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本文结合车辆运行生产实际,采用试验对比及数理统计方法,实施信息反馈,验证并在必要时对前期理论研究阶段所得到的模型解进行修正,以便最终确定国产第二代主力车型的最优维护周期。 相似文献
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为了解决京津冀地区农村冬季采暖存在的环境污染问题,以邯郸地区示范项目典型农宅为例,提出了一种新型的分体式地源热泵系统。首先,利用TRNSYS软件建立分体式地源热泵系统模型,模拟分析了系统的长期运行特性;再通过费用年值法和污染物排放量计算,对比分析该地区常见的4种采暖方式的经济性和环境效益;最后选出最合理的运行系统。结果表明:1)分体式地源热泵系统运行高效且稳定,运行期间系统COP达3.5以上,热泵机组COP达4.0以上;2)在间歇运行方式下,土壤平均温度一年的降幅为0.8%,十年的降幅为3.6%;3)在4种采暖方式综合对比下,分体式地源热泵系统运行费用较低且环保性较好。分体式地源热泵系统的运行性能研究为户用分体式地源热泵系统在京津冀地区典型农宅的应用推广提供了参考借鉴。 相似文献
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为优化密拼式叠合板侧向拼缝处的连接构造,设计一种在拼缝处设置抗剪键槽的密拼式钢筋桁架叠合楼板。利用ABAQUS有限元软件对7个密拼叠合楼板进行四点弯曲模拟研究,针对普通密拼式叠合板与不同形式的抗剪键槽密拼式叠合板的承载能力进行对比分析。结果表明:新型密拼式叠合楼板的承载能力较好,相较于普通密拼式叠合板提升了17%左右;当达到极限荷载时,其内置钢筋所受应力明显低于普通密拼式叠合板。通过对不同开槽形式叠合板的受弯性能进行对比分析,明确了新型抗剪键槽叠合板拼缝处设计的合理性,为新型拼缝叠合楼板在工程实践中的应用提供了理论依据。 相似文献
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为了提高空气源热泵采暖系统的热效率,开发了可同时吸收太阳辐射和空气中热量的直膨式太阳能/空气源热泵(DX-SASIHP)机组采暖系统。利用Matlab软件以多元非线性回归方法建立了DX-SASIHP机组的半经验数学模型,并利用TRNSYS 17软件二次开发功能建立新模块(TYPE 200),在新模块的基础上建立DX-SASIHP机组和空气源热泵(ASHP)机组采暖系统的地板辐射仿真模型。对DX-SASIHP机组和ASHP机组在典型采暖季中的制热量、耗电功率、COP值和建筑热舒适性指标等进行对比分析,结合实测数据验证了模型的准确性。结果表明: DX-SASIHP机组采暖季月平均制热量相比ASHP机组增长17.15%;采暖季累计耗电量相比ASHP机组下降12.89%;月平均COP值相比ASHP机组增长21.38%。DX-SASIHP机组运行期间可以营造热舒适Ⅰ级的建筑环境,室内温度、PMV和PPD等建筑热舒适指标均优于ASHP机组。研究成果拓展了TRNSYS 17软件的应用范围,验证了DX-SASIHP机组在独立建筑中的实际运行性能和采暖热舒适性效果,可为今后在农村清洁能源采暖中推广DX-SASIHP机组提供理论依据。 相似文献
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从凝汽器最佳真空的原理入手,分析探讨了目前火电厂循环水系统的运行优化问题.对水量不连续变化的单元制循环水系统提出了一种离散优化模型,该模型以等效益点迭代计算来决定泵组切换时的临界工况.以十里泉电厂300MW机组为例,利用本模型对循环水系统进行了运行方式的优化研究,确定了机组在不同循环水温、不同负荷最经济的循环水泵运行编组方式,编制了循环水系统最优化运行工况图,为运行中实现指导循环泵的科学经济调度提供了量的依据.效益分析表明,对于300MW机组,循环水系统离散优化可使电厂标准煤耗降低0.5~0.7g/kW.h.实践表明该方法简便易行,运行可操作性强,节能效果明显,而且无须增加额外的支出,有很好的推广价值. 相似文献
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中国石油西北销售公司针对多资源点、多到货点、多运输方式并且存在中转和运力约束的难题,近年来在优化运输结构、提高运行效率、降低整体运费方面进行了探索和实践,提出了分步式优化整体运输方案的方法,即通过逐次计算公路经济配送半径、不同运输组合成本、全局最优运输方案,逐步得出整体成本最小的运输方案. 相似文献
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为推进严寒地区建筑节能进程,通过更经济的节能改造策略适应不断提高的建筑节能要求,针对哈尔滨市某9层住宅楼,以提高围护结构保温性能和改设双向通风窗两种策略建立两类节能模型,利用能耗软件模拟分析两类模型较基本模型的节能性和经济性。对比改用双向通风窗前后的能耗变化情况可知:基本模型节能率提高约15%,每年每平方米节约费用1.87元;第一类模型节能率平均提高约13%,每年每平方米平均节约费用1.42元。与提高围护结构保温性能来达到节能效果的方式相比,采用双向通风窗即可在保证空气品质的同时,获得较好的节能效果。研究结果可为严寒地区的居住建筑节能改造提供参考。 相似文献
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根据我国国情,在建设资源节约型、环境友好型社会的思想指导下,采暖住宅建筑设计必须以降低建筑使用能耗、提高能源利用效率和保护环境为目的。建筑设计师应从合理布置建筑平面,控制建筑体形系数,加强围护主结构的保温,提高外门窗的保温能力,重视室内外过渡空间的保温等诸方面入手,实现建筑节能。 相似文献
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为了提高酚试剂法测定室内空气中甲醛的准确性,优化实验条件,系统研究了盐酸介质浓度、显色剂加入量、显色时间、显色反应温度和稀释液类型等因素对吸光度的影响,研究结果表明,采用0.1 mol/L盐酸配制的硫酸铁铵显色剂,显色剂加入量对吸光度影响不显著,最佳加入量为0.4 mL;显色反应温度对吸光度影响明显,最佳温度应控制在25~35℃范围内;稳定的显色反应时间应控制在18~30 min内,以20 min为宜;当甲醛质量浓度较高时,可选用去离子水或酚试剂吸收液进行适当的稀释。在较优的实验条件下,测定的甲醛质量浓度与吸光度在0~2.0μg/mL范围内呈良好的线性关系,r=0.999 9。 相似文献
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《Food Policy》2019
There are a number of potential pathways leading from agricultural input decisions to nutrition outcomes of farm households. These have special resonance in less developed areas of South Asia given widespread undernutrition problems, market failures and restricted access to land and other key assets and inputs, as well as ongoing debates around the implications that the green revolution has held for nutritional outcomes. A number of initiatives, including the Leveraging Agriculture for Nutrition in South Asia (LANSA) project have been undertaking research that addresses these linkages. The objectives of this paper are to systematically review the recent evidence on linkages between agricultural inputs and diet and nutrition outcomes of farm