期刊文献+
共找到1,611篇文章
< 1 2 81 >
每页显示 20 50 100
Efficiency and safety of laparoscopic left hemihepatectomy: A study of intrathecal vs extrathecal Glissonean pedicle techniques
1
作者 Li-Min Kang Lei Xu +2 位作者 Fu-Wei Zhang Fa-Kun Yu Li Lang 《World Journal of Gastrointestinal Surgery》 SCIE 2024年第8期2612-2619,共8页
BACKGROUND Selective hemihepatic vascular occlusion is utilized in both right and left hemihepatectomies to preserve blood supply to the intact lobe,maintain hemo-dynamic stability,and mitigate surgical risks.While th... BACKGROUND Selective hemihepatic vascular occlusion is utilized in both right and left hemihepatectomies to preserve blood supply to the intact lobe,maintain hemo-dynamic stability,and mitigate surgical risks.While this technique encompasses both intrathecal and extrathecal Glissonean pedicle transection methods,there is a lack of systematic comparative reports on these two approaches.AIM To retrospectively analyze the clinical data of patients with hepatocellular carcinoma(HCC)undergoing laparoscopic anatomical hepatectomy in our hospital to explore the feasibility,safety,and short-and long-term efficacy of extrathecal and intrathecal Glissonean pedicle transection methods in laparo-scopic left hemihepatectomy.METHODS A retrospective study was performed to analyze the clinical data of 49 HCC patients who underwent laparoscopic left hemihepatectomy from January 2019 to December 2022 in our hospital.These patients were divided into extrathecal Glissonean pedicle transection(EGP)group(n=24)and intrathecal Glissonean pedicle transection(IGP)group(n=25)according to the different approaches used for selective hemihepatic vascular occlusion.The perioperative indicators,liver function indexes,complications,and follow-up findings were compared between these two groups.RESULTS The surgeries were smooth in both groups,and no perioperative death was noted.The hepatic pedicle transection time and the operation time were(16.1±2.3)minutes and(129.6±19.0)minutes,respectively,in the EGP group,which were significantly shorter than those in the IGP group[(25.5±2.4)minutes and(184.8±26.0)minutes,respectively],both P<0.01.There were no significant differences in intraoperative blood loss,time to anal exhaust,hospital stay,drain indwelling time,and postoperative liver function between the two groups(all P>0.05).The incidence of postoperative complications showed no significant difference[16.67%(4/24)vs 16.0%(4/25),P>0.05].All the 49 HCC patients were followed up after surgery(range:11.2-53.3 months;median:36.4 months).The overall survival rate and disease-free survival rate were not significantly different(both P>0.05).CONCLUSION Both extrathecal and intrathecal Glissonean pedicle approaches are effective and safe hepatic inflow occlusion techniques in laparoscopic left hemihepatectomy for HCC.However,the extrathecal approach simplifies the hepatic pedicle transection,shortens the operation time,and increases the surgical efficiency,making it a more feasible technique. 展开更多
关键词 Hepatocellular carcinoma LAPAROSCOPY Extra-Glissonian approach Intra-Glissonian approach Surgical efficiency Surgical safety
下载PDF
Artificial-intelligent-powered safety and efficiency improvement for controlling and scheduling in integrated railway systems
2
作者 Jun Liu Gehui Liu +1 位作者 Yu Wang Wanqiu Zhang 《High-Speed Railway》 2024年第3期172-179,共8页
