Thermal expansion of graphite-epoxy between 116 K and 366 K

A Priest laser interferometer was developed to measure the thermal strain of composite laminates. The salient features of this interferometer are that: (1) it operates between 116 K and 366 K; (2) it is easy to operate; (3) minimum specimen preparation is required; (4) coefficients of thermal expansion in the range of 0-5 micro epsilon/K can be measured; and (5) the resolution of thermal strain is on the order of micro epsilon. The thermal response of quasi-isotropic, T300/5208, grahite-epoxy composite material was studied with this interferometer. The study showed that: (1) for the material tested, thermal cycling effects are negligible; (2) variability of thermal response from specimen to specimen may become significant at cryogenic temperatures; and (3) the thermal response of 0.6 cm and 2.5 cm wide specimens are the same above room temperature

Development of a Priest interferometer for measurement of the thermal expansion of a graphite epoxy in the temperature range 116-366 K

The thermal expansion behavior of graphite epoxy laminates between 116 and 366 degrees Kelvin was investigated using as implementation of the Priest interferometer concept. The design, construction and use of the interferometer along with the experimental results it was used to generate are described. The experimental program consisted of 25 tests on 25.4 mm and 6.35 mm wide, 8 ply pi/4 quasi-isotropic T300-5208 graphite/epoxy specimens and 3 tests on a 25.4 mm wide unidirectional specimen. Experimental results are presented for all tests along with a discussion of the interferometer's limitations and some possible improvements in its design

Edwards entropy and compactivity in a model of granular matter

Formulating a statistical mechanics for granular matter remains a significant challenge, in part, due to the difficulty associated with a complete characterization of the systems under study. We present a fully characterized model of a granular material consisting of $N$ two-dimensional, frictionless, hard discs, confined between hard walls, including a complete enumeration of all possible jammed structures. We show the properties of the jammed packings are independent of the distribution of defects within the system and that all the packings are isostatic. This suggests the assumption of equal probability for states of equal volume, which provides one possible way of constructing the equivalent of a microcanonical ensemble, is likely to be vaild for our model. An application of the second law of thermodynamics involving two subsystems in contact shows that the expected spontaneous equilibration of defects between the two is accompanied by an increase in entropy and that the equilibirum, obtained by entropy maximization, is characterized by the equality of compactivities. Finally, we explore the properties of the equivalent to the canonical ensemble for this system.Comment: Accepted PR

Jammed Disks of Two Sizes in a Narrow Channel

A granular-matter model is exactly solved, where disks of two sizes and weights in alternating sequence are confined to a narrow channel. The axis of the channel is horizontal and its plane vertical. Disk sizes and channel width are such that under jamming no disks remain loose and all disks touch one wall. Jammed microstates are characterized via statistically interacting particles constructed out of two-disk tiles. Jammed macrostates depend on measures of expansion work, gravitational potential energy, and intensity of random agitations before jamming. The dependence of configurational entropy on excess volume exhibits a critical point

Differentiating Simple Hepatic Cysts from Mucinous Cystic Neoplasms: Radiological Features, Cyst Fluid Tumour Marker Analysis and Multidisciplinary Team Outcomes

Background: Differentiating hepatic mucinous cystic neoplasms (MCNs) from simple hepatic cysts (SCs) preoperatively is a challenging task. Our aim was to determine whether radiological features on ultrasound scan (USS), CT or MRI, cyst fluid tumour markers, or multidisciplinary team (MDT) outcomes could differentiate MCN from SC. Methods: A retrospective review of radiological features, cyst fluid tumour marker levels and MDT outcomes in 52 patients was performed. Results: There were 13 patients with MCN, 38 with SC and one ciliated foregut cyst. MCNs were more often solitary (p = 0.006). Although no other individual radiological characteristic on USS, CT or MRI was predictive of MCN, MDT outcomes stating that a cyst was complex in nature were highly predictive (p = 0.0007). Cyst fluid carbohydrate antigen 19-9, carcino-embryonic antigen and cancer antigen 125 were unable to differentiate MCN from SC (p = 0.45, p = 0.49, and p = 0.73, respectively). Conclusions: MDT outcomes are of greatest value when trying to differentiate MCN from SC, as well as having a solitary cyst on imaging. Conventional cyst fluid tumour markers are unhelpful. All suspicious cystic liver lesions should be discussed pre-operatively by a hepatobiliary MDT to determine the most appropriate surgical approach

Development and Preliminary Application of Mathematical Models to the Weber Basin

The adoption of stream standards, whether for direct application or for the establishment of realistic effluent standards, creates a need to predict the impact of pollution loads on river water quality during critical flow periods or as the result of future user demands. Because of the complexity of aquatic systems, mathematical models are an excellent medium for bringing together the state-of-the-art knowledge from a variety of disciplines into a form which can be readily applied to practical problems. Applying a mathematical model to a river system has the added advantage of providing a structure for the systematic consideration of the many diverse aspects of water quality phenomena. This report describes the development of a river simulation model (QUAL-U) for predicting water quality and its preliminary application to the Weber River drainage basin in northeastern Utah. The model involves the numerical solution of a set of differential equations representing the aquatic system under steady state conditions. The development and use of a second model which provides the flow boundary conditions for the first model is also described. This model is a simple interactive procedure for obtaining flows at specified locations on the river system given the measured flows at other locations and typical flow ranges of headwater, diversions, surface and subsurface lateral inflows, and point loads. Previous river water quality models are reviewed and the structure of QUAL-U is presented. The economic and physical characteristics of the study area are described and the Weber River system is represented by subbasins, reaches, and computational units. Model calibration was based on water quality data collected at over eighty sampling locations in the study area during a four day period in September, 1973. Each of the sampling points was subsequently surveyed to obtain representative hydraulic characteristics for each reach of the river system. Coefficients for the mathematical equations representing hydraulic characteristics and chemical and biological reactions were estimated and adjusted during the model calibration procedure until model responses satisfactorily resembled the observed data. Results for the calibration period and also for studies involving critical low flow conditions are described and model limitations are considered. The work on which this report is based was performed for the State of Utah, Department of Social Services, Division of Health as part of a Waste Load Allocation Study on the Weber River. The scope of this project provided only for supplying the calibrated model to the client and does not include predictive runs or interpretation of management alternatives

