bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of orexin-B-saporin-induced lesions of the lateral hypothalamus on performance on a progressive ratio schedule
Authors: Olarte-Sánchez CM , Valencia Torres L , Body S , Cassaday HJ , Bradshaw CM , Szabadi E
Published: September 2011

It has been suggested that a sub-population of orexinergic neurones whose somata lie in the lateral hypothalamic area (LHA) play an important role in regulating the reinforcing value of both food and drugs. This experiment examined the effect of disruption of orexinergic mechanisms in the LHA on performance on the progressive ratio schedule of reinforcement, in which the response requirement increases progressively for successive reinforcers. The data were analysed using a mathematical model which yields a quantitative index of reinforcer value and dissociates effects of interventions on motor and motivational processes. Rats were trained under a progressive ratio schedule using food-pellet reinforcement. They received bilateral injections of conjugated orexin-B-saporin (OxSap) into the LHA or sham lesions. Training continued for a further 40 sessions after surgery. Equations were fitted to the response rate data from each rat, and the parameters of the model were derived for successive blocks of 10 sessions. The OxSap lesion reduced the number of orexin-containing neurones in the LHA by approximately 50% compared with the sham-lesioned group. The parameter expressing the incentive value of the reinforcer was not significantly altered by the lesion. However, the parameter related to the maximum response rate was significantly affected, suggesting that motor capacity was diminished in the OxSap-lesioned group. The results indicate that OxSap lesions of the LHA disrupted food-reinforced responding on the progressive ratio schedule. It is suggested that this disruption was brought about by a change in non-motivational (motor) processes.
Resilience as a predictor of treatment response in patients with posttraumatic stress disorder treated with venlafaxine extended release or placebo
Authors: Davidson Jonathan , Stein Dan J , Rothbaum Barbara O , Pedersen Ron , Szumski Annette , Baldwin David S
Published: September 2011

This post-hoc analysis evaluated resilience as a predictor of treatment response in patients with posttraumatic stress disorder (PTSD). Data were pooled from two randomized, double-blind studies conducted with adult outpatients treated with flexible doses of venlafaxine extended release (ER) 37.5 to 300 mg/day or placebo. The 17-item Clinician-Administered Posttraumatic Stress Disorder Scale (CAPS-SX17) was the primary outcome measure. Baseline Connor–Davidson Resilience Scale (CD-RISC) scores for the 25-, 10-, and 2-item versions were used to predict changes in PTSD symptom severity at week 12 and symptomatic remission (CAPS-SX17 ≤ 20). Analyses were conducted for the overall population and separately for the individual treatment groups. In total, pretreatment resilience predicted a positive treatment response. For the overall population, all versions of the CD-RISC predicted CAPS-SX17 change scores and remission after controlling for variables such as treatment group and baseline symptom severity. For venlafaxine ER-treated patients, all versions of the CD-RISC were predictive of remission, but only the 10-item version was predictive of CAPS-SX17 change score. Our results suggest that higher pretreatment resilience is generally associated with a positive treatment response. Future research may be warranted to explore the relationship between response to active treatment and the spectrum of resiliency.
Fear-induced suppression of nociceptive behaviour and activation of Akt signalling in the rat periaqueductal grey: role of fatty acid amide hydrolase
Authors: Butler Ryan K , Ford Gemma K , Hogan Michelle , Roche Michelle , Doyle Karen M , Kelly John P , Kendall David A , Chapman Victoria , Finn David P
Published: September 2011

The endocannabinoid system regulates nociception and aversion and mediates fear-conditioned analgesia (FCA). We investigated the effects of the fatty acid amide hydrolase (FAAH) inhibitor URB597, which inhibits the catabolism of the endocannabinoid anandamide and related N-acylethanolamines, on expression of FCA and fear and pain related behaviour per se in rats. We also examined associated alterations in the expression of the signal transduction molecule phospho-Akt in the periaqueductal grey (PAG) by immunoblotting. FCA was modelled by assessing formalin-evoked nociceptive behaviour in an arena previously paired with footshock. URB597 (0.3 mg/kg, i.p.) enhanced FCA and increased fear-related behaviour in formalin-treated rats. Conditioned fear per se in non-formalin-treated rats was associated with increased expression of phospho-Akt in the PAG. URB597 reduced the expression of fear-related behaviour in the early part of the trial, an effect that was accompanied by attenuation of the fear-induced increase in phospho-Akt expression in the PAG. Intra-plantar injection of formalin also reduced the fear-induced increase in phospho-Akt expression. These data provide evidence for a role of FAAH in FCA, fear responding in the presence or absence of nociceptive tone, and fear-evoked increases in PAG phospho-Akt expression. In addition, the results suggest that fear-evoked activation of Akt signalling in the PAG is abolished in the presence of nociceptive tone.
Associations between lipid levels and migraine: Cross-sectional analysis in the Epidemiology of Vascular Ageing Study
Authors: Rist Pamela M , Tzourio Christophe , Kurth Tobias
Published: September 2011

Background: Migraine with aura has been associated with increased prevalence of cardiovascular risk factors, including elevated levels of some vascular biomarkers. However, little research has been done on this association among the elderly. We examined the associations of lipid levels with headache and migraine in a cohort of elderly individuals.

