• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.574-579
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• 2000

In this study. an off-design performance prediction program for centrifugal pumps is developed. To estimate the losses in an impeller flow passage, two-zone model and two-element in series(TEIS) model are used. At impeller exit. the mixing process occurs with an increase in entropy. In two-zone model. there are both primary zone and secondary zone for an isentropic core flow and an average of all non-isentropic streamtubes respectively. The level of the core flow diffusion in an impeller was calculated by using TEIS model. While internal losses in an impeller an automatically estimated by using the above models, some empirical correlations far estimating external losses. far example, disk friction loss, recirculation loss and leakage loss are used. In order to analyze the vaneless diffuser flow. the momentum equations for the radial and tangential directions are used and solved together with continuity and energy equations.

• Asian-Australasian Journal of Animal Sciences
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• 제31권2호
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• pp.293-300
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• 2018

Objective: This study observed the effects of cooking method and final core temperature on cooking loss, lipid oxidation, aroma volatiles, nucleotide-related compounds and aroma volatiles of Hanwoo brisket (deep pectoralis). Methods: Deep pectoralis muscles (8.65% of crude fat) were obtained from three Hanwoo steer carcasses with $1^+$ quality grade. Samples were either oven-roasted at $180^{\circ}C$ (dry heat) or cooked in boiling water (moist heat) to final core temperature of $70^{\circ}C$ (medium) or $77^{\circ}C$ (well-done). Results: Boiling method reduced more fat but retained more moisture than did the oven roasting method (p<0.001), thus no significant differences were found on cooking loss. However, samples lost more weight as final core temperature increased (p<0.01). Further, total saturated fatty acid increased (p = 0.02) while total monounsaturated fatty acid decreased (p = 0.03) as final core temperature increased. Regardless the method used for cooking, malondialdehyde (p<0.01) and free iron contents (p<0.001) were observed higher in samples cooked to $77^{\circ}C$. Oven roasting retained more inosinic acid, inosine and hypoxanthine in samples than did the boiling method (p<0.001), of which the concentration decreased as final core temperature increased except for hypoxanthine. Samples cooked to $77^{\circ}C$ using oven roasting method released more intense aroma than did the others and the aroma pattern was discriminated based on the intensity. Most of aldehydes and pyrazines were more abundant in oven-roasted samples than in boiled samples. Among identified volatiles, hexanal had the highest area unit in both boiled and oven-roasted samples, of which the abundance increased as the final core temperature increased. Conclusion: The boiling method extracted inosinic acid and rendered fat from beef brisket, whereas oven roasting intensified aroma derived from aldehydes and pyrazines and prevented the extreme loss of inosinic acid.

• 한국통신학회논문지
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• 제17권8호
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• pp.816-822
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• 1992

본 논문에서는 중심코어가 사다리꼴분포를 갖는 segmented core 단일모드 광섬유의 전파특성을 \ulcorner=1.55um에서 영분산을 만족하는 조건하에서 상대 굴절율차비의 변화에 대해 이론적으로 조사하였다. 기존의 광섬유(삼각형 굴정율, 이중형 코어)와 곡률손실을 비교한 결과 크게 감소함을 확인하였다. 그리고 코어내의 모드필드의 집속효과가 기존의 사다리꼴 굴절율 광섬유보다 28% 더 향상되었다. 기존의 삼각형 분포를 갖는 segmented core 광섬유와 비교하여 여러 장점들을 제시 하였다.

• 한국철도학회논문집
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• 제15권4호
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• pp.376-380
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• 2012

IPMSM의 구동 중에 발생되는 철손은 코어 재료 특성에 의해 크게 좌우되며, 일반적으로 회전형 전동기에서는 모든 자속의 흐름 방향으로 자기적 특성이 동일한 무방향성 전기강판이 코어 재료로 사용된다. 무방향성 전기강판과 비교하여 방향성 전기강판은 자속의 흐름 방향으로의 자기적 특성이 우수한 장점을 가지고 있다. 따라서 본 연구에서는 IPMSM의 철손을 저감시키기 위하여 코어 재료로써 무방향성 전기강판과 방향성 전기강판을 동시에 사용하는 구조를 제안하였다. IPMSM의 고정자에 자속 흐름의 방향으로 가공된 방향성 전기강판을 이용한 분할 티스 구조를 적용함으로써 기존의 110kW급 IPMSM과 비교하여 거의 40% 정도의 철손 저감 효과를 얻을 수 있었다.

• 반도체디스플레이기술학회지
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• 제21권2호
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• pp.95-100
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• 2022

In this paper, a power loss analysis technique of a high-frequency transformer of a bidirectional DAB (Dual Active Bridge) converter is reported. To miniaturize the transformer of the dual active bridge converter, a resonant inductor was designed with an air gap included low-coupled rate state core to combine leakage inductor with the resonant inductor which is required for soft-switching. In this paper, leakage inductance and magnetizing inductance, core material, type of winding and winding method are included in the dual active bridge transformer loss analysis process to enable optimal design at the initial design stage. Transformer loss analysis for dual active bridge with a switching frequency of 200 kHz and maximum output of 5 kW was executed, and elements necessary for design based on the number of turns on the primary side were graphed while maintaining the transformer turns ratio and window area. In particular, it was possible to determine the optimal number of turns and thickness of the transformer, and ultimately, the total loss of the transformer could be estimated.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.93-97
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• 2001

A new compact, low-energy electron beam irradiator has been developed. The core-loss of silicon steels can be reduced by magnetic-domain refinement method. The irradiator was developed for the application of core-loss reduction using the method. The beam energy of the irradiator can be varied from 35 to 80 keV and the maximum current is 3mA. The irradiation area is designed to be $30\times30mm2$ now and will be upgraded to $30\times150mm2$ using a scanning magnet and scanning cone. The electron beam generated from 3 mm diameter LaB6 is extracted to the air for the irradiation of the silicon steels in the air. A special irradiation port was developed for this low-energy irradiator. A havar foil with $4.08{\mu}m$ thickness were used for the window and a cold air-cooling system keeps the foil structure by removing heat at the window. The irradiator system and its operation characteristics will be discussed.

