Sheltering effect of punched steel plate sand fences for controlling blown sand hazards along the Golmud-Korla Railway:Field observation and numerical simulation studies

Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studies have assessed the protective effect of PSP sand fences,especially through field observations.This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics(CFD)numerical simulation.The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8%and 70.8%,respectively.Moreover,the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8%and 81.1%,respectively.The sand-resistance efficiency of the double-row PSP sand fences was 65.4%.Sand deposition occurred close to the first-row sand fence;however,there was relatively little sand on the leeward side of the second-row sand fence.The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations,indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences.This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas.The output of this work is expected to improve the future application of PSP sand fences.

Local corruption and corporate cash holdings:Sheltering assets or agency conflict?

This study investigates the impact of corruption on corporate cash holdings in China. The political extraction argument predicts that firms might shelter liquid assets to avoid extraction by corrupt officials. Using data on A-shared listed firms between 2007 and 2012, we find that firms located in more corrupt regions hold less cash, supporting this hypothesis. Political resources help to diminish the risk of exploitation, reducing the extent to which liquid assets are sheltered. We find that the negative association between corruption and cash holding is more significant for non-state-owned enterprises(Non-SOEs)than for state-owned enterprises(SOEs). Moreover, the cash holdings of Non-SOEs without political connections are more sensitive to corruption than those of Non-SOEs with political connections. These findings demonstrate that expropriation by corrupt officials is an important factor driving firms to manage liquidity.

Design of Barrier-free Evacuation for Diverse Crowd on Campus Based on Evacuation Simulation: A Case Study of North China University of Technology

By using evacuation simulation technology and taking North China University of Technology as an example,the barrier-free evacuation design scheme for groups with different needs in campus environment was deeply discussed.Based on the data of building layout,population composition,road system and distribution of shelters in the school,a detailed evacuation model was constructed in the Pathfinder emergency evacuation simulation system.By the simulation during the daytime and at night,the total evacuation time of the whole school,evacuation completion time of each building,selection of evacuation paths and shelter utilization were analyzed in detail.The simulation results show that the distribution of shelters on campus is uneven,and their capacity is limited.As a result,the evacuation paths of the disabled,the elderly and children need to be adjusted frequently,which affects the overall evacuation efficiency.In view of this,the optimization strategies of road renovation and entrances of shelters and buildings were put forward from the perspective of space planning.From the perspective of emergency management,it is suggested to improve the campus evacuation infrastructure and strengthen the evacuation drill for teachers and students.These results provide a solid theoretical support for enhancing the construction of campus barrier-free environment and improving the level of emergency management.

A TWO-DIMENSIONAL NUMERICAL STUDY OF WIND SHELTERING EFFECTS OF SHELTERBELTS

Based on the dynamic and thermodynamic equations in the SBL,the protection characteristics and mech- anism of shelterbelts are numerically studied in this paper.The results are in consistent with those ob- served in fields and wind-tunnels.Research shows that the belts with a permeability of 0.3—0.4 have the maximum sheltering effects.The distance where wind speed reduces at least by 20% is at 18—19 times of tree height(H)behind belts.The protection distance reduces fast with the increase of the permeability and slowly with its decrease.The belts have weaker sheltering effects in upstream,generally beyond 6H in front of belts there are no sheltering effects.In addition,the belts with low permeability at top and high permeability at bottom have much better sheltering effects than the belts with high permeability at top and low permeability at bottom.The belts with 50% overall permeability reduce wind speed at least,by 20% at the distance of 5H on the leeward side and by 10% at 11H.When the air is unstable,the protecting effects will be reduced.For the uniform belts with a permeability of 0.35,the distance where wind speed reduces at least by 20% is 15H under the unstable air and 13H under very unstable air.The belts reduce the turbulent diffusion coefficient at the bottom of belts,but increase it at the top.

