Twinning aspects and their efficient roles in wrought Mg alloys:A comprehensive review

Twinning is widely recognized as an effective and cost-efficient method for controlling the microstructure and properties of wrought magnesium(Mg)alloys.Specifically,twins play a crucial role in initiating dynamic recrystallization(DRX),while twin regions experience rapid recrystallization during static recrystallization(SRX).The activation of twinning can lead to changes in lattice orientation,significantly impacting the final texture in Mg alloys.The active roles of twinning are influenced by various factors during the activation process,and the mobility of twin boundaries(TB)can be amplified by stress effects,dislocation interactions,and thermal effects.Conversely,annealing treatments that involve proper segregation or precipitation on TBs serve to stabilize them,restraining their motion.Events such as segregation may also alter the twinning propensity in Magnesium-rare earth(Mg-RE)alloys.While{10–11}contraction twins(CT)and{10–11}-{10–12}double twins(DT)can promote dynamic recrystallization(DRX),they also pose a risk as potential sources of voids and cracks.Additionally,understanding the nucleation and growth mechanisms of twinning is crucial,and these aspects are briefly reviewed in this article.Considering the factors mentioned above,this article summarizes the recent research progress in this field,shedding light on advancements in recent eras.

Microstructure characteristics and mechanical properties of Al/Mg joints manufactured by magnetic pulse welding

The effective connection of 1050 Al and AZ31 Mg was realized by magnetic pulse welding.The maximum tensile-shear force of the dissimilar Al/Mg metal lap joint reached 97%of that of the 1050 Al alloy base material by optimizing the process parameters.The microstructure of dissimilar Al/Mg welded joints was analysed by Scanning Electron Microscope(SEM),Energy Dispersive Spectrometer(EDS)and Electron Backscattered Diffraction(EBSD).The results show that the key to obtaining high shear strength of Al/Mg dissimilar metal joints is mainly due to the following two reasons.On the one hand,grain refinement and element interdiffusion occur at the interface.On the other hand,no intermetallic compounds are formed at the interface.

Revealing the grain size dependent hot workability and deformation mechanisms in a Mg-Zn-Y alloy

Despite the industrial significance of grain size for enhancing mechanical properties and formability,the in-depth deformation mechanisms at elevated temperature are still unclear.To investigate the functions of grain size on hot workability and deformation mechanisms,three groups of Mg-1.2Zn-0.2Y alloy specimens with different grain sizes were hot compressed and then studied by combining constitutive model,processing map and microstructural observations.The results showed that the enhanced hot workability accompanying low deformation activation energy and small instability regime was obtained with refined grain size.During hot deformation,the decreased grain size in Mg1.2Zn-0.2Y alloy mainly improved the plastic deformation homogeneity,especially for the weakened local straining around grain boundaries.As a result,the dynamic recrystallization nucleation and texture development at lower strain level were influenced by the initial grain size.At higher strain magnitude,the growth and coarsening of dynamic recrystallized grains would further release strain localization and improve hot workability,while the texture was less impacted.Further,unlike the primary basal slip and deformation twinning in the specimen with coarse grain at low temperature,non-basal slips of dislocations were initiated with less deformation twins in the specimens with refined grain size.

Perceptions of Rice Farmers towards Production Constraints: Case Study of Niger State of Nigeria and Hainan of China

Rice yield is still low in Nigeria despite the ecological advantages. Several challenges has been traced it production. The study intend to investigate if other rice producing nations are faced with similar challenges and at what magnitude and more importantly, what can be learn to improve the rice yield in Nigeria. Based on 2013/2014 survey, a total sample of 400 famers were randomly interviewed;164 from Niger State of Nigeria and 236 from Hainan province of China. The study collate the perception of farmers to rice production constraints categorized into biotic, abiotic and socioeconomics. Biplot analysis was employed to examine multivariate pattern of their perceptions towards production constraints. The multivariate technique simultaneously displaying different yield levels and factor constraints in data matrix providing the inter-unit distances, variance and correlations of variables. According to the study, Niger state farmers identified socioeconomic constraint as the major factors to production and attributed it to lack of or insufficient investment while the Hainan farmers majorly identified abiotic constraints. The study also indicated that great potential remain to further improve rice yield in both regions especially in Nigeria given the appropriate investment on essential inputs. This study is of great use to extension officers more so, given the investment in Africa, policy makers take advantage of the bilateral and multilateral relationship to invest ease transfer of agricultural information and technologies between or among partners.

