• 응용통계연구
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• 제33권4호
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• pp.409-420
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• 2020

사업체조사에서는 흔히 수정절사법이 사용되며 이 방법을 사용함으로써 표본의 수를 줄이면서도 추정의 정확성을 향상 시킬 수 있다. 그러나 전수층의 무응답률은 크게 높아지고 있으며 예비표본을 이용한 표본대체가 불가능하기 때문에 전수층에서 발생한 무응답은 추정의 정확성을 크게 떨어뜨리고 있다. 특히 무응답이 관심변수에 영향을 받는 경우에는 편향이 발생할 가능성이 매우 높기 때문에 이를 적절히 처리하는 것은 매우 중요하다. 본 연구에서는 전수층에서 발생한 무응답을 적절히 처리하는 방법의 하나로 편향보정 추정법을 제안하였다. 특히 Chung과 Shin(2020)에서 제안한 편향보정 추정량을 전수층 편향보정에 적용하였으며 전수층이라는 특수한 경우에 맞는 새로운 추정 방법을 제안하였다. 또한 모의실험을 통해 제안된 방법의 우수성을 살펴보았으며 실제 자료 분석을 실시하여 본 논문에서 제안한 방법의 우수성을 확인하였다.

• Journal of the Korean Data Analysis Society
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• 제20권6호
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• pp.2953-2966
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• 2018

주택가격은 거시경제상황을 나타내는 다양한 변수들과 밀접한 관계를 지니고 있다. 다수의 선행연구에서는 경제상황 변화 하에서의 주택가격 행태나 여러 변수들과의 관계성에 초점을 맞추고 있다. 본 논문에서는 선행연구를 참고하되 데이터에 근거한 새로운 시각의 실증분석을 실시하고자 하였다. 주택가격에 미치는 잠재적 영향요인들 중 정책금리에 초점을 맞추고 금리충격에 대한 여타 주요 변수들의 비선형적 반응 행태를 분석하였다. 데이터마이닝 기법 중 하나인 랜덤 포레스트 알고리즘을 이용하여 선행연구에서 제시되었던 거시경제변수들의 변수 중요도 점수를 산출하였다. 이 과정을 통해 변수를 선택한 뒤, 비선형성을 포착할 수 있는 모형을 사용하여 충격반응을 산출하였다. 동 모형에 따르면 주택가격의 경우에 있어서 금리 인상 시에만 충격반응이 유의미하게 나타났다. 특히 기존 전통적 VAR(vector autoregression) 방법론에서 포착하지 못한 비선형적 특징에 기인하여 금리 인상 충격의 크기가 커질 경우 그 효과가 정률적으로만 증가하는 것이 아니라 그 이상 증폭될 수 있다는 분석 결과를 얻었다. 이러한 파급효과의 비선형성, 비대칭성은 정책 수단으로서의 금리를 보다 신중한 시각에서 접근해야 함을 의미한다고 하겠다.

• 응용통계연구
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• 제34권6호
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• pp.923-936
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• 2021

표본조사에서는 다수의 무응답이 발생하며 이를 적절히 처리하는 다양한 방법이 개발되었다. 특히 무응답이 관심변수에 영향을 받고 이로 인해 발생한 편향은 추정의 정확성을 크게 떨어뜨리며 무응답 처리를 어렵게 한다. 최근 Chung과 Shin (2017, 2020)은 알려진 모수적 초모집단 모형과 응답률 모형을 이용하여 추정의 정확성을 향상한 추정량을 제안하였다. 본 연구에서는 초모집단 모형의 형태를 일반화하여 비모수적 함수 형태를 설정한 후 이를 기반으로 얻어진 편향을 적절히 처리한 편향 보정 평균추정량을 제안하였다. 모의실험을 통해 본 연구에서 제안한 방법의 우수성을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.143-147
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• 1998

In this study, nonlinear stiffness characteristics of a discharge valve in a small hermetic compressor was considered. It was approximated, with piecewise-linearity, and cubic or quintic nonlinearity by the static load-displacement experimental results. Based on the fluid-structure interaction effects and mass flow rate, the derived 1-DOF equation of motion for the valve model was analyzed. Finally, the dynamic response of the discharge valve was studied with parameters such as the ratio of the running frequency of the compressor to the linear natural frequency of the valve.

