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Influence of main site factors on Fraxinus mandshurica (Oleaceae) plantation 被引量:5
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作者 苏含英 林代斌 《Journal of Forestry Research》 SCIE CAS CSCD 2003年第1期83-86,共4页
the investigation was carried out on 10-year-old plantation of Fraxinus mandshurica in Mao抏r Mountain Experimental Station of Northeast Forest University. Tree height (H), diameter at breast height (D1.3) and the inc... the investigation was carried out on 10-year-old plantation of Fraxinus mandshurica in Mao抏r Mountain Experimental Station of Northeast Forest University. Tree height (H), diameter at breast height (D1.3) and the increment of tree height in 5 years (H5), the thickness of humus layer, as well as the soil moisture were measured for the plantation and the growth indexes (H, D1.3, H5) for different site conditions were analyzed. The results showed that main site factors influencing the growth of Fraxinus mandshurica were soil moisture, gradient and location of slope in order. The growth of Fraxinus mandshurica was better on the middle- or up-slope site than on the down-slope site. Soil moisture and late frost caused by terrain are the main reasons that limit the growth of Fraxinus mandshurica plantation. 展开更多
关键词 Fraxinus mandshurica PLANTATION site factors
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QUANTITATIVE ANALYSIS OF RELATIONSHIP BETWEEN ARMILLARIA ROOT ROT AND SITE FACTORS IN PINUS RADIATA PLANTATIONS
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作者 Shu Qinglong He Min +1 位作者 Song Shumei Zhao Weizhong(Department of Forestry,Anhui Agricultural University,Hefei 230036)(School of Forestry,University of Canterbury,Christchurch,New Zealand)(Shanxi Agricultura1 University,Taigu,shanxi.) 《生物数学学报》 CSCD 北大核心 1995年第3期9-14,共6页
Incidence of Armillaria infection was quantified based on site factors in New Zealand Pinus radiata plantations.A linear multiple regression model was derived to predict infection levels of Armillaria root rot.Factors... Incidence of Armillaria infection was quantified based on site factors in New Zealand Pinus radiata plantations.A linear multiple regression model was derived to predict infection levels of Armillaria root rot.Factors positivily associated with the infection were:previous vegetation(native bush,pine);soil type(pumice);landform (valley,gully,flat)and the interaction between them.This model could assist in management planning with regard to the predisposition of particular stand to Armillaria infection.Keywods:Armillaria root rot,Disease incidence,Site factors,Quantification,Pinus radiata. 展开更多
关键词 site ROOT ROOT QUANTITATIVE ANALYSIS OF RELATIONSHIP BETWEEN ARMILLARIA ROOT ROT AND site factorS IN PINUS RADIATA PLANTATIONS
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RELATIONSHIPS BETWEEN LARCH GROWTH AND FOREST SITE FACTORS
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作者 Wang Zhcngquan (1) Wang Fenguou (1) Gong Weiguang (1) 《Journal of Northeast Forestry University》 SCIE CAS CSCD 1990年第1期42-54,共13页
Dahurian larch (Larix gmelinii Rupr.) Rupr is one of the dominant species in bothnatural and man-made forests in northeast China.Effects of site factors,including topography,soilproperties and nutrient elements(P,Ca,K... Dahurian larch (Larix gmelinii Rupr.) Rupr is one of the dominant species in bothnatural and man-made forests in northeast China.Effects of site factors,including topography,soilproperties and nutrient elements(P,Ca,K,Mg,Mn,Zn,Cu,Ag,Co and Ni)on the growth of larchwere analyzed in detail,qualitatively and quantitatively.The ordination technique was used to groupthe site factors and to classify sites for larch.Analysis indicated that height growth,diameter(DBH)and volume of the larch varied among site types and this will be of theoretical and practical signifi-canee in developing larch plantations. 展开更多
关键词 LARIX gmelinii. FOREST site site factors NORTHEAST China
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Prevalence and Risk Factors for Surgical Site Infection Following Cesarean Section in a Tertiary Care Hospital
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作者 Nafisa Ahamed Md. Alimur Reza +3 位作者 Kakali Saha Rabeya Khanom Shovana Talukder Arifa Akram 《Open Journal of Obstetrics and Gynecology》 2025年第2期261-271,共11页
Background: Cesarean sections have become increasingly prevalent in both developed and developing nations. Nevertheless, postoperative complications, including surgical site infections (SSIs), remain a substantial con... Background: Cesarean sections have become increasingly prevalent in both developed and developing nations. Nevertheless, postoperative complications, including surgical site infections (SSIs), remain a substantial concern that contributes to heightened morbidity and mortality. This study is designed to evaluate the frequency and key determining factors associated with surgical site infections following cesarean section procedures in a tertiary care hospital in Bangladesh. Materials and Methods: This observational cross-sectional study, conducted at the Gynecology Department of Dhaka Medical College Hospital, involved 100 patients aged 15 - 45 who had cesarean deliveries. Data was collected during hospitalization and post-discharge and analyzed to determine the prevalence and relationship between socio-demographic characteristics and surgical site infection. Results: Among the study participants, 14% developed surgical site infections following cesarean operations. More than half of these patients were under the age of 25, with a mean age of 24.45 ± 4.44 years. Surgical site infections were more prevalent in individuals over 30 years old (P-value Conclusion: Post-cesarean surgical site infections are notably prevalent among the participants in this study. Several risk factors have been identified, including age, body mass index (BMI), socioeconomic status, anemia, preterm delivery, personal hygiene practices, regular menstrual cycles, and adherence to antenatal check-ups. The implementation of an effective awareness program, coupled with updated antibiotic protocols, is crucial for significantly reducing the incidence of these infections. 展开更多
关键词 Surgical site Infection (SSI) Cesarean Section Risk factors
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Incidences and Risk Factors for Surgical Site Infections in Koutiala, Mali
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作者 Mahamadou Coulibaly Moussa Diassana +9 位作者 Issiaka Diarra Bréhima Bengaly Birama Togola Drissa Ouattara Souleymane Sanogo Samuel Kletigui Dembélé Cheick Aka Waigalo Brehima Ballo Drissa Traoré Nouhoum Ongoiba 《Surgical Science》 2024年第7期465-469,共5页
Purpose: This paper aims to assess the incidences and risk factors for surgical site (ISO) infections in the general surgery department of the Koutiala District Hospital. Patients and Methods: This was a prospective a... Purpose: This paper aims to assess the incidences and risk factors for surgical site (ISO) infections in the general surgery department of the Koutiala District Hospital. Patients and Methods: This was a prospective and descriptive study from August 1, 2017 to October 31, 2020 involving all patients who underwent laparotomy in the general surgery department of the Koutiala District Hospital. Patients who were not operated on and who did not have a laparotomy were not included. Age, sex, frequency, patient history, National Nosocomial Infections Surveillance (NNIS) index, time to occur, bacteriological test results and course of infection were analyzed. Results: Fifty patients were registered. The average age was 34.2 ± 21.2 years old. Eleven patients were 60 years old or older. The hospital incidence rate was 4.3% and the community incidence rate was 6.1 cases per 100,000 population. The concept of smoking was noted in 15 patients. Patients were operated on in emergency 84% of cases. Peritonitis was the most common initial lesion with 32% of cases. Our patients had an NNIS index greater than 0 in 84% of cases. The time to develop infection from the surgical site was less than 3 days in 8 patients (16% of cases). Depending on the depth of the infection, it was superficial (cutaneous) in 39 patients (78%) and deep (subcutaneous and organic) in 11 patients (22%). Escherichia coli was the most common germ with 72% followed by staphylococcus aureus at 24%. We noted 22% morbidity. The median length of hospitalization was 9 ± 2.2 days. Conclusion: ISO is common in our service. Prevention and mastery require knowledge of risk factors. 展开更多
关键词 Surgical site Infection INCIDENCE Risk factors SURGERY
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Studying the depth-dependent variation of site magnification factor in Dongchuan by earthquakes observed in borehole
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作者 罗娣华 蒋乐群 +3 位作者 陈敏恭 叶建庆 蔡少平 刘学军 《Acta Seismologica Sinica(English Edition)》 EI CSCD 2001年第1期72-81,118,共11页
