An innovative fabrication of nano-HA coatings on Ti-CaP nanocomposite layer using a combination of friction stir processing and electrophoretic deposition

In the present study, a combination of friction stir processing and electrophoretic deposition was used to fabricate nano-hydroxyapatite coatings on the Ti-CaP nanocomposite surface layer. A constant tool rotation rate of 250 rpm, travel speed of 16 mm/min and plunge depth of 1.2 mm with a tool tilt angle of 3° were used to incorporate nano-hydroxyapatite particles into Ti–6Al–4V substrates. Microstructure of the stir zone was analyzed using optical and scanning electron microscopy. Microhardness profile and AFM analysis of substrates were then studied. The electrophoretic deposition of nano-HA particles was carried out at constant voltage of 30 V after 60 s. The as-deposited nano-HA coating was characterized employing scanning electron microscope and X-ray diffraction. The results of adhesion test and potentiodynamic polarization measurements showed that Ti-CaP nanocomposite layer could effectively increase the bonding strength between coating and substrate as well as corrosion resistance.     

The anti-allodynic effects of amitriptyline, gabapentin, and lidocaine in a rat model of neuropathic pain

The management of patients with neuropathic pain is challenging. There are only a few reports regarding the acute effects of the commonly used adjuvant drugs amitriptyline (AMI), gabapentin (GBP), and lidocaine (LDC) on neuropathic pain behaviors in animal models. Thus, the purpose of this study was to investigate the acute effects of AMI, GBP, and LDC on behavioral signs of mechanical allodynia and the site of action of these drugs using a rat model of neuropathic pain. Under general anesthesia with halothane, neuropathic injury was produced in rats by tightly ligating the left L5 and L6 spinal nerves. In Experiment 1, baseline mechanical allodynia data were recorded, and the animals were randomly divided into five groups: Group 1 received saline intraperitoneally (IP), Group 2 received AMI (1.5 mg/kg IP); Group 3 received GBP (50 mg/kg IP), Group 4 received an IV saline infusion for 10 min, and Group 5 received LDC (10-mg/kg IV infusion) for 10 min. Measurements of mechanical allodynia were repeated 0.5, 1, 2, and 4 h and 1, 3, and 7 days after treatment. In Experiment 2, rats were prepared similarly to the first experiment, and a single unit activity of continuous discharges of injured afferent fibers was recorded from the left L5 fascicles before and until 1 h after treatment. All animals developed neuropathic pain behavior within 7 days after surgery. All three tested drugs were effective in increasing the threshold for mechanical allodynia as early as 30 min after treatment, and the effect lasted for at least 1 h. Furthermore, AMI and LDC reduced the rate of continuing discharges of injured afferent fibers, whereas GBP did not influence these discharges. Our findings clearly demonstrate an attenuation of neuropathic pain behavior in rats treated with AMI, GBP, or LDC. Finally, the site of action of LDC seems to be primarily in the periphery, and that of GBP is exclusively central, whereas that of AMI seems to have both peripheral and central components. IMPLICATIONS: In the present study, we examined the effectiveness of three drugs commonly used for the treatment of neuropathic pain. Systemic injections of amitriptyline, gabapentin, or lidocaine produced pain-relieving effects in this established model for neuropathic pain in rats, which supports their clinical use in managing patients with neuropathic pain syndromes.     

A New Analysis Method of the Dry Sliding Wear Process Based on the Low Cycle Fatigue Theory and the Finite Element Method

In the present work, a combination of a dynamic explicit finite element model and the low cycle fatigue theory is used to simulate the steady-state abrasive wear occurring between an as-cast eutectoid steel and a carbide-tungsten disk. While the low cycle fatigue theory has been used to model wear in softer non-ferrous alloys, this work shows its applicability and accuracy for use in harder alloys, such as the eutectoid steel used in this research which is strengthened with added chromium. The novelty of this work lies in calculating the Manson-Coffin relation constants from a coupled finite element model with experimental tests instead of the previously used Slip line method. The D Manson-Coffin constant, obtained around 2, is in agreement with previous works given in the literature showing that the low cycle fatigue is a general wear mechanism in the steady-state wear of the alloy tested in this work.     

Evaluation of the robustness of the enzymatic hydrolysis in batch and continuous mode by a central composite design

The main purpose of this work is to study the ability of the enzymatic reaction. For the performance of the experiment, it is desirable to control variations so that they are minimized to the maximum extend and therefore an optimum operating point can be maintained. To achieve this target, the central composite design takes into account all interaction effects that may be useful for creating a mathematical model in agreement with the validity criteria. The model showed to be more suitable for the saccharification experiments in batch mode than in continuous mode. In batch mode, a correlation coefficient close to unity (R² = .98) was obtained. Moreover, the resulting mathematical model was satisfactory in accordance with the validation criteria. For continuous mode, the coefficient value obtained was R² = .83 indicating that the model to study the ability of the enzymatic reaction was inferior than the batch mode conditions of the analysis.

Practical applications

• The ability of the enzymatic reaction to maintain its performance at small experimental condition variations was studied.
• The central composite design conformed to criterion validity.
• A correlation coefficient close to unity (R² = .98) was obtained.

     

Study on the Pre-Treatment,Physical and Chemical Properties of Ramie Fibers Reinforced Poly (Lactic Acid) (PLA) Biocomposite

The comparative advantage of using vegetable fibers as reinforcement (fillers) attracted manufacturing industries over conventional composites. Natural fibers are purely green features that can easily decompose in a normal way to water and CO₂ when encountered with moisture during their disposal. In this research, the effect of pre-treatment and properties of ramie fibers reinforced polylactic acid (PLA) composite were studied. Before the composite preparation, ramie fibers were soaked in a solution of alkali (sodium hydroxide) and silane coupling agent to provide better compatibility between ramie fibers and PLA interface. Additionally, a design containing nine samples was conducted to study the effect of temperature, fiber volume ratio, molding pressure and time on composite fabrication. From the results, optimum processing parameters were identified based on the tensile, bending and impact strengths improvement from various tested samples. Furthermore, this study highlights the degradation process and properties of ramie fibers reinforced PLA composites by underground burial experimental procedures.     

Maximum power point tracking of a proton exchange membrane fuel cell system using PSO-PID controller

Fuel cells output power depends on the operating conditions, including cell temperature, oxygen partial pressure, hydrogen partial pressure, and membrane water content. In each particular condition, there is only one unique operating point for a fuel cell system with the maximum output. Thus, a maximum power point tracking (MPPT) controller is needed to increase the efficiency of the fuel cell systems. In this paper an efficient method based on the particle swarm optimization (PSO) and PID controller (PSO-PID) is proposed for MPPT of the proton exchange membrane (PEM) fuel cells. The closed loop system includes the PEM fuel cell, boost converter, battery and PSO-PID controller. PSO-PID controller adjusts the operating point of the PEM fuel cell to the maximum power by tuning of the boost converter duty cycle. To demonstrate the performance of the proposed algorithm, simulation results are compared with perturb and observe (P&O) and sliding mode (SM) algorithms under different operating conditions. PSO algorithm with fast convergence, high accuracy and very low power fluctuations tracks the maximum power point of the fuel cell system.     

Thermo-Mechanical Challenges in Stacked Packaging

The convergence of computing and communications dictates building up rather than out. As consumers demand more functionality in their hand-held devices, the need for more memory in a limited space is increasing, and integrating various functions into the same package is becoming more crucial. Over the past few years, die stacking has emerged as a powerful tool for satisfying these challenging integrated circuit (IC) packaging requirements. In this paper, a review of thermo-mechanical challenges for stacked die packaging is discussed.