Assessing mixing uniformity in microreactors via in-line spectroscopy

Mixing behavior is critical for enhancing the selectivity of fast chemical reactions in microreactors.A high Reynolds number(Re)improves the mixing rate and selectivity of the reactions,but some exceptions of increasing side product yield with the higher Re have been reported.This study investigated the mixing uniformity in microreactors with in-line UV-vis spectroscopy to clarify the relationship between reaction selectivity and chaotic mixing with the higher Re.A colorization experiment of thymolphthalein in an acidic solution was conducted with an excess acid amount to the base to indicate a non-uniformly mixed region.Non-uniformity significantly increased with Re.At the same time,the degree of mixing,which was measured by a usual decolorization experiment,showed that the mixing rate increased with Re.The in-line analysis of the Villermaux-Dushman reaction during the mixing clarified that side product yield significantly increased with Re at around 300 and then decreased at around 1100.These results suggest the compensation effect between the mixing uniformity and mixing rate on the selectivity of the mixing-sensitive reactions.Faster mixing,characterized by a larger Re,can disturb mixing uniformity and,in some cases,decrease reaction selectivity.

Effect of coil and chamber structure on plasma radial uniformity in radio frequency inductively coupled plasma

Enhancing plasma uniformity can be achieved by modifying coil and chamber structures in radio frequency inductively coupled plasma(ICP)to meet the demand for large-area and uniformly distributed plasma in industrial manufacturing.This study utilized a two-dimensional self-consistent fluid model to investigate how different coil configurations and chamber aspect ratios affect the radial uniformity of plasma in radio frequency ICP.The findings indicate that optimizing the radial spacing of the coil enhances plasma uniformity but with a reduction in electron density.Furthermore,optimizing the coil within the ICP reactor,using the interior point method in the Interior Point Optimizer significantly enhances plasma uniformity,elevating it from 56%to 96%within the range of the model sizes.Additionally,when the chamber aspect ratio k changes from 2.8 to 4.7,the plasma distribution changes from a center-high to a saddleshaped distribution.Moreover,the plasma uniformity becomes worse.Finally,adjusting process parameters,such as increasing source power and gas pressure,can enhance plasma uniformity.These findings contribute to optimizing the etching process by improving plasma radial uniformity.

Customized modulation on plasma uniformity by non-uniform magnetic field in capacitively coupled plasma

A two-dimensional fluid model based on COMSOL Multiphysics is developed to investigate the modulation of static magnetic field on plasma homogeneity in a capacitively coupled plasma(CCP)chamber. To generate a static magnetic field, direct current is applied to a circular coil located at the top of the chamber. By adjusting the magnetic field's configuration, which is done by altering the coil current and position, both the plasma uniformity and density can be significantly modulated. In the absence of the magnetic field, the plasma density exhibits an inhomogeneous distribution characterized by higher values at the plasma edge and lower values at the center. The introduction of a magnetic field generated by coils results in a significant increase in electron density near the coils. Furthermore, an increase in the sets of coils improves the uniformity of the plasma. By flexibly adjusting the positions of the coils and the applied current,a substantial enhancement in overall uniformity can be achieved. These findings demonstrate the feasibility of using this method for achieving uniform plasma densities in industrial applications.

Effect of dielectric material on the uniformity of nanosecond pulsed dielectric barrier discharge

Dielectric barrier discharge(DBD)is considered as a promising technique to produce large volume uniform plasma at atmospheric pressure,and the dielectric barrier layer between the electrodes plays a key role in the DBD processes and enhancing discharge uniformity.In this work,the uniformity and discharge characteristics of the nanosecond(ns)pulsed DBD with dielectric barrier layers made of alumina,quartz glass,polycarbonate(PC),and polypropylene(PP)are investigated via discharge image observation,voltage-current waveform measurement and optical emission spectral diagnosis.Through analyzing discharge image by gray value standard deviation method,the discharge uniformity is quantitatively calculated.The effects of the space electric field intensity,the electron density(Ne),and the space reactive species on the uniformity are studied with quantifying the gap voltage Ug and the discharge current Ig,analyzing the recorded optical emission spectra,and simulating the temporal distribution of Ne with a one-dimensional fluid model.It is found that as the relative permittivity of the dielectric materials increases,the space electric field intensity is enhanced,which results in a higher Ne and electron temperature(Te).Therefore,an appropriate value of space electric field intensity can promote electron avalanches,resulting in uniform and stable plasma by the merging of electron avalanches.However,an excessive value of space electric field intensity leads to the aggregation of space charges and the distortion of the space electric field,which reduce the discharge uniformity.The surface roughness and the surface charge decay are measured to explain the influences of the surface properties and the second electron emission on the discharge uniformity.The results in this work give a comprehensive understanding of the effect of the dielectric materials on the DBD uniformity,and contribute to the selection of dielectric materials for DBD reactor and the realization of atmospheric pressure uniform,stable,and reactive plasma sources.

