Search results for: High Numerical Aperture
Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 7808

Search results for: High Numerical Aperture

6098 HOPF Bifurcation of a Predator-prey Model with Time Delay and Habitat Complexity

Authors: Li Hongwei

Abstract:

In this paper, a predator-prey model with time delay and habitat complexity is investigated. By analyzing the characteristic equations, the local stability of each feasible equilibria of the system is discussed and the existence of a Hopf bifurcation at the coexistence equilibrium is established. By choosing the sum of two delays as a bifurcation parameter, we show that Hopf bifurcations can occur as  crosses some critical values. By deriving the equation describing the flow on the center manifold, we can determine the direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions. Numerical simulations are carried out to illustrate the main theoretical results.

Keywords: Predator-prey system, delay, habitat complexity, HOPF bifurcation.

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6097 Allocation of Mobile Units in an Urban Emergency Service System

Authors: Dimitra Alexiou

Abstract:

In an urban area the location allocation of emergency services mobile units, such as ambulances, police patrol cars must be designed so as to achieve a prompt response to demand locations. In this paper the partition of a given urban network into distinct sub-networks is performed such that the vertices in each component are close and simultaneously the sums of the corresponding population in the sub-networks are almost uniform. The objective here is to position appropriately in each sub-network a mobile emergency unit in order to reduce the response time to the demands. A mathematical model in framework of graph theory is developed. In order to clarify the corresponding method a relevant numerical example is presented on a small network.

Keywords: Distances, Emergency Service, Graph Partition, location.

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6096 Delay-Dependent Stability Criteria for Linear Time-Delay System of Neutral Type

Authors: Myeongjin Park, Ohmin Kwon, Juhyun Park, Sangmoon Lee

Abstract:

This paper proposes improved delay-dependent stability conditions of the linear time-delay systems of neutral type. The proposed methods employ a suitable Lyapunov-Krasovskii’s functional and a new form of the augmented system. New delay-dependent stability criteria for the systems are established in terms of Linear matrix inequalities (LMIs) which can be easily solved by various effective optimization algorithms. Numerical examples showed that the proposed method is effective and can provide less conservative results.

Keywords: Neutral systems, Time-delay, Stability, Lyapunovmethod, LMI.

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6095 Simulation of Solar Assisted Absorption Cooling and Electricity Generation along with Thermal Storage

Authors: Faezeh Mosallat, Eric L. Bibeau, Tarek El Mekkawy

Abstract:

Parabolic solar trough systems have seen limited deployments in cold northern climates as they are more suitable for electricity production in southern latitudes. A numerical dynamic model is developed to simulate troughs installed in cold climates and validated using a parabolic solar trough facility in Winnipeg. The model is developed in Simulink and will be utilized to simulate a trigeneration system for heating, cooling and electricity generation in remote northern communities. The main objective of this simulation is to obtain operational data of solar troughs in cold climates and use the model to determine ways to improve the economics and address cold weather issues. In this paper the validated Simulink model is applied to simulate a solar assisted absorption cooling system along with electricity generation using Organic Rankine Cycle (ORC) and thermal storage. A control strategy is employed to distribute the heated oil from solar collectors among the above three systems considering the temperature requirements. This modelling provides dynamic performance results using measured meteorological data recorded every minute at the solar facility location. The purpose of this modeling approach is to accurately predict system performance at each time step considering the solar radiation fluctuations due to passing clouds. Optimization of the controller in cold temperatures is another goal of the simulation to for example minimize heat losses in winter when energy demand is high and solar resources are low. The solar absorption cooling is modeled to use the generated heat from the solar trough system and provide cooling in summer for a greenhouse which is located next to the solar field. The results of the simulation are presented for a summer day in Winnipeg which includes comparison of performance parameters of the absorption cooling and ORC systems at different heat transfer fluid (HTF) temperatures.

Keywords: Absorption cooling, parabolic solar trough, remote community, organic Rankine cycle.