Methods: Cross-sectional study among 1155 participants enrolled in the Epidemiology of Vascular Ageing Study with available information on headache and blood biomarkers. We used multinomial logistic regression to evaluate the association between biomarker tertiles and headache categories.

Results: 925 people had no severe headache, 64 people had non-migraine headache and 166 people had migraine, of whom 23 had aura. Compared with participants without headache, we observed strong associations between increasing tertiles of total cholesterol and migraine with aura. The odds ratio (95% confidence interval) was 4.67 (0.99–21.97) for the 2nd tertile and 5.97 (1.29–27.61) for the 3rd tertile. We also found strong associations between triglycerides and migraine with aura (odds ratio for 3rd tertile: 4.42 (1.32–14.77)). We did not see significant associations between increased biomarker levels and any other headache group.

Conclusions: Elevated levels of total cholesterol and triglycerides are associated with migraine with aura but not other headache forms in the elderly.
Supramolecular Self-assembly of Monoend-functionalized Methoxy Poly(ethylene glycol) and α-Cyclodextrin: From Micelles to Hydrogel
Authors: Long Youyu , Song Hongmei , He Bin , Lai Yusi , Liu Rong , Long Chunyan , Gu Zhongwei
Published: September 2011

An effective strategy was developed to fabricate a supramolecular hydrogel with the complexation of α-cyclodextrins (α-CDs) and monoend-functionalized low molecular weight methoxy poly(ethylene glycol) (mPEG, Mn=2000) micelles. Hydrophobic cinnamic acid was immobilized on methoxy poly(ethylene glycol) via L-lysine as linker to prepare amphiphilic mPEG. The monoend-functionalized mPEG self-assembled micelles in aqueous solution. The size and size distribution of the micelles were tested by dynamic laser scattering (DLS). The morphology of the micelles was observed by SEM, TEM and AFM. The critical micelle concentration (CMC) was tested and it was 42.5 mg/L. The monodisperse micelles had core-shell structure and the mean diameter was around 40 nanometers. α-cyclodextrins were added in the suspension of micelles to form supramolecular hydrogel with the polypseudorotaxanes complexation. Hydrophilic drug doxorubicin hydrochloride was used as model drug to study the release profile. The results showed that the hydrogel was a promising carrier for drug delivery.
Review paper: Critical Issues in Tissue Engineering: Biomaterials, Cell Sources, Angiogenesis, and Drug Delivery Systems
Authors: Naderi Hojjat , Matin Maryam M. , Bahrami Ahmad Reza
Published: September 2011

Tissue engineering is a newly emerging biomedical technology, which aids and increases the repair and regeneration of deficient and injured tissues. It employs the principles from the fields of materials science, cell biology, transplantation, and engineering in an effort to treat or replace damaged tissues. Tissue engineering and development of complex tissues or organs, such as heart, muscle, kidney, liver, and lung, are still a distant milestone in twenty-first century. Generally, there are four main challenges in tissue engineering which need optimization. These include biomaterials, cell sources, vascularization of engineered tissues, and design of drug delivery systems. Biomaterials and cell sources should be specific for the engineering of each tissue or organ. On the other hand, angiogenesis is required not only for the treatment of a variety of ischemic conditions, but it is also a critical component of virtually all tissue-engineering strategies. Therefore, controlling the dose, location, and duration of releasing angiogenic factors via polymeric delivery systems, in order to ultimately better mimic the stem cell niche through scaffolds, will dictate the utility of a variety of biomaterials in tissue regeneration. This review focuses on the use of polymeric vehicles that are made of synthetic and/or natural biomaterials as scaffolds for three-dimensional cell cultures and for locally delivering the inductive growth factors in various formats to provide a method of controlled, localized delivery for the desired time frame and for vascularized tissue-engineering therapies.
In vitro antibacterial activity and cytocompatibility of bismuth doped micro-arc oxidized titanium
Authors: Lin Dan-Jae , Tsai Ming-Tzu , Shieh Tzong-Ming , Huang Heng-Li , Hsu Jui-Ting , Ko Yi-Chun , Fuh Lih-Jyh
Published: September 2011

