Forests of West Virginia,U.S.A. and Shaanxi,China:a study in forest exploitation and recovery

A review of the period of unregulated exploitation of forests in the state of West Virginia (U.S.) and in Shaanxi Province, PRC was presented. Economic and ecological recovery from exploitation has been different in the two regions due to basic differences in nature of the forest and in the degree and persistence of exploitive pressures. After a century since unregulated exploitation, West Virginia forests are well on the road to management for sustainability and conservation. Shaanxi's recovery from overuse and unregulated exploitation is less certain; forests are still in the early phases of ecological recovery there. Full recovery to a period of sustainability will take a century or longer. Suggestions are made for measures needed to enhance the forest recovery. Keywords Forests - Shaanxi - West Virginia - Central China - Forest exploitation - Recovery CLC number S754 Document code A Article ID 1007-662X(2004)01-0049-06 Foundation item: The project was sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (2002–2004) and Shaanxi Provincial Foreign Expert Bureau (2003).Biography: Jack E. Coster (1935-), male, professor of West Virginia University, Morgantown, West Virginia. U.S.A.Responsible editor: Song Funan

FISH ASSEMBLAGE RESPONSES TO DIFFERENT SECONDARY CHANNEL DESIGNS IN THE LOWER MISSISSIPPI RIVER,U.S.A.:A TEMPLATE FOR RIVER RESTORATION

The lower Mississippi River(LMR) has been heavily modified for multiple human purposes such as navigation, flood control, and bank stabilization. However, the LMR simultaneously supports a diverse fish fauna that includes recreational and commercial fisheries. Due to river training and diversion structures constructed during the past 80 years, the historic characteristics of the LMR have been drastically altered and have likely influenced fishes and fisheries in the system. One common restoration measure used throughout the LMR has been to "notch" wing-dike structures that close secondary(side) river channels. Dike notching allows year-round flows through secondary channels, which enhances habitat diversity and promotes biological productivity at the ecosystem scale. Although notching is presumed good for LMR fishes and other biota, few studies have examined its effects on fish assemblages. In this study, fish assemblages were sampled at seven LMR secondary channels spanning from river kilometer(rkm) 628(Louisiana-Mississippi, U.S.A.) upstream to rkm 1504(Missouri-Kentucky, U.S.A.). Four secondary channels were termed "permanent"(i.e.,with notched dikes) while three secondary channels were termed "temporary"(i.e., without notched dikes).Fishes were sampled by boat-mounted electrofishing conducted during falling and low stages from1995—1997. Fish assemblages differed between permanent and temporary secondary channels, and varied somewhat between falling and low stages. Gizzard shad(Dorosoma cepedianum), threadfin shad(D. petenense), and white bass(Morone chrysops) demonstrated consistent preferences for low-current conditions associated with temporary secondary channels. Conversely, blue catfish(Ictalurus furcatus), flathead catfish(Pylodictis olivaris), and freshwater drum(Aplodinotus grunniens) were more associated with permanent secondary channels. Future restoration strategies in the LMR should consider dike notching and resultant maintenance of permanent secondary channels in selected river reaches. However, temporary secondary channels also contain unique fish species, and also appear to be important sites of riverine primary production. Restoration strategies should consider a balance of both secondary channel types, which should support the greatest biodiversity for the LMR ecosystem.

基于双随机森林的发热待查智能诊断方法

在机器学习预测模型中,不平衡数据集会降低少数类的预测准确性。针对发热待查数据集的不平衡特性,该文提出了一种基于K-Means聚类欠采样的双随机森林病因预测方法。首先通过K-Means聚类欠采样构建一个平衡数据集,并在此基础上创建一个基于CART投票机制的随机森林预测模型。然后对初始数据集用同样的方法创建一个随机森林预测模型。最后将两个随机森林预测模型联合,使用两者的CART一起投票预测。该文提出的方法增加了CART的数量,在保持原有数据集特性的同时,提高了少数类的投票权重。在发热待查数据集上的实验表明,该文所提方法不仅改善了少数类的预测性能,对其他类别的预测性能也有一定程度的提升。

