bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructures and growth characteristics of polyelectrolytes on silicon using layer-by-layer assembly
Authors: Bragaru Adina , Kusko Mihaela , Radoi Antonio , Danila Mihai , Simion Monica , Craciunoiu Florea , Pascu Razvan , Mihalache Iuliana , Ignat Teodora
Published: November 2012

Growth processes of nanocomposite layers obtained by polyelectrolytes, poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC), self-assembled on silicon surface using layer-by-layer (LbL) technique were investigated, and theoretical and experimental data are herein reported. Complementary microstructural and compositional analyses techniques (scanning electron microscopy, ellipsometry, X-ray reflectivity, zeta (ξ) potential measurements and attenuated total reflection infrared spectroscopy) were used for deep characterization of the multilayer structure formation. Electrophoretic zeta (ξ) potential measurements indicated that the surface charge was either positive or negative, depending on the polyelectrolyte used (PDADMAC or PSS). ATR-IR spectra confirmed the successfully silanization process and then, the building up of the nanocomposite layer. Morphological investigation and X-ray reflectivity demonstrated the growth process and cross-section size of the bilayers. Ellipsometric measurements were in very good agreement with SEM and XRR, showing once again the successful deposition of polyelectrolyte multilayers.
Racism, College, and the Power of Words
Authors: Minikel-Lacocque Julie
Published: November 2012

Based on interview data from a collective case study, this article uses current notions of racial microaggressions to explore this “subtle” racism through the voices of six Latino/a students as they transition to a predominantly White university. Using critical race theory as a framework, I argue for greater understanding and increased use of the term racial microaggressions within education generally and specifically with regard to higher education. I also, however, argue for specific changes in the existing framework of racial microaggressions, contending that the term microaggression is at times misused within academia and that this misuse has potentially negative consequences. Implications for discussions of racism writ large as well as for specific changes on college campuses are discussed.
Lipids of Prokaryotic Origin at the Base of Marine Food Webs
Authors: De Carvalho Carla , Caramujo Maria
Published: November 2012

In particular niches of the marine environment, such as abyssal trenches, icy waters and hot vents, the base of the food web is composed of bacteria and archaea that have developed strategies to survive and thrive under the most extreme conditions. Some of these organisms are considered “extremophiles” and modulate the fatty acid composition of their phospholipids to maintain the adequate fluidity of the cellular membrane under cold/hot temperatures, elevated pressure, high/low salinity and pH. Bacterial cells are even able to produce polyunsaturated fatty acids, contrarily to what was considered until the 1990s, helping the regulation of the membrane fluidity triggered by temperature and pressure and providing protection from oxidative stress. In marine ecosystems, bacteria may either act as a sink of carbon, contribute to nutrient recycling to photo-autotrophs or bacterial organic matter may be transferred to other trophic links in aquatic food webs. The present work aims to provide a comprehensive review on lipid production in bacteria and archaea and to discuss how their lipids, of both heterotrophic and chemoautotrophic origin, contribute to marine food webs.
Epstein-Barr Virus (EBV)-associated Gastric Carcinoma
Authors: Iizasa Hisashi , Nanbo Asuka , Nishikawa Jun , Jinushi Masahisa , Yoshiyama Hironori
Published: November 2012

The ubiquitous Epstein-Barr virus (EBV) is associated with several human tumors, which include lymphoid and epithelial malignancies. It is known that EBV persistently infects the memory B cell pool of healthy individuals by activating growth and survival signaling pathways that can contribute to B cell lymphomagenesis. Although the monoclonal proliferation of EBV-infected cells can be observed in epithelial tumors, such as nasopharyngeal carcinoma and EBV-associated gastric carcinoma, the precise role of EBV in the carcinogenic progress is not fully understood. This review features characteristics and current understanding of EBV-associated gastric carcinoma. EBV-associated gastric carcinoma comprises almost 10% of all gastric carcinoma cases and expresses restricted EBV latent genes (Latency I). Firstly, definition, epidemiology, and clinical features are discussed. Then, the route of infection and carcinogenic role of viral genes are presented. Of particular interest, the association with frequent genomic CpG methylation and role of miRNA for carcinogenesis are topically discussed. Finally, the possibility of therapies targeting EBV-associated gastric carcinoma is proposed.
Analytical Psychology
Authors: Jung Carl Gustav
Published: November 2012

Ce texte est une première publication en français d’un extrait des notes du séminaire donné par C.G. Jung, en 1925 : Conférence 7, du 4 mai 1925 (p. 50 à 56), C.G. Jung, The Seminars, vol. 3, Analytical Psychology, Notes of the Seminar Given in 1925, Edited by William Mc Guire, London, Routledge, 1990. Avec l’aimable autorisation de Michel Cazenave et des éditions Albin Michel. La publication de l’ensemble de ce séminaire paraîtra prochainement chez Albin Michel, dans sa nouvelle version révisée par Sonu Shamdasani et parue en 2012 dans les Philemon Series. La traduction en français en est assurée par Karen Hainsworth et Viviane Thibaudier.
Ouverture des marchés cinématographiques et remise en cause de la diversité des expressions culturelles
Authors: Vlassis Antonios
Published: November 2012

