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Reinforcement
Kinds of Reinforcement Terms modified by Reinforcement Selected AbstractsRELATIVE ABUNDANCE AND THE SPECIES-SPECIFIC REINFORCEMENT OF MALE MATING PREFERENCE IN THE CHRYSOCHUS (COLEOPTERA: CHRYSOMELIDAE) HYBRID ZONEEVOLUTION, Issue 12 2005Merrill A. Peterson Abstract Most studies of reinforcement have focused on the evolution of either female choice or male mating cues, following the long-held view in sexual selection theory that mating mastakes are typically more costly for females than for males. However, factors such as conspecific sperm precedence can buffer females against the cost of mating mistakes, suggesting that in some hybrid zones mating mistakes may be more costly for males than for females. Thus, the historical bias in reinforcement research may underestimate its frequency. In this study, we present evidence that reinforcement has driven the evolution of male choice in a hybrid zone between teh highly promiscuous lealf beetles chyrsochus cobaltinus and C. auratus, the hybrids of which have extremely low fitness. In addition, there is evidence for male choice in these beetles and that male mating mistakes may be costly, due to reduced opportunities to mate with conspecific females. The present study combines laboratory and field methods to quantify the strenght of sexual isolation, test the hypothesis of reproductive character displacement, and assess the link between relative abundance and the strenght of selection against hybridization. We document that, while sexual isolation is weak, it is sufficient to produce positive assortative mating. In addtion, reproductive character displacement was only detected in the relatively rare species. The strong postzygotic barriers in this system are sufficient to generate the bimodality that characterizes this hybrid zone, but the weak sexual isolation is not, calling into question whether strong prezygotic isolation is necessary for the maintenance of bimodality. Growing evidence that the cost of mating mistakes is sufficient to shape the evolution of male mate choice suggests that the reinforecement of male mate choice may prove to be a widespread occurrence. [source] REINFORCEMENT AND THE GENETICS OF NONRANDOM MATINGEVOLUTION, Issue 1 2000Maria R. Servedio Abstract., The occurrence of reinforcement is compared when premating isolation is caused by the spread of a gene causing females to prefer to mate with males carrying a population-specific trait (a "preference" model) and by a gene that causes females to prefer to mate with males that share their own trait phenotype (an "assortative mating" model). Both two-island models, which have symmetric gene flow, and continent-island models, which have one-way gene flow, are explored. Reinforcement is found to occur much more easily in a two-island assortative mating model than in any of the other three models. This is due primarily to the fact that in this model the assortative mating allele will automatically become genetically associated in each population with the trait allele that is favored by natural selection on that island. In contrast, natural selection on the trait both favors and opposes the evolution of premating isolation in the two-island preference model, depending on the particular population. These results imply that species recognition in the context of mating may evolve particularly easily when it targets cues that are favored by natural selection in each population. In the continent-island models, reinforcement is found to occur more often under the preference model than the assortative mating model, thus reversing the trend from the two-island models. Patterns of population subdivision may therefore play a role in determining what types of premating isolation may evolve. [source] TETRAPLEGIA IN A PATIENT WITH HUGE HETEROTOPIC OSSIFICATION OF THE HIP JOINT AFTER TOTAL HIP ARTHROPLASTY: ADDITION OR REINFORCEMENT OF HANDICAPSJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 8 2003Satoshi Ishikawa MD No abstract is available for this article. [source] Use of a Deep Polypropylene Suture during Earlobe Repair: A Method to Provide Permanent Reinforcement in the Prevention of Recurrent Earlobe Tract ElongationDERMATOLOGIC SURGERY, Issue 11 2005Joseph F. Greco MD Background. Cosmetic repair of elongated or lacerated earlobe tracts is a commonly encountered dermatologic procedure. For esthetic purposes, patients may choose to repierce the repaired lobe over the original site. Subsequent piercing within a scarred area potentially increases the risk of recurrent tract elongation secondary to the reduced tensile strength of the scar. Objective. To strengthen a damaged earlobe by incorporating a nonabsorbable, dermal polypropylene suture during earlobe repair. Methods. The technique is described within the text. Results. A deep polypropylene suture placed within a repaired earlobe tract provides a permanent barrier above which repiercing can be performed. Conclusion. Permanent reinforcement of the repaired earlobe serves to reduce the possibility of recurrent elongation of the earlobe tract. The technique is relevant when repeat piercing is desired over the original site. JOSEPH F. GRECO, MD, CHRISTINE S. STANKO, MD, AND STEVEN S. GREENBAUM, MD, HAVE INDICATED NO SIGNIFICANT INTEREST WITH COMMERCIAL SUPPORTERS. [source] Surgery in thoracic esophageal perforation: primary repair is feasibleDISEASES OF THE ESOPHAGUS, Issue 3 2002S. W. Sung SUMMARY. Prompt diagnosis and effective treatment are important for thoracic esophageal perforations. The decision for proper management is difficult especially when diagnosed late. However, there is an increasing consensus that primary repair provides good results for repair of thoracic esophageal perforations, which are not diagnosed on time. Primary repair for thoracic esophageal perforations was applied in 20 out of 25 consecutive patients. The time interval between perforation and repair was less than 24 h in six patients (group I), and more than 24 h in 14 patients (group II). The remaining five patients underwent esophagectomy with simultaneous or staged reconstruction because of incorrectable underlying esophageal pathology. Group I had much more iatrogenic causes (P < 0.05). Preoperative sepsis occurred only in group II (P=0.05) and was highly associated with Boerhaave syndrome (P=0.001). Regional viable tissue was used to reinforce the sites of primary repair (n=15, 75%). All of the postoperative morbidity (n=9, 45%) including esophageal leaks (n=6, 30%) and operative death (n=1, 5%) occurred in group II. In patients with postoperative leaks, five eventually healed, but one became a fistula that required reoperation. Primary healing with preservation of the native esophagus was achieved in all 19 patients except one operative death. In addition, the increased incidence of leak and morbidity did not lead to an increase in mortality. In the esophagectomy group, there was no mortality, but one minor suture leak. Regardless of the time interval between the injury and the operation, primary repair is recommended for non-malignant, thoracic, esophageal perforations, but not for anastomotic leaks. Reinforcement that may change the nature of a possible leak is also useful. For incorrectable underlying esophageal pathology, esophagectomy with simultaneous or staged reconstruction is indicated. [source] Community reinforcement and family training: an effective option to engage treatment-resistant substance-abusing individuals in treatmentADDICTION, Issue 10 2010Hendrik G. Roozen ABSTRACT Aims Many individuals with substance use disorders are opposed to seeking formal treatment, often leading to disruptive relationships with concerned significant others (CSOs). This is disturbing, as untreated individuals are often associated with a variety of other addiction-related problems. Community Reinforcement and Family Training (CRAFT) provides an option to the more traditional treatment and intervention approaches. The objective of this systematic review was to compare CRAFT with the Alcoholics Anonymous/Narcotics Anonymous (Al-Anon/Nar-Anon) model and the Johnson Institute intervention in terms of its ability to engage patients in treatment and improve the functioning of CSOs. Methods The electronic databases PubMed, PsycINFO, EMBASE, CINAHL and the Cochrane Library were consulted. Four high-quality randomized controlled trials were identified, with a total sample of 264 CSOs. Data were synthesized to quantify the effect with 95% confidence intervals, using the random effects model. Results CRAFT produced three times more patient engagement than Al-Anon/Nar-Anon [relative risk (RR) 3.25, 95% confidence interval (CI) 2.11,5.02, P < 0.0001; numbers needed to treat (NNT) = 2] and twice the engagement of the Johnson Institute intervention (RR 2.15, 95% CI 1.28,3.62, P = 0.004; NNT = 3). Overall, CRAFT encouraged approximately two-thirds of treatment-resistant patients to attend treatment, typically for four to six CRAFT sessions. CSOs showed marked psychosocial and physical improvements