• 한국통신학회논문지
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• 제35권11C호
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• pp.901-906
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• 2010

겔러거와 맥케이에 의해 처음 소개된 LDPC(Low density parity check)부호는 성능의 우수함 및 간단한 복호과정으로 많은 관심을 받아 왔으며, 특히 DVB-Satellite 2, DVB-Cable 2, DVB-Terrestrial 2 등의 차세대 방송시스템에서 널리 사용되고 있다. LDPC 부호의 성능은 충분히 긴 길이의 부호어와 iterative decoder를 사용함으로서 샤논의 한계에 거의 근접하는 성능을 보여준다. 그러나, LDPC 부호는 현재 이동통신에서 널리 사용되고 있는 Turbo 부호와 비교해서 복잡한 부호화 과정이 단점으로 지적되고 있다. 본 논문에서는 IRA 부호기를 사용하여 DVB-S2 LDPC 부호기의 성능을 향상 시킬 수 있는 방안을 제안한다.

• 한국산학기술학회논문지
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• 제15권6호
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• pp.3455-3459
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• 2014

본 논문은 전자기 발사체에서 피투사체의 높은 발사력을 위한 코일건 설계 및 실험을 다루고 있다. 현재 코일건은 전자기 발사체에 적용하기 위해 많은 연구가 진행되고 있다. 코일건은 솔레노이드 형태의 코일에 전류 인가 시, 플레밍의 오른손 법칙에 의하여 발생하는 전자기력에 의해 피투사체를 추진시키는 원리이다. 피투사체의 발사력은 코일에 흐르는 전류가 생성하는 자기력과 비례한다. 전류는 코일의 수명에 영향을 미치므로 전류의 한계점이 존재한다. 따라서, 전류의 한계점을 초과하지 않고 피투사체가 받는 자기력이 최대가 되는 코일건의 설계가 요구된다. 이를 위해 먼저 코일건의 자속밀도, 자기력을 계산하고, Onderdonk's 식을 이용하여 코일의 전류 한계점을 찾는다. 솔레노이드를 설계하기 위해서 전류 한계점을 초과하지 않는 조건을 만족하며 코일건의 자기력을 최대로 가지는 권수를 알아낸다. 설계 결과에 따라 시제품을 제작하여 피투사체의 속도를 측정하기 위한 실험을 하였다. 발사된 피투사체는 CCD 카메라를 이용하여 촬영 및 분석하였으며, 평균속도 21m/s임을 알 수 있었다. 또한, 상용 전자기 해석 소프트웨어 MAXWELL을 이용한 자속 밀도 해석값와 실험값을 비교한 결과, 오차는 약 9.5%이었다.

• 해양환경안전학회지
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• 제21권2호
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• pp.171-178
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• 2015

본 연구는 제한속력 설정 모델 개발을 위한 1차 연구로서 제한속력 설정 시 고려요소에는 어떤 것이 있으며, 각 요소별 중요도는 얼마나 되는지에 대한 연구의 결과이다. 고려요소 식별과 중요도 산정을 위해 델파이(Delphi)기법과 AHP(Analytic Hierarchy Process)기법을 이용하였다. 델파이 설문은 3차에 걸쳐 수행하였고 3차에 걸친 설문을 통해 5개 상위요소(Level 1)와 23개 하위요소(Level 2)가 식별되었다. 3차 델파이 설문과정에서 내용타당도비율(CVR)값이 0.4~1.0 범위에 있으면 제한속력 설정 시 고려요소로서 반영하였고 0.4 미만의 값은 고려요소에서 제외하였다. 2차 델파이 설문과정에서 33개 고려요소가 식별되었으나 3차 설문을 통해 23개 항목으로 축소되었다. 델파이 3차 분석을 통해 얻은 23개 항목을 대상으로 AHP 설문을 수행하였다. AHP 설문 결과, 5개 상위요소(Level 1)에 대한 중요도는 교통조건이 가장 중요한 요소로 평가되었고, 선박조건, 항로조건, 자연조건, 외부지원 및 기타 조건 순으로 평가되었다. 23개 하위요소 중에서 시정이 가장 중요(1위)하다고 평가되었으며, 선박조종성능, 항로 내 수중장애물, 교통량 및 밀도, 통항선박간 거리, 타효가능속력, 조류 순으로 평가되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.582-587
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• 2002

Current information storage devices, such as HDD, CD/DVD-ROM/RW, probe-based memory and hologram memory, are compared with biological information storage mechanisms in DNA and brain memory. Newly developed approaches to overcome the limit of storage capacity are introduced in both magnetic and optical recording devices. Linear and areal density of information stored in the biological and mechanical storages are compared for the applications and developments of new storage devices.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.1023-1027
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• 1996

In this paper, the new technology and R&D status is presented, which accelerates the projectile using the electrical energy to overcome the limit of the conventional gun. The ETC (electro_thermal_chemical) gun, one kind of electric guns, seems to be the highly probable candidate as the next generation gun. The high density power supply and the forming and control of the current pulse are required to develop the ETC gun. And, the interior ballistics considered the mechanism of ETC gun must to be studied.

