• Progress in Medical Physics
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• v.7 no.1
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• pp.53-64
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• 1996

Purpose: The purposes of this paper are to develop a theoretical basis that the beam directions should be considered when the mechanical accuracy of teletherapy machine is evaluated by the star pattern test, to develop methods using asymmetric field in length to simulate beam direction for the case that beam direction does not appear on film. Method: In evaluating mechanical rotational accuracy of the gantry of teletherapy unit by the star pattern test, the direction of radiation beams was considered. A star pattern using some narrow beams was made. Density profiles at 10cm far from estimated gantry axis on the star pattern were measured using an optical densitometer. On each profile, one coordimate of a beam axis was determined. A pair of coordinates on a beam axis form an equation of the axis. Assume that a unit vector equation omitted is with same direction as radiation beam and a vector equation omitted is a vector directing to the beam axis from the estimated gantry axis. Then, a vector product equation omitted ${\times}$ equation omitted is an area vector of which the absolute value is equal to the distance from the estimated gantry axis to the beam axis. The coordinate of gantry axis was obtained by using least-square method for the area vectors relative to the average of whole area vectors. For the axis, the maximum of absolute value of area vectors would be an accuracy of the gantry rotation axis. For the evaluation of mechanical accuracies of collimator and couch axes for which beam direction could not be depicted on a star pattern test film, narrow beams asymmetric in field length was used to simulate beam direction. Result: For a star test pattern to evaluate the mechanical accuracy of rotational axes of a telectherapy machine, the result considering beam direction was different from that ignoring beam direction. For the evaluation of mechanical accuracies of collimator and couch axes by means of a star pattern test, narrow asymmetric beams could simulate beam direction. Conclusion: When a star pattern test is used to evaluate the mechanical accuracy of a teletherapy unit, beam direction must be considered or simulated, and quantitatively evaluated.

• Polymer(Korea)
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• v.39 no.1
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• pp.151-156
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• 2015

Herein, novel porous structures were fabricated from monomer solutions of dimethylsiloxane and benzene by directional crystallization in twice. First, a honeycomb-like structure was fabricated by $1^{st}$ directional crystallization of solvent. By infiltration of the solution and subsequent $2^{nd}$ directional crystallization, novel structures of different pores in the honeycomb-like structure were fabricated. The porous materials prepared by the repeated directional crystallization have higher indentation modulus and hardness than those of the samples prepared by single directional crystallization. When a higher solution concentration was used in $2^{nd}$ directional crystallization, the maximum increase (indentation modulus: 2140% increase, indentation hardness: 2330% increase) was obtained. On the other hand, porosity and contact angle were lower in the samples from $2^{nd}$ directional crystallization than those from $1^{st}$ directional crystallization. A large decreases was observed, when a relatively high concentration was used in $2^{nd}$ directional crystallization (porosity: 21% decrease, contact angle: 36% decrease).

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1560-1561
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• 2011

본 논문에서는 전력케이블에서 부분방전이 발생했을 시 부부분방전 발생 진행 방향을 알 수 있는 펄스 진행 방향 분석 알고리즘 개발 및 검증을 하였다. 측정 센서로는 케이블 표면에 취부가 쉬운 UHF센서를 사용하였으며 고성능의 오실로 스코프와 방향추정 S/W에 알고리즘을 적용하여 모의 선로가 있는 실험실 환경에서 검증하였다.

• Journal of Broadcast Engineering
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• v.1 no.1
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• pp.35-43
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• 1996

In this paper, we present efficient six-connected contour coding algorithms which can uniquely reconstruct any contour image and efficiently compress the contour data. We first design chain difference codes using two onward direction states, based on the fact that the probability distribution of the direction vectors of horiwntal/vertical direction state is different from that of the direction vectors of diagonal direction state. In order to increase coding efficiency, we also design chain difference codes using five states which are classified according to current and previous onward direction vectors. In addition, we also remove the END codeword to reduce total codeword occurrency. Experimental results show that when using 2 states and 5 states without END codeword total entropy decreases by about 12% and 14% for real images and by about 10% and 26% for a synthetic image, respectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.1
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• pp.69-72
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• 2013

In long-range ultrasonic testing, a phased array probe composed of multiple identical transducers with an uniform interval of one quarter wavelength is usually used for the transmission or reception directivity control. This paper shows that the propagation directions of individual echoes can be identified in real time by displaying the inputs of a process for summing the constitution reception signals after compensating the phase difference due to the transducer interval, together with the output of the process. A constructive interference of the constitution echoes indicates a forward direction echo propagating along an intended direction while a destructive interference implies a reverse direction echo propagating along the direction opposite to the intended one.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.606-608
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• 1999

