Showing papers in "International Journal of Technology in 2014"

Impact resistance and strength reliability of fiber-reinforced concrete in bending under drop weight impact load

Abstract: This paper presents an experimental investigation on the Impact failure energy and strength reliability of fiber reinforced concrete (FRC) by using a simple drop weight test which was based on the testing procedure recommended by ACI committee 544. Two different steel fibers were used as the reinforcing material in various volume fractions such as 0%, 0.5%, 1.0% and 1.5% with a water cement ratio of 0.42. Furthermore, the two-parameter weibull distribution was used to analyze the experimental data in order to sort out a variation of test results. Using the weibull distribution, the impact failure strength reliability, in other words, the probability distribution according to which the concrete will fail, was obtained. The results indicated that the concrete containing a 1.5% volume fraction of fiber gave the best performance followed by 1.0% and 0.5% under impact loading. It was proven that the probabilistic distributions of the impact failure energy of seven types of samples approximately follow two-parameter Weibull distribution.

Method and model development for manufacturing cost estimation during the early design phase related to the complexity of the machining processes

Abstract: Product manufacturing cost estimation in the early stages of the design process is useful for accelerating product time to market, reducing costs, and increasing quality in order to obtain products with a high level of competitiveness in the free market. Complexity and machining cost are important variables to estimate the final cost of the product. However, current cost estimation models only consider their calculations based on the design which has been determined beforehand, so that it is difficult to apply a cost estimation model early on in the design process because of minimal information. Therefore, in this research, a new method to produce a cost estimation model during the early stage of the design process is proposed. The new model was developed by correlating the cost calculation with the complexity of the machining process based on product features. By using this model, the designers are able to put through design changes quickly by modifying revisions at the manufacturing stage. In this paper, the development and implementation of the proposed cost estimation model which involves the milling process is known as the SPMF (Single Product Multi-Features) Product model is explained in detail. The proposed method shows that the SPMF Product model can be used to produce a manufacturing cost estimation based on process complexity.

Subcritical water extraction and direct formation of microparticulate polysaccharide powders from ganoderma lucidum

Abstract: Ganoderma lucidum (hereafter G. lucidum) has been known as a food and raw material used in the development of medications because of its high content of polysaccharides, or β-glucans, which support the immune function. In this work, subcritical water was applied to utilize G. lucidum for the extraction of polysaccharides at temperatures of 373–463K and a pressure level of 4.0 MPa using a semi-batch system. Furthermore, these extracts were atomized and contacted with hot air to produce microsphere particles. During extraction, thermal softening of G. lucidum occurred, allowing the removal of the polysaccharides and protecting other constituents in G. lucidum via hydrolysis. Scanning electron microscope (SEM) images showed that the microsphere particles formed were spherical and dimpled or shriveled particles with diameters varying from 1 to 6 m. Characteristics of the molecular mass revealed that main massed peaks of water soluble products were distributed at around 688–2636 m/z with a peakto-peak mass difference of 162 m/z, consistent with the repeating unit of the glucans.

Preparation and characterization of alginate beads by drop weight

Abstract: The preparation and characterization of macro alginate beads are always associated with appropriate techniques involving precise measurement of shape, size, volume and density of the products. Depending on the type of application, encapsulation of macro alginate beads can be accomplished by various techniques including chemical, ionotropic, physical and mechanical methods. This work describes a method for preparing macro alginate beads through drop weight. The macro beads (2.85–3.85 mm) were prepared via different concentrations of alginate (0.5, 1.0, 1.5 and 2.0 g/L), dripping tip size (0.04–0.14 cm) and immersion into a predetermined concentration of calcium chloride (CaCl2) bath. A custom made dripping vessel fabricated from acrylic plastic, connected to an adjustable dripping clamp was used to simulate the dripping process of the molten alginate at different tip sizes. It was observed that at different dripping tips, the correction factor for the alginate slurry was found in the range of 0.73–0.83. Meanwhile, the lost factor, KLF was observed at 0.93–2.3 and the shrinkage factors were limited to 2.00% from the overall distributed data. It was concluded that liquid properties had no effect on the liquid lost factor. The bead size prediction for different concentrations of alginate solution was compared to the experimental data. Subsequently, it was concluded that increasing the tip size caused the bead size to deviate almost 20% when compared to the experimental and predicted values, respectively.