Massive Sheltering Phase Begins

The resettlement of millions of destitute earthquake victims is the government’s next priority One of the first tasks of central and local governments after the col- lapse of infrastructure following the May 12 quake has been to devise a plan to settle the victims by mobilizing all resources and setting up relief centers

Nutrient retranslocation strategies associated with dieback of Pinus species in a semiarid sandy region of Northeast China

In the semiarid sandy region of Northeast China,Mongolian pine(Pinus sylvestris var.mongolica)suffers dieback after the age of 35,while Japanese red pine(Pinus densiflora)and Chinese pine(Pinus tabuliformis)stay healthy.Foliar nutrient retranslocation reflects the nutrient conservation and utilization mechanism of plants in response to their habitats.However,the nutrient retranslocation strategies employed by three Pinus tree species to cope with nutrient limitations remain largely unknown.For this study,we investigated the seasonal variations in nitrogen(N)and phosphorus(P)concentrations of Mongolian pine,Japanese red pine,and Chinese pine plantations in terms of the green needles of all ages,senesced needles,and soil.Further,the N retranslocation efficiency(NRE),and P retranslocation efficiency(PRE),and correlations between the N:P ratios of needles and soil were analyzed.The results showed that,except for the spring NRE in 1-year-old needles of Mongolian pine,the spring NRE and PRE in 1-and 2-year-old needles of the three tree species were greater than zero.The autumn PRE was higher than zero for Mongolian pine,but lower than zero for Japanese red pine and Chinese pine.Among the three Pinus species,Mongolian pine showed greater spring PRE in 2-year-old needles,and PRE from 1-to 2-yearold needles,and from 2-year-old needles to litter.However,Japanese red pine had higher P concentrations and lower N:P ratios in senesced needles,while greater PRE was found in Chinese pine litter.Significant relationships between the N:P ratios were found in the current year and 1-year-old needles and soil in the Mongolian pine plantation,while there was an insignificant relationship between the N:P ratios of the needles and soil in the Chinese pine plantation.Thus,for Mongolian pine,the removal of P from needles in autumn,and higher P translocation from older needles under P-deficient soil may have contributed to the tree dieback.In contrast,Japanese red pine and Chinese pine stored P in their needles during autumn.Japanese red pine returned more P to the soil via litter,while Chinese pine maintained N:P homeostasis and increased P withdrawal prior to needle abscission.

Temporal and Spatial Distribution of SARS-CoV-2 Aerosols in a Large-Scale Fangcang Shelter Hospital in Shanghai,China

The coronavirus disease 2019(COVID-19)pandemic caused by frequently mutating severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has had a worldwide impact.However,detailed data on the potential aerosol transmission of SARS-CoV-2 in real-world and controlled laboratory settings remain sparse.During the COVID-19 pandemic in Shanghai,China in 2022,samples were collected in a Fangcang shelter hospital,a large-scale temporary hospital rapidly built by converting the existing National Exhibition and Convention Center(Shanghai)into a health care facility.Aerosol samples at different sites and intervals around patients and in public areas,surface samples,and pharyngeal swab samples from corresponding patients were included.Samples were tested for SARS-CoV-2 using real-time quantitative polymerase chain reaction(RT-qPCR)assays,followed by sequencing if the cycle threshold(Ct)value was<30.The positivity rate for SARS-CoV-2 in aerosol samples was high in contaminated zones(37.5%,104/277),especially around the bed(41.2%,68/165)and near ventilation inlets(45.2%,14/31).The prevalence of SARS-CoV-2 around the bed,public areas,and air inlets of exhaust vents fluctuated and was closely related to the positivity rate among patients at corresponding sampling sites.Some surface samples of different personal protective equipment from medical staff had high positivity rates.Sixty sequences of joined ORF1ab and spike genes obtained from sixty samples represented two main clusters of Omicron SARS-CoV-2.There was consistency in virus sequences from the same patient and their environment,and the detected virus sequences matched those of virus strains in circulation during the collection periods,which indicated a high likelihood of cross-contamination in the Fangcang shelter hospital.In summary,the results provide a quantitative and real landscape of the aerosol transmission of SARS-CoV-2 and a patient-centered view of contamination in large and enclosed spaces and offer a useful guide for taking targeted measures to avoid nosocomial infections during the management of SARS-CoV-2 or other respiratory virus diseases in a Fangcang shelter hospital.

