• 동력기계공학회지
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• 제3권4호
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• pp.22-27
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• 1999

Single phase heat transfer coefficients were measured for turbulent water flow in a plate & shell heat exchangers by using Wilson plot method. An experiment for counterflow heat exchange between the plate and shell was performed. The shell side heat transfer resistance was varied and the overall heat transfer coefficients were measured. The single-phase heat transfer coefficients in a plate side were obtained by Wilson plot method. Single-phase heat transfer correlations based on projected heat transfer area have been proposed for a plate & shell heat exchanger.

• 한국재료학회지
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• 제26권11호
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• pp.644-648
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• 2016

In order to examine how the solid-liquid interface responds to temperature variation depending on the materials characteristics, i.e. faceted phase or nonfaceted phase, the moving solid-liquid interface of transparent organic material, as a model substance for metallic materials (pivalic acid, camphene, salol, and camphor-50wt% naphthalene) was observed in-situ. Plots of the interface movement distance against time were obtained. The solid-liquid interface of the nonfaceted phase is atomically rough; it migrates in continuous mode, giving smooth curves of the distance-time plot. This is the case for pivalic acid and camphene. It was expected that the faceted phases would show different types of curves of the distance-time plot because of the atomically smooth solid-liquid interface. However, salol (faceted phase) shows a curve of the distance-time plot as smooth as that of the nonfaceted phases. This indicates that the solid-liquid interface of salol migrates as continuously as that of the nonfaceted phases. This is in contrast with the case of naphthalene, one of the faceted phases, for which the solid-liquid interface migrates in "stop and go" mode, giving a stepwise curve of the distance-time plot.

• 설비공학논문집
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• 제10권4호
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• pp.423-430
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• 1998

Single phase heat transfer coefficients were measured for turbulent water flow in a micro-fin tube by using Wilson plot technique. An experiment for counterflow heat exchange between the micro-fin tube and its outer annulus passage was performed. The annulus side heat transfer resistance was varied and the overall heat transfer coefficients were measured. The single-phase heat transfer coefficients in a micro-fin tube were obtained by Wilson plot technique. Nusselt numbers based on the real heat transfer area and the nominal area were about 35% and 50% larger than those for smooth tube respectively Also, single-phase heat transfer correlations based on real heat transfer area and nominal area have been proposed for a micro-fin tube.

• 설비공학논문집
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• 제12권4호
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• pp.422-429
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• 2000

Plate and shell heat exchanger(P&SHE) is widely applied as evaporators or condensers in the refrigeration and air conditioning systems for their high efficiency and compactness. In order to set up the database for the design of the P&SHE, heat transfer and pressure drop characteristics for single phase flow of water in a plate & shell heat exchanger are experimentally investigated in this study. Single phase heat transfer coefficients were measured for turbulent water flow in a plate and shell heat exchangers by Wilson plot method. The shell side heat transfer resistance was varied and the overall heat transfer coefficients were measured. The single-phase heat transfer coefficients in a plate side were obtained by Wilson plot method. Single-phase heat transfer correlations based on projected heat transfer area and friction factor correlations have been proposed for single phase flow in a plate and shell heat exchanger.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.799-805
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• 1996

In many cases, the magnetic farce model is linearized at the origin in designing the controller of a magnetic bearing system. However. this linear assumption is violated by the unmodeled nonlinear effect such as sensor dislocation and backup bearing dislocation. Therefore, a direct probe into the nonlinear magnetic force model in an active magnetic bearing system is necessary. To analyze the nonlinear magnetic force model of a magnetic bearing system, phase plot analysis which is to plot the numerical solution of the nonlinear equation in several initial points in the interested region is applied. Phase plot analysis is used to observe a nonlinear dynamic system qualitatively (not quantitatively). With this method, we can get much useful information of the nonlinear system. Among this information, a bifurcation graph that represents stability and locations of fixed points is essential. From the bifurcation graph, a stability criterion of magnetic bearing system is derived.

• Smart Structures and Systems
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• 제11권3호
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• pp.299-314
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• 2013

This paper presents a nonlinear time series analysis technique for evaluating machine defect severity, based on the Recurrence Plot (RP) entropy. The RP entropy is calculated from the probability distribution of the diagonal line length in the recurrence plot, which graphically depicts a system's dynamics and provides a global picture of the autocorrelation in a time series over all available time-scales. Results of experimental studies conducted on a spindle-bearing test bed have demonstrated that, as the working condition of the bearing deteriorates due to the initiation and/or progression of structural damages, the frequency information contained in the vibration signal becomes increasingly complex, leading to the increase of the RP entropy. As a result, RP entropy can serve as an effective indicator for defect severity assessment of rolling bearings.