Chemical manipulations of the implant surface produce a bactericidal feature to prevent infections around dental implants. Despite the successful use of bismuth against mucosal and dermis infections, the antibacterial effect of bismuth in the oral cavity remains under investigation. The aim of this study was to evaluate the antibacterial activities of bismuth compounds against Actinobacillus actinomycetemcomitans, Staphylococcus mutans, and methicillin-resistant Staphylococcus aureus (MRSA), and to investigate the antimicrobial effects of bismuth doped micro-arc oxidation (MAO) titanium via an agar diffusion test. Cell viability, alkaline phosphatase activity, and mineralization level of MG63 osteoblast-like cells seeded on the coatings were evaluated at 1, 7, and 14 days. The results demonstrate that bismuth nitrate possess superior antibacterial activity when compared with bismuth acetate, bismuth subgallate, and silver nitrate. The bismuth doped MAO coating (contained 6.2 atomic percentage bismuth) had good biological affinities to the MG63 cells and showed a higher antibacterial efficacy against Actinobacillus actinomycetemcomitans and MRSA, where the reduction rates of colony numbers is higher than that of the control group by 1.5 and 1.9 times, respectively. These in vitro evaluations demonstrate that titanium implants with bismuth on the surface may be useful for better infection control.
Proliferation of meniscal fibrochondrocytes cultured on a new polyurethane scaffold is stimulated by TGF-β
Authors: de Mulder Eric LW , Hannink Gerjon , Giele Maud , Verdonschot Nico , Buma Pieter
Published: September 2011

The aim of this study was to investigate if newly developed polyurethane (PU) scaffolds are suitable as scaffold for cell-seeded meniscus tissue engineered constructs. Scaffolds were seeded with goat meniscal fibrochondrocytes and cultured to assess changes in biological and mechanical properties. Furthermore, the effect of TGF-β on these properties was investigated. PU scaffolds were made from poly d/l lactide and caprolactone as soft segments and 1,4-butanediisocyanate for the urethane hard segments. The porosity of the scaffolds was 95%. Isolated goat meniscal fibrochondrocytes were seeded on the scaffolds and cultured with or without the addition of 10 ng/mL TGF-β in standard culture medium. After 2, 4, and 6 weeks of culture, scaffolds were analyzed for cell proliferation, matrix synthesis, and mechanical properties. Scanning electron microscopy and histology showed that the scaffolds had an interconnected isotropic pore structure. Without the addition of TGF-β, cells did not proliferate during the culture period and isolated meniscus fibrochondrocytes were more frequently located in the peripheral parts of the scaffold. Fibrochondrocytes supplemented with TGF-β were distributed throughout the construct. Clustered cells were surrounded by matrix which stained slightly positive for glycosaminoglycans (GAGs). Also, collagen production was increased significantly after 4 and 6 weeks of culture compared to cultures without TGF-β and also more GAG staining was found after 4 and 6 weeks in the sections of the TGF-β stimulated cultures. Despite the increase in matrix production, the compressive stiffness of the constructs was not increased during the culture period. Meniscal fibrochondrocytes were able to adhere to the PU scaffold. However, the scaffold itself does not stimulate proliferation and matrix production. The addition of TGF-β resulted in a strong induction of both proliferation and extracellular matrix production.
Assessing the Effects of Technical Variance on the Statistical Outcomes of Web Experiments Measuring Response Times
Authors: Brand Andrew , Bradley Michael T.
Published: September 2011

A simulation was conducted to assess the effect of technical variance on the statistical power of web experiments measuring response times. The results of the simulation showed that technical variance reduced the statistical power and the accuracy of the effect size estimate by a negligible magnitude. This finding therefore suggests that researchers’ preconceptions concerning the unsuitability of web experiments for conducting research using response time as a dependent measure are misguided.
Children’s art: Work or play? Preschoolers considering the economic questions of their theatre performance
Authors: Stolp Marleena
Published: September 2011

During their theatre project, a group of 6-year-old children tried to pursue the role of active actors, decision-makers and producers. For them their theatrical activity was viewed as work, despite the fact that adults tend to count it as play. Children were also eager to earn from their performance. Money was a sign of appreciation and status, and it determined for its part children’s position as genuine actors in an artistic project. The article considers whether some of children’s activity could be understood as work.
A generalisation of Altmann's linkage
Authors: Baker J E
Published: September 2011

The overconstrained six-bar kinematic chain bearing Altmann's name has been extensively explored, but it has resisted complete understanding because of an apparent contradiction in its relationship with Bricard's trihedral linkage. This difficulty can now be easily surmounted, and the study of the broad characteristics of Altmann's loop can be expanded to treat a less restricted six-bar. The article deals with these matters in a manner intended to assist the reader in appreciating the value of the analytical procedures adopted. As well, a special case of Altmann's linkage is examined to reveal a rare kind of symmetry.
Synthesis of cam profile using classical splines and the effect of knot locations on the acceleration, jump, and interface force of cam follower system
Authors: Chavan U , Joshi S
Published: September 2011