Uniformity Control of Scanned Beam in 300 MeV Proton and Heavy Ion Accelerator Complex at SESRI

In recent years,heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy.Usually,a very high uniformity in the irradiation area is required for the extracted ion beams,which is crucial because it directly affects the experimental precision and therapeutic effect.Specifically,ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design.In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure(SESRI),proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals.In order to achieve the required large irradiation area of 320 mm×320 mm,horizontal and vertical scanning magnets are used in the extraction beam line.However,considering the various requirements for beam species and energies,the tracking accuracy of power supplies(PSs),the eddy current effect of scanning magnets,and the fluctuation of ion bunch structure will reduce the irradiation uniformity.To mitigate these effects,a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI.In the experiment,the uniformity is successfully optimized from 75%to over 90%after five iterations of adjustment to the PS waveforms.In this paper,the method and experimental results were introduced.

Harmonic balance simulation of the influence of component uniformity and reliability on the performance of a Josephson traveling wave parametric amplifier

A Josephson traveling wave parametric amplifier(JTWPA),which is a quantum-limited amplifier with high gain and large bandwidth,is the core device of large-scale measurement and control systems for quantum computing.A typical JTWPA consists of thousands of Josephson junctions connected in series to form a transmission line and hundreds of shunt LC resonators periodically loaded along the line for phase matching.Because the variation of these capacitors and inductors can be detrimental to their high-frequency characteristics,the fabrication of a JTWPA typically necessitates precise processing equipment.To guide the fabrication process and further improve the design for manufacturability,it is necessary to understand how each electronic component affects the amplifier.In this paper,we use the harmonic balance method to conduct a comprehensive study on the impact of nonuniformity and fabrication yield of the electronic components on the performance of a JTWPA.The results provide insightful and scientific guidance for device design and fabrication processes.

Experimental Investigation of Particles Dynamics and Solid-Liquid Mixing Uniformity in a Stirred Tank

Particle suspension and deposition dynamics are significant factors affecting the level of mixing quality in solidliquid two-phase stirring processes. In general, the ability to increase the suspension rate and minimize depositioneffects is instrumental in improving the uniformity of particle mixing, accelerating the reaction of involved solidliquid two-phase, and improving the efficiency of production operations. In this work, suspension and depositionindicator based on the Betti number and a uniformity indicator are introduced and obtained by means of imageanalysis. The influence of the blade type, rotation speed, blade diameter and blade bottom height on the particlesuspension/deposition characteristics and mixing uniformity are carefully investigated. The experimental resultsshow that the two-phase motion region can be divided into three local regions, including a bottom motion alongthe wall, a low-degree suspension region under the blade and a high suspension region above the blade. The bestdegree of particle suspension is attained by the double-inclined blade paddle at a speed of 270 r/min, a paddlediameter ratio of 0.414, and a height-diameter ratio of 0.086. The double-inclined blade paddle has a better effecton promoting particle suspension and solid-liquid two-phase mixing uniformity.

Experimental Study on Gas Flow Uniformity in a Diesel Particulate Filter Carrier

A Diesel Particulate Filter(DPF)is a critical device for diesel engine exhaust products treatment.When using active-regeneration purification methods,on the one hand,a spatially irregular gas flow can produce relatively high local temperatures,potentially resulting in damage to the carrier;On the other hand,the internal temperature field can also undergo significant changes contributing to increase this risk.This study explores the gas flow uniformity in a DPF carrier and the related temperature behavior under drop-to-idle(DTI)condition by means of bench tests.It is shown that the considered silicon carbide carrier exhibits good flow uniformity,with a temperature deviation of no more than 2%with respect to the same radius measurement point at the outlet during the regeneration stage.In the DTI test,the temperature is relatively high within r/2 near the outlet end,where the maximum temperature peak occurs,and the maximum radial temperature gradient is located between r/2 and the edge.Both these quantities grow as the soot load increases,thereby making the risk of carrier burnout greater.Finally,it is shown that the soot load limit of the silicon carbide DPF can be extended to 11 g/L,which reduces the frequency of active regeneration by approximately 40%compared to a cordierite DPF.

