• Journal of the Korean Vacuum Society
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• v.2 no.3
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• pp.331-334
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• 1993

여러 종류의 수직 또는 수평 형태의 field emitter array가 연구되었다. 그 중 수평형의 FEA는 emitter가 동일 평면 위에 구성되어 있고, gate는 고주파의 응용을 위하여서는 더욱 적합하다. 이 빗살 모양의 FEA의 구조, emission 성질, 응용에 대하여 설명한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1198-1204
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• 2013

As a microwave near field probe for near field scanning optical microscope(NSOM) system, H-shaped(ridge type) small aperture is proposed and its performances from the viewpoints of the transmission efficiency(transmission cross section) and spatial confinement(beam spot size) are compared with those of the previous narrow rectangular aperture type. While the transmission efficiencies are comparable to each other for the two structures, the transmitted beam spot size for the proposed H-shaped aperture is much smaller than that for the previous rectangular aperture. This strong point of the H-shaped aperture is expected to significantly improve near-field optical applications such as optical data storage, nanolithography and nanomicroscopy. It is also observed that the transmission efficiency can be improved if the coupling aperture is implemented in the type of the transmission cavity.

• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.282-284
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• 1995

Grey leaf spot on tomato plants was first observed in Sedo-myeon, Puyo-kun, Chungnam province of Korea in 1994. This disease which had not been reported before in Korea exhibited different symptoms from those of other leaf spot diseases on tomato plants. The symptoms were characterized by small irregular-shaped spots on leaves at the initial stage of the infection, subsequent spread and coalescence of the spots throughout the leaves with ultimate necrosis, and abscission from the plants. When healthy tomato plants were inoculated with a conidial suspension of the fungus isolated from the lesion of a diseased plant in a field, the same characteristic symptoms as those in the field were produced. Furthermore, the same pathogen could be reisolated from the lesions formed buy the inoculation. Conidial characteristics of the pathogen were as follows; oblong shape with constricted 3 transverse septa, round-shaped base, round- or point-shaped apex, size of 45~75$\times$12.5~17.5 ${\mu}{\textrm}{m}$, and 3.5 : 1 ratio of length to width. The pathogen was identified as Stemphylium lycopersici and thus this is the first report on the occurrence of grey leaf spot disease on tomato plants caused by s. lycopersici in Korea.

• Journal of Hydrogen and New Energy
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• v.29 no.2
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• pp.205-211
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• 2018

Performance evaluation of a regenerative pump has been compared with a conventional open channel impeller and a S-shaped continuous impeller designed newly. To analyze flow field for both pumps, analysis code, CFX, is employed. Unstructured grids are used to represent a composite geometryincluding blade, casing and ducts. Throughout the comparisons between numerical simulation and experiments, the predicted efficiency has a good agreement with the experimental one. It is noted that the pump having a S-shaped continuous impeller is about 4.8 percent more efficient than conventional one, which is due to the relatively large pressure increase. Detailed flow field inside the pump is also analyzed and compared.

• Transactions on Electrical and Electronic Materials
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• v.6 no.3
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• pp.110-114
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• 2005

We present a micro fluxgate magnetic sensor having solenoid coils and racetrack shaped magnetic core, which was designed to decrease the .operating power and magnetic flux leakage. Electroplated copper coils of $6\;{\mu}m$ thickness and the core of $3\;{\mu}m$ thickness were separated by benzocyclobutane (BCB) having a high insulation and good planarization characters. Permalloy $(Ni_{0.8}Fe_{0.2})$ as a magnetic core was also electroplated under 2000 gauss to induce the magnetic anisotropy. The core had the high DC effective permeability of $\~1,300$ and coercive field of $\~0.1$ Oe. The fabricated fluxgate sensor had the very small actual size of $3.0\times1.7\;mm^2$. The fluxgate sensor with a racetrack shaped core had the high sensitivity .of $\~350$ V/T at excitation condition of 3 $V_{P-P}$ and 2 MHz square wave. When two fluxgates were perpendicularly aligned in terrestrial field, their two-axis output signals were very useful to commercialize an electronic azimuth compass for the portable navigation system.

