bluuebunny/crossref_metadata_2025 huggingface dataset:
New Beginnings: Evidence That the Meditational Regimen Can Lead to Optimization of Perception, Attention, Cognition, and Other Functions
Authors: Bushell William C.
Published: August 2009

A “framework” is presented for understanding empirically confirmed and unconfirmed phenomena in the Indo‐Tibetan meditation system, from an integrative perspective, and providing evidence that certain meditative practices enable meditators to realize the innate human potential to perceive light “at the limits imposed by quantum mechanics,” on the level of individual photons. This is part of a larger Buddhist agenda to meditatitively develop perceptual/attentional capacities to achieve penetrating insight into the nature of phenomena. Such capacities may also allow advanced meditators to perceive changes in natural scenes that are “hidden” from persons with “normal” attentional capacities, according to research on “change blindness,” and to enhance their visual system functioning akin to high‐speed and time‐lapse photography, in toto allowing for the perception, as well as sophisticated understanding, of the “moment to moment change or impermanence” universally characteristic of the phenomenal world but normally outside untrained attention and perception according to Buddhist doctrine.
A partnership model of early intervention in psychosis programme – a Canadian experience
Authors: Oyewumi Lamidi Kola , Savage Troy
Published: August 2009

Aim: To describe how a new partnership model of early intervention in psychosis, early intervention in psychosis (EIP) programme delivery in Canada attracted the interest of the community and acquired government funding.

Methods: The process by which a few individuals used a conceptual framework of integrated, collaborative, flexible and recovery focused principles to engage community partners and attract government funding is described.

Results: The establishment of a small EIP programme and its expansion to a regional programme serving an area of 20 000 square kilometers and a population of approximately 500 000 people were achieved. A programme specific logic prototype was developed. A synergy of public, private and academic services emerged with an infrastructure for ongoing cohesiveness and productivity. Annual clinic visits increased from 641 in 2002 to 1904 in 2007 and annual new patients enrollments grew from 46 to 128 within the same period. Staffing grew from an interdisciplinary staff of 1.5 full‐time equivalent (FTE) to the current 10.0 FTE.

Conclusions: A carefully orchestrated programme organization that is inclusive rather than exclusive can produce a balance of evidence‐based best practices in client focused service, community mental health integration and academic productivity.
Paediatric major depressive disorder: neurobiology and implications for early intervention
Authors: Cullen Kathryn , Klimes‐Dougan Bonnie , Kumra Sanjiv , Schulz S. Charles
Published: August 2009

Aim: Paediatric major depressive disorder (MDD) is associated with chronicity and poor outcomes. The goals of this review are (i) to integrate how developing biological systems contribute to the pathophysiology of paediatric MDD, and (ii) to consider the role of early intervention for depressed youth.

Methods: A developmental perspective is applied herein to review and integrate key neurobiological systems that are implicated in paediatric MDD. We also review recent treatment research for adolescents with MDD.

Results: Available evidence in paediatric and adult populations support an integrative model for the pathophysiology of MDD that involves fronto‐limbic neural circuitry and the neuroendocrine stress response system. Evidence from treatment research supports the efficacy of available treatments modalities, including antidepressant medications, cognitive behavioral therapy, and their combination, for the majority of adolescents with moderate to severe MDD.

Conclusions: Since the biological systems implicated in MDD mature through adolescence, adolescents may be more susceptible to developing depression but also may be more amenable to treatment interventions. Early identification and treatment of paediatric MDD may be able to divert negative trajectories and lead to improved outcomes.
Obstetric complications and risk for conversion to psychosis among individuals at high clinical risk
Authors: Mittal Vijay A. , Willhite Rachael , Daley Melita , Bearden Carrie E. , Niendam Tara , Ellman Lauren M. , Cannon Tyrone D.
Published: August 2009

Aim: Examining risk factors among high‐risk populations stands to inform treatment and to elucidate our understanding of the pathophysiology of schizophrenia. Despite substantial evidence implicating the incidence of obstetric complications (OCs) as a risk factor for schizophrenia, little is known about the relationship between OCs and risk for conversion among high‐risk individuals.

Methods: We prospectively followed individuals at high risk for developing psychotic disorders for a two‐year period to determine if a history of OCs is associated with conversion.

Results: Individuals who converted to psychosis had significantly more OCs when compared to non‐converting participants; a history of OCs was associated with increased odds of conversion (odds ratio = 4.90, confidence interval :1.04/22.20). OCs were positively associated with prodromal symptomatology.

Conclusions: To date, this report represents the first empirical evidence suggesting that OCs confer increased risk of conversion to psychosis. It is possible that OCs interact with brain maturational processes in the pathophysiology of schizophrenia and can serve as a risk marker.
The Somerset team for early psychosis
Authors: Burbach Frank R. , Grinter David J. , Bues Sonia E. A.
Published: August 2009

Aim: To describe the development of an early intervention (EI) service in Somerset, and evaluate the progress after the first 2 years.

