipment to be protected. The length of SPD connecting leads shall be as short as possible. Long connecting leads will degrade the protection effect of SPDs. In this paper, the influences of the length of connecting leads on the energy sharing in a coordinated SPD system were investigated experimentally, and the simulation of determining the energy sharing and protection voltage level of each SPD depending on the length of connecting leads was carried out by using P-spice program. It was confirmed that the protection voltage level and energy sharing in coordinated SPD systems are strongly influenced by the length of connecting leads.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.68-75
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• 2014

Cascaded applications of surge protective devices(SPDs) are required in order to reduce the stress on the electrical and electronics equipment being protected, and the energy coordination between the cascaded SPDs is very important. This paper deals with the experimental results obtained from the installation conditions of full-scale SPDs. The energy coordination between the upstream Class I SPD and the downstream Class II SPD was measured using a $10/350{\mu}s$ impulse current due to direct lightning flashes. The distances between the cascaded SPDs were 3, 10, and 50m, and the maximum test current was 12.5kA. As a result, the energy sharing between cascaded SPDs was dependent on the voltage protection level of each SPD and the distance between two SPDs. An overview of how to select SPD ratings in applications of cascaded SPDs system was discussed based on the energy coordination between the two SPDs. The proposed test results for the energy coordination between two-stage cascaded SPDs can be used in effective applications of SPDs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.916-919
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• 2000

A great deal of research has been done in the field of characterization for piezoelectric thin films after the first report on the measurement for the piezoelectric coefficient of thin films in 1990. The main idea of this research is to provide a distinctive solution for the measurement of both the longitudinal and the transverse piezoelectric d-coefficients, d$\sub$33/ and d$\sub$3l/, of ferroelectric thin films and also thick films. In general, to get these two coefficients of thin films, two different measuring systems are required. Here, we propose the improved method for the evaluation of these two coefficients with single equipment and with the relatively convenient procedure. The two-step loading process of applying the both positive and the negative pressure has been designed to acquire the piezoelectric coefficients. These results have beer calibrated for both the longitudinal and the transverse piezoelectric d-coefficients, d$\sub$33/ and d$\sub$31/, of thin films. In the first stage of the experiments, we have obtained d$\sub$33/ of 108pC/N and d$\sub$31/ of 57pC/N for the PZT thin films.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1643-1645
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• 2005

A newly-built inverter has to undergo a series of stress tests in the final stage of production line. This can be achieved by connecting it to a dynamometer consisting of a three-phase machine joined by a rigid shaft to a DC load machine. The latter is controlled to create some specific load characteristic needed for the test. In this paper a test method is proposed, in which no mechanical equipment is needed. The suggested test stand consists only of a inverter to be tested and a simulator converter. Both devices are connected back- to-back on the AC-side via smoothing reactors. The simulator operates in real-time as an equivalent load circuit, so that the device under test will only notice the behaviour of a three-phase machine under consideration of the load. In odor to wove rightness of the suggested test method, the simulation and actural experiment rallied out emulation for a 2.2kW induction motor.