Permeability evolution mechanism and the optimum permeability determination of uranium leaching from low-permeability sandstone treated with low-frequency vibration

Low-frequency vibrations can effectively improve natural sandstone permeability,and higher vibration frequency is associated with larger permeability.However,the optimum permeability and permeability evolution mechanism for uranium leaching and the relationship between permeability and the change of chemical reactive rate affecting uranium leaching have not been determined.To solve the above problems,in this study,identical homogeneous sandstone samples were selected to simulate lowpermeability sandstone;a permeability evolution model considering the combined action of vibration stress,pore water pressure,water flow impact force,and chemical erosion was established;and vibration leaching experiments were performed to test the model accuracy.Both the permeability and chemical reactions were found to simultaneously restrict U6þleaching,and the vibration treatment increased the permeability,causing the U6þleaching reaction to no longer be diffusion-constrained but to be primarily controlled by the reaction rate.Changes of the model calculation parameters were further analyzed to determine the permeability evolution mechanism under the influence of vibration and chemical erosion,to prove the correctness of the mechanism according to the experimental results,and to develop a new method for determining the optimum permeability in uranium leaching.The uranium leaching was found to primarily follow a process consisting of(1)a permeability control stage,(2)achieving the optimum permeability,(3)a chemical reactive rate control stage,and(4)a channel flow stage.The resolution of these problems is of great significance for facilitating the application and promotion of lowfrequency vibration in the CO_(2)+O_(2) leaching process.

Mechanisms of low-frequency sea level fluctuations in the Hangzhou Bay

-low-frequency sea level fluctuations in the Hangzhou Bay in winter and summer, 1973-1974 are analyzed in this paper. The established multi-spectrum response models effectively identify the different dynamical factors and their contributions to the low-frequency sea level fluctuations inside the bay. The results show that the Ekman transport due to longshore winds is the major mechanism to induce the sea level fluctuations, more important than the frictional effect of local winds. There also exists obviously the influental effect of the free fluctuations of the continental shelf. In addition ,a simple estimation suggests that the remarkable sea level fluctuation of 0. 4 d-1 in the bay is related to the resonance of the Huanghai Sea and the Bohai Sea (taken as a single bay).

One Possible Mechanism for the Principal Mode of Atmospheric Low-Frequency Variabilityin the Northern Hemisphere Winter

With the specified basic flow in the Northern Hemisphere winter, a study is made of the structure characteristics and mechanism of the principal mode of atmospheric low-frequency variability in terms of a linear barotropic model. Statistical and dynamical analyses of the model results indicate that the mode and the related dominant-forcing excitation zone are featured by evident spatial distribution and that the mechanism responsible for the mode bears fetation to the zonal asymmetry of the basic flow and the associated barotropic energy conversion.

High mechanical strength Si anode synthesis with interlayer bonded expanded graphite structure for lithium-ion batteries

Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries,their widespread commercial adoption is still hindered by significant volume expansion during cycling,especially at high active mass loadings crucial for practical use.The root of these challenges lies in the mechanical instability of the material,which subsequently leads to the structural failure of the electrode.Here,we present a novel synthesis of a composite combining expanded graphite and silicon nanoparticles.This composite features a unique interlayer-bonded graphite structure,achieved through the application of a modified spark plasma sintering method.Notably,this innovative structure not only facilitates efficient ion and electron transport but also provides exceptional mechanical strength(Vickers hardness:up to658 MPa,Young's modulus:11.6 GPa).This strength effectively accommodates silicon expansion,resulting in an impressive areal capacity of 2.9 mA h cm^(-2)(736 mA h g^(-1)) and a steady cycle life(93% after 100cycles).Such outsta nding performance is paired with features appropriate for large-scale industrial production of silicon batteries,such as active mass loading of at least 3.9 mg cm^(-2),a high-tap density electrode material of 1.68 g cm^(-3)(secondary clusters:1.12 g cm^(-3)),and a production yield of up to 1 kg per day.

Research on Mechanism of Overcurrent and Overvoltage When Contactless Tap Changer Switch Regulates Voltage on Load

Analyzes the mechanism of overvoltage when contactless tap changer switch which is applied in distributing transformer converted directly.When the device convert the tap off,it employs the way that the SSR is switched on when voltage through zero and switched off when current through zero.But in the experiment we found that overvoltage will occur in the process of changing tap changer.The paper illustrates the mechanism of overvoltage in theory by analyzing the equivalent circuit and using analytic method of transition process.