Large positive acceleration against a load creates cam follower interface force that can cause excessive wear. Negative acceleration tends to reduce the cam follower interface force, and if the negative acceleration is sufficiently large, jump between the cam and follower can occur. Hence, these are the two main concerns of cam designers. This study presents a new approach to adjust the acceleration, interface force, and jump in the early phase of cam design. Knot locations of polynomial pieces of spline curves are considered as design variables which gives variety of cam profiles. Here, design process starts from displacement profile and there is no need for predefined acceleration curves. A single dwell cam displacement function is defined by classical spline curve, made up of four polynomial pieces that are tied together at their ends, called knots. Specifications of these knots are considered for synthesis and analysis of cam follower system. Mathematical relation between interface force and knot locations is presented as wear and jump models. These models are useful to reduce wear and jump by proper placement of the knots on the basis of interface force. By dynamic simulation of cam follower system, cam curves are drawn for different cases of knot locations and good resemblance was found with theoretical curves. This study suggests the cam designers have the added option to control the kinematic and dynamic quantities without changing the physical parameters of cam follower system.
Deformation and mechanical analyses of silo foil tube
Authors: Fenyvesi L , Bellus Z , Csorba L , Csatár A
Published: September 2011

This research represents one piece of the modern storage and conservation technology, where the fermentation and the long-life conservation of the product have been realized through filling it into plastic tubes. The previously made investigations in the literature are basically dealing with the technical applicability of various machinery and facilities; therefore, this research focused on the conservation technology and the geometric and mechanic analyses of filled foil tubes.

The mechanical and deformation investigations of the foil tubes filled with winter barley were carried out in our laboratory as well as on the field. The most important static features of the foil samples were determined in our laboratory and all other properties were field-tested to promote our further deformation calculations. The change in the cross-section of a foil tube was analysed through an elliptic line fitted on the measurement points.

The radius of the osculating circle was calculated at discrete points in time; furthermore, the cross-strain of a given foil was measured, too, which helped us to determine the specific strain and stress values close to the above measurement points. After the radii of the osculating circles fitted on some chosen measurement points were determined, the filling load under the foil shell could have been calculated. The partial rheological analysis of the filled foil tubes at this point seemed to be the most effective.
A study on the effect of the rake angle on the performance of marine propellers
Authors: Hayati A N , Hashemi S M , Shams M
Published: September 2011

In this study, the open water performance of three propellers with diverse rake angles was investigated by computational fluid dynamics method. The objective of this study was to find out the influence of the rake angle on the performance of conventional screw propellers. For this purpose, first, the obtained results for three B-series propellers were validated against the empirical results and then by modifying the rake angle, different models were investigated by the same method. Flow characteristics were examined for the models and the evolvement of vortices on different planes around the propeller were compared. The results suggest that in case of conventional screw propellers with linear rake distribution, while the effect of the rake angle on the propeller efficiency is not significant, the augmentation of this parameter improves the propeller thrust, especially at high propeller loads, but at the same time, the required torque increases, which is not desirable for the propeller design process.
Study on the generation of spiral bevel gears with spherical involute tooth profile by the tracing line
Authors: Zhang X C , Wang X , Yu L J , Yang Z J
Published: September 2011

In this article, a new gear generating method for the spiral bevel gear with spherical involutes tooth curves was proposed. It was analysed that the tooth flank with cone-spiral involute surface could be formed by the space trajectory of a straight line. The straight line was named as a tracing line. In the method, three motions were demanded; those were the rotary motion of the workpiece, the rectilinear motion of the end of the tracing line along the dedendum, and the rotary motion of the tracing line in the plane. The motion equations were derived. The plate milling cutter with face cutting edges could be used to machine the spiral bevel gears and the chord line of the face circle worked as the tracing line. By the method, the spiral bevel gears without principle errors whose tooth flanks are exact spherical involute curves that could be achieved.
Mechanical behaviour of bistable struts
Authors: Cai J G , Xu Y X , Feng J , Zhang J
Published: September 2011

The mechanical behaviour of a bistable structural element, which is based on the snap-through and bifurcation properties of the von Mises truss, has been investigated in this article. By assuming the joint behaviour as ideal hinges and using the large deformation theory based on a linear elastic material, a simple analytical model for the stability of the von Mises truss was formulated. The governing set of non-linear equilibrium equations was obtained by applying the principle of stationary total potential energy. Then, the formulae of the snap-through and bifurcation buckling loads and the equilibrium path were given. In addition to the well-known cases of primary and secondary branches, a third type that the bifurcation buckling point lying on the descending branch of the load versus displacement curve was discussed. In this case, although its upper bifurcation load is lower than its upper snap-through buckling load, the truss experiences a symmetric snap-through mode first, and hence the bifurcation point is not physically relevant. Finally, the assumptions of the classical von Mises truss analysis are discussed.
Development and validation of a model for wall-flow type selective catalytic reduction system
Authors: Park S-Y , Rutland C J , Narayanaswamy K , Schmieg S J , He Y-S , Brown D B
Published: September 2011

