• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2007년도 추계학술발표회
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• pp.211-214
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• 2007

본 논문에서는 800MHz대역의 TRS(Trunked Radio System)대역을 비롯한, GSM(Global System for Mobile telecommunication), CDMA(Code Division Multiple Access) 대역을 통합할 수 있는 광대역 마이크로스트립 안테나를 설계하고자 한다. 그리고 선박 및 해상 안전에 상용 가능한 선박 기지국 중계기용 안테나를 설계하였다. 마이크로 스트립 안테나의 협대역을 개선하기 위해서 직사각형 패치에 U자 형태의 급전구조를 갖고, 그라운드와 급전 사이에 유전체(${\varepsilon}_T$ = 2.1), 패치와 급전 사이에는 유전체 (${\varepsilon}_T$ = 1)인 서로 다른 유전체를 사용하여 이중 공진 효과를 이용하였다. 설계된 안테나의 주파수 대역폭(VSWR 2:1)은 $780MHz{\sim}1.83GHz$로 2.61GHz의 광대역 특성을 보였으며. 또한 E-평면과 H-평면 모두 이득은 9.dBi이상. 3dB 빔폭은 E-평면 과 H-평면 $60^{\circ}$이상의 개선된 특성을 보였다.

• 한국분무공학회지
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• 제26권3호
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• pp.127-134
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• 2021

Fire sprinkler initial spray was analyzed by Large eddy simulation (LES) and Volume of Fluid (VoF) integrated method. The IsoAdvector geometric VoF was used to identify the liquid-gas interface clearly even with the large Courant-Friedrichs-Lewy number. To reduce the computational costs, sector meshes and Adaptive Mesh Refinement up to level 3 were used. Base mesh size was 1 mm, which is roughly equivalent to the initial sprinkler droplet. Top surface radius of boss and deflector size were modified to investigate the effects of sprinkler head design on primary breakup process. When top surface radius of boss was increased, vertical liquid sheet was formed. This phenomenon reduced the sheet breakup radius, sheet thickness and velocity. Due to reduced liquid sheet thickness, a large amount of ligaments was created from the liquid sheet. As a result, there was a dramatic decrease in volume per surface area, indicating an increase in breakup process. Spray pattern viewed in radial direction also changed when top surface radius of boss increased. When top surface radius of boss was increased, a T-shaped pattern was observed while a V-shaped pattern was observed in all other cases. When the deflector size increases, the spray pattern remains V-shaped, even if the top surface radius of boss increased. Further studies on promoting atomization of the water supplied to the lower part of the sprinkler head in the T-shape pattern should be conducted.

• 대한화학회지
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• 제36권1호
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• pp.87-94
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• 1992

본 연구는 폴리스티렌(PS), 폴리메틸메타크릴레이트(PMMA), 및 폴리부타디엔(PB) 등 동종 중합체들(homopolymers), 그리고 폴리스티렌-폴리메틸메타크릴레이트 block 혼성중합체들(SM block copolymers) 및 스티렌-폴리부타디엔 star shaped 혼성중합체들(PS-PB star shaped copolymers)을 선택하여 다리걸친 폴리스티렌 겔 상에서의 용리거동을 비교 조사하였다. 선택한 이동상으로는 테트라히드로퓨란(THF), 톨루엔(TOL), 클로로포름(CHL), 메틸렌클로라이드(MC), 테트라히드로퓨란-시클로헥산(CH) 혼합용매의 5가지 시스템이며, 이동상 변화에 따른 시료들의 hydrodynamic 부피와 머무른 부피 사이에 플롯의 이동에 관한 현상을 조사하였으며, 또한 시료의 머무름을 예측하기 위해 다중 다단계 회귀분석(multiple stepwise regression analysis)을 수행한 결과, 각 중합체들에 대한 적절한 크기 파라미터를 찾았다. 또한, network-limited 분리 메카니즘에 의해 GPC에서 시료와 겔사이의 상호작용에 대한 분포계수 $K_p$를 각 이동상 시스템에서 구하였는데, PS와 PB의 kp값은 거의 1에 가까운 값을 나타내었고 PMMA인 경우는 적합 용매에서는 분자량이 증가할수록 $K_p$값은 다소 감소하였으나 부적합 용매에서는 분자량이 증가함에 따라 $K_p$값은 함께 증가하였다. 혼성중합체의 $K_p$값은 조성 및 분자량에 따라 달라짐을 알 수 있었고, 이로부터 SM block 혼합중합체의 형태는 무작정상(random phase)을 가지는 것으로 예측된다. 아울러 $K_p$값을 이용하여 동종중합체 및 폴리스티렌 혼성중합체들의 분자량을 측정하기 위해 이들의 새로운 머무름 파라미터$(V_r-V_o)/K_p$와 log[η]M을 플룻을 한 결과 좋은 직선성을 보이는 하나의 보편적 검정곡선을 얻었다.

