采用直线电机的Jobs LinX机床系列

从1980年起,Jobs就开始生产大功率高速的3～5轴铣削机床和自动化系统.Jobs的解决方案遍布中小型企业和大公司,采用高技术含量的工艺过程.Jobs的产品有80%出口.由于公司技术、设计、生产的发展及专业化高附加值的服务,也由于在新的设计和制造技术方面的不断投资,Jobs向市场提供的是顶尖级性能的产品.

神灯里的妖气

Studio Job喜欢通过设计作品讲故事,在夸张的造型背后,是他们对现实世界的观察与讽喻。

Effects of freeze–thaw cycles on soil N_2O concentration and flux in the permafrost regions of the Qinghai–Tibetan Plateau

Nitrous oxide(N_2 O) is one of the most important greenhouse gases in the atmosphere; freeze–thaw cycles(FTCs) might strongly influence the emission of soil N_2 O on the Qinghai–Tibetan Plateau(QTP). However, there is a lack of in situ research on the characteristics of soil N_2 O concentration and flux in response to variations in soil properties caused by FTCs.Here, we report the effect of FTC-induced changes in soil properties on the soil N_2 O concentration and flux in the permafrost region of the higher reaches of the Shule River Basin on the northeastern margin of the QTP. We measured chemical properties of the topsoil, activities of soil microorganisms, and air temperature(AT), as well as soil N_2 O concentration and flux, over an annual cycle from July 31, 2011, to July 30, 2012. The results showed that soil N_2 O concentration was significantly affected by soil temperature(ST), soil moisture(SM), soil salinity(SS), soil polyphenol oxidase(SPO), soil alkaline phosphatase(SAP), and soil culturable actinomycetes(SCA), ranked as SM>SS>ST>SPO>SAP>SCA, whereas ST significantly increased soil N_2 O flux, compared with SS. Overall, our study indicated that the soil N_2 O concentration and flux in permafrost zone FTCs were strongly affected by soil properties, especially soil moisture, soil salinity, and soil temperature.

先进的模具加工方案

每一个模具厂都面临着模具形状越来越复杂但用户的质量要求越来越高，交货周期也越来越短的用户需求，要想满是这些需求，必须投资购置先进的高效率加工机床。

An alternative approach for sustainable sheep meat production:implications for food security

Background:A pelleted diet containing camelina hay(CAMH)or camelina meal(CAMM)as a supplement along with a control pellet(CONT)diet formulated with commonly available feeds during summer was used to investigate an alternative pathway for sustainable meat production.Sustainable meat production was based on a simple estimation of income from meat produced versus feed costs if animals were fed for an extended period over summer compared to early slaughter at the beginning of summer.Eighty maternal composite wether lambs(Composite)based on Coopworth genetics and 80 pure Merino wether yearlings were divided into 10 groups within breed(n=8)using stratified randomisation based on liveweights.Following 1 week of adaptation to experimental diets,animals were fed experimental diets for up to10 weeks.Results:Animals were slaughtered after either 8,9 or 10 weeks of full feeding when the average liveweight of diet/genetic combination reached a weight appropriate for either‘heavy lamb’or‘heavy hogget’production,which occurred between 8 and 10 weeks of full feeding.There was no diet×breed interactions except for dressing percentage(DP),where Composite lambs fed the CAMH diet had the greatest DP(48.1±0.35)and the Merino yearlings fed the CAMM diet the lowest DP(45.8±0.33).Composite lambs gained 17.6–20.3 kg and Merino yearlings gained 10.7–12.9 kg liveweight.Based on their DP,this resulted in the production of approximately 8.3–9.5 kg additional carcass weight in Composites and 4.9–5.7 kg in Merinos,which in turn produced greater profit per Composite lamb and a small profit per Merino yearling.Conclusions:Composite lambs fed CAMM and CAMH had 5%greater carcass weights at slaughter compared to the CONT group,but dietary treatments did not change carcass weight of Merino yearlings at slaughter.The extended feeding approach offered the producer an estimated economic gain of AUD$20.00 to$25.00 when yearly average prices were used(Method 1)and AUD$40.00 to$47.70 when pre-and post-summer average prices were used(Method 2)per Composite lambs,but extra carcass gain did not result in the same profit per Merino yearling.Among the Composites,the profit for animals fed the CAMH and CAMM were AUD$2.75 to$4.50 greater than CONT group when full year average prices were applied while AUD$3.50 to$5.50 greater than CONT group when pre-and post-summer average prices were applied.However,we acknowledge a combination approach of extended feeding for a portion of animals already on ground and selling the remaining animals pre-summer with joining of additional ewes is the most likely strategy.Considering the scenario of extended feeding for 3 weeks,based on the growth rates observed for Composite lambs,if an additional 2 kg carcass weight per animal can be gained for 50%of the 22 million lambs slaughtered in Australia(=11 million animals),it would potentially supply an additional 22 million kg of lamb carcasses produced per annum.This is equivalent to producing an extra 1 million lamb carcasses per annum weighing 22 kg each.Feeding Composite lambs for an extended period and selling Merino yearlings pre-summer may be a good option due to faster growth rate of Composites that may help quick turn-over to market.

