某大型工业运输钢桁架通廊振动测试分析

皮带机运输通廊钢桁架作为工业运输通道最为常用的大跨结构形式,因其结构存在自身稳定性能差、刚度小、质量轻等特点,在皮带机高速运营过程中结构易产生振动.为确保运营安全,该文以某皮带机运输通廊钢桁架为例,对该通廊结构在各种运行工况下进行现场振动测试并结合理论分析找出结构振动原因,同时对其运行状态安全性作出验算分析,为进一步进行结构减振控制研究及加固处理提供依据.     

贵州某高速公路弃土场边坡稳定性分析

随着交通工程逐渐往山区延伸,越来越多的工程设施受限于地形条件.隧道开挖后形成的弃土场若不进行合理的布置,将为桥梁、道路工程的修建造成工程隐患.通过对某隧道出口弃土场边坡进行的工程地质调查,分析了拟建桥梁与边坡的相互作用关系,完成了岩土体力学参数取值.选取典型断面在天然工况和暴雨工况下进行了数值计算,使用了sigma/w和slope/w两个模块进行了数值计算,揭示了边坡的变形机理与稳定性状况和发展趋势,结果显示:若不采取合理的治理措施,在不利工况下,边坡将失稳,因此提出了设置抗滑桩的处置措施.     

In-situ self-reconstruction of Ni–Fe–Al hybrid phosphides nanosheet arrays enables efficient oxygen evolution in alkaline

Developing efficient oxygen evolution reaction (OER) electrocatalysts with earth-abundant elements is very important for sustainable H₂ generation via electrochemical water splitting. Here we design a crystalline-amorphous Ni–Fe–Al hybrid phosphides nanosheet arrays grown on NiFe foam for efficient OER application. Dynamic surface reorganization of phosphides at anodic/cathodic polarizations is probed by in situ Raman spectroscopy. The reconstructed amorphous Ni(Fe)OOH species are determined as the active phases that facilitate the OER process. This unique electrode shows highly catalytic activity toward water oxidation, achieving the current densities of 10 and 100 mA cm^?2 at 181 and 214 mV in 1 M KOH, respectively. Meanwhile, it also exhibits excellent stability at a large current density of 100 mA cm^?2 for over 60 h. This work reveals the dynamic structural transformation of pre-catalyst in realistic conditions and highlights the important role of oxyhydroxides as real reactive species in OER process with high activity.     

Worldwide aflatoxin contamination of agricultural products and foods: From occurrence to control

Aflatoxins represent a global public health and economic concern as they are responsible for significant adverse health and economic issues affecting consumers and farmers worldwide. Produced by fungal species from the Aspergillus genus, aflatoxins are a toxic, mutagenic, and carcinogenic group of fungal metabolites that routinely contaminate food and agricultural products. Climate and diet are essential factors in the aflatoxin contamination of food and subsequent human exposure process. Countri es with warmer climates and staple foods that are aflatoxin-susceptible shoulder a substantial portion of the global aflatoxins burden. Enactment of regulations, prevention of pre- and postharvest contamination, decontamination, and detoxification have been used to prevent human dietary exposure to aflatoxin. Exploiting their chemical and structural properties, means are devised to detect and quantify aflatoxin presence in foods. Herein, recent developments in several important aspects impacting aflatoxin contamination of the food supply, including: fungal producers of the toxin, occurrence in food, worldwide regulations, detection methods, preventive strategies, and removal and degradation methods were reviewed and presented. In conclusion, aflatoxin continues to be a major food safety problem, especially in developing countries where regulatory limits do not exist or are not adequately enforced. Finally, knowledge gaps and current challenges in each discussed aspect were identified, and new solutions were proposed.     

