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temporal evolution of scour at bridge abutments in compound channels

International Journal of Sediment Research 2022年第5期37卷 662-674页

作者： Yifan Yang Bruce W.Melville Xiaozhou Xiong Lu Wang School of Engineering The University of Waikato Risland New Zealand Department of Civil and Environmental Engineering The University of Auckland State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource and Hydropower Sichuan University

Bridge abutment-induced sediment scour in compound river channels is time-sensitive during floods, and, thus, estimating the scour rate has significance in design. In the current study, large-scale laboratory experiments were done to examine the influence of multiple factors on scour evolution,including channel geometry, bed mobility(clear-water or live-bed), and lateral(embankment intrusion) and vertical(deck submergence) flow contractions. A new method is applied for scour measurement and determination of characteristic scour trends. Results show that the nondimensional time scale is related to flow intensity and may peak before reaching the clear-water scour threshold; the corresponding equations also are derived. It is found that the use of scour countermeasures has a significant impact on the scour rate, and the existing equations for unprotected abutments have limitations. Under clear-water conditions, the scour rate is closely related to the overall flow contraction, which can be better reflected by the ratio of the approaching unit discharge to that at the bridge section. Specifically, the effect of vertical flow contraction on scour rate is more dominant than other factors. Two scour rate curves are derived to suit different structural and flow contraction types for clear-water scour. In contrast, the live-bed scour rate data are generally consistent and fall in a narrow band, showing less dependence on other factors. Finally, a new design approach is established to estimate the time scale and scour rate using the new equations proposed in this paper.

关键词： Abutment scour temporal evolution Compound channel Time scale Scour rate

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Rationale of a Cross-Sectional Descriptive Study on temporal evolution of Frequency, Risk Factors and Complications of Preeclampsia in the University Clinics of Kinshasa, DR Congo

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Open Journal of Obstetrics and Gynecology 2023年第9期13卷 1469-1477页

作者： Muela Andy Mbangama Otem Christian Ndesanzim Ambis Joëlle Lumaya Nkongolo Freddy Muamba Mubalamata Eugène-Patrick Lukusa Nkashama Bienvenu Kazadi Ndombasi Nelda Lemba Banza Jésual Lotoy Feruzi Michel Mangala Department of Gynecology and Obstetrics University Clinics of Kinshasa The Democratic Republic of the Congo

Background: Knowledge of temporal evolution of preeclampsia (PE) in its various aspects is essential in strategies to reduce maternal and perinatal morbidity and mortality. Preeclampsia is a public health problem due to maternal mortality associated with it worldwide (5.6%). Improving quality of its management is a major challenge in low-income countries where, despite progress made in this field, PE remains a major factor in maternal morbidity and mortality. Objective: To evaluate temporal evolution of frequency, risk factors and complications of PE at the University clinics of Kinshasa (UCK). Methods: Descriptive and cross-sectional study concerning minimum simple size of 119 pregnant women who consulted for antenatal care at the University clinics of Kinshasa from January 2012 to December 2022. Results will be reported as percentage proportion, mean and standard deviation. Comparison of proportion and means between groups will be made using Student’s t-test and Pearson’s chi-square test, respectively. The test will be statistically significant for a p value ≤ less than 0.05. Data will be collected and analysed anonymously and confidentially. Conclusion: This study will allow us to evaluate the effectiveness of different prevention and treatment modalities used over time in management of preeclampsia in our setting.

关键词： temporal evolution Preeclampsia Frequency Risk Factors Complications

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Settling and spreading behaviour of particle clusters in quiescent liquids in confined vessels

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Particuology 2023年第12期83卷 91-100页

作者： Sayan Pal Amol A.Kulkarni Chemical Engineering&Process Development Division CSIR-National Chemical LaboratoryPune411008India Academy of Scientific and Innovative Research(AcSIR) Ghaziabad 201002India University College London Torrington PlaceLondonWC1E 7JEUK

Here we report experiments on particle cluster settling at high Reynolds number in quiescent liquid contained in a *** particles were observed to spread at the vessel bottom surface in a near-circular annular shape after settling irrespective of the shape of the vessel cross-section and particle shape,size,and *** of different parameters such as mass,type and aspect ratio of the particles,height,and viscosity of liquid was investigated on spreading *** of the hemispherical bottom cap of the cluster that bounces upon hitting the vessel bottom surface was found to be responsible for the final circular annular shape of the settled *** leakage from the cluster was seen in the form of a *** the liquid having viscosity beyond 100 cP,cluster breakage was observed that resulted in hindered settling and asymmetric shapes of finally settled *** observations are useful to understand the overall area over which settling and spreading of such clusters can be observed.

