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Various Designs (various + design)
Selected AbstractsAnalysis and optimization of low-pressure drop static mixersAICHE JOURNAL, Issue 9 2009Mrityunjay K. Singh Abstract Various designs of the so called Low-Pressure Drop (LPD) static mixer are analyzed for their mixing performance using the mapping method. The two types of LPD designs, the RR and RL type, show essentially different mixing patterns. The RL design provides globally chaotic mixing, whereas the RR design always yields unmixed regions separated by KAM boundaries from mixed regions. The crossing angle between the elliptical plates of the LPD is the key design parameter to decide the performance of various designs. Four different crossing angles from 90° to 160° are used for both the RR and RL designs. Mixing performance is computed as a function of the energy to mix, reflected in overall pressure drop for all designs. Optimization using the flux-weighted intensity of segregation versus pressure drop proves the existence of the best mixer with an optimized crossing angle. The optimized angle proves to be indeed the LLPD design used in practice: the RL-120 with , = 120°, although RL-140 , = 140° performs as good. Shear thinning shows minor effects on the mixing profiles, and the main optimization conclusions remain unaltered. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Finite element analysis of vent/hand hole designs for corrugated fibreboard boxesPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2007Jongkoo Han Abstract Corrugated fibreboard is an economical and efficient material for fabricating shipping containers that are widely used for the distribution, transportation and storage of goods. Corrugated fibreboard is usually considered to be an orthotropic material because the principal fibre directions, machine direction (MD) and cross-machine direction (CD), are identical to the fibres in paperboard, which has apparent directional property differences. The purpose of this study is to investigate the principal design parameters of ventilation holes and hand holes in the faces of the shipping container, (corrugated fibreboard boxes), using finite element analysis (FEA). Various designs of ventilation holes were studied with respect to stress distribution and stress level. It was found that the appropriate pattern and location of the ventilation holes were vertical oblong-shaped and symmetrically positioned within a certain extent of distance to the right and left from the centre of the front and rear faces of the boxes. On the other hand, the appropriate location and pattern of the hand holes were a short distance from the centre to the top of the boxes on both side faces. The appropriate pattern was a modified shape, such as the radius of curvature of both sides in horizontal oblong. The pattern and location of both the ventilation holes and the hand holes determined by the FEA simulation generally agreed well with laboratory experimental results. The decrease in compression strength of the box could be minimized with identical area of the ventilation holes if the length of the major axis of the ventilation hole is less than 1/4 of the depth of the box and the ratio of the minor axis to the major axis is 1/3.5,1/2.5, provided that even-numbered holes are located symmetrically. Copyright © 2006 John Wiley & son, Ltd. [source] Enhancement of electrokinetically driven microfluidic T-mixer using frequency modulated electric field and channel geometry effectsELECTROPHORESIS, Issue 18 2009Deguang Yan Abstract This study reports improved electrokinetically driven microfluidic T-mixers to enhance their mixing efficiency. Enhancement of electrokinetic microfluidic T-mixers is achieved using (i) an active approach of utilizing a pulsating EOF, and (ii) a passive approach of using the channel geometry effect with patterned blocks. PDMS-based electrokinetic T-mixers of different designs were fabricated. Experimental measurements were carried out using Rhodamine B to examine the mixing performance and the micro-particle image velocimetry technique to characterize the electrokinetic flow velocity field. Scaling analysis provides an effective frequency range of applied AC electric field. Results show that for a T-mixer of 10,mm mixing length, utilizing frequency modulated electric field and channel geometry effects can increase the mixing efficiency from 50 to 90%. In addition, numerical simulations were performed to analyze the mixing process in the electrokinetic T-mixers with various designs. The simulation results were compared with the experimental data, and reasonable agreement was found. [source] Selection of Antiepileptic Drug Polytherapy Based on Mechanisms of Action: The Evidence ReviewedEPILEPSIA, Issue 11 2000Charles L. P. Deckers Summary: Purpose: When monotherapy with antiepileptic drugs (AEDs) fails, combination therapy is tried in an attempt to improve effectiveness by improving efficacy, tolerability, or both. We reviewed the available studies (both animal and human) on AED polytherapy to determine whether AEDs can be selected for combination therapy based on their mechanisms of action, and if so, which combinations are associated with increased effectiveness. Because various designs and methods of analysis were used in these studies, it was also necessary to evaluate the appropriateness of these approaches. Methods: Published papers reporting on AED polytherapy in animals or humans were identified by Medline search and by checking references cited in these papers. Results: Thirty-nine papers were identified reporting on two-drug AED combinations. Several combinations were reported to offer improved effectiveness, but no uniform approach was used in either animal or human studies for the evaluation of pharmacodynamic drug interactions; efficacy was often the only end point. Conclusions: There is evidence that AED polytherapy based on mechanisms of action may enhance effectiveness. In particular, combining a sodium channel blocker with a drug enhancing GABAergic inhibition appears to be advantageous. Combining two GABA mimetic drugs or combining an AMPA antagonist with an NMDA antagonist may enhance efficacy, but tolerability is sometimes reduced. Combining two sodium channel blockers seems less promising. However, given the incomplete knowledge of the pathophysiology of seizures and indeed of the exact mechanisms of action of AEDs, an empirical but rational approach for evaluating AED combinations is of fundamental importance. This would involve appropriate testing of all possible combinations in animal models and subsequent evaluation of advantageous combinations in clinical trials. Testing procedures in animals should include the isobologram method, and the concept of drug load should be the basis of studies in patients with epilepsy. [source] Up-to-date cancer survival: Period analysis and beyondINTERNATIONAL JOURNAL OF CANCER, Issue 6 2009Hermann Brenner Abstract Since its introduction in 1996, period analysis has been shown to be useful for deriving more up-to-date cancer survival estimates, and the method is now increasingly used for that purpose in national and international cancer survival studies. However, period analysis, like other commonly employed methods, is just a special case from a broad class of design options in the analysis of cancer survival data. Here, we explore a broader range of design options, including 2 model-based approaches, for deriving up-to-date estimates of 5- and 10-year relative survival for patients diagnosed in the most recent 5-year interval for which data are available. The performance of the various designs is evaluated empirically for 20 common forms of cancer using more than 50-year long time series of data from the Finnish Cancer Registry. Period analysis as well as the 2 model-based approaches, one using a "cohort-type model" and another using a "period-type model", all performed better than traditional cohort or complete analysis. Compared with "standard period analysis", the cohort-type model further increased up-to-dateness of survival estimates, whereas the period-type model increased their precision. While our analysis confirms advantages of period analysis over traditional methods in terms of up-to-dateness of cancer survival data, further improvements are possible by flexible use of model-based approaches. © 2008 Wiley-Liss, Inc. [source] Designs and analyses of various fuzzy controllers with region-wise linear PID subcontrollersINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 12 2001C. W. Tao To reduce the complexity of PID-like fuzzy controllers with three inputs, designs and analyses of various fuzzy controllers with region-wise linear PID subcontrollers are presented in this paper. The proposed region-wise linear PID subcontrollers are composed of one dimensional fuzzy mechanism. And the triangular-type membership functions are adopted for the input variables of the fuzzy controllers. All the possible structures of fuzzy controllers with region-wise linear PID subcontrollers are discussed. According to the number of one-dimensional fuzzy mechanisms included in the structure of the fuzzy controllers, the fuzzy controllers are classified into three main categories. An algorithm is provided to construct effective fuzzy controllers with lowest complexity among all the possible structures. Also, the properties of various designs of fuzzy controllers with region-wise linear PID subcontrollers are compared. The simulation results are included to demonstrate the performances of three basic types of proposed fuzzy controllers with the linear, nonlinear, and delayed plants. © 2001 John Wiley & Sons, Inc. [source] Investigating the Effectiveness of Equating Designs for Constructed-Response Tests in Large-Scale AssessmentsJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 2 2010Sooyeon Kim Using data from a large-scale exam, in this study we compared various designs for equating constructed-response (CR) tests to determine which design was most effective in producing equivalent scores across the two tests to be equated. In the context of classical equating methods, four linking designs were examined: (a) an anchor set containing common CR items, (b) an anchor set incorporating common CR items rescored, (c) an external multiple-choice (MC) anchor test, and (d) an equivalent groups design incorporating rescored CR items (no anchor test). The use of CR items without rescoring resulted in much larger bias than the other designs. The use of an external MC anchor resulted in the next largest bias. The use of a rescored CR anchor and the equivalent groups design led to similar levels of equating error. [source] Analysis and optimization of low-pressure drop static mixersAICHE JOURNAL, Issue 9 2009Mrityunjay K. Singh Abstract Various designs of the so called Low-Pressure Drop (LPD) static mixer are analyzed for their mixing performance using the mapping method. The two types of LPD designs, the RR and RL type, show essentially different mixing