大语言模型时代下徽文化海外传播的问题与对策:一项基于“他者”视角的个案参照

“他者”指自我以外的一切人与事物,是一个与主体既有区别,又有联系的参照物,通过“他者”视角能更好地认识自我。徽文化是中华传统文化最典型的地域亚文化之一,其海外传播是国家文化战略的重要一环,值得深入研究。本文以俄亥俄州立大学东亚语文资源中心为个案参照,分析当前徽文化海外传播存在的诸多问题并进行“他者”对比,如力量分散、手段单一等,继而提出从主体受众、项目引领、技术赋能等方面积极开展应对策略,以期开创文化交流新格局,助力大语言模型时代的徽文化海外传播。

Assessment of Wet Season Precipitation in the Central United States by the Regional Climate Simulation of the WRFG Member in NARCCAP and Its Relationship with Large-Scale Circulation Biases

Assessment of past-climate simulations of regional climate models(RCMs)is important for understanding the reliability of RCMs when used to project future regional climate.Here,we assess the performance and discuss possible causes of biases in a WRF-based RCM with a grid spacing of 50 km,named WRFG,from the North American Regional Climate Change Assessment Program(NARCCAP)in simulating wet season precipitation over the Central United States for a period when observational data are available.The RCM reproduces key features of the precipitation distribution characteristics during late spring to early summer,although it tends to underestimate the magnitude of precipitation.This dry bias is partially due to the model’s lack of skill in simulating nocturnal precipitation related to the lack of eastward propagating convective systems in the simulation.Inaccuracy in reproducing large-scale circulation and environmental conditions is another contributing factor.The too weak simulated pressure gradient between the Rocky Mountains and the Gulf of Mexico results in weaker southerly winds in between,leading to a reduction of warm moist air transport from the Gulf to the Central Great Plains.The simulated low-level horizontal convergence fields are less favorable for upward motion than in the NARR and hence,for the development of moist convection as well.Therefore,a careful examination of an RCM’s deficiencies and the identification of the source of errors are important when using the RCM to project precipitation changes in future climate scenarios.

基于射频波强化的试验型水热反应器研究

针对水热提取反应目前主要依靠微波强化,存在穿透深度小、加热均匀性差的问题,利用加热均匀性更好的射频波为热源,基于常见的水平式平行极板射频加热系统设计了一套适用于射频强化的水热反应器。该水热反应器主要由双层反应釜、压力调节装置、光纤测温计和气动磁力搅拌器4部分构成,首先对整机结构及工作原理进行阐述,然后基于内压薄壁圆筒应力分析理论和磁力耦合传动理论对双层反应釜和气动磁力搅拌器的关键零部件进行设计,并完成了压力调节装置和测温方式的设计和选型,最后完成射频强化水热反应试验平台的搭建,并选取搅拌转速、液固比和射频极板间距对水热反应器的搅拌和升温性能进行了测试。结果表明:当液固比大于20 mL/g时,搅拌转速与对照样品纯水无显著差异(p>0.05),此时液固比不再是影响搅拌转速的主要因素;当液固比小于40 mL/g、搅拌转速大于150 r/min时,极板间距是影响物料升温速率的主要因素,随着极板间距的减小,升温速率不断加快,当极板间距为130 mm时,升温速率可达到8~10℃/min。

可延展压电薄膜基底结构界面脱粘的预测与调控

调控薄膜基底结构的表面不稳定性已被成功应用于制备可延展的新型电子设备中。然而,该类电子器件在工作中需要承受外部载荷作用,致使薄膜-基底结构界面处残余应力集中,容易诱发薄膜电子器件与基底脱粘与分层。该文将从理论分析和数值仿真角度,研究压电薄膜在柔性基底表面上的失稳特性。由于压电薄膜变形具有大位移小应变的特点,该文基于非线性Euler-Bernoulli梁理论与能量最小化原理,建立压电薄膜基底结构无屈曲、褶皱、局部屈曲及全脱层屈曲模式的理论分析模型;从能量角度定量分析了薄膜-基底结构4种模式相互演变的临界条件;通过数值仿真,验证了该文解析结的有效性,定量、定性的讨论了薄膜基底结构的材料、几何参数对4种模式演变的影响。研究结果表明:改变基底弹性模量、预应变、物理场强度和界面粘附系数能够调控压电薄膜基底结构的屈曲模式;通过调控温度变化量和电压的方式,能够实现对压电薄膜基底结构的失稳特性精细化调控。该文的研究结果将为提升薄膜基底型的电子器件的稳定性及优化设计提供理论支持。

