Non-linear analysis of finite hydrodynamic journal bearings in laminar and turbulent flow regimes

The Navier-Stokes equations were modified by adopting the non-linear turbulence theory proposed by Constantinescu to take into account the turbulent stresses. The modified equations were solved by the finite element method using Galerkin's technique and a suitable iterative procedure.The performance characteristics of a finite hydrodynamic journal bearing (aspect ratio b = 1) were studied in terms of the load-carrying capacity, non-dimensional stiffness and damping coefficients and critical journal mass at various eccentricities for Reynolds' numbers up to 13 300. The computed results are compared with those obtained using the twodimensional triangular element formulation and the linearized turbulence theory.     

Effect of Penetration Enhancers on Transdermal Delivery of Timolol Maleate

In vitro skin permeation of Timolol maleate through human cadaver skin was studied using Franz diffusion cell. The results indicate that the drug penetrates poorly through human cadaver skin. However, skin penetration enhancers such as dimethyl sulfoxide (DMSO), oleic acid (OA) and lauryl chloride (LC) enhanced the permeability of Timolol maleate (TM) through human cadaver skin. The permeation enhancement of drug was maximum by lauryl chloride amongst the three enhancers. Moreover, lauryl chloride increases the permeation of drug through skin with increase in the time of application and concentration on skin. The change in lag time was also observed.     

31P nuclear magnetic resonance study of phospholipids in ischemia/reperfusion injury in a rat fatty liver model

Obese Zucker rats are susceptible to increased hepatic ischemia/reperfusion (I/RP) injury. Increased lipid peroxidation occurs in this model with warm ischemia. We hypothesized that a severe depletion of phospholipids (PL) occurs with warm I/RP in fatty livers. Obese (Ob) and lean (Ln) Zucker rats were subjected to 90 min of in vivo partial hepatic warm I followed by RP. Total lipids extracted from one gm of liver (median lobe) taken at the end of 1, 2 and 6 hr of RP and sham (Sh) surgery (n=5 Ln & Ob) were analyzed by 202.3 MHz 31P NMR, which provided good resolution of individual PL. Obese (Sh) rats contained 22% more PL than Ln (P= < 0.01). Ischemia caused similar decreases in PL in both Ob (to 67% Sh) and Ln rats (62%). Following 2 hr RP, PL in Ob rats decreased further (46% Sh) and recovered only marginally at 6 hr (53%), in marked contrast to the rapid recovery in Ln to preischemic levels (110% Sh at both 2 and 6 hr; P=<0.001). Mole percents of individual PL did not change significantly except for lysophosphatidylcholine, which increased from 0.43 to 1.3% (Sh vs. 6 hr RP) in the Ob, but decreased from 0.98 to 0.52% in Ln animals (P = <0.001). Fatty livers thus are more vulnerable to phospholipid depletion in response to warm ischemia/reperfusion than normal livers.     

A general method to locate a body in 3-D space using X-ray exposures in two oblique planesUne methode geenrale pour identifier un corps dans l'escape tridimensionnel par l'emploi d'images radiographiques dans les plans obliques

Based on the data obtained from X-rays taken in two oblique planes, this paper presents a generalized method to locate the position of a point in a fixed frame of reference. In particular, based on an estimate of over-all error, the paper illustrates a method to obtain the bounded region within which the object point may lie.     

Anomalous electrical transport behavior in nanocrystalline nickel

We have prepared nanocrystalline Ni (n-Ni) samples of grain sizes 40-100?nm using a polyol method and investigated the electrical transport on their compacted pellets in the temperature range 3-300?K. The resistivity, ρ, decreases nearly linearly with increase in compaction pressure but without a change in its slope, dρ/dT. ρ is anomalously large, and is strongly temperature and grain-size dependent. The resistivity at room temperature, ρ(300?K), is in the range ～40-759?μΩ?cm but with a positive coefficient of resistivity α (metallic). This is associated with the significantly enhanced dρ/dT with increase in residual resistivity ρ(0). These characteristics are attributed to the disorder in the grain boundaries that represents effectively a series resistor network.     

The fate of chlorine in recirculating cooling towers Field results

Chlorine and chloramines are volatile compounds which are stripped (“flashed off”) from recirculating cooling water systems by the large volumes of air which flow through the water in the cooling tower. The fraction of a volatile gas, such as hypochlorous acid (HOCl), which is removed by stripping is determined by Henry's constant H for that gas: H = X_G/X_L, where X_G is the mole fraction of the gas in the air and X_L is the mole fraction of the gas in the water. We have measured H for HOCl, OCl⁻, NH₃, NH₂Cl, NHCl₂ and NCl₃ at 20 and 40°C. We found H = 0.076 for HOCl, compared to 0.71 for NH₃, at 20°C. At 40°C, H was about 2.5-fold larger for HOCl. This means that 10–15% of the HOCl is stripped from cooling water on each passage through a typical cooling tower. The measured flashoff of free available chlorine (HOCl + OCl⁻) was markedly pH-sensitive with a pK of 7.5, exactly as expected if HOCl is volatile but OCl⁻ is not. The data permit a quantitative understanding of the fate of chlorine in cooling systems. The values of H at 40°C for NH₂Cl, NHCl₂ and NCl₃ were 1.28, 3.76 and 1067. This means that all of the chloramines are quickly stripped in a cooling tower.     