The two-way diesel particulate filter (DPF)/selective catalytic reduction (SCR) emissions-reduction system has recently been extensively studied due to its potential cost savings and packing flexibility. Unlike a conventional emissions-reduction system that consists of a DPF and an SCR for reduction of both particulate matter and nitrogen oxides (NO x), this two-way system incorporates SCR function into a wall-flow DPF as a single device by coating SCR catalysts into the filter wall of the DPF. Such a combinatorial system has the advantage of lower system volume and cost, since exhaust gas undergoes soot filtering and NO x reduction reaction simultaneously as it passes through the channels and filter wall. In this work, the mathematical formulations which govern the physical and chemical phenomena in the two-way DPF/SCR are derived and a computer simulation model is developed based on these formulations. The model has been validated and tested with experimental data from a reactor flow bench in a systematic manner, which captures ammonia adsorption/desorption and NO x reduction of the blended two-way DPF/SCR device.
A study on axle gear whine noise reduction with deflection test
Authors: Choi B-J , Yoon J-H , Oh J-E
Published: September 2011

Hypoid gears are used in rear drive and four-wheel drive (4WD) vehicle axles. For this reason, hypoid gear whine noise has long been recognized as a problem, but there have been few or no studies of problem-solving techniques or procedures. This study analysed the possible causes of hypoid gear whine noise for its reduction and investigated the data that should be considered for the optimal shape design of hypoid gears in axle-based vehicles and the procedures for using the data for optimization. For these purposes, a hot deflection test was performed, using an actual gear mounting and the temperature of a cast-aluminium axle housing, with completely processed gear. This test covered the operating range of gear loads, from ‘no load’ to ‘peak load’. Under peak load conditions, the contact pattern extended to the tooth boundaries without showing a concentration at any point on the tooth surface. The transmission error was tested on an axle assembly triaxial real car load and at the correct temperature condition of the axle housing.
Subcooled boiling heat transfer modelling for internal combustion engine applications
Authors: Li Z , Huang R-H , Wang Z-W
Published: September 2011

Any boiling-based strategy in developing cooling systems of internal combustion (IC) engines requires an accurate prediction of coolant-side heat transfer. The computational fluid dynamics (CFD) simulation incorporating subcooled boiling models is an effective approach for such analyses. However, most of the existing models are developed in some special flow and boiling conditions differing from that in IC engines, which inevitably leads to great discrepancies when they are directly applied to CFD analyses inside IC engine cooling galleries.

A modified model with adjustable parameters is proposed based on the division description method in this paper. The predicted heat fluxes by different boiling models are compared against experimental data obtained in a cooling gallery simulator passage. The results indicate that a higher precision can be obtained by the modified model in predicting the boiling heat flux over a wide range of operating conditions as long as the parameters are accurately corrected. The performance of the modified model for practical IC engine applications is further assessed and the results show that the computational error is effectively reduced due to the incorporation of the modified model in the conjugate heat transfer simulation of the cylinder head and cylinder head cooling gallery.
Brake judder analysis using a car rigid–flexible coupling model
Authors: Chen S M , Wang D F , Zan J M
Published: September 2011

In order to understand the brake judder of a passenger car, the brake judder test of a passenger car was performed with initial speeds of 90, 120, and 150 km/h, end speed of 20  km/h, and pedal forces of 25, 30, 35, and 40 N on a roller dynamometer in a semi-anechoic chamber. The pressure fluctuation of the brake fluid pipe was presented. The accelerations of the steering wheel were recorded at vertical, lateral, and radial directions respectively, and the frequency analysis of the brake judder was also performed. The frequency response functions of the steering system were measured in order to understand the cause of the brake judder. Meanwhile, the multibody system dynamics model of the test vehicle was created with a flexible body and steering system. The brake torque calculated with the brake fluid pressure of the brake pipe in the brake judder test was exerted on the brake systems. The simulated accelerations of the steering wheel were calculated at three different directions, and the frequency analysis of the brake judder was also presented. The design of experiment was presented in order to reduce the brake judder and improve the comfort of the vehicle. An orthogonal array table was designed with 13 factors and 3 levels. The optimum combination was confirmed. The brake judder was also simulated, and the accelerations of the steering wheel were also calculated. Furthermore, the optimization results were verified by the brake judder test. The verification of the optimization indicates that the optimization results are correct and effective.
An approximate non-linear model for aeroengine control
Authors: Yu D , Zhao H , Xu Z , Sui Y , Liu J
Published: September 2011

Control-oriented non-linear modelling is the requirement of reliable non-linear control for aeroengines. The complex engine model must be simplified such that advanced non-linear control techniques can be applied. Some simplified engine models lose the physical interpretability, and further, the analysability of stability and performance of the real closed-loop system, which eventually hinders their industrial implementation. Linear parameter-varying model attains certain success in aeroengine control in recent years, but its potential drawback has also been proposed in theoretical research. This article proceeds to reveal this problem from a model perspective. Then, an approximate non-linear model for aeroengine control is introduced, followed by an identification procedure for more efficient modelling. Simulations show good precision of this model in capturing the non-linear behaviour of a turbofan engine. Theoretically, controllers designed with this model can guarantee local stability and performance for the real plant.
Flame stabilization in a supersonic combustor with hydrogen injection upstream of cavity flame holders: experiments and simulations
Authors: Sun M-B , Wu H-Y , Fan Z-Q , Wang H-B , Bai X-S , Wang Z-G , Liang J-H , Liu W-D
Published: September 2011

