In this study, factors considered to be causes of promotion of densification of sintered pellets identified during phase change are reviewed. As a result, conclusions shown below are obtained for each factor. In order for MA powder to soften, a temperature of 1,000 K or higher is required. In order to confirm the temporary increase in density throughout the sintered pellet, the temperature rise due to heat during phase change was found not to have a significant effect. While examining the thermal expansion using the compressed powder, which stopped densification at a temperature below the MA powder itself, and the phase change temperature, no shrinkage phenomenon contributing to the promotion of densification is observed. The two types of powder made of Ti-silicide through heat treatment are densified only in the high temperature region of 1,000 K or more; it can be estimated that this is the effect of fine grain superplasticity. In the densification of the amorphous powder, the dependence of sintering pressure and the rate of temperature increase are shown. It is thought that the specific densification behavior identified during the phase change of the Ti-37.5 mol.%Si composition MA powder reviewed in this study is the result of the acceleration of the powder deformation by the phase change from non-equilibrium phase to equilibrium phase.

It is generally believed that the meaning of “Yi (泗)” in the Book of Songs has been nasal fluids since Mao Heng, and has been explained from the perspective of borrowing, phonetic and ideographic word-formation, etc. However, there are still seven questions about the exact meaning of “Si (泗)”, which arouses different doubts about it. From the perspectives of handed-down documents and unearthed documents, variant relationships, literary meanings, contexts, dialects and so on, the word “Yi (泗)” of “Ti Si Pang Tuo (涕泗滂沱)” should be “Yi (㳑)” meaning that the water is full and flowing out. Furthermore, “Yi (泗)” has heterogeneous relationships with “Yi (益)”, “Yi (㳑)”, “Yi (溢)”, “Yi (洫)” and “Yi (泆)”, and has homologous relationships with “Ti (涕)”, “Yi (洟)” and “Ti (嚏)”, and has an isomorphic relationship with “Si (泗)” of “Si Shui (泗水)”. These relationships can be used to collate unearthed and handed-down documents.

Two different casting speeds of 60 and 80mm/min are adopted to determine the effect of casting speed on the microstructure and mechanical properties of Al-Mg-Si/Al hybrid material prepared by duo-casting. The obtained hybrid material has a uniform and straight macro-interface between the pure Al side and the Al-Mg-Si alloy side at both casting speeds. When the casting speed is increased to 80mm/min, the size of primary α phases in Al-Mg-Si alloy decreases, without change of shape. Although the Al-Mg-Si alloy produced at higher casting speed of 80mm/min shows much higher ultimate tensile strength (UTS) and 0.2 % proof stress and lower elongation, along with higher bending strength compared to the case of the 60mm/min in casting speed, the tensile properties and bending strength of the hybrid material, which are similar to those of pure Al, are the same regardless of the increase of casting speed. Despite the different casting speeds, deformation and fracturing in hybrid materials are observed only on the pure Al side. This indicates that the macro-interface is well-bonded, allowing it to endure tensile and bending deformation in all hybrid materials.

In this study, three kinds of metal chills such as SS400, AC4CH and brass, with different thicknesses of 40 ~ 80 mm, were applied for low pressure casting of Al-Si alloy to control cooling rate. The microstructural characteristics with increasing cooling rate were represented using factors including D1, D2, size of primary α phases and shape factor and size of eutectic Si. The tensile properties were investigated and additionally analyzed based on the microstructural characteristics. As the cooling rate increased, D1, D2, and sizes of primary α phases and eutectic Si apparently decreased and the shape factor of eutectic Si increased to over 0.8. The ultimate tensile strength (UTS) and yield strength (YS) increased with decreasing D1, D2, and size of primary α phases, while elongation increased with decreasing size of eutectic Si and concurrently increasing shape factor of eutectic Si. This indicated that the primary α phases and eutectic Si in Al-Si alloy were refined with increasing cooling rate, resulting in improvement of UTS and YS without sacrificing elongation. After the tensile test, preferential deformation of primary α phases was observed in the Al-Si alloy produced at higher cooling rates of more than 0.1 K/s.