whether they were assigned to CRAFT, Al-Anon/Nar-Anon or the Johnson Institute intervention within the 6-month treatment window. Conclusion CRAFT has been found to be superior in engaging treatment-resistant substance-abusing individuals compared with the traditional programmes. [source] REINFORCEMENT AND THE GENETICS OF NONRANDOM MATINGEVOLUTION, Issue 1 2000Maria R. Servedio Abstract., The occurrence of reinforcement is compared when premating isolation is caused by the spread of a gene causing females to prefer to mate with males carrying a population-specific trait (a "preference" model) and by a gene that causes females to prefer to mate with males that share their own trait phenotype (an "assortative mating" model). Both two-island models, which have symmetric gene flow, and continent-island models, which have one-way gene flow, are explored. Reinforcement is found to occur much more easily in a two-island assortative mating model than in any of the other three models. This is due primarily to the fact that in this model the assortative mating allele will automatically become genetically associated in each population with the trait allele that is favored by natural selection on that island. In contrast, natural selection on the trait both favors and opposes the evolution of premating isolation in the two-island preference model, depending on the particular population. These results imply that species recognition in the context of mating may evolve particularly easily when it targets cues that are favored by natural selection in each population. In the continent-island models, reinforcement is found to occur more often under the preference model than the assortative mating model, thus reversing the trend from the two-island models. Patterns of population subdivision may therefore play a role in determining what types of premating isolation may evolve. [source] High Strength Lead-Free Composite Solder Materials using Nano Al2O3 as ReinforcementADVANCED ENGINEERING MATERIALS, Issue 11 2005X. Zhong High strength light weight lead-free composite solder materials containing varying amount of nano-alumina particulates were synthesized by powder metallurgy process employing different extrusion temperatures. The presence of nano Al2O3 particulates not only enhanced strength and improved dimensional stability but also reduced the weight of the solder alloy matrix. Fairly uniform distribution of the nano-alumina particulates was observed in the composites. [source] Sol,Gel Coatings as Active Barriers to Protect Ceramic Reinforcement in Aluminum Matrix Composites,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2004J. Rams Silica obtained through a sol,gel process is used as a coating for ceramic reinforcements (SiC) in aluminium matrix composite materials. The interaction between molten aluminium and the coated particles during material casting can be controlled by means of the thermal treatment given to the coating. Wettability is increased because the coating reacts with molten aluminium, and the formation of the degrading aluminium carbide is inhibited. [source] Molecular-Level Dispersion of Graphene into Poly(vinyl alcohol) and Effective Reinforcement of their NanocompositesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Jiajie Liang Abstract Despite great recent progress with carbon nanotubes and other nanoscale fillers, the development of strong, durable, and cost-efficient multifunctional nanocomposite materials has yet to be achieved. The challenges are to achieve molecule-level dispersion and maximum interfacial interaction between the nanofiller and the matrix at low loading. Here, the preparation of poly(vinyl alcohol) (PVA) nanocomposites with graphene oxide (GO) using a simple water solution processing method is reported. Efficient load transfer is found between the nanofiller graphene and matrix PVA and the mechanical properties of the graphene-based nanocomposite with molecule-level dispersion are significantly improved. A 76% increase in tensile strength and a 62% improvement of Young's modulus are achieved by addition of only 0.7,wt% of GO. The experimentally determined Young's modulus is in excellent agreement with theoretical simulation. [source] Concurrent Q-learning: Reinforcement learning for dynamic goals and environmentsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 10 2005Robert B. Ollington This article presents a powerful new algorithm for reinforcement learning in problems where the goals and also the environment may change. The algorithm is completely goal