Optimization Model of Cattle Husbandry for Rural Household in Cambodia

Cambodia is one of the Southeast Asia. With the agricultural market integration, Cambodia rural household is adjusting livestock structure naturally. In order to provide suitable support for agriculture policy, the authors conducted a survey on 204 rural household in Cambodia. This article uses the optimization model, considering rural labor, cattle size, and animal disease risk, to analyze and get optimum result range. The result shows that the more off-farm job opportunity, suitable cattle feed structure, and investment on public health for cattle, the household income in rural Cambodia will increase.

Farmers’ Access to Agricultural Information Sources: Evidences from Rural Pakistan

The current study was conducted to probe farmers’ accessible agricultural information sources in rural areas of Pakistan. For this purpose a random sample of 160 households from four districts of the Punjab province of Pakistan was selected. Data were collected using validated and expert reviewed questionnaire with the help of interview method. The results revealed that majority of farmers (47.5%) ranked neighbor-friends-relatives as first source of information while 31.9% of farmers ranked this source as second and 33.7% farmers’ ranked it as third major source. With contrast to this very less farmers (10%) ranked agricultural extension staff as first information source. Keeping in view the study results, the performance of extension staff is not encouraging;therefore government should plan and launch a policy to foster performance of public agricultural extension system to fulfill the advanced technological needs of farmers to flourish sustainable agriculture and rural development.

Could Rice Yield Change Be Caused by Weather?

Data from 4 counties of Hainan Province of China from 1991-2012 was used to determine the weather impact on rice yields in both early and late rice seasons with multiple regression models. The results show there is normal weather environment for rice in the heading stage for early season rice in May and the milking stage for late season rice in November. For early season rice, more rain in April and June is better for rice to boot and milk, the average temperature has negative effect for the season rice yield;for late season rice, the average temperature have positive effect for the difference between rice yield and the mean of total years but in seedling and booting stage;the rice yield difference between double season is compared and analyzed through the difference of meteorological factors, the results show that the precipitation gap in tillering stage has positive effect to rice yield increasing, but against in booting stage. The relative results should be use to forecast rice yield, and further provide the rice production guiding.

Recent progress and perspectives in additive manufacturing of magnesium alloys

Magnesium alloys remain critical in the context of light-weighting and advanced devices. The increased utilisation of magnesium(Mg)each year reveals growing demand for its Mg-based alloys. Additive manufacturing(AM) provides the possibility to directly manufacture components in net-shape, providing new possibilities and applications for the use of Mg-alloys, and new prospects in the utilisation of novel physical structures made possible from ‘3D printing’. The review herein seeks to holistically explore the additive manufacturing of Mg-alloys to date, including a synopsis of processes used and properties measured(with a comparison to conventionally prepared Mg-alloys). The challenges and possibilities of AM Mg-alloys are critically elaborated for the field of mechanical metallurgy.

Optimisation of alloy composition for highly-formable magnesium sheet

The effectiveness of Ca or Gd addition on ductility and formability of Mg-Zn-Zr based dilute alloys in deep drawing has not been systematically compared previously.In this study,formable Mg-Zn-Gd-Zr and Mg-Zn-Ca-Zr sheet alloys are produced by hot rolling.These sheets have similarly weakened basal texture,but the sheet of the Mg-Zn-Gd-Zr alloys has higher ductility and formability than that of Mg-Zn-Ca-Zr alloys.The combined addition of 0.2wt%Ca and 0.4wt%Gd to the Mg-1Zn-0.5Zr(wt%)alloy leads to a Mg-1Zn-0.4Gd-0.2Ca-0.5Zr alloy that has even better ductility,and its formability during deep drawing is comparable to the benchmark Al6016 sheet.An increase in Ca content from 0.2wt%to 0.5wt%leads to decreased sheet ductility and formability,predominantly due to grain boundary embrittlement.

Urban Residents' Consumption Risk Perception about the Dairy Products

Based on the continuous downturn puzzle of Chinese dairy consumption,with the perception of consumption risk as a starting point,the paper deeply analyzes the main factors which cause the downturn of dairy product consumption of Chinese residents. The results show that the income elasticity of dairy consumption of Chinese urban residents is still notable; the occurrence of dairy safety incidents improves the perception of consumption risk,and accordingly it reduces the promoting role of income to the dairy consumption; the safety incident is the key factor which leads to the fall of dairy consumption of urban residents in recent years,and the perception of consumption risk of lower income group is clearly higher than that of higher income group.

