Implementation and analysis of a Navier-Stokes algorithm on parallel computers

The results of the implementation of a Navier-Stokes algorithm on three parallel/vector computers are presented. The object of this research is to determine how well, or poorly, a single numerical algorithm would map onto three different architectures. The algorithm is a compact difference scheme for the solution of the incompressible, two-dimensional, time-dependent Navier-Stokes equations. The computers were chosen so as to encompass a variety of architectures. They are the following: the MPP, an SIMD machine with 16K bit serial processors; Flex/32, an MIMD machine with 20 processors; and Cray/2. The implementation of the algorithm is discussed in relation to these architectures and measures of the performance on each machine are given. The basic comparison is among SIMD instruction parallelism on the MPP, MIMD process parallelism on the Flex/32, and vectorization of a serial code on the Cray/2. Simple performance models are used to describe the performance. These models highlight the bottlenecks and limiting factors for this algorithm on these architectures. Finally, conclusions are presented

Solving the Cauchy-Riemann equations on parallel computers

Discussed is the implementation of a single algorithm on three parallel-vector computers. The algorithm is a relaxation scheme for the solution of the Cauchy-Riemann equations; a set of coupled first order partial differential equations. The computers were chosen so as to encompass a variety of architectures. They are: the MPP, and SIMD machine with 16K bit serial processors; FLEX/32, an MIMD machine with 20 processors; and CRAY/2, an MIMD machine with four vector processors. The machine architectures are briefly described. The implementation of the algorithm is discussed in relation to these architectures and measures of the performance on each machine are given. Simple performance models are used to describe the performance. These models highlight the bottlenecks and limiting factors for this algorithm on these architectures. Conclusions are presented

Implementation and Performance Analysis of Numerical Algorithms on the MPP, Flex/32, and Cray/2

This dissertation presents the results of the implementation of a number of numerical algorithms on three parallel/vector computers. The object of this research is to determine how well, or poorly, a number of numerical algorithms would map onto three different architectures and to analyze the performance of these architectures using these algorithms. These algorithms are: a relaxation scheme for the solution of the Cauchy-Riemann equations, an ADI method for the solution of the diffusion equation, and a compact difference scheme for the solution of two-dimensional Navier-Stokes equations. The computers were chosen so as to encompass a variety of architectures. They are: the MPP, an SIMD machine with 16K bit serial processors; Flex/32, an MIMD machine with 20 processors; and the Cray/2. The machine architectures are briefly described. The implementation of these algorithms is discussed in relation to these architectures and measures of the performance on each machine are given. The basic comparison is among SIMD instruction parallelism on the MPP, MIMD process parallelism on the Flex/32, and vectorization of a serial code on the Cray/2. Simple performance models are used to describe the performance. These models highlight the bottlenecks and limiting factors for these algorithms on these architectures. Finally conclusions are presented

Managing Logistics Activities for Improving Business Performance

This paper examines the relationships between three logistics activities: customer service, warehouse management, and distribution activity on business performance. The research adopts a quantitative research approach. A survey was utilized to assess managing logistics activities and business performance and evaluate the created research hypotheses. The author tests the hypotheses with a sample in Nawras Company in Erbil with SmartPLS version 4.0 to evaluate and process the data. The results show that the three logistics activities positively related to business performance. The research guides logistics managers in understanding how logistics activities enhance business performance. This research is one of the scholarly works to uncover the logistics activities performed by the company rather than outsourcing logistics activities for enhancing business performance in the Kurdistan region of Iraq

Chronic Nicotine Selectively Enhances α4β2* Nicotinic Acetylcholine Receptors in the Nigrostriatal Dopamine Pathway

