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Predicting short-term thromboembolic risk following Roux-en-Y gastric bypass using supervised machine learning

World Journal of Gastrointestinal Surgery 2024年第4期16卷 1097-1108页

作者： Hassam Ali Faisal Inayat Vishali Moond Ahtshamullah Chaudhry Arslan Afzal Zauraiz Anjum Hamza Tahir muhammad Sajeel Anwar Dushyant Singh Dahiya muhammad sohaib Afzal Gul Nawaz Amir H Sohail muhammad Aziz Department of Gastroenterology East Carolina University Brody School of MedicineGreenvilleNC 27834United States Department of Internal Medicine Allama Iqbal Medical CollegeLahorePunjab 54550Pakistan Department of Internal Medicine Saint Peter's University Hospital and Robert Wood Johnson Medical SchoolNew BrunswickNJ 08901United States Department of Internal Medicine St.Dominic's HospitalJacksonMS 39216United States Department of Internal Medicine Rochester General HospitalRochesterNY 14621United States Department of Internal Medicine Jefferson Einstein HospitalPhiladelphiaPA 19141United States Department of Internal Medicine UHS Wilson Medical CenterJohnsonNY 13790United States Division of Gastroenterology Hepatology and MotilityThe University of Kansas School of MedicineKansasKS 66160United States Department of Internal Medicine Louisiana State University HealthShreveportLA 71103United States Department of Surgery University of New Mexico School of MedicineAlbuquerqueNM 87106United States Department of Gastroenterology and Hepatology The University of ToledoToledoOH 43606United States

BACKGROUND Roux-en-Y gastric bypass(RYGB)is a widely recognized bariatric procedure that is particularly beneficial for patients with class III *** aids in significant weight loss and improves obesity-related medical *** its effectiveness,postoperative care still has *** evidence shows that venous thromboembolism(VTE)is a leading cause of 30-d morbidity and mortality after ***,a clear unmet need exists for a tailored risk assessment tool for VTE in RYGB *** To develop and internally validate a scoring system determining the individualized risk of 30-d VTE in patients undergoing *** Using the 2016–2021 Metabolic and Bariatric Surgery Accreditation Quality Improvement Program,data from 6526 patients(body mass index≥40 kg/m^(2))who underwent RYGB were analyzed.A backward elimination multivariate analysis identified predictors of VTE characterized by pulmonary embolism and/or deep venous thrombosis within 30 d of *** resultant risk scores were derived from the coefficients of statistically significant *** performance of the model was evaluated using receiver operating curves through 5-fold *** Of the 26 initial variables,six predictors were *** included a history of chronic obstructive pulmonary disease with a regression coefficient(Coef)of 2.54(P7%(Coef 1.19,P<0.001),venous stasis history(Coef 1.43,P<0.001),and preoperative anticoagulation use(Coef 1.24,P<0.001).These variables were weighted according to their regression coefficients in an algorithm that was generated for the model predicting 30-d VTE risk *** risk model's area under the curve(AUC)was 0.79[95%confidence interval(CI):0.63-0.81],showing good discriminatory power,achieving a sensitivity of 0.60 and a specificity of *** training,the same model performed satisfactorily

关键词： Roux-en-Y gastric bypass Venous thromboembolism Machine learning Bariatric surgery Predictive modeling

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Long-term outcomes of titanium-nitride-oxide coated stents and drug-eluting stents in acute coronary syndrome:A systematic review and meta-analysis

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World Journal of Cardiology 2024年第5期16卷 293-305页

作者： muhammad Ahmed Ali Fahim Afia Salman Hira Anas Khan Syed muhammad Hasan Muskan FatimaBhojani Sarah Aslam Amna Zia Ul Haq Vishal Reddy Bejugam Beena Muntaha Nasir Wajiha Gul Abdul Moeed Abdelrahman S Abdalla muhammad Majid muhammad sohaib Asghar Md Al Hasibuzzaman Department of Internal Medicine Dow University of Health SciencesKarachi 74200Pakistan Department of Internal Medicine North Central Bronx HospitalBronxNY 10467United States Department of Urology Center for Academic MedicineStanford University School of MedicinePalo AltoCA 33872United States Department of Cardiovascular Imaging Cleveland ClinicClevelandOH 44195United States Division of Nephrology and Hypertension Mayo Clinic RochesterRochesterMN 55905United States Institute of Nutrition and Food Science University of DhakaDhaka 1000Bangladesh

