The effect of sintering time on the densification and mechanical properties of a mechanically alloyed Cr–Mn–N stainless steel

Sintering is an essential stage in powder metallurgy, which affects the final microstructure and performance of the part. This study is concerned with the sintering and mechanical behaviors of Fe–18Cr–8Mn–0.9N stainless steel prepared from mechanically alloyed amorphous/nanocrystalline powders. The contribution of sintering time to the densification at 1100 °C is considered and a sluggish densification is found for the alloy. Furthermore, the correlation between the microstructure and mechanical properties of the fabricated porous parts is studied. It is found that the yield stress is affected by both porosity and the material’s intrinsic yield strength. Nonetheless, the effect of porosity on the overall hardness typically prevails over the effect of matrix hardness. Interestingly, even after sintering at 1100 °C for up to 20 h, the nanometric structure of the material is retained.     

New Sizing Agents and Flocculants Derived From Chitosan

Approaches for development of novel textile sizing agents and flocculants based on acid‐hydrolyzed and carboxymethylated chitosans were undertaken. Factors affecting both hydrolysis and carboxymethylation were investigated. Aqueous solutions of hydrolyzed chitosans or carboxymethyl chitosans were applied to light cotton to test the feasibility of such water‐soluble chitosans for textile sizing. The size add‐on on the light fabric is directly related to the concentration of the hydrolyzed or carboxymethyl chitosan in the sizing solution and so does the apparent viscosity of the latter. Hundred percent size removal could be achieved with the hydrolyzed chitosans. A different situation was encountered with carboxymethyl chitosan where the percent size removal increases from 81% to 95% by increasing its concentration in the sizing solution from 5% to 15%. The tensile strength of the sized fabrics increased by about 55% and the elongation at break decreased on average by about 3%. The suitability of the hydrolyzed chitosans and carboxymethyl chitosans as flocculants was also investigated. The degree of flocculation was followed at different pHs by determination of the transmission%. Efficiency of flocculation at pH 6 was greater than at pH 8.     

Air-breathing microbial fuel cell with enhanced performance using nanocomposite proton exchange membranes

This work aims to improve the performance of air-breathing microbial fuel cells (MFCs) through using hydrocarbon polymer based nanocomposite proton exchange membranes. Accordingly, nanocomposite membranes based on sulfonated poly(ether ether ketone) (SPEEK) and montmorillonite (MMT) were investigated for such an application. Although the incorporation of MMT into SPEEK membranes resulted in reduced oxygen permeability as well as proton conductivity, but the overall selectivity was found to be improved. MFC tests revealed that using the optimized nanocomposite membrane (SPEEK-70/MMT-3 wt%) results in a considerably higher open circuit voltage (OCV) compared to the corresponding neat membrane. Moreover, it was found that the SPEEK-70/MMT-3 wt% membrane is able to provide about 40% more power output than Nafion^®117. On the account of high proton conductivity, low oxygen permeability, high electrochemical performance, ease of preparation and low cost, hydrocarbon based nanocomposite PEMs could be considered as promising electrolytes to enhance the performance of MFCs.     

Synergistic use of ultra-high-performance fiber-reinforced concrete (UHPFRC) and carbon fiber-reinforced polymer (CFRP) for improving the impact resistance of concrete-filled steel tubes

Concrete-filled steel tubes (CFSTs) have received growing attention, owing to their rapid construction, reduced labor requirement, and reasonable material cost. While in service, the CFSTs can be subjected to unexpected impact loads, originating from vehicle and vessel collision, as well as water- and wind-borne debris impact. Such extreme loading events often cause a partial or complete failure of conventional CFSTs, risking the safety and performance of the entire structural systems that rely on them. To address this issue, the current study explores how two advanced composite materials, including ultra-high-performance fiber-reinforced concrete (UHPFRC) and carbon fiber-reinforced polymer (CFRP), can be utilized to provide superior mechanical properties and minimize the vulnerability of CFSTs to impact loads. The composite materials under consideration are appropriate for both new and existing structures, in which normal-strength concrete can be replaced with UHPFRC, while CFRP sheets can further strengthen the CFSTs. For obtaining in-depth insights, a computational framework validated with the experimental tests was developed in the current study. Using a set of representative impact scenarios, various response measures, such as internal forces and deflections, as well as the energy absorbed by the CFSTs, were recorded during impact simulations. The investigations were then further extended to capture the influence of the main design parameters related to concrete, CFRP, and steel tube. From the conducted investigations, an energy absorption index was introduced, as a measure to evaluate the performance of CFSTs under impact loads.     

Multiple human 3D pose estimation from multiview images

Multimedia Tools and Applications - Multiple human 3D pose estimation is a challenging task. It is mainly because of large variations in the scale and pose of humans, fast motions, multiple persons...     

