• Applied Chemistry for Engineering
• /
• v.27 no.4
• /
• pp.444-448
• /
• 2016

Hollow silicon/carbon (H-Si/C) composites as anode materials for lithium ion batteries were investigated to overcome the large volume expansion. H-Si/C composites were prepared as follows; hollow $SiO_2\;(H-SiO_2)$ was prepared by adding $NaBH_4$ to $SiO_2$ synthesized using $st{\ddot{o}}ber$ method followed by magnesiothermic reduction and carbonization of phenolic resin. The H-Si/C composites were analyzed by XRD, SEM, BET and EDX. To improve the capacity and cycle performance, the electrochemical characteristics of H-Si/C composites synthesized with various $NaBH_4$ contents were investigated by charge/discharge, cycle, cyclic voltammetry and impedance tests. The coin cell using H-Si/C composite ($SiO_2:NaBH_4=1:1$ in weight) in the electrolyte of $LiPF_6$ dissolved in organic solvents (EC : DMC : EMC = 1 : 1 : 1 vol%) has better capacity (1459 mAh/g) than those of other composition coin cells. It is found that the coin cell ($SiO_2:NaBH_4=1:1$ in weight) has an excellent capacity retention from 2nd cycle to 40th cycle.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.5
• /
• pp.716-721
• /
• 2010

LCA (Life Cycle Assessment) carried out to estimate carbon footprint and to establish of LCI (Life Cycle Inventory) database of rice production system. The results of collecting data for establishing LCI D/B showed that organic fertilizer and chemical fertilizer input to 4.29E-01 kg $kg^{-1}$ rice and 2.30E-01 kg $kg^{-1}$ rice for rice cultivation. It was the highest value among input for rice cultivation. And direct field emission was 3.23E-02 kg $kg^{-1}$ during rice cropping. The results of LCI analysis focussed on greenhouse gas (GHG) was showed that carbon footprint was 8.70E-01 kg $CO_2$-eq. $kg^{-1}$ rice. Especially for 80% of $CO_2$ in the GHG and 7.02E-01 kg of its $CO_2$-eq. $kg^{-1}$ rice. Of the GHG emission $CH_4$, and $N_2O$ were estimated to be 13% and 5%, respectively. With LCIA (Life Cycle Impact Assessment) for rice cultivation system, it was observed that fertilizer process might be contributed to approximately 80% of GWP (global warming potential).

• Clean Technology
• /
• v.18 no.4
• /
• pp.440-445
• /
• 2012

15 carbon footprint product (CFP) schemes, including Korea Carbon Footprint Label, UK Carbon Trust's Carbon Reduction Label and Japan CFP are implemented in the world. A CFP describes green house gases (GHGs) emissions emitted throughout product's life cycle and is intended to reduce GHGs emissions by labeling a CFP result on product. This study calculates Korea, UK and Japan CFP result of vacuum cleaner, detergent, packagin material in order to analyze the Korea, UK and Japan CFP standards. Our results demonstrate significant differences among then calculated results because of criteria, emission factors, etc. Therefore, there are many difficulties in providing various CFP results and the international standard and guidelines for product category are needed.

• Journal of the korean Society of Automotive Engineers
• /
• v.7 no.3
• /
• pp.83-93
• /
• 1985

The prediction of emission concentrations in a 4cycle spark ignition engine was made by considering nonuniform model with thermodynamics, chemical equilibrium and kinetic mechanism of nitric oxide. Calculation of this model shows that a temperature difference of the order of 500K can be established across he cylinder. Results of the kinetic calculation of nitric oxide show that the temperature gradient across the cylinder has a profound effect on the nitric oxide formation. The predicted values for nitric oxide, carbon dioxide and carbon monoxide agree with measured ones for a variety of equivalence ratio.

• Journal of Photoscience
• /
• v.6 no.1
• /
• pp.29-36
• /
• 1999

Chlorophasts are a central structural feature of stomatal guard cells. Guard cell chloroplasts have both photosystems I and II (PS I and II), carry out O2 evoluation , cyclic and noncyclic photophosporylation, and possess the Calvin-Benson cycle enzymes involved in CO2 fixation. These imply that guard cell chloroplasts have a normal photosynthetic carbon reduction pathway just like their mesophyll counterparts, indicating similar fuctional organization of thylakoid membranes in both types of mesophyll and guard cell chloroplasts. It has been, however, found that guard cell chloroplasts have distinctive and comparative properties in their photosynthetic performance. In this article, I review the intrinsic features on the light reaction of and carbon reduction by guard cell chloroplasts.