The digital seismometers with high accuracy are installed at depths of -200 m, -100 m in borehole and on the surface in Dongchuan. By analysis of spectra ratio, the local events (with epicentral distances between 8.5 ... The digital seismometers with high accuracy are installed at depths of -200 m, -100 m in borehole and on the surface in Dongchuan. By analysis of spectra ratio, the local events (with epicentral distances between 8.5 km and 95 km, magnitudes ML = 1.3-5.1) recorded are used to calculate site magnification factor at different depths (-100 m and surface) in Dongchuan. Comparing results with that at the depth of -200 m, the site magnification factors at three components of N-S, E-W and U-D corresponding to the depth of -100 m at 8 frequencies (f = 0.75, 1.0, 1.5, 2, 3, 4, 6, and 12 Hz) are 1.0-1.49 when 0.75 Hz- [less-than or equal to] f [less-than or equal to] 2 Hz and 0.47-0.99 when 2 Hz less than or equal f less than or equal 12 Hz. On the surface, site magnification factors at three components are all greater than 1, i.e. between 1.6 and 7.63. The correlation coefficients of site magnification factors for S wave and coda at the depth of -100 m and on surface are 0.82 and 0.81 when 0.75 Hz [less-than or equal to] f [less-than or equal to] 2 Hz, 0.47 and 0.45 when 2 Hz less than or equal f less than or equal 12 Hz, respectively. 展开更多
关键词 S wave CODA noise site magnification factor
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Identifying changes in punitive transcriptional factor binding sites from regulatory single nucleotide polymorphisms that are significantly associated with disease or sickness 被引量:1
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作者 Norman E Buroker 《World Journal of Hematology》 2016年第4期75-87,共13页
AIM To identify punitive transcriptional factor binding sites(TFBS) from regulatory single nucleotide polymorphisms(rS NPs) that are significantly associated with disease.METHODS The genome-wide association studies ha... AIM To identify punitive transcriptional factor binding sites(TFBS) from regulatory single nucleotide polymorphisms(rS NPs) that are significantly associated with disease.METHODS The genome-wide association studies have provided us with nearly 6500 disease or trait-predisposing SNPs where 93% are located within non-coding regions such as gene regulatory or intergenic areas of the genome. In the regulatory region of a gene, a SNP can change the DNA sequence of a transcriptional factor(TF) motif and in turn may affect the process of gene regulation. SNP changes that affect gene expression and impact gene regulatory sequences such as promoters, enhancers, and silencers are known as rS NPs. Computational tools can be used to identify unique punitive TFBS created by rS NPs that are associated with disease or sickness. Computational analysis was used to identify punitive TFBS generated by the alleles of these rS NPs.RESULTS r SNPs within nine genes that have been significantly associated with disease or sickness were used to illustrate the tremendous diversity of punitive unique TFBS that can be generated by their alleles. The genes studied are the adrenergic, beta, receptor kinase 1, the v-akt murine thymoma viral oncogene homolog 3, the activating transcription factor 3, the type 2 demodkinase gene, the endothetal Per-Arnt-Sim domain protein 1, the lysosomal acid lipase A, the signal Transducer and Activator of Transcription 4, the thromboxane A2 receptor and the vascular endothelial growth factor A. From this sampling of SNPs among the nine genes, there are 73 potential unique TFBS generated by the common alleles comparedto 124 generated by the minor alleles indicating the tremendous diversity of potential TFs that are capable of regulating these genes.CONCLUSION From the diversity of unique punitive binding sites for TFs, it was found that some TFs play a role in the disease or sickness being studied. 展开更多
关键词 REGULATORY single nucleotide polymorphisms Alleles TRANSCRIPTIONAL factors TRANSCRIPTIONAL factor binding sites Linkage disequilibrium DISEASE or SICKNESS
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Surgical Site Infection (SSI) in the National Referral General Hospital of Ndjamena (Chad): Survey about Risk Factors
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作者 Hassan Mahamat Ali Yeri Esther Hien +7 位作者 Cheikna Zongo Denis Erbi Ali Haroun Hissein François Tapsoba Abacar Mahamat Tahir Brahim Adoum Ahamt Yves Traore Aly Savadogo 《Journal of Biosciences and Medicines》 2021年第5期1-11,共11页