patterns. The RL design provides globally chaotic mixing, whereas the RR design always yields unmixed regions separated by KAM boundaries from mixed regions. The crossing angle between the elliptical plates of the LPD is the key design parameter to decide the performance of various designs. Four different crossing angles from 90° to 160° are used for both the RR and RL designs. Mixing performance is computed as a function of the energy to mix, reflected in overall pressure drop for all designs. Optimization using the flux-weighted intensity of segregation versus pressure drop proves the existence of the best mixer with an optimized crossing angle. The optimized angle proves to be indeed the LLPD design used in practice: the RL-120 with , = 120°, although RL-140 , = 140° performs as good. Shear thinning shows minor effects on the mixing profiles, and the main optimization conclusions remain unaltered. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Reduction of bias in static closed chamber measurement of ,13C in soil CO2 effluxRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2010K. E. Anders Ohlsson The 13C/12C ratio of soil CO2 efflux (,e) is an important parameter in studies of ecosystem C dynamics, where the accuracy of estimated C flux rates depends on the measurement uncertainty of ,e. The static closed chamber method is frequently used in the determination of ,e, where the soil CO2 efflux is accumulated in the headspace of a chamber placed on top of the soil surface. However, it has recently been shown that the estimate of ,e obtained by using this method could be significantly biased, which potentially diminish the usefulness of ,e for field applications. Here, analytical and numerical models were used to express the bias in ,e as mathematical functions of three system parameters: chamber height (H), chamber radius (Rc), and soil air-filled porosity (,). These expressions allow optimization of chamber size to yield a bias, which is at a level suitable for each particular application of the method. The numerical model was further used to quantify the effects on the ,e bias from (i) various designs for sealing of the chamber to ground, and (ii) inclusion of the commonly used purging step for reduction of the initial headspace CO2 concentration. The present modeling work provided insights into the effects on the ,e bias from retardation and partial chamber bypass of the soil CO2 efflux. The results presented here supported the continued use of the static closed chamber method for the determination of ,e, with improved control of the bias component of its measurement uncertainty. Copyright © 2009 John Wiley & Sons, Ltd. [source] Collection efficiencies of various designs of post-cycloneTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2001Wennan Zhao Abstract Post-cyclone (PoC) is a novel secondary dust separator, which collects a certain fraction of the particles escaping through the vortex finder of a reverse flow cyclone. Due to the residual swirl in the vortex finder, the particles in the effluent air are concentrated at the wall of the vortex finder in an outer annulus. The particles in the outer annulus are split from the main stream and collected in a bleed flow. This paper presents the experimentally determined collection efficiencies of various designs of PoC. Depending on the design, operating conditions and the size and density of the particles, PoC can reduce the emission of the parent cyclones by 5% to 50%. In some experiments, the bleed flow from PoC is recycled back to the inlet of the cyclone. Significant improvement in the removal of fines occurs when the bleed flow is recycled to the inlet. Le post-cyclone (PoC) est un nouveau séparateur de poussières secondaire, qui récupère une partie des particules s'échappant du dispositif de capture du vortex d'un cyclone à écoulement inverse. À cause du tourbillon résiduel présent dans ce dispositif, les particules dans l'air de l'effluent sont concentrees à la paroi du dispositif dans un espace annulaire extérieur. Les particules dans l'espace annulaire extérieur sont séparées du courant principal et récupérées dans un écoulement de purge. On présente dans cet article les rendements de récupération déterminées expérimentalement pour diverses conceptions de PoC. Selon la conception, les conditions opératoires ainsi que la taille et la rnasse volumique des particules, le PoC peut réduire l'émission des cyclones parents de 5% à 50%. Dans certaines expériences, l'écoulement de purge venant d'un PoC est recyclé de nouveau vers l'entrée du cyclone. Une amélioration significative est obtenue dans le retrait des fines lorsque l'écoulernent de purge est recyclé vers l'entrée. [source] Self-ligating brackets in orthodontics: do they deliver what they claim?AUSTRALIAN DENTAL JOURNAL, Issue 1 2009PG Miles Abstract Self-ligating brackets have enjoyed recent popularity in the orthodontic marketplace with various claims made including faster ligation, lower friction, faster treatment, less pain, waking up the tongue, and fewer appointments. Although various designs of self-ligating brackets have been available for many years they have only recently surged in popularity on the back of these claims but what evidence is there to support these claims? This review article examines the current available evidence regarding treatment duration, influence on archform, and the speed of tying and untying self-ligating brackets compared with conventional brackets and methods of ligation. [source] | |||||||||||||