• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.40-46
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• 2004

The equivalent source method (ESM) uses two groups of equivalent source positions. One group includes the first order images of the sound source inside the enclosure. The positions of the other group are usually on a spherical surface some distance outside the enclosure. A proper selection of the positions for the far field sources could greatly improve the performance of the modeling accuracy and reduce the number of the sources to achieve the required accuracy. This study uses optimally distributed far field source positions on the surface of enlarged version of the rectangular enclosure instead of using typical spherical distribution. Simulations using various sizes of the box shaped distribution are executed and optimal positions are searched using an optimization technique from the larger number of candidate positions. The results of using these far field source positions are compared and analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.217-227
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• 2000

A rectangular ceramic dielectric antenna, placed on the top of a ground plane and fed by coaxial probe, is analyzed by using the finite element method. To verify the proposed code, a rectangular ceramic dielectric antenna was fabricated and the characteristics of antenna were measured. The numerical data obtained is in good agreements with experimental result. Thus we checked the validity of our FEM code, and it can be possible to extend the analysis of the arbitrary 3-D antenna on a ground plane fed by coaxial probe.

• The KIPS Transactions:PartB
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• v.9B no.2
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• pp.237-244
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• 2002

In this paper, we propose a stereo image recognition-based method for measuring the volume of the rectangular parallelepiped. The method measures the volume from two images captured with two CCD (charge coupled device) cameras by sequential processes such as ROI (region of interest) extraction, feature extraction, and stereo matching-based vortex recognition. The proposed method makes it possible to measure the volume of the 3D object at high speed because only a few features are used in the process of stereo matching. From experimental results, it is demonstrated that this method is very effective for measuring the volume of the rectangular parallelepiped at high speed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1622-1629
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• 2002

To enhance isothermal characteristics of glass-farming surface, a rectangular parallelepiped heat pipes was fabricated, tested, and analyzed. The working fluid was sodium and the wall material was stainless steel 304. The dimension of the heat pipe was 210 (L) $\times$ 140(W) $\times$ 92(H)mm. A lattice structure covered with screen mesh was inserted to promote return of working fluid. The bottom side of heat pipe was heated electrically and the top side was cooled by liquid circulation. The temperature distribution at the bottom surface was of major concern and was monitored to determine isothermal characteristics. A frozen start-up of rectangular parallelepiped liquid metal heat pipe was tested. The operating mode of the sodium heat pipe was affected by the temperature of cooling zone, input heat flux, and the operating temperature of heat pipe. The heat pipe operated in a normal fashion as long as the heat flux was over 5.78W/cm$^2$, and the inside wall temperature of condenser part was above 95$^{\circ}C$ The maximum temperature difference at the bottom surface was observed to be 32$^{\circ}C$ when the operating temperature of the heat pipe was operating normally around 50$0^{\circ}C$. The result showed that a sodium heat pipe was very effective in reducing significantly the temperature difference in the glass-forming surface.

• Solar Energy
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• v.15 no.3
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• pp.15-27
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• 1995

This study presents experimental and numerical results of the temperature characteristics, the heat transfer phenomema, and the heat storage quantity during the heat storage process with sodium phyrophosphate decahydrate($Na_4P_2O_7{\cdot}10H_2O$)-Phase Change Material(PCM) in a latent heat storage tank(cubic type). It was proved that heat transfer by conduction was dominant because PCM($Na_4P_2O_7{\cdot}10H_2O$) during heating processes was gel phase, not liquid phase The gap ratio(rate of air content) of PCM became smaller, the thermal capacity of PCM became larger, therefore the temperature distribution of PCM slowly increased than that of large gap ratio. There was maximum 15% difference between measured temperatures and calculated temperatures.

• 한국HCI학회:학술대회논문집
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• 2007.02b
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• pp.264-269
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• 2007

본 논문에서는 감각형 객체(Tangible Object)를 이용한 테이블에서의 2D/3D 상호작용 시스템을 제안한다. 제안된 시스템은 기존의 ARTable[1]에 직육면체 형태의 감각형 객체와 카메라가 장착된 이동형 모니터를 추가하여 제작되었다. 감각형 객체는 모든 면에 ARToolkit[3]에서 쓰이는 마커가 부착되어 있으며, 내부에는 진동자와 불루투스 통신 모듈이 삽입되어 있다. 또한 카메라가 달린 모니터는 모니터 암에 연결되어 사용자가 이동하며 ARTable 상판을 관측할 수 있도록 부착되어 있다. 이 시스템를 이용하여 사용자는 디스플레이형 테이블인 ARTable 위에서 가상공간을 네비게이션(2D 상호작용)할 때 정확한 길을 찾아가기 위한 도움을 받을 수 있을 뿐만 아니라, 증강현실 환경에서 가상객체와 3D 상호작용을 할 수 있다. 또한 진동 모듈과 이를 제어하기 위한 블루투스 모듈이 내장 되어있어, 특정한 이벤트 발생시 진동자를 이용하여 사용자에게 촉각 감응 효과를 줄 수 있다. 제안된 시스템은 교육, 엔터테이먼트, 등 다양한 분야에서 사용될 수 있다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.2
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• pp.44-54
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• 1985