BACKGROUND In severe cases of coronary artery disease,percutaneous coronary intervention provide promising *** stent used could be a drug-eluting stent(DES)or a titanium-nitride-oxide coated stent(TiNOS).AIM To compare the 5-year effectiveness and safety of the two stent *** The following systematic review and meta-analysis was conducted in accordance with the preferred reporting items for systematic reviews and meta-analysis guidelines,and PubMed/MEDLINE,Scopus,and Cochrane Central were searched from inception till August *** outcomes were major adverse cardiac events(MACE),cardiac death,myocardial infarction(MI),cardiac death or MI,and ischemia-driven total lesion revascularization(ID-TLR).RESULTS Four randomized controlled trials(RCT),which analyzed a sum total of 3045 patients with acute coronary syndrome(ACS)after a median follow-up time of 5 years were *** statistically insignificant,an increase in the ID-TLR was observed in patients receiving TiNOSs vs *** addition,MI,cardiac death and MI,and definite stent thrombosis(DST)were significantly decreased in the TiNOS *** analysis revealed no significant results with meta-regression presenting non-ST elevated MI(NSTEMI)as a statistically significant covariate in the outcome of *** TiNOS was found to be superior to DES in terms of MI,cardiac death or MI,and DST outcomes,however,the effect of the two stent types on ID-TLR and MACE was not significant.A greater number of studies are required to establish an accurate comparison of patient outcomes in TiNOS and DES.

关键词： Stents Drug-eluting Major adverse cardiac events All-cause death Meta-analysis

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Impact of COVID-19 on liver transplant recipients: A nationwide cohort study evaluating hospitalization, transplant rejection, and inpatient mortality

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World Journal of Transplantation 2024年第2期14卷 62-75页

作者： Faisal Inayat Pratik Patel Hassam Ali Arslan Afzal Hamza Tahir Ahtshamullah Chaudhry Rizwan Ishtiaq Attiq Ur Rehman Kishan Darji muhammad sohaib Afzal Gul Nawaz Alexa Giammarino Sanjaya K Satapathy Department of Internal Medicine Allama Iqbal Medical CollegeLahorePunjab 54550Pakistan Division of Gastroenterology Mather Hospital and Zucker School of Medicine at Hofstra UniversityPort JeffersonNY 11777United States Division of Gastroenterology and Hepatology East Carolina University Brody School of MedicineGreenvilleNC 27834United States Department of Internal Medicine Jefferson Einstein HospitalPhiladelphiaPA 19141United States Department of Internal Medicine St.Dominic's HospitalJacksonMS 39216United States Department of Internal Medicine Saint Francis Hospital and Medical CenterHartfordCT 06105United States Division of Hepatology Geisinger Wyoming Valley Medical CenterWilkes-BarrePA 18711United States Department of Internal Medicine Campbell University and Cape Fear Valley Medical CenterFayettevilleNC 28301United States Department of Internal Medicine North Shore University Hospital and Zucker School of Medicine at Hofstra UniversityManhassetNY 11030United States Division of Hepatology North Shore University Hospital and Zucker School of Medicine at Hofstra UniversityManhassetNY 11030United States

