A New Rapid and Batch-oriented Crushing Method for DNA Extraction from Maize Leaves

The crushing of leaves is the most time and effort-consuming part in DNA extraction which is a fundamental step in the study of molecular biology. In this study, a new rapid and batch-oriented crushing method for DNA extraction from maize leaves was developed. In addition, the practicability of the developed method in molecular marker-assisted breeding was verified using SSR molecular maker technology so as to provide a rapid, batch-oriented, low-cost and non-toxic leafcrushing method for a large number of molecular marker tests, improving test efficiency.

Drilling-based measuring method for the c-φ parameter of rock and its field application

The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(RCZ) is built. The formula for an ultimate cutting force is established based on the limit equilibrium principle. The relationship between digital drilling parameters(DDP) and the c-φ parameter(DDP-cφ formula, where c refers to the cohesion and φ refers to the internal friction angle) is derived, and the response of drilling parameters and cutting ratio to the strength parameters is analyzed. The drillingbased measuring method for the c-φ parameter of rock is constructed. The laboratory verification test is then completed, and the difference in results between the drilling test and the compression test is less than 6%. On this basis, in-situ rock drilling tests in a traffic tunnel and a coal mine roadway are carried out, and the strength parameters of the surrounding rock are effectively tested. The average difference ratio of the results is less than 11%, which verifies the effectiveness of the proposed method for obtaining the strength parameters based on digital drilling. This study provides methodological support for field testing of rock strength parameters.

A combined method to model grain crushing with DEM

This paper presents a combined method to model grain crushing effects with discrete element method.This method combines the two most commonly used concepts to model grain crushing in DEM,i.e.the replacement method and the agglomerate method,so that it is both accurate and efficient.The method can be easily implemented.The performance is shown by several DEM simulations of biaxial tests.Particles with different crush-abilities are modeled.DEM simulation results with and without grain crushing are compared and discussed.The change of grain size distribution due to grain crushing is also investigated.

Failure probability analysis of coal crushing induced by uncertainty of influential parameters under condition of in-situ reservoir

The uncertainties of some key influence factors on coal crushing,such as rock strength,pore pressure and magnitude and orientation of three principal stresses,can lead to the uncertainty of coal crushing and make it very difficult to predict coal crushing under the condition of in-situ reservoir.To account for the uncertainty involved in coal crushing,a deterministic prediction model of coal crushing under the condition of in-situ reservoir was established based on Hoek-Brown criterion.Through this model,key influence factors on coal crushing were selected as random variables and the corresponding probability density functions were determined by combining experiment data and Latin Hypercube method.Then,to analyze the uncertainty of coal crushing,the firstorder second-moment method and the presented model were combined to address the failure probability involved in coal crushing analysis.Using the presented method,the failure probabilities of coal crushing were analyzed for WS5-5 well in Ningwu basin,China,and the relations between failure probability and the influence factors were furthermore discussed.The results show that the failure probabilities of WS5-5 CBM well vary from 0.6 to 1.0; moreover,for the coal seam section at depth of 784.3-785 m,the failure probabilities are equal to 1,which fit well with experiment results; the failure probability of coal crushing presents nonlinear growth relationships with the increase of principal stress difference and the decrease of uniaxial compressive strength.

High-Efficiency Video Coder in Pruned Environment Using Adaptive Quantization Parameter Selection

The high-efficiency video coder(HEVC)is one of the most advanced techniques used in growing real-time multimedia applications today.However,they require large bandwidth for transmission through bandwidth,and bandwidth varies with different video sequences/formats.This paper proposes an adaptive information-based variable quantization matrix(AIVQM)developed for different video formats having variable energy levels.The quantization method is adapted based on video sequence using statistical analysis,improving bit budget,quality and complexity reduction.Further,to have precise control over bit rate and quality,a multi-constraint prune algorithm is proposed in the second stage of the AI-VQM technique for pre-calculating K numbers of paths.The same should be handy to selfadapt and choose one of the K-path automatically in dynamically changing bandwidth availability as per requirement after extensive testing of the proposed algorithm in the multi-constraint environment for multiple paths and evaluating the performance based on peak signal to noise ratio(PSNR),bit-budget and time complexity for different videos a noticeable improvement in rate-distortion(RD)performance is achieved.Using the proposed AIVQM technique,more feasible and efficient video sequences are achieved with less loss in PSNR than the variable quantization method(VQM)algorithm with approximately a rise of 10%–20%based on different video sequences/formats.

