Multi-criteria analysis for screening of reversible metal hydrides in hydrogen gas storage and high pressure delivery applications

Metals and alloys forming reversible hydrides with hydrogen gas are potential building blocks for compact, solid state hydrogen storage systems. Based on the materials’ thermodynamic characteristics, their use as temperature-swing gas compression and delivery systems in the hydrogen economy is also possible. Given the wide variety of materials developed and tested at laboratory and pilot scales, a harmonized method of selecting the feasible material(s) for a particular real-life application is required. This study proposes a system selection framework based on a normalized, multi-criteria metric. Using calculated values of multi-criteria metric, multi-criteria screening and ranking of potential materials has been demonstrated for a particular use case. It is found that the alloy TiMn_1.52 having value of additive metric between 0.25 and 0.35 represents the best material for a single stage system. The alloy pair CaNi₅–Ti_1.5CrMn represents the best alternative for a two-stage system with additive metric values between 0.63 and 0.82. Energy and economic characteristics of the metal hydride gas compression and delivery systems are evaluated and compared with an equivalent mechanical compression system producing the same final effect (i.e., delivery of a given quantity of gas at a defined pressure).     

Optimization of hydrogen enrichment via palladium membrane in vacuum environments using Taguchi method and normalized regression analysis

In this study, the separation of hydrogen from gas mixtures using a palladium membrane coupled with a vacuum environment on the permeate side was studied experimentally. The gas mixtures composed of H₂, N₂, and CO₂ were used as the feed. Hydrogen permeation fluxes were measured with membrane operating temperature in the range of 320–380 °C, pressures on the retentate side in the range of 2–5 atm, and vacuum pressures on the permeate side in the range of 15–51 kPa. The Taguchi method was used to design the operating conditions for the experiments based on an orthogonal array. Using the measured H₂ permeation fluxes from the Taguchi approach, the stepwise regression analysis was also employed for establishing the prediction models of H₂ permeation flux, followed by the analysis of variance (ANOVA) to identify the significance and suitability of operating conditions. Based on both the Taguchi approach and ANOVA, the H₂ permeation flux was mostly affected by the gas mixture composition, followed by the retentate side pressure, the vacuum degree, and the membrane temperature. The predicted optimal operating conditions were the gas mixture with 75% H₂ and 25% N₂, the membrane temperature of 320 °C, the retentate side pressure of 5 atm, and the vacuum degree of 51 kPa. Under these conditions, the H₂ permeation flux was 0.185 mol s^?1 m^?2. A second-order normalized regression model with a relative error of less than 7% was obtained based on the measured H₂ permeation flux.     

Formation of acrylamide in microwave-roasted sorghum and associated dietary risk

The effect of microwave roasting parameters (300, 450 and 600 W; 5, 10 and 15 min) on acrylamide content in sorghum grain was determined using High Pressure Liquid Chromatography (HPLC)-photo diode array (PDA) detector coupled with C-18 column. Samples roasted at 300 and 450 W did not possess acrylamide, whereas 600 W (15 min) favoured formation of 2740.19 µg/kg of acrylamide, levels far exceeding the defined European Union (EU) limits. The chronic daily intake (CDI) for acrylamide through consumption of such grain flour was 3.25–9.5-fold higher to Joint FAO/WHO Expert Committee on Food Additives (JECFA) defined high exposure limits. The margin of exposure (MOE) values ranged from 4.3 to 12.76 and from 11.07 to 32.27 for neoplastic and neurological effects, respectively, demonstrating high exposure and serious health concerns associated with dietary intake of this toxicant. This study assesses the risk for the Indian population and highlights the importance of optimising process parameters for food product to minimise such exposure risks.     

A novel pre-dilution,swirling jet diffuser to enhance effluent mixing: Hydrodynamics and dilution performance

Diffusers are widely-used to quickly dilute effluents in receiving water bodies. This study proposed a novel diffuser that pre-mixes effluent with ambient water before discharging and that uses the swirling jet to further enhance near-field dilution. The nozzle of the diffuser was examined in two ambient flow conditions: co-flow and counter-flow that are commonly-met in the environment such as oceans due to tidal effect. Physical experiments were first conducted in co-flow on its dilution performance and hydrodynamics, using heated water as the effluent. A 3-D CFD model was developed and calibrated the co-flow scenarios, and then used to investigate the diffuser in counter-flow. The results showed that the nozzle can effectively reduce the maximum temperature rise of the effluent by about 50 % before discharging. The swirling jet from the outlet has a larger shear area, half-width and entrainment rate, enabling the effluent to be rapidly diluted to a minimum of around 10 times at x/D = 6 in co-flow, whereas the dilution for conventional nozzles is about 1 because of the potential core. The flow amplification ratio (α) decreases gradually with increasing velocity ratio in co-flow but increases with increasing velocity ratio in counter-flow. The counter-flow reduces the water drawn into the device; however, the pre-dilution effect at the outlet remains stable. The near-field dilution in counter-flow was significantly enhanced than that in co-flow. Environmental regulations at outfalls and mixing zones can be more easily met using this novel diffuser.     

