Investigation of effects of sulfur on dry reforming of biogas over nickel–iron based catalysts

The aim of this study is to maintain and increase the activity of the catalyst in the presence of H₂S with the addition of iron to the Ni catalyst. Alumina-supported monometallic iron and bimetallic nickel-iron catalysts with different weight percentages (8% Fe, 3% Ni – 3% Fe and 8% Ni – 8% Fe) were synthesized using the wet impregnation method in this study. Alumina was prepared by the sol-gel method. The activities of these synthesized catalysts in the methane dry reforming reaction were investigated at different H₂S concentrations (0 ppm, 2 ppm, and 50 ppm) with a total flow rate of 60 mL/min containing an equimolar ratio of CH₄, CO₂, and Ar at 750 °C and atmospheric pressure. To investigate the effect of sulfur compounds on the catalytic activity, the catalysts were also exposed to different gas compositions such as the mixture of H₂S + He, H₂S + CO₂ + He, and H₂S + CO₂ + CH₄ + He. In this case, FT-IR with a gas cell was used to determine the components in the gas stream at the reactor outlet. To explain catalytic performance, characterization studies were carried out using XRD, N₂ adsorption/desorption, DRIFT, SEM, TGA, and XPS analysis. All-synthesized materials showed Type-IV isotherm with a hysteresis loop corresponding to an ordered mesoporous structure. The DRIFT analysis showed a decrease in the Lewis acid sites after the addition of iron into the Ni-catalysts. In the activity test carried out in the presence of 50 ppm H₂S, it was observed that the iron-containing 8Ni–8Fe@SGA catalyst increased the sulfur resistance slightly, compared to the monometallic 8Ni@SGA catalyst. TGA analysis showed that Fe addition reduced coke deposition, as the Ni–Fe catalyst had a lower nickel crystal size than the Ni-based catalyst. FTIR analysis with a gas cell showed that sulfur in H₂S transformed to other sulfur compounds such as COS and/or SO₂ during dry reforming of biogas over alumina-supported Ni–Fe catalysts.     

氢氧化镁阻燃剂的研究进展

主要论述了国内外阻燃剂的种类和发展,指出由于环境和健康的原因,无机阻燃剂是最有发展前途的,其中的氢氧化镁因其特有的性质,在无机阻燃剂中尤为突出.考虑到氢氧化镁的广泛应用的前景和其本身的缺点,对其改性成为业界的研究重点,其中主要介绍了钛酸酯、硬脂酸(盐)、镁盐晶须和胶囊化等技术,指出以后的发展方向是在改性基础上的协同作用.     

大功率白光LED加速寿命试验研究

对新型大功率GaN基蓝光芯片激发荧光粉发射白光的LED进行电流应力加速寿命测试和可靠性研究,考察白光LED主要性能参数随老化时间的变化,结果表明:经过5000多小时的老化,光通量平均降至初始值的77.5%;发光效率变化趋势与光通量变化基本一致;峰值波长没有明显的变化趋势,而相关色温随老化时间增加逐渐升高;正向导通电压也随老化时间增加而升高.实验表明样品参数型失效主要包括发光效率的降低和荧光粉转换效率的降低.     

Compressive strength loss and reinforcement degradations of reinforced concrete structure due to long-term exposure

Degradations due to long-term weathering actions on a reinforced concrete structure were investigated. Compressive strength and reinforcement corrosion developments of a prototype RC structure were monitored for 6 years using destructive and non-destructive tests which include periodic coring, compressive strength, rebound hammer, ultrasonic pulse velocity, carbonation, half-cell and tensile strength tests. Eventually, results have shown that more than a quarter of peak compressive strength can be lost within 5 years of continuous exposure. Corrosion of the exposed bars within the range of the testing period was also observed to be quite alarming. Thus, defects caused by prolonged actions of environmental factors may pose serious threats on the integrity of partially completed structures especially abandoned projects.     

两种新型双脊波导传输特性的研究

为了寻找最佳传输特性的对称双脊波导结构,提出了三角形和倒梯形两种新型对称双脊波导．应用有限元分析方法计算了这两种新型对称双脊波导TE模式的传输特性,即截止波长和单模带宽．分析传输特性随对称脊波导结构尺寸的变化关系曲线,得到脊间距越小,单模带宽越高,且单模带宽最大达8.0173;倒梯形对称双脊波导的截止波长较同尺寸矩形、三角形和梯形大,最大达9.5．这些结果将为脊波导器件的小型化提供指导．绘出的主模与第一个高次模的场结构图表明,在三角形对称双脊波导的顶点处场强变化最大,能量损失大．     

A Novel Fault Location Algorithm for Double-Circuit Transmission Lines based on Distributed Parameter

1 IntroductionWith the development of the power system,thedouble circuit transmission lines have been widely used.The increased complexities of power transmission systemmake the transmission line fault location studies morecomplicated and important.The fault location for thesemore complex lines has raised great attentions.Differentfault location algorithms can be developed depending onthe extracted data from one or both ends of thetransmission lines.The method using one end data isaffected by…     

