• 전기전자학회논문지
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• 제11권1호통권20호
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• pp.1-14
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• 2007

In this paper, a design of an integral augmented nonlinear optimal variable structure system(INOVSS) is presented for the prescribed output control of uncertain MIMO systems under persistent disturbances. This algorithm basically concerns removing the problems of the reaching phase and combining with the nonlinear optimal control theory. By means of an integral nonlinear sliding surface, the reaching phase is completely removed. The ideal sliding dynamics of the integral nonlinear sliding surface is obtained in the form of the nonlinear state equation and is designed by using the nonlinear optimal control theory, which means the design of the integral nonlinear sliding surface and equivalent control input. The homogeneous $2{\upsilon}(\kappa)$ form is defined in order to easily select the $2{\upsilon}$ or even $(\kappa)-form$ higher order nonlinear terms in the suggested sliding surface. The corresponding nonlinear control input is designed in order to generate the sliding mode on the predetermined transformed new surface by means of diagonalization method. As a result, the whole sliding output from a given initial state to origin is completely guaranteed against persistent disturbances. The prediction/predetermination of output is enable. Moreover, the better performance by the nonlinear sliding surface than that of the linear sliding surface can be obtained. Through an illustrative example, the usefulness of the algorithm is shown.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권1호
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• pp.96-99
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• 2014

In high-${\kappa}$/metal-gate (HK/MG) metal-oxide-semiconductor field-effect transistors (MOSFETs) at 45-nm and below, the metal-gate material consists of a number of grains with different grain orientations. Thus, Monte Carlo (MC) simulation of the threshold voltage ($V_{TH}$) variation caused by the workfunction variation (WFV) using a limited number of samples (i.e., approximately a few hundreds of samples) would be misleading. It is ideal to run the MC simulation using a statistically significant number of samples (>~$10^6$); however, it is expensive in terms of the computing requirement for reasonably estimating the WFV-induced $V_{TH}$ variation in the HK/MG MOSFETs. In this work, a simple matrix model is suggested to implement a computing-inexpensive approach to estimate the WFV-induced $V_{TH}$ variation. The suggested model has been verified by experimental data, and the amount of WFV-induced $V_{TH}$ variation, as well as the $V_{TH}$ lowering is revealed.

• Restorative Dentistry and Endodontics
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• 제49권1호
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• pp.3.1-3.8
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• 2024

This article is a narrative review that discusses the recommended sample size requirements to design a pilot study to assess the reliability of a questionnaire. A list of various sample size tables that are based on the kappa agreement test, intra-class correlation test and Cronbach's alpha test has been compiled together. For all calculations, type I error (alpha) was set at a maximum value of 0.05, and power was set at a minimum value of 80.0%. For the kappa agreement test, intra-class correlation test, and Cronbach's alpha test, the recommended minimum sample size requirement based on the ideal effect sizes shall be at least 15, 22, and 24 subjects respectively. By making allowances for a non-response rate of 20.0%, a minimum sample size of 30 respondents will be sufficient to assess the reliability of the questionnaire. The clear guideline of minimum sample size requirement for the pilot study to assess the reliability of a questionnaire is discussed and this will ease researchers in preparation for the pilot study. This study provides justification for a minimum requirement of a sample size of 30 respondents specifically to test the reliability of a questionnaire.

• 한국산업보건학회지
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• 제28권2호
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• pp.190-199
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• 2018

Objectives: The purpose of this case study is to assess the current airflow and find the ideal ventilation conditions in tank reactors for minimizing the possibility of exposure respiratory dusts(size of $2.5{\mu}m$, $10{\mu}m$) when workers exchange catalysts in the tank reactors. Methods: A Numerical study was performed to determine ideal ventilation conditions, We considered two sizes of airborne respiratory particles($2.5{\mu}m$, $10{\mu}m$) at 12points from the bottom of tank reactor. We changed input & output ventilation conditions and analyzed the particle motion in the tank reactor. The star-ccm+, computational fluid dynamics tool was used to predict air & particle flow patterns in the tank reactor and a numerical simulation was achieved by applying the realized ${\kappa}-{\varepsilon}$ turbulence model and the Lagrangian particle tracking method. Results: From the results, the increase of recirculation air had a significant impact on removing dusts because they are removed by HEPA filter. To the contrary, Increasing the clean air quantity or changing the input position of clean air is not good for workers because it causes the exit of respiratory dusts through workers' entrance or cause it to remail suspended in the air in the workplace tank.