The risk to develop an infection after surgery depends on several factors. Those factors may be interdependent or not, depending on the nature of the surgery and the general condition of the patient. The aim of the pr... The risk to develop an infection after surgery depends on several factors. Those factors may be interdependent or not, depending on the nature of the surgery and the general condition of the patient. The aim of the present study was to identify the factors involved in the occurrence of the Surgical Site Infections (SSI) in the <strong><em>National referral general hospital </em></strong>of N’djamena (Chad). We first realized an interview in the emergency services and in the general surgery of the hospital. The information collected allowed us to draw up survey sheets. An investigation was then conducted on 152 patients who had surgery and were hospitalized during the study period. The frequency of the SSI was 33.6% (51/152). The main risk factors that we identified were the duration of hospitalization, the category of the hospitalization room, the urgent aspect of the surgical intervention, the patient’s nutritional status and the associated diseases with diabetes, which was present in 52.38% (11/21) of cases of associated pathologies. Analysis of the antibiotic prophylaxis administered to patients showed that ciprofloxacin was more effective in SSI prevention. Indeed, this antibiotic showed the fewest cases of infection with only 1.9% of patients having developed SSI. Our results show a very high frequency of SSI at the <strong><em>National referral general hospital</em></strong> of N’djamena. Poor hospital practices and factors associated to patients seem to be the most factors implicated in the SSI. 展开更多
关键词 Surgical site Infections Risk factors Nutritional Status Associated Diseases CHAD
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The Measurement and Uncertainty Analysis of Antenna Factor of Microwave Antennas Based on Standard Site Method
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作者 Chaochan Chen Hong Shi +1 位作者 Yi Miao Yu Sang 《International Journal of Communications, Network and System Sciences》 2017年第5期138-145,共8页
A method of Standard Site Method (SSM) in the American National Standards Institute’s ANSI C63.5 is described in the frequency ranges from 30 MHz to 1000 MHz. And a measurement system is set up for determining antenn... A method of Standard Site Method (SSM) in the American National Standards Institute’s ANSI C63.5 is described in the frequency ranges from 30 MHz to 1000 MHz. And a measurement system is set up for determining antenna factors (AF) of antennas on an Open Area Test Sites (OATS). AF of antennas including log-periodic antenna and biconical antenna is measured with SSM method by Shanghai Institute of Measurement and Testing Technology (SIMT), which shows good agreement to data measured by National Institute of Metrology (NIM). In the end, it analyzes the measurement uncertainty of SIMT in the 30 MHz to 1000 MHz frequency band and does comparison to that of NIM. 展开更多
关键词 ANTENNA factorS Standard site Method (SSM) MEASUREMENT UNCERTAINTY
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A distribution pattern assisted method of transcription factor binding site discovery for both yeast and filamentous fungi
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作者 Jinnan Hu Chenxi Chen +1 位作者 Kun Huang Thomas K. Mitchell 《Advances in Bioscience and Biotechnology》 2013年第4期509-517,共9页
Transcription factors (TFs) are the core sentinels of gene regulation functioning by binding to highly specific DNA sequences to activate or repress the recruitment of RNA polymerase. The ability to identify transcrip... Transcription factors (TFs) are the core sentinels of gene regulation functioning by binding to highly specific DNA sequences to activate or repress the recruitment of RNA polymerase. The ability to identify transcription factor binding sites (TFBSs) is necessary to understand gene regulation and infer regulatory networks. Despite the fact that bioinformatics tools have been developed for years to improve computational identification of TFBSs, the accurate prediction still remains changeling as DNA motifs recognized by TFs are typically short and often lack obvious patterns. In this study we introduced a new attribute-motif distribution