The multi-mode integrated railway system,anchored by the high-speed railway,caters to the diverse travel requirements both within and between cities,offering safe,comfortable,punctual,and eco-friendly transportation s... The multi-mode integrated railway system,anchored by the high-speed railway,caters to the diverse travel requirements both within and between cities,offering safe,comfortable,punctual,and eco-friendly transportation services.With the expansion of the railway networks,enhancing the efficiency and safety of the comprehensive system has become a crucial issue in the advanced development of railway transportation.In light of the prevailing application of artificial intelligence technologies within railway systems,this study leverages large model technology characterized by robust learning capabilities,efficient associative abilities,and linkage analysis to propose an Artificial-intelligent(AI)-powered railway control and dispatching system.This system is elaborately designed with four core functions,including global optimum unattended dispatching,synergetic transportation in multiple modes,high-speed automatic control,and precise maintenance decision and execution.The deployment pathway and essential tasks of the system are further delineated,alongside the challenges and obstacles encountered.The AI-powered system promises a significant enhancement in the operational efficiency and safety of the composite railway system,ensuring a more effective alignment between transportation services and passenger demands. 展开更多
关键词 High-speed railway Multi-mode railway system Artificial intelligence Large-scale mode system framework safety and efficiency improvement
下载PDF
Analysis on Operational Safety and Efficiency of FAO System in Urban Rail Transit
3
作者 Kaige Guo Jin Zhou +3 位作者 Xiaoming Zhang Di Sun Zishuo Wang Lixian Zhao 《Computers, Materials & Continua》 SCIE EI 2023年第12期3677-3696,共20页
This paper discusses two urgent problems that need to be solved in fully automatic operation(FAO)for urban rail transit.The first is the analysis of safety in FAO,while another is the analysis of efficiency in FAO.Fir... This paper discusses two urgent problems that need to be solved in fully automatic operation(FAO)for urban rail transit.The first is the analysis of safety in FAO,while another is the analysis of efficiency in FAO.Firstly,this paper establishes an operational safety evaluation index system from the perspective of operation for the unique or typical risk sources of the FAO system,and uses the analytic hierarchy process(AHP)to evaluate the indicators,analyzes various factors that affect the safe operation of FAO,and provides safety management recommendations for FAO lines operation to maintain the FAO system specifically.Secondly,taking the Yanfang Line as an example,this paper uses OpenTrack software to analyze the efficiency of FAO operation,and conducts simulation calculations for key links such as the mainline tracking interval,train entry and exit,and return limit interval.The fault impact surface of the FAO trains is simulated and discussed to verify whether FAO can meet the long-term operation requirements of Yanfang Line.Finally,this paper compares the simulation data of FAO on the Yanfang Line with manual operation(MO)to verify the advantages of FAO and guide the engineering construction of subsequent fully automated driving lines. 展开更多
关键词 Fully automatic operation safety analysis efficiency analysis OpenTrack simulation
下载PDF
Impact of countdown signals on traffic safety and efficiency:a review and proposal
4
作者 Fuquan Pan Jingzhou Yang +3 位作者 Lixia Zhang Changxi Ma Jinshun Yang Pingxia Zhang 《Digital Transportation and Safety》 2023年第3期200-210,共11页
Countdown signals for motorized vehicles,which are intended to ensure safety on the road and regulate motor vehicle speed limits at road intersections,are still considered a relatively novel concept.These signals have... Countdown signals for motorized vehicles,which are intended to ensure safety on the road and regulate motor vehicle speed limits at road intersections,are still considered a relatively novel concept.These signals have been adopted by only a few countries,and the number of cities that use them is limited.This review aims to summarize the effects of countdown signals on traffic safety and efficiency and to determine the consistency and differences of existing research propositions on the matter.Based on the review,considerable research presents