SHAPE OPTIMIZATION DESIGN OF CRUSH TOOTH USING FINITE ELEMENT METHOD

The load condition of the mineral sizer is discussed. Acoording to three typical load cases presented, FEM and optimization models are established. Computed the model problems by use of ANSYS software and sequential unconstrained minimization technique, the stress distribution on c rush tooth and it's optimal shape are aquired. After analyzing the results, the relation between stress distribution and structural parameters is presented.

干湿循环作用下堆石料宏细观力学特性的离散元模拟研究

堆石料的物理力学特性在干湿循环作用下会发生明显劣化。基于堆石料颗粒三维扫描结果,建立了宽粒径范围的堆石料颗粒模板库。考虑干湿循环对颗粒强度、颗粒间接触模量和摩擦系数的影响,提出了一种考虑堆石颗粒干湿循环劣化的颗粒破碎模拟方案。在此基础上,采用FDM-DEM耦合方法对不同干湿循环作用下的堆石料试样进行一系列三轴压缩试验,讨论了在三轴压缩条件下干湿循环对堆石料宏细观力学特性的影响规律。结果表明:堆石料的初始模量和峰值强度随着干湿循环次数N的增加而呈非线性降低,干湿循环对体变曲线在初始阶段的剪缩和加载后期的剪胀有抑制作用,当N增大至某一值时,干湿循环对堆石料的宏观变形和强度的影响逐渐不明显。干湿循环次数越大,试样内部平均配位数越大,接触滑移比越大,试样内部的偏组构呈非线性减小,即各向异性程度在逐渐减小,这说明干湿循环对试样内部的各向异性发展有抑制作用。

矿石破碎颗粒黏结模型黏结键特征及表征

目的针对矿石颗粒黏结模型与实际矿石破碎特性存在差异造成的仿真不准确问题,重点对不同粒级矿石颗粒黏结模型中的黏结键特征进行研究。方法依据矿石强度尺寸效应理论,设计铜矿石颗粒黏结模型中基础颗粒间的黏结键参数,应用离散元方法对30,40,60 mm三种粒级铜矿石矿样进行落重试验和破碎仿真。本文给出黏结键等效临界变形的概念,讨论了矿石落重试验t10和冲击能量的关系,探讨黏结键参数变化规律。结果结果表明,三种粒级铜矿石颗粒黏结模型破碎仿真与落重试验粒级质量分数的平均误差分别为1.75%,1.66%,1.84%,试验和仿真得到的破碎粒度质量分数具有很好的一致性;法向和切向等效临界变形可以表征黏结键强度,单位冲击能量下落重试验的tn10可以表征矿石强度。结论利用黏结键等效临界变形和tn10的对应关系确定黏结键参数,提高了矿石颗粒黏结模型的建模效率和仿真精度。

疏解工艺对簕竹重组材力学性能及尺寸稳定性的影响

本文以簕竹为原料制备重组材,研究了不同疏解工艺对簕竹重组材力学性能和尺寸稳定性的影响,并通过与毛竹重组材对比,探讨其利用价值。结果表明:随着疏解程度的增加,竹束的载胶量增大,竹青竹黄的存在使竹束对胶黏剂的吸附能力下降;相同条件下,簕竹重组材与毛竹重组材水平剪切强度相当,弹性模量及静曲强度约为毛竹的2倍左右,经28 h循环水处理吸水厚度膨胀率约为毛竹的1/2;带青带黄疏解有利于提高簕竹重组材的抗弯性能,制备的重组竹静曲强度达215 MPa,弹性模量达28 GPa,分别高于常规疏解的8.64%和12.92%,但其水平剪切强度略有下降。竹青的存在可以提高簕竹表面的耐水性,簕竹青黄宽疏解在60 s时接触角仍能达到60°,较其余条件耐水性高。以簕竹开发制备重组材在工程应用上具有较大潜力。

