Improving the performance of HTTP over high bandwidth-delay product circuits

As the WWW continues to grow, providing adequate bandwidth to countries remote from the geographic and topological center of the network, such as those in the Asia/Pacific, becomes more and more difficult. To meet the growing traffic needs of the Internet some Network Service Providers are deploying satellite connections. Through discrete event simulation of a real HTTP workload with differing international architectures this paper is able to give guidance on the architecture that should be deployed for long distance, high capacity Internet links. We show that a significant increase in the time taken to fetch HTTP requests can be expected when traffic is moved from a long distance international terrestrial link to a satellite link. We then show several modifications to the network architecture that can be used to greatly improve the performance of a satellite link. These modifications include the use of an asymmetric satellite link, the multiplexing of multiple HTTP requests onto a single TCP connection and the use of HTTP1.1

Configurations and relative efficiencies of shrimp trawls employed in southeastern United States waters

Common shrimp trawl designs employed in the southeastern United States shrimp fishery are the flat, balloon, semiballoon, jib, and super X-3. Recent innovations in trawl design and rigging, including the twin trawl rigging and tongue trawl design, have improved the efficiency of shrimp trawling gear. A description of the construction techniques for the different designs indicate differences which affect gear performance. Measurements of horizontal spread and vertical opening for 76 trawl configurations indicate the relative efficiencies of the different designs. Maximum horizontal spreading efficiency was achieved by the "twin" and "tongue" trawl designs followed by the super X-3, jib, balloon, and semiballoon designs. Designs having the greatest vertical openings were the tongue and flat trawl designs followed by the semiballoon. Maximum total gape dimension was demonstrated by the "Mongoose" tongue trawl. Comparison of trawl spreading efficiency and door area to headrope length ratio indicates that a range of 70-80 in square (per door) of door area is required for each foot of trawl headrope length for maximum efficiency with conventional trawl designs and 66-75 in square per foot of headrope for tongue trawl designs. (PDF file contains 18 pages.

The probability of cost-effectiveness

BACKGROUND: The study of cost-effectiveness comparisons between competing medical interventions has led to a variety of proposals for quantifying cost-effectiveness. The differences between the various approaches can be subtle, and one purpose of this article is to clarify some important distinctions. DISCUSSION: We discuss alternative measures in the framework of individual, patient-level, incremental net benefits. In particular we examine the probability of cost-effectiveness for an individual, proposed by Willan. SUMMARY: We argue that this is a useful addition to the range of cost-effectiveness measures, but will be of secondary interest to most decision makers. We also demonstrate that Willan's proposed estimate of this probability is logically flawed

Optimal Capacity Decisions in a Developing Fishery

The problem of estimating optimal fishing capacity for a developing fishery is discussed, using the methods of Bayesian decision analysis. The results obtained indicate that quite good decisions can often be made on the basis of limited prior information as to fish stock productivity, particularly if a conservative approach allowing for subsequent increases in capacity is employed.Environmental Economics and Policy, International Development, International Relations/Trade, Resource /Energy Economics and Policy,

A Critical Assessment of Theories of Strain Gradient Plasticity

Theories to extend plasticity to the micron scale have been in existence for over a decade, complemented by a growing body of experimental data. Here, materials and mechanics aspects of two prominent strain gradient theories of plasticity, due to Nix and Gao and to Fleck and Hutchinson, are assessed within the context of simple bending. Differences between the theories are highlighted. The theories predict different trends relative to the size dependence of initial yielding and rate of hardening. The dislocation mechanics underpinning the two theories is addressed. Distinctions between lower-order theories and higher-order theories are also drawn, emphasizing the flexibility of higher-order theories to solve problems for a wide range of boundary conditions, especially those where, locally, the dislocations are blocked (pile up) and the plastic strain is zero.Engineering and Applied Science

Modeling inflation in Kenya: Comparison of SARIMA and Generalized Least Squares models

