一种基于软阈值方法的改进A1/A2极化干涉分类算法

在分析了极化干涉技术的发展现状和发展趋势的基础上,从极化干涉的特殊性入手,分析了干涉相干系数在极化干涉分类中的作用,并且系统分析了基于相干最优优化后的相干系数进行极化干涉分类过程的原理,总结了现有极化干涉分类算法在阈值选择方面存在的不足,阐述了硬阈值方法和软阈值方法的基本原理和它们之间的区别,最后提出基于软阈值方法的改进A1/A2非监督极化干涉分类算法,解决了极化干涉分类现有的分类空间中的阈值问题。实验表明这种方法能够得到更好的分类结果,做出了改进。     

Occurrence and characteristics of Vibrio vulnificus in retail marine shrimp in China

Vibrio vulnificus is a gram-negative bacterium that naturally occurs in estuarine waters and marine environment. Consumption of seafood contaminated with V. vulnificus or exposure to the contaminated water causes septicemia, gastroenteritis or wound infections in humans. This study aimed at identifying the prevalence of V. vulnificus in shrimps in Chinese seafood market. From June to September 2009, 239 samples encompassing six shrimp species were collected from ten cities in China. To quantify the prevalence and the levels of V. vulnificus in shrimps, the most probable number (MPN) method was used combining with the polymerase chain reaction (PCR) which was used to classify the isolates by detecting V. vulnificus hemolysin gene (vvhA). One hundred and forty out of 239 samples were positive for V. vulnificus, with the geometric mean level at 153.3 MPN/g. The prevalence and levels of V. vulnificus in shrimps varied in different geographic areas, with the values for the samples in the South cities (179.6 MPN/g) remarkably higher than that in the North cities (7.6 MPN/g). In addition, we found that 61.7% (79/128) of the V. vulnificus positive samples contained C-type (Clinical) strains and 8 contained E-type (Environmental) strains. The antimicrobial susceptibility of the isolates to 12 antibiotics was tested as well. Most of the 169 isolates remained susceptible to the majority of antimicrobials tested, whereas some strains tend to be less sensitive to amikacin, ampicillin, tetracycline and gentamicin. In conclusion, V. vulnificus is commonly found in retail marine shrimp in Chinese seafood market, and most of the shrimp samples contained C-type strains, which may pose a potential threat to human health.     

Baushinger’s Effect in Wear of Materials

The response of Cu–40%Zn alloy to wear during unidirectional and bidirectional abrasion processes was investigated. It was observed that the mass loss of the alloy decreased as the number of times of changing the sliding direction was increased. Corresponding to this decrease in mass loss, hardness of the worn surface increased initially and then decreased. Cracking in the surface layer was analyzed to get an insight into the mechanism involved. Results of the study suggest that Baushinger’s effect played a role when the sliding direction was alternated.     

A Follow-up Study on Bauschinger’s Effect in Bidirectional Wear of Cu-40%Zn against Different Types of Counter-Face

Previously, we demonstrated a decrease in wear loss of Cu-40%Zn against a steel wheel during bidirectional sliding ascribed to Bauschinger’s effect associated with diminished strain-hardening. However, the situation changed when the alloy was worn by a ceramic-grinding wheel. It was observed that the mass loss continuously increased with reversal of the sliding-direction although the corresponding hardness of worn surface also decreased. In this case, Bauschinger effect still functioned but the failure mode varied, leading to the different trend of response to wear against the ceramic-grinding wheel in comparison with that against the steel counter-face.     

针灸治疗强直性脊柱炎临床研究进展

强直性脊柱炎是一种原因不明,以中轴关节慢性炎症为主的全身性疾病,主要累及骶髂关节、髋关节、椎间关节、肋椎关节、以骶髂关节病变最为多见.其主要病理改变是关节和关节周围组织、韧带、椎间的韧带钙化,最终发生骨性强直.强直性脊柱炎多见于青年男性,发病年龄多在15-35岁.40岁以后发病者少见,男性患病是女性的5倍.一项研究对我国6000名风湿病患者调查统计,强直性脊柱炎患者占18%,一般人群的调查发病率0.3%,即1000人中有一位患病,全国将近12万人患此病,这一数据表明该病对家庭和社会是一个沉重负担.     

The influence of oxygen and nitrogen contamination on the densification behavior of cryomilled copper powders during spark plasma sintering

It has been found difficult to fully densify some mechanically milled pure metal powders by spark plasma sintering (SPS). In this study, the densification behavior of cryomilled, nanostructured (NS) Cu powders during SPS was related to changes to the chemistry of the powders. The results showed that the presence of very small amounts of O and N in the powders, which were introduced during cryomilling and handling, significantly influenced the densification response. Moreover, reduction/removal of O/N via thermal annealing of the powders before SPS led to complete densification of the powders during subsequent SPS. The mechanisms responsible for this behavior were ascertained: O and N existed in the cryomilled powders in the form of thermally unstable compounds, and the subsequent thermal decomposition of these compounds during SPS generated the gaseous species, leading to porosity formation and incomplete densification; annealing of the powders before SPS removed the gases which resulted from thermal decomposition, thereby facilitating complete consolidation during subsequent SPS.     

Calculation of all cubic single-crystal elastic constants from single atomistic simulation: Hydrogen effect and elastic constants of nickel

Previous direct methods for evaluating all elastic constants require separate molecular dynamics runs with different loads. Here, we show that only a single run is enough to evaluate all elastic constants of cubic crystals. We evaluate the temperature dependence of all elastic constants of Ni to check the reliability of the embedded-atom method potential developed by Angelo et al. and study the effects of hydrogen on elastic constants.     

模铸连浇中间包控流装置优化的水模实验

通过水力学模拟实验,优化了模铸连浇中间包控流装置。结果表明,安装控流装置,并将开孔设于挡墙下部正中间时,流体在中间包内的停留时间较长,死区体积最小,夹杂物上浮率也较高,而且不存在短路流。因此,经过控流装置优化,流体在中间包内的流场也得到明显改善,流动模式较合理,有利于钢中夹杂物的上浮去除,可以保证浇注大钢锭的质量。     

Improvement of slurry erosion resistance of martensite/ferrite duplex stainless steel by hot rolling

Test samples of martensite/ferrite duplex stainless steels (M/Fss) were prepared using thermal-mechanical processes and their slurry erosion behaviors were systematically studied. Test results show that hot rolling is an attractive process for improving erosion resistance. This improvement is more evident at higher impinging angles and larger reduction ratios. The thermal-mechanical-treated samples exhibit higher slurry erosion resistance for all impinging angles compared to that obtained by conventional quenching treatment without rolling. The variation tendency of the erosion rate versus the impinging angle for samples rolled with different degrees of reduction is similar in that the erosion rate initially increases and then decreases as the impinging angles increase from 15° to 90°, reaching a maximum at approximately 30°. After impingement erosion, the surface morphologies of the samples exhibit many long furrows and ridges at a low impinging angle of 30°. At a high impinging angle of 90°, the samples exhibit a worn surface with abundant overlapping and irregular concavities. The surface hardness of the samples after impingement erosion increases as the impinging angles and reduction ratios increase due to the enhanced effects of both work hardening and the formation of straininduced martensite.