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991.
张咏祀 《西华师范大学学报(哲学社会科学版)》2008,29(4)
为了研制恩施州马尾松人工林地位指数表,对恩施州的8个县市进行马尾松人工林标准地调查.利用查资料拟合的树高——年龄导向曲线回归方程为:H=10^1.39-7.32/A,其离回归标准误SH/A=1.0m,相关系数r=-996.由拟合的树高——年龄导向曲线回归方程和外业调查资料,用标准差法编制出14—30龄阶的10—18地位数的马尾松人工林地位指数表.本表较好地反映了当地马尾松人工林的生长和立地条件的关系,对恩施州林业产经营有较好的指导和参考意义. 相似文献
992.
Liushanfeng 《科技信息》2008,(29)
本文所提出的初值设定方法简单、实用,可以直接应用于快速解耦法的潮流计算中。与平起动(即初值:电压幅值为1.0p.u.,相角为0度)相比,这种方法可以有效地减少总的迭代次数,加快计算进程,提高求解的稳定性。 相似文献
993.
Yajing Zhang 《Journal of Mathematical Analysis and Applications》2008,344(2):682-686
In this paper, we study the following integral equation:
994.
Marcelo Montenegro Augusto C. Ponce 《Proceedings of the American Mathematical Society》2008,136(7):2429-2438
We extend the method of sub and supersolutions in order to prove existence of -solutions of the equation in , where is a Carathéodory function. The proof is based on Schauder's fixed point theorem.
995.
Yang-Shin Liu Akira Yamaguchi Yue Yang An Niza El Aisnada Sho Uchida Hideki Abe Shigenori Ueda Kenji Yamaguchi Toyokazu Tanabe Masahiro Miyauchi 《Angewandte Chemie (International ed. in English)》2023,62(17):e202300640
An unexplored tin oxide crystal phase (Sn3O4) was experimentally synthesized via a facile hydrothermal method. After tuning the often-neglected parameters for the hydrothermal synthesis, namely the degree of filling of the precursor solution and the gas composition in the reactor head space, an unreported X-ray diffraction pattern was discovered. Through various characterization studies, such as Rietveld analysis, energy dispersive X-ray spectroscopy, and first-principles calculations, this novel material was characterized as orthorhombic mixed-valence tin oxide with the composition SnII2SnIVO4. This orthorhombic tin oxide is a new polymorph of Sn3O4, which differs from the reported conventional monoclinic structure. Computational and experimental analyses showed that orthorhombic Sn3O4 has a smaller band gap (2.0 eV), enabling greater absorption of visible light. This study is expected to improve the accuracy of hydrothermal synthesis and aid the discovery of new oxide materials. 相似文献
996.
Bingyu Liu Junjie Gao Prof. Aiyou Hao Prof. Pengyao Xing 《Angewandte Chemie (International ed. in English)》2023,62(25):e202305135
Multiple constituent coassembly is an emerging strategy to manipulate supramolecular chirality and chiroptical properties such as circularly polarized luminescence (CPL). However, the second or third constituent could not be removed from pristine self-assembly. Here we developed a constitute-removable chiral coassembly using sublimation that could realize coassembly with tunable supramolecular chirality, luminescence and CPL properties. Octafluoronapthalene (OFN) with small sublimation enthalpy formed coassemblies with perylene-conjugated peptoids via arene-perfluoroarene (AP) interaction that induced the emergence of macroscopic chirality and hypsochromic luminescence from yellow to green. Coassembly with OFN accelerated one-dimensional growth and induced the emergence of macroscopic chirality and CPL. Despite the stability at ambient conditions, vacuum-treatment triggered fast sublimation of OFN, which behaved as a sacrificial template. Physical removal of OFN retained the helical nanoarchitectures as well as the basic features of Cotton effects and CPL activities. X-ray diffraction suggested the back-fill consolidation occurred on the molecular voids by OFN removal that slightly varied the templated molecular arrangements. Sublimation of perfluorinated building units is green and efficient and non-destructive, which is potentially applicable in constructing template-directed chiroptical materials and devices. 相似文献
997.