pattern (MDP) to assist in TFBS prediction. MDP was developed using a TF distribution pattern curve generated by analyzing 25 yeast TFs and 37 of their experimentally validated binding motifs, followed by calculating a scoring value to quantify the reliability of each motif prediction. Finally, MDP was tested using another set of 7 TFs with known binding sites to in silico validate the approach. The method was further tested in a non-yeast system using the filamentous fungus Magnaporthe oryzae transcription factor MoCRZ1. We demonstrate superior prediction reranking results using MDP over the commonly used program MEME and the other four predictors. The data showed significant improvements in the ranking of validated TFBS and provides a more sensitive statistics based approach for motif discovery. 展开更多
关键词 Transcription factor Binding site DISCOVER Distribution Pattern SACCHAROMYCES CEREVISIAE MAGNAPORTHE ORYZAE MoCRZ1
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A Study on the Influencing Factors on Ground Motion in a Valley Site
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作者 LI Ping BO Jingshan +1 位作者 XIAO Ruijie ZHANG Yudong 《Earthquake Research in China》 CSCD 2019年第1期62-73,共12页
A trapezoid valley site is chosen as a research site,and according to numerical models based on orthogonal design,the factors influencing ground motion in the valley site are studied with two-dimensional finite differ... A trapezoid valley site is chosen as a research site,and according to numerical models based on orthogonal design,the factors influencing ground motion in the valley site are studied with two-dimensional finite difference method. The influencing factors are ranked,and then the calculation results are verified by ground motion analysis. The conclusions are as follows:there are four factors that have important effects on ground motion of trapezoid valley sites,but the effects are different as the location of sites changes,the influencing factors rank differently with different site locations; The ranking of the influencing factors is the same for all the sites located within a distance of 40m from the valley's side,among them,the most effective one is the valley slope angle ranks,followed by depth-to-width ratio,overburden thickness,at last the input ground motion intensity.The impact of the factors on surface ground motion is roughly the same in the valley sites within a certain distance to the valley side,and the geometric parameters of the valley terrain play a greater part in influencing ground motion. With the increase of distance away from the valley's side,the ranking of the influencing factors also changes,the rating of slope angle moves backward,the ranking of the input ground motion and overburden thickness move ahead. The effect of valley geometric parameters on ground motions is gradually weakened,but the effect of other two influence factors are gradually increased,similar to cases of a horizontal layered site. Strong motion records in Anning River valley site were analyzed,and the results show that the valley topography has a significant amplification effect on ground motion,and that the numerical results of this paper are credible. 展开更多
关键词 VALLEY site Ground motion FINITE DIFFERENCE Influencing factorS
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Risk Factors for Surgical Site Infections in Patients Operated at the University Clinic of Traumatology-Orthopedics and Restorative Surgery of the National Hospital and University Center Hubert Koutoukou Maga in Cotonou
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作者 Comlan Cyriaque Dégbey Charles Patrick Makoutodé +1 位作者 Narjolès Augustino Houngnandan Badirou Aguemon 《Open Journal of Epidemiology》 2023年第1期1-15,共15页
Background: Operative site infections (ISO) are typically nosocomial. According to the WHO the incidence of ISO varies from 0.5% to 15% and exceeds 25% in developing countries. They result from the combined action of ... Background: Operative site infections (ISO) are typically nosocomial. According to the WHO the incidence of ISO varies from 0.5% to 15% and exceeds 25% in developing countries. They result from the combined action of several factors and represent a concern for public health. To study the contributing factors of surgical site infections in patients operated at the University Clinic of Orthopedic Traumatology of CNHU-HKM of Cotonou. Method: This was an analytical cross-sectional study that involved 