Structuring communication software for quality-of-serviceguarantees

We propose architectural mechanisms for structuring host communication software to provide QoS guarantees. We present and evaluate a QoS sensitive communication subsystem architecture for end hosts that provides real time communication support for generic network hardware. This architecture provides services for managing communication resources for guaranteed QoS (real time) connections, such as admission control, traffic enforcement, buffer management, and CPU and link scheduling. The architecture design is based on three key goals: maintenance of QoS guarantees on a per connection basis, overload protection between established connections, and fairness in delivered performance to best effort traffic. Using this architecture we implement real time channels, a paradigm for real time communication services in packet switched networks. The proposed architecture features a process per channel model that associates a channel handler with each established channel. The model employed for handler execution is one of “cooperative” preemption, where an executing handler yields the CPU to a waiting higher priority handler at well defined preemption points. The architecture provides several configurable policies for protocol processing and overload protection. We present extensions to the admission control procedure for real time channels to account for cooperative preemption and overlap between protocol processing and link transmission at a sending host. We evaluate the implementation to demonstrate the efficacy with which the architecture maintains QoS guarantees on outgoing traffic while adhering to the stated design goals     

The held out wings (how) Drosophila gene encodes a putative RNA-binding protein involved in the control of muscular and cardiac activity

In an attempt to identify genes that are involved in Drosophila embryonic cardiac development, we have cloned and characterized a gene whose function is required late in embryogenesis to control heart rate and muscular activity. This gene has been named held out wings (how) because hypomorphic mutant alleles produce adult animals that have lost their ability to fly and that keep their wings horizontal at a 90 degree angle from the body axis. In contrast to the late phenotype observed in null mutants, the How protein is expressed early in the invaginating mesoderm and this expression is apparently under the control of twist. When the different mesodermal lineages segregate, the expression of How becomes restricted to the myogenic lineage, including the cardioblasts and probably all the myoblasts. Antibodies directed against the protein demonstrate that How is localized to the nucleus. how encodes a protein containing one KH-domain which has been implicated in binding RNA. how is highly related to the mouse quaking gene which plays a role at least in myelination and that could serve to link a signal transduction pathway to the control of mRNA metabolism. The properties of the how gene described herein suggest that this gene participates in the control of expression of as yet unidentified target mRNAs coding for proteins essential to cardiac and muscular activity.     

Reading in Arabic orthography: the effect of vowels and context on reading accuracy of poor and skilled native Arabic readers in reading paragraphs, sentences, and isolated words

This study investigated the effect of vowels and context on the reading accuracy of poor and skilled native Arabic readers in reading paragraphs, sentences, and words. Central to this study is the belief that reading theory today should consider additional variables, especially when explaining the reading process in Arabic orthography among poor and normal/skilled readers. This orthography has not been studied. Reading theory today is the sum of conclusions from studies conducted in Latin orthography. The subjects were 77 native Arabic speakers, 34 of them poor readers and 44 normal/skilled readers. The subjects had to read in Arabic 15 paragraphs, 60 sentences, and 210 words. There were three reading conditions: fully vowelized, partially vowelized, and unvowelized texts. The results showed that vowels and contexts were important variables to facilitate word recognition in poor and normal/skilled readers in Arabic orthography.     

Viscoelastic response of solid rocket motor components for service life assessment

A methodology for determining the response of rocket motor materials and bondlines to thermal loadings by measuring their dynamic mechanical properties is reported. The critical temperatures at which debonding and/or propellant cracking occur and the number of thermal cycles required to induce failure were evaluated. These results were compared with those from instrumented rocket motors subjected to similar thermal loadings. A model, developed for fibre reinforced composites, was applied to the propellant-inhibitor bimaterial obtained from a rocket motor. The internal energy dissipation due to a lack of perfect adhesion at the propellant–inhibitor interface, tan δ_adh, was used to give an indication of the failure mode of the bondline (i.e., adhesive failure at the interface or cohesive failure in the propellant) and the bond adhesion parameter, C, was related to the bond strength measured by rectangular bond-in-tension tests. This revised version was published online in November 2006 with corrections to the Cover Date.     

Mathematical foundations for error estimation in numericalsolutions of integral equations in electromagnetics

The problem of error estimation in the numerical solution of integral equations that arise in electromagnetics is addressed. The direct method (Green's theorem or field approach) and the indirect method (layer ansatz or source approach) lead to well-known integral equations both of the first kind [electric field integral equations (EFIE)] and the second kind [magnetic field integral equations (MFIE)]. These equations are analyzed systematically in terms of the mapping properties of the integral operators. It is shown how the assumption that field quantities have finite energy leads naturally to describing the mapping properties in appropriate Sobolev spaces. These function spaces are demystified through simple examples which also are used to demonstrate the importance of knowing in which space the given data lives and in which space the solution should be sought. It is further shown how the method of moments (or Galerkin method) is formulated in these function spaces and how residual error can be used to estimate actual error in these spaces. The condition number of all of the impedance matrices that result from discretizing the integral equations, including first kind equations, is shown to be bounded when the elements are computed appropriately. Finally, the consequences of carrying out all computations in the space of square integrable functions, a particularly friendly Sobolev space, are explained     

Designing better adaptive sampling algorithms for ECG Holtersystems

Let Ψ be any adaptive sampling algorithm that can run in real time on a tapeless multichannel electrocardiogram (ECG) Holter system. Simple methods which can significantly improve Ψ's fidelity are described and their results are compared in this paper. It is shown that by adding some simple tests to Ψ, the signals reconstructed by Ψ can be improved as much as 5.45 dB. It is also shown that under the same data rate, a good data compressor with slowly sampled input ECG is preferable to a bad data compressor with highly sampled input ECG     

A fast spatial-domain method for the suppression ofexcitation-induced spurious modes in SCN TLM

An efficient method for the suppression of excitation-induced spurious modes in the symmetrical condensed node (SCN) transmission-line matrix (TLM) method is presented for the general case of dielectric, anisotropic, or lossy media in planar structures. A special mapping of the field-excitation onto the wave amplitudes of the TLM algorithm completely prevents the emanation of the spurious modes. The application of the mapping in the k-ω space can be done for waveguides with low computational effort. The method is generalized for planar structures with high spatial frequencies of the field at the discontinuities. We use precomputed field templates at the entrance of the three-dimensional (3-D) structures. The mapping is mainly done in the space domain based on the quasi-TEM propagation of the guided waves to keep the computational effort low. Instead of the four-dimensional (4-D) k-ω transformation, only independent one-dimensional (1-D) transformations to the wave coefficient of the conductors direction and ω are necessary. In the case of propagation with low dispersion, the expenditure can be further reduced to 1-D transformations with respect to ω. The efficiency of the present method is demonstrated by investigation of a coplanar waveguide and a triplate waveguide     

Pressure ratings of mechanical seals

Although mechanical seals are widely used in many machines, there is no universally accepted system for establishing limits of pressure, temperature, and speed. As a result, manufacturers of mechanical seals may use different methods for establishing these limits. In turn, users of mechanical seals sometimes have their own rating system. Presented here is a general discussion of the difficulties involved in establishing limits along with some specific issues related to seals used in centrifugal pumps.