• Coupled systems mechanics
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• 제8권1호
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• pp.19-38
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• 2019

The influence of torsional rigidity of hinged flexible appendage on the linear dynamics of flexible spacecrafts with liquid on board was analyzed by considering the spacecraft's main body as a rigid tank, its flexible appendages as two elastically supported elastic beams, and the onboard liquid as an ideal liquid. The meniscus of the liquid free surface due to surface tension was considered. Using the Lagrangian of the spacecraft's main body (rigid tank), onboard liquid, and two beams (flexible appendages) in addition to assuming the system moved symmetrically, the coupled system frequency equations were obtained by applying the Rayleigh-Ritz method. The influence of the torsional rigidity of the flexible appendages on the spacecraft's coupled vibration characteristics was primary focus of investigation. It was found that coupled vibration modes especially that of appendage considerably changed with torsion spring parameter ${\kappa}_t$ of the flexible appendage. In addition, variation of the main body displacement with system parameters was investigated.

• Journal of Preventive Medicine and Public Health
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• 제43권1호
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• pp.9-17
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• 2010

Objectives: Parkinson's disease is one of the most common neurodegenerative diseases in the elderly population. In order to estimate the prevalence of Parkinson's disease in the community, the application of a good screening tool is essential. We evaluated the validity and reliability of a Parkinson's disease screening questionnaire and propose an alternative measure to improve its validity for use in community surveys. Methods: We designed the study in a three-phase approach consisting of a screening questionnaire, neurologic examination, and confirmatory examination. A repeated survey was administered to patients with disease detected in the community and on 150 subjects. We examined internal consistency using Cronbach's alpha test, test-retest reliability using the kappa statistic, and validity using sensitivity, specificity, and ROC curves. Unadjusted odds ratios were utilized for the estimation of weights for each questionnaire item. Results: The Cronbach's alpha of the questionnaire was 0.708. The kappa statistic for test-retest reliability was good to generally fair in most of the items. When newly proposed weighting scores were used, the optimum cut-off value was 7/8. When cut-off value was 5/6 for surveying prevalence in a community, the sensitivity was 0.98, and the specificity was 0.61, with simultaneous improvement in reliability. Conclusions: We recommend 5/6 as the ideal cut-off value for the survey of PD prevalence in community. This questionnaire designed for the Korean community could help future epidemiologic studies of PD.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.23-23
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• 2009

It has been challenging to increase the thermoelectric figure of merit ($ZT=S^2{\sigma}T/\kappa$) of materials, which determine the efficiency of thermoelectric devices, because the three parameters Seebeck coefficient (S), electrical conductivity ($\sigma$), and thermal conductivity ($\kappa$) of bulk materials are inter-dependent. With the development of nanotechnology, ZT values of nanostructured materials are predicted to be enhanced by classical size effects and quantum confinement effects. In particular, Bi nanowires were suggested as one of ideal thermoelectric materials due to the expected quantum confinement effects for the simultaneous increase in Sand. In this work, we have investigated the thermal conductivity of individual single crystalline Bi nanowires with d = 98 nm and d = 327 nm in the temperature range 40 - 300 K using MEMS devices. The for the Bi nanowire with d = 98 nm was observed to be ~ 1.6 W/m-K at 300 K, which is much lower than that of Bi bulk (8 W/m-K at 300 K). This indicates that the thermal conductivity of the Bi suppressed due to enhanced surface boundary scattering in one-dimensional structures. Our results suggest that Bi nanowires grown by stress-induced method can be used for high-efficiency thermoelectric devices.

• 한국임상수의학회지
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• 제28권1호
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• pp.52-56
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• 2011

