Trace Cobalt Doping and Defect Engineering of High Surface Area α-Ni(OH)_(2) for Electrocatalytic Urea Oxidation

Owing to the intrinsically sluggish kinetics of urea oxidation reaction(UOR)involving a six-electron transfer process,developing efficient UOR electrocatalyst is a great challenge remained to be overwhelmed.Herein,by taking advantage of 2-Methylimidazole,of which is a kind of alkali in water and owns strong coordination ability to Co^(2+)in methanol,trace Co(1.0 mol%)addition was found to induce defect engineering onα-Ni(OH)_(2)in a dual-solvent system of water and methanol.Physical characterization results revealed that the synthesized electrocatalyst(WM-Ni_(0.99)Co_(0.01)(OH)_(2))was a kind of defective nanosheet with thickness around 5-6 nm,attributing to the synergistic effect of Co doping and defect engineering,its electron structure was finely altered,and its specific surface a rea was tremendously enlarged from 68 to 172.3 m^(2)g^(-1).With all these merits,its overpotential to drive 10 mA cm^(-2)was reduced by 110 mV.Besides,the interfacial behavior of UOR was also well deciphered by operando electrochemical impedance spectroscopy.

Ignition characteristics and combustion performances of a LO_2/GCH_4 small thrust rocket engine

A 500 N model engine filled with LO2/GCH4 was designed and manufactured.A series of ignition attempts were performed in it by both head spark plug and body spark plug.Results show that the engine can be ignited but the combustion cannot be sustained when head spark plug applied as the plug tip was set in the gaseous low-velocity zone with thin spray.This is mainly because flame from this zone cannot supply enough ignition energy for the whole chamber.However,reliable ignition and stable combustion can be achieved by body spark plug.As the O/F ratio increases from 2.61 to 3.49,chamber pressure increases from 0.474 to 0.925 MPa and combustion efficiency increases from 57.8%to 95.1%.This is determined by the injector configuration,which cannot produce the sufficiently breakup of the liquid oxygen on the low flow rate case.

Monolithic Catalysts with Low Noble-Metal Content for Exhaust Purification of Small Gasoline Engines

A series of low noble-metal coment monolithic catalysts for exhaust purification of small gasoline engines was investigated, and it was found that the Pt/Rh-OSM/Al2O3 （where OSM was oxygen storage material） catalyst with Ce0.5Zr0.5-MnOx（3%MnOx） OSM held low light-off temperature for CO, HC, and NO; quite wide three-way window, and outstanding thermal stability. The catalyst could efficiently comrol exhaust emission of small gasoline engines.

Operation and Innovation of Software Engineering Education for Very Small Entities

This paper illustrates some exploration and innovation of software engineering education for VSEs under the background of Chinese "double first-class" new situation and new engineering subject, including academic strategy, curriculum system, ability training, teaching methods, project practice, and so on. Based on the actual situations and characteristics of Hunan University, this paper focuses on some undergraduate education practice, so that students can adapt software engineering development in VSEs with ISO/IEC 29110 series of standards and guides.

A review from mesenchymal stem-cells and their small extracellular vesicles in tissue engineering

This review aims to offer a vision of the clinical reality of cell therapy today in intensive medicine.For this,it has been carried out a description of the properties,functions,and Mesenchymal Stem Cells(MSCS)sources to subsequently address the evidence in preclinical models and studies clinical trials with whole cells and models attributed to small extracellular vesicles(sEVs),nanoparticles made up of microvesicles secreted by cells with an effect on the extracellular matrix,and their impact as an alternative towards cell-free regenerative medicine.MSCs are cells that enhance the regenerative capacity which can be differentiated typically in different lineages committed as bone,cartilage,and adipose tissue.On the other hand,small extracellular vesicles are structures that participate notoriously and crucially in intercellular communication,which has led to a change in the concept of the functions and the role that these vesicles play in living organisms,in the restoration of damaged tissues and the inflammatory response and immunological.We present the mechanisms that are involved in the applications of MSCS as whole cells and their sEVs in cell therapy and cell-free therapy as an alternative in regenerative medicine.Considering the structural loss that occurs after surgical procedures for cystic and tumoral pathology in periodontitis,as well as the maxillary atrophy that determines the rehabilitation with dental implants,it is imperative to find satisfactory solutions.The opportunity provided by the findings in stem cells is a recent introduction in the field of oral surgery,based on the regenerative potential that these cells possess to restore defects at different levels of the oral cavity.This review aims to discover the real applications that stem cells may have in our treatments shortly.