One desire by the policy makers in a country is to have access to reliable forecast of inflation rate. This is only achievable if the right model with high predictive accuracy is used. In this paper, seasonal auto regressive integrated moving average (SARIMA) and Generalized Least Squares regression models are developed to predict Kenya's inflation using quarterly data for the period 1981 to 2013. SARIMA (0,1,0)(0,0,1)4 was chosen as the model with the least Akaike Information Criterion and Bayesian Information Criterion. The parameters were then estimated. The residuals were checked to find out if they follow a white noise process by using residual Q-Q and normality test plots. The Test for normality of residual was also done. Given the high p-values (0.0639237) associated with the statistics as compared to 0.05, we fail to reject the null hypothesis that an error is normally distributed in this residual series. Thus, we conclude that the model provides an adequate fit for the data. In an effort to improve this, inflation was also modeled using Generalized Least Squares regression model.. The data was first checked for heteroscedasticity using the Breusch-Pagan test. Based on the p-value=0.000, which is less than alpha (of 5%), we conclude that there is substantial amount heteroscedasticity in the data. A regression model that forecasts inflation using its lags was constructed. The residuals were checked for normality using q-q plot. Additionally, the Shapiro-Wilk normality test was carried out. Its p-value was 0.08178 and since its greater than 0.05, its concluded that the residuals does not deviate from normality A comparison was made on the predictive ability of both models. SARIMA (0,1,0)(0,0,1)4 model had the least values of MAPE, MAE and RMSE with the corresponding values given by MAPE=14.155, RMSE=0.2871and MAE=0.23692 Keywords: SARIMA, Generalized Least Squares, Akaike Information Criterion ,Bayesian Information Criterion, Shapiro-Wilk normality test and Breusch-Pagan tes

Oxylipins in triglyceride-rich lipoproteins of dyslipidemic subjects promote endothelial inflammation following a high fat meal.

Elevated triglyceride-rich lipoproteins (TGRL) in circulation is a risk factor for atherosclerosis. TGRL from subjects consuming a high saturated fat test meal elicited a variable inflammatory response in TNFα-stimulated endothelial cells (EC) that correlated strongly with the polyunsaturated fatty acid (PUFA) content. This study investigates how the relative abundance of oxygenated metabolites of PUFA, oxylipins, is altered in TGRL postprandially, and how these changes promote endothelial inflammation. Human aortic EC were stimulated with TNFα and treated with TGRL, isolated from subjects' plasma at fasting and 3.5 hrs postprandial to a test meal high in saturated fat. Endothelial VCAM-1 surface expression stimulated by TNFα provided a readout for atherogenic inflammation. Concentrations of esterified and non-esterified fatty acids and oxylipins in TGRL were quantified by mass spectrometry. Dyslipidemic subjects produced TGRL that increased endothelial VCAM-1 expression by ≥35%, and exhibited impaired fasting lipogenesis activity and a shift in soluble epoxide hydrolase and lipoxygenase activity. Pro-atherogenic TGRL were enriched in eicosapentaenoic acid metabolites and depleted in esterified C18-PUFA-derived diols. Abundance of these metabolites was strongly predictive of VCAM-1 expression. We conclude the altered metabolism in dyslipidemic subjects produces TGRL with a unique oxylipin signature that promotes a pro-atherogenic endothelial phenotype

Imaging and Analysis of Void-defects in Solder Joints Formed in Reduced Gravity using High-Resolution Computed Tomography

As a part of efforts to develop an electronics repair capability for long duration space missions, techniques and materials for soldering components on a circuit board in reduced gravity must be developed. This paper presents results from testing solder joint formation in low gravity on a NASA Reduced Gravity Research Aircraft. The results presented include joints formed using eutectic tin-lead solder and one of the following fluxes: (1) a no-clean flux core, (2) a rosin flux core, and (3) a solid solder wire with external liquid no-clean flux. The solder joints are analyzed with a computed tomography (CT) technique which imaged the interior of the entire solder joint. This replaced an earlier technique that required the solder joint to be destructively ground down revealing a single plane which was subsequently analyzed. The CT analysis technique is described and results presented with implications for future testing as well as implications for the overall electronics repair effort discussed

Performance Evaluation of a Hydraulic Asphalt Concrete Pavement Capping a Hazardous Waste Site

Hydrologic Consultants, Inc. was contracted to undertake the closure of a former pesticide facility. While pesticide compounds were present on the site, they were located primarily in the top two feet of soil. Five remedial action alternatives for the site were reviewed; the remedial action selected was to cap the site. Because of the expense of obtaining clay in sufficient quantities, a less costly alternative to clay was adopted: a high-bitumen-content hydraulic asphalt concrete (HAC) pavement. For preliminary design purposes, a performance assessment was conducted utilizing the Hydraulic Evaluation of Landfill Performance (HELP) model to compare the relative performance of clay and asphalt capping material. The results of model simulations indicated that the asphalt pavement design with a permeability value of 10-