客家传统服饰刺绣图案

 从客家服饰刺绣图案的分类、刺绣技法、图案构成、色彩运用角度入手，总结出客家传统服饰刺绣图案按其表现题材可分为动植物、几何图纹、人物、文字、生活器物等五大类；刺绣技法分为七大系列二十七种针法；图案构成以边缘式、主题式与对称式为主；服饰图案色彩对比强烈、具有尚“俗”审美情趣且倾向装饰功利性。得出客家传统服饰图案在构图、表现题材、技法、用色等方面呈现地域性特征，并且具有深沉的中原汉民族审美情感倾向。     

Extraction and analysis of multiple time window features associated with muscle fatigue conditions using sEMG signals

In this work, an attempt has been made to differentiate surface electromyography (sEMG) signals under muscle fatigue and non-fatigue conditions with multiple time window (MTW) features. sEMG signals are recorded from biceps brachii muscles of 50 volunteers. Eleven MTW features are extracted from the acquired signals using four window functions, namely rectangular windows, Hamming windows, trapezoidal windows, and Slepian windows. Prominent features are selected using genetic algorithm and information gain based ranking. Four different classification algorithms, namely naïve Bayes, support vector machines, k-nearest neighbour, and linear discriminant analysis, are used for the study. Classifier performances with the MTW features are compared with the currently used time- and frequency-domain features. The results show a reduction in mean and median frequencies of the signals under fatigue. Mean and variance of the features differ by an order of magnitude between the two cases considered. The number of features is reduced by 45% with the genetic algorithm and 36% with information gain based ranking. The k-nearest neighbour algorithm is found to be the most accurate in classifying the features, with a maximum accuracy of 93% with the features selected using information gain ranking.     

Stress relaxation behavior of an Al–Zn–Mg–Cu alloy in simulated age-forming process

The stress relaxation behavior of age-forming for an Al–Zn–Mg–Cu alloy was studied using a designed device that can simulate the age forming process. The mechanism of stress relaxation was also revealed through calculating thermal activation parameters and analyzing the microstructures. The results suggested that the stress relaxation behavior of the Al–Zn–Mg–Cu alloy in the simulated age-forming process can be divided into three stages according to the stress level. The three stages of stress relaxation are: (i) the initial high stress stage, (ii) the subsequent middle stress transition stage and (iii) the last low stress equilibrium stage, respectively. The deformation activation energies are 132 kJ/mol in the initial high stress stage, 119 kJ/mol in the subsequent middle stress transition stage and 91 kJ/mol in the last low stress equilibrium stage, respectively. The analysis of the thermal activation parameters and microstructures revealed that dislocation creep was the dominant deformation mechanism in the initial and subsequent stages of the stress relaxation; whereas diffusion creep is the mechanism in the last stage of the stress relaxation. Additionally, a special threshold stress phenomena was present in the stress relaxation of the age-forming process, which was scribed to the interaction between precipitation and dislocation in the Al–Zn–Mg–Cu alloy     

Changes in flavour characteristics and bacterial diversity during the traditional fermentation of Chinese rice wines from Shaoxing region

As a traditional alcoholic beverage, Chinese rice wine is quite popular for its unique flavor and high nutritional value. In this study, we investigated the changes of flavor compounds in varying stages of fermentation by HS-SPME-GC-MS and HPLC. In addition, 16s rDNA-PCR was utilized to analyze the changes of bacterial communities during fermentation of Chinese rice wine from the Shaoxing region. It was noted that the content of flavor compounds including esters, higher alcohols, amino acids and organic acids was different in varying stages of fermentation. In general, the flavor compounds of Chinese rice wine were mainly produced after pre-fermentation. The results also showed that the bacterial community structures and diversity of Chinese rice wine varied significantly during different fermentation stages, and more than 10 genera of bacteria was detected in Chinese rice wine fermentation broth. Among these specific bacteria identified in the study, Lactobacillus (the predominant genus) and Bacillus might take an active part in flavor development in Chinese rice wine. This implied that these bacteria might play significant contributions on the flavor of Chinese rice wine.     

Atomic layer deposition of platinum thin films on anodic aluminium oxide templates as surface-enhanced Raman scattering substrates

Platinum thin films are deposited on anodic aluminium oxide (AAO) templates by atomic layer deposition (ALD). The highly ordered island-like platinum nanostructures formed on the AAO template produce a high Raman scattering signal because of the periodical hexagonal arrangement. As an illustration, dramatic enhancement is achieved using Rhodamine 6G (R6G) as a molecular probe.Field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) show that the gap between the island-like structures is below 10 nm. Owing to activation by the incident laser beam, the localized electromagnetic field on the platinum island surface can be dramatically enhanced by the sub-10 nm regime subsequently amplifying the Raman signal. Finite-difference time-domain (FDTD) calculation matches the experimental phenomena suggesting that the excellent surface-enhanced Raman scattering (SERS) characteristics of the platinum structure arise from the high density and abundance of hot spots. Because the platinum film is inert in air, the SERS enhancing substrate can be used reliably in many trace chemical and biological detection applications.     

