Search results for: surface layer

Authors: A. M. Tahsini

Abstract:

Numerical study of two dimensional supersonic hydrogen-air mixing layer is performed to investigate the effect of turbulence and chemical additive on ignition distance. Chemical reaction is treated using detail kinetics. Advection upstream splitting method is used to calculate the fluxes and one equation turbulence model is chosen here to simulate the considered problem. Hydrogen peroxide is used as an additive and the results show that inflow turbulence and chemical additive may drastically decrease the ignition delay in supersonic combustion.

Keywords: Ignition, Mixing layer, Numerical simulation, Supersonic combustion, Turbulence

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Authors: Manivannan A, Velmurugan M

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Solar air heater is a type of heat exchanger which transforms solar radiation into heat energy. The thermal performance of conventional solar air heater has been found to be poor because of the low convective heat transfer coefficient from the absorber plate to the air. It is attributed to the formation of a very thin boundary layer at the absorber plate surface commonly known as viscous sub-layer. Thermal efficiency of solar air heater can be improved by providing the artificial roughness on absorber plate is the most efficient technique. In this paper an attempt is made to provide artificial roughness by incorporating inclined multiple V-ribs in the underside of the absorber plate. 60˚V – ribs are arranged inclined to the direction of air flow. Performance of collector estimated theoretically and experimentally. Results of the investigation reveal that thermal efficiency of collector with multiple V-ribs increased by 14%.

Keywords: Artificial roughness, inclined multiple V-ribs, performance, Solar air collector.

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Authors: O. Alizadeh Sahraei, A. Khodadadi, Y. Mortazavi, M. Vesali Naseh, S. Mosadegh

Abstract:

A composite made of plasma functionalized multiwall carbon nanotubes (MWNTs) coated with SnO2 was synthesized by sonochemical precipitation method. Thick layer of this nanocomposite material was used as ethanol sensor at low temperatures. The composite sensitivity for ethanol has increased by a factor of 2 at room temperature and by a factor of 13 at 250°C in comparison to that of pure SnO2. SEM image of nanocomposite material showed MWNTs were embedded in SnO2 matrix and also a higher surface area was observed in the presence of functionalized MWNTs. Greatly improved sensitivity of the composite material to ethanol can be attributed to new gas accessing passes through MWNTs and higher specific surface area.

Keywords: Carbon nanotube, Functionalized, Gas sensor, Low temperature, Nanocomposite, Tin oxide.

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Authors: Shiang-Cheng Jeng, Horng-Shing Chiou

Abstract:

A first intermediate roll of Sendzirmir mills was failure by surface spalling during operation. After analyzing by visual, stereo microscope, optical microscope, scanning electron microscope, glow-discharged spectrometer and hardness test, respectively, the results show that some voids and cracks existed on the contact surface as well as subsurface. Further examination verified inadequate hardness and inclusions were responsible for the failure of surface spalling.

Keywords: Sendzirmir mills; surface spalling; fatigue failure;inclusion; contact stress

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Authors: Hiroshi Hirano, Joji Kadota, Toshiyuki Yamashita, Yasuyuki Agari

Abstract:

It is well known that enhancing interfacial adhesion between inorganic filler and matrix resin in a composite lead to favorable properties such as excellent mechanical properties, high thermal resistance, prominent electric insulation, low expansion coefficient, and so on. But it should be avoided that much excess of coupling agent is reacted due to a negative impact of their final composite-s properties. There is no report to achieve classification of the bonding state excepting investigation of coating layer thickness. Therefore, the analysis of the bonding state of the coupling agent reacted with the filler surface such as BN particles with less functional group and silica particles having much functional group was performed by thermal gravimetric analysis and pyrolysis GC/MS. The reacted number of functional groups on the silane-coupling agent was classified as a result of the analysis. Thus, we succeeded in classifying the reacted number of the functional groups as a result of this study.

