• 설비공학논문집
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• 제13권11호
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• pp.1125-1133
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• 2001

Since the surface temperature of the evaporating tube in an ammonia unit cooled is lower than the dew point of atmosphere, the moisture in the atmosphere condenses and the frost grows on the tube. The frost of liquid film decreases the heat transfer rate. The reliable analysis of the heat transfer is required for the prediction of the optimal design of the ammonia unit cooler. For the specific commercial model, the performance was numerical1y estimated for the variation of operating condition and geometric configuration. It is found that there exists an optimum range for the parameters such as mass flow rate of air and refrigerant, humidity, refrigerant quality, fin pitch, the number of step, the number of rows and the pattern of refrigerant path.

• 설비공학논문집
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• 제13권11호
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• pp.1079-1088
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• 2001

A dynamic simulation model was developed to analyse the transient characteristics of a multi-inverter heat pump. The programs included a basic air conditioning system such as a evaporator, condenser, compressor, linear electronic expansion valve (LEV) and by-pass circuit. The theoretical model was derived from mass conservation and energy conservation equations to predict the performance of the multi-inverter heat pump at various operating conditions. Calculated results were compared with the values obtained from the experiments at different operation frequencies of compressor, area of the LEV and configuration of indoor units operation. The results of the simulation model showed a good agreement with the experimental ones, so that the model could be used as an efficient tool for thermodynamic design and control factor design of air-conditioners.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.596-599
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• 2000

A natural admittance control system design is presented for a particular type of interaction controller that achieve high-performance and guarantees stability. The admittance control Significantly improves performance when Coulomb friction is present in the one link robot system. The technique requires a careful choice of the target impedance. Experimental performance results are presented for a two-mass system with internal Coulomb friction. Results demonstrate that the admittance control law is successful in rejecting internal Coulomb friction force disturbances. The controller was designed and implemented on our system that we set up one link robot system and hardware configuration system, and performance results are presented.

• 한국결정성장학회지
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• 제13권4호
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• pp.187-198
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• 2003

Zinc selenide (ZnSe) single crystals hold promise for many electro-optics, acousto-optic and green laser generation applications. This material is prepared in closed ampoules by the physical vapor transport (PVT) growth method based on the dissociative sublimation. We investigate the effects of diffusive-convection on the crystal growth rate of ZnSe with a low vapor pressure system in a horizontal configuration. Our results show that for the ratios of partial pressures, s=0.2 and 2.9, the growth rate increases with the Peclet number and the temperature differences between the source and crystal. As the ratio of partial pressures approaches the stoichiometric value of 2, the rate increases. The mass fluk based on one dimensional (1D model) flow for low vapor pressure system fall within the range of the predictions (2D model) obtained by solving the coupled set of conservation equations, which indicates the flow fields would be advective-diffusive. Therefore, the rate and the flow fields are independent of gravity acceleration levels.

• 항공우주시스템공학회지
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• 제13권5호
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• pp.9-15
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• 2019

In this paper, dynamic analysis of a nonlinear active vibration absorber is conducted with a time delay acceleration feedback to suppress the vibration of a nonlinear single degree of freedom primary system. The primary system consisting of linear and nonlinear cubic springs, mass, and damper is subjected to the multi-harmonic hard excitation with a parametric excitation. It is proposed to reduce the vibration of the primary system and the absorber by using a lead zirconate titanate (PZT) stack actuator in series with a spring in the absorber which configures as an active vibration absorber. The method of multiple scales (MMS) is used to obtain the approximate solution of the system under the internal resonance, subharmonic, superharmonic, and principal parametric resonance conditions simultaneously. Frequency and time responses of the system are investigated considering a delay in the feedback for the various parameters of the absorber configuration and controlling force.

• 한국기계가공학회지
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• 제20권9호
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• pp.57-62
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• 2021

CNC machining is used to fabricate various components. This has led to the development of processing-based industries for the production of automobile, appliances, semiconductors, and rockets. Additionally, this machining has enabled economical mass production of high-quality products in industries. Magnesium alloy with a hexagonal closed packed configuration is prone to difficulties during plastic machining, has a high oxygen affinity, and exhibits poor corrosion resistance to seawater and the atmosphere. In this research, Al alloy A5083 was used to investigate and analyze the surface roughness with a certain depth of cut fixed by the machining center (DVM-500II) and various feed rates, speeds, and processing methods after modeling and simulated machining with Gibbs CAM.

