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Generating attosecond pulses with controllable polarization from cyclic H_(3)^(2+) molecules by bichromatic circular fields
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作者 张思琪 张冰 +2 位作者 闫博 姜向前 孙秀冬 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第2期305-310,共6页
We investigate the polarization properties of harmonics from the cyclic H_(3)^(2+) molecular ions in tailored bichromatic counter-rotating circularly polarized(BCCP)fields by solving the time-dependent Schrödinge... We investigate the polarization properties of harmonics from the cyclic H_(3)^(2+) molecular ions in tailored bichromatic counter-rotating circularly polarized(BCCP)fields by solving the time-dependent Schrödinger equation.The allowed harmonics and their helicities are associated with the symmetry compatibility of the field-target systems,and large intensity difference between adjacent harmonics with opposite helicities appears in a wide spectral range when the BCCP field is at certain rotation angles.We try to explain the intensity difference by using a recombination model based on the quantum-orbit theory and by analyzing the ionization pathways.Moreover,to synthesize attosecond pulse trains with tunable polarization,the intensity difference is manipulated by introducing a seed XUV field,and by changing the relative amplitude ratio as well as the helicity of BCCP fields. 展开更多
关键词 high-order harmonic generation attosecond pulse multi-center interference
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Spin Evolution of the Magnetar SGR J1935+2154
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作者 Ming-Yu Ge Yuan-Pei Yang +11 位作者 Fang-Jun Lu Shi-Qi Zhou Long Ji Shuang-Nan zhang bing zhang Liang zhang Pei Wang Kejia Lee Weiwei Zhu Jian Li Xian Hou Qiao-Chu Li 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第1期201-211,共11页
Fast radio bursts(FRBs)are short pulses observed in radio frequencies usually originating from cosmological distances.The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154sugg... Fast radio bursts(FRBs)are short pulses observed in radio frequencies usually originating from cosmological distances.The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154suggests that at least some FRBs can be generated by magnetars.However,the majority of X-ray bursts from magnetars are not associated with radio emission.The fact that only in rare cases can an FRB be generated raises the question regarding the special triggering mechanism of FRBs.Here we report long time spin evolution of SGR J1935+2154 until the end of 2022.According to v and v,the spin evolution of SGR J1935+2154 could be divided into two stages.The first stage evolves relatively steady evolution until 2020 April 27.After the burst activity in2020,the spin of SGR J1935+2154 shows strong variations,especially for v.After the burst activity in 2022October,a new spin-down glitch with△v/v=(-7.2±0.6)×10^(-6)is detected around MJD 59876,which is the second event in SGR J1935+2154.At the end,spin frequency and pulse profile do not show variations around the time of FRB 200428 and radio bursts 221014 and 221021,which supply strong clues to constrain the trigger mechanism of FRBs or radio bursts. 展开更多
关键词 (stars:)pulsars:general (stars:)pulsars:individual(SGR J1935+2154) X-rays:bursts
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Heterogeneously elevated branched-chain/aromatic amino acids among new-onset type-2 diabetes mellitus patients are potentially skewed diabetes predictors