본 논문에서는 이동 로봇의 유연하고 짧은 경로 계획을 위하여 기존의 그리드 셀(grid cell)로 구성되는 지도 대신에 삼각형을 이용하여 지도를 구성하는 새로운 방법을 제안한다. 기존의 그리드 셀로 구성되는 지도의 경우 이동 로봇가 현재 셀에서 다음 셀로 진행시 진행 방향이 8 방향이나, 본 논문에서 제안한 방법에 의해 구성된 새로운 지도는 셀을 삼각형으로 표현함으로써, 이동 로봇의 진행 방향이 12 방향이 된다. 이와 같이 이동 로봇의 진행 방향이 증가한다는 것은 이동 로봇이 더욱 유연하게 장애물을 회피하며 더욱 짧은 경로로 주행할 수 있는 가능성을 의미한다. 한편, 본 논문에서 제안한 삼각형 지도 작성 방법의 효율성을 기존의 그리드 셀을 이용한 경로 계획 알고리즘인 거리 변환(path transform) 경로 계획을 통하여 증명한다. 또한 새로운 삼각형 지도 구성이 메모리의 효율성 위해 이동 로봇의 주행 환경을 장애물이 비어있는 공간을 가능한 하나의 셀로 병합하는 4진트리 방법(quadtree method)에도 적용 가능함을 보인다.

• Korean Journal of Cognitive Science
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• v.10 no.3
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• pp.67-75
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• 1999

We investigated whether human could perceive the heading direction from the optic flow made from random dots and real images simulating the motion of the observer and objects. When an object moves across the focus of expansion(FOE) in random dot simulation. the observer perceived the focus of expansion biased toward the motion direction of the object. supporting the hypothesis that the direction repulsion is produced between the expansional and the horizontal planar motion components. With real image display observers tended to perceive one's heading direction biased toward the c center of the scene regardless of the direction and position of moving 0bcts. And it was observed that the deeper the depth of the background was the larger the judgment error was. These results suggest it is more likely that human depends on different cues than the optic flow when they perceive or judge one's heading direction in the real environment.

• Korean Journal of Optics and Photonics
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• v.11 no.4
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• pp.227-231
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• 2000

Thermal cesium atomic beam was collimated by transversely cooling of atoms, for which circularly polarized ($\sigma^+$ and $\sigma^-$ polarized) laser light was illuminated to the atomic beam from two perpendicular directions. As a result, the temperature corresponding to the transverse velocity component could be decreased from 430 mK to 60 11K. In addition, the spatial atomic distribution was observed according to the power difference of the two laser beams and the magnetic field applied, and the result was qualitatively coincided with the calculation result by the Doppler cooling theory. heory.

• Explosives and Blasting
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• v.21 no.1
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• pp.69-76
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• 2003

Test blasting has been performed with V-cut to investigate the characteristics. Blasting vibrations were measured at two directions, the proceed direction and side direction. Propagation characteristics were determined by regression analysis; square root scaled distance and cube root scaled distance with maximum charge per delay of the blast. Testing result, The cross point was 62m in the allowable vibration velocity of 3mm/sec and 46m In 5mm/sec. Also, vibration level with measuring point was highest and decayed fastest, adapting to cube root scaled distance, for the proceed direction on ground.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.362-366
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• 2005

종방향 유속의 연직분포 흐름 특성을 파악하기 위해서 중심각이 $180^{\circ}$인 급변곡선수로에서 실험을 수행하였다. 3차원 유속장 측정은 side-looking ADV를 이용하였다. 실험결과, 흐름이 하류 방향으로 진행함에 따라서 최대 종방향 유속이 하상 근처에서 발생하였으며, 이차류에 의한 이송모멘텀의 분포 값이 바뀌는 단면에서 종방향 유속의 연직분포가 대수분포를 만족하지 않음을 파악하였다 직선하천과는 달리 만곡부 내에서 흐름이 하류방향으로 진행함에 따라서 종방향 유속의 연직분포가 변형되는 현상과 관련된 메카니즘은 지형학적 원인에 의한 원심력 작용은 이차류를 발생시키며, 이로 인해 이송 모멘텀이 종방향 유속의 연직분포를 변형시킨다.