Second generation (low modulus) titanium alloys in total hip arthroplasty

Titanium alloys ‐ type (α+β) ‐ like Ti6Al7Nb or Ti6Al4V are widely used in cementless total hip arthroplasty due to their lower modulus, biocompatibility and enhanced corrosion resistance in comparison to Stainless Steel or Cobalt‐Chromium implant materials. Several articles report about atrophy of the proximal femur in cases where long stems with a big diameter made of (α+β) Titanium alloys with a relatively high value of the Youngs’ Modulus (110 GPa) in comparison to the Youngs’ Modulus of cortical bone (15–25 GPa) have been implanted using a prosthesis design with distal anchorage technique. Meanwhile several implant manufacturers have developed a new group of biocompatible Beta‐Titanium alloys with a lower Youngs’ Modulus around 70 GPa. This article gives an overview of the current status of available low modulus Titanium alloys including their mechanical characteristics and future developments.     

A novel data hiding scheme based on modulus function

Four criteria are generally used to evaluate the performance of data hiding scheme: the embedding capacity, the visual quality of the stego-image, the security, and the complexity of the data-embedding algorithm. However, data hiding schemes seldom take all these factors into consideration. This paper proposes a novel data hiding scheme that uses a simple modulus function to address all the performance criteria listed above. According to the input secret keys, the encoder and decoder use the same set-generation functions H_r() and H_c() to first generate two sets Kr and Kc. A variant Cartesian product is then created using Kr and Kc. Each cover pixel then forms a pixel group with its neighboring pixels by exploiting an efficient modulus function; the secret data are then embedded or extracted via a mapping process between the variant of the Cartesian product and each pixel group. The proposed scheme offers several advantages, namely (1) the embedding capacity can be scaled, (2) a good visual quality of the stego-image can be achieved, (3) the computational cost of embedding or extracting the secret data is low and requires little memory space, (4) secret keys are used to protect the secret data and (5) the problem of overflow or underflow does not occur, regardless of the nature of the cover pixels.We tested the performance of the proposed scheme by comparing it with Mielikainen’s and Zhang and Wang’s schemes for gray-scale images. The experimental results showed that our proposed scheme outperforms Mielikainen’s in three respects, namely scalable embedding capacity, embedding rate, and level of security. Our data hiding scheme also achieved a higher embedding capacity than Zhang and Wang’s. The proposed scheme can easily be applied to both gray-scale and color images. Analyses of its performance showed that our proposed scheme outperforms Tsai and Wang’s in terms of its time complexity and memory space requirement.     

模数法设计金属型铸造铝活塞保温冒口

根据保温冒口的散热特征,引用有效散热系数修正凝固模数,进一步修正金属型铸造的凝固比得出金属型保温胃口方程式.并设计了东风EQ140汽车活塞的保温冒口.浇注实验结果显示:铸造工艺出品率提高到84.9%,显著提高了冒口有效补缩效率.     

MAS小波的钢板表面缺陷边缘检测的研究

针对钢板表面缺陷与背景的对比度差、边缘复杂、采光不均、噪声较大等特点,应用一种基于MAS小波变换进行钢板表面缺陷边缘检测。该方法由Lipschitz指数阐明了图像的边缘几何结构,通过分析图像中不同类型的奇异点,并结合尺度独立算法区分了目标图像中不同类型的边缘,有效的提取了钢板表面缺陷图像的边缘。实验结果表明,基于MAS小波算法可以有效提取图像中阶梯型边界,检测到的缺陷边缘轮廓较为清晰,且去噪能力较强,检测效果优于传统的同类方法。     

氧化铝材料力学性能的分子动力学模拟

基于Al2O3材料在各大领域的重要性,提出了运用分子动力学方法来计算Al2O3材料的力学性能(杨氏模量、体模量、剪切模量、柯西压等),所得的结果与材料的实际值相近。计算结果不仅对Al2O3材料的力学性能进行了预示,还从侧面验证了该方法的准确性与可靠性,为材料的研究提供了一种可靠的理论方法。     

基于遗传算法的水声信道常模类盲均衡算法研究

为了解决CMA盲均衡算法收敛速度缓慢、稳态误差大的问题,考虑到初始化权值对CMA算法的重要影响,利用了遗传算法对CMA算法进行有效改进,引入了小样本重用的思想,给出了一种新的适用于水声信道的常模类盲均衡算法,计算机仿真研究证明,该算法不仅大大加快了收敛速度,而且有效的降低了稳态误差。     

Detection of singularities in the pressure fluctuations of circulating fluidized beds based on wavelet modulus maximum method

Pressure fluctuations are often selected to analyze the dynamic changes in the gas-solid fluidized bed. In this study, the wavelet modulus maximum method is applied to analyze the pressure fluctuations in a circulating fluidized bed. Continuous wavelet transform is put on the pressure signals, then, maxima lines are extracted and the Lipschitz exponent, α, of every maximum line is calculated using the non-linear least-squares method. The mean of the negative α is adopted to describe the hydrodynamic characteristics in the circulating fluidized bed. The value of the mean of the negative α increases with the superficial gas velocity and turns stable when the flow regime is fast fluidization. This method has been tested effective under various operation conditions.     

Study of the modulus of elasticity of polymer concrete compounds and comparative assessment of polymer concrete and portland cement concrete

The main aim of this study is to assess the modulus of elasticity of polymer concrete (PC) compounds produced using two types of binders: orthophtalic or isophtalic polyester. The compositions used were selected from a previous study that identified cost-effective PC compositions. Based on those data, the concentrations of polymer used were 12% of orthophtalic polyester and 13% of isophtalic polyester by weight of the dry materials. Fly ash was used as a filler and compositions with 8%, 12%, 16% and 20% of ash by weight of aggregate were studied. Results indicate that all compositions assessed in this study display high modulus of elasticity values. Statistical analysis of the data reveals that the type of resin and the concentration of fly ash, both in isolation and in combination, have a significant effect on the modulus of elasticity of these compounds.     

垫层对CFG桩复合地基影响的分析

探讨了CFG桩复合地基垫层厚度和模量对桩土应力比、桩侧摩阻力、沉降变形、承载力的影响，并得出一些规律。     

Determination of micromechanical properties of a hen’s eggshell by means of nanoindentation

The work describes the suitability and applicability of the nanoindentation method for the determination of the micromechanical properties of a hen’s eggshell. The values of elastic modulus E were monitored in five different locations along the eggshell’s meridian line. Detailed maps of elastic moduli at particular eggshell cross-sections revealed high variations in local values of E-moduli at individual points, but not significant differences of their means at distant parts of the eggshell. Mean values of E-modulus in different meridian positions did not vary significantly and ranged from 47.4 to 53 GPa. Experimental histograms were created of all elastic moduli showing the frequency of their occurrence and these revealed a rather high variation in E-moduli throughout the cross-section. The probability density function can be characterised by a symmetrical shape and the distribution of E-moduli can be approximated with the Gauss distribution. The nanoindentation technique proved to be a suitable, easy-to-use, and powerful tool for assessing local variations of the mechanical properties of hen’s eggshells.