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141.
Artificial neural networks are new methods for classification. We investigate two important issues in building neural network models; network architecture and size of training samples. Experiments were designed and carried out on two-group classification problems to find answers to these model building questions. The first experiment deals with selection of architecture and sample size for different classification problems. Results show that choice of architecture and choice of sample size depend on the objective: to maximize the classification rate of training samples, or to maximize the generalizability of neural networks. The second experiment compares neural network models with classical models such as linear discriminant analysis and quadratic discriminant analysis, and nonparametric methods such as k-nearest-neighbor and linear programming. Results show that neural networks are comparable to, if not better than, these other methods in terms of classification rates in the training samples but not in the test samples. 相似文献
142.
Michael L. Gargas Robin L. Norton Mark A. Harris Dennis J. Paustenbach Brent L. Finley 《Risk analysis》1994,14(6):1019-1024
Biomonitoring programs for urinary chromium (Cr) typically attempt to evaluate occupational exposure via the inhalation route. This study investigated whether Cr can be detected in the urine of people following the ingestion of soils that contain relatively high concentrations of chromium in chromite ore processing residue (COPR). To evaluate the reasonableness of using urinary monitoring to assess environmental exposure, six volunteers ingested 400 mg of soil/day (low-dose group), two others ingested 2.0 g of soil/day (high-dose group) for 3 consecutive days, and one person ingested a placebo on each of 3 days. The soil and COPR mixture contained concentrations of total chromium (Cr) and hexavalent chromium [Cr(VI)] of 103 ± 20 and 9.3 ± 3.8 mg/kg, respectively. Therefore, the low-dose group ingested 41 μg Cr/day [including 3.7 μg Cr(VI)] and the high-dose group ingested 206 μg Cr/day [including 18.6 μg Cr(VI)] on each of 3 consecutive days. All urine samples were collected and analyzed individually for total Cr on the day prior to dosing, during the 3 days of dosing, and up to the first void 48 h after the last dose. No significant increases in urinary Cr excretion were found when background excretion data were compared with data following each of the 3 days of dosing or in daily mean urine concentrations of the high- vs the low-dose groups. It appears that Cr present in a soil and COPR mixture at Cr doses up to 200 μg/day is not sufficiently bioavailable for biomonitoring of urine to be informative. These results are consistent with previously published findings suggesting that incidental exposure to dusts and soils containing comparable levels of Cr will not result in increased concentrations of Cr in urine. 相似文献
143.
This paper examines factors associated with feeling suicidal in a large sample of urban men in Sydney and Melbourne, aged 18-50, including heterosexual, gay and bisexual men, HIV antibody positive and HIV antibody negative. As in previous research, sexuality (being homosexual or bisexual) was found to be a major predictor of suicidality. The research went some way towards explaining the close relationship between feeling suicidal and sexual orientation. Sexuality interacts with feeling bad in that, once men feel moderately bad/depressed, they are more likely to feel suicidal if they are homosexual or bisexual than if they are heterosexual. In addition, the research found that experience of verbal abuse and physical assault (harassment) increased feeling suicidal for both heterosexual and gay/bisexual men, not just for homosexual men as suggested by previous research, and that social isolation in the form of living alone is a further risk factor. Seeking counseling help and taking sexual risks were also independently associated with feeling suicidal. These actions may result from feeling suicidal rather than the reverse, and their association with feeling suicidal warrants further research. Many of the 46 independent variables examined in the research, including HIV antibody status and closeness to the HIV/ AIDS epidemic, were related to feeling suicidal only through their association with being gay/bisexual. Celibacy and general risk taking were not related to feeling suicidal in this study. 相似文献
144.
145.
Urban Ecosystems - Residential yardscapes are at the forefront of human interaction with nature for those living in urban areas across Europe and North America. In recent years a significant amount... 相似文献
146.
Urban Ecosystems - Critical resources for birds nesting in cities can support populations in spite of the challenges imposed by urbanization, and the identification of such resources can shed light... 相似文献
147.
148.
Lesbian, gay, bisexual, transgender, queer, and other sexual/gender minority (LGBTQ+) health care providers face both general work-related stresses and working in heteronormative settings with ill-informed or hostile coworkers and patients, yet there has been little study of whether the coping strategies are specific to LGBTQ+ stress. We analyzed qualitative data from 277 health care professionals. Sources of stress included religiously and politically conservative coworkers, coworker/patient lack of knowledge, stresses of being closeted, and concerns about being out to patients. Consequences of being out as LGBTQ+ included lack of promotions, gossip, refusals of tenure, and anti-LGBTQ+ comments and behaviors in the workplace. Respondents showed mostly positive coping strategies to deal with stress, including becoming educators/advocates and self-care activities. Self-care options were common in rural areas with few LGBTQ+ social resources. Negative coping strategies were reported by 18% of respondents. The study highlights the extra burden of stress on LGBTQ+ health care providers. 相似文献
149.
We assess the effects of the population age structure and the population dynamics on economic growth. Following recent research, we focus on the generational turnover effect to characterize the influence of birth and death rates, depending on the age profile of individual consumption, the extent of annuity market imperfections, and the willingness of households to shift consumption over time. Using data from the National Transfer Accounts on age profiles of consumption for a number of different countries, we assess—in a comparative way—the sign and the magnitude of the generational turnover effect and its impact on economic growth. We find considerable cross-country differences and trace them back to the underlying variation in demography and in the age structure of consumption. 相似文献
150.
Michael Faust Jürgen Kädtler 《KZfSS K?lner Zeitschrift für Soziologie und Sozialpsychologie》2018,70(1):167-194
Since the 1990s the financialization of the enterprise is an increasingly important aspect of capitalist development also in Germany. However, more recently a growing number of scholars point at a problematic conceptual stretching of financialization. The term has been defined too differently and ambiguously and has not been distinguished sufficiently from seemingly similar concepts. Financialization has been prematurely identified with a set of fixed effects often condensed to stagist concepts of capitalist development. When analyzing effects financialization has been regarded in isolation without considering interaction effects with other structurations of fields and hence the multi-referentiality of the enterprise. In order to overcome these shortcomings the article proposes a concept for the analysis of firm level financialization which draws on a more general sociological concept of field structuration and dynamics in which the “multi-referential enterprise” operates. Based on this concept the article analyses episodes of financialization in Germany showing its dynamics and limits. Financialization of enterprises proves to be structurally limited, institutionally contested, and unfolds its effects in deferent actor constellations at firm level due to its multiple and contradictory embeddedness. 相似文献