This paper deals with the collision of sphere shape grenades with sand media.The central issue of the article is the establishing of an empirical velocity equation of the grenade while impacting on sand that is used t...This paper deals with the collision of sphere shape grenades with sand media.The central issue of the article is the establishing of an empirical velocity equation of the grenade while impacting on sand that is used to solve motion equations of the mechanical mechanism inside the impact grenade fuze.The paper focuses on impact velocities that are lower than 5 m s^(-1).An experiment was conducted to study the velocity of the grenade while impacting on dry sand.A high-speed camera video was used to capture the grenade positions.The grenade velocity in the impact process was generated from these video data.Some types of fitting curves are used to regress the velocity equation of the grenade while interacting with the sand media and the best-fitting model is chosen.The result shows the regression curve has a high correlation with the experiment data for grenade velocities below 5 m s^(-1).The received regression equation is useful for analyzing the working ability of the inertial mechanism inside the impact grenade or analyzing and choosing the appropriate parameters of each part in the inertial mechanism to meet the required characteristics of the mechanism.展开更多
At the beginning of 2024,the cosmetic industry is bustling with prosperity and depression.On one hand,the perfume brand DOCUMENTS and the biotechnology company BIO-REGEN received financial investments.The medical comp...At the beginning of 2024,the cosmetic industry is bustling with prosperity and depression.On one hand,the perfume brand DOCUMENTS and the biotechnology company BIO-REGEN received financial investments.The medical company Trautec started pre-listing counseling.The first new raw material in the new year was registered.While on the other hand,the packaging material company Yiside declared bankruptcy.The beauty brand MAOGEPING failed to go public through an IPO again,after eight years’failure.Jinfa Labi,Watsons and Zhonghao Biology were all mired in recession.Hope and challenge hung over the first half month of 2024.With such a“magical”start,2024 will be definitely a year full of uncertainty.展开更多
This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that ...This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that the Co-bearing steel exhibits finer blocks and a lower ductile-brittle transition temperature than the steel without Co.Moreover,the Co-bearing steel reveals higher transformation rates at the intermediate stage with bainite volume fraction ranging from around 0.1 to 0.6.The improved impact toughness of the Co-bearing steel results from the higher dense block boundaries dominated by the V1/V2 variant pair.Furthermore,the addition of Co induces a larger transformation driving force and a lower bainite start temperature(BS),thereby contributing to the refinement of blocks and the increase of the V1/V2 variant pair.These findings would be instructive for the composition,microstructure design,and property optimization of high-strength steels.展开更多
Continuous carbon fiber reinforced silicon carbide(C/SiC)composites are often subjected to low-velocity impacts when utilized as structural materials for thermal protection.However,research on in-plane impact damage a...Continuous carbon fiber reinforced silicon carbide(C/SiC)composites are often subjected to low-velocity impacts when utilized as structural materials for thermal protection.However,research on in-plane impact damage and multiple impact damage of C/SiC composites is limited.To investigate the in-plane impact damage behavior of C/SiC composites,a drop-weight impact test method was developed for strip samples,and these results were subsequently compared with those of C/SiC composite plates.Results show that the in-plane impact behavior of C/SiC strip samples is similar to that of C/SiC composite plates.Variation of the impact load with displacement is characterized by three stages:a nearly linear stage,a severe load drop stage,and a rebound stage where displacement occurs after the impact energy exceeds its peak value.Impact damage behavior under single and multiple impacts on 2D plain and 3D needled C/SiC composites was investigated at different impact energies and durations.Crack propagation in C/SiC composites was studied by computerized tomography(CT)technique.In the 2D plain C/SiC composite,load propagation between layers is hindered during impact,leading to delamination and 90°fiber brittle fracture.The crack length perpendicular to the impact direction increases with impact energy increases,resulting in more serious 0°fiber fracture and a larger area of fiber loss.In the 3D needled C/SiC composite,load propagates between the layers during impact through the connection of needled fibers.The fibers continue to provide substantial structural support,with notable instances of fiber pull-off and debonding.Consequently,the impact resistance is superior to that of 2D plain C/SiC composite.When the 3D needled C/SiC composite undergoes two successive impacts of 1.5 J,the energy absorption efficiency of the second impact is significantly lower,accompanied by a smaller impact displacement.Moreover,the total energy absorption efficiency of these two impacts of 1.5 J is lower than that of a single 3.0 J impact.展开更多
Millet [Pennisetum glaucum (L.) R. Br. (Poaceae)] is one of the most widely consumed crops in Niger. Its production, despite the efforts of farmers, is confronted with weed problems, in particular Sesbania pachycarpa ...Millet [Pennisetum glaucum (L.) R. Br. (Poaceae)] is one of the most widely consumed crops in Niger. Its production, despite the efforts of farmers, is confronted with weed problems, in particular Sesbania pachycarpa DC. (Fabaceae). The aim of the present study in this area is to assess the impact of Sesbania pachycarpa on millet growth and yield. To achieve this objective, a completely randomized Fisher block design of twenty-four elementary plots was set up with four replications. The data collected were millet plant heights and plot yields. The data collected were subjected to analysis of variance and Duncan’s test at the 5% threshold for comparisons of mean heights and yields with the control kept clean from sowing to millet harvesting. The results showed the sensitivity of millet plants to Sesbania pachycarpa. The results revealed that the threshold density for damage could be estimated at 6 Sesbania pachycarpa plants/m2 and the critical interference period at the fourth week after sowing. This study showed that the presence of Sesbania pachycarpa influences millet yield. Indeed, the best yields were obtained in plots without Sesbania pachycarpa. Millet yield decreased with increasing Sesbania pachycarpa density. The average percentage yield reduction was 36.79%, with a minimum of 21.25% and a maximum of 80%. The findings of this study complete the efforts of developing weed control techniques in pearl millet fields densely populated with Sesbania pachycarpa.展开更多
