Investigation of the Failure Mechanism of HTPB/AP/Al Propellant by In‐situ Uniaxial Tensile Experimentation in SEM

The failure mechanism of a propellant consisting of hydroxyl terminated poly‐butadiene filled with ammonium perchlorate and aluminum (HTPB/AP/Al) was determined by performing in‐situ uniaxial tensile tests in a scanning electron microscope (SEM). The experimental test plan contained uniaxial tensile test experiments performed at room temperature (25 °C) at three different strain rates (30, 150 and 750 μm min⁻¹). The in‐situ images and in‐situ videos collected by the SEM were correlated with the stress‐strain diagrams created with the tensile experiments, in order to relate the failure mechanism to the features found in the stress‐strain diagram. No significant strain rate dependency of the failure mechanism was observed when working with strain rates up to 750 μm min⁻¹ and working at room temperature. The stress‐strain diagram showed indications of existing cracks and voids opening up prior to the creation of new cracks and/or voids in the sample, debonding of binder with AP particles as well as nucleation and coalescence of voids. On the fracture surfaces of the samples, it was apparent that the binder cleanly separated from the large AP particles but had a better bond with the aluminum particles. However, a difference in the appearance of a short drawing phase in the stress‐strain diagram of the propellant is observed at different strain rates. The presented results clearly demonstrate the major advantage of the combination of microscopic tensile tests with microscopic observations, linking the stress‐strain behavior to the mechanical deformation processes taking place in these propellant samples at the microscopic level.     

How suitable is LR for renewal of inner city areas? An analysis for Turkey

The land readjustment (LR) method has been compared to traditional urban renewal models’ substantial potential in fulfilling specific functions, e.g., land assembly, self-finance, the protection of social capital, and results in a certain time. However, there is limited information on the use of LR in urban renewal areas. For example, it is not known how suitable LR is for renewal of inner city areas or whether LR can be a remedy to the problems in urban renewal. This paper answers these questions by focusing on Turkey. The paper is based on discussion and comparison of the existing approaches in fulfilling specific functions in urban renewal, and the compatibility and contribution of LR to the framework. The result reveals that a private initiative (landowner associations or cooperatives) LR model can be a suitable instrument for urban renewal in Turkey.     

Noise spectroscopy: Z-determination by statistical count-rate analysis (Z-scan)

We introduce Noise Spectroscopy (NS) and show the results of an analysis of three data-sets demonstrating the feasibility of this technique. The NS effect is first shown to be present in a set of X-ray radiography images of low- and high-Z materials taken using the 6 MV Rapiscan Eagle P60HP portal cargo inspection system. Image-Based NS is, however, relatively insensitive. Using a data-set obtained using a fast plastic scintillator and photo-multiplier tube (PMT), we demonstrate that NS works very well when using fast detectors, fast electronics and waveform digitization. Another data-set was taken using Lutetium-Yttrium Ortho-Silicate (LYSO), which is suitable for use in X-ray cargo radiography. Although LYSO is slower than plastic scintillator, it was shown that NS also works very well using this material, paving the way for NS to be implemented using the primary imaging array of X-ray cargo inspection systems.     

The Effect of Aliphatic Carboxylic Acids on Olfaction-Based Host-Seeking of the Malaria Mosquito <Emphasis Type="Italic">Anopheles gambiae sensu stricto</Emphasis>

The role of aliphatic carboxylic acids in host-seeking response of the malaria mosquito Anopheles gambiae sensu stricto was examined both in a dual-choice olfactometer and with indoor traps. A basic attractive blend of ammonia + lactic acid served as internal standard odor. Single carboxylic acids were tested in a tripartite blend with ammonia + lactic acid. Four different airflow stream rates (0.5, 5, 50, and 100 ml/min) carrying the compounds were tested for their effect on trap entry response in the olfactometer. In the olfactometer, propanoic acid, butanoic acid, 3-methylbutanoic acid, pentanoic acid, heptanoic acid, octanoic acid, and tetradecanoic acid increased attraction relative to the basic blend. While several carboxylic acids were attractive only at one or two flow rates, tetradecanoic acid was attractive at all flow rates tested. Heptanoic acid was attractive at the lowest flow rate (0.5 ml/min), but repellent at 5 and 50 ml/min. Mixing the air stream laden with these 7 carboxylic acids together with the headspace of the basic blend increased attraction in two quantitative compositions. Subtraction of single acids from the most attractive blend revealed that 3-methylbutanoic acid had a negative effect on trap entry response. In the absence of tetradecanoic acid, the blend was repellent. In assays with MM-X traps, both a blend of 7 carboxylic acids + ammonia + lactic acid (all applied from low density polyethylene-sachets) and a simple blend of ammonia + lactic acid + tetradecanoic acid were attractive. The results show that carboxylic acids play an essential role in the host-seeking behavior of An. gambiae, and that the contribution to blend attractiveness depends on the specific compound studied.     