The high resolution of positron emission tomography, in particular, requires the use of detector crystals of narrow width but still with sufficiently high detection efficiency. If the crystal width is reduced to several millimeters, degradation of detection efficiency and leakage coefficient becomes significant, particularly in case of obliquely incident photons. Alleviation of such a problem can be made possible by modification of the detector shape from the conventional rectangular type to a wed농e type. The Proposed wedge shape makes the absorption length longer for obliquely incident photons, thus increasing the detection efficiency and suppressing leakage coefficient. For the BGO detectors of 4-8mm width, the computer simulation result of the system using wedge detectors reveals resolution improvement to the system using conventional detectors. For the system composed of 200 BGO detectors of 8mm width with 2 point sampling motion, the simulation resolution system using conventional detectors. For the very high resolution system of 3-7mm FWHM, the characteristics of the detector shape and size is studied by computer simulation.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.157-168
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• 2014

거친 표면 위에서 물방울은 Wenzel (WZ) 상태와 Cassie-Bexter (CB) 상태로 존재할 수 있으며, 특히 돌기 사이를 채우고 있는 물 분자의 상태 (액체 또는 기체)로 물방울이 어떤 상태인지를 알아 낼 수 있다. 본 연구에서는 열역학적 이론과 격자 기체 기반의 몬테카를로 방법을 사용하여 표면 위에 존재하는 돌기의 크기와 모양이 돌기 사이에서 일어나는 물 분자의 액체-기체 상전이에 미치는 영향에 대해 살펴보았다. 돌기의 너비와 높이가 일정한 비율을 유지하고 있을 경우, 직육면체 (Square) 돌기의 경우 그 크기가 커질수록 CB 상태로의 상전이가 잘 일어나는 반면, 원통형 (Circular) 돌기의 경우 매우 큰 크기에서 더 이상 CB 상태로의 상전이가 일어나지 않는 것을 확인하였다.

• Radiation Oncology Journal
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• v.18 no.4
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• pp.337-344
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• 2000

Purpose :To design and test test CT simulator phantom for geometrical test. Materials and Methods : The PMMA phantom was designed as a cylinder which is 20 cm in diameter and 24 cm in length, along with a 25$\times25\times31cm^{3}$ rectangular parallelepiped. Radio-opaque wires of which diameter is 0.8 mm are attached on the other surface of the phantom as a spiral. The rectangular phantom was made of four 24$\times24\times0.5 cm^{3}$ square plates and each plate had a 24$\times24 cm^{2}$, 12$\times12cm^{2}$, 6$\times6 cm$^{2}$ square line. The squares were placed to face the cylinder at angles 0 $^{\circ}$ , 15 $^{\circ}$ , 30 $^{\circ}$ ,respectively. The rectangular phantom made it possible to measure the field size, couch angle, the collimator angle, the isocenter shift and the SSD, the measurements of the gantry angle from the cylindrical part. A virtual simulation software, AcOSim, offered various conditions to perform virtual simulations and these results were used to perform the geometrical Quality assurance of CT simulator. Results : A 0.3$\~$0.5 mm difference was found on the 24 cm field size which was created with the DRR measurements obtained by scanning of the rectangular phantom. The isocenter shift, the collimator rotation, the couch rotation, and the gantry rotation test showed 0.5$\~$1 mm, 0.5$\~$l$^{\circ}$ 0.5$\~$ 1$^{\circ}$ , and 0.5-1 $^{\circ}$ differences, respectively. We could not find any significant differences between the results from the two scanning methods. Conclusion :The geometrical test phantom developed in the study showed less than 1 mm (or 1 $^{\circ}$ ) differences. The phantom could be used as a routine geometrical QC/QA tools, since the differences are within clinically acceptable ranges.

• Progress in Medical Physics
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• v.14 no.4
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• pp.225-233
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• 2003

The goal of a radiation treatment plan is to deliver a homogeneous dose to a target with minimal irradiation of the adjacent normal tissues. Dose uniformity is especially important for stereotactic radiosurgery using a linear accelerator. The dose uniformity and high dose delivery of a single spherical dose distribution exceed 70％. This also results with a similar stereotactic radiosurgical plan using a Gamma Knife. The dose distribution produced in a stereotactic radiosurgical plan using a Gamma Knife and Linear accelerator is spherical, and the application of the sphere packing arrangement in a real radiosurgical plan requires much time and skill. In this study, we found a characteristic of dose distribution with transformation of beam parameters that must be considered in a radiosurgical plan for effective radiosurgery. First, we assumed a cylinder type tumor model and a cube type tumor model. Secondly, the results of the tumor models were compared and analyzed with dose profiles and DVH_(Dose Volume Histogram) representative dose distribution. We found the optimal composition of beam parameters_(i.e. collimator size, number of isocenter, gap of isocenters etc.), which allowed the tumor models to be involved in the isodose curve at a high level. In conclusion, the characteristics found in this study are helpful for improving the effectiveness and speed of a radiosurgical plan for stereotactic radiosurgery.