These electrophysiological experiments, in slices and intact animals, study the effects of in vivo chronic exposure to nicotine on functional α4β2* nAChRs in the nigrostriatal dopaminergic (DA) pathway. Recordings were made in wild-type and α4 nicotinic acetylcholine receptor (nAChR) subunit knock-out mice. Chronic nicotine enhanced methyllycaconitine citrate hydrate-resistant, dihydro-β-erythroidine hydrobromide-sensitive nicotinic currents elicited by 3–1000 µM ACh in GABAergic neurons of the substantia nigra pars reticulata (SNr), but not in DA neurons of the substantia nigra pars compacta (SNc). This enhancement leads to higher firing rates of SNr GABAergic neurons and consequently to increased GABAergic inhibition of the SNc DA neurons. In the dorsal striatum, functional α4* nAChRs were not found on the neuronal somata; however, nicotine acts via α4β2* nAChRs in the DA terminals to modulate glutamate release onto the medium spiny neurons. Chronic nicotine also increased the number and/or function of these α4β2* nAChRs. These data suggest that in nigrostriatal DA pathway, chronic nicotine enhancement of α4β2* nAChRs displays selectivity in cell type and in nAChR subtype as well as in cellular compartment. These selective events augment inhibition of SNc DA neurons by SNr GABAergic neurons and also temper the release of glutamate in the dorsal striatum. The effects may reduce the risk of excitotoxicity in SNc DA neurons and may also counteract the increased effectiveness of corticostriatal glutamatergic inputs during degeneration of the DA system. These processes may contribute to the inverse correlation between tobacco use and Parkinson's disease

CNS Localization of Neuronal Nicotinic Receptors

Nicotinic acetylcholine receptors (nAChRs) are members of the Cys-loop superfamily of pentameric ligand-gated ion channels, which include GABA (A and C), serotonin, and glycine receptors. Currently, 12 neuronal nAChR subunits have been identified (α2–10 and β2–4) and are generally grouped into α subunits, which contain two adjacent cysteine residues essential for ACh binding, and α subunits, which lack these residues. The majority of neuronal nAChRs fall into two categories: those that bind agonist with high affinity (nMconcentrations); and those that bind with lower affinity (µM concentrations). The low-affinity receptors are presumably homomeric α7 receptors that are α-bungarotoxin sensitive, whereas α4β2 nAChRs account for >90% of the high-affinity nicotinic receptors in the brain (Whiting and Lindstrom, 1986). Their physiological contributions to neurotransmission, signaling, and behavior are not completely understood. Precise mapping of subcellular and neuroanatomical localizations of neuronal nAChR subunits will help elucidate the physiological role of neuronal nAChRs and their role in nicotine addiction

Emerging Technologies, Signal Processing and Statistical Methods for Screening of Cervical Cancer In Vivo: Are They Good Candidates for Cervical Screening?

The current cervical cancer screening test (the Pap smear) is a manual cytological procedure. This cytology test has various limitations and many errors. Excellent candidates for improving the performance of the cervical cancer screening procedure are electro-optical systems (EOSs), used for assessment of the cervical cancer precursors in vivo, such as digital spectroscopy, digital colposcopy and bioelectrical phenomena-based systems. These EOSs use the advantages of signal processing methods and can replace the qualitative assessments, with objective metrics. The EOSs can be used as an adjunct to the current screener or as a primary screener. We analyse and discuss the effectiveness of the signal processing and statistical methods for diagnosis of cervical cancer in vivo. This analysis is reinforced by the presentation of the scientific and clinical contributions of these methods in clinical practice. As a result of this analysis, we outline and discuss the well-established estimates of the signal processing features and the ambiguous features, that are used for classification of the cervical pre-cancer in vivo

Effective lock handling in stateless model checking.

Stateless Model Checking (SMC) is a verification technique for concurrent programs that checks for safety violations by exploring all possible thread interleavings. SMC is usually coupled with Partial Order Reduction (POR), which exploits the independence of instructions to avoid redundant explorations when an equivalent one has already been considered. While effective POR techniques have been developed for many different memory models, they are only able to exploit independence at the instruction level, which makes them unsuitable for programs with coarse-grained synchronization mechanisms such as locks. We present a lock-aware POR algorithm, LAPOR, that exploits independence at both instruction and critical section levels. This enables LAPOR to explore exponentially fewer interleavings than the state-of-the-art techniques for programs that use locks conservatively. Our algorithm is sound, complete, and optimal, and can be used for verifying programs under several different memory models. We implement LAPOR in a tool and show that it can be exponentially faster than the state-of-the-art model checkers