Scale and scope economies in small household rice farming in Vietnam

The Vietnamese agricultural sector has experienced a dramatic structural change based on increased specialization in rice cultivation.However,small-scale rice-farmers have continued to grow multiple crops,especially in less developed provinces.While the literature advocates crop diversification for reasons of both economic and ecological sustainability,there lacks empirical evidence as to whether crop diversification brings efficiency and productivity gains to small farms.The present study is the first applications of the input-oriented stochastic distance function approach in estimating scale and scope economies using data of multi-crop farming households in Vietnam.We find strong evidence of product-specific economies of scale.Scope economies are also present for rice,vegetable,and other annual crop production.This suggests that crop diversification enhances efficiency and productivity.However,there still exists significant technical inefficiency in crop production,indicating opportunities to expand farm output at the existing level of inputs and technologies.More specifically,our empirical results indicate that it is desirable to expand vegetable and other annual crop production in mountainous areas while rice cultivation can be further expanded in delta and coastal regions.

胸怀大志，非同凡“想”——解密“苹果教父”史蒂夫·乔布斯的成功法宝

黑T恤、牛仔裤、运动鞋——这是“苹果教父”史蒂夫·乔布斯在世人面前的招牌装束。 简约，正如他所创造出的苹果系列产品，让人们能够更为快捷方便地操作科技产品，正如他一直秉承的“去繁从简”的原则。

Pay-based Screening Mechanism: Personnel Selection in the View of Economics Theory

Based on economic theories, the paper studies the personnel selection at the asymmetric job market using signaling and screening model. The authors hold the opinion that an organization can screen the candidates' signaling based on the self-selection principle by providing an appropriate compensation choice. A pay-based screening mechanism is proposed to help the organization drive away the nonqualified applicants and retain the excellent applicants.

The Optimization of Preventive Maintenance Scheduling for Production Machine of Production System in Finite Time Horizon

The recursion relation of preventive maintenance (PM) cycle is built up concerning the concept of effective age and age setback factor proposed in this paper, which illustrates the dynamic relationship between failure rate and preventive maintenance activity. And the nonlinear optimal PM policy model satisfying the reliability constraints in finite time horizon following Weibull distribution is proposed. The model built in this paper avoids the shortcoming of steady analytical PM model in infinite time horizon and can be used to aid scheduling the maintenance plan and providing decision supporting for job shop scheduling.

Supplying Skills

THE age of 24 is often regarded as the prime of life - in which young people make the most of their time in college and plan their dream job. But for Li Qiang, the age of 24 means a turning point in his career. An auto mechanic with five years of experience in the trade in Shijiazhuang, north China＇s Hebei Province, Li was re- cently promoted as the head of a team of 10 mechanics in a car repair workshop, ＂1 failed the entrance exam for high school and had to attend a vocational school. I never expected this choice could lead me to the career of my interest.＂ Li told ChinAfrica.