evidently different conclusions in the areas of driver red-light running and traffic safety.Particularly,some studies propose that countdown signals reinforce traffic safety,whereas others consider that such signals adversely affect traffic safety.Meanwhile,related literature provides varying conclusions on the aspect of traffic efficiency for vehicle headway.At present,the number of studies conducted regarding the driving behaviors of motorists toward countdown-signalized intersections is insufficient.Accordingly,such inadequate diversity in research causes difficulty in completely assessing the benefits and disadvantages of countdown signals.In this paper,an important future research direction on microcosmic driving psychological and physiological data combined with macro-driving behavior is proposed. 展开更多
关键词 Countdown signals Driving behavior Red-light running Traffic safety Traffic efficiency
下载PDF
Ultrasound-guided Thrombin Injection:An Alternative Treatment for Femoral Artery Pseudoaneurysm with Better Efficiency and Safety 被引量:4
5
作者 姚青海 丛洪良 +4 位作者 吴尚勤 孙姗 董其克 陈冬梅 李鹏 《Journal of Huazhong University of Science and Technology(Medical Sciences)》 SCIE CAS 2008年第3期373-374,共2页
The aim of this study was to evaluate the efficiency and safety of ultrasound-guided thrombin injection on femoral pseudoaneurysm (FPA) as compared to ultrasound-guided local oppression. Eleven cases of FPA were enr... The aim of this study was to evaluate the efficiency and safety of ultrasound-guided thrombin injection on femoral pseudoaneurysm (FPA) as compared to ultrasound-guided local oppression. Eleven cases of FPA were enrolled and 7 cases received ultrasound-guide thrombin injection (injection group), and the remaining 4 cases were treated with local oppression (oppression group). Efficiency and safety were analyzed by ultrasound and subsequent follow-up. The results showed that 1 case relapsed in oppression group while no relapse occurred in thrombin injection group. Ultrasound-guided thrombin injection is better for treatment of FPA in terms of effectiveness and safety. 展开更多
关键词 pseudo aneurysm ultrasound thrombin injection efficiency safety
下载PDF
Efficiency assessment of coal mine safety input by data envelopment analysis 被引量:22
6
作者 TONG Lei DING Ri-jia 《Journal of China University of Mining and Technology》 EI 2008年第1期88-92,共5页
In recent years improper allocation of safety input has prevailed in coal mines in China, which resulted in the frequent accidents in coal mining operation. A comprehensive assessment of the input efficiency of coal m... In recent years improper allocation of safety input has prevailed in coal mines in China, which resulted in the frequent accidents in coal mining operation. A comprehensive assessment of the input efficiency of coal mine safety should lead to improved efficiency in the use of funds and management resources. This helps government and enterprise managers better understand how safety inputs are used and to optimize allocation of resources. Study on coal mine's efficiency assessment of safety input was con- ducted in this paper. A C^2R model with non-Archimedean infinitesimal vector based on output is established after consideration of the input characteristics and the model properties. An assessment of an operating mine was done using a specific set of input and output criteria. It is found that the safety input was efficient in 2002 and 2005 and was weakly efficient in 2003. However, the efficiency was relatively low in both 2001 and 2004. The safety input resources can be optimized and adjusted by means of projection theory. Such analysis shows that, on average in 2001 and 2004, 45% of the expended funds could have been saved. Likewise, 10% of the safety management and technical staff could have been eliminated and working hours devoted to safety could have been reduced by 12%. These conditions could have Riven the same results. 展开更多
