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Improve Strategy for Transient Power Angle Stability Control of VSG Combining Frequency Difference Feedback and Virtual Impedance

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Energy Engineering 2025年第2期122卷 651-666页

作者： Dianlang Wang Qi Yin Haifeng Wang Jing Chen Hong Miao Yihan Chen Substation Management office Qujing Bureau of CSG EHV Power Transmission CompanyQujing655000China College of Electrical Engineering SichuanUniversityChengdu610065China

As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become *** view of the situation that the grid impedance ratio(R/X)is high and affects the transient power angle stability of VSG,this paper proposes a VSG transient power angle stability control strategy based on the combination of frequency difference feedback and virtual *** improve the transient power angle stability of the VSG,a virtual impedance is adopted in the voltage loop to adjust the impedance ratio R/X;and the PI control feedback of the VSG frequency difference is introduced in the reactive powervoltage link of theVSGto enhance the damping ***-orderVSGdynamic nonlinearmodel considering the reactive power-voltage loop is established and the influence of different proportional integral(PI)control parameters on the system balance stability is ***,the impact of the impedance ratio R/X on the transient power angle stability is presented using the equal area *** the simulations,during the voltage dips with the reduction of R/X from 1.6 to 0.8,Δδ_(1)is reduced from 0.194 rad to 0.072 rad,Δf_(1)is reduced from 0.170 to 0.093 Hz,which shows better transient power angle *** results verify that compared with traditional VSG,the proposedmethod can effectively improve the transient power angle stability of the system.

关键词： Transient synchronous stability virtual synchronous generator impedance ratio

Use of Human Excreta as Manure in Rural China

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Journal of Integrative Agriculture 2014年第2期13卷 434-442页

作者： LIU Ying HUANG Ji-kun Precious Zikhali School of Economics and Management Beihang University Center for Chinese Agricultural Policy Institute of Geographical Sciences and Natural Resources ResearchChinese Academy of Sciences International Water Management Institute Southern Africa Regional Office

Empirical research has shown that the use of manure significantly improves crop yield, soil fertility and water and moisture conservation. Despite these documented benefits, however, there is a concern on the downward trend of manure use in agriculture in China. This paper examines factors contributing to this downward trend, with a particular focus on human excreta used in agriculture. Empirical analysis based on data from stratified random sampling of rural households in five provinces of China shows that about 85% of human excreta was still used as manure in agriculture in 2007 which was less than a decade ago when nearly all human excreta was used as manure. Econometric results suggest that income growth, rising population density and improvement in rural transportation significantly contribute to declining use of human excreta as manure in agriculture. These results imply that the current downward trend will continue given China＇s rising economic growth, urbanization and rural infrastructural improvement.

关键词： manure human excreta recycling China

Estimation of Economic Value of Agroforestry Systems at the Local Scale in eastern Sudan

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Journal of Geoscience and Environment Protection 2015年第9期3卷 38-56页

作者： Bashir Awad El Tahir Akshay Vishwanath Freelance Consultant Agroforestry and Ecosystems Analysis El Obeid Sudan People and Landscapes Programme Eastern and Southern Africa Regional Office (ESARO) International Union for Conservation of Nature (IUCN) Nairobi Kenya

The objective of this paper is to institute farmers’ own perceptions of the on-and off-farm benefits of agroforestry systems (AFS). Using use value approach, this paper presents empirical evidence on the use values of three types of AFS practiced by the refugees and their hosting communities in eastern Sudan. The total economic value (TEV) was applied as a framework to estimate the ecosystem values of AFS under study. Goods values were estimated using specific market values, while the services values were qualitatively described according to local perceived values of the local communities. Perceived TEV of AFS includes marketable and non-marketable goods and services. The main direct marketable and sustainable high value products include: food, cash crops, firewood, gum, fodder, NTFPs medicine, fodder, and honey. The valuation results reveal that AFS in the project sites have significantly contributed to the livelihoods of the local communities. Overall, the average net direct-use value of marketable products across all sites was estimated at 7,346,000.0 SDG (1,335,636.36 US$) HH/annum. Gum Arabic alone accounted for 38%, followed by sorghum grain and fodder 35%, and cash crops (sesame) 18%. This value would be many time higher if other indirect values (non-marketable) services such as shade, aesthetic and recreation, environmental protection, biodiversity and carbon sequestration are quantified. The goods and services mentioned above provide sustainable income to the farmer directly and viable benefits to the region indirectly. Hence, AFS in the study sites shows the way to reconcile two conflicting goals: short-term food and livelihood needs with long-term environmental conservation and improvement. The study provides evidence that the high local perceived values of AFS in the study sites constitute a central means of livelihood, whereas its contribution to the local economy. The study stresses the need to quantify the monetary values of non-marketed products to c