Centromere repositioning and shifts in wheat evolution

The centromere is the region of a chromosome that directs its separation and plays an important role in cell division and reproduction of organisms.Elucidating the dynamics of centromeres is an alternative strategy for exploring the evolution of wheat.Here,we comprehensively analyzed centromeres from the de novoassembled common wheat cultivar Aikang58(AK58),Chinese Spring(CS),and all sequenced diploid and tetraploid ancestors by chromatin immunoprecipitation sequencing,whole-genome bisulfite sequencing,RNA sequencing,assay for transposase-accessible chromatin using sequencing,and comparative genomics.We found that centromere-associated sequences were concentrated during tetraploidization and hexaploidization.Centromeric repeats of wheat(CRWs)have undergone expansion during wheat evolution,with strong interweaving between the A and B subgenomes post tetraploidization.We found that CENH3 prefers to bind with younger CRWs,as directly supported by immunocolocalization on two chromosomes(1A and 2A)of wild emmer wheat with dicentromeric regions,only one of which bound with CENH3.In a comparison of AK58 with CS,obvious centromere repositioning was detected on chromosomes 1B,3D,and 4D.The active centromeres showed a unique combination of lower CG but higher CHH and CHG methylation levels.We also found that centromeric chromatin was more open than pericentromeric chromatin,with higher levels of gene expression but lower gene density.Frequent introgression between tetraploid and hexaploid wheat also had a strong influence on centromere position on the same chromosome.This study also showed that active wheat centromeres were genetically and epigenetically determined.

Resequencing of 145 Landmark Cultivars Reveals Asymmetric Sub-genome Selection and Strong Founder Genotype Effects on Wheat Breeding in China

Controlled pedigrees and the multi-decade timescale of national crop plant breeding programs offer a unique experimental context for examining how selection affects plant genomes.More than 3000 wheat cultivars have been registered,released,and documented since 1949 in China.In this study,a set of 145 elite cultivars selected from historical points of wheat breeding in China were re-sequenced.A total of 43.75 Tb of sequence data were generated with an average read depth of 17.94x for each cultivar,and more than 60.92 million SNPs and 2.54 million InDels were captured,based on the Chinese Spring RefSeq genome v1.0.Seventy years of breeder-driven selection led to dramatic changes in grain yield and related phenotypes,with distinct genomic regions and phenotypes tar-geted by different breeders across the decades.There are very clear instances illustrating how introduced Italian and otherforeign germplasm was integrated into Chinese wheat programs and reshaped the genomic landscape of local modern cultivars.Importantly,the resequencing data also highlighted significant asymmetric breeding selec-tion among the three sub-genomes:this was evident in both the collinear blocks for homeologous chromosomes and among sets of three homeologous genes.Accumulation of more newly assembled genes in newer cultivars implied the potential value of these genes in breeding.Conserved and extended sharing of linkage disequilibrium(LD)blocks was highlighted among pedigree-related cultivars,in which fewer haplotype differences were detected.Fixation or replacement of haplotypes from founder genotypes after generations of breeding was related to their breeding value.Based on the haplotype frequency changes in LD blocks of pedigree-related cultivars,we propose a strategy for evaluating the breeding value of any given line on the basis of the accumulation(pyramiding)of bene-ficial haplotypes.Collectively,our study demonstrates the influence of "founder genotypes" on the output of breeding efforts over many decades and also suggests that founder genotype perspectives are in fact more dy-namic when applied in the context of modern genomics-informed breeding.

Insect-plant-pathogen interactions as shaped by future climate effects on biology, distribution, and implications for agriculture

Carbon dioxide （CO2） is the main anthropogenic gas which has drastically increased since the industrial revolution, and current concentrations are projected to double by the end of this century. As a consequence, elevated CO2 is expected to alter the earths＇ climate, increase global temperatures and change weather patterns. This is likely to have both direct and indirect impacts on plants, insect pests, plant pathogens and their distribution, and is therefore problematic for the security of future food production. This review summarizes the latest findings and highlights current knowledge gaps regarding the influence of climate change on insect, plant and pathogen interactions with an emphasis on agriculture and food production. Direct effects of climate change, including increased CO2 concentration, temperature, patterns of rainfall and severe weather events that impact insects （namely vectors of plant pathogens） are discussed. Elevated CO2 and temperature, together with plant pathogen infection, can considerably change plant biochemistry and therefore plant defense responses. This can have substantial consequences on insect fecun- dity, feeding rates, survival, population size, and dispersal. Generally, changes in host plant quality due to elevated CO2 （e.g., carbon to nitrogen ratios in C3 plants） negatively affect insect pests. However, compensatory feeding, increased population size and distribution have also been reported for some agricultural insect pests. This underlines the importance of additional research on more targeted, individual insect-plant scenarios at specific locations to fully understand the impact of a changing climate on insect-plant-pathogen interactions.