Surface hardening of tool steel by plasma arc with multiple passes

Abstract: Plasma arc surface hardening is an alternative selective surface hardening method that is effective, economical and a promising technology in heat treatment industries. In the present work, an investigation was carried out to study the hardness distributions of multiple passes in surface hardening of tool steel by plasma arc. The effects of multiple passes with overlapping and non-overlapping scans were investigated. The results show that the hardness is higher at centre of the plasma arc hardening tracks, and then decreasing in the region adjacent to each plasma arc track. It was found that the formation of hardened zone hardness in multiple passes non-overlapping scan is more uniform on the each scan when compared to the overlapping scan. However, hardness distribution of overlapping scan in width direction shows that it was more uniform compared with non-overlapping scan.

Trend analysis of hydro-meteorological variables using the mann-kendall trend test: application to the niger river and the benue sub-basins in nigeria

Abstract: This paper presents the outcome of the trend analysis of hydro-meteorological variables in the Niger River and the Benue sub-basins in Nigeria. A non-parametric Mann-Kendall trend test was used to analyse the trends exhibited by the variables. The results revealed that precipitation exhibits insignificant positive trends in five locations, while insignificant negative trends were exhibited in the remaining six locations. This implies that the increase or decrease in precipitation would not be noticeable in all the locations, since the changes are statistically insignificant. The evaporation exhibits a significant positive trend in three locations, while in another three locations it exhibits an insignificant positive trend and also exhibits an insignificant negative trend in the remaining five locations. This is an indication that the incremental change in evaporation would be noticeable in three locations, while the increase or decrease would not be noticed in the remaining eight locations. In the case of minimum and maximum temperature, the trends in almost all the locations, except Ibi, are statistically significant positive. However, the runoff and water level in five locations out of six locations exhibit a significant negative trend. The downward trends exhibited by the runoff and water level in the two sub-basins may be due to the effect of climate variability on the hydrometeorological variables. The reduction of runoff is an indication of the decrease in water resources in the sub-basins and this can result in low reservoir inflow to the Kainji and Jebba hydropower dams located in the basin.

Synthesis of Titania nanotubes and Titania nanowires by combination sonication-hydrothermal treatment and their photocatalytic activity for hydrogen production

Abstract: Titania nanotubes (TiO2 NT) and Titania nanowires (TiO2 NW) were fabricated using TiO2 Degussa P25 (TiO2 P25) nanoparticle as precursors via a sonication-hydrothermal combination approach. The prepared catalysts were characterized by means of an X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), ultravioletvisible diffuse reflectance spectroscopy (DRS) and the Brunauer-Emmett-Teller technique (BET). The photocatalytic activity of prepared catalysts was evaluated for photocatalytic H2 evolution from an aqueous methanol solution. The results showed that activity of the catalyst not only depends on the morphology of its catalysts, but also on the crystalinity and surface area. Hydrogen production of TiO2 NT was about three times higher than TiO2 P25 and TiO2 NW was two times higher than TiO2P25.

A comprehensive solution to automated inspection device selection problems using electre methods

Abstract: Selection of an automated inspection device for an explicit industrial application is one of the most challenging problems in the current manufacturing environment. It has become more and more complicated due to increasing complexity, advanced features and facilities that are endlessly being integrated into the devices by different manufacturers. Selection of inspection devices plays a significant role in a manufacturing system for cost effectiveness and improved productivity. This paper focuses on the application of a very popular Multi-Criteria DecisionMaking (MCDM) tool, i.e. ELimination and Et Choice Translating REality (ELECTRE) for solving an automated inspection device selection problem in a discrete manufacturing environment. Using a sample case study from the published literature, this paper attempts to show how different variants of the ELECTRE method, namely ELECTRE II, IS, III, IV and TRI can be suitably applied in choosing the most efficient alternative that accounts for both the decision maker’s intervention and other technical elements. Using different ELECTRE methods, a list of all the possible choices from the best to the worst suitable devices is obtained while taking into account different selection attributes. The ranking performance of these methods is also compared with that of the past researchers.