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作者 Min Wang Yang Ou +7 位作者 Xiang-Lian Yuan Xiu-Fang Zhu Ben Niu Zhuang Kang bing zhang Anwar Ahmed Guo-Qiang Xing Heng Su 《World Journal of Diabetes》 SCIE 2024年第1期53-71,共19页
BACKGROUND The lack of specific predictors for type-2 diabetes mellitus(T2DM)severely impacts early intervention/prevention efforts.Elevated branched-chain amino acids(BCAAs:Isoleucine,leucine,valine)and aromatic amin... BACKGROUND The lack of specific predictors for type-2 diabetes mellitus(T2DM)severely impacts early intervention/prevention efforts.Elevated branched-chain amino acids(BCAAs:Isoleucine,leucine,valine)and aromatic amino acids(AAAs:Tyrosine,tryptophan,phenylalanine)show high sensitivity and specificity in predicting diabetes in animals and predict T2DM 10-19 years before T2DM onset in clinical studies.However,improvement is needed to support its clinical utility.AIM To evaluate the effects of body mass index(BMI)and sex on BCAAs/AAAs in new-onset T2DM individuals with varying body weight.METHODS Ninety-seven new-onset T2DM patients(<12 mo)differing in BMI[normal weight(NW),n=33,BMI=22.23±1.60;overweight,n=42,BMI=25.9±1.07;obesity(OB),n=22,BMI=31.23±2.31]from the First People’s Hospital of Yunnan Province,Kunming,China,were studied.One-way and 2-way ANOVAs were conducted to determine the effects of BMI and sex on BCAAs/AAAs.RESULTS Fasting serum AAAs,BCAAs,glutamate,and alanine were greater and high-density lipoprotein(HDL)was lower(P<0.05,each)in OB-T2DM patients than in NW-T2DM patients,especially in male OB-T2DM patients.Arginine,histidine,leucine,methionine,and lysine were greater in male patients than in female patients.Moreover,histidine,alanine,glutamate,lysine,valine,methionine,leucine,isoleucine,tyrosine,phenylalanine,and tryptophan were significantly correlated with abdominal adiposity,body weight and BMI,whereas isoleucine,leucine and phenylalanine were negatively correlated with HDL.CONCLUSION Heterogeneously elevated amino acids,especially BCAAs/AAAs,across new-onset T2DM patients in differing BMI categories revealed a potentially skewed prediction of T2DM development.The higher BCAA/AAA levels in obese T2DM patients would support T2DM prediction in obese individuals,whereas the lower levels of BCAAs/AAAs in NW-T2DM individuals may underestimate T2DM risk in NW individuals.This potentially skewed T2DM prediction should be considered when BCAAs/AAAs are to be used as the T2DM predictor. 展开更多
关键词 Hyperaminoacidemia Branched-chain/aromatic amino acids New-onset type-2 diabetes Predictor Obesity SEX
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全无机钙钛矿量子点的疏水改性及LED应用——推荐一个本科生综合化学实验
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作者 周文理 张兵 +5 位作者 宋文丽 张吉林 邱忠贤 韩跃 李承志 余丽萍 《大学化学》 CAS 2023年第8期192-199,共8页
介绍一个综合化学实验——全无机钙钛矿量子点的疏水改性及LED应用。我们以三甲基氯硅烷和莫来石纤维增强SiO_(2)气凝胶的疏水性和韧性,获得疏水SiO_(2)气凝胶,随后以该疏水SiO_(2)气凝胶吸附全无机钙钛矿量子点形成CsPbX_(3)@SiO_(2)... 介绍一个综合化学实验——全无机钙钛矿量子点的疏水改性及LED应用。我们以三甲基氯硅烷和莫来石纤维增强SiO_(2)气凝胶的疏水性和韧性,获得疏水SiO_(2)气凝胶,随后以该疏水SiO_(2)气凝胶吸附全无机钙钛矿量子点形成CsPbX_(3)@SiO_(2)气凝胶复合材料。通过接触角、红外光谱、X射线衍射等表征手段证实SiO_(2)气凝胶的成功改性,并制作了LED器件。本实验涉及材料的合成、表征和应用,可作为化学和应用化学专业学生的综合化学实验,有助于提高学生的科学素养,激发对科学研究的兴趣。 展开更多
关键词 钙钛矿量子点 疏水SiO_(2)气凝胶 综合化学实验 教学设计
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Experimental and theoretical study on the dynamic effective stress of loaded gassy coal during gas release 被引量:2
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作者 bing zhang Hanpeng Wang +2 位作者 Peng Wang Guofeng Yu Shitan Gu 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2023年第3期339-349,共11页
