• 대한임상검사과학회지
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• 제50권2호
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• pp.136-143
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• 2018

심근부담률은 심근산소소비량을 간접적으로 측정하는 지표로 심박수와 수축기 혈압의 곱으로 나타내며, 심근이 받는 부담을 나타낸다. 본 연구는 한국성인을 대상으로 트레드밀 운동부하 검사시 대사증후군에 따른 심근부담률의 적정 수준을 제시함으로써 대사증후군 유병률을 낮추기 위한 심근부담률의 목표치를 설정하여 그 기준을 제시하고자 하였다. 대사증후군 진단은 National Cholesterol Education Program (NCEP)의 Adult Treatment Panel (ATP) III에서 제시한 5가지 진단기준 중 3개 이상 충족하는 경우 대사증후군 진단군(MetS, N=25), 1~2개의 기준에 해당하는 경우를 대사증후군 전단계군(Pre-MetS, N=106), 5개의 진단기준에 해당하지 않는 경우는 대사증후군 위험요인이 없는군(Non-MetS, N=65)으로 분류하였다. 운동부하검사는 Bruce 프로토콜에 따라 시행하였다. 심근부담률은(심박수${\times}$수축기 혈압)${\div}1,000$으로 구하였다. 본 연구결과 대사증후군 진단군에서 도달한 일량이 낮음에도 불구하고 최대 수축기 혈압이 높은 것으로 나타났다. 또한 대사증후군에 따른 운동부하 검사시 심근부담률의 최적 임계점은 운동부하검사 1단계에서는 $12.56mmHg{\times}beats/min{\times}10^{-3}$, 운동부하검사 2단계는 $16.94mmHg{\times}beats/min{\times}10^{-3}$, 운동부하검사 3단계에서는 $21.11mmHg{\times}beats/min{\times}10^{-3}$로 나타났다.

• 한국산업융합학회 논문집
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• 제25권3호
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• pp.357-363
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• 2022

In this study, in order to develop an non-slip metal grating, the stability of the grating according to the span of the grating and the gap and height of the bearing bar was evaluated. The optimal shape design of the grating was performed using the results of determining the stability of the grating. The purpose of this study is to determine the stability according to the spacing and height of the bearing bar by applying the design pressure at the design stage to develop the anti-skid grating, and to design the optimal shape for cost reduction. In the optimal design, the target variable was set as the mass, and the optimal design of the grating was performed based on about 20%. Regardless of the height of the bearing bar of the grating, the stress and deformation of the span and the grating showed a proportional tendency to each other, and it was found that the stress decreased as the height of the bearing bar increased. Based on the structural analysis results, an optimal design was performed using mass as the objective variable, and the existing 2mm thickness was changed to 1.6mm, reducing the mass by about 19%. The stress increased by about 4.4% compared to the maximum stress of the existing grating, but the minimum safety factor was 3.1, indicating that the optimally designed grating was stable.

• 한국환경과학회지
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• 제21권5호
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• pp.613-622
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• 2012

A pilot-scale pulse-jet bagfilter was designed, built and tested for the effects of four operating conditions (filtration velocity, inlet dust concentration, pulse pressure, and pulse interval time) on the total system pressure drop, using coke dust from a steel mill factory. Two models were used to predict the total pressure drop according to the operating conditions. These model parameters were estimated from the 180 experimental data points. The empirical model (EM) with filtration velocity, areal density, inlet dust concentration, pulse interval time and pulse pressure shows the best correlation coefficient (R=0.971) between experimental data and model predictions. The empirical model was used as it showed higher correlation coefficient (R=0.971) compared to that of the Multivariate linear regression(MLR) (R=0.961). The minimum pulse pressure predicted by empirical model (EM) was 5kg/$cm^2$.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.578-595
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• 2020

