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New Resolution to Coupling Loss Factor of Beam Plate Structure
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作者 刘景泉 姚德源 《Journal of Beijing Institute of Technology》 EI CAS 2000年第3期267-272,共6页
The transmission of transverse vibrational energy of a vertically rigid beam plate coupled structure is analyzed to get the theoretical results of coupling loss factor(CLF), a very important parameter in statistical ... The transmission of transverse vibrational energy of a vertically rigid beam plate coupled structure is analyzed to get the theoretical results of coupling loss factor(CLF), a very important parameter in statistical energy analysis(SEA). The modal analysis method is used to discuss the vibration energy of the typical model, as well as the power flow between the two subsystems. Furthermore, the resolution to the coupling loss factor is also derived and compared with the measured values. The analytical results of the coupling loss factor agree with the measured ones fully, this new resolution is significant for the application of SEA. 展开更多
关键词 statistical energy analysis coupling loss factor modal analysis method
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Simulation of higher order modes and loss factor of a new type of 500-MHz single cell superconducting cavity at SSRF 被引量:2
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作者 YU Haibo LIU Jianfei +5 位作者 HOU Hongtao LU Changwang WEI Yelong MA Zhenyu FENG Ziqiang MAO Dongqing 《Nuclear Science and Techniques》 SCIE CAS CSCD 2011年第5期257-260,共4页
In this paper,higher order modes(HOMs) and loss factor of a new type of 500-MHz superconducting cavity is studied,by simulating its broadband HOMs damping at different positions of the ferrite HOM-absorber and differe... In this paper,higher order modes(HOMs) and loss factor of a new type of 500-MHz superconducting cavity is studied,by simulating its broadband HOMs damping at different positions of the ferrite HOM-absorber and different lengths of the ferrite.The results show that the impedance and Q value of the HOMs in transverse and longitudinal modes could be greatly reduced.The HOM longitudinal impedance could be damped to meet the requirement of SSRF beam instability threshold.The calculated loss factor of the new SC cavity was compared with cavities at SSRF.It was estimated that the HOM absorber could absorb a total power of 3.16 kW at 4-mm beam bunch length. 展开更多
关键词 损耗因子 高阶模 超导腔 光源 上海 模拟 单细胞 纵向阻抗
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Loss Factors and their Effect on Resonance Peaks in Mechanical Systems 被引量:1
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作者 Roman Vinokur 《Sound & Vibration》 EI 2023年第1期1-13,共13页
The loss factors and their effects on the magnitude and frequency of resonance peaks in various mechanical sys-tems are reviewed for acoustic,vibration,and vibration fatigue applications.The main trends and relationsh... The loss factors and their effects on the magnitude and frequency of resonance peaks in various mechanical sys-tems are reviewed for acoustic,vibration,and vibration fatigue applications.The main trends and relationships were obtained for linear mechanical models with hysteresis damping.The well-known features(complex module of elasticity,total loss factor,etc.)are clarified for practical engineers and students,and new results are presented(in particular,for 2-DOF in-series models with hysteresis friction).The results are of both educational and prac-tical interest and may be applied for NVH analysis and testing,mechanical and aeromechanical design,and noise and vibration control in buildings. 展开更多
关键词 Mechanical loss factor resonance peak ACOUSTICS VIBRATION structural failure noise NVH engineering systems
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Power Transformer No-Load Loss Prediction with FEM Modeling and Building Factor Optimization 被引量:2
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作者 Ehsan Hajipour Pooya Rezaei +1 位作者 Mehdi Vakilian Mohsen Ghafouri 《Journal of Electromagnetic Analysis and Applications》 2011年第10期430-438,共9页