Introduction: In Africa, care during childbirth depends on routine practices to the detriment of quality. The aim of this study was to assess the quality of delivery care at the Coronthie CMC. Methods: The study was c...Introduction: In Africa, care during childbirth depends on routine practices to the detriment of quality. The aim of this study was to assess the quality of delivery care at the Coronthie CMC. Methods: The study was carried out at the Coronthie Community Medical Center. It was a cross-sectional, descriptive and analytical study lasting 6 months, from July 01 to December 31, 2021. Parturients whose term was ≥28 SA and who agreed to participate in the study were included. Excluded were those with a term Results: The frequency of quality care is 36.7%. The average age of parturients was 28.6 ± 5 years. Most parturients (89.7%) were married women with secondary education (35%) and self-employed (32%). Pauciparous women accounted for 43.80%, and most parturients (59.8%) were delivered by Caesarean section. We found that 21.5% of parturients had developed complications. These complications were perineal trauma and post-partum haemorrhage. There were no maternal deaths, and the neonatal mortality rate was 20/1000 NV. Acute fetal distress was the main cause of perinatal death. Conclusion: Correct management of factors influencing childbirth could improve maternal and neonatal prognosis.展开更多
Background: Severe acute malnutrition (SAM) is one of the major public health problems associated with increased mortality in under-five children. In low-income countries, renal dysfunction (RD) contributes to about 3...Background: Severe acute malnutrition (SAM) is one of the major public health problems associated with increased mortality in under-five children. In low-income countries, renal dysfunction (RD) contributes to about 34% mortality in under-five children with severe acute malnutrition. This study aimed to determine the impacts of severe acute malnutrition on the kidney among the admitted under-five children. Methods: In this prospective longitudinal observational study, a total of 190 children aged 6 to 59 months were enrolled from Iringa and Dodoma tertiary hospitals. Socio-demographic, clinical and laboratory data were collected using a structured questionnaire. Estimated Glomerular Filtration Rate (eGFR) and urine albumin creatinine ratio (uACR) were used to determine RD. Data analysis was done using SPSS version 26 and statistical significance was assumed for factors with p-value Results: Out of 190 children with severe acute malnutrition, 36 (19%) had renal dysfunction. Factors associated with RD in malnourished children were the history of local herbs used within one week (AOR = 5.85, 95% CI [1.41, 24.319], p = 0.0152), Acute watery diarrhea with severe dehydration (AOR = 2.15, 95% CI [1.033, 4.711], p = 0.0166), and positive urine leukocytes (AOR = 19.91, 95% CI [4.09, 96.989], p = 0.0002). At three months of follow up, out of 36 children with RD, 20 (55.56%) attained full recovery, while 4 (11.11%) developed chronic kidney disease (CKD). Children with RD had prolonged hospital stays for more than 14 days with a mean 12.25 ± 5.00 days compared to those with no RD with a mean 6.29 ± 1.68 days (p Conclusion: Renal dysfunction is common among children with severe acute malnutrition. It is associated with prolonged hospital stays and increased mortality. Further studies which can determine the burden of RD in children with severe acute malnutrition as compared to those with no severe acute malnutrition are needed.展开更多
Although hunting in the north-eastern Atlantic forest of Brazil began more than 500 years ago, no study to date has evaluated its impacts on the region’s mammalian fauna. For one year we carried out diurnal and noctu...Although hunting in the north-eastern Atlantic forest of Brazil began more than 500 years ago, no study to date has evaluated its impacts on the region’s mammalian fauna. For one year we carried out diurnal and nocturnal surveys using the Line Transect method in seven forest fragments varying from 7.32 ha to 469.76 ha, within a 4000 ha forest island archipelago, in Pernambuco State, Atlantic forest of northeastern Brazil. We calculated species density, population size, biomass and synergetic biomass, and recorded direct and indirect human impacts along the study transects. We recorded 44 mammalian species, of which 45.5% (n = 20) went extinct through hunting. The smallest forest fragment had the lowest richness, diversity, population size, and total biomass. It also had no synergetic biomass. The largest fragment had the highest richness, total density, and population size. There was a statistically significant relationship between fragment area and number of gunshots heard and suspended hunting platforms found;between population size and gunshots heard, suspended hunting platforms, free-roaming and feral dogs, and between total density and free-roaming and feral dogs. After more than 500 years of colonization hunting is still devastating, with larger fragments being linked to more hunters. Higher mammal abundances attracted more free-roaming and feral dogs, which have adapted to hunt wildlife on their own. Unless we protect every single forest fragment and create sustainable landscapes, we will not be able to save this hotspot’s hotspot.展开更多
Coronavirus is a Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) caused by a novel coronavirus belonging to the family Coronaviridae. The disease was first discovered in December 2019 in Wuhan City, Hubei...Coronavirus is a Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) caused by a novel coronavirus belonging to the family Coronaviridae. The disease was first discovered in December 2019 in Wuhan City, Hubei Province, China. A few months later, the disease spread all over the world and became an epidemic. The infection for most people is mild to moderate but in Vulnerable groups, if they have the infections, they might experience severe COVID-19. Saudi Arabia initiated its response plan early, and all sectors and agencies worked in an integrated way to combat the disease. It has maintained proper communication during the pandemic and ensured community involvement, epidemiologic surveillance, and activation of rapid response teams. The COVID-19 pandemic significantly affected daily lives. Schools and daycares were closed, education was online, traveling stopped, work was suspended, gathering in social activities and practicing religious rituals, like praying or doing Umrah or Hajj, were banded. Changing lifestyles as a response to COVID-19 impacted whole communities with different categories of children, parents, and