检索结果-南通市图书馆

Biodiesel Production from Oils Extracted from Date pits

在线全文

学校读者我要写书评

暂无评论

Green and Sustainable Chemistry 2017年第1期7卷 48-56页

作者： Sulaiman Al-Zuhair Hanifa Taher Salama Al Dhaheri Shereen Wajeeh Mutasim Nour Emad El-Najjar Chemical and Petroleum Engineering Department UAE University Al Ain United Arab Emirates Chemical and Environmental Engineering Department Masdar Institute Abu Dhabi United Arab Emirates Mechanical Engineering Department UAE University Al Ain United Arab Emirates School of Engineering & Physical Sciences Heriot-Watt University Dubai Campus Dubai United Arab Emirates

Biodiesel production had received a considerable attention as a green, non-toxic and renewable alternative to petroleum diesel. To avoid using vegetable oils, which are expensive and compete with food, as feedstock, waste oils have been proposed. However, these waste materials contain a large amount of free fatty acids that complicates the production process. In this work, biodiesel production using an alternative feedstock;namely oils from date-pits, has been investigated. These oils have the same favorable features of straight oils, and at the same time are considered waste, since they are extracted from a waste material. The yield of oils extracted using n-hexane in a Soxhlet apparatus was compared to that of oils extracted using methanol-chloroform solvent mixture. The extracted oils were then converted to biodiesel via transesterification with methanol in presence of Novozym𪥣 or Eversa®Transform. The highest oils extraction yield of 11.7%, per dry weight sample, was obtained using Soxhlet extraction apparatus compared to 8.9% using methanol-chloroform mixture. The highest biodiesel production yield was 30% of the oil used, achieved after 6 hours using Novozym𪥣 at 40°C, 5:1 methanol to oil molar ratio and 10wt% enzyme loading. By using a chemical alkaline catalyst, NaOH, at the same conditions, the yield was 27%.

关键词： Date pits Soxhlet Lipase Biodiesel Enzymatic Reaction

Pit density reduction for AlN epilayers grown by molecular beam epitaxy using Al modulation method

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2024年第10期33卷 95-101页

作者： Huan Liu Peng-Fei Shao Song-Lin Chen Tao Tao Yu Yan Zi-Li Xie Bin Liu Dun-Jun Chen Hai Lu Rong Zhang Ke Wang Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials School of Electronic Science and EngineeringNanjing UniversityNanjing 210093China Hefei National Laboratory Hefei 230088China Xiamen University Xiamen 361005China

We have investigated homoepitaxy of AlN films grown by molecular beam epitaxy on AlN/sapphire templates byadopting both the continuous growth method and the Al modulation epitaxy(AME)growth *** continuous growthmethod encounters significant challenges in controlling the growth *** the precise Al/N=1.0 ratio is difficult toachieve,either the excessive Al-rich or N-rich growth mode *** contrast,by adopting the AME growth method,sucha difficulty has been effectively *** manipulating the supply time of the Al and nitrogen sources,we were able toproduce AlN films with much improved surface *** first step of the AME method,only supplying Al atoms,is important to wet the surface and the Al adatoms can act as a *** of the initial Al supply time caneffectively reduce the pit density on the grown AlN *** pits density dropped from 12 pits/μm^(2)to 1 pit/μm^(2)andthe surface roughness reduced from 0.72 nm to 0.3 nm in a 2×2μm^(2)area for the AME AlN film homoepitaxially grownon an AlN template.

关键词： Al modulation epitaxy molecular beam epitaxy AlN pits

Reliability analysis of GaN-based light emitting diodes for solid state illumination

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2008年第7期17卷 2696-2700页

作者：杨凌马晓华冯倩郝跃 Key Laboratory of Ministry of Education for Wide Band Gap Semiconductor Material and Device Institute of MicroelectronicsXidian University

In this paper, we have discussed the effect of electrical stress on GaN light emitting diode （LED）. With the lapse of time, the LED with an applied large current stress can reduce its current more than without such a stress under a large forward-voltage drop. Its scanning electron microscopy （SEM） image shows that there exist several pits on the surface of the p-metal. With an electrical stress applied, the number of pits greatly increases. We also find that the degradation of GaN LED is related to the oxidized Ni/Au ohmic contact to p-GaN. The electrical activation of H-passivated Mg acceptors is described in detail. Annealing is performed in ambient air for 10 min and the differential resistances at a forward-voltage drop of 5 V are taken to evaluate the activation of the Mg acceptors. These results suggest some mechanisms of degradation responsible for these phenomena, which are described in the paper.

关键词： GaN based LED electrical stress pits annealing mechanism of degradation

Etching Effect on CMP of Different GaN Layers

在线全文

学校读者我要写书评

暂无评论

稀有金属材料与工程 2011年第S3期40卷 276-280页

作者： Siche Dietmar Rost Hans-Joachim Schulz Tobias Albrecht Martin Institute of Crystal Growth Max-Born-Str. 2 12489 Berlin Germany

Chemical mechanical polishing (CMP) was used to etch various GaN materials, such as GaN layers on sapphire and silicon carbide substrates grown by metal-organic chemical vapor deposition and thick GaN layers grown by physical vapor transport. It was found that CMP could reveal the dislocations in GaN surfaces due to a selective etching component. After the optimization of CMP condition, the surface finish improved and the subsurface damage was almost completely removed, demonstrated by atomic force microscopy and an electron back-scattered diffraction technique. This study established the correlation between the dislocation density and film quality. The crystalline perfection and optical properties of GaN layers were characterized by high resolution X-ray diffraction and photoluminescence.

关键词： surface etch pits CMP GaN

Cloth simulation-based construction of pitfree canopy height models from airborne LiDAR data

在线全文

学校读者我要写书评

暂无评论

Forest Ecosystems 2020年第1期7卷 1-13页

作者： Wuming Zhang Shangshu Cai Xinlian Liang Jie Shao Ronghai Hu Sisi Yu Guangjian Yan State Key Laboratory of Remote Sensing Science Jointly Sponsored by Beijing Normal University and Institute of Remote Sensing and Digital Earth of Chinese Academy of SciencesBeijing Engineering Research Center for Global Land Remote Sensing ProductsInstitute of Remote Sensing Science and EngineeringFaculty of Geographical ScienceBeijing Normal UniversityBeijing 100875China Department of Remote Sensing and Photogrammetry Finnish Geospatial Research Institute02431 MasalaFinland College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China ICube Laboratory UMR 7357 CNRS-University of Strasbourg300 bd Sebastien BrantCS10413F-67412 Illkirch CedexFrance Institute of Remote Sensing and Digital Earth Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Background:The universal occurrence of randomly distributed dark holes(i.e.,data pits appearing within the tree crown)in LiDAR-derived canopy height models(CHMs)negatively affects the accuracy of extracted forest inventory ***:We develop an algorithm based on cloth simulation for constructing a pit-free ***:The proposed algorithm effectively fills data pits of various sizes whilst preserving canopy *** pitfree CHMs derived from point clouds at different proportions of data pits are remarkably better than those constructed using other algorithms,as evidenced by the lowest average root mean square error(0.4981 m)between the reference CHMs and the constructed pit-free ***,our pit-free CHMs show the best performance overall in terms of maximum tree height estimation(average bias=0.9674 m).Conclusion:The proposed algorithm can be adopted when working with different quality LiDAR data and shows high potential in forestry applications.

关键词： Data pits Tree crown Canopy height models Cloth simulation Pit-free

An Efficient Method on Deriving Topographic Index from DEM for Land Surface Hydrological Model Simulations

在线全文

学校读者我要写书评

暂无评论

Acta meteorologica Sinica 2009年第5期23卷 609-616页

作者：徐精文张万昌孙成武符淙斌 Key Laboratory of Regional Climate-Environment Research for Temperate East Asia Institute of Atmospheric PhysicsChinese Academy of Sciences College of Resource and Environment Sichuan Agricultural University Graduate School of the Chinese Academy of Sciences Linyi Bureau of Meteorology

As a kernel parameter of the TOPMODEL-concept-based land surface model （LSM）, topographic in- dex （TI） is commonly derived from high resolution digital elevation model （DEM）. Various approaches to compute TI by using different algorithms have been developed in previous literature. However, fiat areas and pits in DEMs of real watershed sometimes impose an arbitrary and spatially constant drainage density which may cause conventional retrieval methods to be very computer-intensive, especially for regional or global climate simulations where rugged mountainous areas are mixed with fiat terrains in the DEM. In this paper, we propose a new approach to overcome this shortcoming by introducing a quantile classification to sort the DEM into eight categories at first and then using a fast and simple algorithm to process the fiat areas, fill up pits in the DEM, and make it undulating. Thereafter, the algorithm can be directly applied to assigning flow directions of each cell of the processed DEM rather than taking the complicated approach of Jenson and Domingue. This approach dramatically promotes the computing efficiency with a much easier and faster processing. In addition, the effects of different TI computing approaches on the TOPMODEL-concept-based hydrological simulations are investigated based on experimental simulations over a small-scale watershed gauged by the Yonshuijie hydrological station and a large-scale watershed controlled by the Hanzhong hydrological station, respectively. The results show that the new approach is 13 times faster than the conventional one in TI retrieving, and no evident differences are found in rainfall- runoff simulations when using different algorithms in TI computations. These suggest that the proposed new approach for TI computation can be taken as an alternative and used in the TOPMODEL-concept- based hydrological simulations owning to its simplicity and high efficiency, especially for relevant regional and global studies.

关键词： TOPMODEL topographic index (TI) digital elevation model (DEM) pits fiat areas

Topography and functional information of plasma membrane

在线全文

学校读者我要写书评

暂无评论

Science China(Life Sciences) 2008年第2期51卷 95-103页

作者： SUN DeLan1, CHEN JianMin1, SONG YanMei1, ZHU ChuanFeng2, PAN GeBo2 & WAN LiJun2 1 Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China 2 Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China Key Laboratory of Photosynthesis and Environmental Molecular Physiology Institute of Botany Chinese Academy of Sciences Beijing China Institute of Chemistry Chinese Academy of Sciences Beijing China

By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40―60 nm, and a range of 1.8―5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12―40 nm for their diameter and 0.7―2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 μm2. According to their size, we clas

关键词： atomic force microscope winter wheat protoplast plasma membrane surface membrane protein invaginated pits

In vitro inhibitory effects on a-glucosidase and a-amylase level and antioxidant potential of seeds of Phoenix dactylifera L.

在线全文

学校读者我要写书评

暂无评论

Asian Pacific Journal of Tropical Biomedicine 2016年第4期6卷 322-329页

作者： Shah Alam Khan Amira Rashid Al Kiyumi Manal Saif Al Sheidi Tagreed Salim Al Khusaibi Noura Mohammed Al Shehhi Tanveer Alam Department of Pharmacy Oman Medical College Oman Medicinal Plants & Marine Natural Products University of Nizwa

Objective:To evaluate and compare the antioxidant activity,total phenolic contents(TPCs) and in vitro antidiabetic activity of various pits extracts obtained from five Omani date ***:Sun-dried mature fruits of five Omani date varieties,namely,Fardh,Naghal,Khalas,Khinazi and Khasab were purchased from the local market in Muscat,Oman in the month of September *** seed extracts ***,ethanol,methanol and acetone were prepared for each date variety and their antioxidant activities were investigated by 1,1-diphenyl-2-picrylhydrazyl,hydrogen peroxide scavenging method and reducing power assay method,*** vitro antidiabetic activity of the date pit extracts was evaluated by measuring their inhibitory effect on a-glucosidase and aamylase *** were also quantified ***:The results indicated that TPC of date seeds was solvent ***,ethanol and methanol were found to be significantly better solvents than water in extracting phenolic compounds from the date *** extracts exhibited moderate to good in vitro antioxidant activity and increased reducing *** all date pit extracts,water extract exhibited significant in vitro antidiabetic activity in comparison to standard drug,***:The present study confirms that disposed waste of Omani dates is a rich source of dietary antioxidant because of its high *** pits due to their inhibitory effects on a-glucosidase and a-amylase level could be used as a monotherapy along with an appropriate diabetic diet and exercise or might be in conjunction with antidiabetic therapy to manage and prevent progression of diabetes.

关键词： Phoenix dactylifera L. Antioxidant In vitro antidiabetic activity Date pits

Hillock Sn whiskers growth behaviors in Sn0.3Ag0.7Cu/Cu solder joints during corrosion

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

High Technology Letters 2018年第1期24卷 113-116页

作者：张亮 Liu Zhiquan Sun Lei Yang Fan Zhong Sujuan School of Mechanical & Electrical Engineering Jiangsu Normal University Xuzhou 221116 P. R. China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 P. R. China State Key Laboratory of Advanced Brazing Filler Metals & Technology Zhengzhou Research Institute of Mechanical Engineering Zhengzhou 450001 P. R. China

Hillock Sn whiskers in Sn0.3Ag0.7Cu solder are investigated in 20 seconds in corrosive climate(95% methanol and 5% nitric acid),and the growth mechanism of hillock Sn whiskers is *** results indicate that hillock Sn whiskers are formed near the interface of Sn0.3Ag0.7Cu/Cu solder joints,and small corrosion pits provide conceive sites for Sn whiskers. Moreover,compressive stress induced by IMC reaction and oxidation for the whisker growth may be suggested as the driving force.

关键词： Sn whisker solder joints corrosion pits conceive sites