Experimental and numerical investigation on the uniformity of nanosecond pulsed dielectric barrier discharge influenced by pulse parameters

Nanosecond(ns)pulsed dielectric barrier discharge(DBD)is considered as a promising method to produce controllable large-volume and high activity low-temperature plasma at atmospheric pressure,which makes it suitable for wide applications.In this work,the ns pulse power supply is used to excite Ar DBD and the influences of the pulse parameters(voltage amplitude,pulse width,pulse rise and fall times)on the DBD uniformity are investigated.The gas gap voltage(Ug)and conduct current(Ig)are separated from the measured voltage and current waveforms to analyze the influence of electrical parameters.The spectral line intensity ratio of two Ar excited species is used as an indicator of the electron temperature(Te).The time resolved discharge processes are recorded by an intensified charge-coupled device camera and a one-dimensional fluid model is employed to simulate the spatial and temporal distributions of electrons,ions,metastable argon atoms and Te.Combining the experimental and numerical results,the mechanism of the pulse parameters influencing on the discharge uniformity is discussed.It is shown that the space electric field intensity and the space particles'densities are mainly responsible for the variation of discharge uniformity.With the increase of voltage and pulse width,the electric field intensity and the density of space particles increased,which results in the discharge mode transition from non-uniform to uniform,and then non-uniform.Furthermore,the extension of pulse rise and fall times leads to the discharge transition from uniform to nonuniform.The results are helpful to reveal the mechanism of ns pulsed DBD mode transition and to realize controllable and uniform plasma sources at atmospheric pressure.

Design and Structure Optimization of Plenum Chamber with Airfoil Baffle to Improve Its Outlet Velocity Uniformity in Heat Setting Machines

The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly affecting the heat setting performance.In a traditional heat setting machine,the outlet airflow maldistribution of the plenum chamber still exists.In this study,a novel plenum chamber with an airfoil baffle was established to improve the uniformity of the velocity distribution at the outlet in a heat setting machine.The structural influence of the plenum chamber on the velocity distribution was investigated using a computational fluid dynamics program.It was found that a chamber with a smaller outlet partition thickness had a better outlet velocity uniformity.The structural optimization of the plenum chamber was conducted using the particle swarm optimization algorithm.The outlet partition thickness,the transverse distance and the longitudinal distance of the optimized plenum chamber were 20,686.2 and 274.6 mm,respectively.Experiments were carried out.The experimental and simulated results showed that the optimized plenum chamber with an airfoil baffle could improve the outlet velocity uniformity.The air outlet velocity uniformity index of the optimized plenum chamber with an airfoil baffle was 4.75%higher than that of the plenum chamber without an airfoil baffle and 5.98%higher than that of the conventional chamber with a square baffle in a commercial heat setting machine.

Demonstration of Center Pivot Uniformity Evaluation and Retrofit to Improve Water Use Efficiency

Agricultural irrigation is a primary user for freshwater withdrawal. Irrigation plays an important role in crop production, as it provides the benefit of reducing the effects of prolonged dryness and erratic precipitation. Center pivot irrigation system is the most common irrigation system in agriculture. As the center pivot irrigation system ages, the system could develop a leaking joint, clogged sprinklers, and physical damage. This can cause areas of non-uniformity that can lead to under- or over-irrigated in some areas of the land, resulting in excess energy use and cost, wasting resources, and environmental impacts. Thus, it is important to evaluate the performance of a center pivot irrigation system regularly to maximize return on investments and minimize wasting resources. This study focuses on evaluating the impacts and benefits of improved center pivot irrigation distribution uniformity by performing distribution uniformity evaluations pre- and post-retrofit. This study also focused on demonstrating an unmanned aerial vehicle (UAV) to assess the performance of the center pivot irrigation system in two irrigated farmlands. The Coefficient of Uniformity (CU), Distribution Uniformity (DU), and Scheduling Coefficient (SC) were calculated based on the catch can test data. The values were utilized to evaluate water and energy savings from the improved coefficients. The team has found that replacing sprinkler packages increased the CU from 78 to 89 and the DU from 77 to 82, and reduced the SC from 1.3 to 1.2 in Field A. In Field B, replacing sprinkler packages increased the CU from 73 to 91 and the DU from 62 to 84 and reduced the SC from 1.6 to 1.2. The estimated water savings in Field A due to the reduced scheduling coefficient was approximately 151,000 liters/hectare/year, with consideration of the corn and soybean rotation field in Michigan. The estimated water savings in Field B was 608,000 liters/hectare/year. The data from this demonstration study showed the value of distribution uniformity evaluation and retrofit of irrigation systems. This information will encourage farmers and agricultural industries to consider performing more distribution uniformity evaluations, ultimately improving irrigation water use efficiency and supporting sustainable water management in agriculture.