families. Women usually take the majority of daily responsibilities. The sudden change in lifestyle during COVID-19 put pressure on mothers, especially those who are working to balance work and family obligations. This study aims to identify the impact of Coronavirus disease 2019 on working mothers in Saudi Arabia. Method: Data of the study was collected through survey posted on social media and analyzed through Excel. It focuses on five aspects: health, lifestyle, social relations, work production and financial status. Our target population was working mothers in Saudi Arabia aged at least 25 years. Results: In this study, all factors affected working mothers categorized under two groups: Social Economic Status and Work suspension. For Social Economic Status factors, we find five factors which are monthly income, main breadwinner, number of children at school age, type of housing, and type of work. Almost all mothers include spiritual activities to their routine to cope with stress during this period. About half of our sample have negative impact on their mental health because they are the main breadwinner, and mothers with a smaller number of children at school age have more challenges to cope up. We found that mothers who own a house or work at governmental sector have better outcome of health. After analyzing data related to Work suspension, we found that mothers who have work support have better management for life circumstances, however their health outcomes were negatively affected. In addition, mothers working at education sector have the highest positive impact among other sectors. Our data shows that working mothers’ abilities to follow up with their children decreased. This study recommends that there is need to invest more in working mothers’ research and supportive programs and ensure collaboration globally to address working mothers’ needs and share experiences.展开更多
This article is descriptive research that takes into account the growing concerns of the authorities of the municipality of Coyah regarding waste management, as well as our desire to contribute to improving the living...This article is descriptive research that takes into account the growing concerns of the authorities of the municipality of Coyah regarding waste management, as well as our desire to contribute to improving the living conditions of the inhabitants of this region. The main objective is to assess the environmental impacts of uncontrolled waste collection points on the receiving environments, by characterizing and evaluating them. This will make it possible to propose appropriate measures for rational and sustainable management of the environment in Coyah. The study addresses the characterization and assessment of pollution of receiving environments, including water, soil and air. Environmental analyses were carried out according to standard methods of EPA (1997), adapted to the equipment of the companies Hach, Millipore and Verlan. During the environmental impact assessment, we identified the sources of pollution and assessed the potential impacts. This research highlighted the pollution of receiving environments by waste located in the vicinity of collection points, while considering solutions for efficient and sustainable waste management.展开更多
During times of war, it is rare to find a government willing and able to require the military to fund and support environmental impact studies. In the 1960s, many United States scientists expressed concerns about the ...During times of war, it is rare to find a government willing and able to require the military to fund and support environmental impact studies. In the 1960s, many United States scientists expressed concerns about the use of herbicides during the Vietnam War. This protest was led by Dr. Arthur Galston and eventually included scientists with the National Academy of Science. By 1970, the Department of Defense (DoD) was ordered to permit the scientists to visit South Vietnam during the war to document these impacts. In all 1500 scientist days were spent in South Vietnam. In addition, the US government and military funded research studies on the impact of herbicides on animals. The goal of military use of herbicides, as chemical weapons, was to defoliate jungle forests and destroy food crops as a strategy to win battles and the war. The primary objective of this research study is to describe how it is possible for a country to fund and carry out scientific studies during the conduct of a war rather than decades later. The environmental impact study findings often lack boots on the ground validation and can be inaccurate or misleading in some situations. The United States (US) and other countries, including Russia and Ukraine, need to learn the historical lessons from the US use of herbicides, containing dioxin TCDD and/or arsenic (As), as chemical weapons during the Vietnam War.展开更多
Razavi et al.'s recent article,“ Im pact of the COVID-19 pandemic on research publications in emergency medicine” discussed “the evolving impact of the top Emergency Medicine journals through the COVID-19 pande...Razavi et al.'s recent article,“ Im pact of the COVID-19 pandemic on research publications in emergency medicine” discussed “the evolving impact of the top Emergency Medicine journals through the COVID-19 pandemic”.^([1]) Subsequently,it seems appropriate to offer some valuable insights to the emergency medicine community,which is responsible for such a large proportion of COVID-19 publications.Emergency departments faced unprecedented challenges from the COVID-19 pandemic,handling surges in critically ill patients and implementing infection control measures.Simultaneously,the need for swift,reliable information on COVID-19 catalyzed a surge in research activity.The pandemic era has underscored both the strengths and weaknesses of the emergency medicine research ecosystem,highlighting issues such as publication speed,research quality,methodological rigor,and ethics.[2] We aimed to further explore how the pandemic shifted research priorities,created challenges in publication practices,accelerated innovations in research methodologies,and left behind valuable lessons for future crisis research in emergency medicine.展开更多
The literature within the field of emergency medicine(EM) as well as the larger field of medicine over the past three years has been productive in adding to the collective library of scientific knowledge in the midst ...The literature within the field of emergency medicine(EM) as well as the larger field of medicine over the past three years has been productive in adding to the collective library of scientific knowledge in the midst of the COVID-19 pandemic.^([1]) Healthcare systems,notably emergency departments,experienced an intense upsurge in patient volume and acuity,followed by staffing shortages.Due to the urgent nature of the pandemic caused by a novel virus,the uncertainty of treatment and outcome,and the need for immediate and effective communication,EM research and medical research in general experienced a rapid escalation in publication within this period.展开更多