BACKGROUND The coronavirus disease 2019(COVID-19)pandemic has posed a major public health concern *** with comorbid conditions are at risk of adverse outcomes following *** organ transplant recipients with concurrent immunosuppression and comorbidities are more susceptible to a severe COVID-19 *** could lead to higher rates of inpatient complications and mortality in this patient ***,studies on COVID-19 outcomes in liver transplant(LT)recipients have yielded inconsistent *** To evaluate the impact of the COVID-19 pandemic on hospital-related outcomes among LT recipients in the United *** We conducted a retrospective cohort study using the 2019–2020 National Inpatient Sample *** with primary LT hospitalizations and a secondary COVID-19 diagnosis were identified using the International Classi-fication of Diseases,Tenth Revision coding *** primary outcomes included trends in LT hospitalizations before and during the COVID-19 *** outcomes included comparative trends in inpatient mortality and transplant rejection in LT *** A total of 15720 hospitalized LT recipients were *** 0.8% of patients had a secondary diagnosis of COVID-19 *** both cohorts,the median admission age was 57 *** linear trends for LT hospitalizations did not differ significantly before and during the pandemic(P=0.84).The frequency of in-hospital mortality for LT recipients increased from 1.7% to 4.4% between January 2019 and December *** to the pre-pandemic period,a higher association was noted between LT recipients and in-hospital mortality during the pandemic,with an odds ratio(OR)of 1.69[95% confidence interval(CI):1.55-1.84),P<0.001].The frequency of transplant rejections among hospitalized LT recipients increased from 0.2%to 3.6% between January 2019 and December *** hospitalizations during the COVID-19 pandemic had a higher associ

关键词： Liver transplant recipients Solid organ transplantation COVID-19 Hospitalization Transplant rejection Mortality

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Association between acute peripancreatic fluid collections and early readmission in acute pancreatitis:A propensity-matched analysis

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World Journal of Experimental Medicine 2024年第2期14卷 75-88页

作者： Hassam Ali Faisal Inayat Waqas Rasheed Arslan Afzal Ahtshamullah Chaudhry Pratik Patel Attiq Ur Rehman muhammad Sajeel Anwar Gul Nawaz muhammad sohaib Afzal Amir H Sohail Subanandhini Subramanium Dushyant Singh Dahiya Deepa Budh Babu P Mohan Douglas G Adler Department of Gastroenterology and Hepatology East Carolina University Brody School of MedicineGreenvilleNC 27834United States Department of Internal Medicine Allama Iqbal Medical CollegeLahorePunjab 54550Pakistan Department of Internal Medicine Texas Tech University Health Sciences CenterLubbockTX 79430United States Department of Internal Medicine St.Dominic’s HospitalJacksonMS 39216United States Department of Gastroenterology Mather Hospital and Hofstra University Zucker School of MedicinePort JeffersonNY 11777United States Department of Hepatology Geisinger Wyoming Valley Medical CenterWilkes-BarrePA 18711United States Department of Internal Medicine UHS Wilson Medical CenterJohnson CityNY 13790United States Department of Internal Medicine Louisiana State University HealthShreveportLA 71103United States Department of Surgery University of New Mexico School of MedicineAlbuquerqueNM 87106United States Division of Gastroenterology Hepatologyand MotilityThe University of Kansas School of MedicineKansas CityKS 64108United States Department of Internal Medicine St.Barnabas Hospital and Albert Einstein College of MedicineBronxNY 10457United States Department of Gastroenterology and Hepatology University of Utah School of MedicineSalt Lake CityUT 84132United States Center for Advanced Therapeutic Endoscopy Porter Adventist HospitalCentura HealthDenverCO 80210United States