Dynamic modeling of tree-type robotic systems by combining $3\times3$ rotation and 4×4$4\times4$ transformation matrices

The objective of this article is to present a systematic method of deriving the mathematical formulation for the oblique impact of a tree-type robotic manipulator. The dynamic response of this system (confined within a curved-wall environment) is expressed by two diverse models. A set of differential equations is employed to obtain the dynamic behavior of the system when it has no contact with any object in its environment (flying phase), and a set of algebraic equations is used to describe the collision of the system with the curved walls (impact phase). The Gibbs–Appell formulation in recursive form and the Newton’s impact law are utilized to derive the governing equations of this robotic system for the flying and impact phases, respectively. The main innovation of this article is the development of an automatic approach based on the combination of \(3\times3\) rotation and \(4\times4\) transformation matrices. In fact, this is the first time the merits of \(3\times3\) rotation matrices (i.e., improving the computational efficiency of the developed algorithm) have been merged with the capabilities of \(4\times4\) transformation matrices (i.e., deriving more compact motion equations by combining rotations with translations). Finally, a case study involving a tree-type robotic system with 12 degrees of freedom has been simulated to show the efficiency of the proposed dynamic modeling.     

Adaptive green traffic signal controlling using vehicular communication

The importance of using adaptive traffic signal control for figuring out the unpredictable traffic congestion in today’s metropolitan life cannot be overemphasized. The vehicular ad hoc network (VANET), as an integral component of intelligent transportation systems (ITSs), is a new potent technology that has recently gained the attention of academics to replace traditional instruments for providing information for adaptive traffic signal controlling systems (TSCSs). Meanwhile, the suggestions of VANET-based TSCS approaches have some weaknesses: (1) imperfect compatibility of signal timing algorithms with the obtained VANET-based data types, and (2) inefficient process of gathering and transmitting vehicle density information from the perspective of network quality of service (QoS). This paper proposes an approach that reduces the aforementioned problems and improves the performance of TSCS by decreasing the vehicle waiting time, and subsequently their pollutant emissions at intersections. To achieve these goals, a combination of vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications is used. The V2V communication scheme incorporates the procedure of density calculation of vehicles in clusters, and V2I communication is employed to transfer the computed density information and prioritized movements information to the road side traffic controller. The main traffic input for applying traffic assessment in this approach is the queue length of vehicle clusters at the intersections. The proposed approach is compared with one of the popular VANET-based related approaches called MC-DRIVE in addition to the traditional simple adaptive TSCS that uses the Webster method. The evaluation results show the superiority of the proposed approach based on both traffic and network QoS criteria.     

叔丁醇脱水制备异丁烯新方法

叔丁醇脱水生产异丁烯的关键是如何及时将叔丁醇生产异丁烯过程中的副产水移去。本实验首次采用三元共沸脱水剂的新技术，及时把副产物移走，以保证异丁烯生成速率高且平稳。实际生产表明：运用该新技术生产异丁烯比目前国内其它生产技术生产异丁烯速度提高５～６倍。     

Controlled release from polyurethane films: Drug release mechanisms

In this study, polyurethane-films loaded with diclofenac were used to analyze the drug release kinetics and mechanisms. For this purpose, the experimental procedures were developed under static and dynamic conditions with different initial drug loads of 10, 20, and 30%. In the dynamic condition, to better simulate the biological flow, drug release measurements were investigated at flow rates of 7.5 and 23.5 ml/s. These values indicate the flow rate of the internal carotid artery (ICA) for a normal state of a body and for a person during the exercise, respectively. The experimental data were analyzed and adjusted by Higuchi, Korsmeyer–Peppas, First-order, zero-order, and Peppas–Sahlin models in order to understand the mechanisms contributed. Finally, drug release mechanisms were specified by investigating the model correlation coefficients. Experimental results showed that increasing the flow rate and initial drug loads enhance drug liberation. In addition, the rate of release is more influenced by the drug dosage in the static state. The analysis revealed that diffusion, burst, and osmotic pressure are the principal mechanisms contributed. Moreover, Fickian type was the dominant mechanism at all duration of release. However, it was discovered using Peppas–Sahlin model that the contribution of the diffusion mechanism decreases with increasing flow rate and initial dosage. Furthermore, the tests at different drug dosages showed that the number of stages in medication release profile is independent of the flow rate and the medicine percentage. One can conclude that the drug release kinetic in static state is more influenced by drug dosage compared with dynamic state.     

用自组织方法分析油藏动态

数据组合处理方法（GMDH）是70年代发展起来的一种启发式自组织建模方法,由前苏联学者伊万年科（Ivakhnenko,1970）借助生物控制论中的自组织原理,用启发式的方法提出的;它能有效的解决复杂非线性系统的建模问题.简单介绍了此方法的基本原理及计算步骤,首次探讨了在分析油藏动态方面的应用,并以南阳油田的实际数据为例,建立了区块地层压力预测模型和区块产量预测模型,其预测相对误差在5%以内,表明该方法实用可行.最后还讨论了该方法在油田开发中的应用前景.