In the process of mining coalbed methane(CBM),an unsteady state often arises due to the rapid extraction,release and pressure relief of CBM.In this case,the effective stress of coal changes dynamically,affecting the s... In the process of mining coalbed methane(CBM),an unsteady state often arises due to the rapid extraction,release and pressure relief of CBM.In this case,the effective stress of coal changes dynamically,affecting the stability of the gassy coal seam.In this paper,gas release tests of gassy coal under conventional triaxial compression were performed,and the dynamic effective stress(DES)during gas release was obtained indirectly based on a constitutive equation and deformation of coal.The results show that the maximum increases in DES caused by the release of free gas and adsorbed gas under the stress of 1.1 MPa were 0.811 and 5.418 MPa,respectively,which seriously affected the stress state of the coal.During the gas release,the free gas pressure and the adsorbed gas volume were the parameters that directly affected the DES and showed a positive linear relationship with the DES with an intercept of zero.The DES of the coal sample increased exponentially with time,which was determined by the contents of free and adsorbed gas.Based on the experimental results and theoretical analysis,an effective stress model was obtained for loaded gassy coal during gas release.The results of verification indicated accuracy greater than 99%. 展开更多
关键词 Gassy coal Dynamic effective stress Gas release Gas-solid coupling Mathematical model
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脊柱内镜辅助斜外侧椎间融合术与经椎间孔腰椎椎体间融合术治疗腰椎不稳伴腰椎间盘突出症的疗效观察 被引量:2
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作者 何彪 李世伟 +4 位作者 谢永波 张兵 郑科 徐阳 杨果 《中国内镜杂志》 2023年第1期29-37,共9页
目的 探究脊柱内镜辅助斜外侧椎间融合术(OLIF)与经椎间孔腰椎椎体间融合术(TLIF)治疗腰椎不稳伴腰椎间盘突出症的疗效。方法 选取2017年9月-2019年8月该院诊治的腰椎不稳伴腰椎间盘突出症的患者87例,根据不同手术方式分为OLIF组与TLIF... 目的 探究脊柱内镜辅助斜外侧椎间融合术(OLIF)与经椎间孔腰椎椎体间融合术(TLIF)治疗腰椎不稳伴腰椎间盘突出症的疗效。方法 选取2017年9月-2019年8月该院诊治的腰椎不稳伴腰椎间盘突出症的患者87例,根据不同手术方式分为OLIF组与TLIF组,OLIF组44例,TLIF组43例。OLIF组患者选用脊柱内镜辅助OLIF方式进行手术,TLIF组患者选用脊柱内镜辅助TLIF方式进行手术。比较两组患者术前、术后和末次随访的视觉模拟评分(VAS)、Oswestry功能障碍指数(ODI)、影像学参数(腰椎矢状位Cobb角、腰椎冠状位Cobb角以及顶椎中心偏移距离),比较两组患者初次下床行走时间、住院时间、融合率、塌陷率和并发症发生率,评估两组患者治疗效果。结果 时间上,术前、术后和末次随访时VAS和ODI比较,差异均有统计学意义(P <0.05)。组别上,术前、术后和末次随访时OLIF组与TLIF组VAS和ODI比较,差异均无统计学意义(P> 0.05);OLIF组和TLIF组腰椎矢状位Cobb角大于手术前,腰椎冠状位Cobb角以及顶椎中心偏移距离小于术前,差异均有统计学意义(P <0.05),且OLIF组3种影像学参数恢复情况均优于TLIF组,差异有统计学意义(P <0.05);OLIF组术后首次下床时间和住院时间明显短于TLIF组,差异有统计学意义(P <0.05);OLIF组与TLIF组椎间融合器融合率比较,差异无统计学意义(P> 0.05)。OLIF组椎间融合器塌陷率低于TLIF组,差异有统计学意义(P <0.05)。结论 脊柱内镜辅助下,OLIF比TLIF治疗腰椎不稳伴腰椎间盘突出症的疗效更好,患者恢复更快,值得临床推广应用。 展开更多
关键词 脊柱内镜 斜外侧椎间融合术(OLIF) 经椎间孔腰椎椎体间融合术(TLIF) 腰椎间盘突出症
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Recent advances in the nanoconfinement of Mg-related hydrogen storage materials:A minor review 被引量:1
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作者 Jingjing zhang bing zhang +7 位作者 Xiubo Xie Cui Ni Chuanxin Hou Xueqin Sun Xiaoyang Yang Yuping zhang Hideo Kimura Wei Du 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2023年第1期14-24,共11页
