企业财务业绩与现金流量分析

对传统财务业绩评价体系及其所提供的会汁信息质量进行了分析，认为财务分析应以现金流量力核心，通过现金流量指标分析企业的获利能力和支付能力更具可行性．笔者认为，以现金流量为核心，将现金流量分析指标溶于其他财务分析中，能够对企业当前存在的报表粉饰，利润操纵等现象进行充分的揭示，有助于重新构建出一套更为科学、合理的财务分析评价体系。     

Assessing the aerodynamic effects of tail elongations in the house martin (Delichon urbica): implications for the initial selection pressures in hirundines

Of the three species of hirundine that breed sympatrically across the U.K., one, the barn swallow, has outer tail feathers elongated into streamers, whereas the other two species, the house martin and the sand martin, do not. The tail streamer of the barn swallow is regarded as a classic example of a sexually selected trait. Recent evidence, however, has suggested that streamers may have evolved largely through natural selection for enhanced flight performance and increased maneuverability. We tested the hypotheses that small streamers (1) increase performance in turning flight, but (2) decrease performance in flight variables related to velocity. We manipulated the lengths of house martin outer tail feathers and measured changes in their free-flight performance, using stereo-video to reconstruct the birds" three-dimensional flight paths. Five flight variables were found to best describe individual variation in flight performance. Of these five, the three variables determining maneuverability predicted that flight performance would be optimized by a 6- to 10-mm increase in the length of the outer tail feathers. In contrast, for mean velocity and mean acceleration, extension of the outer tail feathers appears to have a detrimental effect on flight performance. We suggest that the initial selection pressure for streamers in ancestral short-tailed "barn swallows" was via natural selection for increased maneuverability. In addition, we propose that the benefits of increased maneuverability have differed between hirundines in the past, such that the cost of increasing the length of the outer tail feather has, to date, outweighed the benefits of doing so in streamerless hirundines. Received: 14 February 2000 / Revised: 2 July 2000 / Accepted 18 July 2000     

Improvement in collective performance with experience in ants

We show that entire ant colonies can improve their collective performance progressively when they repeat the same process. Colonies of Leptothorax albipennis can reduce their total emigration times over successive emigrations. We show that this improvement is based on experience and some memory-like process, rather than a coincidental developmental change or an increased general level of arousal. We demonstrate that the benefits of experience can be lost (i.e. forgotten) if the interval between successive emigrations is too long. We also show that the benefits of experience are more likely to be retained over a longer period if the collective performance has been repeated several times. This is a new demonstration of a process akin to learning in ants and we briefly discuss how it may involve not only improvements in individual performance but also improvements in the ways in which the ants interact with one another.Communicated by L. Sundström     

The importance of spatial autocorrelation,extent and resolution in predicting forest bird occurrence

Concerns about declines in forest biodiversity underscore the need for accurate estimates of the distribution and abundance of organisms at large scales and at resolutions that are fine enough to be appropriate for management. This paper addresses three major objectives: (i) to determine whether the resolution of typical air photo-derived forest inventory is sufficient for the accurate prediction of site occupancy by forest birds. We compared prediction success of habitat models using air photo variables to models with variables derived from finer resolution, ground-sampled vegetation plots. (ii) To test whether incorporating spatial autocorrelation into habitat models via autologistic regression increases prediction success. (iii) To determine whether landscape structure is an important factor in predicting bird distribution in forest-dominated landscapes. Models were tested locally (Greater Fundy Ecosystem [GFE]) using cross-validation, and regionally using an independent data set from an area located ca. 250 km to the northwest (Riley Brook [RB]). We found significant positive spatial autocorrelation in the residuals of at least one habitat model for 76% (16/21) of species examined. In these cases, the logistic regression assumption of spatially independent errors was violated. Logistic models that ignored spatial autocorrelation tended to overestimate habitat effects. Though overall prediction success was higher for autologistic models than logistic models in the GFE, the difference was only significantly improved for one species. Further, the inclusion of spatial covariates did little to improve model performance in the geographically discrete study area. For 62% (13/21) of species examined, landscape variables were significant predictors of forest bird occurrence even after statistically controlling for stand-level variability. However, broad spatial extents explained less variation than local factors. In the GFE, 76% (16/21) of air photo and 81% (17/21) of ground plot models were accurate enough to be of practical utility (AUC > 0.7). When applied to RB, both model types performed effectively for 55% (11/20) of the species examined. We did not detect an overall difference in prediction success between air photo and ground plot models in either study area. We conclude that air photo data are as effective as fine resolution vegetation data for predicting site occupancy for the majority of species in this study. These models will be of use to forest managers who are interested in mapping species distributions under various timber harvest scenarios, and to protected areas planners attempting to optimize reserve function.     