关键词 safety input coal mining enterprise efficiency assessment data envelopment analysis (DEA)
下载PDF
Carbon emission efficiency of forest processing industries in China
7
作者 GUAN Zhi-jie Yahaya Idris MUSA +1 位作者 ZHANG Ya-xin GUO Zhi-yuan 《Ecological Economy》 2023年第3期217-232,共16页
This paper uses an input-output table of China's provinces(2007-2016) to measure carbon emissions of these industries.It employs a Malmquist-Luenberger(ML) index with expected and undesired outputs,and an absolute... This paper uses an input-output table of China's provinces(2007-2016) to measure carbon emissions of these industries.It employs a Malmquist-Luenberger(ML) index with expected and undesired outputs,and an absolute β convergence and a conditional β convergence model,to conduct an in-depth analysis of dynamic changes and spatial convergence.Carbon emission efficiency of forest processing industries in 25 regions,including Shanghai,Chongqing,Zhejiang,and Jiangsu are increasing,whereas those of Tianjin,Liaoning,Heilongjiang,and Tibet are decreasing.The main contributing factors of carbon emission efficiency in three major regions vary over time.Further,carbon emission efficiency in the eastern,central,and western regions all have absolute β convergence and conditional β convergence,indicating that different regions are developing toward their own goals and industry,yet regions with lower efficiency are catching up with those where with more efficient strategies in place.Finally,this paper proposes according recommendations. 展开更多
关键词 input-output model ML index CONVERGENCE carbon emission efficiency forest industry production
下载PDF
Novel insights for improving the therapeutic safety and efficiency of mesenchymal stromal cells 被引量:1
8
作者 Mehdi Najar Johanne Martel-Pelletier +1 位作者 Jean Pierre Pelletier Hassan Fahmi 《World Journal of Stem Cells》 SCIE 2020年第12期1474-1491,共18页
Mesenchymal stromal cells(MSCs)have attracted great interest in the field of regenerative medicine.They can home to damaged tissue,where they can exert pro-regenerative and anti-inflammatory properties.These therapeut... Mesenchymal stromal cells(MSCs)have attracted great interest in the field of regenerative medicine.They can home to damaged tissue,where they can exert pro-regenerative and anti-inflammatory properties.These therapeutic effects involve the secretion of growth factors,cytokines,and chemokines.Moreover,the functions of MSCs could be mediated by extracellular vesicles(EVs)that shuttle various signaling messengers.Although preclinical studies and clinical trials have demonstrated promising therapeutic results,the efficiency and the safety of MSCs need to be improved.After transplantation,MSCs face harsh environmental conditions,which likely dampen their therapeutic efficacy.A possible strategy aiming to improve the survival and therapeutic functions of MSCs needs to be developed.The preconditioning of MSCs ex vivo would strength their capacities by preparing them to survive and to better function in this hostile environment.In this review,we will discuss several preconditioning approaches that may improve the therapeutic capacity of MSCs.As stated above,EVs can recapitulate the beneficial effects of MSCs and may help avoid many risks associated with cell transplantation.As a result,this novel type of cell-free therapy may be safer and more efficient than the whole cell product.We will,therefore,also discuss current knowledge regarding the therapeutic properties of MSC-derived EVs. 展开更多
关键词 Cell-therapy Mesenchymal stromal cells safety Extracellular vesicles efficiency PRECONDITIONING
下载PDF
Safety-efficiency trade-offs in the cotton xylem:acclimatization to different soil textures 被引量:1
9
作者 WANG Zhongyuan XIE Jiangbo LI Yan 《Journal of Arid Land》 SCIE CSCD 2016年第3期443-452,共10页
