Experimental Study on the Resistance and Splash Performances of Water Collecting Devices for Mechanical Draft Cooling Towers

In recent years,water collecting systems,with the associated advantages of energy saving and noise reduction,have become the foundation for the development of a scheme to optimize the structure of cooling towers.To explore the feasibility of this approach for mechanical draft cooling towers,a small-scale experimental device has been built to study the resistance and splash performances of three U-type water collecting devices(WCDs)for different water flow rates and wind speeds.The experimental results show that within the considered ranges of wind speed and water flow rate,the pressure drop of the different WCDs can vary significantly.The resistance and local splash performances can also be remarkably different.Some recommendations about the most suitable system are provided.Moreover,a regression analysis of the experimental data is conducted,and the resulting fitting formulas for resistance and splash performance of WCD are reported.

Explosion resistance performance of reinforced concrete box girder coated with polyurea:Model test and numerical simulation

To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyurea coating).The failure characteristics and dynamic responses of the specimens were compared through conducting explosion tests.The reliability of the numerical simulation using LS-DYNA software was verified by the test results.The effects of different scaled distances,reinforcement ratios,concrete strengths,coating thicknesses and ranges of polyurea were studied.The results show that the polyurea coating can effectively enhance the anti-explosion performance of the girder.The top plate of middle chamber in specimen G forms an elliptical penetrating hole,while that in specimen PCG only shows a very slight local dent.The peak vertical displacement and residual displacement of PCG decrease by 74.8% and 73.7%,respectively,compared with those of specimen G.For the TNT explosion with small equivalent,the polyurea coating has a more significant protective effect on reducing the size of fracture.With the increase of TNT equivalent,the protective effect of polyurea on reducing girder displacement becomes more significant.The optimal reinforcement ratio,concrete strength,thickness and range of polyurea coating were also drawn.

Relationship Between Thermal Shock Behavior and Cutting Performance of a Functionally Gradient Ceramic Tool

Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in this paper, according to which an Al 2O 3-TiC functionally gradient ceramic tool material FG-1 was synthesized by powder-laminating and uniaxially hot-pressing technique. The thermal shock resistance of the Al 2O 3-TiC functionally gradient ceramics FG-1 was evaluated by water quenching and subsequent three-point bending tests of flexural strength diminution. Comparisons were made with results from parallel experiments conducted using a homogeneous Al 2O 3-TiC ceramics. Functionally gradient ceramics exhibited higher retained strength under all thermal shock temperature differences compared to homogeneous ceramics, indicating the higher thermal shock resistance. The experimental results were supported by the calculation of transient thermal stress field. The cutting performance of the Al 2O 3-TiC functionally gradient ceramic tool FG-1 was also investigated in rough turning the cylindrical surface of exhaust valve of diesel engine in comparison with that of a common Al 2O 3-TiC ceramic tool LT55. The results indicated that the tool life of FG-1 increased by 50 percent over that of LT55. Tool life of LT55 was mainly controlled by thermal shock cracking which was accompanied by mechanical shock. While tool life of FG-1 was mainly controlled by mechanical fatigue crack extension rather than thermal shock cracking, revealing the less thermal shock susceptibility of functionally gradient ceramics than that of common ceramics.

Effect of Streamlined Nose Length on the Aerodynamic Performance of a 800 km/h Evacuated Tube Train

The aerodynamic resistance of a train running in the open air limits the maximum speed that can be attained by the train.For this reason,evacuated tube trains(ETT)are being considered as valid alternatives to be implemented in the future.The atmosphere in the tube,the so-called blocking ratio and the length of the streamlined nose are the key factors affecting the aerodynamic performances of these trains.In the present work,we investigate evacuated tube trains with different lengths of the streamline nose on the basis of computational fluid dynamics(CFD).The three-dimensional steady compressible Navier-Stokes equations are solved.The running speed of the ETT is 800 km/h and the blocking ratio is 0.2.Results show that with the increase of the streamlined nose length,the aerodynamic drag and lift forces of the head car decrease gradually,and the drag and lift forces of the middle car change slightly.For the tail car,the drag force decreases,whereas the absolute value of the lift force increases.At a speed of 800 km/h,a slight shock wave appears at the rear of the tail car,which affects the aerodynamic forces acting on the train.