固废粗集料平均弹性模量与混凝土弹性模量的相关性

试验研究了12种不同固废粗集料压碎值试验中σ-ε曲线与配制混凝土的静态弹性模量之间关系,进行了压碎值试验固废粗集料变形的离散元数值模拟,分析了国内外主要标准中公式计算固废粗集料混凝土弹性模量误差偏大的原因。研究结果表明:基于中国、美国和欧洲标准的普通密度固废粗集料混凝土弹性模量计算值分别高出实测值45.5%、15.8%和52.5%;固废粗集料在压碎值试验σ-ε曲线的线性区间主要发生弹性变形;建立的固废粗集料σ-ε曲线指数模型拟合度高,R^(2)均大于0.99;通过在传统的压碎值试验中引入粗集料平均弹性模量、含水系数等参数,回归建立了固废粗集料混凝土弹性模量半经验公式,R^(2)为0.867。利用已有文献数据对半经验公式的普适性进行了检验,高判定系数(R^(2)=0.895)实测值与预测值的比较表明模型具有有效性,为快速、可靠预测固废粗集料混凝土弹性模量提供了依据。

糖基化乳清分离蛋白制备共轭亚油酸水包油乳液稳定性分析

目的研究糖基化乳清分离蛋白(whey protein isolate,WPI)对制备的共轭亚油酸(conjugated linoleic acid,CLA)乳液的物理稳定性、抗氧化能力及脂质氧化稳定性的影响。方法以CLA为原料,分别采用葡萄糖(glucose,Glu)和半乳糖(galactose,Gal)对WPI进行糖基化改性,超声破碎法制备CLA水包油乳液,研究在不同盐离子浓度、pH和温度下CLA乳液平均粒径变化、抗氧化能力及贮藏过程中脂质氧化产物含量变化。结果同对照组WPI-CLA相比,经糖基化改性后制备的WPI-Glu-CLA和WPI-Gal-CLA乳液受到盐离子浓度、pH和加热温度的影响,其平均粒径变化较小,且分布均匀。WPI-CLA、WPI-Glu-CLA和WPI-Gal-CLA乳液对1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基达到100%清除时的质量浓度分别为10、4、4 mg/mL,对2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐[2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate),ABTS]阳离子自由基达到100%清除时的质量浓度分别为8、6、6 mg/mL。在贮藏过程中,WPI-Glu-CLA和WPI-Gal-CLA乳液的氢过氧化物及次级脂质氧化产物含量均低于对照组WPI-CLA乳液。结论经糖基化改性修饰,增强了CLA乳液的物理稳定性,提高了抗氧化能力,有效减缓了脂质氧化产物的生成。

不同养护方式对铁尾矿砂制备的再生粗骨料性能影响

为了提高铁尾矿沙的利用率,本文采用成球技术使用铁尾矿沙制备粗骨料,将经过界面预处理后的铁尾矿砂采用喷洒预处理液水雾,同时撒入胶凝材料的方式生成骨料颗粒,最后将骨料颗粒进行养护得到再生粗骨料。探究不同的养护方式对再生粗骨料的性能的影响,结合SEM和MIP探究养护方式对再生粗骨料微观形貌和孔结构的影响。结果表明:改进的成球技术制备铁尾矿沙再生粗骨料具有一定的可行性。另外,自然养护条件骨料的性能表现最差,蒸汽养护骨料的压碎指标最小,碳化养护骨料的吸水率最小。从微观结构来看碳化养护的骨料体系结构致密,孔隙和微裂缝含量相对较少,因此骨料吸水率最小;蒸汽养护水化产物含有大量的凝胶状和网状结构的水化硅酸钙、针状钙矾石和少量的氢氧化钙晶体,这是压碎指标小的原因。这些研究结果为铁尾矿沙制备再生粗骨料应用于混凝土的后期服役过程中提供了指导意义。