Experimental observations and numerical simulation were conducted to study the flame characteristics and flame stabilization mechanism in a supersonic combustor with hydrogen injection upstream of cavity flame holders. OH radical distribution of the reacting flowfield was obtained using OH spontaneous emission and OH-PLIF (planar laser-induced fluorescence). The supersonic combustion flowfield with L/ D = 7 cavity was calculated by large eddy simulation. The turbulence–combustion interaction model was based on a partially premixed flamelet model with a level-set approach. The results showed that hydrogen fuels were transported into the cavity shear; lean mixture and rich mixture were produced in the internal cavity and the declining jet, respectively. An approximately steady partially premixed flame front exists in the cavity shear layer. The flame front propagates and extends to the region around the fuel jet due to the interaction of counter-rotating vortices induced by the jet with the cavity shear layer. The flame front sustained in the shear layer likely penetrates the jet core and ignites the whole jet. Behind the flame front, most of the jet beam is burned as diffusion flames. The physical process of the flame stabilization demonstrated the similarity with triple flame characteristics, which indicted that triple flame theory might be the basic flame stabilization mechanism of the cavity flame holders.
A cooperative guidance law for target estimation by multiple unmanned aerial vehicles
Authors: Lee W , Bang H , Leeghim H
Published: September 2011

A new cooperative guidance law is proposed for target estimation of multiple unmamed aerial vehicles (UAVs) without involving numerical computational work. The guidance law derivation is based upon the Fisher Information Matrix (FIM) to quantify the amount of target information. For two UAVs, an analytical one-step determinant of FIM is introduced, which sufficiently reflects the trend of previous well-known optimal manoeuvers. Therefore, by considering only one-step information, as opposed to accumulated total information, a new feedback guidance law with intuitive physical analysis is induced and then its validity is verified by comparing it with the results of previous approaches. To apply the proposed idea to more multiple UAVs, a generalized formulation is derived as a weighted combination of each guidance law. Also, for more realistic application, the proposed guidance law is modified to deal with an avoidance problem of risk zone.
Detection of delamination in cross-ply composite-laminated beams utilizing irregularity of mode shapes
Authors: Bazardehi S R Kazemi , Kouchakzadeh M A
Published: September 2011

In this study, irregularities of the mode shapes are utilized to determine the delamination situation in a composite laminated beam. Modal analysis is used to obtain the mode shapes of the beam; afterwards, the mode shapes are filtered to extract their irregularities. Presence of any delamination and its situation (number, size, and location along the length and thickness of the beam) affect the extracted irregularities. Here, detection of delamination is based on these irregularities of the mode shapes. One of the most important advantages of this method is that unlike many other similar methods, in many cases, the mode shapes of the damaged beam are sufficient and the mode shapes of the intact beam are not required. The method is validated by utilizing the analytical and numerical data for a delaminated beam model. As it will be illustrated, the method can be applied to obtain a very reasonable approximation on the presence of delamination, its size, its location along the length, and number of delaminations for various boundary conditions. In addition, the results show that at least about 15 points of data measurement are required along the length of the beam, and the interval of the points should not exceed 1.5 times the delamination size to be detected.
Two-dimensional stress analysis of the aircraft hydraulic system pipeline
Authors: Ouyang X P , Gao F , Yang H Y , Wang H X
Published: September 2011

Pipeline vibration in aircraft hydraulic systems has drawn more attention in recent years. There are still a lot of problems unresolved in the field, due to the complex non-linearity of fluid–structure interaction. Two-dimensional stress analysis of pipeline in an aircraft hydraulic system has been carried out in this study. As the classical theory on the fluid-filled pipe is based on one-dimensional model, a two-dimensional model has been developed to study the stress distribution around the section vertical to the pipe axis, which affects the fatigue life of the pipeline. Influences of curvature and stress concentration have been included in the model. Three-dimensional finite element method model for a pipe section between the pump and the first pressure filter in backup system of the aircraft hydraulic system has been constructed to improve the one-dimensional theoretical model. Simulation and experimental results can match each other well in stress analysis. Some discussion about the parameters in the developed theory model is given.
Effect of the tip clearance variation on the performance of a centrifugal compressor with considering impeller deformation
Authors: Wang H-L , Xi G , Li J-Y , Yuan M-J
Published: September 2011