A fast and practical method to pack spheres for mesh generation

Sphere packing is an attractive way to generate high quality mesh. Several algorithms have been proposed in this topic, however these algorithms are not sufficiently fast for large scale problems. The paper presents an efficient sphere packing algorithm which is much faster and appears to be the most practical among all sphere packing methods presented so far for mesh generation. The algorithm packs spheres inside a domain using advancing front method. High efficiency has resulted from a concept of 4R measure, which localizes all the computations involved in the whole sphere packing process.

Numerical modelling of nonlinear extreme waves in presence of wind

A numerical wave flume with fully nonlinear free surface boundary conditions is adopted to investigate the temporal characteristics of extreme waves in the presence of wind at various speeds. Incident wave trains are numerically generated by a piston-type wave maker, and the wind-excited pressure is introduced into dynamic boundary conditions using a pressure distribution over steep crests, as defined by Jeffreys＇ sheltering mechanism.A boundary value problem is solved by a higher-order boundary element method（HOBEM） and a mixed Eulerian-Lagrangian time marching scheme. The proposed model is validated through comparison with published experimental data from a focused wave group. The influence of wind on extreme wave properties,including maximum extreme wave crest, focal position shift, and spectrum evolution, is also studied. To consider the effects of the wind-driven currents on a wave evolution, the simulations assume a uniform current over varying water depth. The results show that wind causes weak increases in the extreme wave crest, and makes the nonlinear energy transfer non-reversible in the focusing and defocusing processes. The numerical results also provide a comparison to demonstrate the shifts at focal points, considering the combined effects of the winds and the wind-driven currents.

美国SI模式对我国大学英语教学的启示

掩蔽式教学是美国从事基础教育的学校对英语语言学习者采用的一种教学模式,它强调知识和语言并重,注重对适当的教学策略的运用。文章从SI视角下的美国Broadmor小学五年级的一次主题阅读课出发,探讨SI模式对我国大学英语教学中教师的专业和教学水平的提高、课程设置的改革等五个方面的启示,希望对大学英语教学与改革起到积极地参考作用。

Development of cork oak (Quercus suber L.) seedlings in response to tree shelters and mulching in northwestern Tunisia

The need for reforestation in cork oak （Quercus suber L.） areas is challenged by difficulties. Principal among these is herbivory of young plants, vegetative competition, and slow growth rates of cork oak seedlings. We evaluated the early development of cork oak seedlings treated using tree shelters and mulching in northwestern Tunisia. We tested three tree shelter treatments （non-vented, vented, and control） to shield seedlings from animal damage and five mulch types to control competing vegetation （Italian Stone Pine, Lentisk, combination of Italian Stone Pine and Lentisk （organic mulches）, gravel （inorganic mulch） and no mulch）. At the end of the two-year experiment, sheltered seedlings were 89-99% taller than unshelteredseedlings and had higher numbers and lengths of shoot growth flushes. In contrast, both stem diameter growth and dry weight biomass （from samples extracted after two years） were significantly reduced inside tree shelters. Root-to-shoot ratio was not significantly different in sheltered vs. unsheltered seedlings, suggesting that tree shelters do not adversely affect this parameter. Mulching alone did not favour growth, but could be beneficial when combined with tree shelters. The combination of vented tree shelters and gravel mulch was the most effective treatment for promoting diameter, height and stem volume growth.

