课程文献中心 更多>>

关键词： 小区育种   北斗定位系统   编码器   自校正  

摘要： 在小区育种试验的播种环节过程中,小区行长和间隔的精准控制尤为关键,现常用的控制方式为北斗定位系统控制和编码器控制,但目前民用的北斗定位模块经过差分处理后,基本上接收北斗卫星发送的信号频率只能达到20 Hz,造成整个控制过程不是连续的。根据编码器的基本原理可知,控制精度虽低于北斗卫星,但编码器两个脉冲发送间隔低于北斗定位系统接收频率。为此,将编码器与北斗定位系统相互融合,设计了一种高净度的小区播种机自校正系统。大量田间试验结果表明:所研究的小区播种机自校正系统能够将小区长度误差精度控制在0.67%以内,相较于传统的编码器和北斗定位模式而言精度大大提升。

关键词： Snail shell   Biodiesel   CCD-RSM   Optimization   WCO   PALM KERNEL OIL   FREE FATTY-ACID   CALCIUM-OXIDE   LOW-COST   TRANSESTERIFICATION   CAO   EGG   ASH   METHANOL   CRAB  

摘要： In the present study, labuk tharoi (Angulyagra oxytropis), and ningkhabi tharoi (Bellamya crassa) were utilized to produce CaO catalyst for biodiesel production using waste cooking oil (WCO). The snail shells were calcined at a temperature of 800-1000 degrees C for 4 h and characterized using XRD, FTIR, BET, SEM, and EDX analysis. Central composite design-response surface methodology (CCD-RSM) was employed, and the input parameters considered for optimization were (i) catalyst calcination temperature (800-1000 degrees C), (ii) methanol: oil ratio (molar) (6:1-12:1), (iii) catalyst loading (3-7 wt.%), and (iv) reaction temperature (55-75 degrees C). A quadratic regression model was aliased by CCD-RSM with R2 values of 0.9291 and 0.976 for waste cooking oil methyl ester-labuk tharoi (WCOME-LT), and waste cooking oil methyl ester-ningkhabi tharoi (WCOME-NT) models indicating a good fit. An optimum biodiesel yield of (95.87, 95.91 %) was obtained at catalyst calcination temperature (891, 886 degrees C), methanol to oil molar ratio (9.89:1, 9.67:1), catalyst loading weight % (7, 7 wt.%), and reaction temperature (75, 75 degrees C) for WCOME-LT and WCOME-NT model respectively. The calcination temperature has a major impact on the biodiesel yield as per analysis of variance. The catalyst reusability was up to four cycles with a biodiesel yield of more than 83 %.

关键词： 煤矿瓦斯   传感器网络   瓦斯监测   预警系统   ZigBee  

摘要： 针对瓦斯监测效果差、预警困难等特点,基于传感器网络技术,设计了一套煤矿瓦斯监测与预警系统。该系统采用分布式部署的瓦斯传感器节点实时采集矿井内部的瓦斯浓度数据,并通过ZigBee无线通信网络将数据传输到地面监控中心。经实验测试,传感器节点的采样精度优于±0.5%LEL,重复性误差小于1%。系统设计了基于动态阈值的瓦斯报警算法,可根据瓦斯浓度变化趋势自适应调整报警阈值,在保证报警及时性的同时,将误报率降低了60%以上。当瓦斯浓度超限时,系统能够在1 s内发出报警,且准确率达到98%以上。通过在开滦(集团)钱家营煤矿的试点应用,证实该系统能够对矿井瓦斯进行全方位的实时监测,瓦斯事故预警的平均提前量提高到30 min以上,有效提升了煤矿安全生产水平。

关键词： FBG密集分布式光纤传感技术   超长灌注桩   承载变形特性   数值模拟   侧阻力  

摘要： 为探究不同地质条件下超长桩承载变形特性及数值模拟中摩擦系数对桩-土相互作用的影响,以深圳湾超级总部某项目系列试桩为背景,采用FBG密集分布式光纤传感技术进行基桩内力测试,并采用ABAQUS有限元软件进行数值模拟,对比分析桩、土界面采用不同摩擦系数取值方式时土层平均侧阻力模拟结果。结果表明:(1)灌注桩承载变形特性与桩长和持力层性质密切相关,超长桩轴力沿深度方向基本呈线性递减,端阻比明显减小;持力层为强风化花岗岩层时,试桩轴力沿深度方向呈“大肚形”递减,端阻比低于17.1%。(2)数值模拟中摩擦系数取值方式会对土体侧阻力模拟结果产生较大影响,根据土层性质差异,对桩土界面采用多个摩擦系数能够提高模拟结果准确性。

关键词： Spent coffee ground   Electrolysis   Transesterification   RSM   CCD   Biodiesel  

摘要： Background The disposal of waste spent coffee grounds (SCG) presents a pressing environmental concern, necessitating effective pre-treatment strategies to mitigate potential damage. Transesterification emerges as a viable solution for converting SCG lipids into biodiesel, offering both environmental and economic benefits. Methods In this study, the utilization of SCG as a renewable feedstock for biodiesel production through an innovative electrolysis process has been explored, aiming to address the dual challenges of waste management and sustainable energy production. To obtain maximum conversion of SCG oil to biodiesel, a comprehensive analysis of the fatty acid profile using Gas Chromatography-Mass Spectrometry (GC–MS), was conducted allowing for precise characterization of lipid content. Additionally, Fourier Transform Infrared (FTIR) spectroscopy was employed to categorize functional groups and Nuclear Magnetic Resonance ( 1 H NMR) spectroscopy was utilized to analyze the molecular structure of the SCG oil. Optimization of process parameters namely, catalyst concentration, electrolysis time, and direct current (DC) voltage was performed using Response Surface Methodology (RSM) and Artificial Neural Network (ANN) techniques. The ANN model, with its ability to capture complex nonlinear relationships, was particularly effective in identifying the optimal combination of parameters, thereby maximizing biodiesel yield. Significant findings The extracted SCG oil was characterized using FTIR, GC–MS and 1 H NMR analysis. The GC- MS analysis of bio-oil has reported 44.6 % Linoleic acid, 31.6 % Palmitic acid. The extracted oil had got significant amount of key saturated and unsaturated fatty acid making it suitable for transesterification process. Through ANN, the optimal combination of parameters for electrolytic transesterification i.e.,0.75 wt% catalyst loading, 2 h electrolysis time, and 40 V DC voltage, yielded the highest biodiesel production (98.32 wt.%). Comparativ

