Enhancing Hydrophilicity of Thick Electrodes for High Energy Density Aqueous Batteries

Thick electrodes can substantially enhance the overall energy density of batteries.However,insufficient wettability of aqueous electrolytes toward electrodes with conventional hydrophobic binders severely limits utilization of active materials with increasing the thickness of electrodes for aqueous batteries,resulting in battery performance deterioration with a reduced capacity.Here,we demonstrate that controlling the hydrophilicity of the thicker electrodes is critical to enhancing the overall energy density of batteries.Hydrophilic binders are synthesized via a simple sulfonation process of conventional polyvinylidene fluoride binders,considering physicochemical properties such as mechanical properties and adhesion.The introduction of abundant sulfonate groups of binders(i)allows fast and sufficient electrolyte wetting,and(ii)improves ionic conduction in thick electrodes,enabling a significant increase in reversible capacities under various current densities.Further,the sulfonated binder effectively inhibits the dissolution of cathode materials in reactive aqueous electrolytes.Overall,our findings significantly enhance the energy density and contribute to the development of practical zinc-ion batteries.

Analysis of Light Load Efficiency Characteristics of a Dual Active Bridge Converter Using Wide Band-Gap Devices

In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (Co,tr) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low Co,tr operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.

Addition of cerium and yttrium to ferritic steel weld metal to improve hydrogen trapping efficiency

The applicability of Ce and Y as promising candidate elements to form irreversible traps in weld metal was investigated by thermal desorption spectroscopy(TDS) with gas chromatography(GC). The precise nature of the precipitate particles newly formed in the weld metal by the addition of Ce and Y to a certain alloy system was characterized. Moreover,the hydrogen trapping efficiency expressed as the reduction of the diffusible hydrogen in the weld metal was analyzed. The results showed that the addition of Ce and/or Y to this alloy system led to the formation of a mixed type of(Ce,Ti)-based oxide,(Y,Ni)-based carbide,or(Ce,Y,Ti)-based oxide particles. Because of the high activation energy of the mixed type of particles(≥ 150 k J/mol),the trapping efficiency for hydrogen was considered to be sufficiently high to effectively reduce the diffusible hydrogen content.

Improved tensile properties of AZ31 Mg alloy subjected to various caliber-rolling strains

A multi-pass caliber rolling has attracted attentions as an alternative to severe plastic deformation processes.The present study enhanced strength and ductility of AZ31 Mg alloy simultaneously through the application of caliber rolling.The improving trends in tensile properties were interpreted with various caliber-rolling strains.The oval/circular-shaped calibers imposed a high plastic strain at the center of crosssection,leading to effective grain refinement to submicron scale.This work also confirmed the texture randomizing effect of caliber rolling.Such microstructural evolutions gave rise to the fabrication of high-strength material.Moreover,the caliber-rolled AZ31 Mg alloys exhibited an improvement in ductility as compared to the as-received sheet-rolled material.This was discussed in terms of activation of non-basal slip systems and suppression of mechanical twinning.This study successfully proved the possibility of caliber rolling to produce a bulk Mg rod with enhanced tensile properties.

Tailoring strength-ductility balance of caliber-rolled AZ31 Mg alloy through subsequent annealing

Recently,multi-pass caliber rolling has been shown to be effective for Mg alloys.This study investigated the effect of subsequent annealing on the mechanical properties of a caliber-rolled AZ31 Mg alloy to modulate the strength-ductility relationship.This annealing gave rise to different trends in mechanical properties depending on the temperature regime.Low-temperature annealing(T≤473 K)exhibited a typical trade-off relationship,where an increase in annealing temperature resulted in increased ductility but decreased strength and hardness.Such a heat treatment did not degrade the high strength-ductility balance of the caliber-rolled alloy,suggesting that the mechanical properties could be tailored for different potential applications.In contrast,high-temperature annealing(T>473 K)caused a simultaneous deterioration in strength,hardness,and ductility with increasing annealing temperature.These differences are discussed in terms of the varying microstructural features under the different investigated annealing regimes.

