A numerical and analytical study of two holes doped into the 2D t--J model

Exact diagonalization numerical results are presented for a 32-site square cluster, with two holes propagating in an antiferromagnetic background described by the t-J model. We characterize the wave function of the lowest energy bound state found in this calculation, which has d_{x^2-y^2} symmetry. Analytical work is presented, based on a Lang-Firsov-type canonical transformation derived quasiparticle Hamiltonian, that accurately agrees with numerically determined values for the electron momentum distribution function and the pair correlation function. We interpret this agreement as strong support for the validity of this description of the hole quasiparticles.Comment: 3 pages, REVTeX, to appear in the proceedings of the Fifth International Conference on Spectroscopies in Novel Superconductors, September 14-18, 1997, Cape Cod, Massachusett

The Market for Guayule Rubber

In 1980, IIASA joined with the Centro de Investigacion en Quimica Aplicada (CIQA) to study resource development alternatives for arid and semi-arid regions. This joint effort is motivated by the perception that planning and programming of development projects, as they typically are applied to projects for drylands, are inadequate and pose serious obstacles to successful development of these regions. Two characteristics distinguish the problem of planning and programming development projects for drylands. First, all of the common difficulties that beset development planning and programming (e.g., inadequate data, importance of poorly understood social and cultural relations, inadequate infrastructure, inadequate organizational capacity) are present in the extreme. Second, even very modest-sized development projects are usually enormous in relation to the social, economic, and technical structure of drylands regions; their ramifications are little short of revolutionary. To focus our efforts to improve planning and programming methodologies for dryland regions, it was decided to examine a specific problem: the prospects for developing a dryland region in northern Mexico based on the exploitation of 6 vegetal resources native to the region. A description of this effort is available in: Anderson, R.J., E. Campos-Lopez, and D. Gourmelon. An Analysis of Renewable Resource Development Alternatives for the Northern Arid Region of Mexico: Study Prospectus. WP-81-7. International Institute for Applied Systems Analysis. (January, 1981). Guayule (parthenium argentatum gray) is one of the vegetal resources under investigation in this study. Guayule shrub, which grows wild on the sierras of the Chihuahuan desert, produces a high molecular weight hydrocarbon that can be processed into a premium-quality rubber. For approximately 50 years during the first half of this century a small but important guayule rubber industry operated in Mexico. The Mexican government currently plans to reactivate the guayule rubber industry using shrub harvested from wildstands as the basic source of shrub. This paper examines a critical aspect of this plan, the future market conditions under which a guayule rubber industry would operate. In subsequent papers, projected demand conditions will be compared to information concerning probable production costs to determine whether guayule rubber production is feasible economically

Estimation of the Mass Density of Guayule from Height Data

In 1980, IIASA joined with the Centro de Investigacion en Quimica Aplicada (CIQA) to study resource development alternatives for arid and semi-arid regions. This joint effort is motivated by the perception that planning and programming of development projects, as they typically are applied to projects for drylands, are inadequate and pose serious obstacles to successful development of these regions. Two characteristics distinguish the problem of planning and programming development projects for drylands. First, all of the common difficulties that beset development planning and programming (e.g., inadequate data, importance of poorly understood social and cultural relations, inadequate infrastructure, inadequate organizational capacity) are present in the extreme. Second, even very modest-sized development projects are usually enormous in relation to the social, economic, and technical structure of drylands regions; their ramifications are little short of revolutionary. To focus our efforts to improve planning and programming methodologies for dryland regions, it was decided to examine a specific problem: the prospects for developing a region in northern Mexico based on the exploitation of 6 vegetal resources native to the region. A description of this study is available in: Anderson, R.J., E. Campos-Lopez, and D. Gourmelon. An Analysis of Renewable Resource Development Alternatives for the Northern Arid Region of Mexico: Study Prospectus. WP-81-7. International Institute for Applied Systems Analysis. (January, 1981). Guayule (parthenium argentatum gray) is one of the vegetal resources under investigation in this study. Guayule shrub, which grows wild on the sierras of the Chihuahuan desert, produces a high molecular weight hydrocarbon that can be processed into a premium-quality natural rubber. For approximately 50 years during the first half of this century a small but important guayule rubber industry operated in Mexico. The Mexican government currently plans to reactivate the guayule rubber industry using shrub harvested from wildstands as the basic source of shrub. This paper examines a critical aspect of this plan, the inventory of guayule shrub available for harvest. More specifically, the paper examines a new shrub inventory technique that has been proposed, and attempts to account for differences between the results obtained when this technique is used in place of standard inventory methods

