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从化肥造成食品污染、破坏土壤肥力和污染生态环境三方面分析了人们对化肥的误解。并对化肥作为污染物的证据和对化肥误解的原因进行了剖析。指出化肥本身并不是污染物,仅能称为污染因子,造成化肥污染的根本原因是施肥不当。文章最后提出了解决我国化肥污染问题的措施。 相似文献
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本文根据施肥研究和调查资料以及有关统计数据 ,对我国施肥中存在问题进行了分析 .目前化肥总量不足、施肥和肥料结构不合理、肥料分配不当、化肥施用不合理 ,浪费严重 ,并且已引起环境污染、科学施肥到位率低等是我国现阶段存在的主要问题 .提高化肥利用率、减少化肥对环境的污染将是今后施肥工作的主要任务 相似文献
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“把化肥直接卖到农民手里,成为中国农民最大的化肥供应商”。
“未来,中化化肥要建立一套完善的面向基层的营销网络体系。”在中化国际化肥贸易公司CIO范贺军的眼里,他的这个销售网络,分销业务要覆盖到全国每一个县。实际上,从2003年6月213,中化国际化肥贸易公司第一家化肥专营店在山东苍山县大炉乡开张时算起,到现在, 相似文献
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盆栽试验表明,氮素化肥和有机肥对水稻生物学特性影响差异明显。按同等养分量施化肥比单施有机肥明显增产;有机肥施用达到一定量后可以提高土壤中氮素含量,而化肥对于土壤氮素提高不明显。 相似文献
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土壤质量与土壤的生物学性质密切相关,施肥制度对土壤生物学特性的影响研究对土壤质量管理具有重要的意义.本文以沈阳农业大学长期肥料定位试验为基地,研究长期不同施肥制度对土壤理化性质,过氧化氢酶、脱氢酶活性和动力学特征的影响.主要研究结果:施用化肥、有机肥配施化肥降低土壤pH值,提高4种土壤全量养分(全C、全P、全S、全N)含量,有机肥配施化肥提高土壤速效N含量;低量化肥配施有机肥显著提高土壤过氧化氢酶活性及Vmax/Km值和Vmax值,低量化肥配施有机肥显著提高脱氢酶活性及Vmax/Km值,降低脱氢酶Km值.本文的研究表明,合理的化肥施用量及配施有机肥是提高土壤生物学活性的有效手段. 相似文献
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土壤呼吸是土壤有机C矿化分解,释放无机养分的重要生物化学过程。对公主岭地区长期有机肥(不施有机肥、施中量和高量有机肥处理)与化肥(不施化肥、施用N、NP、NPK化肥)配合施用的12个处理的黑土进行室内好气培养(196天),采用一级动力学方程模拟土壤的呼吸过程,结果表明,有机肥和化肥的施用能显著增加土壤呼吸释放的CO2 -C的累积量,提高土壤中潜在矿化的有机碳含量及其占土壤有机质的比例,促进土壤有机质中无机养分的释放,有利于提高土壤养分的有效性,改善黑土的供肥状况。有机肥与NPK化肥配合施用效果更为明显。 相似文献
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寄存器队列装置及其设计方法 总被引:1,自引:0,他引:1
介绍了寄存器堆队列装置(FIFO)的作用和设计原理。传统寄存器队列的设计多采用串行输入一串行输出,或者并行输入-并行输出的方式,该文介绍了两种并行输入-并行输出而且可以“边进边出”的寄存器队列装置,该装置可用于总线接口和先行控制处理机的设计中。 相似文献
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《Computers & Industrial Engineering》2004,46(2):267-273
Surface design and structure design are two aspects of product design. Product information can be perfectly described only if both of them are organically united. The impact of a product's appearance on its performance and decoration has been given much attention in engineering and on the market. The existing CAD system does not suffice for surface design, which is still designed with experience and handicraft. This case does not accommodate new market development. To grapple with this problem, a representation of appearance features, an aided design of the figure and the surface design, which is based on mapping, are detailed in this paper. A design system of surface design and an instance of its application are given at the end of the paper. 相似文献
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周宇 《数码设计:surface》2009,(4):136-138
创新来源于实践。创新设计人才培养离不开具有创新特色的设计教育。实践教学是设计教育培养创新型设计人才的有效途径。实践教学改革应围绕创新设计人才培养,在坚持教育观念是先导、教学环节是核心和教学管理是保障的原则下创新。 相似文献
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Kuang-Hua Chang 《Structural and Multidisciplinary Optimization》2008,37(1):91-106
This paper presents shape design sensitivity analysis (DSA) and design studies for recreational waterslides represented in
computer-aided design (CAD) environment. The mathematical representations of a number of commonly used flume sections that
serve as the building blocks for waterslide configurations are created in CAD tools. Geometric dimensions of the individual
sections that affect not only their geometric shape but also the overall configurations are identified as design variables.
These design variables can be varied to search for better design alternatives, for example, safer waterslides. A set of coupled
differential equations based on Lagrange’s equations of motion that describe the motion of the riding object are derived.
The equations of motion incorporate friction forces between the riding object and the surface of the flume sections. These
second-order differential equations are then solved using Mathematica. Based on the equations of motion and design variables
identified, a set of differential equations are derived for calculating shape DSA coefficients. These equations are solved
numerically again using Mathematica. The major contribution of the paper are (1) extending waterslide design parameterization
and shape DSA computation to true CAD-based flume sections, which greatly alleviates the design for manufacturing issues previously
encountered, (2) incorporating friction forces into shape DSA computation, and (3) developing a design scenario that includes
sensitivity display and what-if studies for a compromised design that is safer and with a larger acceleration, therefore,
higher excitement levels. Incorporating friction forces into the computation supports design for rider’s excitement levels,
which are related to accelerations. Waterslide design will not be realistic without including friction forces. 相似文献
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In this paper, the past and current issues involved in the design of decentralized networked control systems are reviewed. The basic models of interconnected systems described as continuous-time linear time-invariant systems in the time domain serve as a framework for the inclusion of communication channels in the decentralized feedback loop. The I/O-oriented models and the interaction oriented models with disjoint subsystems and interactions are distinguished. The overview is focused on packet dropouts, transmission delays, and quantization effects which are included in the time-driven design of feedback loop components. Single- and multiple-packet transmissions are considered in this contents. The design of decentralized state feedback gain matrices with delayed feedback uses the methodology of sampled-data feedback design for continuous-time systems, while the decentralized H∞ quantizer design is based on the static output controller. The Liapunov stability approach results in computationally efficient decentralized control design strategies described by using linear matrix inequalities. 相似文献
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基于知识的设计过程保存与重构 总被引:1,自引:0,他引:1
提出基于知识的广义特征信息模型和记录设计历史的广义特征CSG树的表示方法.通过对设计知识与广义特征的封装,构建了广义特征信息模型,在该模型基础上用CSG树的方法表示了设计过程.广义特征信息模型和广义特征CSG树存储于XML格式的广义特征信息表中,实现了设计过程的保存.通过对广义特征信息表的导入和解析,重构了设计过程,实现了设计过程和设计知识的重用.最后给出了在涡轮叶片设计中的实例. 相似文献
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高校计算机实验室设计与建设 总被引:1,自引:0,他引:1
本文对高校计算机实验室的设计与建设方案进行了研究,提出了网络化环境下的计算机实验室构架设计的基本思路、设计方法和设计目标,且以我院计算机实验室的建设情况作为研究范例进行计算机实验室的规划与设计,以最终实现实验教学资源共享和管理信息数字化。 相似文献
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详细地介绍了X ilinx公司的一种数字系统设计输入工具Log iBLOX,阐明了Log iBLOX的功能和特点,总结了Log iBLOX的输入和输出形式,并通过一个设计输入实例说明了Log iBLOX在数字系统设计输入中的应用。 相似文献
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李程 《数码设计:surface》2009,(3):5-7
本文根据国外设计产业发展的过程总结出设计发展的条件,提出了设计发展的阶段性与规律性,落脚于对中国设计的发展现况的解读与国内设计发展未来情况的分析。提出我们要借鉴美国经验,提供开放自由的设计平台,在设计界形成一个良性的竞争环境。 相似文献