Correct composition of dephased behavioural models

This research is supported by EPSRC grant EP/M014290/1.Scenarios of execution are commonly used to specify partial behaviour and interactions between different objects and components in a system. To avoid overall inconsistency in specifications, various automated methods have emerged in the literature to compose (behavioural) models. In recent work, we have shown how the theorem prover Isabelle can be combined with the constraint solver Z3 to efficiently detect inconsistencies in two or more behavioural models and, in their absence, generate the composition. Here, we extend our approach further and show how to generate the correct composition (as a set of valid traces) of dephased models. This work has been inspired by a problem from a medical domain where different care pathways (for chronic conditions) may be applied to the same patient with different starting points.Postprin

Designing for time-dependent material response in spacecraft structures

To study the influence on overall deformations of the time-dependent constitutive properties of fiber-reinforced polymeric matrix composite materials being considered for use in orbiting precision segmented reflectors, simple sandwich beam models are developed. The beam models include layers representing the face sheets, the core, and the adhesive bonding of the face sheets to the core. A three-layer model lumps the adhesive layers with the face sheets or core, while a five-layer model considers the adhesive layers explicitly. The deformation response of the three-layer and five-layer sandwich beam models to a midspan point load is studied. This elementary loading leads to a simple analysis, and it is easy to create this loading in the laboratory. Using the correspondence principle of viscoelasticity, the models representing the elastic behavior of the two beams are transformed into time-dependent models. Representative cases of time-dependent material behavior for the facesheet material, the core material, and the adhesive are used to evaluate the influence of these constituents being time-dependent on the deformations of the beam. As an example of the results presented, if it assumed that, as a worst case, the polymer-dominated shear properties of the core behave as a Maxwell fluid such that under constant shear stress the shear strain increases by a factor of 10 in 20 years, then it is shown that the beam deflection increases by a factor of 1.4 during that time. In addition to quantitative conclusions, several assumptions are discussed which simplify the analyses for use with more complicated material models. Finally, it is shown that the simpler three-layer model suffices in many situations

Summary Report: Updating the Estimation of Water Surface Elevation Probabilities and Associated Damages for Great Salt Lake

Problem Statement: Rising levels of the Great Salt Lake are severely impacting private and public property. in the private sector, the mineral industry, the railroad, and a number of recreation enterprises are suffering major damages. In the publi sector, the State of Utah is esperiencing large losses inflicted on roads and highways, waterfowl and related wildlife areas, and park and recreation facilities. The lake is partitioned by a semipervious railroad causeway into a north and a south arm with the sourth arm having about twice the water surface area and usually being two or three feet higher because it receibes nearly all the surface runoff from tributary rivers. in the last two years, the largest rainfall years of record (exceeded only the approximations made for 1866), record inflows, and record low evaporation rates have brought the largest historical rise in the lake water surface. Over this period, the sourth arm lake level rose to 4200.25 (June 1981), dropped to 4198.20 (October 1981), rose to 4200.85 (June 1982), dropped to 4199.80 (September 1982), and then rose to 4205.00 (July 1983). The south arm level dropped to about 4204.6, on August 15, but by January 15, 1984, the water surface reached an elevation of 4206.15. The north arm was about 2.5 feel lower. The lake level was the highest since 1887 when the lake was retreating from a high of 4207.7 in the previous year. The measured inflow of 5.3 million acre feet (maf) during the water year ending Sept. 1983, was the largest of record, surpassing estimated and more approximate values of 4.5 maf for 1872 and of 4.1 maf for 1909. The rise of 5.2 feet in 1983 surpassed the previously highest values of 3.4 feet in 1862 and 1907. in 1983, precipitation was 68 percet above normal, and evaporation was 86 percent of normal. Sequences from water years 1851 through 1983 of river inflows (Bear, Weber and Jordan), precipitation on the lake, evaporation from the lake, and annual high stages are given in Table 1. The flows are adjusted to represent present land and water use conditions, lake levels are historical readings on the south arm, and numbers given for the earlier years were not measured (except for two intermittent precipitation gages in the Salt Lake City area) but estimated through correlations and lake water blanace computations by the Utah Division of Water Resources and the Utah Water Research Laboratory. Objective planning of a strategy for dealing with this problem requires defining technically workable control methods, estimating their effects on probable lake lebels, translating effects on levels to effects on damges, and comparing the benefits of the damage reduction achieved with costs. This summary report presents estimates of probable lake levels under current conditions and the changes in these probabilities that could be expected with various lake level control alternatives (breaching the causeway, pumping into the western desert, and constructing reservoirs for irrigation development in the tributary basin). It also presents benfit estimates for these alternatives. Methodology is described in Bowles, James, and Chadwick (1984)