An Estimate of the Maximum Sustainable Yield from Harvest of Guayule Wildstands in the Vicinity of Cedros

In 1980, IIASA joined together with the Centro de Investigacion en Quimica Aplicada (CIQA) to study resource development alternatives for arid and semi-arid regions. This joint effort is motivated by the perception that planning and programming of development projects, as they typically are applied to projects for drylands, are inadequate and pose serious obstacles to successful development of these regions. Two characteristics distinguish the problem of planning and programming development projects for drylands. First, all of the common difficulties that beset development planning and programming (e.g., inadequate data, importance of poorly understood social and cultural relations, inadequate infrastructure, inadequate organizational capacity) are present in the extreme. Second, even very modest-sized development projects are usually enormous in relation to the social, economic, and technical structure of drylands regions; their ramifications are little short of revolutionary. To focus our efforts to improve planning and programming methodologies for dryland regions, it was decided to examine a specific problem: the prospects for developing a dryland region in northern Mexico based on the exploitation of 6 vegetal resources native to the region. A description of this effort is available in: Anderson, R.J., E. Campos-Lopez, and D. Gourmelon. An Analysis of Renewable Resource Development Alternatives for the Northern Arid Region of Mexico: Study Prospectus. WP-81-7. International Institute for Applied Systems Analysis. (January, 1981). Guayule (parthenium argentatum gray) is one of the vegetal resources under investigation in this study. Guayule shrub, which grows wild on the sierras of the Chihuahuan desert, produces a high molecular weight hydrocarbon that can be processed into a premium-quality natural rubber. For approximately 50 years during the first half of this century a small but important guayule rubber industry operated in Mexico. The Mexican government currently plans to reactivate the guayule rubber industry using shrub harvested from wildstands as the basic source of shrub. This paper examines a critical aspect of this plan, the limits on the amount of shrub that can be harvested without exhaustion of the wildstands and without reforestation or other forestry management methods

Uncertainty and the Choice of Policy Instruments for Meeting an Environmental Quality Standard

Broadly stated, there are three steps in environmental quality management. These are (1) selection of environmental quality standards, (2) determination of feasible programs for reducing discharges to the environment or for increasing its assimilative capacities, and (3) implementation of a policy to bring about discharge reductions and/or expansion of assimilative capacity. Much of REN's research program has been devoted to state-of-the-art analysis of the effects of discharges on environmental systems and modifications in environmental systems that could be made to enhance systems' abilities to assimilate discharges. For example, case studies of Lake Balaton in Hungary and Attersee and Neusiedlersee in Austria have advanced the state of the art of modeling water quality and are providing a menu of feasible programs for managing the quality of these lakes. Subsequent REN studies will build on these modeling efforts to evaluate alternative management plans and policies. This working paper is the first of a series of reports that are planned to result from these efforts. It considers the problem of choosing a policy instrument (i.e. a means to implement environmental quality standards) that is both effective (i.e. will result in the environmental quality standard being met) and efficient (i.e. will meet standard at least cost). Three alternative policy instruments are considered. These are (1) emission standards, which prescribe maximum allowable rates of discharges of pollutants to the environment, (2) emission charges, which prescribe payments that emitters must make per unit of pollution discharged to the environment, and (3) transferable emission permits, which entitle their holder to a face value quantity of emissions, and which may be transferred among emitters. REN's analyses of specific environmental management problems dramatically illustrate that uncertainty pervades the modeling and management process. Until recently, this fact of the modeling and management problem (i.e. uncertainty) was largely ignored in studies of the policy instrument question. This paper builds on the recent literature to show how, in the presence of uncertainty, policy might best be fashioned to meet an environmental quality standard efficiently