Multiband bandpass filter (bpf) based on folded dual crossed open stubs

Abstract: A compact multiband bandpass filter (BPF) based on folded dual crossed open stubs (DCOS) is designed and analyzed. Two Crossed Open Stubs (COS) are used to generate concurrent sixband BPF, where the center frequency located at 0.95 GHz, 1.85 GHz, 2.65 GHz, 3.35 GHz, 4.375 GHz, and 5.25 GHz. The proposed BPF based on folded Dual Crossed Open Stubs (DCOS) is an expansion of tri-band BPF based on a single COS, where the second COS is used to generate second additional tri-band. To achieve miniaturization structure of proposed BPF, the DCOS is folded. The proposed BPF will be designed and analyzed by using Advanced System Design (ADS). The performances of multiband BPF which characterized by return loss, insertion loss, voltage standing wave ratio (VSWR), and group delay, are conducted by simulation, measurement and analysis. It is shown that the simulation and fabrication results of insertion loss, return loss, VSWR, and group delay of the proposed multiband BPF are satisfied to design requirements. However, the center frequencies of fabricated the proposed multiband BPF are shifted average to 530 MHz lead to simulated results. This is due to some errors in fabricated process including imperfect dimension of fabricated BPF, soldering between connector to substrate and cable losses.

λ-Statistical Convergence of a Sequence of Random Variables in Probability

Abstract: In this paper the ideas of two types of convergences of a sequence of random variables, namely, λ -statistical convergence in probability and λ - statistical convergence in mean of order r are introduced and the interrelationship between them is investigated. Also their certain basic properties are studied.

Changes of the Geomagnetic Signals Linked to Tohoku Earthquake on March 11th 2011

Abstract: The geomagnetic fields in the atmosphere can be affected by phenomena in the Earth, so that changes of geomagnetic intensity might be used as an indicator of earthquake occurrences. Variations of geomagnetic data have been analyzed in association with the Tohoku Earthquake on March 11th 2011. The Geomagnetic data have been derived from Memambetsu (MMB), Kakioka (KAK) and Kanoya (KNY) Observatories, which are INTERMAGNET observatories. The analysis was performed by calculating the power spectral density (psd) of the ULF signal of Z and H components and then polarizations are observed by comparing the psd of Z and of H. The results showed the difference psd of Z and of H between the KAK observatory (the nearest position to the epicenter) with MMB and KNY (at some greater distance from the epicenter) is quite significant, which can be observed over a period of 10 days before the earthquake occurrence. The polarizations of Z/H in KAK indicate a highest change of intensity which occurred at 18 days prior to the earthquake.

Decomposition of carbon dioxide in the three-pass flow dielectric barrier discharge plasma reactor

Abstract: Chemical Engineering Department, Faculty of Engineering, Universitas Indonesia, Kampus Baru UI, Depok 16424, Indonesia (Received: April 2013 / Revised: May 2013 / Accepted: December 2013) ABSTRACT Carbon dioxide (CO2) as one of the greenhouse gas emissions was decomposed to Carbon Monoxide (CO) and Oxygen (O2) in the three-pass flow Dielectric Barrier Discharge (DBD) plasma reactor, a new designed reactor that having special configuration of its reactant gas flow. This configuration can simultaneously cools the High Voltage Electrode (HVE) during the reaction process; and preheats the gas feed flow before entering plasma zone as well. This article explains the result of a preliminary research which aims to observe the performance of this reactor in utilizing CO2, mixed with CH4 to produce synthesis gas CO and H2, in a CO2 reforming process. This research was conducted using 3 (three) different reactor lengths, they were 36, 24 and 12 cm (Re1, Re2 and Re3), to observe the results of CO2 decomposition performance in the difference reactor lengths, and to observed the occurrence of reverse reaction inside the Re1 reactor. Other parameters were feed flow rates and the reactor voltage. Applied CO2 flow rates were 500, 1000 and 1500 SCCM/minute and applied reactor voltage were 5.4; to 9.5 kV. Results show that the conversion of CO2 was increased with the increasing of reactor voltage and longer reactor. The highest conversion was achieve at the lowest feed flow rate 500 SCCM/minute, this mean in the longest residence time. However, CO2 was only reaching the maximum conversion value on the reaction time of 2.1 minute, and dropped off after that. It is possibly caused by occurring of the reversed reaction due to the high temperature plasma reaction. At that point, the Specific Energy (SE) was 270 kJ/mol. This value is lower compare to the previous research results, as well as compare to its energy bonding, that shows the more energy efficient performance of this reactor.

Microalloying of Fe-Cr by using ultrasonic irradiation

Abstract: In this work the formation of Fe-Cr microalloy by ultrasonic irradiation at a frequency of 20 kHz is presented. Two sample series were produced with different ultrasonic irradiation procedures. For the first sample, Fe and Cr powder were each separately brought into the ultrasonic device before they were mixed in 7:1 weight ratio and then together retreated using the ultrasonic method. Secondly, Fe and Cr powder with same weight ratio were mixed and directly ultrasonically irradiated. During the ultrasonic irradiation process both samples were put in a toluene solution of 99%. The formation of the Fe-Cr microstructure in conjunction with ultrasonication time were investigated by using Scanning Electron Microscopy (SEM ), X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). After 40 hours of ultrasonic irradiation the particle sizes of the Fe powder of the first samples became significantly smaller; some particles were also fused together. However, with the exception of smaller-sized particles no fused Cr powders can be found even after 63 hours of ultrasonic irradiation. After both experiments Fe and Cr were mixed and again ultrasonically irradiated for 20 hours. Some particles indicated as Fe-Cr alloys containing 24.34 wt.% Fe and 67.43 wt.% Cr were observed. In the sample produced from the second procedure in which both Fe and Cr powders were irradiated together by an ultrasonic method for 50 hours, some powder particles formed a Fe-Cr microalloy with the composition of 96.27 wt.% Fe and 3.73 wt.% Cr. The XRD analysis revealed that the Fe-Cr alloy from the first samples has a BCC structure with a mass fraction of Fe:Cr:Fe-Cr which is equal to 0.836:0.0294:0.135, while the mass fraction of the Fe-Cr alloy from the second sample series is equal to 0.736:0.0808:0.183, respectively. Analysis of the TEM selected area diffraction patterns (SAED) confirmed that the Fe-Cr microalloy occured originaly from the precursor Fe and Cr particles of size smaller than 2 µm. The Fe-Cr microalloy has been successfully synthesized by using an ultrasonic process.

Effect of Permeable Boundary in the Bénard-Marangoni Convection in a Relatively Hotter or Cooler Liquid Layer

Abstract: We utilize the modified linear stability analysis to study the problem of the onset of convection in a horizontal liquid layer heated from below with permeable lower boundary on which boundary condition of the type specified by Beavers and Joseph [2] is applicable, while the driving mechanism is surface tension at the upper free surface. A Fourier series method is used to obtain the characteristic value equation for the Marangoni number M . It is established numerically that the principle of exchange of stabilities is valid for the problem under consideration. The numerical results are obtained for both thermally conducting and thermally insulating cases of the lower boundary, for various values of the boundary parameter K characterizing the permeable nature of the lower boundary. It is shown that there is a smooth increase in the value of the critical Marangoni number with increase in value of K irrespective of whether the liquid layer is relatively hotter or cooler. Further, it is observed that the limiting cases of the parameter K , give rise to the particular cases namely, when the lower boundary surface is either dynamically free ( K →0 ) or rigid ( K→ ∞).

