• 한국재료학회지
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• 제17권3호
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• pp.142-146
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• 2007

Vacuum brazing method has been coming to an important process as one of the new fabricating techniques of metals and alloys. In this study, a vacuum brazing of SUS304 stainless steel with BNi-2 filler metal was carried out in $1{\times}10^{4}$ Torr of vacuum atmosphere. The formation of brittle intermetallic compounds in brazed joints between SUS304 stainless steel and BNi-2 filler metal is a major concern, since they considerably degrade the mechanical properties of joints. To obtain enough stable joining strength, it is necessary to understand the unique properties of brazing process with Ni-based filler metals containing boron. So, in this research we investigated the performance of SUS304/BNi-2 brazed system and the brazed joint properties were evaluated at room temperature by using tensile test. Metallurgical and fractographic analysis were used to characterize the microstructure, the mechanisms of brazing, and joint failure modes.

• 한국토양비료학회지
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• 제20권4호
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• pp.309-314
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• 1987

화력발전소(火力發電所)에서 부생(副生)되는 Fly ash의 비료자원(肥料資源) 가능성(可能性)을 검토(檢討)하기 위해 국내산(國內産) 무연탄(無煙炭) 및 도입(導入) 유연탄(有煙炭)의 회(灰)에 대한 광물학적(鑛物學的) 특성(特性)을 분석(分析)하였다. Fly ash는 규소(珪素), 알미늄이 주성분(主成分)으로서 전형적(典型的)인 규산(珪酸)알미늄 광물(鑛物)의 특성(特性)을 지니고 있었다. 그러나 비료자원(肥料資源)으로서 규소(珪素) 및 가리(加里)는 식물(植物)에 쉽게 이용(利用)될 수 없는 성분(成分)이었다. X-선회석분석(線回析分析), 시차열분석(示差熱分析), 적외선분광분석(赤外線分光分析) 및 Scanning Electron Micrography 분석(分析)에 의하여 새로운 광물(鑛物)인 Mullite의 형성(形成)을 확인(確認)하였으며 괴상(塊狀)의 규산물질(珪酸物質)이 생성(生成)되었다.

• Bulletin of the Korean Chemical Society
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• 제25권6호
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• pp.889-894
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• 2004

Polyaddition reactions of 1,1-diethynyl-3-triethylsilyl-1-silacyclopent-3-ene with several organoborane derivatives have afforded the oligomeric materials containing organosilacyclic group and organoboron moiety along the oligomer main chains. All of these materials are soluble in THF as well as chloroform, and their molecular weights are in the range of 1,990/1,190-21,950/7,050 ($M_w/M_n$) with the polydispersity indexes of 1.67-3.43. The prepared oligomers are characterized by several spectroscopic methods such as $^1H,\;^{13}C, \;^{29}Si,\;^{11}B$ NMR and FTIR spectra along with elemental analysis. FTIR spectra of all the oligomers show that the new strong C=C stretching frequencies appear at 1599-1712 $cm^{-1}$, in particular. The UV-vis absorption spectra of the materials in THF solution exhibit the strong absorption bands at the ${\lambda}_{max}$ of 268-275 nm. The oligomeric materials show that the strong excitation peaks appear at the ${\lambda}_{max}$ of 255-279 nm and the strong fluorescence emission bands at the ${\lambda}_{max}$ of 306-370 nm. All the spectroscopic data suggest that the obtained materials contain both the organoboron ${\pi}$-conjugation moiety of C=C-B-C=C and the organosilacyclic group of 3-triethylsilyl-1-silacyclopent-3-ene along the oligomer main chains. The oligomers are thermally stable up to 162-200 $^{\circ}C$ under nitrogen.

• Advanced Composite Materials
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• 제17권4호
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• pp.373-407
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• 2008

This paper will examine the possibilities of the virtual tests of composite structures by simulating mechanical behaviors by using supercomputing technologies, which have now become easily available and powerful but relatively inexpensive. We will describe mainly the applications of large-scale finite element analysis using the direct numerical simulation (DNS), which describes composite material properties considering individual constituent properties. DNS approach is based on the full microscopic concepts, which can provide detailed information about the local interaction between the constituents and micro-failure mechanisms by separate modeling of each constituent. Various composite materials such as metal matrix composites (MMCs), active fiber composites (AFCs), boron/epoxy cross-ply laminates and 3-D orthogonal woven composites are selected as verification examples of DNS. The effective elastic moduli and impact structural characteristics of the composites are determined using the DNS models. These DNS models can also give the global and local information about deformations and influences of high local in-plane and interlaminar stresses induced by transverse impact loading at a microscopic level inside the materials. Furthermore, the multi-scale models based on DNS concepts considering microscopic and macroscopic structures simultaneously are also developed and a numerical low-velocity impact simulation is performed using these multi-scale DNS models. Through these various applications of DNS models, it can be shown that the DNS approach can provide insights of various structural behaviors of composite structures.