Thermal effect on endurance performance of 3-dimensional RRAM crossbar array

Three-dimensional（3D） crossbar array architecture is one of the leading candidates for future ultra-high density nonvolatile memory applications. To realize the technological potential, understanding the reliability mechanisms of the3 D RRAM array has become a field of intense research. In this work, the endurance performance of the 3D 1D1 R crossbar array under the thermal effect is investigated in terms of numerical simulation. It is revealed that the endurance performance of the 3D 1D1 R array would be seriously deteriorated under thermal effects as the feature size scales down to a relatively small value. A possible method to alleviate the thermal effects is provided and verified by numerical simulation.

Parental Migration’s Effects on the Academic and Non-Academic Performance of Left-Behind Children in Rural China

This study investigates the impact of parental labor migration on the academic achievements and non-academic growth of left-behind children in fourth and seventh grades. Employing survey data collected from rural China in 2014, 2015, and 2016, we examine the effect of parental absence on children's academic achievement using Propensity Score Matching(PSM) and Difference in Difference(DID) methods. The results demonstrate that left-behind children whose parents have migrated for one year have statistically significantly lower academic scores. Academic scores drop lower for fourthgrade students and students from higher-income families. There are also adverse effects on left-behind children's confidence, teacher-student relationships, subjective well-being, and educational expectations if parents migrate for one year. Surprisingly, if parental migration lasts longer(totaling two years), these adverse effects disappear, and student's educational expectations even improve. These results may be because, over time, the adverse effects that occur immediately after parental migration are offset by the positive effects of migration(i.e. higher income). These conclusions can inform migrant parents on ways to utilize their resources to improve the academic performance of their left-behind children.

Corrosion resistance and anti-soiling performance of micro-arc oxidation/graphene oxide/stearic acid superhydrophobic composite coating on magnesium alloys

Magnesium(Mg)alloys,the lightest metal construction material used in industry,play a vital role in future development.However,the poor corrosion resistance of Mg alloys in corrosion environments largely limits their potential wide applications.Therefore,a micro-arc oxidation/graphene oxide/stearic acid(MAO/GO/SA)superhydrophobic composite coating with superior corrosion resistance was fabricated on a Mg alloy AZ91D through micro-arc oxidation(MAO)technology,electrodeposition technique,and self-assembly technology.The composition and microstructure of the coating were characterized by scanning electron microscopy,X-ray diffraction,energy dispersive spectroscopy,and Raman spectroscopy.The effective protection of the MAO/GO/SA composite coating applied to a substrate was evaluated using potentiodynamic polarization,electrochemical impedance spectroscopy tests,and salt spray tests.The results showed that the MAO/GO/SA composite coating with a petal spherical structure had the best superhydrophobicity,and it attained a contact angle of 159.53°±2°.The MAO/GO/SA composite coating exhibited high resistance to corrosion,according to electrochemical and salt spray tests.

Influence of Plasma Modified Carbon Nanotubes on the Resistance Sensitiveness of Cement

The surface of carbon nanotubes(CNTs)was modified by plasma to improve the dispersion,conductivity and adsorption properties of carbon nanotubes.Cement-based composites made with plasmatreated carbon nanotubes(P-CNTs)at different perntages were tested under repeated cyclic axial compressive stress by four electrode methods to measure the electric resistance.Those made with CNTs without plasma treatment as controls were tested also.The results showed that electric resistance change values of the cement mortar with P-CNT and CNT were all monatomic corresponding to the cyclic loading.When the water-cement ratio of the mortar was fixed,increasing of the P-CNT/CNT content would increase the resistance change value of the mortars added with P-CNT/CNT,and the sensitivity performance.It has certain engineering application value.

