bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical simulation of different turbulence models aiming at perdicting the flow and temperature separation in a Ranque-Hilsch vortex tube
Authors: Azizi Hossein , Saleh Reza , Kahrom Mohsen , Andalibi Reza
Published: November 2012

A computational fluid dynamics (CFD) model is used to compare the effect of
different Reynolds Averaged Navier-Stokes (RANS) based turbulence models in
predicting the temperature separation and power separation in a Ranque-Hilsch
vortex tube. Three first order turbulence models (standard k-?, Renormalized
group RNG and shear stress transport (SST) K-? model) together with a second
order numerical scheme are surveyed in the present work. The simulations are
done in 2D steady, axisymetric with high swirl flow model. The performance
curves (hot and cold outlet temperatures and power separation versus hot
outlet mass fraction) obtained by using these turbulence models are compared
with the experimental results in different cold mass fractions. The aim is to
select an appropriate turbulence model for the simulation of the flow
phenomena. Because of large discrepancy between 2D and experiment, validation
in 3D model is also considered. The performance analysis shows that among all
the turbulence models investigated in this study, temperature separation
predicted by the Renormalized group RNG model is closer to the experimental
results.
Programmed cell death in sepsis in Balkan nephropathy
Authors: Savin Marina
Published: November 2012

nema
Plasma Resistin Is Associated With Single Nucleotide Polymorphisms of a Possible Resistin Receptor, the Decorin Gene, in the General Japanese Population
Authors: Onuma Hiroshi , Tabara Yasuharu , Kawamura Ryoichi , Ohashi Jun , Nishida Wataru , Takata Yasunori , Ochi Masaaki , Nishimiya Tatsuya , Kawamoto Ryuichi , Kohara Katsuhiko , Miki Tetsuro , Osawa Haruhiko
Published: November 2012

Resistin is an adipokine secreted from adipocytes in mice. We previously reported that a single nucleotide polymorphism (SNP) –420 (rs1862513) in the human resistin gene (RETN), is correlated with plasma resistin. Decorin is a multifunctional proteoglycan, and its isoform, lacking 14 amino acids from the N terminal region of mature core decorin, recently was identified as a resistin receptor in mice. To examine whether SNPs in the vicinity of the human decorin gene (DCN) are associated with plasma resistin, we cross-sectionally analyzed six tag SNPs selected around DCN in the same linkage disequilibrium block in 2,078 community-dwelling Japanese subjects. Plasma resistin was associated with the rs7139228, rs7956537, rs516115, and rs3138167 genotypes in DCN. A multiple regression analysis revealed that the genotype of rs7308752 (G/G) or rs516115 (C/C) was associated with decreased plasma resistin after adjusted for age, sex, BMI, and the RETN SNP rs1862513. The effect of rs7139228 and rs1862513 seemed to be additive without synergistic interaction. Therefore, plasma resistin was associated with some tag SNPs around DCN in the general Japanese population. The possibility that human decorin is a human resistin receptor should be pursued.
Fibroblast Growth Factor 21 Levels in Young Healthy Females Display Day and Night Variations and Are Increased in Response to Short-Term Energy Deprivation Through a Leptin-Independent Pathway
Authors: Foo Joo-Pin , Aronis Konstantinos N. , Chamberland John P. , Paruthi Jason , Moon Hyun-Seuk , Mantzoros Christos S.
Published: November 2012

OBJECTIVE

Fibroblast growth factor (FGF)-21 is an endocrine factor with potent metabolic effects. Its day–night patterns of secretion and/or its physiological response to energy deprivation and relationship to free fatty acids (FFAs) and/or leptin remain to be fully elucidated. We aim to elucidate day–night pattern of FGF-21 levels and its relationship to FFA, to assess whether energy deprivation alters its circulating patterns, and to examine whether leptin may mediate these changes.

RESEARCH DESIGN AND METHODS

Six healthy lean females were studied for 72 h in a cross-over interventional study under three different conditions: on isocaloric diet and in a fasting state with administration of either placebo or metreleptin in physiological replacement doses. Blood samples were obtained hourly from 8:00 a.m. on day 4 until 8:00 a.m. on day 5.

RESULTS

FGF-21 exhibited day–night variation pattern during the isocaloric fed state. Fasting significantly increased FGF-21 levels (P < 0.01) via a leptin-independent pathway. Day–night variation pattern in the fed state was lost on fasting. Leptin replacement in the hypoleptinemic state restored approximate entropy of FGF-21 time series but did not alter circulating levels. FGF-21 levels were closely cross-correlated with FFA levels in all three states.

CONCLUSIONS

A day–night variation in the levels of FGF-21 exists in young lean females in the fed state. Energy deprivation increases FGF-21 levels via a leptin-independent pathway. The interaction between FGF-21 and starvation-induced lipolysis, as indicated by its close cross-correlations with FFA in both fed state and energy deprivation, needs to be studied further.
Assessment of Barriers to Improve Diabetes Management in Older Adults
Authors: Munshi Medha N. , Segal Alissa R. , Suhl Emmy , Ryan Courtney , Sternthal Adrianne , Giusti Judy , Lee Yishan , Fitzgerald Shane , Staum Elizabeth , Bonsignor Patricia , DesRochers Laura , McCartney Richard , Weinger Katie
Published: November 2012

OBJECTIVE

To evaluate whether assessment of barriers to self-care and strategies to cope with these barriers in older adults with diabetes is superior to usual care with attention control. The American Diabetes Association guidelines recommend the assessment of age-specific barriers. However, the effect of such strategy on outcomes is unknown.

RESEARCH DESIGN AND METHODS

We randomized 100 subjects aged ≥69 years with poorly controlled diabetes (A1C >8%) in two groups. A geriatric diabetes team assessed barriers and developed strategies to help patients cope with barriers for an intervention group. The control group received equal amounts of attention time. The active intervention was performed for the first 6 months, followed by a “no-contact” period. Outcome measures included A1C, Tinetti test, 6-min walk test (6MWT), self-care frequency, and diabetes-related distress.

RESULTS

We assessed 100 patients (age 75 ± 5 years, duration 21 ± 13 years, 68% type 2 diabetes, 89% on insulin) over 12 months. After the active period, A1C decreased by −0.45% in the intervention group vs. −0.31% in the control group. At 12 months, A1C decreased further in the intervention group by −0.21% vs. 0% in control group (linear mixed-model, P < 0.03). The intervention group showed additional benefits in scores on measures of self-care (Self-Care Inventory-R), gait and balance (Tinetti), and endurance (6MWT) compared with the control group. Diabetes-related distress improved in both groups.

CONCLUSIONS

Only attention between clinic visits lowers diabetes-related distress in older adults. However, communication with an educator cognizant of patients’ barriers improves glycemic control and self-care frequency, maintains functionality, and lowers distress in this population.
Pulse perturbation technique for determination of piroxicam in pharmaceuticals using an oscillatory reaction system
Authors: Pejić Nataša , Sarap Nataša , Maksimović Jelena , Anić Slobodan , Kolar-Anić Ljiljana
Published: November 2012

A simple and reliable novel kinetic method for the determination of piroxicam (PX) was proposed and validated. For quantitative determination of PX, the Bray-Liebhafsky (BL) oscillatory reaction was used in a stable non-equilibrium stationary state close to the bifurcation point. Under the optimized reaction conditions (T = 55.0°C, [H2SO4]0 = 7.60×10−2 mol L−1, [KIO3]0 = 5.90×10−2 mol L−1, [H2O2]0 = 1.50×10−1 mol L−1 and j 0 = 2.95×10−2 min−1), the linear relationship between maximal potential shift ΔE m , and PX concentration was obtained in the concentration range 11.2–480.5 µg mL−1 with a detection limit of 9.9 µg mL−1. The method had a rather good sample throughput of 25 samples h−1 with a precision RSD = 4.7% as well as recoveries RCV ≤ 104.4%. Applicability of the proposed method to the direct determination of piroxicam in different pharmaceutical formulations (tablets, ampoules and gel) was demonstrated.
A comparison of fluorescein and deuterated water as tracers for determination of constructed wetland retention time
Authors: Holcová Veronika , Šíma Jan , Dušek Jiří
Published: November 2012

Retention time of treated water in a horizontal subsurface flow constructed wetland was determined in the non-vegetative period using fluorescein and deuterium oxide. Fluorescein served as one of the most frequent tracers detectable at extremely low concentrations by fluorimetry; however, deuterated water (concentrations of deuterium measured by IRMS and expressed as δ (‰) against VSMOW) was used to precisely simulate the treated water flow movement. Tracer retention time (TRT) of fluorescein was 194 h while deuterated water TRT was 192 h. TRT and nominal hydraulic retention time (nHRT, 190 h) were nearly exactly equal. The tracer behavior of deuterated water was almost ideal. On the other hand, the fluorescein movement through the system was slightly influenced by the interaction with the vegetation bed (sorption causing the tailing of tracer-response curves). Nevertheless, both tracers can be successfully used and provide similar results. Retention time is a very important characteristic of a constructed wetland. It is closely connected with the efficiency of the contaminant removal from treated water. It has to be determined correctly when wetland operation parameters are optimized. The choice of the suitable and reliable tracer is always necessary. Fluorescein takes preference with respect to its simple and inexpensive determination.
Mechanical, thermal and surface properties of polyacrylamide/dextran semi-interpenetrating network hydrogels tuned by the synthesis temperature
Authors: Dinu Maria , Cazacu Maria , Drăgan Ecaterina
Published: November 2012

The mechanical, rheological, thermal, and surface behaviors of three polyacrylamide/dextran (PAAm/Dx) semi-interpenetrating polymer network (semi-IPN) hydrogels, prepared at 22°C, 5°C and −18°C, were investigated. The results were compared with those obtained on cross-linked PAAm without Dx synthesized under the same conditions. Hydrogels prepared at the lowest temperature were the most mechanically stable. The thermal stability of the semi-IPN hydrogels is slightly lower than the corresponding PAAm gels, irrespective of preparation temperature. The water vapor sorption capacity depended on the presence of Dx as well as preparation temperature, which determines the network morphology.
Rapid flow injection electrochemical detection of 3,3′,4,4′ tetrachlorobiphenyl using stabilized lipid membranes with incorporated sheep antibody
Authors: Nikolelis Dimitrios , Psaroudakis Nikolas , Michaloliakos Antonis , Nikoleli Georgia-Paraskevi , Scoullos Michael
Published: November 2012

An electrochemical biosensor based on a supported polymerized lipid film with incorporated sheep anti-3,3′,4,4′ tetrachlorobiphenyl (PCB congener 77) antibody using flow injection analysis was developed. The polymerized lipid film contained 85% (w/w) dipalmitoylphosphatidylcholine (DPPC) and 15% (w/w) dipalmitoylphosphatidic acid (DPPA), methacrylic acid, ethylene glycol dimethacrylate, AIBN and sheep anti-congener 77 antiserum. Congener 77 was injected into flowing carrier electrolyte and the flow stopped to detect the antigen. These membranes gave only a single transient proportional to log [congener 77] from 10−8 to 10−5 M, with a detection limit of ca. 10−8 M. A membrane containing 35% (w/w) DPPA was used to examine regeneration. The maximum number of cycles was about 5.
Electrode processes of selected redox active substances on poly(o-aminophenol) film electrode
Authors: Marczewska Barbara , Przegaliński Marek
Published: November 2012

Using the method of cyclic voltammetry, the electrode process of Ni2+, Pb2+, Cu2+ and pyrocatechin on a poly(o-aminophenol) (PoAP) modified glassy carbon electrode (GCE) was investigated. The PoAP polymer was found to affect the redox process of copper and pyrocatechin. The use of polymer of different thicknesses showed that the obtained film has a dense, nonporous structure. The redox process of the examined substances may be considered as proceeding on the polymer surface. The PoAP polymer obtained in the described conditions takes part in charge transfer.
Antioxidative responses to seasonal changes and chemiluminescence assay of Astragalus onobrychis leaves extract
Authors: Miladinović Dragoljub , Ilić Budimir , Najman Stevo , Cvetković Olga , Šajnović Aleksandra , Miladinović Marija , Nikolić Nikola
Published: November 2012

The aim of this study was to research the seasonal changes of antioxidant enzyme activity and total antioxidant capacity in leaves of Astragalus onobrychis L. subsp. chlorocarpus (Griseb.) S. Kozuharov et D.K. Pavlova. Leaves of A. onobrychis were collected during the different stages of growth and analyzed for antioxidant enzyme activity: superoxide dismutase, catalase, guaiacol peroxidase, glutathione peroxidase. Quantities of malonyldialdehyde, superoxide radicals, and hydroxyl radicals were measured as well as the content of soluble proteins. Furthermore, total antioxidant capacity was determined by the inhibition of chemiluminescence activity of blood phagocytes by leaf extracts. Stages of vegetation significantly affected the accumulation of superoxide radicals, but there were no significant differences in hydroxyl radical quantity and lipid peroxidation levels during vegetation. Soluble proteins vary greatly between different stages of growth. Seasonal changes were found to have an effect on enzymatic activities. During the spring season, guaiacol peroxidase showed the highest levels. Catalase and glutathione peroxidase increased their activities in summer, while, during the autumn season, superoxide dismutase showed maximum activity. On the basis of chemiluminescence assay, it can be concluded that leaf extract of A. onobrychis possesses a significant antioxidant capacity thus protecting plants during environmental stress.
The Art of Directly Interfacing Sensors to Microcontrollers
Authors: Reverter Ferran
Published: November 2012

This paper reviews the direct connection of sensors to microcontrollers without using any analogue circuit (such as an amplifier or analogue-to-digital converter) in the signal path, thus resulting in a low-cost, lower-power sensor electronic interface. It first discusses the operating principle and explains how resistive and capacitive sensors with different topologies (i.e., single, differential and bridge type) can be directly connected to a microcontroller to build the so-called direct interface circuit. It then shows some applications of the proposed circuits using commercial devices and discusses their performance. Finally, it deals with the power consumption and proposes some design guidelines to reduce the current consumption of such circuits in active mode.
Victor Hugo, la créativité libérée
Authors: Barbet-Massin Arnaud
Published: November 2012

Les dessins de Victor Hugo sont une source inépuisable pour qui veut approcher sa créativité et comprendre son cheminement. « Il fut peintre avant d’être écrivain », affirmait Théophile Gautier, le premier à relever que la sensibilité de Victor Hugo était d’abord visuelle. Feuilleter certains de ses dessins les plus connus permet de comprendre comment sa plume puise dans cette sensibilité pour d’incessants va-et-vient entre le verbe et l’image. Le moment clef survient en 1856 avec les Dessins Fantasques qui révèlent la crise identitaire de Victor Hugo. En s’appuyant sur les travaux de Marion Milner, l’auteur tente de comprendre la recherche identitaire de Hugo et d’éclairer ainsi le jaillissement créatif, sans négliger la fusion, à plus d’un titre exceptionnelle, entre l’écrit et le dessin que recèle Les Travailleurs de la Mer .
Qatar : une voie singulière
Authors: Abidi Hasni
Published: November 2012

Résumé Comment expliquer qu’un pays peuplé d’un million d’habitants, dont seulement 180 000 Qataris, ose ainsi défier ses voisins les plus puissants et forcer le respect de ses amis et de ses ennemis ? Seul pays wahhabite en dehors de l’Arabie Saoudite, le Qatar a tenu, au lendemain du coup d’État de 1995, à marquer sa différence par rapport à Riyad et à ses voisins et à se démarquer de la politique conduite par l’ancien émir. Tout en étant conscient de ses limites face à l’imposant voisin saoudien et iranien, le Qatar s’accommode habilement de cette géopolitique défavorable. Ambitieux et audacieux, le jeune prince Hamad a choisi de prendre le pouvoir vite et changer le destin de son pays.
La politique étrangère du Qatar : de l'intermédiation à l'engagement
Authors: Mongrenier Jean-Sylvestre
Published: November 2012

Résumé Le caractère spectaculaire des investissements extérieurs du Qatar et la « diplomatie du tapis volant » tendent à occulter les lignes de force de sa politique étrangère. À l’abri du « parapluie » américain, l’émirat du Qatar constitue l’élément agile du Conseil de coopération du Golfe. Il entend jouer un rôle moteur dans un monde arabe sunnite en cours de recomposition. En toile de fond, l’opposition entre régimes arabes sunnites et Iran chiite. Le Qatar ne pourra jouer cette partie sans le renforcement des solidarités entre pays du Golfe.
Le Qatar : un paradoxe géopolitique et une anomalie géoéconomique
Authors: Rigoulet-Roze David
Published: November 2012

Résumé Le Qatar apparaît à bien des égards comme un point d’interrogation. Émirat indépendant depuis 1971, cet État se présente comme un « nain » géographique mais dévoré d’ambitions géopolitiques et disposant d’une manne financière qui lui donne les moyens de ses prétentions. Depuis quelques années, il fait montre d’une suractivité diplomatique. Voire davantage, comme dans le cas de l’« affaire libyenne » dans laquelle une participation directe de Doha pour le renversement du régime de Kadhafi est désormais avérée, ainsi que dans l’« affaire syrienne » à cette même participation pour favoriser la chute du régime de Bachar al-Assad est en passe de l’être. Comment expliquer alors ce positionnement stratégique inédit au regard de la place demeurée longtemps modeste du Qatar ? Le Qatar constitue en réalité une sorte de paradoxe géopolitique autant qu’une anomalie géoéconomique.
Hacia un ranking bibliométrico de editoriales científicas de libros. Primera aproximación utilizando el «Book Citation Index»
Authors: Torres-Salinas Daniel , Robinson-García Nicolás , Jiménez- Contreras Evaristo , Delgado López-Cózar Emilio
Published: November 2012

La ausencia de libros y capítulos de libros en los índices de citas presentes en las bases de datos de la Web of Science ha sido tradicionalmente una de sus más importantes debilidades. Sin embargo, Thomson Reuters en Octubre de 2010 lanzó el Book Citation Index, un nuevo índice de citas que contaba con 29.618 libros y 379.082 capítulos de libros. Este producto ha abierto nuevas posibilidades para el análisis bibliométrico de campos como las Humanidades y las Ciencias Sociales. Precisamente el objetivo principal de esta nota es analizar a través de diferentes indicadores las editoriales de los ámbitos de Humanidades y Ciencias Sociales indexadas en el Book Citation Index durante los años 2006-2011. Más concretamente se ha probado la posibilidad de desarrollar un ranking de editoriales de libros basado en la citación y la producción de las mismas. Para ello se presentan una colección de rankings con seis indicadores bibliométricos para un total de 19 disciplinas científicas.
Influence of physical and chemical properties on the low‐frequency complex conductivity of peat
Authors: Ponziani M. , Slob E.C. , Vanhala H. , Ngan‐Tillard D.J.M.
Published: November 2012

Organic layers are heterogeneous in space and their composition changes over time. This poses challenges to ecohydrologists, subsurface hydrologists and ground engineers in characterizing subsurface peat structures and predicting their behaviour over time. Peat deposits can be characterized by performing electrical surveys, provided that the complex conductivity of peat is understood and connected to its physical and chemical properties. Low‐frequency (0.1–1000 Hz) induced polarization measurements were carried out to investigate the correlation between the chemical and physical properties of several peat samples and their electrical properties. A Cole‐Cole model was fit to the peat spectra to obtain the model parameters and study their relationship with the sample properties. All the samples were characterized by analysing their degree of humification, water content, organic content, cation exchange capacity, pH and conductivity of the pore‐fluid. Two significant correlations between physical, chemical and electrical properties are found. The peat bulk conductivity is directly correlated with the pore fluid conductivity, whereas the degree of humification of peat shows an inverse correlation with the phase angle. This study presents results that have implications for peatland characterization with frequency dependent or single frequency analysis of induced polarization measurements.
Effect of antenna‐medium coupling in the analysis of ground‐penetrating radar data
Authors: Lambot Sébastien , André Frédéric , Slob Evert , Vereecken Harry
Published: November 2012

Physically‐based ground‐penetrating radar (GPR) data processing is essential for quantitative characterization of soils and materials. A novel near‐field GPR antenna model coupled with layered media Green's functions was used to investigate the effect of antenna‐medium coupling in the analysis of GPR data. The radar antennas are modelled using an equivalent set of infinitesimal electric dipoles and characteristic, frequency‐dependent, global reflection and transmission coefficients. These coefficients determine through plane wave decomposition, wave propagation between the radar reference plane, point sources and field points. We calibrated an actual commercial 400 MHz time‐domain antenna, from which synthetic GPR data sets were generated. We observed that, depending on the model configuration, antenna effects may affect the topography of the objective function in full‐waveform inverse problems. In addition, antenna‐medium coupling has a significant impact on the medium surface reflection, whether in terms of amplitude or propagation time (which usually defines the so‐called time zero). We also showed that an effective source cannot be used for simulating near‐field radar data as the antenna‐medium coupling strongly depends on medium properties. In this respect, numerical experiments demonstrated promising perspectives for simultaneous estimates of medium permittivity and conductivity from antenna‐medium coupling.
The Effect of Laser Cutting Parameters on the Aerospace Structure Panel of CFRP Composite Material
Authors: Saidin Wahab , Rahim Erween Abdul , Mustafa Mohd Sukri , Rahman Norzaina Abdul
Published: November 2012

This paper presents a research progress on the laser cutting characteristic of the carbon fiber reinforced plastic (CFRP) composites material for the aerospace structure panel. The CFRP is a high performance material and become one of the most important materials in the aerospace industry. The current machining techniques used by the aerospace composites manufacturing for cutting and trimming process have created some quality issues such as fiber pulled out and delamination. The use of laser cutting technology has shows promising advantages. However, the Laser cutting represents the interaction between laser beam and the CFRP composites, that produce heat affected zone (HAZ), kerf width and taper angle. Thermal damage is a direct consequence of the large difference in thermal properties of the carbon fiber and the polymer matrix. Therefore, the effect of laser cutting parameters such as pulse energy, pulse repetition rate, cutting speed and pulse duration need to be taken into consideration. A 300W Pulsed Nd:YAG laser machine was used in the experiment and successfully cut or trim the 1.5mm thickness of the CFRP component. The results also showed that the pulse energy and pulse repetition rate gave the most significant effect on the cutting characteristic in particular of kerf width, HAZ and taper angle.
A Study on the Effect of Upstream Square Blockage of a Rotating Cylinder
Authors: Cheong X.H. , Rafie Azmin Shakrine Mohd , Romli Fairuz Izzuddin , Sultan Mohamed Thariq Hameed , Yidris Noorfaizal
Published: November 2012

A study on the effect of allocating a square blockage in front of a rotating cylinder is presented. The aim of the study is to determine the optimum design of the blockage to enhance the lift generating performance of the rotating cylinder. A numerical simulation is carried out to investigate the effect of different sizes of blockage towards the lift generating performance of the rotating cylinder. The simulation adopted a fully turbulent flow, having Reynolds number of 600. The cylinder is spinning at 5000 RPM. The validation of the simulation RANS code FLUENT is done through comparison with the published results from past studies. In general, the results suggest that the lift generating performance of the rotating cylinder will be improved by placing a blockage in front of it.
Modal Properties of a Cantilevered Laminated Woven Composite Plate as Affected by Stacking Sequence and Fiber Orientation: An Experimental Study
Authors: Majid Dayang Laila , Sani Mohd Norhasani Abdullah , Mustapha Faizal , Hanafi Hafiz , Sultan Mohamed Thariq Hameed
Published: November 2012

The use of laminated composites in aircraft structures is not totally new. However, the idea of using woven fiber glass as reinforcement in primary structural members is not widely addressed as compared to unidirectional fibers. In an effort to characterize the dynamic behavior of a woven laminated composite subject to dynamic loads, modal testing is performed experimentally on a cantilevered laminated woven glass fiber/epoxy composite flat plate which resembles an aircraft wing with aspect ratio of 5. To that end, the effect of stacking sequence and fiber orientation of the laminated composite plate on the modal properties is assessed. 6-layer laminated composite configurations with various stacking sequence and fiber orientation are fabricated so as to generate variable stiffness plates. The modal test employs the single roving hammer technique to obtain the frequency response of the plate and the results of the first five modes against the fiber orientation and stacking sequence are analyzed.
Computational Simulation for Static and Dynamic Load of Rectangular Plate in Elastic Region for Analysis of Impact Resilient Structure
Authors: Djojodihardjo Harijono , Jamali Hamed , Shokrani Alireza , Mustapha Faizal , Zahari Rizal , Wiriadidjaja Surjatin
Published: November 2012

Impact resilient structures are of great interest in many engineering applications varying from civil, land vehicle, aircraft and space structures, to mention a few examples. To design such structure, one has to resort fundamental principles and take into account progress in analytical and computational approaches as well as in material science and technology. With such perspective, the first objective of this work is to develop a computational algorithm to analyze flat plate as a generic structure subjected to impact loading for numerical simulation and parametric study without considering the surface impact effect. The analysis is carried out from first principles for static and dynamic analysis; the latter is based on dynamic response analysis in the elastic region. The second objective is to utilize the computational algorithm for direct numerical simulation, and as a parallel scheme, commercial off-the shelf numerical code is utilized for parametric study, optimization and synthesis. Through such analysis and numerical simulation, effort is devoted to arrive at optimum configuration in terms of loading, structural dimensions, and material properties, among others. The codes developed are validated for generic cases. Further simulations are carried out using commercial codes for some sample applications to explore impact resilient structural characteristics in the elastic region.
Beneficial Patch Repair Effect on Fatigue Crack Growth of Al-Alloy 7050
Authors: Benachour Mustapha , Seriari Fatima Zohra , Benachour Nadjia , Benguediab Mohamed
Published: November 2012

Fatigue problems become an important topic in the maintenance of aircraft structures. Efficient repair technique, called composite patch repair, was used to reinforce the damaged structures and extend the service life. In this paper, using empirical approach, the effect of composite patch repair on fatigue crack growth was investigated on 7050 aluminum alloy. In additional, loading parameters associated with patch repair (Graphite/Epoxy) was studied in order to show their influence on fatigue life and fatigue crack growth rate, namely stress ratio. Results provide an increasing in fatigue life and fatigue crack growth rate in increased stress ratio. A delayed in fatigue life and diminution of FCGRs is the results of composite patch repair. Effect of patch repair was shown highly at high stress intensity factor when maximum applied loading is kept constant.
An Investigation on the Effect of Variable Valve Timing on Piston Engine for Lightweight Aircraft
Authors: Sabaruddin Ainul Aniyah , Wiriadidjaja Surjatin , Majid Dayang Laila Abang Abdul , Djojodihardjo Harijono , Ahmad Mohamed Tarmizi
Published: November 2012

As the Lycoming engine had failed its attempt on using variable valve timing for aircraft piston engine back in 1940s, the idea of the technology was abandoned as the turbines were then introduced in the aviation for better performance and greater power. Since piston engines produce smaller power efficiently in the low speed than turbine engines, they are presently still practically used in most of lightweight aircraft. With the use of a variable valve timing mechanism, it may help to increase the amount of air inlet and to provide more power output with lesser fuel consumption. With the use of this new valve system, improvements in the performance of automobile engines have been recorded. The indicated improvements, however, are limited to automobile engines running with high revolutions only. Engine simulation program was run in this investigation as an attempt to predict engine performances that are appropriate for lightweight aircraft.
Preliminary Design of Solar Powered Unmanned Aerial Vehicle
Authors: Jashnani Sumit , Shaholia Prahsant , Khamker Ali , Ishfaq Muhammad , Nada Tarek
Published: November 2012

Applications involving the use of alternate, renewable energy sources are expanding exponentially, and are in high demand. Solar power has long been harnessed for such applications and aviation is no stranger to it with its strong drive towards becoming an environment-friendly industry. This paper describes a straight forward procedure to design and test a solar powered unmanned aerial vehicle that can fly continuously for 24 hours at any day of the year. The paper introduces the modeling and preparation of hardware testing of the propulsion and power sub-system. The main components of this sub-system are solar panels, the electromechanical drive train and the propeller. A design for a thrust stand to measure the performance of the system is also introduced.
Model Reference Adaptive Control Design for a Ducted Fan Air Vehicle in Vertical Plane
Authors: Fadaeian Ehsan , Banazadeh Afshin
Published: November 2012

Ducted fan aerial vehicles have drawn many attentions in the world because of their successful involvement in non-traditional reconnaissance and surveillance missions. However, due to inherent dynamic uncertainties as well as inconsistent responses, significant control challenges are still to be addressed. In this study, a non-linear dynamic model for ducted fan is firstly proposed to be employed for control design. This model is then validated by performing a series of standard simulation scenarios. Afterwards, an adaptive control method, named as model reference is utilized to design perfect controllers in hover as well as vertical flight. The capability of the adaptive laws to update the controller gains are evaluated for different initial conditions and command inputs. The results show that the controller is well able to regulate the state variables as well as to follow the desired commands in the presence of dynamic coupling and aerodynamic uncertainties when the vehicle flies in vertical plane and near hover condition.
Investigation on a Flexible Tether Slackness Based on In- and Out-of Plane Libration Angles
Authors: Hong Aaron Aw Teik , Varatharajoo Renuganth
Published: November 2012

Tethered Satellite Systems (TSS) have been used in various applications such as in performing space interferometry, orbit transfer and other relevant fields. As far as the operation system of a TSS is concerned, it is crucial to ensure that the tether will not go slack as its slackness would adversely affects the overall operation outcome due to an undesirable system dynamics. Therefore, it is important to investigate the types of conditions that will cause the tether slackness. Investigations on in-plane and out-of plane libration angles can be utilized to measure at what point that the tether will go slack. Based on previous research works, usually a rigid tether comprising of a uniformed mass is considered while the connecting two satellites are regarded as point masses in order to simplify the governing dynamics equation of motion. However, in order to develop a much more accurate modeling, a flexible tether is chosen by further incorporating the reeling mechanism, attitude dynamics of rigid bodies and tether deformations. Furthermore, a tether has a tendency to go slack if the in-plane and out-of plane libration angle exceeds 65° and 60° respectively regardless of the types of tether utilized whether it being a rigid or a flexible one. Thus, the tension of the tether will serves as a constraint and plotted against the in-plane and out-of plane libration motions that would be attained via the generalized forces. The results will then be analyzed to establish in-plane and out-of plane libration boundaries. Subsequently, the in-plane and out-of plane operation contrains are established for TSS corresponding to a reference mission.
Spacecraft Attitude and System Identification Using Marginal Reduced UKF Utilizing the Sun and Calibrated TAM Sensors
Authors: Kiani Maryam , Pourtakdoust Seid H.
Published: November 2012

This paper deals with attitude determination, parameter identification and reference sensor calibration simultaneously. A LEO satellite’s attitude, inertia tensor as well as calibration of Three-Axis-Magnetometer (TAM) are estimated during a maneuver designed to satisfy persistency of excitation condition. For this purpose, kinematic and kinetic state equations of spacecraft motion are augmented for the determination of inertia tensor and TAM calibration parameters including scale factors, misalignments and biases along three body axes. Attitude determination is a nonlinear estimation problem. Unscented Kalman Filter (UKF) as an advanced nonlinear estimation algorithm with good performance can be used to estimate satellite attitude but its computational cost is considerably larger than the widespread, low accuracy, Extended Kalman Filter (EKF). Reduced Sigma Points Filters provide good solutions and also decrease run time of UKF. However, in contrast to nonlinear problem of attitude determination, parameter identification and sensor calibration have linear dynamics. Therefore, a new Marginal UKF (MUKF) is proposed that combines the utility of Kalman Filter with Modified UKF (MMUKF). The proposed MMUKF utilizes only 14 sigma points to achieve the complete 25-dimensional state vector estimation. Additionally, a Monte Carlo simulation has demonstrated a good accuracy for concurrent estimation of attitude, inertia tensor as well as TAM calibration parameters in significantly less time with respect to sole utilization of the UKF.
Soret Measurement for Multi-Component Hydrocarbon Mixtures from Space Experiment Conducted Onboard FOTON M3 Unmanned Satellite
Authors: Saghir M. Ziad , Srinivasan Seshasai , Van Vaerenbergh Stefan
Published: November 2012

In an unprecedented experimental investigation, a binary, a ternary and a four-component hydrocarbon mixture at different pressure have been studied in a nearly convection free environment to understand the thermodiffusion process. Experimental investigations of the mixtures have been conducted in space onboard the spacecraft FOTON-M3. The experiment objective was to measure the thermodiffusion coefficient for multi-component hydrocarbon mixtures. Then the experimental results have also been used to test a thermodiffusion model that has been calibrated based on the results of previous experimental investigations. Results showed a good agreement with current theoretical results except for the four-component system where discrepancies were found and discussed.
Designing and Developing a Ground Operation Software for Picosatellite Operation and Data Processing
Authors: Fadlie Sabri Sharizal , Salleh Nor'Asnilawati , Leng Elena Woo Lai
Published: November 2012

Ground operation software (GOS) plays an important role in satellite operations. The software need to be able to retrieve, decode, display and archive the telemetry data as well as send command to control the satellite. These are mandatory functions which will allow satellite operators to communicate and command the satellite in ensuring its mission is executed as designed. Researchers in Agensi Angkasa Negara (ANGKASA) are currently developing a picosatellite as a research project using various Commercial Off-The-Shelf (COTS) components. Even the software algorithm and coding are being developed from scratch. Compared to bigger sized satellites, the picosatellite has a much simpler architecture, modules and mission, thus the required functions on GOS are greatly reduced. The communication protocol used is unique yet simple, which means the GOS will not require any additional modules to understand and interpret either the telemetry data or payload data received as it is already in an easy-to-understand format. GOS was developed using .Net platform with several modules for easy maintenance and expansion of the system. Closed-loop simulation was applied to test the functionalities of GOS as well as for debugging purposes. Results of the simulation are presented at the end of the paper. In conclusion, the GOS may require a few upgrades due to a change of hardware. However, it will still remain as the main reference for future development of GOS.
A Study of Flight Pad Time for Scheduling Process
Authors: Romli Fairuz Izzuddin , Seng Mah Ban
Published: November 2012

Flight delays have become a big problem for current air transportation system, especially in busy domestic markets like those in the United States. This situation is predicted to worsen in the future with progressive increase in the air traffic demands. Since on-time performance has become a main competitive element for market success, many airlines resort to the flight padding practice as a means to improve their ranking. In brief, flight padding time is the additional time incorporated into the flight schedule to compensate for predicted delays. This study explores flight padding practices by identifying the factors that can influence the decision-making process for the required amount of pad time to be added for a particular flight route. Examples of ATL-JFK and ATL-SFO flight routes have been used to demonstrate the results of this study. All in all, it is shown that the flight padding practice is widely-used by airlines and scheduling factors such as departure time and month of flight have high influences in dictating the amount of the required pad time.
Aerodynamic Interference Correction Methods Case: Subsonic Closed Wind Tunnels
Authors: Wiriadidjaja Surjatin , Rafie Azmin Shakrine Mohd , Romli Fairuz Izzuddin , Ariff Omar Kassim
Published: November 2012

The approach to problems of wall interference in wind tunnel testing is generally based on the so-called classical method, which covers the wall interference experienced by a simple small model or the neo-classical method that contains some improvements as such that it can be applied to larger models. Both methods are analytical techniques offering solutions of the subsonic potential equation of the wall interference flow field. Since an accurate description of wind tunnel test data is only possible if the wall interference phenomena are fully understood, uncounted subsequent efforts have been spent by many researchers to improve the limitation of the classical methods by applying new techniques and advanced methods. However, the problem of wall interference has remained a lasting concern to aerodynamicists and it continues to be a field of active research until the present. The main objective of this paper is to present an improved classical method of the wall interference assessment in rectangular subsonic wind tunnel with solid-walls.
A Fire Disaster Intelligence Alarm System Applicable to Underground Space
Authors: Zhang Yan
Published: November 2012