关键词： Local Perceived Values Marketable Products Natural Products Gum Arabic Non-Timber Forest Products

Market and Value Chain Analyses of Marketable Natural Products from Agroforestry Systems in eastern Sudan

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Journal of Geoscience and Environment Protection 2015年第9期3卷 57-73页

作者： Bashir A. El Tahir Akshay Vishwanath Freelance Consultant Agroforestry and Ecosystems Analysis El Obeid Sudan People and Landscapes Programme Eastern and Southern Africa Regional Office (ESARO) International Union for Conservation of Nature (IUCN) Nairobi Kenya

The objectives of the present study were: 1) to identify the prioritized marketable natural products (NPs) from agroforestry systems (AFS), and 2) to conduct market value chain analyses of the most important and prioritized NPs to identify markets and marketing channels;actors, functions and characteristics;constraints and opportunities to entry and growth;opportunities for value addition, and conduct analysis of strengths, weaknesses, opportunities and threats (SWOT analysis). The study was conducted in the Refugees’ camps and their hosting communities in eastern Sudan. Using the participatory value chain analysis (PVCA) approach, it was found that communities in the project sites obtained a multiplicity of NPs for sustenance and for increasing their incomes. Eight products were identified and ranked as the most important NPs with greatest opportunities for enterprise development at the community level. These are: gum Arabic, honey, fodder, non-timber forest products (NTFPs) and tree seeds. Gum Arabic has been shown to score higher ranks in terms of a) marketability b) ecological suitability (availability), c) social suitability, and d) potential for value addition. The results show that marketing of gum Arabic in the study site is characterized by a large number of producers and relatively few traders and companies work through seven marketing channels. The results demonstrate that in the customary marketing channel there is an upward skewed benefit distribution among the value chain actors. The total relative commercialization margin was 80% indicating that “traders” accrued higher proportion, while “producers”, receive less income (20%) of the end market price. Poor land security, one-sided prices, taxes and levies, lack of finance and appropriate skills are major impediments to gum commodity growth and development. One of the most important opportunities for growth and entry of Gum Arabic are: it is natural organic product and thus well-fit for fair trade, envi

关键词： Gum Arabic Agroforestry Systems Value Chain Sudan Natural Products

Investigation of spatiotemporal distribution and formation mechanisms of ozone pollution in eastern Chinese cities applying convolutional neural network

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Journal of Environmental Sciences 2025年第2期148卷 126-138页

作者： Qiaoli Wang Dongping Sheng Chengzhi Wu Xiaojie Ou Shengdong Yao Jingkai Zhao Feili Li Wei Li Jianmeng Chen 无 College of Environment Zhejiang University of TechnologyHangzhou 310032China Key Laboratory of Biomass Chemical Engineering of the Ministry of Education Institute of Industrial Ecology and EnvironmentCollege of Chemical and Biological EngineeringZhejiang University(Zijingang Campus)Hangzhou 310027China Trinity Consultants Inc.(China office)Hangzhou 310012China Zhejiang University of Science&Technology Hangzhou 310023China