The acclimatization of plant xylem to altered environmental conditions has attracted considerable attention from researchers over several decades. Plants growing in natural environments must seek a balance between wat... The acclimatization of plant xylem to altered environmental conditions has attracted considerable attention from researchers over several decades. Plants growing in natural environments must seek a balance between water uptake and the water loss of leaves from evaporation. Thus, the adaptation of xylem to different soil textures is important in maintaining plant water balance. In this study, we investigated the xylem changes of cotton(Gossypium herbaceum L.) xylem in sandy, clay and mixed soils. Results showed that soil texture had a significant effect on xylem vessel diameter and length of stems and roots. Compared with G. herbaceum growing in the clay soil, those plants growing in the sandy soil developed narrower and shorter xylem vessels in their roots, and had a higher percentage of narrow vessels in their stems. These changes resulted in a safer(i.e. less vulnerable to cavitation), but less-efficient water transport system when soil water availability was low, supporting the hydraulic safety versus efficiency trade-off hypothesis. Furthermore, in sandy and mixed soils, the root: shoot ratio of G. herbaceum increased twofold, which ensures the same efficiency of leaves. In summary, our finding indicates that the morphological plasticity of xylem structure in G. herbaceum has a major role in the acclimatization of this plant species to different soil textures. 展开更多
关键词 acclimatization soil texture xylem structure hydraulic acclimation safety vs. efficiency
下载PDF
Safety,efficiency and cost effectiveness of Bivalirudin:A systematic review
10
作者 Melorin Mehrzad Rasikh Tuktamyshov Raman Mehrzad 《World Journal of Cardiology》 CAS 2017年第9期761-772,共12页
AIM To review the early and more recent studies of Bivalirudin, to assess the safety, effectiveness, and cost benefits of this drug.METHODS Literature search of MEDLINE and Pub Med databases from 1990 to 2017 using ke... AIM To review the early and more recent studies of Bivalirudin, to assess the safety, effectiveness, and cost benefits of this drug.METHODS Literature search of MEDLINE and Pub Med databases from 1990 to 2017 using keywords as "bivalirubin" and "angiomax", combined with the words "safety", "effectiveness", "efficiency", "side effects", "toxicity", "adverse effect", and "adverse drug reaction".RESULTS A total of 66 publications were reviewed. The changes in clinical practice and differences in clinical protocols make it difficult to do direct comparisons of studies among each other. However, most trials showed decreased bleeding complications with bivalirudin, although ischemic complications and mortality were mostly comparable, with some favor towards bivalirudin.CONCLUSION Bivalirudin and heparin are both acceptable options according to current ACA/AHA guidelines. Authors conclude however, that that due to bivalirudin safer bleeding profile, it should be the preferred medication for anticoagulation. 展开更多
关键词 efficiency Cost effectiveness BIVALIRUDIN safety
下载PDF
A Study on Input-Output Efficiency of Citrus in Jiangxi Province
11
作者 Yu ZHONG 《Asian Agricultural Research》 2018年第1期10-15,共6页
This paper analyzes the citrus input-output efficiency by using the DEA-Malmquist productivity index methods based on the data of six counties in Jiangxi Province from 2010 to 2013.The result shows that TFP of Jiangxi... This paper analyzes the citrus input-output efficiency by using the DEA-Malmquist productivity index methods based on the data of six counties in Jiangxi Province from 2010 to 2013.The result shows that TFP of Jiangxi citrus is at low level overall,but the development is rapid.Technological progress is the driving force to promote productivity growth.Based on the static analysis study of six counties in 2013,it is found that the available input factors on the whole are in an ideal condition,and the citrus input factors in a few counties are redundant.Therefore,according to the results,the following policy recommendations are proposed:speeding up the intensive production of citrus in Jiangxi Province,to maximize the scale effect;adjusting the input ratio of various factors of production,so as to improve the citrus input-output efficiency. 展开更多