households in South Asia, place relevant LANSA research within the context of this review, and draw implications for policy, practice and the future research agenda. We focus on land and livestock assets and the set of productivity enhancing inputs in the form of irrigation, seed and agrochemicals. We report on a systematic review of recent evidence based on observational data on the links between these agricultural inputs and assets and diet and nutrition outcomes of farm households in India, Pakistan, Bangladesh, Afghanistan and Nepal. We find that the literature has slowly but steadily grown since previous reviews conducted in the early 2010s, but that there is still a long way to go. Review results suggest that while there is no indication that land ownership or size by themselves have clear associations with farm household dietary or nutrition outcomes, land productivity is more clearly associated with improved outcomes. Yet the literature linking specific inputs such as improved seeds or irrigation with nutrition remains very thin. The literature appears strongest for the case of links between livestock keeping and dietary and nutrition outcomes. This is particularly the case with animals reared for milk, with the evidence indicating milch animal ownership improves household milk intakes and thereby influences the growth of children. Priorities for future research include the formulation and testing of more specific hypotheses relating to input-nutrition linkages and more strenuous efforts to improve causal identification in this literature. 相似文献
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In models of optimal household behavior, the value of housing affects consumption, savings and other variables. But homeowners do not know the value of their house for certain until they sell, so while they live in their home they must rely on local house price data to estimate its value. This article uses data from the recent housing boom and bust to demonstrate that changes in households' self‐assessed home values are strongly consistent with the predictions of a model in which households optimally filter available house price data. Specifically, we show that self‐assessed house prices did not increase as rapidly as house price indexes during the boom and did not decline as severely during the bust. A Kalman filter model nearly perfectly replicates these data. These findings have direct implications for economists studying asking prices during booms and busts, optimal default decisions and other key housing‐related phenomena. 相似文献
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Michael A. Arnold 《Real Estate Economics》1992,20(1):89-106
This article investigates the principal-agent relationship between the owner of a house and her real estate broker. The principal's (owner's) problem is to design a contract that induces the agent (broker) to adopt a selling strategy that maximizes the owner's expected return. A sequential search model is utilized to analyze this principal-agent relationship. Three different systems for paying the broker are considered: fixed-percentage commission, flat-fee, and consignment. Both the discount factors of the owner and the broker and the net costs of ownership incurred while attempting to sell the house play a central role in determining the nature of the optimal contract. The analysis demonstrates that the fixed-percentage commission system is the only one of the three systems considered that can induce a first-best, incentive-compatible contract. A numerical analysis provides insights regarding the effect of the fixed-percentage commission system on competition in the real estate brokerage industry. 相似文献