• Journal of Electrochemical Science and Technology
• /
• 제14권4호
• /
• pp.361-368
• /
• 2023

In lithium-sulfur (Li-S) batteries, encapsulation of sulfur in activated carbon (AC) materials is a promising strategy for preventing the dissolution of lithium polysulfide into electrolytes and enhancing cycle life, because instead of solid-liquid-solid reactions, quasi-solid-state (QSS) reactions occur in the AC micropores. While a high weight fraction of sulfur in S/AC composites is essential for achieving a high energy density of Li-S cells, the deterioration mechanisms under such conditions are still unclear. In this study, we report the deterioration mechanisms during charge-discharge cycling when the discharge products overflow from the AC. Analysis using scanning electron microscopy and energy-dispersive X-ray spectrometry confirms that the sulfur in the S/AC composites migrates outside the AC as cycling progresses, and it is barely present in the AC after 20 cycles, which corresponds to the capacity decay of the cell. Impedance analysis clearly shows that the electrical resistance of the S/AC composite and the charge-transfer resistance of QSS reactions significantly increase as a result of sulfur migration. On the other hand, the charge-discharge cycling performance under limited-capacity conditions, where the discharge products are encapsulated inside the AC, is extremely stable. These results reveal the degradation mechanism of a Li-S cell with micro-porous carbon and provide crucial insights into the design of a S/AC composite cathode and its operating conditions needed to achieve stable cycling performance.

• 대한기계학회논문집A
• /
• 제37권1호
• /
• pp.17-23
• /
• 2013

지하철 전동차에는 2 차 현가장치인 공기스프링의 횡강성 저하특성을 보강하기 위해 대차와 차체 사이에 횡댐퍼를 설치하게 되는데, 이 횡댐퍼는 주행 시 차체의 횡진동을 감소시키는 역할을 수행한다. 그러나, 횡댐퍼의 감쇠력이 저하될 경우 전동차의 주행안정성과 승차감이 함께 악화되며, 차체의 횡방향 운동이 증가되는 요인으로 작용하게 된다. 본고에서는 전동차 주행 시 비정상적으로 발생하는 충격에 대하여 그 원인을 살펴보고 해결방안을 마련하고자 횡댐퍼의 감쇠력에 따른 차체의 횡변위를 동역학 시뮬레이션을 통해 검토하였으며, 그에 따라 충격에 의한 이상진동 및 소음의 발생 유무를 파악하였다. 그로부터 충격이 발생되지 않는 적정 감쇠력을 구하고자 하였다.

• 한국초지조사료학회지
• /
• 제14권2호
• /
• pp.132-141
• /
• 1994

본 시험은 reed canarygrass silage의 품질을 향상시키고 호기적 변패를 방지시킬 목적으로 재료를 약 1.5cm 길이로 절단하여 formic acid, caproic acid 및 두가지 산을 혼합하여 첨가한 silage를 9개의 처리구로 나누어 실험용 silo에 제조하였으며, silage의 품질분석을 위해서 두께 0.1mm, 용량 50kg의 vinyl bag을 이용하였다. 또한 호기적 상태에서의 온도변화, 질소 함량 변화 및 변패방지를 위한 silage의 안정성 시험은 지름 25cm$\times$높이 30cm의 plastic용기를 이용하여 개봉 직후와 7일간의 호기적 조건에서 실시한 결과를 요약하면 다음과 같다. 2. Silage의 화학적 조성에서 개봉 직후의 조단백질과 NFE함량은 formic acid와 caproic acid를 혼합 첨가함으로서 높았으며(P<0.01), 7일간의 호기적 상태에서는 혼합 첨가를 함으로서 조섬유와 ADF함량이 낮게 나타났다.(PM0.01). 2. Silage의 온도변화는 formic acid를 첨가함으로서 개봉 2일에 최고온도($34.4^{\circ}C$)에 도달했으며, caproic acid의 첨가와 formic acid + caproic acid의 혼합첨가를 함으로서 온도상승을 방지할 수 있었다. 3. 호기적 상태에서 silage의 pH변화는 formic acid를 첨가할 경우에는 효과가 없었으나, caproic acid를 첨가함으로서 silage의 pH는 안정되었다. 4. 총 질소에 대한 암모니아태 질소의 함량비율은 formic acid첨가구>caproic acid 첨가구>혼합첨가구 순으로 유의적으로 나타났다(P<0.01) 5. Caproic acid 1.2%첨가와 formic acid의 혼합 첨가(1.2%+1.2%)를 함으로서 mould의 성장을 억제하는 효과가 크게 나타났다.