Keywords: Inorganic filler, boron nitride, surface treatment, coupling agent, analysis of bonding state

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Authors: Ssu-Han Chen, Der-Baau Perng

Abstract:

Molding process in IC manufacturing secures chips against the harms done by hot, moisture or other external forces. While a chip was being molded,defects like cracks, dilapidation, or voids may be embedding on the molding surface. The molding surfaces the study poises to treat and the ones on the market, though, differ in the surface where texture similar to defects is everywhere. Manual inspection usually passes over low-contrast cracks or voids; hence an automatic optical inspection system for molding surface is necessary. The proposed system is consisted of a CCD, a coaxial light, a back light as well as a motion control unit. Based on the property of statistical textures of the molding surface, a series of digital image processing and classification procedure is carried out. After training of the parameter associated with above algorithm, result of the experiment suggests that the accuracy rate is up to 93.75%, contributing to the inspection quality of IC molding surface.

Keywords: Molding surface, machine vision, statistical texture, discrete Fourier transformation.

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Authors: Yusmeeraz Yusof, Yoshiyuki Yanagimoto, Shigeyasu Uno, Kazuo Nakazato

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We demonstrate a nonfaradaic electrochemical impedance spectroscopy measurement of biochemically modified gold plated electrodes using a two-electrode system. The absence of any redox indicator in the impedance measurements provide more precise and accurate characterization of the measured bioanalyte at molecular resolution. An equivalent electrical circuit of the electrodeelectrolyte interface was deduced from the observed impedance data of saline solution at low and high concentrations. The detection of biomolecular interactions was fundamentally correlated to electrical double-layer variation at modified interface. The investigations were done using 20mer deoxyribonucleic acid (DNA) strands without any label. Surface modification was performed by creating mixed monolayer of the thiol-modified single-stranded DNA and a spacer thiol (mercaptohexanol) by a two-step self-assembly method. The results clearly distinguish between the noncomplementary and complementary hybridization of DNA, at low frequency region below several hundreds Hertz.

Keywords: Biosensor, electrical double-layer, impedance spectroscopy, label free DNA.

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Authors: M. Maronek, J. Barta, P. Palcek, K. Ulrich

Abstract:

Low carbon deep drawing steel DC 01 according to EN 10130-91 was nitrooxidized in dissociated ammonia at 580°C/45 min and consequently oxidised at 380°C/5 min in vapour of distilled water. Material after nitrooxidation had 54 % increase of yield point, 34 % increase of strength and 10-times increased resistance to atmospheric corrosion in comparison to the material before nitrooxidation. The microstructure of treated material consisted of thin ε-phase layer connected to layer containing precipitated massive needle shaped Fe4N - γ' nitrides. This layer passed to a diffusion layer consisting of fine irregular shaped Fe16N2 - α'' nitrides regularly dispersed in ferritic matrix. Fatigue properties were examined under bending load with frequency of 20 kHz and sinusoidal symmetric cycle. The results confirmed positive influence of nitrooxidation on fatigue properties as fatigue limit of treated material was double in comparison to untreated material.

Keywords: steel sheet, fatigue, nitrooxidation, S-N diagram

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Authors: Z. Dibi, F. Djeffal, N. Lakhdar

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In this paper, we have developed an explicit analytical drain current model comprising surface channel potential and threshold voltage in order to explain the advantages of the proposed Gate Stack Double Diffusion (GSDD) MOSFET design over the conventional MOSFET with the same geometric specifications that allow us to use the benefits of the incorporation of the high-k layer between the oxide layer and gate metal aspect on the immunity of the proposed design against the self-heating effects. In order to show the efficiency of our proposed structure, we propose the simulation of the power chopper circuit. The use of the proposed structure to design a power chopper circuit has showed that the (GSDD) MOSFET can improve the working of the circuit in terms of power dissipation and self-heating effect immunity. The results so obtained are in close proximity with the 2D simulated results thus confirming the validity of the proposed model.

Keywords: Double-Diffusion, modeling, MOSFET, power.

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Authors: Aimeng Wang, Dejun Ma, Hui Wang

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The paper presents a detailed calculation of characteristic of five different topology permanent magnet machines for high performance traction including hybrid -electric vehicles using finite element analysis (FEA) method. These machines include V-shape single layer interior PM, W-shape single-layer interior PM, Segment interior PM and surface PM on the rotor and with distributed winding on the stator. The performance characteristics which include the back-emf voltage and its harmonic, magnet mass, iron loss and ripple torque are compared and analyzed. One of a 7.5kW IPM prototype was tested and verified finite-element analysis results. The aim of the paper is given some guidance and reference for machine designer which are interested in IPM machine selection for high performance traction application.

Keywords: Interior permanent magnet machine, finite-element analysis (FEA), five topologies, electric vehicle.