关键词： Particle cluster temporal evolution Settling Spreading

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资源型城市转型绩效评价——以陕甘宁能源富集区为例

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Journal of Geographical Sciences 2023年第11期33卷 2321-2337页

作者：文琦方杰施琳娜吴昕燕罗安梦丁金梅 School of Architecture Ningxia UniversityYinchuan 750021China School of Geography and Planning Ningxia UniversityYinchuan 750021China

Resource-based cities are important bases for resources and energy in ***,the world and the country’s sustainable development goals require them to undergo *** complexity of this transformation poses challenges for these *** study aims to evaluate the transformation performance of resource-based cities in Shaanxi,Gansu,and *** findings will help understand their capabilities and achievements in transformation and provide guidance for future transformation *** evaluate the transformation performance,this study employs the entropy weight Technique for Order of Preference by Similarity to Ideal Solution *** index system is constructed,including the industrial diversification and specialization *** indices serve as benchmarks for assessing the transformation *** period 2010–2019 is considered,and the transformation performance of resource-based cities is evaluated based on different development stages and *** results reveal the following insights:(1)Most resource-based cities demonstrate favorable transformation *** variations exist between cities,the gaps are gradually narrowing.(2)Over an extended period,the transformation performance of each city undergoes continuous changes,with high-performing areas shifting.(3)The transformation performance of resource-based cities varies significantly across different development stages.(4)An imbalance exists among the regions where resource-based cities are located,and a diffusion effect can be ***,the following enlightenment and policy suggestions are obtained:(1)exploring targeted management policies for resource-based cities;(2)fostering a dynamic and open transformation environment;(3)promoting the concept of regional cooperation in transformation;(4)improving the business environment;(5)promoting enterprise innovation;(6)establishing and improving a long-term mechanism for sustainable development and a comp

关键词： resource-based city urban transformation performance evaluation temporal evolution spatial evolution Shaanxi-Gansu-Ningxia region

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Research progress and prospect of grassland degradation based on bibliometrics analysis during 1970–2020

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Ecological Economy 2020年第4期16卷 291-306页

作者： LI Tong XU Zhi-hong SONG Xiu-fang CUI Xiao-yong WANG Yan-fen University of Chinese Academy of Sciences Beijing 100049CHINA Environmental Futures Research Institute Griffith UniversityNathanBrisbaneQLD 4111AUSTRALIA CAS Center for Excellence in Tibetan Plateau Earth Science Chinese Academy of SciencesBeijing 100101CHINA Yanshan Earth Critical Zone and Surface Fluxes Research Station Chinese Academy of SciencesBeijing 100049CHINA National Science Library Chinese Academy of SciencesBeijing 100190CHINA

To understand the research trends and areas of focus on the grassland degradation(GD),a bibliometric study based on the Science Citation Index-Expanded(SCI-E)was *** study presented a comprehensive overview of the field based on the annual papers,research areas,temporal trends in keywords,marked journals,institutions,and *** the SCI-E database,GD publications first appeared ***,we chose the study period between 1970 and *** results showed that the annual number of publications increased in exponential model,with an especially rapid increase after *** S.K.,Wang S.P.,and Liu *** the most competitive authors based on their large numbers of papers and citations.A keyword analysis indicated that“grazing,alpine grassland,soil carbon and nitrogen,plant diversity,vegetation restoration”was the most popular study *** institution with the greatest research publications and most citations was the Chinese Academy of *** of Arid Environments was one of the most popular journals for researchers to publish their research and had greater influence in the field with larger citations than other *** science and ecology,soil science,plant science,biodiversity protection,geoscience,and water resources were the most popular Web of Science research *** keywords knowledge map mainly divides into four clusters,which are“vegetation”,“soil carbon”,“climate change”,and“grazing”.The ten clusters of the author’s co-occurrence analysis showed that the research areas of GD mainly concentrate on alpine grassland of Qinghai Tibetan Plateau and temperate steppe of Inner *** under global climate change and the increasing human activities,they were continually increasing close attention to the *** research methods are mainly in the combination of micro and macro view,such as high-throughput sequencing of the microbial community,remote sensing,quantitative analysis of models,*** current inter