Preparation,Performance and Slag Resistant Mechanism of Low Thermal Conductivity Microporous Corundum

The microporous corundum material was prepared using alumina micro-powder as the main raw material, alumina sol and starch as binders by a wet process, achieving the bulk density of 3.05 g · cm^-3, the apparent porosity of 9. 1%, the closed porosity of 12.3%, the median pore diameter of 0. 43 μm, and the thermal conductivity of 6. 5 W· m^-1· K^-1 at 800 ℃ which is 41.6% lower than that of common corundum. The slag resistance of the microporous corundum material was studied by immersion and compared with that of the common corundum aggregate, and the slag resistant mechanism of microporous corundum material was revealed. The results show that the slag resistance of the microporous corundum material is superior to that of the common corundum aggregate, the SEM and EDX show that on the reaction interface between microporous corundum and molten, slag, a continuous isolation layer with a large quantity of CA2 and CA6 columnar crystals is formed; while the common corundum aggregate reacts with the molten slag interface to form a discontinuous isolation layer of columnar crystals, through which a lot of molten slag corrodes or permeates into the aggregate. The mechanism is mainly that the microporous structure is more advantageous to nucleation and growth of CA2 and CA6 columnar crystals; in the reaction with the aggregate, the molten slag gets saturated and the critical solution thickness of the microporous corundum and the common corundum is 0. 16 μm and 0. 34 μm, respectively, this is caused by the smaller microporous corundum aggregate pores; and the smaller pores also increase the second phase ripening rate of microporous corundum, which is 9. 7 times of that of the common corundum.

Study on the Performance Optimization of Knitted Fabric Anti-Roll by Tissue Structure

Will use the same number of positive and negative coil longitudinal organization of fabric is ta edge sex used in the work of the organization to warp fabric edge sex, between restrained knitting principle, design a kind of weft basketwork weaving method, especially in weft knitting machine woven from has the edge of weft knitted fabric performance weaving method. In order to overcome the existing technology aims to make weft basketwork structure of a single organization, edge sex is bad, or can’t produce rich weft knitted fabric appearance of shortage, provide a resistance to edge weft knitted fabric weaving method.

Comparison of Genetic Diversity and Growth Performance between the Selected Population and Hybridized Population of Litopenaeus vannamei at Low Temperature

[Objective] This study was conducted to compare the genetic diversity and growth performance of two Litopenaeus vannamei populations at low temperature. [Method] One population（selected population, SP） was produced through inbreeding and 3 years of selection from seven popula- tions of L. vannamei introduced from the United States and Singapore. The other population （hybridized population, HP） was the F1 generation of the crosses between Population SP and some excellent populations introduced from South Korea and Singapore. The growth performance of the two populations at low temperature was compared, and the genetic diversity and genetic differentiation between the two populations were assessed using 13 microsatellite loci. [Result] The shrimps of population HP had better growth performance than those of population SP. The average body weight （BW） for population HP, which was （13.18±3.65） g/ind., was significantly higher than that of population SP, which was （12.20±3.14） g/ind. The coefficient of variation in body weight for population SP was 25.74%, and that for population HP was 27.69%. The other growth indices of popula- tion HP were all higher than those of population SP. One-way analysis of variance （ANOVA） indicated that there were highly significant differences in both BW and width of third abdominal segment （WTAS） between HP and SP（P〈0.001）. The specific growth rate （SGR） and absolute growth rate （AGR） for population HP were （5.09±0.61） %/d and （0.26±0.60） g/d, respectively, while the SGR and AGR for population SP were （4.94±0.57） %/d and （0.24±0.63） g/d., both significantly lower than those of population HP （P〈0.001）. Genetic diversity analysis revealed that the number of alleles （Na） of population HP （Na=7.9） was slightly higher than that of population SP （Na=7.6）. The average polymorphic information content （PIC） of HP and SP populations was similar 0.63 and 0.62, both indicating high level of genetic diversity. The average observed heterozygosity （HQ） of HP and SP was 0.492 and 0.483, and the expected heterozygosity（He） was 0.675 and 0.663, respectively. Both Ho and He of population HP were higher than those of population SP, suggesting that HP had higher genetic diversity than population SP. Moreover, the mean of FsT values at the 13 microsatellite loci between HP and SP was 0.155 6, suggesting there was a significant genetic differentiation between the two populations. [Conclusion] Our results provide a theoretical basis for the breeding of new L. vannamei strains that are resistant to low temperature.

