Use of axial dispersion model for determination of Sherwood number and mass transfer coefficients in a perforated rotating disc contactor

The mass transfer process in a perforated rotating disk contactor (PRDC) using a toluene-acetone-water system was investigated.The volumetric overall mass transfer coefficients are calculated in a PRDC column.Both mass transfer directions are considered in experiments.The influences of operating variables containing agitation rate,dispersed and continuous phase flow rates and mass transfer in the extraction column are studied.According to obtained results,mass transfer is significantly dependent on agitation rate,while the dispersed and continuous phase flow rates have a minor effect on mass transfer in the extraction column.Furthermore,a novel empirical correlation is developed for prediction of overall continuous phase Sherwood number based on dispersed phase holdup,Reynolds number and mass transfer direction.There has been great agreement between experimental data and predicted values using a proposed correlation for all operating conditions.     

Three modified activated carbons by different ligands for the solid phase extraction of copper and lead

In the presented work, 5,5-diphenylimidazolidine-2,4-dione (phenytoin) (DFTD), 5,5-diphenylimidazolidine-2-thione-,4-one (thiophenytoin) (DFID) and 2-(4'-methoxy-benzylidenimine) thiophenole (MBIP) modified activated carbons have been used for the solid phase extraction of copper and lead ions prior to their flame atomic absorption spectrometric determinations. The influences of the various analytical parameters including pH, amounts of reagent, sample volume and eluent type, etc. on the recovery efficiencies of copper and lead ions were investigated. The influences of alkaline, earth alkaline and some transition metals on the adsorption of the analytes were also examined. The detection limits by three sigma for analyte ions were 0.65 and 0.42 microg L(-1) using activated carbon modified with DFID; 0.52 and 0.37 microg L(-1) using activated carbon modified with DFTD and 0.46 and 0.31 microg L(-1) using activated carbon modified with MBIP for Pb(II) and Cu(II), respectively. The procedure was applied to the determination of analytes in natural waters, soil, and blood samples with satisfactory results (recoveries greater than 95%, R.S.D.'s lower than 4%).     

弯剪作用下螺栓角部连接的性能分析

研究了腹板角钢尺寸对双腹板顶底角钢的弯曲-转动性能影响。研究中采用了多个三维有限元模型,以其几何和材料特性作为影响参数。在这些模型中,所有的连接组件,如梁、柱、角钢及螺栓都采用实体单元建模。构件间的相互作用效应,如螺栓滑移和摩擦,采用表面接触算法建模。为更精确地评估连接件的性能,在栓杆上施加预拉力作为第一荷载。     

An Ultra-Low-Power Pulse Oximeter Implemented With an Energy-Efficient Transimpedance Amplifier

Pulse oximeters are ubiquitous in modern medicine to noninvasively measue the percentage of oxygenated hemoglobin in a patient's blood by comparing the transmission characteristics of red and infrared light-emitting diode light through the patient's finger with a photoreceptor. We present an analog single-chip pulse oximeter with 4.8-mW total power dissipation, which is an order of magnitude below our measurements on commercial implementations. The majority of this power reduction is due to the use of a novel logarithmic transimpedance amplifier with inherent contrast sensitivity, distributed amplification, unilateralization, and automatic loop gain control. The transimpedance amplifier, together with a photodiode current source, form a high-performance photoreceptor with characteristics similar to those found in nature, which allows LED power to be reduced. Therefore, our oximeter is well suited for portable medical applications, such as continuous home-care monitoring for elderly or chronic patients, emergency patient transport, remote soldier monitoring, and wireless medical sensing. Furthermore, our design obviates the need for an A-to-D and digital signal processor and leads to a small single-chip solution. We outline how extensions of our work could lead to submilliwatt oximeters.      