independent, allowing the mechanics of the environment to be learned independently of the task that is being undertaken. Conventional reinforcement learning techniques, such as Q-learning, are goal dependent. When the goal or reward conditions change, previous learning interferes with the new task that is being learned, resulting in very poor performance. Previously, the Concurrent Q-Learning algorithm was developed, based on Watkin's Q-learning, which learns the relative proximity of all states simultaneously. This learning is completely independent of the reward experienced at those states and, through a simple action selection strategy, may be applied to any given reward structure. Here it is shown that the extra information obtained may be used to replace the eligibility traces of Watkin's Q-learning, allowing many more value updates to be made at each time step. The new algorithm is compared to the previous version and also to DG-learning in tasks involving changing goals and environments. The new algorithm is shown to perform significantly better than these alternatives, especially in situations involving novel obstructions. The algorithm adapts quickly and intelligently to changes in both the environment and reward structure, and does not suffer interference from training undertaken prior to those changes. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 1037,1052, 2005. [source] Dialogue and the Reinforcement of Orthodoxy in International RelationsINTERNATIONAL STUDIES REVIEW, Issue 1 2003Steve Smith First page of article [source] Reinforcement and antioxidation effects of fullerenol-containing natural rubberJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Hiroaki Kondo Abstract Natural rubber (NR) containing fullerenol, C60-OH, was prepared by two methods; one by mixing C60-OH aqueous solution to NR latex followed by coagulation (wet method) and the other by mixing C60-OH powder with solid rubber by an open roll mixer (dry method). C60-OH mixed by wet method was homogeneously dispersed in the rubber, while one mixed by dry method was particles in the size up to 70 ,m. The former exhibited large reinforcing and antiaging effect than the latter. The large antiaging effect was explained by the finding that C60-OH had large radical scavenging ability and gel forming ability during heat treatment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Fracture Force, Deflection, and Toughness of Acrylic Denture Repairs Involving Glass Fiber ReinforcementJOURNAL OF PROSTHODONTICS, Issue 4 2008Ioannis Kostoulas DDS Abstract Purpose: Fractures in acrylic resin dentures occur quite often in the practice of prosthodontics. A durable repairing system for denture base fracture is desired to avoid recurrent fracture. The purpose of this study was to evaluate the fracture force, deflection, and toughness of a heat-polymerized denture base resin repaired with autopolymerized resin alone (C), visible light-polymerizing resin (VLC), or autopolymerizing resin reinforced with unidirectional (Stick) (MA-FS) and woven glass fibers (StickNet) (MA-SN). Another group was repaired with autopolymerized resin after wetting the repair site with methyl methacrylate (MA-MMA) for 180 seconds. A group of intact specimens was used as control. Materials and Methods: Heat-polymerizing acrylic resin was used to fabricate the specimens. The specimens (10 per group) were sectioned in half, reassembled with a 3-mm butt-joint gap, and repaired. A cavity was included when glass fibers were used. Three-point bending was used to test the repaired site, and data were analyzed with one-way ANOVA and the Tukey's post hoc test (,, 0.05). Results: Fracture force, deflection, and toughness for the repaired groups without reinforcement (MA: 46.7 ± 8.6 N, 2.6 ± 0.3 mm, 0.08 ± 0.001 J; MA-MMA: 41.0 ± 7.2 N, 2.7 ± 0.4 mm, 0.07 ± 0.002 J) were significantly lower (p < 0.05) than the control group (C: 78.6 ± 9.6 N, 5.9 ± 0.4 mm, 0.27 ± 0.003 J). Repair with visible light-polymerizing resin (VLC, 15.0 ± 4.0 N, 1.2 ± 0.4 mm, 0.02 ± 0.0001 J) resulted in significant reduction of mechanical properties (p < 0.05). Reinforcement with glass fibers restored (MA-SN: 75.8 ± 9.2 N) or increased (MA-FS: 124.4 ± 12.5 N) the original strength. Conclusion: The most effective repair method was the use of autopolymerized resin reinforced with unidirectional glass fibers. [source] Impact of Sex: Determination of Alcohol Neuroadaptation and ReinforcementALCOHOLISM, Issue 2 2006Kristine M. Wiren This article represents the proceedings of a symposium at