Functional regionalization with the restriction of ecological shelter zones： A case of Zhaotong in Yunnan

Ecological shelter zones reconstruction is an ecosystem restoration and conservation project aimed to the ecological safety of nations, regions and basins. Reconstruction of ecological shelter zones of the upper reaches of the Yangtze River became one of the most important tasks of Western Development strategy. This article, taking Zhaotong as an example, studies the functional regionalization of ecological shelter zones. The study supplies a case for functional regionalization of small and medium regions whose main tasks are environment reservation. With the guidance of theories of functional regionalization, and based on the analysis of Zhaotong＇s natural, ecological and socioeconomic factors, the paper suggests five principles for factors selection. These principles include： （1） reversing order evaluation; （2） selecting main factors; （3） keeping the integrality of administrative regions of towns; and （4） making the products acceptable by local government. To analyze spatial status of selected factors, LUCC data in 2002, 1：50,000 relief maps and town-unit socioeconomic statistical data in 2004 are used. RS and GIS tools are also applied to melt traditional and modern geographical methods. This would be useful to functional regionalization research in mountainous areas. As a conclusion, the leading functional regions of ecological conservation or economic development are suggested, respectively. Zhaotong city is divided into two-level functional regions. The first-level includes three leading functional regions and they will lead developing direction of sub-regions. The second-level includes eight sub-regions, which are policy implemented regions, and will supply guidance to Zhaotong＇s ecological shelter zones reconstruction.

Non-Structural Mitigation Programs For Sediment-Related Disasters after the Chichi Earthquake in Taiwan

Following the Chichi Earthquake （ML=7.3） in 1999, sediment-related disasters, such as landslides and debris flows, have become more frequent in Taiwan. Because engineering structures cannot be fully and rapidly emplaeed, the government has initiated non-structural hazard mitigation programs. Initially, community debris flow evacuation drills were promoted in 2000. Typhoon Toraji caused numerous debris flow events in July 2001, and some communities evacuated according to the drills, significantly reducing the numbers of possible casualties. Based on that result, the government expanded the program for evacuation drills. Secondly, the early warning system created after the Chichi Earthquake will prevent many potential future casualties. Rainfall threshold values for debris flow warnings in different areas are determined from information received from local weather stations and modified for local geomorphologic situations. Real- time information is gradually being integrated to create a debris flow disaster warning system, the goal of which is to provide warnings to zones in which debris flows are likely. The warning system was launched in 2005 and has two levels of alarms： yellow and red. The final, red alarm triggers enforced evacuation. Overall, the decrease in casualties from debris flows during the decade after the Chichi Earthquake is not the result of a decrease in number or severity of sediment related disasters, but is more directly related to the gradually improved early warning and evacuation system. However, the compound hazards resulting from Typhoon Morakotin 2009 remind us of the ongoing need for improving the existing mitigation system.

SUSTAINABLE RURAL LIVELIHOOD AND ECOLOGICAL SHELTER CONSTRUCTION IN UPPER REACHES OF CHANGJIANG RIVER——Case Study of Zhaotong of Yunnan Province

Sustainable livelihood theory provides a comprehensive framework for understanding the interactions between livelihoods of peasant households and regional environment change in low-income areas. Based on field survey and 946 questionnaires from peasant household conducted in the case study area of Zhaotong, Yunnan Province, the paper has analyzed the basic characteristics of the rural livelihoods, including the asset base status, the income-generating activities, the energy consumption pattern, and the fertility behavior, in the upper reaches of the Changjiang (Yangtze) River. The micro-level findings show the conflicts among extensive agricultural development models, rural energy consumption structures heavily relying on biomass and the environment protection. The conversion of cropland to forest and grass program(CCFGP) has exerted an important influence on the livelihoods of the peasant households, but its design has given little considerations to their long-term livelihood sources, which will affect its sustainability to a great extent. From the perspective of sustainable livelihoods framework, the objectives that must be addressed in the ecological shelter construction in the upper reaches of the Changjiang River should include, first, facilitating access of peasant households to credit, technology and public services, second, encouraging the peasant households to adopt agricultural technology with environmental benefits and strengthen resources-conserving investments, and third, paying close attention to the rural energy problems and the long-term livelihood sources of the households with CCFGP. Given the weak asset base and difficulties of livelihood strategies shift, ecological shelter construction in the upper reaches of the Changjiang River will take a long time.

