Random Allocation Scheme Research Articles

Effects of organism allocation on toxicity test results

AbstractThe purpose of this study was to investigate the effect of nonrandom allocation of organisms to treatments in aquatic toxicity tests on lethal concentration estimates. Random allocation of organisms is prescribed to avoid the introduction of systematic bias in these tests; however, completely random assignment is usually impractical. A source of systematic bias in a nonrandom allocation scheme is the potential inverse relationship between organism hardiness and the order in which organisms are captured for assigning to treatment (i.e., less hardy and hence more sensitive individuals are captured first). A Monte Carlo simulation experiment was performed to examine such an inverse relationship for a variety of random allocation schemes, focusing on the mortality endpoint in the fathead minnow larval survival and growth toxicity test. Results of the computer simulation experiment indicated that nonrandom allocation of organisms can produce significant bias in estimates of lethal concentration values. Any attempt at randomization resulted in approximately unbiased estimates of lethal concentration values; however, variance of the estimates increased as allocation schemes deviated from the completely random allocation. This study illustrates the importance of proper training of laboratory personnel to implement some form of random organism allocation. Furthermore, many partial random allocation schemes (i.e., those allocating more than one organism at a time) may still yield unbiased estimates of potency endpoints.

EFFECTS OF ORGANISM ALLOCATION ON TOXICITY TEST RESULTS

The purpose of this study was to investigate the effect of nonrandom allocation of organisms to treatments in aquatic toxicity tests on lethal concentration estimates. Random allocation of organisms is prescribed to avoid the introduction of systematic bias in these tests; however, completely random assignment is usually impractical. A source of systematic bias in a nonrandom allocation scheme is the potential inverse relationship between organism hardiness and the order in which organisms are captured for assigning to treatment (i.e., less hardy and hence more sensitive individuals are captured first). A Monte Carlo simulation experiment was performed to examine such an inverse relationship for a variety of random allocation schemes, focusing on the mortality endpoint in the fathead minnow larval survival and growth toxicity test. Results of the computer simulation experiment indicated that nonrandom allocation of organisms can produce significant bias in estimates of lethal concentration values. Any attempt at randomization resulted in approximately unbiased estimates of lethal concentration values; however, variance of the estimates increased as allocation schemes deviated from the completely random allocation. This study illustrates the importance of proper training of laboratory personnel to implement some form of random organism allocation. Furthermore, many partial random allocation schemes (i.e., those allocating more than one organism at a time) may still yield unbiased estimates of potency endpoints.

Radio resource management in future wireless networks: requirements and limitations

Comparing market estimates for wireless personal communication and considering proposals for wideband multimedia services with the existing spectrum allocations for these types of systems show that spectrum resource management remains an important topic in the near and distant future. In this article the authors start by presenting a quite general formulation of the radio resource management problem where the three key allocation decisions are concerned with waveforms ("channels"), access ports (or base stations), and, finally, with transmitter power. Some approaches to these problems found in the literature are reviewed. In particular, the principles of random channel allocation schemes, as found in frequency-hopping or direct-sequence CDMA systems, are compared with deterministic dynamic channel allocation schemes. The article closes by giving an outlook of some of the key problems in resource management in future wireless multimedia systems.

Distributed multicast address management in the global Internet

We describe a distributed architecture for managing multicast addresses in the global Internet. A multicast address space partitioning scheme is proposed, based on the unicast host address and a per-host address management entity. By noting that port numbers are an integral part of end-to-end multicast addressing we present a single, unified solution to the two problems of dynamic multicast address management and port resolution. We then present a framework for the evaluation of multicast address management schemes, and use it to compare our design with three approaches, as well as a random allocation strategy. The criteria used for the evaluation are blocking probability and consistency, address acquisition delay, the load on address management entities, robustness against failures, and processing and communications overhead. With the distributed scheme the probability of blocking for address acquisition is reduced by several orders of magnitude, to insignificant levels, while consistency is maintained. At the same time, the address acquisition delay is reduced to a minimum by serving the request within the host itself. It is also shown that the scheme generates much less control traffic, is more robust against failures, and puts much less load on address management entities as compared with the other three schemes. The random allocation strategy is shown to be attractive primarily due to its simplicity, although it does have several drawbacks stemming from its lack of consistency (addresses may be allocated more than once). >

Rearrangeable operation of large crosspoint switching networks

A major impediment to building large crosspoint chips for configuring crosspoint switching networks is the simultaneous switching (Delta-I) noise problem that is caused by the switching of a large number of line drivers driving the output pins of the package. This limits the size of the largest crosspoint chips that can be operated reliably. An architectural solution to this problem is presented for networks constructed from one-sided crosspoint switching chips. The approach seeks to minimize the maximum number of active drivers in the individual chips by distributing the active drivers in the network uniformly among the chips by allowing rearrangements of existing connections when a new connection is made. A graph model is used to determine the number and location of rearrangements. An allocation scheme based on a simplified graph model that achieves a 50% reduction in the maximum number of active drivers per chip as compared to a random allocation strategy is presented. A maximum of three rearrangements is sufficient to obtain this reduction.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Limit Theorems for the Number of Empty Cells in an Equiprobable Scheme for Group Allocation of Particles

Limit Theorems for the Number of Empty Cells in an Equiprobable Scheme for Group Allocation of Particles

Limit Theorems in a Model of Distribution of Particles of Two Types

Previous article Next article Limit Theorems in a Model of Distribution of Particles of Two TypesT. Yu. PopovaT. Yu. Popovahttps://doi.org/10.1137/1113066PDFBibTexSections ToolsAdd to favoritesExport CitationTrack CitationsEmail SectionsAbout[1] B. A. Sevast'yanov, Convergence of the distribution of the number of empty boxes to Gaussian and Poisson processes in the classical ball problem, Theory Prob. Applications, 12 (1967), 126–134 10.1137/1112016 LinkGoogle Scholar[2] V. P. Chistyakov, On the calculation of the power of the test of empty boxes, Theory Prob. Applications, 9 (1964), 648–653 10.1137/1109089 LinkGoogle Scholar Previous article Next article FiguresRelatedReferencesCited byDetails The Number of Collisions for the Occupancy Problem with Unequal Probabilities22 February 2016 | Advances in Applied Probability, Vol. 46, No. 01 Cross Ref The Number of Collisions for the Occupancy Problem with Unequal Probabilities22 February 2016 | Advances in Applied Probability, Vol. 46, No. 1 Cross Ref Integral Transforms That Preserve Schur Convexity with an Application to Occupancy Problem with Collisions Cross Ref Poisson Limit Joint Distributions for a Random Allocation Scheme of Two-Type ParticlesV. V. Gaas6 June 2008 | Theory of Probability & Its Applications, Vol. 52, No. 2AbstractPDF (160 KB)Occupancy with two types of balls1 March 1988 | Annals of the Institute of Statistical Mathematics, Vol. 40, No. 1 Cross Ref Asymptotic Normality of a Class of Statistics in the Multinomial SchemeG. I. Ivchenko and V. V. Levin17 July 2006 | Theory of Probability & Its Applications, Vol. 21, No. 1AbstractPDF (519 KB)Convergence of Point Complexes in $Z^n $ to Poisson ProcessesRobert Hafner28 July 2006 | Theory of Probability & Its Applications, Vol. 18, No. 1AbstractPDF (1494 KB) Volume 13, Issue 3| 1968Theory of Probability & Its Applications History Submitted:20 December 1966Published online:17 July 2006 InformationCopyright © Society for Industrial and Applied MathematicsPDF Download Article & Publication DataArticle DOI:10.1137/1113066Article page range:pp. 511-516ISSN (print):0040-585XISSN (online):1095-7219Publisher:Society for Industrial and Applied Mathematics