Melt processing of nanocomposites of cellulose nanocrystals with biobased thermoplastic polyurethane

Nanocomposites of thermoplastic polyurethane (TPU) with cellulose nanocrystals (CNC) without and with surface treatment are obtained by melt processing. Nanocomposites are obtained with nanofiller weight content near of the theoretical percolation threshold (3.9 wt%). Visual observation of CNC agglomerates is sufficient to prove the inefficiency of the mixing in systems with untreated CNC. The crystallization kinetics of the TPU changes with the addition of CNC and this is confirmed by differential scanning calorimetry analysis. Thermogravimetric analysis prove that the addition of CNC increases the thermal stability of the TPU. From the rheological analysis it is possible to verify the absence of percolation and an intermediate state of sol–gel transition in the nanocomposites. CNC/TPU nanocomposites with 5 wt% of treated CNC present better mechanical performance than de neat TPU and the other processed nanocomposites and display around 130% increase in Young's modulus while retaining significant values of toughness, tensile strength and elongation at break.     

The challenge of predicting spinnability: Investigating benefits of adding lignin to cellulose solutions in air-gap spinning

In this study, the underlying mechanism for improved spinnability when mixing lignin and cellulose in solution was investigated. Co-processing of lignin and cellulose has previously been identified as a potential route for production of inexpensive and bio-based carbon fibers. The molecular order of cellulose contributes to the strength of the fibers and the high carbon content of lignin improves the yield during conversion to carbon fibers. The current work presents an additional benefit of combining lignin and cellulose; solutions that contain both lignin and cellulose could be air-gap spun at substantially higher draw ratios than pure cellulose solutions, that is, lignin improved the spinnability. Fibers were spun from solutions containing different ratios of lignin, from 0 to 70 wt%, and the critical draw ratio was determined at various temperatures of solution. The observations were followed by characterization of the solutions with shear and elongational viscosity and surface tension, but none of these methods could explain the beneficial effect of lignin on the spinnability. However, by measuring the take-up force it was found that lignin seems to stabilize against diameter fluctuations during spinning, and plausible explanations are discussed.     

太赫兹光谱识别木材的影响因素研究

径向变异和不同切面是影响太赫兹光谱识别木材的重要因素。为了探讨径向变异和不同切面对太赫兹光谱识别木材的影响,利用太赫兹时域光谱技术获取杉木和柳杉样品的太赫兹光谱数据,共600组木材光谱数据,分析太赫兹光谱,基于BP神经网络建立木材识别模型,比较模型预测的正确率。发现木材样品太赫兹光谱因为径向变异和不同切面而存在差异,预测样品与建模样品径向部位相同时和不同时的模型预测正确率差异较小,最高正确率达到96.25%,预测样品与建模样品切面相同时和不同时的正确率差异较大。结果表明,基于太赫兹时域光谱技术能够准确实现木材识别,径向变异对木材识别影响较小,不同切面对木材识别影响较大。     

Prevention of steel corrosion in concrete exposed to seawater with submerged sacrificial anodes

This paper presents the results of a study of the effectiveness of submerged sacrificial anodes in preventing the onset of pitting corrosion in the emerged part of marine piles. Experimental tests were carried out on reinforced concrete columns with steel embedded both in chloride free concrete and chloride contaminated concrete in order to compare the effects of sacrificial anodes on passive steel and on corroding steel. Results have shown, at least under the present testing conditions, that sacrificial anodes may be more effective in preventing corrosion initiation (i.e. in providing cathodic prevention) than in controlling ongoing pitting corrosion (i.e. in guaranteeing cathodic protection). Monitoring criteria for this type of prevention are also discussed.     

