Leguminosae plants play a key role in affecting soil physical-chemical and biological properties during grassland succession after farmland abandonment in the Loess Plateau,China

Leguminosae are an important part of terrestrial ecosystems and play a key role in promoting soil nutrient cycling and improving soil properties.However,plant composition and species diversity change rapidly during the process of succession,the effect of leguminosae on soil physical-chemical and biological properties is still unclear.This study investigated the changes in the composition of plant community,vegetation characteristics,soil physical-chemical properties,and soil biological properties on five former farmlands in China,which had been abandoned for 0,5,10,18,and 30 a.Results showed that,with successional time,plant community developed from annual plants to perennial plants,the importance of Leguminosae and Asteraceae significantly increased and decreased,respectively,and the importance of grass increased and then decreased,having a maximum value after 5 a of abandonment.Plant diversity indices increased with successional time,and vegetation coverage and above-and below-ground biomass increased significantly with successional time after 5 a of abandonment.Compared with farmland,30 a of abandonment significantly increased soil nutrient content,but total and available phosphorus decreased with successional time.Changes in plant community composition and vegetation characteristics not only change soil properties and improve soil physical-chemical properties,but also regulate soil biological activity,thus affecting soil nutrient cycling.Among these,Leguminosae have the greatest influence on soil properties,and their importance values and community composition are significantly correlated with soil properties.Therefore,this research provides more scientific guidance for selecting plant species to stabilize soil ecosystem of farmland to grassland in the Loess Plateau,China.

Friedel-Crafts烷基化反应研究进展

Friedel-Crafts烷基化反应是一类重要的有机人名反应,常用于构建碳-碳键,在有机合成及药物化学等领域具有广泛的应用前景。本文介绍了Friedel-Crafts烷基化反应的基本原理,以及近年来利用金属催化、有机小分子催化、可见光催化、酶催化和电化学催化等策略所取得的新发展。将本科教学知识与前沿研究有机结合,有利于提高学生的学习兴趣,培养学生思维拓展能力。

Analysis and verification of electrodynamic force,thermal stress and current sharing for CRAFT converter structure design

In the design realm of fusion power supplies,structural components play a pivotal role in ensuring the safety of fusion devices.To verify the reliability of the converter structure design at the Comprehensive Research Facility for Fusion Technology(CRAFT),meticulous analysis of the converter's dynamic impact is carefully performed based on the worst fault current(400k A),firstly.Subsequently,the thermal stress analysis based on the maximum allowable steadystate temperature is finished,and the equivalent thermal stress,thermal deformation,maximum shear stress of a single bridge arm and the whole converter are studied.Furthermore,a simple research method involving the current-sharing characteristics of a bridge arm with multithyristor parallel connection is proposed using a combination of Simplorer with Q3D in ANSYS.The results show that the current-sharing characteristics are excellent.Finally,the structural design has been meticulously tailored to meet the established requirements.

Evolution of Handicraft Industries in the Textile Sector in Saudi Arabia: A Comprehensive Analysis of Trends and Innovations

This review explores the evolution of the textile handicraft industry in Saudi Arabia, emphasizing its cultural and economic significance. The study highlights the transition from traditional practices to modern innovations and examines the impact of globalization and technological advancements on the industry. Key innovations are discussed, demonstrating their role in enhancing textile production while preserving cultural heritage. Major challenges, such as competition from industrial textiles and the need for sustainable practices, are identified. Opportunities for growth are explored, including leveraging tourism and international markets to promote Saudi handicrafts. The social and cultural impacts of the sector are underscored, particularly in sustaining community traditions and providing economic opportunities for artisans. Strategic recommendations for supporting and advancing the industry are offered, ensuring its continued relevance and sustainability in a rapidly changing global market. This analysis provides a robust framework for understanding the current state and future potential of Saudi Arabia’s textile handicraft industry.

有机催化吲哚的不对称Friedel-Crafts烷基化反应研究进展

功能化吲哚在许多研究领域有广泛的应用,因此旋光性吲哚衍生物的合成在有机合成中有重要的意义。催化不对称Friedel-Crafts烷基化是研究吲哚区域选择性功能化最直接、最彻底的方法。本文综述了近二十年来有机催化剂催化吲哚的不对称Friedel-Crafts烷基化反应的进展,并对此作出总结与展望。

布洛芬生产工艺中Friedel-Crafts酰化反应的无溶剂连续流工艺设计

针对传统布洛芬生产工艺过程的Friedel-Crafts酰化反应中存在工艺复杂、能耗大、环境压力大的问题,本研究将无溶剂连续流合成技术应用于2-氯丙酰氯与异丁基苯的Friedel-Crafts酰化反应,设计了一个无溶剂连续流反应体系,通过考察停留时间、温度、总流量和物质的量比等因素,优化工艺并获得最佳的生产条件,安全有效地实现了高腐蚀性汽液混合物的连续流合成反应中高质量芳基酮的制备,异丁基苯的转化率和芳基酮的纯度可达99%左右。本研究为药物合成领域的连续流合成工艺与相关Friedel-Crafts酰化反应的同系列研究提供参考依据。

