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        • KCI등재

          Effects of Pressure and Deposition Time on the Characteristics of In2Se3 Films Grown by Magnetron Sputtering

          Yong Yan,Shasha Li,Yufeng Ou,Yaxin Ji,Zhou Yu,Lian Liu,Chuanpeng Yan,Yong Zhang,Yong Zhao 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.6

          Crystalline In2Se3 films were fabricated by magnetron sputtering from a sintered In2Se3-compound target and the effects of the deposition parameters, including the working pressure and deposition time, on the phase composition, structure, morphology, and optical properties were clarified. Single-phase κ-In2Se3 was prepared at 4.0 Pa, but γ-In2Se3 was recognized when the working pressure was lower than 4.0 Pa. The optical transmittance of the films decreased to 45% and the optical band gap varied from 2.9 to 2.0 eV with increasing film thickness from 80 to 967 nm. Metal-semiconductor-metal (MSM) photodetectors based on γ-In2Se3 thin films with various thicknesses were also fabricated. The result of photosensitivity research on such MSM photodetectors suggests that it may be impossible to fabricate wide-absorption-range MSM devices by just using a single material (γ-In2Se3) because of spatial potential fluctuations in the layers.

        • KCI등재

          Control over the Preferred Orientation of CIGS Films Deposited by Magnetron Sputtering Using a Wetting Layer

          Yong Yan,Fan Jiang,Lian Liu,Zhou Yu,Yong Zhang,Yong Zhao 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.1

          A growth method is presented to control the preferred orientation inchalcopyrite CuInxGa1-xSe2 (CIGS) thin films grown by magnetronsputtering. Films with (220/204) and (112) preferred orientation aswell as randomly oriented films were prepared. The effects of anIn2Se3 wetting layer and the working pressure on the texture transitionphenomena were examined. A large-grained CIGS film with (220/204) texture was formed at 400°C with the inclusion of a thin (80 nm)In2Se3 layer and liquid phase (excess copper selenide phase)formation, and the reaction mechanism is proposed. The devicedeposited at 2.0 Pa on an In2Se3 layer exhibited the optimal electricalproperties.

        • KCI등재

          피해목 위치자료를 이용한 북한산 국립공원 참나무시들음병 공간분석

          ( Yongyan Zhu ),( Dongfan Piao ),이우균 ( Woo-kyun Lee ),전성우 ( Seong-woo Jeon ) 대한원격탐사학회 2017 大韓遠隔探査學會誌 Vol.33 No.5

          본 연구에서는 북한산국립공원을 대상으로 참나무시들음병 피해지내의 지형적 특성을 파악하고 피해확산 예측지도를 작성하였다. 피해대상지 고도인자 분석결과 피해목은 고도 200 m~500 m 사이에 많이 분포되어 있는 것으로 탐지 되었고, 고도 500 m 이상에서는 피해목수가 급격히 줄어드는 것으로 나타났다. 경사인자 분석결과 전체 92%의 피해목이 경사 20-40도 사이에서 탐지 되었고 경사 40도 이상에서는 피해가 급격히 줄어드는 것으로 나타났다. 방위 분석결과 주로 남향에서 피해가 많이 발생 되는 것으로 나타났다. 피해 대상지내에서의 참나무시들음병 피해목은 군집형태로 존재하는 것으로 나타났고 CART 분석결과 경사의 영향이 가장 큰 것으로 나타난 반면 방위의 영향은 적은 것으로 분석되었다. 그 다음으로 지표면 온도와 고도의 영향이 비슷하게 나타났고 CART 분석결과를 토대로 각 요소별 가중치를 적용하여 피해확산 예측지도를 작성하였다. 그 결과 북한산국립공원의 동북방향에 위치하여 있는 도봉산방향으로 피해가 확산 될 것으로 판단된다. This study is a preliminary research conducted in Buhansan mountain National Park to develop a management system to predict and control oak wilt disease by indicating spatial factors which affect diffusion of the disease. After analysing altitude factor during the estimation of spatial analysis of damaged area, it is indicated that damaged trees are mainly distributed at altitude of 200-500 m and number decreased drastically over the altitude of 500 m. The result showed that 92% of total damaged trees are on slope between 20~40 degrees and the number decreased drastically on slope steeper than 40 degrees. It is indicated that damaged area is mainly distributed on southern aspect. It is estimated by using CART that slope factor affected the diffusion of disease mostly but aspect factor did not. Surface temperature and altitude showed similar effect. By simulating possible diffusion scenario, it is estimated that the disease could spread to DO-BONG Mt., northeast of Bukhansan mountain.