35 operated patients and ten nurses. Were included in our study: 1) All patients, without distinction of sex or age, having been operated on in the university clinic of orthopedic traumatology, during the survey period;2) Patients hospitalized for post-operative care during the survey period;3) The nursing staff on duty during our study period. The usual statistical measures were used according to the type of variables: means, standard deviations, percentages. Data analysis first involved calculating percentages for the qualitative variables and means followed by their standard deviations for the quantitative variables. Next, the Pearson Chi-square test was used to test the association between the dependent variable and the independent variables of interest. The significance level is set at p Results: The prevalence of surgical site infections was 28.58%. The main factors contributing to the occurrence of SSIs that were found were the patient’s level of education (p = 0.003) and the reuse of bandages used for dressing (p = 0.004). Other potential factors such as the economic status of the patient, the poor quality of technical dressings, and the preoperative stay were also highlighted. Conclusion: Surgical site infections remain a global concern. Risk factors were found on both the patient and nurse sides. It is urgent to address these various factors to minimize the occurrence of surgical site infections. 展开更多
关键词 Surgical site Infection Nosocomial Infections Risk factors Patient BENIN
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Risk Factors for Surgical Site Infection after Hip Arthroplasty: A Multicentric Study
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作者 Gabriel B. Tofani Gustavo P. Irffi +4 位作者 Lucas F. Silva Cynthia C. M. da Silva Bráulio R. G. M. Couto Gilberto D. Miranda Carlos E. F. Starling 《Surgical Science》 2016年第2期58-64,共7页
The objective of this study is to answer three main questions: What is the risk of wound infection for patients undergoing hip arthroplasty? What are the main etiologicagents of surgical site infection (SSI)? What are... The objective of this study is to answer three main questions: What is the risk of wound infection for patients undergoing hip arthroplasty? What are the main etiologicagents of surgical site infection (SSI)? What are the risk factors most associated with surgical site infection? Method: This was a multicentric, retrospective cohort study which analyzed data collected in five general hospitals in Belo Horizonte, Brazil, between the period of January 2009 and December 2013. The continuous parameters studied were age, length of hospital stay before surgery, duration of surgery, number of professionals at surgery and number of hospital admissions. Categorical variables were surgical wound classification (clean, clean contaminated, contaminated, dirty/infected), American Society of Anesthesiologists (ASA) score (I, II, III, IV, V), type of surgery (elective, emergency), general anesthesia (yes, no), prophylactic antibiotic (yes, no), trauma surgery (yes, no) and Nosocomial Infections Surveillance (NNIS) risk index (IRIC = 0, 1, 2, 3). Results: Estimated SSI risk was 3.2% (95% C.I. = 2.6% to 4.1%) and risk of osteomyelitis was 0.6% (95% C.I. = 0.4% to 1.1%). ASA score > 2, general anesthesia, length of hospital stay before surgery higher than four days, more than two professionals at surgical field and duration of surgery higher than five hours were risk factors for SSI after hip prosthesis (p < 0.05). The final multiple logistic regression analysis indicated that the modified NNIS risk was independently associated with surgical site infection after arthroplasty of hip. Conclusion: Despite the modified NNIS index being a risk factor for SSI, none of its independent variables was statistically significantly in the logistic model (p > 0.100). Each modified NNIS risk category increased the chance of a patient being infected by almost three times, when compared with the previous category (OR = 2.82;p = 0.011). 展开更多
关键词 Surgical site Infection Hip Arthroplasty Hip Replacement Risk factors
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Hazardous and Harmful Factors on Construction Sites and Their Prevention
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作者 ZHENG Huanqiang ZHANG Zaiwang RONG Kun 《Journal of Landscape Research》 2019年第1期20-23,28,共5页