Responses of microbial activities and soil physical-chemical properties to the successional process of biological soil crusts in the Gurbantunggut Desert,Xinjiang

Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0-2 cm. Varia- tions of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that micro- algal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients （organic C, total N, total P, available N, available P and available K） were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly decreased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme activities increased soil fertility and promoted the growth of cyanobacteria, eukary- otic algae and heterotrophic microorganism, with the accelerating succession of BSCs. The present research found that microalgal-microbial biomass and enzyme activities played important roles on the contents of nutrients in the successional stages of BSCs and helped us to understand developmental mechanism in the succession of BSCs.

基于机器学习的单脉冲搜索候选体识别对FAST观测CRAFTS数据的应用研究

单脉冲搜索作为脉冲星探测的有力工具,在探测旋转射电暂现源以及快速射电暴中扮演着重要角色。为了从海量的射电巡天数据中快速筛选出最有价值的单脉冲搜索候选体,候选体识别已经从早期启发式阈值判断发展到基于机器学习自动识别。对于FAST观测,研究了基于机器学习的单脉冲搜索候选体识别应用到CRAFTS(the commensal radio astronomy FAST survey)超宽带脉冲星数据的性能表现。在评估过程中,使用单脉冲事件组识别(SPEGID)和单脉冲搜索器(SPS)两类自动识别方法,通过7种不同机器学习分类器对CRAFTS基准数据集产生的单脉冲搜索候选体进行自动识别;作为对比,也使用了启发式阈值判断的方法(RRATtrap和Clusterrank)。结果表明,SPEGID具有最好的性能表现(最高的F1-score值95.1%、次高的召回率95.4%、最低的假阳性率4.7%),SPS具有最快的筛选速度(平均每小时筛选4010个候选体)。通过对比分析结果,探讨了如何基于FAST观测数据开展高效的单脉冲搜索候选体识别。

Contribution to Comparative Study of Physical-Chemical Characteristics of Diack Basalt and Bandia Limestone for Use in Railway Engineering

This paper presents a comparative study of Physical-Chemical characteristics of Limestone and Basalt (from Senegalese quarries). First, chemical tests show that Basalt is richer in silica 51.59% versus 2.84% for Limestone. Basalt is made up of silica minerals and essentially carbonated minerals with a CaO percentage of 50.05%. Chemical results also show that Basalt is richer in iron 12.71% versus 0.44% for Limestone. Finally, they revealed a fire loss of 40.91% for Limestone and 2.44% for Basalt. Second, physical analysis results show that Diack Basalt has the best characteristics with a flattening coefficient of 5% between 5% and 20%;the percentage of pollutants is 0.36% less than 1%;the Los Angeles coefficient is 12.21% below 15, while Bandia Limestone gives a flattening coefficient of 3%;the Los Angeles coefficient of 40.17% and the percentage of pollutant (2.4%) well above 2%. It is noted that the percentage of Limestone pollutant is too high. These important results show the net advantage of Basalt compared to Limestone in terms of physical-chemical characteristics.

CRAFT超导磁体电源控制策略设计

聚变堆主机关键系统综合研究设施(CRAFT)的超导磁体是大惯性负载,其测试电流达到120kA。超导磁体电源需要并联运行输出功率,在电流反馈控制模式,输出电压快速变化和变流器之间的负荷分配是很大的问题。针对输出电压快速变化问题,设计了基于神经元的PID参数自适应的控制方法,减小了系统的超调量;针对变流器并联运行的负荷分配问题,在研究变流器环电流特性的基础上,设计了基于虚拟环流阻抗的均流控制策略,保证了变流器之间负荷的平均分配。最后通过仿真和实验验证了设计方法的可行性。

QSPR between Physical-Chemical Properties and Molecule Parameters of Alkanes

A set of molecule parameters, namely, N, N′, p, q, n, were used to express the structures of alkanes. A correlative model was established between certain physical-chemical properties and molecular parameters of alkanes by regression method. Eight physical-chemical properties, such as evaporation heat （△vHm^20）, density（D^20 ）, capacity （C^20）, surface tension （δ^20）, boiling point （Tb）, critical temperature（Tc）, critical pressure（Pc） and critical volume（Vc）, of fifty-six C3-C16 alkanes were calculated directly from the model in this paper. The calculated values are in good accordance with the literature ones reported for alkanes, and the correlation coefficients （R） equal or exceed 0.99 . The research results indicate that the principle of the method is simple and clear, the method is practical, the correlativity is excellent, and the predicted data are credible.