The pressure and temperature increase resulting from the impact of different threats onto target materials is analyzed with a unified laboratory-scale setup.This allows deriving qualitative information on the occurrin...The pressure and temperature increase resulting from the impact of different threats onto target materials is analyzed with a unified laboratory-scale setup.This allows deriving qualitative information on the occurring phenomenology as well as quantitative statements about the relative effects sizes as a function of target material and threat.The considered target materials are steel,aluminum,and magnesium.As threats,kinetic energy penetrator,explosively formed projectile,and shaped charge jet are used.For the investigated combinations,the measured overpressures vary by a factor of up to 5 for a variation of the material,by a factor of up to 7 for a variation of the threat,and by a factor larger than 15for a simultaneous variation of both.The obtained results as well as the experimental approach are relevant for the basic understanding of impact effects and risks due to material reactivity.The paper combines two main aims.Firstly,to provide a summary of own prior work in a coherent journal article and,secondly,to review and discuss these earlier results with a new perspective.展开更多
It is widely known that the hypervelocity impact of orbital debris can cause serious damage to spacecraft,and enhancing the impact resistance is the great concern of spacecraft shield design.This paper provides a comp...It is widely known that the hypervelocity impact of orbital debris can cause serious damage to spacecraft,and enhancing the impact resistance is the great concern of spacecraft shield design.This paper provides a comprehensive overview of advances in the development of bumper materials for spacecraft shield applications.In particular,the protective mechanism and process of the bumper using different materials against hypervelocity impact are reviewed and discussed.The advantages and disadvantages of each material used in shield were discussed,and the performance under hypervelocity impact was given according to the specific configuration.This review provides the useful reference and basis for researchers and engineers to create bumper materials for spacecraft shield applications,and the contemporary challenges and future directions for bumper materials for spacecraft shield were presented.展开更多
The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control...The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control during debris flows is crucial but difficult.Herein,an eco-friendly control system featuring anchoring natural boulders(NBs)with(negative Poisson's ratio)NPR anchor cables is proposed to form an NB-NPR baffle.A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact.The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow,primarily in the form of changes in the depositional properties and impact intensities.The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition.The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29%to 79%compared to that of the control group in the basic experiment.The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics,including consistent resistance,large deformation,and substantial energy absorption.The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders.Overall,this research serves as a basis for future field experiments and applications.展开更多
This work addresses challenges and opportunities in the evaluation of solar power plant impacts,with a particular focus on thermal effects of solar plants on the environment and vice-versa.Large-scale solar power plan...This work addresses challenges and opportunities in the evaluation of solar power plant impacts,with a particular focus on thermal effects of solar plants on the environment and vice-versa.Large-scale solar power plants are often sited in arid or desert habitats,which tend to include fauna and flora that are highly sensitive to changes in temperature and humidity.Our understanding of both shortwave(solar)and longwave(terrestrial)radiation processes in solar power plants is complete enough to render the modeling of radiation fluxes with high confidence for most applications.In contrast to radiation,the convective environment in large-scale solar power plants is much more difficult to characterize.Wind direction,wind speed,turbulence intensity,dust concentration,ground condition,panel configuration density,orientation and distribution throughout the solar field,all affect the local environment,the balance between radiation and convection,and in turn,the performance and thermal impact of solar power plants.Because the temperatures of the two sides of photovoltaic(PV)panels depend on detailed convection-radiation balances,the uncertainty associated with convection affects the heat and mass transfer balances as well.Those balances are critically important in estimating the thermal impact of large-scale solar farms on local habitats.Here we discuss outstanding issues related with these transfer processes for utility-scale solar generation and highlight potential pathways to gain useful knowledge about the convective environment directly from solar farms under operating conditions.展开更多
Aerodynamic and dynamic interference from trains is a key issue of concern for the safety of road vehicles travelling on single-level rail-cum road bridges.Based on the wind-road vehicle-train-bridge(WRTB)coupled vibr...Aerodynamic and dynamic interference from trains is a key issue of concern for the safety of road vehicles travelling on single-level rail-cum road bridges.Based on the wind-road vehicle-train-bridge(WRTB)coupled vibration system developed herein,this study examines the dynamic characteristics when road vehicles meet trains in this situation.The influence of load combination,vehicle type and vehicle location is analyzed.A method to obtain the aerodynamic load of road vehicles encountering the train at an arbitrary wind speed is proposed.The results show that due to the windproof facilities and the large line distance between the railway and highway,the aerodynamic and dynamic influence of trains on road vehicles is slight,and the vibration of road vehicles depends on the road roughness.Among the road vehicles discussed,the bus is the easiest to rollover,and the truck-trailer is the easiest to sideslip.Compared with the aerodynamic impact of trains,the crosswind has a more significant influence on road vehicles.The first peak/valley value of aerodynamic loads determines the maximum dynamic response,and the quick method is optimized based on this conclusion.Test cases show that the optimized method can produce conservative results and can be used for relevant research or engineering applications.展开更多
