• International Journal of Highway Engineering
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• v.12 no.4
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• pp.139-145
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• 2010

An integrity testing for stone columns was attempted using crosshole S-wave logging. The method is conceptionally quite similar to the crosshole sonic logging (CSL) for drilled piers. The critical difference in the logging is the use of S-wave rather than P-wave, which is used in CSL, because swave is the only wave sensing the stiffness of slower unbounded materials than water. An electro-mechanical source, which can generate reversed Swave signals, was utilized in the logging. The stone column was delineated using the S-wave travel times across the stone column, the S-wave velocity profile of the crushed stone($V_{cs}$-profile) and that of surrounding soil($V_s$-profile). In the calculation of $V_{cs}$-profile of the crushed stone, its friction angle and Ko (coefficient of lateral earth pressure at rest) are recommended to be used. The calculation of the column diameter is not much affected by the values of friction angle and Ko.

• Korean Journal of Construction Engineering and Management
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• v.9 no.1
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• pp.66-76
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• 2008

Plant project is a complex project that consists of civil engineering, building, mechanical and electronic works. The schedule management is one of important factors in plant project because the construction duration of the project is very short comparing with the other construction projects. Specially, 4D CAD system needs to visualize construction schedule information in those complex projects. This study suggests methodologies for improving 4D CAD functions by considering those project characteristics. To develop a plant 4D CAD system, this study includes to develop new functions by analyzing actual schedule information from the plant construction sites.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.554-557
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• 2005

The bipolar plate is a major component of the PEM fuel cell stack, which takes a large portion of stack cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. To achieve desired electric properties, specimens made with different mixing ratio, processing pressure and temperature were tested. To increase mechanical strength, one or two layer of woven carbon fabric were added to the original graphite and resin composite. Thus, the composite material is consisted of the three phases: graphite particles, epoxy resin, and carbon fabric. By increasing mixing ratio, fabricated pressure and process temperature, electric conductivity was improved. The results of tensile test showed that the tensile strength of two-phase graphite composite was about 5MPa, and that of three-phase composite was increased to 54MPa.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.222-226
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• 1995

인공심장에서의 박출량제어는 전부하에 따른 심박출균형, 심실내 완전충만과 완전구출을 구현하는데 그 목적이 있다. 본 논문에서는 인공심장 내부의 심실간 공간 압력파형을 심박출량의 제어에 활용하였다. 이를 위해서는 심실간 공간의 압력파형을 심실 유입부와 유출부의 혈류량에 대한 정보, 이동작동기의 위치신호와 동기시켜 해석하는 것이 필요하다. 이러한 압력파형의 해석을 바탕으로, 심실간 공간의 음압 크기로 좌,우 심방압을 추정하고 작동기의 좌,우 수축기때 심실간 공간의 음압크기를 비슷하게 유지하도록 작동거리를 제어하면 좌우 심박출 균형을 이룰 수 있음을 확인하였다. 또한, 심실의 완전충만과 완전구출의 실현을 위한 심실 충만 정도를 추정할 수 있게 하는 인자를 제시하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.168-173
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• 2008

In this paper, we have designed transmit/receive Module for X band which can be applied to active phase array radar system. AESA(active electrically beam steered array) is able to transmit high power as like TWTA with composition of TH Module and steer a main beam faster than mechanically steering system. The proposed structure of T/R Module for X band is brick type for physical structure, common leg structure electrically and small size design as MCM(multi chip module). The results show that the characteristic of proposed T/R module can fully cover the specification of required military radar application.

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.281-286
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• 1996

For the accurate analysis of motional characteristics of electrical machines, it is needed to solve the motion equations together with the electromagnetic field equations. In this paper the sequential coupling of systems, the spring mass system and the electromagnetic system, is adopted. The induced current and the magnetic fields are calculated by finite element method(FEM) with given speed. And then, with the computed elec-tromagnetic force, the mechanical equations are solved by the Runge-Kutta method. The above two processes are repeated sequentially to obtain the time domain solutions. The resultant values are applied to the energy conservation law to prove the usefulness of the proposed sequential method.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.37-42
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• 2011

In this paper, novel carbon nanotube (CNT)-filled Solderable electrically conductive adhesive (ECA) and joining process have been developed. To investigate the bonding characteristics of CNT-filled Solderable ECA, three types of Solderable ECAs with different CNT weight percent (0, 0.1, 1wt%) were formulated. For a joining process, the quad flat package (QFP) chip was used. The QFP chip had a size of $14{\times}14{\times}2.7$ mm and a 1 mm lead pitch. The test board had a Cu daisy-chained pattern with 18 ${\mu}m$ thick. After the bonding process, the bonding characteristics such as morphology of conduction path, electrical resistance and pull strength were measured for each formulated ECAs. As a result, the electrical and mechanical bonding characteristics for a QFP joints using CNT-filled ECA were improved about 10% compared to those of QFP joints using ECA without CNT.

• Composites Research
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• v.17 no.6
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• pp.22-27
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• 2004

The objective of this work is to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that is asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials are selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSSFIP elements inserted into structural layers were designed fur satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was $16{\;}{\tiems}{\;}8$ array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75 (1.875kN) load level, Experimental results were compared with single load level fatigue life prediction equations (SFLPE) and in good agreement with SFLPE. SAS concept is the first serious attempt at integration fur both antenna and composite engineers and promises innovative future communication technology.

• Journal of Sensor Science and Technology
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• v.3 no.3
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• pp.45-53
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• 1994

A new type of Si diaphragm was fabricated using Si-wafer direct bonding and two-step electrochemical etch-stopping methods. Using the new diaphragm structure in mechanical sensors, more precise control of cavity depth and diaphragm thickness was achievable. Also, the propagation of the stress, which was generated near the bonding interface, to the surface can be avoided. Finally, a piezoresistive-type Si pressure sensor was fabricated utilizing the diaphragm and a digital pressure gauge, which can display units of pressure, was realized.

• Journal of the Korean Magnetics Society
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• v.6 no.2
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• pp.106-111
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• 1996

Electric machines such as motors which have rmving parts are designed for producing mechanical force or torque. The accurate calculations of electromagnetic force and torque are important in the design these machines. Electromagnetic force calculation method using the results of Finite Element Method(FEM) has been presented variously in 2-D problems. Typically the Maxwell's Stress Tensor method and the method of virtual work are used. The former calculates forces by integrating the surface force densities which can be expressed in terms of Maxwell Stress Tensor(MST), and the latter by differentiating the electromagnetic energy with respect to the virtual dis¬placement of rigid bodies of interest. In the problems including current source, magnetic vector potentials(MVP) have rmstly been used as unknown variables for field analysis by a numerical method; e. g. FEM. This paper, thus, introduces the two both methods using MVP in 3-D case. To verify the usefulness of presented methods, a solenoid model is chosen and analyzed by 3-D and axisymmetric FEM. It is found that the force calculation results are in good agreement for several mesh schemes.