        • KCI등재

          An Outlook on Rotordynamic Pump Theory Development

          Yongyan Ni,Zhongyong Pan 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.2

          ECHO progress was defined to depict the rotordynamic pump theory development. Experience (E) era for pumps lasted nearly one and a half hundred years before the Industrial Revolution due to the low rotation speed of motor and undeveloped manufacture ability. Classic (C) theory referring to quasi-static performance as well as the items those were not able to be steadily resolved under the level were briefly and sophisticated outlined. Since 1962, flow instabilities and the dynamic responses had come into main attention with the development of the modern technologies such as ballistic missile, rocket and space shuttle main engine, and were finally heuristically (H) elucidated by talented scholars and researchers. Recently, new applications for the pumps open (O) to the surrounding fluid and diversity of the medium such as multiphase flow need more studies and some examples were briefly introduced to display the potential problems lastly.

        • KCI등재

          Thrust Characteristics and Nozzle Role of Water Jet Propulsion

          Yongyan Ni,Weimin Liu,Zhanhao Shen,Xiwei Pan 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.1

          Surface pressure integration and momentum method were respectively performed to evaluate the impeller thrust and the system thrust of a contra-rotating axial flow water jet propulsion, and an interesting phenomenon so-called thrust paradox was revealed. To explain the paradox, the impeller thrust and the system thrust were physically and theoretically analyzed, the results show that the impeller thrust is head involved and is determined by the hydraulic parameters upstream and downstream the impeller, while the momentum method depicted by a classic equation is valid simply under the best efficiency point. Consequently, the role of a water jet propulsion nozzle was deduced that the nozzle is mainly to limit the flow rate that crosses the impeller and to assure the system working under the best efficiency condition apart from its ability to produce momentum difference. Related mathematical formula expressed the nozzle diameter is the dominant variable used to calculate the working condition of the water jet propulsion. Therefore the nozzle diameter can be steadily estimated by the former expression. The system thrust scaling characteristics under various speeds were displayed lastly.

        • KCI등재

          Numerical investigation on radial impeller induced vortex rope in draft tube under partial load conditions

          Yongyan Ni,Renqing Zhu,Xiao Zhang,Zhong-yong Pan 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

          The vortex rope phenomena appearing in a draft tube under partial load operations were investigated. The efforts were carried out by using a homogeneous equilibrium vapor-liquid two-phase model and a blending SST turbulence model, and the former takes account of the weak compressibility of mixed media. The vortex rope phenomena were induced by the radial impeller and three kinds of flow regimes were illustrated. Vortex rope was visible at some conditions and it displayed various patterns, while no obvious vortex rope was found under some conditions. It was found that the plant cavitation number determines that whether the vortex rope was visible or invisible. An interesting profile was that a secondary vortex filament ring entwining the vortex rope appeared clearly near the design condition. Both flow structures and pressure characteristics were studied to depict the vortex mechanism and the characteristics of the η-σ curves. Further analysis found that the shedding frequency of the vortex ring is similar with that of the precession movement.

