Heavy Metal Control in Domestic Rubbish by Source Screening and Suitability of Nutrient Elements as Turfgrass Medium

This paper, probing into heavy metal control in domestic rubbish by source screening and nutrient element analysis, revealed the feasibility of source control of heavy metals and the suitability of rubbish as turfgrass medium. Heavy metals in domestic rubbish were controlled by source screening before composting. The study consisted of a control with garden soil. The contents of main mineral elements and heavy metals in rubbish compost and control were determined by the method of ICP-AES. The results showed that heavy metal concentrations in rubbish were lower than those in garden soil, and little difference occurred between rubbish and garden soil in main mineral element concentrations. Based on this, it was concluded that rubbish compost was favorable for using as turfgrass medium and heavy metal control in rubbish by source screening was effective.

Using Prostatic Fluid Levels of Some Trace Elements and Their Combinations in Non-Invasive and Highly Accurate Screening for Prostate Cancer

Objective: Prostate specific antigen (PSA) does not provide the high reliability and precision that is required for an accurate screening for prostate cancer?(PCa). The aim of our study was to search for a simple, rapid, direct, preferably non-invasive, and highly accurate biomarker and procedure for the screening for PCa. Method: The levels of trace elements (TE) Br, Fe, Rb, Sr,?and Zn were prospectively evaluated in expressed prostatic fluid (EPF). Also?Zn/Br, Zn/Fe, Zn/Rb, Zn/Sr concentration ratios as well as ZnRb and (ZnRb)/Fe concentration combinations were calculated for EPF samples, obtained from 38 apparently healthy males and from 33, 51, and 24 patients with chronic prostatitis, benign prostatic hyperplasia, and PCa, respectively. Measurements were performed using an energy dispersive X-ray fluorescent (EDXRF) microanalysis. Results: It was found that in the EPF of cancerous prostates the levels of Rb, Zn, Zn/Br, Zn/Fe, Zn/Sr, ZnRb, and (ZnRb)/Fe were significantly lower in comparison with those in the EPF of normal, inflamed, and hyperplastic prostates. For example, in comparison hyperplastic?with cancerous prostates p values obtained using Student’s t-test and?Wilcoxon-Mann-Whitney U-test were Conclusions: The levels of TE and their combinations in EPF, obtained by EDXRF, is a fast, reliable, andnon-invasive diagnostic tool that can be successfully used by local, non- urologist physicians at the point-of-care to provide a highly effective PCa screening and as an additional confirmatory test before a prostate gland biopsy.

Modeling screening efficiency with vibrational parameters based on DEM 3D simulation

The efficiency of particle screening was studied over a range of vibrational parameters including amplitude, frequency and vibrational direction. The Discrete Element Method (DEM) was used to simulate the screening process. A functional relationship between efficiency and the parameters, both singly and combined, is established. The function is a complicated exponential. Optimal amplitude and frequency values are smaller for particles near the mesh and larger for other particles. The optimum vibration angle is 45° for nearly all kinds of particles. A transverse velocity, V⊥, was defined and V⊥=0.2 m/s was identified to be the most efficient operating point by both simulation and experimental observation. Comparison of these results with those reported by others is included.

Application of the DEM to screening process:a 3D simulation

The discrete element method(DEM) has been widely used to simulate microscopic interactions between particles.Screening is a deeply complicated process when considering the law of motion for the particles,themselves.In this paper,a numerical model for the study of a particle screening process using the DEM is presented.Special attention was paid to the modeling of a vibrating screen that allows particles to pass through,or to rebound,when approaching the screen surface.Inferences concerning screen length and vibrating frequency as they relate to screening efficiency were studied.The conclusions were:three-dimensional simulation of screening efficiency along the screen length follows an exponential distribution;when the sieve vibrates over a certain frequency range the screening efficiency is stable;and,higher vibration frequencies can improve the handling capacity of the screening machine.

DEM simulation of particle flow on a single deck banana screen

A mathematical study of particle flow on a banana screen deck using the discrete element method (DEM) was presented in this paper. The motion characteristics and penetrating mechanisms of particles on the screen deck were studied. Effects of geometric parameters of screen deck on banana screening process were also investigated. The results show that when the values of inclination of discharge and increment of screen deck inclination are 10° and 5° respectively, the banana screening process get a good screening performance in the simulation. The relationship between screen deck length and screening efficiency was further confirmed. The conclusion that the screening efficiency will not significantly increase when the deck length L≥430 mm (L/B ≥ 3.5) was obtained, which can provide theoretical basis for the optimization of banana screen.

