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Cao, Leichang,Yu, Iris K.M.,Cho, Dong-Wan,Wang, Di,Tsang, Daniel C.W.,Zhang, Shicheng,Ding, Shiming,Wang, Linling,Ok, Yong Sik Elsevier 2019 Bioresource technology Vol.273 No.-
<P><B>Abstract</B></P> <P>In this study, red seaweed (<I>Gracilaria lemaneiformis</I>) food waste with high carbohydrate content was valorized into levulinic acid (LA) and algae hydrochar through microwave-assisted low-temperature hydrothermal treatment in dilute acid solution. Various parameters including treatment temperature (160–200 °C), reaction time (1–40 min), acid concentration (0–0.6 M), and biomass-to-liquid ratio (1%–10%, w/v) were examined. The energy efficiency and carbon recovery of the proposed process were investigated. Under the experimental conditions of 5% (w/v) biomass loading, 0.2 M H<SUB>2</SUB>SO<SUB>4,</SUB> 180 °C, and 20 min, the highest levulinic acid yield of 16.3 wt% was produced. The resulting hydrochar showed approximately 45–55% energy yield and higher heating values of 19–25 MJ kg<SUP>−1</SUP>. The energy efficiency of the present study (1.31 × 10<SUP>−6</SUP> g LA/J) was comparable to those of the conventional hydrothermal treatment of lignocellulosic biomass, while the reaction time (20 min) was much shorter with a high carbon recovery (73.3%).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Red seaweed food waste was used as a sustainable feedstock for LA production. </LI> <LI> Microwave-assisted hydrothermal treatment facilitated fast red seaweed conversion. </LI> <LI> High LA yield of 16.3 wt% was obtained from <I>Gracilaria lemaneiformis</I>. </LI> <LI> Algae hydrochar recovered can serve as a potential solid fuel. </LI> <LI> Energy efficiency of 1.31 × 10<SUP>−6</SUP> g LA/J and high carbon recovery of 73.3% were achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
D. Cao,D. Zhang,J. W. Kolar,J. Huber 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
Future particle accelerators for high-energy physics experiments such as the Future Circular Collider (FCC) at CERN employ high-temperature-superconducting (HTS) magnets to guide and focus the particle beams. However, the high-current/large-cross-section copper conductors used to connect the HTS magnet coils to the power supply conventionally located outside of the cryostat create a thermal leakage path, which ultimately results in high energy consumption of the cryocoolers. The heat leak-in could be reduced by power delivery through the cryostat’s heat shield at higher voltage levels and hence with lower currents. However, then a power electronic conversion to the low voltage and high current needed by the HTS magnets must be provided inside of the cryostat. Given the increased complexity, such a concept is only sensible if the resulting total heat load, i.e., the sum of the converter losses and the (then lower) leak-in losses, is so low that a clear improvement of the overall energy efficiency results. In this paper, we therefore conceptualize a cryogenic power supply for a 250-A HTS magnet, which operates at 60 K. Considering the strict EMI limits applicable in the CERN environment, a codesign method for the current leads and a full-bridge multiphase buck dc-dc converter is introduced and used to explore the design trade-offs. The results indicate that a reduction of the total heat load by about a factor of three to four compared to the state of the art seems feasible, i.e., from about 21W to about 5W.
