• 한국정보통신학회논문지
• /
• 제4권5호
• /
• pp.971-976
• /
• 2000

The main objective of this paper is to present the rain cell size distribution observed during squall line episodes in the Sudano-Sahelian region. The used data were collected during the EPSAT Program [Etude des Precipitation par SATellite (Satellites Study of Precipitation)] which has been developed since 1958, on an experimental area located near Niamey, Niger (2 10′32"E, 13 28′38"N). The data were obtained with a C-band radar and a network composed of approximately 100 raingages over a 10,000 $\textrm{km}^2$. In this work a culling of the squall line episodes was made for the 1992 rainy season. After radar data calibration using the raingage network a number of PPI (Plan Position Indicator) images were generated. Each image was then treated in order to obtain a series of radar reflectivity (Z) maps. To describe the cell distribution, a contouring program was used to analyze the areas with rain rate greater than or equal to the contour threshold (R$\geq$$\tau$). 24700 contours were generated, where each iso-pleth belongs to a predefined threshold. Computing each cell surface and relating its area to an equi-circle (a circle having the same area as the cell), a statistical analysis was made. The results show that the number of rain cells having a given size is an inverse exponential function of the equivalent radius. The average and median equivalent radii ate 1.4 and 0.69 In respectively. Implications of these results for the precipitation estimation using threshold methods are discussed.

• Journal of Chest Surgery
• /
• 제40권7호
• /
• pp.526-528
• /
• 2007

골조직에 발생하는 거대세포종은 국소적으로는 양성이지만 재발률이 매우 높고, 아주 드물게 원격전이를 일으킬 수 있다. 우측 요골에 발생한 거대세포종이 치료 후 재발되어, 요골을 제거한 후, 다시 동측 흉벽 연부조직에 전이된 29세의 남자환자를 보고하는 바이다. 종양은 흉벽의 골조직과는 연관이 없었다. 수술은 주위 연부조직과 함께 광범위 절제하였으며, 조직학적 검사상 악성 종양을 시사하는 소견은 없었다.

• Journal of electromagnetic engineering and science
• /
• 제4권1호
• /
• pp.30-36
• /
• 2004

We determined equivalent circuit parameters of a 1.5 cell S-band RF gun cavity from the resonant characteristics of its decoupled cavities(half cell and full cell) using the code SUPERFISH. Equivalent circuit parameters of the 1.5 cell RF gun cavity resonated in the 0-mode were obtained easily from the circuit parameters of each decoupled cavities. In order to obtain equivalent circuit parameters for the $\pi$ -mode cavity, we calculated the differences of the resonant frequencies and the equivalent resistances between the 0- and $\pi$ -modes with slight variations of the radius and thickness of the coupling iris. From those differences, we obtained R/Q value and equivalent resistance of the $\pi$ -mode, which are directly related to the equivalent circuit parameters of the coupled cavity. Using calculated R/Q value, we can express equivalent inductance, capacitance and resistances of the RF gun cavity resonated in the $\pi$ -mode, which can be useful for analyzing coupled cavities in a steady state.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.189-189
• /
• 2012