关键词 input-output efficiency Total factor productivity Citrus industry Technological progress
下载PDF
Holistic Approach to Safety and Operational Stability: Analyzing VVER-1200 Reactor Dynamics in SGTR and AC Power Loss
12
作者 Shaon Md Tariqur Rahman Md. Sadman Anjum Joarder +2 位作者 Antor Mahamudul Hashan Sharon Md Mahabubur Rahman Redar Hameed Ali 《Journal of Power and Energy Engineering》 2024年第9期102-130,共29页
VVER-1200 (Water-Water Energetic Reactor) represents a significant advancement in nuclear power generation, emphasizing the continuous analysis and enhancement of safety systems for reliable operation. The proposed st... VVER-1200 (Water-Water Energetic Reactor) represents a significant advancement in nuclear power generation, emphasizing the continuous analysis and enhancement of safety systems for reliable operation. The proposed study focuses on simulating combined scenarios involving steam generator tube rupture (SGTR) and AC power loss using core algorithms and models within personal computer transient analyzer (PCTRAN). Reactor kinetic equations, thermal-hydraulic balance, and safety system models are discussed to elucidate their role in simulating SGTR and AC power loss. Safety criteria, boundaries and initial conditions are outlined to provide a comprehensive understanding of the simulation framework. The analysis delves into dynamic behavior of VVER-1200, placing emphasis on thermal-hydraulic implications, essential reactor parameters, and radiation monitoring to facilitate impact evaluation. Continuous monitoring and maintenance of safety systems are underscored to ensure stable core cooling, particularly during proposed transient conditions. Through meticulous analysis and comparison with established benchmarks, this study contributes to bolstering the safety and reliability of VVER-1200 reactors by identifying vulnerabilities, assessing mitigation strategies, and refining emergency response protocols. Practical implications of this study offer a crucial understanding of reactor behavior, safety system performance, and emergency response strategies, thereby improving safety, optimizing operational practices, and reducing risks in nuclear reactor accidents. 展开更多
关键词 VVER-1200 Nuclear Technology safety Systems Operational efficiency Transient Events
下载PDF
Safety in Surgery:Evaluation of Safety and Efficiency in Use of Aminoglycosides in Acute Appendicitis
13
作者 Tadeja Pintar Bojana Beovic 《Surgical Science》 2020年第5期99-110,共12页
Background: Aminoglycosides are used as empirical antibiotic treatment of intraabdominal infections which are caused by Gram negative bacteria and for which the treatment of choice is surgery. Aminoglycosides maintain... Background: Aminoglycosides are used as empirical antibiotic treatment of intraabdominal infections which are caused by Gram negative bacteria and for which the treatment of choice is surgery. Aminoglycosides maintain good efficacy against these bacteria and reduce the need for prescribing fluoroquinolone, cephalosporin and carbapenem antibiotics which contribute to the development of resistant bacterial strains. In recent years, several clinical trials and international guidelines have advised against the use of aminoglycosides owing largely to doubts about their effectiveness and to the concern for their known nephrotoxicity and ototoxicity. Aim: In our study, we aimed to prove whether aminoglycosides are appropriate agents in the treatment of acute appendicitis. Methods: Retrospectively, patients with acute appendicitis we included in the trial. Demographic characteristics, comorbidities, clinical