the Research Society on Alcoholism meeting in Santa Barbara, California. The organizers/chairs were Kristine M. Wiren and Deborah A. Finn. Following a brief introduction by Deborah Finn, the presentations were (1) The Importance of Gender in Determining Expression Differences in Mouse Lines Selected for Chronic Ethanol Withdrawal Severity, by Kristine M. Wiren and Joel G. Hashimoto; (2) Sex Differences in Ethanol Withdrawal Involve GABAergic and Stress Systems, by Paul E. Alele and Leslie L. Devaud; (3) The Influence of Sex on Ethanol Consumption and Reward in C57BL/6 Mice, by Kimber L. Price and Lawrence D. Middaugh; and (4) Sex Differences in Alcohol Self-administration in Cynomolgus Monkeys, by Kathleen A. Grant. [source] Reinforcement of Calcium Phosphate Cement by Bio-Mineralized Carbon NanotubeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007Xiupeng Wang Bio-mineralized carbon natotubes (CNTs) were prepared by soaking carboxyl functionalized CNTs in a simulating body fluid (SBF). A uniform hydroxyapatite layer was precipitated on the outer walls of CNTs after 7 days of soaking. The results showed that, by addition of the as-received CNTs and bio-mineralized CNTs, the compressive strength of the calcium phosphate cement (CPC) increased by 24% and 120%, respectively. The modified interfacial bonding between the bio-mineralized CNTs and CPC accounted for the significant improvement in the mechanical property by addition of the bio-mineralized CNTs as compared with the as-received CNTs. [source] Reinforcement of rigid PVC/wood-flour composites with multi-walled carbon nanotubesJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2008Omar Faruk Multi-walled carbon nanotubes (CNT) were compounded with PVC by a melt blending process based on fusion behaviors of PVC. The effects of CNT content on the flexural and tensile properies of the PVC/CNT composites were evaluated in order to optimize the CNT content. The optimized CNT-reinforced PVC was used as a matrix in the manufacture of wood-plastic composites. Flexural, electrical, and thermal properties of the PVC/wood-flour composites were evaluated as a function of matrix type (nonreinforced vs. CNT-reinforced). The experimental results indicated that rigid PVC/wood-flour composites with properties similar to those of solid wood can be made by using CNT-reinforced PVC as a matrix. The CNT-reinforced PVC did not influence the electrical and thermal conductivity of the PVC/wood-flour composites. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers. [source] Ionized-Air-Treated Curaua Fibers as Reinforcement for Phenolic MatricesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 6 2008Wanderson Gonçalves Trindade Abstract Curaua fibers were treated with ionized air to improve the fiber/phenolic matrix adhesion. The treatment with ionized air did not change the thermal stability of the fibers. The impact strength increased with increase in the fiber treatment time. SEM micrographs of the fibers showed that the ionized air treatment led to separation of the fiber bundles. Treatment for 12 h also caused a partial degradation of the fibers, which prompted the matrix to transfer the load to a poorer reinforcing agent during impact, thereby decreasing the impact strength of the related composite. The composites reinforced with fibers treated with ionized air absorbed less water than those reinforced with untreated fibers. [source] Chemically Extracted Cornhusk Fibers as Reinforcement in Light-Weight Poly(propylene) CompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 3 2008Shah Huda Abstract Flexural, impact resistance, tensile, and sound absorption properties of composites from cornhusk fiber (CHF) and PP have been investigated. The effect of holding temperature, CHF length, CHF concentration, and enzyme treatment of CHF on mechanical properties and the effect of the latter two on sound absorption have been studied. Compared with jute/PP composites, CHF/PP composites have similar impact resistance, 33% higher flexural strength, 71% lower flexural modulus, 43% higher tensile strength, 54% lower tensile modulus, and slightly higher noise reduction coefficient. Enzyme treatment of CHF results in increased mechanical and sound absorption properties. [source] Unmodified and Modified Surface Sisal Fibers as Reinforcement of Phenolic and Lignophenolic Matrices Composites: Thermal Analyses of Fibers and CompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2006Jane Maria Faulstich de Paiva Abstract Summary: The study and development of