Q235钢—冷模具钢轧制复合刀片的组织性能

本文对Ｑ２３５钢－冷模具钢轧制复合刀片的组织和性能进行了研究。结果表明，Ｑ２３５钢－冷模具钢轧制度合界面部位形成了冶金结合，轧制复合刀片的整体力学性能优于整体刀片和焊接复合刀片。     

Trust fraud: A crucial challenge for China’s e-commerce market

Currently, China’s e-commerce market is growing at an unprecedented pace, however, it is faced with many challenges, among which the trust fraud problem is the biggest issue. In this article, we use Taobao as an example and conduct a thorough investigation of the trust fraud phenomenon in China’s e-commerce market. We present the development history of trust fraud, summarize its unique characteristics, and explore the reasons why so many sellers commit fraud. We further propose a dynamic time decay trust model that aims to deter trust fraud by raising its cost and promote the growth of small and medium-sized sellers. The model utilizes detailed seller ratings as the data source, and incorporates a transaction amount weight, a time decay coefficient, and three trust factors in the calculation of trust. We test the model on real transaction data from Taobao, and the experimental results verify its effectiveness. Our proposed trust model yields a practical approach to online trust management not only in the Taobao market but also for other e-commerce platforms.     

Large wood aids spawning Chinook salmon (Oncorhynchus tshawytscha) in marginal habitat on a regulated river in California

To determine whether large wood (LW, ≥1‐m length, ≥10‐cm diameter) plays a role in Chinook salmon (Oncorhynchus tshawytscha) redd (i.e. egg nest) placements in a regulated, Mediterranean‐climate, medium‐sized river (where channel width is less than the upper quartile of length of potential instream wood pieces), characteristics of 527 large wood pieces, locations of 650 redds, and mesohabitat delineations (riffle, run, glide, pool) were collected during a spawning season along a 7.7 km reach directly below Camanche Dam on the Mokelumne River, CA. LW was regularly distributed across the study reach an average 70 LW pieces km^‐1. Some LW clustering was evident at islands and meander bends. Spawners built 85% of redds within one average channel width (31 m) of LW. Spawners utilized LW within a 10 m radius 36% of the time in the upper 3 km rehabilitated reach, and 44% of the time in the lower 4.7 km marginal habitat reach. A greater percentage of LW was utilized in riffles in the upper 3 km reach where 90% of redds were built, while a larger percentage of spawners used LW in riffles in the lower 4.7 km reach. LW‐redd interactions occurred at greater rates than by random chance alone in the lower 4.7 km reach, which implies that LW aids spawning in marginal habitats. River managers and salmonid spawning habitat rehabilitation (SHR) projects should take LW additions into consideration as an important component of river rehabilitation. Copyright © 2010 John Wiley & Sons, Ltd.     

基于均匀颜色空间的木材分类研究

木材材色在各种颜色空间中的分布范围都比较窄,而利用CIEl976L*a*b*均匀颜色空间的等距性和色差高分辨力的特点可以很好地对其进行测量与辨别.在l*a*b*颜色空间中,提取了东北常见的5种树种的径切和弦切木材图像的颜色特征,然后采用模拟退火算法对这些特征进行了选择,并结合BP神经网络和k-近邻两种分类方法进行了仿真试验,得到了满意的分类结果.     

晋中装饰图案分析

晋中装饰图案主要集中在砖雕、木雕、石雕艺术上,其造型不拘一格,具有复杂多变、丰富多样的构成形式,给人以规模宏大、气势壮观、装饰精致、构思巧妙的艺术美感。本文从晋中木雕装饰图案这一个方面进行归纳分析,阐述晋中装饰图案的特点及形式美感。     

基于修正的卡尔曼滤波自适应跟踪算法

针对卡尔曼滤波对匀速运动目标能有效的跟踪,但是当目标出现转弯时,很难达到跟踪精度的要求,甚至丢失目标的现象.对卡尔曼滤波算法进行了改进,在观测向量中引入了两个加速度误差变量,它们动态地修正状态估计误差从而减少跟踪精度误差,形成了修正的Kalman算法.但是由于状态变量维数增加,使得计算量增加,实时性下降,将卡尔曼滤波算法与修正的卡尔曼滤波算法两种算法相结合,提出了基于修正的卡尔曼滤波自适应跟踪算法.仿真结果表明,具有良好的稳定性和精确度,优于一般的卡尔曼滤波算法.