Investigation of the residence time distribution in a plate heat exchanger with series and parallel arrangements using a non-ideal tracer detection technique

The objective was to study the flow pattern in a plate heat exchanger (PHE) through residence time distribution (RTD) experiments. The tested PHE had flat plates and it was part of a laboratory scale pasteurization unit. Series flow and parallel flow configurations were tested with a variable number of passes and channels per pass. Owing to the small scale of the equipment and the short residence times, it was necessary to take into account the influence of the tracer detection unit on the RID data. Four theoretical RID models were adjusted: combined, series combined, generalized convection and axial dispersion. The combined model provided the best fit and it was useful to quantify the active and dead space volumes of the PHE and their dependence on its configuration. Results suggest that the axial dispersion model would present good results for a larger number of passes because of the turbulence associated with the changes of pass. This type of study can be useful to compare the hydraulic performance of different plates or to provide data for the evaluation of heat-induced changes that occur in the processing of heat-sensitive products. (C) 2011 Elsevier Ltd. All rights reserved.

Distributed Estimation Over an Adaptive Incremental Network Based on the Affine Projection Algorithm

We study the problem of distributed estimation based on the affine projection algorithm (APA), which is developed from Newton`s method for minimizing a cost function. The proposed solution is formulated to ameliorate the limited convergence properties of least-mean-square (LMS) type distributed adaptive filters with colored inputs. The analysis of transient and steady-state performances at each individual node within the network is developed by using a weighted spatial-temporal energy conservation relation and confirmed by computer simulations. The simulation results also verify that the proposed algorithm provides not only a faster convergence rate but also an improved steady-state performance as compared to an LMS-based scheme. In addition, the new approach attains an acceptable misadjustment performance with lower computational and memory cost, provided the number of regressor vectors and filter length parameters are appropriately chosen, as compared to a distributed recursive-least-squares (RLS) based method.

Bifurcation in growth patterns for arrays of parallel Griffith, edge and sliding cracks

This paper presents the recent finding by Muhlhaus et al [1] that bifurcation of crack growth patterns exists for arrays of two-dimensional cracks. This bifurcation is a result of the nonlinear effect due to crack interaction, which is, in the present analysis, approximated by the dipole asymptotic or pseudo-traction method. The nonlinear parameter for the problem is the crack length/ spacing ratio lambda = a/h. For parallel and edge crack arrays under far field tension, uniform crack growth patterns (all cracks having same size) yield to nonuniform crack growth patterns (i.e. bifurcation) if lambda is larger than a critical value lambda(cr) (note that such bifurcation is not found for collinear crack arrays). For parallel and edge crack arrays respectively, the value of lambda(cr) decreases monotonically from (2/9)(1/2) and (2/15.096)(1/2) for arrays of 2 cracks, to (2/3)(1/2)/pi and (2/5.032)(1/2)/pi for infinite arrays of cracks. The critical parameter lambda(cr) is calculated numerically for arrays of up to 100 cracks, whilst discrete Fourier transform is used to obtain the exact solution of lambda(cr) for infinite crack arrays. For geomaterials, bifurcation can also occurs when array of sliding cracks are under compression.

Data partitioning for parallel spatial join processing

The cost of spatial join processing can be very high because of the large sizes of spatial objects and the computation-intensive spatial operations. While parallel processing seems a natural solution to this problem, it is not clear how spatial data can be partitioned for this purpose. Various spatial data partitioning methods are examined in this paper. A framework combining the data-partitioning techniques used by most parallel join algorithms in relational databases and the filter-and-refine strategy for spatial operation processing is proposed for parallel spatial join processing. Object duplication caused by multi-assignment in spatial data partitioning can result in extra CPU cost as well as extra communication cost. We find that the key to overcome this problem is to preserve spatial locality in task decomposition. We show in this paper that a near-optimal speedup can be achieved for parallel spatial join processing using our new algorithms.