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6094 Efficacy of Self-Assessment in Written Production among High School Students

Authors: Yoko Suganuma Oi

Abstract:

The purpose of the present study is to find the efficacy of high school student self-assessment of written production. It aimed to explore the following two research questions: 1) How is topic development of their written production improved after student self-assessment and teacher feedback? 2) Does the consistency between student self-assessment and teacher assessment develop after student self-assessment and teacher feedback? The data came from the written production of 82 Japanese high school students aged from 16 to 18 years old, an American English teacher and one Japanese English teacher. Students were asked to write English compositions, about 150 words, for thirty minutes without using dictionaries. It was conducted twice at intervals of two months. Students were supposed to assess their own compositions by themselves. Teachers also assessed students’ compositions using the same assessment sheet. The results showed that both teachers and students assessed the second compositions higher than the first compositions. However, there was not the development of the consistency in coherence.

Keywords: Feedback, self-assessment, topic development.

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6093 Comparison of Physico-Chemical Properties And Fatty Acid Compostion of Elateriospermum Tapos (Buah Perah), Palm Oil And Soybean Oil

Authors: Siti Hamidah, Lee Nian Yian, Azizi Mohd

Abstract:

Elateriospermum tapos seed (buah perah) is the one of the rich sources of polyunsaturated fatty acids. It contains high percentage of oleic acid which is the important component to develop nervous system and also α-linolenic acid (ALA) which is the precursor of omega-3 fatty acids series to synthesize eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, there is less study about this valuable oilseed and exploit its potential. Therefore, this paper is to assess the comparison of physico-chemical properties and fatty composition of perah oil to palm oil and soybean oil. From the comparison, perah oil shows low peroxide value means it has good oxidative stability and also high iodine values shows that it can be used in paint industry. The study shown that perah oil is comparable to palm oil and soybean oil, so it has high potential to be exploited in the oleochemical, pharmaceutical, cosmetics and paint industries.

Keywords: α-linolenic acid, palm oil, perah oil, soybean oil

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6092 Buckling Analysis of a Five-walled CNT with Nonlocal Theory

Authors: Alireza Bozorgian, Navid Majdi Nasab, Abdolreza Memari

Abstract:

A continuum model is presented to study vdW interaction on buckling analysis of multi-walled walled carbon nanotube. In previous studies, only the vdW interaction between adjacent two layers was considered and the vdW interaction between the other two layers was neglected. The results show that the vdW interaction cofficients are dependent on the change of interlayer spacing and the radii of tubes. With increase of radii the vdW coefficients approach a constant value. The numerical results show that the effect of vdW interaction on the critical strain for a doublewalled CNT is negligible when the radius is large enough for the both the cases of before and after buckling.

Keywords: Buckling, Carbon nanotube, van der Waals interaction, Multi-walled Carbon nanotube, Critical Strain, Prebuckling Pressure

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6091 Analytical Solutions of Three Dimensional Steady-State Heat Transfer in Rectangular Ribs

Authors: Tao Nie, Weiqiang Liu

Abstract:

In order to obtain an accurate result of the heat transfer of the rib in the internal cooling Rectangular channel, using separation of variables, analytical solutions of three dimensional steady-state heat conduction in rectangular ribs are given by solving three dimensional steady-state function of the rectangular ribs. Therefore, we can get solution of three dimensional temperature field in the rib. Based on the solution, we can get how the Bi number affected on heat transfer. Furthermore, comparisons of the analytical and numerical results indicate agreement on temperature field in the rib.

Keywords: variable separation method, analytical solution, rib, heat transfer

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6090 The Impact of Germination and In Vitro Digestion on the Formation of Angiotensin Converting Enzyme (ACE) Inhibitory Peptides from Lentil Proteins Compared to Whey Proteins

Authors: F. Bamdad, Sh. Dokhani, J. Keramat, R. Zareie

Abstract:

Biologically active peptides are of particular interest in food science and human nutrition because they have been shown to play several physiological roles. In vitro gastrointestinal digestion of lentil and whey proteins in this study produced high angiotensin-I converting enzyme inhibitory activity with 75.5±1.9 and 91.4±2.3% inhibition, respectively. High ACE inhibitory activity was observed in lentil after 5 days of germination (84.3±1.2%). Fractionation by reverse phase chromatography gave inhibitory activities as high as 86.3±2.0 for lentil, 94.8±1.8% for whey and 93.7±1.7% at 5th day of germination. Further purification by HPLC resulted in several inhibitory peptides with IC50 values ranging from 0.064 to 0.164 mg/ml. These results demonstrate that lentil proteins are a good source of peptides with ACE inhibitory activity that can be released by germination or gastrointestinal digestion. Despite the lower bioactivity in comparison with whey proteins, incorporation of lentil proteins in functional food formulations and natural drugs look promising.

Keywords: ACE inhibitory peptides, digestion, germination, lentil proteins, whey proteins

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6089 Miniature Fast Steering Mirrors for Space Optical Communication on NanoSats and CubeSats

Authors: Sylvain Chardon, Timotéo Payre, Hugo Grardel, Yann Quentel, Mathieu Thomachot, Gérald Aigouy, Frank Claeyssen

Abstract:

With the increasing digitalization of society, access to data has become vital and strategic for individuals and nations. In this context, the number of satellite constellation projects is growing drastically worldwide and is a next-generation challenge of the New Space industry. So far, existing satellite constellations have been using radio frequencies (RF) for satellite-to-ground communications, inter-satellite communications, and feeder link communication. However, RF has several limitations, such as limited bandwidth and low protection level. To address these limitations, space optical communication will be the new trend, addressing both very high-speed and secured encrypted communication. Fast Steering Mirrors (FSM) are key components used in optical communication as well as space imagery and for a large field of functions such as Point Ahead Mechanisms (PAM), Raster Scanning, Beam Steering Mirrors (BSM), Fine Pointing Mechanisms (FPM) and Line of Sight stabilization (LOS). The main challenges of space FSM development for optical communication are to propose both a technology and a supply chain relevant for high quantities New Space approach, which requires secured connectivity for high-speed internet, Earth planet observation and monitoring, and mobility applications. CTEC proposes a mini-FSM technology offering a stroke of +/-6 mrad and a resonant frequency of 1700 Hz, with a mass of 50 g. This FSM mechanism is a good candidate for giant constellations and all applications on board NanoSats and CubeSats, featuring a very high level of miniaturization and optimized for New Space high quantities cost efficiency. The use of piezo actuators offers a high resonance frequency for optimal control, with almost zero power consumption in step and stay pointing, and with very high-reliability figures > 0,995 demonstrated over years of recurrent manufacturing for Optronics applications at CTEC.

Keywords: Fast steering mirror, feeder link, line of sight stabilization, optical communication, pointing ahead mechanism, raster scan.

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6088 Single Valued Neutrosophic Hesitant Fuzzy Rough Set and Its Application

Authors: K. M. Alsager, N. O. Alshehri

Abstract:

In this paper, we proposed the notion of single valued neutrosophic hesitant fuzzy rough set, by combining single valued neutrosophic hesitant fuzzy set and rough set. The combination of single valued neutrosophic hesitant fuzzy set and rough set is a powerful tool for dealing with uncertainty, granularity and incompleteness of knowledge in information systems. We presented both definition and some basic properties of the proposed model. Finally, we gave a general approach which is applied to a decision making problem in disease diagnoses, and demonstrated the effectiveness of the approach by a numerical example.

Keywords: Single valued neutrosophic hesitant set, single valued neutrosophic hesitant relation, single valued neutrosophic hesitant fuzzy rough set, decision making method.

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6087 3D Quantum Numerical Simulation of Horizontal Rectangular Dual Metal Gate\Gate All Around MOSFETs

Authors: M. Khaouani, A. Guen-Bouazza, B. Bouazza, Z. Kourdi

Abstract:

The integrity and issues related to electrostatic performance associated with scaling Si MOSFET bulk sub 10nm channel length promotes research in new device architectures such as SOI, double gate and GAA MOSFET. In this paper, we present some novel characteristic of horizontal rectangular gate\gate all around MOSFETs with dual metal of gate we obtained using SILVACO TCAD tools. We will also exhibit some simulation results we obtained relating to the influence of some parameters variation on our structure, that having a direct impact on their threshold voltage and drain current. In addition, our TFET showed reasonable ION/IOFF ratio of (104) and low drain induced barrier lowering (DIBL) of 39 mV/V.

Keywords: GAA, SILVACO, QUANTUM, MOSFETs.

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6086 Cognitive SATP for Airborne Radar Based on Slow-Time Coding

Authors: Fanqiang Kong, Jindong Zhang, Daiyin Zhu

Abstract:

Space-time adaptive processing (STAP) techniques have been motivated as a key enabling technology for advanced airborne radar applications. In this paper, the notion of cognitive radar is extended to STAP technique, and cognitive STAP is discussed. The principle for improving signal-to-clutter ratio (SCNR) based on slow-time coding is given, and the corresponding optimization algorithm based on cyclic and power-like algorithms is presented. Numerical examples show the effectiveness of the proposed method.

Keywords: Space-time adaptive processing (STAP), signal-to-clutter ratio, slow-time coding.

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6085 Methods for Material and Process Monitoring by Characterization of (Second and Third Order) Elastic Properties with Lamb Waves

Authors: R. Meier, M. Pander

Abstract:

In accordance with the industry 4.0 concept, manufacturing process steps as well as the materials themselves are going to be more and more digitalized within the next years. The “digital twin” representing the simulated and measured dataset of the (semi-finished) product can be used to control and optimize the individual processing steps and help to reduce costs and expenditure of time in product development, manufacturing, and recycling. In the present work, two material characterization methods based on Lamb waves were evaluated and compared. For demonstration purpose, both methods were shown at a standard industrial product - copper ribbons, often used in photovoltaic modules as well as in high-current microelectronic devices. By numerical approximation of the Rayleigh-Lamb dispersion model on measured phase velocities second order elastic constants (Young’s modulus, Poisson’s ratio) were determined. Furthermore, the effective third order elastic constants were evaluated by applying elastic, “non-destructive”, mechanical stress on the samples. In this way, small microstructural variations due to mechanical preconditioning could be detected for the first time. Both methods were compared with respect to precision and inline application capabilities. Microstructure of the samples was systematically varied by mechanical loading and annealing. Changes in the elastic ultrasound transport properties were correlated with results from microstructural analysis and mechanical testing. In summary, monitoring the elastic material properties of plate-like structures using Lamb waves is valuable for inline and non-destructive material characterization and manufacturing process control. Second order elastic constants analysis is robust over wide environmental and sample conditions, whereas the effective third order elastic constants highly increase the sensitivity with respect to small microstructural changes. Both Lamb wave based characterization methods are fitting perfectly into the industry 4.0 concept.

Keywords: Lamb waves, industry 4.0, process control, elasticity, acoustoelasticity.

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6084 Harvesting of Kinetic Energy of the Raindrops

Authors: K. C. R. Perera, B. G. Sampath, V. P. C. Dassanayake, B. M. Hapuwatte.

Abstract:

This paper presents a methodology to harvest the kinetic energy of the raindrops using piezoelectric devices. In the study 1m×1m PVDF (Polyvinylidene fluoride) piezoelectric membrane, which is fixed by the four edges, is considered for the numerical simulation on deformation of the membrane due to the impact of the raindrops. Then according to the drop size of the rain, the simulation is performed classifying the rainfall types into three categories as light stratiform rain, moderate stratiform rain and heavy thundershower. The impact force of the raindrop is dependent on the terminal velocity of the raindrop, which is a function of raindrop diameter. The results were then analyzed to calculate the harvestable energy from the deformation of the piezoelectric membrane.

Keywords: Raindrop, piezoelectricity, deformation, terminal velocity.

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6083 Thixomixing as Novel Method for Fabrication Aluminum Composite with Carbon and Alumina Fibers

Authors: Ebrahim Akbarzadeh, Josep A. Picas Barrachina, Maite Baile Puig

Abstract:

This study focuses on a novel method for dispersion and distribution of reinforcement under high intensive shear stress to produce metal composites. The polyacrylonitrile (PAN)-based short carbon fiber (Csf) and Nextel 610 alumina fiber were dispersed under high intensive shearing at mushy zone in semi-solid of A356 by a novel method. The bundles and clusters were embedded by infiltration of slurry into the clusters, thus leading to a uniform microstructure. The fibers were embedded homogenously into the aluminum around 576-580°C with around 46% of solid fraction. Other experiments at 615°C and 568°C which are contained 0% and 90% solid respectively were not successful for dispersion and infiltration of aluminum into bundles of Csf. The alumina fiber has been cracked by high shearing load. The morphologies and crystalline phase were evaluated by SEM and XRD. The adopted thixo-process effectively improved the adherence and distribution of Csf into Al that can be developed to produce various composites by thixomixing.

Keywords: Aluminum, carbon fiber, alumina fiber, thixomixing, adhesion.

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6082 Influence of Paralleled Capacitance Effect in Well-defined Multiple Value Logical Level System with Active Load

Authors: Chih Chin Yang, Yen Chun Lin, Hsiao Hsuan Cheng

Abstract:

Three similar negative differential resistance (NDR) profiles with both high peak to valley current density ratio (PVCDR) value and high peak current density (PCD) value in unity resonant tunneling electronic circuit (RTEC) element is developed in this paper. The PCD values and valley current density (VCD) values of the three NDR curves are all about 3.5 A and 0.8 A, respectively. All PV values of NDR curves are 0.40 V, 0.82 V, and 1.35 V, respectively. The VV values are 0.61 V, 1.07 V, and 1.69 V, respectively. All PVCDR values reach about 4.4 in three NDR curves. The PCD value of 3.5 A in triple PVCDR RTEC element is better than other resonant tunneling devices (RTD) elements. The high PVCDR value is concluded the lower VCD value about 0.8 A. The low VCD value is achieved by suitable selection of resistors in triple PVCDR RTEC element. The low PV value less than 1.35 V possesses low power dispersion in triple PVCDR RTEC element. The designed multiple value logical level (MVLL) system using triple PVCDR RTEC element provides equidistant logical level. The logical levels of MVLL system are about 0.2 V, 0.8 V, 1.5 V, and 2.2 V from low voltage to high voltage and then 2.2 V, 1.3 V, 0.8 V, and 0.2 V from high voltage back to low voltage in half cycle of sinusoid wave. The output level of four levels MVLL system is represented in 0.3 V, 1.1 V, 1.7 V, and 2.6 V, which satisfies the NMP condition of traditional two-bit system. The remarkable logical characteristic of improved MVLL system with paralleled capacitor are with four significant stable logical levels about 220 mV, 223 mV, 228 mV, and 230 mV. The stability and articulation of logical levels of improved MVLL system are outstanding. The average holding time of improved MVLL system is approximately 0.14 μs. The holding time of improved MVLL system is fourfold than of basic MVLL system. The function of additional capacitor in the improved MVLL system is successfully discovered.

Keywords: Capacitance, Logical level, Constant current source

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6081 Hole Configuration Effect on Turbine Blade Cooling

Authors: A.Hasanpour, M. Farhadi, H.R. Ashorynejad

Abstract:

In this paper a numerical technique is used to predict the metal temperature of a gas turbine vane. The Rising combustor exit temperatures in gas turbine engines necessitate active cooling for the downstream turbine section to avoid thermal failure. This study is performed the solution of external flow, internal convection, and conduction within the metal vane. Also the trade-off between the cooling performances in four different hole shapes and configurations is performed. At first one of the commonly used cooling hole geometry is investigated; cylindrical holes and then two other configurations are simulated. The average temperature magnitude in mid-plan section of each configuration is obtained and finally the lower temperature value is selected such as best arrangement.

Keywords: Forced Convection, Gas Turbine Blade, Hole Configuration

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6080 A Review of Heat Pipe Heat Exchangers Activity in Asia

Authors: Ehsan Firouzfar, Maryam Attaran

Abstract:

Heat pipes are two-phase heat transfer devices with high effective thermal conductivity. Due to the high heat transport capacity, heat exchanger with heat pipes has become much smaller than traditional heat exchangers in handling high heat fluxes. With the working fluid in a heat pipe, heat can be absorbed on the evaporator region and transported to the condenser region where the vapour condenses releasing the heat to the cooling media. Heat pipe technology has found increasing applications in enhancing the thermal performance of heat exchangers in microelectranics, energy saving in HVAC systems for operating rooms,surgery centers, hotels, cleanrooms etc, temperature regulation systems for the human body and other industrial sectors. Development activity in heat pipe and thermosyphon technology in asia in recent years is surveyed. Some new results obtained in Australia and other countries are also included.

Keywords: Heat pipe heat exchanger, Thermosyphone, effectiveness, HVAC system, energy saving, temperature regulation.

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6079 Development of a Paediatric Head Model for the Computational Analysis of Head Impact Interactions

Authors: G. A. Khalid, M. D. Jones, R. Prabhu, A. Mason-Jones, W. Whittington, H. Bakhtiarydavijani, P. S. Theobald

Abstract:

Head injury in childhood is a common cause of death or permanent disability from injury. However, despite its frequency and significance, there is little understanding of how a child’s head responds during injurious loading. Whilst Infant Post Mortem Human Subject (PMHS) experimentation is a logical approach to understand injury biomechanics, it is the authors’ opinion that a lack of subject availability is hindering potential progress. Computer modelling adds great value when considering adult populations; however, its potential remains largely untapped for infant surrogates. The complexities of child growth and development, which result in age dependent changes in anatomy, geometry and physical response characteristics, present new challenges for computational simulation. Further geometric challenges are presented by the intricate infant cranial bones, which are separated by sutures and fontanelles and demonstrate a visible fibre orientation. This study presents an FE model of a newborn infant’s head, developed from high-resolution computer tomography scans, informed by published tissue material properties. To mimic the fibre orientation of immature cranial bone, anisotropic properties were applied to the FE cranial bone model, with elastic moduli representing the bone response both parallel and perpendicular to the fibre orientation. Biofiedility of the computational model was confirmed by global validation against published PMHS data, by replicating experimental impact tests with a series of computational simulations, in terms of head kinematic responses. Numerical results confirm that the FE head model’s mechanical response is in favourable agreement with the PMHS drop test results.

Keywords: Finite element analysis, impact simulation, infant head trauma, material properties, post mortem human subjects.

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6078 Ordinary Differential Equations with Inverted Functions

Authors: Thomas Kampke

Abstract:

Equations with differentials relating to the inverse of an unknown function rather than to the unknown function itself are solved exactly for some special cases and numerically for the general case. Invertibility combined with differentiability over connected domains forces solutions always to be monotone. Numerical function inversion is key to all solution algorithms which either are of a forward type or a fixed point type considering whole approximate solution functions in each iteration. The given considerations are restricted to ordinary differential equations with inverted functions (ODEIs) of first order. Forward type computations, if applicable, admit consistency of order one and, under an additional accuracy condition, convergence of order one.

Keywords: Euler method, fixed points, golden section, multi-step procedures, Runge Kutta methods.

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6077 Unsteady Reversed Stagnation-Point Flow over a Flat Plate

Authors: Vai Kuong Sin, Chon Kit Chio

Abstract:

This paper investigates the nature of the development of two-dimensional laminar flow of an incompressible fluid at the reversed stagnation-point. ". In this study, we revisit the problem of reversed stagnation-point flow over a flat plate. Proudman and Johnson (1962) first studied the flow and obtained an asymptotic solution by neglecting the viscous terms. This is no true in neglecting the viscous terms within the total flow field. In particular it is pointed out that for a plate impulsively accelerated from rest to a constant velocity V0 that a similarity solution to the self-similar ODE is obtained which is noteworthy completely analytical.