Effect of Pulse and dc Formation on the Performance of One-Transistor and One-Resistor Resistance Random Access Memory Devices

We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor （1 T1R） resistance random access memory （RRAM） device. All the devices are operated under the same test conditions, except for the initial formation process with different modes. Based on the statistical results, the high resistance state （FIRS） under the dc forming mode shows a lower value with better distribution compared with that under the pulse mode. One of the possible reasons for such a phenomenon originates from different properties of conductive filament （CF） formed in the resistive switching layer under two different modes. For the dc forming mode, the formed filament is thought to be continuous, which is hard to be ruptured, resulting in a lower HRS. However, in the case of pulse forming, the filament is discontinuous where the transport mechanism is governed by hopping. The low resistance state （LRS） can be easily changed by removing a few trapping states from the conducting path. Hence, a higher FIRS is thus observed. However, the HRS resistance is highly dependent on the length of the gap opened. A slight variation of the gap length will cause wide dispersion of resistance.

Marine antifouling behavior of the surfaces modified by dopamine and antibacterial peptide

Marine biofouling causes serious harms to surfaces of marine devices in transportation,aquaculture,and offshore construction.Traditional antifouling methods pollute the environment.A novel and green antifouling strategy was developed to prevent effectively the adhe sion of bacteria and microalgae.An antifouling surface was fabricated via coating Turgencin BMox2(TB)onto dopamine-modified 304stainless steel(304 SS).The surface physical and chemical properties before and after modification were characterized by Fourier transform infrared spectrometer(FTIR),X-ray photoelectron spectrometer(XPS),contact angle measurement(CA),3D optical profilometer,ellipsometer,and atomic force microscope(AFM).Antimicrobial peptide was coated onto the surface of 304 SS successfully,and the surface morphology and wettability of the modified sample were modified.Moreover,cytocompatibility of the peptide was evaluated by co-culture of peptide and cells,indicating promising cell biocompatibility at the modified sample surface.At last,antifouling performance and electrochemical corrosion were tested.Results show that the adhesion rates of Vibrio natriegens and Phaeodactylum tricornutum on the antifouling surface were reduced by 99.85% and 67.93%,respectively from those of untreated samples.Therefore,the modified samples retained superior corrosion resistance.The study provide a simply and green way against biofouling on ship hulls and marine equipment.

Encapsulated peracetic acid as a valid broad‑spectrum antimicrobial alternative,leading to beneficial microbiota compositional changes and enhanced performance in broiler chickens

Background Antimicrobial alternatives are urgently needed,including for poultry production systems.In this study,we tested the potential broad-range antimicrobial alternative peracetic acid,delivered in feed via the hydrolysis of encapsulated precursors through a 28-day study using 375 Ross 308 broiler chickens.We tested two peracetic acid concentrations,30 and 80 mg/kg on birds housed on re-used litter,and we evaluated the impact of both levels on gut microbial communities,bacterial concentration,antimicrobial resistance genes relative abundance and growth performance when compared to control birds housed on either clean or re-used litter.Results Body weight gain and feed conversion ratio improved in peracetic acid fed birds.At d 28,birds given 30 mg/kg of peracetic acid had a decreased Firmicutes and an increased Proteobacteria abundance in the jejunum,accompanied by an increase in Bacillus,Flavonifractor and Rombustia in the caeca,and a decreased abundance of tetracycline resistance genes.Chicken given 80 mg/kg of peracetic acid had greater caecal abundance of macrolides lincosamides and streptogramins resistance genes.Growth performance on clean litter was reduced compared to reused litter,which concurred with increased caecal abundance of Blautia,decreased caecal abundance of Escherichia/Shigella,Anaerostipes and Jeotgalicoccus,and greater gene abundance of vancomycin,tetracycline,and macrolides resistance genes.Conclusions Peracetic acid could be used as a safe broad-spectrum antimicrobial alternative in broilers.Encapsulated precursors were able to reduce the bacterial concentration in the jejunum whilst promoting the proliferation of probiotic genera in the caeca,especially at the low peracetic acid concentrations tested,and improve growth performance.Moreover,our findings offer further insights on potential benefits of rearing birds on re-used litter,suggesting that the latter could be associated with better performance and reduced antimicrobial resistance risk compared to clean litter rearing.

