Three-dimensional finite element analysis of acoustic instability of solid propellant rocket motors

A three dimensional finite element solution of the acoustic vibration problem in a solid propellant rocket motor is presented. The solution yields the natural circular frequencies of vibration and the corresponding acoustic pressure mode shapes, considering the coupled response of the propellant grain to the acoustic oscillations occurring in the motor cavity. The near incompressibility of the solid propellant is taken into account in the formulation. A relatively simple example problem is solved in order to illustrate the applicability of the analysis and the developed computer code

Pultrusion process characterization

Pultrusion is a process through which high-modulus, lightweight composite structural members such as beams, truss components, stiffeners, etc., are manufactured. The pultrusion process, though a well-developed processing art, lacks a fundamental scientific understanding. The objective here was to determine, both experimentally and analytically, the process parameters most important in characterizing and optimizing the pultrusion of uniaxial fibers. The effects of process parameter interactions were experimentally examined as a function of the pultruded product properties. A numerical description based on these experimental results was developed. An analytical model of the pultrusion process was also developed. The objective of the modeling effort was the formulation of a two-dimensional heat transfer model and development of solutions for the governing differential equations using the finite element method

How Do You Mobilize Public Support for Infrastructural Investment in California’s Aging Water System?

This paper looks at how the state of California maintains an aging water system – the California State Water Project (SWP) – that will threaten California’s water supply if further maintained, and concludes that the system faces three major problems that are of concern in 2017 – aging pipes, health hazards, and environmental threats. What needs to be done in order to address these issues is to invest in a new and improved SWP that will save water, protect the water supply from contamination of hazardous particles, and replenish the ecosystems within piping range that it has depleted. To do this, I propose to launch the Eliminate California’s Aging Water System campaign that will expose each of these problems to the public, and work towards garnering support from water customers, voters, state and federal officials, local water agencies, environmental groups, farmers, and labor unions to want to help pay for the a new SWP that will be modernized, reliable, and sustainable. The campaign will also advocate for a general obligation bond measure to be placed onto the statewide ballot in 2020, which will go towards funding a portion of the project. It is important to motivate civic engagement in a country that lacks an informed population of the problems in which the state’s infrastructure faces today – with its outdated systems, as well as the risks to the public’s health, and the endangerment of species. That is why the campaign will conduct widespread outreach to inform Californian residents about how they can contribute their time and money to a project that will protect their health, and prevent a major failure and contamination of the water system over the next 100 years, which could leave millions without clean water for an extended period of time

Predicting preferential DNA vector insertion sites: implications for functional genomics and gene therapy

Viral and transposon vectors have been employed in gene therapy as well as functional genomics studies. However, the goals of gene therapy and functional genomics are entirely different; gene therapists hope to avoid altering endogenous gene expression (especially the activation of oncogenes), whereas geneticists do want to alter expression of chromosomal genes. The odds of either outcome depend on a vector's preference to integrate into genes or control regions, and these preferences vary between vectors. Here we discuss the relative strengths of DNA vectors over viral vectors, and review methods to overcome barriers to delivery inherent to DNA vectors. We also review the tendencies of several classes of retroviral and transposon vectors to target DNA sequences, genes, and genetic elements with respect to the balance between insertion preferences and oncogenic selection. Theoretically, knowing the variables that affect integration for various vectors will allow researchers to choose the vector with the most utility for their specific purposes. The three principle benefits from elucidating factors that affect preferences in integration are as follows: in gene therapy, it allows assessment of the overall risks for activating an oncogene or inactivating a tumor suppressor gene that could lead to severe adverse effects years after treatment; in genomic studies, it allows one to discern random from selected integration events; and in gene therapy as well as functional genomics, it facilitates design of vectors that are better targeted to specific sequences, which would be a significant advance in the art of transgenesis

Ka-band Ga-As FET noise receiver/device development

The development of technology for a 30 GHz low noise receiver utilizing GaAs FET devices exclusively is discussed. This program required single and dual-gate FET devices, low noise FET amplifiers, dual-gate FET mixers, and FET oscillators operating at Ka-band frequencies. A 0.25 micrometer gate FET device, developed with a minimum noise figure of 3.3 dB at 29 GHz and an associated gain of 7.4 dB, was used to fabricate a 3-stage amplifier with a minimum noise figure and associated gain of 4.4 dB and 17 dB, respectively. The 1-dB gain bandwidth of this amplifier extended from below 26.5 GHz to 30.5 GHz. A dual-gate mixer with a 2 dB conversion loss and a minimum noise figure of 10 dB at 29 GHz as well as a dielectric resonator stabilized FET oscillator at 25 GHz for the receiver L0. From these components, a hybrid microwave integrated circuit receiver was constructed which demonstrates a minimum single-side band noise figure of 4.6 dB at 29 GHz with a conversion gain of 17 dB. The output power at the 1-dB gain compression point was -5 dBm

From the Associate Editors of Education/Minority and International Business

From the editors of the Spring 2010 Special Section—Entrepreneurial Education, Minority and International Business

Stations, trains and small-world networks

The clustering coefficient, path length and average vertex degree of two urban train line networks have been calculated. The results are compared with theoretical predictions for appropriate random bipartite graphs. They have also been compared with one another to investigate the effect of architecture on the small-world properties.Comment: 6 pages, prepared in RevTe

Electrochemistry of proteins at the interface between two immiscible electrolyte solutions

The electrochemistry of proteins at the interface between two immiscible electrolyte solutions (ITIES) is discussed, with detection capabilities based on protein-facilitated anion transfer, and which has enabled protein detection via adsorptive stripping voltammetry. Targeting an enzymatic biomarker has achieved detection at picomolar concentrations, whilst studies into structural aspects of proteins at the ITIES have revealed formation of oligomers (cytochrome c) and unfolded protein (lysozyme) together with alterations to the protein secondary structures