Keywords: reversed stagnation-point flow, similarity solutions, analytical solution, numerical solution

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6076 New Delay-Dependent Stability Criteria for Neural Networks With Two Additive Time-varying Delay Components

Authors: Xingyuan Qu, Shouming Zhong

Abstract:

In this paper, the problem of stability criteria of neural networks (NNs) with two-additive time-varying delay compenents is investigated. The relationship between the time-varying delay and its lower and upper bounds is taken into account when estimating the upper bound of the derivative of Lyapunov functional. As a result, some improved delay stability criteria for NNs with two-additive time-varying delay components are proposed. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.

Keywords: Delay-dependent stability, time-varying delays, Lyapunov functional, linear matrix inequality (LMI).

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6075 High Efficiency, Selectivity against Cancer Cell Line of Purified L-Asparaginase from Pathogenic Escherichia coli

Authors: Hazim Saadoon Aljewari, Mohammed Ibraheem Nader, Abdul Hussain M. Alfaisal, NatthidaWeerapreeyakul, Sahapat

Abstract:

L-asparaginase was extracted from pathogenic Escherichia coli which was isolated from urinary tract infection patients. L-asparaginase was purified 96-fold by ultrafiltration, ion exchange and gel filtration giving 39.19% yield with final specific activity of 178.57 IU/mg. L-asparaginase showed 138,356±1,000 Dalton molecular weight with 31024±100 Dalton molecular mass. Kinetic properties of enzyme resulting 1.25×10-5 mM Km and 2.5×10-3 M/min Vmax. L-asparaginase showed a maximum activity at pH 7.5 when incubated at 37 ºC for 30 min and illustrated its full activity (100%) after 15 min incubation at 20-37 ºC, while 70% of its activity was lost when incubated at 60 ºC. L-asparaginase showed cytotoxicity to U937 cell line with IC50 0.5±0.19 IU/ml, and selectivity index (SI=7.6) about 8 time higher selectivity over the lymphocyte cells. Therefore, the local pathogenic E. coli strains may be used as a source of high yield of L-asparaginase to produce anti cancer agent with high selectivity.

Keywords: L-asparaginase, Purification, Cytotoxicity, selectivity index

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6074 A Sliding Mesh Technique and Compressibility Correction Effects of Two-equation Turbulence Models for a Pintle-Perturbed Flow Analysis

Authors: J. Y. Heo, H. G. Sung

Abstract:

Numerical simulations have been performed for assessment of compressibility correction of two-equation turbulence models suitable for large scale separation flows perturbed by pintle strokes. In order to take into account pintle movement, a sliding mesh method was applied. The chamber pressure, mass flow rate, and thrust have been analyzed, and the response lag and sensitivity at the chamber and nozzle were estimated for a movable pintle. The nozzle performance for pintle reciprocating as its insertion and extraction processes, were analyzed to better understand the dynamic performance of the pintle nozzle.

Keywords: Pintle, sliding mesh, turbulent model, compressibility correction.

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6073 Optimization of Multifunctional Battery Structures for Mars

Authors: James A Foster, Guglielmo S Aglietti

Abstract:

Multifunctional structures are a potentially disruptive technology that allows for significant mass savings on spacecraft. The specific concept addressed herein is that of a multifunctional power structure. In this paper, a parametric optimisation of the design of such a structure that uses commercially available battery cells is presented. Using numerical modelling, it was found that there exists several trade-offs aboutthe conflict between the capacity of the panel and its mechanical properties. It was found that there is no universal optimal location for the cells. Placing them close to the mechanical interfaces increases loading in the mechanically weak cells whereas placing them at the centre of the panel increases the stress inthe panel and reduces the stiffness of the structure.

Keywords: Design Optimization, Multifunctional Structures, Power Storage.

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6072 Algebraic Riccati Matrix Equation for Eigen- Decomposition of Special Structured Matrices; Applications in Structural Mechanics

Authors: Mahdi Nouri

Abstract:

In this paper Algebraic Riccati matrix equation is used for Eigen-decomposition of special structured matrices. This is achieved by similarity transformation and then using algebraic riccati matrix equation to triangulation of matrices. The process is decomposition of matrices into small and specially structured submatrices with low dimensions for fast and easy finding of Eigenpairs. Numerical and structural examples included showing the efficiency of present method.