• Journal of Species Research
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• 제5권3호
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• pp.318-323
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• 2016

Acrobeles ciliatus (von Linstow, 1877) and Plectus parietinus (Bastian, 1865) are newly collected from Korea. Acrobeles is similar to those nematode belongs to Rhabditidae and Panagrolaimidae by having terminal bulb without medium bulb but different by having complex, vines shaped labial attachment. A. ciliatus differed from other Acrobeles species by lateral fields with two incisures, primary axils U-shaped, and secondary axils V-shaped. Head region set off with the neck, three high labial probolae present, each having 5 tines at inner margins and 5-7 at outer margins, and two elongate apical tines. Also, it differs from the longer female body. Plectus parietinus is distinguished from all other species of Plectus by the prominent hypodermal glands, the relatively small amphid, the distinct and well set-off lips and by the subdorsal distal caudal seta on the left side of the tail. Stoma without stylet. Oesophagus about 1/4 of total body length with terminal bulb. Anus ca. $100{\mu}m$ from posterior extremity. Vulva is at middle of body. Have spinneret on tail tip.

• 소성∙가공
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• 제13권1호
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• pp.33-38
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• 2004

A new approach for the design of extrusion die surface of arbitrarily shaped section is presented. In order to generate the extrusion die surface. an automatic surface construction method based on B-spline surface and scalar field theory is proposed. The isothermal lines and stream lines designed in the scalar field are introduced to find the control points which are used in constructing B-spline surfaces. Intersected points between the isothermal lines and stream lines are used to construct B-spline surfaces. The inlet and outlet profiles are precisely described with B-spline curves by using the centripetal method for uniform parameterization. The extrusion die surface is generated by using the cubic curve interpolation in the u- and v-directions. A quantitative measure for the control of surface is suggested by introducing the tangential vectors at the inlet and outlet sections. To verify the validity and effectiveness of the proposed method, automatic surface generation is carried out for extrusion dies of arbitrarily shaped sections.

• 한국군사과학기술학회지
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• 제8권2호
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• pp.58-66
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• 2005

This paper presents miniaturized setback generators based on the conversion of mechanical energy into electrical energy for military applications, especially power supply for electronic fuzes. In order to minimize the volume of setback generators, a ring-shaped magnet enclosing a coil assembly is adopted. A mechanical safety system, shear plate, is used as a release mechanism of the setback generators to prevent the generators from operating accidentally. The setback generators are intended not to ignite an electrical detonator but to charge a capacitor which is capable of driving electronic circuit of fuze. We design the setback generators using the simulation results of an electromagnetic analysis tool, $Maxwell^{(R)}$ 2D. In experimental study, we perform safety tests of the shear plate and firing tests of the fabricated setback generators. The present setback generators show that the voltage of 14.2V is charged at the capacitor of $30{\mu}F$ within the charging time of 0.68msec and the critical acceleration for safety is 5,000G, thus verifying that the setback generators with a ring-shaped permanent magnet can be applicable to the power supply of small-caliber electronic fuze.