In this paper, the status quo of safety production on construction sites and the hazardous and harmful factors in the construction process were analyzed, and corresponding suggestions were proposed to make up for the ... In this paper, the status quo of safety production on construction sites and the hazardous and harmful factors in the construction process were analyzed, and corresponding suggestions were proposed to make up for the shortcomings of the safety production assurance system standards on construction sites. 展开更多
关键词 CONSTRUCTION site Safety PRODUCTION MANAGEMENT Identification of hazardous and harmful factorS
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Risk Factor of Postoperative Lumbar Surgical Site Infection: A Literature Review
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作者 Tark Hung Chang Santosh Kumar Sah +1 位作者 Chong Zhang Xiao Tao Wu 《Open Journal of Orthopedics》 2021年第4期97-109,共13页
Nowadays there have been various advanced techniques to overcome disparate types of lumbar degenerative diseases. However, post-operation complications such as Surgical Site Infection (SSI) still give the surgeon with... Nowadays there have been various advanced techniques to overcome disparate types of lumbar degenerative diseases. However, post-operation complications such as Surgical Site Infection (SSI) still give the surgeon with a big challenge. This article is going to study the risk factor that causes the lumbar SSI by reviewing all the articles that can be assessed through PubMed, websites of science and other internet data base. Numerous articles have stated different reported prevalence rates of 0.7% to 16% for surgical site infection. This article will document the most common and significant risk factors for SSI. At last, we suggest that there should be preoperative patient screening and postoperative internal environment maintenance, this will be the best way to reduce postoperative SSI rate or prevent SSI from happening. 展开更多
关键词 Surgical site Infection (SSI) Post-Operative Lumbar Surgery Risk factor Lumbar Fusion REVIEW
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Factors influencing knowledge contribution:An empirical investigation of social networking website users
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作者 Shengli DENG Ting ZHOU Min ZHANG 《Chinese Journal of Library and Information Science》 2012年第4期37-50,共14页
Purpose: In the Web 2.0 era,leveraging the collective power of user knowledge contributions has become an important part of the study of collective intelligence. This research aims to investigate the factors which inf... Purpose: In the Web 2.0 era,leveraging the collective power of user knowledge contributions has become an important part of the study of collective intelligence. This research aims to investigate the factors which influence knowledge contribution behavior of social networking sites(SNS) users.Design/methodology/approach: The data were obtained from an online survey of 251 social networking sites users. Structural equation modeling analysis was used to validate the proposed model.Findings: Our survey shows that the individuals' motivation for knowledge contribution,their capability of contributing knowledge,interpersonal trust and their own habits positively influence their knowledge contribution behavior,but reward does not significantly influence knowledge contribution in the online virtual community.Research limitations: Respondents of our online survey are mainly undergraduate and graduate students. A limited sample group cannot represent all of the population. A larger survey involving more SNS users may be useful.Practical implications: The results have provided some theoretical basis for promoting knowledge contribution and user viscosity.Originality/value: Few studies have investigated the impact of social influence and user habits on knowledge contribution behavior of SNS users. This study can make a theoretical contribution by examining how the social influence processes and habits affect one's knowledge contribution behavior using online communities. 展开更多
关键词 Social networking sites(SNS) Network user Knowledge contribution User behavior Influencing factor
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异地研发中心设立对企业全要素生产率的影响研究
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作者 程晨 穆靖昊 后青松 《经济问题》 北大核心 2025年第3期1-13,91,共14页
