Fluid-Dynamics Analysis and Structural Optimization of a 300 kW MicroGas Turbine Recuperator

Computational Fluid Dynamics(CFD)is used here to reduce pressure loss and improve heat exchange efficiency in the recuperator associated with a gas turbine.First,numerical simulations of the high-temperature and lowtemperature channels are performed and,the calculated results are compared with experimental data(to verify the reliability of the numerical method).Second,the flow field structure of the low-temperature side channel is critically analyzed,leading to the conclusion that the flow velocity distribution in the low-temperature side channel is uneven,and its resistance is significantly higher than that in the high-temperature side.Therefore,five alternate structural schemes are proposed for the optimization of the low-temperature side.In particular,to reduce the flow velocity in the upper channel,the rib length of each channel at the inlet of the low-temperature side region is adjusted.The performances of the 5 schemes are compared,leading to the identification of the configuration able to guarantee a uniform flow rate and minimize the pressure drop.Finally,the heat transfer performance of the optimized recuperator structure is evaluated,and it is shown that the effectiveness of the recuperator is increased by 1.5%.

Simulation and Optimization of the Fluid Solidification Process in Brazed Plate Heat Exchangers

When a brazed plate heat exchanger is used as an evaporator,the working mass in the channel may undergo soli-dification,thereby hindering the refrigeration cycle.In this study the liquid solidification process and its optimi-zation in a brazed plate heat exchanger are investigated numerically for different inlet velocities;moreover,different levels of corrugation are considered.The results indicate that solidificationfirst occurs around the con-tacts,followed by the area behind the contacts.It is also shown that deadflow zones exist in the sharp areas and such areas are prone to liquid solidification.After optimization,the solidification area attains its smallest value when a corrugation spacingλ=4.2 mm is considered.

A Robotic System with Robust Remote Center of Motion Constraint for Endometrial Regeneration Surgery

Surgical robots have been widely used in diferent procedures to improve and facilitate the surgery.However,there is no robot designed for endometrial regeneration surgery,which is a new therapy for restoring fertility in women using stem cells.Endometrial regeneration surgery requires processing of the endometrium and transplantation of stem cells with minimal trauma to the uterus.In this paper,we introduce a surgical robotic system that consists of a dexterous hysteroscope,supporting arm,and additional novel instruments to facilitate the operation and decrease trauma to the uterus.Remote center of motion(RCM)constraint is required to protect the cervix of the uterus.First,the supporting arm and hysteroscope are controlled separately in kinematics to ensure that the RCM constraint and hysteroscope’s shape and posture are predictable.Then,a task-decoupled method is used to improve the robustness of the RCM constraint.Experiments confrm that the proposed method is more robust and achieves higher RCM accuracy.In addition,the master-slave control of a robot with RCM constraint is also verifed.This study proposes the realization of a robot with robust RCM control for endometrial regeneration surgery.

Multi-View Point-Based Registration for Native Knee Kinematics Measurement with Feature Transfer Learning

Deep-learning methods provide a promising approach for measuring in-vivo knee joint motion from fast registration of two-dimensional(2D)to three-dimensional(3D)data with a broad range of capture.However,if there are insufficient data for training,the data-driven approach will fail.We propose a feature-based transfer-learning method to extract features from fluoroscopic images.With three subjects and fewer than 100 pairs of real fluoroscopic images,we achieved a mean registration success rate of up to 40%.The proposed method provides a promising solution,using a learning-based registration method when only a limited number of real fluoroscopic images is available.