Unconventional resources (oil, gas, and geothermal) are often buried deep underground within dense rock strata and complex geological structures, making it increasingly difficult to create volumetric fractures through...Unconventional resources (oil, gas, and geothermal) are often buried deep underground within dense rock strata and complex geological structures, making it increasingly difficult to create volumetric fractures through conventional hydraulic fracturing. This paper introduces a novel method of supercritical energetic fluid thermal shock fracturing. It pioneers a CO_(2) deflagration impact triaxial pneumatic fracturing experimental system, using high-strength similar materials to simulate deep, hard rock masses. The study investigates the rock-breaking process and crack propagation patterns under supercritical CO_(2) thermal shock, revealing and discussing the types of thermal shock-induced fractures, their formation conditions, and discrimination criteria. The research indicates that higher supercritical CO_(2) thermal shock pressures and faster pressure release rates facilitate the formation of radial branching fractures, circumferential cracks, and branch cracks. Typically, CO_(2) thermal shock generates 3–5 radial main cracks, which is significantly more than the single main crack formed by hydraulic fracturing. The formation of branched cracks is often caused by compression-shear failure and occurs under relatively harsh conditions, determined by the confining pressure, rock properties, peak thermal shock pressure, and the pressure sustained post-decompression. The findings are expected to offer a safe, efficient, and controllable shockwave method of supercritical fluid thermal shock fracturing for the exploitation of deep unconventional oil and gas resources.展开更多
基金supported by the research project of the University of Defence in Brno DZRO-FVT22-VAROPS。
文摘This paper deals with the collision of sphere shape grenades with sand media.The central issue of the article is the establishing of an empirical velocity equation of the grenade while impacting on sand that is used to solve motion equations of the mechanical mechanism inside the impact grenade fuze.The paper focuses on impact velocities that are lower than 5 m s^(-1).An experiment was conducted to study the velocity of the grenade while impacting on dry sand.A high-speed camera video was used to capture the grenade positions.The grenade velocity in the impact process was generated from these video data.Some types of fitting curves are used to regress the velocity equation of the grenade while interacting with the sand media and the best-fitting model is chosen.The result shows the regression curve has a high correlation with the experiment data for grenade velocities below 5 m s^(-1).The received regression equation is useful for analyzing the working ability of the inertial mechanism inside the impact grenade or analyzing and choosing the appropriate parameters of each part in the inertial mechanism to meet the required characteristics of the mechanism.
文摘At the beginning of 2024,the cosmetic industry is bustling with prosperity and depression.On one hand,the perfume brand DOCUMENTS and the biotechnology company BIO-REGEN received financial investments.The medical company Trautec started pre-listing counseling.The first new raw material in the new year was registered.While on the other hand,the packaging material company Yiside declared bankruptcy.The beauty brand MAOGEPING failed to go public through an IPO again,after eight years’failure.Jinfa Labi,Watsons and Zhonghao Biology were all mired in recession.Hope and challenge hung over the first half month of 2024.With such a“magical”start,2024 will be definitely a year full of uncertainty.
基金supported by the National Natural Science Foundation of China(No.52271089)the financial support from the C hina Postdoctoral Science Foundation(No.2023M732192)。
文摘This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that the Co-bearing steel exhibits finer blocks and a lower ductile-brittle transition temperature than the steel without Co.Moreover,the Co-bearing steel reveals higher transformation rates at the intermediate stage with bainite volume fraction ranging from around 0.1 to 0.6.The improved impact toughness of the Co-bearing steel results from the higher dense block boundaries dominated by the V1/V2 variant pair.Furthermore,the addition of Co induces a larger transformation driving force and a lower bainite start temperature(BS),thereby contributing to the refinement of blocks and the increase of the V1/V2 variant pair.These findings would be instructive for the composition,microstructure design,and property optimization of high-strength steels.
基金Aeronautical Science Foundation of China(2021Z057053001)。
文摘Continuous carbon fiber reinforced silicon carbide(C/SiC)composites are often subjected to low-velocity impacts when utilized as structural materials for thermal protection.However,research on in-plane impact damage and multiple impact damage of C/SiC composites is limited.To investigate the in-plane impact damage behavior of C/SiC composites,a drop-weight impact test method was developed for strip samples,and these results were subsequently compared with those of C/SiC composite plates.Results show that the in-plane impact behavior of C/SiC strip samples is similar to that of C/SiC composite plates.Variation of the impact load with displacement is characterized by three stages:a nearly linear stage,a severe load drop stage,and a rebound stage where displacement occurs after the impact energy exceeds its peak value.Impact damage behavior under single and multiple impacts on 2D plain and 3D needled C/SiC composites was investigated at different impact energies and durations.Crack propagation in C/SiC composites was studied by computerized tomography(CT)technique.In the 2D plain C/SiC composite,load propagation between layers is hindered during impact,leading to delamination and 90°fiber brittle fracture.The crack length perpendicular to the impact direction increases with impact energy increases,resulting in more serious 0°fiber fracture and a larger area of fiber loss.In the 3D needled C/SiC composite,load propagates between the layers during impact through the connection of needled fibers.The fibers continue to provide substantial structural support,with notable instances of fiber pull-off and debonding.Consequently,the impact resistance is superior to that of 2D plain C/SiC composite.When the 3D needled C/SiC composite undergoes two successive impacts of 1.5 J,the energy absorption efficiency of the second impact is significantly lower,accompanied by a smaller impact displacement.Moreover,the total energy absorption efficiency of these two impacts of 1.5 J is lower than that of a single 3.0 J impact.
文摘Millet [Pennisetum glaucum (L.) R. Br. (Poaceae)] is one of the most widely consumed crops in Niger. Its production, despite the efforts of farmers, is confronted with weed problems, in particular Sesbania pachycarpa DC. (Fabaceae). The aim of the present study in this area is to assess the impact of Sesbania pachycarpa on millet growth and yield. To achieve this objective, a completely randomized Fisher block design of twenty-four elementary plots was set up with four replications. The data collected were millet plant heights and plot yields. The data collected were subjected to analysis of variance and Duncan’s test at the 5% threshold for comparisons of mean heights and yields with the control kept clean from sowing to millet harvesting. The results showed the sensitivity of millet plants to Sesbania pachycarpa. The results revealed that the threshold density for damage could be estimated at 6 Sesbania pachycarpa plants/m2 and the critical interference period at the fourth week after sowing. This study showed that the presence of Sesbania pachycarpa influences millet yield. Indeed, the best yields were obtained in plots without Sesbania pachycarpa. Millet yield decreased with increasing Sesbania pachycarpa density. The average percentage yield reduction was 36.79%, with a minimum of 21.25% and a maximum of 80%. The findings of this study complete the efforts of developing weed control techniques in pearl millet fields densely populated with Sesbania pachycarpa.
文摘Introduction: In Africa, care during childbirth depends on routine practices to the detriment of quality. The aim of this study was to assess the quality of delivery care at the Coronthie CMC. Methods: The study was carried out at the Coronthie Community Medical Center. It was a cross-sectional, descriptive and analytical study lasting 6 months, from July 01 to December 31, 2021. Parturients whose term was ≥28 SA and who agreed to participate in the study were included. Excluded were those with a term Results: The frequency of quality care is 36.7%. The average age of parturients was 28.6 ± 5 years. Most parturients (89.7%) were married women with secondary education (35%) and self-employed (32%). Pauciparous women accounted for 43.80%, and most parturients (59.8%) were delivered by Caesarean section. We found that 21.5% of parturients had developed complications. These complications were perineal trauma and post-partum haemorrhage. There were no maternal deaths, and the neonatal mortality rate was 20/1000 NV. Acute fetal distress was the main cause of perinatal death. Conclusion: Correct management of factors influencing childbirth could improve maternal and neonatal prognosis.
文摘Background: Severe acute malnutrition (SAM) is one of the major public health problems associated with increased mortality in under-five children. In low-income countries, renal dysfunction (RD) contributes to about 34% mortality in under-five children with severe acute malnutrition. This study aimed to determine the impacts of severe acute malnutrition on the kidney among the admitted under-five children. Methods: In this prospective longitudinal observational study, a total of 190 children aged 6 to 59 months were enrolled from Iringa and Dodoma tertiary hospitals. Socio-demographic, clinical and laboratory data were collected using a structured questionnaire. Estimated Glomerular Filtration Rate (eGFR) and urine albumin creatinine ratio (uACR) were used to determine RD. Data analysis was done using SPSS version 26 and statistical significance was assumed for factors with p-value Results: Out of 190 children with severe acute malnutrition, 36 (19%) had renal dysfunction. Factors associated with RD in malnourished children were the history of local herbs used within one week (AOR = 5.85, 95% CI [1.41, 24.319], p = 0.0152), Acute watery diarrhea with severe dehydration (AOR = 2.15, 95% CI [1.033, 4.711], p = 0.0166), and positive urine leukocytes (AOR = 19.91, 95% CI [4.09, 96.989], p = 0.0002). At three months of follow up, out of 36 children with RD, 20 (55.56%) attained full recovery, while 4 (11.11%) developed chronic kidney disease (CKD). Children with RD had prolonged hospital stays for more than 14 days with a mean 12.25 ± 5.00 days compared to those with no RD with a mean 6.29 ± 1.68 days (p Conclusion: Renal dysfunction is common among children with severe acute malnutrition. It is associated with prolonged hospital stays and increased mortality. Further studies which can determine the burden of RD in children with severe acute malnutrition as compared to those with no severe acute malnutrition are needed.
文摘Although hunting in the north-eastern Atlantic forest of Brazil began more than 500 years ago, no study to date has evaluated its impacts on the region’s mammalian fauna. For one year we carried out diurnal and nocturnal surveys using the Line Transect method in seven forest fragments varying from 7.32 ha to 469.76 ha, within a 4000 ha forest island archipelago, in Pernambuco State, Atlantic forest of northeastern Brazil. We calculated species density, population size, biomass and synergetic biomass, and recorded direct and indirect human impacts along the study transects. We recorded 44 mammalian species, of which 45.5% (n = 20) went extinct through hunting. The smallest forest fragment had the lowest richness, diversity, population size, and total biomass. It also had no synergetic biomass. The largest fragment had the highest richness, total density, and population size. There was a statistically significant relationship between fragment area and number of gunshots heard and suspended hunting platforms found;between population size and gunshots heard, suspended hunting platforms, free-roaming and feral dogs, and between total density and free-roaming and feral dogs. After more than 500 years of colonization hunting is still devastating, with larger fragments being linked to more hunters. Higher mammal abundances attracted more free-roaming and feral dogs, which have adapted to hunt wildlife on their own. Unless we protect every single forest fragment and create sustainable landscapes, we will not be able to save this hotspot’s hotspot.