Hydrogen is an ideal clean energy because of its high calorific value and abundance of sources.However,storing hydrogen in a compact,inexpensive,and safe manner is the main restriction on the extensive utilization of ... Hydrogen is an ideal clean energy because of its high calorific value and abundance of sources.However,storing hydrogen in a compact,inexpensive,and safe manner is the main restriction on the extensive utilization of hydrogen energy.Magnesium(Mg)-based hydrogen storage material is considered a reliable solid hydrogen storage material with the advantages of high hydrogen storage capacity(7.6wt%),good performance,and low cost.However,the high thermodynamic stability and slow kinetics of Mg-based hydrogen storage materials have to be overcome.In this paper,we will review the recent advances in the nanoconfinement of Mg-related hydrogen storage materials by loading Mg particles on different supporting materials,including carbons,metal-organic frameworks,and other materials.Perspectives are also provided for designing high-performance Mg-based materials using nanoconfinement. 展开更多
关键词 magnesium-based materials hydrogen storage NANOCONFINEMENT carbon materials
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Performance releaser with smart anchor learning for arbitrary‐oriented object detection
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作者 Tianwei W.zhang Xiaoyu Y.Dong +4 位作者 Xu Sun Lianru R.Gao Ying Qu bing zhang Ke Zheng 《CAAI Transactions on Intelligence Technology》 SCIE EI 2023年第4期1213-1225,共13页
Arbitrary‐oriented object detection is widely used in aerial image applications because of its efficient object representation.However,the use of oriented bounding box aggravates the imbalance between positive and ne... Arbitrary‐oriented object detection is widely used in aerial image applications because of its efficient object representation.However,the use of oriented bounding box aggravates the imbalance between positive and negative samples when using one‐stage object detectors,which seriously decreases the detection accuracy.We believe that it is the anchor learning strategy(ALS)used by such detectors that needs to take the responsibility.In this study,three perspectives on ALS design were summarised and ALS—Performance Releaser with Smart Anchor Learning(PRSAL)was proposed.Performance Releaser with Smart Anchor Learning is a dynamic ALS that utilises anchor classification ability as an equivalent indicator to anchor box regression ability,this allows anchors with high detection potential to be filtered out in a more reasonable way.At the same time,PRSAL focuses more on anchor potential and it is able to automatically select a number of positive samples that far exceed that of other methods by activating anchors that previously had a low spatial overlap,thereby releasing the detection performance.We validate the PRSAL using three remote sensing datasets—HRSC2016,DOTA and UCAS‐AOD as well as one scene text dataset—ICDAR 2013.The experimental results show that the proposed method gives substantially better results than existing models. 展开更多
关键词 anchor learning strategy deep learning object detection remote sensing
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Study on Recognition Method of Similar Weather Scenes in Terminal Area
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作者 Ligang Yuan Jiazhi Jin +2 位作者 Yan Xu Ningning zhang bing zhang 《Computer Systems Science & Engineering》 SCIE EI 2023年第2期1171-1185,共15页