polymeric composite materials, especially using lignocellulosic fibers, have received increasing attention. This is interesting from the environmental and economical viewpoints as lignocellulosic fibers are obtained from renewable resources. This work aims to contribute to reduce the dependency on materials from nonrenewable sources, by utilizing natural fibers (sisal) as reinforcing agents and lignin (a polyphenolic macromolecule obtained from lignocellulosic materials) to partially substitute phenol in a phenol-formaldehyde resin. Besides, it was intended to evaluate how modifications applied on sisal fibers influence their properties and those of the composites reinforced with them, mainly thermal properties. Sisal fibers were modified by either (i) mercerization (NaOH 10%), (ii) esterification (succinic anhydride), or (iii) ionized air treatment (discharge current of 5 mA). Composites were made by mould compression, of various sisal fibers in combination with either phenol-formaldehyde or lignin-phenol-formaldehyde resins. Sisal fibers and composites were characterized by thermogravimetry (TG) and DSC to establish their thermal stability. Scanning electron microscopy (SEM) was used to investigate the morphology of unmodified and modified surface sisal fibers as well as the fractured composites surface. Dynamic mechanical thermoanalysis (DMTA) was used to examine the influence of temperature on the composite mechanical properties. The results obtained for sisal fiber-reinforced phenolic and lignophenolic composites showed that the use of lignin as a partial substitute of phenol in phenolic resins in applications different from the traditional ones, as for instance in other than adhesives is feasible. Micrograph of the impact fracture surface of phenolic composite reinforced with mercerized sisal fiber (500 X). [source] Polyhedral Oligomeric Silsesquioxane (POSS) Nanoscale Reinforcement of Thermosetting Resin from Benzoxazine and BisoxazolineMACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2005Qiao Chen Abstract Summary: The reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and 2,2,-(1,3-phenylene)-bis(4,5-dihydro-oxazoles) (PBO) over different temperature ranges was confirmed by FT-IR spectroscopy. The OAPS was used to modify benzoxazine (BZ) in the presence of PBO. The novel polybenzoxazine (PBZ)-PBO/OAPS hybrid nanocomposite was prepared by solvent methods. Dynamic mechanical analyses indicated that the nanocomposites exhibited much higher Tg values than the pristine PBZ and PBZ-PBO resin, and the storage modulus of the nanocomposites was maintained at higher temperatures, although only a small amount of OAPS was incorporated into the systems. Dynamic thermogravimetric analysis showed that the thermal stability of the hybrid was also improved by the inclusion of OAPS. DMA of PBZ (a), PBZ-PBO (b), and PBZ-PBO/OAPS nanocomposites (c,e). [source] Reinforcement of Biodegradable Poly(DL -lactic acid) Material by Equal-Channel Angular ExtrusionMACROMOLECULAR SYMPOSIA, Issue 1 2006Hongxiang Cui Abstract The purpose of this study was to reinforce biodegradable poly(DL -lactic acid) (PDLLA) material using a new method, equal-channel angular extrusion (ECAE). Different processing parameters, including the number of extrusion passes and the process temperature, were investigated to analyze their effect on the PDLLA properties. Experimental results indicate that the mechanical strength of PDLLA increased with the number of extrusion passes. The extrusion temperature also affected the mechanical strength of the PDLLA. After two ECAE passes, the bending strength of PDLLA increased from 83.3 to 178.7 MPa. The bending fracture mode for PDLLA changed from brittle failure for initial specimens to ductile fracture after ECAE processing. SEM micrographs showed that the longitudinal split surfaces of PDLLA are of a fibrillar structure. Taken together, the results suggest that ECAE might represent a useful approach for the preparation of reinforced PDLLA. [source] Corrosion of Steel Reinforcement in ConcreteMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2009Michael Raupach [source] Herstellung verbundverstärkter Aluminiumprofile für ultraleichte Tragwerke durch StrangpressenMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 7 2004M. Kleiner Extrusion; Aluminum; Continuously Reinforcement; Special Tool Abstract Auf Grund ähnlicher spezifischer Steifigkeits- und Festigkeitseigenschaften von Aluminium und Stahl lassen sich in der Anwendung bei leichten Rahmenstrukturen durch gegenseitige