Lesser sunda islands earthquake inter-occurrence times distribution modeling

Abstract: This paper is aimed towards analyzing and modeling earthquake interoccurence times in the Lesser Sunda Islands region using Weibull distribution. The data were classified into three categories, based on their magnitude; i.e. weak, medium, and strong earthquakes. Cumulative distribution functions and hazard rates are also explored in order to obtain the characteristics of earthquake inter-occurrences time data. Empirical results indicate the probability and rate of an earthquake recurrence time with a certain magnitude and in a certain time. Medium and weaker earthquakes have a higher chance of occurrence, reaching up to a 100% probability for the following 60 months. Meanwhile, the stronger earthquake has a 75.80% probability of occurrence. It can be seen that the earthquake occurrence probability increases together with the time increment factor.

Development and Evaluation of Mucoadhesive Sustained Release Tablet using Tamarindus indica Gum

Abstract: In the present work, the mucoadhesive tablet of diclofenac (as a model drug) by using Tamarindus indica fruit gum as a binder was formulated. The preliminary evaluation of Tamarindus indica gum showed that bulk density 0.50 ± 0.4 g/cm3, tapped density 0.35 ± 0.8 g/cm3 and angle of repose 280 ± 0.26. The six tablet formulation were prepared by using 0.25%, 0.50%, 0.75%, 1%, 1.25% and 1.50% w/w of Tamarindus indica gum by direct compression (F1,F2,F3,F4 and F5 respectively). Tablets were subjected for evaluation of uniformity of weight, hardness, friability, drug content uniformity, swelling behaviour, release rate study, mucoadhesive study, and tensile strength study. Formulation was studied for drug additive interaction (FTIR). F4 is found to be optimized formulation. The in-vitro drug release of F4 formulation exhibits complete release of Diclofenac Sodium with nonfiction first order release kinetic. The formulation F4 exhibited tensile strength 0.27 N with 10 hrs of mucoadhesion. From the study it can be conclude that the Tamarindus indica gum used as mucoadhesive sustained release tablet.

Hall Effect on Thermal Convection of a Nanofluid Layer Saturating a Porous Medium

Abstract: The present paper investigates the stability analysis of an electrically conducting horizontal layer of nanofluid in the presence of Hall currents saturating a porous medium for bottom heavy distribution of nanoparticles. Hall currents are the effects whereby a conductor carrying an electric current perpendicular to an applied magnetic field develops a voltage gradient which is transverse to both the current and the magnetic field. The nanofluid layer incorporates the effect of Brownian motion and the rmophoresis while Darcy's law is used for the porous medium. The analysis is carried out in the framework of linear stability theory, normal mode technique and Galerkin type weighted residuals method. The present formulation of the problem leads to oscillatory mode of instability whereas for top heavy arrangement of nanoparticles the instability is invariably through stationary convection. The reason for the oscillatory mode of convection is the competition between the density gradient caused by bottom heavy nanoparticle distribution with the density variation caused by heating from the bottom. Further, it is found that the effect of magnetic field is to postpone the onset of instability while that of Hall currents and porosity is to hasten the onset of thermal convection.

Enhanced Clustering for Forensic Analysis

Abstract: In todays digital world, the forensic analysis is of great importance. Huge amount of data has been examined by analyst to present evidences in court. But, usually the files in those computers consist of data is in unstructured form. Thus, it is very difficult to analyze such data. To overcome this difficulty, the automatic analyses of data are of great interest. The algorithms for automatic clustering can be used to retrieve the interesting knowledge and useful information from the data which is unstructured and unorganized. We will propose the algorithm for clustering of data in automatic manner useful for computer forensic experts for the analysis of data. We will experiment for such things by proposing an approach of enhanced K-medoid algorithm with representatives over well known clustering algorithms. We performed experiment on the data collected from different real time crime data sources found in Police investigation FIRs'. We will propose the enhanced preprocessing techniques which can be beneficial over the well known stemmer algorithms. Finally, we summarize the results using good visualization techniques.