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Authors: Adekitan I. Aderibigbe, Fakolujo A. Olaosebikan

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The parameters of a two-layer soil can be determined by processing resistivity data obtained from resistivity measurements carried out on the soil of interest. The processing usually entails applying the resistivity data as inputs to an optimisation function. This paper proposes an algorithm which utilises the square error as an optimisation function. Resistivity data from previous works were applied to test the accuracy of the new algorithm developed and the result obtained conforms significantly to results from previous works.

 

Keywords: Algorithm, earthing, resistivity, two-layer soil-model.

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Authors: A. T. Eswara

Abstract:

This paper analyses the unsteady, two-dimensional stagnation point flow of an incompressible viscous fluid over a flat sheet when the flow is started impulsively from rest and at the same time, the sheet is suddenly stretched in its own plane with a velocity proportional to the distance from the stagnation point. The partial differential equations governing the laminar boundary layer forced convection flow are non-dimensionalised using semi-similar transformations and then solved numerically using an implicit finitedifference scheme known as the Keller-box method. Results pertaining to the flow and heat transfer characteristics are computed for all dimensionless time, uniformly valid in the whole spatial region without any numerical difficulties. Analytical solutions are also obtained for both small and large times, respectively representing the initial unsteady and final steady state flow and heat transfer. Numerical results indicate that the velocity ratio parameter is found to have a significant effect on skin friction and heat transfer rate at the surface. Furthermore, it is exposed that there is a smooth transition from the initial unsteady state flow (small time solution) to the final steady state (large time solution).

Keywords: Forced flow, Keller-box method, Stagnation point, Stretching flat sheet, Unsteady laminar boundary layer, Velocity ratio parameter.

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Authors: W. J. Stępniowski, W. Florkiewicz, M. Norek, M. Michalska-Domańska, E. Kościuczyk, T. Czujko

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In this paper, two options of anodic alumina barrier layer thinning have been demonstrated. The approaches varied with the duration of the voltage step. It was found that too long step of the barrier layer thinning process leads to chemical etching of the nanopores on their top. At the bottoms pores are not fully opened what is disadvantageous for further applications in nanofabrication. On the other hand, while the duration of the voltage step is controlled by the current density (value of the current density cannot exceed 75% of the value recorded during previous voltage step) the pores are fully opened. However, pores at the bottom obtained with this procedure have smaller diameter, nevertheless this procedure provides electric contact between the bare aluminum (substrate) and electrolyte, what is suitable for template assisted electrodeposition, one of the most cost-efficient synthesis method in nanotechnology.

Keywords: Anodic aluminum oxide, anodization, barrier layer thinning, nanopores.

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Authors: Punit Kumar, Niraj Kumar

Abstract:

The influence of transverse surface roughness on EHL characteristics has been investigated numerically using an extensive set of full EHL line contact simulations for shear-thinning lubricants under pure sliding condition. The shear-thinning behavior of lubricant is modeled using Carreau viscosity equation along with Doolittle-Tait equation for lubricant compressibility. The surface roughness is assumed to be sinusoidal and it is present on the stationary surface. It is found that surface roughness causes sharp pressure peaks along with reduction in central and minimum film thickness. With increasing amplitude of surface roughness, the minimum film thickness decreases much more rapidly as compared to the central film thickness.

Keywords: EHL, Carreau, Shear-thinning, Surface Roughness, Amplitude, Wavelength.

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Authors: Somkiat Tangjitsitcharoen, Siripong Damrongthaveesak

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This paper presents an advance in monitoring and process control of surface roughness in CNC machine for the turning and milling processes. An integration of the in-process monitoring and process control of the surface roughness is proposed and developed during the machining process by using the cutting force ratio. The previously developed surface roughness models for turning and milling processes of the author are adopted to predict the inprocess surface roughness, which consist of the cutting speed, the feed rate, the tool nose radius, the depth of cut, the rake angle, and the cutting force ratio. The cutting force ratios obtained from the turning and the milling are utilized to estimate the in-process surface roughness. The dynamometers are installed on the tool turret of CNC turning machine and the table of 5-axis machining center to monitor the cutting forces. The in-process control of the surface roughness has been developed and proposed to control the predicted surface roughness. It has been proved by the cutting tests that the proposed integration system of the in-process monitoring and the process control can be used to check the surface roughness during the cutting by utilizing the cutting force ratio.

Keywords: Turning, milling, monitoring, surface roughness, cutting force ratio.

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Authors: A. Rabin, G. Mazor, I. Ladizhenski, R. Z. Shneck

Abstract:

The hardness and hardenability of AISI D2 cold work tool steel with conventional quenching (CQ), deep cryogenic quenching (DCQ) and rapid deep cryogenic quenching heat treatments caused by temporary porous coating based on magnesium sulfate was investigated. Each of the cooling processes was examined from the perspective of the full process efficiency, heat flux in the austenite-martensite transformation range followed by characterization of the temporary porous layer made of magnesium sulfate using confocal laser scanning microscopy (CLSM), surface and core hardness and hardenability using Vickers hardness technique. The results show that the cooling rate (CR) at the austenite-martensite transformation range has a high influence on the hardness of the studied steel.

Keywords: AISI D2, controllable cooling, magnesium sulfate coating, rapid cryogenic heat treatment, temporary porous layer.

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Authors: Hee-Chang Lim

Abstract:

The study aims to understand the surface pressure distribution around the bodies such as the suction pressure in the leading edge on the top and side-face when the aspect ratio of bodies and the wind direction are changed, respectively. We carried out the wind tunnel measurement and numerical simulation around a series of rectangular bodies (40^d×80^w×80^h, 80^d×80^w×80^h, 160^d×80^w×80^h, 80^d×40^w×80^h and 80^d×160^w×80^h in mm³) placed in a deep turbulent boundary layer. Based on a modern numerical platform, the Navier-Stokes equation with the typical 2-equation (k-ε model) and the DES (Detached Eddy Simulation) turbulence model has been calculated, and they are both compared with the measurement data. Regarding the turbulence model, the DES model makes a better prediction comparing with the k-ε model, especially when calculating the separated turbulent flow around a bluff body with sharp edged corner. In order to observe the effect of wind direction on the pressure variation around the cube (e.g., 80^d×80^w×80^h in mm), it rotates at 0º, 10º, 20º, 30º, and 45º, which stands for the salient wind directions in the tunnel. The result shows that the surface pressure variation is highly dependent upon the approaching wind direction, especially on the top and the side-face of the cube. In addition, the transverse width has a substantial effect on the variation of surface pressure around the bodies, while the longitudinal length has little or no influence.

Keywords: Rectangular bodies, wind direction, aspect ratio, surface pressure distribution, wind-tunnel measurement, k-ε model, DES model, CFD.

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Authors: Smriti H. Bhandari, S. M. Deshpande

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Surface metrology with image processing is a challenging task having wide applications in industry. Surface roughness can be evaluated using texture classification approach. Important aspect here is appropriate selection of features that characterize the surface. We propose an effective combination of features for multi-scale and multi-directional analysis of engineering surfaces. The features include standard deviation, kurtosis and the Canny edge detector. We apply the method by analyzing the surfaces with Discrete Wavelet Transform (DWT) and Dual-Tree Complex Wavelet Transform (DT-CWT). We used Canberra distance metric for similarity comparison between the surface classes. Our database includes the surface textures manufactured by three machining processes namely Milling, Casting and Shaping. The comparative study shows that DT-CWT outperforms DWT giving correct classification performance of 91.27% with Canberra distance metric.

Keywords: Dual-tree complex wavelet transform, surface metrology, surface roughness, texture classification.

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Authors: Ebadollah Zohrevandi, Rasoul Roustaei, Omid Moradtalab

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In this paper, we first consider the quality of service problems in heterogeneous wireless networks for sending the video data, which their problem of being real-time is pronounced. At last, we present a method for ensuring the end-to-end quality of service at application layer level for adaptable sending of the video data at heterogeneous wireless networks. To do this, mechanism in different layers has been used. We have used the stop mechanism, the adaptation mechanism and the graceful degrade at the application layer, the multi-level congestion feedback mechanism in the network layer and connection cutting off decision mechanism in the link layer. At the end, the presented method and the achieved improvement is simulated and presented in the NS-2 software.

Keywords: Congestion, Handoff, Heterogeneous wireless networks, Adaptation mechanism, Stop mechanism, Graceful degrade.