The effect of intercritical annealing temperature on the microstructure and mechanical properties of Fe-9Mn-0.2C- 3Al-0.5Si medium manganese steels containing Cu and Ni is investigated in this study. Six kinds of medium manganese steels are fabricated by varying the chemical composition and intercritical annealing temperature. Hardness and tensile tests are performed to examine the correlation of microstructure and mechanical properties for the intercritical annealed medium manganese steels containing Cu and Ni. The microstructures of all the steels are composed mostly of lath ferrite, reverted austenite and cementite, regardless of annealing temperature. The room-temperature tensile test results show that the yield and tensile strengths decrease with increasing intercritical annealing temperature due to higher volume fraction and larger thickness of reverted austenite. On the other hand, total and uniform elongations, and strain hardening exponent increase due to higher dislocation density because transformation-induced plasticity is promoted with increasing annealing temperature by reduction in reverted austenite stability.

In this study, the effects of Sm addition (0, 0.05, 0.2, 0.5 wt%) on the microstructure, hardness, and electrical and thermal conductivity of Al-11Si-1.5Cu aluminum alloy were investigated. As a result of Sm addition, increment in the amount of α-Al and refinement of primary Si from 70 to 10 μm were observed due to eutectic temperature depression. On the other hand, Sm was less effective at refining eutectic Si because of insufficient addition. The phase analysis results indicated that Sm-rich intermetallic phases such as Al-Fe-Mg-Si and Al-Si-Cu formed and led to decrements in the amount of primary Si and eutectic Si. These microstructure changes affected not only the hardness but also the electrical and thermal conductivity. When 0.5 wt% Sm was added to the alloy, hardness increased from 84.4 to 91.3 Hv, and electric conductivity increased from 15.14 to 16.97 MS/m. Thermal conductivity greatly increased from 133 to 157 W/m·K.

목적 : 경북 경산시 내외의 2학년 초등학생들의 굴절상태와 교정상태를 비교 분석하였다. 방법 : 2015년 경산교육지원청 주관 ‘밝고 투명한 아이(eye)만들기’사업의 2차 사업으로 경산지역 전체 초등학교 31개교 중 27개교가 참여한 2학년 초등학생 1,662명(3,324안)을 대상으로 굴절상태와 안경착용 상태를 검사하였다. 도시지역과 농촌지역으로 구분하여 등가구면굴절력을 기초로 굴절이상을 비교 분석하였다. 결과 : 검사에 참여한 전체 초등학생 1,662명 중 207안(6.23%)이 정시, 3,117안(93.77%)이 평균 –1.01±1.32 D의 비정시로 나타났으며, 비정시중 근시성이 2693안으로 평균 –1.27±1.19 D 그리고 원시성이 424안으로 평균 0.62±0.79 D이었고, 근시안과 원시안의 비율은 전체 대상자에서 각각 81.02%와 12.75%를 보였다. 이 비정시안 들 중 454명(27.31%)이 안경을 착용하고 있었으며, 655안(19.70%)이 시력 0.7 이하로 교정이 필요한 상태였다. 지역 간 비교에서 도시와 농촌지역 초등학생들의 굴절이상도는 각각 –1.01±1.35 D와 –0.87±1.23 D로 통계적으 로 유의한 차이(p<0.010, t=-3.06)를 보였다. 근시성 굴절이상의 비교에서는 도시지역은 -1.32±1.23 D, 농촌지 역은 –1.20±1.14 D로 도시지역 학생들이 더 많은 근시성 굴절이상을 갖고 있었지만(p<0.010, t=2.74), 원시성에 는 유의한 차이를 보이지 않았다(p>0.050, t=1.71). 안경착용은 도시지역 초등학생들이 농촌지역 학생들 비해 5.78% 정도 더 많은 안경을 착용하고 있었다(p=0.001). 결론 : 굴절이상의 변화에 있어 중요한 시기인 저학년만을 대상으로 한 본 연구 결과에서 도시와 농촌 지역에 관계없이 근시가 주된 굴절이상의 원인으로 나타났으며, 앞으로 급속히 증가하는 초등학생 근시의 변화 추적 및 예방을 위해 지속적인 연구와 대책이 필요할 것으로 보인다.