Metal-free catalyst fabrication by incorporating oxygen groups on the surface of the carbonaceous sample and efficient hydrogen production from NaBH4 methanolysis

In the present study, metal-free catalysts for efficient H₂ generation from NaBH₄ methanolysis was produced for the first time from apricot kernel shells with two-step activation. The first stage of the two-stage activation includes the production of activated carbon with the KOH agent (AKOH), and the second stage includes hydrothermally HNO₃ activation with oxygen doping (O doped AKOH + N). The hydrogen production rate (HGR) and the activation energy (Ea) of the reaction with the obtained metal-free catalyst (10 mg) were determined as 14,444 ml min^?1 g^?1 and 7.86 kJ mol^?1, respectively. The structural and physical-chemical properties of these catalysts were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), elemental CHNS analysis, FT-IR (Fourier transform infrared spectroscopy), and nitrogen adsorption analysis. Also, the reusability results of this metal-free catalyst for H₂ production are promising.     

以新发展理念引领高校专业基础课教学改革

以“创新、协调、绿色、开放、共享”为内核的新发展理念，是对马克思主义发展理念的继承和发扬，极具时代精神，富含问题意识，为高校思想政治教育发展、教育教学改革实践提供了强大的理论支撑。本文以“通信原理”为例，阐述了新发展理念在课程改革中的思路和方法，实现了思想政治教育与专业基础课程有机融合，为深化高校教学改革、创新人才培养模式提供了思路。     

基于VMD和BSA-KELM的高陡边坡位移预测模型研究

边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明：和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。     

Simulation of hydrogen and coal gas fueled flat-tubular solid oxide fuel cell (FT-SOFC)

Solid oxide fuel cells (SOFCs) are considered an important technology in terms of high efficiency and clean energy generation. Flat-tubular solid oxide fuel cell (FT-SOFC) which is a combination of tubular and planar cell geometries stands out with its performance values and low costs. In this study, the performance of an FT-SOFC is analyzed numerically by using finite element method-based design as a result of changing parameters by using different fuels which are pure hydrogen and coal gas with various proportions of CO. In addition, cell performance values for different temperatures were analyzed and interpreted. Analyzes have been performed by using COMSOL Multiphysics software. The rates of CO composition used are 10%, 20%, and 40%, respectively. In addition, the air was used as the oxidizer in all cases. The cell voltage and average cell power of the FT-SOFC were examined under the 800 °C operating condition. The maximum power value and current density value were obtained as 710 W/m² and 1420 A/m² for the flat-tubular cell, respectively. As a result of the study, it was observed that the maximum cell power densities increased with increasing temperature. Analysis results showed that FT-SOFCs have suitable properties for different fuel usage and different operating temperatures. High-performance values and design features in different operating conditions are expected to make FT-SOFC the focus of many studies in the future.     

基于滚动摩擦作用下玉米颗粒在模拟筒仓卸料中的力链分析（网络首发、推荐阅读）

针对颗粒滚动摩擦作用对筒仓中玉米颗粒的力链空间分布进行研究，通过EDEM离散元软件建立筒仓模型与仿真玉米颗粒模型进行卸粮仿真模拟，并与筒仓卸料实验作流态对比，验证模型与仿真结果的准确性。通过对模拟仓进行切片观察和数据处理，对比分析了不同摩擦情况下力链的细观参数随时间演化规律。模拟结果表明：颗粒间摩擦系数越大，卸粮完成的最终时间越长；颗粒间滚动摩擦系数越小，颗粒由整体流转变为管状流的时间越早。对于有漏斗的筒仓来说，减小颗粒间摩擦会改变整体流和管状流之间的极限，从而增加产生管状流的面积。标准滚动摩擦系数下玉米颗粒在卸料过程中会出现起拱-塌陷效应；减小滚动摩擦，玉米颗粒卸料较稳定，未出现起拱的应力突增、以及拱塌陷的应力衰减；增大颗粒间滚动摩擦不但会增加拱效应，且出现成拱高度距离漏斗口更高。     

Generation,validation and application of dynamic load profiles in flow measurement using cavitating Herschel–Venturi nozzles

Today, utility meters for water are tested for measurement behavior at stable operating conditions at specified flow rates as part of the approval process. The measurement error that occurs during start and stop or when changing between flow rates may not be taken into account. In addition, there are new technologies whose measuring behavior under real-world conditions is only known to a limited extend. To take these facts into account, a new method has been developed and tested to determine the measurement behavior of water meters under dynamic load profiles as they occur in the real application. For this purpose, a test rig for flow rate measurement was extended by a cavitation nozzle apparatus and the generation of dynamic load profiles was validated. For the cavitation nozzles used, possible factors influencing the flow rate, such as temperature and purity of the water as well as the upstream pressure were investigated. Using different types of domestic water meters, the applicability of the dynamic test procedure was demonstrated and the measurement behavior of the meters was characterised.