气体流量对管材气辅挤出的影响

将气体简化为广义牛顿流体,并作为单独的内外两层,针对管材型气辅挤出口模,建立了二维有限元模型,并进行了数值模拟,研究了气体流量对口模出口处剪切速率、熔体速度及口模流道中心处熔体压力的影响。研究表明,当气体流入口模流道内,聚合物熔体在口模出口处厚度为-0.85~0.85 mm剪切速率为零,为促使聚合物熔体既满足表面质量不因剪切速率不均引起表面质量缺陷,又满足在厚度方向的尺寸要求(即2 mm),故需将聚合物熔体与气体相汇处的流道沿厚度方向扩大0.3 mm;同时也为了进一步降低因速度梯度大而引起的表面质量缺陷,文中进气体流量为2.512×10-3m/s最佳。因此,当气体作为一种辅助工艺引入到聚合物挤出成型当中,需在两相流相汇处流道沿厚度方向预留足够的空间(本文是预留制品厚度的20%的尺寸)以满足制品的尺寸及表面质量要求。     

真彩色航空摄影影像质量控制方法与评定标准

本文针对当前国内航空摄影生产的实际情况,总结了近几年生产作业经验,通过对大量数据的测定、比较与分析,介绍了真彩色航空摄影质量控制方法与质量评定标准,该方法和标准对完成好真彩色航空摄影任务具有较好的指导意义,同时,对国内同行也具有一定的参考价值。     

Influence of luminance and resolution on the perceived quality of black-and-white images on soft displays

Abstract

The perceived quality of an image displayed on a computer monitor depends on a number of different factors that can affect viewers' preferences. Two of these are the luminance of the monitor display and the resolution of the image. The effect of luminance is of interest for applications such as on-line access of images where the computer displays used for viewing these images could have different luminance settings. A relationship between cathode-ray tube (CRT) display luminance and resolution has been shown in previous studies. It was therefore interesting to investigate whether there is a relationship between image resolution and CRT display luminance on perceived image quality. Image resolution is related to the image file size, which is an important factor for applications such as on-line access of images. This work used a CRT display to study the effect of the above-mentioned factors on the perceived quality of the displayed image. Three sets of black-and-white images, each set with a different resolution, were presented to observers at three brightness settings of the computer monitor. Results are discussed regarding the effect of monitor display luminance and image resolution on perceived image quality and the interaction between them. Evaluation of results is further extended to the influence of the different backgrounds of the images. The scene content of the images was also shown to affect the viewers' judgement.     

航摄底片扫描数字化生产的质量控制

如何高精度高质量地对航摄底片进行扫描数字化生产,并对生产过程及成果进行质量控制与检查,确保数字化影像数据准确可靠,是保证全数字摄影测量成图成果质量的一个基础环节。文章围绕这一环节,并结合笔者多年来管理扫描数字化生产的实践经验,就原始底片扫描的硬件平台、软件模块及生产过程的质量控制进行论述。     

秦兵马俑博物馆陶器库房冬季室内空气质量初步研究

于2008年1月30日～3月3日,在秦始皇兵马俑博物馆陶器库开展了室内大气环境调查,同步采集了大气悬浮颗粒PM2.5和NH3样品,获得了PM2.5颗粒中的离子组成,并实时监测了SO2、NOx的浓度变化。结果表明,陶器库中PM2.5平均质量浓度为76.1μg/m3,室外PM2.5平均质量浓度为153.9μg/m3,约为室内浓度的2倍。室内PM2.5中水溶性离子主要由SO42-、NO3-和NH4+组成,平均质量浓度分别为17.5、5.2、5.5μg/m3,它们分别占PM2.5质量浓度的19.7%、5.2%、5.8%。库内NH3平均浓度为4.8μg/m3,室外NH3平均浓度6.6μg/m3,约为室内的1.4倍。室内NO、NO2、NOx浓度日平均分别为4.8×10-9、3.2×10-9、8.0×10-9,SO2浓度日平均为0.9×10-9。研究表明,库内人为活动量对质量浓度、离子浓度和污染气体均有一定影响,库房相对于室外对阻挡颗粒物减少外界影响方面对文物有一定的保护作用,但在阻隔空气污染物和恒温恒湿方面的作用还有待加强。     

空调用电子膨胀阀流量特性研究

本文通过实验研究了电子膨胀阀流量与开度的关系。实验表明家用变频空调器中的电子膨胀阀开度与制冷量近似成线形关系，从而为电子膨胀阀的正确选用和变频空调器性能的进一步优化提供理论依据。     

An epidemiological study of the risk of cycling in the dark: The role of visual perception,conspicuity and alcohol use

