超音速火焰喷涂与激光重熔Al0.2CrFeNi(Co,Cu)合金的干滑动磨损及氧化性能对比研究

用超音速火焰喷涂(HVOF)法在316L不锈钢基体上沉积Al0.2CrFeNiCo和Al0.2CrFeNiCu两种高熵合金涂层,然后对涂层进行激光重熔(LR)以改善其显微组织.研究LR工艺对涂层干滑动磨损和氧化行为的影响.结果表明,将粉末与单体元素混合导致HVOF涂层中形成内氧化物.LR消除了氧化物和气孔.LR后,两种...     

The prevalence of rheumatoid arthritis in affluent and poor urban communities of Pakistan

Using previously applied methods a survey of joint symptoms was undertaken among 4232 adults, evenly distributed between affluent and poor areas of Karachi, Pakistan. Only six cases of definite rheumatoid arthritis (RA) (1958 ARA criteria) were identified in the 245 persons who complained of joint problems of at least 4 weeks duration. The prevalence was 0.9 [confidence interval (CI) 0.21-3.61] and 1.98 (CI 0.55-5.1) per thousand in the poor and affluent districts, respectively. These were substantially less than prevalence rates reported in the West but were similar to figures derived from other developing countries. There was no obvious impact of current living standards on the findings. The relative paucity of older female subjects in both the affluent and poor communities may account at least in part for the low rates observed. The infrequency of rheumatoid nodules in Southern Asians with RA illustrates the difficulty of applying existing diagnostic criteria to this community.     

Power generation expansion planning with adaptive simulated annealing genetic algorithm

In this paper, an adaptive simulated annealing genetic algorithm is proposed to solve generation expansion planning of Turkey's power system. Least‐cost planning is a challenging optimization problem due to its large‐scale, long‐term, nonlinear, and discrete nature of power generation unit size. Genetic algorithms have been successfully applied during the past decade, but they show some limitations in large‐scale problems. In this study, simulated annealing is used instead of mutation operator to improve the genetic algorithm. The improved algorithm is applied to the power generation system with seven types of generating units and a 20‐year planning horizon. The planning horizon is divided into four equal periods. The new algorithm provides approximately 6.6 billion US$ (3.2%) cheaper solution than GA and also shows faster convergence. Copyright © 2006 John Wiley & Sons, Ltd.     

Circular Elastic Plate Resting on Tensionless Pasternak Foundation

In this technical note, a thin circular plate resting on a two-parameter (Pasternak-type) foundation is studied under concentrated central and distributed loads. The governing equations of the plate are derived for static loading case considering the lift off (uplift) of the plate from the foundation. For the approximate solution, a Galerkin technique is adopted and the free vibration mode shapes of the completely free plate are chosen as the displacement functions. The technique yields a system of algebraic nonlinear equations, and its solution is accomplished by using an iterative method. The numerical results are obtained for evaluation of the behavior of the plate and then given comparatively in figures. Although in the case of a tensionless Winkler foundation, the lift off of the plate from the foundation takes place, when the displacement of plate is negative, while in case of the two-parameter foundation the lift off appears when the slopes of the foundation surface and that of the plate are not equal.     

Preparation of active antibacterial biomaterials based on sparfloxacin,enrofloxacin, and lomefloxacin deposited on polyethylene

Bacterial contamination is one of the biggest drawbacks of implanted biomaterials, which may cause nosocomial infection. Avoiding bacterial adhesion onto the biomaterial surface by preparing active antibacterial biomaterials is an accurate solution. In this study, three of the fluoroquinolones: sparfloxacin, enrofloxacin, and lomefloxacin were selected due to their broad bactericidal effect and immobilized onto low‐density polyethylene surface at two different pH values (pH 3 and pH 6), after tailoring the surface by plasma treatment followed by grafting of polymer brush of N‐allylmethylamine. Surface wettability test and morphological investigations were carried out by water contact angle measurement and scanning electron microscopy analysis, respectively. Chemical characterizations were carried out by Fourier transform infrared spectra and X‐ray photoelectron spectroscopy. Antibacterial activity was checked against Staphylococcus aureus and Escherichia coli strains and results revealed that prepared surfaces were more effective against E. coli than S. aureus especially those prepared at pH 6. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46174.     