Method: The Somerset Team for Early Psychosis (STEP) has been developed in stages from 2003 to the present ‘hub‐and‐spoke’ model. The framework, which the team operates, is outlined, the assessment and outcome measures are presented, and the interventions, with the emphasis on working with families, are discussed.

Results: Two hundred fifty‐nine referrals have been received in the first 2 years, with the caseload currently standing at 153. The mean duration of untreated psychosis of STEP clients was just over 9 months; when those who developed psychosis before 2004 (pre‐STEP) were removed, this was reduced to 6.4 months. Eighty‐four per cent of STEP clients have had their families involved with our service in some way. Relapse rates of clients in the service for over 12 months have been encouragingly low (17%).

Conclusions: We reflect on the challenges faced in relation to the EI service model described in the Department of Health's Policy Implementation Guide and, in particular, on having successfully built on the existing family interventions service.
The South‐to‐North Water Transfer Project of China: Environmental Implications and Monitoring Strategy1
Authors: Zhang Quanfa
Published: August 2009

Abstract: In 2002, China launched the South‐to‐North Water Transfer Project after completing a 50‐year feasibility study. By 2050, the three‐route (i.e., East, Middle, and West) project will be capable of transferring 44.8 billion m3/year of water from the water rich Yangtze River to the arid north to alleviate water shortage and help secure a balanced social and economic development across the nation. However, diversion of such a large quantity of water could profoundly change the riverine environment of the upper Yellow River and the lower reach of the Han River, a tributary of the Yangtze River and the water supplying area of the project’s Middle Route, because of changes in the annual discharge. Secondary salinization seems inevitable in the water receiving areas of the North China Plain, and decrease in the discharge of the Yangtze River will result in seawater intrusion into the Yangtze Delta. This paper describes the project and discusses its environmental implications. Additionally, a long‐term monitoring strategy under the umbrella of the Chinese Ecological Research Network is proposed for environmental monitoring.
Early cortical lens opacities: a short overview
Authors: Vrensen Gijs F.J.M.
Published: August 2009

Cataract is still the dominant cause of blindness worldwide. Cortical cataract is the most prevalent of the age‐related changes in the human lenses that require surgical intervention to restore vision. The absence of adequate cataract surgery in most developing countries is the main cause of the high prevalence of cataract blindness worldwide. Lens ageing is accompanied by dramatic increases in stiffness, light scattering and coloration of the lens nucleus. These changes start to become manifest as early as the fourth or fifth decade of life and lead to nuclear cataract in old age. In the same period the equatorial deep lens cortex starts to show small opaque shades, which eventually grow out to segmental and annular opacities. These opaque shades are filled with small vesicles and contain abnormal amounts of cross‐linked proteins, cholesterol and phospholipids. They are bordered by membranes that are rich in square arrays, have ‘degenerate’ gap junctions and have few intramembranous particles. It has been shown that the opaque shades represent cohorts of locally affected fibres segregated from unaffected neighbouring fibres by ‘non‐leaky’ membranes. This segregation is an effective mechanism delaying the outgrowth of these opacities to cuneiform cataracts entering the pupillary space and thus leading to blinding cortical cataracts. Although cataract formation is mostly considered to be a multi‐factorial disease, oxidative stress might be one of the leading causes for both nuclear and cortical cataract. In cortical cataracts shear stress between cortex and nucleus during accommodation may also play a significant role.
Investigating Second Language Learner Self‐Efficacy and Future Expectancy of Second Language Use for High‐Stakes Program Evaluation
Authors: Gorsuch Greta
Published: August 2009

Abstract: As part of a larger summative evaluation of a foreign language department and a two‐year foreign language core competency, the researcher investigated fourth‐semester student self‐efficacy (a person's belief, rooted in experience, that they can do something) and future expectancy of second language use. In effect, this was also an evaluation of program theory, which sought to determine what faculty members thought second‐year learners ought to know and be able to do at the end of their study, and the extent to which those learners felt they knew and could do these activities. Using questionnaire data from 150 students in nine divisions (Arabic, Chinese [Mandarin], French, German, Italian, Japanese, Portuguese, Russian, and Spanish), this study found that learners had at least a modicum of self‐efficacy for the things that faculty members and instructors thought they ought to know and be able to do. It was recommended that (1) practice and language use opportunities probably require more attention within divisions so that learner self‐efficacy might be further developed, and (2) divisions and students might benefit from having instructors more explicitly connect potentially undiscussed classroom processes (staying in the second language [L2], interacting with classmates in the L2) with successful class outcomes.
Walking in Simulated Martian Gravity: Influence of the Portable Life Support System’s Design on Dynamic Stability
Authors: Scott-Pandorf Melissa M. , O’Connor Daniel P. , Layne Charles S. , Josić Krešimir , Kurz Max J.
Published: August 2009