在新时代中国经济高质量发展的要求下,利用2009—2023年上市公司数据样本,考察了异地研发中心设立对企业全要素生产率的影响。研究发现:企业设立异地研发中心能够显著提升其全要素生产率,并且是通过拓展技术领域和提高创新质量的路径实... 在新时代中国经济高质量发展的要求下,利用2009—2023年上市公司数据样本,考察了异地研发中心设立对企业全要素生产率的影响。研究发现:企业设立异地研发中心能够显著提升其全要素生产率,并且是通过拓展技术领域和提高创新质量的路径实现的。进一步,在大型企业、国有企业、非高新技术行业的企业以及技术能力较强的企业中,异地研发中心设立对企业全要素生产率的提升效果更加凸显。为缓解反向因果和不可观测因素引致的内生性问题,进行了基于工具变量、倾向得分匹配和双重差分模型的因果识别,并排除了市场拓展效应和融资效应的竞争性假设,研究结论依然成立。研究检验了异地研发中心设立对企业全要素生产率的促进作用,能够为企业提高全要素生产率提供经验证据,有利于政府制定鼓励企业高质量发展的政策,为经济发展注入新动能。 展开更多
关键词 异地研发中心 企业全要素生产率 知识吸收 创新质量
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基于立地、土壤养分及其交互作用的湖南杉木人工林立地指数模型
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作者 刘俊成 朱光玉 吕勇 《生态学报》 北大核心 2025年第3期1339-1350,共12页
研究林分立地因子、土壤养分因子及其交互作用对平均优势木生长的影响,分别构建含立地、土壤养分及其交互作用的立地指数模型,为杉木人工林立地质量评价提供一种新思路。基于40块湖南杉木人工林样地中平均优势木的解析木数据,采用数量... 研究林分立地因子、土壤养分因子及其交互作用对平均优势木生长的影响,分别构建含立地、土壤养分及其交互作用的立地指数模型,为杉木人工林立地质量评价提供一种新思路。基于40块湖南杉木人工林样地中平均优势木的解析木数据,采用数量化方法Ⅰ、随机森林算法、K-means聚类和非线性混合效应回归分析,确定显著影响优势高生长的立地与土壤养分因子;筛选最优基础模型并构建含立地、土壤养分及其交互效应的非线性混合立地指数模型,运用AIC、BIC和R~2等3个评价指标评价模型拟合效果,导出最优立地指数模型。结果表明:对优势木平均高影响显著的因子为:海拔、坡度、土壤类型、有机质、全氮、全钾,立地因子显著性顺序为海拔>坡度>土壤类型,土壤养分因子重要性顺序为有机质>全氮>全钾;7个候选模型中最优基础模型为坎派兹式(Gompertz)(R^(2)=0.6876,MAE=6.6922,RMSE=2.7448);构建含立地、土壤养分及其交互类型效应的混合模型精度分别提升至0.7827、0.7765、0.8400;以精度≥95%的标准聚类,构建含立地类型组、土壤养分类型组和立地-土壤养分交互类型组的混合模型精度相比基础模型分别提升了13.05%、12.52%和21.42%,相比各类型效应的混合模型AIC、BIC均有所降低。表明立地、土壤养分及其交互作用均对平均优势木生长有显著影响,含交互效应的混合模型拟合效果优于单独立地、土壤养分效应,基于立地-土壤养分交互类型组的多形立地指数曲线模拟平均优势木的生长规律更为准确,最终构建以立地-土壤养分交互类型组为随机效应的最优立地指数模型为:H_(jSSNMTG)=a_(jSSNMTG)×exp(-b×exp(-c×T_(jSSNMTG)))+ε_(jSSNMTG),可以用于湖南复杂立地条件下杉木人工林立地质量评价。 展开更多
关键词 杉木人工林 立地因子 土壤养分因子 交互作用 立地指数模型
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A stochastic based approach for a new site classification method:application to the Algerian seismic code 被引量:3
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作者 Mohamed Beneldjouzi Nasser Laouami 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2015年第4期663-681,共19页
Building codes have widely considered the shear wave velocity to make a reliable subsoil seismic classification, based on the knowledge of the mechanical properties of material deposits down to bedrock. This approach ... Building codes have widely considered the shear wave velocity to make a reliable subsoil seismic classification, based on the knowledge of the mechanical properties of material deposits down to bedrock. This approach has limitations because geophysical data are often very expensive to obtain. Recently, other alternatives have been proposed based on measurements of background noise and estimation of the H/V amplification curve. However, the use of this technique needs a regulatory framework before it can become a realistic site classification procedure. This paper proposes a new formulation for characterizing design sites in accordance with the Algerian seismic building code (RPA99/ver.2003), through transfer functions, by following a stochastic approach combined to a statistical study. For each soil type, the deterministic calculation of the average transfer function is performed over a wide sample of 1-D soil profiles, where the average shear wave (S-W) velocity, V<sub>s</sub>, in soil layers is simulated using random field theory. Average transfer functions are also used to calculate average site factors and normalized acceleration response spectra to highlight the amplification potential of each site type, since frequency content of the transfer function is significantly similar to that of the H/V amplification curve. Comparison is done with the RPA99/ver.2003 and Eurocode8 (EC8) design response spectra, respectively. In the absence of geophysical data, the proposed classification approach together with micro-tremor measures can be used toward a better soil classification. 展开更多
关键词 random field transfer function soil classification RPA99/ ver. 2003 EC8 site factor response spectrum
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大跨径悬索桥主缆线形影响因素分析
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作者 陈焕勇 张兴标 +2 位作者 姚志安 刘健 唐茂林 《世界桥梁》 北大核心 2025年第1期56-63,共8页
为提高大跨径悬索桥主缆线形的架设精度,以深中通道深中大桥为背景,进行主缆线形影响因素分析。根据国内外已建桥梁的实测数据,分析现有工艺技术条件下主缆实际制索精度;采用BNLAS软件建立该桥有限元模型,从材料参数和现场施工两方面分... 为提高大跨径悬索桥主缆线形的架设精度,以深中通道深中大桥为背景,进行主缆线形影响因素分析。根据国内外已建桥梁的实测数据,分析现有工艺技术条件下主缆实际制索精度;采用BNLAS软件建立该桥有限元模型,从材料参数和现场施工两方面分析主缆弹性模量、索股自重、温度及桥塔偏位对主缆线形的影响,计算各因素对主缆空缆各跨跨中标高的影响系数。结果表明:现有工艺条件下的制索精度无法满足标记点对位架设的精度要求;主缆弹性模量、索股自重、温度及桥塔偏位对各跨主缆线形有不同程度的影响,主缆弹性模量偏大时,各跨线形偏低,对中跨跨中标高的影响系数约为-0.1100 m/%;索股自重偏大时,中跨跨中标高偏低,影响系数约为-0.0941 m/(kN·m);温度越低,跨中标高越高,对中跨跨中标高的影响系数约为-6.266 cm/℃;桥塔纵向偏向某跨时,该跨线形偏低,桥塔塔顶标高变高时,相邻两跨线形偏高。 展开更多
关键词 悬索桥 主缆 线形 制索精度 材料参数 现场施工 影响因素 有限元法
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