BACKGROUND Patients with acute pancreatitis(AP)frequently experience hospital readmissions,posing a significant burden to healthcare *** peripancreatic fluid collection(APFC)may negatively impact the clinical course of *** could worsen symptoms and potentially lead to additional ***,clinical evidence regarding the specific association between APFC and early readmission in AP remains *** the link between APFC and readmission may help improve clinical care for AP patients and reduce healthcare *** To evaluate the association between APFC and 30-day readmission in patients with *** This retrospective cohort study is based on the Nationwide Readmission Database for *** with a primary diagnosis of AP were *** were categorized into those with and without APFC.A 1:1 propensity score matching for age,gender,and Elixhauser comorbidities was *** primary outcome was early readmission *** outcomes included the incidence of inpatient complications and healthcare *** analyses used Mann-Whitney U andχ2 tests,while Cox regression models assessed 30-day readmission risks and reported them as adjusted hazard ratios(aHR).Kaplan-Meier curves and log-rank tests verified readmission *** A total of 673059 patients with the principal diagnosis of AP were *** these,5.1%had APFC on initial *** propensity score matching,each cohort consisted of 33914 *** with APFC showed a higher incidence of inpatient complications,including septic shock(3.1%vs 1.3%,P<0.001),portal venous thrombosis(4.4%vs 0.8%,P<0.001),and mechanical ventilation(1.8%vs 0.9%,P<0.001).The length of stay(LOS)was longer for APFC patients[4(3-7)vs 3(2-5)days,P<0.001],as were hospital charges($29451 vs$24418,P<0.001).For 30-day readmissions,APFC patients had a higher rate(15.7%vs 6.5%,P<0.001)and a longer median readmission LOS(4 vs 3 days,P<0.001).The APF

关键词： Acute pancreatitis Acute peripancreatic fluid collections Readmission predictors Inpatient complications Healthcare utilization and costs

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Liver-Tumor Detection Using CNN ResUNet

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Computers, Materials & Continua 2021年第5期67卷 1899-1914页

作者： muhammad sohaib Aslam muhammad Younas muhammad Umar Sarwar muhammad Arif Shah Atif Khan MIrfan Uddin Shafiq Ahmad muhammad Firdausi Mazen Zaindin Department of Computer Science Government College University FaisalabadFaisalabad38000Pakistan Department of IT and Computer Science Pak-Austria Fachhochschule Institute of Applied Sciences and TechnologyHaripur22620Pakistan Department of Computer Science Islamia College PeshawarPeshawarKPPakistan Institute of Computing Kohat University of Science and TechnologyKohatPakistan Department of Industrial Engineering College of EngineeringKing Saud UniversityRiyadh11421Saudi Arabia Department of Statistics and Operations Research College of ScienceKing Saud UniversityRiyadh11421Saudi Arabia

Liver tumor is the fifth most occurring type of tumor in men and the ninth most occurring type of tumor in women according to recent reports of Global cancer statistics *** are several imaging tests like Computed Tomography(CT),Magnetic Resonance Imaging(MRI),and ultrasound that can diagnose the liver tumor after taking the sample from the tissue of the *** tests are costly and *** paper proposed that image processing through deep learning Convolutional Neural Network(CNNs)ResUNet model that can be helpful for the early diagnose of tumor instead of conventional *** existing studies have mainly used the two Cascaded CNNs for liver segmentation and evaluation of Region Of Interest(ROI).This study uses ResUNet,an updated version of U-Net and ResNet Models that utilize the service of Residential *** apply over method on the 3D-IRCADb01 dataset that is based on CT slices of liver tumor affected *** results showed the True Value Accuracy around 99%and F1 score performance around 95%.This method will be helpful for early and accurate diagnose of the Liver tumor to save the lives of many patients in the field of Biotechnology.

关键词： Liver tumor diagnose ResUNet CNNs segmentation

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Global trends and knowledge-relationship of symptom clusters in cancer research:a bibliometric analysis over the past 20 years

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Frontiers of Nursing 2023年第3期10卷 273-288页

作者： Ran An Yuan Luo Wen-Feng Chen muhammad sohaib Mei-Zi Liu Xiangya School of Nursing Central South UniversityChangshaHunan 410013China Teaching and Research Section of Clinical Nursing Xiangya Hospital Central South UniversityChangshaHunan 410013China Children Hospital and Institute of Child Health Multan 60000Pakistan

