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财务基准收益率是建设项目财务评价指标计算中的重要判据参数。对于该参数的确定目前流行使用资本资产定价模型法(CAPM)。本文从资本资产定价模型法入手分析,介绍的相关概念和计算方法。并从理论和实证支持两个方面给与说明,指出该方法在目前市场中不具备使用的条件。 相似文献
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Based on paper of “Theoretical derivation of risk-ratios for assessing wind damage in coastal forest“,wind damage in the pine coasteal forest,which was thinned at four levels in December of 1997,was investigated for four successive growing seasons.Besides wind damage,the wind profiles outside and inside the coastal forest stand and the distributions of optical stratification porosity (OSP) were also observed.Based on these data,risk-ratios of wind damage for both individual trees and stands were estimated according to the methods developed in “Theoretical derivation of risk-ratios for assessing wind damage in a coastal forest“.The results showed that risk-ratios of wind damage,which were calculated from the meen height and diameter only and from the combination of wind and stand sructure profiles,accurately predicted wind damage in the plantation.Relationships between different thinning ratios and incidence of wind damage showed that stand stability decreased soon after the thinning.This was due to the immediate effects of thinning on increasing the canopy roughness and wind load,and on decreasing the sheltering effects from surrounding trees.However,thinning strategies could improve the stability by long-term effects on growthand development of trees against extreme wind.Only canopy damage was recorded during the experimental period,no stem damage was found,even though the maximum 10-min wind speed outside the coastal forest attained 30.2m s^-1.The results obtained in this study indicate that thinning is the most effective silvicultural strategy available for managing coastal forest despite the increased probability of wind damage soon after thinning. 相似文献
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基于2011-2020年郑州市基地草莓中有机磷、有机氯、拟除虫菊酯及新烟碱类药物的监测数据,确定上市草莓被农药污染特征,并对其膳食摄入进行风险评估;采用点评估模型分别计算检出农药对各年龄段人群的安全系数(IFS)、平均安全系数■、安全系数之和(ΣIFS)以及各种检出农药的风险系数R等多种参数。结果表明:检出的农药中多数为草莓上未登记且无限量标准的农药,以微、低、中等毒性农药居多,高毒农药较少。检出频次最高的农药为百菌清,2011-2016和2017-2020年间检出率分别为31.3%和20.0%;其次为腐霉利,2017-2020年间检出率为30.0%;氯氰菊酯含量存在超标现象,超标率为1.4%。2017-2020年,含多种农药残留的样品占40%,残留农药种数2~5种。整体而言,2011-2020年郑州市草莓质量安全状况可以接受,但因未考虑个体间差异而存在一定的不确定性;就检出农药风险系数而言,氯氰菊酯给郑州市草莓安全品质带来的风险较高,其风险系数为2.5。 相似文献
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基层动物防疫积极贯彻"防重于治"的方针,为畜牧业健康发展和人民身体健康起到了保驾护航的作用;但是基层动物防疫仍存在一些不容忽视的问题,使养殖业风险系数大大提升. 相似文献
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通过对西昌市大型葡萄生产基地上市的69个批次葡萄进行了农药残留检测,通过食品安全指数(IFS)和风险系数(R)对儿童和成人膳食摄入风险进行评估。结果表明:所检69批次葡萄中有1批次超标,超标率为1.45%,除了丙环唑无法进行判定外,其余均合格;检出种类最多的为杀菌剂22种,检出率最高的农药为嘧霉胺(85.51%),存在杀菌剂混用或复配现象;通过IFS分析可知,所检测农药对葡萄质量影响风险在可接受范围内;R分析所检农药除螺螨酯是中风险农药外,其余均为低风险,应加强螺螨酯农药在葡萄上的使用监督。 相似文献
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为评估山西省韭菜中农药残留现状及居民膳食摄入风险,利用GC-MS/MS和UPLC-MS/MS技术对山西省韭菜主产区6个不同地区共计121个待上市韭菜样品中13种农药残留进行了精准定量,进而通过食品安全指数(IFS)法和危害物风险系数法对样品中检出的农药进行风险评估。结果显示,韭菜样品的农药检出率为97.5%,农药残留超标率为32.2%,其中腐霉利是造成韭菜中农药残留超标的主要农药,另检出克百威、毒死蜱、甲拌磷3种禁止在蔬菜上使用的农药,农药多残留检出率为57.0%。韭菜中检出的农药残留种类和数量存在采样时间、种植地区和种植模式上的差异。IFS法评估结果显示,12种检出农药的IFS值均小于1,膳食摄入风险在可接受范围;而危害物风险系数法评估结果表明腐霉利、甲拌磷、毒死蜱、克百威、二甲戊灵和氯氟氰菊酯6种农药为高度风险农药。总之,山西省韭菜质量安全风险仍在可接受范围,但存在高度风险农药使用情况,韭菜质量安全监管工作仍需进一步加强。 相似文献