Fabrication and Wear Behavior of Nanostructured Plasma-Sprayed 6061Al-SiCp Composite Coating

6061Al powder with 15 wt.% SiC particulate (SiC_p) reinforcement was mechanically alloyed (MA) in a high-energy attrition mill. The MA powder was then plasma sprayed onto weathering steel (Cor-Ten A242) substrate using an atmospheric plasma spray process. Results of particle size analysis and scanning electron microscopy show that the addition of SiC particles as the reinforcement influences on the matrix grain size and morphology. XRD studies revealed embedment of SiC_p in the MA-processed composite powder, and nanocrystals in the MA powder and the coating. Microstructural studies showed a uniform distribution of reinforced SiC particles in the coating. The porosity level in the coating was as low as 2% while the coating hardness was increased to 232VHN. The adhesion strength of the coatings was high and this was attributed to higher degree of diffusion at the interface. The wear rate in the coatings was evaluated using a pin-on-disk type tribometer and found to decrease by 50% compared to the 6061Al matrix coating. The wear mechanism in the coating was delamination and oxidative type.     

Enhanced mechanical strength and biocompatibility of electrospun polycaprolactone-gelatin scaffold with surface deposited nano-hydroxyapatite

In this study for the first time, we compared physico-chemical and biological properties of polycaprolactone-gelatin-hydroxyapatite scaffolds of two types: one in which the nano-hydroxyapatite (n-HA) was deposited on the surface of electrospun polycaprolactone-gelatin (PCG) fibers via alternate soaking process (PCG-HA_AS) and other in which hydroxyapatite (HA) powders were blended in electrospinning solution of PCG (PCG-HA_B). The microstructure of fibers was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which showed n-HA particles on the surface of the PCG-HA_AS scaffold and embedded HA particles in the interior of the PCG-HA_B fibers. PCG-HA_AS fibers exhibited the better Young's moduli and tensile strength as compared to PCG-HA_B fibers. Biological properties such as cell proliferation, cell attachment and alkaline phosphatase activity (ALP) were determined by growing human osteosarcoma cells (MG-63) over the scaffolds. Cell proliferation and confocal results clearly indicated that the presence of hydroxyapatite on the surface of the PCG-HA_AS scaffold promoted better cellular adhesion and proliferation as compared to PCG-HA_B scaffold. ALP activity was also observed better in alternate soaked PCG scaffold as compared to PCG-HA_B scaffold. Mechanical strength and biological properties clearly demonstrate that surface deposited HA scaffold prepared by alternate soaking method may find application in bone tissue engineering.     

Novel thermal treatment model to decontaminate airborne SARS Cov-2 virus for residential and commercial buildings

In the COVID-19 pandemic, control of airborne virus transmission is exceptionally challenging as it is attached to suspended particles in the air and stays for an extended time. Air contaminated with airborne viruses holds a substantial risk for household transmission. In this study, a novel thermal treatment system is modeled based on porous heating for the decontamination of airborne SARS-Cov-2. The model includes an air heating domain, insulated chamber, buffer tank and heat exchanger. The airborne SARS-Cov-2 is decontaminated when passing through a porous heat pipe and the insulated chamber for an anticipated dwelling period of more than 5 min at 105°C and further stored in a buffer tank for natural cooling. The obligatory decontaminated air is allowed in the residential space under ambient conditions passing through a heat exchanger. The numerical investigation of the porous pipe model at different L/D ratios with altered porosities aims to establish the best-performing porous domain. Besides this, the buffer tank is intended to maintain buffer storage of the treated air and significant natural cooling before passing to the heat exchanger. A solar PV module is proposed to meet the prerequisite energy requirements of the equipped devices.     

A study on thermal behavior of a poly(VDF‐CTFE) copolymers binder for high energy materials

This article describes a study on thermal behavior of poly(vinylidene fluoride‐chlorotrifluoroetheylene) [poly(VDF‐CTFE)] copolymers as polymeric binders of specific interest for high energy materials (HEMs) composites by thermal analytical techniques. The non‐isothermal thermogravimetry (TG) for poly (VDF‐CTFE) copolymers was recorded in air and N₂ atmospheres. The results of TG thermograms show that poly(VDF‐CTFE) copolymers get degrade at lower temperature when in air than in N₂ atmosphere. In the derivative curve, there was single maximum degradation peak (T_max) indicating one‐stage degradation of poly(VDF‐CTFE) copolymers for all the samples. The other thermal properties such as glass transition temperature (T_g) and degradation temperature (T_d) for poly(VDF‐CTFE) copolymers were measured by employing differential scanning calorimeter (DSC) technique. The kinetic parameters related to thermal degradation of poly(VDF‐CTFE) copolymers were investigated through non‐isothermal Kissinger kinetic method using DSC method. The activation energies for thermal degradation of poly(VDF‐CTFE) copolymers were found in a range of 218–278 kJ/mol. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013