A GOOD DIFFUSION LAYER CANDIDATE FOR SHARK

In this paper, a good diffusion layer candidate for SHARK is developed. The diffusion layer presented here is only concerned with 64-bit cipher based on 2-DM diffusion matrixes, which is heavily inspired by James Massey work on the design of SAFER K-64. However, it can be easily extended for a longer size cipher without any extra works and it may serve as a good candidate for other block ciphers.     

Inhibition of Fatty Acid Synthase by Orlistat Accelerates Gastric Tumor Cell Apoptosis in Culture and Increases Survival Rates in Gastric Tumor Bearing Mice In Vivo

Orlistat, an anti-obesity drug, is a potent inhibitor of fatty acid synthase (FAS) and tumor cell viability. It can also induce apoptotic cancer cell death. We examined the effects of Orlistat on cultured NUGC-3 gastric cancer cells. We identified that inhibition of FAS via Orlistat exposure results in rapid cellular damage preceded by a direct but short-lived autophagic response. The Orlistat induced damage can be reversed through the addition of lipid containing media in a process that normally leads to cell death. By limiting exogenous lipid availability and inhibiting FAS using Orlistat, we demonstrated both a greater sensitivity and amplified cancer cell death by activation of apoptosis. We have identified “windows of opportunity” at which time apoptosis can be aborted and cells can be reversed from the death pathway. However, when challenged beyond the window of recovery, cell death becomes all but certain as the ability to be rescued decreases considerably. In vivo examination of Orlistat’s ability to inhibit gastrointestinal cancer was examined using heterozygous male C57BL/6J APC-Min mice, which spontaneously develop a fatal gastrointestinal cancer. Mice were fed either a high fat (11%) or low fat (1.2%) diet containing no Orlistat or 0.5 mg Orlistat/g of chow. Orlistat treated mice fed the high fat, but not low fat diet, survived 7–10% longer than the untreated controls.     

用罗布河块矿作烧结铺底料的探讨

论述了烧结铺料的必要性及其作用。对用烧结矿和罗布河块矿作铺底料的效果进行了比较。     

尾缘双穿孔对翼型性能影响研究

相关研究表明多孔尾缘在降低翼型噪声的同时,对其气动性能也有一定影响,且穿孔几何尺寸和位置是影响尾缘翼型噪声与气动特性的重要参数。针对NACA65019翼型,在来流雷诺数Re=2×105条件下,采用计算流体力学方法研究具有不同穿孔孔径和位置的尾缘双穿孔翼型绕流特征和噪声特性,并通过部分实验验证模拟的可靠性。研究结果表明：尾缘双穿孔翼型在小攻角下,升阻比较原翼型有较明显的提升,当来流攻角大于12 °后,升阻比开始小于原翼型;在一定来流攻角范围内,尾缘双穿孔翼型可延迟吸力面分离,降低吸力面边界层厚度;边界层厚度的降幅与穿孔孔径、穿孔位置密切相关,最大可达28.8%。根据相关声学理论模型,分析了穿孔孔径及位置对尾缘双穿孔翼型噪声特性的影响,经数值研究表明：α=6°时,在100~7 kHz频率范围,不同的尾缘双穿孔翼型相较于原翼型噪声降低最高可达10.7 dB;d=1.0 mm和Xc/c=0.82翼型效果最佳。     

叶片前缘开缝对离心风机气动及噪声的影响研究

将前缘缝翼思想运用到离心风机中,研究了叶片前缘开缝设计参数对离心风机内部流场及其声辐射的影响规律。研究表明:叶片前缘开缝使气流通过狭缝得到加速,抑制后叶片吸力面边界层分离;同时,开缝设计使叶轮内部压力脉动明显减弱,降低离心风机气动噪声源强度,存在最佳开缝参数组合使离心风机流动与降噪效果达到最佳;设计工况下,当开缝位置L/C=0.30,前叶偏转角θ=4°,且前、后叶片最大相对厚度相等时,离心风机全压提高7%,效率提高2%,其远场噪声各测点总声压级平均下降3.5 dB。     

Mono‐diffusive Hadley‐Prats flow in a horizontal porous layer subject to variable gravity and internal heat generation

Analysis of internal heated and gravity effect on the onset of Hadley‐Prats flow in a horizontal porous layer with inclined temperature gradients is investigated using the linear and nonlinear instability analysis. The transformed eigenvalue problem is evaluated numerically to find the eigenvalue, which is treated as a vertical thermal Rayleigh number (R_z). It is evaluated by applying shooting and Runge‐Kutta method. Also, the critical R_z is investigated for different parameters governing the flow. A theoretical study is made to understand the influence of gravity field on the mechanism of mono‐diffusive instability of Hadley‐Prats convection in a fluid saturated horizontal porous layer. Nonlinear stability is evaluated by using energy functional. The comparison between linear and nonlinear instability results are presented and it is noted that linear theory of instability may not be useful to capture the complete picture of stability and instabilities may arise before one attains the linear stability threshold. This subcritical instability region is identified between the linear and energy thresholds in the parameter space of the problem considered.     