With human exploration of the moon and Mars on the horizon, research considerations for space suit redesign have surfaced. The portable life support system (PLSS) used in conjunction with the space suit during the Apollo missions may have influenced the dynamic balance of the gait pattern. This investigation explored potential issues with the PLSS design that may arise during the Mars exploration. A better understanding of how the location of the PLSS load influences the dynamic stability of the gait pattern may provide insight, such that space missions may have more productive missions with a smaller risk of injury and damaging equipment while falling. We explored the influence the PLSS load position had on the dynamic stability of the walking pattern. While walking, participants wore a device built to simulate possible PLSS load configurations. Floquet and Lyapunov analysis techniques were used to quantify the dynamic stability of the gait pattern. The dynamic stability of the gait pattern was influenced by the position of load. PLSS loads that are placed high and forward on the torso resulted in less dynamically stable walking patterns than loads placed evenly and low on the torso. Furthermore, the kinematic results demonstrated that all joints of the lower extremity may be important for adjusting to different load placements and maintaining dynamic stability. Space scientists and engineers may want to consider PLSS designs that distribute loads evenly and low, and space suit designs that will not limit the sagittal plane range of motion at the lower extremity joints.
Effect of Non-Newtonian Behavior on Hemodynamics of Cerebral Aneurysms
Authors: Fisher Carolyn , Rossmann Jenn Stroud
Published: August 2009

Blood flow dynamics near and within cerebral aneurysms have long been implicated in aneurysm growth and rupture. In this study, the governing equations for pulsatile flow are solved in their finite volume formulation to simulate blood flow in a range of three-dimensional aneurysm geometries. Four constitutive models are applied to investigate the influence of non-Newtonian behavior on flow patterns and fluid mechanical forces. The blood’s non-Newtonian behavior is found to be more significant, in particular, vascular geometries, and to have pronounced effects on flow and fluid mechanical forces within the aneurysm. The choice of constitutive model has measurable influence on the numerical prediction of aneurysm rupture risk due to fluid stresses, though less influence than aneurysm morphology.
Development of Biomechanical Response Corridors of the Head to Blunt Ballistic Temporo-Parietal Impact
Authors: Raymond David , Crawford Greg , Van Ee Chris , Bir Cynthia
Published: August 2009

There is a need to study the biomechanical response of the head to blunt ballistic impact. While the frequency of less-lethal munition impacts to the head may be less than other vital body regions, more serious injuries have been attributed to these impacts. This study aims to establish biomechanical response corridors for the temporo-parietal region for future development of biomechanical surrogate devices. Seven unembalmed post-mortem human subject specimens were exposed to blunt ballistic temporo-parietal head impact (103 g, 38 mm diameter impactor) to determine the force-time, deformation-time, and force-deformation responses. Comparisons were made to responses from prior blunt ballistic head impact studies, as well as automotive-related impact studies. Peak forces for impact condition A (19.5±2.6 m/s) were 3659±1248 N with deformations at peak force of 7.3±2.1 mm. Peak forces for impact condition B (33.6±1.4 m/s) were 5809±1874 N with deformations at peak force of 9.9±2.6 mm. Seven fractures were produced in the seven specimens. Depressed comminuted fracture types were documented in six of the seven cases. The average stiffness of the temporo-parietal region under blunt ballistic impact was 0.46±0.14 kN/mm. Stiffness results indicate that the response of the temporo-parietal region is similar to the forehead under blunt ballistic loading conditions. In addition, the response is significantly less stiff when compared with temporo-parietal impacts performed in automotive-related studies. These data provide the foundation for future research in the area of blunt ballistic head impact research including the development of biomechanical surrogates and computational models.
Cortical Screw Purchase in Synthetic and Human Femurs
Authors: Zdero Rad , Elfallah Khaled , Olsen Michael , Schemitsch Emil H.
Published: August 2009

Biomechanical investigations of orthopedic fracture fixation constructs increasingly use analogs like the third and fourth generation composite femurs. However, no study has directly compared cortical screw purchase between these surrogates and human femurs, which was the present aim. Synthetic and human femurs had bicortical orthopedic screws (diameter=3.5 mm and length=50 mm) inserted in three locations along the anterior length. The screws were extracted to obtain pullout force, shear stress, and energy-to-pullout. The four study groups (n=6 femurs each) assessed were the fourth generation composite femur with both 16 mm and 20 mm diameter canals, the third generation composite femur with a 16 mm canal, and the human femur. For a given femur type, there was no statistical difference between the proximal, center, or distal screw sites for virtually all comparisons. The fourth generation composite femur with a 20 mm canal was closest to the human femur for the outcome measures considered. Synthetic femurs showed a range of average measures (2948.54–5286.30 N, 27.30–35.60 MPa, and 3.63–9.95 J) above that for human femurs (1645.92–3084.95 N, 17.86–24.64 MPa, and 1.82–3.27 J). Shear stress and energy-to-pullout were useful supplemental evaluators of screw purchase, since they account for material properties and screw motion. Although synthetic femurs approximated human femurs with respect to screw extraction behavior, ongoing research is required to definitively determine which type of synthetic femur most closely resembles normal, osteopenic, or osteoporotic human bone at the screw-bone interface.
Instantaneous Local Heat Flux Measurements in a Small Utility Engine
Authors: Hendricks Terry , Ghandhi Jaal , Brossman John
Published: August 2009