Research on low-frequency mechanical characteristics of the MR dampers in ship isolators

A new isolator composed of a steel rope spring and a magneto-rheological(MR) damper was designed and a study on low-frequency mechanical characteristics of MR dampers in isolators was carried out.It used the characteristics of the MR damper,such as fast response,controllable damping,small energy consumption,wide dynamic scope,and great adaptation.The relationships between MR damping forces and influencing factors were analyzed based on experimental data.The results show that damping force is not only related to structural dimensions,but also closely related to controllable current and vibration frequency.Finally,the empirical formula for damping forces was corrected,and the relationship between correction coefficients and factors analyzed.

Design Research on Drive System of Underwater Tapping Machine

The underwater tapping machine is composed of a center bit, a tapping cutter, a seal box, a main drive box, a boring bar assembly, a envelop, a gear case, a counter and so on. The drive system in underwater tapping machine consists of a worm drive, a gear drive system and a screw drive. The worm drive is in the main drive box. The worm is connected with a hydraulic motor and driven by the hydraulic motor. The gear drive system is a combined gear train which is the combinations of the fixed axes and differential gear train in the gear case. On the one hand, by means of the fixed axes gear trains the turn and power of transmission shaft are transferred to the boring bar and the screw rod, causing differential turn between the boring bar and the screw rod. On the other hand, the turns of the boring bar and the screw rod are transferred to the differential gear train. The differential gear train is used to drive a special counter to count axial travel of the boring bar. The screw drive is composed of a feed screw and a nut on the boring bar. There is the differential turn between the boring bar and the feed screw. By means of the nut, the boring bar can feed automatically. With the movement of the sliding gear 7 in the gear case, the designed drive system can also be provided with the ability of fast forward and fast backward movement of the boring bar in its idle motion, resulting in the increase of the tapping efficiency.

PAM Templating Mechanism for Synthesis of A Novel LiFePO_4 Cathode Material

A novel templated LiFePO_4 cathode material was prepared with linear polyacrylamide, which exhibited excellent electrochemical properties, such as a 109.3 mA·h/g capacity at a rate of C/3 and a 120 mA·h/g capacity at a rate of C/6 as well as a good cycliability. We proposed the templating mechanism based upon the precursors′ TG-DTA curves, X-ray diffraction patterns and FTIR spectra of the samples at different temperatures. A tapping-mode atomic force microscope was used to investigate the surfaces of the end products. We found that the polyacrylamide template produced metal organic compounds in the cross-linked gel precursor, and thereby modified the crystallization and particle surfaces during calcining. The template was “removed” in the end, which was partially pyrolyzed into the spiral carbon to form a conductive network with nanocrys\|talline LiFePO_4 highly monodispersed in it.

Advances in Structure-function Relationships and Mechanism of Transporter Associated with Antigen Processing

The transporter associated with antigen processing （TAP） belongs to the ATP-binding cassette （ABC） transporter superfamily. Driven by ATP hydrolysis, TAP translocates antigenic peptides from the cytosol into the ER （endoplasmic reticulum） lumen where the antigenic peptides are loaded onto the HLA class I molecules. Recently, numerous studies show that TAP is closely related with various diseases such as viral infections, autoimmune diseases, and different malignancies. In consideration of important roles of TAP in human adaptive immunity, this review summarizes the recent advances in structure-function relationships of crucial domains and transport mechanism systematically. The challenging problems and potential methods are also pointed out for in-depth researches.

基于换档全过程振动强度的变压器CM型有载分接开关机械故障诊断方法

变压器有载分接开关(on-load top changer,OLTC)的主要故障类型是机械故障,现有大多数研究仅诊断切换开关故障,难以辨识影响换档全过程的传动机构故障。为准确诊断切换开关与传动机构故障,该文提出一种基于换档全过程振动强度的OLTC机械故障诊断方法。首先,将多通道切换开关振动爆发数据转换为时域波形图输入改进的卷积神经网络(convolutional neural network,CNN),以获取池化层特征。然后,提出换档全过程振动强度特征,将换档全过程振动信号划分为多个区间,统计各区间中幅值超过阈值的点数,以表征各时间段平均振动强度。最后,提出一种新的特征处理方法改变以上两种特征的相对大小,并融合两种特征训练分类器诊断机械故障类型。实例分析表明:相比于现有OLTC机械故障诊断方法,所提方法能有效辨识传动机构故障,进一步提升对切换开关故障的诊断精度,具有较强的鲁棒性与泛用性,可为OLTC机械故障诊断研究提供新的思路。