Chen Zhang Jiali Song Jingwei Xue Shijie Wang Zhongwei Ge Yuheng Man Prof. Wei Ma Prof. Yanming Sun 《Angewandte Chemie (International ed. in English)》2023,62(40):e202308595
Oligomer acceptors have recently emerged as promising photovoltaic materials for achieving high power conversion efficiency (PCE) and long-term stability in organic solar cells (OSCs). However, the limited availability of diverse acceptors, resulting from the sole synthetic approach, has hindered their potential for future industrialization. In this study, we present a facile and effective stepwise approach that utilizes two consecutive Stille coupling reactions for the synthesis of oligomer acceptors. To demonstrate the feasibility of the novel approach, we successfully synthesize a trimer acceptor, Tri-Y6-OD, and further systematically investigate the impact of oligomerization on device performance and stability. The results reveal that this approach has significant advantages compared to the conventional method, including reduced formation of unwanted by-products and lower difficulties in purification. Remarkably, the OSC based on PM6 : Tri-Y6-OD achieves an impressive PCE of 18.03 % and maintains 80 % of the initial PCE (T80) for 1523 h under illumination, surpassing the performance of the corresponding small molecule acceptor Y6-OD-based device. Furthermore, the versatility of the synthetic strategy in obtaining diverse acceptors is further demonstrated. Overall, our findings provide a facile, versatile and stepwise way for synthesizing oligomer acceptors, thereby facilitating the development of stable and efficient OSCs. 相似文献
998.
Dr. Wenjun Zhang Dr. Shanshan Liu Dr. Yue Yang Dr. Haifeng Qi Dr. Shibo Xi Dr. Yanping Wei Dr. Jie Ding Prof. Zhu-Jun Wang Prof. Qunxiang Li Prof. Bin Liu Prof. Zupeng Chen 《Angewandte Chemie (International ed. in English)》2023,62(23):e202219241
Metal-organic framework catalysts bring new opportunities for CO2 electrocatalysis. Herein, we first conduct density-functional theory calculations and predict that Co-based porphyrin porous organic layers (Co-PPOLs) exhibit good activity for CO2 conversion because of the low *CO adsorption energy at Co-N4 sites, which facilitates *CO desorption and CO formation. Then, we prepare two-dimensional Co-PPOLs with exclusive Co-N4 sites through a facile surfactant-assisted bottom-up method. The ultrathin feature ensures the exposure of catalytic centers. Together with large specific area, high electrical conductivity and CO2 adsorption capability, Co-PPOLs achieve a peak faradaic efficiency for CO production (FECO=94.2 %) at a moderate potential in CO2 electroreduction, accompanied with good stability. Moreover, Co-PPOLs reach an industrial-level current above 200 mA in a membrane electrode assembly reactor, and maintain near-unity CO selectivity (FECO>90 %) over 20 h in CO2 electrolysis. 相似文献
999.
Video-imaging is one method of analyzing the shrinkage of resins. For the measurement, a drop of resin is placed near an illumination source and its contour is imaged from the front with a camera. This paper presents a further development, detailed investigation and verification of this technique to analyze the chemical shrinkage of thermally cured epoxy resins during cure. A new cylindrical sample holder was developed which enables the automated detection of the baseline, as well as defining the scale within the pictures. In a test series, the resin's volume was varied, as well as its contour. The findings confirm that the measured volume shrinkage is independent of the drop shape.Finally, the obtained shrinkage results were verified and evaluated in comparison with values measured by a mercury dilatometer and a rheometer. The shrinkage results of the investigated new method are in good accordance with the more established methods. 相似文献
1000.
Systematic approach to optimize a pretreatment method for ultrasensitive liquid chromatography with tandem mass spectrometry analysis of multiple target compounds in biological samples 下载免费PDF全文
Kazutaka Togashi Kuninori Mutaguchi Setsuko Komuro Makoto Kataoka Hiroshi Yamazaki Shinji Yamashita 《Journal of separation science》2016,39(16):3212-3220
In current approaches for new drug development, highly sensitive and robust analytical methods for the determination of test compounds in biological samples are essential. These analytical methods should be optimized for every target compound. However, for biological samples that contain multiple compounds as new drug candidates obtained by cassette dosing tests, it would be preferable to develop a single method that allows the determination of all compounds at once. This study aims to establish a systematic approach that enables a selection of the most appropriate pretreatment method for multiple target compounds without the use of their chemical information. We investigated the retention times of 27 known compounds under different mobile phase conditions and determined the required pretreatment of human plasma samples using several solid‐phase and liquid–liquid extractions. From the relationship between retention time and recovery in a principal component analysis, appropriate pretreatments were categorized into several types. Based on the category, we have optimized a pretreatment method for the identification of three calcium channel blockers in human plasma. Plasma concentrations of these drugs in a cassette‐dose clinical study at microdose level were successfully determined with a lower limit of quantitation of 0.2 pg/mL for diltiazem, 1 pg/mL for nicardipine, and 2 pg/mL for nifedipine. 相似文献