A predictive model for failure properties of thermoset resins

A predictive model for the three-dimensional failure behavior of engineering polymers has been developed in a recent NASA-sponsored research program. This model acknowledges the underlying molecular deformation mechanisms and thus accounts for the effects of different chemical compositions, crosslink density, functionality of the curing agent, etc., on the complete nonlinear stress-strain response including yield. The material parameters required by the model can be determined from test-tube quantities of a new resin in only a few days. Thus, we can obtain a first-order prediction of the applicability of a new resin for an advanced aerospace application without synthesizing the large quantities of material needed for failure testing. This technology will effect order-of-magnitude reductions in the time and expense required to develop new engineering polymers

Assessment of Control Alternatives for the Great Salt Lake

Introduction: Over the last few years, the rising level of the Great Salt Lake has changed Utah. It has inundated vast waterfowl feeding areas, crippled the salt industry, required raising transcontinental freeways and railroads, threatened metropolitan waste treatment plants, caused a major electrical outage, and damaged many properties. If nothing is done, approximately $3.6 billion of damages in 1985 dollars can be expected by 2050 (James et al, 1985, p.4). This threat led the State Legislature to set aside$100 million (an amount approximating the damages that had then occurred) in January 1985 to identify, select, and implement remedial measures. The rise has slowed. However, the lake entered February 1986 at its highest level since 1877, and a large storm of tripical origins brought a record one-month rise, tying the high of the previous spring at 4209.95, with heavy snowpacks in the mountains and at least three months of precipitation left before the normal date of the annual peak. Nevertheless, the legislature is diverting some of the funds to other purposes. As shown in Figure 2, the rise has greatly enlarged the surface area of a shallow water body. Table 1 shows how the historic variation has increased the lake surface area from 587,000 to 1,556,0000 acres, a range that varies normal annual evaporation from 1,470,000 to 4,800,000 acre feet. The lake will rise as long as inflow exceed actual evaporation. Total inflows were 5,300,000 acre feet in 1983, 6,200,000 acre feet in 1984, and 3,800,000 acre feet in 1985. The rise continued in 1985 because of abnormally low evapoartion

If We Build It Will They Come? Creating a Virtual Classroom in Second Life

The Second Life Multi-User Virtual Environment (MUVE) has been used as an educational resource in many different ways, ranging from simulating the traditional classroom, though interactive experiences, to practical creational activities. Supporting resources can include traditional multimedia, simulation tools and programming languages. Learning experiences may vary from the wholly extrinsic, learning about the outside world, to more intrinsic study of Second Life’s ecosystems and its built environment, or wholly in-world creative work. Within this broad scope, there is an opportunity to support many types of learning, and distance learning in particular. In this paper we propose an analytical framework for virtual learning environments in Second Life based on current practice. We describe the creation of a learning space within Second Life designed to explore how we might support distance learners using traditional environments for extrinsic learning experiences. We reflect on the utility of the framework in understanding the various forces at work in virtual learning contexts and evaluate the student experience. We conclude that despite the potential for Second Life to support distance learners with a broad set of tools and resources, technical constraints suggest that a more effective option would be to provide focused creative tasks for students in a managed laboratory environment

Update on Estimation of Water Surface Elevation Probabilities for the Great Salt Lake

The techniques of operational hydrology, employing an autoregrssive moving average (ARMA (1,0) model were used to replicate historical patterns of streamflow into, precipitation on, and evaporation from the Great Salt Lake. The results were combined with a lake water balance model to simulate lake stage sequences beginning with known initial conditions and extending up to 125 years into the future and used to generate probability distributions for future lake stages. Starting with a spring 1980 high stage of 4200.45 ft msl, the best estimate is that the 1981 spring high will be 4200.19, but there is one change in four that it will reach 4200.74 and one in ten that it will research 4201.24. Over the long run, an average spring high of 4195.20 is forecast with one year in a hundred reaching as high as 4205.21 and one year in a hundred with a pring high only 4185.19 and dropping as low as 4183.5. Followup annual forecast updates will be published about each July 1

Loran-C Latitude-Longitude Conversion at Sea : Programming Considerations

To aid programmers of Loran-C latitude-longitude conversion, we : 1. Provide reference to the literature. 2. Compare digital “processings-noise” for several arc-length methods. 3. Discuss some practical aspects of overland signal propagation (ASF) modeling for offshore navigation. Comparisons are made of the precision of arc-length routines as computer precision is reduced. Overland propagation delays (ASF's) are discussed and illustrated with observations from offshore New England. Present practice of Loran-C error budget modeling is then reviewed with the suggestion that additional terms be considered in future modeling

Estimation of water surface elevation probabilities and associated damages for the Great Salt Lake