Werkstoffsubstitution nur geringe Leichtbaugewinne erzielen. Lediglich die Verwendung von z.,B. Kohlefaserwerkstoffen oder Höchstleistungsstählen lässt eine Gewichtsreduktion für den Einsatz von Rohren oder Profilen in ultraleichten Strukturen erwarten. Am Lehrstuhl für Umformtechnik (LFU) der Universität Dortmund ist ein Verfahren entwickelt worden, das durch ein modifiziertes Strangpressen zur Herstellung von Verbundprofilen geeignet ist. Ausgehend von konventionellen Aluminium-Pressblöcken werden hierbei verschiedenartige endlose Verstärkungselemente innerhalb der Wandstärke der Profilmatrix eingebettet. Für das Verfahren, das im Rahmen des Sonderforschungsbereiches SFB/TR10 erforscht wird, ist die Entwicklung neuartiger Strangpresswerkzeuge erforderlich. Durch experimentelle Untersuchungen auf einer 2,5 MN Laborstrangpresse wurden erfolgreich erste Verbundprofile hergestellt. Zur Vertiefung des Prozessverständnisses und der Prognose der Wirksamkeit neuer Werkzeugkonzepte wurden parallel FEM-Simulationen durchgeführt. Die mit Hilfe des Verfahrens hergestellten geraden Verbundprofile lassen sich auf Grund möglicher Gefügeschädigungen nicht biegen. In Kombination mit dem ebenfalls am LFU entwickelten Verfahren Runden beim Strangpressen werden diese Verbundprofile jedoch auch mit gekrümmter Kontur herstellbar sein. Manufacture of Extruded and Continuously Reinforced Aluminum Profiles for Ultra-Lightweight Constructions Due to similar specific properties of aluminum and steel regarding stiffness and mechanical strength only minor achievements as to their application in lightweight space-frame structures can be attained by substituting one material for the other. Only the usage of carbon fibre materials or high performance steels promises a weight reduction as to the application of pipes and profiles in ultra-lightweight structures. At the Chair of Forming Technology of the University of Dortmund a process has been developed which is suitable for the manufacturing of continuously reinforced profiles by means of a modified direct extrusion process. Starting from conventional aluminum billets, various continuously reinforcing elements are being embedded in the wall thickness of the profile matrix. For this process, which is being investigated in the context of the Collaborative Research Centre SFB/TR10, new extrusion dies have to be developed. During experimental studies on a 2.5 MN laboratory direct extrusion press first reinforced profiles were manufactured successfully. In order to improve the understanding of the process and to predict the efficiency of new tool concepts, FEM simulations were carried out simultaneously. Reinforced straight profiles produced with the help of this method cannot be bend due to possible damages to the microstructure. However, in combination with the process of Rounding During Extrusion, which also has been developed at the Chair of Forming Technology, these reinforced profiles will be producible with a curved contour as well. [source] Reinforcement of a thin plate by a thin layerMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2008Leila Rahmani Abstract We study the bending of a thin plate, stiffened with a thin elastic layer, of thickness ,. We describe the complete construction of an asymptotic expansion with respect to , of the solution of the Kirchhoff,Love model and give optimal estimates for the remainder. We identify approximate boundary conditions, which take into account the effect of the stiffener at various orders. Thanks to the tools of multi-scale analysis, we give optimal estimates for the error between the approximate problems and the original one. We deal with a layer of constant stiffness, as well as with a stiffness in ,,1. Copyright © 2007 John Wiley & Sons, Ltd. [source] Carbon Nanotubes Functionalized in Oxygen and Water Low Pressure Discharges used as Reinforcement of Polyurethane CompositesPLASMA PROCESSES AND POLYMERS, Issue S1 2009Lenka Zají, ková Abstract The functionalization of multi-walled CNTs in O2/Ar and H2O/Ar low pressure capacitive discharges was studied by XPS and FT-IR. The pristine and functionalized CNTs were used as fillers in polyurethane paints. Successful plasma functionalization was confirmed by changes in atomic composition and chemical shift of the XPS atomic signals. The functionalization was indicated also by the shift of IR absorption peaks corresponding to the motion of carbon skeleton, especially the peak at about 1,560,cm,1. The presence of carbonyl was confirmed by IR absorption peak at 1,723,cm,1 only for O2/Ar