A NEW VIEW OF INFORMATION MODELING

The information model was conceived to address the complexities of managing large volumes of data, processes, designs, and tools that are shared by many business users with differing requirements. Because an information model derives much of its features from data models, the distinction between information modeling and data modeling is sometimes unclear. One perspective is that information modeling is context dependent: when a model is viewed as a representation scheme for users to comprehend, it is an information model. When used as a representation scheme to be processed by a computer, it is a data model.     

The isolated air perfused rat heart

A simple method has been developed for continuous monitoring of metabolic activity of an isolated, perfused rat heart by O2/CO2 respirometer. Since respirometer provides vital data on oxygen consumption and carbon dioxide production of a preserved organ on a continuous basis over a long period of time, it will be possible to use this method to monitor viability of not only isolated heart but also any given donor organ under preservation.     

Mathematical and Scientific Foundations for an Integrative Engineering Curriculum

All fields of engineering, whether chemical, civil, electrical, materials, mechanical, etc., encompass a common body of essential mathematics and science. In the freshman year of Drexels E⁴ program, this common mathematical and scientific foundation is cultivated in the Mathematical and Scientific Foundations of Engineering I, II and III (MSFE I, MSFE II, MSFE III). In an integrated fashion, MSFE I presents the essential calculus, physics and engineering mechanics vital to the freshman engineering student. In the first two quarters, MSFE II presents chemistry with clearly defined engineering applications and significance: in the third quarter, MSFE II presents living systems with the same thrust. Also in the third quarter, MSFE III presents basic circuits and circuit elements, and a brief introduction to electromagnetic theory.     

Multistep temperature prediction for proactive thermal management on chip multiprocessors

The Journal of Supercomputing - In chip multiprocessors, the thermal hot spot prediction is vital to take proactive thermal management decisions for mitigating its impact on the performance of the...     

Casting/mold thermal contact heat transfer during solidification of Al-Cu-Si alloy (LM 21) plates in thick and thin molds

Heat flow at the casting/mold interface was assessed and studied during solidification of Al-Cu-Si (LM 21) alloy in preheated cast iron molds of two different thicknesses, coated with graphite and alumina based dressings. The casting and the mold were instrumented with thermocouples connected to a computer controlled temperature data acquisition system. The thermal history at nodal locations in the mold and casting obtained during experimentation was used to estimate the heat flux by solving the one-dimensional inverse heat conduction problem. The cooling rate and solidification time were measured using the computer-aided cooling curve analysis data. The estimated heat flux transients showed a peak due to the formation of a stable solid shell, which has a higher thermal conductivity compared with the liquid metal in contact with the mold wall prior to the occurrence of the peak. The high values of heat flux transients obtained with thin molds were attributed to mold distortion due to thermal stresses. For thin molds, assumption of Newtonian heating yielded reliable interfacial heat transfer coefficients as compared with one-dimensional inverse modeling. The time of occurrence of peak heat flux increased with a decrease in the mold wall thickness and increase in the casting thickness.     

Hybrid Authentication Using Node Trustworthy to Detect Vulnerable Nodes

An ad-hoc sensor network (ASN) is a group of sensing nodes that transmit data over a wireless link to a target node, direct or indirect, through a series of nodes. ASN becomes a high-risk group for several security exploits due to the sensor node’s limited resources. Internal threats are more challenging to protect against than external attacks. The nodes are grouped, and calculate each node’s trust level. The trust level is the result of combining internal and external trust degrees. Cluster heads (CH) are chosen based on the anticipated trust levels. The communications are then digitally signed by the source, encoded using a key pair given by a trustworthy CH, decoded by the recipient, and supervised by verifications. It authenticates the technique by identifying the presence of both the transmitter and the recipient. Our approach looks for a trustworthy neighboring node that meets the trust threshold condition to authenticate the key produced. The companion node reaffirms the node’s reliability by getting the public-key certification. The seeking sensor node and the certification issuer node must have a close and trusting relationship. The results of the proposed hybrid authentication using a node trustworthy (HANT) system are modeled and tested, and the suggested approach outperforms conventional trust-based approaches in throughput, latency, lifetime, and vulnerability methods.     

Comparison of the indentation and elasticity of E. coli and its spheroplasts by AFM

Atomic force microscopy (AFM) provides a unique opportunity to study live individual bacteria at the nanometer scale. In addition to providing accurate morphological information, AFM can be exploited to investigate membrane protein localization and molecular interactions on the surface of living cells. A prerequisite for these studies is the development of robust procedures for sample preparation. While such procedures are established for intact bacteria, they are only beginning to emerge for bacterial spheroplasts. Spheroplasts are useful research models for studying mechanosensitive ion channels, membrane transport, lipopolysaccharide translocation, solute uptake, and the effects of antimicrobial agents on membranes. Furthermore, given the similarities between spheroplasts and cell wall-deficient (CWD) forms of pathogenic bacteria, spheroplast research could be relevant in biomedical research. In this paper, a new technique for immobilizing spheroplasts on mica pretreated with aminopropyltriethoxysilane (APTES) and glutaraldehyde is described. Using this mounting technique, the indentation and cell elasticity of glutaraldehyde-fixed and untreated spheroplasts of E. coli in liquid were measured. These values are compared to those of intact E. coli. Untreated spheroplasts were found to be much softer than the intact cells and the silicon nitride cantilevers used in this study.     

Monitoring multivariate process variability when sub-group size is small

The current practice of multivariate process variability monitoring, when sub-group size is small, has nothing to do with probability of false alarm (PFA). Consequently, the reliability of the existing control charts remains undetermined. In this article, we propose a control chart which is reliable, very sensitive to the change in variance for small or moderate correlation, and provides a root causes analysis of an out-of-control signal. To illustrate these advantages, an industrial example is presented and the results are compared with those issued from the existing methods.     

Synthetic Applications of Carbohydrate-derived Donor-Acceptor Cyclopropanes

In this account, we elaborate our group's contribution towards understanding the chemistry of carbohydrate-derived donor-acceptor (DA) cyclopropanes. Our work was mainly focused on the ring opening of these versatile chiral synthons under the influence of Lewis acid promoters like electrophilic halogen species, TMSOTf, BF₃.OEt₂, etc. We studied various modes of ring opening on these DA cyclopropanes, envisaging the access to intriguing molecular architectures. These modes of reaction of the DA cyclopropanes can be controlled by strategically introducing an electron-withdrawing group (EWG) onto the cyclopropane ring, which could direct the ring cleavage by polarizing the cyclopropane C−C bond. Our studies also revealed that the ring opening is sluggish in the absence of an EWG. Using this concept, we demonstrated the synthesis of various biologically interesting molecular skeletons, viz., glycoamino acids (GAA), GAA nucleotides, α-levoglucosan amino acid, and septano-oligosaccharides, with high selectivity. We also applied our understanding to the first stereoselective synthesis of (S)-(−)-longianone and confirmed its absolute configuration. Apart from the inherently activated DA cyclopropanes, we introduced the in situ generation of DA cyclopropanes, starting from vinylcyclopropanes (VCPs). The ring-opening and ring-expansion chemistry of these easily accessible synthons was studied. The chemistry developed for carbohydrate-fused cyclopropanes was also applied for carbohydrate-derived spiro-cyclopropanes. The Lewis-acid-mediated ring opening of spiro-DA-cyclopropanes enabled easy access to fused furopyrans and spirolactones.