Résumé Comme le montre la condamnation par l’Organisation mondiale du commerce (OMC) des règlements audiovisuels de la Chine et l’accord de libre-échange entre la Corée du Sud et les États-Unis, la conquête des marchés cinématographiques asiatiques reste un enjeu économique considérable pour les États-Unis et Hollywood. D’ailleurs, l’ouverture du marché cinématographique chinois illustre une défaite paradoxale de la Convention sur la diversité des expressions culturelles (CDEC). Le système chinois quasi-imperméable tend à s’ouvrir de plus en plus aux produits audiovisuels non nationaux grâce au principe du libre-échange, tandis que, jusqu’à présent, les Parties à la CDEC souhaitaient privilégier le consensus politique plutôt que dénoncer des politiques culturelles strictes qui interdisent les échanges culturels équitables.
Aproximación teórica a la relación entre los términos gestión documental, gestión de información y gestión del conocimiento
Authors: Gauchi Risso Verónica
Published: November 2012

El objeto de esta exposición consiste en el abordaje teórico de los términos gestión documental, gestión de información y gestión del conocimiento y las relaciones existentes entre ellos. Este trabajo corresponde a un estudio de revisión o compilación de tipo descriptivo, en el que los términos seleccionados son descritos uno a uno en sus características y que tiene por finalidad transmitir informaciones válidas científicamente con el objeto de establecer una relación entre los términos propuestos. Tres aspectos confluyen en la conceptualización: documentos, tecnologías de la comunicación y personas; la combinación de todas ellas da lugar a una serie de capacidades que son lo que constituye el capital de toda organización; este proceso evidencia una relación estrecha entre la gestión documental, de información y del conocimiento que conforman un equipo complementario e imprescindible en toda organización.
An overview of the spectral induced polarization method for near‐surface applications
Authors: Kemna Andreas , Binley Andrew , Cassiani Giorgio , Niederleithinger Ernst , Revil André , Slater Lee , Williams Kenneth H. , Orozco Adrián Flores , Haegel Franz‐Hubert , Hördt Andreas , Kruschwitz Sabine , Leroux Virginie , Titov Konstantin , Zimmermann Egon
Published: November 2012

Over the last 15 years significant advancements in induced polarization (IP) research have taken place, particularly with respect to spectral IP (SIP), concerning the understanding of the mechanisms of the IP phenomenon, the conduction of accurate and broadband laboratory measurements, the modelling and inversion of IP data for imaging purposes and the increasing application of the method in near‐surface investigations. We summarize here the current state of the science of the SIP method for near‐surface applications and describe which aspects still represent open issues and should be the focus of future research efforts. Significant progress has been made over the last decade in the understanding of the microscopic mechanisms of IP; however, integrated mechanistic models involving different possible polarization processes at the grain/pore scale are still lacking. A prerequisite for the advances in the mechanistic understanding of IP was the development of improved laboratory instrumentation, which has led to a continuously growing data base of SIP measurements on various soil and rock samples. We summarize the experience of numerous experimental studies by formulating key recommendations for reliable SIP laboratory measurements. To make use of the established theoretical and empirical relationships between SIP characteristics and target petrophysical properties at the field scale, sophisticated forward modelling and inversion algorithms are needed. Considerable progress has also been made in this field, in particular with the development of complex resistivity algorithms allowing the modelling and inversion of IP data in the frequency domain. The ultimate goal for the future are algorithms and codes for the integral inversion of 3D, time‐lapse and multi‐frequency IP data, which defines a 5D inversion problem involving the dimensions space (for imaging), time (for monitoring) and frequency (for spectroscopy). We also offer guidelines for reliable and accurate measurements of IP spectra, which are essential for improved understanding of IP mechanisms and their links to physical, chemical and biological properties of interest. We believe that the SIP method offers potential for subsurface structure and process characterization, in particular in hydrogeophysical and biogeophysical studies.
Improvement in time‐domain induced polarization data quality with multi‐electrode systems by separating current and potential cables
Authors: Dahlin Torleif , Leroux Virginie
Published: November 2012

Measuring induced polarization in the time domain with relatively compact multi‐channel multi‐electrode systems is attractive because of the simplicity of the procedure and thus its efficiency in the field. However the use of this technique is sometimes discouraged by the bad quality of the measurements in cases of high electrode contact resistances that can render data interpretation infeasible or at least unreliable. It is proposed that capacitive coupling in the multi‐core electrode cables has a significant role in creating this problem.

In such cases separation of current and potential circuits by using separate multi‐conductor cable spreads can yield significant improvement in data quality. The procedure is relatively simple and can be implemented with common resistivity and time‐domain IP equipment.

We show here three field examples from Southern Sweden, all measured as 2D electrical imaging sections. The first one is an example where the use of a single cable spread is sufficient thanks to moderate electrode contact resistance and high signal levels. The following two examples are from sites where induced polarization measurements could not yield consistent results using only a single multi‐conductor cable spread. Useful results were subsequently obtained by using separate cable spreads.