Estimation of power transformer no-load loss is a critical issue in the design of distribution transformers. Any deviation in estimation of the core losses during the design stage can lead to a financial penalty for t... Estimation of power transformer no-load loss is a critical issue in the design of distribution transformers. Any deviation in estimation of the core losses during the design stage can lead to a financial penalty for the transformer manufacturer. In this paper an effective and novel method is proposed to determine all components of the iron core losses applying a combination of the empirical and numerical techniques. In this method at the first stage all computable components of the core losses are calculated, using Finite Element Method (FEM) modeling and analysis of the transformer iron core. This method takes into account magnetic sheets anisotropy, joint losses and stacking holes. Next, a Quadratic Programming (QP) optimization technique is employed to estimate the incomputable components of the core losses. This method provides a chance for improvement of the core loss estimation over the time when more measured data become available. The optimization process handles the singular deviations caused by different manufacturing machineries and labor during the transformer manufacturing and overhaul process. Therefore, application of this method enables different companies to obtain different results for the same designs and materials employed, using their historical data. Effectiveness of this method is verified by inspection of 54 full size distribution transformer measurement data. 展开更多
关键词 BUILDING factor CORE lossES FINITE ELEMENT Method Power Transformer
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On-line Monitoring of Insulation Dielectric Loss Factor Based on Balance Principle
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作者 Tianxiang CHEN Zhenhua SHAO +1 位作者 Shaozhen QIN Hong TIAN 《电力系统自动化》 EI CSCD 北大核心 2013年第21期180-183,共4页
关键词 介质损耗因数 平衡原则 在线监测 绝缘 相位误差 高精确度 电流传感器 位移传感器
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Activation of hypoxia-inducible factor 1 attenuates periapical inflammation and bone loss 被引量:23
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作者 Kimito Hirai Hisako Furusho +1 位作者 Kiichi Hirota Hajime Sasaki 《International Journal of Oral Science》 SCIE CAS CSCD 2018年第2期92-101,共10页
Hypoxia(low oxygen level) is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation... Hypoxia(low oxygen level) is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation of hypoxia-inducible factor 1(HIF-1).Hypoxia interferes degradation of HIF-1 alpha subunit(HIF-1α), leading to stabilisation of HIF-1α, heterodimerization with HIF-1 beta subunit(HIF-1β) and subsequent activation of HIF-1 pathway. Apical periodontitis(periapical lesion) is a consequence of endodontic infection and ultimately results in destruction of tooth-supporting tissue, including alveolar bone. Thus far, the role of HIF-1 in periapical lesions has not been systematically examined. In the present study, we determined the role of HIF-1 in a wellcharacterised mouse periapical lesion model using two HIF-1α-activating strategies, dimethyloxalylglycine(DMOG) and adenovirusinduced constitutively active HIF-1α(CA-HIF1 A). Both DMOG and CA-HIF1 A attenuated periapical inflammation and tissue destruction. The attenuation in vivo was associated with downregulation of nuclear factor-κappa B(NF-κB) and osteoclastic gene expressions. These two agents also suppressed NF-κB activation and subsequent production of proinflammatory cytokines by macrophages. Furthermore, activation of HIF-1α by DMOG specifically suppressed lipopolysaccharide-stimulated macrophage differentiation into M1 cells, increasing the ratio of M2 macrophages against M1 cells. Taken together, our data indicated that activation of HIF-1 plays a protective role in the development of apical periodontitis via downregulation of NF-κB, proinflammatory cytokines, M1 macrophages and osteoclastogenesis. 展开更多
关键词 CA Activation hypoxia-inducible factor attenuates periapical inflammation bone loss HIF
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Identification of Modal Loss Factor of a Sandwich Composite Structure with Polyethylene Terephthalate Core in the Aspect of Core Properties Determination
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作者 Krzysztof Marynowski Katarzyna Grochowska 《Materials Sciences and Applications》 2015年第6期473-488,共16页