Nano SiC-Nickel Composite Coatings from a Sulfamat Bath Using Direct Current and Pulsed Direct Current

Composite plating is a method through which the fine particles of metallic or non-metallic compounds are co-deposited in a plated layer to improve surface properties such as lubrication, wear resistance, and corrosion resistance. In this study, nano-sized SiC particles were co-deposited with nickel from sulfamat bath using pulsed and direct currents. Scanning electron microscopy, microhardness, wear, and corrosion tests were carried out to characterize the coating properties. The results showed that microhardness, wear resistance, and corrosion resistance of Ni-SiC composite coatings increased compared to those of Ni films.     

Infrared waveguide fabrications with an E-beam evaporated chalcogenide glass film

Chalcogenide glasses have a variety of unique optical properties due to the intrinsic structural flexibility and bonds metastability. They are desirable materials for many applications, such as infrared communication sensors, holographic grating, optical imaging, and ultrafast nonlinear optic devices. Here, we introduce a novel electron-beam evaporation process to deposit the good quality arsenic trisulfide (As₂S₃) films and then the As₂S₃ films were used to fabricate the As₂S₃ waveguides with three approaches. The first method is photoresist lift-off. Because of the restriction of thermal budget of photoresist, the As₂S₃ film must be deposited at the room temperature. The second one is the silicon dioxide lift-off process on sapphire substrates, in which the As₂S₃ film could be evaporated at a high temperature (>180 °C) for better film quality. The third one is the plasma etching process with a metal protective thin layer in the pattern development process.     

A new approach to the cell formation problem with alternative processing routes and operation sequence

Cellular manufacturing (CM) is an important application of group technology in manufacturing systems. One of the crucial steps in the design of CM is the identification of part families and manufacturing cells. This problem is referred to as cell formation problem (CFP) in the literature. In this article, a solution approach is proposed for CFP, which considers many parameters such as machine requirement, sequence of operations, alternative processing routes, processing time, production volume, budget limitation, cost of machines, etc. Due to the NP-hardness of CFP, it cannot be efficiently solved for medium- to large-sized problems. Thus, a genetic algorithm (GA) is proposed to solve the formulated model. Comparison of the results obtained from the proposed GA to the globally optimum solutions obtained by Lingo Software and those reported in the literature reveals the effectiveness and efficiency of the proposed approach.     

Relationship between pore coarsening and mass loss during supersolidus liquid phase sintering of alpha brass

ABSTRACT

The effect of sintering variables on the zinc loss during sintering of brass was investigated. Zinc loss, evident through mass change, starts during heating of the powder at approximately 700°C. By supersolidus liquid phase sintering of the cold-pressed brass powder, the maximum amount of zinc loss occurred at lower temperatures and prolonged sintering times. At higher temperatures, especially near the zinc boiling point, the rate of zinc loss from the surface is surprisingly moderate since closing of the pores causes zinc to be trapped in the samples. At lower temperatures, in contrast, when the pores in the surface are open and there is also a lower volume fraction of liquid phase, zinc can easily escape from the samples. Generally, it was thus concluded that during sintering, zinc loss depends more strongly on the pore connectivity and the specific surface than just on the nominal vapour pressure.     

Development and optimization of self-nanoemulsifying drug delivery systems (SNEDDS) for curcumin transdermal delivery: an anti-inflammatory exposure

The purpose of this work is to develop novel lipid-based self-nanoemulsifying drug delivery systems (SNEDDS) as carriers for transdermal delivery of curcumin. SNEDDS containing black seed oil, medium chain mono- and diglycerides and surfactants, were prepared as curcumin delivery vehicles. Their formation spontaneity, morphology, droplet size, and drug loading were evaluated. Gel preparation containing two of the SNEDDS formulations were used in the carrageenan induced paw edema to evaluate the anti-inflammatory effect. Results showed droplet size as low as 71?nm. The highest drug loading was observed with SNEDDS-F6 of ～45?mg/g. In in-vivo investigation, SNEDDS-F6 exhibited significant anti-inflammatory activities in terms of 80% reduction in paw edema when compared with positive control. The prepared SNEDDS with the elevated entrapment efficiency, good transdermal penetration ability could be a suitable candidate for effective transdermal curcumin skin delivery.