海南省野生维管植物编目和分布数据集

海南省是我国热带雨林连片面积较大的地区,是我国物种多样性最为丰富的生物多样性关键地区之一,关于海南省植物编目的工作在2012–2015年间就取得了较好的进展,陆续出版了《海南植物物种多样性编目》《海南植物名录》和《海南植物图志》。但是随着对海南植物研究的深入,原来所记录的一些维管植物类群经过分类修订后名称发生了变化,科属分类及其名称需要进行调整,同时原来所采用的分类系统也亟需更新。本文在《海南植物名录》和《海南植被图志》的基础上,结合历年实际野外调查经验,通过系统检索文献资料和查阅相关书籍对现有编目数据进行查漏补缺,修订名称、更新分类系统,完善植物分布区、保护等级状况等相关信息,最终完成海南省野生维管植物编目和分布数据集。截至2023年2月,该数据集共有数据4,945条,其中包括石松类植物2科6属39种,蕨类植物32科121属531种,裸子植物6科10属27种,被子植物181科1,380属4,348种;数据集中列入《国家重点保护野生植物名录(2021)》的有173种(其中一级8种,二级165种);本土野生植物共有216科1,448属4,769种(含海南特有植物516种),外来逸生及归化植物有176种(含入侵植物63种)。与2013年出版的第一版《海南植物名录》相比,野生维管植物总物种数增加225种。本数据集可作为海南省维管植物多样性监测和保护的重要基础数据。

Core-shell TiO_(2)/ZnO nanorod array films on FTO:Two-step synthesis and improved ethanol sensing performance

In this work,highly regular TiO_(2)nanorod array films were synthesized in situ on FTO by a facile hydrothermal method,and then ZnO shell layers were grown on the surface of the nanorods to form a coreshell structure via an ion-layer adsorption-reaction way.Compared to the TiO_(2)nanorods,the prepared TiO_(2)/ZnO nanocomposites exhibited enhanced ethanol sensing performances,including a low working temperature,higher sensitivity,and faster response capability.The optimum sensor based on 2c-TiO_(2)/ZnO exhibited the maximum response value of 30.85 toward 50×10^(-6)C_(2)H_(5)OH at 340℃,which was almost 4.15 times higher than that of the TiO_(2)sensor.The improved ethanol sensing mechanism was discussed in relation to the unique nanorod array structure and the heterojunctions between TiO_(2)and ZnO.

Coal and rock dynamic disaster prevention and control technology in the large mining face of a deep outburst mine

In this study, we systematically studied the occurrence regularity of in situ stress in the Pingdingshan mine. The critical criterion model of coal-rock destabilization was established based on the theoretical framework of fracture mechanics. Furthermore, we analyzed the coupling destabilization mechanism of in situ stress and gas and studied the influence of the variation between original rock stress and mining-induced stress on the critical criterion. Through field experiments and applications, we established a three-dimensional gas drainage technology system for areas with a large mining height and long work face. Based on our research, a demonstration project was developed for deep mine dynamic disaster control. The technical system included the arrangement and optimization of pre-drainage holes along the coal seam, technology, and optimization of gas drainage through the bottom drainage tunnel and upper corner, gas drainage technology through sieve tubes, and a two plugging with one injection under pressure sealing technology. The implementation of the demonstration project effectively reduced the gas content and pressure of the coal seam in the deep mine, and the project increased the critical strength of the instability and failure of coal and rock.

Study on in situ stress testing method based on Kaiser effect of acoustic emission and COMSOL simulation

In situ stress testing can improve the safety and efficiency of coal mining.Identifying the Kaiser effect point is vital for in situ stress calculations;however,the in situ stress calculation is limited by the rock sampling angle.Here,the Kaiser effect point identification theory is established and applied to the Xuyong Coal Mine.Uniaxial compression and acoustic emission experiments were carried out on sandstone with 6 sampling directions.Furthermore,COMSOL simulation is applied to study the in situ stress distribution in the coal mine to verify the calculation accuracy.The results are as follows.1)The failure mode of non-bedded and vertical-bedded rocks is primarily tensile shear failure with obvious brittleness in mechanical and acoustic emission characteristics.Shear slip along the bedding plane is the primary failure mode of inclined-bedded rock.Additional take-off points exist in the AE count curve.2)The Kaiser point identification method based on the variation of AE count curve parametersΔti andτi can effectively calculate the in situ stress.According to the numerical value of Kaiser point and sampling direction,the in situ stress of the conveyor roadway in the Xuyong Coal Mine was calculated asσ1=22.81 MPa,σ2=10.87 MPa andσ3=6.14 MPa.3)By the COMSOL simulation study,it was found that a stress concentration zone of 16.13 MPa exists near the two sides roadway.Compared with the Kaiser effect method,the deviation rates of the three-direction principal stress calculated by COMSOL were all less than 5%.This verifies that the in situ stress calculation by Kaiser effect in this study can be applied to the Xuyong Coal Mine.