Perceptual complexity of soil-landscape maps: a user evaluation of color organization in legend designs using eye tracking

We compared the ability of two legend designs on a soil-landscape map to efficiently and effectively support map reading tasks with the goal of better understanding how the design choices affect user performance.Developing such knowledge is essential to design effective interfaces for digital earth systems.One of the two legends contained an alphabetical ordering of categories,while the other used a perceptual grouping based on the Munsell color space.We tested the two legends for 4 tasks with 20 experts(in geography-related domains).We analyzed traditional usability metrics and participants’eye movements to identify the possible reasons behind their success and failure in the experimental tasks.Surprisingly,an overwhelming majority of the participants failed to arrive at the correct responses for two of the four tasks,irrespective of the legend design.Furthermore,participants’prior knowledge of soils and map interpretation abilities led to interesting performance differences between the two legend types.We discuss how participant background might have played a role in performance and why some tasks were particularly hard to solve despite participants’relatively high levels of experience in map reading.Based on our observations,we caution soil cartographers to be aware of the perceptual complexity of soil-landscape maps.

An improved culturing method for opiine fruit fly parasitoids and its application to parasitoid monitoring in the field

Good culturing methods play an important role in the study of insect behavior and its application to pest management. Here, we describe and validate a new method for rearing the parasitoid wasp, Diachasmirnorpha kraussii, which attacks some of the world＇s worst fruit fly pests and is an internationally used biological control agent. Our method differs from standard culturing approaches by presenting adult wasps with host- infested artificial media within a ＂culturing bag,＂ which mimics a natural （fruit） oviposition substrate. In laboratory trials using wild collected D. kraussii, the culturing bag method was compared to the use of host-infested nectarines, and a commonly used laboratory method of presenting host-infested artificial media within Petri dishes. The culturing bag method proved to be a significant improvement on both methods, combining the advantages of high host survival in artificial media with parasitism levels that were the equivalent to those recorded using host-infested fruits. In our field study, culturing bags infested with the Queensland fruit fly, Bactrocera tryoni, and hung in a mixed peach and nectarine orchard proved to be effective ＂artificial fruits＂ attracting wild D. kraussii for oviposition. Significantly more adult wasps were reared from the culturing bags compared to field collected fruits. This was shown to be due to higher fruit fly larval density in the bags, as similar percentage parasitism rates were found between the culturing bags and ripe fruits. We discuss how this cheap, time-efficient method could be applied to collecting and monitoring wild D. kraussii populations in orchards, and assist in maintaining genetic variability in parasitoid laboratory cultures.

Is there evidence of selection in the dopamine receptor D4 gene in Australian invasive starling populations？

Although population genetic theory is largely based on the premise that loci under study are selectively neutral, it has been acknowledged that the study of DNA sequence data under the influence of selection can be useful. In some circumstances, these loci show increased population differentiation and gene diversity. Highly polymorphic loci may be especially useful when studying populations having low levels of diversity overall, such as is often the case with threatened or newly established inva- sive populations. Using common starlings Sturnus vulgaris sampled from invasive Australian populations, we investigated se- quence data of the dopamine receptor D4 gene （DRD4）, a locus suspected to be under selection for novelty-seeking behaviour in a range of taxa including humans and passerine birds. We hypothesised that such behaviour may be advantageous when species encounter novel environments, such as during invasion. In addition to analyses to detect the presence of selection, we also esti- mated population differentiation and gene diversity using DRD4 data and compared these estimates to those from microsatellite and mitochondrial DNA sequence data, using the same individuals. We found little evidence for selection on DRD4 in starlings. However, we did find elevated levels of within-population gene diversity when compared to microsatellites and mitochondrial DNA sequence, as well as a greater degree of population differentiation. We suggest that sequence data from putatively non- neutral loci are a useful addition to studies of invasive populations, where low genetic variability is expected