The first example is a 280 m long line measured over an old covered municipal waste deposit where the waste body stands out as a zone of high chargeability. The second example is a 120 m line measured on a sandy glaciofluvial structure that is host to an aquifer of regional importance. The improvement led to discrimination between materials of different grain sizes, with potential bearing for understanding the aquifer. The third example is a 300–400 m line measured across an esker lying on clay till. The improvement led to a clear visualization of the esker and to the identification of a possible fault in the underlying gneissic bedrock.

In all cases pseudosections and examples of chargeability decay curves are shown and discussed as tools for assessing data quality. Inversion results are shown together with background geological information and it is concluded that they are in good agreement.
Integrated analysis of waveguide dispersed GPR pulses using deterministic and Bayesian inversion methods
Authors: Bikowski Jutta , Huisman Johan A. , Vrugt Jasper A. , Vereecken Harry , Kruk Jan van der
Published: November 2012

Ground‐penetrating radar (GPR) data affected by waveguide dispersion are not straightforward to analyse. Therefore, waveguide dispersed common midpoint measurements are typically interpreted using so‐called dispersion curves, which describe the phase velocity as a function of frequency. These dispersion curves are typically evaluated with deterministic optimization algorithms that derive the dielectric properties of the subsurface as well as the location and depth of the respective layers. However, these methods do not provide estimates of the uncertainty of the inferred subsurface properties. Here, we applied a formal Bayesian inversion methodology using the recently developed DiffeRential Evolution Adaptive Metropolis algorithm. This Markov Chain Monte Carlo simulation method rapidly estimates the (non‐linear) parameter uncertainty and helps to treat the measurement error explicitly. We found that the frequency range used in the inversion has an important influence on the posterior parameter estimates, essentially because parameter sensitivity varies with measurement frequency. Moreover, we established that the measurement error associated with the dispersion curve is frequency dependent and that the estimated model parameters become severely biased if this frequency‐dependent nature of the measurement error is not properly accounted for. We estimated these frequency‐dependent measurement errors together with the model parameters using the algorithm. The posterior distribution of the model parameters derived in this way compared well with inversion results for a reduced frequency bandwidth which is an alternative, yet subjective method to reduce the bias introduced by this frequency‐dependent measurement error. Altogether, our inversion procedure provides an integrated and objective methodology for the analysis of dispersive GPR data and appropriately treats the measurement error and parameter uncertainty.
Mapping of landfills using time‐domain spectral induced polarization data: the Eskelund case study
Authors: Gazoty A. , Fiandaca G. , Pedersen J. , Auken E. , Christiansen A.V.
Published: November 2012

This study uses time‐domain induced polarization data for the delineation and characterization of the former landfill site at Eskelund, Denmark. With optimized acquisition parameters combined with a new inversion algorithm, we use the full content of the decay curve and retrieve spectral information from time‐domain IP data. Thirteen IP/DC profiles were collected in the area, supplemented by el‐log drilling for accurate correlation between the geophysics and the lithology. The data were inverted using a laterally constrained 1D inversion considering the full decay curves to retrieve the four Cole‐Cole parameters. For all profiles, the results reveal a highly chargeable unit that shows a very good agreement to the findings from 15 boreholes covering the area, where the extent of the waste deposits was measured. The thickness and depth of surface measurements were furthermore validated by el‐log measurements giving in situ values, for which the Cole‐Cole parameters were computed. The 3D shape of the waste body was pinpointed and well‐defined. The inversion of the IP data also shows a strong correlation with the initial stage of the waste dump and its composition combining an aerial map with acquired results.
Optimization of the Composite Truncated Cone Structure Layers under Buckling Load
Authors: Pour Hadi Samareh Salavati , Sadighi Mojtaba , Kami Abdolvahed
Published: November 2012

The orientation of fibers in the layers is an important factor that must be obtained in order to predict how well the finished composite product will perform under real-world working conditions. In this research, a five-layer glass-epoxy composite truncated cone structure under buckling load was considered. The simulation of the structure was done utilizing finite element method and was confirmed comparing with the published experimental results. Then the effect of different orientation of fibers on the buckling load was considered. For this, a computer programing was developed to compute the buckling load for different orientations of fibers in each layer. These orientations were produced randomly with the delicacy of 15 degrees. Finally, neural network and genetic algorithm methods were utilized to obtain the optimum orientations of fibers in each layer using the training data obtained from finite element simulation. There are many parameters such as the number of hidden layers, the number of neurons in each hidden layer, the training algorithm, the activation function and so on which must be specified properly in development of a neural network model. The number of hidden layers and number of neurons in each layer was obtained by try and error method. In this study, multilayer back-propagation (BP) neural network with the Levenberg-Marquardt training algorithm (trainlm) was used. Finally, the results showed that the truncated cone with optimum layers withstand considerably more buckling load.
Multiple Delaminations Growth in Composite Laminates under Compressive Cyclic Loading in Post-Buckling
Authors: Hosseini-Toudeshky Hossein , Goodarzi M. Saeed , Mohammadi Bijan
Published: November 2012