• 센서학회지
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• 제29권4호
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• pp.275-278
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• 2020

In this study, we evaluated the temperature-dependent characteristics of homojunction InGaAs vertical Fin-shaped Tunnel Field-Effect Transistors (Fin TFETs), which were fabricated using a novel nano-fin patterning technique in which the Au electroplating and the high-temperature InGaAs dry-etching processes were combined. The fabricated homojunction InGaAs vertical Fin TFETs, with a fin width and gate length of 60 nm and 100 nm, respectively, exhibited excellent device characteristics, such as a minimum subthreshold swing of 80 mV/decade for drain voltage (V_DS) = 0.3 V at 300 K. We also analyzed the temperature-dependent characteristics of the fabricated TFETs and confirmed that the on-state characteristics were insensitive to temperature variations. From 77 K to 300 K, the subthreshold swing at gate voltage (V_GS) = threshold voltage (V_T), and it was constant at 115 mV/decade, thereby indicating that the conduction mechanism through band-to-band tunneling influenced the on-state characteristics of the devices.

• JSTS:Journal of Semiconductor Technology and Science
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• 제3권3호
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• pp.145-152
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• 2003

Electrical gate and drain characteristics of double heterostructure InAlAs/InGaAs pseudomorphic HEMTs have been investigated under sub-bandgap photonic excitation ($hv). Drain $(V_{DS})-,{\;}gate($V_{DS})-$, and optical power($P_{opt}$)-dependent variation of the abnormal gate leakage current and associated physical mechanisms in the PHEMTs have been characterized. Peak gate voltage ($V_{GS,P}$) and the onset voltage for the impact ionization ($V_{GS.II}$) have been extracted and empirical model for their dependence on the $V_{DS}$ and $P_{opt} have been proposed. Anomalous gate and drain current, both under dark and under sub-bandgap photonic excitation, have been modeled as a parallel connection of high performance PHEMT with a poor satellite FET as a parasitic channel. Sub-bandgap photonic characterization, as a function of the optical power with $h\nu=0.799eV$, has been comparatively combined with those under dark condition for characterizing the bell-shaped negative humps in the gate current and subthreshold drain leakage under a large drain bias.

• 수산해양기술연구
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• 제13권2호
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• pp.1-4
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• 1977

원뿔대 모양의 은대구 통발을 권양할 때의 류휴저항을 측정하고, 그로부터 모랫줄의 굵기,권양의 소요 순마력등을 추산하는 식을 유도했다. 1.통발의 권양속도 v(m/sec)와 류휴저항(수중중량 포함)T(kg)사이에는 대체로 다음과 같은 관계가 성립한다. (a)빈통발을 직립으로 권양할 때: T=$48v^{1\cdot0}$ $45^\circ$ 경사지게 권양할 때: T=$50v^{1\cdot1}$ (단 $0.3\leqq v \leqq1.3$) 이고,이들 사이에 유의차는 없다. (b)밑면에 천을 깐 통발을 직립으로 권양할 때: T=$120^{1\cdot1}$ $45^\circ$ 경사지게 권양할 때: T=98v$^{1=cdot1}$ (단 $0.3\leqq v \leqq0.8$) 2.통발의 유류저항의 최대치를 T=$120v^{1\cdot1}$ (단 $0.3\leqq v \leqq0.8$)이라 보고, 모릿줄로써 P.P.3년 로우프를 쓴다면 d(mm)는 대략 $d=72\frac{D}{H}v^{1\cdot1}$ 을 만족시켜야 한다. 3.권양의 순마력 P(ps)는 $P=\frac{75}{120}\frac{D}{H}v^{2\cdot1}$ 이상일 것이 요구된다.

• 수산해양기술연구
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• 제35권4호
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• pp.391-396
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• 1999

It is well known that fish hear a wide frequency range of sound using both laterial line and inner ear, and the sound is probably the most effective channel for long-range communication underwater than any other stimulus.The auditory threshold of svenband grouper, Epinephelus septem fasciatus was determined by conditioning method using a sound coupled with electric shock in a tank. The audio-signals and electric shock used in the experiment were pure tones of 100 to 1000Hz and DC 6n.The response of fish to the sound was observed by ECG intervals from precordial leads method (V1·V2 method). The auditory threshold curve for sevenband grouper was V-shaped, with most sensitive threshold at 350Hz in the range of 100~1000Hz. The Sevenband grouper were more sensitive to sounds of 200~400Hz than to adjacent frequencies.