Novel method for treatment of hollow fiber membranes using hypochlorite

A novel hypochlorite treatment method that enhances hydraulic permeability of hollow fiber membranes used in ultra-filtration was successfully devised and tested. Dope containing polysulfone/poly vinyl pyrrolidon (PVP-K90)/N-methyl-2-pyrrolidone (NMP) in mass ratio of 15:5:80, respectively, were used to produce hollow fibers via dry-jet wet spinning process. NMP in 1:1 ratio and distilled water were used as bore fluid. Hollow fiber membrane samples were post-treated using the novel, 95°C water and traditional hypochlorite treatments. State of membranes before and after post-treatment were morphologically compared using SEM microphotographs of fiber cross-section in conjuncton with image proceesing techniques. It was observed that in general both the novel and the traditional methods results in elimination of PVP swelling alone with alteration of pore size and pore distribution. This was confirmed by an increase in water flux of the hollow fibers that were subjected to these two post-treatment methods. Atomic force microscopy analysis vividly pointed to an intense increase in the roughness of the inner and outer surfaces of the membranes. This was attributed to the effect of post-treatment methods. It was found that in general post-treatments involving hypochlorite, increases the surface roughness of the membranes. However, increase in rate of the roughness of inner surface of traditionally hypochlorite treated hollow fiber membrane was found to be much higher than those subjected to the novel treatment method. It was established that the developed novel hypochlorite treatment method can be successfully used for production of high permeable hollow fiber membranes which have vast potential in therapeutic applications.     

Limiting electromagnetic interference due to on-board devices from on-bench tests

Electromagnetic interference due to on-board devices may differ from what can be expected after on-bench tests. An approach, aimed at ensuring that the on-board device performance is satisfactory, is presented. It is based on the computation of new limits for on-bench tests and is illustrated in a very simple configuration.     

Adaptive methods to preserve power amplifier linearity under antenna mismatch conditions

Under antenna mismatch conditions at high output power, voltage clipping (due to collector voltage saturation) is the main cause of power amplifier linearity degradation. To preserve linearity under mismatch three adaptive methods are presented that make use of the detected minimum collector peak voltage. This detected signal controls either the amplifier output power, load-line, or supply voltage. These concepts are generalized analytically, and calculated results compare well to simulations. Measurements demonstrate am error vector magnitude reduction of 5% and an adjacent channel power ratio improvement of 10 dB at a voltage standing wave ratio of 4 for an EDGE amplifier with adaptively controlled output power. These adaptive methods offer a cost and size effective alternative to the use of an isolator.     

The Value of the Sense of Community and Neighbouring

Today, urbanites are less involved in local communities which has resulted in a claim that the significance of local communities and the role of space and neighbourhood layout in the creation of local communities has been exaggerated. Such claims imply that feeling a sense of community among neighbourhood’s residents or an attachment to the community is not a value to the neighbourhood. Community research has developed a few indices for evaluating the sense of community and community attachment, but has not focused on the significance of a sense of community in neighbourhoods. The aim of this paper is to explore and review the significance of the sense of community, community attachment and neighbouring in the context of neighbourhoods. This review suggests that feeling a sense of community, attachment to community and neighbouring relationships can increase the feeling of safety and security, residential satisfaction, community identity, civic participation and mental health and well-being.     

Flavour Les Houches Accord: Interfacing flavour related codes

We present the Flavour Les Houches Accord (FLHA) which specifies a set of conventions for flavour-related parameters and observables. The FLHA uses the generic SUSY Les Houches Accord (SLHA) file structure. It defines the relevant Standard Model masses, Wilson coefficients, decay constants, bag parameters, flavour observables, etc. The accord provides a universal and model-independent interface between codes evaluating and/or using flavour-related observables.     