Microstructure and texture in an extruded Mg-Al-Ca-Mn flat-oval tube

In the present study,mechanical property,microstructure and texture of an extruded Mg–1.0Al–1.5Ca–1.0Mn(wt.%)flat-oval tube in both the flat and the oval regions were systematically studied.Our results show that there exists a great difference in microstructure and texture between the flat and the oval regions.Both the flat and the oval regions have fine DRXed grains of 3–4μm,while more row stacked grains are observed in the flat region.A large number of fine particles with a size of about 0.5μm are dispersed in both the grain boundary and grain interior.The particles exhibit a uniform distribution in the oval region,while they tend to aggregate into bands along the extrusion direction(ED)in the flat region.The texture in the oval region is similar to that in extruded Mg rods with a preferred distribution of prismatic planes and random distribution of(0002)poles around the ED,while that in the flat region is close to that in extruded sheets containing two texture components,<0002>//normal direction(ND)and<0002>//transverse direction(TD).A high fraction of<0002>//TD component,about 52–62%,is observed in the flat region.The flat region has a tensile yield strength of 254 MPa,an ultimate tensile strength of 290 MPa and an elongation to failure of 4.3%.

Study on Food Import in D. R. Congo

Democratic Republic of Congo is a developing country located in Central Africa with a population of over 75 million. Generally, it relies on import in international market for food as it has constantly been experiencing domestic crisis which hinders production. Given the importance of shores price policy and income policy, the government pays meticulous attention to these factors to meet the present and future food security. In order to understand the import behavior related to GDP and international trade prices, the study employs Almost Idea Demand System (AIDS) model using FAO data. The result explains that price effect is more useful to the food security of the country than the income effect, thus this study suggest the government should give priority to policy on price.

The Impact of Poverty Alleviation Policy on Urban Household Demand

Many policies and measures for poverty alleviation have been undertaken by the Chinese government, but few researchers have explored its experience and lessons. This research focuses on household needs like food, clothing, housing, household equipment and supplies, transportation and communication, education and entertainment, healthcare;and also focuses on food items such as grains, meat, eggs, milk, vegetables, fruits and others in urban China. In poor households, the average disposable income per capita is less than or near per capita expenditure;and the Engels coefficient is often over 40%. The data from 1997-2012 in this research is in the provincial level from the Information Website of Development Research Center of the State Council (or “DRCnet”). The authors used the two stage ELES-AIDS (Almost Ideal Demand System) to estimate the price elasticity and expenditure elasticity of the household’s expenditures. According to the results, it is recommended that the government should follow economic law and improves policy efficiency, especially its food policy to alleviate the poverty of low income residents.

Study on Sesame Export for Sudan Based on Gravity Model

This study aimed to investigate the effect of social and economic differences between importer and exporter countries on trade flows of Sesame seed product. The analysis was carried out by estimating the gravity model. The sample covered a total of 14 countries for the period from 1997 to 2009. The results showed that the social and economic differences between countries have a significant and positive or negative effect on Sesame seeds trade. Furthermore, we found that the same language, distance and sesame production in export country have positive effect for the sesame export from Sudan.

Potentials and Constraints of Small-Scale Livestock Productions in Cambodia

Livestock husbandry plays a very important role in rural areas of Cambodia. Farmers mostly have complained about the declining revenue from livestock production which supports their livelihood. Therefore, the study aimed at investigating the potentials and constraints of smallholder livestock productions in Battambang province. Primary and secondary data were collected to meet the objectives. Data were collected interviewing 204 households. Some of the advantages of the Cambodia livestock subsector are the increasing market demand: increasing domestic market for livestock and increasing demand from neighboring countries (especially cattle);the rich source of manure and other agricultural input such as transportation means, ploughing etc. More so, there is high expectation of the farmers experiencing increase in production since more supports are provided by both governmental and non-governmental organizations. On the other hand, the subsector witnesses some constraints including the low level of education of the livestock farmers, erratic market prices as a result of too many middlemen, local breed with low productivity and traditional management system still dominates the sub- sector. Scarcity of abled labor and seasonal cost is also one of the factors impeding the subsector to reaching it potential. This study suggests that to reach full potential in the livestock sector of Battambang of Cambodia, the government needs to address the infrastructural problems and private sector needs to be encouraged to invest in the sector in livestock input industries.