Heat flux measurements were performed in an air-cooled utility engine using a fast-response coaxial-type surface thermocouple. The surface heat flux was calculated using both analytical and numerical models. The heat flux was found to be a strong function of engine load. The peak heat flux and initial heat flux rise rate increase with engine load. The measured heat flux data were used to estimate a global heat transfer rate, and this was compared with the heat transfer rate calculated by a single-zone heat release analysis. The measured values of heat transfer were higher than the calculated values largely because of the lack of spatial averaging. The high load data showed an unexplainable negative heat flux during the expansion stroke while the gas temperature was still high. A 1D and 2D finite difference numerical model utilizing an adaptive timestep Crank-Nicholson (CN) integration routine was developed to investigate the surface temperature measurement. Applying the measured surface temperature profile to the 1D model, the resultant surface heat flux showed excellent agreement with the analytical inversion solution and captured the reversal of the energy flow back into the cylinder during the expansion stroke. The 2D numerical model was developed to observe transient lateral conduction effects within the probe and incorporated the various materials used in the construction and assembly of the heat flux sensor. The resulting average heat flux profile for the test case is shown to be slightly higher in peak and longer in duration when compared with the results from the 1D analytical inversion, and this is attributed to contributions from the high thermal diffusivity constituents in the sensor. Furthermore, the negative heat flux at high load was not eliminated suggesting that factors other than lateral conduction may be affecting the measurement accuracy.
Examination of Initialization and Geometric Details on the Results of CFD Simulations of Diesel Engines
Authors: Bergin Mike , Musu Ettore , Kokjohn Sage , Reitz Rolf D.
Published: August 2009

Computational Fluid Dynamic (CFD) simulations using the AVL Fire and Kiva 3v codes were performed to examine commonly accepted techniques and assumptions used when simulating direct injection diesel engines. Simulations of a steady state impulse swirl meter validated the commonly used practice of evaluating the swirl ratio of diesel engines by integrating the valve flow and torque history over discrete valve lift values [1]. The results indicate the simulations capture the complex interactions occurring in the ports, cylinder and honeycomb cell impulse swirl meter. The commonly adopted axisymmetric assumption for an engine with a centrally located injector was tested by comparing the swirl and emissions history for a motored case and a double injection low temperature combustion case. Consideration of the detailed engine geometry including valve recesses in the piston and the head lowered the peak swirl ratio at TDC by approximately 10% compared to the simplified no-recess case. The corresponding combusting cases also had different heat release and emissions predictions but could be partially compensated for by lowering the initial swirl ratio for the axisymmetric case.
Simulation Study of Advanced Variable Displacement Engine Coupled to Power-Split Hydraulic Hybrid Powertrain
Authors: Tavares Fernando , Johri Rajit , Filipi Zoran
Published: August 2009

The simulation-based investigation of the variable displacement engine is motivated by a desire to enable unthrottled operation at part load, and hence eliminate pumping losses. The mechanism modeled in this work is derived from a Hefley engine concept. Other salient features of the proposed engine are turbocharging and cylinder deactivation. The cylinder deactivation combined with variable displacement further expands the range of unthrottled operation, while turbocharging increases the power density of the engine and allows downsizing without the loss of performance. While the proposed variable displacement turbocharged engine (VDTCE) concept enables operations in a very wide range, running near idle is impractical. Therefore, the VDTCE is integrated with a hybrid powertrain allowing flexibility in operating the engine, elimination of idling and mitigation of possible issues with engine transients and mode transitions. The engine model is developed in AMESim using physical principles and 1-D gas dynamics. A predictive model of the power-split hydraulic hybrid driveline is created in SIMULINK, thus facilitating integration with the engine. The integrated simulation tool is utilized to address design and control issues, before determining the fuel economy potential of the powertrain comprising a VDTCE engine and a hydraulic hybrid driveline.
A Numerical Simulation of the Coupling Between Dynamic Behavior and Tribological Behavior in Cylinder-Piston System in IC Engine
Authors: Dai Xudong , Meng Xianghui , Xie Youbai
Published: August 2009

A mathematical model for cylinder-piston system considering the coupling between dynamic behavior and tribological behavior is presented in this paper. The three-dimensional finite element method is used to compute the engine block vibrations. The lubrication of cylinder-piston pair was described by an average Reynolds equation considering the piston second-vibration and asperity contact of rough surface. The corresponding computing program developed can be used to calculate the engine block vibrations, the entire piston trajectory, the Piston slap forces, friction forces and oil film thickness etc. as functions of crank angle under engine running conditions. The numerical simulation results show that the coupling between engine block dynamical behavior and lubrication has big influence for the secondary motion of piston and the engine block vibration in cylinder-piston system. It is essential to consider the engine block vibration in the analysis of cylinder-piston tribology.
Diagnosing Irregularities of Nonlinear Dynamic Systems With Implementation of Periodicity-Ratio
Authors: Dai Liming , Wang Guoqing
Published: August 2009