Engineered mesenchymal stem cell-derived small extracellular vesicles for diabetic retinopathy therapy through HIF-1α/EZH2/PGC-1αpathway

Diabetic retinopathy(DR)is a leading cause of blindness worldwide with limited treatment options.Mesenchymal stem cell-derived small extracellular vesicles(MSC-sEVs)hold promise as a cell-free therapy for retinal diseases.In this study,we present evidence that the intravitreal injection of MSC-sEVs improved retinal function and alleviated retinal apoptosis,inflammation,and angiogenesis in both db/db mice and streptozotocin-induced diabetic rats.Mechanistically,hyperglycemia-induced activation of hypoxia-inducible factor-1α(HIF-1α)inhibited the tripartite motif 21(TRIM21)-mediated ubiquitination and degradation of enhancer of zeste homologue 2(EZH2),ultimately resulting in the downregulation of peroxisome proliferator-activated receptor-γcoactivator-1α(PGC-1α)through EZH2-induced methylation modification.The presence of miR-5068 and miR-10228 in MSC-sEVs targeted the HIF-1α/EZH2/PGC-1αpathway.The blockade of miR-5068 and miR-10228 abolished the retinal therapeutic effects of MSC-sEVs.Additionally,we engineered MSC-sEVs with elevated levels of miR-5068 and miR-10228 to enhance retinal repair efficiency.Together,our findings provide novel insights into the mechanism underlying DR progress and highlight the potential of MSC-sEVs,especially engineered MSC-sEVs,as a therapeutic option for DR.

基于ArcGIS Engine的小型地籍信息管理系统的开发

在地籍信息的管理建设中,将地籍数据的属性数据与矢量数据一体化,建立小型的地籍信息管理系统,可以降低管理成本,为地籍信息管理工作提供便捷的管理手段和有效的决策。本文对地籍信息管理系统的现状进行了研究,总结了系统的总体框架,并且阐述了所涉及的关键技术,选用.NET架构搭建平台,利用C/S模式实现了小型地籍信息管理系统的开发。根据系统的需求与数据的特征,以ArcGIS Engine、VS2010、C#为开发工具,在ArcCatalog中建立文件地理数据库,实现了查询、统计、数据的编辑更新、空间分析、专题图制作、统计与输出等功能。通过实验数据验证,本系统操作简便,可满足对地籍数据管理的需要。

Numerical calculation of hydrodynamic characteristics of tidal currents for submarine excavation engineering in coastal area

In coastal areas with complicated flow movement, deposition and scour readily occur in submarine excavation projects. In this study, a smallscale model, with a high resolution in the vertical direction, was used to simulate the tidal current around a submarine excavation project. The finite volume method was used to solve Navier-Stokes equations and the Reynolds stress transport equation, and the entire process of the tidal current was simulated with unstructured meshes, generated in the irregular shape area, and structured meshes, generated in other water areas.The meshes near the bottom and free surface were densified with a minimum layer thickness of 0.05 m. The volume of fluid method was used to track the free surface, the volume fraction of cells on the upstream boundary was obtained from the volume fraction of adjacent cells, and that on the downstream boundary was determined by the water level process. The numerical results agree with the observed data, and some conclusions can be drawn: after the foundation trench excavation, the flow velocity decreases quite a bit through the foundation trench, with reverse flow occurring on the lee slope in the foundation trench; the swirling flow impedes inflow, leading to the occurrence of dammed water above the foundation trench; the turbulent motion is stronger during ebbing than in other tidal stages, the range with the maximum value of turbulent viscosity, occurring on the south side of the foundation trench at maximum ebbing, is greater than those in other tidal stages in a tidal cycle, and the maximum value of Reynolds shear stress occurs on the south side of the foundation trench at maximum ebbing in a tidal cycle. The numerical calculation method shows a strong performance in simulation of the hydrodynamic characteristics of tidal currents in the foundation trench, providing a basis for submarine engineering construction in coastal areas.

