摘要:

AbstractOur concern is with protection against natural catastrophes through financial insurance. Development of appropriate premium rates requires consideration of a wide variety of variables entering into the occurrence of the disaster, and a broad range of scientific and statistical investigations results. Topics discussed include: premium computation, distribution of large earthquakes in time, ground motion at sites, attenuation of energy with distance, damage description and actual practice in various countries. Statistical considerations that arise include: description, stochastic modelling, conditioning, spatial processes, (marked) point processes, uncertainty estimation and robust/resistant procedures. Study of the insurance problem is scientifically enlightening because it requires one to focus on the whole context of the problem; geology, seismology, earthquake engineering, and damage.

ISSN:1180-4009    

DOI:10.1002/env.3170040102

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe statistical analysis of the concentration of air pollutants in the atmosphere is generally applied to a time series of average concentrations. Statistical difficulties arise from the non stationarity of the series, the nonnormality of the measured concentration, the lack of independence and the important influence of external factors. A new model is proposed for the time series consisting of daily averages of ground level ozone. The annual trend is modelled by a function of the length of day, the nonnormality is taken into account by a Box‐Cox transformation and the errors are supposed to be autoregressive of order 1. This method is applied to the analysis of NABEL (Nationales Beobachtungsnetz für Luftfremdstoffe) data (two years data from two locations), Switzerla

ISSN:1180-4009    

DOI:10.1002/env.3170040103

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe accident in the nuclear power plant at Chernobyl led to a fall‐out and wash‐out of radionuclides, especially radiocesium, with a broad geographic variation in the South‐German State of Bavaria. For a younger adult, the additional effective lifetime dose from external exposure and ingestion of radiocesium varies between 1.2 mSv and 8.7 mSv, depending on the region. This is about 2%, respectively 16%, of the natural lifetime gamma dose. In none of the Bavarian regions with different levels of radiation exposure has the incidence of congenital heart defects in Bavarian children increased since the time of the accident. The results indicate that geographically no effects on such malformations can be attached to the additional radiation exposure resulting from the Chernobyl acc

ISSN:1180-4009    

DOI:10.1002/env.3170040104

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractCoral reefs are subject to attack and predation by the starfishAcanthaster plancior crown‐of‐thorns. This paper describes a simulation model of the natural processes of a coral reef and its reaction to, and recovery from starfish attacks. The modelling of a reef section is based on a pixel representation of the area. On this are imposed the normal reef processes of coral recruitment, growth, competition and mortality. These were represented in computer form and a suitable computer package was produced and tuned to represent a typical hard coral mid‐shelf reef of the Great Barrier Reef. Fine tuning required the inclusion of a background mortality to ensure that the output extended over centuries, and exhibited the essential properties of real coral communities.The second phase of the simulation was to model the effects of a starfish attack, its likelihood of occurrence, strength and dietary preferences. Again, these may be tuned to represent the before and after effects of attacks as observed on the reef.The results of the simulations lead to the conclusion that the modelled coral community exhibited considerable stability (persistence and resilience) in the face of frequent and severeAcanthasteroutbreaks. Regardless of the outbreak intensity, the coral community rapidly regained its pre‐outbreak cover of the area in about eight years. Some changes in the community composition were found in the periods immediately after outbreaks. However, the pre‐outbreak composition of the community was always restored within 20

ISSN:1180-4009    

DOI:10.1002/env.3170040105

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe Baltic Sea has been subject to an increased load of nutrients during the last century. The effect of this load is obscured sometimes by a lack of data but always by large seasonal variations. A non‐parametric method was used for trend tests at nine different sampling stations from the whole Baltic Sea. Time series from 1968–1990, based on data from HELCOM and ICES databases, were analyzed for trend in concentrations of NO3, NH4, PO4, total phosphorous and total nitrogen.About 60% of the test statistics gave significant trends at 5% confidence levels. Total nitrogen, total phosphorous, NO3, and PO4have generally increased in the Baltic Sea. The increase is in the range of 1–4% yr−1. Ammonium shows decreasing trend in the Baltic Sea, with a slope of 3–8% yr−1. Regional differences are, however, found for most of the c

ISSN:1180-4009    

DOI:10.1002/env.3170040106

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractWhile estimators of the relative frequency of responding cells in limiting dilution assays (LDAs) have been critically evaluated, other statistical issues concerning this quantal assay have not received similar attention. This study investigates LDA validity tests designed to detect deviations from the single‐hit Poisson model. The method employed by Armitage (1959) to detect host variability, or a variable number of false negatives, is extended to other violations of the single‐hit Poisson model. In general, this methodology, based on the general theory of Neyman (1955), is shown to produce asymptotically most powerful and locally most efficient tests for many alternative hypotheses. In addition to composite hypotheses, this method can be extended to produce tests for separate families of hypotheses. These methods are compared with existing LDA validity tests including the weighted regression method of Gart and Weiss (1967), the double‐hit model of Cox (1962), and the general chi‐square goodness‐of‐fit statistic. Monte Carlo simulations show that these score tests have good power and acceptable rejection levels at 0.05 and 0.01. In particular, the score test designed to detect deviations from the Weibull model is shown to produce good power for many alternative models. The chi‐square goodness‐of‐fit statistic, the most widely used LDA validity test, is shown to lack power in detecting many alter

ISSN:1180-4009    

DOI:10.1002/env.3170040107

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:1180-4009    

DOI:10.1002/env.3170040109

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY