• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1701-1704
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• 2002

In this paper, we investigate the effect of power control step size on the performance of the SIC scheme in DS/CDMA systems. We investigate the average power control iteration and its standard deviation and evaluate the outage performance for several different values of power control step size. Because the SIC scheme requires fine control in the received signal power, the better outage performance is obtained fer the smaller power control step size. However, the smaller power control step size requires larger amount of power control iteration in order to make the power control converge to the steady state. Under the simulated environment, the proper power control step size is about 0.3-0.4dB from both convergence speed of power control algorithm and outage performance points of view.

• 조명전기설비학회논문지
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• 제27권11호
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• pp.20-26
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• 2013

This paper proposes the maximum power point tracking(MPPT) control of photovoltaic system using fuzzy based variable step size perturbation & observation(FVSS-PO) method. Conventional PO and incremental conductance(IC)MPPT control algorithm generally uses fixed step size. A small fixed step size will cause the tracking speed to decrease and tracking accuracy of the MPP will decrease due to large fixed step size. Therefore, the fixed step size can't be satisfying both the tracking speed and the tracking accuracy. This paper proposes FVSS-PO MPPT algorithm that adjusts automatically step size of PO by fuzzy control according to operating conditions. The validity of MPPT algorithm proposed in this paper prove through compare with conventional PO MPPT algorithm.

• 한국구조물진단유지관리공학회 논문집
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• 제25권1호
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• pp.41-50
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• 2021

본 연구에서는 MR Damper의 제어력을 결정하는 다양한 요인들 중, 유로폭(Gap Size)을 다르게 선정하여 그에 따른 제어력의 변화를 확인하였다. 이를 위해 Gap Size 1.0mm, 1.5mm인 MR Damper 두 대를 제작하고 인가전류와 가진조건을 정하였으며 그에 따른 동하중 실험을 수행하였다. 실험결과 최소제어력은 Gap Size 1.0mm 조건이 Gap Size 1.5mm 조건보다 3.2배 높았으며 최대제어력은 Gap Size 1.0mm 조건이 Gap Size 1.5mm 조건보다 2.3배 높았다. 또한, 인가전류에 따른 제어력의 증가폭은 Gap Size 1.0mm일 때 34N, Gap Size 1.5mm일 때 12.7N으로 나타났다. Gap Size가 커질수록 전체 제어력과 인가전류에 따른 제어력의 증가는 감소하였다. 두 개의 MR Damper의 동적범위를 확인해 본 결과 Gap Size 1.0mm일 때 평균 2.3, Gap Size 1.5mm일 때 평균 2.8인 것을 볼 때 두 MR Damper의 준능동제어장치로써 사용가능성을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.958-959
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• 2015

This paper proposes adaptive incremental conductance(A-IC) algorithm for maximum power point tracking(MPPT) control of photovoltaic. Conventional Perturbation & Observation(PO) and IC MPPT control algorithm generally uses fixed step size. A small fixed step size will cause the tracking speed to decrease and tracking accuracy of the MPP will decrease due to large fixed step size. Therefore, this paper proposes N-IC MPPT algorithm that adjust automatically step size according to operating conditions. To improve tracking speed and accuracy, when operating point is far from maximum power point(MPP), step size uses maximum value and when operating point is near from MPP, step size uses variable step size that adjust according to slope of P-V curve. The validity of MPPT algorithm proposed in this paper prove through compare with conventional IC MPPT algorithm.

• Journal of Biosystems Engineering
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• 제25권1호
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• pp.11-18
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• 2000

In precision chemical application increment of biological efficacy with less chemical is the virtue. spraying rate and droplet size is closely related to biological efficacy. this study was performed to develope a spray-control-system that could control spraying rate and droplet size independently. Twin-fluid nozzles were selected and tested to certify if the nozzles were suitable for the objective of this study. Characteritics of the nozzles i.e., spraying rte and droplet size change u8nder the changes of spraying pressure and air pressure were statistically modeled. The model had I to 1 matching property between dependent variables and independent variables. Using the property and the model, inverse relationship could be determined between variables. A feedback spray control system was developed and tested with predetermined error of 5 % in pressure. The system showed 4 % error in spraying rate and 9 % error in droplets size. Performance of the system could be upgraded by fine tuning but, in practical sense keeping air pressure in the field sprayer was the bottle neck of commercialization of the spray system.