我国体育用品制造产业集群成熟度模型构建及其实证研究

通过构建体育用品制造产业集群成熟度评价指标体系对我国8个典型体育用品制造产业集群成熟度进行实证评价,发现:(1)目前在我国典型体育用品制造产业集群中,除江苏江都运动护具制造产业集群之外,其他集群成熟度评价得分均>8,评价等级隶属于“较高”,说明我国体育用品制造产业集群经过多年发展已经进入到成熟阶段。(2)在集群组织生产成熟度、集群知识创新成熟度、集群社会网络成熟度、集群发展环境成熟度4个一级评价指标中,我国典型体育用品制造产业集群的集群发展环境成熟度评分得分均>8,评价等级隶属于“较高”,说明我国体育用品制造产业集群发展环境普遍较优;集群知识创新成熟度得分均<8,评价等级隶属于“一般”与“较高”之间,说明我国体育用品制造产业集群的知识创新普遍较差并滞后于集群整体成熟度。(3)进一步分析,发现目前我国体育用品制造产业集群处于成熟巩固期向成熟创新期过渡的阶段。由此,提出我国培育世界级先进体育用品制造产业集群的建议:合理把握发展时长,制定梯次发展目标;明确发展主体,发挥主体作用;制定合理战略,注重融合发展;注重驱动机制创新,设计多种实施路径。

与机器交流:人机传播领域的未来轨迹

机器行为者(machine actor)融入日常生活的现象不仅模糊了人机之间的界限,更带来了机遇和挑战。在此背景下,人机传播研究立足前沿,探索新兴的人机互动现象。这个由机器驱动的时代正在快速发展,本研究展望未来,讨论人机传播领域如何继续发展和扩展其研究范式。具体而言,本研究深入探讨人机传播的理论基础和方法论,考量以社会临场感和信任为中心的两个研究前沿,从不同角度探讨人机传播的重要意义并对人机传播未来的研究提出方向。

文化研学:来华留学项目的新尝试与新启示

文章从美国中文教学近年的发展情况出发,论述了赴华留学与文化研学对海外中文教学发展的重大意义,继而探讨了赴华留学项目面对的挑战与改进思路。借助具体案例,建议通过建立与时俱进的新型文化研学活动与课堂教学二者相结合的留学项目模式,解决海外留学中的重要难题———融入中国社会。毫无疑问,留学项目的成功将极大提升留学生的中文水平,增强对中国文化与社会的了解和认识,并最终对美国中文教育的发展和不同国家之间的文明交流互鉴起到积极的促进作用。

Assimilation of GOES-R Geostationary Lightning Mapper Flash Extent Density Data in GSI 3DVar, EnKF, and Hybrid En3DVar for the Analysis and Short-Term Forecast of a Supercell Storm Case

Capabilities to assimilate Geostationary Operational Environmental Satellite “R-series ”(GOES-R) Geostationary Lightning Mapper(GLM) flash extent density(FED) data within the operational Gridpoint Statistical Interpolation ensemble Kalman filter(GSI-EnKF) framework were previously developed and tested with a mesoscale convective system(MCS) case. In this study, such capabilities are further developed to assimilate GOES GLM FED data within the GSI ensemble-variational(EnVar) hybrid data assimilation(DA) framework. The results of assimilating the GLM FED data using 3DVar, and pure En3DVar(PEn3DVar, using 100% ensemble covariance and no static covariance) are compared with those of EnKF/DfEnKF for a supercell storm case. The focus of this study is to validate the correctness and evaluate the performance of the new implementation rather than comparing the performance of FED DA among different DA schemes. Only the results of 3DVar and pEn3DVar are examined and compared with EnKF/DfEnKF. Assimilation of a single FED observation shows that the magnitude and horizontal extent of the analysis increments from PEn3DVar are generally larger than from EnKF, which is mainly caused by using different localization strategies in EnFK/DfEnKF and PEn3DVar as well as the integration limits of the graupel mass in the observation operator. Overall, the forecast performance of PEn3DVar is comparable to EnKF/DfEnKF, suggesting correct implementation.

