Design Guide for glass fiber reinforced metal pressure vessel

Design Guide has been prepared for pressure vessel engineers concerned with specific glass fiber reinforced metal tank design or general tank tradeoff study. Design philosophy, general equations, and curves are provided for safelife design of tanks operating under anticipated space shuttle service conditions

Analysis of filament reinforced metal-shell pressure vessels

Computer program analyzes design requirements and computes designs for metal-lined filament-wound pressure vessels with either geodesic /helical/ or in-plane filament winding patterns on the cylindrical portion and over the ends, reinforced by circumferential windings on the cylindrical portion

Analysis of filament-wound dome and polar boss of metal-lined glass-filament-wound pressure vessels

Structural analysis of glass filament wound, aluminum lined pressure vessel design

Growth and Equity Effects of Agricultural Marketing Efficiency Gains in India

Agriculture is the largest source of employment in India, and food accounts for about half of consumer expenditures. Moving agricultural products from the farm to consumers more efficiently could result in large gains to producers, consumers, and India’s overall economy. This analysis uses a computable general equilibrium model with agricultural commodity detail and households disaggregated by rural, urban, and income class to study the potential impacts of reforms that achieve efficiency gains in agricultural marketing and reduce agricultural input subsidies and import tariffs. More efficient agricultural marketing generates economywide gains in output and wages, raises agricultural producer prices, reduces consumer food prices, and increases private consumption, particularly by low-income households. These gains could help to offset some of the medium-term adjustment costs for some commodity markets and households associated with reducing agricultural subsidies and tariffs.India, agriculture, policy reform, marketing efficiency, tariffs, subsidies, households, computable general equilibrium model., Agricultural and Food Policy, Agricultural Finance, Crop Production/Industries, International Relations/Trade, Marketing,

Frictional dynamics of viscoelastic solids driven on a rough surface

We study the effect of viscoelastic dynamics on the frictional properties of a (mean field) spring-block system pulled on a rough surface by an external drive. When the drive moves at constant velocity V, two dynamical regimes are observed: at fast driving, above a critical threshold Vc, the system slides at the drive velocity and displays a friction force with velocity weakening. Below Vc the steady sliding becomes unstable and a stick-slip regime sets in. In the slide-hold-slide driving protocol, a peak of the friction force appears after the hold time and its amplitude increases with the hold duration. These observations are consistent with the frictional force encoded phenomenologically in the rate-and-state equations. Our model gives a microscopical basis for such macroscopic description.Comment: 10 figures, 7 pages, +4 pages of appendi

Tuning spreading and avalanche-size exponents in directed percolation with modified activation probabilities

We consider the directed percolation process as a prototype of systems displaying a nonequilibrium phase transition into an absorbing state. The model is in a critical state when the activation probability is adjusted at some precise value p_c. Criticality is lost as soon as the probability to activate sites at the first attempt, p1, is changed. We show here that criticality can be restored by "compensating" the change in p1 by an appropriate change of the second time activation probability p2 in the opposite direction. At compensation, we observe that the bulk exponents of the process coincide with those of the normal directed percolation process. However, the spreading exponents are changed, and take values that depend continuously on the pair (p1, p2). We interpret this situation by acknowledging that the model with modified initial probabilities has an infinite number of absorbing states.Comment: 9 pages, 11 figure

The thin film microwave iris

Development of waveguide iris for microwave coupling applications using thin film techniques is discussed. Production process and installation of iris are described. Iris improves power transmission properties of waveguide window

Exploring Community Land Trusts as an Alternative to Mainstream Models of Affordable Housing and Envisioning a CLT in Lewiston, Maine

Community Land Trusts (CLTs) are non-profit organizations that create perpetually affordable housing through decommodification of the land. CLTs essentially serve as community stewards of land by acquiring the land that the housing is on and maintaining ownership of it through a ground lease document and use of a resale formula to determine a fair sale price of the home. Initially founded in the United States by Black farmers and civil rights activists in rural Georgia in the 1960s as a response to structural racism excluding people of color from accessing land, there are now over 200 CLTs in the US alone today, with many of them located in urban areas. Through an analysis of the different ways that CLTs choose to operate, this project attempts to understand what factors contribute to CLTs with an enhanced ability to provide fully democratized housing for residents on top of just an affordable home to live in. This thesis explores what conditions lead to CLTs that are able to empower residents in all aspects of decision making processes. Findings indicate that CLTs are most effective when they collaborate with actors both inside and outside of traditional systems which often looks like partnering with both grassroots organizations and city government. Rooted in place, the goal of this thesis is to provide resources for anyone assisting in the process of starting a CLT in the Tree Streets Neighborhood of Lewiston and apply CLT best practices to the context of Lewiston. While it is necessary to acknowledge the ways that CLTs are forced to operate under the constraints of capitalism, hindering their ability to transform in certain scenarios, the CLT model does provide a viable alternative option to more mainstream affordable housing models. The process of establishing a CLT is time consuming and involves many actors, but hopefully this thesis will serve as a baseline resource for anyone interested in taking up the project of establishing a CLT in Lewiston

Differential expansion fitting for cryogenic liquid tanks

Sliding contact between liner and interior surface of fitting accommodates stresses and strains developed in shell composite and metal liner system. Stresses and strains are transmitted to liner portion which is recessed in fitting and which acts as differential expansion fitting

Filament-reinforced metal composite pressure vessel evaluation and performance demonstration

Two different Kevlar-49 filament-reinforced metal sphere designs were developed, and six vessels of each type were fabricated and subjected to fatigue cycling, sustained loading, and hydrostatic burst. The 61 cm (24 inch) diameter Kevlar-49/cryoformed 301 stainless steel pressure vessels demonstrated the required pressure cycle capability, burst factor of safety, and a maximum pressure times volume divided by weight (pV/W) performance of 210 J/g (834 000 in-lb/lbm) at burst; this represented a 25 to 30% weight saving over the lightest weight comparable, 6A1-4V Ti, homogeneous pressure vessel. Both the Kevlar/stainless steel design and the 97 cm (38 inch) diameter Kevlar-49/2219-T62 aluminum sphere design demonstrated nonfragmentation and controlled failure mode features when pressure cycled to failure at operating pressure. When failure occurred during pressure cycling, the mode was localized leakage and not catastrophic. Kevlar/stainless steel vessels utilized a unique conical boss design, and Kevlar/aluminum vessels incorporated a tie-rod to carry port loads; both styles of polar fittings performed as designed during operational testing of the vessels