• Journal of Gastric Cancer
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• v.10 no.3
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• pp.133-136
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• 2010

Purpose: The aim of this study was to evaluate the effectiveness of our retraction method for achieving a good operative field for the adequate lymph node dissection during laparoscopic gastrectomy in view of short term surgical outcome. Materials and Methods: This study prospectively enrolled 19 patients who underwent laparoscopic gastrectomy for early gastric cancer. The procedure was simply performed by putting the laparoscopic sigle suture in the phrenoesophageal ligament, and then the string was pulling and tying over the sternum. Surgical outcomes of these patients were evaluated. Results: Under V-shaped liver retraction, the mean operating time and mean number of retrieved lymph nodes was 166.3 minute and 31.37, respectively. And the results were satisfactory compared to open or conventional laparoscopic gastric surgery. Conclusions: V-shaped liver retraction requires no extra port or assistant's hands, and prevents additional injury to any intra-abdominal organ. And this method can easily, efficiently and safely enable to achieve a good operative field for the lymph node dissection near the lesser curvature of the stomach.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.506-509
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• 2006

Shaped Sound Focusing is defined as the generation of acoustically bright shape in space using multiple sources. The acoustically bright shape is a spatially focused region with relatively high acoustic potential energy level. In view of the energy transfer, acoustical focusing is essential because acoustic energy is very small to use other type of energy. Practically, focused sound shape control not a point is meaningful because there are so many needs to enlarge the focal region especially in clinical uses and others. If focused sound shape can be controlled, it offers various kinds of solutions for clinical uses and others because a regional focusing is essentially needed to reduce a treatment time and enhance the performance of transducers. For making the shaped-sound field, control variables, such as a number of sources, excitation frequency, source positioning, etc., should be taken according to geometrical sound shape. To verify these relations between them, wavenumber domain matching method is suggested because wavenumber spectrum can provide the information of control variables of sources. In this paper, the procedures of shaped sound focusing using wavenumber domain matching and relations between control variables and geometrical sound shape are covered in case of an acoustical ring.

• Journal of electromagnetic engineering and science
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• v.17 no.1
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• pp.1-8
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• 2017

This paper introduces a technique to obtain the broadband characteristics of circularly polarized antennas using an L-shaped probe. A waveguide antenna is suitable for obtaining high gain and handling convenience in some applications; however, the asymmetrical structure of the L-shaped probe results in cross-polarization and frequency dependence on the field distribution of higher-order modes (HOM). In addition to the basic characteristics of a waveguide antenna with an L-shaped probe, the author discusses some techniques to reduce the HOM and cross-polarization. As a result, the 3-dB axial ratio (AR) is obtained with the fundamental mode even when the frequency is expanded to the region for HOM of TM. This reduction is mainly due to the cutoff structure to the TM mode around the short wall of the waveguide. Furthermore, some aperture modification techniques can reduce the cross-polarization in a wide range of angles in the radiation pattern. Such techniques and their mechanisms are discussed in this paper. The obtained performance shows that the proposed antennas have a wide range of angles of 3-dB AR in the radiation pattern, broadband characteristics in impedance and AR, and low variation in group velocity.

• Geomechanics and Engineering
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• v.7 no.2
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• pp.165-181
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• 2014

In the past decade, different types of underreamed ground anchors have been developed for substructures requiring uplift resistance. This article introduces a new type of umbrella-shaped anchor. The uplift behavior of this ground anchor in clay is studied through a series of laboratory and field uplift tests. The test results show that the umbrella-shaped anchor has higher uplift capacity than conventional anchors. The failure mode of the umbrella-shaped anchor in a large embedment depth can be characterized by an arc failure surface and the dimension of the plastic zone depends on the anchor diameter. The anchor diameter and embedment depth have significant influence on the uplift behavior. A finite element model is established to simulate the pullout of the ground anchor. A parametric study using this model is conducted to study the effects of the elastic modulus, cohesion, and friction angle of soils on the load-displacement relationship of the ground anchor. It is found that the larger the elastic modulus and the shear strength parameters, the higher the uplift capacity of the ground anchor. It is suggested that in engineering design, the soil with stiffer modulus and higher shear strength should be selected as the bearing stratum of this type of anchor.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.4
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• pp.535-540
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• 1986

본 연구에서는 소재의 3차원 변형, 즉 평면변형(sidewise spread)과 벌징변형 을 동시에 고려할 수 있는 간단한 동적가용 속도장을 제안하고 이를 클로버(clover) 시편의 업세팅 단조 해석에 적용해보기로 한다. 상계이론에 의한 전체 에너지 소비 율을 최소화시키면서 그때 그때의 높이 감소에 따른 단조 하중과 변형 형상을 구한다. 실험은 SM15C 탄소강을 이용하여 시편의 형상과 윤활조건을 바꿔가면서 상온에서 수행 한다.