Thermal stress analysis method considering geometric effect of risers in sand mold casting process

Solidif ication and f luid f low analysis using computer simulation is a current common practice. There is also a high demand for thermal stress analysis in the casting process because casting engineers want to control the defects related to thermal stresses, such as large deformation and crack generation during casting. The riser system is an essential part of preventing the shrinkage defects in the casting process, and it has a great inf luence on thermal phenomena. The analysis domain is dramatically expanded by attaching the riser system to a casting product due to its large volume, and it makes FEM mesh generation diff icult. However, it is diff icult to study and solve the above proposed problem caused by riser system using traditional analysis methods which use single numerical method such as FEM or FDM. In this paper, some research information is presented on the effects of the riser system on thermal stress analysis using a FDM/FEM hybrid method in the casting process simulation. The results show the optimal conditions for stress analysis of the riser model in order to save computation time and memory resources.

The Phenomenon of High Hardness Values on the S-Phase Layer of Austenitic Stainless Steel via Screen Plasma Nitriding Process

The purpose of this study is to improve the surface properties of austenitic stainless steel using the double-folded electrode screen plasma nitriding (SPN) process. In general, the S-phase is well-known for its excellent properties such as improved hardness and wear resistance along with sustained corrosion resistance. The concentrated nitrogen via SPN process was injected to form S-phase with time at 713 K. This study was carried out under the conditions of 44 at% of nitrogen injection, which was higher than 25 at% known as the condition of no precipitation of S-phase formed by the SPN process, and 20 K higher than the maximum temperature without precipitation phase. The hardness analysis of stainless steel sample treated by the SPN process at 713 K showed a much higher value than the typical nitriding hardness at a depth of lower nitrogen than the maximum nitrogen concentration. The SPN 20 hr treated specimen showed the average value of 2339 HV while 40 hr showed the average value of 2215 HV. The result is attributed to the concentrated nitrogen formed in the SPN process reacting with the alloying elements contained in the base material to form fine precipitates, thus producing a synergy effect of the extreme hardening effect;that is, the movement of precipitates and dislocations due to the GP-zone (Guinier-Preston zone).

Quantifying growth and breakage of agglomerates in fluid-particle flow using discrete particle method

The cohesive solids in liquid flows are featured by the dynamic growth and breakage of agglomerates, and the difficulties in the development, design and optimization of these systems are related to this significant feature.In this paper, discrete particle method is used to simulate a solid–liquid flow system including millions of cohesive particles, the growth rate and breakage rate of agglomerates are then systematically investigated. It was found that the most probable size of the agglomerates is determined by the balance of growth and breakage of the agglomerates the cross point of the lines of growth rate and breakage rate as a function of the particle numbers in an agglomerate, marks the most stable agglomerate size. The finding here provides a feasible way to quantify the dynamic behaviors of growth and breakage of agglomerates, and therefore offers the possibility of quantifying the effects of agglomerates on the hydrodynamics of fluid flows with cohesive particles.

Understanding of Ultrasonic Assisted Machining with Diamond Grinding Tool

In this work, machining test was carried out in various machining conditions using ultrasonic vibration capable CNC machine. For work material, alumina ceramic (Al2O3) was used while for tool material diamond electroplated grinding wheel was used. To evaluate ultrasonic vibration effect, grinding test was performed with and without ultrasonic vibration in same machining condition. In ultrasonic mode, ultrasonic vibration of 20 kHz was generated by HSK 63 ultrasonic actuator. On the other hand, grinding forces were measured by KISTLER dynamometer. And an optimal sampling rate for grinding force measurement was obtained by a signal processing and frequency analysis. The surface roughness of the ceramic was also measured by using stylus type surface roughness instrument and atomic force microscope (AFM). Besides, the scanning electron microscope (SEM) was used for observation of surface integrality.