이 연구는 2016년 9월에 강원도 양양군 남애리, 경상북도 포항시 구룡포읍 석병2리에 설치한 인공어초를 대상으로 해조류 군집 변화를 관찰하기 위하여 연구를 수행하였다. 현장조사는 2017년 2월, 5월, 8월, 11월에 계절별 1회씩 SCUBA Diving으로 수행하였으며, 정량조사와 정성 조사를 병행하였다. 본 연구에서 녹조류 11종, 갈조류 15종, 홍조류 68종을 포함하여 총 94종 이 채집되었으며, 양양에서 66종(녹조류 8종, 갈조류 9종, 홍조류 49종), 포항에서 65종(녹조류 7종, 갈조류 9종, 홍조류 49종)이 채집 및 동정되었다. 중요도를 기반으로 판단한 우점종의 경 우, 양양은 다시마(Saccharina japonica)가 우점종, 구멍갈파래(Ulva australis)가 준우점종이었으 며 포항은 불레기말(Colpomenia sinuosa), 우뭇가사리(Gelidium elegans) 순으로 우점하였다. 두 해역 모두 어초 설치 초기에 각각 파래류, 불레기말이 착생한 후, 다시마, 감태, 우뭇가사리 등 다년생 해조가 생육하며 우점하여 기존의 천이 패턴과 유사하였다. 해조상 변화를 통해 군집 관계를 명확히 하기 위해서는 추후 지속적인 모니터링을 통해 장기적인 변화를 관찰하여 해조 군락이 안정되기까지의 천이 과정에 관한 모니터링이 필요한 것으로 판단된다.

본고는 1999년 7월에 경기도 하남시의 이성산성(二聖山城)에서 출토된 목제 요고(要鼓)의 특징과 사용연대를 규명하기 위해 중국 요고의 연원과 변화양상을 심도 있게 고찰한 것이다. 현재 한반도에서 출토된 요고 실물 중에서 고려시대 이전에 속하는 것은 2010년 충남 연기군 나성리 유적에서 출토된 도제 요고와 이성산성에서 출토된 목제 요고 2점뿐이다. 전자는 백제(5세기 후반)의 것으로 현재 가장 이른 시기에 속하는 실물자료이지만 그 형태적 특징이 초기형태의 요고와 상이하기 때문에 악기로 사용된 것인지에 대해 좀 더 신중한 검토가 필요해 보인다. 이성산성에서 출토된 목제 요고의 제작연대에 대해 현재 고구려와 통일신라시대의 것으로 보는 2개의 견해가 존재한다. 목제 요고의 형태적 특징을 보면, 고구려 벽화에 보이는 요고의 중간 부분이 가느다란 특징보다는 통일신라시대 감은사 사리기의 요고상에 더 가깝다고 할 수 있다. 필자가 보기에 이성산성의 요고는 중국 북위시대(北魏: 386∼534) 에 속하는 산서(山西) 대동(大同) 운강석굴(雲岡石窟)의 요고, 하남(河 南) 공현석굴(鞏縣石窟)의 요고와 매우 유사한 특징을 가진 것으로 파악된다. 따라서 이성산성에서 출토된 목제 요고의 제작연대를 고구려(475년 이후)까지 소급할 개연성이 충분하다. 결론적으로 현재 형태적인 특징만으로 이성산성의 요고를 통일신 라시대의 것으로 단정하는 것은 재고의 여지가 있다. 다만 현재 고구려와 관련된 요고 실물 자료를 직접적으로 확인할 수 없다는 점이 아쉽다. 차후 삼국시대 요고에 관한 실물 자료들이 추가적으로 발견 되어 이에 관한 논의가 심화될 수 있기를 기대한다.

Recently, research on cost reduction and efficiency improvement of crystalline silicon(c-Si) photovoltaic(PV) module has been conducted. In order to reduce costs, the thickness of solar cell wafers is becoming thinner. If the thickness of the wafer is reduced, cracking of wafer may occur in high temperature processes during the c-Si PV module manufacturing process. To solve this problem, a low temperature process has been proposed. Conductive paste(CP) is used for low temperature processing; it contains Sn57.6Bi0.4Ag component and can be electrically combined with solar cells and ribbons at a melting point of 150℃. Use of CP in the PV module manufacturing process can minimize cracks of solar cells. When CP is applied to solar cells, the output varies with the amount of CP, and so the optimum amount of CP must be found. In this paper, in order to find the optimal CP application amount, we manufactured several c-Si PV modules with different CP amounts. The amount control of CP is fixed at air pressure (500 kPa) and nozzle diameter 22G(outer diameter 0.72Ø, inner 0.42Ø) of dispenser; only speed is controlled. The c-Si PV module output is measured to analyze the difference according to the amount of CP and analyzed by optical microscope and Alpha-step. As the result, the optimum amount of CP is 0.452 ~ 0.544 g on solar cells.