Molecular approaches to study probiotic bacteria

Functional foods comprising probiotic bacteria are receiving increasing attention from the scientific community and science funding agencies [1]. An essential aspect relating to the functionality of probiotic-based foods is to develop molecular methods to determine the presence, activity and viability of probiotic bacteria in the human gastrointestinal (GI) tract [2]. The GI tract is composed of a complex ecosystem of various microbial habitats colonized by numerous different commensal micro-organisms. This indigenous gut microbiota is essential to the overall health of the host by performing important physiological functions. In particular, they protect against pathogenic bacteria and drive the development of the immune system during neonatal life. Further metabolic activities of the GI microbiota that beneficially affect the host include continued degradation of food components, vitamin production, and production of short chain fatty acids that feed the colonic mucosa. It is clear that factors such as diet, sickness, stress, or medication can result in loss of well-being of the host, and it is assumed that some of these symptoms are due to perturbation of what is termed the normal balance of the gut microbiota. Knowledge of the structure and function of the standard microbiota, and its response to diet, genetic background and lifetime of the host must be taken into account when designing probiotic-based functional foods. The application of molecular techniques for detection and identification of microbes has provided a major breakthrough in the analysis of microbial ecosystems and their function [3]. The successful application and further potential of these molecular methods to study probiotic bacteria and their impact on the standard GI microbiota is discussed below.     

Spectral Analysis of Stochastically Sampled Dynamic Systems

In this paper a spectral analysis methodology is introduced for stochastically sampled linear, dynamic, and stochastic continuous-time systems. This particular problem is considered for the purpose of investigating the spectral analysis issues associated with turbulent velocity measurements. The properties of the equivalent linear discrete-time system allow for the determination of the covariance between observations as a function of the number of in-between measurements. Subsequently, this autocovariance function is analyzed in the frequency domain. Date received: March 31, 1998. Date revised: November 11, 1999.     

Reasoning about Information Change

In this paper we introduce Dynamic Epistemic Logic, which is alogic for reasoning about information change in a multi-agent system. Theinformation structures we use are based on non-well-founded sets, and canbe conceived as bisimulation classes of Kripke models. On these structures,we define a notion of information change that is inspired by UpdateSemantics (Veltman, 1996). We give a sound and complete axiomatization ofthe resulting logic, and we discuss applications to the puzzle of the dirtychildren, and to knowledge programs.     

ECONOMIC DISPARITY UNDER CONDITIONS OF INTEGRATION — A LONG TERM VIEW OF THE EUROPEAN CASE

ABSTRACT This paper examines the development of disparities between the regions of the European Union over a very long period of time. It does so by reviewing the relevant theoretical, empirical and prospective literature. First, the contributions of the; different schools of thought on regional growth are reviewed. They are inconclusive as to the outcome of the process in terms of convergence or divergence. Next, empirical studies into the differential development of European regions are reviewed, covering the whole period of the industrial revolution to our present time. The resulting picture reveals a considerable diversity of patterns. Over the postwar period, characterized by increased economic integration, a decrease in disparity has been recorded. Poorer regions have used their improved access to the European market and their better opportunities for attracting mobile capital to each up the likely behavior of the regional system of Europe are examined. In the future, new forms of economic integration (deepening like the EMU, and widening with the central European countries) will to a large extent shape the environment for regional developments. All in all, these factors are likely to bring more disparity. Therefore, increased attention should be given to policies that stimulate new ways of mobilizing the diverse potential of the various regions of the enlarged Europe.