Practical parallel coset enumeration

Coset enumeration is a most important procedure for investigating finitely presented groups. We present a practical parallel procedure for coset enumeration on shared memory processors. The shared memory architecture is particularly interesting because such parallel computation is both faster and cheaper. The lower cost comes when the program requires large amounts of memory, and additional CPU's. allow us to lower the time that the expensive memory is being used. Rather than report on a suite of test cases, we take a single, typical case, and analyze the performance factors in-depth. The parallelization is achieved through a master-slave architecture. This results in an interesting phenomenon, whereby the CPU time is divided into a sequential and a parallel portion, and the parallel part demonstrates a speedup that is linear in the number of processors. We describe an early version for which only 40% of the program was parallelized, and we describe how this was modified to achieve 90% parallelization while using 15 slave processors and a master. In the latter case, a sequential time of 158 seconds was reduced to 29 seconds using 15 slaves.

Computational chemistry on Fujitsu vector-parallel processors: Development and performance of applications software

In this and a preceding paper, we provide an introduction to the Fujitsu VPP range of vector-parallel supercomputers and to some of the computational chemistry software available for the VPP. Here, we consider the implementation and performance of seven popular chemistry application packages. The codes discussed range from classical molecular dynamics to semiempirical and ab initio quantum chemistry. All have evolved from sequential codes, and have typically been parallelised using a replicated data approach. As such they are well suited to the large-memory/fast-processor architecture of the VPP. For one code, CASTEP, a distributed-memory data-driven parallelisation scheme is presented. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

Target similarity effects: Support for the parallel distributed processing assumptions

Recent research has begun to provide support for the assumptions that memories are stored as a composite and are accessed in parallel (Tehan & Humphreys, 1998). New predictions derived from these assumptions and from the Chappell and Humphreys (1994) implementation of these assumptions were tested. In three experiments, subjects studied relatively short lists of words. Some of the Lists contained two similar targets (thief and theft) or two dissimilar targets (thief and steal) associated with the same cue (ROBBERY). AS predicted, target similarity affected performance in cued recall but not free association. Contrary to predictions, two spaced presentations of a target did not improve performance in free association. Two additional experiments confirmed and extended this finding. Several alternative explanations for the target similarity effect, which incorporate assumptions about separate representations and sequential search, are rejected. The importance of the finding that, in at least one implicit memory paradigm, repetition does not improve performance is also discussed.

Parallel processing and image analysis in the eyes of mantis shrimps

The compound eyes of mantis shrimps, a group of tropical marine crustaceans, incorporate principles of serial and parallel processing of visual information that may be applicable to artificial imaging systems. Their eyes include numerous specializations for analysis of the spectral and polarizational properties of light, and include more photoreceptor classes for analysis of ultraviolet light, color, and polarization than occur in any other known visual system. This is possible because receptors in different regions of the eye are anatomically diverse and incorporate unusual structural features, such as spectral filters, not seen in other compound eyes. Unlike eyes of most other animals, eyes of mantis shrimps must move to acquire some types of visual information and to integrate color and polarization with spatial vision. Information leaving the retina appears to be processed into numerous parallel data streams leading into the central nervous system, greatly reducing the analytical requirements at higher levels. Many of these unusual features of mantis shrimp vision may inspire new sensor designs for machine vision

Neuroarchitecture of the color and polarization vision system of the stomatopod haptosquilla