Severe ground-level ozone(O_(3))pollution over major Chinese cities has become one of the most challenging problems,which have deleterious effects on human health and the sustainability of *** study explored the spatiotemporal distribution characteristics of ground-level O_(3) and its precursors based on conventional pollutant and meteorological monitoring data in Zhejiang Province from 2016 to ***,a high-performance convolutional neural network(CNN)model was established by expanding the moment and the concentration variations to general ***,the response mechanism of O_(3) to the variation with crucial influencing factors is explored by controlling variables and interpolating target *** results indicated that the annual average MDA8-90th concentrations in Zhejiang Province are higher in the northern and lower in the *** the wind direction(WD)ranges from east to southwest and the wind speed(WS)ranges between 2 and 3 m/sec,higher O_(3) concentration prone to *** different temperatures(T),the O_(3) concentration showed a trend of first increasing and subsequently decreasing with increasing NO_(2) concentration,peaks at the NO_(2) concentration around 0.02mg/m^(3).The sensitivity of NO_(2) to O_(3) formation is not easily affected by temperature,barometric pressure and dew point ***,there is a minimum IRNO_(2) at each temperature when the NO_(2) concentration is 0.03 mg/m^(3),and this minimum IRNO_(2) decreases with increasing *** study explores the response mechanism of O_(3) with the change of driving variables,which can provide a scientific foundation and methodological support for the targeted management of O_(3) pollution.

关键词： Ozone Spatiotemporal distribution Convolutional neural network Ozone formation rules Incremental reactivity

Heightened risk of unintended pregnancy among sex workers and sex worker organizations’response during the stringent COVID-19 containment measures in East and southern africa

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China Population and Development Studies 2023年第1期7卷 37-47页

作者： Innocent Modisaotsile Maria Stacey Willis Odek Daughtie Ogutu Rosemary Kindyomunda UNFPA regional office for East and southern africa JohannesburgSouth Africa Independent Consultant Cape TownSouth Africa africa Key Population Experts Group-AKPEG NairobiKenya

The UNFPA 2022 State of the World Population(SWOP)report recognises that certain populations of young women and girls are at a higher risk of unintended pregnancy,but did not adequately address the grave situation of female sex workers(FSWs),who experience the worst sexual and reproductive health outcomes,especially during humanitarian *** study assesses the risks of unintended pregnancy among FSWs and sex worker organizations?response during the stringent COVID-19 containment measures in East and southern africa(ESA).A mixed-methods approach consisting of a desk review,key informant interviews and an online survey was used for data *** informants and survey respondents included representatives of sex worker-led organisations and networks,organisations providing services to sex workers,development partners,advocacy organisations and donors,with priority given to key informants who had direct experience of providing services to sex workers during the COVID-19 *** total,21 key informants were interviewed and 69 respondents participated in the online survey,with representation from 14 out of 23 countries in the ESA *** study findings show that the disruption to livelihoods and threats to human rights occasioned by the stringent COVID-19 containment measures intersected with sex workers’access to contraception and risk of unintended ***ing to the uncertain future of humanitarian crises,the study concludes by outlining critical issues that need to be addressed to ensure resilience of SRHR services for populations in vulnerable positions,such as sex workers.

关键词： COVID-19 Female Sex Workers SRHR Unintended pregnances Access

Prevalence and risk factors of postpartum depression in a populationbased sample of women in Tangxia Community,Guangzhou

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Asian Pacific Journal of Tropical Medicine 2014年第3期7卷 244-249页

作者： Ai-Wen Deng Ri-Bo Xiong Ting-Ting Jiang Ying-Ping Luo Wang-Zhong Chen Department of Rehabilitation the Third Affiliated Hospital of Southern Medical University Editorial office of Journal of southern Medical University

Objective:To investigate the prevalence and analyze the risk factors of postpartum depression(PPD)in Tangxia ***,a community representative of the process of urbanization in ***:A total of 1 823 delivery women in Tangxia *** were screened with the Chinese Version of Edinburgh Postnatal Depression Scale,Hamilton Depression Scale and Social Support Rating *** risk factors were evaluated by self-made questionnaire based on literature interview combined with expert *** data collected were analyzed using Student's t test and logistic regression in ***:The prevalence of PPD in Tangxia Community,Guangzhou was 27.37%.Mutivariant logistic regression analysis identified mode of delivery,puerperanl from one-child family,relationship between mother-in-law atul daughter-in-law and fetus gender as the risk factors of PPD while housing condition was negatively correlated with the incidence of PPD with OR value of *** the total score of social support rating scale,the score of objective support,subjective support and social utilization degree were significantly reduced in women with PPD in contrast with women without ***:The incidence of PPD was slightly higher than other regions of ***'s of great importance to distinguish risk factors in regional culture context and develop health promotion program in order to enhance the well-being of delivery women.