Lead sulfide (PbS) nanocrystal quantum dots (NQDs) are promising materials for various optoelectronic devices, especially solar cells, because of their tunability of the optical band-gap controlled by adjusting the diameter of NQDs. PbS is a IV-VI semiconductor enabling infrared-absorption and it can be synthesized using solution process methods. A wide choice of the diameter of PbS NQDs is also a benefit to achieve the quantum confinement regime due to its large Bohr exciton radius (20 nm). To exploit these desirable properties, many research groups have intensively studied to apply for the photovoltaic devices. There are several essential requirements to fabricate the efficient NQDs-based solar cell. First of all, highly confined PbS QDs should be synthesized resulting in a narrow peak with a small full width-half maximum value at the first exciton transition observed in UV-Vis absorbance and photoluminescence spectra. In other words, the size-uniformity of NQDs ought to secure under 5%. Second, PbS NQDs should be assembled carefully in order to enhance the electronic coupling between adjacent NQDs by controlling the inter-QDs distance. Finally, appropriate structure for the photovoltaic device is the key issue to extract the photo-generated carriers from light-absorbing layer in solar cell. In this step, workfunction and Fermi energy difference could be precisely considered for Schottky and hetero junction device, respectively. In this presentation, we introduce the strategy to obtain high performance solar cell fabricated using PbS NQDs below the size of the Bohr radius. The PbS NQDs with various diameters were synthesized using methods established by Hines with a few modifications. PbS NQDs solids were assembled using layer-by-layer spin-coating method. Subsequent ligand-exchange was carried out using 1,2-ethanedithiol (EDT) to reduce inter-NQDs distance. Finally, Schottky junction solar cells were fabricated on ITO-coated glass and 150 nm-thick Al was deposited on the top of PbS NQDs solids as a top electrode using thermal evaporation technique. To evaluate the solar cell performance, current-voltage (I-V) measurement were performed under AM 1.5G solar spectrum at 1 sun intensity. As a result, we could achieve the power conversion efficiency of 3.33% at Schottky junction solar cell. This result indicates that high performance solar cell is successfully fabricated by optimizing the all steps as mentioned above in this work.

• 대한골관절종양학회지
• /
• 제1권2호
• /
• pp.145-153
• /
• 1995

Giant cell tumor is most frequently found in juxtaarticular region, and difficult to treat because of local recurrence. Although primary resections reduce recurrence, the joint function will be markedly impaired. Techniques involving physical adjuncts(high speed burr and electric cauterization), acrylic cement or en bloc resection with VFG(vascularized fibular graft) have been employed to reduce local recurrence. From October 1984 to April 1994, twenty-nine patients diagnosed as giant cell tumor were treated at department of Orthopaedic Surgery, School of Medicine, Kyung Hee University. There were eleven men and 18 women, ranging in age from 17 to 52 years(mean: 34 years). The average follow-up period was four years and five months. The location of the lesion was around the knee in 15, distal radius in three, femoral head in three, and others in eight patients. Fifteen patients around the knee joint were treated with several modalities; curettage with bone graft in five, curettage with cement filling in three, curettage with bone graft and physical adjuncts in five, en bloc resection with VFG in one and en bloc resection with arthroplasty in one patient. The functional results, according to the Marshall's knee score, were excellent in one, good in two, and fair in two after the curettage with bone graft, good in three after the curettage with bone cement filling, excellent in one, good in four after the curettage with bone graft and physical adjuncts, and good in two after the en bloc resection with VFG or arthroplasty. Three patients had local recurrence among 15 patients with giant cell tumor around knee. Vascularized fibular graft around wrist joint provided good functional restoration without local recurrence in all three patients who had giant cell tumor in distal radius. Although there is no statistical significance, it seems that curettage with bone graft using physical adjuncts or acrylic cement reveals better results than simple curettage with bone graft. Excellent functional result were obtained without local recurrence by using vascularized fibular graft after en bloc resection.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.493-493
• /
• 2014

