Determination of the Thermal Diffusivity of a Zr/PbCrO4 Pyrotechnical Mixture and of the arrhenius parameters of the ignition reaction in presence of an oxidizing atmosphere

An experimental device with main features closely related to those of Cook-Off type⁽¹⁾ devices has been developed to attain the specific study requirements. The tested product is a pyrotechnical compound containing zirconium and lead chromate in the proportion of 60% Zr and 40% PbCrO₄. An iterative calculation method has been developed to determine thermal diffusivity without any reaction and to evaluate the Arrhenius kinetic parameters of the product ignition reaction. The Zr/PbCrO₄ compounds appear as cylindrical tablets dia. 14 mm and 11.7 mm high. From room temperature to about 100°C, thermal diffusivity ranges between 3.2 and 3.9. 10⁷ m²/s. The ignition reaction kinetic parameters in an oxidizing atmosphere are as follows: Ea = 47 kJ/mol and Z = 10 · s⁻¹. With the results from thermal analysis, we demonstrate that initiation can be attributed to the oxygen contained in air, which diffuses into the product porosities. Lead chromate behaves as an inert substance throughout the ignition phase.     

Numerical Determination of the Thermal Diffusivity and Kinetic Parameters of Solid Explosives

The thermal diffusivity and the kinetic parameters (activation energy and pre-exponential factor) of explosive substances are determined numerically using an iterative method. A numerical modelling based on a finite difference approximation of the equation of unsteady heat allows simulations of the thermal behaviour of the product in the absence of any reaction and phase change. The comparison of simulation and measured results allows the convergence towards the thermal diffusivity of the substance under test. The principle is the same for kinetic parameters. In this latter case, the modelling involves the equation of unsteady heat flow with an internal energy source. The governing partial differential equation is processed using Zinn and Mader's method.     

Interoperability Verification in ISO 18000-7 Active RFID Systems: Experimental Setup and Results

Interoperability in an RFID system conforming to ISO 18000-7 standard is defined as the ability of any commercial interrogator to communicate with any commercial tag. A possibility that conformance verification in the physical communication layer between active tags and interrogators (readers) does not satisfy the interoperability property is established. Challenging the traditional or matrix test to verify interoperability, a novel methodology to verify interoperability for active RFID systems in particular and all communication systems following a command-reply protocol in general is introduced in a prior publication. In this article, the methodology is experimentally implemented using industry standard laboratory equipment and automation tools to develop a fully automated interoperability test suite. The automated test system design considerations, challenges and results are discussed in detail. For a particular equipment, the NI-5671 Radio Frequency Signal generator, the maximum number of samples that can be tested for different parameters of the physical communication layers are provided. The equipment limitations are discussed to provide the reader with guidelines to experiment with, and a reference to evaluate the resolution (one measure of the accuracy of the test) of different equipment. The different parameters considered in the test and their interactions in determining the interoperability property are recorded.     

Application of CDMA for anti-collision and increased read efficiency of multiple RFID tags

This research presents analysis and demonstration of the application of code-division multiple access (CDMA) to radio frequency identification (RFID), particularly for the simultaneous reading of multiple RFID tags. The research investigates current techniques and algorithms for resolving collisions among multiple tags while they are transmitting simultaneously. Typical store and warehouse environments under possible worst-case scenarios have been studied. The result of this research is the recommended implementation of a CDMA RFID method of reducing the number of reads and the removal of some inter-tag interference.     

Blood lead levels in children aged 5-9 years living in Cartagena, Colombia

During June-August 2004, blood lead (BPb) levels and various hematological parameters were evaluated in children aged 5-9 years old at ten primary schools located in eight neighborhoods in Cartagena, Colombia. The schools selected for this study are attended mainly by children from families of low income. A total of 189 subjects participated in the survey. The arithmetic mean+/-standard error BPb level was 5.49+/-0.23 microg/dL (range<1.0-21.0 microg/dL). The geometric mean was 4.74 microg/dL (95% CI: 4.29-5.18). A proportion of the children (7.4%) had BPb levels above the US Centers for Disease Control and Prevention's threshold of concern (10 microg Pb/dL). BPb levels were correlated weakly, but significantly and positively, with red blood cell count (RBC), and negatively with child body size, age, mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH). BPb levels did not differ significantly between boys and girls but significant differences were observed between neighborhoods (P<0.001). Activities such as metal melting-related processes and fishing net sinker production are the main sources of Pb exposure in Cartagena.     