To curtail the rising numbers of cyclists seriously injured in road crashes, more insights are needed into the factors that contribute to these crashes. For instance, darkness is known to be associated with higher injury rates, but little is known about the relative influence of factors such as poor conspicuity, impaired perception and alcohol use among cyclists. To examine these factors, the present study analyzed the epidemiological crash data for three meteorological light conditions: daylight, late evening darkness and early morning darkness; for two crash types: crashes with (M-crashes) and without motorized traffic (NM-crashes); and for different age groups. The relative injury rates (injury risk per distance travelled in darkness corrected for daylight injury risks for each age group) confirmed findings from earlier studies that cycling in late evening darkness is associated with higher injury rates than cycling in daylight conditions. This is the case for both crash types with only small differences between the age groups suggesting that poor conspicuity (M-crashes) and impaired perception (NM-crashes) may play a role. In comparison to late evening darkness, relative injury rates in early morning darkness are much higher. This is the case for both crash types with large differences among the age groups, suggesting that in addition to the absence of daylight also age related risk factors are at play. Support for this hypothesis was found from the analyses of hospital records, showing that the proportion of seriously injured cyclists who have been drinking is highest in early morning darkness and has strongly increased over the last decades. These insights provide input for the selection of countermeasures such as improved lighting (both street and bicycle lights) and interventions targeting alcohol use among cyclists.     

风机盘管机组测试用风量测量装置的设计

风量测量装置是空气焓差法测试系统中的重要部件,主要包括：围护结构、温湿度取样装置、喷嘴等部件,本文阐述了以上部件的设计思路,并结合实例,分析了各部件的技术难点及解决方案,研究结果对该装置的推广具有重要的指导意义。     

民国书刊封面设计文化中的"传统"与"西化"

以民国时期我国本土书刊装帧设计中西文化交融为启示,分析了民国书刊封面装帧的主要题材为文字与图文并茂,归纳了其从呈现传统本土装帧形式逐步演变成中西结合的现代装帧形式,进而分析了其设计文化内涵表现出浓郁的现代艺术气息;提出了民国书刊封面设计的审美表现:传统审美体验表现为体舒与神怡相携,西艺之美表现为抽象艺术与构成主义相合;进一步诠释了中西杂糅影响下书刊装饰设计的多样性。     

机械冷板冷藏车冷板融冰过程数值计算

用焓法模型建立了冷板融冰过程的数学模型，采用控制容积法对方程进行离散化，并用三对角矩阵算法求解出各节点的焓值和温度，分析了冷板厚度和车内空气温度对冷板融冰过程的影响；结果表明，冷板中心融解缓慢，冷板厚度对融冰过程影响比车内空气的影响大，减少冷板厚度将大大减少融冰时间。     

块体非晶合金剪切带温度的变化分析

通过对Zr41.2Ti13.8Cu12.5Ni10Be22.5(Vit 1)压缩实验,发现应力-应变关系曲线的锯齿流变特性随应变的增加而更为明显。并通过对简单剪切断裂面的分析,表明在剪切滑移过程中剪切带有一个形核和生长的过程。采用剪切带逐步扩展模型计算剪切带中温度的变化,通过计算表明剪切带形成中前期的温升不足以达到非晶合金的熔点,且剪切带温升与单个锯齿卸载部分形成过程所持续的时间和每次剪切滑移过程中载荷的变化量紧密相关。     

环境空气中氟化物监测的质量控制方法探讨

本文从点位布设、样品采集、样品保存、样品分析等环节对监测环境空气中氟化物的质量控制方法进行了探讨,在实际工作中具有很好的操作性。     

论感知精度在产品设计中的应用方法

论述了感知精度的概念及其在设计中的至关重要性,并结合学习和设计实践的过程,分析了感知精度在产品设计中的应用方法,以及设计者在产品设计过程中如何提升自己的感知精度,进而分析了感知精度的培养对提高设计水平大有裨益,最后得出感知精度能够锻炼设计者正确把握产品的精度和美感,并对产品物化的实现和提高消费价值有着积极的作用。     

露天土岩爆破工程的质量与安全控制

文章介绍了阜新(西)露天一期工程深孔爆破剥离11559 m3土岩的质量与安全控制过程及爆破参数的选择和确定.提出了几点质量与安全的注意事项,对于类似工程有借鉴作用.     

绿色经济背景下的品牌绿色形象设计

在绿色经济背景下,绿色形象设计对品牌塑造与发展有着重要的价值。企业应根据客观发展来确定品牌的位置和方向,使消费者对产品或品牌价值产生清晰的认知。在此基础上通过理性诉求、感性诉求等诉求方式,并运用联想法、直接展示法等广告表现手法,传达出品牌核心理念的基本信息,以提升企业品牌形象。     

A New Approach for Calculating the Mass Flow Rate of Entrained Air in a Freefalling Material Stream

This article presents the outcomes from a series of physical experiments to measure the air entrainment rates encountered within a stream of freefalling particles. The experimental work presented spans a range of particle parameters and hopper geometries. From these results a new theory for the prediction of air entrainment is developed and presented. This new method was developed specifically to facilitate a better understanding in the area of fugitive dust control associated with material handling systems, which are driven by the air entrainment during freefalling. From the work presented in this article, a better prediction capability of freefalling bulk materials in either constrained, or unconstrained systems, will allow for the optimization of either passive or active dust control strategies. This article presents several distinct sections that detail the experimental work used to determine the freefall stream parameters that were conducted to allow the development of the entrainment equations.