• 대한기계학회논문집B
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• 제24권7호
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• pp.916-923
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• 2000

Numerical study of three-dimensional turbulent flow in a forward curved centrifugal fan is presented. Standard $k-{\varepsilon}$ turbulence model and non-orthogonal curvilinear coordinates arc used to consider the turbulent flow field and complex geometry. Finite Volume approach is adopted for discretization scheme and structured grid system is used to help convergence. Multiblock grid system is used for flow field and divided into five domains that are inlet, outlet, impeller, tip clearance and scroll. It is assumed that the flow field is steady and incompressible. These numerical results are compared with the experimental data inside a rotor and at the fan outlet. Most important flow features are captured through this numerical approach. Finally details of flow field inside a fan are described and analyzed.

• Multiscale and Multiphysics Mechanics
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• 제1권3호
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• pp.261-270
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• 2016

The longitudinal velocity (forward speed) having significant importance in proper running of railway wheelset on track, depends greatly upon the adhesion ratio and creep analysis by implementation of suitable dynamic system on contamination. The wet track condition causes slip and slide of vehicle on railway tracking, whereas high speed may also increase slip and skidding to severe wear and deterioration of mechanical parts. The basic aim of this research is to design appropriate model aimed estimator that can be used to control railway vehicle forward velocity to avoid slip. For the filtration of disturbance procured during running of vehicle, the kalman filter is applied to estimate the actual signal on preferered samples of creep co-efficient for observing the applied attitude of noise. Thus error level is detected on higher and lower co-efficient of creep to analyze adhesion to avoid slip and sliding. The skidding is usually occurred due to higher forward speed owing to procured disturbance. This paper guides to minimize the noise and error based upon creep coefficient.

• Journal of Advanced Marine Engineering and Technology
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• 제20권3호
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• pp.286-286
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• 1996

A neural predictive tracking system for the control of structure-unknown dynamic system is presented. The control system comprises a neural network modelling mechanism for the the forward and inverse dynamics of a plant to be controlled, a feedforward controller, feedback controller, and an error prediction mechanism. The feedforward controller, a neural network model of the inverse dynamics, generates feedforward control signal to the plant. The feedback control signal is produced by the error prediction mechanism. The error predictor adopts the neural network models of the forward and inverse dynamics. Simulation results are presented to demonstrate the applicability of the proposed scheme to predictive tracking control problems.

• Journal of Advanced Marine Engineering and Technology
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• 제20권3호
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• pp.154-161
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• 1996

A neural predictive tracking system for the control of structure-unknown dynamic system is presented. The control system comprises a neural network modelling mechanism for the the forward and inverse dynamics of a plant to be controlled, a feedforward controller, feedback controller, and an error prediction mechanism. The feedforward controller, a neural network model of the inverse dynamics, generates feedforward control signal to the plant. The feedback control signal is produced by the error prediction mechanism. The error predictor adopts the neural network models of the forward and inverse dynamics. Simulation results are presented to demonstrate the applicability of the proposed scheme to predictive tracking control problems.

• Physical Therapy Rehabilitation Science
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• 제10권3호
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• pp.251-256
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• 2021

Objective: The forward head posture (FHP) is strongly related to the rounded shoulder posture (RSP), which is associated with shoulder pain. Design: Observational cross sectional study design Methods: A total of 37 were enrolled in the study, 22 individuals with FHP(experimental group) and 15 healthy adults(control group). Correlation with differences between groups was analysed through craniovertebral angle (CVA) representing FHP for both groups, neck disability index (NDI) indicating neck pain, disability of the arm, shoulder and hand (DASH) indicating shoulder pain. Results: There was a significant difference in the results of CVA, NDI, and DASH in FHP and healthy adults (p<0.05). Significant correlations were found between DASH and CVA in FHP participants (r = -0.656, p = 0.001). Also, in the regression analysis results of DASH and CVA, the regression model was found to be suitable and the variation in DASH could be explained by 43% (F = 15.118, p = 0.001). Conclusions: Shoulder pain and neck discomfort are potentially related, and an increase in shoulder pain can increase FHP.

• 전자공학회논문지A
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• 제32A권8호
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• pp.64-70
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• 1995

A new DC drain-current model of GaAs MESFET with improved accuracy is proposed in this paper. The proposed model includes the decrease of current slope according to gate voltages. It is possible to represent a transconductance compression using the proposed model. It shows improved transconductance and output resistance in accuracy from the forward biased gate region to near the cutoff region. The wquaer error of saturation current is decreased by 46% compared with Statz model. The proposed model can be useful for the simulation of large-signal operation and harmonic distortion.