Customizable design ofmultiple-biomolecule delivery platform for enhanced osteogenic responses via‘tailored assembly system’

Porous titanium(Ti)scaffolds have been extensively utilized as bone substitute scaffolds due to their superior biocompatibility and excellent mechanical properties.However,naturally formed TiO2 on the surface limits fast osseointegration.Different biomolecules have been widely utilized to overcome this issue;however,homogeneous porous Ti scaffolds could not simultaneously deliver multiple biomolecules that have different release behaviors.In this study,functionally graded porous Ti scaffolds(FGPTs)with dense inner and porous outer parts were fabricated using a two-body combination and densification procedure.FGPTs with growth factor(BMP-2)and antibiotics(TCH)exhibited suitable mechanical properties as bone substituting material and presented good structural stability.The release of BMP-2 was considerably prolonged,whereas the release of TCH was comparable to that of homogenous porous titanium scaffolds(control group).The osteogenic differentiation obtained using FGPTs was maintained due to the prolonged release of BMP-2.The antimicrobial properties of these scaffolds were verified using S.aureus in terms of prior release time.In addition,various candidates for graded porous Ti scaffolds with altered pore characteristics were presented.

滩海吹填粉细砂地基长期承载力特性试验研究

对某运行10年以上出现沉陷冒水现象的滩海人工岛吹填粉细砂地基承载力进行分析,基于螺旋板载荷试验结果,研究了标贯击数、动探击数与地基承载力的关系,拟合了经验公式,在此基础上综合分析粉细砂地基承载力现状,探究地基长期承载力特性。研究结果表明,吹填粉细砂形成的滩海人工岛地基在长期反复的水力作用下可进一步密实,承载力有所提高,有利于场地的运行安全。但鉴于其松散特性,水力作用下易流失,防渗措施不到位可能导致沉陷脱空、冒水等工程问题,影响场地安全运行。因此,针对本工程沉陷冒水现象,需采取原位固化、帷幕封闭等防渗措施进行处理。

不同工况下水库大坝固化灰浆防渗墙防渗效果数值分析

针对山东东营孤东水库坝体渗漏问题,提出了大坝的防渗加固方案,对加固后的大坝渗流及稳定性进行数值计算。结果表明,固化灰浆防渗墙方案能很好地解决大坝渗漏问题,加固后设计蓄水位下出逸比降低于允许渗透比降。在水位骤降的条件下,大坝内部压力水头线下降,安全系数提高到1.40;在地震荷载的工况下,安全系数提高到1.32~1.44。加固后围坝的安全系数满足规范值,保证满足大坝的防渗要求,各工况的安全系数也都符合规范要求,可为类似加固工程提供可靠参考。

Similarity measure on intuitionistic fuzzy sets

Study of fuzzy entropy and similarity measure on intuitionistic fuzzy sets (IFSs) was proposed and analyzed. Unlike fuzzy set, IFSs contain uncertainty named hesitance, which is contained in fuzzy membership function itself. Hence, designing fuzzy entropy is not easy because of many entropy definitions. By considering different fuzzy entropy definitions, fuzzy entropy on IFSs is designed and discussed. Similarity measure was also presented and its usefulness was verified to evaluate degree of similarity.

真空联合堆载预压法在寒区筑坝工程中的应用

真空联合堆载预压法是中国沿海地区常用的软基处理方法,但在北方地区筑坝工程中缺少工程案例和施工经验,具体表现在传统的插板工艺、密封墙工艺对复杂地层适应性不明确,大体积坝体堆载后密封膜的密封效果未知,冬季低温冻结力会破坏饱水的密封和排水系统。为此依托中国北方某土坝工程,选取先导试验段,分别开展塑料排水板插板工艺试验、密封墙成墙试验、密封膜保护试验和坝基防冻试验。研究结果表明:履带式振动插板工艺能有效穿透上覆硬壳层,其施工效率优于引孔+振动插板工艺;采用1.2 m双排泥浆搅拌墙方案能起到良好的负压密封效果;在密封膜表面铺设无纺布、编织布,过渡层采用轻型压实能有效保护真空密封膜。在土坝上层和坡脚填筑2 m的防冻层,可有效防止地基土层和排水系统冻结,冬歇期后真空排水系统可正常运行。