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Authors: Siddhartha Bhattacharyya, Paramartha Dutta, Ujjwal Maulik, Prashanta Kumar Nandi

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A multilayer self organizing neural neural network (MLSONN) architecture for binary object extraction, guided by a beta activation function and characterized by backpropagation of errors estimated from the linear indices of fuzziness of the network output states, is discussed. Since the MLSONN architecture is designed to operate in a single point fixed/uniform thresholding scenario, it does not take into cognizance the heterogeneity of image information in the extraction process. The performance of the MLSONN architecture with representative values of the threshold parameters of the beta activation function employed is also studied. A three layer bidirectional self organizing neural network (BDSONN) architecture comprising fully connected neurons, for the extraction of objects from a noisy background and capable of incorporating the underlying image context heterogeneity through variable and adaptive thresholding, is proposed in this article. The input layer of the network architecture represents the fuzzy membership information of the image scene to be extracted. The second layer (the intermediate layer) and the final layer (the output layer) of the network architecture deal with the self supervised object extraction task by bi-directional propagation of the network states. Each layer except the output layer is connected to the next layer following a neighborhood based topology. The output layer neurons are in turn, connected to the intermediate layer following similar topology, thus forming a counter-propagating architecture with the intermediate layer. The novelty of the proposed architecture is that the assignment/updating of the inter-layer connection weights are done using the relative fuzzy membership values at the constituent neurons in the different network layers. Another interesting feature of the network lies in the fact that the processing capabilities of the intermediate and the output layer neurons are guided by a beta activation function, which uses image context sensitive adaptive thresholding arising out of the fuzzy cardinality estimates of the different network neighborhood fuzzy subsets, rather than resorting to fixed and single point thresholding. An application of the proposed architecture for object extraction is demonstrated using a synthetic and a real life image. The extraction efficiency of the proposed network architecture is evaluated by a proposed system transfer index characteristic of the network.

Keywords: Beta activation function, fuzzy cardinality, multilayer self organizing neural network, object extraction,

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Authors: Harun Gülan, Muhsin Tunay Gencoglu, Mehmet Cebeci

Abstract:

The main function of the insulators used in high voltage (HV) transmission lines is to insulate the energized conductor from the pole and hence from the ground. However, when the insulators fail to perform this insulation function due to various effects, failures occur. The deterioration of the insulation results either from breakdown or surface flashover. The surface flashover is caused by the layer of pollution that forms conductivity on the surface of the insulator, such as salt, carbonaceous compounds, rain, moisture, fog, dew, industrial pollution and desert dust. The source of the majority of failures and interruptions in HV lines is surface flashover. This threatens the continuity of supply and causes significant economic losses. Pollution flashover in HV insulators is still a serious problem that has not been fully resolved. In this study, a water jet test system has been established in order to investigate the behavior of insulators under dirty conditions and to determine their flashover performance. Flashover behavior of the insulators is examined by applying impulse voltages in the test system. This study aims to investigate the insulator behaviour under high impulse voltages. For this purpose, a water jet test system was installed and experimental results were obtained over a real system and analyzed. By using the water jet test system instead of the actual insulator, the damage to the insulator as a result of the flashover that would occur under impulse voltage was prevented. The results of the test system performed an important role in determining the insulator behavior and provided predictability.

Keywords: Insulator, pollution flashover, high impulse voltage, water jet model.

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Authors: Md. Ashikur Rahman Khan, M. M. Rahman

Abstract:

Electrical discharge machining (EDM) is a relatively modern machining process having distinct advantages over other machining processes and can machine Ti-alloys effectively. The present study emphasizes the features of the development of regression equation based on response surface methodology (RSM) for correlating the interactive and higher-order influences of machining parameters on surface finish of Titanium alloy Ti-6Al-4V. The process parameters selected in this study are discharge current, pulse on time, pulse off time and servo voltage. Machining has been accomplished using negative polarity of Graphite electrode. Analysis of variance is employed to ascertain the adequacy of the developed regression model. Experiments based on central composite of response surface method are carried out. Scanning electron microscopy (SEM) analysis was performed to investigate the surface topography of the EDMed job. The results evidence that the proposed regression equation can predict the surface roughness effectively. The lower ampere and short pulse on time yield better surface finish.

Keywords: Graphite electrode, regression model, response surface methodology, surface roughness.

