• 한국재료학회지
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• 제16권9호
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• pp.529-532
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• 2006

Sn-filled $Co_8Sb_{24}$ skutterudites were synthesized by the encapsulated induction melting process. Single ${\delta}-phase$ was successfully obtained by subsequent annealing and confirmed by X-ray diffraction analysis. Temperature dependences of Seebeck coefficient, electrical resistivity and thermal conductivity were examined from 300 K to 700 K. The positive Seebeck coefficient confirmed the p-type conductivity of the Sn-filled $Co_8Sb_{24}$. Electrical resistivity increased with increasing temperature, which shows that the Sn-filled $Co_8Sb_{24}$ skutterudite is a highly degenerate semiconductor. Thermal conductivity was reduced by Sn-filling because the filler atoms acted as phonon scattering centers in the skutterudite lattice. Thermoelectric figure of merit was enhanced by Sn filling and its optimum filling content was considered to be $z{\leq}0.5$ in the $Sn_zCo_8Sb_{24}$ system.

• 한국물환경학회지
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• 제21권5호
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• pp.500-504
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• 2005

Water samples were collected at 7 sites located along the River Nakdong on 30 occasions. Water qualities, size and fractal dimension ($d_F$) of suspended particles were measured. Laser light scattering method was used to obtain the size and $d_F$ of suspended particles. The average size of particles in this river ranged from $89{\mu}m$ and $169{\mu}m$, which appears to be relatively coarse compared with other rivers worldwide. The average $d_F$ of suspended particles in this study ranged from 1.8 to 1.9. The correlation analysis showed that DO, TN, $NO_3$ and chlorophyll-${\alpha}$ had significant positive relationships with particles size, whereas flow rates and TSS had negative relationships. Interestingly, the factors of which had positive relationships with particles size showed negative relationship with the fractal dimension ($d_F$) of suspended particles. Generally, as the size of particles increased, the fractal dimension of particles decreased which was indicating the shape of the larger particles became more irregular.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1994년도 제6회 학술발표회 논문개요집
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• pp.35-35
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• 1994

The surface segragation of NiZr, CuZr alloy has been studied wi th X-ray Imotoelectron spectroscopy(XPS), Auger electron spectroscopy(AES) and low energy ion scattering(LEIS). The composition of outmost atomic layer has been determinded by the use of LEIS at several incident energies using Ar+ ion. In the LEIS analysis, the effect of charge exchange has been estimated by a novel measurment of the charge exchange parameters while simul taneous determining the relative concentrations of Ni and Zr and the complementary information obtained will be described. The composition of the clean annealed surface, measured with AES only, will be contrasted wi th the surface concentration of the preferentially sputtered surface. The experimental results has been clearly demonstrated that when the NiZr ruld CuZr alloys are exposed to continuous Ar+ ion bombardment the outermost atomic layer is Zr rich due to preferential sputtering of Ni atoms. where Ni is preferentially sputtered, but the difference in sputtering yields is not sufficient to explain the observed composition. Therefore, it is necessary to consider other processes such as Radiation Induced Segregation(RIS). The surface composition of the heated sample surface predicts that Zr should surface segregate which futher supports the view that part of the Zr enrichment is due to RIS.to RIS.

• 전자공학회논문지A
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• 제33A권10호
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• pp.71-80
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• 1996

Sattering problem of electromagnetic waves by periodic strip grating with two dielectrics over a ground plane in case of oblique incidence and arbitrary polarization is analyzed by the vector floquet mode expansion method and the moment mehtod from the viewpoint of soft and hard boundary value problem. To confirm proposed analysis methods, we examine the solution convergence for the scattering problem. And some numerical results of artificially soft and hard surfaces using the structure filled with single dielectric slab between periodic strip grating and gorund plane is compared with previous results. Some interesting results for soft and hard surfaces using periodic strips loaded with two layered dielectric slabs over a ground plane are given.

• 전자공학회논문지A
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• 제33A권10호
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• pp.90-97
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• 1996

A numerical method for scattering of electromagnetic waves from a periodic strip grating over a grounded dielectric slab is considered for TE and TM polarization cases from the viewpoints of both reflection grating problem and leaky wave antenna problem. The analysis is based on a mode expansion method, floquet's theorem, and the method of moments. Numerical results involving some combinations of geometric parameters are presented in terms of complex propagation constant (kd-$\beta$d diagram), radiation pattern, and relative scattered powers of spectral modes. In particular, the relationship between complex propagatio constnat form the viewpoint of leaky wqve antenna problem and Off-bragg and bragg blazing phenomena from the viewpoint of reflecton graing problem is investigated.