        • KCI등재

          The Role of Endoscopic Ultrasound-Guided Ki67 in the Management of Non-Functioning Pancreatic Neuroendocrine Tumors

          YongYan Cui,Lauren G. Khanna,Anjali Saqi,John P. Crapanzano,James M. Mitchell,Amrita Sethi,Tamas A. Gonda,Michael D. Kluger,Beth A. Schrope,John Allendorf,John A. Chabot,John M. Poneros 대한소화기내시경학회 2020 Clinical Endoscopy Vol.53 No.2

          Background/Aims: The management of small, incidentally discovered nonfunctioning pancreatic neuroendocrine tumors (NF-PNETs)has been a matter of debate. Endoscopic ultrasound with fine-needle aspiration (EUS-FNA) is a tool used to identify and risk-stratifyPNETs. This study investigates the concordance rate of Ki67 grading between EUS-FNA and surgical pathology specimens in NF-PNETs and whether certain NF-PNET characteristics are associated with disease recurrence and disease-related death. Methods: We retrospectively reviewed the clinical history, imaging, endoscopic findings, and pathology records of 37 cases of NF-PNETs that underwent pre-operative EUS-FNA and surgical resection at a single academic medical center. Results: There was 73% concordance between Ki67 obtained from EUS-FNA cytology and surgical pathology specimens; concordancewas the highest for low- and high-grade NF-PNETs. High-grade Ki67 NF-PNETs based on cytology (p=0.028) and histology (p=0.028)were associated with disease recurrence and disease-related death. Additionally, tumors with high-grade mitotic rate (p=0.005), tumorsize >22.5 mm (p=0.104), and lymphovascular invasion (p=0.103) were more likely to have poor prognosis. Conclusions: NF-PNETs with high-grade Ki67 on EUS-FNA have poor prognosis despite surgical resection. NF-PNETs withintermediate-grade Ki67 on EUS-FNA should be strongly considered for surgical resection. NF-PNETs with low-grade Ki67 on EUS-FNA can be monitored without surgical intervention, up to tumor size 20 mm.

        • KCI등재

          $w$-Matlis cotorsion modules and $w$-Matlis domains

          Yongyan Pu,Gaohua Tang,Fanggui Wang 대한수학회 2019 대한수학회보 Vol.56 No.5

          Let $R$ be a domain with its field $Q$ of quotients. An $R$-module $M$ is said to be weak $w$-projective if $\Ext^1_R(M,N)=0$ for all $N\in \mathcal{P}^{\dag}_w$, where $\mathcal{P}^{\dag}_w$ denotes the class of $\GV$-torsionfree $R$-modules $N$ with the property that $\Ext^k_R(M,N)=0$ for all $w$-projective $R$-modules $M$ and for all integers $k\geq 1$. In this paper, we define a domain $R$ to be $w$-Matlis if the weak $w$-projective dimension of the $R$-module $Q$ is $\leq1$. To characterize $w$-Matlis domains, we introduce the concept of $w$-Matlis cotorsion modules and study some basic properties of $w$-Matlis modules. Using these concepts, we show that $R$ is a $w$-Matlis domain if and only if $\Ext^k_R(Q,D)=0$ for any $\mathcal{P}^{\dag}_w$-divisible $R$-module $D$ and any integer $k\geq1$, if and only if every $\mathcal{P}^{\dag}_w$-divisible module is $w$-Matlis cotorsion, if and only if w.$w$-$\pd_RQ/R\leq1$.

        • KCI등재

          Pullbacks of $\mathcal{C}$-hereditary domains

          Yongyan Pu,Gaohua Tang,Fanggui Wang 대한수학회 2018 대한수학회보 Vol.55 No.4

          Let $(RDTF,M)$ be a Milnor square. In this paper, it is proved that $R$ is a $\mathcal{C}$-hereditary domain if and only if both $D$ and $T$ are $\mathcal{C}$-hereditary domains; $R$ is an almost perfect domain if and only if $D$ is a field and $T$ is an almost perfect domain; $R$ is a Matlis domain if and only if $T$ is a Matlis domain. Furthermore, to give a negative answer to Lee$^,$s question, we construct a counter example which is a $\mathcal{C}$-hereditary domain $R$ with $w.gl.\dim(R)=\infty$.

        • SCOPUSKCI등재
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