The effects of impeller tip clearance variation on centrifugal compressor performance have been investigated experimentally and numerically in a centrifugal compressor. In order to accurately calculate the real tip clearance, the influence of impeller geometry deformation caused by the thermal load (temperature variation) and mechanical loads (aerodynamic pressure and centrifugal force) under working condition on the compressor aerodynamic performance is taken into account by fluid/solid interaction method during the computational fluid dynamics flow field analysis process. In this article, tip clearance flow under the real working environment is investigated with three different tip clearance cases. The impeller deformation combined with the adjustment of tip clearance causes some influence on the aerodynamic performance and on the structure reliability of the compressor system. For the aerodynamic design, an increase in the impeller tip clearance decreases the overall pressure rise and isentropic efficiency of the compressor, mainly due to the tip clearance loss in the impeller. Regarding structure design, the uniform relative tip clearance from the inlet to the outlet CR = 7.3 per cent is changed to non-uniform distribution from 6.4 per cent to 4.15 per cent. The largest deformation location occurs at the blade inducer and trailing-edge tip. The relative clearance near the outlet of the blade is reduced about 3.15 per cent which will cause great influence on the impeller working reliability.
Robust partial control design for non-linear control systems: a guidance application
Authors: Binazadeh T , Yazdanpanah M-J
Published: September 2011

In this paper, a general approach for robust partial stabilization of uncertain non-linear systems is presented. In this approach, the non-linear dynamic system is divided into two subsystems, called the first and the second subsystems. This division is done based on the required stability properties of the system’s states. The reduced input vector (the vector that includes components of the input vector appearing in the first subsystem) is designed to asymptotically stabilize the first subsystem. The proposed scheme is then applied for designing a guidance law as a potential application. Indeed, the paper presents a new approach to the missile guidance problem and shows that asymptotic stability behaviour is not realistic for all states of the guidance system. The effectiveness of the proposed guidance law in interception of manoeuvring targets is demonstrated analytically and through computer simulations.
Novel adaptive fuzzy neural network controller for a class of uncertain non-linear systems
Authors: Shih K S , Li T H S , Tsai S H
Published: September 2011

In this paper, an adaptive fuzzy neural network (AFNN) controller with a state observer approach based on novel adaptive particle swarm optimization-simulated annealing (NAPSO-SA) for a class of non-linear systems is proposed. First, NAPSO-SA is used to adjust the parameters of the FNN, while adaptive laws are used to approximate unknown non-linear functions and the unknown upper bounds of uncertainties respectively. Second, a state observer is applied for estimating all states that are not available for measurement in the system. By using the strictly-positive-real (SPR) stability theorem, the proposed controller not only guarantees the stability of a class of non-linear systems but also maintains good tracking performance. The novel intelligence algorithm generates optimal parameters for the control schemes and is developed to guarantee the asymptotically stability of the system. Finally, simulation results substantiate the fact that the proposed method stands out as offering better properties than the observer-based adaptive fuzzy control (OBAFC) for tracking performance.
Fault-tolerant H∞ control for active suspension vehicle systems with actuator faults
Authors: Li H , Gao H , Liu H , Liu M
Published: September 2011

This paper investigates the problem of fault-tolerant H∞ control for a class of quarter-car active suspension systems with actuator faults. The corresponding state-space form is established via taking into account the active suspension system performance: namely, ride comfort, road holding, suspension deflection, and maximum actuator force limitation for control strategy. Different from the traditional actuator model, in this paper, the actuator failures are modelled as random variables governed by a homogeneous Markov chain. A fault-tolerant H∞ controller is designed such that the resulting control system is reliable since it has the capability of guaranteeing asymptotic stability and H∞ performance, and simultaneously satisfying the constraint performance in the scenarios of three types of actuator failures. Simulation results are provided to illustrate the effectiveness of the proposed controller design methodology.
Approximate synchronization of two non-linear systems via impulsive control
Authors: Wang J , Tang W S , Zhang J X
Published: September 2011

In this paper, the approximate synchronization problem of two non-identical non-linear systems is investigated. Based on the impulsive control method, a sufficient condition is given to guarantee the approximate synchronization. Furthermore, the optimal impulsive interval problem is studied which can reduce the cost of impulsive controller, and the maximum impulsive interval is obtained by solving a non-linear optimization problem via a mixed algorithm combining chaos optimization and linear matrix inequality method. Two different chaotic systems and two different complex dynamical networks are presented respectively to verify the effectiveness of the proposed methods.
Language Anxiety
Authors: Cheng Rui , Erben Antony
Published: September 2011

It is very common for Chinese graduate students to experience language anxiety in the U.S. higher institutions, yet the literature on this topic is limited. This research study focused on the influence of the length of stay in U.S. higher institutions, various programs, gender, and acculturation process on Chinese graduate students’ language anxiety levels from 156 students in a public university in the United States. Mixed methods were applied and the results showed that students who stayed longer and were in art-related majors had the lowest anxiety. What also revealed from this study was that gender and acculturation did play some roles on language anxiety levels. The findings of this research enriched the list of variables correlated with language anxiety. The educational implications of these findings were also discussed.
Academic Mobility, Language, and Cultural Capital
Authors: Pherali Tejendra Jnawali
Published: September 2011