小区播种机锥体投种器分种均匀性的试验研究

为了提高小区播种机锥体分种器分种均匀性和自动化水平,解决传统小区播种机作业时分种不均匀、人工投种作业强度大、投种器水平度难以持续稳定调节等问题,设计了一种基于现有手动调节水平的自动调平投种装置。首先,为确保投种器分种均匀性与作业的稳定性,对投种器的结构进行设计;然后,对种子的落种过程进行理论分析,确定了关键部件结构;最后,利用SPSS25.0软件设计三因素三水平试验,分析了影响投种器分种均匀性的主要因素,结果表明:各因素对投种器分种均匀性影响程度的主次顺序为锥体角度、导种管直径、漏斗口直径。最优参数条件下分种时,投种器分种均匀性较好,能够满足小区播种机投种器分种作业的需求。研究结果可为小区播种机分种均匀性问题的深入研究提供参考。

微波技术在食品和农产品加工中应用研究进展

微波加热技术具有速度快、可控性高等特点,在食品和农产品的热加工过程中具有较强的应用潜力。该文在分析微波加热原理的基础上,从技术应用、设备研制和仿真研究等方面介绍微波加热应用现状,如在农产品干燥、杀菌、萃取和膨化等方面进行深入研究和应用。指出微波加热在机理解析、工艺局限性、加热不均匀性和能量利用低等问题,尤其是微波场对物料内极性成分作用机制的研究深度、微波加热时在物料内温度和水分分布的不均匀性规律定量表征等方面,严重影响产品质量稳定性和能量充分利用。从揭示微波在加热腔体内传递和物料内吸收的机理,提高微波加热均匀性和改善加工质量,以及研制智能化工业用微波加工设备等方面,指出微波加热技术在食品和农产品加工中应用热点研究方向。针对微波加热技术在农产品和食品加工中科学问题、技术需求和设备现状,为发挥技术优势、拓展应用领域,该文提出微波加热理论研究与技术应用的发展趋势,以期提高微波热加工技术工业化应用适用性、保证产品质量和能量利用率。

紫花苜蓿地下滴灌灌水均匀性与适宜灌溉定额研究

研究主要探究不同灌溉方式紫花苜蓿地下滴灌灌水均匀性差距,并提出适宜的灌水定额。采用田间试验,设3个地下滴灌灌水定额(20、25、30 mm),2个埋设深度(10、20 cm)和2个滴头流量(1.38、2.0 L/h),研究了滴灌带流量、埋深在不同紫花苜蓿生育期内的灌水均匀度差异,同时进一步探究了不同灌水处理对紫花苜蓿株高、产量等参数的影响。滴灌带滴头流量对滴灌灌水均匀性的影响相对较大。在相同的滴灌带滴头流量下,滴灌带埋设深度10 cm与20 cm对滴灌灌水均匀系数影响不显著。当耗水量为456.69 mm时,紫花苜蓿干草产量最大,为12847.78 kg/hm-2。基于节水效果、产量和高效等多生产因素的综合考虑,建议鄂尔多斯鄂托克前旗地区紫花苜蓿地下滴灌灌水定额为25 mm,灌水12~14次。

余热回收喷淋塔喷淋优化研究

针对喷淋塔内烟气偏流影响烟气与下落液滴群热质交换的问题,构建并通过试验验证了喷淋塔内气液流动及余热回收理论模型,基于液滴自调整效应,运用CFD技术模拟研究4种喷淋层布置方式下余热回收喷淋塔的性能,获得了最佳喷淋方案及其喷淋参数。结果表明:与常规单层均匀喷淋方式相比,增设半层喷淋能够有效提升塔内烟气流动均匀性,塔内烟气均匀度由1降至0.3左右,喷淋塔全热交换效率最多可提升20%;半层喷淋最佳布置位置在烟气入口中心线上3 m处;综合考虑余热回收效果和运行成本,最佳喷淋液滴直径为0.6~0.8 mm,最佳水气比为5 kg/kg。构建的喷淋塔内烟气余热回收模型与提出的喷淋优化方法可为其特性分析、工艺优化、参数设计及运行提供理论指导。