Machine Learning Assisted Design of Natural Rubber Composites with Multi⁃Performance Optimization

Multi⁃performance optimization of tread rubber composites is a key issue of great concern in automotive industry.Traditional experimental design approach via“trial and error”or intuition is ineffective due to mutual inhibition among multiple properties.A“Uniform design⁃Machine learning”strategy for performance prediction and multi⁃performance optimization of tread rubber composites was proposed.The wear resistance,rolling resistance,tensile strength and wet skid resistance were simultaneously optimized.A series of feasible optimization designs were screened via statistical analysis and machine learning analysis,and were experimentally prepared.The verification experiments demonstrate that the optimization design via machine learning analysis meets the optimization requirements of all target performance,especially for Akron abrasion and 60℃tanδ(about 21%and 9%lower than the design targets,respectively)due to the inhibition of mechanical degradation and good dispersion of fillers.

Effects of Filler-Asphalt Ratio on the Properties of Lignin and Polyester Fiber Reinforced SMPU/SBS Modified Asphalt Mortar

To understand the effects offiller-asphalt ratio on different properties of lignin and polyesterfiber reinforced shape memory polyurethane(SMPU)/styrene butadiene styrene(SBS)composite modified asphalt mortar(PSAM),as well as to reveal the reinforcing and toughening mechanisms of lignin and polyesterfibers on PSAM,SMPU,SBS and mineral powder werefirst utilized to prepare PSAM.Then the conventional,rheological and anti-cracking properties of ligninfiber reinforced PSAM(LFAM)and polyesterfiber reinforced PSAM(PFAM)at dif-ferentfiller-asphalt ratios were characterized.Test results indicate that the shear strength,deformation resistance and viscosity are increased after adding 0.8wt%ligninfiber or polyesterfiber and increasing thefiller-asphalt ratio from 0.8 to 1.2.The optimalfiller-asphalt ratio of 1.0 is proposed after comprehensive performance assessments of PSAM.Polyesterfiber shows a better reinforcing effect than ligninfiber,but its improvement in the thermal stability of PSAM is not significant at high temperatures.Additionally,the complex modulus,storage modulus,loss modulus and rutting resistance factor of PSAM are improved after adding ligninfiber and polyesterfiber,as well as show an increasing trend as thefiller-asphalt ratio is raised,but the phase angle is gradually decreased.Further,the increase of elastic components in PSAM effectively enhances the anti-deformation ability of PSAM at high temperatures,and polyesterfiber more obviously improves the high-temperature deformation resistance of PSAM than ligninfiber.Finally,the anti-cracking performance of PFAM and LFAM at low temperatures is reduced by 74.2%and 46.7%,respectively,as thefiller-asphalt ratio is raised from 0.8 to 1.2.The low-temperature anti-cracking performance of LFAM is lower than that of PFAM at the samefiller-asphalt ratio,even lower than that of PSA.Compared with ligninfiber,the anti-cracking performance and deformation resistance of PSAM at low temperature is more greatly enhanced by polyester fiber.

Ultrasonic solidification mechanism and optimized application performances of ternary Mg_(71.5)Zn_(26.1)Y_(2.4) alloy

One dimensional(1D) and three dimensional(3D) ultrasound sources were applied to the solidification process of Mg_(71.5)Zn_(26.1)Y_(2.4) alloy.The acoustic spectra were in-situ measured, based on which the cavitation intensities and dynamic solidification mechanism were further investigated. With the increase of ultrasonic dimension and amplitude, the primary Mg_(3)Zn_(6)Y phase was significantly refined from petals to nearly pentagonal shape. The sound field measurements showed that the transient cavitation played a decisive role in generating a high local undercooling, which facilitated the formation of icosahedral clusters and promoted the nucleation of primary Mg_(3)Zn_(6)Y phase. The morphological transition of(α-Mg+Mg_(3)Zn_(6)Y) eutectic from lamellar to anomalous structure occurred under 3D ultrasonic condition. The stable cavitation took the main responsibility because the high pressure excited by nonlinearly oscillating bubbles induced the preferential nucleation of α-Mg phase rather than Mg_(3)Zn_(6)Y phase. As compared with its static values, the tensile strength and compression plasticity of this alloy were increased by the factors of 1.9 and 2.1, and its corrosion resistance was also improved with the corrosion current density decreased by one order of magnitude.