Feasibility is investigated for reduction of chromium ore by Si sludge with mixed silicothermic and carbothermic reaction. The reduction behavior of chromium ore using Si sludge is investigated precisely to determine the effects of carbon addition, reaction time, and reaction temperature. The pellets are dropped into the furnace after temperature stabilized. As the amount of C addition increases, the amounts of CO and CO2 gas generation increase. After the dropping of the pellets, the pellets are heated and the reaction starts at about 1,573 K or higher. The pellets maintain their shape until 10 min after the drop, and then melted. As the holding time increased, the size of the reduced metal particles increased. The chromium ore is rapidly reduced by the Si sludge, and the slag penetrated into the chromium ore and reduction progressed inside. As the reduction temperature increased, the reaction initiation time is shortened and the reaction fraction of the reduction reaction increased. As the reaction temperature increased, agglomeration of reduced ferrochrome metal is promoted.

We investigate the characteristics of self-assembled quantum dot infrared photodetectors(QDIPs) based on doping level. Two kinds of QDIP samples are prepared using molecular beam epitaxy : n+-i(QD)-n+ QDIP with undoped quantum dot(QD) active region and n+-n−(QD)-n+ QDIP containing Si direct doped QDs. InAs QDIPs were grown on semi-insulating GaAs (100) wafers by molecular-beam epitaxy. Both top and bottom contact GaAs layer are Si doped at 2×1018/cm3. The QD layers are grown by two-monolayer of InAs deposition and capped by InGaAs layer. For the n+-n−(QD)-n+ structure, Si dopant is directly doped in InAs QD at 2×1017/cm3. Undoped and doped QDIPs show a photoresponse peak at about 8.3 μm, ranging from 6~10 μm at 10 K. The intensity of the doped QDIP photoresponse is higher than that of the undoped QDIP on same temperature. Undoped QDIP yields a photoresponse of up to 50 K, whereas doped QDIP has a response of up to 30 K only. This result suggests that the doping level of QDs should be appropriately determined by compromising between photoresponsivity and operating temperature.

Nb-Si-B alloys with Nb-rich compositions are fabricated by spark plasma sintering for high-temperature structural applications. Three compositions are selected: 75 at% Nb (Nb0.7), 82 at% Nb (Nb1.5), and 88 at% Nb (Nb3), the atomic ratio of Si to B being 2. The microstructures of the prepared alloys are composed of Nb and T2 phases. The T2 phase is an intermetallic compound with a stoichiometry of Nb5Si3-xBx (0 ≤ x ≤ 2). In some previous studies, Nb-Si- B alloys have been prepared by spark plasma sintering (SPS) using Nb and T2 powders (SPS 1). In the present work, the same alloys are prepared by the SPS process (SPS 2) using Nb powders and hypereutectic alloy powders with composition 67at%Nb-22at%Si-11at%B (Nb67). The Nb67 alloy powders comprise T2 and eutectic (T2 + Nb) phases. The microstructures and hardness of the samples prepared in the present work have been compared with those previously reported; the samples prepared in this study exhibit finer and more uniform microstructures and higher hardness.

이 연구는 포항지역을 중심으로 발생된 땅밀림지의 지질, 지형, 물리적 특성 등 여러 가지 특성을 분 석하여 땅밀림 발생 방지를 위한 기초자료를 제공하기 위하여 실시하였다. 2017년 3월부터 2018년 11 월까지 현장 조사를 실시하였다. 4개 땅밀림지의 평균면적은 34,541.3 m2이었다. 포항지역에서 발생한 땅밀림지의 지층 및 주 구성암석을 조사한 결과 땅밀림에 취약한 지역으로 나타났다. 땅밀림지의 불연 속면의 경사는 네 지역 모두 사면방향과 동일하게 나타났으며, 절리 수는 네 지역 모두 3개 이상으로 나타났고, 절리간격은 조밀(6-20 mm) 또는 매우 조밀한(6 mm 이하) 것으로 나타났다. 토양형은 사방 지 토양이거나 건조한 산림토양이었다. 토심은 네 지역 모두 30 cm 이하로 나타났다. 조사지역은 모두 완구릉지에 해당하였으며, 지형상 평면형은 凸상미근형과 凹상완상형을 나타내었다. 4개 땅밀림 지역에 서는 모두 땅밀림지 하단부와 인장균열 하단부 등에 지하수가 유출되고 있으며, 땅밀림 유형은 풍화암 땅밀림과 붕적토 땅밀림이었다. 땅밀림지의 인장균열지 하단부는 토양교란으로 인해 토양경도와 토양의 투수계수는 인장균열지 상단부보다 불규칙적인 패턴을 나타내는 것으로 나타내었다.