Screening efficiency and screen length of a linear vibrating screen using DEM 3D simulation

The effect of screen length on the screening efficiency of particles is studied under various single parameter conditions including frequency, amplitude, vibration angle, and screen inclination. The Discrete Element Method (DEM) has been used to simulate the screening process. A functional relationship between screening efficiency and screen length is established. It is shown that screening efficiency and screen length have a complicated exponential relationship. Relationships between them are profoundly discussed and conclusions are easily drawn: low values of the parameters do not benefit screening; screening efficiency generally increases with screen length; screening efficiency reaches a plateau when these parameters are in range frequently encountered in practical applications.

Influence of vibration mode on the screening process

The screening of particles with different vibration modes was simulated by means of a 3D discrete element method (3D-DEM). The motion and penetration of the particles on the screen deck were analyzed for linear, circular and elliptical vibration of the screen. The results show that the travel velocity of the particles is the fastest, but the screening efficiency is the lowest, for the linear vibration mode. The circular motion resulted in the highest screening efficiency, but the lowest particle travel velocity. In the steady state the screening efficiency for each mode is seen to increase gradually along the longitudinal direction of the deck. The screening efficiency increment of the circular mode is the largest while the linear mode shows the smallest increment. The volume fraction of near-mesh size particles at the underside is larger than that of small size particles all along the screen deck. Linear screening mode has more near-mesh and small size particles on the first three deck sections, and fewer on the last two sections, compared to the circular or elliptical modes.

考虑风载因素的玻璃幕墙清洁机器人设计

围绕高楼玻璃幕墙机器人自动清洁中的风载问题,设计了一款考虑风载因素的真空吸盘吸附的框架式爬壁机器人。针对玻璃幕墙清洁机器人的框架式结构进行步态规划。基于空间力学理论建立了玻璃幕墙清洁机器人在风载下的力学平衡模型,得到了风载大小与机器人吸盘吸附力之间的力平衡方程。在Workbench中对风载作用下的清洗机器人本体进行了有限元分析,得到了机器人模型的应力云图与变形云图。实验测试结果表明:在极限风载作用下,机器人的最大应力点位于吸盘支架,最大变形点位于主架板中心。在真实风载下对机器人进行攀爬运动仿真分析,机器人可以在极限风载下稳定地工作,不会发生滑移和倾覆,验证了力学模型和设计模型的正确性。

物料冲击对椭圆振动筛筛分性能的动态影响

为了研究物料冲击对振动筛动态特性的影响,加工了某型三轴椭圆振动筛样机。首先,建立简化后的筛机模型,采用离散元法与多体动力学相结合的方法对椭圆振动筛的筛分过程进行数值模拟;其次,引入有限元法对物料冲击下的筛面进行分析,以筛分效率、物料运输速度、筛上物质量和最大冲击力为筛分性能的评价指标;最后,通过试验对其不同工况下的结构振动和应变信号进行了测试和分析,研究了振幅、振频、筛面倾角以及入料速度对筛分性能的影响,揭示了常规筛机评价指标与振动参数之间的关系,为多目标评价和振动筛机优化设计提供了参考。

基于活性炭颗粒的圆振动筛主要技术参数优化分析

为验证圆运动振动筛在对活性炭颗粒筛分时,振动筛各运动参数对筛分效率的影响,采用平均筛分效率来代表活性炭筛分效果。采用Box-Behnken响应面分析来研究圆运动振动筛的振动幅度、运动倾角以及振动频率对筛分效果的影响并进行仿真模拟,探讨3个因素之间对活性炭筛分的影响作用。验证结果表明:对筛分效果影响最大的是振动频率,影响最弱的是运动倾角,振动幅度和运动倾角之间具有显著影响作用,在振动幅度为4.21 mm、运动倾角16.07°以及振动频率13.83 Hz时筛分效果达到最大值40.86%。通过该方法优化的圆振动筛,可提高活性炭的筛分效率。

新型螺旋筛面旋振筛的参数优化

为研究螺旋筛面旋振筛的筛分效率与筛分参数之间的非线性关系,文章使用神经网络对其筛分参数综合寻优,得到最佳筛分参数及筛分效率。首先,建立不同结构参数的螺旋筛面旋振筛三维模型,利用离散单元法对其仿真模拟,获取不同参数下的筛分效率数据。然后,利用神经网络对样本数据进行训练、验证及得到预测数据。研究结果表明:通过神经网络的训练和测试,证明神经网络可以用于螺旋筛面旋振筛的参数优化;在螺旋升角为11.613°、振动频率为15.720 Hz、振动幅度为1.481 mm、螺旋圈数为1.468圈、内外径比值为0.256时,螺旋筛面旋振筛获得最佳筛分效率,并且优化了螺旋圈数,缩短了筛长。