关键词： 球罐   衍射时差法超声检测   夹杂物   缺陷   判别  

摘要： 对某中厚板球罐焊接接头进行衍射时差法超声检测(TOFD)中发现大量密集显示点状缺陷,排除焊接原因后,通过取样进行低倍检测、金相组织检验分析,确认TOFD图谱显示与母材中存在的条状MnS夹杂物,聚集态的含Nb、Ti的氮化物夹杂物有关,二者大量存在对接头焊接质量产生直接影响。通过调整扫查方式对缺陷位置进行确认,为TOFD检出缺陷的识别与判定提供借鉴。

关键词： YOLOv8算法   目标检测   AlphaPose姿态识别   作弊行为检测  

摘要： 在考试监控领域,深度学习技术的应用对于提高作弊检测的准确性和效率至关重要。结合YOLOv8算法和AlphaPose姿态识别模型,构建一个既能快速检测异常行为又能精准判断作弊行为的考试作弊行为检测系统。通过改进数据结构和优化网络结构,仅使用身体数据进行模型训练,使得模型更加专注检测与作弊行为相关的身体动作,从而提高系统的鲁棒性和适用性。实验结果表明:系统对作弊检测的实际准确率在95%左右,能够有效区分正常行为和作弊行为,为考试监管提供了强有力的技术支持。

关键词： MEMS   电容薄膜   真空计   微弱电容   电子测量  

摘要： 为了满足空间环境探测对真空测量仪器准确度高、体积小、质量轻、功耗低的应用需求,基于微机电系统(MEMS)的小型化电容薄膜真空计应运而生。针对MEMS电容薄膜真空计微小电容测量需求,设计了一种基于CDC电容数字转换器的微电容检测系统,获得了fF级微电容检测分辨率。采用温度漂移误差自校准技术,解决了测量压力受温度扰动影响的问题。地面样机测试与验证表明,该检测系统具有宽量程、高分辨率和低功耗检测的优点,为MEMS电容薄膜真空计实现空间应用奠定了技术基础。

关键词： 乘数效应   技术创新成果   瑕疵品   检测系统   重大项目   推动经济社会发展   峰会   机器人  

摘要： 基于AI算力底座的瑕疵品检测系统、配网带电作业机器人、5G智能制鞋生产线……在5月24日至25日举行的第七届数字中国建设峰会(以下简称“峰会”)上,一系列数字技术创新成果集中亮相,一大批数字经济重大项目集中签约,展现出数字经济的巨大活力,尽显数据要素赋能新质生产力进而推动经济社会发展的乘数效应。

关键词： Lithium   Adsorption   Characterization   Kinetics   Response surface methodology   Regeneration   AAS   Atomic adsorption spectrophotometer   AC   Activated carbon   ANOVA   Analysis of variance   APHA   American Public Health Association   AP   Adequate Precision   BBD   Box-Behnken design   BET   Brunauer–Emmett–Teller   CCD   Central composite design   CI   Confidence Interval   CV   Coefficient of Variance   df   Degree of freedom   DOE   Department of environment   EPA   Environmental protection agency   FESEM   Field emission scanning electron microscopy   FTIR   Fourier transform infrared spectroscopy   RSM   Response surface methodology   SAP   Surface area porosity   XRD   X-Ray Diffraction   ppm   Parts per million  

摘要： Lithium (Li)recovery is significant due to an increasing need for Li in diverse applications, particularly in the energy storage domain. In this study, a synthesized adsorbent was developed and utilized to efficiently recover Li. Therefore, this research aims to assess the effectiveness of using the synthesized adsorbent LiHMO to recover Li from the aqueous solution. The surface area and characteristics of the synthesized adsorbent were subjected to analysis utilizing different methods and techniques, including scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Fourier-transform infrared spectroscopy (FTIR). The findings indicated that the synthesized adsorbent demonstrated exceptional adsorption capabilities for Li recovery. Characterization analysis revealed a well-defined porous structure and functional groups on the adsorbent's surface, facilitating adsorption. The surface area of the adsorbent was determined to be 25.54 m²/g, providing a substantial active surface for adsorption processes. The Box-Behnken response surface method (RSM) was utilized to optimize the recovery process for key factors such as pH, adsorbent dose, time, and concentration. The critical operating parameters identified included a pH of 4, initial concentration of 900 mg/L, contact time of 460 min, and adsorbent dosage of 1300 mg/L. The obtained data were analyzed using a quadratic model, yielding an R² value of 0.9538, indicating that the adsorbent is effective in Li adsorption. The optimal conditions for maximizing Li recovery were found to be 95 % and 89 % for maximum and minimum recovery, respectively. The amount of adsorbate adsorbed (q e ) was determined to be 6.2 mg g -1 . Various kinetic models and isotherms were utilized to conform to these parameters. The Freundlich isotherm and the intraparticle diffusion model showed strong fits, as evidenced by their R² results of 0.9876 and 0.9862, respectively. The kinetic study suggeste