Improved sampling strategies for ensemble-based optimization

We are concerned with the efficiency of stochastic gradient estimation methods for large-scale nonlinear optimization in the presence of uncertainty. These methods aim to estimate an approximate gradient from a limited number of random input vector samples and corresponding objective function values. Ensemble methods usually employ Gaussian...

A study on event triggering criteria for estimation

To reduce the amount of data transfer in networked systems measurements are usually taken only when an event occurs rather than periodically in time. However, a fundamental assessment on the response of estimation algorithms receiving event sampled measurements is not available. This research presents such an analysis when new measurements are...

JEMs and incompatible occupational coding systems: Effect of manual and automatic recoding of job codes on exposure assignment

Background: In epidemiological studies, occupational exposure estimates are often assigned through linkage of job histories to job-exposure matrices (JEMs). However, available JEMs may have a coding system incompatible with the coding system used to code the job histories, necessitating a translation of the originally assigned job codes. Since...

Validated sampling strategy for assessing contaminants in soil stockpiles

Dutch legislation on the reuse of soil requires a sampling strategy to determine the degree of contamination. This sampling strategy was developed in three stages. Its main aim is to obtain a single analytical result, representative of the true mean concentration of the soil stockpile. The development process started with an investigation into...

Personal exposure to ultrafine particles in the workplace: Exploring sampling techniques and strategies

Recently, toxicological and epidemiological studies on health effects related to particle exposure suggest that 'ultrafine particles' (particles with an aerodynamic diameter of <100 nm) may cause severe health effects after inhalation. Although the toxicological mechanisms for these effects have not yet been explained, it is apparent that...

Knowledge-based sampling strategy for soil stockpiles

Over the last three years the Centre for Soil Treatment has sampled 2570 soil stockpiles for the assessment of soil quality. For all stockpiles the same sampling strategy was used. 100 increments of approximately 180 grams were taken and collected into two batch samples. Appropriate sample pre-treatment and analyses resulted in two sets of...

Working paper on monitoring strategies in the United Kingdom, Federal Republic of Germany and United States of America

This study is a working paper on monitoring strategies used in the U.K., the FRG and the USA to assess exposure to airborne chemical substances. After a brief description of the basic philosophy on monitoring strategies, the requirements formonitoring from the different legal systems in the three countries are presented. The monitoring...