Variation of soil physical-chemical characteristics in salt-affected soil in the Qarhan Salt Lake,Qaidam Basin

Soil salinization has adverse effects on the soil physical-chemical characteristics.However,little is known about the changes in soil salt ion concentrations and other soil physical-chemical characteristics within the Qarhan Salt Lake and at different soil depths in the surrounding areas.Here,we selected five sampling sites(S1,S2,S3,S4,and S5)alongside the Qarhan Salt Lake and in the Xidatan segment of the Kunlun Mountains to investigate the relationship among soil salt ion concentrations,soil physical-chemical characteristics,and environmental variables in April 2019.The results indicated that most sites had strongly saline and very strongly saline conditions.The main salt ions present in the soil were Na^(+),K^(+),and Cl^(-).Soil nutrients and soil microbial biomass(SMB)were significantly affected by the salinity(P<0.05).Moreover,soil salt ions(Na^(+),K^(+),Ca2+,Mg^(2+),Cl^(-),CO_(3)^(2-),SO_(4)^(2-),and HCO_(3)^(-))were positively correlated with electrical conductivity(EC)and soil water content(SWC),but negatively related to altitude and soil depth.Unlike soil salt ions,soil nutrients and SMB were positively correlated with altitude,but negatively related to EC and SWC.Moreover,soil nutrients and SMB were negatively correlated with soil salt ions.In conclusion,soil nutrients and SMB were mainly influenced by salinity,and were related to altitude,soil depth,and SWC in the areas from the Qarhan Salt Lake to the Xidatan segment.These results imply that the soil quality(mainly evaluated by soil physical-chemical characteristics)is mainly influenced by soil salt ions in the areas surrounding the Qarhan Salt Lake.Our results provide an accurate prediction of how the soil salt ions,soil nutrients,and SMB respond to the changes along a salt gradient.The underlying mechanisms controlling the soil salt ion distribution,soil nutrients,and SMB in an extremely arid desert climate playa should be studied in greater detail in the future.

Physical-Chemical Aggressiveness of Solutions of Medicines as a Factor in the Rheology of the Blood inside Veins and Catheters

In experiments in vitro and observations in the clinic in vivo studied the state of the lumen of subcutaneous veins and blood rheology of patients after their interaction with vascular catheters and solutions of medicines based on the values of temperature, volume, concentration, osmotic activity and pH. It is shown that heparin injection in blood not prevent, but solution of 4% sodium bicarbonate injection prevents blood clotting, blood clots and blockage blood clots of veins and of catheters. It is shown that the heating to a temperature of＋42 ℃ with the solution of 4% sodium bicarbonate provides softening action on old dry blood clots in 1 min, and their subsequent irrigation with a warm solution of 4% sodium bicarbonate and 3% hydrogen peroxide provides complete destruction and discoloration of the remaining spots of blood during 2 s. Proposed new medicines and hygiene products for the protection of the veins and installed in them vascular catheters from blockage of blood clots, and for removing blood stains from clothes and body surface patients.

Compatible stability study of Xing NaoJing injection based on physical-chemical properties analysis

Objective:The clinical treatment of brain diseases is urgent. Xingnaojing (XNJ) injection is often used in combination with other injection drugs. Due to the possible interaction between the injections in vivo, the particle size, osmotic pressure, pH value change and component stability decrease, that is one of the important factors causing various adverse reactions. Based on the above situation, this study investigated the physical properties and chemical composition changes of XNJ injection and its compatibility solvent and 13 kinds of clinical injection, speculated the possible interactions between the drugs in vivo from the perspective of in vitro compatibility stability, find out the safety risks of adverse reactions and provide guidance for the safe and rational use of XNJ injection. Methods:According to the clinical application, XNJ injection was mixed with 13 combination injections based on 250 mL 5% glucose injection, and placed at room temperature for 6 h. Then, the clarity, particle size, pH, osmolality, and the contents of camphor, d-borneol, and muscone of the compatible solutions were detected at 0, 1, 2, 4, and 6 h, respectively. Results:The results showed that the physical-chemical properties of compatibility solution were slightly influenced when XNJ was combined with Alprostadil injection and Danhong injection. The change of particle size and the degradation of muscone content were the main factors affecting the compatibility stability of XNJ injection, indicating that there are some problems in compatibility stability, which may be one of the causes of clinical adverse reactions. Conclusion:This study suggests that XNJ injection in combination with other injections during intravenous administration should be performed cautiously.