• Advances in environmental research
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• 제3권3호
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• pp.231-251
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• 2014

The present study examines the phosphate adsorption potential and behavior of mixture of Ground Burnt Patties (GBP), a solid waste generated from cooking fuel used in earthen stoves and Red Soil (RS), a natural substance in fixed bed column mode operation. The characterization of adsorbent was done by Proton Induced X-ray Emission (PIXE), and Proton Induced ${\gamma}$-ray Emission (PIGE) methods. The FTIR spectroscopy of spent adsorbent reveals the presence of absorbance peak at $1127cm^{-1}$ which appears due to P = O stretching, thus confirming phosphate adsorption. The effects of bed height (10, 15 and 20 cm), flow rate (2.5, 5 and 7.5 mL/min) and initial phosphate concentration (5 and 15 mg/L) on breakthrough curves were explored. Both the breakthrough and exhaustion time increased with increase in bed depth, decrease in flow rate and influent concentration. Thomas model, Yoon-Nelson model and Modified Dose Response model were used to fit the column adsorption data using nonlinear regression analysis while Bed Depth Service Time model followed linear regression analysis under different experimental condition to evaluate model parameters that are useful in scale up of the process. The values of correlation coefficient ($R^2$) and the Sum of Square Error (SSE) revealed the Modified Dose Response model as the best fitted model to the experimental data. The adsorbent mixture responded effectively to the desorption and reusability experiment. The results of this finding advocated that mixture of GBP and RS can be used as a low cost, highly efficient adsorbent for phosphate removal from aqueous solution.

• 대한약리학회지
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• 제31권2호
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• pp.251-259
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• 1995

Pharmacokinetics and pharmacodynamics of metoprolol, a selective beta-l blocker, were examined for 360 minutes after intravenous bolus administration of metoprolol to 6 dogs. Plasma concentration and excreted amount in the urine metoprolol were measured by liquid chromatography with fluorescence detection. PR interval and heart rate were measured by ECG monitoring. Blood pressure was monitored through intraarterial catheter in femoral artery and cardiac output by thermodilution method using Swan-Ganz catheter. To analyze the effect site concentration-response relationship, plasma concentration and pharmacological effects were simultaneously fitted to a two pharmacokinetic compartment linked to pharmacodynamic model with NONLIN program. Results are as follows. 1) The plasma concentration of metoprolol after intrvenous injection decreased biexponentially. The terminal half-life estimated was $1.33{\pm}0.40$ hours and the volume of distribution at steady state (Vdss) and the total body clearance were $1.04{\pm}0.4\;L/kg,\;6.55{\pm}2.21\;L/hr$, respectively. The central compartment volume of distribution and peripheral compartment volume of distribution were $0.35{\pm}0.14L/kg\;and\;0.69{\pm}0.34L/kg$. The renal clearance and intercompartment clearance were $0.53{\pm}0.25\;L/min\;and\;0.35{\pm}0.19\;L/min$. 2) Simulated biophase concentration-response curve shows hyperbolic relationship and the estimated concentration-effect relationship was best explained by Emax model when the prolongation of PR interval and the reduction of the heart rate were used as pharmacodynamic parameters. Emax and EC50 were estimated to be $26.3{\pm}4.7\;msec\;and\;88.8{\pm}82.3\;g/ml$ for PR interval, and $48.7{\pm}18.8\;beats/min\;and\;113.5{\pm}78.7\;ng/ml$ for heart rate, respectively. 3) The changes of cardiac output-effect site concentration relationship was best fitted by a linear model and the slope of the relationship was $0.005{\pm}0.003$. Diastolic blood pressure-effect site concentration relationship was also explained by the linear model and the slope of the relationship was $0.038{\pm}0.034$.