Acute renal injury induced by ischemia is a major cause of high morbidity and mortality in hospitalized patients and a common complication in hospitalized patients. Thus, the work with acute renal failure and renal ischemia has been studied for many years. Although serum creatinine concentration that is widely used as an index of renal function performs fairly well for estimating kidney function in patients with stable chronic kidney disease, it performs poorly in the setting of acute disease. Thus, an ideal biomarker for acute kidney injury would help clinicians and scientists diagnose the most common form of acute kidney injury in hospitalized patients, acute tubular necrosis, early and accurately, and may aid to risk-stratify patients with acute kidney injury by predicting the need for renal replacement therapy, the duration of acute kidney injury, the length of stay and mortality. In this study, renal ischemia and reperfusion were performed by clapming and un-clamping right renal artery in miniature pigs. Plasma blood urea nitrogen (BUN) and creatinine were examined at pre- clamping, after-clamping at 0, 1 and 3 hours. And we searched initial indicators in these samples. Also, renal tissue was collected and searched the initial indicator by PCR and western blotting. As a result, hypoxia inducible factor $1{\alpha}$ ($HIF1{\alpha}$), nuclear factor kappa-B ($NF{\kappa}B$), $I{\kappa}B$, erythropoietin (EPO), erythropoietin receptor (EPOR), angiopoietin-1 and vascular endothelial growth factor (VEGF) were showed significant changes among the renal protein. $HIF1{\alpha}$, EPO, and EPOR were showed significant changes among the renal gene. Thus, these markers will be used as initial diagnosis of acute renal failure.

• 한국농공학회논문집
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• 제57권6호
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• pp.91-97
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• 2015

The Unmanned Aerial Vehicles (UAVs) have several advantages over conventional RS techniques. They can acquire high-resolution images quickly and repeatedly. And with a comparatively lower flight altitude i.e. 80~400 m, they can obtain good quality images even in cloudy weather. Therefore, they are ideal for acquiring spatial data in cases of small agricultural field with mixed crop, abundant in South Korea. This paper discuss the use of low cost UAV based remote sensing for classifying crops. The study area, Gochang is produced by several crops such as red pepper, radish, Chinese cabbage, rubus coreanus, welsh onion, bean in South Korea. This study acquired images using fixed wing UAV on September 23, 2014. An object-based technique is used for classification of crops. The results showed that scale 250, shape 0.1, color 0.9, compactness 0.5 and smoothness 0.5 were the optimum parameter values in image segmentation. As a result, the kappa coefficient was 0.82 and the overall accuracy of classification was 85.0 %. The result of the present study validate our attempts for crop classification using high resolution UAV image as well as established the possibility of using such remote sensing techniques widely to resolve the difficulty of remote sensing data acquisition in agricultural sector.

• 미생물학회지
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• 제52권4호
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• pp.421-427
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• 2016

여드름은 만성 염증 질환으로 주로 청소년기에 발생하는 것으로 알려져 있으나 대기오염, 약물 남용 등의 원인에 의해 아동기 및 성인기에도 나타날 수 있다고 알려져 있다. 여드름을 유발하는 정확한 원인은 밝혀져 있지 않으나 한 가지 원인보다 스트레스, 호르몬의 변화, 유전, 외부 환경 등 다양한 요인들이 복합적으로 작용한다고 여겨지고 있다. Propionibacterium acnes (P. acnes)는 여드름을 유발하는 균으로 모낭 내에 상주하여 피지의 중성지방을 분해하고 유리 지방산을 형성하여 모낭 내 염증을 유발한다. 따라서 피지의 생성 증가는 P. acnes의 생존에 좋은 영향을 주고 피부에서 염증반응을 유발하는 monocytic cell의 활성화와 염증성 사이토카인(pro-inflammatory cytokine)의 증가를 유발한다. 따라서 여드름 치료를 위해서는 P. acnes의 증식 억제 및 염증반응을 최소화하는 것이 중요하다. 본 논문에서는 유칼립투스(Eucalyptus globules) 추출물이 P. acnes에 의한 염증반응에 나타내는 효과를 확인하고자 하였다. 유칼립투스 추출물 처리는 P. acnes가 유도하는 염증 매개자로 알려진 $TNF-{\alpha}$, $IL-1{\beta}$, IL-2와 인플라마좀 복합체인 NLRP3의 유전자 발현을 효과적으로 감소시키는 것을 확인하였다. 뿐만 아니라 염증성 사이토카인의 유전자 발현에 중요하다고 알려진 전사인자(transcription factors) $NF-{\kappa}B$와 NFAT의 활성 역시 유칼립투스 추출물을 처리하였을 때 감소하는 것을 알 수 있었다. 따라서 본 논문을 통해 유칼립투스 추출물이 P. acnes에 의해 초래되는 여드름의 치료 보조제로 사용될 수 있으며, 천연 추출물의 사용이 항생제 장기 복용으로 인해 유발되는 항생제 내성을 해결하는 좋은 대안이 될 것이라고 예상할 수 있다.