Like the building on the ground, there are also many factors causing fire disaster in the underground building. There the disaster often happened, e. g in 1972 and l980 in Japan and in 1969 and1988 in China, the fire disaster took place in the underground spate which brought about a large amount of loss of property and casualties. The paper proposed a fire disaster intelligence alarm system. It is composed of a main computer system and several branch computer unit and it is useful for preventing fire in the underground building.
Performance-Based Seismic Analysis of Infilled Wall Frames Structure
Authors: Wang Shu He , Wang Jin Long , Mu Zai Gen , Zhang Ju Bing , Liu Ya Ting
Published: November 2012

In the practical engineer, the infilled-wall frame structure is widely used by its economy and applicability. Under the project research, the paper establishes a finite element model for infilled-brick-wall structure based on the infilled-wall frame structure performance and after Pushover's analyses,it obtains the inter-story displacement angle, which is anti-seismic performance index to the point each floor of the infilled-wall structure under the different earthquake action . The paper analysis and assesses the infilled-wall frame structure anti-seismic performance based on the anti-seismic performance index and it provides a reference and basis for anti-seismic standard's development towards based-performance direction.
Research Progress of Smart Concrete Structures Reinforced by Shape Memory Alloy
Authors: Cui Di , Zhang Yan , Guan Ping
Published: November 2012

As a smart material, the study of shape memory alloy in civil engineering mainly in the self-monitoring and self-repairing of concrete beams, earthquake resistance and reinforcement of concrete columns, seismic damping of concrete structures, etc. The development of shape memory alloy and its main features are outlined; research progress of the shape memory effect and superelasticity of shape memory alloys in smart concrete application are introduced; the factors which affect the development of smart concrete structure and the development direction are pointed out.
Vibration Analysis of the Load on Helicopter Swashplate Rod
Authors: Wang Fang , Chen Ming
Published: November 2012

The swashplate rod is a key component of helicopter control system. The vibration environment of helicopter is quite complex. The natural frequency of the swashplate rod is generally low. So resonance occurs easily. Resonance could reduce control precision or even damage the whole control system. Established dynamic and mathematical model of swashplate rod. Analyzed the vibration characteristics. Obtained the natural frequency and vibration mode function of the rod. In the compression, tension and free state, the natural frequency of the rod is basically the same. Made flight experiment with a developing helicopter as object. Measured the load of the swashplate rod in flight conditions. Make Fourier analysis to the load. Obtained the frequencies of the load on the rod. The frequencies coincide with 1 and 2 times of the rotor speed.
The Research on the Nonlinear Stability of the Steel Spatial Arch Truss with 120m
Authors: Liu Jing , Li Hai Wang , Sun Yue Nan , Shu Xue Feng
Published: November 2012

In this paper, the elastic stability and elasto-plastic stability analysis on the steel spatial arch truss with 120m span and 0.2 rise-span ratio is carried out with the finite element program ANSYS. In the analyses, three conditions which are the geometric ,the geometric and material nonlinear, double nonlinear under different initial geometric defects are considered. The results show that the instability mode of arch trusses are all asymmetric instability of plane, and that the buckling load of considering double nonlinear is 13.84% that of considering geometry nonlinear, and that the coupling effect of geometry nonlinear and material nonlinear has accelerated reducing the stiffness of structure and bearing stable capacity ,and that the ratio for the buckling load of the four arch trusses with L/500, L/400, L/300 and L/200 initial geometric defects is 1.0: 0.927: 0.904: 0.87: 0.804, and that load-displacement process curves of feature node are the same change for the structures under different initial geometric defects.
Effect of Geometric Nonlinear Behaviour of a Guyed Transmission Tower under Downburst Loading
Authors: Ladubec Chris , El Damatty Ashraf A. , El Ansary Ayman M.
Published: November 2012

Downburst winds, which are a source of extreme wind loading and are referred to as high intensity wind (HIW) loads, have caused numerous transmission tower failures around the world. A previous investigation was conducted to study the performance of a transmission tower under downburst wind loading, where the behaviour of the tower was limited to a linear response. In the current study, a nonlinear frame element is used to assess the performance of the tower under downburst wind loading. The behaviour is studied using downburst wind field data obtained from a computational fluid dynamics (CFD) model. In order to assess the geometric nonlinear behaviour of the tower, the results are compared to a previous linear analysis for a number of critical configurations of a downburst. The nonlinear analysis predicted that peak axial loads in certain members can be up to 34% larger than those predicted by the linear analysis.
Numerical Simulation of Wave Overtopping of Breakwater Armored with Porous Layers and Water-Structure Impaction
Authors: Huang Zong Liu , Lin Peng Zhi
Published: November 2012

A numerical model has been developed to study wave overtopping of permeable units protected breakwater and water-structure impactions. The numerical model solves the Reynolds Averaged Navier-Stokes equations outside of porous media and solves the spatially averaged Navier-Stokes equations in porous media, respectively. The numerical model is first validated by experimental data. The validated model is then employed to investigate the breaking wave overtopping porous media protected breakwater. The overtopping discharge and impact forces on the structures behind the crown wall in different wave conditions are studied. The increase of wave height brings increasing maximum overtopping discharges and different spatial distribution of water behind the crown wall. The impact forces on the structures are determined by both incident wave height and relative positions of the structures.