Relevancy and role of whole-farm models in supporting smallholder farmers in planning their agricultural season

The way a model is designed to assist farmers in their decision-making may influence how it is understood and perceived by farmers and shape interactions between farmers and model users (researcher, advisor). This study compared the strengths and weaknesses of three types of whole farm models used by researchers to assist 18 crop-livestock farmers in Burkina Faso in planning the next agricultural season. Due to its simplicity, the static simulation tool of annual farm stocks and flows led to superior changes in the farmers' knowledge and practices. The rule-based dynamic simulation tool helped the researchers grasp farmers' decision-making processes but was difficult for farmers to understand due to the discrepancy between its multi-annual time step and the farmers' short-term planning horizon. The optimisation tool stimulated more strategic discussions regarding paths to improve farm income despite a design that was distant from the farmers' reality.     

High-accuracy finite-difference methods for the valuation of options

A finite-difference scheme often employed for the valuation of options from the Black–Scholes equation is the Crank–Nicolson (CN) scheme. The CN scheme is second order in both time and asset. For a rapid valuation with a reasonable resolution of the option price curve, it requires extremely small steps in both time and asset. In this paper, we present high-accuracy finite-difference methods for the Black–Scholes equation in which we employ the fourth-order L-stable Simpson-type (LSIMP) time integration schemes developed earlier and the well-known Numerov method for discretization in the asset direction. The resulting schemes, called LSIMP–NUM, are fourth order in both time and asset. The LSIMP–NUM schemes obtained can provide a rapid, stable and accurate resolution of option prices, allowing for relatively large steps in both time and asset. We compare the computational efficiency of the LSIMP–NUM schemes with the CN and Douglas schemes by considering valuation of European options and American options via the linear complementarity approach.     

Mechanical Properties of Multiblock Polyamide-Polyoxirane Copolymers

Abstract

The mechanical properties of alternating polyamide-polyoxirane copolymers (P₁-P₂)_n were evaluated. The polyamide component of these copolymers consisted of poly(lactams), of poly(N-methyllactams) or of their statistical copolymers with a molecular weight ranging from 1,400 up to 15,000. Two different molecular weights (1,400 and 9,000) were chosen for the polyoxirane component. The dynamic mechanical spectra were determined with a Rheovibron viscoelastometer at a frequency 110 Hz and within a temperature range from - 190°C to 60°C. The stress-strain curves were measured with a table model of an INSTRON tester at room temperature. The dynamic mechanical behaviour indicates a reduced crystallinity of N-methyl substituted polyamides with respect to unsubstituted polyamides and a microdomain structure of some of the polyamide-polyoxirane copolymers. The stress-strain curves reflect the temperature position of the main transition, the fraction and molecular weight of the polyoxirane component and the possibility of a strain hardening of the material. The copolymer samples exhibited both plastic and viscoelastic deformation mechanism which was reflected in a delayed elasticity after unloading. Some of the samples exhibited an unusually high strain-at-break, i.e. up to 1,500%. A repeated testing of fragments of once broken test pieces showed that after drawing there was a large increase in tensile strength of some samples, up to six times the original value.     

如何成为一名出色的业主方建设工程项目经理

结合多年的建设单位工程项目建设的实践经验,就工程项目管理中,项目经理如何通过项目管理实现项目目标,阐述笔者的观点。     

图片文字翻译策略探析——基于功能翻译理论三法则

文章基于功能翻译理论的目的性法则、连贯性法则和忠实性法则，结合图片文字翻译方面的相关译例，旨在探究一个更为完善的适于图片文字翻译的方法体系。研究发现：结合图片及所附文字信息，分别或联合使用直译、释义、删译、增加背景信息、改写等五种翻译方法，有助于更有效地翻译图片文字、增加图片文字的感染力。     

特种设备焊工考试新旧标准对比分析

为了更好地实施《特种设备焊接操作人员考核细则》,结合锅炉制造行业工作情况,分析了该标准对承压类设备焊接操作人员的考核程序与要求,并且与旧标准进行TIC比分析。《特种设备焊接操作人员考核细则》发生了较大的变动,其中焊工考试范围增大,增加了焊接母材、焊接方法、角焊缝考试要求,延长了焊工证书有效期,提出了复审要求,提高了考试机构条件。《特种设备焊接操作人员考核细则》使焊工考试更加合理化,焊工考试管理更加规范化、透明化。     

基于数据挖掘的电子商务推荐系统

基于数据挖掘的电子商务推荐系统,通过使用关联规则算法来对客户的事务执行购物篮分析,知道那些产品比较热销,以及一个特定商品与另一个商品被一起购买的可能性有多大。从而通过商品的推荐和捆绑销售,为客户提供个性化服务,同时实现利益的最大化。在总结前人挖掘模型的基础上,设计了基于Apriori算法的电子商务推荐系统。Apriori算法作为最有影响的挖掘布尔关联规则频繁项集的算法,简单可靠,适合于机器学习。     

内蒙古珠尔嘎钼及银铅锌矿成矿地质特征及规律分析

内蒙古锡林浩特地区大地构造环境复杂,成矿地质条件优越,有色金属矿床类型多样,找矿潜力巨大。文章通过对内蒙古东乌珠穆沁旗珠尔嘎钼及银铅锌矿地质特征、地球化学特征及矿体特征进行分析,总结了其成矿规律:矿体均赋存于燕山早期(黑云母)二长花岗(斑)岩(ηγ52)与泥盆系上统安格尔音乌拉组(D3a)变质粉砂质细砂岩及变质中酸性火山碎屑岩的内外接触带中,(黑云母)二长花岗(斑)岩体为成矿提供了含矿热液,北东向断裂构造为成矿提供了运移通道和容矿空间。故建议在矿区西南一带靠近主断裂及岩体的内接触带附近进一步加强银铅锌钼多金属的找矿勘查工作。     

数据挖掘技术在煤炭系统体育比赛中应用研究

将计算机技术应用到煤炭系统体育领域中来,能够有效地促进煤炭系统体育竞技水平的提高。本文在煤炭系统体育竞技中引入数据挖掘技术,科学地分析煤炭系统体育比赛的各种数据,从而能够促进煤炭系统体育竞技的技战术水平的提高。基于乒乓球技战术原型分析系统的基础上,文中在煤炭行业工业控制计算机网络基础之上,对数据挖掘技术进行了仔细的研究,采用了关联规则算法,并提供了开发类库的中间件,使之能够成为煤炭系统体育竞技比赛的分析技战术的一个有效工具,应用到乒乓球技战术分析系统中去,促进了乒乓球技战术的提高。     

安徽巢北凤凰山地区地层及其部分成因分析

通过对巢湖凤凰山地区自然露头和人工揭露的地质点进行系统的地质观测,收集各种地表地质信息等有关资料,研究地表地质活动规律,包括地层划分和层序、岩性组合及岩相特征、地质构造及构造变动、岩浆活动及有用矿产的赋存规律。通过对各地层的岩性的分析,可以了解到当地的古地质环境、古构造环境,对于了解当地的能源聚集关系有较大的指导的作用。