• Smart Structures and Systems
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• 제24권6호
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• pp.683-692
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• 2019

Traditional damage detection methods for nonlinear structures are often based on simplified models, such as the mass-spring-damper and shear-building models, which are insufficient for predicting the vibration responses of a real structure. Conventional global nonlinear finite element model updating methods are computationally intensive and time consuming. Thus, they cannot be applied to practical structures. A decentralized approach for identifying the nonlinear material parameters is proposed in this study. With this technique, a structure is divided into several small zones on the basis of its structural configuration. The unknown material parameters and measured vibration responses are then divided into several subsets accordingly. The structural parameters of each subset are then updated using the vibration responses of the subset with the Newton-successive-over-relaxation (SOR) method. A reinforced concrete and steel frame structure subjected to earthquake loading is used to verify the effectiveness and accuracy of the proposed method. The parameters in the material constitutive model, such as compressive strength, initial tangent stiffness and yielding stress, are identified accurately and efficiently compared with the global nonlinear model updating approach.

• Earthquakes and Structures
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• 제21권6호
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• pp.577-585
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• 2021

In this research, a neural network (NN) method was developed, which combines H-infinity and fuzzy control for the purpose of stabilization and stability analysis of nonlinear systems. The H-infinity criterion is derived from the Lyapunov fuzzy method, and it is defined as a fuzzy combination of quadratic Lyapunov functions. Based on the stability criterion, the nonlinear system is guaranteed to be stable, so it is transformed to be a linear matrix inequality (LMI) problem. Since the demo active vibration control system to the tuning of the algorithm sequence developed a controller in a manner, it could effectively improve the control performance, by reducing the wind's excitation configuration in response to increase in the cost efficiency, and the control actuator.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.251-252
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• 2022

The microfluidic controlled droplet manufacturing system is one of the most powerful methods for capsule manufacturing. The microfluidic control method can control the type and size of the capsule by changing the size and configuration of the channel. In addition, by increasing the number of channels, capsules of uniform size can be mass-produced. In this paper, a capsule manufacturing system including flow-focusing and T junction method was designed. In addition, the effectiveness of this system was verified by manufacturing multi-emulsion capsules with a size of 2.2 to 3 mm.

• Asian-Australasian Journal of Animal Sciences
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• 제17권9호
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• pp.1296-1302
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• 2004

This study was conducted to evaluate the possible application of 2 D-SDS-PAGE (2 DE)-based proteome analysis techniques to the assessment of extreme proteolysis in postmortem skeletal muscle. Eight Hanwoo longissimus muscles were incubated immediately after slaughter for 24 h at 5$^{\circ}C$, 15$^{\circ}C$ or 36$^{\circ}C$. Warner Bratzler (WB)-shear force and ultrastructural configuration were determined at 24 h, and rate of proteolysis to 24 h was determined by 1 D-SDS-PAGE (1 DE) and 2 DE. In addition, tentative protein identification was performed from peptide mass fingerprints of MALDI-ToF analysis of major protein groups on 2 DE profiles. The result showed that although ultrastructural configuration was similar between the 5$^{\circ}C$ and 36$^{\circ}C$ treatments, meat at 5$^{\circ}C$ had higher WBshear force (approximately 5 kg greater). A higher rate of protein degradation at 36$^{\circ}C$ was observed based on Troponin-T degradation, 1 DE, and 2 DE analysis. This indicates that proteolysis during the early postmortem period was a significant determinant of shear force at 24 h. Little difference in proteolysis between 5$^{\circ}C$ and 15$^{\circ}C$ treatments was found based on classic 1 DE profile assessment. Meanwhile, considerable differences in the 2 DE profiles between the two treatments were revealed, with substantially higher rate of proteolysis at 15$^{\circ}C$ compared to 5$^{\circ}C$. Nuclease treatment improved 2 DE profile resolution. 400 ${\mu}$g and 600 ${\mu}$g of sample loading appeared to be appropriate for 24 cm pH 3-10 and pH 5-7 IPG strips, respectively. Protein detection and quantification of the 5$^{\circ}C$, 15$^{\circ}C$ and 36$^{\circ}C$ 2 DE profiles revealed 78, 163 and 232 protein spots respectively that were differentially modified in terms of their electrophoretic properties between approximately pI 5.3-7.7 with the molecular weight range of approximately 71-12 kDa. The current results demonstrated that 2 DE was a superior tool to 1 DE for characterising proteolysis in postmortem skeletal muscle.