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Feasibility Study of R134a/R404a Cascade Heat Pump Cycle in Heat Pump Dryers with Electrical Heaters at Low Temperatures

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Journal of Thermal Science 2015年第5期24卷 463-467页

作者： Ji woo Jeong Young Lim lee Dept. of Mechanical Engineering Kongju National University Dept. of Mechanical and Automotive Engineering Kongju National University

Heat pump cycles have been widely applied to dryers for their high efficiency. However, low–efficiency electrical heaters are often used during early drying stage for frozen foods or winter since a standard heat pump cycle cannot operate at low temperature. This study introduced cascade heat pumps replacing electrical heaters to improve dryer performance at low temperatures. Experiments were performed to examine changes in performance of the cascade heat pump dryers in relation to ambient temperature, low-stage cycle mass flow rate, and high-stage cycle mass flow rate. The results showed a significant improvement in low-temperature dryer performance with the introduction of cascade heat pump cycles.

关键词： Cascade cycle R134a/R404a Heat pump dryer COP Energy efficiency

Transparent Supercapacitors: From Optical Theories to Optoelectronics Applications

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Energy & Environmental Materials 2020年第3期3卷 265-285页

作者： Sang-woo Kim Sang-Young lee Department of Energy Engineering School of Energy and Chemical EngineeringUlsan National Institute of Science and Technology(UNIST)Ulsan 689-798Korea

The ever-increasing demand for smart optoelectronics spurs the relentless pursuit of transparent wireless devices as a game-changing technology that can provide unseen visual information behind the *** enable successful operation of the transparent wireless devices,their power sources should be highly transparent in addition to acquiring reliable electrochemical *** various transparent power sources,supercapacitors(SCs)have been extensively investigated as a promising candidate due to their exceptional cyclability,power capability,material diversity,and scalable/low-cost ***,we describe current status and challenges of transparent SCs,with a focus on their core materials,performance advancements,and integration with application devices.A special attention is devoted to transparent conductive electrodes(TCEs)which act as a keyenabling component in the transparent *** on fundamental understanding of optical theories and operating principles of transparent materials,we comprehensively discuss materials chemistry,structural design,and fabrication techniques of *** addition,noteworthy progresses of transparent SCs are briefly overviewed in terms of their architectural design,opto-electrochemical performance,flexibility,form factors,and integration compatibility with transparent flexible/wearable devices of ***,development direction and outlook of transparent SCs are explored along with their viable roles in future application fields.

关键词： energy storage flexibility optoelectronics transparent conductive electrodes transparent supercapacitors

Response of phenology- and yield-related traits of maize to elevated temperature in a temperate region

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The Crop Journal 2017年第4期5卷 305-316页

作者： Dana Shim Kyu-Jong lee Byun-woo lee Department of Plant Science Seoul National University Seoul 151-921 Republic of Korea Research Institute for Agriculture and Life Sciences Seoul National University Seoul 151-921 Republic of Korea

Extreme high temperatures detrimental to maize production are projected to occur more frequently with future climate *** and yield-related traits were investigated under several levels of elevated temperature in two early-maturing hybrid cultivars:Junda 6(grown in northeastern China)and Chalok 1(grown in South Korea).They were cultivated in plastic houses in Suwon,Korea(37.27°N,126.99°E)held at target temperatures of ambient(AT),AT+1.5°C,AT+3°C,and AT+5°C at one sowing date in 2013 and three different sowing dates in *** and reproductive growth durations showed variation depending on sowing date,experimental year,and *** duration tended to decrease,but not necessarily,with temperature elevation,but somewhat increased again above a certain *** temperature-dependent variation was greater during grain filling than in the vegetative period before *** temperature showed no significant effects on duration or peak dates of silking and anthesis,and thus on anthesis–silking *** yield tended to decrease with temperature elevation above ambient,showing a sharper linear decrease with mean growing season temperature increase in Junda 6 than in Chalok *** decrease in kernel number accounted for a much greater contribution to the yield reductions due to temperature elevation than did the decrease in individual kernel weight in both *** harvestable kernel weight was not significantly affected by temperature elevation *** number showed a linear decrease with mean growth temperature from early ear formation to early grain-filling stage,with Junda 6 showing a much severer decrease than Chalok *** number reduction due to temperature elevation was attributable more to the decrease in differentiated ovule number than to the decrease in kernel set in Chalok 1,but largely to the decrease of kernel set in Junda 6.

