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Quantification of the Energy Flows during Ultrasonic Wire Bonding under Different Process Parameters
Yangyang Long,Friedrich Schneider,Chun Li,Jörg Hermsdorf,Jens Twiefel,Jörg Wallaschek 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.6 No.3
Despite of its wide and long-term application for interconnections in the field of microelectronics packaging, a quantitative understanding on the mechanisms of ultrasonic (US) wire bonding is still lacked. In this work, the energy flows from the electrical input energy to the different mechanisms during the US bonding process are quantified based on real-time observations via which the relative motions at the wire/substrate and the wire/tool interfaces can be detected. The relative motions at the two interfaces are proved to be caused by both the continuous plastic deformation and the US vibration. The normal force and US power interdependently affect the relative motion amplitudes. The deduced energy flows show that the energy from the transducer mainly flows to the vibration induced friction at the two interfaces and the microwelds formation, deformation and breakage. Despite of their significance to the process, the other mechanisms receive only little amount of energy. The impacts of the process parameters including normal force, US power and time on the energy flows are quantitatively investigated. A good coupling of the normal force and the US power guides more energy to the formation of microwelds while a long process time would increase the friction induced energy consumption.
Yan-Chun Li,Fan-Long Jin,박수진 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.10
We report spinel-type CoFe2O4 nanocrystals (NCs) synthesized through facile hydrothermal growth and their attachment on a cage-like carbon (CC) for efficient and durable oxygen evolution/reduction reaction (OER/ORR) performance. As a catalyst, the so-constructed CoFe2O4 NCs show significantly higher OER performance than bare CoFe2O4 and CC, leading to an overpotential of 1.59 V for the OER at a current density of 10mA/cm. Furthermore, CoFe2O4 NCs on CC electrodes also exhibit good ORR performance, which is comparable to Pt/C, significantly higher than that of bare carbon fiber paper, and acts as a bifunctional electrocatalyst. The CoFe2O4 NCs anchored on the CC electrodes exhibit remarkably long-term stability, which is evaluated by continuous cycling (over 5,000 cycles), without any morphological change, but preserving all the materials within the electrode. The results indicate that the CoFe2O4 NCs have a promising potential for efficient, cost-effective, and durable oxygen electrocatalysis at large scales using earth-abundant materials and low-cost fabrication processes.
Association between Timed Up and Go Test and Subsequent Functional Dependency
Ji Eun Lee,Hyejin Chun,Young Sang Kim,Hee-Won Jung,Il-Young Jang,Hyun-Min Cha,손기영,Be Long Cho,권인순,윤종률 대한의학회 2020 Journal of Korean medical science Vol.35 No.3
Background: This study aimed to evaluate the association between baseline results of the Timed Up and Go (TUG) test and subsequent functional dependency occurrence. Methods: From the National Health Insurance Service-Senior Cohort database, we identified 39,519 people who participated in the National Screening Program for Transitional Ages at the age of 66 during 2007–2008. Impaired mobility was defined as taking 10 seconds or longer to perform the TUG test. Functional dependency occurrence was defined as the initiation of receiving national Long-Term Care Insurance services—home care or admission to long-term care facilities. Cox proportional hazard regression models were used to assess the hazard ratios (HRs) for dependency occurrence according to baseline TUG test results. Results: The mean follow-up period was 5.7 years. Occurrence rates of dependency were 2.0 and 3.4 cases per 1,000 person-years in the normal and impaired TUG groups, respectively. Impaired mobility was associated with a higher risk of functional dependency occurrence (adjusted HR [aHR], 1.65; 95% confidence interval [CI], 1.40–1.95; P < 0.001). Additionally, in the subgroup analysis for the participants with intact baseline activities of daily living, impaired mobility was associated with a higher risk of dependency occurrence (aHR, 1.65; 95% CI, 1.33–2.04; P < 0.001). Conclusion: The TUG test might be a useful predictive marker of subsequent functional dependency occurrence. Intervention to prevent functional dependency may be helpful for older adults with impairment on the TUG test.