Due to discontinuity of mechanical properties in composite laminates, failure occurs in different damage mechanisms. Delamination growth of adjacent layers is a major failure mechanism in laminates with various layup configurations. Pre existing delamination may initiate in composite laminate before use, due to impact in assembly and fabrication process. Cyclic compressive loading may cause delamination growth due to both post-bucking behavior and fatigue nature of loading. In this paper, a 3D mixed-mode interface element model has been developed to simulate the growth of multiple delaminations under compressive cyclic loading. For this purpose, the presented model should be able to handle the geometry nonlinearity of post-buckling and material nonlinearity of cohesive zone constitutive law under cyclic loading at interfaces. Because of mixed-mode condition of stress field at the delamination-front of post-buckled laminates, a mixed-mode bilinear constitutive law has been used as user material in this model. Paris Law has been used to relate the energy release rate to the fatigue crack growth in cohesive zone. A composite laminate with pre-existing delamination under buckling load, available from the literature has been reproduced with the present approach. Finally, laminates containing multiple delaminations in various interface layers have been analyzed under compressive fatigue loading. It is shown that the pre-existing delamination with more depth from the surface of laminate causes more initial static and fatigue delamination growth rate.
Composite Repair of Curved Stiffened Aluminum Panels under Combined Tension and Shear Cyclic Loadings
Authors: Hosseini-Toudeshky Hossein , Ghaffari Mir Ali , Mohammadi Bijan
Published: November 2012

In this study, finite element method is used to investigate the fracture analyses, crack growth trajectory and fatigue life of curved stiffened panels repaired with composite patches subjected to combined tension and shear cyclic loadings. For this purpose, 3-D finite element modeling are performed for consideration of real 3-D crack-front in general mixed-mode conditions. Contact elements are used between the crack surfaces on two crack sides to prevent interferences of crack surfaces and a complementary program was developed to handle the automatic fatigue crack growth modeling. The effects of various patch layups and shear-tension loading ratios on fracture parameters of the aluminum panel are investigated. It is shown that in low shear to tension ratios like 0.4, the patch layup of [90]4 (perpendicular to the initial crack) is more efficient than the patch with layups angle along the tension loading. As the shear to tension ratio increases, effect of patch layups with orientations of almost perpendicular to the crack trajectory on fatigue crack growth life is increased comparing with the patch layups parallel to the tension orientation like [90]4.
Investigation into the Temperature Impact on O-Ring’s Sealing Performance Using Advanced Stress Relaxation Test
Authors: Liu Yue , Wilson Christopher W.
Published: November 2012

Due to the lack of historical data, sealing performance of O-rings in the fuel system of aircraft engines is particularly difficult to study. As great efforts are being made to develop alternative fuels in aviation industry, their compatibility issue with elastomeric O-ring materials has become a major concern. So far, no data has been published on how O-rings would behave in alternative fuel scenario while taking the temperature factor into consideration. The purpose of this paper is to investigate into O-ring’s sealing performance under various temperature conditions, with comparison between Gas-to-Liquid (GtL) synthetic fuel and Jet A-1. Technique used to stimulate the real service scenario for O-rings is the stress relaxation test. Distinguishing from regular relaxation techniques, an advanced stress relaxation rig (Elastocon EB17) with the capability of temperature cycling was employed for this study. Nitrile and fluorosilicone O-ring materials which are commonly found in the fuel system were tested respectively. Three sets of tests were designed to look at how each O-ring material will behave under different temperature conditions. Results obtained so far indicated under extremely low temperature conditions, the relaxation processes of both O-ring materials seem to be ‘frozen’ as the sealing force stops decreasing and maintains a relatively stable level. No fuel preference has shown during the process as O-rings in both GtL and Jet A-1 behaved similarly. Nitrile O-ring showed better relaxation characteristic in Jet A-1 than that in GtL under the 24-hour temperature cycling test; while fluorosilicone presented little differences in these two fuels.
Mathematical Model Development of TMM25-Single Shaft Turbojet Engine
Authors: Azzabi Khaled I. , Elmahmodi Aiman
Published: November 2012

A nonlinear mathematical model with thermodynamic relations permitting an accurate assessment of the dynamic influence on performance is developed in this study. The model is used within the framework of engine design in the development stage and in implementation stage. The use of simulations can give an invaluable insight into transient response and control problems; a significant saving is achieved with minimum test bed hardware development without endangering an engine. Successful simulations have been carried out using the proposed algorithm; an application utilizing Object Orientated Programming (OOP) was developed. The results obtained by the present developed model are in fair agreement with available experimental data.
A New Concurrent Engineering – Multi Criteria Decision Making Technique for Conceptual Design Selection
Authors: Fatchurrohman Nanang , Sulaiman Shamsuddin , Sapuan S.M. , Ariffin Mohd Khairol Anuar , Baharudin B.T. Hang Tuah
Published: November 2012