Comparison of the loss factor determination methods of the sandwich composite structure with polyethylene terephthalate core in the aspect of core material rheological parameters identification was the purpose of the ... Comparison of the loss factor determination methods of the sandwich composite structure with polyethylene terephthalate core in the aspect of core material rheological parameters identification was the purpose of the study. Three frequency bandwidths n dB: 1 dB, 2 dB, 3 dB methods, the resonant amplitude method and the fit method of the response of the one degree of freedom model system are taken into considerations. Identification procedure, according to ASTM E756-2005 [1] based on experimental studies of the forced vibrations of the composite structure was presented in the paper. To determine the function of the complex shear modulus of the core material, the Nelder-Mead method is applied. Shear modulus and loss factor identification results were presented on the plots in the frequency domain. The results in a quantitative manner set the applied methods and their practical utility in order. 展开更多
关键词 Composite Material RHEOLOGICAL Fractional Model VISCOELASTICITY loss factor Shear MODULUS
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Factor value determination and applicability evaluation of universal soil loss equation in granite gneiss region
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作者 Wen-hai ZHANG Xing-nan ZHANG Zhi-dong GAO 《Water Science and Engineering》 EI CAS 2009年第2期87-97,共11页
Six types of runoff plots were set up and an experimental study was carried out to examine natural rate of soil and water loss in the granite gneiss region of northern Jiangsu Province in China. Through correlation an... Six types of runoff plots were set up and an experimental study was carried out to examine natural rate of soil and water loss in the granite gneiss region of northern Jiangsu Province in China. Through correlation analysis of runoff and soil loss during 364 rainfall events, a simplified and convenient mathematical formula suitable for calculating the rainfall erosivity factor (R) for the local region was established. Other factors of the universal soil loss equation (USLE model) were also determined. Relative error analysis of the soil loss of various plots calculated by the USLE model on the basis of the observed values showed that the relative error ranged from -3.5% to 9.9% and the confidence level was more than 90%. In addition, the relative error was 5.64% for the terraced field and 12.36% for the sloping field in the practical application. Thus, the confidence level was above 87.64%. These results provide a scientific basis for forecasting and monitoring soil and water loss, for comprehensive management of small watersheds, and for soil and water conservation planning in the region. 展开更多
关键词 granite gneiss region soil erosion universal soil loss equation factor value applicability evaluation
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Analysis on the Influence Factors of Capacitor Voltage Transformer Dielectric Loss Measurement
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作者 Yongdong Li Qing-da Meng +3 位作者 Po Yang Zheyuan Zhao Wei Zhang Zhuo Pan 《Energy and Power Engineering》 2013年第4期1240-1242,共3页
Capacitor voltage transformer (CVT), which is with simple structure, convenient maintenance, functional diversity and high impact pressure strength, is widely used. And its capacitance and dielectric loss Angle measur... Capacitor voltage transformer (CVT), which is with simple structure, convenient maintenance, functional diversity and high impact pressure strength, is widely used. And its capacitance and dielectric loss Angle measurement is an important test on testing the insulation of the equipment. This paper is mainly to introduce and discuss one of the CVT test methods——the “self excitation method”, combined with the actual situation encountered in the work, sums up and expounds the maintenance of CVT and preventive test of influence factors. 展开更多
关键词 Capacitive VOLTAGE TRANSFORMER DIELECTRIC loss the Influencing factorS
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Effects of Orlistat - induced Weight Loss on Cardiovascular Risk Factors in Obese Chinese Subjects
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作者 徐明彤 吴木潮 +3 位作者 黎锋 周淑娴 程桦 傅祖植 《South China Journal of Cardiology》 CAS 2003年第1期1-4,共4页