Thermodynamic simulation and structural optimization of the collimator in the drift duct of EAST-NBI
Tang Ning,Hu Chun-dong,Xie Yuan-lai,Wei Jiang-long,Cui Zhi-Wei,Xie Jun-Wei,Pan Zhuo,Jiang Yao 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11
The collimator is one of the high-heat-flux components used to avoid a series of vacuum and thermal problems. In this paper, the heat load distribution throughout the collimator is first calculated through experimental data, and a transient thermodynamic simulation analysis of the original model is carried out. The error of the pipe outlet temperature between the simulated and experimental values is 1.632%, indicating that the simulation result is reliable. Second, the model is optimized to improve the heat transfer performance of the collimator, including the contact mode between the pipe and the flange, the pipe material and the addition of a twisted tape in the pipe. It is concluded that the convective heat transfer coefficient of the optimized model is increased by 15.381% and the maximum wall temperature is reduced by 16.415%; thus, the heat transfer capacity of the optimized model is effectively improved. Third, to adapt the long-pulse steady-state operation of the experimental advanced superconducting Tokamak (EAST) in the future, steady-state simulations of the original and optimized collimators are carried out. The results show that the maximum temperature of the optimized model is reduced by 37.864% compared with that of the original model. The optimized model was changed as little as possible to obtain a better heat exchange structure on the premise of ensuring the consumption of the same mass flow rate of water so that the collimator can adapt to operational environments with higher heat fluxes and long pulses in the future. These research methods also provide a reference for the future design of components under high-energy and long-pulse operational conditions
국내 뷰티 관련 고등교육 프로그램의 현황 및 교과과정 조사 연구
( Long Chun Li ),안춘순 ( Cheun Soon Ahn ),( Lkhagva Narantuya ),박선화 ( Seon Hwa Park ),조설 ( Xue Zhao ) 한국의류학회 2016 한국의류학회지 Vol.40 No.2
This research investigates the current state of beauty related curriculums and departments of undergraduate and graduate programs in Korea. The results also compared beauty related programs at selected overseas universities. A comprehensive list of 4-year universities with beauty related undergraduate and/or graduate programs were surveyed using the KCUE University Entrance Information (http://www.adiga.kr) site provided by the Korean Council for University Education. Information on the name of the department, curriculum, and year of foundation were obtained from the websites of individual universities. There were 58 universities which have beauty related higher education programs; 43 undergraduate programs, 12 graduate programs, and 40 special graduate programs. The number of special graduate departments were 3.7 times larger than the graduate departments; in addition, 43.9% of the special graduate departments were located in the Seoul/Gyeonggi/Incheon area. The curriculums of beauty related 4-year undergraduate departments were focused on the ‘Beauty care service’ area (50.2%), whereas the curriculums of graduate departments were focused on the ‘Cosmetic science’ area (40.8%). In case of the special graduate programs, there was little difference between the ‘Beauty care service’ area (24.4%) and the ‘Cosmetic science’ area (27.7%). Beauty related programs of overseas universities were mostly focused on cosmetic science with some universities specialized in the marketing aspect.
Chun-Long XU,Min-Cang ZHANG 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.2
The arbitrary l-wave solutions to the Schr¨odinger equation for the deformed hyperbolic Manning- Rosen potential is investigated analytically by using the Nikiforov-Uvarov method, the centrifugal term is treated with an improved Greene and Aldrich’s approximation scheme. The wavefunctions depend on the deformation parameter q, which is expressed in terms of the Jocobi polynomial or the hypergeometric function. The bound state energy is obtained, and the discrete spectrum is shown to be independent of the deformation parameter q.
The interdependence between China and the United States: a two-Level analysis
Chun Long Lua,Min Xia 한국국방연구원 2010 The Korean Journal of Defense Analysis Vol.22 No.3
This paper constructs a two-level model to explain China-U.S. relations. We find that at the state level, the interdependence between China and the United States, which comes from their bilateral trade and foreign direct investment, is asymmetric. Such asymmetric interdependence favors the United States in pushing the Chinese government to make concessions when they have conflicts. However, at the society level, China can penetrate into American society to intervene or influence American foreign policymaking. In this paper, it is argued that the outcome of China-U.S. relations is determined not only by the asymmetric interdependence at the state level or societal penetration respectively, but also by the interaction of these two factors in the process. Finally, the new development of China-U.S. relations since the inauguration of the Obama administration is also examined.
Disambiguate Chinese Word Sense Based on Linguistics Knowledge
Chun-Xiang Zhang,Long Deng,Xue-Yao Gao,Zhi-Mao Lu 보안공학연구지원센터 2014 International Journal of Database Theory and Appli Vol.7 No.6
Word sense disambiguation (WSD) is important to many application problems in natural language processing fields, such as machine translation, parsing analysis and information retrieval. In this paper, we propose a new method to determine correct sense categories of Chinese words based on linguistics knowledge. The left word string and the right word string around the ambiguous word are respectively analyzed. Their syntactic structures are obtained for determining its intended sense. Syntactic category and part of speech are extracted as disambiguation features. A naive bayesian model is used as the classifier. Experimental results showed that the accuracy rate of classification arrives at 64%. The performance of disambiguation is improved.