• Journal of Mechanical Science and Technology
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• 제18권4호
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• pp.689-698
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• 2004

Uncertainties generated from the individual measured variables have an influence on the uncertainty of the experimental result through a data reduction equation. In this study, a performance test of a single stage axial type turbine is conducted, and total-to-total efficiencies are measured at the various off-design points In the low pressure and cold state. Based on an experimental apparatus, a data reduction equation for turbine efficiency is formulated and six measured variables are selected. Codes are written to calculate the efficiency, the uncertainty of the efficiency, and the sensitivity of the efficiency uncertainty by each of the measured quantities. The influence of each measured variable on the experimental result is figured out. Results show that the largest uncertainty magnification factor (UMF) value is obtained by the inlet total pressure among the six measured variables, and its value is always greater than one. The UMF values of the inlet total temperature, the torque, and the RPM are always one. The uncertainty percentage contribution (UPC) of the RPM shows th, lowest influence on the uncertainty of the turbine efficiency, but the UPC of the torque has the largest influence to the result among the measured variables. These results are applied to find the correct direction for meeting an uncertainty requirement of the experimental result in the planning or development Phase of experiment, and also to offer ideas for preparing a measurement system in the planning phase.

• Wind and Structures
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• 제31권1호
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• pp.59-73
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• 2020

Wind fragility analysis (WFA) of concrete chimney is often executed disregarding temperature effects. But combined wind and temperature effect is the most critical limit state to define the safety of a chimney. Hence, in this study, WFA of a 70 m tall RC chimney for combined wind and temperature effects is explored. The wind force time-history is generated by spectral representation method. The safety of chimney is assessed considering limit states of stress failure in concrete and steel. A moving-least-squares method based dual response surface method (DRSM) procedure is proposed in WFA to alleviate huge computational time requirement by the conventional direct Monte Carlo simulation (MCS) approach. The DRSM captures the record-to-record variation of wind force time-histories and uncertainty in system parameters. The proposed DRSM approach yields fragility curves which are in close conformity with the most accurate direct MCS approach within substantially less computational time. In this regard, the error by the single-level RSM and least-squares method based DRSM can be easily noted. The WFA results indicate that over temperature difference of 150℃, the temperature stress is so pronounced that the probability of failure is very high even at 30 m/s wind speed. However, below 100℃, wind governs the design.

• 시스템엔지니어링학술지
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• 제11권1호
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• pp.55-65
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• 2015

In steel making plant, sampling system for raw material such as iron ore, limestone is necessary for quality control purpose. For the sake of efficiency and productivity, automation of the sampling system is highly desirable. From technical standpoint, the development of the automated system requires multi-disciplinary domain knowledge such as mechanical engineering, industrial engineering, information technology and computer engineering. Up to present time, the development has been mainly carried out by a single domain expert with project manager. The automated system developed in this way caused problems in the final system. This paper suggests a systems engineering approach to the development of automation for raw material sampling plant via a tailored process called Plant Systems Engineering (PSE) Process based on ISO/IEC 15288. Through the PSE process, we could derive right requirements and architecture of the Systems Of Interest (SOI), and we were convinced that the PSE Process can be applied to many other Plant Systems.

• Journal of Communications and Networks
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• 제8권1호
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• pp.116-122
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• 2006

Most of the multimedia applications require strict quality of service (QoS) guarantee during the communication between a single source and multiple destinations. This gives rise to the need for an efficient QoS multicast routing strategy. Determination of such QoS-based optimal multicast routes basically leads to a multi-objective optimization problem, which is computationally intractable in polynomial time due to the uncertainty of resources in Internet. This paper describes a network model for researching the routing problem and proposes a new multicast tree selection algorithm based on genetic algorithms to simultaneously optimize multiple QoS parameters. The paper mainly presents a QoS multicast routing algorithm based on genetic algorithm (QMRGA). The QMRGA can also optimize the network resources such as bandwidth and delay, and can converge to the optimal or near-optimal solution within few iterations, even for the networks environment with uncertain parameters. The incremental rate of computational cost can close to polynomial and is less than exponential rate. The performance measures of the QMRGA are evaluated using simulations. The simulation results show that this approach has fast convergence speed and high reliability. It can meet the real-time requirement in multimedia communication networks.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.204-207
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• 2006

COMS will receive two different meteorological signals in S-Band from IDACS (Image Data Acquisition and Control System) in ground station before transmitting them in L-Band to user station. MODCS (Meteorological Ocean Data Communication Subsystem) in satellite released the value of required PFD (Power Flux Density) to receive two signals. Thus, DATS (Data Acquisition and Transmission Subsystem) needs to send two signals to satellite with a satisfied EIRP. The value of minimum HPA (High Power Amplifier) output power was estimated by subtracting antenna directional gain and path loss between antenna and HPA from the needed EIRP in this paper. Besides the minimum output power of HPA, the maximum output power was also calculated with considering IMD (Inter-Modulation Distortion) characteristics. IMD is always occurred in the output of HPA when LRIT and HRIT are amplified by using single HPA as COMS application. In this paper, the setting of maximum output power was determined when the IMD of modelled HPA was corresponded to the requirement of MODCS.