Present situation of the research and application of engineering multiwave seismic prospecting in China

In four aspects, which are the leading exploration of mine and tunnel f engineering geological hazard prospecting and engineering shock resistance; non-destructive testing of engineering quality 1 the measurement of rock physical properties, this pope gives a detailed summary and some comments on the present situation of the research and application of the ideas, theories and methods of engineering multiwave seismic prospecting. The content includes: the prospecting of coal field caved pillar, underground gallery, underground cavity and the fault ahead of tunnel; the exploration of earth surface Karst collapse, active fault, and shock resistance Of underground lifeline engineering; the dynamic non-destructive testing of quality and boring capacity of pile foundation, the non-destructive testing of strength, thickness and defects of concrete pavement, and the non-destructive testing of sub marine tunnel engineering quality ; the measurement of rock physical properties under high temperature and high pressure and the determination of physical properties of irregular rock samples. Some existing problems are discussed and the direction which should be developed in the future is proposed.

Fabrication of a Bi-layer Tubular Scaffold Consisted of a Dense Nanofibrous Inner Layer and a Porous Nanoyarn Outer Layer for Vascular Tissue Engineering

Recent years, it has attracted more attentions to increase the porosity and pore size of nanofibrous scaffolds to provide the for the cells to grow into the small-diameter vascular grafts. In this study, a novel bi-layer tubular scaffold with an inner layer and an outer layer was fabricated. The inner layer was random collagen/poly （ L-lactide-co-caprolactone ） I P （ LLA- CL） ] nanofibrous mat fabricated by conventional electrospinning and the outer layer was aligned collagen/P （LLA-CL） nanoyarns prepared by a dynamic liquid dectrospinning method. Fourier transform infrared spectroscopy （FTIR） was used to characterize the chemical structure. Scanning electron microscopy （ SEM ） was employed to observe the morphology of the layers and the cross- sectioned bi-layer tubular scaffold. A liquid displacement method was employed to measure the porosities of the inner and outer layers. Stress-strain curves were obtained to evaluate the mechanical properties of the two different layers and the bi-layer membrane. The diameters of the nanofibers and the nanoyarns were （480 ± 197 ） nm and （ 19.66 ± 4.05 ） μm, respectively. The outer layer had a significantly higher porosity and a larger pore size than those of the inner layer. Furthermore, the bi-layer membrane showed a good mechanical property which was suitable as small-diameter vascular graft. The results indicated that the bi-layer tubular scaffold had a great potential application in small vascular tissue engineering.

小流域生态-岩土协同减灾原理与方法初探

随着全球变暖,极端降雨事件增多,导致山区小流域灾害频发,严重威胁人民生命财产安全。小流域防灾减灾形式多样,其中生态工程措施与岩土工程措施相结合协同减灾的方式,不仅能够充分发挥两种措施在不同时间段的减灾作用,而且能够增加整体减灾功效。目前,受限于生态工程措施与岩土工程措施协同减灾原理不明,评估方法缺乏,导致二者无法有机结合并开展综合减灾效益评估。本文在基于自然解决方案的基础上,提出了山区小流域生态-岩土措施协同减灾的原理,即利用生态工程与岩土工程协作,通过坡面防护和沟道调控,形成稳定阶梯-深潭结构的生态工程-岩土工程措施协同减灾原理。在此基础上,结合地理信息系统和最优化原理,给出基于能量消减的小流域生态工程-岩土工程协同减灾功效的定量化评价方法,为规划、设计、物种选择以及生态工程与岩土工程对策的结合提供依据。

高速公路小净距互通立交车辆纵向运行特性

为明确车辆在高速公路小净距互通立交的纵向运行特性,在G50沪渝高速公路重庆段的白杨沟立交和跑马坪立交,开展了38位被试的实车驾驶试验。利用车载仪器采集了自然驾驶状态下的车辆运行速度以及纵向加速度等参数,计算了速度极差、带宽以及聚集系数,分析了驾驶行为的约束性以及速度变化特征。提取了纵向加速度连续变化曲线的峰值,研究了纵向加速度的累积频率、概率分布特性以及特征百分位值。结果表明:在小净距区段,合流区与分流区相互重叠,车辆交织行为增多,车辆间干涉严重,速度极差较大,离散性较高;断面速度总体呈现偏态分布,小净距区段断面速度区间大于其它断面。纵向加速概率分布曲线总体呈现偏态分布,加速度负值分布区间大于正值分布区间;小净距区段交通环境相对更复杂,驾驶人操作更加谨慎,与常规净距立交相比,小净距立交纵向加速度平均值低0.28 m/s^(2)。汇入过程中,驾驶人对加速度的选择存在一定差异,偏向于较大的加速度正值(0.542 m/s^(2))与较低的加速度负值(-0.081 m/s^(2))。然而,驶出过程中,驾驶人对加速度的选择具有一定趋同性,加速度正值(0.300 m/s^(2))与负值(-0.350 m/s^(2))差异性小;男性驾驶人纵向操作频率高于女性,幅度低于女性,不同驾驶风格驾驶人纵向加速度变化趋势具有一定的趋同性。

