LHAP: A lightweight network access control protocol for ad hoc networks

Most ad hoc networks do not implement any network access control, leaving these networks vulnerable to resource consumption attacks where a malicious node injects packets into the network with the goal of depleting the resources of the nodes relaying the packets. To thwart or prevent such attacks, it is necessary to employ authentication mechanisms to ensure that only authorized nodes can inject traffic into the network. We propose LHAP, a hop-by-hop authentication protocol for ad hoc networks. LHAP resides in between the network layer and the data link layer, thus providing a layer of protection that can prevent or thwart many attacks from happening, including outsider attacks and insider impersonation attacks. Our detailed performance evaluation shows that LHAP incurs small performance overhead and it also allows a tradeoff between security and performance.     

Pattern Recognition of Canine Duodenal Contractile Activity

An application of statistical pattern recognition technique to the classification of canine duodenal contractile activity resulting from the ingestion of three different test meals, viz. water, acid, and solid, is described. Feature vectors were extracted from the contractile activities recorded by means of strain gauges, and were based on average duration, number, and intensities of contractions, as well as their frequency and propagational characteristics. Pattern training and classification were performed via the Bayes decision rule. The resuits indicate that the three different meals give rise to three different kinds of contractile activities. An improvement in the classifier's performance was observed when it was updated with correctly classified patterns. The results appear to suggest that pattern analysis techniques add a new dimension to the study of gastrointestinal motility in health and disease. For example, pattern recognition techniques can also be extended to identify contractile patterns altered due to such pathological conditions as irritable bowel syndrome and postoperative diarrhea and, hence, elucidate the underlying relationship between contractile activity and distal propulsion of contents.     

One-dimensional flow of a real gas in a diverging channel with generalized Ohm's law

The present analysis gives the effects of the thermoelectric currents on the quasi-one-dimensional flow of a real gas in a diverging channel. Numerical solutions are obtained for generator and accelerator modes with subsonic and supersonic flows. the variation of current and power density are presented for the special cases of (i) a linearly diverging channel and (ii) a constant velocity channel. It is observed that the rate of change of the transverse current and the power is slower owing to the influence of thermoelectric currents.     

Dynamic modeling of the fixture-workpiece system

This paper presents a methodology for dynamic modeling and simulation of a fixture-workpiece system. A simulation approach is required since standards typically do not exist for dynamic situations like machining operations. In addition, an accurate model is developed for the contact interface at each locating and clamping region on the workpiece's surface. An end milling operation is simulated to analyze the effects of various factors on workpiece accuracy and demonstrate the advantage of the simulation approach. The clamping forces required to keep the workpiece in contact with its locators are obtained, and the influences of locator placement, clamp placement, clamping forces, and clamping sequence on linear and angular errors are reported. Elastic effects of the locator-workpiece and clamp-workpiece contacts, yielding nonlinear dynamic equations of motion, are included in the model. Since system dynamics are considered, results are obtained as a function of time. The study compares well with previous experimental work by other investigators, and the method shows promise as a fixture design tool.     

A Computer Model of Human Colonic Electrical Control Activity (ECA)

Human colonic electrical control activity (ECA) was recorded from 17 subjects postoperatively by chronically implanted electrodes. The ECA pattern showed phase-unlocked control waves with variable frequencies and waxing and waning amplitudes. This was modeled by a tubular structure of bidirectionally coupled rings of bidirectionally coupled synthesized relaxation oscillators. The model explores the basis of the observed organization of ECA which is consistent with the colonic function of temporary storage of contents.