The new antiepileptic drugs: a systematic review of their efficacy and tolerability

PURPOSE: Gabapentin (GBP), lamotrigine (LTG), tiagabine (TGB), topiramate (TPM), vigabatrin (VGB), and zonisamide (ZNS) are all in use as "add-on" treatment for patients with refractory epilepsy. There have been no comparative randomized controlled trials allowing an evidence-based choice between these drugs. We report a series of meta-analyses of randomized placebo-controlled add-on trials in which these drugs have been tested in patients with partial epilepsy. This work provides an estimate of each drug's efficacy and tolerability compared with placebo. These estimates are compared across drugs to give broad estimates of comparative efficacy and tolerability. METHODS: Trial reports were found by searching Medline, by searching through journals by hand, and by contacting the pharmaceutical industry. The outcomes chosen were the proportion of patients who (a) have a > or = 50% reduction in seizure frequency (50% responders); (b) withdrew from the study (any reason); or (c) reported the following side effects: ataxia, dizziness, fatigue, nausea, or somnolence. Overall odds ratio (OR) with 95% confidence intervals (CIs; 50% responders) or 99% CIs; side effects) were calculated. RESULTS: Twenty-nine trials were included, representing 4,091 randomized patients. The ORs for 50% response (95% CI) were GBP, 2.29 (1.53-3.43); LTG, 2.32 (1.47-3.68); TGB, 3.03 (2.01-4.58); TPM, 4.07 (2.87-5.78); VGB, 3.67 (2.44-5.51); and ZNS, 2.7 (1.36-4.47). ORs for discontinuation were GBP, 1.36 (0.75-2.49); LTG, 1.19 (0.79-1.79); TGB, 1.81 (1.21-2.70); TPM, 2.56 (1.64-4.00); VGB, 2.58 (126-5.27); and ZNS, 4.23 (1.71-10.49). CONCLUSIONS: We have clear evidence that each of these drugs is better than placebo at preventing seizures. When results are compared across drugs, the confidence intervals overlap, and we have no conclusive evidence of differences in efficacy or tolerability. Despite this, the agent that appears most effective may be twice as effective as the agent that appears least effective, and the agent that appears most likely to cause discontinuation may be 4 times more likely to do so than the treatment that appears least likely to do so. Comparative randomized studies are needed further to evaluate these drugs.     

Numerical study of radiative Maxwell viscoelastic magnetized flow from a stretching permeable sheet with the Cattaneo–Christov heat flux model

In this article, the Cattaneo–Christov heat flux model is implemented to study non-Fourier heat and mass transfer in the magnetohydrodynamic flow of an upper-convected Maxwell fluid over a permeable stretching sheet under a transverse constant magnetic field. Thermal radiation and chemical reaction effects are also considered. The nonlinear partial differential conservation equations for mass, momentum, energy and species conservation are transformed with appropriate similarity variables into a system of coupled, highly nonlinear ordinary differential equations with appropriate boundary conditions. Numerical solutions have been presented for the influence of elasticity parameter (α), magnetic parameter (M ²), suction/injection parameter \((\lambda ),\) Prandtl number (Pr), conduction–radiation parameter (R _d ), sheet stretching parameter (A), Schmidt number (Sc), chemical reaction parameter \(\left( {\gamma_{c} } \right)\), modified Deborah number with respect to relaxation time of heat flux (i.e., non-Fourier Deborah number) on velocity components, temperature and concentration profiles using the successive Taylor series linearization method (STSLM) utilizing Chebyshev interpolating polynomials and Gauss–Lobatto collocation. The effects of selected parameters on skin friction coefficient, Nusselt number and Sherwood number are also presented with the help of tables. Verification of the STSLM solutions is achieved with existing published results demonstrating close agreement. Further validation of skin friction coefficient, Nusselt number and Sherwood number values computed with STSLM is included using Mathematica software shooting quadrature.