考虑小应变刚度特性的软土边界面模型与应用

基坑开挖导致周边土体经历复杂的加卸载应力路径,传统的本构模型难以同时反映此过程中土体的超固结和小应变刚度特性。在现有的边界面模型中,引入土体小应变刚度特性,提出软土边界面模型小应变刚度修正方法。基于一种高效的半隐式应力更新算法,将改进后的边界面模型采用UMAT子程序二次开发嵌入有限元软件ABAQUS中,并应用于某地铁车站深基坑开挖工程的数值模拟。分析结果表明,采用改进模型准确地反映了上海地区典型土层的小应变状态本构关系和土体的应变刚度相关性;由于改进的边界面模型能够同时反映土体超固结和小应变刚度特性,计算的围护结构变形与现场监测数据吻合较好。

小肠黏膜下层脱细胞基质复合外泌体构建组织工程尿道

背景:小肠黏膜下层脱细胞基质已被临床与基础研究证实可用于尿道的修复重建,但其单独应用时存在宿主细胞生长缓慢、支架血管化不足而成活困难、重建尿道狭窄梗阻等问题,仅适用于较短的尿道狭窄。目的:探讨应用小肠黏膜下层脱细胞基质复合外泌体构建组织工程尿道的可行性。方法:从新西兰大白兔骨髓间充质干细胞中分离提取外泌体;制备猪小肠黏膜下层脱细胞基质,将外泌体负载于小肠黏膜下层脱细胞基质上。将小肠黏膜下层脱细胞基质-外泌体(PKH26染料标记)复合物与脐静脉内皮细胞共培养12 h,观察细胞摄取外泌体情况。选取生长状态良好的脐静脉内皮细胞,分3组培养:空白组常规培养,对照组加入小肠黏膜下层脱细胞基质,实验组加入小肠黏膜下层脱细胞基质-外泌体复合物,通过划痕实验、成管实验、血管生成因子分泌检测评估血管生成情况。取30只新西兰大白兔,建立长段(3 cm)尿道缺损模型,采用随机数字表法分3组干预(n=10):单独材料组植入小肠黏膜下层脱细胞基质,对照组植入小肠黏膜下层脱细胞基质-骨髓间充质干细胞复合物,实验组植入小肠黏膜下层脱细胞基质-外泌体复合物,植入后12周进行尿道造影、尿动力学检查及重建尿道切片病理观察。结果与结论:(1)荧光显微镜下可见小肠黏膜下层脱细胞基质中的外泌体可被脐静脉内皮细胞摄取。(2)与空白组、对照组相比,实验组材料可促进脐静脉内皮细胞的迁移、成血管能力以及成血管因子血管内皮生长因子、肝细胞生长因子、白细胞介素8的分泌(P <0.05)。(3)尿道造影结果显示,单独材料组10只兔均出现尿道狭窄,对照组10只兔中2只出现尿道狭窄,实验组10只兔均未出现尿道狭窄。尿动力检查结果显示,单独材料组兔材料植入后12周的最大尿道压高于术前(P <0.05),对照组、实验组兔植入后12周的最大尿道压均低于空白组(P <0.05)。苏木精-伊红、Masson与免疫组化染色显示,单独材料组可见明显的再生上皮层、少量的皮下平滑肌与血管,以纤维组织增生为主,伴有明显炎性细胞浸润;对照组可见较完整的再生上皮与少量胶原,可见大量的皮下血管与平滑肌,伴有炎性细胞浸润;实验组可见完整的再生上皮层与大量的皮下血管、平滑肌,未见明显炎性细胞浸润,实验组AE1/AE3、ɑ-平滑肌肌动蛋白、CD31阳性表达均高于单独材料组、对照组(P <0.05)。(4)结果表明,小肠黏膜下层脱细胞基质-外泌体组织工程尿道可通过促进血管生成来修复尿道缺损。