• 한국주거학회논문집
• /
• 제20권1호
• /
• pp.83-90
• /
• 2009

The present study is a preliminary research improving the dwelling quality of apartment house as a kind of multi-family housing. The purpose of the study is to find out the actual state on characteristics of indoor noise including residents' living in apartment units. The method was field survey consisted of field measurements on equivalent noise level, observation on noise type, and interview on residents' responses. Field survey were carried out in 20 occupied apartment units from January to March 2007. The results are as follows. 1) Averages of indoor noise levels including residents' living noise were measured as $43.9{\sim}62.2\;dB(A)_{Leq5min}$, the average of each house except one was higher than the permissible level, 45 dB(A). 2) The noise types observed were mostly residents' living noise and classified into 'water hammer', 'living equipment noise', 'noise by family', 'hood noise', 'kitchen noise' in own unit, 'walking and talking noise in stairs and corridors', 'noise by neighborhood house', 'noise by the upper story' in building, and outdoor noise. 3) The residents showed slightly non-positive responses at 'noise by the upper story', 'noise by neighborhood house', 'water hammer', and 'noise by family'. Therefore, it is required to plan for preventing deterioration of the dwelling quality by residents' living noise in own unit as well as by neighborhood houses.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.125.2-125.2
• /
• 2016

Semiconductor nanowires are essential building blocks for various nanotechnologies including energy conversion, optoelectronics, and thermoelectric devices. Bottom-up synthetic approach utilizing metal catalyst and vapor phase precursor molecules (i.e., vapor - liquid - solid (VLS) method) is widely employed to grow semiconductor nanowires. Al has received attention as growth catalyst since it is free from contamination issue of Si nanowire leading to the deterioration of electrical properties. Al-catalyzed Si nanowire growth, however, unlike Au-Si system, has relatively narrow window for stable growth, showing highly tapered sidewall structure at high temperature condition. Although surface chemistry is generally known for its role on the crystal growth, it is still unclear how surface adsorbates such as hydrogen atoms and the nanowire sidewall morphology interrelate in VLS growth. Here, we use real-time in situ infrared spectroscopy to confirm the presence of surface hydrogen atoms chemisorbed on Si nanowire sidewalls grown from Al catalyst and demonstrate they are necessary to prevent unwanted tapering of nanowire. We analyze the surface coverage of hydrogen atoms quantitatively via comparison of Si-H vibration modes measured during growth with those obtained from postgrowth measurement. Our findings suggest that the surface adsorbed hydrogen plays a critical role in preventing nanowire sidewall tapering and provide new insights for the role of surface chemistry in VLS growth.

• KIEAE Journal
• /
• 제15권6호
• /
• pp.63-68
• /
• 2015

Purpose: Most if buildings need various repair works for preventing or delaying the deterioration which gives rise to affect the living condition or function after constructed. Therefore, a long-term repair schedule should be planned and a repair cost is required. In this paper, it aimed at providing the statistical forecast model for a repair cost in roof water-proofing work and elevator work using statistical approach with three variables such as number of household, management area and a elapsed year. Data are collected in apartment housings which are located in Seoul area and conducted with interview and questionnaire sheet. Each analyzed work is divided into a partly work and fully work. Results of this study are shown that, first, the regression model takes a multiplying type like a Cobb-Douglas function and is changed into the log-linear type to include the three variable simultaneously. Second, the goodness-of-fit of the repair cost forecasting model has a good statistics in determinant's coefficient and Dubin-Watson value. Third, the management area is stronger factor than other the number of household and an elapsed year in roof water-proofing work and elevator work.