signs and symptoms, the type of antibiotic and surgical treatment were analyzed. The effect of independent variables on the occurrence of complications was calculated using Student’s T-test and Fisher’s precise test. The effect of aminoglycosides on the loss of kidney function was determined by means of a linear regression method. Results: 300 patients proved acute appendicitis were included in the study. Univariate statistical analysis showed that the risk factors for postoperative complications in treating acute appendicitis were: age over 76 years (p Conclusion: Aminoglycoside antibiotics are a safe and effective treatment of acute appendicitis;our not published data are positive of AGs use in acute cholecystitis and left colon diverticulitis which requires surgery. If used for a limited time period, they do not increase the risk for kidney injury and remain a stable low level of all over complications. 展开更多
关键词 IAI(Intraabdominal Infections) AMINOGLYCOSIDES Acute Appendicitis safety Use and efficiency
下载PDF
Perceptions of People on Police Efficiency and Crime Prevention in Urban Areas in Malaysia
14
作者 Suryati Ishak 《Economics World》 2016年第5期243-248,共6页
Crime cases from snatch thefts to murders, are becoming increasingly common in Malaysia according to the database of the Royal Malaysian Police (RMP), the current overall Crime Index in Malaysia was 147,062 for 2013... Crime cases from snatch thefts to murders, are becoming increasingly common in Malaysia according to the database of the Royal Malaysian Police (RMP), the current overall Crime Index in Malaysia was 147,062 for 2013 compared with 65,237 in 1977. The database also revealed that the number of property crimes reported in this country has always exceeded the number of violent crimes. Although in 2013, crimes related to property are higher (117,687) than violent crime (29,375), the gradual increase in the latter does worry Malaysians. Likewise, Malaysian Government had implemented a "safe community" concept, inspired by the Malaysian Crime Prevention Foundation (MCPF), a non-government organization, as they were concerned that the threat of violent crime and non-violent crime would eventually reduce the quality of life for many individuals. The concept is very important to the public as it is perceived as improved safety for the public with less crime. This study analyzes the public safety through their perceptions on the effectiveness of the policeman and suggesting few prevention actions against crime. The data were collected using a self-administered survey questionnaire. Specifically, this study focuses on the more developed states in this country. From the cross tabulation analysis, the majority of respondents agreed that the police are effective in controlling crime. Approximately, 72.1% of respondents felt that the police are efficient in controlling crime. 展开更多
关键词 CRIME crime prevention perceptions of people police efficiency public safety quality of life
下载PDF
The Efficiency Control Assessment for Electronic System
15
作者 S.K.Meshaninov 《Journal of Electronic Research and Application》 2018年第2期24-27,共4页
The data of the analytical estimation on the efficiency of providing safety control of the radioelectronic system are given.The review is based on the investigation of the information interaction of the radio-electron... The data of the analytical estimation on the efficiency of providing safety control of the radioelectronic system are given.The review is based on the investigation of the information interaction of the radio-electronic system(RS)with monitoring subsystem.The problem of optimal safety operational subsystem control of the RS and the generalized criterion for the effectiveness of decision making by the control system of the RS are formulated.Analytical expressions that allow making the choice of optimal ratio between the safe and the most effective modes of the control system operation are obtained. 展开更多