基于EDEM与BP神经网络的平-摆筛参数化研究

为直观分析振动参数与料体分层效果复杂映射关系及筛分过程物料松散规律,以便振动筛参数化研究的开展。首先以振动筛简化后三维模型导入EDEM软件,利用正交试验法进行设计,并将试验方案中对应筛机参数分别导入EDEM中。基于平动与摆动双运行模式振动筛,提出以分层沉降比的定义对料体分层效果进行表征,以离散元软件分析振动筛的振幅、振动频率、振动方向角和摆动频率四个参数对分层效果的影响,将获得的仿真数据导入BP神经网络进行深度学习。采用集成学习的训练集对训练好的模型进行筛机参数影响权重的分析,得出振动频率、振动幅度,振动方向角和摆动频率和对分层效果有较大影响,故以这四种参数组合表征振动筛运行状态,对不同参数组合对应筛分效率进行分析。振动频率与振动幅度增加,可以增大筛面的振动强度,不仅加速物料松散速率,优化物料的分层效果,又可以改善物料的堵筛情况,但振动强度过大时,物料跃迁时间过长,使得物料与筛面接触时间变短,分层效果下降;随着振动方向角的增加可以加速物料的铺展速率,但角度过大时,会降低物料与筛面的碰撞概率,弱化物料的分层效果,从而影响筛分效果。当振幅为3.6mm、振频为18.3Hz、振动方向角为39.1°、摆动频率为13.8Hz时,振动筛的分层沉降比为0.77,分层效果最优,此时的分层构型最便于筛分的进行,此研究对平动与摆动双运行模式的振动筛优化设计具有一定指导意义。

Optimized design of a linear vibrating screen based on efficiency maximisation and mesh wear minimisation employing discrete element method

This article investigates the combined effect and the order of influence of feed rate,inclination angle,vibration amplitude,frequency,and angle on the efficiency and mesh wear rate of a linear vibrating screen,as well as the average velocity,and mass of the accumulated particles.The discrete element modeling simulations were conducted using LIGGGHTS open-source code to analyze particles behaviour.The Taguchi method was employed to evaluate the combined effect of the parameters.Finally,the simulation results were analyzed using analysis of variance.The optimal values of the parameters for maximising efficiency and minimising mesh wear were determined using grey relational analysis.The results indicated that the most effective parameters on screening efficiency and average velocity of particles were the inclination angle,vibration angle,frequency,amplitude,and feed rate,respectively.The most influential parameters on screen mesh wear rate were feed rate,inclination angle,vibration angle,frequency,and amplitude,respectively.

双层直线振动筛的筛分性能模拟研究

为了强化双层直线振动筛对塑料颗粒的筛分性能,采用离散元法建立双层直线振动筛和塑料颗粒模型,仿真研究塑料颗粒在筛分中的运动特性,利用单因素控制变量法和四因素四水平的正交试验法分析振动频率、振动方向角、振幅和筛面倾角对双层直线振动筛筛分性能的影响。结果表明,塑料颗粒在筛面上可快速达到稳定筛分阶段;两层筛面的透筛分别发生在筛面入料口附近和筛面前中段;振动方向角增加,上层筛面筛分效率稳定在92%,下层筛面筛分效率先减小后增大;振幅增大,两层筛面的筛分效率都减小;振动频率或筛面倾角增加,都会导致上层筛面筛分效率先增大后减小,下层筛面筛分效率下降。采用双层直线振动筛筛分塑料颗粒的最优参数组合为振动频率15 Hz、振动方向角40°、振幅5 mm和筛面倾角4°。研究结果为双层直线振动筛性能提升提供依据。

曲轴连杆式大型弛张筛关键部件动态特性

弛张筛作为选煤厂原煤干法深度筛分的关键装备,尤其曲轴连杆式弛张筛稳定性较好,在大型动力煤选煤厂得到广泛应用。曲轴连杆机构为该大型弛张筛的核心关键部件,其可靠性对筛分效果与后续分选环节均有重要影响。基于此,采用有限元仿真计算,聚焦曲轴连杆机构的动态特性,围绕哈尔乌素大型动力煤选煤厂大型弛张筛,构建曲轴连杆结构有限元模型并进行模态分析,进而基于模态叠加法进行简谐载荷作用下的谐响应分析,最后通过边界条件模拟其在筛机运行下的运动状态,对其进行了动力学分析。结果表明,其固有频率均远大于系统工作时的激振频率,曲轴连杆结构无共振风险;工作状态下曲轴连杆产生的应力集中在曲轴表面以及连杆的轴承处,最大应变为1.10×10^(-4),满足设计要求;同时,确定了连杆与曲轴间的机械碰撞是结构产生材料变形的主要原因。本研究结果为大型曲轴连杆式弛张筛的选型设计、结构优化以及工程实践提供了理论与技术参考。