Objectives To observe the influence of weight loss induced by orlistat on several cardiovascular diseases risk factors in obese Chinese subjects. Methods Sixty obese Chinese patients participated in a 24 week clinical... Objectives To observe the influence of weight loss induced by orlistat on several cardiovascular diseases risk factors in obese Chinese subjects. Methods Sixty obese Chinese patients participated in a 24 week clinical trial. Participants were prescribed a slightly hypocaloric diet and exercise, then they were randomly assigned double -blind treatment with either orlistat 120 mg three times a day or placebo. Their body weight, blood pressure, fasting glucose, insulin, HbA1c, and serum lipid profile were performed before and after the weight loss intervention. Results After 24 weeks, orlistat -treated group lost more of their body weight than placebo group (6. 66 ± 0. 52 kg, 8. 44±4.08% and 1. 98 ± 0. 44 kg, 2. 44±1. 74 % , respectively, P < 0. 05) . Moreover, after treatment, orlistat - treated patients showed significant decreases in serum levels of total cholesterol, low density lipoprotein - cholesterol and high density lipoprotein - cholesterol ( P < 0.01), but in placebo group we found no change. Both systolic blood pressure and diastolic blood pressure fell significantly in orlistat - treated group. Fasting glucose and HOMA - IR in orlistat - treated group was distinctly reduced if compared with placebo group. Conclusions Weight loss resulting from orlistat treatment and slightly hypocaloric diet has produced favorable effects on several cardiovascular risk factors in obese Chinese subjects. 展开更多
关键词 Orlistat Weight loss Cardiovascular risk factors
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Investigation of Pile Construction and Productivity Loss: An Analysis of Macro Impact Factor
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作者 Minhaz Ahmed Wang Xu 《World Journal of Engineering and Technology》 2023年第4期932-964,共33页
Pile foundations are challenging to build due to subsurface obstacles, contractor ignorance, and difficulties with site planning. Given the unpredictable environment of the construction site, productivity losses durin... Pile foundations are challenging to build due to subsurface obstacles, contractor ignorance, and difficulties with site planning. Given the unpredictable environment of the construction site, productivity losses during pile work are to be thought possible. Prior to finishing a site pre-investigation, a foundation’s area is usually sampled for statistical reasons. There are studies on pile construction outside of Bangladesh that are supported by relevant empirical data in the literature. Since Bangladesh, which is regarded as a third-world country, is ignored in this regard, the literature currently available about pile building and the associated productivity loss is unable to provide adequate information or appropriate empirical data. Due to this pile-building sector in Bangladesh has been experiencing a decline in production for quite some time now. Before attempting to increase productivity in pile construction, it is essential to investigate the potential losses and the variables that might have an influence. This study aims to accomplish the following objectives: 1) identify the primary factors that have an impact on pile construction;2) develop an SVR model that accurately predicts productivity loss;and 3) figure out the projected loss by basing it on the historical scenario that is the most comparable to the current one. A Support Vector Regression (SVR) model was developed after a study of the relevant literature. This model enabled the collection of 110 pile building projects from five significant locations in Bangladesh. The model was constructed using a list of eight inputs in addition to a list of five macro elements (labor, management, environment, material, and equipment) (soil condition, pile type, pile material, project size, project location, pile depth, pile quantity, and equipment quantity). Using 10-way cross validation, the SVR achieves an accuracy of 87.2% in its predictions. On the basis of what has occurred in the past, we are able to estimate that there will be a loss of around 18.55 percent of the total output. A new perspective for engineers studying the delay factors with productivity loss is provided by the outcome of important tasks as it relates to loss in productivity and overall factors faced. In the building construction industry, effective management should place more emphasis on the correlation between productivity loss and the factors that cause it. Therefore, to represent the effect on productivity loss, real factors can be summed up as a decline in productivity loss. The findings of the study would urge specialists to concentrate on waste as a means of increasing overall production. 展开更多