• 태양에너지
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• 제18권3호
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• pp.137-146
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• 1998

In this paper, the current status of manufacturing technologies for GaAs/Si solar cell were revived and provied new MOCVD. In the manufacturing process of GaAs/Si solar cells and an experiment to get the high efficiency GaAs solar cells, we must investigate the optimum growth conditions to get high quality GaAs films on Si substrates by MOCVD. The GaAs on Si substrates has been recognized as a lightweight alternative to pure substrate for space applicaton. Because its density is less the half of GaAs or Ge.So GaAs/Si has twofold weight advantage to GaAs monolithic cell. The theoretical conversion efficiecy limit of tandem GaAs/Si solar cell is 32% under AM 0 and $25^{\circ}C$ condition. It was concluded that the development of cost effective MOCVD technologies shoud be ahead GaAs solar cells for achived move high efficiency III-V solar cells involving tandem structure.

• Current Optics and Photonics
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• 제2권4호
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• pp.378-382
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• 2018

In most previous investigations of plasmonic and metamaterial applications, the metallic film has been regarded as a perfect electrical conductor. Here we demonstrate the resonance characteristics of THz metamaterials fabricated from metal film that has a finite dielectric constant, using finite-difference time-domain simulations. We found strong redshift and spectral broadening of the resonance as we decrease the metal's plasma frequency in the Drude free-electron model. The frequency shift can be attributed to the effective thinning of the metal film, originating from the increase in penetration depth as the plasma frequency decreases. On the contrary, only peak broadening occurs with an increase in the scattering rate. The metal-thickness dependence confirms that the redshift and spectral broadening occur when the effective metal thickness drops below the skin-depth limit. The electromagnetic field distribution illustrates the reduced field enhancement and reduced funneling effects near the gap area in the case of low plasma frequency, which is associated with reduced charge density in the metal film.

• 전자통신동향분석
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• 제36권3호
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• pp.23-33
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• 2021

Two main technologies of III-V/Si laser diode for optical communication, direct epitaxial growth, and wafer bonding were studied. Until now, the wafer bonding has been vigorously studied and seems promising for the ideal III-V/Si laser. However, the wafer bonding process is still complicated and has a limit of mass production. The development of a concise and innovative integration method for silicon photonics is urgent. In the future, the demand for high-speed data processing and energy saving, as well as ultra-high density integration, will increase. Therefore, the study for the hetero-junction, which is that the III-V compound semiconductor is directly grown on Si semiconductor can overcome the current limitations and may be the goal for the ideal III-V/Si laser diode.

• 방사성폐기물학회지
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• 제18권spc호
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• pp.1-19
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• 2020

Based on the current high-level radioactive waste management basic plan and the analysis results of spent nuclear fuel characteristics, such as dimensions and decay heat, an improved geological disposal concept for spent nuclear fuel from domestic nuclear power plants was proposed in this study. To this end, disposal container concepts for spent nuclear fuel from two types of reactors, pressurized water reactor (PWR) and Canada deuterium uranium (CANDU), considering the dimensions and interim storage method, were derived. In addition, considering the cooling time of the spent nuclear fuel at the time of disposal, according to the current basic plan-based scenarios, the amount of decay heat capacity for a disposal container was determined. Furthermore, improved disposal concepts for each disposal container were proposed, and analyses were conducted to determine whether the design requirements for the temperature limit were satisfied. Then, the disposal efficiencies of these disposal concepts were compared with those of the existing disposal concepts. The results indicated that the disposal area was reduced by approximately 20%, and the disposal density was increased by more than 20%.

• 대한화학회지
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• 제57권3호
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• pp.322-328
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• 2013

Copper iodide was employed as a modifier for preparation of a new carbon ceramic electrode. For the first time, the catalytic oxidation of amoxicillin (AMX) was demonstrated by cyclic voltammetry, chronoamperometry and amperometry methods at the surface of this modified carbon ceramic electrode. The copper iodide modified sol-gel derived carbon ceramic (CIM-SGD-CC) electrode has very high catalytic ability for electrooxidation of amoxicillin. The catalytic oxidation peak current was linearly dependent on the amoxicillin concentration and the linearity range obtained was 100 to 1000 ${\mu}mol\;L^{-1}$ with a detection limit of 0.53 ${\mu}mol\;L^{-1}$. The diffusion coefficient ($D=(1.67{\pm}0.102){\times}10^{-3}\;cm^2\;s^{-1}$), and the kinetic parameter such as the electron transfer coefficient (${\alpha}$) and exchange current density ($j_0$) for the modified electrode were calculated. The advantages of the modified CCE are its good stability and reproducibility of surface renewal by simple polishing, excellent catalytic activity and simplicity of preparation.