The Probability Distribution of Water Inputs and the Economic Benefits of Supplementary Irrigation

Several of REN's studies have examined the effect of risk and uncertainty on the status and management of environmental resources. This paper examines some of the effects of risk and uncertainty on the economics of production processes that depend upon randomly-varying environmental resource inputs. Work on this topic is continuing in the context of REN's studies in its Regional Water Management, Ecological Modeling, and Climate tasks

On the Complexity of List Ranking in the Parallel External Memory Model

We study the problem of list ranking in the parallel external memory (PEM) model. We observe an interesting dual nature for the hardness of the problem due to limited information exchange among the processors about the structure of the list, on the one hand, and its close relationship to the problem of permuting data, which is known to be hard for the external memory models, on the other hand. By carefully defining the power of the computational model, we prove a permuting lower bound in the PEM model. Furthermore, we present a stronger \Omega(log^2 N) lower bound for a special variant of the problem and for a specific range of the model parameters, which takes us a step closer toward proving a non-trivial lower bound for the list ranking problem in the bulk-synchronous parallel (BSP) and MapReduce models. Finally, we also present an algorithm that is tight for a larger range of parameters of the model than in prior work

Smooth vortex precession in superfluid 4He

We have measured a precessing superfluid vortex line, stretched from a wire to the wall of a cylindrical cell. By contrast to previous experiments with a similar geometry, the motion along the wall is smooth. The key difference is probably that our wire is substantially off center. We verify several numerical predictions about the motion, including an asymmetry in the precession signature, the behavior of pinning events, and the temperature dependence of the precession.Comment: 8 pages, 8 figure

IUPUI mechanical engineering technology senior assessment

This paper discusses the methods and analysis of 6-semesters of senior assessment examination data identifying the courses and subject material students found the most difficult to solve in the MET program Senior Assessment Examination. The analysis results indicate that MET 111 (Applied Statics), MET 213 (Dynamics), and MET 348 (Engineering Materials) are courses in need of potential improvement. Furthermore, subject areas such as the calculation of entropy change, the calculation of pressure drop flow through a pipe, and Hooke's Law are subject material that poses greatest problems for senior students. For the past 12 years, the Mechanical Engineering Technology (MET) Program faculty at IUPUI require all seniors to take a MET Senior Assessment Examination that is similar in content to the Fundamentals of Engineering (FE) examination. This paper discusses the methods used to provide insightful and actionable inputs for the IUPUI MET program process improvements plan. The raw data consists of test scores from 123 senior students who took the examination from 2014 through 2016. The Accreditation Board for Engineering & Technology (ABET) is an organization that ensures universities and institutions like IUPUI meet certain accreditation requirements and requires that each program develops a continuous improvement plan. The improvement plan typically consists of a compilation of student materials, employer surveys, and course evaluations used to ensure continuous improvement within a program. In 2004 IUPUI, MET program faculty decided that a standardized senior examination would be part of the program process improvement process, [1]

An Analysis of Renewable Resource Development Alternatives for the Northern Arid Region of Mexico: Study Prospectus

In 1980, IIASA joined with the Centro de Investigation en Quimica Aplicada (CIQA) in order to study alternative production chains based on the renewable resources of the Northern Arid Region of Mexico. This study applied the "WELMM Approach" developed at IIASA. Its objective was to account for the basic resources used and processed along alternative production chains, from cultivation and harvesting of the plants to the final products. WELMM analyses of each of the production chains are now being completed, and IIASA and CIQA have decided to expand their cooperative efforts to include an analysis of alternative development projects for the Northern Arid Region based on these production chains. This paper presents a prospectus for the expanded study