• 한국재료학회지
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• 제15권12호
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• pp.786-790
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• 2005

We investigated the particularity of temperature and composition changes in $xNa_2O{\cdot}(52.5-x)B_2O_3{\cdot}47.5SiO_2$ glasses by use of FT-IR, $^{11}B$ NMR, Raman spectrometer. From FT-IR and $^{11}B$ NMR spectrometer, we thought that tetrahedral boron, $BO_4$ units are created $N_4$ increasing tendency generated near $600^{\circ}C$. It's expected that composition ana heat treatment directly contributed to structural changes, this changes are following to $Na_2O$ increasing or decreasing. caused by $N_4\;and\;BO_4$ units are caused by relatively increasing or decreasing in the glasses' structure. Particularly, $BO_4$ units are converted to $BO_3$ units after $600^{\circ}C$ heat treatment for 50h in the composition of $x<18(R<0.5,\;R=Na_2O/B_2O_3\;mol\%)$. On the order hand, $BO_3$ units are converted to, $BO_4$ units after $600^{\circ}C$ heat treatment for 50h in the composition of $x{\geq}18\;(R>0.5)$. This particularity of composition and temperature dependence of structural changes are similarly represented by Raman analysis results.

• 한국전기전자재료학회논문지
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• 제35권6호
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• pp.616-621
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• 2022

Numerical simulation is a good way to predict the conversion efficiency of solar cells without a direct experimentation and to achieve low cost and high efficiency through optimizing each step of solar cell fabrication. TOPCon industrial solar cells fabricated with n-type silicon wafers on a larger area have achieved a higher efficiency than p-type TOPCon solar cells. Electrical and optical losses of the front surface are the main factors limiting the efficiency of the solar cell. In this work, an optimization of boron-doped emitter surface and front electrodes through numerical simulation using "Griddler" is reported. Through the analysis of the results of simulation, it was confirmed that the emitter sheet resistance of 150 Ω/sq along the front electrodes having a finger width of 20 ㎛, and the number of finger lines ~130 for silicon wafer of M6 size is an optimized technology for the front emitter surface of the n-type TOPCon solar cells that can be developed.

• 한국초전도ㆍ저온공학회논문지
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• 제26권1호
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• pp.14-19
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• 2024

In this study, we explore the anisotropy of electron-phonon coupling (EPC) constant in epitaxially grown MgB₂ films on c-axis oriented Al₂O₃, examining its correlation with the critical temperature (T_c) and local structural disorder assessed through polarized Raman scattering. Analysis of the polarized Raman spectra reveals angle-dependent variations in the intensity of the phonon spectra. The Raman active mode originating from the boron plane, along with two additional phonon modes from the phonon density of states (PDOS) induced by lattice distortion, was distinctly observed. Persistent impurity scattering, likely attributed to oxygen diffusion, was noted at consistent frequencies across all measurement angles. The EPC values derived from the primary Raman active phonon do not significantly vary with changing observation angles, followed by that the T_c values calculated using the Allen and Dynes formula remain relatively constant across all polarization angles. Although the E_2g phonon mode plays a crucial role in the EPC mechanism, the determination of T_c values in MgB₂ involves not only electron-E_2g coupling but also contributions from other phonon modes.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4431-4446
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• 2023

A Multiphysics coupling framework, MPCORE, has been developed to analyze safety parameters using the best estimate codes. The framework contains neutron kinetics (NK), thermal hydraulics (TH), and fuel performance (FP) codes to analyze fuel burnup, radial power distribution, and coolant temperature (T_bc). Shuffling and rotation capabilities have been verified on the Watts Bar reactor for three cycles. This study focuses on two coupling approaches for TH and FP modules. The one-way coupling approach involves coupling the FP code with the NK code, providing no data to the TH modules but getting T_bc as boundary condition from TH module. The two-way coupling approach exchanges information from FP to TH modules, so that the simplified heat conduction solver of the TH module is not used. The power profile in both approaches does not differ significantly, but there is an impact on coolant and cladding parameters. The one-way coupling approach tends to over-predict the cladding hydrogen concentration (CHC). This research highlights the difference between one-way and two-way coupling on critical boron concentration, T_bc, CHC, oxide surface temperature, and pellet centerline temperature. Overall, MPCORE framework with two-way coupling provides a more accurate and reliable analysis of safety parameters for nuclear reactors.