Balanced Incomplete Block Design (Bibd) Using Hadamard Rhotrices

Abstract: Hadamard matrices have received much attention in the recent past, owing to their well-known and promising applications. Various researchers have used Hadamard matrices to find their applications in image analysis, signal processing, coding theory, cryptology and combinatorial designs. Now, Hadamard rhotrices have been introduced in the literature for the above said applications. Balanced incomplete block design has its wide use in design of experiments in statistics and error-correcting codes. Design of experiments has broad applications across all the natural and social sciences, and engineering. Here, in the present paper, we develop balanced incomplete block design (BIBD) using Hadamard rhotrices.

Magnetotelluric investigations in the way umpu geothermal prospect area, lampung province, indonesia

Abstract: The Geological Research Center’s (GRC) or Pusat Sumber Daya Geologi (PSDG) previous research estimated that the Way Umpu 1 Hot Springs in the Way Umpu geothermal prospect area reflects a reservoir temperature of 160°C–195°C. From geological observations, the main fault structure in that area is the Way Umpu Fault, which has a strike direction of NE–SW and the area is dominated by volcanic rocks. Many joints are also found along the fault line. The Way Umpu-1 Hot Springs is controlled by these geologic structures. The previous research and field observations lead us to carry out continuing research in this area, which is aimed at determining its resistivity structure to a depth of 4 km. For this purpose, we carried out field measurements using Audiomagnetotelluric (AMT) and Magnetotelluric (MT) methods. The work presented in this paper is the result of 1-D and 2-D inversion modeling from 8 MT soundings. We compared inversion models using the 1-D Bostick transformation scheme, 1-D Occam model, and 2-D Nonlinear Conjugate Gradient (NLCG) algorithms. The study results reveal the existence of a strike as indicated from the geological data and a low resistivity zone at a shallow surface to a depth of 2 km that is most probably associated with partial melting and intrusion at a greater depth.

Declining Trend of Water Inflow in the Dams of Rajasthan State

Abstract: Rajasthan is a semi arid state with the highest of the geographical area (343,000.00 square km) of the Indian subcontinent. Annual rainfall variation is very high over the state ranging from 100 mm to 1000 mm from west to south/east. Matter of water resources planning is of prime importance for the state. There are 237 blocks, out of which 200 blocks are declared as dark zone due to over exploitation of ground water. In these circumstances, it becomes necessary to plan the storage and uses of surface as well as subsurface water (conjunctive use) with maintaining the ecological sustainability. Surface water reservoirs are becoming dry year after year. It was observed from the annual storage data of the dams that water inflow is declining year after year due to various reasons like changes in land use and land pattern, change in hydro geological conditions, changes in environmental factors e.g. temporal and spatial distribution of rainfall, indiscriminate infrastructural development. Due to less water inflow in the dams and increase in the number of dark zone blocks, state is facing the water stress problem. With the increasing population, it will become more severe with the passage of time. Therefore, an effort is being made through this research to test the hypothesis whether there is an appreciable change in water inflow in the dams of Rajasthan state. A total of 115 nos of major & medium dams in the state have been selected by cluster sampling to test the hypothesis. Chi Square test has been conducted for testing the hypothesis and found that there is declining trend of water inflow in the dams and dependabilities of the river basins have been reduced.

Simulation and Visualization of Thermal Metaphor in a Virtual Environment for Thermal Building Assessment

Abstract: La reference est presente sur HAL mais est incomplete (il manque les co-auteurs et le fichier pdf).