The manufacturing cost of thin-film photovoltics can potentially be lowered by minimizing the amount of a semiconductor material used to fabricate devices. Thin-film solar cells are typically only a few micrometers thick, whereas crystalline silicon (c-Si) wafer solar cells are $180{\sim}300\mu}m$ thick. As such, thin-film layers do not fully absorb incident light and their energy conversion efficiency is lower compared with that of c-Si wafer solar cells. Therefore, effective light trapping is required to realize commercially viable thin-film cells, particularly for indirect-band-gap semiconductors such as c-Si. An emerging method for light trapping in thin film solar cells is the use of metallic nanostructures that support surface plasmons. Plasmon-enhanced light absorption is shown to increase the cell photocurrent in many types of solar cells, specifically, in c-Si thin-film solar cells and in poly-Si thin film solar cell. By proper engineering of these structures, light can be concentrated and coupled into a thin semiconductor layer to increase light absorption. In many cases, silver (Ag) nanoparticles (NP) are formed either on the front surface or on the rear surface on the cells. In case of poly-Si thin film solar cells, Ag NPs are formed on the rear surface of the cells due to longer wavelengths are not perfectly absorbed in the active layer on the first path. In our cells, shorter wavelengths typically 300~500 nm are also not effectively absorbed. For this reason, a new concept of plasmonic nanostructure which is NPs formed both the front - and the rear - surface is worth testing. In this simulation Al NPs were located onto glass because Al has much lower parasitic absorption than other metal NPs. In case of Ag NP, it features parasitic absorption in the optical frequency range. On the other hand, Al NP, which is non-resonant metal NP, is characterized with a higher density of conduction electrons, resulting in highly negative dielectric permittivity. It makes them more suitable for the forward scattering configuration. In addition to this, Ag NP is located on the rear surface of the cell. Ag NPs showed good performance enhancement when they are located on the rear surface of our cells. In this simulation, Al NPs are located on glass and Ag NP is located on the rear Si surface. The structure for the simulation is shown in figure 1. Figure 2 shows FDTD-simulated absorption graphs of the proposed and reference structures. In the simulation, the front of the cell has Al NPs with 70 nm radius and 12.5% coverage; and the rear of the cell has Ag NPs with 157 nm in radius and 41.5% coverage. Such a structure shows better light absorption in 300~550 nm than that of the reference cell without any NPs and the structure with Ag NP on rear only. Therefore, it can be expected that enhanced light absorption of the structure with Al NP on front at 300~550 nm can contribute to the photocurrent enhancement.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 하계종합학술대회 논문집
• /
• pp.65-68
• /
• 1999

In this paper the Wideband DS/CDMA system capacity variation is analyzed by the impact of imperfect sectorization and man-made noise, which is more predominant in urban area than thermal noise. In general man-made noise is increasing as the electronic machines are increasing nowadays. It shows that user capacity and cell radius variation are much sensitive by the man-made noise.

• ETRI Journal
• /
• 제35권2호
• /
• pp.332-335
• /
• 2013

In this letter, the acoustic noise due to long term evolution (LTE) user equipment (UE) is investigated with various transmitting powers of the LTE UE by using the Monte Carlo method in a practical acoustic noise experiment.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 추계학술대회 논문집
• /
• pp.495-497
• /
• 1999

In order to determine what influences the interfacial breakdown in EPDM/XLPE laminates, We made the breakdown test ceil and this was pressure controllable breakdown test cell. We make the needle electrode (tip radius: about 10 micrometer) using electrochemical method. We studied the interfacial silicone oil was higher than that with silicone grease. As a function of heat treatment time in a vacuum, interfacial breakdown strength increased much in XLPE/EPDM laminates pasted with silicone grease but increased a little in that with silicone oil.

• 한국통신학회논문지
• /
• 제39C권10호
• /
• pp.937-945
• /
• 2014

LTE/LTE-adv. 서비스 도입에 따라 높은 데이터 전송률을 요하는 다양한 서비스들이 제공되면서 모바일 트래픽은 더욱 가파르게 증가하고 있다. 이러한 트래픽 수요의 폭발적인 증가에 대응하기 위한 새로운 주요 기술로 소형셀 기술이 각광받고 있다. 소형셀 기술은 셀 반경을 현격히 줄여서 소형 기지국의 수를 증가시킴으로써 수용 가능한 트래픽 양을 늘릴 수 있다. 본 논문은 동종네트워크의 outdoor 환경에서 소형셀 도입에 따른 셀 치밀화(cell densification) 효과에 대해 셀 분할 효과와 단위 면적당 UE 수를 별도로 고려하여 SINR(Signal to Interference-Noise Ratio)과 UE(User Equipment)당 평균 수율 변화를 분석하였다. 또한 셀이 소형화되면 셀 간 간격이 좁아지면서 인접셀 간 간섭이 심화되어 SINR이 열화되기 때문에 본 논문은 간섭 제어가 적절하게 이루어졌을 때의 SINR 이득을 보임으로써 소형셀 환경에서의 간섭 제거 기법의 효과를 검증하였다.