Objective:To use Cite Space and VOSviewer to investigate the scientific production in the field of symptom clusters in cancer ***:The search was performed using the terms“symptom clusters,”“cancer,”and“oncology”on the Web of Science Core Collection *** retrieval time was from 2001 to 2021,which covers the last 2 *** on the production theory of scientific knowledge and the data mining of citations,data pertaining to the annual publications,journals,countries,organizations,authors,and keywords that produce symptom clusters in cancer research,as well as their cooperation(collaboration network),were extracted,and then both were clarified by the software tools VOSviewer(version 1.6.16)and Cite Space(version 6.1.R2).Results:A total of 1796 publications were retrieved between 2001 and 2021,and 473 relevant publications were included after *** results showed an increasing trend in published *** United States had the largest number of publications(261/473,55.18%),followed by China and *** University of California,San Francisco,was the most productive *** research hotspots included the analysis of symptom clusters and symptom management in patients with breast cancer and lung cancer,as well as any advanced cancer and cancer cachexia;fatigue-related symptom clusters and depression-anxiety symptom cluster;and the impacts of symptom clusters on quality of *** research frontiers included analysis between health-related quality of life and symptom clusters,data mining in symptom clusters,research on the mental health status of cancer patients,and study of the mechanism and biological pathways of symptom ***:The study provides insight into the global research perspective for the scientific progress on cancer symptom clusters,which suggests a growing scientific interest in this field,and more studies are warranted to guide symptom management.

关键词： bibliometrics cancer Citespace symptom clusters systematic review VOSviewer

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AI-Driven Learning Management Systems:Modern Developments, Challenges and Future Trends during theAge of ChatGPT

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Computers, Materials & Continua 2024年第8期80卷 3289-3314页

作者： Sameer Qazi muhammad Bilal Kadri muhammad Naveed Bilal AKhawaja sohaib Zia Khan muhammad Mansoor Alam Mazliham Mohd Su’ud Department of Computer Science Faculty of EngineeringScience and TechnologyIQRA UniversityKarachi75500Pakistan College of Computer and Information Sciences Prince Sultan UniversityRiyadh11586Saudi Arabia Faculty of Engineering Department of Electrical EngineeringIslamic University of MadinahP.O.BOX 170Madinah41411Saudi Arabia Faculty of Engineering Department of Mechanical EngineeringIslamic University of MadinahP.O.BOX 170Madinah41411Saudi Arabia Faculty of Computing Riphah International UniversityIslamabad46000Pakistan Faculty of Computing and Informatics(FCI)Multimedia University Cyberjaya63100Malaysia Faculty of Engineering and Information Technology School of Computer ScienceUniversity of Technology SydneySydneyNSW 2007Australia

COVID-19 pandemic restrictions limited all social activities to curtail the spread of the *** foremost and most prime sector among those affected were schools,colleges,and *** education system of entire nations had shifted to online education during this *** shortcomings of Learning Management Systems(LMSs)were detected to support education in an online mode that spawned the research in Artificial Intelligence(AI)based tools that are being developed by the research community to improve the effectiveness of *** paper presents a detailed survey of the different enhancements to LMSs,which are led by key advances in the area of AI to enhance the real-time and non-real-time user *** AI-based enhancements proposed to the LMSs start from the Application layer and Presentation layer in the form of flipped classroom models for the efficient learning environment and appropriately designed UI/UX for efficient utilization of LMS utilities and resources,including AI-based *** layer enhancements are also required,such as AI-based online proctoring and user authentication using *** extend to the Transport layer to support real-time and rate adaptive encrypted video transmission for user security/privacy and satisfactory working of *** also needs the support of the Networking layer for IP-based geolocation features,the Virtual Private Network(VPN)feature,and the support of Software-Defined Networks(SDN)for optimum Quality of Service(QoS).Finally,in addition to these,non-real-time user experience is enhanced by other AI-based enhancements such as Plagiarism detection algorithms and Data Analytics.

