基于CES生产函数的企业安全投资决策方法研究

在分析当前我国安全投资决策研究基础上,讨论安全投资的边际效益理论,并利用其确定安全投资总量的合理值。利用不变替代弹性(CES)生产函数建立安全投入产出效益函数,反映安全投资结构对安全产出的影响,通过模型求解得到企业安全资源分配的优化结构和投资额。按边际效益理论和安全投资效益模型将有限的资源科学地配置到安全生产过程中去,有利于节约资本,实现安全效益最大化。     

政府主导农地流转的价格机制及政策效应研究

为适应农村劳动力转移、解决今后谁来种粮、发展现代农业所衍生的政府主导农地流转现象,有其现实背景和政策逻辑,并能在短期内带来农地规模经营的正向预期。但现实中,很多时候政府行为很难"合意"其政策目标,这使得探究政府行为对农地流转市场和经营行为的影响及其政策效应具有农业供给侧结构性改革背景下的时代意义。基于此,本文依据全国11个国家现代农业示范区调研数据和资料,对政府主导行为对流转市场的分割、价格机制的作用,承包户询价逻辑的激励及短期平均成本的影响进行了分析,同时构建Translog形式成本函数,对政府主导和市场配置两种方式下的农地经营"成本弹性"进行了测度和估计。结果显示:1政府行为放大需求弹性诱致"地租乘数"促使流转价格溢价;2政府介入流转扭曲了流转市场供求关系,将原本市场配置下的供需均衡变为有利于"卖方垄断"的供需失衡;3承包户议价地位提升后基于"劳动力双重成本负担"的询价逻辑又助推了流转溢价的"棘轮效应";4依靠政府主导流转而非市场配置所形成的大规模农地经营,其成本弹性未显现可预期的小于1,即未出现规模效益与成本随规模扩张递减。政府行为与政策效应背离,有其深层次的认识误区及其行为逻辑谬误。表现在:一是错误认为推动农地规模流转可以实现农业规模经营是直接原因;二是执拗相信只要扩大农地经营规模就能提高劳动生产率是其主因;三是渴望借助农机替代劳动力进而实现规模效应和收益最大化,试图套用所谓的"工业化大生产理念"谋划农地经营是其动因所在;四是政府行为扰乱市场配置资源作用造成政策效应失灵。     

关于"环境贴现率"问题的探讨

推导一个描述私人利润率和社会利润率之间的新公式。该公式涉及的２个相关的环境参数为：环境投资占国民收入的百分比（λ）;从环境投资角度出发定义的环境改善的弹性（η）。公式表明,从环境的观点出发,社会利润率或环境贴率应该随则系统地降低。此外,本文还引用了“环境阻力”的概念来论述模型的意义,同时还简要地讨论了环境阻力的计算方法。     

黄河中游河龙区间径流量变化趋势及其归因

黄河水沙变化关乎黄河流域生态安全和全流域的高质量发展。近年来黄河水量出现大幅锐减,制约了当地社会经济和下游可持续发展。量化气候变化和人类活动对径流量减少的贡献对于解析黄河水沙变化动因具有重要意义。由于研究尺度和研究方法的不同,径流量变化的因素和影响程度存在较大差异。本文采用MK趋势检验和双累积曲线法系统分析黄河中游河龙区间四个典型流域（皇甫川、窟野河、无定河、延河）1960—2015年间水文要素的变化趋势,利用Budyko水热平衡方程阐明气候变化和人类活动对流域径流变化的作用。结果表明：1960—2015年皇甫川、窟野河、无定河、延河流域径流量均显著下降（P<0.01）,且径流量均在1979年和1999年前后发生突变,而降水量变化不显著。同基准期（1960—1979年）相比,P2时期（1980—1999年）气候变化对径流减少的贡献率达64%~76%;随着退耕还林还草工程的大规模实施,P3时期（2000—2015年）人类活动成为径流减少的主要影响因素,其贡献率达71%~88%。     

节庆营销对景区年内客流量的边际弹性及调节限度--以内蒙古阿拉善盟5个4A级景区为例

节庆营销是影响旅游活动年内变化的重要因素。优化节庆活动,拉长旅游活动“旺季”,是推动旅游业平稳发展的重要问题。以内蒙古阿拉善盟5个4A级景区为例,采用带虚拟变量的回归模型分析了节庆营销对景区客流量年内变化的边际弹性。结果发现:5个景区4年节庆活动边际弹性≥3.0,气候舒适度边际弹性≥1.0。为缓解旅游活动的年内集中性,需要把节庆活动调整至4—9月,平滑客流量的年内分布。     