     

Synthesis,thermal degradation and dielectric properties of poly[2-hydroxy,3-(1-naphthyloxy)propyl methacrylate]

2-Hydroxy-3-(1-naphthyloxy)propyl methacrylate (NOPMA) monomer was synthesized from reaction of 2-[(2-naphthyloxy)methyl]oxirane with methacrylic acid in the presence of pyridine. The polymerization of NOPMA was carried out by free radical polymerization method in the presence of AIBN at 60 °C. The structure of monomer and polymer was characterized by ¹H-NMR, ¹³C-NMR and FT-IR spectroscopy techniques. The glass transition temperature and average-molecular weights of poly(NOPMA) were measured using differential scanning calorimetry and gel permeation chromatography, respectively. The thermal degradation behavior of poly(NOPMA) has been investigated by FT-IR studies of the partially degraded polymer and thermogravimetry. The cold ring fractions (CRFs) were collected at two different temperatures, initially fraction-1 (CRF₁) is from room temperature to 320 °C, and the other fraction-2 (CRF₂) is from 320 to 500 °C. The volatile products of the degradation were trapped at ?195 °C (in liquid nitrogen). All the fractions were characterized by FT-IR, ¹H and ¹³C-NMR spectroscopic techniques, and the cold ring fractions (CRFs) were also characterized by GC–MS. For the degradation of polymer, the major compound between products of CRFs is α-naphthol. The GC–MS, FT-IR and NMR data showed that depolymerization corresponding to monomer was not prominent below 320 °C in the thermal degradation of poly(NOPMA). The mode of thermal degradation containing formation of the major products was identified. The dielectric permittivity (ε′), the loss factor (ε″) and conductivity (σ_ac) were measured using a dielectric analyzer in the frequency range of 50 Hz to 20 kHz.     

异质富勒烯C26BN各种可能异构体的芳香性和动力学稳定性研究

用拓扑共振能（TRE）和百分拓扑共振能（%TRE）方法,对由富勒烯C₂₈（T_d）产生的C₂₆BN各种可能异构体和它们阴离子的芳香性进行了研究。探讨了C₂₆BN异构体稳定性与杂原子取代位置间的关系。最后,用最小键共振能（min BRE）方法对C₂₈（T_d）和C₂₆BN分子离子的动力学稳定性进行了研究。研究结果表明C₂₈（T_d）和C₂₆BN在中性状态下,因TRE为负值被预测为具有反芳香性。Min BRE方法研究结果证明了C₂₈（T_d）和C₂₆BN的动力学不稳定性与分子中具有较高反芳香性键直接有关。TRE和min BRE方法研究结果表明,C₂₈^4-和C₂₆BN^4-各异构体不仅具有较高的芳香性而且也有较高的动力学稳定性。     

Investigations of friction stir welding process using finite element method

The aim of this study is to investigate the process of friction stir welding (FSW) by using finite element method (FEM). Currently, the materials that are difficult to be joined with conventional fusion methods can now be easily joined with the method of friction stir welding. In this paper, the welding capability of many different materials with this method has been investigated by using analytical and numeric methods. In this study, a finite element (FE) model was developed for welding process with friction stir welding of AZ31 magnesium alloy. This model was performed by the software of DEFORM 3D finite element in 960, 1,964, and 2,880 rpm rotational speeds and in 10 and 20 mm?min^?1 transverse speeds. The temperature values taken from experiments and the temperature values with FEM are compared, and according to these results, it can be stated that the FE model gives reasonable results with experimental results based on temperatures values. Hence, the FE model can be used to predict other parameters of FSW process in future studies.