Machine learning-guided accelerated discovery of structure-property correlations in lean magnesium alloys for biomedical applications

Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability,biocompatibility,and impressive mechanical characteristics.However,their rapid in-vivo degradation presents challenges,notably in upholding mechanical integrity over time.This study investigates the impact of high-temperature thermal processing on the mechanical and degradation attributes of a lean Mg-Zn-Ca-Mn alloy,ZX10.Utilizing rapid,cost-efficient characterization methods like X-ray diffraction and optical microscopy,we swiftly examine microstructural changes post-thermal treatment.Employing Pearson correlation coefficient analysis,we unveil the relationship between microstructural properties and critical targets(properties):hardness and corrosion resistance.Additionally,leveraging the least absolute shrinkage and selection operator(LASSO),we pinpoint the dominant microstructural factors among closely correlated variables.Our findings underscore the significant role of grain size refinement in strengthening and the predominance of the ternary Ca_(2)Mg_(6)Zn_(3)phase in corrosion behavior.This suggests that achieving an optimal blend of strength and corrosion resistance is attainable through fine grains and reduced concentration of ternary phases.This thorough investigation furnishes valuable insights into the intricate interplay of processing,structure,and properties in magnesium alloys,thereby advancing the development of superior biodegradable implant materials.

Study of hybrid nanofluid flow in a stationary cone-disk system with temperature-dependent fluid properties

Cone-disk systems find frequent use such as conical diffusers,medical devices,various rheometric,and viscosimetry applications.In this study,we investigate the three-dimensional flow of a water-based Ag-Mg O hybrid nanofluid in a static cone-disk system while considering temperature-dependent fluid properties.How the variable fluid properties affect the dynamics and heat transfer features is studied by Reynolds's linearized model for variable viscosity and Chiam's model for variable thermal conductivity.The single-phase nanofluid model is utilized to describe convective heat transfer in hybrid nanofluids,incorporating the experimental data.This model is developed as a coupled system of convective-diffusion equations,encompassing the conservation of momentum and the conservation of thermal energy,in conjunction with an incompressibility condition.A self-similar model is developed by the Lie-group scaling transformations,and the subsequent self-similar equations are then solved numerically.The influence of variable fluid parameters on both swirling and non-swirling flow cases is analyzed.Additionally,the Nusselt number for the disk surface is calculated.It is found that an increase in the temperature-dependent viscosity parameter enhances heat transfer characteristics in the static cone-disk system,while the thermal conductivity parameter has the opposite effect.

Theoretical and experimental investigations on an X-shaped vibration isolator with active controlled variable stiffness

A novel X-shaped variable stiffness vibration isolator(X-VSVI)is proposed.The Runge-Kutta method,harmonic balance method,and wavelet transform spectra are introduced to evaluate the performance of the X-VSVI under various excitations.The layer number,the installation angle of the X-shaped structure,the stiffness,and the active control parameters are systematically analyzed.In addition,a prototype of the X-VSVI is manufactured,and vibration tests are carried out.The results show that the proposed X-VSVI has a superior adaptability to that of a traditional X-shaped mechanism,and shows excellent vibration isolation performance in response to different amplitudes and forms of excitations.Moreover,the vibration isolation efficiency of the device can be improved by appropriate adjustment of parameters.

Supposition of graphene stacks to estimate the contact resistance and conductivity of nanocomposites

In this study,the effects of stacked nanosheets and the surrounding interphase zone on the resistance of the contact region between nanosheets and the tunneling conductivity of samples are evaluated with developed equations superior to those previously reported.The contact resistance and nanocomposite conductivity are modeled by several influencing factors,including stack properties,interphase depth,tunneling size,and contact diameter.The developed model's accuracy is verified through numerous experimental measurements.To further validate the models and establish correlations between parameters,the effects of all the variables on contact resistance and nanocomposite conductivity are analyzed.Notably,the contact resistance is primarily dependent on the polymer tunnel resistivity,contact area,and tunneling size.The dimensions of the graphene nanosheets significantly influence the conductivity,which ranges from 0 S/m to90 S/m.An increased number of nanosheets in stacks and a larger gap between them enhance the nanocomposite's conductivity.Furthermore,the thicker interphase and smaller tunneling size can lead to higher sample conductivity due to their optimistic effects on the percolation threshold and network efficacy.