• 한국인터넷방송통신학회논문지
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• 제19권4호
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• pp.99-104
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• 2019

위상응답에 의해 이차전지의 SOH를 측정하기 위하여 유도성 소자의 사용을 제안하였다. 이차전지의 Randles 등가 모델에 대하여 모의 실험한 결과 부하로 사용된 유도성 소자는 고역응답특성을 가지며 최대 위상응답주파수 대역을 증가시킨다. 이차전지에 대한 위상응답특성이 잘 나타나는 주파수대역을 획득하기 위해 유도성 소자의 인덕턴스 값을 변화시켜 위상응답을 측정하였으며, 631Hz에서 최대 위상응답을 보이는 33uH의 유도성 소자를 사용하였다. 각각 다른 SOH를 가진 이차전지에 대하여 위상응답을 측정한 결과 SOH 20% 당 위상응답은 약 $3.7^{\circ}$의 차이를 보여 유도성 소자에 대한 위상측정에 의해 이차전지의 SOH를 진단할 수 있음을 보였다.

• 한국정보통신학회논문지
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• 제26권11호
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• pp.1686-1696
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• 2022

본 논문에서 소개하는 페이저도에 의한 임피던스 정합회로 설계는 회로이론의 임피던스 삼각도에 기초한다. 정합회로 설계에 주어진 값들을 이용하여 페이저 도형의 작도를 통하여 설계하는 기법이다. 설계 패턴은 L형, 역L형, T형, 𝜋형을 기본으로, 미지의 리액턴스 소자를 페이저 도형을 통하여 결정한다. 본 논문에서는 입력과 출력포트가 순저항인 경우와 리액턴스를 갖는 경우의 몇 가지 사례에 대하여 설계하고 이를 직병렬 등가변환에 의하여 설계값을 검증하여 정합이 이루어짐을 확인하였다. 본 설계 기법은 입출력 위상이나 크기를 바로 파악할 수 있어 설계의 변경과 적용이 신속하여 주로 낮은 주파수 대역에서 적용이 기대된다.

• 대한산업공학회지
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• 제36권3호
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• pp.154-163
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• 2010

Process monitoring of output variables affecting final performance have been mainly executed in semiconductor manufacturing process. However, even earlier detection of causes of output variation cannot completely prevent yield loss because a number of wafers after detecting them must be re-processed or cast away. Semiconductor manufacturers have put more attention toward monitoring process inputs to prevent yield loss by early detecting change-point of the process. In the paper, we propose the method to efficiently monitor functional input variables in multi-phase semiconductor manufacturing process. Measured input variables in the multi-phase process tend to be of functional structured form. After data pre-processing for these functional input data, change-point analysis is practiced to the pre-processed data set. If process variation occurs, key variables affecting process variation are selected using contribution plot for monitoring efficiency. To evaluate the propriety of proposed monitoring method, we used real data set in semiconductor manufacturing process. The experiment shows that the proposed method has better performance than previous output monitoring method in terms of fault detection and process monitoring.

• 한국세라믹학회지
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• 제17권1호
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• pp.20-26
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• 1980

The crystallization behaviors of slag-based glass in $CaO-MgO-Al_2O_3-SiO_2(-Na_2O)$ system have been studied. The mother glass containing 16.50 CaO, 7.50MgO, 19.70Al2O3, 50.80SiO3 and 2.09wt% $Na_2O$ was prepared by using Korean domestic raw materials such as granulated slag, serpentine, sea sand and etc. The glass-ceramics composed of major crystalline phase diopside was produced by the heat treatment in a temperature range from 850$^{\circ}$ to 9$25^{\circ}C$ for 0-6hr. The composition and morphology of diopside phase formed in the system were examined by X-ray diffraction analysis and electron microscopy. The kinetic measurements such as J.M. A plot and Arrhenius plot indicated that the process of nucleation of the initially formed diopside phase could be described from the view point of instantaneous nucleation. It was also demonstrated that the linear crystal growth of diopside phase was proceeded by short range diffusion of $Mg^{2+}$ and $Ca^{2+}$ ion. The microstructures of the resulting glass-ceramics were consisted of leafroidal shaped crystalline aggregations.