Failure mechanism of PEM fuel cell under high back pressures operation

Proton exchange membrane fuel cells (PEMFCs) are expected to function under relatively higher back pressures for targeting higher outpower. Under this condition, the durability of fuel cells will be a huge challenge for commercialization. In our study, a 1000-h durability experiment was performed on a PEMFC to investigate the durability under high back pressures. A semi-empirical fuel cell polarization curve model was used to separate the activation and concentration losses, and study their changes with testing time at different current densities. In addition, the charge transfer resistance (R_ct) related to oxygen reduction reaction (ORR) in the catalyst layer was also investigated. Additionally, the mass transfer resistance (Z_d) was investigated using electrochemical impedance spectroscopy (EIS). Moreover, the contact angle and energy-dispersive X-ray spectrum (EDX) of carbon paper surface were characterized. The results indicated that the increase in mass transfer resistance was the biggest contributor to the loss of cell voltage with testing time. The decrease in contact angle of carbon paper surface implied that the weakening of hydrophobicity contributed to an increase in the mass transfer resistance, which comes from the PTFE loss observed from EDX. This may result from the aggravated corrosion of carbon fiber or physical erosion induced by flooding in fuel cell under high back-pressure.     

Magnetic Fe3C@C nanoparticles as a novel cocatalyst for boosting visible-light-driven photocatalytic performance of g-C3N4

In photocatalytic field, it is a significant challenge to synthesize cocatalyst with high performance, noble-metal free and facile methods to recycle. Herein, carbon layer coated Fe₃C (Fe₃C@C) nanoparticles were prepared by one-step method and for the first time utilized as highly efficient cocatalysts for improving visible-light-driven hydrogen evolution activity of g-C₃N₄. The photocatalytic hydrogen evolution rate of optimal Fe₃C@C/g-C₃N₄ was about 27.2 times of bare g-C₃N₄ samples. Furthermore, the Fe₃C@C/g-C₃N₄ composite catalyst showed excellent stability and reusability. The apparent quantum yield (AQY) of the optimized FeC@C/g- C₃N₄ reaches 0.501% and 0.124% at 400 nm and 420 nm, respectively. The AQY of the FeC@C/g- C₃N₄ is 26.2 times higher than that of g-C₃N₄ at 400 nm Fe₃C@C has an extraordinary cocatalytic effect for g-C₃N₄ photocatalytic hydrogen evolution mainly due to three aspects: Firstly, the Fe₃C acts as a trap to lure electrons because of its lower Fermi energy level and higher conductivity, which can increase the hydrogen production activity by trapping the photogenerated electrons produced by g-C₃N₄; Secondly, the coated carbon layer can provide chemical protection for Fe₃C nanoparticles and promote the transfer of photogenic electrons, thus further improving the efficiency and stability of photocatalytic hydrogen production; Thirdly, the strong magnetic property of Fe₃C@C nanoparticles gives Fe₃C@C/g-C₃N₄ photocatalysts the advantages of low cost and high recovery efficiency. It is believed that this work provides a new strategy and possibility for the application of photocatalytic hydrogen production.     

Overpotential analysis of alkaline and acidic alcohol electrolysers and optimized membrane-electrode assemblies

Alcohol electrolysis using polymeric membrane electrolytes is a promising route for storing excess renewable energy in hydrogen, alternative to the thermodynamically limited water electrolysis. By properly choosing the ionic agent (i.e. H⁺ or OH⁻) and the catalyst support, and by tuning the catalyst structure, we developed membrane-electrode-assemblies which are suitable for cost-effective and efficient alcohol electrolysis. Novel porous electrodes were prepared by Atomic Layer Deposition (ALD) of Pt on a TiO₂-Ti web of microfibers and were interfaced to polymeric membranes with either H⁺ or OH⁻ conductivity. Our results suggest that alcohol electrolysis is more efficient using OH⁻ conducting membranes under appropriate operation conditions (high pH in anolyte solution). ALD enables better catalyst utilization while it appears that the TiO₂-Ti substrate is an ideal alternative to the conventional carbon-based diffusion layers, due to its open structure. Overall, by using our developmental anodes instead of commercial porous electrodes, the performance of the alcohol electrolyser (normalized per mass of Pt) can be increased up to ∼30 times.     

A robust electrocatalytic activity and stability of Pd electrocatalyst derived from carbon coating

Palladium (Pd) as an efficient anodic catalyst has been extensively investigated in direct formic acid fuel cells (DFAFCs); while, Pd catalyst is electrochemically unstable in acidic electrolyte resulting in low stability retarding the widespread application of DFAFCs. In this study, a new method is invented to prevent the Pd nanoparticles from rapid dissolution by carbon layer originated from the carbonization of glucose. Ascribing to the presence of carbon layer, Pd electrocatalyst demonstrates much higher stability in comparison with Pd electrocatalyst without carbon layer in the course of stability tests. Robust electrocatalytic activities toward formic acid and methanol/ethanol oxidation are observed for carbon-stabilized Pd electrocatalyst resulted from the higher content of metallic Pd atoms coming from the carbonization process, in which Pd (II) species are further reduced. Moreover, the fuel cell performance of carbon-stabilized Pd electrocatalyst reaches 90 mW cm_Pd⁻² measured with 1 M formic acid; while, power density of bare Pd electrocatalyst is only 74 mW cm_Pd⁻². This work highlights that carbon layer carbonized from glucose improves not only the stability of Pd electrocatalyst, but also the electrocatalytic activity.