ZnO thin-films are grown on a p-Si(111) substrate by RF sputtering. The effects of growth temperature and O2 mixture ratio on the ZnO films are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and roomtemperature photoluminescence (PL) measurements. All the grown ZnO thin films show a strong preferred orientation along the c-axis, with an intense ultraviolet emission centered at 377 nm. However, when O2 is mixed with the sputtering gas, the half width at half maximum (FWHM) of the XRD peak increases and the deep-level defect-related emission PL band becomes pronounced. In addition, an n-ZnO/p-Si heterojunction diode is fabricated by photolithographic processes and characterized using its current-voltage (I-V) characteristic curve and photoresponsivity. The fabricated n-ZnO/p-Si heterojunction diode exhibits typical rectifying I-V characteristics, with turn-on voltage of about 1.1 V and ideality factor of 1.7. The ratio of current density at ± 3 V of the reverse and forward bias voltage is about 5.8 × 103, which demonstrates the switching performance of the fabricated diode. The photoresponse of the diode under illumination of chopped with 40 Hz white light source shows fast response time and recovery time of 0.5 msec and 0.4 msec, respectively.

경주시 사적지, 도시공원지역, 그리고 하천 86개소의 현지조사를 통하여 귀화식물을 조사한 결과 21과 59속 78종 1아종 5변종으로 총 84분류군으로 조사되었다. 이중 사적지는 68분류군, 근린공원 43분류군, 하천 59분류군, 소공원 42분류군 등으로 나타났다. 출현식물 중 널리 분포하나 개체수는 많지 않은 귀화도 3등급 분류군이 31.0%, 널리 분포하고 개체수도 많은 5등급이 29.8%, 국지적으로 분포하고 개체수도 많지 않은 분류군인 2등급이 20.2% 등으로 나타났다. 생태계교란식물은 미국쑥부쟁이, 가시상추, 애기 수영 등 7분류군으로 가시상추는 41.9%로 가장 빈번하게 출현하였고, 미국쑥부쟁이는 34.9%로 하천변에서, 애기수영은 25.6%로 사적지나 소공원 일원에서 빈번하게 출현하였다. 생태계교란식물의 확산을 방지하기 위해서는 지속적인 모니터링이 필요하며, 특히, 정착초기에 물리적 제거나 토양의 대체 등 관리 계획이 필요하다.

“W si wo le” and “W si wo suanle” are two constructions commonly used in modern Chinese spoken language, and they all have a high degree of meaning. The two constructions can sometimes be used interchangeably, there will be some subtle differences in semantics after the switchover; but in some cases, the two are not interchangeable. According to the corpus survey, we found that “W si wo le” is much more commonly used than“W si wo suanle” . “W si wo suanle” as a new construction is used only in a specific context in spoken Chinese, “suanle”as an extremely important component of the construction “W si wo suanle” must affect the choice of the variable W, the meaning of this construction and the syntactic features of this construction. This paper intents to compare the similarities and differences of “W si wo le” and “W si wo suanle” on the use and characteristics of the variable W, the construction meaning and the syntactic features ,we also try to analyze and explain the causes of these differences.

We investigated the characteristics of nano crystalline silicon(nc-Si) thin-film solar cells on graphite substrates. Amorphous silicon(a-Si) thin-film solar cells on graphite plates show low conversion efficiency due to high surface roughness, and many recombination by dangling bonds. In previous studies, we deposited barrier films by plasma enhanced chemical vapor deposition(PECVD) on graphite plate to reduce surface roughness and achieved ~7.8 % cell efficiency. In this study, we fabricated nc-Si thin film solar cell on graphite in order to increase the efficiency of solar cells. We achieved 8.45 % efficiency on graphite plate and applied this to nc-Si on graphite sheet for flexible solar cell applications. The characterization of the cell is performed with external quantum efficiency(EQE) and current density-voltage measurements(J-V). As a result, we obtain ~8.42 % cell efficiency in a flexible solar cell fabricated on a graphite sheet, which performance is similar to that of cells fabricated on graphite plates.