plasma. The plasma functionalized CNTs increased significantly the universal and plastic hardness of the CNTs reinforced polyurethane as compared to the composites with pristine CNTs. [source] Reinforcement of liquid ethylene,propylene,dicyclopentadiene copolymer based elastomer with vinyl functionalized multiwalled carbon nanotubesPOLYMER ENGINEERING & SCIENCE, Issue 7 2010Hongfu Zhou A methodology for reinforcement of liquid ethylene,propylene,dicyclopentadiene copolymer (liquid-EPDM) based elastomer with multiwalled carbon nanotubes (MWCNTs) was proposed. Acid-treated MWCNTs were first reacted with poly(acryloyl chloride) (PACl) leading to a grafted encapsulation, which were subsequently reacted with hydroxy ethyl acrylate (HEA) to generate vinyl groups. Thus obtained vinyl groups functionalized MWCNTs (vinyl-MWCNTs) were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The vinyl-MWCNTs were blended with liquid-EPDM and subjected to co-curing; an intercrosslinked structure was obtained via the free radical polymerization among the vinyl groups on vinyl-MWCNTs and the double bonds on liquid-EPDM. As a result, the vinyl-MWCNTs and the cured EPDM matrix were covalently linked. The chemical interfacial interaction between vinyl-MWCNTs and the cured matrix were observed by scanning electron microscope, which provided obvious reinforcement of elastomer. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers [source] Reinforcement of compatibilized NR/NBR blends by fly ash particles and precipitated silicaPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2009C. Kantala Abstract Effects of precipitated silica (PSi) and silica from fly ash (FA) particles (FASi) on the cure and mechanical properties before and after thermal and oil aging of natural rubber (NR) and acrylonitrile,butadiene rubber (NBR) blends with and without chloroprene rubber (CR) or epoxidized NR (ENR) as a compatibilizer have been reported in this paper. The experimental results suggested that the scorch and cure times decreased with the addition of silica and the compound viscosity increased on increasing the silica content. The mechanical properties for PSi filled NR/NBR vulcanizates were greater than those for FASi filled NR/NBR vulcanizates in all cases. The PSi could be used for reinforcing the NR/NBR vulcanizates while the silica from FA was regarded as a semi-reinforcing and/or extending filler. The incorporation of CR or ENR enhanced the mechanical properties of the NR/NBR vulcanizates, the ENR being more effective and compatible with the blend. The mechanical properties of the NR/NBR vulcanizates were improved by post-curing effect from thermal aging but deteriorated by the oil aging. Copyright © 2008 John Wiley & Sons, Ltd. [source] Dynamic Display, Propaganda, and the Reinforcement of Provincial Power in the Inca EmpireARCHEOLOGICAL PAPERS OF THE AMERICAN ANTHROPOLOGICAL ASSOCIATION, Issue 1 2004Dennis Ogburn A primary objective of the Inca state and other early empires was to maintain control over the inhabitants of conquered territories. In addition to overt tactics such as military force, resettlement, alliance formation, and cultural and economic integration, I suggest that many other activities of the Inca state also served to reinforce state power in the provinces. This was achieved by establishing and maintaining a "psychology of submission" in subject peoples through frequent reminders of imperial power, that is, advertising state control over labor. Display in this form was a major implicit element in various activities of the empire, such as the movement of armies, the transport of building stones from Cuzco to Ecuador, and the construction of imperial temples and palaces. These activities served as potent public demonstrations of the state's ability to mobilize large armies and control enormous amounts of labor. Propaganda also played a major role in maintaining the psychology of submission by disseminating information about those activities having an element of display and about other accomplishments of the state to people who did not witness them firsthand. Considered in light of these mechanisms of display and propaganda, many of the apparently wasteful activities of the Inca state can be understood as deliberate and integral to overall imperial strategies for maintaining control in the provinces. [source] Stem Cell Therapy as the Reinforcement of Organ RegenerationARTIFICIAL ORGANS, Issue 5 2005Dorota Fiszer Dr. No abstract is available for this article. [source] | ||||||||||||||||||||||||||||||||||||||||