Confidentiality control is a major concern of official statistics authorities. Various measures are taken at different stages of the collection and publication of the data. In this regard, controlled rounding has been developed as a technique for confidentiality control of tabular data when it is published. The literature to date presents algorithms for both 2-dimensional and 3-dimensional tables. While fast algorithms are available for the 2-dimensional problem, current methods for 3-dimensional controlled rounding are regarded as too slow for practical implementation. The emphasis of this paper is thus a method for large-scale tables which is sufficiently fast and robust for use in a commercial implementation. It is a two phase method, wherein the first phase solves a network to create a partially feasible solution, while a heuristic employing tabu search methods completes the rounding in the second phase. Minor infeasibility is permissible for the sake of computational speed. Aspects of the methods and the table structure that affect speed of solution are discussed. Results are presented for large tables with up to 200,000 primary entries. Results indicate that the method produces good solutions in acceptable time.

Political redistricting involves the amalgamation of a large number of geographic or statistical units into a smaller set of electoral districts such that the districts satisfy various criteria prescribed by law, judicial mandate, or historical precedent. This paper describes a network-based optimization model that is currently being used by governmental decision-makers in New Zealand to assist in the preliminary stages of determining Parliamentary district boundaries. The model is capable of solving large-scale problems. In the New Zealand case, the procedure has been applied to problems involving over 35,000 geographic units (called “meshblocks”) and 95 Parliamentary districts. The model generates electoral districts that have roughly equal population and are generally compact in shape. One of the key features of the model is its flexibility. On the one hand, it can take into account currently existing features such as topographic terrain or previously existing electoral boundaries. On the other hand, it can also be used to generate an entirely new set of political boundaries as was mandated by the voters in a recent referendum in New Zealand.

While the problem of packing single containers and pallets has been thoroughly investigated very little attention has been given to the efficient packing of multiple container loads. Normally in practice a multiple container load is packed by a single container algorithm used in a greedy fashion. This paper introduces the issues involved in multiple container loading. It lays out three different strategies for solving the problem: sequential packing using a single container heuristic, pre-allocating items to the containers and choosing container loads using simultaneous packing models. The principal simultaneous models are pattern selection IP models. We present an application of packing pipes in shipping containers using two pattern selection IP models, a pattern selection heuristic, a sequential greedy algorithm and a pre-allocation method. The experimental results use randomly generated data sets. We discuss several useful insights into the methods and show that for this application the pattern selection methods perform best.

this report whether or not due tonegligence on the part of the University, its contributors, employees or students.Optimal Scheduling of Hydro Stations: An Integer Programming ModelEnergy Modelling Research Group ii

This paper is motivated by the problem of fitting pipes of different diameters into a shipping container. Here we study the subproblem of fitting circles of different sizes into a rectangle since that problem is a central part of the larger problem. We formulate this situation as a nonlinear mixed integer programming problem and develop a number of heuristic procedures for (approximately) solving this problem. The heuristics are based on a variety of solution building rules that emulate the process of packing a container. Some of these methods, including a genetic algorithm, were based on a more structured design intended to provide solutions which are 'stable' from a stowage viewpoint. These heuristics are described in detail and their relative performances are compared for a sample set of 66 randomly generated problems. Based on this sample, the best performing heuristic methods were a quasi-random technique and a genetic algorithm of the 'stable' solution structure.

The problem of confidentiality control is a significant issue for statistics gathering organisations. Most existing methods suffer from a variety of difficulties for practical implementation. This paper presents techniques for confidentiality control of tabulated data using network formulations to overcome many of the weaknesses of the current methods. These techniques are based on the established methodology of controlled rounding, which preserves additivity in the resulting solution, while adding a number of pieces of new material. Firstly, a controlled rounding formulation is introduced that is designed to provide an unbiased solution. Then we construct three variations of a controlled perturbation technique using different forms of bounds on the cells. Finally, a methodology is explained for disturbing only the small-valued cells of the table using each of the four basic methods. A simple example of the methods and results from experimentation on the use of the methods show that they satisfy the needs of confidentiality and are computationally viable.

In this paper we describe a container loading software package for a pulp and paper manufacturer. The program takes, as input, orders for paper products in sheets or reels. As output it produces precise order quantities, and stowage plans for shipping containers. The program includes a heuristic algorithm for two-dimensional stowing of reels of a common diameter, a bin packing algorithm for combining reels into stacks and a two-dimensional algorithm for stowing pallets of various sizes. Since the order sizes are usually greater than one container load all algorithms are designed for the multi-container case. The program is currently in use and has been effective in several decision situations including (a) good sizes for reel diameters (b) efficient stowage patterns, and (c) production quantities that are compatible with cost efficient shipping. It also reduces the time taken to produce stowage and shipping documents.

There is an extensive literature on heuristic algorithms for two-dimensional cutting problems and three-dimensional packing, but there seems to be very little on the three-dimensional single-box type packing problem. This paper gives a structure for dealing with that problem as a heuristic. It also presents a set of upper bounds on the optimal fit. Finally, the paper compares a particular application of the algorithmic structure with the George and Robinson multiple-box type heuristic.

The problem of rounding in statistical tables to protect confidentiality is an important problem in the area of data publication, especially for official statistics. Controlled rounding involves rounding the table data to a prespecified base while ensuring additivity to totals. Previous research provided a formulation of the controlled rounding problem of a simple two-way table as a transportation problem. This paper extends that work to tables with subtotals by using a capacitated transshipment formulation. It is shown that some forms of tables with subtotals always have a controlled rounding solution. Other table structures cannot be guaranteed such a solution under “zero-restrictedness”. Initial computational experience suggests that the method is viable for use in practical situations.

Vaseline petroleum jelly applied to the substrate was found to be the most effective of five lubricants tested in reducing asexual reproduction (fission) in the planarian flatworm Dugesia tigrina (Girard). Planarians which did not bud attained a much greater size than untreated controls.

AbstractThe posterior apophyses in terminal abdominal segments of female moths form part of the sex pheromone gland in each of three species examined (Choristoneura fumiferana (Clem.) (Tortricidae), Trichoplusia ni (Hübner) (Noctuidae), Orgyia leucosligma (J.E. Smith) (Lymantriidae)). Four groups of paired dorsolateral muscles are attached to the anterior or posterior apophysis and the integument. An additional group is attached to the anterior and posterior apophyses. The probable relationship of these muscles to the eversion, or protrusion, and inversion of sex pheromone glands is discussed.

AbstractMale Grapholitha molesta (Busck) treated with 40 krad of gamma radiation in the late pupal stage reduced egg-hatch by 93.6%, and in the young adult stage by 96.4%, in eggs from untreated virgin females with which they were mated; in addition, hatched larvae failed to complete development. Induced sterility was consistently greater in treated adults as compared with treated pupae. Females in the late pupal stage were sterilized with about 10 krad.Male longevity decreased in proportion to the radiation dosage above 30 krad when caged at a ratio of 3 ♂: 1 ♀. Longevity of untreated males decreased in proportion to the number of females available for mating.Radiation levels of 30 krad or more decreased male mating, especially when applied to the pupal stage, in inverse proportion to dosage, as detected by caging males with three times as many females.The number of matings per untreated male increased with the number of females available up to an average of 3.8 while the number of matings per female averaged approximately 1.6 with from one to three males per female.