文摘Coronavirus is a Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) caused by a novel coronavirus belonging to the family Coronaviridae. The disease was first discovered in December 2019 in Wuhan City, Hubei Province, China. A few months later, the disease spread all over the world and became an epidemic. The infection for most people is mild to moderate but in Vulnerable groups, if they have the infections, they might experience severe COVID-19. Saudi Arabia initiated its response plan early, and all sectors and agencies worked in an integrated way to combat the disease. It has maintained proper communication during the pandemic and ensured community involvement, epidemiologic surveillance, and activation of rapid response teams. The COVID-19 pandemic significantly affected daily lives. Schools and daycares were closed, education was online, traveling stopped, work was suspended, gathering in social activities and practicing religious rituals, like praying or doing Umrah or Hajj, were banded. Changing lifestyles as a response to COVID-19 impacted whole communities with different categories of children, parents, and families. Women usually take the majority of daily responsibilities. The sudden change in lifestyle during COVID-19 put pressure on mothers, especially those who are working to balance work and family obligations. This study aims to identify the impact of Coronavirus disease 2019 on working mothers in Saudi Arabia. Method: Data of the study was collected through survey posted on social media and analyzed through Excel. It focuses on five aspects: health, lifestyle, social relations, work production and financial status. Our target population was working mothers in Saudi Arabia aged at least 25 years. Results: In this study, all factors affected working mothers categorized under two groups: Social Economic Status and Work suspension. For Social Economic Status factors, we find five factors which are monthly income, main breadwinner, number of children at school age, type of housing, and type of work. Almost all mothers include spiritual activities to their routine to cope with stress during this period. About half of our sample have negative impact on their mental health because they are the main breadwinner, and mothers with a smaller number of children at school age have more challenges to cope up. We found that mothers who own a house or work at governmental sector have better outcome of health. After analyzing data related to Work suspension, we found that mothers who have work support have better management for life circumstances, however their health outcomes were negatively affected. In addition, mothers working at education sector have the highest positive impact among other sectors. Our data shows that working mothers’ abilities to follow up with their children decreased. This study recommends that there is need to invest more in working mothers’ research and supportive programs and ensure collaboration globally to address working mothers’ needs and share experiences.
文摘This article is descriptive research that takes into account the growing concerns of the authorities of the municipality of Coyah regarding waste management, as well as our desire to contribute to improving the living conditions of the inhabitants of this region. The main objective is to assess the environmental impacts of uncontrolled waste collection points on the receiving environments, by characterizing and evaluating them. This will make it possible to propose appropriate measures for rational and sustainable management of the environment in Coyah. The study addresses the characterization and assessment of pollution of receiving environments, including water, soil and air. Environmental analyses were carried out according to standard methods of EPA (1997), adapted to the equipment of the companies Hach, Millipore and Verlan. During the environmental impact assessment, we identified the sources of pollution and assessed the potential impacts. This research highlighted the pollution of receiving environments by waste located in the vicinity of collection points, while considering solutions for efficient and sustainable waste management.
文摘During times of war, it is rare to find a government willing and able to require the military to fund and support environmental impact studies. In the 1960s, many United States scientists expressed concerns about the use of herbicides during the Vietnam War. This protest was led by Dr. Arthur Galston and eventually included scientists with the National Academy of Science. By 1970, the Department of Defense (DoD) was ordered to permit the scientists to visit South Vietnam during the war to document these impacts. In all 1500 scientist days were spent in South Vietnam. In addition, the US government and military funded research studies on the impact of herbicides on animals. The goal of military use of herbicides, as chemical weapons, was to defoliate jungle forests and destroy food crops as a strategy to win battles and the war. The primary objective of this research study is to describe how it is possible for a country to fund and carry out scientific studies during the conduct of a war rather than decades later. The environmental impact study findings often lack boots on the ground validation and can be inaccurate or misleading in some situations. The United States (US) and other countries, including Russia and Ukraine, need to learn the historical lessons from the US use of herbicides, containing dioxin TCDD and/or arsenic (As), as chemical weapons during the Vietnam War.
文摘Razavi et al.'s recent article,“ Im pact of the COVID-19 pandemic on research publications in emergency medicine” discussed “the evolving impact of the top Emergency Medicine journals through the COVID-19 pandemic”.^([1]) Subsequently,it seems appropriate to offer some valuable insights to the emergency medicine community,which is responsible for such a large proportion of COVID-19 publications.Emergency departments faced unprecedented challenges from the COVID-19 pandemic,handling surges in critically ill patients and implementing infection control measures.Simultaneously,the need for swift,reliable information on COVID-19 catalyzed a surge in research activity.The pandemic era has underscored both the strengths and weaknesses of the emergency medicine research ecosystem,highlighting issues such as publication speed,research quality,methodological rigor,and ethics.[2] We aimed to further explore how the pandemic shifted research priorities,created challenges in publication practices,accelerated innovations in research methodologies,and left behind valuable lessons for future crisis research in emergency medicine.
文摘The literature within the field of emergency medicine(EM) as well as the larger field of medicine over the past three years has been productive in adding to the collective library of scientific knowledge in the midst of the COVID-19 pandemic.^([1]) Healthcare systems,notably emergency departments,experienced an intense upsurge in patient volume and acuity,followed by staffing shortages.Due to the urgent nature of the pandemic caused by a novel virus,the uncertainty of treatment and outcome,and the need for immediate and effective communication,EM research and medical research in general experienced a rapid escalation in publication within this period.
文摘The pressure and temperature increase resulting from the impact of different threats onto target materials is analyzed with a unified laboratory-scale setup.This allows deriving qualitative information on the occurring phenomenology as well as quantitative statements about the relative effects sizes as a function of target material and threat.The considered target materials are steel,aluminum,and magnesium.As threats,kinetic energy penetrator,explosively formed projectile,and shaped charge jet are used.For the investigated combinations,the measured overpressures vary by a factor of up to 5 for a variation of the material,by a factor of up to 7 for a variation of the threat,and by a factor larger than 15for a simultaneous variation of both.The obtained results as well as the experimental approach are relevant for the basic understanding of impact effects and risks due to material reactivity.The paper combines two main aims.Firstly,to provide a summary of own prior work in a coherent journal article and,secondly,to review and discuss these earlier results with a new perspective.