高效液相色谱法分析水中痕量多环芳烃

本文利用高效液相色谱法测定水中痕量多环芳烃（ＰＡＨｓ）。以二氯甲烷作溶剂,超声提取水中痕量ＰＡＨｓ;甲醇、水作流动相,梯度淋洗,用程序可变波长荧光检测器测定。ＰＨＡｓ浓度为０．００７＝０．６μｇ·ｍｌ＾－１范围时,线性相关系数均在０．９９９９以上;峰高、峰面积的相对标准偏差（ｎ＝１０）分别为１．０１－１．８５％,２．００－３．９４％;检测限（Ｓ／Ｎ＝２）为３．１－２３．０ｐｇ;实际水样的加标回收率     

氮源对气相生物滴滤床净化效果的影响

氮源对于气相生物滴滤床的净化效果有显著的影响。由于喷淋液体在生物滴滤床中分布不均匀 ,导致床层中局部氮源不充足 ,从而使滤床的去除效果降低。提高喷淋液中氮源的浓度 ,可以较大幅度提高净化效率。采用NH-4 N会导致滤床中硝化细菌的生长和累积 ,使得异养菌和硝化细菌在溶解氧、氮源和填料空间上形成竞争 ,并致使氮源分布不均匀 ,而采用NO3 N作为氮源可以改善这种状况     

石油石化企业HSSE管理体系运行模式和推进方法

针对石油石化企业HSSE管理体系运行中存在的问题,基于企业实际情况,采用系统方法设计提出了石油石化企业HSSE管理体系运行模式。从企业整体角度,运用战略思维提出HSSE管理体系运行的推进模型和方法,从战略、组织、能力、信息、流程、绩效6个方面,提出HSSE管理体系运行要求。通过创新HSSE管理体系运行模式和推进方法,企业能够从更加宏观的角度,整合有限资源实现HSSE管理体系有效运行,从而提升企业HSSE绩效。     

橡胶及制品自然贮存老化行为研究进展

针对橡胶及制品自然贮存老化行为的研究现状,从宏观性能、微观结构、自然贮存试验方法等方面进行综述。其中,宏观性能主要包括力学性能和其他宏观性能两个方面;微观结构方面主要包括FTIR技术、热分析技术、SEM及XPS技术等三个方面;自然贮存试验方法方面主要是部分橡胶及制品的相关自然贮存试验规范及标准。橡胶及制品自然贮存老化行为研究应加强自然贮存试验,综合运用分析手段掌握橡胶及制品的真实老化行为,从而改善橡胶性能,延长其使用寿命。     

低贵金属含稀土复合型汽车排气净化催化剂研究

研究了３种低钯含稀土复合型汽车排气净化催化剂的制备工艺条件、活性和热稳定性。结果表明：所研制的催化剂对ＣＯ、ＨＣ的起燃温度分别在１８２℃～２１０℃之间；完全氧化温度在２３０℃～２５０℃之间。具有起燃温度低、活性高的特性。高温处理后，Ｔ５０％和Ｔ１００％仅上升了８℃～２４℃，说明热稳定性良好。少量贵金属Ｐｄ分浸法以及在活性氧化铝涂层上使用无机胶粘剂的制备工艺能提高催化剂的热稳定性     

高效液相色谱法在无机分析中的应用

本文综述了高效液相色谱法在无机分析中的应用进展。分别介绍了正相、反相、离子对、离子交换、排阻和胶束流动相等液相色谱法在有机金属化合物、金属络合物、无机阳离子和阴离子分离及测定上的实际应用。