Evaluating the optimal porosity of fences for reducing wind erosion

Porosity is the most important parameter determining the shelter efficiency of fences. Wind measurements were made around fence models with different porosities in a wind tunnel. The optimal fence porosity is evaluated by means of Gandemer＇s method that combines the effects of wind reduction and turbulence fields on the shelter efficiency for abating wind erosion. Defining the optimal porosity must take into account of its own purposes, required shelter degree and area to be sheltered. Turbulence has profound impacts on the shelter efficiency of high degree. Two concepts： absolute optimal porosity and practical optimal porosity concerning optimal porosity are proposed. Choosing the practical optimal porosity means reducing cost without significant expense of shelter efficiency. According to the evaluation in present study, the absolute optimal porosity for providing high degree of shelter to abate wind erosion is 0.20 while the practical optimal porosity is around 0.40. Ifa less shelter degree but over wider area is required, the absolute optimal porosity ranges from 0.05 to 0.10 and the practical optimal porosity is 0.10. For any degree of shelter for abating wind erosion effectively, the fence porosity must be less than or equal 0.40.

The Relationship between Shell Morphology and Crevice Size Affecting Retreat Selection of the Keeled Box Turtle(Cuora mouhotii)

Rock crevices are important retreat sites for many reptiles.Unlike lizards and snakes,crevicedwelling turtles have rigid shells which severely limit the size and shape of crevices they are able to use.Few studies have addressed the relationship between turtle's shell morphology,behavior,and crevice size.Here,we investigate the relationship between morphology and crevice size selection in the Keeled box turtle(Cuora mouhotii).We radio tracked turtles in the field to document crevice dimensions and turtle behavior associated with crevices,and we conducted a controlled experiment in the lab to understand how a turtle's morphology influences its decision to select crevices with different dimensions.Both laboratory and field experiments demonstrate that turtles select deep and moderately wide crevices that are low enough to barely accommodate the carapace.Crevices used by turtles tend to be about 2 times as wide,1.2 times as high,and 3 times longer than the turtle's shell.Moreover,turtles tended to prefer crevices with horizontal openings in the field and position themselves head first in the crevice.We conclude that morphology,especially carapace height,influences the Keeled box turtles' decision to select specific sizes of crevice.We argue that the tendency for turtles to select crevices that come into contact with their carapace contributes to successful defense against predators,as it would be more difficult for a predator to remove a turtle when the crevice is nearly touching the turtles shell.

Occupational Carbon Monoxide Poisoning Associated with Diesel Motor Operation in an Air-raid Shelter in June 2015, Jinan City, China-An Epidemiological Investigation

Carbon monoxide （CO） is an odorless, colorless gas produced by incomplete combustion of carbonbased compounds. Exposure to CO can cause various adverse health effects ranging from headache and fatigue to coma and death. Thousands of illnesses and deaths have been documented through CO poisoning surveillance systems and accident investigations each year.

Factors Predicting Progression to Severe COVID-19: A Competing Risk Survival Analysis of 1753 Patients in Community Isolation in Wuhan, China