Rising water surface elevations in perennial terminal lakes threaten major damages to shoreline industrial plants, transportation routs, and wetlands. Falling elevations increase pumping costs for industries extracting minerals from the lake water and reduce the quality of shoreline recreation. The managers of these properties need information on future lake level probabilities for planning, and public agencies need information on both probabilities and damages to determine whether lake level control is justified. Standard methods for estimating flood frequency and damages in riverine areas do not work well for terminal lakes because of the interdependency in annual peaks and the long advanced warning and duration of flood events. For this reasons, the methods of operational hydrology were use to simulate lake level and shoreline damage sequences for the Great Salt Lake. Both ARMA (1,0) and ARMS (1,1) models were tried in generating multivariate sequences of precipitation, evaporation, and three river flows for 1937-1977. The multivariate Markov model was the only one able to preserve historical sequences, but recommendations for improved parameter solution techniques for the ARMA (1,) model are made to help future users take better advantages of its theoretically greater ability to preserve hydrologic persistence. The Markov model was used to generate 100 and 125 year lake sequences as inputs to a lake water balance model which used them to generate 125 year lake stage sequences. The generated sequences showed lake level probabilities for current land and water use conditions the tributary area to be affected by known present conditions for about 35 years after which they stabilize in a normal distribution of mean 4196.42 and standard deviation of 4.56. The one-percent high event has a value of 4207.0, and the one-percent low event is 4191.5, and the amount by which these values exceed the forecast stages is indicative of the long term downward trend in lake stage caused by increasing upstream water use. The model developed with the capability of estimating low future lake level probabilities would be affected by upstream water development and by pumping water from the lake during high stages into the western desert. Data on damages to 21 cost centers were collected, and a damage simulation model was developed to use them to estimate average annual damages under current conditions and benefits from lake level control efforts. Averages annual damages to the mineral industry, railroads, highways, wetlands, and other properties were estimated to be currently $1,550,000. The computer programs for multivariate stochastic flow generation, lake water level simulation, and damage estimation are reproduced and documented in the appendices. The models will be available for future use in re-estimating probabilities and damages as initial lake stages and lake use conditions change, additional years of input data are collected, and the state of the art stochastic flow generation is refined

Improving the Education and Training of State and Local Environmental Health Practitioners

Since the publication of the Institute of Medicine report The Future of Public Health in 1988, much of the effort to improve the public health infrastructure in the United States has focused on improving the knowledge, skills and abilities (KSA's) of the public health workforce. The first step in workforce development has been to define the competencies or KSA's needed by public health workers. Competencies have been defined in three categories: basic knowledge of public health: core competencies; and technical, or discipline-specific competencies. The next step is to develop curricula to address the gap between KSA's needed and the KSA's required by public health workers. The environmental health segment of the workforce has been included in public health workforce development efforts. The Public Health Faculty/Agency Forum, the National Environmental Health Association, the Centers for Disease Control and Prevention, and others have defined the competencies needed by this discipline. Development efforts for this segment of the public health workforce face unique challenges: environmental health practitioners be employed by a variety of public agencies and current environmental health practitioners enter the profession with a variety of academic backgrounds. For the most part, these sets of competencies reflect expert opinion with little review and input from state and local practitioners. However, state and local agencies can use these competencies as a framework for improving the education and training of their environmental health practitioners, building on initial efforts that encompass the general public health workforce.Master of Public Healt

A User\u27s Manual for Computer Programs Used in: Model Choice: An Operational Comparison of Stochastic Streamflow Models for Droughts

The rapid development of stochastic or operational hydrology over the past 10 years has led to the need for some comparative analyses of the currently available long-term persistence models. Five annual stochastic streamflow generation models (autoregressive, autoregressive-moviing-average (ARMA), ARMA-Markov, fast fractional Gaussian noise, and broken line) are compared on their ability to preserved drought-related time series properties and annual statistics. Using Monto Carlo generation procedures and comparing the average generated statistics and drought or water supply properties, a basis is established to evaluated model performance on four different Utah study streams. A seasonal disaggregation model is applied to each of the generated annual models for each of the four study streams at a monthly disaggregation level. A model choice strategy is presented for the water resources engineer to select an annual stochastic streamflow model based on values of the historic time series; lag-one serial correlation and Hurst coefficient. Procedures are presented for annual and seasonal model parameter estimation, calibration, and generation. Techniques to ensure a consistent matrix for successful matric decomposition are included such as normality, trend-analysis, and choice of model. User oriented model parameter estimation techniques that are easy and efficient to use are presented in a systematic manner. The ARMA-Markov and ARMA models are judged to be the best overall models in terms of preserving the short and long term persistence statistics for the four historic time series studied. The broken line model is judged to be the best model in terms of minimizing the economic regret as determined by an agricultural crop production function. Documentation and listings of the computer programs that were used for the stochastic models\u27 parameter estimation, generation, and comparison techniques are presente in a supplementary appendix