The apposition compound eyes of stomatopod crustaceans contain a morphologically distinct eye region specialized for color and polarization vision, called the mid-band. In two stomatopod superfamilies, the mid-band is constructed from six rows of enlarged ommatidia containing multiple photoreceptor classes for spectral and polarization vision. The aim of this study was to begin to analyze the underlying neuroarchitecture, the design of which might reveal clues how the visual system interprets and communicates to deeper levels of the brain the multiple channels of information supplied by the retina. Reduced silver methods were used to investigate the axon pathways from different retinal regions to the lamina ganglionaris and from there to the medulla externa, the medulla interna, and the medulla terminalis. A swollen band of neuropil-here termed the accessory lobe-projects across the equator of. the lamina ganglionaris, the medulla externa, and the medulla interna and represents, structurally, the retina's mid-band. Serial semithin and ultrathin resin sections were used to reconstruct the projection of photoreceptor axons from the retina to the lamina ganglionaris. The eight axons originating from one ommatidium project to the same lamina cartridge. Seven short visual fibers end at two distinct levels in each lamina cartridge, thus geometrically separating the two channels of polarization and spectral information. The eighth visual fiber runs axially through the cartridge and terminates in the medulla externa. We conclude that spatial, color, and polarization information is divided into three parallel data streams from the retina to the central nervous system. (C) 2003 Wiley-Liss, Inc.

Using multidimensional projection techniques for reaching a high distinguishing ability in biosensing

Recent advances in the control of molecular engineering architectures have allowed unprecedented ability of molecular recognition in biosensing, with a promising impact for clinical diagnosis and environment control. The availability of large amounts of data from electrical, optical, or electrochemical measurements requires, however, sophisticated data treatment in order to optimize sensing performance. In this study, we show how an information visualization system based on projections, referred to as Projection Explorer (PEx), can be used to achieve high performance for biosensors made with nanostructured films containing immobilized antigens. As a proof of concept, various visualizations were obtained with impedance spectroscopy data from an array of sensors whose electrical response could be specific toward a given antibody (analyte) owing to molecular recognition processes. In addition to discussing the distinct methods for projection and normalization of the data, we demonstrate that an excellent distinction can be made between real samples tested positive for Chagas disease and Leishmaniasis, which could not be achieved with conventional statistical methods. Such high performance probably arose from the possibility of treating the data in the whole frequency range. Through a systematic analysis, it was inferred that Sammon`s mapping with standardization to normalize the data gives the best results, where distinction could be made of blood serum samples containing 10(-7) mg/mL of the antibody. The method inherent in PEx and the procedures for analyzing the impedance data are entirely generic and can be extended to optimize any type of sensor or biosensor.

Alternatives for parallel Krylov subspace basis computation

Numerical methods related to Krylov subspaces are widely used in large sparse numerical linear algebra. Vectors in these subspaces are manipulated via their representation onto orthonormal bases. Nowadays, on serial computers, the method of Arnoldi is considered as a reliable technique for constructing such bases. However, although easily parallelizable, this technique is not as scalable as expected for communications. In this work we examine alternative methods aimed at overcoming this drawback. Since they retrieve upon completion the same information as Arnoldi's algorithm does, they enable us to design a wide family of stable and scalable Krylov approximation methods for various parallel environments. We present timing results obtained from their implementation on two distributed-memory multiprocessor supercomputers: the Intel Paragon and the IBM Scalable POWERparallel SP2. (C) 1997 by John Wiley & Sons, Ltd.

An Eight-week, Multicentric, Randomized, Interventional, Open-label, Phase 4, Parallel Comparison of the Efficacy and Tolerability of the Fixed Combination of Timolol Maleate 0.5%/Brimonidine Tartrate 0.2% Versus Fixed Combination of Timolol Maleate 0.5%/Dorzolamide 2% in Patients With Elevated Intraocular Pressure

