Low-complexity audio CODEC for resource-scarce embedded system with fixed-point arithmetic

This work presents a low-complexity audio coder-decoder (CODEC) based on fixed-point arithmetic to save the usage of system resources in a low-end embedded system. To reduce time complexity and memory usage, a simplified discrete wavelet transform (DWT) with only integer operations is developed. The simplified DWT reduces the computation that is required for the trigonometric operations in the fixed-point system. Moreover, separating the even and odd orders of wavelet coefficients halves the computation time of the original DWT. Additionally, a tri-mode zeroes recording algorithm (TZRA) is proposed. The proposed TZRA utilizes different encoding modes with their corresponding bit data structures to record the locations of zero wavelet coefficients, and determines the optimal encoding mode that uses the fewest bits. To further improve the compression performance, a dynamic wavelet level selecting algorithm is developed to decide the wavelet level for compressing each of frame. This algorithm can dynamically select the optimal wavelet level with the fewest bits by using the determined mode from the TZRA. The experimental results herein reveal that the encoder in the proposed CODEC can multiply computation by factors of 164 and 112 and reduce the size of the execution file by approximately 95.61 and 98.42% relative to baseline audio compression CODECs. Such results indicate that the efficiency when used in real consumer products with fixed-point arithmetic.     

用微波炉熔化磷酸盐玻璃

用微波炉熔化Na2O-B2O3-P2O5玻璃。测定了磷酸盐玻璃的X射线衍射曲线、变形点、软化点、热膨胀以及水溶性。结果表明微波炉比马弗炉熔化玻璃降低能源消耗。根据测试数据证实此微波熔化的磷酸盐玻璃可用作玻璃润滑剂。     

Accurate buckling load calculations of a thick orthotropic sandwich panel

This paper is concerned with the buckling of thick sandwich panels with orthotropic elastic face sheets bonded to a linear elastic orthotropic core. When such panels are analyzed for axial load carrying capacity, it is now commonplace to adopt the finite element method to carry out computations. The accuracy of the numerical results will depend not only on roundoff and algorithmic errors, but additionally on the approximations made in computing the incremental (second order) work associated in computing the change of configuration from the unbuckled to the buckled state. Here we show that, particularly for orthotropic thick sandwich structures, large errors can be incurred in computing buckling loads with available commercial software, unless the proper work conjugate measures of stress and strain with their stress-dependent tangential moduli are used in the buckling formulation.     

A rapid method for simultaneous determination of triterpenoid saponins in Pulsatilla turczaninovii using microwave-assisted extraction and high performance liquid chromatography–tandem mass spectrometry

In the present study, a microwave-assisted extraction (MAE) and high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) method was developed for the simultaneous determination of seven triterpenoid saponins in Pulsatilla turczaninovii. Operational conditions of MAE were optimized using a central composite design. Multiple-reaction monitoring was employed for quantification while switching the electrospray ion source polarity between positive and negative modes. Full validation of the method was carried out (linearity, precision, accuracy, limit of detection and limit of quantification). The results indicated that the method was rapid, specific and reliable. The developed method was successfully applied to determine the investigated compounds in nine batches of P. turczaninovii. These samples were collected in different seasons from the Liaoning province and varied greatly. The total triterpenoid saponins content was the highest in April, the seedling stage, and decreased from May to August. The contents of total triterpenoid saponins decreased significantly after the blooming period.     

Functionalized silicon quantum dots by N-vinylcarbazole: synthesis and spectroscopic properties

Silicon quantum dots (Si QDs) attract increasing interest nowadays due to their excellent optical and electronic properties. However, only a few optoelectronic organic molecules were reported as ligands of colloidal Si QDs. In this report, N-vinylcarbazole - a material widely used in the optoelectronics industry - was used for the modification of Si QDs as ligands. This hybrid nanomaterial exhibits different spectroscopic properties from either free ligands or Si QDs alone. Possible mechanisms were discussed. This type of new functional Si QDs may find application potentials in bioimaging, photovoltaic, or optoelectronic devices.     

DMA thermal analysis of different parts of potato tuber

Dynamic mechanical analysis (DMA) was applied to three potato tissues (‘cortex’, ‘pith’, and ‘side’ surface) of two cultivars (more waxy ‘Nicola’ and more mealy ‘Saturna’) in temperature scans in the range 30–90 °C and constant air humidity of 90%. The obtained scans indicate peaks in both storage and loss module of elasticity (SM and LM, respectively) at temperatures higher than 70 °C – so called ‘starch’ peak (SP) – as was observed previously. The peak value increase with increasing potato dry matter (DM) content, below DM content approximately 14% no SP is observed (‘Nicola pith’). Slope analysis of the basic parameters: SM, LM, and loss tangent (LT) was performed and further characteristic points on the temperature plots were found: (i) in temperature range A (30–40 °C) maximum of SM and LM and minimum of LT, (ii) in temperature range B (40–50 °C) minimum of SM and LM slopes corresponding to point of inflection on SM-T and LM-T plots, (iii) at about 50 °C, big peak in LT in side tissue only, (iv) at about 70 °C just prior the ‘starch’ peak, big peak in LT that is more marked in ‘pith’; this peak denoted as ‘I’ influenced the ‘starch’ peak ‘II’. It was found that both cultivar and part of the tuber influences the DMA temperature plots.     

空气潜孔锤钻井工艺在煤层气井中的应用

本文主要介绍了空气潜孔锤在煤层气钻井中工作原理、钻具组合、主要技术参数的计算选择和钻进中的注意事项,并尝试采用三牙轮钻头进行冲击回转钻进第四系,提高整体钻进效率。     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over mesoporous nickel–alumina xerogel catalysts prepared by a single-step carbon-templating sol–gel method

A series of mesoporous nickel–alumina xerogel catalysts (denoted as CNAX) were prepared by a single-step carbon-templating sol–gel method using different amount of carbon template (X), and they were applied to the hydrogen production by steam reforming of liquefied natural gas (LNG). Textural properties of CNAX catalysts were improved with increasing the amount of carbon template. CNAX catalysts exhibited diffraction peaks corresponding to nickel aluminate phase, while CNA18 and CNA24 catalysts showed additional bulk nickel oxide phase. From TPR measurements, it was revealed that the interaction between nickel species and alumina in the CNAX catalysts became weakened with increasing the amount of carbon template. Crystallite size of metallic nickel in the reduced CNAX catalysts showed a volcano-shaped trend with respect to the amount of carbon template. In the steam reforming of LNG, CNAX (X = 0, 6, 12, and 18) catalysts exhibited a stable catalytic performance during the reaction, while CNA24 catalyst showed a significant catalyst deactivation. Crystallite size of metallic nickel served as an important factor determining the catalytic performance in the steam reforming of LNG. Initial LNG conversion and initial hydrogen yield increased with decreasing crystallite size of metallic nickel of the catalysts. Among the catalysts tested, CNA12 catalyst with the smallest crystallite size of metallic nickel showed the best catalytic performance.