Theory of the halftone process I. The penumbra theory

A method of calculating the tone reproduction curve of a halftone from the light distribution behind the halftone screen, or vice versa, is described. The actual light distribution is found to check satisfactorily with the distribution calculated from geometrical optics, i.e., penumbra theory, when coarse screens and abnormally short screen distances are used, except in the regions of very low light intensity. With fine screens and normal screen distances, both dot shape and tone reproduction differ markedly from the calculated results and can only be explained by the effects of diffraction.     

Dynamics of cholera transmission model with imperfect vaccination and demographics on complex networks

Cholera is a waterborne infectious disease that continually emerges and remains an important global health burden. We formulate and investigate a cholera model with imperfect vaccination and demographics on complex networks, in which two transmission pathways, indirect environment-to-human and direct human-to-human transmissions, are incorporated simultaneously. The contacts among humans are treated as a heterogeneous network and the contacts between environment and humans as homogenous mixing. Using the spectral analysis method, the basic reproduction number is defined and verified to be a sharp threshold which completely determines global dynamical properties of model. Numerical simulations are performed to confirm the theoretical results. The results demonstrate that demographics and the degree distribution of the network are of great importance in cholera propagation, and that the degree distribution is time-dependent until the stationary state is reached. Furthermore, demographics have a significant influence on the basic reproduction number. By increasing the vaccination rate and decreasing the rate at which the vaccine wears off, cholera infection can be effectively controlled.     

浅析单张纸双面双色印刷中影响套印精度的因素及应对

通常按照两个标准来评价印刷品的质量:一个是色彩的还原程度,另一个则是套印的精度。彩色制版是一个色彩的分解过程,而彩色印刷是一个色彩的组合过程,这个色彩的组合过程就叫套印。实现良好而准确的套印对于印出好的产品是非常的重要。套印准确的要求不仅仅局限于同一张印刷品上的不同色,而且同一印刷品的正背两面,同一批产品的印张之间都应当达到相应的标准。在实际印刷中容易导致套印不准的原因多种多样,其产生的原因也是各不相同。文章就套印精度对印品色彩再现的影响和双面印刷过程中较常见的影响套印精度的因素与应对进行简要的探究与分析。     

动物繁殖学教学方法研究

动物繁殖学是一门讲授动物繁殖方法的课程,对大学生这个敏感的群体而言,传统授课方法中的师生互动、图片展示、视频讲解都较难获得预期效果。我们分别采用局域网授课和传统授课的方法进行教学,课后考试对比两种教学方法的效果。结果表明局域网授课的方法可以显著提高学生的考试成绩,尤其是女生的考试成绩。因此,局域网教学更适合动物繁殖学教学。     

警惕仓库内的隐形杀手-黄曲霉毒素

黄曲霉毒素的毒性很强,是重要的致癌物质。本文介绍了黄曲霉毒素的产生和基本特点,探讨了它的生长条件和实验方法,最后研究了它的繁衍规律及防除措施。     

基于知识活动系统全息性的U/I知识联盟的理论构建

从马克思的社会再生产理论出发,将人类的社会再生产活动系统分为知识生产系统、知识传播系统和知识应用系统,并分析了人类知识活动系统的全息性理论,进而运用这一理论从知识的视角为U／I知识联盟的构建寻找理论支撑．     

刺五加的有性生殖与营养繁殖

刺五加 Eleutherococcus senticosus (Rupr.et Maxim.)Maxim,既可进行有性繁殖,又可进行营养繁殖。本文报道其三类花丝长度不同的植株每个花序的花朵数量、座果率、饱满种子率及根茎形态和形态发生的某些特点。通过人工受精,检测了其繁育系统。结果表明:长花丝植株不座果,短花丝植株座果,但不同年份、不同生境中座果率不同,中花丝植株也座果但饱满种子率教低。在正常年份,短花丝植株的座果率接近40％，并且林缘的座果率稍高于皆伐迹地和次生林下的。考虑到中花丝植株在所研究地区居群数很少，我们认为绝大多数刺五加种子是异花传粉的产物，其有性生殖与营养繁殖相配合，在无人为破坏的前提下，该物种不应该濒危。     

Ultrasonic delay lines

This paper deals with the experimental aspects of ultrasonic delay lines in liquid media and is a sequel to a previous paper treating the general theory of such devices.Delay devices employing ultrasonic propagation through liquids have proved satisfactory for delay times of the order of 3 milliseconds or less. Such devices can be made broadband and give excellent reproduction of pulse shape. The design considerations for such devices are discussed and illustrated by actual examples.     

Effects of acidified water on fish

The acidification of water leads to disturbances in the water and ion metabolism of fish, including the acid-base balance. Many fish probably possess physiological mechanisms to eliminate these disturbances completely or in part. However successful they may be in the short term, such adaptation mechanisms nevertheless require additional energy, thus causing growth and reproduction to be retarded. Taking into account the high sensitivity of fish eggs and larvae to acidification, these phenomena are probably a major contributory factor to the decline of fish stocks in acidified water.     