• 한국항공운항학회지
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• 제21권4호
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• pp.34-40
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• 2013

Attitude command response type required for enhanced handling qualities of helicopter can be implemented by mechanical automatic flight control system with SAS actuators which have limited authorities. However, the early saturation of SAS actuator hinders the helicopter from following the attitude command for large stick command. Auto-trim controller can delay SAS actuator's saturation by utilizing trim actuators and allows the attitude command response type for larger stick command. This paper describes the control law for limited authority system of helicopter with auto-trim. Limited authority system is applied to BO-105 linear dynamic model and simulation is performed along with handling quality analysis.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1305-1308
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• 2003

A new technique is presented to construct a predictive model of plasma etch process. This was accomplished by combining a backpropagation neural network (BPNN) and a genetic algorithm (GA). The predictive model constructed in this way is referred to as a GA-BPNN. The GA played a role of controlling training factors simultaneously. The training factors to be optimized are the hidden neuron, training tolerance, initial weight magnitude, and two gradients of bipolar sigmoid and linear functions. Each etch response was optimized separately. The proposed scheme was evaluated with a set of experimental plasma etch data. The etch process was characterized by a $2^3$ full factorial experiment. The etch responses modeled are aluminum (A1) etch rate, silica profile angle, A1 selectivity, and dc bias. Additional test data were prepared to evaluate model appropriateness. The GA-BPNN was compared to a conventional BPNN. Compared to the BPNN, the GA-BPNN demonstrated an improvement of more than 20% for all etch responses. The improvement was significant in the case of A1 etch rate.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권2호
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• pp.82-90
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• 2003

The work presented here is a design and an implementation of PID control system to regulate a supply duct outlet air temperature in PEM (Personal Environment Module). In PEM, the air is heated to the required temperature while it flows through the supply duct without any mixing chamber. This makes the control of air temperature in PEM difficult. A simulation is done first to understand the relationship between a temperature distribution in working area, flow rate and the outlet air temperature of PEM. Then a linear dynamic model of heating process in PEM is derived. P, PD and PID type control systems, to provide the rapid response without overshoot and saturation in heater command voltage, are designed using a linear model obtained. Experimentally obtained data shows that the control system satisfies the design criteria and works properly in controlling the supply duct outlet air temperature.

• Advanced Composite Materials
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• 제17권1호
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• pp.57-73
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• 2008

The present paper focuses on experimental verification of the ply-by-ply basis inelastic analysis of multidirectional laminates. First of all, rate dependence of the tensile behavior of balanced symmetric cross-ply T800H/epoxy laminates with a $[0/90]_{3S}$ lay-up under off-axis loading conditions at $100^{\circ}C$ is examined. Uniaxial tension tests are performed on plain coupon specimens with various fiber orientations $[{\theta}/(90-{\theta})]_{3S}$ ($\theta$ = 0, 5, 15, 45 and $90^{\circ}C$) at two different strain rates (1.0 and 0.01%/min). The off-axis stress.strain curves exhibit marked nonlinearity for all the off-axis fiber orientations except for the on-axis fiber orientations $\theta$ = 0 and $90^{\circ}$, regardless of the strain rates. Strain rate has significant influences not only on the off-axis flow stress in the regime of nonlinear response but also on the apparent off-axis elastic modulus in the regime of initial linear response. A macromechanical constitutive model based on a ply viscoplasticity model and the classical laminated plate theory is applied to predictions of the rate-dependent off-axis nonlinear behavior of the cross-ply CFRP laminate. The material constants involved by the ply viscoplasticity model are identified on the basis of the experimental results on the unidirectional laminate of the same carbon/epoxy system. It is demonstrated that good agreements between the predicted and observed results are obtained by taking account of the fiber rotation induced by deformation as well as the rate dependence of the initial Young's moduli.