• 소성∙가공
• /
• 제21권6호
• /
• pp.341-347
• /
• 2012

The metallic bipolar plates of the molten carbonate fuel cell(MCFC) are composed of shielded slot plates and a center-plate. The shielded slot plates support the center-plate and the membrane electrode assembly. Compressive forces are applied to the shielded slot plate in order to increase the contact area between shielded slot plates and the membrane electrode assembly (MEA). In the design of the shielded slot plate, it is necessary to predict the mechanical behavior of the shielded slot plate. The shielded slot plates are manufactured by a three-stage forming process consisting of slitting, preforming and the final forming process. The mechanical behavior of the shielded slot plate is largely affected by the forming process. In this study, the simulation of the three-stage forming process was used to predict the mechanical behavior of the shielded slot plate. The present simulation approach showed good agreements with the experimental results.

• International Journal of Aeronautical and Space Sciences
• /
• 제16권2호
• /
• pp.123-136
• /
• 2015

The present study numerically investigates the effect of shield on the flow characteristics of Hartmann whistle. The flow characteristics of un-shielded Hartmann whistle are compared with whistles of different shield heights 15 mm, 17 mm, 20 mm, 25 mm and 30 mm. The comparison of Mach number contours and transient velocity vectors of shielded Hartmann whistles with un-shielded ones for the same conditions reveal that the presence of shield causes the exiting jet to stick to the wall of the shield without causing spill-over around the cavity inlet, thus sustaining the shock oscillation as seen in the unshielded Hartmann whistle, which has intense flow/shock oscillation and spill-over around the cavity mouth. The velocity vectors indicate jet regurgitance in shielded whistles showing inflow and outflow phases like un-shielded ones with different regurgitant phases. The sinusoidal variation of mass flow rate at the cavity inlet in un-shielded Hartmann whistle indicates jet regurgitance as the primary operating mode with large flow diversion around the cavity mouth whereas the non-sinusoidal behavior in shielded ones represent that the jet regurgitance is not the dominant operating mode. Thus, this paper sufficiently demonstrates the effect of shield in modifying the flow/shock oscillations in the vicinity of the cavity mouth.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1993년도 춘계학술대회
• /
• pp.45-48
• /
• 1993

High-order field gradients are useful for spatial localization of a volume of interest and dynamic range improvement of signal detection in NMR (Nuclear Magnetic Resonance) spectroscopy and imaging. This paper proposes a design method of shielded high-order gradient coils to reduce tile effect of eddy current on tile spectroscopy and imaging results. According to the experimental results, the shielded gradient coils produce less than 2 % eddy current compared to non-shielded coils. Two shielded $z^2$ gradient coils have been designed and constructed for 1.5 T whole-body and 3.0 T animal NMR imaging systems. Experimental results are in good agreement with the theoretically expected behavior and show the utility of the shielded high-order gradient coils.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제48권3호
• /
• pp.173-178
• /
• 1999

In this paper, the characteristics of the shielded inductive superconducting fault current limiter(FCL) were simulated and analyzed. After determining parameters fo design for superconducting tube, iron core and primary coil, simple power system composed of shielded inductive FCL was simulated by the numerical analysis. The currents flowing under the fault condition could be limited below 50 A successfully. It was suggested that as the important factors of operational characteristics, the turns of primary coil and size of iron core play a major role for whether the shielded inductive SCFCL operated as inductive type or resistive type FCL.

• 한국산학기술학회논문지
• /
• 제6권2호
• /
• pp.122-128
• /
• 2005

본 연구에서는 구조용강 SM520을 사용하여 교량용 박스 제작시 플럭스 코어드 아크용접법에서 가스실드방식과 셀프실드방식의 두 공정으로 제작된 용접부를 건전성, 기계적 성질 및 미세조직에서 비교하였다. 그 결과 두 용접 프로세스에 의해 제작된 용접부들은 매크로 조직 및 비파괴 검사 결과 건전성이 입증되었고, 항복 및 인장강도가 각각 $462{\sim}549\;MPa$와 $548{\sim}640\;MPa$였고, CVN 충격치는 $-20^{\circ}C$에서 요구값인 40J을 충족하였다. 결과적으로, 고속철도나 고속도로 건설시 사용되는 교량용 SM520강 박스 제조시 고소 및 강풍 조건하에서 용접할 때 셀프실드 아크용접법은 기존의 가스실드 아크 용접법과 비교하여 대등한 용접 특성들을 보였기 때문에 현장 시공시 적용 타당성이 있다고 사료된다.

