基于自适应阈值活动语音检测和最小均方误差对数谱幅度估计的低信噪比降噪算法

针对低信噪比(SNR)环境下传统方法对声信号降噪的局限性，提出了一种联合自适应阈值活动语音检测（VAD）算法和最小均方误差对数谱幅度估计（MMSE-LSA）的实时降噪算法。首先，在VAD算法中通过基于能量概率最大值的概率统计来对背景噪声进行估计，对得到的背景噪声进行实时更新并保存；然后，将实时更新的背景噪声作为MMSE-LSA的参考噪声，并对噪声幅度谱进行自适应更新，最后进行降噪处理。通过在真实场景中对四类声信号进行实验，结果表明，该算法在保证对低SNR声信号的实时处理的情况下，相较于传统MMSE-LSA算法，降噪信号的SNR能够提高10~15 dB，且不存在信号过减的情况，可应用于实际工程。     

Thermodynamic modeling of gas solubility in aqueous sodium chloride solution

An electrolyte Equation of State is presented by combining the Cubic Plus Association Equation of State,Mean Spherical Approximation and the Born equation.This new model uses experimental relative static permittivity,intend to predict well the activity coefficients of individual ions (ACI) and liquid densities of aqueous solutions.This new model is applied to model water + NaCl binary system and water + gas +NaCl ternary systems.The cation/anion-water interaction parameters of are obtained by fitting the exper-imental data of ACI,mean ionic activity coefficients (MIAC) and liquid densities of water + NaCl binary system.The cation/anion-gas interaction parameters are obtained by fitting the experimental data of gas solubilities in aqueous NaCl solutions.The modeling results show that this new model can correlate well with the phase equilibrium and volumetric properties.Without gas,predictions for ACI,MIAC,and liquid densities present relative average deviations of 1.3％,3.6％ and 1.4％ compared to experimental ref-erence values.For most gas-containing systems,predictions for gas solubilities present relative average deviations lower than 7.0％.Further,the contributions of ACI,and salting effects of NaCl on gases are ana-lyzed and discussed.     

基于Android平台的路径日记系统开发与设计

随着世界信息产业和通讯设备制造产业的迅猛发展,手机已经成为人们日常生活中不可缺少的一部分。智能手机日益趋向于移动智能综合服务平台方向的发展。可以预想在未来的世界,手机将为人们提供移动办公、信息分享和获取、电子支付、游戏娱乐等等的服务,而地图导航就是其中一个非常重要的应用服务。     

SO3 decomposition over β–SiC and SiO2 supported CuFe2O4: A stability and kinetic study

CuFe₂O₄/β–SiC and CuFe₂O₄/SiO₂ catalysts were prepared by wet impregnation method, following the high temperature solid state route and their catalytic performance is evaluated in the SO₃ decomposition reaction of the Sulfur–Iodine (S–I) cycle for hydrogen production. The synthesized catalysts are characterized by XRD, FT–IR, TGA, XPS, N₂–BET, TEM, HR–TEM, FESEM–EDS and elemental mapping. CuFe₂O₄/β–SiC catalyst shows higher activity and stability while sintering is observed in the spent CuFe₂O₄/SiO₂ whose activity decreased during the reaction time on stream. Kinetic studies were performed over CuFe₂O₄/β-SiC in the temperature range of 800–900 °C using wide range of space time, 6.54–44.40 kg h kmol⁻¹. A heterogeneous kinetic model was developed based on the product distribution and the reaction rates determined by the model fitted well with the experimental rates at different temperatures.     

Microenvironmental engineering:An effective strategy for tailoring enzymatic activities

Rationally, engineering a favorable physicochemical microenvironment for enzymes has recently emerged as an effective strategy to improve their catalytic performance. In this review, we discuss four microenvironmental effects according to the mechanism of action: localizing and excluding reactants and regulators, regulating microenvironmental pH, creating a water-like microenvironment, and increasing the local temperature. These mechanisms are enzyme-independent and can in principle be used in combination to tailor enzyme behaviors,offering new approaches to enabling, enhancing, and regulating enzyme catalysis in diverse applications without the need for genetic engineering.     

Effect of mass transfer on the deactivation model and GPLE parameters of Co/γ-Al2O3 catalysts in the Fischer Tropsch synthesis

The activity of catalysts with various sizes was compared in a fixed-bed Fischer–Tropsch reactor under similar operating conditions by determining the deactivation model. Catalyst size had no impact on the type of deactivation model. The smaller catalyst showed a smaller deactivation constant of catalyst (k_d) and a lower deactivation rate in the initial stage. The decline in the activities of the catalyst with a mesh size of 40 was lower than the other catalysts, suggesting its higher long-term stability (a_ss). Larger catalyst sizes led to the fouling of carbon and heavy hydrocarbons, decreasing the specific surface of the catalyst, thus increasing the pore diffusion resistance and further decrementing the catalyst activities.