基于改进的CRAFT的光学字符分割算法

现有的场景文字检测算法存在特征能力提取不足和无法适应场景文本大小变化多端的问题。针对这些不足,对CRAFT算法进行改进,把原本的VGG16_bn特征提取网络替换成ESPANet网络,使网络能够适应文字的大小变化,同时加入一种融合注意力机制让网络学习到空间和位置上的权重,达到增强重要特征、抑制无用特征的效果,从而提升在不同场景下字符的分割质量和分割能力。在ICDAR2013和ICDAR2015两个数据集上进行验证,实验结果表明改进之后的算法在准确率、召回率以及调和平均数三个指标都表现优异,更优于原CRAFT算法及其他文字检测算法。

跟方块世界告别——Minecraft杂谈

前言自2013年初首次在《少年电脑世界》上介绍Minecraft,已经过去十载有余。小约想了许久在最后一期该介绍些什么,终究没有找到一个应景的选题,于是便有了这么一篇杂谈,回答大家在邮件中提出的问题,浅谈一些未能完整介绍的内容。既是对这段漫长旅程的回顾,也是对未来的小小展望吧。

科创企业创始人的角色塑造与转换及其对突破性创新的作用机制

科创企业是实现科技自主创新和服务国家重大战略的重要载体,其创始人如何塑造与转换角色是企业创新突破的关键,但现有研究缺乏对科创企业创始人角色塑造与转换的条件、过程及结果的理论探讨。本文采用单案例分析方法,探究科创企业创始人的角色塑造与转换及其对突破性创新的作用机制。研究发现:外部情境和创始人特质双重因素是创始人角色塑造与转换的先决条件;角色塑造与转换对突破性创新的作用机制是创始人依次触发角色动机、建构角色定位,进而执行角色行为、形成角色效应的过程;随着外部环境的阶段性变化和创始人特质的阶段性凸显,创始人的角色动机依次实现从核心技术自主动机、应用技术转化动机到生态技术深化动机的转变,角色定位呈现“技术领头羊—战略驾驭者—创新文化引领者”的演变,角色行为也从资源自建转变为资源杠杆再转变为资源共创,推动企业依次形成核心技术突破效应、应用技术占有效应、生态技术赋能效应。本文研究结论为科创企业创始人角色管理和创新实践提供了借鉴。

酸性离子液体催化Friedel-Crafts烷基化反应研究进展

介绍了Friedel-Crafts烷基化反应的催化反应机理,综述了Lewis酸性离子液体、Bronsted酸性离子液体、Bronsted-Lewis双酸性离子液体的结构特性及其在催化Friedel-Crafts烷基化反应中的应用研究进展,并对未来发展方向进行了总结和展望。

发展型人力资源管理实践对员工主动变革行为的影响机制:中庸思维的调节作用

作为新兴的人力资源管理实践,发展型人力资源管理实践能够对员工的工作动机、行为产生积极影响。然而,在中国本土文化情境下,鲜有文献涉及发展型人力资源管理实践如何影响员工主动变革行为。基于资源保存理论和“能力—动机—机会(AMO)”框架,探讨发展型人力资源管理实践对员工主动变革行为的影响机制和边界条件。通过对三阶段349份有效样本的分析发现,发展型人力资源管理实践对员工主动变革行为具有显著正向影响;员工工作重塑在发展型人力资源管理实践与员工主动变革行为间发挥部分中介作用;中庸思维会进一步强化发展型人力资源管理实践与主动变革行为间关系,且该调节效应会被工作重塑中介。

Friedel-Crafts烷基化反应就地增容WPS/OBC合金研究

采用不同种类的回收废旧聚苯乙烯(PS)与乙烯辛烯嵌段共聚物(OBC)进行Friedel-Crafts烷基化反应,考察了催化剂无水AlCl_(3)用量对废旧PS接枝率和共混物结构、性能的影响。结果表明:由于杂质的存在,回收造粒的发泡PS废旧制件(WEPS)不能与OBC直接进行Friedel-Crafts烷基化反应;而回收造粒的非发泡PS废旧制件(WPS)可以与OBC进行Friedel-Crafts烷基化反应,生成OBC-g-WPS接枝物;当反应温度为140℃,WPS、OBC、无水AlCl_(3)质量比为50.0/50.0/0.4时,WPS接枝率达到了23.5%,与WPS/OBC简单共混物相比,WPS/OBC/无水AlCl_(3)共混物拉伸强度和断裂伸长率分别增加了125.4%和2913.5%;WPS/OBC/无水AlCl_(3)共混物中OBC的熔点和结晶温度均降低,OBC和WPS两相的相容性得到明显提高;以WPS/OBC/无水AlCl_(3)(质量比50.0/50.0/0.4)共混物为增容母料增韧WEPS,制备了WEPS/增容母料(质量比40.0/60.0)共混物,其冲击强度比纯WEPS提高了1044.4%,比WEPS/OBC共混物提高了415.0%。