关键词 Productivity loss Macro-Effect factor Pile Construction Regression Model SVR Model
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Sensitivity of Pion versus Parton-Jet Nuclear Modification Factors to the Path-Length Dependence of Jet-Energy Loss at RHIC and LHC
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作者 Barbara Betz Miklos Gyulassy 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第12期30-34,共5页
We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a patton-jet nuclear modification factor at RHIC and LHC, and contrast the predictions based on a linear pQCD and a... We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a patton-jet nuclear modification factor at RHIC and LHC, and contrast the predictions based on a linear pQCD and a highly non-linear hybrid AdS holographic model of jet-energy loss. It is found that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In the case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extracted data can be characterized without a reduced jet-medium coupling at LHC energies. It is concluded that when the reconstructed jets are sensitive to both quarks and gluons and thus provide more information than the pion nuclear modification factor, their information regarding the jet-medium coupling is limited due to the superposition with NLO and medium effects. Hence, a detailed description of the underlying physics requires both the leading hadron and the reconstructed jet nuclear modification factor. Unfortunately, the results for both the pion and the parton-jet nuclear modification factor are insensitive to the jet-path dependence of the models considered. 展开更多
关键词 LHC Sensitivity of Pion versus Parton-Jet Nuclear Modification factors to the Path-Length Dependence of Jet-Energy loss at RHIC and LHC
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Navigating Silence: A Comprehensive Review of Parental Roles in the Rehabilitation of Children with Hearing Loss
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作者 Kondwani Hamanjila Marirajan Thiruppathi Harrison Phiri 《Open Journal of Pediatrics》 2024年第2期364-378,共15页
This narrative literature review delves into the multifaceted realm of parental involvement in the rehabilitation of children with permanent hearing loss. While existing research has made strides in elucidating parent... This narrative literature review delves into the multifaceted realm of parental involvement in the rehabilitation of children with permanent hearing loss. While existing research has made strides in elucidating parental roles in this context, critical gaps persist, necessitating a comprehensive exploration to inform future endeavors. Our review synthesizes a wide array of studies, identifying these gaps and emphasizing the significance of addressing them. Themes emerging from the literature include the varying degrees of parental engagement, the impact of cultural and socio-economic factors, and the challenges faced by families navigating rehabilitation processes. The synthesis of this literature not only highlights the current state of knowledge but also provides a roadmap for future research efforts. By addressing these gaps, we aim to contribute to a more nuanced understanding of parental involvement in the rehabilitation of children with permanent hearing loss, ultimately fostering improved support systems and holistic care for affected families. 展开更多
关键词 Parental Involvement REHABILITATION CHILDREN Permanent Hearing loss Socioeconomic factors Cultural Influences
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Selective deletion of the soluble Colony-Stimulating Factor 1 isoform in vivo prevents estrogen-deficiency bone loss in mice