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Authors: H. S. Lim, M. Z. MatJafri, K. Abdullah, N. Mohd. Saleh

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Retrieval of the surface reflectance is important in the remotely sensed data analysis to obtain the atmospheric reflectance or atmospheric correction. The relationship between visible and mid infrared reflectance over land was investigated and developed in this study. The surface reflectances of the two visible bands were measured using a handheld spectroradiometer collected around Penang Island. In this study, we use the assumption that the 2.1 μm band is not affected by aerosol and it is transparent to most aerosol types (except dust). Therefore the satellite observed signal is the same as the surface signal in 2.1 μm band. The correlation between the surface reflectance measured by the spectroradiometer in the blue and red region and the 2.1 μm observed by the satellite has been established. We investigate five dates of Landsat TM scenes in this study. The finding obtained by this study indicates that the surface reflectance can be retrieved from the 2.1 μm band.

Keywords: Surface Reflectance, Landsat TM, Aerosol, Spectroradiometer.

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Authors: Jennifer Penton, Charitha Pattiaratchi

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Surface currents play a major role in the distribution of contaminants, the connectivity of marine populations, and can influence the vertical and horizontal distribution of nutrients within the water column. This paper aims to determine the effects of sea breeze-wind patterns on the climatology of the surface currents on the continental shelf surrounding Rottnest Island, WA Australia. The alternating wind patterns allow for full cyclic rotations of wind direction, permitting the interpretation of the effect of the wind on the surface currents. It was found that the surface currents only clearly follow the northbound Capes Current in times when the Fremantle Doctor sets in. Surface currents react within an hour to a change of direction of the wind, allowing southerly currents to dominate during strong northerly sea breezes, often followed by mixed currents dominated by eddies in the inter-lying times.

Keywords: HF radar, surface currents, sea breeze.

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Authors: Dhahri Maher, Aouinet Hana

Abstract:

The presence of bubbles in the boundary layer introduces corrections into the log law, which must be taken into account. In this work, a logarithmic wall law was presented for bubbly two phase flows. The wall law presented in this work was based on the postulation of additional turbulent viscosity associated with bubble wakes in the boundary layer. The presented wall law contained empirical constant accounting both for shear induced turbulence interaction and for non-linearity of bubble. This constant was deduced from experimental data. The wall friction prediction achieved with the wall law was compared to the experimental data, in the case of a turbulent boundary layer developing on a vertical flat plate in the presence of millimetric bubbles. A very good agreement between experimental and numerical wall friction prediction was verified. The agreement was especially noticeable for the low void fraction when bubble induced turbulence plays a significant role.

Keywords: Bubbly flows, log law, boundary layer.

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Authors: Saroj Kumar Sarangi, M. C. Ray

Abstract:

This paper deals with the analysis of active constrained layer damping (ACLD) of doubly curved laminated composite shells using active fiber composite (AFC) materials. The constraining layer of the ACLD treatment has been considered to be made of the AFC materials. A three dimensional energy based finite element model of the smart doubly curved laminated composite shell integrated with a patch of such ACLD treatment has been developed to demonstrate the performance of the patch on enhancing the damping characteristics of the doubly curved laminated composite shells. Particular emphasis has been placed on studying the effect of variation of piezoelectric fiber orientation angle in the constraining AFC layer on the control authority of the ACLD patch.

Keywords: Active constrained layer damping, Active fibercomposites, Finite element modeling, First order shear deformationtheory.

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Authors: P. R. Prabhu, S. M. Kulkarni, S. S. Sharma

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Deep cold rolling (DCR) and low plasticity burnishing (LPB) process are cold working processes, which easily produce a smooth and work-hardened surface by plastic deformation of surface irregularities. The present study focuses on the surface roughness and surface hardness aspects of AISI 4140 work material, using fractional factorial design of experiments. The assessment of the surface integrity aspects on work material was done, in order to identify the predominant factors amongst the selected parameters. They were then categorized in order of significance followed by setting the levels of the factors for minimizing surface roughness and/or maximizing surface hardness. In the present work, the influence of main process parameters (force, feed rate, number of tool passes/overruns, initial roughness of the work piece, ball material, ball diameter and lubricant used) on the surface roughness and the hardness of AISI 4140 steel were studied for both LPB and DCR process and the results are compared. It was observed that by using LPB process surface hardness has been improved by 167% and in DCR process surface hardness has been improved by 442%. It was also found that the force, ball diameter, number of tool passes and initial roughness of the workpiece are the most pronounced parameters, which has a significant effect on the work piece-s surface during deep cold rolling and low plasticity burnishing process.