Microstructure and texture evolution in fully pearlitic steel during wire drawing

The evolution of morphology of pearlite and crystallographic texture of ferrite matrix in fully pearlitic steels during wire drawing were quantitatively investigated.The study revealed that a fiber structure of the pearlite morphology and a <110> fiber texture of the ferrite matrix begin to take shape and develop gradually with increasing strain.The growth rates of the fiber structure and the <110> texture are different in different regions within the wires with increasing drawing strain.There is a close relationship between the pearlite morphology and the crystalline texture during wire drawing.The pearlite interlamellar spacing(ILS) and thickness of cementite lamellae(T) decrease gradually both in longitudinal and transverse sections.The definition of pearlite colony should be reconsidered for describing microstructure of the wire drawing deformed pearlitic steels.     

Fire retardant evaluation of carbon nanofiber/graphite nanoplatelets nanopaper-based coating under different heat fluxes

Three types of carbon nanofiber based nanopapers, namely, 1Clay/5CNF/9APP, 1xGnP/5CNF/9APP, and 3xGnP/1CNF/9APP were made and their flame retardant efficiency was compared with thermogravimetric analysis and cone calorimeter test with 50 kW/m² of heat flux. The nanopaper of 3xGnP/1CNF/9APP was selected for experimental study because of its relatively good bonding with underlying structure and flame resistance performance. The fire response of glass fiber reinforced polyester composites with and without the selected nanopaper coating was thoroughly examined with cone calorimeter test using varied heat fluxes. It was found that at higher heat flux, the nanopaper demonstrated better flame retardant efficiency. Specifically, at 100 kW/m² of heat flux, the 1st and 2nd PHRR of the nanopaper-coated sample were more than 32% and 47% lower than the PHRR of control sample, respectively. In order to gain an insight into the pyrolysis process and flame retardation mechanism, the temperature profiles at the middle and back of the samples subjected to different heat fluxes were recorded. At 100 kW/m² of heat flux, the final temperature within the nanopaper-coated sample was roughly 280 ^oC, which is lower than control sample. The degradation rates in flexural moduli of the samples with coupon shape were determined using three-point bending. The three-point bending test results showed when the sample was exposed to 25 kW/m² heat flux for 240 seconds, the flexural modulus of control sample almost reduced to zero, whereas the nanopaper-coated sample still retained a half of its original flexural modulus. Finally, flame retardation mechanism was proposed for the nanopaper-coated composites.     

冲击荷载作用下含水泥质粉砂岩的损伤规律研究

采用分离式霍普金森压杆(SHPB)试验装置,对泥质粉砂岩进行了不同含水状态下的动态力学性能试验,分析了含水率变化对泥质粉砂岩动力特性的影响,并基于连续损伤理论及统计强度理论建立了泥质粉砂岩的动态损伤力学模型,得到了相应的损伤演化规律。研究结果表明,采用基于Weibull分布建立的动态时效损伤模型,其理论拟合曲线与实测曲线具有较好的一致性,损伤参数F0与弹性模量及冲击速度有一定的相关性,弹性模量越大,损伤参数F0也越大,含水率的变化对岩石动力特性具有较大的影响。     

线性调频信号低旁瓣脉压窗函数的优化设计

由于线性调频(LFM)信号的幅度谱不是标准的矩形形状,常用的窗函数有时无法将脉压旁瓣降得足够低,因此提出了LFM 信号低旁瓣脉压窗函数的优化设计方法。首先,将频域窗函数的求解表示为一个最优化问题,即在保证设计窗函数下的脉压主瓣与期望主瓣的差别小于给定值的条件下,使设计窗函数下的脉压旁瓣尽可能低;然后,将问题表示为标准二阶锥规划形式并求解。仿真实例表明,设计窗的脉压旁瓣显著低于海明窗的脉压旁瓣,设计窗脉压主瓣的无约束部分有所展宽,两个窗函数下脉压信噪比相同。     

重塑黏土临界状态线随初始含水率的变化规律

针对具有不同初始含水率的两种饱和重塑黏土进行了一系列的三轴固结不排水剪切试验,探讨初始含水率对黏土临界状态的影响,得到了不同初始含水率重塑土的应力-应变关系和有效应力路径。根据应力-应变关系曲线发现不同初始含水率重塑土均存在临界状态应力比。基于临界状态土力学理论研究了在p´-q平面和v-lnp´平面内临界状态线随初始含水率的变化规律,并分析了初始含水率对临界状态参数的影响。