• 한국경영과학회지
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• 제34권1호
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• pp.29-37
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• 2009

This paper proposes a curtailed-sequential probability ratio test (SPRT) control chart. For using the conventional SPRT control chart, the number of items inspected in a sampling point should have no restriction since items in a sampling point are inspected one by one until an SPRT Is terminated. The number of observations taken in a sampling point, however, has an upper bound since sampling and testing of an item is time-consuming or expensive. When the sample size reaches the upper bound without evidence of an in-control or out-of-control state of a process, the proposed chart makes a decision using the sample mean of all observations taken in a sampling point. The properties of the Proposed chart are obtained by a Markov chain approach and the performance of the chart is compared with fixed sample size (FSS) and variable sample size (VSS) control charts. A comparative study shows that the proposed chart performs better than VSS control charts as well as conventional FSS control charts.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2688-2691
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• 2008

This study addresses a microfluidic method to uniformly form diacetylene (DA) liposomes and control their size. DA liposomes are biochemical sensor materials with a unique property such that when they are polymerized to polydiacetylene (PDA) they exhibit non-fluorescent blue to fluorescent red phase transition upon chemical or thermal stress. The liposome size and distribution are important because they significantly affect the phase transition. So far, DA Liposomes, have been prepared by mixing of bulk phases leading to heterogeneous, polydisperse distribution in size. Therefore, additional post-processes are required such as sonication or membrane extrusion to obtain an appropriate size of liposomes. Here, we report a novel strategy using a microfluidic chip and hydrodynamic focusing to form DA liposomes and control their size. Preliminary results obtained by scanning electron microscope (SEM) and dynamic light scattering (DLS) show that the microfluidic strategy generates more monodispersed liposomes than a bulk method.

• Genomics & Informatics
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• 제10권2호
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• pp.117-122
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• 2012

A sample size with sufficient statistical power is critical to the success of genetic association studies to detect causal genes of human complex diseases. Genome-wide association studies require much larger sample sizes to achieve an adequate statistical power. We estimated the statistical power with increasing numbers of markers analyzed and compared the sample sizes that were required in case-control studies and case-parent studies. We computed the effective sample size and statistical power using Genetic Power Calculator. An analysis using a larger number of markers requires a larger sample size. Testing a single-nucleotide polymorphism (SNP) marker requires 248 cases, while testing 500,000 SNPs and 1 million markers requires 1,206 cases and 1,255 cases, respectively, under the assumption of an odds ratio of 2, 5% disease prevalence, 5% minor allele frequency, complete linkage disequilibrium (LD), 1:1 case/control ratio, and a 5% error rate in an allelic test. Under a dominant model, a smaller sample size is required to achieve 80% power than other genetic models. We found that a much lower sample size was required with a strong effect size, common SNP, and increased LD. In addition, studying a common disease in a case-control study of a 1:4 case-control ratio is one way to achieve higher statistical power. We also found that case-parent studies require more samples than case-control studies. Although we have not covered all plausible cases in study design, the estimates of sample size and statistical power computed under various assumptions in this study may be useful to determine the sample size in designing a population-based genetic association study.

• 품질경영학회지
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• 제25권3호
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• pp.74-85
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• 1997

In this paper we calculate the subgroup size necessary for detecting the change of percent defective with several detection probabilities for orginal population fraction nonconforming p, changed population fraction nonconforming $p^*$, and the ratio k=$p^*$/p in the usage of p control charts. From our calculation we can know the error level of normal a, pp.oximation in detection probability calculation and recommend the subgroup size with lower error levels of normal a, pp.oximation, and then we show the reasonable subgroup size necessary for p, $p^*$, k, and the detection probability of the change of fraction nonconforming in a process. The information that we here show in tables will be useful when p control chart users decide the subgroup size in the p control chart users decide the subgroup size in the p control chart.

• 한국안전학회지
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• 제18권3호
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• pp.34-38
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• 2003

The large eddy simulation based Fire Dynamics Simulator was utilized to investigate the effects of the size of an opening on smoke removal performance for the three smoke control systems-ventilation purge, and extraction. Three different opening sizes, $r_A$=1, 2, and 3 were investigated while the flow rate remained 0.75 $m^3/s$ at the inlet or outlet depending on the systems. Increase of the opening size did not give a significant difference in the smoke removal rate for the three smoke control systems, though the increasing opening size slightly improved smoke removal. The extraction system was shown the best smoke control system, and the purge system yielded low performance compared to the other two systems for all the different opening sizes.