Gravel hardness effect on compaction characteristics of gravelly soil

The compaction characteristics of gravelly soil are affected by gravel hardness.To investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil,heavy compaction tests and crushing tests were conducted on gravelly soils with gravels originated from hard,soft and extremely soft rocks.According to orthogonal experiments and variance analysis,it was found that hardness has a significant impact on the maximum dry density of gravelly soil,followed by gravel content,and lastly,moisture content.For gravel compositions with an average saturated uniaxial compressive strength less than 60 MPa,the order of compacted maximum dry density is soft gravels>hard gravels>extremely soft gravels.Each type of gravelly soil has a threshold for gravel content,with 60%for hard and soft gravels and 50%for extremely soft gravels.Beyond these thresholds,the compacted dry density decreases significantly.There is a certain interaction between hardness,gravel content,and moisture content.Higher hardness increases the influence of gravel content,whereas lower hardness increases the influence of moisture content.Gravelly soils with the coarse aggregate(CA)between 0.7 and 0.8 typically achieve higher dry densities after compaction.In addition,the prediction equations for the particle breakage rate and CA ratio in the Bailey method were proposed to estimate the compaction performance of gravelly soil preliminarily.The results further revealed the compaction mechanism of different gravelly soils and can provide reference for subgrade filling construction.

弧形负泊松比蜂窝结构抗冲击性能的有限元分析

拉胀蜂窝因其轻质、抗冲击和吸能强等特点,引起了学者们的广泛关注。采用有限元法探讨一类弧形蜂窝结构(arc-star-shaped honeycomb,ASSH)的整体面内冲击动力学行为,比较冲击速度对ASSH和传统星型蜂窝结构(SSH)的变形模式、动态响应和能量吸收能力的影响。结果表明,同等情况下,ASSH比SSH具有更好的抗冲击性能。此外,还研究了胞元壁厚和弧角等参数对ASSH吸能的影响,相关结果有望为负泊松比材料和结构的设计提供一定的参考。

浅谈机制砂石骨料生产线破碎设备选型

在新发展理念指引下,作为国家基础设施建设中不可或缺的砂石行业,在产业调控的政策因素、需求变化的市场因素等影响下,正在从增量扩张进入存量提质增效的高质量发展新阶段。对于砂石生产企业来讲,关注市场需求、强抓产品质量管理和可持续发展,促进资源价值开发利用最大化,将有助于企业把握竞争机遇,在新发展阶段抢占市场份额,取得良好的经济效益和社会效益。笔者以已投产骨料机制砂生产线破碎设备选型为例,解析不同的矿石生产机制砂石骨料产品最佳破碎选型方案,供借鉴参考。

小麦籽粒Ab-T10破碎模型参数标定

离散元法在粮食颗粒中的研究应用较为广泛,但是小麦颗粒在破碎仿真过程中数学模型参数的研究较为匮乏。为了寻找在破碎仿真过程中更适合小麦籽粒的破碎参数设定,以小麦籽粒为研究对象,搭建了冲击落锤破碎试验平台,通过试验得到了参数标定目标值,采用最陡爬坡试验和Box-Behnken响应面试验,根据回归方程与响应面分析得到适用于模拟仿真小麦籽粒快速破碎模型Ab-T10中关键参数的最优组合,并对标定参数进行多组交叉验证。研究结果表明:颗粒特性选择函数参数S为0.00146 kg/J;颗粒参考最小破碎比能E_(ref)为85.74 J/kg、筛下物占初始粒度中径10%的最大累计质量分数M_(t10)为4.97%;仿真试验与实际试验最大相对误差为2.4%,说明标定的参数可有效表征小麦籽粒冲击破碎过程。研究结果对后续小麦加工中的研磨破碎分析具有一定的参考价值。

