Hydroxyapatite deposition study through polymeric process on commercially pure Ti surfaces modified by laser beam irradiation

Many techniques have been used to coat metallic substrate with bioceramics. The aim of this study was to study the physical-chemical characteristics of polyvinylidene fluoride (α-PVDF)/hydroxyapatite (HA) composite coating, obtained by casting method, on commercially pure titanium (α-CP Ti) substrate surface modified by laser beam irradiation. The preparation of coating was done for mixing α-PVDF pellets shape dissolved in dimethylacetamide (DMA) with HA/DMA emulsion. The mixture was poured onto the α-CP Ti sample and left to dry in an oven. CP Ti plates were coated with α-PVDF/HA composite film, in proportions of 100/00 and 60/40 in weight, and characterized by particle size analysis, scanning electron microscopy, energy dispersive spectroscopy (EDS), X-ray diffractometry, thickness measurement and contact angle. Uniform coating with a small thickness variation along the coated surface was successfully obtained.     

An integrated qualitative and quantitative modeling framework for computer‐assisted HAZOP studies

The article proposes a novel practical framework for computer‐assisted hazard and operability (HAZOP) that integrates qualitative reasoning about system function with quantitative dynamic simulation in order to facilitate detailed specific HAZOP analysis. The practical framework is demonstrated and validated on a case study concerning a three‐phase separation process. The multilevel flow modeling (MFM) methodology is used to represent the plant goals and functions. First, means‐end analysis is used to identify and formulate the intention of the process design in terms of components, functions, objectives, and goals on different abstraction levels. Based on this abstraction, qualitative functional models are constructed for the process. Next MFM‐specified causal rules are extended with systems specific features to enable proper reasoning. Finally, systematic HAZOP analysis is performed to identify safety critical operations, its causes and consequences. The outcome is a qualitative hazard analysis of selected process deviations from normal operations and their consequences as input to a traditional HAZOP table. The list of unacceptable high risk deviations identified by the qualitative HAZOP analysis is used as input for rigorous analysis and evaluation by the quantitative analysis part of the framework. To this end, dynamic first‐principles modeling is used to simulate the system behavior and thereby complement the results of the qualitative analysis part. The practical framework for computer‐assisted HAZOP studies introduced in this article allows the HAZOP team to devote more attention to high consequence hazards. © 2014 American Institute of Chemical Engineers AIChE J 60: 4150–4173, 2014     

Preparation of rare earth-doped ZnO hierarchical micro/nanospheres and their enhanced photocatalytic activity under visible light irradiation

Rare earth-doped ZnO hierarchical micro/nanospheres were prepared by a facile chemical precipitation method and characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, UV-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. The results showed that the as-synthesized products were well-crystalline and accumulated by large amount of interleaving nanosheets. It was also observed that the rare earth doping increased the visible light absorption ability of the catalysts and red shift for rare earth-doped ZnO products appeared when compared to pure ZnO. The photocatalytic studies revealed that all the rare earth-doped ZnO products exhibited excellent photocatalytic degradation of phenol compared with the pure ZnO and commercial TiO₂ under visible light irradiation. Nd-doped ZnO had the highest photocatalytic activity among all of the rare earth-doped ZnO products studied. The optimal Nd content was 2.0 at% under visible light irradiation. The enhanced photocatalytic performance of rare earth-doped ZnO products can be attributed to the increase in the rate of separation of photogenerated electron–hole pairs and hydroxyl radicals generation ability as evidenced by photoluminescence spectra.     

Thermal behavior in a 180-deg turned channel with the perforation divider under rotational condition

This study provided a new configuration of the 180-deg turned channel with a perforation divider. The perforations cross the divider let the coolant at the first duct to bypass into the second duct early, preventing from the local high temperature at the downstream zone. Additionally, the perforation-induced disturbing flow should enhance the total heat transfer. This work experimentally investigated the heat transfer behaviors of such system under the rotational condition. The results indicated that the perforation would reduce the raise of the local heat transfer at the turned region. Besides, the rotation would obviously influence the local heat transfer on the leading and trailing surfaces. Furthermore, the effect of rotation on the total heat transfer was insignificant. Finally, the perforation system with the relative perforation diameter d/D_h = 2/4 had the similar total heat-transfer capacity with that without perforation; the total heat-transfer capacity of the perforation system with d/D_h = 1/4 was around 20% higher than the non-perforation one.     

Implementation of a novel large moving range submicrometer positioner

A novel, compact and two degree-of-freedoms (DOF) submicrometer positioner with a large moving range is presented in this paper. The design of the positioner utilizes a monolithic parallel flexure mechanism with built-in electromagnetic actuators and eddy current sensors to achieve the precision 2-DOF motion. The travel range of the positioner is 1000 μm/5 mrad and which depend on the eddy current sensor’s range of measurement (ROM) and electromagnetic actuator’s effective length. The analytical model and its dynamics were analyzed and derived. The whole control architecture takes the measured configuration parameters and endeavors to control the positioner motion by regulating the currents in the electromagnetic actuators. To increase the compactness and stability of the positioner, a self-tuning adaptive (STA) controller was analyzed and proposed. From the experimental results, satisfactory performances of the system, including stiffness and precision, have been successfully demonstrated.     

One-dimensional ZnO nanorods doped with neodymium for enhanced resorcinol degradation under sunlight irradiation

Neodymium-doped ZnO nanorods (Nd/ZNRs) were prepared for the first time by a simple and surfactant-free solvothermal route. The synthesized samples were characterized using different instrumental techniques. The photoluminescence results showed that the Nd(2.0 at%)/ZNRs exhibited the highest separation rate of charge carriers and the highest formation rate of hydroxyl radicals. The photocatalytic activities of synthesized samples were investigated toward the degradation of endocrine disrupting chemical resorcinol under natural sunlight irradiation. Among the samples, Nd(2.0 at%)/ZNRs showed considerable improvement in the photocatalytic activity for the resorcinol degradation as compared to ZNRs and commercial TiO₂. Kinetic studies revealed that the photocatalytic degradation of resorcinol obeyed pseudo-first-order kinetic. The high-performance liquid chromatography and total organic carbon analyses also demonstrated the progressive mineralization of resorcinol into carbon dioxide and water. Furthermore, high stability of Nd/ZNRs in photocatalytic reaction also demonstrated promising potential toward practical applications in purifying environmental pollutants.     

A Simulation Study of a Hybrid Channel Assignment Scheme for Cellular Land-Mobile Radio Systems with Erlang-C Service

This paper presents a simulation study of a cellular highcapacity land-mobile radio system using the hybrid channel assignment scheme with Erlang-Cservice. The performance of this system in regard to the probability of queueing, the average queueing time, and the average number of queued calls is evaluated and compared with that of the systems employing either the fixed or the dynamic channel assignment scheme.     

Abrasive wear mechanisms and the grit size effect

The classical cutting model for abrasive wear deviates from reality in that it cannot predict the effect of grit size on wear and that the observed wear rates are at least an order of magnitude smaller than the predicted values. Through experimental and theoretical work it is shown in this paper that the grit size effect is a consequence of the transition from a cutting mechanism to a sliding wear mechanism. The wear coefficient is shown to be less than that predicted by a cutting model owing to the plastic deformation of the surface being worn.     

An automatic thin-film thickness indicator implemented with a Z-80 microcomputer

An automatic display of thin-film thickness during vacuum deposition based on Z-80 microcomputer is demonstrated. The film thickness can be displayed directly in nm during deposition whenever a key is touched. The maximum deposition thickness and the measuring accuracy can be easily adjusted by loading a proper time constant to channels 0 and I of the counter-timer-circuit.