在线招聘——移动互联时代的就业转型

2020年春节期间,新型冠状病毒肺炎疫情在全国迅速蔓延,经济运行相应受到冲击。在经济下行压力较大的背景下,疫情对企业发展带来了诸多问题和巨大挑战。据清华经管学院中国企业发展与并购重组研究中心发布的《新冠肺炎疫情对我国大中型企业影响调研报告》显示,疫情对企业的具体影响主要体现在限制开工(56.13%)、订单下降(41.98%)、人工成本负担过重(29.72%)、资金短缺(25.94%),部分企业面临供应链中断(21.23%)、人员不足(21.23%)、租金等固定成本负担重(16.04%)、信用和债务危机(11.79%)等方面。

The Battle to Sequence the Bread Wheat Genome:A Tale of the Three Kingdoms

In the year 2018,the world witnessed the finale of the race to sequence the genome of the world’s most widely grown crop,the common wheat.Wheat has been known to bear a notoriously large and complicated genome of a polyploidy nature.A decade competition to sequence the wheat genome initiated with a single consortium of multiple countries,taking a conventional strategy similar to that for sequencing Arabidopsis and rice,became ferocious over time as both sequencing technologies and genome assembling methodologies advanced.At different stages,multiple versions of genome sequences of the same variety(e.g.,Chinese Spring)were produced by several groups with their special strategies.Finally,16 years after the rice genome was finished and 9 years after that of maize,the wheat research community now possesses its own reference genome.Armed with these genomics tools,wheat will reestablish itself as a model for polyploid plants in studying the mechanisms of polyploidy evolution,domestication,genetic and epigenetic regulation of homoeolog expression,as well as defining its genetic diversity and breeding on the genome level.The enhanced resolution of the wheat genome should also help accelerate development of wheat cultivars that are more tolerant to biotic and/or abiotic stresses with better quality and higher yield.

Current issues involved with the identification and nutritional value of wood grubs consumed by Australian Aborigines

The so called witchetty grub is a publicized food source for Australian Aborig- ines. Despite heavy use, the identities and number of species consumed is still not known because of the lack of identified voucher specimens. Taxonomy based on adults makes identification of larval forms difficult. Dwelling in the root, trunks, and stems of woody plants, grubs are a reliable and highly valued food source that may be in decline. Much information on edible insects may already be lost in parts of Australia heavily settled by Europeans. However, there are many parts of Australia where information on edible insects is still strong and needs to be recorded accurately for long-term use. Recent iden- tification of＂witchetty grubs＂ from the witchetty bush at Barrow Creek has revealed that those there, based on their DNA, are not Endoxyla leucomochla. As grubs are collected and eaten before they mature and scientific taxonomy is based on adults, there are many unanswered questions on the grub identification and biology, host plants, and plant and grub distributions.

Responses to defoliation and fertiliser,corm development and chemical control of onion grass(Romulea rosea)in the Mediterranean environment of southern Australia

Background:Onion grass(Romulea rosea)is a common weed that infests native and improved pastures in the Mediterranean environments of southern Australia.It is a very challenging weed to control due to its distinctive growth and survival mechanisms involving corms.Methods:Three glasshouse experiments were conducted in Australia to investigate the response of onion grass to defoliation and fertiliser application,the development and growth of onion grass corms and the chemical control of the weed in winter and spring.Results:Defoliating consistently to 1 cm above ground reduced corm weight by 84%compared with the control.Medium or high fertiliser application did not increase herbage mass of onion grass compared with the nonfertilised treatment.The corm weight of onion grass declined from Weeks 1 to 8 after emergence,remained at 53-60 mg dry matter(DM)corm−1 from Weeks 8 to 19 and then declined on average to 37mgDMcorm−1 up to Week 26 after emergence.New corms started to develop at Week 6 after emergence.A small proportion of the onion grass plants(7.5%)developed multiple new corms(3-6 corms)from a single old corm.The most effective herbicide control was a winter application of metsulfuron methyl or imazamox as an alternative product to protect clover.Conclusions:This study has identified the growth and development patterns of onion grass corms,how the plant responded to defoliation and fertiliser application and effective chemical control of this weed.These findings have significant practical implications for the improvement of onion grass-infested pastures.