Submarine pressure hulls must withstand high hydraulic pressure and be free of defects. To improve the precision of defect detection, we herein examined different probes for optimal defect assessment by applying the Phased Array Ultrasonic Testing (PAUT) method. Two sets of probe design parameters were selected by considering pressure hull characteristics and analyzed through modeling. PAUT probes were applied, and defect assessment results were compared based on ultrasonic signals of various simulated defects in specimens designed to be the same as actual pressure hulls. The final selected design parameters for the submarine probe, which were designed to minimize the grating lobe of wave interference effect and improve the ultrasonic resolution of pressure hull welds, were identified through the experiment. The improvement in the probe's ability to detect defects in a pressure hull was verified. Furthermore, the accuracy of defect length measurement was improved, enhancing the applicability of the technique.

• 한국초전도ㆍ저온공학회논문지
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• 제8권3호
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• pp.5-8
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• 2006

The effect of annealing time in Metal Organic Deposition(MOD) method was investigated at reduced total pressure. As the total annealing pressure was reduced, the growth rate of YBCO films increased from 0.14nm/sec at atmospheric pressure to 4.2nm/sec at 1 Torr. For the total pres sure of 700, 500, 300, 100, and 1 Torr, the optimal annealing times of 60, 40, 20, 10, 2minutes were found in our experimental conditions. When the an nealing time was short, poor crystallinity or un-reacted phase was obtained. Also, the degradation of YBCO films occurred when exposed longer to the humid ambient at the high annealing temperature. The reduced pressure was found effective to in crease the growth rate and to control the pore size of the YBCO films in MOD method. A fast growth of MOD-YBCO films was realized with high critical current density over $1MA/cm^2$ using reduced pressure annealing. Large pores, usually observed at atmospheric pressure in MOD method, disappeared and also, the number of pores was reduced.

• 한국터널지하공간학회 논문집
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• 제14권1호
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• pp.37-53
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• 2012

터널 설계 시 사용되는 지반 물성치는 불확실성을 내포한다. 본 연구에서는 최적의 지반물성치를 찾기 위해 터널 계측자료를 활용하여 MATLAB 프로그램의 인공신경망 분석 기능을 이용한 역해석을 수행하였다. 터널 내공변위에 많은 영향을 주는 탄성계수와 측압계수를 변화시켜 총 81개의 학습자료를 구축하였다. 최적의 학습모델을 구축하기 위해 은닉층 수와 노드(node) 수 및 학습율과 관성항을 변화시켜가며 매개변수 연구를 수행하였다. 한편 최적의 학습모델은 평균제곱오차(MSE, Mean Squared Error)와 결정계수($R^2$)를 비교하여 선정되었고, 이를 이용하여 정확한 지층의 탄성계수와 측압계수를 찾았다. 향후 주어진 지반조건에서 최적의 터널 지보패턴을 결정하는 등의 목적으로 본 연구에서 제시된 방법이 적용될 수 있을 것으로 기대된다.

• Membrane and Water Treatment
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• 제11권4호
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• pp.303-312
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• 2020

This study aims to investigate at a laboratory scale fluorides removal from an industrial wastewater having excessive F^- concentration through a hybrid process combining neutralization and membrane separation. For the membrane separation operation, both Reverse Osmosis (RO) and Nanofiltration (NF) were investigated and confronted. The optimized neutralization step with hydrated lime allowed reaching fluoride removal rates of 99.1± 0.4 %. To simulate continuous process, consecutive batch treatments with full recirculation of membrane process brines were conducted. Despite the relatively high super saturations with respect to CaF₂, no membrane cloaking was observed. The RO polishing treatment allowed decreasing the permeate fluoride concentration to 0.9± 0.3 mg/L with a fluoride rejection rate of 93± 2% at the optimal transmembrane pressure of around 100 psi. When NF membrane was used to treat neutralization filtrate, the permeate fluoride concentration dropped to 1.1± 0.4 mg/L with a fluoride rejection rate of 88± 5% at the optimal pressure of around 80 psi. Thus, with respect to RO, NF allowed roughly 20% decrease of the driving pressure at the expense of only 5% drop of rejection rate. Both NF and RO permeates at optimal operating transmembrane pressures respect environmental regulations for reject streams discharge into the environment.