平衡计分卡在公共部门预算绩效管理中的应用分析——基于学习与成长视角的考察

作为平衡计分卡的基础,学习与成长视角不仅是平衡计分卡价值创造的动力和源泉,而且融入了预算绩效管理的各个环节。但是在具体应用中,平衡计分卡仍然面临着学习反馈与人才培养机制有待完善、预算绩效信息质量急需提高等一系列挑战。在未来的改革中,应不断优化预算绩效管理中的学习反馈机制,将奖惩激励措施有机融入人才培养机制,通过多元化数据来源和建立平衡计分卡专项数据库等手段,持续提升预算绩效信息管理的技术水平。

大跨度上承式钢管混凝土拱桥受力性能分析

研究目的:为系统地掌握西北地区大温差、峡谷风、高震区共存的复杂建设条件下上承式钢管混凝土拱桥的力学性能,以一座净跨400 m的公路同类型拱桥为例,按照现行设计规范,采用统一模量法建立三维杆系有限元模型,对概率极限状态设计方法要求的静力性能、稳定性、动力特性、抗震性能的组合工况进行全面、系统地分析和计算,为同类型桥梁设计提供参考。研究结论:(1)温度效应大于汽车荷载效应,拱脚处横风效应突出;(2)双向偏压、偏拉组合受力为单弦杆控制设计状态,拱顶为桁式拱肋承载力的薄弱位置;(3)腹杆、横撑、平联等构件与弦杆构造匹配性较好时,承载力及疲劳性能等易满足受力需求;(4)温度、徐变预拱度比车道荷载大很多;(5)主拱圈在材料、几何、双重非线性下稳定性分别下降了5.5%、11.9%、17.1%;(6)振型相对密集、频率值较小,主振型为面外弯扭振动,具有多方向和多角度耦联性;(7)时程分析结果大于反应谱分析结果,但小于静力工况,拱桥抗震性能好;(8)上承式钢管混凝土拱桥在复杂建设条件下具有良好的受力性能。

超低阻呼吸防护用聚乳酸纳米纤维膜制备及长效过滤性能

长期暴露于大气环境中高浓度的细颗粒物(PM_(2.5))会对人类的长期健康效应产生消极影响,传统空气过滤材料难以兼顾高效、低阻的防护效果,且不可降解,不仅加剧全球塑料污染,还易产生更强的微塑料危害。为此,制备了一种具有空气滑移效应、自供能且可生物降解的纳米纤维膜,以保障长效、低阻呼吸防护。提出两步水热法制备平均粒径49.6 nm、易分散的BaTiO_(3)电介质,同时利用“静电纺丝-静电喷雾”法将BTO纳米颗粒(BTO NPs)原位嵌入PLA纤维膜,利用BTO NPs的摩擦电效应和尺寸效应同步调控纤维膜的过滤效率和空气阻力。通过控制喷雾悬浮液中BTO NPs的浓度,探讨其与PLA/BTO纤维膜电活性、过滤性能和力学性能之间的关系。微观表征和性能测试结果表明:PLA/BTO纤维膜具有优异的电活性、过滤性能及力学性能。PLA/BTO纤维膜表面电势可高达5.9 kV,介电常数达1.20 F/m,平均输出电压高达12.4 V;得益于增强的空气分子滑移效应和电活性,PLA/BTO10纤维膜在显著降低空气阻力(低至20 Pa)的同时,对PM_(0.3)过滤效率提升了7.78%~9.05%,对PM_(2.5)过滤效率提升了2.90%~13.19%,即使在85 L/min高测试流量下仍能保证高达97.25%的PM_(2.5)过滤效率;同时,PLA/BTO纤维膜拉伸强度增幅高达60%(拉伸强度22.5 MPa),断裂伸长率增幅高达68%(断裂伸长率25%),而断裂韧性最高可提升1.3倍(断裂韧性3.6 MJ/m^(3))。因此,提出的兼具长效、低阻过滤且可降解纤维膜在呼吸防护领域具有广阔的应用前景,也为缓解废弃口罩加剧的塑料污染现状提供了一种新思路。