基于改进YOLOv4-Tiny的矿井电机车多目标实时检测

为解决煤矿巷道环境恶劣以及人工疲劳驾驶电机车导致煤矿井下有轨电机车事故频发的问题,提出一种基于改进YOLOv4-Tiny算法的YOLOv4-Tiny-4S矿井电机车多目标实时检测方法。首先,为了提高网络模型对于小目标的检测能力,将传统YOLOv4-Tiny的两尺度预测增加至四尺度预测,并且在网络模型的颈部引入空间金字塔池化（SPP）模块,以丰富特征融合信息,增大网络模型的感受野;其次,以煤矿巷道中的行人、电机车、信号灯以及碎石作为检测目标,创建矿井电机车多目标检测数据集,并分别采用K-means和K-means++聚类分析算法对数据集重新聚类,通过对比分析验证了K-means++算法具有更好的聚类效果;最后,通过对传统YOLOv4-Tiny算法的消融实验,进一步直观了不同改进措施对网络模型检测性能的影响,并在电机车运行的煤矿巷道场景中,对比分析了YOLOv4-Tiny-4S算法与其他几种算法的检测性能。实验结果表明：YOLOv4-Tiny-4S算法能够准确检测并识别出图像中的各类目标,其平均检测精度（mAP）为95.35%,对小目标“碎石”的平均检测精度（AP）为86.69%,相比传统YOLOv4-Tiny算法分别提高了12.38和41.66个百分点;改进后算法的平均检测速度达58.7帧/秒（FPS）,模型内存仅为26.3Mb,YOLOv4-Tiny-4S算法的检测性能优于其他算法。本文提出的基于YOLOv4-Tiny-4S矿井电机车多目标实时检测方法可为实现矿井电机车的无人驾驶提供技术支撑。     

三通球阀式高速开关阀稳态液动力分析与结构改进

对于微小型高速开关阀,大流量和高频响都会增大阀芯所受的液动力进而影响其运动状态,因此,对液动力进行分析与补偿是提升高速开关阀性能的关键因素之一。为了解决球阀式高速开关阀在高频启闭状态下流场结构复杂导致传统的稳态液动力理论计算公式已不适用的问题,基于CFD数值计算方法对液动力进行研究。首先,利用COMSOL软件建立阀内流场流体域的几何模型;随后,选用弱可压缩流体、标准k-ε湍流模型并运用动网格技术,得到流体域的压力和流线分布图、流量曲线以及不同阀口开度下阀球和阀芯的稳态液动力变化曲线;最后,为了补偿阀口启闭过程中所减小的稳态液动力,根据不同的阀口结构参数与阀芯受力及阀口启闭时间之间的变化关系,对阀口结构进行优化并确定最优参数。结果表明：进油孔阀球所受的稳态液动力会随着阀口的开启产生先减小后增大的现象,但由于进油孔阀球的稳态液动力相比于回油孔阀球较小,故阀芯上的稳态液动力变化与回油孔阀球上的稳态液动力变化近似;适当减小阀球推杆直径及将靠近阀口的流道改成渐扩型流道能够有效地补偿启闭过程中所减小的稳态液动力,改进后的最优结构相较于原结构的一个周期启闭时间从1.047 ms下降到0.714 ms,稳态液动力补偿效果明显。     

A multi-criteria decision making analysis for feasibility of nanoparticle addition in biohydrogen production enhancement for scaling-up studies

Nanoparticles (NPs) thanks to their unique features such as large surface area, high catalytic activity and intra-cellular electron transfer ability used as an enhancement additive in biohydrogen production. Up to date, inorganic, organic and their mixtures of various NPs were produced from different input sources and synthesis methodology. The NPs properties and cost minimization are the critical factors for the scale up studies of industrial applications. Nevertheless, there have not been any study on the determination of the most efficient and feasible NPs in biohydrogen production for the scaling up the process. In this study, the NPs used for biohydrogen production enhancement over Clostridium sp. by dark fermentation were examined and these studies were evaluated to determine the most effective and feasible NPs using the two-stage TOPSIS method. As a result, iron-containing NPs (hematite, magnetite) were determined as the most effective and economical NPs for increasing the yield.     

An alternative pathway from hot dry rock to green hydrogen by organic Rankine cycle applications

Some researchers have been focused on electricity generation using thermal energy extraction from HDRs via Organic Rankine cycles. This new research topic creates a new pathway to reach green hydrogen for countries that have geothermal power such as Turkey. In this study, a well in the Nevşehir region that does not has the potential to be used in direct geothermal energy applications due to the absence of water was examined. By using the heat obtained from HDR by injected water, the estimated amount of electricity that can be produced with a single shaft binary organic Rankine cycle was revealed by calculating the thermal energy that can be obtained from the wells which have a surface temperature of 183 °C at 2900 m 2900 m depth. In the next step, the hydrolysis of water with electricity obtained from renewable energy and the hydrogen potential that can be produced were revealed. This hydrogen, which is estimated to be produced, can be fed directly to the natural gas lines or subjected to processes such as storage or industrial usage.