Among the irregular responses of nonlinear dynamic systems, chaotic responses of nonlinear systems are probably the most attractive phenomena along with the new observations in the last decades. A nonlinear deterministic system may behavior chaotically under regular such as periodic excitations. Regular motion of a system subjected to periodic exertions is usually periodic. In contrast with regular motions, final states of chaotic vibrations are extremely nonperiodic. This research is to analyzing the irregular behavior of dynamic systems with implementation of a newly developed criterion named Periodicity-Ratio. The development of a methodology for diagnosing the irregular motions from the regular motions of a dynamic system is presented. The Periodicity-Ratio describes the degree of periodicity of motion and can be conveniently used to distinguish a nonperiodic motion from a regular vibration or oscillation and to diagnose whether or not a motion is chaotic and the other irregular responses of the nonlinear dynamic systems, without plotting any figures. The analyses on the irregular behavior of nonlinear dynamic systems with the implementation of the Periodicity-Ratio will be demonstrated.
Tightness Investigation on Hydraulic Seat Valves
Authors: Schmidt Matthias , Murrenhoff Hubertus , Lohrberg Henrik , Ko¨rber Franz-Josef
Published: August 2009

Hydraulic valves are commonly divided into spool and seat valves. The latter provide the advantage of being able to isolate a hydraulic pressure nearly without leakage. However, in certain applications any leakage whatsoever is prohibited. Therefore, efforts are carried out to increase the tightness of the metallic sealing. For this purpose, a test rig was designed and manufactured to investigate different seat geometries in combination with varying hydraulic and mechanical parameters. To exclude the influence on the leakage of other seals, the flow is measured at the low pressure side of the seat. By means of a structured approach, the influences of factors on leakage as well as their interdependencies are being investigated. Within this paper measurement results of the leakage’s dependency on time, contact force and geometry are presented. For this purpose basic correlations are introduced, verified by the results of three different valve geometries.
Numerical Study of Wing Aerodynamics in Ground Proximity
Authors: Ockfen Alex E. , Matveev Konstantin I.
Published: August 2009

Experimental design and optimization of innovative ground-effect transportation means is an iterative process which requires a large amount of time and resources. To avoid the large experimental expense, numerical modeling can be used to investigate Wing-in-Ground (WIG) vehicle flight. In this paper, modeling technique is applied for a two dimensional NACA 4412 airfoil in viscous flow in and out of ground effect. The numerical method consists of a steady state, incompressible, finite volume method utilizing the Spalart-Allmaras turbulence model. Grid generation and solution of the Navier-Stokes equations are completed using FLUENT 6.3. The modeling procedures are first validated against published experimental data for unbounded flow around an airfoil. Wing section aerodynamic characteristics are then studied for varying ground heights and two separate boundary conditions: fixed ground and moving ground. Ground effect calculations are compared to several previous studies, and our results are found to correlate with published aerodynamic trends in ground effect, although all studies appear to predict different magnitudes of aerodynamic forces.
Why Engineering Curricula Should Include Alternative Methodology for Heat Transfer Coefficient
Authors: Adiutori Eugene F.
Published: August 2009

Convective heat transfer problems are of two types: 1. Problems that are solved in a direct and simple manner using heat transfer coefficients. 2. Problems that must be solved in an indirect manner (ie by iteration or trial-and-error) if heat transfer coefficients are used, but can be solved in a direct and simple manner if heat transfer coefficients are not used. Type (1) problems include those in which heat flux is proportional to temperature difference (as in forced convection), and those in which temperature differences are given. Type (2) problems are those in which heat flux is a nonlinear function of temperature difference (as in natural convection, boiling, and condensation), and temperature differences are not given. Engineering curricula should stress that heat transfer coefficient is a contrived and unnecessary parameter, and should include alternative methodology that allows Type (2) problems to be solved in a direct and simple manner. The alternative methodology presented herein is readily grasped by students because problems are solved with the primary variables separated (the methodology learned and used in pure mathematics) rather than combined (as required in heat transfer coefficient methodology). The application of the alternative methodology to the solution of Type (2) problems is demonstrated in the text.
Parmeterization of the Total Pressure Distribution Along a Low-Pressure Axial Fan Blade According to the Design Requirements
Authors: Pascu Maria , Epple Philipp , Delgado Antonio , Durst Franz
Published: August 2009