Analysis of Evacuation of Tourists Based on the Louvre’s Emergency

Due to France has suffered from many terrorist attacks and the number of visitors to the Louvre has gradually increased in recent years, a good evacuation plan for the Louvre is of vital significance. We use the minimization of the total evacuation time of all tourists as the optimization goal to find an optimal path. For conventional emergencies, a static model is built to evacuate visitors. And then we establish a nonlinear programming model. Using Lingo software, we get the distribution information of the visitors in different exhibition halls. For unconventional emergencies, we establish an adaptive dynamic model of tourist evacuation based on genetic algorithm. The sensitivity analysis of the model is considered by adding new paths. By solving the nonlinear programming problem with the double objective function of maximizing evacuation time and balancing the number of people in every path, we get the evacuation time last 1582.74 s. Finally, according to our result, we built mathematical models for the evacuation after an emergency and analyzed how to adapt and implement our models for other large and crowded structures.

生物启发的被动式微型飞行器

随着仿生学和空气动力学的发展以及制造技术的不断进步,微型飞行器的一个重要发展趋势是更加小型化和更加智能化.传统的主动式微型飞行器通常使用喷气、旋翼或扑翼的驱动方式提供飞行的动力,但往往需要较大的能量供给,难以实现较长时间滞空与远距离巡航.受生物启发的被动式微型飞行器依赖自身结构的空气动力学特性以实现无动力飞行,具有质量轻、成本低、无噪音、能耗低等优势,还可以通过集成微电子系统以实现环境探测、人口监测和疾病追踪等功能.本文从被动式微型飞行器的分类出发,将其分为滑翔机形、直升机形和降落伞形微型飞行器,阐述其仿生学原理,介绍了该领域的研究进展,最后对被动式微型飞行器领域的未来发展方向与挑战进行了展望.通过结合柔性电子技术以及更加先进的制备工艺,集成电源、传感、运算、存储和通信等模块,并结合环境中的大范围部署,可望构建具有超高空间深度与时间广度的低成本实时监测系统,对环境和生态学研究具有重要的意义.

Progress of Jinping Underground laboratory for Nuclear Astrophysics(JUNA)

Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of^(25)Mg(p,γ)^(26)Al,^(19)F(p,α)^(16)O,^(13)C(α,n)^(16)O and ^(12)C(α,γ)^(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.

Effects of alkalinity on interaction between EPS and hydroxy-aluminum with different speciation in wastewater sludge conditioning with aluminum based inorganic polymer flocculant

Extracellular polymeric substances(EPS)form a stable gel-like structure to combine with water molecules through steric hindrance,making the mechanical dewatering of wastewater sludge considerably difficult.Coagulation/flocculation has been widely applied in improving the sludge dewatering performance,while sludge properties(organic fraction and solution chemistry conditions)are highly changeable and have important effects on sludge flocculation process.In this work,the alkalinity effects on sludge conditioning with hydroxy-aluminum were comprehensively investigated,and the interaction mechanisms between EPS and hydroxy-aluminum with different speciation were unraveled.The results showed that the effectiveness of hydroxy-aluminum conditioning gradually deteriorated with increase in alkalinity.Meanwhile,the polymeric hydroxy-aluminum(Al 13)and highly polymerized hydroxy-aluminum(Al 30)were hydrolysed and converted into amorphous aluminum hydroxide(Al(OH)3),which changed the flocculation mechanism from charge neutralization and complexing adsorption to hydrogen bond interaction.Additionally,both Al 13 and Al 30 showed higher binding capacity for proteins and polysaccharides in EPS than monomeric aluminum and Al(OH)3.Al 13 and Al 30 coagulation changed the secondary structure of proteins in EPS,which caused a gelation reaction to increase molecular hydrophobicity of proteins and consequently sludge dewaterability.This study provided a guidance for optimizing the hydroxy-aluminum flocculation conditioning of sludge with high solution alkalinity.

A proposed direct measurement of cross section at Gamow window for key reaction 19F(p,α) 16O in Asymptotic Giant Branch stars with a planned accelerator in CJPL

In 2014, the National Natural Science Foundation of China （NSFC） approved the Jinping Underground Nuclear Astrophysics laboratory （JUNA） project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch （AGB） stars, measuring the key 19F（p,a）16O reaction at effective burning energies （i.e., at Gamow window） is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions.