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81.
The paper reports a recent International Wool Secretariat (I.W.S.) study to measure the overall effect on sales of fibre advertising, based on annual data for eight major wool-consuming countries, collected from 1960 to 1970. An economic model of the fibre market is set up, and multiple linear regression is used to demonstrate a significant positive relationship between fibre sales and advertising. The effect of wool advertising is quantified, using the estimated regression coefficients, and its cost is compared with the estimated benefits to the wool industry in terms of increased revenue. Possible drawbacks of the approach described are considered, and aspects of the work requiring further study are also mentioned. 相似文献
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83.
Restoring complex vegetation in urban settings: The case of tidal freshwater marshes 总被引:2,自引:0,他引:2
Andrew H. Baldwin 《Urban Ecosystems》2004,7(2):125-137
Tidal freshwater marshes have diverse plant communities that vary spatially and temporally due to hydrology, animal activity, and other factors. Development of urban centers along rivers of the U.S. Atlantic coast has reduced the historic extent and quality of these and other coastal wetlands. Because the vegetation of these wetlands is more complex than that of salt and brackish marshes (where restoration of vegetation typical of natural systems has sometimes been successful), restoration of tidal freshwater marsh vegetation is likely to be more difficult, particularly in urban areas. Watershed urbanization alters hydrology, sediment load, propagule availability and composition, nutrient status, and other variables that together create an environment different from that of wetlands in less developed areas, possibly precluding restoration of typical marsh vegetation. Tidal freshwater wetlands were historically extensive along the Anacostia River in Washington, DC, but most of these were lost due to filling, dredging, or hydrologic alteration. Over the last decade, the U.S. Army Corps of Engineers has implemented projects designed to restore tidal freshwater wetlands along the Anacostia, which involved increasing elevation with dredged river sediment and planting native vegetation. To illustrate some of the mechanisms affecting vegetation development in restored tidal freshwater marshes in urban areas, I present a case study on one of these wetlands, Kingman Marsh, that also includes research at another restored wetland and two natural reference sites. Studies by my research groups indicate that the restored wetlands undergo essentially a planting-modified process of primary succession. Low densities of seeds are initially present in the substrate, and prolific seed dispersal into the restored sites results in high initial plant diversity comprised of plantings and ruderal (i.e. weedy) natives and exotics. Seed banks develop rapidly at the restored sites, probably due to colonization and early reproduction by ruderal species. Hydrology and disturbance by non-native animals (including resident Canada goose) are important variables controlling establishment of vegetation in these systems. Recent literature and the case study indicate that the environmental conditions of urban settings impose constraints in restored wetlands that result in plant communities more like those of urban natural wetlands than those of wetlands in less urbanized watersheds. This suggests that rather than design wetland restoration projects with the goal of creating pristine wetland vegetation, restorationists must identify, accept, and if possible capitalize on the ecological constraints of the urban environment in setting achievable and desirable restoration goals. 相似文献
84.
This article presents the results of an experiment designed to determine the impact of a group discussion about second-hand consequences of alcohol use on college students' intentions to consume alcohol. Participants were students enrolled in two large Community Health courses at a large Midwestern university (n = 184). After randomization of class sections into an intervention or a control group, intervention group students participated in a class discussion on the negative consequences college students experience as a result of other students' drinking behavior, prior to answering survey questions regarding their drinking behavior intent. Compared to controls who completed the questionnaire only, intervention group participants reported intent to limit themselves to fewer drinks per drinking occasion (p = .003) and fewer drinks per week (p = .004). The effects of the brief educational intervention were analyzed using structural equation modeling, to test the feasibility of a hypothesized intervention mechanism. 相似文献
85.
86.
There has been relatively little previous research examining differences between subgroups of child sex offenders. In this study, we compared a group of familial and non-familial child sex offenders attending a community based treatment program on a number of relationship dimensions thought to be important in explaining offending. No statistically significant differences were found between these groups on measures of general empathy, intimacy and loneliness, although non-familial offenders were found to have higher levels of cognitive empathy and a more internal locus of control than familial offenders. These findings are discussed in terms of their possible implications for service delivery. 相似文献
87.
Hagerty Michael R. Cummins Robert A. Ferriss Abbott L. Land Kenneth Michalos Alex C. Peterson Mark Sharpe Andrew Sirgy Joseph Vogel Joachim 《Social indicators research》2001,55(1):1-96
A number of governments and public policy institutes have developed Quality of Life Indexes – statistics that attempt to measure the quality of life for entire states or regions. We develop 14 criteria for determining the validity and usefulness of such QOL indexes to public policy. We then review 22 of the most-used QOL indexes from around the world. We conclude that many of the indexes are successful in that they are reliable, have established time series measures, and can be disaggregated to study subpopulations. However, many fall short in four areas: (1) indexes vary greatly in their coverage and definitions of domains of QOL, (2) none of the indexes distinguish among the concepts of input, throughput, and output that are used by public policy analysts, (3) they fail to show how QOL outputs are sensitive to public policy inputs, and (4) none have examined convergent validity against each other. We conclude that many of these indexes are potentially very useful for public policy and recommend research to further improve them. 相似文献
88.
May RK Whelan JP Steenbergh TA Meyers AW 《Journal of gambling studies / co-sponsored by the National Council on Problem Gambling and Institute for the Study of Gambling and Commercial Gaming》2003,19(4):339-357
Instruments to assess individuals' self-efficacy for the control of addictive behaviors have been useful for monitoring behavior change, predicting maintenance of treatment gains, and identifying potential relapse situations. The Gambling Self-Efficacy Questionnaire (GSEQ) was developed to assess perceived self-efficacy to control gambling behavior. A demographically diverse sample of 309 adult gamblers completed an initial set of 42 items, of which 16 were selected to form the final version of the GSEQ. The GSEQ showed high internal consistency ( = .96) and good test-retest reliability (r = .86). A factor analysis provided some support for a unitary factor structure. As expected, GSEQ scores were negatively correlated with reports of problematic gambling behavior. Participants experiencing problems related to their gambling behavior scored significantly lower on the GSEQ than those who were not experiencing gambling problems. This psychometric examination of the GSEQ supported its potential utility for treatment planning and outcome evaluation with problem gamblers. 相似文献
89.
Andrew Z Szendrovits 《Omega》1980,8(6):623-629
The model presented in this paper assumes that a uniform lot size is produced through a series of manufacturing stages, with a single set-up and without interruption at each stage. Transportation of partial lots, called batches, is allowed between stages after the whole batch is completed. The batch sizes must be equal at any particular stage, but the optimal number of equal-sized batches may differ across stages. Of course, the set-up costs, the inventory-holding costs and the transportation costs influence both the optimal batch-sizes at the various stages and the uniform lot size. An optimization method for this deterministic model is developed and is illustrated by an example. 相似文献
90.