In the field of axial flow turbomachines, the two–dimensional cascade model is often used experimentally or numerically to investigate fundamental flow characteristics and overall performance of the impeller. The core of the present work is a design method for axial fan cascades aiming to derive inversely the optimum blade shape based on the requirements of the impeller and not using any predefined airfoil profiles. While most design strategies based on the airfoil theory assume constant total pressure at all streamlines, i.e. free–vortex flow, this paper investigates the possibility of varying the total pressure along the blade and based on that, an analytical expression of the outlet blade angle is determined. When computing the blade profile at specified radius, critical parameters reflecting on the flow characteristics are observed and adjusted, i.e. sufficient lift and controlled deceleration of the flow on the contour so that the resulting profile is derived for minimum losses. The validation of this design strategy is given by the numerical results obtained when employed as an optimization tool for an industrial fan: 10–20% absolute increase in the efficiency of the optimized impeller.
Grading Rubrics for Engineering Presentations and Reports
Authors: Bauer Candice
Published: August 2009

Rubrics for grading technical presentations and reports are presented. The rubrics are easy to use because the skills are judged as met standard or did not meet standard (check or minus; pass or fail). Each standard is detailed and presented with a strategy to recognize its successful completion.
Axially Loaded Pressurized Thin-Walled Circular Tubes Used as Adaptive Energy Absorbers
Authors: Zhang X. W. , Yu T. X.
Published: August 2009

By filling compressed air into cellular materials, honeycombs or thin-walled structures, their energy absorption can be greatly enhanced, while this enhancement can be controlled by the applied pressure. This concept shines a light on the possibility of achieving adaptive energy absorption. To investigate the effect of the internal pressure on the response of the structures under impact loadings, the present paper reports our study on the axial crushing behavior of pressurized thin-walled circular tubes. Three groups of thin-walled circular tubes with the radius/thickness ratio between 120 and 200 were employed in the experiments and two working modes were studied: mode-I (with constant internal pressure) and mode-II (closed tubes with finite leakage). In the tests of mode-I, the influences of internal pressure on the deformation mode and energy absorption of the tubes were investigated. The results show that with the increase of internal pressure, the deformation mode switches from diamond mode with sharp corners to that with round corners, and eventually to ring mode. In diamond mode, the mean force of the tubes increases linearly with the internal pressure. The enhancement comes from two mechanisms: direct effect of the pressure and indirect effect due to the interaction between the pressure and the tube wall. After the deformation switches to ring mode, the enhancement resulted from the second mechanism becomes weaker. Based on the results of mode-I, the mode-II was experimentally investigated both quasi-statically and dynamically. The results are compared with the predictions obtained from a semi-empirical formula, showing good agreements.
Predictive Method of Initial Shapes for Doubly Curved Ship Hull Plates by the Minimum Potential Energy Method
Authors: Baek Kyung-Lok , Shin Sang-Beom
Published: August 2009

The purpose of this study is to design the initial shape of doubly curved hull surfaces. In this paper, the development method of the hull surfaces was suggested by minimizing potential energy between initial and final shapes. In order to do this, the values of strains and stresses were defined through finite element analysis and genetic algorithm was used to estimate the initial shape which is the state of minimum potential energy. Validity of the prediction method was verified by comparing the estimated contour lengths with those obtained by the commercial software for sheet metal forming. It was founded that the established prediction method using genetic algorithms would enable to determine the initial contour of the doubly curved surfaces with maximum deviation of 0.7%.
Numerical Modelling of Internal Combustion Engines Fuelled by Hydrogen-Natural Gas Blends
Authors: Mariani Antonio , Morrone Biagio , Unich Andrea
Published: August 2009

The strict rules that European Community has given for reducing vehicle emissions require new views on the choice of combustion engines and fuels. In fact, the rules will probably introduce in the near future limitations on carbon dioxide (CO2) emissions. Internal combustion engines are responsible for emission of unburned hydrocarbons (HC), nitrogen oxides (NOx) and particulate matter (PM). The aim of the present paper is the study of the effects of hydrogen-natural gas blends (HCNG) on the performance, efficiency and NOx emissions of internal combustion engines (ICE). A numerical engine model has been developed to display how the presence of hydrogen in such mixtures impacts on flame speed and burn rates. The model allows the comparison of different fuels, in terms of engine brake efficiency and pollutant emissions. An important variable for the combustion process is the ignition timing which is set employing Maximum Brake Torque (MBT) spark advance. Engine operating conditions considered in the numerical analysis have been obtained by imposing engine speed and load. Brake power, efficiency and NOx emissions are calculated for the most frequent operating conditions met by automotive engines, i.e. part load and low speed. The effect of natural gas (NG) enrichment by hydrogen on flame speed has been considered. Thus, faster combustion and the reduction of energy content in the air-fuel mixtures due to the lower density of hydrogen are taken into account. Hydrogen enrichment of natural gas improves combustion stability in critical conditions, allowing the use of extremely lean mixtures or high Exhaust Gas Recirculation rates. The results show that by employing an MBT spark advance, the HCNG blends furnish improvements of engine brake efficiency compared with compressed natural gas (CNG), which are more relevant at part loads and for the higher hydrogen content. Anyway, higher NOx emissions are observed due to the increased temperatures into the cylinders. Thus, the analysis also takes into account the Exhaust Gas Recirculation (EGR) dilution technique to reduce the NOx emissions. A large reduction of such pollutant, which has been estimated greater than 50%, can be achieved by using a 10% EGR. Furthermore higher engine efficiency is obtained using EGR due to reduced pumping work, reduced heat loss to the walls because of lower gas temperature and a reduction in the degree of dissociation in the high temperature burned gases.
Interfacial-Tension-Directed Self-Assembly of Nanowires on Superhydrophobic Surfaces
Authors: Tsai Yao-Tsan , Xu Wei , Yang Eui-Hyeok , Choi Chang-Hwan
Published: August 2009