HSCA高效无声破碎剂在北沟隧道石方开挖中的应用

随着现代施工技术的不断发展,只有通过不断寻求新技术、新工艺、新材料、新设备,才能提高企业的竞争力和可持续发展能力。在北沟隧道开挖位置受限的条件下,采用HSCA高效无声破碎剂胀裂石方,具有无振动、无噪声等优点。文章主要就HSCA高效无声破碎剂的作用机理、破碎方法以及在施工过程中的应用情况进行简单阐述,为同类工程提供借鉴。

基于离散单元法的双辊餐厨垃圾破碎机产物粒径影响因素仿真分析

餐厨垃圾的处理包括对餐厨垃圾实施破碎、压榨、分选等操作,以实现固体破碎、固液分离、油水分离,进而达成无害化处理或资源回收利用目的。双刀辊破碎装置是实现餐厨垃圾固体破碎的高效设备之一,其作用是将大块物料粉碎成粒径细小且均匀的物料颗粒,以便于进行后续处理和存储运输。基于离散单元法,采用仿真软件EDEM的Edinburgh Elasto-Plastic Adhesion和Tavares UFRJ Breakage接触模型,模拟了双辊转速分别为10、15、20、25、30 rad/s和物料颗粒初始半径分别为10、15、20、25、30 mm时破碎装置的工作情况。结果表明:刀辊转速和初始颗粒半径都对破碎装置的破碎效率及出料颗粒粒径分布具有显著影响;双辊转速越快,完成破碎作业所需时间越短但出料颗粒里小粒径占比会降低;入料半径15 mm时作业效率最高,而入料半径30 mm时出料颗粒里小粒径颗粒占比最高。

热油柱成型法制备高强度球形氧化铝载体研究

针对传统热油柱成型工艺制备的球形氧化铝载体强度偏低、比表面积偏低、孔结构弥散等问题,考察了在铝溶胶合成阶段添加柠檬酸,在老化阶段添加醇类助剂和改变老化条件,在焙烧阶段改变焙烧温度对球形氧化铝物化性能的影响规律。结果表明:柠檬酸的加入可提高氧化铝载体的抗压碎强度和比表面积,孔径分布更加集中;在载体堆密度和孔结构性能满足要求的前提下,在老化阶段添加适量丙三醇,适当降低老化温度和缩短老化时间,适当调整焙烧温度,可有效提高载体的抗压碎强度。经优化工艺条件,该方法可制备出抗压碎强度大于60 N/颗,比表面积大于100 m^(2)/g,比孔容接近0.70 cm^(3)/g的δ/θ–Al_(2)O_(3)载体。

大掺量橡胶沥青同步碎石封层的试验研究

将橡胶沥青中橡胶粉掺量提升的研究和应用愈发增多,其中大掺量橡胶沥青适用于同步碎石封层的应用场景,可有效起到应力吸收的功能性作用,充分发挥大掺量胶粉具有优异弹性与疲劳特性的特点,大掺量胶粉的橡胶沥青同步碎石封层以层间的抗剪性能为基础,通过研究对比材料性能、用量及路用性能。研究将通理论法和力学-经验设计方法设计同步碎石下封层的配合比,以层间抗剪强度为设计指标,选取斜剪试验进行模拟,进行大掺量橡胶沥青同步碎石封层材料的组成设计试验。并以普通掺量下即18%橡胶沥青制作碎石封层的性能对比,以此为实现大掺量橡胶沥青在同步碎石封层中的应用,解决半刚性基层反射裂缝的问题,实现废旧轮胎的高质化、高效化再利用进行基础技术储备。试验结果显示:基于力学-经验法或理论法均可以设计出性能更优良的大掺量橡胶沥青同步碎石封层,两者差异不大,相对18%橡胶沥青制作碎石封层,大掺量橡胶沥青同步碎石封层具有很高的抗拉强度、抗剪强度和动稳定度。