关键词： Maize Elevated temperature Phenology Yield Yield-related traits

Sub-2 nm mixed metal oxide for electrochemical reduction of carbon dioxide to carbon monoxide

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Journal of Energy Chemistry 2023年第9期84卷 303-310页

作者： Devina Thasia Wijaya Andi Haryanto Hyun woo Lim Kyoungsuk Jin Chan woo lee Department of Chemistry Kookmin UniversitySeoul 02707Republic of Korea Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea Department of Chemistry Korea UniversitySeoul 02841Republic of Korea

Mixed metal oxide(MMO) represents a critical class of materials that can allow for obtaining a dynamic interface between its components:reduced metal and its metal oxide counterpart during an electrocatalytic ***,a synthetic method utilizing a MOF-derived micro/mesoporous carbon as a template to prepare sub-2 nm MMO catalysts for CO_(2) electro reduction is *** from the zeolite imidazolate framework(ZIF-8),the pyrolyzed derivatives were used to synthesize sub-2 nm Pd-Ni MMO with different *** Ni-rich(Pd_(20)-Ni_(80)/ZC) catalyst exhibits unexpectedly superior performance for CO production with an improved Faradaic efficiency(FE) of 95.3% at the current density of 200 mA cm^(-2) at-0.56 V *** hydrogen electrode(RHE) compared to other Pd-Ni compositions.X-ray photoelectron spectroscopy(XPS) analysis confirms the presence of Ni^(2+) and Pd^(2+) in all compositions,demonstrating the presence of *** functional theory(DFT) calculation reveals that the lower CO binding energy on the surface of the Pd_(20)-Ni_(80) cluster eases CO desorption,thus increasing its *** work provides a general synthetic strategy for MMO electrocatalysts and can pave a new way for screening multimetallic catalysts with a dynamic electrochemical interface.

关键词： Carbon dioxide reduction Mixed metal oxide Nanoalloy Carbon monoxide Metal-organic framework

Biomass seaweed-derived n itrogen self-doped porous carb on anodes for sodium-ion batteries:Insights into the structure and electrochemical activity

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Journal of Energy Chemistry 2022年第1期31卷 286-295,I0008页

作者： Chenrayan Senthil Jae woo Park Nitheesha Shaji Gyu Sang Sim Chang woo lee Department of Chemical Engineering(Integrated Engineering)&Center for the SMART Energy Platform College of EngineeringKyung Hee University1732 Deogyeong-daeroCihuengYonginGyeonggi 17104South Korea

Sustainable transformation and efficient utilization of biomasses and their derived materials are environ-mentally as well as economically compliant *** seaweed-derived nitrogen self-doped porous carbon with tailored surface area and pore structures are prepared through carb on izatio n and *** in fluence of carb on ization temperature on morphology,surface area,and heteroatom dopants are investigated to optimize sodium-ion storage ***-derived nitrogen selfdoped activated carbon(SAC)as anode materials for sodium-ion batteries exhibits remarkable reversible capacity of 303/192 mAh g^(-1) after 100/500 cycles at current densities of 100/200 mA g^(-1) respectively,and a good rate *** interconnected and porous conducting nature along with the heteroatom dopant role in creating defective sites and charge stabilization are favorable for ion storage and diffusion and electron transport,indicating the electrodes can offer improved electrochemical *** addition,post-mortem analysis of the cycled carbon electrodes through ex-situ tools demonstrates the sodium-ion storage mechanism.

关键词： Biomass Heteroatom self-doping Porous carbon Anode Sodium-ion batteries Post-mortem ex-situ analysis

Portable nano probe for micro/nano mechanical scratching and measuring

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 205-209页

作者： woo-Park JEONG Chang-Choi SOO Cho HYUN woo-lee DEUG Department of Mechanical Design Engineering Chosun University Department of Nano Fusion Technology Pusan National University Department of Nano-mechatronics Engineering Pusan National University

A nano probe system which can measure precise contact force in mN scale was demonstrated. The nano probe micro parts or optical parts in nanometer range resolution and scratch was originally designed for on-machine measuring applications and one kind of contact type measuring probes was designed for miniaturized or microfactory system. It ideally should be of small size and able to measure surface topography in nanometer scale. A commercial capacitive displacement sensor was proposed. It was a new concept in nano probe systems which can measure the displacement of shaft driven by the variation of surface topography. The nano probe mainly consisted of three parts： a capacitive displacement sensor, a porous type air slide and a contact probe part with various tip radiuses. The porous type air slide assured the shaft slided smoothly with controllable normal force in mN scale and had high positioning accuracy. The probe part which was directly in contact with target surface, can be applied to micro/nanoscale scratching as well as the measurement of sample topography by a simple tip change.