This paper describes a novel method of nanowire assembly using a superhydrophobic surface as a template. Well-defined superhydrophobic structures on a template surface direct the site-specific self-assembly of nanowires due to interfacial tension in evaporation, enabling simple but highly-efficient and ordered assembly of nanowires. High-aspect-ratio (HAR) microstructures with tapered tips are fabricated by deep reactive ion etch (DRIE) and are coated with a self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) for hydrophobicity. Nickel nanowires are fabricated in a porous alumina membrane by electrodeposition. A uniformly-dispersed nanowire suspension is dispensed and evaporated on the superhydrophobic template surface. Due to surface superhydrophobicity, a three-phase (i.e., liquid-solid-gas) interface is created on the surface structures, enabling the nanowires to reside only over the interface. After complete evaporation, the nanowires are mostly left on the structural tips, driven by the interfacial forces constituted at the three-phase boundary. Although the alignment yield rate of the nanowires to the surface pattern has not reached 100%, current experimental results demonstrate that the idea of using interfacial tension on superhydrophobic surfaces can serve as a novel nano-assembly technique with high throughput and high rate. The key parameters affecting the yield of self-assembly and alignment will continue to be studied for further improvement.
Microscale Thermoplastic Forming of Bulk Metallic Glasses: Numerical Simulations and Experiments
Authors: Henann David L. , Anand Lallit
Published: August 2009

An extremely promising microscale processing method for bulk metallic glasses called thermoplastic forming has emerged in recent years. However, most of the recent experimental thermoplastic forming studies have been conducted by trial-and-error. In this paper, the large-deformation constitutive theory of Henann and Anand [1] is used as a numerical simulation tool for the design of micro-hot-embossing processes. This numerical simulation capability is used to determine appropriate processing parameters in order to carry out several successful micron-scale hot-embossing operation on the metallic glass Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy-1). By carrying out the corresponding physical experiments, it is demonstrated that microscale features in Vitreloy-1 may be accurately replicated under the processing conditions determined by use of the numerical simulation capability.
Characterization of a Microfluidic Based Direct-Methanol Fuel Cell
Authors: Sprague Isaac B. , Dutta Prashanta , Ha Su
Published: August 2009

The performance of a membraneless laminar flow micro fuel cell was evaluated under different operating conditions. The fuel cell was microfabricated in poly-dimethyl-siloxane using standard soft-lithography techniques. It used methanol solution as the fuel for the anode side, and oxygen saturated sulfuric acid for the cathode. The parameters studied were the methanol concentration and the concentration of sulfuric acid in the anode stream. The performance was characterized by V-I plots, stability of open circuit potential, and anode polarization curves. Our results show that the power output of the device decreases with increase in the methanol concentration. It is shown that these trends are caused by the cell’s internal resistance to proton transport. The addition of sulfuric acid to the fuel significantly decreases this resistance. The device open circuit potential was not stable over extended operation, and could drop by more than 150 mV in 72 hours.
Characterization of Nonlinear Coupled Dynamics in Sandwich Structures
Authors: Georgiou Ioannis T.
Published: August 2009

In this work, the nonlinear coupled dynamics of a sandwich structure with hexagonal honeycomb core are characterized in terms of Proper Orthogonal Decomposition modes. A high fidelity nonlinear finite element model is derived to describe geometric nonlinearity and displacement and rotation fields that govern the coupled dynamics. Contrary to equivalent continuum models used to predict vibration properties of lattice and sandwich structures, a high fidelity finite element model allows for a quite detailed description of the distributed complicated geometric nonlinearity of the core. It was found that the free dynamics excited by a blast load and the forced dynamics excited by a harmonic force posses POD modes which are localized in space and time. The processing of the simulated dynamics by the Time Discrete Proper Transform forms a means to study the nonlinear coupled dynamics of sandwich structures in the context of nonlinear normal modes of vibration and reduced order models.
An Analytical Model of Collaboration Between Engineers Working on Team and on Individual Projects
Authors: Takai Shun
Published: August 2009