分布式技术在大模型训练和推理中的应用

近几年,人工智能被广泛应用于多个领域,大语言模型(以下简称大模型)的“预训练-微调”成为人工智能的最新范式。分布式技术存在于大模型生命周期的每一环,为大模型的发展助力。在数据获取环节,针对海量小文件的存储问题,研发了文件系统SuperFS,能够同时满足低延迟和可扩展的要求。在数据预处理环节,针对从分布式文件系统读取数据开销大的问题,研发了高效大数据处理引擎“诸葛弩”。在模型训练环节,针对检查点文件读写性能差的问题,提出了分布式检查点策略,加快了检查点文件的读写速度。在模型推理环节,针对KVCache对存储系统的挑战,研发了高吞吐推理方案FastDecode以及大模型推理架构Mooncake。分布式技术的应用,使大模型能够充分利用计算资源,加快训练速度,有利于人工智能领域的发展。

小惯性热电偶动态校准及频域分析

发动机进气温度畸变影响发动机的稳定性,通常使用小惯性热电偶来测量其快速变化的气流温度。为准确全面获取小惯性热电偶的动态特性,提出了一种小惯性热电偶的动态特性校准及评价方法,并阐述了小惯性热电偶动态校准装置的构建、校准试验以及频域分析。采用脉冲激光器与校准风洞相结合的小惯性热电偶动态校准方法,通过幅频特性和相频特性分析,拓展了小惯性热电偶的动态特性评价方法。用该校准方法对小惯性热电偶进行动态校准,结果A类相对不确定度最大值由7.2%减小到2.4%,可应用于30 ms以下量级快响应温度传感器的动态校准,为发动机进气温度畸变等高频动态温度测量提供技术参考。

刍议中小型国际工程承包商的比较优势

国际工程承包商在国际工程市场竞争中保持优势必须要有自身的核心竞争力,对于无明显技术、资源、规模、及融资能力优势的的中小型国际工程承包商,用诚信合规来赢得市场显得尤为重要。文中提出中小型国际工程承包商应从用诚信合规构建企业软实力的角度,在企业中确立诚信合规的经营理念,并积极倡导诚信合规的企业文化,从而用“诚信合规”构建企业的比较优势。

SBAS-InSAR技术融合CNN-LSTM模型的矿区开采沉陷监测与预测

针对传统矿区开采沉陷监测方法耗费人力财力和预测预警模型较少的问题,研究提出一种基于短基线集合成孔径雷达干涉测量(Small Baseline Subset-Interferometry Synthetic Aperture Radar,SBAS-InSAR)技术和卷积神经网络(Convolutional Neural Networks,CNN)与长短期记忆网络(Long Short-Term Memory,LSTM)相结合的矿区开采沉陷监测预测方法。首先,利用SBAS-InSAR技术对建新煤矿进行矿区开采沉陷监测,获取了该矿区的年平均沉降速率和累计沉降值。用GNSS监测数据与SBAS-InSAR结果进行对比验证,其拟合效果较好。其次,在此基础上利用CNN-LSTM模型预测后6期沉降数据,其结果与CNN和LSTM预测结果进行对比。研究显示,CNN-LSTM模型的平均绝对误差(S_(MAE))和均方根误差(S_(RMSE))比单一的CNN和LSTM分别至少降低了44.8%和40.6%,其决定系数均高于98%。最后,进一步预测前6期和中6期沉降数据,验证了CNN-LSTM预测模型在时间上的一致性。因此,SBAS-InSAR融合CNN-LSTM模型在类似矿山开采沉陷监测和预测中有较好的应用前景。

小晶粒高硅铝比NaY分子筛低温合成研究

采用自制的偏铝酸钠为合成导向剂,在低温下水热晶化合成出了小晶粒高硅铝比的NaY分子筛。考察了合成导向剂的陈化温度、陈化时间、晶化碱度、晶化温度和晶化时间对产品的影响,得到了制备NaY分子筛最佳的工艺条件,并进行了放大制备。在此条件下,NaY分子筛结晶度(峰面积)≥90%,结晶度(峰高)≥85%,硅铝比≥5.5,晶粒尺寸均在(100~200)nm,不仅优于工业标样的指标要求,且易于放大。

基于SPOC&PBL混合教学模式的实践研究——以机械零件数控铣削加工为例

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