机械割胶装备切割仿形机构设计与试验

割胶是收获胶乳的重要途径,传统人力割胶技术专业性强且难度大,劳动强度高,近十年,机械采胶装备研发已成为破解产业掣肘的重要方向。为进一步提高割胶机械的割胶质量和工作平稳性,减少机械割胶伤树,按照传统人工割胶方式建立橡胶树割面的割胶轨迹方程,设计一种由导向器、割胶刀体、斜度装配体等部件组成的能够限深限厚的切割仿形机构。分析导向器、割胶刀体、斜度装配体等关键部件在割胶过程中的理论受力,并以手持式自动割胶机为试验本体,对设计的仿形切割机构开展大田割胶试验。结果表明:使用切割仿形机构割胶,更加贴合割面和割线,能够沿割胶轨迹切割出条状树皮,能够进行限深限厚仿形切割,减少伤树,切割平均负载电流稳定在1.0~1.5 A,与传统割胶模式相比,耗皮量比设置的上限值平均降低约10%,割胶深度约增加8%,验证切割仿形机构的设计,满足割胶技术要求。为天然橡胶产业机械化、智能化割胶装备关键切割部件的研发提供参考。

油液环境中有载分接开关快速机构切换特性

利用基于移动粒子半隐式方法的Particleworks,分析有载分接开关快速机构在油液环境中的切换特性.介绍有载分接开关快速机构的工作原理,设计有载分接开关快速机构的机械结构,给出快速机构在油液环境下的动力学计算基础.建立该有载分接开关快速机构在油液环境中的动力学仿真模型,对照了该快速机构在有无变压器油液环境中的切换特性差异,得到驱动电机的驱动扭矩要求大于40 N·m.分析油液黏度和储能弹簧刚度对该快速机构切换特性的影响,得到快速机构在油液环境下切换过程中飞轮受到的油液阻力矩的变化规律,通过流场分析揭示了飞轮受到的阻力矩变化和波动的原因.

基于PLC的橡胶树皮非线性力学性能探测装置设计与试验

为了获取橡胶树皮结构力学特性参数,解决机械化采胶装备研发中采胶深度精准探测和耗皮厚度精准控制技术无可靠依据提供参考的问题,设计一种基于可编程序逻辑控制器(programmable logic controller, PLC)的橡胶树皮非线性力学性能测量的试验装置,实现橡胶树皮力学特性的自动化连续探测和数据采集,以及树皮厚度的高精低损测量。并应用于热研7-33-97和PR107两个品系的15龄、20龄、25龄橡胶树上进行树皮力学性能试验研究,建立刺入过程中刺入力随刺入深度变化的数学模型。结果表明:该装置工作性能稳定,不同品系、不同树龄的树皮刺入力随刺入深度的变化曲线形态相近,均呈高-低-高的趋势变化,并与树皮结构分层特性高度相关;相同树龄下,热研7-33-97和PR107两个品系的刺入力情况差异不明显,同品系的大树龄比小树龄刺入力更大,在1.0 mm针刺下,刺入力最大峰值可达48.5 N。该试验装置满足橡胶树皮结构力学特性参数的探测需求,并为机械化采胶装备的研发提供理论基础。

农机农艺融合的高效割胶技术优化设计与应用

割胶是橡胶树收获胶乳的重要途径,便携式机械化割胶是实现产业升级和节本增效的途径之一。为进一步提高机械割胶效果,根据采胶生理特殊性、割胶工况复杂多变性、橡胶树收获物胶乳黏弹特性、橡胶树生长差异性、割胶形式多样性等农机农艺融合问题对割胶机械的设计需求,优化设计便携式电动割胶装备的切割刀片、电子调速器、导向器等零部件。优化结果表明:采用刃高≥10 mm的刀片割胶,可以轻松切断旧胶线;电子调速器在电机转速为3 201~8 459 r/min区间调速时,灵敏度高,单次割胶轨迹连续平稳;导向器形状从“L”型优化为“T”型,减少旧胶线对割胶机械的干预。优化后的技术,提高便携式割胶机械对割胶农艺的适应性,降低操作技术难度和单株割胶时间,胶工更容易快速掌握。

电驱动偏摆式天然橡胶割胶装置设计及运动特性分析

天然橡胶是我国重要的战略物资,针对当前胶工流失严重、割胶作业难以实现机械化等问题,设计一种电驱动偏摆式割胶装置。以理论分析结合数学建模为基础进行,通过Adams与ANSYS建立传动结构的有限元模型,并阐述运动特征规律,来验证模型的构建准确性,分析传动部件在运动情况过程下的应力分布、动态特性及振动机理,为便携式割胶装置的设计以及后期改进提供参照途径。通过运动学分析,刀片摆幅、传动结构受力与理论计算值误差分别为4%和3%;在数值模拟中传动结构的最大应力出现在Y型驱动叉与刀座的连接处,XYZ三个方向面的等效应力均小于材料屈服极限,故不会发生失效与出现共振;通过试验分析,偏摆式割胶装置样机相较于传统人工割胶刀,在割胶速度、耗皮厚度以及割胶深度上的平均值相差分别为42.3%、4.3%、0.6%,其中割胶速度差异较为显著。割胶装置的理论模型分析结果与实际样机加工制造的试验情况基本符合。