Weather is a key factor affecting the control of air traffic.Accurate recognition and classification of similar weather scenes in the terminal area is helpful for rapid decision-making in air trafficflow management.Curren... Weather is a key factor affecting the control of air traffic.Accurate recognition and classification of similar weather scenes in the terminal area is helpful for rapid decision-making in air trafficflow management.Current researches mostly use traditional machine learning methods to extract features of weather scenes,and clustering algorithms to divide similar scenes.Inspired by the excellent performance of deep learning in image recognition,this paper proposes a terminal area similar weather scene classification method based on improved deep convolution embedded clustering(IDCEC),which uses the com-bination of the encoding layer and the decoding layer to reduce the dimensionality of the weather image,retaining useful information to the greatest extent,and then uses the combination of the pre-trained encoding layer and the clustering layer to train the clustering model of the similar scenes in the terminal area.Finally,term-inal area of Guangzhou Airport is selected as the research object,the method pro-posed in this article is used to classify historical weather data in similar scenes,and the performance is compared with other state-of-the-art methods.The experi-mental results show that the proposed IDCEC method can identify similar scenes more accurately based on the spatial distribution characteristics and severity of weather;at the same time,compared with the actualflight volume in the Guangz-hou terminal area,IDCEC's recognition results of similar weather scenes are con-sistent with the recognition of experts in thefield. 展开更多
关键词 Air traffic terminal area similar scenes deep embedding clustering
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Atlas of dynamic spectra of fast radio burst FRB 20201124A
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作者 王铂钧 胥恒 +64 位作者 姜金辰 徐江伟 牛佳瑞 陈平 李柯伽 张冰 朱炜玮 东苏勃 张春风 傅海 周德江 张永坤 王培 冯毅 李晔 李冬子 鲁文宾 杨元培 RNCaballero 蔡策 陈卯蒸 戴子高 艾力·伊沙木丁 甘恒谦 韩金林 郝龙飞 黄玉祥 姜鹏 李承奎 李菂 李辉 李新乔 李志玄 刘志勇 罗睿 门云鹏 牛晨辉 彭文溪 钱磊 宋黎明 孙京海 王发印 汪敏 王娜 王维扬 吴雪峰 肖硕 熊少林 徐永华 徐仁新 杨俊 杨轩 姚蕊 易祁彬 岳友岭 于东俊 余文飞 袁建平 张彬彬 张松波 张双南 赵一 郑伟康 朱岩 邹金航 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第2期1-4,共4页
Fast radio bursts(FRBs) are highly dispersed millisecond-duration radio bursts,[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, ... Fast radio bursts(FRBs) are highly dispersed millisecond-duration radio bursts,[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, we present the collection of 1863 burst dynamic spectra of FRB 20201124A measured with the Five-hundred-meter Aperture Spherical radio Telescope(FAST). The current collection, taken from the observation during the FRB active phase from April to June 2021, is the largest burst sample detected for any FRB so far. The standard PSRFITs format is adopted, including dynamic spectra of the burst, and the time information of the dynamic spectra, in addition, mask files help readers to identify the pulse positions are also provided. The dataset is available in Science Data Bank, with the link https://www.doi.org/10.57760/sciencedb.j00113.00076. 展开更多
关键词 fast radio burst FAST
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Mutation Breeding of Lactobacillus and Its Application in Yoghurt
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作者 Xin LI Shiyun TANG +3 位作者 Fengrong TIAN bing zhang Shijun FU Shijin GUO 《Agricultural Biotechnology》 CAS 2023年第1期31-34,共4页