关键词： nano probe displacement sensor air slide PCD tip

Tailored BiVO_(4)/In_(2)O_(3)nanostructures with boosted charge separation ability toward unassisted water splitting

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Carbon Energy 2023年第6期5卷 45-59页

作者： Mi Gyoung lee Jin wook Yang Ik Jae Park Tae hyung lee Hoonkee Park woo Seok Cheon Sol Alee hyungsoo lee Su Geun Ji Jun Min Suh Jooho Moon Jin Young Kim Ho Won Jang Department of Materials Science and Engineering Research Institute of Advanced MaterialsSeoul National UniversitySeoulRepublic of Korea Country Department of Applied Physics Sookmyung Women's UniversitySeoulRepublic of Korea Department of Materials Science and Engineering Yonsei UniversitySeoulRepublic of Korea Advanced Institute of Convergence Technology Seoul National UniversitySuwonRepublic of Korea

The development of new heterostructures with high photoactivity is a breakthrough for the limitation of solar-driven water ***,we first introduce indium oxide(In_(2)O_(3))nanorods(NRs)as a novel electron transport layer for bismuth vanadate(BiVO_(4))with a short charge diffusion ***_(2)O_(3)NRs reinforce the electron transport and hole blocking of BiVO_(4),surpassing the state-of-the-art photoelectrochemical performances of BiVO_(4)-based ***,a tannin-nickel-iron complex(TANF)is used as an oxygen evolution catalyst to speed up the reaction *** final TANF/BiVO_(4)/In_(2)O_(3)NR photoanode generates photocurrent densities of 7.1 mAcm^(−2) in sulfite oxidation and 4.2 mA cm^(−2) in water oxidation at 1.23 V versus the reversible hydrogen ***,the“artificial leaf,”which is a tandem cell with a perovskite/silicon solar cell,shows a solar-to-hydrogen conversion efficiency of 6.2%for unbiased solar water *** reveal significant advances in the photoactivity of TANF/BiVO_(4)/In_(2)O_(3)NRs from the tailored nanostructure and band structure for charge dynamics.

关键词： bismuth vanadate heterojunction indium oxide nanostructure photoelectrochemical water splitting

Game Selection Method for Game-Based History Learning

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Journal of Contemporary Educational Research 2021年第10期5卷 67-81页

作者： woo-Hyun lee Won-hyung lee Chung-Ang University 84 Heukseok-ro Dongjak-gu 06974Korea

Games that are used in research on game-based learning and serious games that are used for education are usually exclusive,making it difficult for teachers to attempt new methods in *** to the data published in 2009 by the European Schoolnet(EUN),a network of European Ministries of Education,most of the problems that teachers face when using games in class are related to game *** on the aforementioned data,this study presents a set of criteria for selecting games in order to solve the inconvenience experienced by *** games,which are used as teaching materials for game-based learning,have been replaced with commercial games that are easily purchased,rather than serious games that are difficult to obtain the *** on the criteria,two games were selected in this study and the classes were conducted at the educational *** to the group trained with textbooks,it has been confirmed that the effect of game-based learning was *** addition,five out of ten problems that teachers face were resolved.

关键词： Game-based learning History education Commercial game Reenactment of history learning

Diagnostic delay in inflammatory bowel disease increases the risk of intestinal surgery

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World Journal of Gastroenterology 2017年第35期23卷 6474-6481页

作者： Dong-won lee Ja Seol Koo Jung Wan Choe Sang Jun Suh Seung Young Kim Jong Jin Hyun Sung woo Jung Young Kul Jung hyung Joon Yim Sang woo lee Division of Gastroenterology and Hepatology Department of Internal MedicineKorea University Ansan Hospital

AIM To investigate the factors affecting diagnostic delay and outcomes of diagnostic delay in inflammatory bowel disease(IBD) METHODS We retrospectively studied 165 patients with Crohn's disease(CD) and 130 patients with ulcerative colitis(UC) who were diagnosed and had follow up durations > 6 mo at Korea University Ansan Hospital from January 2000 to December 2015. A diagnostic delay was defined as the time interval between the first symptom onset and IBD diagnosis in which the 76^(th) to 100^(th) percentiles of patients were *** The median diagnostic time interval was 6.2 and 2.4 mo in the patients with CD and UC, respectively. Among the initial symptoms, perianal discomfort before diagnosis(OR = 10.2, 95%CI: 1.93-54.3, P = 0.006) was associated with diagnostic delays in patients with CD; however, no clinical factor was associated with diagnostic delays in patients with UC. Diagnostic delays, stricturing type, and penetrating type were associated with increased intestinal surgery risks in CD(OR = 2.54, 95%CI: 1.06-6.09; OR = 4.44, 95%CI: 1.67-11.8; OR = 3.79, 95%CI: 1.14-12.6, respectively). In UC, a diagnostic delay was the only factor associated increased intestinal surgery risks(OR = 6.81, 95%CI: 1.12-41.4).CONCLUSION A diagnostic delay was associated with poor outcomes, such as increased intestinal surgery risks in patients with CD and UC.

关键词： Diagnostic delay Intestinal surgery Inflammatory bowel disease Crohn’s disease Ulcerative colitis