Keywords: Deep cold rolling, burnishing, surface roughness, surface hardness, design of experiments, AISI4140 steel.

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Authors: M. Areekijseree, M. Pumipaiboon, S. Nuamsukon, K. Kittiwattanawong, C. Thongchai, S. Sikiwat, T. Chuen-Im

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There are few studies on eggshell of leatherback turtle which is endangered species in Thailand. This study was focusing on the ultrastructure and elemental composition of leatherback turtle eggshells collected from Andaman Sea Shore, Thailand during the nesting season using scanning electron microscope (SEM). Three eggshell layers of leatherback turtle; the outer cuticle layer or calcareous layer, the middle layer or middle multistrata layer and the inner fibrous layer were recognized. The outer calcareous layer was thick and porosity which consisted of loose nodular units of various crystal shapes and sizes. The loose attachment between these units resulted in numerous spaces and openings. The middle layer was compact thick with several multistrata and contained numerous openings connecting to both outer cuticle layer and inner fibrous layer. The inner fibrous layer was compact and thin, and composed of numerous reticular fibers. Energy dispersive X-ray microanalysis detector revealed energy spectrum of X-rays character emitted from all elements on each layer. The percentages of all elements were found in the following order: carbon (C) > oxygen (O) > calcium (Ca) > sulfur (S) > potassium (K) > aluminum (Al) > iodine (I) > silicon (Si) > chlorine (Cl) > sodium (Na) > fluorine (F) > phosphorus (P) > magnesium (Mg). Each layer consisted of high percentage of CaCO3 (approximately 98%) implying that it was essential for turtle embryonic development. A significant difference was found in the percentages of Ca and Mo in the 3layers. Moreover, transition metal, metal and toxic non-metal contaminations were found in leatherback turtle eggshell samples. These were palladium (Pd), molybdenum (Mo), copper (Cu), aluminum (Al), lead (Pb), and bromine (Br). The contamination elements were seen in the outer layers except for Mo. All elements were readily observed and mapped using Smiling program. X-ray images which mapped the location of all elements were showed. Calcium containing in the eggshell appeared in high contents and was widely distributing in clusters of the outer cuticle layer to form CaCO3 structure. Moreover, the accumulation of Na and Cl was observed to form NaCl which was widely distributing in 3 eggshell layers. The results from this study would be valuable on assessing the emergent success in this endangered species.

Keywords: Leatherback turtle (Dermochelys coriacea), SEM (SEI/EDX), turtle eggshell.

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Authors: Mustafa Resa Becan

Abstract:

Sliding mode control with a fuzzy boundary layer is presented to hydraulic position control problem in this paper. A nonlinear hydraulic servomechanism which has an asymmetric cylinder is modeled and simulated first, then the proposed control scheme is applied to this model versus the conventional sliding mode control. Simulation results proved that the chattering free position control is achieved by tuning the fuzzy scaling factors properly.

Keywords: Hydraulic servomechanism, position control, sliding mode control, chattering, fuzzy boundary layer.

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Authors: S.O. Shazlin, M.S. Nurulakmal

Abstract:

Studies have shown that the SnAgCu solder family has been widely used as a replacement for conventional Sn-Pb solders. An attractive approach is by introducing alloying additives (rare earth elements (RE), Zn, Co, Fe, Ni, Sb) into the SnAgCu solder, which helps in refining the microstructure also improving the mechanical and wetting properties of the solder. The present work focuses on the effect of additions of 0.5% Ce and Fe into Sn-3.0Ag-0.5Cu solder, in attempt to reduce the intermetallic compound (IMC) growth and reflow properties of the solder on Cu and Ni (P) surface finish, as well as effects thermal aging on the formation of intermetallic compound (IMC) on different surface finish. Excessive intermetallic compound growth may effect the interface and solder joint due to the brittle nature of the intermetallic compounds. Thus, by introducing alloying elements, IMC layer thickness can be decrease, resulting in better joint and solder reliability.

Keywords: Alloying Elements, Cu and Ni (P) Substrate, Intermetallic Compound (IMC), Reflow, Thermal Aging.

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