Internal ballistics model update for ASRM dome

A previous report (no. 5-32279, contract NAS8-36955, DO 51) describes the measures taken to adapt the NASA Complex Burning Region Model and code so that is was applicable to the Advanced Solid Rocket Motor as envisioned at that time. The code so modified was called the CBRM-A. CBRM-A could calculate the port volume and burning area for the star, transition, and cylindrically perforated regions of the motor. Described here is a subsequent effort to add computation of port volume and burning area for the Advanced Solid Rocket Motor head dome. Sample output, input, and overview of the models are included. The software was configured in two forms - a stand alone head dome code and a code integrating the head dome solution with the CBRM-A

A Unified and Complete Construction of All Finite Dimensional Irreducible Representations of gl(2|2)

Representations of the non-semisimple superalgebra $gl(2|2)$ in the standard basis are investigated by means of the vector coherent state method and boson-fermion realization. All finite-dimensional irreducible typical and atypical representations and lowest weight (indecomposable) Kac modules of $gl(2|2)$ are constructed explicitly through the explicit construction of all $gl(2)\oplus gl(2)$ particle states (multiplets) in terms of boson and fermion creation operators in the super-Fock space. This gives a unified and complete treatment of finite-dimensional representations of $gl(2|2)$ in explicit form, essential for the construction of primary fields of the corresponding current superalgebra at arbitrary level.Comment: LaTex file, 23 pages, two references and a comment added, to appear in J. Math. Phy

Worker Training in a Restructuring Economy: Evidence from the Russian Transition

We use 1994-1998 data from the Russian Longitudinal Monitoring Survey (RLMS) to measure the incidence and determinants of several types of worker training and to estimate the effects of training on workers' interindustry, interfirm, and occupational mobility, their labor force transitions, and their wage growth in Russia compared to the U.S. We hypothesize that the shock of economic liberalization in Russia may raise the benefits of training, particularly retraining for new jobs, but uncertainty concerning the revaluation of skills may raise the costs, with an overall ambiguous effect on the amount of training undertaken. The RLMS indicates a lower rate of formal training than studies have found for the U.S., suggesting that the second effect dominates. Previous schooling is estimated to affect the probability of training positively, but the relationship is much stronger for additional training in the same field than for retraining for new fields, consistent with the hypothesis that schooling and training are complementary but become more substitutable in a restructuring environment. Foreign ownership of the firm also positively affects the probability of undertaking training, providing evidence of active restructuring by foreigner investors. Additional training in workers' current fields is estimated to reduce mobility and earnings, suggesting inertial programs from the pre-transition era. Retraining in new fields increases all types of worker mobility and has higher returns than those typically observed for training in the U.S., but it also raises the variance of earnings and the probability of employment, consistent with a search view of such retraining. Given the large returns to retraining, the efforts of Russian workers to learn new skills may increase as uncertainty is resolved and restructuring proceeds.http://deepblue.lib.umich.edu/bitstream/2027.42/39715/3/wp331.pd

Using ICT to support public and private community memories: case studies and lessons learned

Information communication technologies (ICTs) enable the development of memories across a variety of communities. We identify a spectrum of deployment from private through to open public spaces. As we move along this spectrum key variables change including mechanisms of trust and accountability and the definition of ownership, authorship and readership. Some challenges however, remain constant such as designing for sustainability and the need to align research and community goals. Private spaces can be created to enhance existing interactions, develop bonding capital and build shared memory. Such spaces allow a defined membership the opportunity to explore new ideas away from the public gaze, using language which may not be intelligible to outsiders. ICTs may be used to bridge internal and external audiences, repurposing content for a wider public. The original content may require alternative presentation, organisation or navigation methods to support its effective use by an external audience. Increasingly, community memories are being developed using social software within the public sphere, however this raises issues of authority, reputation management, and conflict resolution. Unexpected innovation may occur, and issues of sustainability must be addressed. In our analysis we will draw on three ICT initiatives in which we have participated: Bletchley Park Guides’ Forum, Bletchley Park Text and Milton Keynes Open Guide

Design and simulation of a multi-function MEMS sensor for health and usage monitoring.

Health and usage monitoring as a technique for online test, diagnosis or prognosis of structures and systems has evolved as a key technology for future critical systems. The technology, often referred to as HUMS is usually based around sensors that must be more reliable than the system or structure they are monitoring. This paper proposes a fault tolerant sensor architecture and demonstrates the feasibility of realising this architecture through the design of a dual mode humidity/pressure MEMS sensor with an integrated temperature function. The sensor has a simple structure, good linearity and sensitivity, and the potential for implementation of built-in-self-test features. We also propose a re-configurable sensor network based on the multi-functional sensor concept that supports both normal operational and fail safe modes. The architecture has the potential to significantly increase system reliability and supports a reduction in the number of sensors required in future HUMS devices. The technique has potential in a wide range of applications, especially within wireless sensor networks

Sustainable polycarbonate adhesives for dry and aqueous conditions with thermoresponsive properties

Pressure sensitive adhesives are ubiquitous in commodity products such as tapes, bandages, labels, packaging, and insulation. With single use plastics comprising almost half of yearly plastic production, it is essential that the design, synthesis, and decomposition products of future materials, including polymer adhesives, are within the context of a healthy ecosystem along with comparable or superior performance to conventional materials. Here we show a series of sustainable polymeric adhesives, with an eco-design, that perform in both dry and wet environments. The terpolymerization of propylene oxide, glycidyl butyrate, and CO2, catalyzed by a cobalt salen complex bearing a quaternary ammonium salt, yields the poly(propylene-co-glycidyl butyrate carbonate)s (PPGBC)s. This polymeric adhesive system, composed of environmentally benign building blocks, implements carbon dioxide sequestration techniques, poses minimal environmental hazards, exhibits varied peel strengths from scotch tape to hot-melt wood-glue, and adheres to metal, glass, wood, and Teflon® surfaces.Published versio

The Oklo Natural Nuclear Reactors : Evidence of Variable Constants?

There is apparently virtually universal agreement that certain deposits found at the Oklo uranium mine in Gabon, Africa are the remains of “natural nuclear reactors.” This paper examines the make-up and configuration of some of these reactors and shows that these deposits were not capable of a sustained nuclear fission chain reaction if the nuclear characteristics of the isotopes involved were the same as they are today. If these deposits really are the remains of natural nuclear reactors, then they appear to provide support for the hypothesis that nuclear constants have changed over time