• 한국생물공학회:학술대회논문집
• /
• 2004.07a
• /
• pp.35-45
• /
• 2004

This paper reviewed effects of global climatic changes on wetland biogeochemistry, Wetlands play key roles in global as well as local material cycle, which includes carbon sequestration, $CH_4$ emission and DOC leaching, Increased air temperature, elevated $CO_2$ levels and changed precipitation patterns are believed to affect those processes substantially by modifying oxygen supply, carbon sources, and decomposition rates. For example, elevated $CO_2$ may increase $CH_4$ emission as well as DOC leaching from wetlands. In addition, interactions of multiple effects warrant further investigation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.8
• /
• pp.641-648
• /
• 2006

In this study, a two-stage phase-separate cycle was investigated analytically to improve the performance of the $CO_2$ system in the cooling mode. The simulation results were verified with the measured data. The predictions using the simulation model were consistent with the measured data within ${\pm}20%$ deviations. The performance of the modified $CO_2$ system with the two-stage phase-separated cycle was analyzed with the variations of outdoor temperature and EEV opening. The cooling COP decreased with the increase of compressor frequency. The highest COP was 2.7 at compressor frequencies of 30 Hz and 30 Hz for the first and second compressors, respectively. In addition, the cooling COP increased by 9.3% with an application of optimum control of the first and second-stage EEV openings.

• Advanced Composite Materials
• /
• v.16 no.2
• /
• pp.151-166
• /
• 2007

High-cycle fatigue characteristics of quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates [-45/0/45/90]s up to $10^8$ cycles were investigated. To assess the fatigue behavior in the high-cycle region, fatigue tests were conducted at a frequency of 100 Hz, since it is difficult to investigate the fatigue characteristics in high-cycle at 5 Hz. Then, the damage behavior of the specimen was observed with a microscope, soft X-ray photography and a 3D ultrasonic inspection system. In this study, to evaluate quantitative characteristics of both transverse crack propagation and delamination growth in the high-cycle region, the energy release rate associated with damage growth in the width direction was calculated. Transverse crack propagation and delamination growth in the width direction were evaluated based on a modified Paris law approach. The results revealed that transverse crack propagation delayed under the test conditions of less than ${\sigma}_{max}/{\sigma}_b$ = 0.3 of the applied stress level.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.9
• /
• pp.630-639
• /
• 2007

A $CO_2$ cycle shows large throttling loss during the expansion process. The application of an expander into the $CO_2$ cycle can reduce the throttling loss and then improve system performance. In this study, the performance of a transcritical $CO_2$ cycle with an expander was analytically investigated in order to improve the cooling performance of the system. The expander was applied to the single-stage and two-stage compression cycles. The performance was analyzed with the variations of compressor frequency, outdoor temperature, and expander efficiency. The single-stage and two-stage compression cycles with the expander showed COP improvement of 25% and 32%, respectively, over the single-stage cycle with an EEV.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.460-468
• /
• 2008

Recent activities on the scramjet and rocket-ramjet combined-cycle engine of Japan Aerospace Exploration Agency(JAXA) are herein presented. The scramjet engines and combined-cycle engines have been studied in the world and JAXA has also studied such the engines experimentally, numerically and conceptually. Based on the studies, 2 to 3 m long, hydrogen-fueled engine models were designed and tested at the Ramjet Engine Test Facility(RJTF) and the High Enthalpy Shock Tunnel(HIEST). A scramjet engine model was tested in Mach 10 to 14 flight condition at HIEST. A 3 m long scramjet engine model was designed to reduce a dissociation energy loss in a high temperature condition. Drag reduction by a tangential injection and two ways of a transverse fuel injection were examined. Combustor model tests at three operating modes of the combined-cycle engine were conducted, demonstrating the combustor operation and producing data for the engine design at each mode. Aerodynamic engine model tests were conducted in a transonic wind tunnel, demonstrating the engine operation in the ejector-jet mode. A 3 m long combined-cycle engine model has been tested in the ejector-jet mode and the ramjet mode since March 2007. Carbon composite material was examined for application to the engines. Production of the cooling channel on a nickel alloy plate succeeded by the electro-chemical etching.