累积叠轧焊Al/Mg/Al多层复合材料的腐蚀行为

研究累积叠轧焊(ARB)Al1050/AZ31/Al1050多层复合材料的腐蚀行为,腐蚀介质为3.5%Na Cl(质量分数)溶液,分析测试手段包括动电位极化测试(PDP)、电化学阻抗谱(EIS)、扫描电子显微镜(SEM-EDS)、拉曼光谱和X射线衍射(XRD)等。为了深入研究Al1050/AZ31/Al1050多层复合材料的耐腐蚀性和腐蚀产物,对ARB制备的Al1050/Al1050/Al1050多层复合材料进行了相似的测试作为对比。动电位极化曲线和电化学阻抗谱显示,ARB应变水平会显著影响腐蚀速率。与Al1050/Al1050/Al1050样品相比,Al1050/AZ31/Al1050多层复合材料具有更高的腐蚀速率和更低的极化电阻。AZ31层对腐蚀过程起主导作用。拉曼和XRD分析结果表明主要腐蚀产物为Mg(OH)2,且不含任何氯化合物(如(Mg(OH)_(2))·MgCl_(2))。

Upcycling municipal solid waste to sustainable hydrogen via two-stage gasification-reforming

As global municipal solid waste(MSW)quantities continue to escalate,serious socio-environmental challenges arise,necessitating innovative solutions.Waste-to-hydrogen(WTH)via two-stage gasification-reforming(TSGR)presents an emergent technology for MSW upcycling,offering to ease waste management burdens and bolster the burgeoning hydrogen economy.Despite early initiatives to advance TSGR technology,a cohesive and critical analysis of cutting-edge knowledge and strategies to enhance hydrogen production remains lacking.This review aggregates literature on MSW upcycling to hydrogen via TSGR,with a focus on optimizing process control and catalytic efficiency.It underscores technological avenues to augment hydrogen output,curtail catalyst costs,and refine system performance.Particularly,the review illuminates the potential for integrating chemical and calcium looping into TSGR processes,identifying opportunities,and pinpointing challenges.The review concludes with a summary of the current state of techno-economic analysis for this technology,presenting outstanding challenges and future research directions,with the ultimate goal of transitioning WTH from theoretical to practical application.

在复二维仿射锥上的完备余齐性一Kahler度量

In this paper,we revisit the Kahler structures on the affine quadrics M1={z_(1)^(2)+z_(2)^(2)+z_(3)^(2)=1}in the paper by Bo Yang and Fang-Yang Zheng.We found that the Kahler structures on the complex surface are more complicated than what they have thought.We shall also give some detail calculations and found that our results fit quite well with earlier papers of the first author,one of them with X.X.Chen.

Development of Extraction and Detection Method for a Chemotherapeutic Drug with Phenytoin in Biological Samples

Dexamethasone is classified as a corticosteroid and is commonly used among cancer patients to decrease the amount of swelling around the tumor. Among patients with cancer, in particular brain tumors, seizures can become a daily routine in their everyday lives. To counteract the seizures, an antiepileptic drug such as phenytoin is administered to act as an anticonvulsant. Phenytoin and dexamethasone are frequently administrated concurrently to brain cancer patients. A previous study has shown that phenytoin serum concentration decreases when administrated concurrently with dexamethasone. Thus, it is important to monitor the concentration of these two drugs in biological samples to ensure that the proper dosages are administrated to the patients. This study aims to develop an effective extraction and detection method for dexamethasone and phenytoin. A reverse-phase high-performance liquid chromatography (HPLC) method with UV/Vis detection has been developed to separate phenytoin and dexamethasone at 219 nm and 241 nm respectively from urine samples. The mobile phase consists of a mixture of 0.01 M KH2PO4, acetonitrile, and methanol adjusted to pH 5.6 (48:32:20) and is pumped at a flow rate of 1.0 mL/min. Calibration curves were prepared for phenytoin and dexamethasone (r2 > 0.99). An efficient solid-phase extraction (SPE) method for the extraction of dexamethasone and phenytoin from urine samples was developed with the use of C-18 cartridges. The percent recovery for phenytoin and dexamethasone is 95.4% (RSD = 1.15%) and 81.1% (RSD = 3.56%) respectively.

Panel Discussion on“Development Trends of Computer Science in the New Era”

At the panel session of the 3rd Global Forum on the Development of Computer Science,attendees had an opportunity to deliberate recent issues affecting computer science departments as a result of the recent growth in the field.6 heads of university computer science departments participated in the discussions,including the moderator,Professor Andrew Yao.The first issue was how universities are managing the growing number of applicants in addition to swelling class sizes.Several approaches were suggested,including increasing faculty hiring,implementing scalable teaching tools,and working closer with other departments through degree programs that integrate computer science with other fields.The second issue was about the position and role of computer science within broader science.Participants generally agreed that all fields are increasingly relying on computer science techniques,and that effectively disseminating these techniques to others is a key to unlocking broader scientific progress.