Product development process involves conceptual design selection, which is an activity engaging with numerous types of data including technical-customer specifications and current design developments. This paper presents a conceptual design selection which employs a new technique which accommodates Concurrent Engineering (CE) – Multi Criteria Decision Making (MCDM) strategies. This new technique combines Concurrent Network (CE-ANP), Quality Function Deployment (QFD) and Analytical Hierarchy Process (AHP), referred as CoNQA. To illustrate this technique, a case study is presented involving aerospace application which is the selection of wing spar material. The result shows that the proposed new technique proved to be a sound method which considers product performance, product specification, technical specifications and selection of the best alternative in the selection process. This new method should be a useful aid for designers in collaboration with engineers to perform systematic and parallel technique involving early consideration of technical-customer requirements during conceptual design, hence to establish good product design and increase product competitiveness.
Wake Frequency Analysis of a Plunging Airfoil with Trailing-Edge Strips
Authors: Ajalli Fariba , Mani Mahmoud , Gharakhanlou Mozhgan
Published: November 2012

Experimental measurements were conducted on a plunging Eppler 361 strip flapped airfoil to study wake structure in the wake. The heights of strip flap were 2.6% and 3.3% chord. The velocity in the wake was measured by hot-wire anemometry. It was found that the trailing-edge strip had different effects on the plunging wake profile during the oscillation cycle. At initial angle of 0 degree, the trailing-edge strip causes more velocity defect in the oscillation phases of 180º and 270º. At high initial angle 12 degrees, a significant decrease in value of velocity is found at 180º because of the leading edge vortex shedding. The power spectra of dominant frequencies were significantly increased by fitting the strip flap on the plunging airfoil.
Computer Aided Design, Analysis and Prototype Development of 2-Axis Stabilized Aerial Image Capturing
Authors: Zihad Mohamad Mahmud , Ahmad Kamarul Arifin , Kadarman A. Halim
Published: November 2012

This paper presents an ongoing study and research of a 2-Axis stabilized aerial image capturing system to obtain aerial images. Aerial images are commonly used for reconnaissance, area surveying, and also for search and rescue mission. Currently, several methods of remote sensing were developed with multiple objectives either for civil or military applications to obtain high precision images. The study involves the design and fabrication of 2-Axis stabilized image system platform. Rolling and pitching motion of an air vehicle effects while airborne to acquire sharp vertical images are the main consideration in this study.
An Experimental Investigation on the Effect of Various Swirl Atomizer Orifice Geometries on the Air Core Diameter
Authors: Rashid Mohd Syazwan Firdaus Mat , Hamid Ahmad Hussein Abdul , Ow Chee Sheng , Ghaffar Zulkifli Abdul
Published: November 2012

Liquid atomization is a process of changing the liquid into small droplets. There are many applications which are related to liquid atomization including fuel injection in combustion systems and also in agricultural sprays. In pressure swirl atomizer, the liquid is injected into the atomizer through tangential port and a swirling motion is formed inside the swirl chamber. In high strength of swirling motion, an air core will be visible inside the atomizer. The liquid is then discharged from the orifice to form a spray which breaks up the liquid into small droplets. The objective of this research is to investigate the effect of various orifice geometries on the air core diameter. The injection pressure was varied in the range of 2 to 8 bar and water was used as the working fluid. Experiment data shows that the air core diameter increases as the injection pressure increased, regardless the discharge orifice diameter and discharge orifice length. It also found that the air core diameter increases as the discharge orifice length decreases and the discharge orifice diameter increases.
Implementation of Extreme Low Power Micro-Controller for a Wireless Structural Health Monitoring (SHM) System
Authors: Zainol Mohamad Zikri , Mustapha Faizal , Sultan Mohamed Thariq Hameed , Yidris N.
Published: November 2012

This paper presents the newly improved design of wireless sensor technology for Structural Health Monitoring (SHM) system or continuous monitoring for Non Destructive Testing (NDT). Numerous researches have indulged in designing wireless sensor networks where the reliability and the capability to do rapid assessment on the aeronautical, mechanical and civil structure are concerned. A lot of challenges associated with the design have been discussed including on power consumption by the device with regards the operation nature over period of times vs. energy sources. This research project explores the implementation of Nano Watt XLPTM technology microcontroller from Microchip and applicable smart PZT sensors or the newly refined technique in (NDT) that utilise ultrasonic guided waveform response to detect structural defects. The developed SHM system provide low power wireless nodes to perform automatic data collection and analysis with possibilities to integrate with green energy sources more effectively thus reducing the cost of maintenance and increase the reliability of the system.
Performance Analysis of Smart Composite Structure Using Shape Memory Alloy Actuators
Authors: Abdullah Ermira Junita , Abdul Majid Dayang Laila Abang , Yuan Lim Gui , Harun Nurul Fareha
Published: November 2012