• 한국통신학회논문지
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• 제21권12호
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• pp.3215-3226
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• 1996

In this paper a K-band harmonic oscillator competitive to ordinary Push-Push type oscillators is introduced. This oscillator is composed of two-X-band dielectric resonance circuits. To favor its harmonic generation, the load effect and the bias effect are studied to allow the maximum harmonic distortion. As results, the dielectric resonated load and the class A bias are used for the 2nd harmonic generation. analytical study for modelling of voltage controlled dielectric resonator is carried out with theoretical background. The performance of the circuit is evaluated by simulation using harmonic balanced method. The novel structure has ont only a voltage tuning circuit but also an output port at fundamental frequency as the function of prescaler for phase lockede loop application on the just single oscillation structure. In experimentation, the output freqneyc of the 2nd harmonic signal is 20.5GHz and the maximum power level of output is +5.5dBm without additional post amplifiers. the harmonic oscillator exhibits -30dBc of high fundamental frequency rejection without added extra filters. The phase noise of -90dBc/Hz at 100kHz off-carrier has been achieved under free running condition, that satisfies phase noise requirement of IESS 308. The proposed oscillator may be utilized as the clean and stable fixed local oscillator in Transmit Block Upconvertor(TBU) or Low oise Block downconvertor(LNB) for K/Ka-band digital communications and satellite broadcastings.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1222-1225
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• 2004

This paper presents multibit Sigma-Delta ADC using noise-shaped dynamic element matching(DEM). 5-bit flash ADC for multibit quantization in Sigma Delta modulator offers the following advantages such as lower quantization noise, more accurate white-noise level and more stability over single quantization. For the feedback paths consisting of DAC, the DAC element should have a high matching requirement in order to maintain the linearity performance which can be obtained by the modulator with a multibit quantizer. The DEM algorithm is implemented in such a way as to minimize additional delay within the feedback loop of the modulator Using this algorithm, distortion spectra from DAC linearity errors are shaped. Sigma Delta ADC achieves 82dB signal to noise ratio over 615H7z bandwidth, and 62mW power dissipation at a sampling frequency of 19.6MHz. This Sigma Delta ADC is designed to use 0.25um CMOS technology with 2.5V supply voltage and verified by HSPICE simulation.

• 대한전자공학회논문지TC
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• 제39권7호
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• pp.22-29
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• 2002

ATM Forum에서 best-effort 트래픽을 서비스하기 위해서 GFR(Gauranteed Frame Rate) 서비스 클래스를 제안했다. GFR 서비스는 VC에 최소 셀 전송율을 제공하고 남은 잉여대역을 연결된 VC에 공평히 할당하도록 설계되었다. 본 논문에서는 FIFO 기반의 버퍼관리 알고리즘을 제안한다. 제안한 버퍼관리 알고리즘은 GFR VC의 최소 셀 전송율을 보장할 수 있으며, 높은 공평성을 제공할 수 있다. 컴퓨터 시뮬레이션 결과를 통해 제안된 알고리즘이 네트워크 수율을 높이며 GFR의 QoS(Quality of Service)를 충족함을 보였다.

• BMB Reports
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• 제30권4호
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• pp.285-291
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• 1997

It is becoming increasingly evident that significant changes in gene expression occur during the course of neuronal differentiation. Thus, it should be possible to gain information about the biochemical events by identifying differentially expressed genes in neuronal differentiation The PC12 cell line is a useful model system to investigate the molecular mechanism underlying neuronal differentiation and has been used extensively for the study of the molecular events that underlie the biological actions of nerve growth factor (NGF). In this study, we report an application of the recently described mRNA differential display method to analyze differential gene expression during neuronal differentiation. Using this technique, we have identified several cDNA tags expressed differentially during neuronal differentiation. Interestingly, one of these clones was cytochrome c oxidase subunit I (COX I) gene. The differential expression of COX I gene was confirmed by Northern blot analysis as well as RT-PCR. Southern blot analysis of the genomic DNA of PC12 cells revealed that COX I is a single gene. Induction of the oxidative enzyme might reflect the energy requirement in neuronal differentiation.

• 항공우주시스템공학회지
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• 제10권1호
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• pp.51-58
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• 2016

In this paper, we present some results on No-failure accelerated life test of aerial vehicle for reliability demonstration. The design of general accelerated life test consists of the three phases: 1) Estimating normal life test time of a single product from Weibull distribution model; 2) Determining the acceleration factor (AF) by utilizing the relation between the life of mechanical components and the applied torque; 3) Calculating the accelerated life test time, which comes from dividing the estimated normal life test time into AF. Then, we applied the calculated life test time to the real reliability test of the flap actuating system, while considering the requirement specification for mechanical components and operating environment of the actuation system. Real experimental processes and results are presented to validate the theory.