东北地区教学建筑侧窗导光构件形态模拟研究

目的 为解决东北地区教学建筑中自然光分布严重不均衡,而单纯依靠粗放式地提高窗地比采光计算方法无法改善,通过设置导光构件解决自然光分布不均衡的难题。方法 应用Ecotect软件建立典型教室空间和导光构件的参数化模型,分析导光构件内外位置、水平高度、截面尺寸、截面形态、透光度等参数变化对于采光系数、照度、采光均匀度等参数的影响。结果 通过对模拟数据的比较分析发现,导光板在位于侧窗室内一侧、高度为2 400 mm、截面宽度为1 050~1 200 mm、截面形态为弧形向下的情况下,采光照度和均匀度达到最佳平衡状态;导光百叶中的水平内倾百叶的综合性能优于其他类型。结论 横向比较,导光板最优方案在综合性能上优于导光百叶,是东北地区较为适用的导光构件。

基于全国统一大市场建设的社会保障制度改革

建设全国统一大市场是国家为提高资源配置效率、实现高质量发展而做出的重大决策部署。公平统一且设计合理的社会保障制度具有降低商品及生产要素流通成本、释放流通潜力的功能,因此有效的社会保障制度是全国统一大市场的必备要件。然而,现行社会保障制度在公平和效率两个方面都存在不足,尤其是地区间和人群间的制度政策差距大、部分项目资源配置不合理、绩效管理机制缺失等,与建设全国统一大市场的要求不相适应。因此,要全面深化社会保障改革,不断增强制度的公平统一性,提高制度运行效率,逐步统一社会保障权益设置、筹资规则、管理规程和服务规范,为形成全国统一大市场做出积极的贡献。

蔬菜泡沫育苗盘多适应性自动叠盘装置设计与试验

为了提高蔬菜育苗流水线育苗盘转运效率,针对人工取盘叠放存在的劳动强度大和整齐度偏低的问题,设计了一款针对蔬菜漂浮育苗的多适应性自动叠盘装置。该装置由机架、育苗盘输送机构、育苗盘叠盘机构和控制系统组成,装置以200Smart PLC为控制核心,利用主副传送带实现育苗盘的输送,并结合光电传感器实现育苗盘的定位,可以完成不同尺寸泡沫育苗盘的自动叠盘,设计的水平调节单元和减振单元可实现育苗盘在叠盘机构上的水平位置调节并降低叠盘过程的振动冲击。试验结果表明,育苗流水线播种环节在生产率450盘/h下,自动叠盘装置在减振弹簧线径为1.5 mm、主副传送带速度差为0.1 m/s以及电缸升降速度为0.13 m/s时,200孔穴育苗盘叠盘效果最佳,叠盘成功率为100%,叠盘错位差方差为2.32 mm^(2),同时振动检测试验中育苗盘X轴、Y轴、Z轴方向的振幅均未超过0.8 mm,更换135、160孔穴的泡沫育苗盘进行试验,叠盘成功率均为100%,叠盘错位差方差分别为3.94 mm^(2)和5.98 mm^(2),说明该装置满足多适应性的要求。在此最优作业参数下,将育苗流水线播种环节生产率提升至900盘/h时,育苗盘最大振幅为0.709 mm,振幅无明显变化,说明该装置作业稳定性较好。该研究结果可为播种流水线叠盘装置提高叠盘效果和降低叠盘振动等研究提供参考。

中国废旧军服面料回收利用的研究现状及发展前景

为促进废旧军服面料的高值化回收利用,总结了国内07式军服的种类及其面料特征,系统分析了目前开纤纺纱法、再生聚酯切片法、涤棉分离技术等废旧军服面料的回收利用方法,并对废旧军服面料回收再利用的发展前景进行展望。分析表明:目前废旧军服面料的回收利用主要聚焦于简单再利用或回收涤纶组分制备高值再生聚酯切片,较少关注军服面料中其余组分的高值回收利用。针对废旧军服面料中含量相对较高的涤棉混纺面料,采用有效的涤棉分离技术高效分离涤纶和棉纤维,并以此作为原料分别制备再生聚酯切片和再生溶解浆,进一步以再生棉浆粕为原料制备再生纤维素产品将非常有前景。因而,开发高效的涤棉分离、废旧涤纶和棉纤维的高值化利用技术是实现废旧军服面料综合利用的重要发展方向。

中国古代的服制与服色——以职官“四等之服”为例

服色由于其特殊属性而与服制的制定有密切的关系。以职官的“四等之服”为例,通过梳理各类官修史书中的相关记载,结合中国传统色彩观,探讨服色在冠服制度中的表达、变化及其作用。研究表明:职官祭服和朝服在服色表达上更多反映了传统“五行-五色”的色彩观念;祭服自唐代改用青色上衣,朝服经历五色到绛色的变化,常服四等分色后为公服所借鉴;隋唐之前服色用以区分职事的作用更加凸显,品位分等则通过色相和明度区分。