关键词： Learning management systems chatbots ChatGPT online education Internet of Things(IoT) artificial intelligence(AI) convolutional neural networks natural language processing

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巴基斯坦肿瘤科护士职业生活质量与社会支持的相关性研究

巴基斯坦肿瘤科护士职业生活质量与社会支持的相关性研究

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作者： muhammad sohaib（苏海）中南大学

学位级别：硕士

背景:医护人员经常面临与工作有关的压力,这对他们的幸福感、工作满意度以及身心健康都产生了负面影响。近年来,在巴基斯坦甚至全球范围内,临床医务工作者的心理健康已成为主要的研究项目之一。与病人数量相比,肿瘤科的护士人数相当有... 详细信息

背景:医护人员经常面临与工作有关的压力,这对他们的幸福感、工作满意度以及身心健康都产生了负面影响。近年来,在巴基斯坦甚至全球范围内,临床医务工作者的心理健康已成为主要的研究项目之一。与病人数量相比,肿瘤科的护士人数相当有限。护士在临床上提供温馨的人文关怀,肩负着保障人类健康的重要使命,护理工作既是护士的责任,也是护士对病人的义务。护士作为一个面对面为病人服务的群体,承受着巨大的职业压力,长期超负荷的工作容易使其出现身心疲惫,这也会导致同情心疲劳综合征的发生。当护士长期接触遭受病痛折磨的病人时,日复一日的情感付出会给护士自身带来许多负面影响,使其容易出现紧张、焦虑、抑郁、惊恐等不良心理反应,进而造成工作热情降低,工作效率下降,离职率增加等。最早发现和研究"同情心疲劳"的Jonson认为,这是一种由于持续暴露在职业和同情心的压力下而导致医护人员消耗和不稳定的疾病。Stamm修改了由Figley开发的职业生活质量(Pro QOL)量表,该量表最常被用来测量同情心疲劳。社会支持可能减弱或缓冲压力的负面影响。犯错误、没有得到医院管理者的合作以改善工作条件、缺乏资源和设备、感到不足或无能为力以及其他情况被认为是压力最大的,而看到没有得到医疗护理的悲惨的人也会产生压力。在巴基斯坦进行的一项关于"卡拉奇三级医院护士的同情心满意度、二次创伤压力和职业倦怠"的一项研究表明,同情心满意度、同情心疲劳和职业倦怠分别占比70%、84.7%和94.2%,同情心疲劳和职业倦怠在护士中占比非常高。由于疾病的预后不佳,肿瘤学领域更是如此。由于病人的不良预后,护士的压力水平相当高,巴基斯坦还没有关于肿瘤科护士的同情心满意度和同情心疲劳的研究。目的:本研究的目的是考察巴基斯坦肿瘤科护士的职业生活质量,并将其与社会支持联系起来,旨在找出差距,采取有针对性的干预,分析社会支持的现状,探讨肿瘤科护士的职业生活质量(BO、CS、STS)和社会支持(来自他人、家人和朋友的重要支持)之间的关系。方法:本研究是在巴基斯坦旁遮普省进行的一项描述性、横断面、非实验性研究。数据是通过随机的便利抽样收集的,参与者包括目前在肿瘤科住院部门连续工作的持证护士,他们至少拥有护理学学士学位或护理学文凭,在任一科室的临床工作经验不少于6个月,目前在肿瘤科担任护士并直接参与病人护理。护理经理、肿瘤科门诊护士、护理助理、实习生、缺席者、不想参与的人和其他部门的护士都被排除在本研究之外。调查工具包括专业生活质量量表和感知社会支持量表,这两个量表都是自由量表,专业生活质量量表有3个组成部分,每个量表有10个问题;感知社会量表有3个类别:朋友/家人、主管/行政人员、同事,每个类别都有4个问题,这个量表在英文版本中保持不变,并使用英文版本的量表来收集数据。数据分析使用软件SPSS 26.0。使用描述性统计分析人口学特征,包括中位数、频数和频率。Pro QOL与人口统计学因素和社会支持之间采用了皮尔逊相关分析。P<0.05被认为具有统计学意义。结果:调查来自五家肿瘤医院的344名护士回复率为100%大多数(60.8%)参与者为男性,39.2%为女性。参与者很年轻,年龄在18-37岁之间(M=26.13),而大多数参与者的年龄在18-20岁之间(31.97%)。大多数参与者有毕业学位(55.24%),38.95%的人有护理文凭,极少数人有硕士学位(5.81%)。在肿瘤科的平均工作经验是3.55年,大部分人的工作经验在1-2年之间(31.68%),极少数护士的工作经验超过7年(4.36%)。68.9%的人工作6-8小时,4.1%的人工作12小时以上。人口统计学因素和Pro QOL之间的皮尔逊相关分析。R值≤0.2表示弱相关,在0.2.4之间表示中度相关,而≥0.4表示强相关。统计学上观察到BO与工作经验之间存在中等程度的显著正相关关系(r=0.396**,p=0.000)。CS与教育、工作时间和BO高度正相关,(r=0.589**,p=0.000)、(r=0.037**,p=0.000)、(r=0.736**,p=0.000)。STS与教育、CS高度正相关,与BO负相关(r=0.453**,p=0.000)、(r=0.613,p=0.000(r=-0.421**,p=0.001)。工作经验和教育与职业生活质量的相关性分析显示那些有4-5年和<6年工作经验的人与同情心满意度有高度相关的显著正向关系(r=0.465**,p=0.000),那些有1-2年和3-4年工作经验的人与工作疲溃有中度相关的显著正向关系(r=0.311**,p=0.03),(r=0.294**,p=0.003)。同情心满意度与毕业和硕士学位有强烈的相关意义(r=0.612**,p=0.000),(r=0.822**,p=0.000)。二次创伤压力

