北京市地区畜禽养殖污染总量估算

[目的]随着我国经济的发展,畜禽养殖业发展迅速的同时,日益增加的畜禽粪便排放也带来了生态环境污染问题。北京市由于特殊的经济和政策环境,畜禽产品需求量较大从而畜禽粪便排放量进一步增多,因此必须要加强对于北京畜禽养殖产业污染的防治,为生态环境保护及居民身体健康提供坚实保障。[方法]文章采用随机抽调与实地调研相结合的方式,了解北京市地区主要畜禽养殖情况,进一步使用畜禽养殖主要污染物排放量计算参数估算北京地区畜禽养殖主要污染物排放量。[结果]北京地区多以养殖生猪、牛、肉鸡为主;北京市11个区县产污量较大的3个区依次是顺义区、房山区和平谷区,主要污染物为化学耗氧量和总氮;通过实地调研,发现北京地区畜禽养殖存在以下问题:(1)资金技术欠缺,无法按照要求购买必须的污染防治设备;(2)小型养殖户应对风险能力弱;(3)部分养殖户抱侥幸心理,认为投资污染防治设备没有必要。[结论]加大畜禽养殖污染防治财政补贴力度,鼓励养殖者使用新型排污设备;各个区县主管农业的部门定期组织养殖者进行免费培训;加大扶持力度,促进有机肥市场发展;发挥资金及技术优势,优势互补;引导居民调整饮食结构,倡导健康生活与饮食习惯。     

锚杆(锚索)支护设计技术参数与应用

根据锚杆作用的不同机理,结合数据库技术,介绍了锚杆支护参数校核系统的一般原理,着重分析了经验数据在数据库中的表示方法,并且结合应用实例,说明了锚杆支护参数校核系统的优点及实用性。     

On the Application of Conditional Independence to Ordinal Data

A special log linear parameterization is described for contingency tables which exploits prior knowledge that an ordinal scale of the variables is involved. It is helpful, in particular, in guiding the possible merging of adjacent levels of variables and may simplify interpretation if higher-order interactions are present. Several sets of data are discussed to illustrate the types of interpretation that can be achieved. The simple structure of the maximum likelihood estimates is derived by use of Lagrange multipliers.     

Consumer Willingness to Pay for Dairy Products With the 100% Canadian Milk Label: A Discrete Choice Experiment

ABSTRACT

A component of the supply management policy governing the Canadian dairy sector is a requirement that all milk and cream sold in Canada be sourced from Canadian producers. Cheese, yogurt, and ice cream, however, can be made using imported milk components. Recently, the Dairy Farmers of Canada launched a 100% Canadian Milk label for products that contain only milk and milk ingredients produced in Canada. Featuring a discrete choice experiment, a Canada-wide survey of dairy consumers is used to elicit their willingness-to-pay for milk and ice cream carrying the 100% Canadian Milk label. The results show that Canadian consumers are willing to pay more for milk and ice cream products that carry the label. Consumer knowledge of the dairy sector affects their willingness to pay for this labeling information. Implications for the use of the Canadian origin label and suggestions for further research are discussed.     

计算机在实践中的运用

介绍了如何对紫金Ⅱ微机进行改进,使其既保持原有的性能(用高级语言编程)又具有单片机的工控特性。举出了用于控制通风管道温度参数的成功例子。     

Bounding endogenous regressor coefficients using moment inequalities and generalized instruments

The main approach to deal with regressor endogeneity is instrumental variable estimator (IVE), where an instrumental variable (IV) m is required to be uncorrelated to the regression model error term u (COR(m,u)=0) and correlated to the endogenous regressor. If COR(m,u)≠0 is likely, then m gets discarded. But even when COR(m,u)≠0, often one has a good idea on the sign of COR(m,u). This article shows how to make use of the sign information on COR(m,u) to obtain an one‐sided bound on the endogenous regressor coefficient, calling m a ‘generalized instrument’ or ‘generalized instrumental variable (GIV)’. If there are two GIV's m₁ and m₂, then a two‐sided bound or an improved one‐sided bound can be obtained. Our approach is simple, needing only IVE; no non‐parametrics, nor any ‘tuning constants’. Specifically, the usual IVE is carried out, and the only necessary modification is that the estimate for the endogenous regressor coefficient is interpreted as a lower/upper bound depending on the prior notion on the sign of COR(m,u) and some estimable moment. A real data application is done to Korean household data with two or more children to illustrate our approach for the issue of child quantity–quality trade‐off.     

浅谈铣刀和铣削用量的合理选择对数控加工的影响

机械加工的目的为:高质量、高效率和低成本。数控铣床做为一种高效率的加工设备,要想充分发挥其高效的特点,与合理的生产工艺分不开,而铣刀与铣削用量的合理选择是生产工艺中不可缺的一部分。合理的选择铣刀和铣削用量不仅能提高加工效率而且能保证零件的加工质量。     

浅孔爆破在露天场地平整中的应用

文章介绍了浅孔爆破在露天场地平整的应用,通过选取合理的爆破参数,采取有效措施控制爆破飞石、爆破震动,保证了爆破区域周边建筑物安全。     

网络计划技术探讨——虚工作的时间参数是否需要计算

虚工作在网络计划技术中起着非常重要的作用，作为一种特殊的工作， 其时间参数是否应当如常规工作一样计算呢？这个问题是值得加以探讨的，因为众文章或书籍对这一问题处理得较为混乱。本文通过双代号网络与时标网络的对照及论证，以期得以统一、准确的结论。     

Unconditional tests for association in 2 × 2 contingency tables in the total sum fixed design

The asymptotic approach and Fisher's exact approach have often been used for testing the association between two dichotomous variables. The asymptotic approach may be appropriate to use in large samples but is often criticized for being associated with unacceptable high actual type I error rates for small to medium sample sizes. Fisher's exact approach suffers from conservative type I error rates and low power. For these reasons, a number of exact unconditional approaches have been proposed, which have been seen to be generally more powerful than exact conditional counterparts. We consider the traditional unconditional approach based on maximization and compare it to our presented approach, which is based on estimation and maximization. We extend the unconditional approach based on estimation and maximization to designs with the total sum fixed. The procedures based on the Pearson chi‐square, Yates's corrected, and likelihood ratio test statistics are evaluated with regard to actual type I error rates and powers. A real example is used to illustrate the various testing procedures. The unconditional approach based on estimation and maximization performs well, having an actual level much closer to the nominal level. The Pearson chi‐square and likelihood ratio test statistics work well with this efficient unconditional approach. This approach is generally more powerful than the other p‐value calculation methods in the scenarios considered.