Most studies of coronavirus disease 2019(COVID-19)progression have focused on the transfer of patients within secondary or tertiary care hospitals from regular wards to intensive care units.Little is known about the risk factors predicting the progression to severe COVID-19 among patients in community iso-lation,who are either asymptomatic or suffer from only mild to moderate symptoms.Using a multivari-able competing risk survival analysis,we identify several important predictors of progression to severe COVID-19—rather than to recovery—among patients in the largest community isolation center in Wuhan,China from 6 February 2020(when the center opened)to 9 March 2020(when it closed).All patients in community isolation in Wuhan were either asymptomatic or suffered from mild to moderate COVID-19 symptoms.We performed competing risk survival analysis on time-to-event data from a cohort study of all COVID-19 patients(n=1753)in the isolation center.The potential predictors we inves-tigated were the routine patient data collected upon admission to the isolation center:age,sex,respira-tory symptoms,gastrointestinal symptoms,general symptoms,and computed tomography(CT)scan signs.The main outcomes were time to severe COVID-19 or recovery.The factors predicting progression to severe COVID-19 were:male sex(hazard ratio(HR)=1.29,95%confidence interval(CI)1.04–1.58,p=0.018),young and old age,dyspnea(HR=1.58,95%CI 1.24–2.01,p<0.001),and CT signs of ground-glass opacity(HR=1.39,95%CI 1.04–1.86,p=0.024)and infiltrating shadows(HR=1.84,95%CI 1.22–2.78,p=0.004).The risk of progression was found to be lower among patients with nausea or vomiting(HR=0.53,95%CI 0.30–0.96,p=0.036)and headaches(HR=0.54,95%CI 0.29–0.99,p=0.046).Our results suggest that several factors that can be easily measured even in resource-poor set-tings(dyspnea,sex,and age)can be used to identify mild COVID-19 patients who are at increased risk of disease progression.Looking for CT signs of ground-glass opacity and infiltrating shadows may be an affordable option to support triage decisions in resource-rich settings.Common and unspecific symptoms(headaches,nausea,and vomiting)are likely to have led to the identification and subsequent community isolation of COVID-19 patients who were relatively unlikely to deteriorate.Future public health and clinical guidelines should build on this evidence to improve the screening,triage,and monitoring of COVID-19 patients who are asymtomatic or suffer from mild to moderate symptoms.

Emergency Biosafety Management Practice in Laboratory of Shelter Hospital

At the end of 2019,the novel coronavirus infection outbroke in Wuhan,Hubei Province.On Feb.2,2020,Wuhan,as the worst-hit region,began to build“shelter hospital”rapidly to treat patients with mild ilness.The shelter hospital has multiple functions such as emergency treatment,surgical treatment and clinical test,which can adapt to emergency medical rescue tasks.Based on the characteristics that shelter hospital only treats patients with mild ilness,tests of shelter laboratory,including coronavirus nucleic acid detection,IgM/IgG antibody serology detection,monitoring and auxiliary diagnosis and/or a required blood routine,urine routine,C-reactive protein,calcitonin original,biochemical indicators(liver enzymes,myocardial enzymes,renal function,etc.)and blood coagulation function test etc,were used to provide important basis for the diagnosis and treatment of the disease.In order to ensure laboratory biosafety,it is necessary to first evaluate the harm level of various specimens.In the laboratory biosafety management,the harm level assessment of microorganisms is the core work of biosafety,which is of great significance to guarantee biosafety.As an emergency deployment afcted by the environment,shelter laboratory must possess strong mobility.This paper will explore how to combine the biosafety model of traditional laboratory with the particularity of shelter laboratory to carry out effective work in response to the current epidemic.

Characteristics of the soil microbial population in forest land irrigated with saline water in the desert area

The study of soil microbial populations and diversity is an important way to understanding the soil energy process.In this study we analyzed the characteristics of soil microbial populations of the Tarim Desert Highway shelter-forest,by identifying microbial fatty acids and using methods of conventional cul-tivation.The results illustrated that the amount of soil microbial activity and the diversity of soil microbial fatty acid increased significantly with the plantation age of the shelter-forest;the soil microbial population was dominated by bacteria.The fatty acids of C14︰0,C15︰0,C16︰0,C17︰0,C18︰1ω9,C18︰0,C18︰2ω6 and C21︰0 were found to be dominant soil microbial fatty acids in the shelter-forest soil.Prin-cipal analysis and regression analysis showed that(1) concentrations of fatty acids of C14︰0,C16︰0 and C18︰0 could be used as indicators of total soil microbial population;(2) soil bacteria and actinomycetes populations were closely correlated with the amount of fatty acids of C15︰0 and C17︰0;and(3) soil fungi were closely correlated with the amount of fatty acids of C18︰1ω9 and C18︰2ω6.