원자력발전 수용성의 영향요인에 관한 연구: 위험인식과 정부신뢰의 매개효과를 중심으로
조우봉 ( Cao Yupeng ),목진휴 ( Mok Jin W. ) 국민대학교 사회과학연구소 2016 社會科學硏究 Vol.29 No.1
후쿠시마 원자력발전소 사고 이후 국민들의 위험인식이 높아지고 있는 상황에서 잠재적위험이 존재하는 원자력을 전력생산의 동력으로 국민들이 수용할 수 있도록 하는 방안의모색에 정책적 초점이 주어져 있다. 이에 본 연구는 원자력발전 수용성에 영향을 줄 수 있는 요인들을 알아봄과 동시에 이러한 요인들과 수용성과의 관계에서 매개적 영향을 초래할것으로 믿어지는 요인들을 파악하고 이들의 정책적 의미를 찾는데 목적을 두고 있다. 일반국민들의 원자력에 대한 인식조사결과에 따르면, 원자력과 관련된 지식수준이 높으면 원자력발전에 대한 수용성이 높게 나타났으나 원자력정책에 대한 만족여부는 원자력발전에 대한 수용성에 영향을 초래하지 않는 것으로 검증되었다. 반면에 원자력에 대한 위험인식은 지식수준과 수용성의 관계를 매개하지 않으나 정부에 대한 신뢰는 정책만족도와 정책수용의 관계에서 매개효과를 보인다. 특히, 정부를 신뢰하면 할수록 원자력정책에 대한 만족도는 추가원자력 발전소 건설에 대해 긍정적인 영향을 초래하는 것으로 확인되었다. 이러한점은 정부 정책에 대한 국민들의 수용도를 높이기 위해선 국민들이 정부를 신뢰할 수 있도록 해야 한다는 기존의 연구결과를 재차 확인하는 것이며 특히 정부가 원자력 발전소의 추가건설을 위한 노력에는 국민들이 정부의 업무에 대한 전반적인 신뢰가 따라야 한다는 점을 지적하고 있다. This study aims to investigate the mediating role of public trust and risk perception to the relationship between the public acceptance and knowledge level and between the public acceptance and the policy satisfaction. According to the results using the public survey on the public perception on the nuclear issues, the public generally accept the government’s effort to expand nuclear capacity in electricity production and those who have higher level of trust on the government tend to promote the relationship between the policy satisfaction and policy acceptance, though risk perception not showing any mediating effect to the knowledge level and policy acceptance relationship. What this means is to confirm those existing studies that emphasize the role of the trust in government, and to suggest more prudent effort by the government in search of means to promote its level.
Sulfonated biochar as acid catalyst for sugar hydrolysis and dehydration
Xiong, Xinni,Yu, Iris K.M.,Chen, Season S.,Tsang, Daniel C.W.,Cao, Leichang,Song, Hocheol,Kwon, Eilhann E.,Ok, Yong Sik,Zhang, Shicheng,Poon, Chi Sun Elsevier 2018 CATALYSIS TODAY - Vol.314 No.-
<P><B>Abstract</B></P> <P>This study investigated the use of 30 w/v% H<SUB>2</SUB>SO<SUB>4</SUB> sulfonated wood waste-derived biochar as catalysts for production of value-added chemicals from carbohydrates in water as an environmentally benign solvent. Physicochemical characteristics of the sulfonated biochar were revealed by Fourier transform infrared spectroscopy (FTIR), acid-base neutralization titration, gas adsorption analysis, thermogravimetric analysis (TGA), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). Using the sulfonated biochar as catalysts, hydrolysis of maltose at 140–160 °C resulted in the maximum glucose yield of 85.4% and selectivity of 88.2%, whereas dehydration of fructose at 160–180 °C produced the maximum HMF yield of 42.3% and selectivity of 60.4%. A higher range of reaction temperature was required for fructose dehydration due to the higher energy barrier compared to maltose hydrolysis. While increasing the temperature accelerated the catalytic reactions, the maximum product selectivity remained unchanged in the sulfonated biochar-catalyzed systems. The products were stable despite the increase in reaction time, because rehydration and adsorption of products was found to be minor although polymerization of intermediates led to unavoidable carbon loss. This study highlights the efficacy of engineered biochars in biorefinery as an emerging application.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biochar catalyst sulfonated by 30% w/v H<SUB>2</SUB>SO<SUB>4</SUB> achieved 42.3% yield and 58.7% selectivity HMF from fructose. </LI> <LI> Maltose hydrolysis to glucose with yield and selectivity of 85.4% and 88.2% was achieved at lower temperatures. </LI> <LI> Higher temperature accelerated the conversion but did not change the maximum yield and selectivity. </LI> <LI> Energy barrier of dehydration is larger than hydrolysis and requires higher temperature or stronger acidity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>