关键词：护士同情满意度(CS) 职业倦怠(BO) 二次创伤压力(STS) 社会支持(SS) 同情心疲劳(CF)

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阻尼器对斜拉桥索力估算影响的研究

阻尼器对斜拉桥索力估算影响的研究

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作者： muhammad sohaib 哈尔滨工业大学

学位级别：硕士

对于斜拉桥而言,拉索是最关键的承载构件之一。然而,由于拉索自身固有阻尼很小,其在受风荷载等作用下经常产生大幅振动,严重影响拉索的安全与寿命。因此,许多拉索都安装了不同类型的阻尼器,以减少拉索的振动。为了掌握拉索的运行安全状... 详细信息

对于斜拉桥而言,拉索是最关键的承载构件之一。然而,由于拉索自身固有阻尼很小,其在受风荷载等作用下经常产生大幅振动,严重影响拉索的安全与寿命。因此,许多拉索都安装了不同类型的阻尼器,以减少拉索的振动。为了掌握拉索的运行安全状态,需要对拉索索力进行准确的估计。由于安装的阻尼器改变了拉索结构的动力特性,不可避免地会影响拉索索力估算的结果。但是,目前对安装的阻尼器如何影响索力估算精度的研究还很少。在本研究中,我们将系统地研究安装阻尼器对拉索索力识别精度的影响。本文考虑了两种类型的拉索动力模型。在第一个模型中,拉索被模拟为没有下垂的张紧弦模型;在第二个模型中,考虑拉索重力下垂对其动力特性的影响。为了提高有阻尼拉索动力特性计算的效率,在sin形函数的基础上,增加了受阻尼单元荷载作用的拉索静态变形的形状函数,使组合后的振型可以更好地逼近拉索-阻尼组合系统实际模态振型。采用伽辽金法对系统的固有频率进行了分析。还考虑了两种类型的阻尼器模型。在第一个模型中,用一个简单的弹簧和粘性阻尼器模型来模拟阻尼器。在第二个模型中,采用非线性模型对阻尼器进行建模。采用线性化技术,对非线性阻尼模型的索-阻尼系统的固有频率进行了计算。基于上述推导的索-阻尼系统模型,进行了广泛的参数研究,研究了索-阻尼系统的参数,包括阻尼器的安装位置、阻尼器的刚度和阻尼器的阻尼系数对索-阻尼系统固有频率的影响以及拉索索力识别结果的影响,最后总结了阻尼器各个参数对拉索索力估算精度的主要影响。