Flavin Conjugates for Delivery of Peptide Nucleic Acids

Oligonucleotides and their analogues, such as peptide nucleic acids (PNAs), can be used in chemical strategies to artificially control gene expression. Inefficient cellular uptake and inappropriate cellular localization still remain obstacles in biological applications, however, especially for PNAs. Here we demonstrate that conjugation of PNAs to flavin resulted in efficient internalization into cells through an endocytic pathway. The flavin–PNAs exhibited antisense activity in the sub‐micromolar range, in the context of a treatment facilitating endosomal escape. Increased endosomal release of flavin conjugates into the cytoplasm and/or nucleus was shown by chloroquine treatment and also—when the flavin–PNA was conjugated to rhodamine, a mild photosensitizer—upon light irradiation. In conclusion, an isoalloxazine moiety can be used as a carrier and attached to a cargo biomolecule, here a PNA, for internalization and functional cytoplasmic/nuclear delivery. Our findings could be useful for further design of PNAs and other oligonucleotide analogues as potent antisense agents.     

Monitoring the curing process of reinforced plastics structures

The feasibility of monitoring curing processes in large reinforced plastics structures by electrical volume resistivity techniques has been studied. It has been found, by embedding electrodes and thermocouples within a heavy-walled structure during fabricaton and by monitoring the change is resistance during the curing process, that information indicative of the rate and extent of curing can be obtained. The resin system used in this study was Epon 826/MNA/BDMA.     

Confinement of an antiferroelectric liquid crystal in a polymer nanonetwork: thermal and dielectric behaviour

We report the thermal and dielectric investigations on a liquid crystal exhibiting an antiferroelectric phase and confined in a polymer network of sub-micron dimensions. Two different photo-polymerizable monomers have been employed for the purpose: one of them (HDDA) is bereft of any aromatic parts, while the other (RM82) contains aromatic as well as aliphatic units and, in fact, forms a liquid crystalline phase in its monomeric state. The polymerization, which is carried out in the presence of the liquid crystalline host, is expected to yield a nanosegregated structure for HDDA and blended structure for the RM82 case, the difference reflecting the morphologies of the networks, as evidenced by SEM images. Surprisingly, even a small concentration of the latter polymer added to the former variety has substantial influence on the morphology. The main work focusses on calorimetry and dielectric relaxation spectroscopy of the host liquid crystal confined in these nanonetworks created by the polymers, which can be considered to form virtual surfaces with a finite anchoring energy. We have investigated the in-phase and antiphase modes in the antiferroelectric phase, and the soft mode in the paraelectric phase preceding the antiferroelectric phase. The relaxation frequencies of all these modes are substantially influenced by the network, with the results showing certain surprises in cases containing both HDDA and RM82.     

INTEGRATING THE EFFECTS OF PROCESS CONTROLLERS WITH STEADY-STATE, EQUATION-BASED SIMULATION

Process controllers have a significant influence on the steady-state, as well as the dynamic, behavior of chemical processes. Thus, the steady-state simulation of processes should include the effects of control. A new method for including controllers in steady-state simulation is presented in this paper. The method provides equations that represent the steady-state control algorithm and can be solved simultaneously with the process model to yield the steady-slate behaviour of the closed-loop system. Most importantly, the controller models include saturation effects and can be formulated and solved within an open-form model. The method is general and can be applied to single-loop controllers, to complex control designs including split range and signal select, and to several single-loop controllers in a multiloop controller design.     

Brass Rings or Brass Buttons in Engineering Design*

The purpose of this paper is to point out two distinct selections for student design projects. The main decision maker is assumed to be the faculty advisor for the projects, although the students would be expected to have input. The brass ring project involves some aspect of cutting edge technology. The brass button project is one that satisfies the typical criteria of a thoroughly designed, fabricated, and documented “component.” Both types of projects have great value for the students although one is obviously more visible outside the academic community. These two philosophical approaches in engineering design projects reflect the distinction between entrepreneurial and traditional engineering education. As we move from the concept of engineers working for large companies to engineers starting companies, this distinction becomes more important. The primary example base is drawn from electrical and mechanical engineering due to our experiences. While two philosophical approaches are indicated, there are ultimately numerous methodologies and end points possible as a result of diversions along the way.