With the gradual improvement of the quality of people’s life, the disorder of lipid metabolism caused by high-fat diet has become the main reason that affects the health of our people. Hyperlipidemia, hypertension an... With the gradual improvement of the quality of people’s life, the disorder of lipid metabolism caused by high-fat diet has become the main reason that affects the health of our people. Hyperlipidemia, hypertension and hyperglycemia have the effect of causing a large number of serious complications, and are also the main factors of cardiovascular disease. Lactic acid bacteria can avoid hyperlipidemia by inhibiting the excessive growth of harmful intestinal bacteria, maintaining the balance of intestinal microecology, absorbing intestinal cholesterol and regulating lipid metabolism. Therefore, this paper focused on the mutation and breeding of Lactobacillus, and analyzed its application in yoghurt, aiming to provide reference for relevant researchers. 展开更多
关键词 LACTOBACILLUS Mutation breeding YOGURT APPLICATION
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超声引导下经支气管针吸活检在胸部疾病诊断中的意义 被引量:6
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作者 张亚肖 甄强 +3 位作者 赵晓建 王仁峰 张冰 耿丽娜 《中国现代医学杂志》 CAS 2020年第16期59-62,共4页
目的探讨超声引导下经支气管针吸活检(EBUS-TBNA)在诊断胸部疾病中的应用价值。方法选取2016年3月—2019年3月在石家庄市第一医院行EBUS-TBNA检查的患者110例。所有患者行EBUS-TBNA检查前接受CT或正电子发射型计算机断层扫描显像(PET-CT... 目的探讨超声引导下经支气管针吸活检(EBUS-TBNA)在诊断胸部疾病中的应用价值。方法选取2016年3月—2019年3月在石家庄市第一医院行EBUS-TBNA检查的患者110例。所有患者行EBUS-TBNA检查前接受CT或正电子发射型计算机断层扫描显像(PET-CT)进行初步筛查。在彩色多普勒超声指导下,经活检针(18 G)对110例纳入对象行穿刺活检,以病理检查结果作为金标准,分析EBUSTBNA在胸部疾病诊断中的应用价值,计算其相应的敏感性、特异性、准确率、阳性预测值、阴性预测值。分析EBUS-TBNA与病理诊断的一致性,明确Kappa值。结果经CT或PET-CT初步筛查,110例受检者中,疑似胸部恶性肿瘤81例(73.64%),疑似结核病29例(26.36%)。经手术病理诊断,81例疑似胸部恶性肿瘤患者中,75例(92.59%)确诊为恶性肿瘤;29例疑似结核病患者中,22例(75.86%)确诊为结核病。EBUSTBNA诊断胸部恶性肿瘤与病理诊断一致性检验Kappa值为0.749(95%CI:0.711,0.904)。EBUS-TBNA诊断结核病与病理诊断一致性检验Kappa值为0.731(95%CI:0.703,0.917)。EBUS-TBNA诊断恶性瘤纵隔淋巴结转移与病理诊断一致性检验Kappa值为0.604(95%CI:0.697,0.825)。110例受检者中,2例(1.82%)存在轻微不适,但均对该检查方式耐受。结论EBUS-TBNA对胸部恶性肿瘤、结核病及恶性瘤纵隔淋巴结转移的诊断有较高价值,与手术病理诊断呈高度一致性,且安全性高。 展开更多
关键词 胸部疾病 超声检查 活组织检查 针吸 诊断技术 呼吸系统
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PPP项目失败的组态研究——基于30个案例的清晰集定性比较分析 被引量:14
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作者 张兵 王雅 +1 位作者 刘欣 丁翔 《公共行政评论》 CSSCI 北大核心 2019年第4期65-81,M0005,共18页
相较于计划经济时期的“命令-控制”模式和转型时期的“委托-代理”模式,以PPP为代表的公私部门合作“契约模式”是新时代一种新型的公共治理模式,然而由于存在不同层次、不同角度的问题,PPP项目在实施过程中容易出现“1+1<2”的失... 相较于计划经济时期的“命令-控制”模式和转型时期的“委托-代理”模式,以PPP为代表的公私部门合作“契约模式”是新时代一种新型的公共治理模式,然而由于存在不同层次、不同角度的问题,PPP项目在实施过程中容易出现“1+1<2”的失败情况。论文以30个典型PPP项目失败案例为研究对象,采用定性比较分析方法对PPP项目失败的类型及其前因条件的交互作用进行实证检验,结果显示PPP项目失败存在七类主要组态模式,并且各个组态构型呈现出非均匀分布,特别是由于我国是一个发展中国家,PPP失败中的政策法律层面的制度试错风险较高。论文丰富发展了PPP项目的相关理论,并对如何应对PPP项目失败提出了相应的建议和措施。 展开更多
关键词 PPP失败 组态 定性比较分析 清晰集
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中国股市换手特征与“消失”的动量效应 被引量:1
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作者 张兵 张瑞祺 《经济学报》 CSSCI 2022年第4期124-143,共20页
高换手和高散户比例是我国股市的重要特征。本文以这两大重要特征为视角,探讨了其对A股月度动量效应的影响。通过构建交易者模型分析了体现换手特征的信息传递速度和平稳性对月度动量效应的影响。实证部分构造了反映信息传递速度和平稳... 高换手和高散户比例是我国股市的重要特征。本文以这两大重要特征为视角,探讨了其对A股月度动量效应的影响。通过构建交易者模型分析了体现换手特征的信息传递速度和平稳性对月度动量效应的影响。实证部分构造了反映信息传递速度和平稳性的全换手天数、换手率标准差指标,利用1997—2020年数据分析指出,信息传递速度越快、稳定性越差时月度动量效应越不显著。进一步分析中探究了换手特征背后的投资者结构对月度动量效应的影响,理论和实证结果指出知情交易者比例越低时,月度动量效应越不显著。A股市场换手畸高,信息传递速度较快且稳定性差,同时A股市场散户较多,综合作用使得A股月度动量效应不显著。本文的分析丰富了动量效应的研究,也为A股市场月度动量效应不显著提供了全新的解释。 展开更多
关键词 动量效应 信息传递 全换手天数 知情交易概率
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Ni-CH_3CH_2NH_2/H_(1.78)Sr_(0.78)Bi_(0.22)Nb_2O_7复合层状钙钛矿的合成及光催化分解水产氢性能(英文) 被引量:2
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作者 张丙 惠丹屏 +2 位作者 李英宣 赵赫 王传义 《Chinese Journal of Catalysis》 CSCD 北大核心 2017年第12期2039-2047,共9页