• 소성∙가공
• /
• 제21권5호
• /
• pp.298-304
• /
• 2012

The shielded slot plates for a molten carbonate fuel cell(MCFC) have a sheared corrugated trapezoidal pattern. In the FEM simulations for the production of the shielded slot plate, the user material subroutine VUMAT in the commercial FEM software ABAQUS was used to implement a ductile fracture criterion. The critical damage value for the ductile fracture criterion was determined by comparing the experimental results of the shearing process with the simulation results. Using the ductile fracture criterion, the FEM simulation of the three-dimensional forming process of the shielded slot plate was conducted. The effects of the shearing process on the forming process were examined through FEM simulation and experiments. The forming simulation of nine unit cells was conducted. Using the simulation results of the forming process, the deformed shape after springback was calculated. The experimental result shows good agreement with the simulation.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1996년도 추계학술대회
• /
• pp.307-309
• /
• 1996

A new design scheme of actively-shielded x,y-gradient coils for Magnetic Resonance Imaging(MRI) is proposed. An actively-shielded x-gradient coil has been designed as an example and the results are presented. In MRI, gradient coils are needed for spatial selection and position coding to obtain the position information of the NMR signal. They are usually switched on and off during imaging and the eddy current induced by the current switching usually degrades the final image quality To reduce or remove this kind of problems, the active shielding has been proposed few years ago. In this paper, a new design scheme for actively-shielded x,y-gradient coils, namely, a minimum-power design scheme using current-loop elements, has been proposed. Its utility in designing MRI gradient coils has been shown by using simulation. The design scheme seems to be useful for actively-shielded transverse gradient coils, even of non-cylindrical or of arbitrary-selected shapes.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 제40회 하계학술대회
• /
• pp.1513_1514
• /
• 2009

This paper reports on a fabrication of novel substrate integrated waveguide (SIW)-based shielded stripline applicable to the broadband transverse electromagnetic (TEM) single-mode propagation. We suggested a structure for half-SIW and half-shielded stripline, which combined through the benzocyclobutene (BCB) bonding layer. The electrical interconnection between the sidewall of anisotropic wet-etched silicon and patterned BCB layers is measured subsequent to the metalization on the side wall. The proposed SIW-based shielded stripline has great potential in terms of simple fabrication, integration with planar circuits and monolithic system fabricated on a SIW structure.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제2C권5호
• /
• pp.268-272
• /
• 2002

In this paper, we proposed a procedure to analyze a shielded-microstrip step discontinuity using the mode matching method (MMM) combined with the vector finite element method (VFEM), which is used to find the equivalent waveguide-model for a microstrip. In order to calculate the effective-widths and -dielectric permittivity of the equivalent waveguide-model corresponding shielded-microstrip, the propagation constant and characteristic impedance are calculated from the VFEM. MMM is then applied to find the scattering parameter in the planar waveguide. This technique makes it possible to take advantage of the high accuracy of the VFEM as well as the high efficiency of the MMM.

• 한국전기전자재료학회논문지
• /
• 제30권2호
• /
• pp.63-66
• /
• 2017

This research was about shielded trench gate power MOSFET for low voltage and high speed. We used T-CAD tool and carried out process and device simulation for exracting design and process parameters. The exracted parameters was used to design shieled and conventional trench gate power MOSFET. And The electrical characteristics of shieled and conventional trench gate power MOSFET were compared and analyzed for their power device applications. As a result of analyzing electrical characteristics, the recorded breakdown voltages of both devices were around 120 V. The electric distributions of shielded and conventional trench gate power MOSFET was different. But due to the low voltage level, the breakdown voltage was almost same. And the other hand, the threshold voltage characteristics of shielded trench gate power MOSFET was superior to convention trench gate power MOSFET. In terms of on resistance characteristics, we obtained optimal oxied thickness of $3{\mu}m$.