• 한국결정성장학회지
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• 제7권2호
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• pp.197-206
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• 1997

6H-SiC 위에 SiC 에피층이 화학 기상 증착(CVD)에 의하여 성장되었다. 성장된 SiC 에피층의 결정구조는 X-선 회절과 Raman 분광을 사용하여 조사되었으며, 이 에피층은 6H-SiC로서 성장되었음을 확인하였다. 수정된 Lely법으로 성장된 한 SiC 결정 분말의 결정구조를 확인하기 위하여 전형적인 SiC polytype들의 X-선 회절상을 계산하였으며, 측정된 X-선 회절상과 비교하여 이 SiC 결정에는 15R-SiC가 약간 혼재되어 있음을 확인하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.195-198
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• 2008

고체추진제 연소속도 측정을 위한 초음파법은 한 번의 실험으로 연소속도를 측정할 수 있기 때문에 적용되어 왔다. 하지만 스트랜드버너법을 대체하기 위해서는, 초음파법의 정확성과 신뢰성이 증명되어야 한다. 본 논문에서는 초음파법을 이용하여 측정한 연소속도와 스트랜드버너법으로 측정한 결과의 차이를 비교하였다. 그리고 측정된 연소속도의 분산과 고체추진제의 초음파 감쇠와의 연관성을 조사하였다.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1809-1816
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• 2014

This study demonstrates gel-to-fluid transition temperatures of polydiacetylene bilayer vesicles could play important roles in their colorimetric transition temperatures. We prepared five types of polydiaceylene vesicles with 10,12-pentacosadiynoic acid (PCDA) and cholesterol (0-40 mol % of total content). From temperature-dependent observations of the optical signals (colors and UV-vis spectra), the blue-to-red colorimetric transition temperatures of polydiacetylene vesicles were decreased with the cholesterol contents. A further study with microcalorimetry and dynamic light scattering revealed that the polydiacetylene vesicles first underwent gel-to-fluid transitions, which were followed by event(s) responsible for the colorimetric transitions. Energies required for each event were quantified from analysis of the peaks in the microcalorimetry thermograms. The inclusion of cholesterol in the vesicles decreased both the gel-to-fluid and the colorimetric transition temperatures, suggesting that the colorimetric transition of the polydiacetylene vesicles was mediated by the former event although the event was not the direct reason for the color change.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1771-1776
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• 2020

Adverse effects in the measured gamma spectrum caused by radioactive statistical fluctuations, gamma ray scattering, and electronic noise can be reduced by energy spectrum denoising. Wavelet threshold denoising can be used to perform multi-scale and multi-resolution analysis on noisy signals with small root mean square errors and high signal-to-noise ratios. However, in traditional wavelet threshold denoising methods, there are signal oscillations in hard threshold denoising and constant deviations in soft threshold denoising. An improved wavelet threshold calculation method and threshold processing function are proposed in this paper. The improved threshold calculation method takes into account the influence of the number of wavelet decomposition layers and reduces the deviation caused by the inaccuracy of the threshold. The improved threshold processing function can be continuously guided, which solves the discontinuity of the traditional hard threshold function, avoids the constant deviation caused by the traditional soft threshold method. The examples show that the proposed method can accurately denoise and preserves the characteristic signals well in the gamma energy spectrum.

• 한국의학물리학회지:의학물리
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• 제15권3호
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• pp.140-148
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• 2004

본 연구에서는 PTRAN 전산코드를 사용하여 양성자에 대한 물 흡수선량의 분포를 계산하였다. 먼저 양성자와 물과의 상호작용에 대하여 정리하고 흡수선량의 계산과정에 대하여 기술하였다. 또한 PTRAN의 수송 알고리즘, 파일구조, 그리고 실행방법을 제시하였다. 본 결과에서는 양성자 에너지 60, 100, 150, 200, 250 WeV에 대하여 양성자에 의한 물 흡수선량의 분포가 쿨롱 상호작용과 핵반응의 합으로 주어지며, 브레그 봉우리의 형태가 에너지손실의 통계적 성질과 다중산란에 의존함을 보였다. 본 연구를 통하여 양성자에 대한 물 흡수선량의 구조 해석에 PTRAN 코드가 유용함을 알 수 있었다.