基于EDEM的沙棘冻浆果振动清选装置参数优化与分析

针对沙棘冻浆果清选加工中存在清洁率低,筛网易堵塞的问题,采用离散元EDEM软件对振动清选装置的结构和运动参数进行优化。以速冻沙棘枝条果机械脱果后的冻浆果、枝条和果梗等颗粒为试验物料,测定物料的尺寸特征,进行振动清选装置动力学分析和筛上颗粒受力分析。分析筛网不同形状以及尺寸的筛孔组合对振动清选装置清洁率和透筛概率的影响,确定筛网设计参数为第一层筛网为圆孔、孔径为11 mm,第二层筛网为圆孔、孔径为9 mm,第三层筛网为长孔、孔径为5 mm×25 mm。单因素试验结果表明:振幅的改变未显著影响洁净率和透筛率,在保证高清洁率时选取筛体振幅为6 mm。选取振动频率,振动方向角,筛面倾角为试验因素,清洁率和透筛概率为试验指标,设计二次正交旋转组合试验,建立各因素与指标间的数学模型,优化结果最优组合为:振动频率为17.52 Hz、振动方向角为44.7°、筛面倾角为1.56°时,振动清选装置清洁率为99.62%、透筛概率为33.42%。通过台架试验和仿真试验对最优参数组合进行验证,结果表明:台架试验和仿真试验结果基本一致,清洁率的相对误差为1.13%,颗粒透筛数量的相对误差为1.68%。该研究可为沙棘冻浆果振动清选装置的优化设计提供理论依据。

大型振动筛筛梁焊接有限元数值模拟分析与顺序优化

筛梁是影响大型振动筛使用寿命的关键零部件,用数值模拟的方式预测焊接变形与焊后残余应力分布能有效缩短实验周期、减少实验成本。按照不同的焊接顺序设计3种焊接方案,采用Simufact Welding有限元软件分别进行数值模拟,得到焊接变形分布情况,确定最优的焊接方案。对温度场、应力场分布情况进行分析,得知焊缝处温度变化和残余应力最大,随着距离的增加等效应力呈递减趋势,法兰内侧圆角处残余应力较大,外侧直角位置应力最小,但焊接变形较大。通过研究焊接变形和残余应力的分布情况,为改进筛梁的焊接工艺和设计焊接变形矫正装置提供参考。

器内过滤对浆态床反应器操作特性的影响

浆态床反应器是低温费-托合成工艺普遍采用的反应器形式,常采用器内过滤系统连续分离反应生成的液体产品。通过实验方法从不同条件下过滤区域的漏气率与平均气含率的变化及气体反冲洗对床层操作稳定性的影响2个方面,研究了器内过滤对浆态床反应器操作特性的影响。结果表明:因为气体从过滤器处的泄漏,过滤区域平均气含率出现明显降低;过滤压差从8 kPa增至16 kPa,漏气率与气含率均随之增加,但平均气含率的平均增长值从0.0059降至0.0044;气-液体系的漏气率最大,平均气含率相对较低,范围为0.063~0.145;增加浆液颗粒质量分数到5%时,由于漏气率下降,平均气含率范围扩大至0.062~0.146。滤芯孔隙从80μm减小至30μm,气-液体系下漏气率降低幅度增大,平均气含率的平均增长值从0.0040增至0.0049;当加入质量分数为5%的颗粒后漏气率降低幅度开始下降,平均气含率的平均增长值也从0.0018降至0.0012。从过滤区域床层压差波动看,气体反冲洗对浆态床操作稳定性存在明显扰动,且滤芯孔隙越大,这种扰动效应越强烈。

柔性筛板上黏湿煤团解聚及透筛特性研究

振动弛张筛在黏湿细粒煤炭干法筛分领域应用广泛。采用离散元中的API技术,在EDEM软件中构建了一种新型柔性筛面模型,并利用数学理论模型进行验证,此外探究了筛面振幅参数和颗粒表面能大小对黏湿颗粒运动特性的影响规律。结果表明:随着表面能的增大,煤团与筛面碰撞后形成的二次团聚体越大,筛下颗粒数越少,一定范围内,随振幅的增大解聚后的颗粒平均法向速度越大。研究成果为离散元法研究黏湿煤炭筛分提供理论基础。

基于丝网印刷技术的海南旅游文创产品设计研究

借助网印技术提炼和艺术化处理海南的独特元素,如热带植物、海洋文化以及黎族文化元素等,并应用于文创产品设计制作中,以展示海南的独特魅力。文章采用了文献研究法和理论与实践结合法等方法,为海南文创产品设计提供了理论支持与实践指导。