自从分解水产氢被首次报道以来,许多光催化剂被开发出来并用于光催化分解水产氢.然而,由于光生电子和空穴的复合率普遍较高,大部分的光催化剂分解水产氢效率都很低.因此,开发新型高效的光催化材料至关重要.具有(Bi_2O_2)^(2+)(A_(m-1)M_... 自从分解水产氢被首次报道以来,许多光催化剂被开发出来并用于光催化分解水产氢.然而,由于光生电子和空穴的复合率普遍较高,大部分的光催化剂分解水产氢效率都很低.因此,开发新型高效的光催化材料至关重要.具有(Bi_2O_2)^(2+)(A_(m-1)M_mO_(3m+1))^(2-)通式的Aurivillius相层状钙钛矿材料因具有独特的层状结构、元素可调性以及优异的电荷传输和分离能力而广泛应用于光催化分解水和去除有机污染物.此外,当该类层状钙钛矿被剥离成超薄纳米片时,其光催化性能进一步提高.为了进一步提高层状钙钛矿的载流子分离能力,将客体(如贵金属,半导体等)通过化学反应的途径插入到层状钙钛矿的层间区域,从而合成出复合层状钙钛矿被广泛发展和应用.然而,引入的客体主要是贵金属和半导体,这类客体的高成本和不均匀分布制约了其进一步的应用.由于廉价、无毒和稳定等优点,镍基材料如Ni,NiO,Ni_2O_3,NiS,NiS_2,Ni(OH)2和Ni(OH)x等被广泛用作增强电极材料的光电性能和催化剂的光催化分解水产氢性能的助催化剂.本文采用简单的原位化学反应法制备出镍基配合物Ni-CH_3CH_2NH_2(Ni-EA)插层的Ni-CH_3CH_2NH_2/H_(1.78)Sr_(0.78)Bi_(0.22)Nb_2O_7(Ni-EA/HSNNs)复合层状钙钛矿;然后采用X-射线衍射(XRD)、傅立叶变换红外光谱(FTIR)、X-射线光电子能谱(XPS)、紫外-可见漫反射光谱等手段对Ni-EA/HSNNs光催化剂进行了系统的研究.XRD结果表明,引入Ni^(2+)后,HSNNs层间距减小并且平行于钙钛矿层的晶面结晶度增强,证明HSNNs沿垂直于钙钛矿层的方向出现了层层组装.FTIR和XPS结果表明,引入的Ni^(2+)与HSNNs层间和表面的乙胺分子之间存在较强的相互作用,结合高分辨透射电镜图可知,Ni的存在形态可能为配合物Ni-EA.由此可见,当向HSNNs中引入Ni^(2+)时,Ni^(2+)和HSNNs层间和表面的乙胺分子反应生成带正电的配合物Ni-EA,由于Ni-EA与HSNNs的钙钛矿层带有异种电荷,两者之间存在较强的静电相互作用力,从而引起钙钛矿纳米片HSNNs的层层组装,最后形成Ni-EA/HSNNs复合层状钙钛矿.光催化分解水产氢性能测试结果表明,当引入0.5 wt%Ni时,复合层状钙钛矿表现出最优的光催化性能.与HSNNs(241.58μmol/h)相比,0.5%Ni-EA/HSNNs的光催化分解水产氢速率(372.67μmol/h)提高了0.54倍,表现出与0.5%Pt/HSNNs可比拟的光催化活性,可见,非贵金属Ni具有替代贵金属Pt的能力.进一步的研究表明,镍基配合物Ni-EA显著增强了催化剂的光生载流子的传输和分离能力,从而提高了其光催化分解水产氢性能.该文为光催化分解水产氢提供了一种简便的合成非贵金属配合物助催化剂的方法. 展开更多
关键词 Ni-CH3CH2NH2/H1.78Sr0.78Bi0.22Nb2O7 插层 光催化 产氢 纳米片
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反式-4-甲氧基偶氮苯超快激发态性质研究(英文) 被引量:1
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作者 王雅萍 李春华 +2 位作者 张冰 秦晨 张嵩 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2018年第6期749-755,733,共8页
本文利用飞秒瞬态吸收光谱结合量化计算研究了反式-4-甲氧基偶氮苯的超快激发态动力学和光异构过程.瞬态光谱中在400∽480nm波段出现永久的正吸收,表明反式分子被激发到第二激发态后最终产生了顺式结构.在乙醇和乙二醇溶剂环境中分别获... 本文利用飞秒瞬态吸收光谱结合量化计算研究了反式-4-甲氧基偶氮苯的超快激发态动力学和光异构过程.瞬态光谱中在400∽480nm波段出现永久的正吸收,表明反式分子被激发到第二激发态后最终产生了顺式结构.在乙醇和乙二醇溶剂环境中分别获得了三个衰减组分,时间分别为0.11、1.4、2.9ps和0.16、1.5、7.5ps.快速的时间组分是源自第二激发态弛豫到第一激发态的内转换过程.另外两个组分和第一激发态的弛豫相关:一个是经第一激发态的内转化和光异构过程,另一个是顺式结构的振动冷却过程.基于不同溶剂环境中的动力学差别,证实了光异构路径是反转机制而不是旋转机制. 展开更多
关键词 光异构 反式-4-甲氧基偶氮苯 飞秒瞬态吸收光谱
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基于增强LEACH协议的无线传感器恶意节点检测 被引量:1
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作者 张兵 戈军 《计算机仿真》 北大核心 2022年第11期427-431,452,共6页
研究基于增强LEACH协议的无线传感器恶意节点检测方法,改善无线传感器网络由于通信拥堵等情况,造成恶意节点检测效率降低的缺陷。通过当前生存节点数的最佳簇数改进机制获取最佳簇类数量,选取集中式成簇算法依据所确定最佳簇类数量划分... 研究基于增强LEACH协议的无线传感器恶意节点检测方法,改善无线传感器网络由于通信拥堵等情况,造成恶意节点检测效率降低的缺陷。通过当前生存节点数的最佳簇数改进机制获取最佳簇类数量,选取集中式成簇算法依据所确定最佳簇类数量划分无线传感器网络的簇,簇内节点以及簇间节点分别选取LEACH协议以及多跳转发方式通信;通过所划分各簇内节点的直接信誉值与间接信誉值获取节点的综合信誉值;网络中的汇聚节点接收数据包后,通过解析数据包建立可疑节点列表;设置信誉值阈值,对比可疑节点列表中节点综合信誉值以及信誉值阈值,利用对比结果划分节点为正常节点与恶意节点,实现恶意节点检测。仿真测试结果表明,上述方法可精准检测无线传感器网络中的恶意节点,调节参数为0.7时,恶意节点检测误判率低至0.4%。 展开更多
关键词 无线传感器 恶意节点检测 信誉值 最佳簇类数量 可疑节点列表
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基于神经网络的盾构液压推进系统的参数辨识(英文) 被引量:1
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作者 孙振川 张兵 +1 位作者 李阁强 丁银亭 《机床与液压》 北大核心 2019年第24期24-32,共9页
为了提高盾构液压推进系统速度控制的精度,减小建立数学模型与实际系统之间的偏差,提出基于时延神经网络和系统参数上下界值的动态系统参数辨识方法。在建立盾构液压推进系统速度控制模型的基础上,利用神经网络在待辨识参数的范围内对... 为了提高盾构液压推进系统速度控制的精度,减小建立数学模型与实际系统之间的偏差,提出基于时延神经网络和系统参数上下界值的动态系统参数辨识方法。在建立盾构液压推进系统速度控制模型的基础上,利用神经网络在待辨识参数的范围内对系统的不定参数进行辨识,搜索出更逼近实际盾构推进系统的一组参数,满足对系统输入实际信号时能够准确地得到实际系统的输出。利用盾构模拟实验台的另一组采样数据对系统辨识结果进行验证,结果表明:该辨识方法得到的模型能够逼近真实的物理系统。 展开更多
关键词 盾构 推进系统 时延神经网络 参数辨识
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An improved association-mining research for exploring Chinese herbal property theory: based on data of the Shennong's Classic of Materia Medica 被引量:14
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作者 Rui Jin Zhi-jian Lin +1 位作者 Chun-miao Xue bing zhang 《Journal of Integrative Medicine》 SCIE CAS CSCD 2013年第5期352-365,共14页