Investigating the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life by in-situ hydrogen permeation

In this work, we investigate the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life of a high strength pipeline steel. Both fracture toughness test and fatigue life test are carried out under different hydrogen partial pressure. The experimental results show that with the increasing of hydrogen partial pressure, fracture toughness and fatigue life decrease and the decrease trends gradually flatten out. Hydrogen has a larger effect on fatigue life than fracture toughness. Only 3% hydrogen gas can cause a 67.7% decrease of fatigue life. The in-situ hydrogen permeation test is performed respectively in 2 MPa, 5 MPa and 8 MPa hydrogen partial pressure. With the increasing of hydrogen partial pressure, the increase trend of hydrogen permeation current gradually tends to be gentle, which indicates that the hydrogen atoms entering into the material gradually become saturated. This result can be used to clarify the influence mechanism of hydrogen partial pressure on fracture toughness and fatigue life.     

一种远程控制智能防坠楼窗户设计

针对传统窗户和现有的智能窗户进行分析,设计了一种远程控制智能防坠楼窗户,包括基本窗体、电动控制中心、电磁锁、压力传感器、雨滴传感器、烟雾传感器、温湿度传感器等作为系统的信号收集与处理源.电动控制中心通过电机控制窗户左右平移开合,电机作用使窗户停止;通过压力传感器和电磁锁的控制使安全防护网张开;结合App控制窗户开合及环境信息反馈;按下紧急按钮有警示灯光并自动报警.这些对于高空防坠楼、提高生活品质等都有重要意义.     

2-Hydroxy-4-methoxybenzaldehyde inhibits the growth of Aspergillus flavus via damaging cell wall,cell membrane,manipulating respiration thus creating a promising antifungal effect on corn kernels

This study investigated the antifungal activity and the potential antifungal mechanisms of 2-hydroxy-4-methoxybenzaldehyde (HMB) against Aspergillus flavus (A. flavus). The minimum inhibitory concentration (MIC) of HMB in preventing spore germination was 70 μg mL⁻¹. HMB at MIC disrupted cell wall integrity by reducing the number of septa by 86.66% (P < 0.05) in mycelia and increased cell membrane permeability by about 14-fold (P < 0.05) evidenced by propidium iodide (PI) staining. Furthermore, HMB at MIC inhibited respiration by 33.33%. These results revealed that the antifungal activity of HMB against A. flavus could be attributed to the damaged cell wall integrity, cell membrane permeability and respiration metabolism. What’s more, A. flavus was completely restrained in corn kernels due to HMB. Therefore, HMB could be applied as an effective antifungal agent.     

Image authentication and tamper localization based on relative difference between DCT coefficient and its estimated value

Digital images are increasingly transmitted over non-secure channels such as Internet, therefore image authentication techniques have recently gained great attention due to their importance for a large number of multimedia applications. To protect the authenticity of images, several approaches have been proposed. These approaches include conventional cryptography, semi-fragile watermarking and digital signatures. In this paper, we propose two techniques of the same type based on what we call characteristic data digest. Both techniques can blindly detect and localize malicious tampering, while maintaining reasonable tolerance to conventional content-preserving manipulations. The characteristic data is derived from the relative difference between each pair of selected DCT coefficient, AC for one technique and DC for another technique, in a central block and its counterpart estimated by the center block and its adjacent blocks. In order to maintain the relative difference relationship when the image undergoes legitimate processing, we make a pre-compensation for the coefficients. Experimental results show that our techniques are significantly superior to semi-fragile techniques under the condition of the same image fidelity, especially in tolerance range of legitimate processing, and/or the ability to detect and localize the tampered area. Due to the simplicity of the algorithms, our techniques can be used in video frame authentication, and even other digital media. In addition, this kind of proposed techniques can be extended to use other characteristic data, such as high-level moment, statistical data of images, and so on.

     

Observer-based Intermittent Consensus Control of Nonlinear Singular Multi-agent Systems

International Journal of Control, Automation and Systems - This paper studies the leader-following consensus for a class of nonlinear singular multi-agent systems. Unlike the related works, the...