Collaboration of engineers with diverse technical background such as those found in cross-functional teams has been addressed as a key for successful system development. Similarly, the benefit of team-based-project class is increasingly emphasized in curriculum development. In a team project, however, there is always a temptation for a team member to free-ride on other team members’ efforts (i.e., receive the same credit without contributing to the project). This paper presents an analytical model in which two engineers work on a team project, as well as individually on separate projects. The engineers receive the same performance evaluation on their team project (whether they actually contribute to the project or not), but independent evaluations on their individual projects. This paper uses the model to identify conditions that discourage free-riding and encourage collaboration between two engineers. The results of the analysis and implications to team projects in industry and in curriculum are discussed.
Investigation of Dynamics and Vibration of a Three Unit PIG in Oil and Gas Pipelines
Authors: Durali Mohammad , Fazeli Amir , Azimi Mohsen
Published: August 2009

In this paper, the transient motion of a three unit intelligent Pipe Inspection Gauge (PIG) while moving across anomalies and bends inside gas/oil pipeline has been investigated. The pipeline fluid has been considered as isothermal and compressible. In addition, the pipeline itself has also been considered to be flexible. The fluid continuity and momentum equations along with the 3D multi body dynamic equations of motion of the pig comprise a system of coupled dynamic differential equations which have been solved numerically. Pig’s position and velocity profiles as well as upstream and downstream fluid’s pressure waves are presented as simulation results which provide a better understanding of the complex behavior of pig motion through pipelines. This study has been conducted as a part of the design procedure for the Pig which is currently under construction.
Capture, Deformation, Rolling and Detachment of a Cell on an Adhesive Surface in a Shear Flow
Authors: Pappu Vijay , Bagchi Prosenjit
Published: August 2009

Three-dimensional computational modeling and simulation using front tracking method are presented on the motion of a deformable cell over an adhesive surface in a shear flow. The numerical method couples a Navier-Stokes flow solver with cell membrane mechanics, and a Monte Carlo simulation to capture stochastic formation and breakage of receptor/ligand bonds. The entire range of events during cell adhesion, namely, initial arrest of a free-flowing cell, slow rolling of an adherent cell, and detachment off the surface is simulated. Simulations are conducted to signify the role of hydrodynamic lift force that exists for a deformable particle in a wall-bounded flow. Three sets of numerical experiments are presented. In the first set, we consider the initial arrest of the cell, and show that the time needed for the cell to arrest increases with increasing Ca, but rapidly drops and saturates for higher bond strength. In the second set, we consider quasi-steady rolling motion of the cell, and predict the experimentally observed “stop and go” motion of the rolling leukocytes which is characterized by intermittent pauses and sudden jumps in cell velocity. In the third set we consider the detachment of the cell from the surface upon breakage of bonds. The bond strength needed to prevent the detachment of an adherent cell is computed and shown to be maximum for an intermediate Ca.
Characterization of a Resonant MEMS Heat Engine
Authors: Bardaweel H. , Richards R. , Richards C. , Anderson M.
Published: August 2009

The dynamic operation of a MEMS heat engine has been studied using a linear transfer function approach. The engine was operated at resonance and shown to produce a cycle with a PV diagram. A lumped parameter model was developed and validated. The model was used to explore the heat rejection process and its effect on the pressure volume diagram.
Effect of the Frost on the Thermal Performance of the Evaporator for the Residential Heat Pump
Authors: Yoon Shinhyuk , Cho Keumnam
Published: August 2009

The present study investigated the performance of the evaporator for the residential heat pump under frosting condition. The size of all evaporators was 400 × 250 × 12.7 mm (W × H × D). Key experimental parameters were fin type (plate and slit fin), fin pitch (1.3, 1.4 and 1.5 mm), the face velocity of air (0.5, 1.0, 1.5 and 2.0m/s), and the number of row (1 and 2) of the heat exchanger. The ethylene glycol-water mixture was used as a refrigerant. The test was done in a phychrometric calorimeter chamber. The air side pressure drop and heat transfer rate were measured as frost grew. The pressure drop of the evaporator under frosting with the slit fin was higher than that with the plate fin. It increased as the number of rows increased, the fin pitch decreased, and the air velocity decreased for the slit fin. The heat transfer rate of the evaporator under frosting with the slit fin was higher than that with the plate fin. It increased as the air velocity increased even though it was not much affected by the other parameters for the slit fin. The EF decreased as frost grew to be lower than one. The HGR decreased to be lower than one as frost grew. It decreased as the number of row increased.
A Nonlinear Compressible Transversely-Isotropic Viscohyperelastic Constitutive Model of the Periodontal Ligament
Authors: Zhurov Alexei I. , Evans Sam L. , Holt Catherine A. , Middleton John
Published: August 2009

The periodontal ligament may be treated as a transversely-isotropic viscohyperelastic fibre-reinforced compressible material which is subject to large deformations and has an essentially nonlinear behavior. Within these assumptions, a continuum constitutive model of the PDL was proposed recently [48], which involves a number of material parameters that have to be identified from experimental data. An optical motion analysis system was developed [26] to collect data on the deformation of the PDL. In the present paper, an advanced version of the model is suggested, which is based on the assumption of the existence of an additive strain-energy function dependent on a number of principal invariants. The sensitivity analysis of the material parameters is performed and a parameter identification technique is suggested.