Smart structures are able to adapt, alter or change in response to external stimuli. The analysis and design of smart structures involves a highly multi-disciplinary effort which includes structures, materials, dynamics, control and design. Shape memory alloy (SMA) is a suitable candidate for actuator in the smart structure design as it can be activated to alter the shape of the structure. This paper proposes a design for smart composite structure suitable for aerospace applications. Finite element method (FEM) was used to analyze a designer structure which is able to meet the requirements for smart structure as well as determining the placement of the actuators within the structure. Due to the nonlinear behavior of the SMA actuator, it is critical to incorporate a feedback control system that is able to accurately morph the structure. A prototype of the smart composite structure was fabricated and its performance was analyzed.
The Aerodynamics Investigation of Vortex Trap on Helicopter Blade
Authors: Yaakub M.F. , Wahab A.A. , Abdul Ghafir Mohammad Fahmi , Mohd Yunos Siti Nur Mariani , Salleh Siti Juita Mastura Mohd , Kamarudin Qamarul Ezani , Masrom Mohd Fikri Mohd
Published: November 2012

During helicopter forward flight, the retreating blade revolves at high angle of attack compared to advancing blade in order to balance the lift and also to stabilise the helicopter. However, due to the aerodynamics limitations of the retreating blade at forward flight, stall may occur at high angle of attack compared with the advancing blade. This phenomenon is dangerous for pilot when controlling and balancing the helicopter while flying against strong wind. This paper investigates the capabilities of introducing multiple vortex traps on the upper surface of the helicopter airfoil in order to delay the stall angle of retreating helicopter blade. Blade Element Theory (BET) was applied to scrutinize the lift force along the helicopter blade. Computational Fluid Dynamic (CFD) analyses using the Shear-Stress Transport (SST) turbulence model was carried out to investigate the effect of groove on delaying the stall and to predict the separation of flow over the airfoil. Based on the CFD analyses, the optimization of the groove was done by analyzing the numbers and locations of the grooves. Finally, the results from both BET and the CFD analyses were utilised to obtain the lift force achieved by the vortex trap. The study showed that the presence of multiple vortex traps has successfully increased the lift coefficient and most importantly, delaying the stall angle.
Diurnal and Seasonal Variation of Critical Frequency in Malaysia from 2005 to 2007
Authors: Abdullah Sabirin , Mohd Zain Ahmad Faizal
Published: November 2012

Ionospheric layer plays an important role as the main medium for communication of wireless radio in the High Frequency (HF) band. Critical frequencies are important parameters of the ionosphere. Critical frequencies vary diurnally following the pattern of day and night due to the activities of the sun. The critical frequency for Parit Raja station is determined using an ionosonde at latitude 1° 52' N and longitude 103° 48' E, which are close to the geomagnetic equator at geographic latitude 5° N. This work analyses the dependence of the critical frequency during the solar minimum of Solar Cycle 23. From the observations, the critical frequency observed in 2005 was the highest, corresponding to a higher sunspot number of between 11 and 192. The general trend of the daily critical frequency was 6.8 MHz to 12.0 MHz from 00:00 to 17:30 Coordinated Universal Time (UTC) and decreasing to 7.0 MHz from 18:00 to 23:00 UTC. The average value of the critical frequency for 2005 to 2007 was 7.5 MHz, with a minimum of 1.8 MHz and a maximum of 11.0 MHz. The results showed a slow decrease from 2006 to 2007 for the critical frequencies in 2006 and 2007.
Passive Attitude Control Torque Generation Performances of a Gravity Gradient Stabilized Satellite
Authors: Suhadis Nurulasikin Mohd , Varatharajoo Renuganth
Published: November 2012

In this paper, the Proportional-Derivative (PD) based attitude control algorithm of the gravity gradient stabilized satellite has been developed. The satellite is equipped with 3 magnetic torquers where each of the magnetic torquer is placed along the +x, +y, +z axes. The control torque is generated when the magnetic field generated by the magnetic torquers couples with the geomagnetic fields, whereby the vector of the generated torque is perpendicular to both the magnetic fields. The developed control algorithm was simulated using the complex and simplified geomagnetic field models for a Low Earth Orbit (LEO) satellite mission in a nominal attitude operation. Results from simulations exhibit the effectiveness of the attitude control torque generation that fulfills the mission attitude control requirements.
Thermal Analysis of CUBESAT in Worse Case Hot and Cold Environment Using FEA Method
Authors: Thanarasi Karthigesu
Published: November 2012

