Relationship Between Microstructure,Strength, and Fracture in an Al-Zn-Mg Electron Beam Weld: Part I: Microstructure Characterization

This work presents a detailed, multiscale, spatially resolved study of the microstructure of an electron beam butt weld of the EN-AW 7020 (Al-Zn-Mg) alloy. Using a combination of optical, scanning and transmission electron microscopy, differential scanning calorimetry, and small-angle X-ray scattering, the distribution of phases in the different areas of the heat-affected zone and of the fusion zone is quantitatively characterized, for two different aging states: naturally aged after welding and artificially aged at 423 K (150 °C). The heat-affected zone consists of regions experiencing different levels of precipitate dissolution and coarsening during welding as well as new precipitation during post-welding heat treatment (PWHT). The microstructure of the fusion zone is typical from a fast solidification process, with a strong solute segregation in the interdendritic zones. The precipitate distribution after PWHT follows this solute distribution, and the resulting hardness is much lower than the relatively homogeneous value in the base metal and the heat-affected zone.     

Crystallographic Reconstruction Study of the Effects of Finish Rolling Temperature on the Variant Selection During Bainite Transformation in C-Mn High-Strength Steels

The effect of finish rolling temperature on the austenite-(γ) to-bainite (α) phase transformation is quantitatively investigated in high-strength C-Mn steels using an alternative crystallographic γ reconstruction procedure, which can be directly applied to experimental electron backscatter diffraction mappings. In particular, the current study aims to clarify the respective contributions of the γ conditioning during the hot rolling and the variant selection during the phase transformation to the inherited texture. The results confirm that the sample finish rolled at the lowest temperature [1102 K (829 °C)] exhibits the sharpest transformation texture. It is shown that this sharp texture is exclusively due to a strong variant selection from parent brass {110} \( \left\langle {1\bar{1}2} \right\rangle \) , S {213} \( \left\langle {\bar{3}\bar{6}4} \right\rangle \) and Goss {110}〈001〉 grains, whereas the variant selection from the copper {112} \( \left\langle {\bar{1}\bar{1}1} \right\rangle \) grains is insensitive to the finish rolling temperature. In addition, a statistical variant selection analysis proves that the habit planes of the selected variants do not systematically correspond to the predicted active γ slip planes using the Taylor model. In contrast, a correlation between the Bain group to which the selected variants belong and the finish rolling temperature is clearly revealed, regardless of the parent orientation. These results are discussed in terms of polygranular accommodation mechanisms, especially in view of the observed development in the hot-rolled samples of high-angle grain boundaries with misorientation axes between 〈111〉γ and 〈110〉γ.     

Nanoflower hydroxyapatite's effect on the properties of resin-based dental composite

To investigate the reinforcing effect of nanoflower-like hydroxyapatite (NFHA) in resin-based dental composites, we synthesized a novel NFHA using microwave irradiation (MW), hydrothermal treatment (HT), and sonochemical synthesis (SS). Silanized NFHA was then used as the reinforcing filler in dental resin composites. We characterized the structure and morphology of various HA nanostructures using x-ray diffraction, scanning electron microscope, and TEM. The mechanical performance of dental resin composites reinforced with silanized NFHA was measured using a universal testing machine. Spherical HA, synthesized through chemical precipitation (CP), served as the control group. One-way analysis of variance was employed for the statistical analysis of the acquired data. The results demonstrate that the nanoflower morphology significantly was improved mechanical and physical properties. After conducting trials, the NFHA synthesized using MW and HT showed a substantial enhancement in mechanical and physical properties compared to the other structures. Therefore, it can be concluded that NFHA can serve as a novel reinforcing HA filler, providing regenerative properties to resin composites with sufficient mechanical strength.     

Biotransformation of imperatorin by Penicillium janthinellum. Anti-osteoporosis activities of its metabolites

Imperatorin (IMP) is a major constituent of many herbal medicines and possesses anti-osteoporosis activity. The present research work aimed to study the biotransformation processes of IMP and evaluated the anti-osteoporosis activity of the transformed metabolites. Among 18 strains of filamentous fungi screened, Penicillium janthinellum AS 3.510 exhibited good capability to metabolise IMP to the new derivatives. Ten transformed products were isolated and purified, and their structures were identified accurately based on spectroscopic data. Eight metabolites (2–8 and 10) were novel and previously unreported. The major biotransformation reactions involved hydroxylation of the prenyloxy side-chain and the lactone ring-opening reaction of furocoumarin skeleton. In addition, anti-osteoporosis activities of all products (1–10) were evaluated using MC3T3-E1 cells. The results showed that products 5 and 8 had the best bioactivities in increasing MC3T3-E1 cell growth. These products could be used in future therapeutic regimens for treating osteoporosis.     