Purpose: To compare the efficacy and tolerability of the fixed combination of timolol maleate 0.5%/brimonidine tartrate 0.2% versus fixed combination of timolol maleate 0.5%/dorzolamide 2% in patients with elevated intraocular pressure (IOP) over 8 weeks. Patients and Methods: This 8-week, multicentric. interventional, randomized, open-label, parallel group study was conducted Lit 4 centers in Brazil and 1 center in Argentina. Patients with open-angle glaucoma or ocular hypertension were randomized to receive bilaterally fixed combination of brimonidine/timolol maleate 0.5% or fixed combination of dorzolamide 2%/timolol 0.5% twice daily at 8:00 AM and 8:00 PM. A modified diurnal tension curve (8:00 AM 10:30 AM, 02:00 PM, and 4:00 PM) followed by the water drinking test (WDT), which estimates IOP peak of diurnal tension curve, were performed in the baseline and week-8 visits. Adverse events data were recorded at each visit. Results: A total of 210 patients were randomized (brimonidine/timolol, n = 111; dorzolamide/timolol, n = 99). Mean baseline IOP was 23.43 +/- 3.22 mm Hg and 23.43 +/- 4.06 mm Hg in the patients treated with brimonidine/timolol and dorzolamide/timolol, respectively (P = 0.993). Mean diurnal IOP reduction after 8 weeks were 7.02 +/- 3.06 mm Hg and 6.91 +/- 3.67 mm Hg. respectively (P = 0.811). The adjusted difference between groups (analysis of covariance) Lit week 8 was not statistically significant (P = 0.847). Mean baseline WDT peak was 27.79 +/- 4.29 mm Hg in the brimonidine/timolol group and 27.68 +/- 5.46 mm Hg in the dorzolamide/timolol group. After 8 weeks of treatment, mean WDT peaks were 20.94 +/- 3.76 mm Hg (P < 0.001) and 20.98 +/- 4.19 (P < 0.001), respectively. The adjusted difference between groups (analysis of covariance) was not statistically significant (P = 0.469). No statistical difference in terms of adverse events was Found between groups. Conclusions: Both fixed combinations were capable of significantly reducing the mean diurnal IOP, mean diurnal peak, and mean WDT peak after 8 weeks of treatment. Also, both fixed combinations are well tolerated with few side effects.

Self-Esteem, Confidence, and Relationships in Brazilian Men with Erectile Dysfunction Receiving Sildenafil Citrate: A Randomized, Parallel-Group, Double-Blind, Placebo-Controlled Study in Brazil

Psychosocial manifestations of erectile dysfunction (ED) differ across cultures. Understanding the treatment response to ED medications within cultural groups can aid in resource allocation and in developing treatment strategies. Evaluate the effect of sildenafil treatment on self-esteem, confidence, and sexual relationship satisfaction in Brazilian men with ED. The Self-Esteem and Relationship (SEAR) questionnaire, a validated, 14-question instrument developed to specifically address self-esteem and relationship issues within the context of ED. Men aged 18 years or older with a clinical diagnosis of ED (<= 21 on the Sexual Health Inventory for Men) and in a stable relationship with a partner during the study were eligible. The primary end point was a change from baseline in the self-esteem subscale of the SEAR questionnaire. Thirteen Brazilian sites participated in a randomized, double-blind, placebo-controlled trial of sildenafil treatment for ED. Patients were randomized to receive either 50 mg of sildenafil (adjustable to 25 mg or 100 mg based on patient response) or matching placebo approximately 1 hour before anticipated sexual activity but not more than once a day. At the end of double-blind treatment, 63 and 66 patients in the placebo and sildenafil groups, respectively, from 13 Brazilian sites were assessed for efficacy. Brazilian patients receiving sildenafil had significantly greater improvements in their scores on the SEAR self-esteem subscale (42.9 [95% confidence interval 35.7-50.0]) compared with placebo (21.1 [95% confidence interval 13.7-28.6]; P < 0.0001). Effect sizes ranged from 0.91 to 1.25 for individual SEAR components. The psychosocial parameters in Brazilian men with ED assessed by the SEAR questionnaire showed significant improvements in self-esteem, confidence, and relationships after treatment with sildenafil. Glina S, Damiao R, Abdo C, Afif-Abdo J, Tseng L-J, and Stecher V. Self-esteem, confidence, and relationships in Brazilian men with erectile dysfunction receiving sildenafil citrate: A randomized, parallel-group, double-blind, placebo-controlled study in Brazil. J Sex Med 2009;6:268-275.