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作者 Gang-Qing Yao Nancy Troiano +1 位作者 Christine A Simpson Karl L Insogna 《Bone Research》 SCIE CAS CSCD 2017年第4期367-374,共8页
Neutralizing CSF1 in vivo completely prevents ovariectomy (OVX)-induced bone loss in mice. There are two isoforms of CSF1, soluble (sCSF1), and membrane-bound (mCSF1), but their individual biological functions a... Neutralizing CSF1 in vivo completely prevents ovariectomy (OVX)-induced bone loss in mice. There are two isoforms of CSF1, soluble (sCSF1), and membrane-bound (mCSF1), but their individual biological functions are unclear. It had been previously reported that mCSF1 knockout (K/O) and wild type (Wt) female mice experience the same degree of bone loss following OVX. In Wt mice the expression of sCSF1 was elevated fourfold in skeletal tissue following OVX while expression of mCSF1 was unchanged. To examine the role of sCSF1 in OVX-induced bone loss, mice were engineered in which sCSF1 was not expressed but expression of mCSF1 was unaffected (sCSF1 K/O). Isoform-specific reverse transcription PCR confirmed the absence of transcripts for sCSF1 in bone tissue isolated from these animals and no circulating CSF1 was detected by ELISA. Surprisingly, there were no significant differences in bone mineral density (BMD) between sCSF1 K/O mice and Wt controls as assessed by dual-energy X-ray absorptiometry and micro-CT. However, one month after OVX, femoral, spinal and total BMD had declined by 11.2%, 8.9%, and 8.7% respectively in OVX-Wt animals as compared to Sham-OVX. In contrast OVX sCSF1 K/O mice showed changes of +0.1%, - 2.4%, and +2.3% at the same 3 sites compared to Sham-OVX sCSF1 K/O mice. These data indicate important non-redundant functions for the two isoforms of CSF1 and suggest that sCSF1, but not mCSF1, plays a key role in estrogen-deficiency bone loss. 展开更多
关键词 CSF Selective deletion of the soluble Colony-Stimulating factor 1 isoform in vivo prevents estrogen-deficiency bone loss in mice
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Evaluation of C and P Factors in Universal Soil Loss Equation on Trapping Sediment: Case Study of Santubong River 被引量:3
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作者 Kelvin K. K. Kuok Darrien Y. S. Mah P. C. Chiu 《Journal of Water Resource and Protection》 2013年第12期1149-1154,共6页
Universal Soil Loss Equation (USLE) is the most comprehensive technique available to predict the long term average annual rate of erosion on a field slope. USLE was governed by five factors include soil erodibility fa... Universal Soil Loss Equation (USLE) is the most comprehensive technique available to predict the long term average annual rate of erosion on a field slope. USLE was governed by five factors include soil erodibility factor (K), rainfall and runoff erodibility index (R), crop/vegetation and management factor (C), support practice factor (P) and slope length-gradient factor (LS). In the past, K, R and LS factors are extensively studied. But the impacts of factors C and P to outfall Total Suspended Solid (TSS) and % reduction of TSS are not fully studied yet. Therefore, this study employs Buffer Zone Calculator as a tool to determine the sediment removal efficiency for different C and P factors. The selected study areas are Santubong River, Kuching, Sarawak. Results show that the outfall TSS is increasing with the increase of C values. The most effective and efficient land use for reducing TSS among 17 land uses investigated is found to be forest with undergrowth, followed by mixed dipt. forest, forest with no undergrowth, cultivated grass, logging 30, logging 10^6, wet rice, new shifting agriculture, oil palm, rubber, cocoa, coffee, tea and lastly settlement/cleared land. Besides, results also indicate that the % reduction of TSS is increasing with the decrease of P factor. The most effective support practice to reduce the outfall TSS is found to be terracing, followed by contour-strip cropping, contouring and lastly not implementing any soil conservation practice. 展开更多
关键词 Universal Soil loss Equation Crop/Vegetation and Management factor (C) Support Practice factor (P) OUTFALL TOTAL Suspended SOLID % Reduction of TOTAL Suspended SOLID
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Integration of RUSLE Model with Remote Sensing and GIS Tools for Soil Loss Estimation in the Kubanni Drainage Basin, Zaria, Nigeria