• 대한기계학회논문집A
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• 제40권10호
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• pp.879-886
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• 2016

CNG 압력용기 제조를 위한 딥드로잉 공정에 사용되는 트랙트릭스 다이는 블랭크 홀더 없이 성형을 가능하게 한다. 기존의 연구에서는 D.D.I. 공정의 1차 딥드로잉 공정에 트랙트릭스 곡선을 다이에 적용하였을 뿐, 다이의 수명향상 및 제조원가 절감을 위한 형상 최적화에 관한 연구는 전무한 실정이다. 이에 본 논문에서는 트랙트릭스 곡선의 점근선 이동을 통하여 다이의 높이에 따른 딥드로잉 공정의 유한요소해석을 수행하였다. 또한 펀치의 성형하중에 따른 다이 응력집중부의 Von-Mises 응력을 분석하여 최적의 트랙트릭스 다이 형상을 제시하였다.

• 센서학회지
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• 제24권1호
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• pp.10-14
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• 2015

This paper reports the results of a study on the optimization of the etching profile, which is an important factor in deep-reactive-ion etching (DRIE), i.e., dry etching. Dry etching is the key processing step necessary for the development of the Internet of Things (IoT) and various microelectromechanical sensors (MEMS). Large-area etching (open area > 20%) under a high-frequency (HF) condition with nonoptimized processing parameters results in damage to the etched sidewall. Therefore, in this study, optimization was performed under a low-frequency (LF) condition. The HF method, which is typically used for through-silicon via (TSV) technology, applies a high etch rate and cannot be easily adapted to processes sensitive to sidewall damage. The optimal etching profile was determined by controlling various parameters for the DRIE of a large Si wafer area (open area > 20%). The optimal processing condition was derived after establishing the correlations of etch rate, uniformity, and sidewall damage on a 6-in Si wafer to the parameters of coil power, run pressure, platen power for passivation etching, and $SF_6$ gas flow rate. The processing-parameter-dependent results of the experiments performed for optimization of the etching profile in terms of etch rate, uniformity, and sidewall damage in the case of large Si area etching can be summarized as follows. When LF is applied, the platen power, coil power, and $SF_6$ should be low, whereas the run pressure has little effect on the etching performance. Under the optimal LF condition of 380 Hz, the platen power, coil power, and $SF_6$ were set at 115W, 3500W, and 700 sccm, respectively. In addition, the aforementioned standard recipe was applied as follows: run pressure of 4 Pa, $C_4F_8$ content of 400 sccm, and a gas exchange interval of $SF_6/C_4F_8=2s/3s$.

• 설비공학논문집
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• 제17권6호
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• pp.544-551
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• 2005

The flow characteristics have been numerically investigated for various shapes of the diffuser/nozzles which are used for a valveless micro-pump. The important parameters considered in this study are the throat width ($15\~120\mu$m), the taper angle ($3.15\~25.2^{\circ}$), and the diffuser length ( $600\~4,800\mu$m), and the size of the middle chamber ($1\~16mm^2$). To find the optimal values for these parameters, steady state calculations have been performed assuming the constant pressure difference between the inlet and exit of the flow For the taper angle and the throat width, it is found that there exists an optimum at which the net flow rate is the greatest. The optimal taper angle is in the range of $10\~20^{\circ}$ for all the pressure differences; and the throat width indicates an optimal value near $75\mu$m for the case of 35 kPa pressure difference. The net flow rate is also influenced by the size of the middle chamber. With decreasing chamber size, the net flow rate is reduced because of the interference between two streams flowing into the middle chamber. The unsteady pulsating flow characteristics for a micro-pump with a given diffuser/nozzle shape have been also investigated to show the validity of the steady state parametric study.