1980—2016年北京市食物消费的土地需求

社会经济发展和居民食物消费对土地需求之间的矛盾,已成为中国可持续发展亟待解决的关键问题,也是当今社会关注的热点问题之一。然而,目前对城市尺度食物消费的土地需求研究仍存在不足。本文利用CPI指数法,估算了北京市城乡居民1980—2016年的食物消费情况,揭示了居民食物消费结构改变对土地需求的演变特征,并探讨了未来不同消费模式下的土地需求情况,以期为实现居民的可持续消费提供参考,从而更好地解决社会经济发展和居民食物消费对土地需求之间的矛盾。结果表明:北京市食物消费结构已经由“粮食主导”的消费模式逐渐变为多元化的消费模式,且城乡之间存在明显差异;1980—2016年,北京市居民人均食物消费的土地需求量呈“U”型的变化特征,其中粮食消费的土地需求不断减少,而蔬果和动物性食物的土地需求不断增加;在2016年,北京市居民人均食物消费的土地需求量达到了1227.04 m^2/人,使得北京市居民消费的土地需求总量达到了266.62万hm^2,其中动物性食物消费占70.36%,城市居民食物消费占95%以上;在2016年,北京市居民食物消费的土地需求压力达到了14。健康合理的食物消费结构不仅有利于身体健康,也能够缓解食物消费对土地资源的压力;在健康饮食情景下,北京市每年居民食物消费最多可节约95.20~153.32万hm^2的土地面积,相当于北京市现有耕地和果园面积的5~8倍。因此,通过合理的饮食结构调整对解决社会经济发展和居民食物消费对土地需求之间的矛盾具有重要的意义。

河口最大浑浊带研究的回顾与展望

最大浑浊带是河口近岸泥沙含量显著高于上下游,并在一定范围内有规律迁移的浑浊水体,是河流入海泥沙输移过程中的特有现象.它显著体现了河流、海洋及物质能量的耦合作用,其发展动态、研究进展备受关注.本文通过回顾国内外河口最大浑浊带80多年来的研究现状和历程,总结经验、展望未来.既有研究已对河口最大浑浊带的泥沙含量、物质来源及组成等基本特征进行了较为全面的总结,认识到不同类型河口最大浑浊带的形成发育存在不同的主导动力过程和主控影响因素;此外,河口最大浑浊带在中短尺度上的时空变化也得到了比较充分的分析和讨论.相关研究在多方面都取得了瞩目的成果和进展,具有重要的科学价值与现实意义.但是,分析认为仍亟待继续开展并进一步加强最大浑浊带的精准定量识别方法研究、空间立体分布整体特性研究,特别是人类活动加剧和全球自然环境显著变化影响下的长期时空动态特征研究,以促进对河口最大浑浊带现象及其时空演变规律和趋势更加全面、更加深刻的认识和理解,助力社会经济和自然环境健康可持续发展.

王朗国家级自然保护区滑坡体兰科植物分布格局及其保护策略

滑坡体是大熊猫国家公园岷山片区中广泛存在的一种生境,但其在生物多样性研究和保护中的作用却没有得到足够的重视。王朗国家级自然保护区的滑坡体具有丰富的兰科植物资源,其中白沙沟滑坡体最为丰富。本文以白沙沟滑坡体为例,探究岷山地区滑坡体生境中兰科植物的空间分布格局,拟为王朗国家级自然保护区及周边区域的兰科植物保护提供指导。本研究设置4条样带共186个样方,利用除趋势对应分析(DCA)和双向指示种分析(TWINSPAN)研究滑坡体兰科植物的空间分布格局,同时对兰科植物做了种间关联和相关性分析。结果表明,白沙沟滑坡体的草本群落受环境因素的影响,物种间竞争较弱,处于自然演替的初始阶段。郁闭度和水流冲刷对滑坡体兰科植物的分布具有重要影响。受郁闭度和水流干扰因素的影响,滑坡体可分成滑坡体-林缘生境(类型1)、滑坡体生境(类型2)和高郁闭度滑坡体生境(类型3)3种类型。兰科植物在类型1和类型3两种生境中产生了适应性分化。建议在一些兰科物种集中分布的区域设立保护点并进行监测。此外还应对其他不同时间、不同土壤基质形成的滑坡体进行详细的调查,摸清王朗国家级自然保护区甚至岷山地区兰科植物分布的整体情况。