Development of a 20V-LED Driver based on the Boost Converter using a FPGA Module

Abstract: We present the development of a LED (Light Emitting Diode) driver based on the boost power converter. Several DC to DC converter circuits were evaluated to determine their characteristics by varying the components and the duty cycle. The selected driver ́s prototype was realized using a FPGA (Field Programmable Gate Array) module as the switching controller, wherein the implementation using Xilinx ISE14.6 and the measurements were successfully performed. The boost converter topology was investigated to achieve an optimal converter which showed a relatively high gain voltage. A duty cycle of 5% up to 20% was required to obtain the driver output voltage of 20V, revealing the efficiency of approximately 90%.

Improved Floating Point Multiplier Design based on Canonical Sign Digit 22

Abstract: Improved floating point (FP) multiplier based on canonical signed digit code (CSDC) has been reported in this paper. Array structure was implemented through Hatamain’s scheme of partial product generation along with Baugh-Wooley’s (B.W) sign digit multiplication technique. Moreover, CSDC approaches were used for the addition of partial products in constant time without carry propagation and independent of operands. The functionality of these circuits was checked and performance parameters, such as propagation delay, dynamic switching power consumptions were calculated by spice spectre using 90nm CMOS technology. Implementation methodology ensures the stage reduction for floating point multiplier, hence substantial reduction in propagation delay compared with B.W.’s methodology, has been investigated. Implementation result offered propagation delay of the single precision floating point multiplier was only ~14.7ns propagation delay while the power consumption of the same was ~23.7mW. Almost ~40% improvement in speed from earlier reported FP multiplier, e.g. B.W implementation methodology, the best architecture reported so far, has been achieved.

Energy Storage using the Phase Change Materials: Application to the Thermal Insulation

Abstract: The objective of the present study is to investigate numerically the problem of melting phase change material (PCM) containing paraffin where one of the area interfaces moves with time and wherein the result of the fusion between the coupling in the solid phase conduction and convection in the liquid phase, then processes the effect of integration of the material in the walls of the building in order to increase its thermal inertia to validate the result ,we will study the numerically transient and performance of a fixed bed filled with uniform spheres, randomly arranged and each containing a (PCM). So we use a two-dimensional theoretical model applied in two separate phases; it was used to predict the temperature distribution of the fluid and the fusible material along the bed in the energy storage method.

Three-dimensional mapping of static magnetic fields over a semi-anechoic chamber

Abstract: The geomagnetic field is a kind of natural potential field in the Earth. A three-year research program for exploration of this field has been conducted in the Lombok Island-Indonesia, where extreme geomagnetic anomalies with two very strong dipolar structures exist. The research aims to construct a system to collect and concentrate geomagnetic fields, in order to possibly use the concentrated fields for geomagnetic power plants or to integrate the system with a field pick-up unit scheme by means of wireless power transfer. The designed geomagnetic concentrator system has been tested in a self-arranged semi-anechoic chamber with a pair of Helmholtz coils, induced with DC currents to simulate the regional ambient static geomagnetic fields. Several tests have proven the performance of the system in onedimensional space. This paper presents the results of detailed three-dimensional measurements of static magnetic fields in the semi-anechoic chamber. Static magnetic fields over the entire chamber are drawn in their magnitudes and directions, by interpolating data obtained in regular grids of 50cm × 50cm. In specific areas, where the Helmholtz coil is placed, extra grids of 25cm × 25cm are inserted to sharpen the fields’ depictions. Results show that by inducing 1 A current on each of coils will produce magnetic fields, concentrated over the surrounding area of Helmholtz coil. The intensities of magnetic fields over this area are about 15,00045,000 nT, which can be used to model the geomagnetic fields of Lombok Island. Using the results of 3D field mapping, it will be possible to get the optimum placement of the geomagnetic concentrator system when it is tested on the chamber.

An Application of Finite Field in Hill Cipher

Abstract: Lester S. Hill in 1929 introduced non-singular matrices to encrypt and decrypt the message in the symmetric key cryptography. Block ciphers designing and cryptographic hash functions have the use of matrices. Here, we introduce permutations, iterations and finite field in the Hill cipher to provide more security and make it free from vulnerable attacks.