This article is concerned with the experiences of transnational academics teaching and researching in British higher education institutions (HEI). Although there is a plethora of studies related to the issues of international students and Western academics teaching abroad, very little has been written about the recent global phenomenon in which academics from non-English-speaking backgrounds move to English universities. This underresearched area is explored drawing on an in-depth study considering the cases of seven international academics in five different universities. The study identifies a range of their distinctive experiences which constitutes an exigent “field” in their struggle to adapt to the new cultural setting. The “logistic challenges” may exist but are transitory. Although providing an opportunity for professional development is helpful, “the offer of support” is a sensitive notion and may be perceived as a threat to both their status and identity.
Structural Damage Identification with Performance-based Uncertainty Quantification and Feedback Control
Authors: Lew Jiann-Shiun
Published: September 2011

This article presents an investigation of damage detection of a structure with significant uncertainty. The proposed approach integrates the performance-based uncertainty quantification and feedback control techniques for damage identification. A singular value decomposition (SVD) technique is used to decompose parameter variations into principal components that are weighted with the sensitivity of the performance metric for damage identification. This SVD technique can be used to differentiate between dominant uncertainties and minor uncertainties corresponding to damage identification. To improve the performance of damage identification under uncertainty, a feedback controller is incorporated into the structure to reduce the effect of the quantified uncertainty. The probability framework, based on Monte Carlo simulation, is used to predict the false identification of damage. Examples based on the structural dynamics challenge problem issued by Sandia National Laboratories are used to demonstrate the proposed techniques.
Numerical simulation of hybrid composite shape-memory alloy wire-embedded structures
Authors: Ryu Junghyun , Jung Beom-Seok , Kim Min-Saeng , Kong JungPyo , Cho MaengHyo , Ahn Sung-Hoon
Published: September 2011

The large recovery force and non-linear deformation behaviour resulting from a change in the temperature in shape-memory alloys (SMAs) make them attractive materials for applications in smart materials and structures, as well as actuators. However, SMAs are limited in their application because they cannot support general loads such as bending or compression. SMA wire-embedded composite materials, where materials such as glass fibre reinforced plastics (GFRPs) are combined with SMAs, are proposed to overcome these limitations. However, the increased stiffness of GFRPs limits the deformation that can be achieved. The inclusion of more compliant materials, such as silicon rubber, into the matrix can improve the achievable deformation, and the characteristics of the resulting hybrid composite can be controlled by varying the conformation of the material. In this study, a numerical simulation method was developed to predict the deformation behaviour of SMA wire-embedded hybrid composites. To verify the simulation procedure, several conformations of SMA wire-embedded hybrid composites were fabricated, and their deformation behaviours were compared with the simulation results. The simulation was then used to achieve a favourable trade-off between the stiffness and the achievable deformation of the structure.
Posthospital Heart-Healthy Behaviors in Adults With Comorbid Diabetes
Authors: Vanden Bosch Melodee L. , Corser William D. , Xie Yan , Holmes-Rovner Margaret
Published: September 2011

The purpose of these secondary analyses was to examine relationships between patient factors and patient-provider decision-making style (PDM) on heart-healthy behavior changes in 142 adults with diabetes after hospitalization for an acute coronary syndrome (ACS). A clinical trial randomized adults to either control or a telephone coaching intervention. Generalized estimating equations were used to analyze the relationship between patient factors and PDM style on longitudinal postdischarge changes in three heart-healthy behaviors, avoiding high fat foods, weight loss, and increased physical activity. Neither PDM style nor telephone coaching intervention affected heart-healthy behaviors in this population. Although adults with diabetes preferred collaborative patient-provider decision-making, present levels of provider engagement were not sufficient to support behavior change. Results suggest the need for sustained and tailored nursing interventions to facilitate heart-healthy behavior changes in adults with diabetes after ACS hospitalization.
Self-Care and Health Outcomes of Diabetes Mellitus
Authors: Song MinKyoung , Ratcliffe Sarah J. , Tkacs Nancy C. , Riegel Barbara
Published: September 2011

Studies show that self-care improves diabetes mellitus (DM) outcomes; however, previous studies have focused on self-care maintenance, and little is known about self-care management. The objective of this study is to examine the influence of DM self-care maintenance and management on number of hospitalizations and hospitalization days. A cohort design with secondary analysis of data from the Health and Retirement Study 2002-2004 was used. Data from 726 adults with DM were analyzed with logistic regression and negative binomial regression adjusting for covariates. Self-care maintenance and management were significant determinants of hospitalization outcomes. Establishing a goal for HbA1c (self-care management) and eating ≥2 snacks or desserts per day (self-care maintenance) were associated with a decrease in hospitalizations (IRR = 0.860, p = .001; IRR = 0.914, p = .043, respectively). DM self-care maintenance and management influence health outcomes but in different ways. These data provide evidence that both elements are needed in the education of patients about DM.