物理模拟融合油藏精细刻画法表征特低渗油藏中高含水期剩余油分布

中国低渗透油藏分布广泛,其中大部分区块已进入中高含水期,并且由于剩余油类型及成因不明确导致采出程度普遍较低,因此延长低渗透油藏稳产期是亟需解决的问题。结合井口生产资料和储层水驱前缘波及系数对油藏模型进行历史拟合,建立了特低渗油藏剩余油的精细刻画模型,并综合利用静动态物理模拟实验、生产资料动态分析等方法,明确了特低渗油藏中高含水期剩余油成因及类型,据此提出了针对性的剩余油挖潜策略,最终在姬塬油田耿155区长1特低渗油藏进行了现场应用。研究结果表明,特低渗油藏剩余油主要分为储层平面和垂向非均质性导致的储层非均质型剩余油、局部储层注采不对应导致的注采不完善型剩余油以及储层黏土矿物运移膨胀导致的欠注型剩余油,针对性挖潜后目标井组采出程度提高5.1%~12.4%。经现场应用后,预测原油累计采出量相比原始措施提高15.6%~37.3%,为特低渗油藏中高含水期挖潜提供理论和技术支撑。

轻敲式原子力显微镜相位成像的理论和实验研究

原子力显微镜有多种成像模式,轻敲模式是最为常用的扫描方式。轻敲模式能获取样品表面的高度信息和相位信息,其中相位信息具有更多的价值,其能反应样品表面的物理性质。为了理解原子力显微镜的相位成像机理,本文分别使用振动理论和能量理论推导了相位的理论表达式,发现两种理论方法所得到的相位表达式在本质上是一致的,并由理论结果得知相位与背景耗散和激励频率直接相关。其中背景耗散品的存在会掩盖样品表面的信息,降低相位对比度;而激励频率也会对相位产生极大的影响。本文通过理论和实验分析,发现在扫描过程中存在一个使得相位对比度达到最大的最优激励频率。这些结果对于解释原子力显微镜的相位像,进而在实验中优化相位成像具有重要意义。

基于优化TQWT及孪生SVM的有载分接开关机械故障诊断

为进一步提高有载分接开关(on-load tap changer,OLTC)机械状态监测的准确性,文中基于优化品质因数可调小波变换(tunable quality wavelet transform,TQWT)对OLTC切换过程中的振动信号进行了分析。即使用人工鱼群算法(artificial fish swarm algorithm,AFSA)基于分解余量与整体正交系数研究了TQWT的优化分解方法,计算得到了OLTC振动信号的多个子序列,构建了基于优化孪生支持向量机(twin support vector machine,TWSVM)的OLTC机械故障诊断模型。对某CM型OLTC正常与典型机械故障下振动信号的分析结果表明,所提优化TQWT分解方法有效提高了OLTC振动信号分解结果的准确性。相对于其他诊断模型,所构建AFSA-TWSVM的OLTC机械故障诊断模型分类效果好且收敛速度更快。

基于振动信号分析的V型有载分接开关机械故障识别方法

有载分接开关(OLTC)是变压器中唯一频繁动作的关键部件,容易发生机械故障,从而引发严重的安全事故。分析了V型OLTC的切换原理,设置了3种常见机械故障,利用多通道振动传感器采集切换过程的振动信号,提出了一种基于振动信号分析的V型OLTC机械故障识别方法。首先,采用CCEMDAN算法分解振动信号,基于相关系数法构建特征矩阵,利用奇异值分解对振动信号进行特征提取;其次,通过主成分分析与K-means聚类进行振动信号的最优测点选择;最后,基于XGBoost集成学习算法实现了机械故障分类。试验结果表明,OLTC箱体正面所测振动信号能更好地反映其内部机械状态,所提方法对于3种机械故障的识别准确率达到98%,高于随机森林、GBDT等集成学习算法。

换流变有载分接开关动作不一致故障分析

文章以某换流站有载分接开关三相动作不一致故障为例,结合有载分接开关控制机理,阐述了有载分接开关控制回路步进流程。给出了相关故障出现后的一、二次设备检查策略,最后针对提高分接开关可靠运行给出了改进技术措施,可为换流站运维工作提供参考和借鉴。