• 한국운동역학회지
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• 제18권1호
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• pp.203-212
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• 2008

본 연구의 목적은 자진모리장단에 맞추어 3단 디딤새동작의 적합한 모델을 제시하고 이상적인 발 디딤새 동작수행을 위한 자료제공을 목적으로 하였다. 신체중심의 위치변화는 발을 내딛는 순간 신체중심의 높이를 낮추고 발의교차 전진시 전방으로 향하는 직선운동을 수직운동으로 전환하여 동작의 안정성을 유지하며, 좌 우 흔들림 없이 이동하는 것으로 나타났다. 신체중심에 대한 속도변화는 수평방향으로 발을 딛는 순간 신체유동을 작게 하고 전방으로 급격한 이동을 통제하여 안정된 동작을 취하고, 슬관절과 족관절을 수직으로 들어 올려 종골이 지면에 닿을 때 무게중심의 속도가 수평방향으로 빠르게 전진하지 못하게 하는 것으로 나타났다. 관절의 각도변화는 하퇴의 과신전을 막기 위해 고관절은 신전시키고 슬관절은 굴곡 시켜 동작의 안정성을 확보하여 굴곡과 신전이 원활히 이루어지며, 족관절은 중족 에서 발바닥 전체로 무게중심이동시 좌측 발은 배측굴곡을 이룰 때 안정적인 동작이 이루어지는 것으로 나타났다.

• 정보보호학회논문지
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• 제17권5호
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• pp.27-38
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• 2007

전자우편을 사용할 때 고려해야 하는 중요한 보안 이슈 중 하나는 사용자 프라이버시이다. 현재 PGP(Pretty Good Privacy), S/MIME(Secure/Multipurpose Internet Mail Extension) 등의 여러 가지 전자우편 보안 프로토콜이 제안되어 사용되고 있으나, 이들 프로토콜은 안전성을 향상시킬 수 있는 요구사항인 전방향 안전성을 보장하지 못한다. 최근 이 특성을 만족하기 위한 전자우편 프로토콜들이 제안되었으나 실용성과효율성 측면에서 개선이 필요하고, 일부 프로토콜은 실질적으로 완전한 전방향 안전성을 제공하고 있지 못하다. 이 논문에서는 실용성을 갖춘 효율적인 전자우편 보안 프로토콜을 제안한다. 제안하는 프로토콜은 기존의 전자우편 시스템에 영향을 주지 않는 실용적인 모델을 사용하며, 타원곡선 기반의 signcryption 기법을 사용하여 효율적으로 메시지를 인증한다. 추가적으로, 다수의 사람에게 전자우편을 전송할 때에도 적용할 수 있다는 장점이 있다.

• 한국환경과학회지
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• 제9권5호
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• pp.385-388
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• 2000

Visibility reduction is a barometer of air pollution which people can notice easily. First of all we need to measure quantified visibility continuously in order to examine visibility reduction. Prevailing visibility is not practical to measure visibility depending on observer's expertness. Scattering visibility using Forward Scattering Meter(Belfort Visibility Sensor 6230) has been measured at Kwangan-Dong in Pusan and analysed since July 1998. According to the analysis the correlation coefficient(R) between prevailing visibility and scattering visibility was 0.7235. The visibility appeared that each frequency of poor visibility(under 6km) and good visibility(over 25km) was 10.6%, 9.7% on summertime in Pusan and the visibility range from 10km to 20km ranked high frequency as a half of whole ranges. The order of correlation coefficients between visibility an air pollutants are ranking CO. PM10 and NO2 that values are 0.5878, 0.5369,l 0.5284 respectively. In meteorolgical factor the case of poor visibility presented more weakly wind speed and higher relative humidity than the case of good visibility. The correlation coefficient between calculated visibility of multiple linear regression model and observed visibility was 0.7215. But the trend of calculated and observed visibility variation was similar with the exception of several good visibility cases.

• Journal of the Korean Data and Information Science Society
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• 제21권5호
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• pp.901-908
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• 2010

다중회귀모형에서 변수선택법 중에서 전진선택과 후진제거의 과정을 기하학적으로 표현하는 그래픽적 방법을 제안한다. 반지름이 1인 반원의 제1사분면에는 전진선택 과정을, 제2사분면에는 후진제거 과정을 표현한다. 각 단계에서 회귀제곱합을 벡터로 표현하고, 추가제곱합 또는 부분결정계수를 벡터 사이의 각도로 나타내며 벡터의 끝을 연결할 때 통계적으로 유의하면 점선으로 표현하여 부분가설검정의 통계적 분석결과를 인지할 수 있도록 작성한다. 이 방법을 이용하면 전진선택과 후진제거 방법에 의한 최종모형을 비교 분석하고 전체적으로 모형의 적합도를 파악할 수 있다.