• Steel and Composite Structures
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• 제33권6호
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• pp.891-906
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• 2019

This study considers the instability behavior of sandwich plates considering magnetorheological (MR) fluid core and piezoelectric reinforced facesheets. As facesheets at the top and bottom of structure have piezoelectric properties they are subjected to 3D electric field therefore they can be used as actuator and sensor, respectively and in order to control the vibration responses and loss factor of the structure a proportional-derivative (PD) controller is applied. Furthermore, Halpin-Tsai model is used to determine the material properties of facesheets which are reinforced by graphene platelets (GPLs). Moreover, because the core has magnetic property, it is exposed to magnetic field. In addition, Kelvin-Voigt theory is applied to calculate the structural damping of the piezoelectric layers. In order to consider environmental forces applied to structure, the visco-Pasternak model is assumed. In order to consider the mechanical behavior of structure, sinusoidal shear deformation theory (SSDT) is assumed and Hamilton's principle according to piezoelasticity theory is employed to calculate motion equations and these equations are solved based on differential cubature method (DCM) to obtain the vibration and modal loss factor of the structure subsequently. The effect of different factors such as GPLs distribution, dimensions of structure, electro-magnetic field, damping of structure, viscoelastic environment and boundary conditions of the structure on the vibration and loss factor of the system are considered. In order to indicate the accuracy of the obtained results, the results are validated with other published work. It is concluded from results that exposing magnetic field to the MR fluid core has positive effect on the behavior of the system.

• 한국산업융합학회 논문집
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• 제26권2_2호
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• pp.327-332
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• 2023

As interest in eco-friendly and fuel-efficient electric vehicles has increased globally, there has also been a growing interest in the efficiency, vibration, and noise of motors for electric vehicles Electric vehicles generally have significantly lower driving ranges per charge compared to the maximum driving range per fueling of internal combustion engine vehicles. Additionally, there are issues with various vibrations and noise generated by the motor that can cause discomfort for passengers. Therefore, research is necessary to reduce losses, vibration, and noise of the motor to improve the driving range of electric vehicles. IPMSM with a purchased design can obtain additional reluctance torque by utilizing the difference in inductance between the d and q axes. However, due to this reluctance torque, torque ripple occurs larger than other motors. The increase in torque ripple also increases noise and vibration. Since the reluctance torque, which is the main cause of torque ripple, is determined by the shape of the motor components, torque ripple can be reduced through shape optimization. In this paper, a rotor shape for reducing torque ripple and core loss that causes vibration, noise, and efficiency to decrease of IPMSM for electric vehicles was proposed. Optimization design was carried out by changing the shape of the q-axis path of the rotor to reduce the difference in inductance of the d and q-axis of the rotor. Finally, in order to verify the validity of the design variables derived through the optimal design, the original model and the improved model were compared through the FEM. Compared to the original model, the improved model's torque verifying ripple was reduced by about 62% and core loss was reduced by about 29%, the superiority of the improved model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.851_852
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• 2009

Shrink fitting which is assembling process to fix stator core on the motor frame is widely used at the mass production line of motors because of cost and productivity. This process produces compressive stress on a stator core, which causes negative effect for example, core and copper losses on motor performance. Magnetic properties of electrical steel are effected by both compressive and tensile and thermal stresses. Electromagnetic field analysis is considered one of the effective process since one can predict motor performance including core loss precisely. This method can consider non linear magnetic property with magnetic saturation which is typical electrical steel behavior. However this method is strongly depended on non linear magnetic data, one may have different calculation result whether considering mechanical stress or not. This study describes magnetic field analysis of a motor considering mechanical stress from shrink fitting. Analysis results are compared with each stress-free and stressed condition.

• 한국정밀공학회지
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• 제17권9호
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• pp.81-86
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• 2000

This paper was carried out to investigate the characteristics of interlaminar fracture toughness of foam core sandwich structures under opening loading mode by using the double cantilever beam (DCB) specimens in Carbon/Epoxy and foam core composites. instead of using symmetric geometry of DCB specimen non-symmetric DCB specimen was used to calculate the interlaminar fracture toughness. Three approaches for calculating the energy release rate({{{{ {G }_{IC } }}}}) were compared. Fracture toughness of foam core sandwich structures by autoclave vacuum bagging and hotpress were compared and analyzed. Experiment nonlinear beam bending FEM method were performed. Suggested bonding surface compensation and equivalent area inertia moment was used to calculate the energy release rate in nonlinear analytical results. The conclusions among experimental nonlinear analytical and FEM results was observed. The vacuum bagging method was shown to be able to substitute method in stead of autoclave without serious loss of Mode I energy release rate({{{{ {G }_{IC }}}}}) to be able to substitute method in stead of autoclave without serious loss of Mode I energy release rate({{{{ {G }_{IC }}}}}).