关键词：索力识别阻尼器 Galerkin方法线性化

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氮肥和种植密度对晚播棉花产量光合特性和碳代谢的影响

氮肥和种植密度对晚播棉花产量光合特性和碳代谢的影响

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作者： muhammad sohaib Chattha 华中农业大学

学位级别：硕士

棉花是天然纤维的重要来源。中国是世界上重要的产棉国,湖北是中国主要的棉花生产省。长江流域普遍实行两熟制,如棉花-小麦或棉花-油菜。生产利润低,耕作制度繁琐,劳动力向城市转移以及生产支出增加导致棉花种植面积减少。适宜的种植密... 详细信息

棉花是天然纤维的重要来源。中国是世界上重要的产棉国,湖北是中国主要的棉花生产省。长江流域普遍实行两熟制,如棉花-小麦或棉花-油菜。生产利润低,耕作制度繁琐,劳动力向城市转移以及生产支出增加导致棉花种植面积减少。适宜的种植密度和氮肥施用量是棉花高效生产的关键因素。已经发现并实施了一种更好的替代栽培措施,可以降低投入成本而又不影响产量和产量构成部分从而提升效益。这种种植模式的特点是晚播和直播,高密度和低氮肥施用,这在改变当前的高成本棉花生产方面具有极大的优势。但是,在这种模式下,进一步降低人工成本的种植密度和氮肥施用量是多少呢?在华中农业大学进行了为期两年(2018-2019)的田间试验,裂区设计。2个种植密度(D,6株m、D,8株m)为主区,3个氮肥施用量(N,150 kg ha、N,180 kg ha、N,210 kg ha)为副区,4次重复。所有肥料在见花时施用。结果表明,两年内,相对于N较高的氮肥施用量(N和N),籽棉产量分别增加了7.53-15.31%、9.28-14.29%(D),或6.10-7.34%、9.34-10.86%(D)。同时,DN和DN在统计上结果相似。与D相比,D的平均籽棉产量和皮棉产量更高。其他结果总结如下:1.种植密度和氮肥施用量对两年的花铃期都有显著影响,而苗期和蕾期无差异。棉花株高,主茎节数,主茎绿叶数和果枝数也受到种植密度和氮肥施用量的显著影响。但是,营养枝在这两年中都没有受到影响。相对于D,氮肥施用量显著提高了D的叶片鲜重和叶面积,但DN和DN仍在统计学上相似。2.种植密度和施氮量显著影响棉株的光合特性。施氮量较高(N和N)可增加2个密度的净光合作用,气孔导度和蒸腾速率,但DN和DN没有差异。胞间CO浓度随密度和施氮量的增加而降低。3.棉花叶片碳氮含量受种植密度和氮肥施用量的影响。相较于N,较高氮肥(N和N)提高了各个生育时期,棉花叶片氮和碳含量,两年结果一致。相对来说,叶片碳氮含量D高于D。4.叶片蔗糖含量随氮肥用量增加而增加,但叶片淀粉含量却呈现相反趋势。同样,韧皮部渗出液中蔗糖含量,较高氮肥(N和N)较高,较高种植密度(D)较高。5.较高的氮肥(N和N)上调了核糖1、5-二磷酸羧化酶加氧酶(Rubisco)、蔗糖磷酸合酶(SPS)和蔗糖合酶(SS)的活性,但下调了可溶性酸性转化酶(SAI)、6-磷酸葡萄糖脱氢酶(G6PDH)和6-磷酸葡萄糖酸的活性。总体而言,种植密度和氮肥影响了所有酶的活性,但DN和DN之间均无差异。因此,较高氮肥施用量有利于光合作用,提高了碳代谢酶的活性,加快了光同化物转运。DN和DN的籽棉产量基本一致,DN籽棉产量也相当。因此,在新的种植模式中,DN或DN的组合可能是获得更高棉花产量并确保收益的更好选择。

关键词：棉花种植密度氮肥施用产量物候学生长和发育光合作用韧皮部蔗糖碳代谢

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