张家港油品码头升级改造技术方案

为满足生产发展和码头靠泊作业安全的需要,对张家港油品码头进行升级改造。根据原有码头平面布置和结构现状,采用局部加固方式,通过增设10座系靠墩与原有码头相结合,新建2座靠船作业平台,并进行相应的附属设施改造,使原码头从靠泊1万t级油品码头升级为5万t级油品码头。设计方案根据工期要求、系泊特点及工程现状,在对既有码头结构体系进行加固改造时通过计算分析提出了简易的分配系数取值方法,并结合工程特点制定了复杂狭窄水域的沉桩工艺流程,相关成果可以为类似工程提供参考。

分级真空预压加固软土地基位移变化规律模拟

真空预压广泛应用于软土地基加固中。但在深厚软土地基处理中,常规加压方式易使加固区边界土体出现裂缝。而分级真空预压由于真空强度阶段性地分级增长,可有效控制边界区裂缝的出现。本研究采用FLAC3D软件建立分级真空预压的数值模型,并结合现场实测数据对模型的合理性进行验证。在此基础上,对比分析分级加载方式对地基变形的影响。结果表明:分级真空预压能有效减小坝基表层与软土层水平位移的差值,有利于控制裂隙的出现;在各分级加载方式中,方案四10-40-85kPa的加载方案更适用于该项目地基。上述研究成果可为分级真空预压的推广应用提供参考。

融合数据同化与机器学习的流域径流模拟方法

环境变化影响下流域径流的精确模拟对洪涝灾害防治与区域水资源管理都具有重要意义。在径流模拟研究中,现有机器学习模型未能充分考虑水文中间状态变量对降雨-径流过程的影响,本研究基于集合卡尔曼滤波(EnKF)更新水文状态变量,结合主成分分析(PCA)提取预报因子的主要特征,采用长短时记忆神经网络(LSTM)构建考虑水文中间变量的机器学习水文模型EnKF-PCA-LSTM。以赣江流域为例,评估EnKF-PCA-LSTM模型的径流模拟效果,同时将模拟结果与LSTM模型、物理水文模型HYMOD做对比分析。结果表明,EnKF-PCA-LSTM模型模拟径流的纳什效率系数、Kling-Gupta效率系数和对数纳什效率系数分别为0.954、0.971和0.972,比LSTM模型和HYMOD模型具有更好的模拟性能,说明考虑水文状态变量可有效提高机器学习模型的径流模拟精度及稳定性。研究成果可为流域径流模拟提供技术参考。

多水源补给的宿迁市黄河故道水量-水质耦合优化调控

为了实现黄河故道水量和水质双重保障目标下的耦合优化调控,需要综合考虑水量补给渠道、水质改善目标、经济成本和技术难度等多重因素。研究基于黄河故道11级梯级蓄水工程和骆马湖、中运河、洪泽湖对黄河故道的补给关系,充分利用和优化分配周边水系水源,通过建立水量-水质耦合模型,开展多种水资源配置方案的数值模拟与方案比选,提出多水源补给的黄河故道优化调度方案。结果表明:在“高水高用、低水低用”的基础上每月增加小额生态补水量(0.42亿~0.52亿m3),成本适中、技术难度低,且水质改善效果较好,2018年(现状年)和2025年(规划水平年)水质综合改善率分别为22%和9%,水质总体达标率分别为82%和93%,调水成本分别比单一水源(“高水”)成本降低16%和24%。

山区河道水环境综合治理探讨——以綦江区新盛河为例

为落实长江大保护战略,推进长江流域河道水环境治理,以綦江区新盛河作为研究对象,探讨了典型山区河道特征及问题,采用产排污系数法对各类入河污染源进行了估算分析,结果表明:新盛河入河污染总负荷分别为:COD_(Cr) 419.71t/a、NH_(3)-N 46.25t/a、TN 73.23t/a、TP 8.05t/a,生活污染是新盛河最大污染源,其次为农业面源污染和养殖污染,底泥内源污染、工业污染和地表径流污染对各种类型的污染负荷贡献率均相对较小。最后结合河道现状问题及治理目标从水安全、水资源、水环境、水生态、水景观、水管理等六大方面提出了针对性的水环境综合治理思路及措施建议。