关键词 Radio-electronic SYSTEM information efficiency safety COMPLEX ENGINEERING SYSTEM operation
下载PDF
水雾粒子特性对呼吸性粉尘降尘效率影响研究 被引量:2
16
作者 荆德吉 马纪闯 张天 《安全与环境学报》 CAS CSCD 北大核心 2024年第1期169-175,共7页
为有效去除工业生产中的呼吸性粉尘,提高水雾粒子对呼吸性粉尘的捕捉效率,基于三相流理论建立了高速气流中单颗粒雾-尘碰撞耦合数值模型。研究高速气流中单颗粒雾-尘碰撞耦合过程,分析雾-尘粒径比及相对速度对尘粒表面线积分润湿度的影... 为有效去除工业生产中的呼吸性粉尘,提高水雾粒子对呼吸性粉尘的捕捉效率,基于三相流理论建立了高速气流中单颗粒雾-尘碰撞耦合数值模型。研究高速气流中单颗粒雾-尘碰撞耦合过程,分析雾-尘粒径比及相对速度对尘粒表面线积分润湿度的影响。结果表明,对于不同粒径等级的呼吸性粉尘,达到最佳润湿度对应的雾-尘粒径比不同,k(PM1)=15、k(PM2.5)=2和k(PM5)=1。在高速气流中雾-尘相对运动状态不同时,粉尘颗粒的最佳润湿度随雾-尘相对速度U增大而增大。搭建仿真试验模型,研究不同情况下水雾粒子的捕尘效率。结果表明,超音速雾化喷嘴对呼吸性粉尘的降尘效率为95.95%,单流体喷嘴降尘效率为82.98%。结合现场试验对比分析,验证雾-尘粒径比及相对速度对尘粒表面线积分润湿度的影响规律。结果表明,越符合粉尘粒子被捕捉的最佳粒径比的喷嘴的降尘效率越高,提高尘雾粒子碰撞速度可以提高对粉尘粒子的捕捉效率,为治理呼吸性粉尘及清洁化工业生产提供理论依据。 展开更多
关键词 安全卫生工程技术 单颗粒碰撞 呼吸性粉尘 数值模拟 降尘效率
下载PDF
农林保水剂效果评价及其环境风险探讨 被引量:1
17
作者 王小彬 闫湘 +2 位作者 李秀英 孙兆凯 涂成 《中国农业科学》 CAS CSCD 北大核心 2024年第6期1117-1136,共20页
从我国“七五”计划旱农科研项目以来,农林保水剂作为抗旱保水产品受到关注。《农林保水剂》(NY 886)农业行业标准2004年颁布,2010、2016和2022年3次修改,但至今缺乏相关配套的田间试验效果评价体系,极大影响其推广应用。本文结合国内... 从我国“七五”计划旱农科研项目以来,农林保水剂作为抗旱保水产品受到关注。《农林保水剂》(NY 886)农业行业标准2004年颁布,2010、2016和2022年3次修改,但至今缺乏相关配套的田间试验效果评价体系,极大影响其推广应用。本文结合国内外30多年来的相关研发与应用文献分析,针对农林保水剂应用对土壤保水、作物用水、作物产量及其环境影响等效果进行综述研究,结果表明:(1)保水剂适用于改善土壤蓄水保水性能,对旱作地区作物抗旱保苗、节水增产和水分利用效率(WUE)提高有积极影响,尤其是在砂质土壤上。(2)提出农林保水剂效果评价指标,主要包括土壤贮水量、作物耗水量、作物产量及其WUE等指标,以适用于农林保水剂产品的田间试验效果评价。(3)根据农林保水剂对作物产量增减不一和增产与收益不统一等现象,提出农林保水剂应用需要制定相应的技术规程,明确作物适宜的保水剂类型及其施用方式和用量。(4)农林保水剂产品(以聚丙烯酰胺(PAM)和聚丙烯酸(PAA)型材料为主)的环境安全性主要涉及残留单体(丙烯酰胺(AM)和丙烯酸(AA))的生物毒性,以及材料的降解性等。市场上部分PAM和PAA相关产品分别存在残留AM和AA单体含量超标风险,超标率约占22%—100%。研究指出生物质类等天然聚合物类材料是农林保水剂发展方向。研究结果对农林保水剂效果评价标准的制定提供参考。建议相关部门对于PAM和PAA型农林保水剂产品加强残留单体检测及其残留单体的环境安全阈值的研究,并对产品的生物降解性指标与土壤生态环境的安全性的关联性进行探讨,以期为农林保水剂产品的环境安全性提供保障。 展开更多
关键词 农林保水剂 土壤含水量 作物耗水量 水分利用效率 环境安全风险
下载PDF
南水北调中线冬季冰情变化特征及输水能力提升策略研究 被引量:1
18
作者 郭新蕾 潘佳佳 +3 位作者 苑希民 王军 罗秋实 苏霞 《水利学报》 EI CSCD 北大核心 2024年第4期389-402,共14页
南水北调中线工程冰期输水能力受限已成为制约工程安全运行和社会效益发挥的巨大障碍。认识和辨析通水以来中线干渠冬季水温冰情演变规律及影响机理,是中线干渠冬季输水能力提升亟需解决的关键问题。本文基于2011—2023年中线干渠连续1... 南水北调中线工程冰期输水能力受限已成为制约工程安全运行和社会效益发挥的巨大障碍。认识和辨析通水以来中线干渠冬季水温冰情演变规律及影响机理,是中线干渠冬季输水能力提升亟需解决的关键问题。本文基于2011—2023年中线干渠连续12个冬季的气象、水力、冰情等原型观测资料,分析了中线干渠水温冰情时空分布本底和特征规律,明晰了影响中线干渠冰凌生消的关键因素,针对性提出了冬季输水能力提升的相关应对策略。分析表明:通水以来冰情发生的范围和时间相比理论预想偏小、偏短,冰凌影响区为七里河倒虹吸至北拒马河暗渠段,冰塞风险区为滹沱河倒虹吸至北拒马河暗渠段,多年平均冰厚15 cm,历史极端冰塞厚2.9 m,冰凌壅水最高值0.73 m;干渠冬季水温由南向北递减,依次出现岸冰、流冰和冰盖,日均气温转负后相应的断面平均测量水温在2.5、1.0和0.25℃左右,且沿程水温下降速率与流量和气温呈负相关,即增大输水流量可减缓水温下降速度;影响冰凌生消的关键因素是气温、流量、太阳辐射和风速,典型年如2016年的严重冰情与1月低累计负积温、大输水流量和短时寒潮叠加有关,漕河等渡槽失温快产冰量大与风速密切相关。基于上述分析,未来可考虑结合气象、水情、冰情实时监测和智能预警预报,建立水温-水量-水力协同调控和动态调度技术体系,重点从缩短冰期输水时长、降低冰情影响范围、优化关键控制指标和挖潜渠道防冰塞性能等多方面全面提升南水北调中线工程冬季输水能力。 展开更多
关键词 水温冰情 时空分布 南水北调中线 冬季防凌 输水能力
下载PDF
除草剂不同时期应用对机直播稻田杂草的防除作用
19
作者 张建萍 杨永杰 +2 位作者 于晓玥 陆永良 唐伟 《中国稻米》 北大核心 2024年第2期91-94,共4页
为开发机直播水稻田高效安全的封闭除草剂,采用大田试验,比较了不同时期应用含有乙氧磺隆成分的除草剂对阔叶草和莎草科杂草的防除效果。结果发现,播种时同步喷施五氟·乙氧或混配乙氧磺隆与其他除草剂能够有效抑制机直播稻田阔叶... 为开发机直播水稻田高效安全的封闭除草剂,采用大田试验,比较了不同时期应用含有乙氧磺隆成分的除草剂对阔叶草和莎草科杂草的防除效果。结果发现,播种时同步喷施五氟·乙氧或混配乙氧磺隆与其他除草剂能够有效抑制机直播稻田阔叶草和莎草科杂草的萌发和生长,且对水稻出苗安全。机直播后10 d或15 d施用对阔叶草防效下降,但播种15 d后撒施0.65%五氟·乙氧控释颗粒剂97.5 g/hm^(2)对杂草防效较好,密度防效达到90%以上。表明采用五氟·乙氧或混配乙氧磺隆与其他除草剂防除机直播稻田阔叶草,越早施药效果越好。但如果因气候条件或其他因素影响错过施药窗口期时,撒施0.65%五氟·乙氧控释颗粒剂97.5 g/hm^(2)或喷施30%氰氟草酯112.5 g/hm^(2)+30%五氟·乙氧90 g/hm^(2)也可以防控绝大部分直播田杂草。 展开更多
关键词 机直播稻 乙氧磺隆 杂草 阔叶草 防效 水稻安全性
下载PDF
考虑周车主观侵略性的智能车辆换道优化策略
20
作者 殷春芳 岳海波 +2 位作者 施德华 汪少华 安兴科 《重庆理工大学学报(自然科学)》 CAS 北大核心 2024年第9期55-66,共12页
智能车辆换道策略是智能驾驶技术的重要组成部分,在不同场景下的适应能力对于高品质自动驾驶尤为重要。在异质交通流中,智能车辆认知属性的不同会引起换道车辆换道意图及轨迹规划的差异。该策略利用车辆行驶空间、行驶效率参数建立车辆... 智能车辆换道策略是智能驾驶技术的重要组成部分,在不同场景下的适应能力对于高品质自动驾驶尤为重要。在异质交通流中,智能车辆认知属性的不同会引起换道车辆换道意图及轨迹规划的差异。该策略利用车辆行驶空间、行驶效率参数建立车辆的决策代价函数,采用模糊理论从速度系数、空间系数、车道分布等角度实现对周围车辆主观侵略性的量化描述,在此基础上,通过智能驾驶员模型(IDM)预测周车对换道车辆换道意图的行为响应,并根据预测信息优化换道决策。在轨迹规划过程中,将车辆换道轨迹解耦为车辆换道路径及行驶速度,利用车辆主观侵略性及车辆行驶安全场评估车辆换道行驶风险,并将行驶安全场与二次规划相融合,从安全性、舒适性、参考线偏差等角度进行路径及速度优化。仿真结果表明,该优化策略通过换道决策可以有效提高道路通行效率,相较固定五次多项式与单独的安全场换道轨迹,可以有效降低换道过程中横向速度与横向加速度的幅值,改善换道过程中的行驶舒适性。 展开更多
关键词 行驶空间 行驶效率 车道分布 主观侵略性 行驶安全场 二次规划
下载PDF
上一页 1 2 81 下一页 到第
使用帮助 返回顶部