Knowledge Discovery in Databases is gaining attention and raising new hopes for traditional Chinese medicine(TCM)researchers.It is a useful tool in understanding and deciphering TCM theories.Aiming for a better unders... Knowledge Discovery in Databases is gaining attention and raising new hopes for traditional Chinese medicine(TCM)researchers.It is a useful tool in understanding and deciphering TCM theories.Aiming for a better understanding of Chinese herbal property theory(CHPT),this paper performed an improved association rule learning to analyze semistructured text in the book entitled Shennong’s Classic of Materia Medica.The text was firstly annotated and transformed to well-structured multidimensional data.Subsequently,an Apriori algorithm was employed for producing association rules after the sensitivity analysis of parameters.From the confirmed 120 resulting rules that described the intrinsic relationships between herbal property(qi,flavor and their combinations)and herbal efficacy,two novel fundamental principles underlying CHPT were acquired and further elucidated:(1)the many-to-one mapping of herbal efficacy to herbal property;(2)the nonrandom overlap between the related efficacy of qi and flavor.This work provided an innovative knowledge about CHPT,which would be helpful for its modern research. 展开更多
关键词 中国传统医学 产权理论 草药 关联挖掘 神农 关联规则分析 APRIORI 知识发现
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A nano-cocrystal strategy to improve the dissolution rate and oral bioavailability of baicalein 被引量:12
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作者 Jiaxin Pi Shuya Wang +7 位作者 Wen Li Dereje Kebebe Ying zhang bing zhang Dongli Qi Pan Guo Nan Li Zhidong Liu 《Asian Journal of Pharmaceutical Sciences》 SCIE CAS 2019年第2期154-164,共11页
Baicalein(BE) is one of the main active flavonoids representing the variety of pharmacological effects including anticancer, anti-inflammatory and cardiovascular protective activities, but it's very low solubility... Baicalein(BE) is one of the main active flavonoids representing the variety of pharmacological effects including anticancer, anti-inflammatory and cardiovascular protective activities, but it's very low solubility, dissolution rate and poor oral absorption limit the therapeutic applications. In this work, a nano-cocrystal strategy was successfully applied to improve the dissolution rate and bioavailability of BE. Baicalein-nicotinamide(BE-NCT) nanococrystals were prepared by high pressure homogenization and evaluated both in vitro and in vivo. Physical characterization results including scanning electron microscopy, dynamic light scattering, powder X-ray diffraction and differential scanning calorimetry demonstrated that BE-NCT nano-cocrystals were changed into amorphous state with mean particle size of 251.53 nm. In the dissolution test, the BE-NCT nano-cocrystals performed 2.17-fold and 2.54-fold enhancement than BE coarse powder in FaSSIF-V2 and FaSSGF. Upon oral administration, the integrated AUC0-t of BE-NCT nano-cocrystals(6.02-fold) was significantly higher than BE coarse powder(1-fold), BE-NCT cocrystals(2.87-fold) and BE nanocrystals(3.32-fold). Compared with BE coarse powder, BE-NCT cocrystals and BE nanocrystals, BENCT nano-cocrystals possessed excellent performance both in vitro and in vivo evaluations.Thus, it can be seen that nano-cocrystal is an appropriate novel strategy for improving dissolution rate and bioavailability of poor soluble natural products such as BE. 展开更多
关键词 BAICALEIN Nano-cocrystals COCRYSTALS BIOAVAILABILITY
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