关键词： grassland degradation temporal evolution network bibliometrics system analysis

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Nonstandard Unitary Transformations of Quantum States

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Journal of Applied Mathematics and Physics 2023年第9期11卷 2568-2575页

作者： Gombojav O. Ariunbold Department of Physics and Astronomy Mississippi State University Starkville MS USA

In quantum optics, unitary transformations of arbitrary states are evaluated by using the Taylor series expansion. However, this traditional approach can become cumbersome for the transformations involving non-commuting operators. Addressing this issue, a nonstandard unitary transformation technique is highlighted here with new perspective. In a spirit of “quantum” series expansions, the transition probabilities between initial and final states, such as displaced, squeezed and other nonlinearly transformed coherent states are obtained both numerically and analytically. This paper concludes that, although this technique is novel, its implementations for more extended systems are needed.

关键词： Taylor Series Unitary Transformation temporal evolution Displaced State Coherent State Squeezed State Two-Mode Squeezed State Holstein-Primakoff State

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Size characteristics and aging of airborne SiO2 nanoparticles

Size characteristics and aging of airborne SiO2 nanoparticle...

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第十二届全国气溶胶会议暨第十三届海峡两岸气溶胶技术研讨会

作者： Youfeng Wang Guanglu Ge Lan Chen Guolan Tian National Center for Nanoscience and Technology

Exposure to airborne nanoparticles in the occupational setting has been considered as a potential hazard, and has drawn much attention in research. The temporal evolution of airborne nanoparticles and the associated mechanisms need to be understood in order to design better control and protection. In this study, size characteristics and aging of airborne SiO 2 nanoparticles are investigated in a 1.2 m3 chamber under still conditions. The effects of coagulation and surface deposition are quantitatively assessed by measuring particle loss rates and calculating deposition velocity and coagulation coefficient parameters. To simulate workplace environment, the initial SiO 2 nanoparticle concentrations cover the range from 2.16 × 103 cm-3 to 1.79 × 105 cm-3. The results show that the overall loss rates are from 6.97 × 10-5 s-1 to 8.07 ×10-4 s-1. It was revealed that particle loss rates due to coagulation dominate with the fraction over 58%. Finally, it is interesting to find that the evolution of particle size with time is following d /3tefor lognormal-distribution nanoparticles. These findings suggest that the coagulation mechanism may be of more significance in terms of nanoparticles even with lower concentrations in certain workplace environment.

关键词： temporal evolution surface deposition coagulation particle size distribution

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Features of the Three Dimensional Structures in the Pacific Sub-surface Layer in Summer

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Journal of Atmospheric Science Research 2020年第2期3卷 1-10页

作者： Luyuan Chen Rong Cheng Feimin Zhang Kai Yang Chenghai Wang Research and Development Center of Earth System Model(RDCM) Lanzhou UniversityKey Laboratory of Arid Climate Change and Disaster Reduction of Gansu ProvinceCollege of Atmospheric SciencesLanzhou UniversityLanzhouGansu730000China

The anomaly of the summer sea temperature is analyzed by a spatial-temporal synthetically rotated Empirical Orthogonal Function(REOF)at three different depths(0 m,40 m,and 120 m)over the area 110°E^100°W and 30°S^60°*** spatial-temporal distribution shows that the“signal”of annual anomaly is stronger in the sub-surface layer than the surface layer,and it is stronger in the eastern equatorial Pacific than in the western *** spatial structure of the sea temperature anomaly at different layers is related to both the ocean current and the interaction of ocean and *** temporal changing trend of the sub-surface sea temperature in different areas shows that the annual mean sea temperature increases and the annual variability evidently increases since the 1980s,and these keep the same trend with the increasing El Nino phenomenon very well.

关键词： Pacific sea temperature Spatial structure temporal evolution

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