The impact of hospital resources and environmental perturbations to the dynamics of SIRS model

Incorporating the environmental perturbations and available resources of the public health system, we construct both deterministic and stochastic models of SIRS type. The deterministic model exhibits very rich dynamics, such as Hopf bifurcation and backward bifurcation which leads to the co-existence of the stable disease-free state and a stable endemic equilibrium. For the stochastic model, we show that under mild extra conditions, if the basic reproduction number is less than one, then the disease will be eradicated almost surely, and if the basic reproduction number is greater than one, the stochastic model will admit a unique ergodic stationary distribution, which implies that the disease persists almost surely. Part of our numerical simulations indicate that: (i) The introduction of environmental perturbations may drift the endemic equilibrium to the disease-free equilibrium, or vice versa; (ii) Increasing available resources is necessary in order to mitigate the infections.     

中国民间美术造型的艺术特色初探

种族繁衍和祈福纳祥是民间美术造型重要的内容,寓意和联想是民间美术造型的基本特色,完美的形象和浓烈的色彩是民间美术造型鲜明特点,感悟造型是民间美术造型的显著心理特征.     

基于链接的数字图书馆虚拟资源建设的知识产权风险分析

知识产权问题是制约数字图书馆发展的关键因素,本文分析了数字图书馆通过链接和网上资源下载进行虚拟资源建设过程中存在的知识产权风险,厘清了链接过程中所涉及的信息网络传播权、复制权、发行权等一系列知识产权问题及法律问题,最后提出了数字图书馆进行虚拟资源建设时的应对措施。     

多模态广告语篇的概念再现

广告作为一种重要的语篇研究形式,融合了包括文字、图像、声音等多种模态。迄今为止对其研究主要体现在文体、修辞、词汇等语言研究上,而往往忽略了其他模式。本文试图运用社会符号学的多模态来分析广告,重点放在多模态语篇的概念再现意义上,着力探究分类过程、分析过程和象征过程在广告再现意义上的构成和作用,帮助读者了解图像作为社会符号和语言作为符号如何共同作用构成意义,同时提高人们运用多模态理论解读多模态语篇的能力。     

上皮细胞生物学——生物医学多学科交叉的切入点

上皮细胞在机体内分布广泛,介导着包括呼吸、消化、生殖、听觉和免疫防御在内的一系列重要生理功能。上皮细胞功能紊乱将会导致广泛的病例改变和疾病,例如囊性纤维化病。"上皮细胞生物学研究中心"成立10年来,致力于上皮细胞生物学相关的研究,并通过多学科交叉性的合作取得了一定的成果。本文总结了研究中心以上皮细胞作为多学科交叉的切入点的研究进展,并探讨上皮细胞生物学对机体功能与疾病研究的重要性。     

动物繁殖学实验教学改革与创新人才培养探讨

动物繁殖学实验是动物科学专业重要的基础课程,对培养学生的创新精神和实践能力起着十分重要的作用。通过对动物繁殖学实验内容的调整,将实验内容划分为两大模块：室内实验4个,室外实验3个。实验包括验证性实验、综合性实验、设计性实验和开放性实验,重点突出综合实验。实验重视设计性及创新性,引入多媒体辅助教学,并建立全面灵活的考核体系。通过这些改革措施,提高了学生的实验兴趣、增强了学生在实验中的主动性,培养了学生的创新能力。     

基于技术遗传特性的新产品开发研究

摘要：生物界中,遗传与变异现象十分普遍,没有遗传,物种就不可能延续,没有变异,物种就不可能进化。技术也具有遗传特性,依照生物遗传与变异法则,产品开发可由现有技术在遗传与变异的基础上迅速得到。本文结合遗传学、生物学、进化论的相关理论分析了新产品开发中技术的遗传特性,探讨了新产品开发中技术的演变规律以及新产品开发路径。     

信息产品的经济特性与市场机制分析

本文把信息产品作为与物质产品相对应的范畴,分析了信息产品的经济特性与市场机制。经济特性中阐述了信息产品生产与再生产的巨大成本差,信息产品的“准公共物品”性。在分析信息产品市场饥制时,引入了市场需求和社会需求的概念,并依此将信息产品分为三类,对每种类型的信息产品都分析了其成本和收益。     

图书馆真信念及其选择繁殖

知识是被证明的真信念.而图书馆可获得的储存数据并不都是真信念或被证明的真信念.探寻图书馆储存的真信念是知识再生产的重要起点.图书馆用户和馆员在图书馆里淘金是现代社会的重要生产方式.本文重点讨论图书馆真信念的基本特点、生长模型和选择繁殖.     

新生代农民工早婚早育现象研究

在城市“剩男”、“剩女”不断增多,社会晚婚现象逐渐普遍的情况下,对新生代农民工出现的早婚早育现象的研究具有社会意义。在分析新生代农民工早婚早育生成的原因基础上,提出培育新生代农民工现代生育观念的对策建议。     

Theory of the halftone process. III. Dot size and halftone density

The theoretical and experimental quantitative relationships between the dot diameter, dot area, and density of a halftone are given. Experimental results do not agree exactly with the theoretical relationships except for screen negatives and positives with sharp dots.For accurate rendering, highlight dots in a reproduction must increase extremely rapidly in size for small density increments in the highlights of an original. A “emi-dark-field” densitometer is described which eliminates the effect of dot fringe in measuring densities of screen positives. The relationship between density of screen positive and density of proof is briefly discussed.