Rooster Tail Wave Hydraulics of Chutes

Supercritical flow below chute piers generates an aerated flow known as rooster tail. Their behavior varies along the spillway or chute for different Froude numbers. This paper aims to analyze the effect of various parameters including the Froude number, approach flow depth, chute pier width, and presence of a deflector ramp on the rooster tail geometry. Aerator systems, which generally include deflectors in chutes, are effective in the generation of rooster tails. The interaction between a deflector and supercritical flow of chutes causes a higher rooster tail. New equations define the rooster tail geometry in the presence of a deflector. The air concentration profile was measured and the effects of deflectors on the air entrainment were studied.     

Analytical investigation of heat transfer enhancement in a channel partially filled with a porous material under local thermal non-equilibrium condition

Forced convection through a channel partially filled with a porous medium is investigated analytically in the present work. Thermally developed condition is considered and the local thermal non-equilibrium model is utilized to obtain the exact solutions of both fluid and solid temperature fields for flow inside the porous material as well as for flow in the clear region. Nusselt number is obtained in terms of the porous insert thickness (S), porosity (?) as well as pertinent parameters such as thermal conductivity ratio (k), Biot number (Bi), and Darcy number (Da). The values of S by which the temperature difference between the two phases approach to zero, for different values of Bi, k, and Da number are obtained. It is found that three mechanisms affect the Nu number i: clear fluid conduction ii: internal heat exchange in the porous medium iii: channeling effect in the clear flow. The value of S, which yields the highest Nu number is found to vary linearly from 0.8 to 0.97 as the value of Da decreases from 10⁻³ to 10⁻⁷. At the expense of reasonable pressure drop the optimum thickness of porous material in order to enhance the heat transfer rate is found S = 0.8.     

Diffusion and hydrodynamic instabilities in gaseous detonations

To clarify the role played by diffusion in detonation structure, two-dimensional numerical simulations are performed by solving the Navier–Stokes equations and considering the single step Arrhenius kinetic as reaction model. The effect of diffusion on the generation of vortices produced by hydrodynamic instabilities (Richtmyer–Meshkov (RM) and Kelvin Helmholtz (KH) instabilities) is investigated. Mixtures with both low and high activation energies, characterized by their regular and irregular detonation structures, are considered. The computations are performed with resolutions ranging from 25 to 10³ cells per half reaction length of the ZND structure. Resolution studies of the Navier–Stokes solution for irregular detonations in moderate activation energy mixtures shows that to capture a proper structure, to be at least in qualitative agreement with experimental observations, resolution more that 300 cells per half reaction length is required. However, in mixtures with low activation energy a resolution of 25 cells per half reaction length gives a reasonable physical structure of the detonation. Results provided by very high resolution for irregular structure detonations reveal that the major effect of diffusion occurs at shear layers and unburned pockets boundaries. Diffusion suppresses the small-scale vortices produced by KH instabilities and decreases the turbulent mixing rate of burned and partly burned gases at shear layers. However, behind the shock front, where less concentration of small-scale vortices exist, the diffusion of heat and mass from neighboring hot regions of burned material to the unreacted gases increases the burning rate of the un-reacted pockets. Comparison of the structure obtained by solving the Euler equations with the solution of the Navier–Stokes equations shows that, the strength of the shock front in Navier–Stokes solution is higher than that in Euler solution. Due to the absence of hydrodynamic instabilities behind the main front of regular structure detonations, the results obtained by solving the Euler equations and Navier–Stokes equations are similar for detonations with regular structure even in high resolution simulations.     

Controlled Laser Transformation Hardening of Martensitic Stainless Steel by Pulsed Nd：YAG Laser

Laser transformation hardening(LTH) was applied to the surface of the AISI 420 martensitic stainless steel by a pulsed Nd:YAG laser to obtain optimum hardness.The influences of process para-meters(laser pulse energy,duration time,and travel speed) on the depth and hardness of laser treated area were investigated.Image analysis of SEM micros-tructure of AISI 420 showed that plate-like carbide have almost fully and(30~40)% of globular carbide particles dissolved into the matrix after laser transformation hard...