• 한국주거학회논문집
• /
• 제21권6호
• /
• pp.71-80
• /
• 2010

The purpose of this study is to classify defects of the residential building by analyzing the defect specified by prequalification of residential building reconstruction and to suggest the solution of the problem which can be arisen during each stage of plan, construction and maintenance. By sorting the main defects which is specified by pre-qualification of residential building reconstruction for three years from August 2006 to August 2009 into 4 catagories and analyzing the cause of the defects, we draw the way of maintenance to prevent the defects and make pleasant residential environment. The reason for the frequent defects from residential building is mainly deterioration. It occured on the finishing more than on the structure, which means that residents can find defects easier on the finishing than the structure and clear the demand for repair. The result of analyzing of pre-qualification of residential building reconstruction is that the defects mostly caused small, masonry constructed and lower apartment. The apartment which is not into legal right for maintenance naturally have more defects than the others. In conclusion, it is necessary to establish a law of obligation duty of the maintenance of small apartment.

• 조명전기설비학회논문지
• /
• 제25권1호
• /
• pp.85-92
• /
• 2011

The role of RCDs(Residual Current Protective Device) that are installed before the load is very important for preventing electric shock and electrical fire. However, although fault rate of RCD is increasing due to deterioration and long period usage, the RCD is permanently used without a checking of performance evaluation and it causes the electrical accident. In this paper, the amount of airborne chloride is researched in domestic costal area and the accelerated life test is conducted using a salt water spray tester in order to decide the life time of RCD. Aa a result of an accelerated life test, the MTTF(Mean Time To Failure) of RCD is 110.81 hours and B10 life time of RCD is 45.81 hours for the all samples. when an accelerated life test result is applied to within 2 km costal area, the life time of RCD is predicted about 5 years.

• 산업기술연구
• /
• 제24권A호
• /
• pp.179-184
• /
• 2004

Each year, new technological advancements for repair-purpose are being introduced to overlay the old deterioration of RC bridge deck at highway by latex-modified concrete. The days may come when this old problem will be successfully resolved. While the experimental works and researches are very active at both laboratory and field, only a few theoretical studies were performed on interfacial problems, especially on stress distribution and concentration of RC beam overlayed by latex-modified concrete. The repaired and strengthened structures would induce a premature failure due to the stress concentration at the adhesive layer of different material before the design expected failure. This paper investigated and proposed an analytical model for predicting interfacial shear and normal stresses of RC beam repair-purpose overlayed by latex-modified concrete. This would be used for predicting interfacial stresses and preventing premature failure at interfaces. This study modified Smith-Teng method for applying to cementitious repairing material, which was based on a direct governing equation and linear-elastic approach for interfacial normal and shear stresses. The proposed theoretical model was verified using commercial FEA program, LUSAS, in terms of interfacial stresses predicted by the proposed model and calculated by LUSAS.

• 동아시아식생활학회지
• /
• 제10권3호
• /
• pp.222-228
• /
• 2000

The experiment was conducted to investigate the physico-chemical characteristics of vacuum and aerobically packed meat from Elk deer weighing 170 $\pm$ 10kg of 28 to 30 months old, chilled at 4$^{\circ}C$for 10days. The moisture content, crude protein, crude fat and crude ash in deer loin were 74.46%, 22.11%, 1.27% and 1.13%: the leg parts had 75.47%, 22.68%, 1.58% and 1.27%, respectively. The decrease in moisture content was greater in aerobic packaging than in vacuum packaging. The lysine content of loin and leg parts were 2,380mg% and 2,270mg% and the glutamate content of loin and leg parts were 4,145mg% and 3,987.5mg% respectively. On the whole, the loin contained more amino acids than leg part. Of the mineral contents, phosphorus, potassium and sodium were present in large amounts and mineral content was decreased with longer chilling period. The leg parts contained more potassium, sodium, phosphorus, zinc, magnesium and calcium than loin parts. In conclusion, vacuum packaging is considered more advantageous in preventing meat color change and microbial deterioration for consumers interest.