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作者 Kenneth Onyemauche Ezenwa Reuben Jobien Jacob Sadiq Abdullahi Yelwa 《Journal of Geoscience and Environment Protection》 2024年第11期173-190,共18页
The prevalence of unwholesome land use practices and population pressure exacerbates soil loss which is worsening the problem of sedimentation of the Kubanni dam. This study was conducted at the Kubanni drainage basin... The prevalence of unwholesome land use practices and population pressure exacerbates soil loss which is worsening the problem of sedimentation of the Kubanni dam. This study was conducted at the Kubanni drainage basin covering a spatial area of 56.7 Km2 in Samaru, Zaria, Nigeria to estimate annual soil loss using the RUSLE model. Satellite images of Landsat OLI for December 2014, 2016, 2018, February, July and November 2022;soil data, rainfall data from 2010 to 2022, and DEM of 30-meter resolution were utilized for the study. All factors of the RUSLE model were calculated for the basin using assembled data. The erosivity (R-factor) was discovered to be 553.437 MJ∙mm∙ha−1∙h−1∙yr−1. The average erodibility (K-factor) value was 0.1 Mg∙h∙h∙ha−1∙MJ−1∙mm−1∙yr−1. The Slope Length and Steepness factor (LS-factor) in the basin ranged between 0% and 13.47%. The Crop Management Factor (C-factor) values were obtained from a rescaling of the NDVI values derived for the study area and ranged from 0.26 to 0.55. Support practice (P-factors) were computed from the prevalent tillage practice in the basin and ranged from 0.27 to 0.40. The soil loss amount for the Kubanni basin was found to be 28441.482 tons∙ha−1∙yr−1, while the annual soil loss for the entire Kubanni drainage basin was found to be 49780.257 tons∙yr−1. The study has demonstrated the viability of coupling RUSLE model and Remote Sensing and Geographic Information System (GIS) techniques for the estimation of soil loss in the Kubanni drainage basin. 展开更多
关键词 Soil loss Watershed Erosivity (R-factor) Erodibility (K-factor) Cover Management factor (C-factor) Slope Length and Steepness factor (LS-factor) Support Practice factor (P-factor)
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三电平辅助变流器寿命优化控制 被引量:2
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作者 向超群 杜京润 +3 位作者 孙士杰 李佳怡 范子寅 于天剑 《铁道科学与工程学报》 EI CAS CSCD 北大核心 2024年第1期328-341,共14页
辅助变流系统是动车组车辆上关键的电气组成部分,主要为空调机组、风机、照明等交流负载提供稳定的三相电源。结温是影响动车组三电平辅助变流器IGBT(Insulated-gate Bipolar Transistor)模块寿命的主要因素。为了提高动车组三电平中点... 辅助变流系统是动车组车辆上关键的电气组成部分,主要为空调机组、风机、照明等交流负载提供稳定的三相电源。结温是影响动车组三电平辅助变流器IGBT(Insulated-gate Bipolar Transistor)模块寿命的主要因素。为了提高动车组三电平中点钳位(Neutral-Point Clamped,NPC)型辅助变流器寿命,提出一种降低结温的模型预测电流控制(Model Predictive Current Control,MPCC)策略。首先,考虑传统MPCC在每个采样周期需要代入27个电压矢量循环计算,计算量较大,因此将三电平基本电压矢量划分在间隔60°的6个扇区中,通过计算电压矢量在两相静止坐标下的相角,进而判断参考电压矢量所处扇区,将备选矢量数目从27缩减至10,减少了计算量;其次,传统MPCC直接应用于动车组辅助变流器会使IGBT模块的结温较高,老化速度加快,对变流器安全稳定运行产生不可预测的损害,本文对IGBT模块的开关损耗和导通损耗进行近似等效,得到了和集射极电压、集电极电流相关的功率损耗因子。通过预测每相电流的方向,进而预测IGBT模块的开关和导通情况,动态加入功率损耗因子,并在代价函数中约束每相IGBT及其续流二极管(Free Wheeling Diode,FWD)的功率损耗,使得最优电压矢量在降低功率损耗的同时保证一定的控制性能。通过仿真与实验验证,本文所提方法相比传统MPCC策略降低了功率器件的结温,提高了变流器寿命。 展开更多
关键词 三电平中点钳位型辅助变流器 功率损耗 模型预测电流控制 损耗因子 变流器寿命
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Modeling and Analysis of Mechanical Quality Factor of the Resonator for Cylinder Vibratory Gyroscope 被引量:5
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作者 XI Xiang WU Xuezhong +1 位作者 WU Yulie ZHANG Yongmeng 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2017年第1期180-189,共10页
Mechanical Quality factor(Q factor) of the resonator is an important parameter for the cylinder vibratory gyroscope(CVG). Traditional analytical methods mainly focus on a partial energy loss during the vibration p... Mechanical Quality factor(Q factor) of the resonator is an important parameter for the cylinder vibratory gyroscope(CVG). Traditional analytical methods mainly focus on a partial energy loss during the vibration process of the CVG resonator, thus are not accurate for the mechanical Q factor prediction. Therefore an integrated model including air damping loss, surface defect loss, support loss, thermoelastic damping loss and internal friction loss is proposed to obtain the mechanical Q factor of the CVG resonator. Based on structural dynamics and energy dissipation analysis, the contribution of each energy