Keywords: Riccati, matrix equation, eigenvalue problem, symmetric, bisymmetric, persymmetric, decomposition, canonical forms, Graphs theory, adjacency and Laplacian matrices.

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6071 Geometrical Based Unequal Droplet Splitting Using Microfluidic Y-Junction

Authors: Bahram Talebjedi, Amirmohammad Sattari, Ahmed Zoher Sihorwala, Mina Hoorfar

Abstract:

Among different droplet manipulations, controlled droplet-splitting is of great significance due to its ability to increase throughput and operational capability. Furthermore, unequal droplet-splitting can provide greater flexibility and a wider range of dilution factors. In this study, we developed two-dimensional, time-dependent complex fluid dynamics simulations to model droplet formation in a flow focusing device, followed by splitting in a Y-shaped junction with sub-channels of unequal widths. From the results obtained from the numerical study, we correlated the diameters of the droplets in the sub-channels to the Weber number, thereby demarcating the droplet splitting and non-splitting regimes.

Keywords: Microfluidics, unequal droplet splitting, two phase flow, flow focusing device.

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6070 Material Concepts and Processing Methods for Electrical Insulation

Authors: R. Sekula

Abstract:

Epoxy composites are broadly used as an electrical insulation for the high voltage applications since only such materials can fulfill particular mechanical, thermal, and dielectric requirements. However, properties of the final product are strongly dependent on proper manufacturing process with minimized material failures, as too large shrinkage, voids and cracks. Therefore, application of proper materials (epoxy, hardener, and filler) and process parameters (mold temperature, filling time, filling velocity, initial temperature of internal parts, gelation time), as well as design and geometric parameters are essential features for final quality of the produced components. In this paper, an approach for three-dimensional modeling of all molding stages, namely filling, curing and post-curing is presented. The reactive molding simulation tool is based on a commercial CFD package, and include dedicated models describing viscosity and reaction kinetics that have been successfully implemented to simulate the reactive nature of the system with exothermic effect. Also a dedicated simulation procedure for stress and shrinkage calculations, as well as simulation results are presented in the paper. Second part of the paper is dedicated to recent developments on formulations of functional composites for electrical insulation applications, focusing on thermally conductive materials. Concepts based on filler modifications for epoxy electrical composites have been presented, including the results of the obtained properties. Finally, having in mind tough environmental regulations, in addition to current process and design aspects, an approach for product re-design has been presented focusing on replacement of epoxy material with the thermoplastic one. Such “design-for-recycling” method is one of new directions associated with development of new material and processing concepts of electrical products and brings a lot of additional research challenges. For that, one of the successful products has been presented to illustrate the presented methodology.

Keywords: Curing, epoxy insulation, numerical simulations, recycling.

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6069 The Didactic Transposition in Brazilian High School Physics Textbooks: A Comparative Study of Didactic Materials

Authors: Leandro Marcos Alves Vaz

Abstract:

In this article, we analyze the different approaches to the topic Magnetism of Matter in physics textbooks of Brazilian schools. For this, we compared the approach to the concepts of the magnetic characteristics of materials (diamagnetism, paramagnetism, ferromagnetism and antiferromagnetism) in different sources of information and in different levels of education, from Higher Education to High School. In this sense, we used as reference the theory of the Didactic Transposition of Yves Chevallard, a French educational theorist, who conceived in his theory three types of knowledge – Scholarly Knowledge, Knowledge to be taught and Taught Knowledge – related to teaching practice. As a research methodology, from the reading of the works used in teacher training and those destined to basic education students, we compared the treatment of a higher education physics book, a scientific article published in a Brazilian journal of the educational area, and four high school textbooks, in order to establish in which there is a greater or lesser degree of approximation with the knowledge produced by the scholars – scholarly knowledge – or even with the knowledge to be taught (to that found in books intended for teaching). Thus, we evaluated the level of proximity of the subjects conveyed in high school and higher education, as well as the relevance that some textbook authors give to the theme.

Keywords: Magnetism of matter, teaching of physics, didactic transposition, Brazilian physics books.

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