关键词： Postpartum depression Prevalence Risk factors

Application of neutron imaging in observing various states of matter inside lithium batteries

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National Science Review 2023年第11期10卷 192-208页

作者： Lei Gao Songbai Han Haijin Ni Jinlong Zhu Liping Wang Song Gao Yonggang Wang Dubin Huang Yusheng Zhao Ruqiang Zou School of Materials Science and Engineering Peking University Academy for Advanced Interdisciplinary Studies Southern University of Science and Technology Department of Physics Southern University of Science and Technology eastern Institute for Advanced Study

Lithium batteries have been essential technologies and become an integral part of our daily lives, powering a range of devices from phones to electric vehicles. To fully understand and optimize the performance of lithium batteries, it is necessary to investigate their internal states and processes through various characterization methods. Neutron imaging has been an indispensable complementary characterization technique to X-ray imaging or electron microscopy because of the unique interaction principle between neutrons and matter. It provides particular insights into the various states of matter inside lithium batteries,including the Li+concentration in solid electrodes, the Li plating/stripping behavior of Li-metal anodes,the Li+diffusion in solid ionic conductors, the distribution of liquid electrolytes and the generation of *** review aims to highlight the capabilities and advantages of neutron imaging in characterizing lithium batteries, as well as its current state of application in this field. Additionally, we discuss the potential of neutron imaging to contribute to the ongoing development of advanced batteries through its ability to visualize internal evolution.

关键词： lithium battery neutron imaging electrodes electrolytes

An in-depth understanding of the role and mechanisms of T cells in immune organ aging and age-related diseases

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Science China(Life Sciences) 2025年第2期68卷 328-353页

作者： Yudai Xu Zijian Wang Shumin Li Jun Su Lijuan Gao Junwen Ou Zhanyi Lin Oscar Junhong Luo Chanchan Xiao Guobing Chen Department of Microbiology and Immunology School of MedicineInstitute of Geriatric ImmunologySchool of MedicineJinan UniversityGuangzhou 510632China Key Laboratory of Viral Pathogenesis&Infection Prevention and Control(Jinan University) Ministry of EducationGuangzhou 510632China Guangdong-Hong Kong-Macao Great Bay Area Geroscience Joint Laboratory School of MedicineJinan UniversityGuangzhou 510632China First Affiliated Hospital Jinan UniversityGuangzhou 510630China Anti Aging Medical Center Clifford HospitalGuangzhou 511495China Guangdong Provincial People’s Hospital(Guangdong Academy of Medical Sciences) Southern Medical UniversityGuangzhou 510080China Department of Systems Biomedical Sciences School of MedicineJinan UniversityGuangzhou 510632China The Sixth Affiliated Hospital of Jinan University(Dongguan eastern Central Hospital) Jinan UniversityDongguan 523000China Zhuhai Institute of Jinan University Jinan UniversityZhuhai 519070China

T cells play a critical and irreplaceable role in maintaining overall ***,their functions undergo alterations as individuals *** is of utmost importance to comprehend the specific characteristics of T-cell aging,as this knowledge is crucial for gaining deeper insights into the pathogenesis of aging-related diseases and developing effective therapeutic *** this review,we have thoroughly examined the existing studies on the characteristics of immune organ ***,we elucidated the changes and potential mechanisms that occur in T cells during the aging ***,we have discussed the latest research advancements pertaining to T-cell agingrelated *** findings provide a fresh perspective for the study of T cells in the context of aging.

关键词： T cell aging immune organ age-related diseases