loss to the total mechanical Q factor is quantificationally analyzed. For the resonator with radius ranging from 10 mm to 20 mm, its mechanical Q factor is mainly related to the support loss, thermoelastic damping loss and internal friction loss, which are fundamentally determined by the geometric sizes and material properties of the resonator. In addition, resonators made of alloy 3J53 (Ni42CrTiA1), with different sizes, were experimentally fabricated to test the mechanical Q factor. The theoretical model is well verified by the experimental data, thus provides an effective theoretical method to design and predict the mechanical Q factor of the CVG resonator. 展开更多
关键词 mechanical Quality factor cylinder vibratory gyroscope energy loss
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Effects of Dimensional Tolerances on the Friction Power Loss of Hydrodynamic Journal Bearing System 被引量:2
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作者 魏塬 陈照波 +1 位作者 焦映厚 徐武彬 《Journal of Donghua University(English Edition)》 EI CAS 2014年第3期266-271,共6页
According to the dimensional tolerances on hydrodynamic journal bearing system, a nonlinear oil film force model was established,and the Reynolds' equation was solved by adopting finite difference method. In order... According to the dimensional tolerances on hydrodynamic journal bearing system, a nonlinear oil film force model was established,and the Reynolds' equation was solved by adopting finite difference method. In order to fulfill different dimensional tolerances in the system,adopting 2kfactor design and using the eccentricity ratio corresponding to the stability critical curve,the effects of the friction power loss brought by the dimensional tolerances of the dynamic viscosity,bearing width,bearing diameter and journal diameter were analyzed. The effect on dynamic characteristics of the hydrodynamic journal bearing system was quantitatively analyzed,and the nonlinear dynamic analysis, modeling and calculation methods were studied while considering the manufacturing tolerances. The results show that in contrast to the impacts of the tolerances in journal diameter,dynamic viscosity and bearing width,the bearing diameter tolerance would lead to the rise in the power loss, and the dimensional tolerances have different degrees of impacts on the journal bearing system. The friction power loss decreased as the eccentricity ratio increased, and when the eccentricity ratio was 0. 695 the power loss came to the minimum.The investigation would find the best solution and reduce energy consumption,then control varieties of nonlinear dynamical behavior effectively,and provide a theoretical basis for hydrodynamic journal bearing system in parameter design. 展开更多
关键词 hydrodynamic journal bearing dimensional tolerances factor design friction power loss
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Quadratic Boost Converter: An Analysis with Passive Components Losses
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作者 Modou Badiane Prince Abdoul Aziz Honadia +1 位作者 Bernard Zouma Fabé Idrissa Barro 《Open Journal of Applied Sciences》 2021年第2期202-215,共14页
The Cascaded Connected Single Switch Quadratic Boost (C<sup>2</sup>S<sup>2</sup>-QB) is studied first from its ideal model, then with semi-real model taking into account resistive losses throug... The Cascaded Connected Single Switch Quadratic Boost (C<sup>2</sup>S<sup>2</sup>-QB) is studied first from its ideal model, then with semi-real model taking into account resistive losses through the inductors and the capacitor. The continuous conduction mode equations, describing these different models are established, taking into account losses through passive components. From these equations, the voltage gain and the efficiency are determined for the semi-real model. The voltage gain and the efficiency are then analyzed versus duty cycle and the influence of passive component losses on the performance of the quadratic boost converter is carried out for the semi-real model. It has been showed that the quality of the passive components of a converter plays an important role in the quality of the conversion. However, not all passives components affect the converter in the same way. 展开更多
关键词 Quadratic Boost lossES Gain factor EFFICIENCY
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