基金supported by National Natural Science Foundation of China(Grant Nos.12202068,12202087)China National Space Administration Preliminary Research Project(Grant Nos.KJSP2023020201,KJSP2020010402).
文摘It is widely known that the hypervelocity impact of orbital debris can cause serious damage to spacecraft,and enhancing the impact resistance is the great concern of spacecraft shield design.This paper provides a comprehensive overview of advances in the development of bumper materials for spacecraft shield applications.In particular,the protective mechanism and process of the bumper using different materials against hypervelocity impact are reviewed and discussed.The advantages and disadvantages of each material used in shield were discussed,and the performance under hypervelocity impact was given according to the specific configuration.This review provides the useful reference and basis for researchers and engineers to create bumper materials for spacecraft shield applications,and the contemporary challenges and future directions for bumper materials for spacecraft shield were presented.
基金financial support from the National Natural Science Foundation of China(Grant No.41941018).
文摘The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control during debris flows is crucial but difficult.Herein,an eco-friendly control system featuring anchoring natural boulders(NBs)with(negative Poisson's ratio)NPR anchor cables is proposed to form an NB-NPR baffle.A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact.The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow,primarily in the form of changes in the depositional properties and impact intensities.The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition.The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29%to 79%compared to that of the control group in the basic experiment.The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics,including consistent resistance,large deformation,and substantial energy absorption.The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders.Overall,this research serves as a basis for future field experiments and applications.
基金Partial funding from the John Dove Isaacs Endowed Chair for Natural Philosophy in Engineering at UC San Diego。
文摘This work addresses challenges and opportunities in the evaluation of solar power plant impacts,with a particular focus on thermal effects of solar plants on the environment and vice-versa.Large-scale solar power plants are often sited in arid or desert habitats,which tend to include fauna and flora that are highly sensitive to changes in temperature and humidity.Our understanding of both shortwave(solar)and longwave(terrestrial)radiation processes in solar power plants is complete enough to render the modeling of radiation fluxes with high confidence for most applications.In contrast to radiation,the convective environment in large-scale solar power plants is much more difficult to characterize.Wind direction,wind speed,turbulence intensity,dust concentration,ground condition,panel configuration density,orientation and distribution throughout the solar field,all affect the local environment,the balance between radiation and convection,and in turn,the performance and thermal impact of solar power plants.Because the temperatures of the two sides of photovoltaic(PV)panels depend on detailed convection-radiation balances,the uncertainty associated with convection affects the heat and mass transfer balances as well.Those balances are critically important in estimating the thermal impact of large-scale solar farms on local habitats.Here we discuss outstanding issues related with these transfer processes for utility-scale solar generation and highlight potential pathways to gain useful knowledge about the convective environment directly from solar farms under operating conditions.
基金The Research Project of Southwest Municipal Design&Research Institute of China under Grant No.2023KY-KT-02-I。
文摘Aerodynamic and dynamic interference from trains is a key issue of concern for the safety of road vehicles travelling on single-level rail-cum road bridges.Based on the wind-road vehicle-train-bridge(WRTB)coupled vibration system developed herein,this study examines the dynamic characteristics when road vehicles meet trains in this situation.The influence of load combination,vehicle type and vehicle location is analyzed.A method to obtain the aerodynamic load of road vehicles encountering the train at an arbitrary wind speed is proposed.The results show that due to the windproof facilities and the large line distance between the railway and highway,the aerodynamic and dynamic influence of trains on road vehicles is slight,and the vibration of road vehicles depends on the road roughness.Among the road vehicles discussed,the bus is the easiest to rollover,and the truck-trailer is the easiest to sideslip.Compared with the aerodynamic impact of trains,the crosswind has a more significant influence on road vehicles.The first peak/valley value of aerodynamic loads determines the maximum dynamic response,and the quick method is optimized based on this conclusion.Test cases show that the optimized method can produce conservative results and can be used for relevant research or engineering applications.
基金supported by“Intergovernmental Cooperation in Science,Technology and Innovation(ISTI)”Key Special Project 2023“Intergovernmental Cooperation Programme between China and the United States”(Grant No.2023YFE0120500)the National Natural Science Foundation of China(Grant No.41702289)the Foundation of Hubei Key Laboratory of Blasting Engineering(Grant No.HKLBEF202004).
文摘Unconventional resources (oil, gas, and geothermal) are often buried deep underground within dense rock strata and complex geological structures, making it increasingly difficult to create volumetric fractures through conventional hydraulic fracturing. This paper introduces a novel method of supercritical energetic fluid thermal shock fracturing. It pioneers a CO_(2) deflagration impact triaxial pneumatic fracturing experimental system, using high-strength similar materials to simulate deep, hard rock masses. The study investigates the rock-breaking process and crack propagation patterns under supercritical CO_(2) thermal shock, revealing and discussing the types of thermal shock-induced fractures, their formation conditions, and discrimination criteria. The research indicates that higher supercritical CO_(2) thermal shock pressures and faster pressure release rates facilitate the formation of radial branching fractures, circumferential cracks, and branch cracks. Typically, CO_(2) thermal shock generates 3–5 radial main cracks, which is significantly more than the single main crack formed by hydraulic fracturing. The formation of branched cracks is often caused by compression-shear failure and occurs under relatively harsh conditions, determined by the confining pressure, rock properties, peak thermal shock pressure, and the pressure sustained post-decompression. The findings are expected to offer a safe, efficient, and controllable shockwave method of supercritical fluid thermal shock fracturing for the exploitation of deep unconventional oil and gas resources.