Anaerobic phenanthrene biodegradation with four kinds of electron acceptors enriched from the same mixed inoculum and exploration of metabolic pathways

Polycyclic aromatic hydrocarbons (PAHs) are widespread and persistent contaminants worldwide, especially in environments devoid of molecular oxygen. For lack of molecular oxygen, researchers enhanced anaerobic zones PAHs biodegradation by adding sulfate, bicarbonate, nitrate, and iron. However, microbial community reports of them were limited, and information of metabolites was poor except two-ring PAH, naphthalene. Here, we reported on four phenanthrene-degrading enrichment cultures with sulfate, bicarbonate, nitrate, and iron as electron acceptors from the same initial inoculum. The high-to-low order of the anaerobic phenanthrene biodegradation rate was the nitrate-reducing conditions>sulfate-reducing conditions>methanogenic conditions>iron-reducing conditions. The dominant bacteria populations were Desulfobacteraceae, Anaerolinaceae, and Thermodesulfobiaceae under sulfate-reducing conditions;Moraxellaceae, Clostridiaceae, and Comamonadaceae under methanogenic conditions;Rhodobacteraceae, Planococcaceae, and Xanthomonadaceae under nitrate-reducing conditions;and Geobacteraceae, Carnobacteriaceae, and Anaerolinaceae under iron-reducing conditions, respectively. Principal component analysis (PCA) indicated that bacteria populations of longtime enriched cultures with four electron acceptors all obtained significant changes from original inoculum, and bacterial communities were similar under nitrate-reducing and iron-reducing conditions. Archaea accounted for a high percentage under iron-reducing and methanogenic conditions, and Methanosarcinaceae and Methanobacteriaceae, as well as Methanobacteriaceae, were the dominant archaea populations under iron-reducing and methanogenic conditions. The key steps of phenanthrene biodegradation under four reducing conditions were carboxylation, further ring system reduction, and ring cleavage.

NPR1-dependent salicylic acid signaling inhibits Agrobacteriummediated transient expression in Arabidopsis

Dear Editor,Arabidopsis thaliana,as a model plant,is the most well-studied plant species.One of the advantages of using Arabidopsis is that obtaining stably transformed plants using flower-dipping method is easy.However,generating transgenic plants is still time-consuming.Therefore,transient expression is frequently used to characterize protein functions.Several transient expression assays have been developed,including protoplast transfection,biolistic bombardment,and Agrobacterium-mediated transient expression.Among these assays,the

Characterization of a phenanthrene-degrading methanogenic community

Polycyclic aromatic hydrocarbons(PAHs)often occur in oil-contaminated soil,coke wastewater and domestic sludge;however,associated PAH degraders in these environments are not clear.Here we evaluated phenanthrene degradation potential in the mixed samples of above environments,and obtained a methanogenic community with different microbial profile compared to those from sediments.Phenanthrene was efficiently degraded(1.26 mg/L/d)and nonstoichiometric amount of methane was produced simultaneously.16S rRNA gene sequencing demonstrated that bacterial populations were mainly associated with Comamonadaceae Nocardiaceae and Thermodesulfobiaceae,and that methanogenic archaea groups were dominated by Methanobacterium and Methanothermobacter.Substances such as hexane,hexadecane,benzene and glucose showed the most positive effects on phenanthrene degradation.Substrate utilization tests indicated that this culture could not utilize other PAHs.These analyses could offer us some suggestions on the putative phenanthrene-degrading microbes in such environments,and might help us develop strategies for the removal of PAHs from contaminated soil and sludge.