亲水性塑料弹性填料生物膜法处理模拟废水的研究

通过比较普通塑料弹性填料与亲水性改进后的塑料弹性填料在污水生化处理中的应用效果发现 :亲水性改进的塑料弹性填料在污水的厌氧生化处理中可提高污水处理效率 15 %— 30 % ,在好氧生化处理中可提高污水处理效率5 %— 10 % ,且亲水性改进大大提高了塑料弹性填料的挂膜速度。     

Estimating the effectiveness of a vehicle miles travelled tax in reducing particulate matter emissions

This study estimates the effectiveness of a vehicle miles travelled (VMT) tax in controlling mobile-source emissions of particulate matter (PM_2.5) in a non-attainment area located in northern Utah. Using a recently updated household-level dataset, the study finds no evidence of an endogenous relationship between choice of vehicle type and VMT. VMT elasticities are also estimated with respect to cost per mile that are in some cases larger in magnitude than those reported in previous studies. Based on vehicle emissions tests performed by the Houston Advanced Research Center, the study estimates the reduction in particulate emissions that would occur with two different sets of VMT tax rates. Principal findings are that a VMT tax rate of $0.003 per passenger car mile and $0.01 per light-duty truck mile (resulting in a mean annual tax burden of $128 per household in the first year) would reduce annual particulate emissions by between 7% and 11%, depending upon the degree of heterogeneity in household driving behaviour. Assuming constant elasticity, this means that at tax rates of $0.006 and $0.02 per mile for passenger cars and light-duty trucks, respectively (resulting in double the mean annual tax burden), annual particulate emissions would be reduced by between 12% and 23%. Both the advantages and limitations of the VMT tax are discussed.     

Investigating factors influencing pedestrian injury severity at intersections

Objective: Vehicle crashes that involve pedestrians at intersections have been reported occasionally. Pedestrian injury severity in these crashes is significantly related to driver and pedestrian attributes, vehicle characteristics, and the geometry of intersections. Identifying factors associated with pedestrian injury severity (PIS) is critical for reducing crashes and improving safety. For developing the proposed probit models, drivers involved in crashes are classified into 3 groups: young drivers (16 ≤ age ≤ 24), middle-aged drivers (25 ≤ age ≤ 64), and older drivers (age ≥ 65). This study determines that PIS is significantly but differently affected by these grouped drivers with different sets of explanatory variables.

Methods: A total of 2,614 crash records (2011–2012) at intersections in Cook County, Illinois, were collected. An ordered probit modeling approach was employed to develop the proposed model and examine factors influencing PIS. The likelihood ratio test was used to assess model performance. Elasticity analysis was conducted to interpret the marginal effect of contributing factors on PIS associated with different driver groups by age.

Results: The results show that 4 independent variables, including pedestrian age, vehicle type, point of first contact, and weather condition, significantly affect PIS at intersections for all drivers. Two additional independent variables (i.e., number of vehicles and traffic type) affect PIS for young and middle-aged drivers, and 2 other variables (i.e., divided type and hit-and-run related) are significant to PIS for both young and older drivers.

Conclusions: The independent variables significant to PIS at intersections for young, middle-aged, and older driver groups were identified and the marginal effect of each variable to the likelihood of PIS were assessed.     

DEMAND PROJECTIONS CONSIDERING CONSERVATION1

ABSTRACT: Prediction of future water demands depends on the degree to which conservation effects can be anticipated. A model developed for the Corps of Engineers shows that choosing a numerical conservation target to be achieved is more meaningful and yields more predictable results than price or price elasticity manipulations. The method developed and then applied to the Kaneohe Bay region of Oahu considers the following determinants of demand: geographic distribution of the users, indoor and outdoor requirements, time - by year and month of the year, precipitation, historical unit usage rates, gross and irrigable acreage of land uses, price for water, elasticity of demand with respect to price, source of the water supply (local private supplies vs. agency supplies), and the percentage conservation savings anticipated in each future period in indoor and outdoor uses of water in each of 40 possible land uses. While developed for use in Hawaii, the model is applicable generally.     

CONSERVATION PRACTICES AND ATTITUDES AMONG MARYLAND WATER SUPPLY MANAGERS1

ABSTRACT: In addition to offsetting water supply shortages, water conservation is recognized as serving many purposes, ranging from reduced energy consumption to lower capital costs. Since the discussion of these benefits has been a recent development and has generally excluded local water supply managers, a question arises as to whether supply managers are implementing conservation programs to exploit these benefits. A survey of the managers at 35 Maryland water utilities provides insight into the prevailing attitude toward conservation in a water rich eastern state. The results indicate that most managers continue to view conservation only as a short term response to temporary supply shortages. Only 12 Maryland utilities have undertaken any form of water conservation activity and just two systems have ongoing, comprehensive conservation programs. Institutional, perceptual, economic, political, and time constraints all contribute to the managers’attitudes and general inaction. If water conservation is to be widely practiced, these issues must be addressed and the benefits attributed to conservation must be better documented and articulated to supply managers.