One of the necessary parts of CubeSat’s design is the thermal analysis. It will provide the operating temperatures and their distribution for all devices inside the CubeSat. For decision, which temperature standard can be used for components it is necessary to know the maximum and the minimum value of the temperature. In virtue of these results the position of the all devices must be also optimized. Some methods of the thermal control are also proposed. Contrary to most subsystems the thermal subsystem is not independent of the others. All elements in the spacecraft have an influence on the thermal housekeeping by either emitting or absorbing energy or both respectively. The objective of thermal subsystem is to ensure that the spacecraft operate within the spacecraft operating temperature range. There are two types of thermal control technique; passive and active. Due to the size and power constraint of CubeSat, passive thermal control will be more suitable but analysis must be done in order to know that passive control is sufficient. The FEA methodology would be utilized in order to determine the spacecraft operating temperature within the range. To accomplish this, MSC Nastran Patran software will be used as the FEA modeling tool. The MD Patran will act as preprocessing tool whereas MD Nastran will act as post processing tool. If the simulated thermal range is deviates, temperature sensors and heaters will be mounted on the CubeSat to monitor the deviation. Alternatively, mounting Kapton tape onto the CubeSat structure and laying gold coating would be another method to maintain the desired temperature range. The design of the thermal system shall be based on passive methods. This approach is vital to avoid power consumption in cases where it would not be necessary. As conclusion the thermal subsystem is designed to operate the spacecraft throughout its mission phases without any failure.
Application of Back Propagation Neural Network Algorithms on Modeling Failure of B-737 Bleed Air System Valves in Desert Conditions
Authors: Abdelrahman Wael G. , Al-Garni Ahmed Z. , Al-Wadiee Waheed
Published: November 2012

Accurate life prediction of aircraft engine components is very critical because it has a direct impact on aircraft safety and on operators’ profits. The engine bleed air system valves have considerably high failure rates when the engines are operated in desert conditions because of sand particles erosion and blockage. In this work, an Artificial Neural Network (ANN) model for the prediction of failure rate of the most important of these valves in Boeing 737 engines is developed and validated. A previously developed feed-forward back-propagation algorithm is implemented to train the ANN. The effects of changing the number of neurons in the input layer, the number of neurons in the hidden layer, the rate of learning, and the momentum constant are investigated. The model results are validated using comparisons with actual valves failure data from a local operator in Saudi Arabia, as well as comparisons with classical Weibull model results.
Reliability Analysis for the Power and Propulsion System of Stratospheric Airship
Authors: Liu Jian , Wang Quan Bao , Chen Jian , Duan Deng Ping , Wang Shu
Published: November 2012

For meeting requirements of staying in the stratosphere for a long time period more than one year and less of maintenance, the power and propulsion system of the stratospheric airship is required to have high reliability. In this regard, reliability design is a key procedure in the design phase of the power and propulsion system of stratospheric airship. This paper focuses on the quantitative analysis of the reliability for the power and propulsion system of the stratospheric airship. Firstly, the reliability of the solar cell array and the fuel cell of power system are discussed respectively. Then, different topologies of the power system are discussed and compared. The reliability of the propulsion system is also analyzed in different configurations. The reliability of the basic combination of the power and propulsion system is discussed. For improving reliability, a new type of combination for the power and propulsion system is proposed. Reliability models of proposed combination are created through simplification. The ZhiYuan-1 is used as a demonstration problem to show the capability of this reliability-improved method. The result shows that the reliability of ZhiYuan-1 power and propulsion system increases by 12.8%.
Unmanned Aerial Systems Platform Research Prognosis
Authors: Chahl Javaan
Published: November 2012

Much of aerospace academia is anticipating a boom in Unmanned Aerial Vehicle (UAV) funding and research opportunities. The expectation is built on the premise that UAVs will revolutionize aerospace, which is likely based on current trends. There is also an anticipation of an increasing number of new platforms and research investment, which is likely but must be analyzed carefully to determine where the opportunities might lie. This paper draws on the state of industry and a systems engineering approach. We explore what aspects of UAVs really are the results of aerospace science advances and what aspects will be rather more mundane works of engineering.
Cavity Effect of Synthetic Jet Actuators Based on Piezoelectric Diaphragm
Authors: Dahalan Md Nizam , Mansor S. , Ali Airi
Published: November 2012

An active flow control technology known as synthetic jet actuator (SJA) is a zero-net mass-flux device to create pulsed jet that produces momentum to its surroundings and uses a vibrating diaphragm inside the cavity to generate an oscillatory flow through a small orifice. The performance of SJA depends on the design of an orifice and cavity, and oscillating membrane. SJA design based on piezoelectric diaphragm used in this project because of their size, lightweight, no need for external air supply, without the pipe complex, fast response time and low power consumption. This paper describes the cavity effect to SJA designs and experiments were performed to determine the air jet velocity produced through the orifice using a hot-wire anemometer at a different cavity thickness. The results demonstrate that the jet velocity increase would be better if the cavity thickness is reduced. However, more studies are needed to optimize the size of cavity and orifice for appropriate applications.
Experimental and Numerical Investigation onto 1250mm Axial Fan
Authors: Munisamy Kannan M. , Govindasamy Ramies , Thangaraju Savithry K.
Published: November 2012