• 한국진공학회지
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• 제1권1호
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• pp.115-120
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• 1992

SIMS는 뛰어난 원소검출감도와 깊이 분해능을 가지고 있어서 깊이에 따른 미량불 순물 분석에 필수적인 장비이지만, 시료와 불순물의 변화에 따라 이온화율과 깍이는 속도가 달라서 일어나는 matrix effect 때문에 표준 시료없이 정량분석을 할 수 없는 문제점이 있 다. 이런 SIMS의 단점을 보완하기 위한 방법으로 개발된 여러 가지 SNMS 기술 중 SIMS에 아무런 기계장치를 덧붙이지 않고도 정량화 개선효과를 가져오는 CsX+ SNMS에 대한 연구 를 진행하여, 지금까지 밝혀진 실리콘 산화막 등에서의 주성분원소 조성비분석을 통해 SNMS 기능을 확인하고 SIMS의 주 분석대상인 분순물 농도분석에의 적용가능성을 실험해 보았다. 이를 위해 실리콘에 BF2 이온 주입 후 붕소분포 분석시 강한 matrix effect를 나타 내는 불소의 효과를 SNMS와 SIMS로 비교하였으며, 검출한계와 dynamic range도 조사하였 다. 실험결과 CsX+ SNMS 기술은 matrix effect 때문에 실제분포와 다른 값으로 검출되는 불순물 시료분석에 적용할 수 있음을 알았다.

• 한국토양비료학회지
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• 제4권1호
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• pp.13-19
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• 1971

수도생육초기(水稻生育初期)에 흡수조해물질(吸收阻害物質)의 생성집적(生成集積)이 우려(憂慮)되는 전형적(典型的)인 습답(濕畓)의 개량방법(改良方法)을 확립(確立)시키기 위(爲)해서 적지(適地)를 선정(選定) 석회질물질(石灰質物質), 무류산근비료(無硫酸根肥料), 붕소(硼素) 생고등(生藁等)을 첨가처리(添加處理) 한 포장시험(圃場試驗)을 실시(實施)하고 시기별식물체시료(時期別植物體試料)의 채취분석(採取分析)을 실시(實施)하여 그 결과(結果)들을 평가검토(評價檢討)한 결과(結果) 대략(大約) 다음과 같이 요약(要約)할수 있었다. (1) 습답(濕畓)에서는 소석회(消石灰), 규회석(珪灰石)과 같은 석회질물질(石灰質物質)의 첨가(添加) 붕(硼) 사등(砂等)과 같은 미생물(微生物)의 활동억제물질(活動抑制物質), 무류산근비료(無硫酸根肥料)와 같은 유해물질생성원(有害物質生成源)이 없는 물질(物質)의 시용(施用)으로 현저(顯著)한 정조수양증수(精租收量增收)를 기(期)할수있다. (2) 습답(濕畓)에 있어서 작물학적(作物學的)인 감수원인(減收原因)은 주당수수(株當穗數) 수당입수(穗當粒數), 1000입중등(粒重等)이 감소(減少)되는것이다. (3) 습답(濕畓)에서의 식물영양학적(植物營養學的)인 감수원인(減收原因)은 전생육기간(全生育期間)을 통(通)한 질소흡수조해(窒素吸收阻害)와 유수형성기(幼穗形成) 이후(以後)의 인발흡목조해(燐醱吸牧阻害), 수확기고중(收穫期藁中)의 고토(苦土), 석회(石灰) 규산함량(硅酸含量)의 감소(減少)때문이다. (4) 습답(濕畓)에서의 각종성분(各種成分)의 수도체중함량감소원인(水稻體中含量減少原因)은 다음과 같은 관찰사실(觀察事實)로부터 흡수조해물질(吸收阻害物質)의 생성집적(生成集積)으로 인(因)한 근계(根系)의 피해(被害)때문이라고 추정(推定)된다. (가) 흡수조해물질(吸收阻害物質)의 생성집적(生成集積)이 최고(最高)에 이르는 유수형성기(幼穗形成期)에 있어서 인산(燐酸)의 식물체당함량(植物體當含量)은 인산무처리구(燐酸無處理區)보다 인산시용구(燐酸施用區)에서 적었으며 석회질물질시용(石灰質物質施用)으로 중화(中和)된 구(區)에서는 훨씬 많았다. (나) 생고시용구(生藁施用區)에서 유수형성기(幼穗形成期) 식물체중가리함량(植物體中加里含量)은 필경 생고분해과정(生藁分解過程)에서 생성(生成)된 흡수조해물질(吸收阻害物質)때문에 매우 낮었으나 수확기(收穫期)에는 높았으며 필경 피해근(被害根)에 의(依)한 소극적(消極的) 비대사흡수(非代謝吸收) 때문이다. (다) 유기물(有機物)을 분해(分解)하는 미생물(微生物)의 작용(作用)을 조해(阻害)하는 것으로 알려진 붕소(硼素)의 효과(效果)가 현저(顯著)하였다. (라) 유화수소(硫化水素)와 같은 흡수조해물질생성원(吸收阻害物質生成源)이 없는 무류산근비료처리(無硫酸根肥料處理)의 효과(效果)가 현저(顯著)하였다. (마) 흡수조해물질(吸收阻害物質)의 생성집적량(生成集積量)이 최고(最高)에 이르며 근(根)의 활력(活力)이 최저(最低)에 이르는 유수형성기전후(幼穗形成期前後)에 결정(決定)되는 수량구성요소(收量構成要素)들이 모두 감소(減少)된다.