Synthesis and Pharmacological Evaluation of a series of the Agomelatine Analogues as Melatonin MT1/MT2 Agonist and 5‐HT2C Antagonist

Agomelatine is a naphthalenic analogue of melatonin that is in clinical use for the treatment of major depressive disorders. Interestingly, while agomelatine exhibits potent affinity for melatonin receptors, it binds with only moderate affinity to the serotonin 5‐HT_2C receptor. Optimization of agomelatine toward this target could further potentiate its clinical efficacy. To explore this hypothesis and to access derivatives in which a key point of agomelatine metabolism is blocked, a series of naphthalenic derivatives was designed and synthesized as novel analogues of agomelatine. Most of the prepared compounds exhibited good binding affinity at the melatonin MT₁ and MT₂ receptor subtypes. Two compounds, an acetamide and an acrylamide derivative, exhibited good binding affinities at both the human melatonin (MT) receptors and the serotonin 5‐HT_2C receptor subtype, with pK_i values of 7.96 and 7.95 against MT₁, 7.86 and 8.68 against MT2, and 6.64 and 6.44 against 5‐HT_2C, respectively.     

A CMOS adaptive RF front-end receiver for wireless applications

The performance of signal-processing algorithms implemented in hardware depends on the efficiency of datapath, memory speed and address computation. Pattern of data access in signal-processing applications is complex and it is desirable to execute the innermost loop of a kernel in a single-clock cycle. This necessitates the generation of typically three addresses per clock: two addresses for data sample/coefficient and one for the storage of processed data. Most of the Reconfigurable Processors, designed for multimedia, focus on mapping the multimedia applications written in a high-level language directly on to the reconfigurable fabric, implying the use of same datapath resources for kernel processing and address generation. This results in inconsistent and non-optimal use of finite datapath resources. Presence of a set of dedicated, efficient Address Generator Units (AGUs) helps in better utilisation of the datapath elements by using them only for kernel operations; and will certainly enhance the performance. This article focuses on the design and application-specific integrated circuit implementation of address generators for complex addressing modes required by multimedia signal-processing kernels. A novel algorithm and hardware for AGU is developed for accessing data and coefficients in a bit-reversed order for fast Fourier transform kernel spanning over log?₂ N stages, AGUs for zig-zag-ordered data access for entropy coding after Discrete Cosine Transform (DCT), convolution kernels with stored/streaming data, accessing data for motion estimation using the block-matching technique and other conventional addressing modes. When mapped to hardware, they scale linearly in gate complexity with increase in the size.     

Improved Heat Insulation and Mechanical Properties of Highly Porous YSZ Ceramics After Silica Aerogels Impregnation

To further improve heat insulation and mechanical properties, silica aerogels were impregnated into highly porous yttria‐stabilized zirconia (YSZ) ceramics with well‐distributed pores fabricated by tert‐butyl alcohol ‐based gel‐casting process and pressureless sintering. Pore size distribution, room‐temperature thermal conductivities, and compressive strength of the YSZ ceramics before and after impregnation with silica aerogels were examined and compared, respectively. After impregnating porous YSZ ceramics with silica aerogels, the porosity displayed a little decrease, whereas the pore size significantly decreased by one order of magnitude. Based on this microstructure development, the room‐temperature thermal conductivities were significantly lowered and the compressive strength was also promoted. Therefore, the heat insulation and mechanical properties could be simultaneously improved by impregnating porous ceramics with silica aerogels.     

六西格玛理论在机械产品设计中的应用

将产品全寿命周期六西格玛解决方案的六西格玛设计理论IDDOV流程用于复杂环境矿山冶金设备可靠性的设计研究。以某矿冶设备径向轴承润滑设计为例,采用IDDOV流程方法和技术后降低了矿冶设备恶劣环境下因润滑原因产生的零件失效故障率,为矿山机械设备低成本、高质量和稳健性设计难题提供了一种新的解决途径,并对结论进行了验证。     

Learning location-invariant orthographic representations for printed words

Neural networks were trained with backpropagation to map location-specific letter identities (letters coded as a function of their position in a horizontal array) onto location-invariant lexical representations. Networks were trained on a corpus of 1179 real words, and on artificial lexica in which the importance of letter order was systematically manipulated. Networks were tested with two benchmark phenomena – transposed-letter priming and relative-position priming – thought to reflect flexible orthographic processing in skilled readers. Networks were shown to exhibit the desired priming effects, and the sizes of the effects were shown to depend on the relative importance of letter order information for performing location-invariant mapping. Presenting words at different locations was found to be critical for building flexible orthographic representations in these networks, since this flexibility was absent when stimulus location did not vary.     

三甲基戊二醇的合成及应用研究

采用异丁醛缩合、交叉Cannizzaro反应制备了三甲基戊二醇（TMPD）,并利用TMPD合成两种具有重要用途的新型香精青叶恶烷和环状碳酸酯IDDO。 简要介绍子这两种合成香精在食品工业中的应用。