Numerical simulation is of interest for most fan designers to optimize the fan designs. Computational fluid dynamic (CFD) has become an essential tool in almost every branch of fluid dynamics and one of the major tools for fan designs. As the fan designers relying on the numerical simulation, the accuracy of tools such as CFD in predicting the performance has become a subject of interest. This paper validates the CFD modeling of an axial fan design against experimental result. The experimental rig and test procedure are developed with reference to “AMCA standard 210”. The analysis is conducted on 1250mm diameter axial fan with two different blade pitch angle 30° and 40°. Prior to encounter the swirling effect and deflection of velocity vector due to rotor blade, a stator blade with the same profile as rotor blade is used as the outlet guide vanes in opposite direction. The computational model is created according to the experimental condition and applied realistic boundary conditions. The model is simulated using commercial CFD package, ANSYS FLUENT. The results obtained are compared against experimental data (AMCA standard 210) over wide range of flow rate. Provided the modeling strategy is chosen appropriately with correct configuration of mesh density and turbulent model then, the results correlates closely with experimental data. This is shown in this investigation. The guide vane incidence angle determination is also done in this paper for 30° and 40° blade pitch angle. The outcome of this paper would provide confidence for designers in numerical simulation for predicting performance of axial fan. In addition, numerical simulation creates a platform for systems to be optimized with a lower cost and high efficiency outcomes.
Researches on the Structural Influencing Coefficient of Steel Frames under Different Sites Based on the Energy Concept
Authors: Jia Hui Juan , Dai Hang , He Ruo Quan
Published: November 2012

The structure influencing coefficients reflect discount rate on horizontal seismic action of different structure categories. In general, the structure influence coefficients are related with the ductility level and overstrength of the structure. According to Code for seismic design of buildings (GB50011-2008), four models of three story-steel frames are designed for 4 types of site. Dynamic time-history analysis is carried out to study the models with records of seismic waves. The ductility level, the over-strength and Structural Influencing Coefficient are derived by the energy concept in the different sites condition. Structural Influencing Coefficient based on the energy concept is a new attempt. Method of the energy concept and design of structure will become the important development direction to improve the traditional seismic design.
Deep Well of Coal Roadway Bolt-Cable Mechanism Analysis and its Engineering Application
Authors: Tang Bai Xiao , Wang Yong Wei
Published: November 2012

Cable Anchor Supporting mechanism theory analysis, combined with high geostress, composite roof and complex geological conditions, the deep well under conditions of coal roadway by small aperture, anchor on the form of the structure and high prestressed construction technology, engineering practice shows that the technology is simple and applicability,is deep well solve the high stress soft rock tunnel, large sections into bifurcation point supports of the effective way of the problem. Not only reduces the support cost, reduce the workload of the Lane repair, and also greatly reduce the labor intensity of construction personnel, improve the reliability of the engineering safety. Accumulated experience, has broad application prospects for the deep well under the conditions of the other coal mine soft rock roadway
Discussion of Different Methods of Strengthening Masonry Walls with Constructional Column
Authors: Wang Cheng , Luo Yong Kun , Xu Xiao Long
Published: November 2012

With the rapid development of economy and the civil engineering discipline, the seismic performance of existing masonry wall can't satisfy the codes and regional seismic requirements. As a result, strengthening the earthquake resistance of it is put on the agenda. Using large-scale finite element software-abaqus, this paper analyzes different methods of strengthening masonry walls by constructional columns. Under the premise of the cross area of the columns used to reinforce is identical, it shows that the wall strengthened by bilateral constructional columns has a better seismic performance than by unilateral constructional column. The ductility coefficient of the former increases 49.4% than the original masonry, while the latter increases 26.3%. The bilateral constructional column could significantly improve the integrity and ductility of the masonry wall, so does the seismic performance. It has engineering sense for the strengthening work.
Based on the Test of Dynamic Characteristics of the Structure Retrofit Design
Authors: Li Peng , Ma Fu
Published: November 2012

The dynamic characteristics of the building could comprehensively reflect the seismic performance of the building. To make use of high sensitivity vibratory sensor picks up response of the external excitation of the structure. And then the dynamic characteristics of the structural could be obtained. According to it, the relevant judgment of the structural health status might be made. Based on the modal characteristics of the structure, the structure of the overall seismic performance is analyzed. Taking targeted reinforcement measures for seismic system optimization based on dynamic characteristics test results. It may effectively improve the overall seismic performance of the existing structure, avoid the blindness of reinforcement, and reduce the reinforcement costs. This paper takes a teaching building as an example to introduce seismic reinforcement design method that is based on dynamic characteristics of the test.
Study of Performance Levels of Masonry Buildings Based on Damage
Authors: Liu Wei , Xu Peng , Zhang Bo
Published: November 2012

Performance levels in performance-based seismic design are affected by many factors. In this paper, based on the unclear division of the performance levels, finite element models of masonry buildings with windows of different sizes and different structural measures, according to damage constitutive equation of masonry in strain space and damage evolution equation [1], are built, which are analysed by the pushover analysis method. Stiffness change and damage evolution of masonry buildings under earthquake action are quantitatively described by the basic damage index and holistic damage index. In order to show their joint action on seismic performance of masonry buildings, the comprehensive evaluation coefficient is suggested to divide and evaluate performance levels of masonry buildings, which can evaluate overall seismic behavior of masonry buildings.