Search

The superparamagnetic nano-α-FeOOH samples for Radar Absorber Material (RAM) have been synthesized using a facile precipitation method at 40°C. The characterizations of nano-α-FeOOH have been determined using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Vector Network Analyzer (VNA), and Vibrating Sample Magnetometer (VSM). Microwave absorber properties have been investigated at an X-band frequency range of 8-12 GHz. In order to obtain the minimum reflection loss at the desired frequency range, several thickness variations were used: 0.5, 1 and, 2 mm. It was found that the increase in the thickness of the absorber could shift the reflection loss to the lower frequency at the range of 11-12 GHz. The result shows that the effective frequency band of the absorber occurs at 11.740 GHz with -31.190 dB reflection dip with a matching thickness of 1 mm. [ABSTRACT FROM AUTHOR]

Syntheses of LiFe1-xCuxPO4 (x = 1 and 2 at. %) were successfully carried out using the dissolution method. The source of Fe used was the ironstone from South Kalimantan, and the sources of other components were commercial products. The ironstone was treated using the dissolution method with drying and calcination temperatures of 350 °C for 2 hours and 700 °C for 10 hours in the N2 atmosphere, respectively. The samples were characterized using X-ray diffractometer (XRD) and scanning electron microscope (SEM), while the electrochemical performances were examined through the charge/discharge (CD) and the cyclic voltammetry (CV) measurements. XRD patterns showed that only LiFePO4 olivine was identified with successful Cu ions substitution. The specific capacities of the LiFe0.99Cu0.01PO4 and LiFe0.98Cu0.02PO4 powders were 5.2 and 14.5 mAh/g, respectively. The sample would be a potential material for lithium battery applications when a conductive layer such as carbon is introduced. [ABSTRACT FROM AUTHOR]

The error measurements of a ratiometric-macrobending based fiber optic inclinometer with left and right angle tilt sensing capability is discussed and evaluated here. The inclinometer used two fiber sensors on the left and right sides to determine the device tilt direction. The developed inclinometer was based on the pendulum model where a weight was given to pull the inclinometer probe appropriate to the direction of gravity. The probe was placed inside a glass tube where the probe will be pushed by the tube wall and causing macrobending to the left or to the right fiber inside. The resulted R-square value for the right sensor was 96.8772% and the R-square value for the left sensor was 98.2067%. The characterization of the inclinometer shows a maximum error of 1.027° with the lowest R-square of 96.8772%. [ABSTRACT FROM AUTHOR]

TOC is one of the crucial parameter for determine potencial zone of shale hydrocarbon play. TOC can be measured on the core rock but this data is limited. Schmoker – Hester method and Passey method is two of the most popular method to predict TOC value. These methods are determined from TOC data of marine and pre-tertiary shale rock in United States and Canada. Meanwhile, shale rock in Indonesia (mainly in Western Indonesia) is originated from lacustrine depositional environment and tertiary aged. So generally, shale rock (as source rock) in Western Indonesia has a different characteristic with shale in United States and Canada. This paper tried compare the result of TOC prediction by Schmoker – Hester method, Passey method, and Multi Linear Regression (MLR) method. The results show that the three methods have the same trend in TOC prediction curve, but the regression values are not the same. The TOC prediction has validated by TOC measurement of Rock Evaluation Instruments (core data). This research shows that MLR method gives the better TOC prediction than Schmoker-Hester method and Passey method. It is case study in Banuwati Shale Member Formation, Asri Basin, Indonesia. [ABSTRACT FROM AUTHOR]

Thermoelectric coolers (TECs) work according to the Peltier effect. The effect produces a temperature difference by transferring heat between two electrical junctions. TECs are not only used in single mode but can also be in cascade. To drive or control the TECs, variable voltage or current circuits are needed. In this study, the TECs were simply controlled by the H-bridge driver, where the voltage applied to each TEC was modulated by the pulse width modulation (PWM) method. Three TECs were stacked each other. Each electrode is connected to the H-bridge drivers which are connected to the Arduino MEGA microcontroller. The result was that the PWM can effectively drive the cascaded TECs from a small PWM duty cycle. The performance of the cascaded TEC was studied, where the interface between TECs had temperatures far higher from the coolest side. Furthermore, the higher PWM duty cycles applied make temperature difference linearly higher. However, the temperatures of the modules were increased slowly by time and were relatively unstable. [ABSTRACT FROM AUTHOR]

Synthesis of zircon solid ceramics with the addition of B2O3 as a sintering agent has been carried out using the Arch Plasma Sintering (APS) method. The raw zircon powder was prepared from local zircon sand. The zircon and the B2O3 powders were milled for 1 hour at a speed of 150 rpm. The amount of B2O3 was varied at 0, 3, and 6 wt%. The conditions of the APS sintering included a current of 60 A and a holding time of 8 minutes, where the plasma was exposed only on one side of the samples. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to characterize the phase and microstructure, while the Archimedes method was used as a principle for measuring density. The XRD data analysis showed that monoclinic zirconia was found in the ceramic samples without the addition of B2O3, while those with B2O3 were able to retain the single zircon phase. The micrographic observations using SEM showed that the B2O3-added samples had a higher density level as compared to those without B2O3 addition. The highest density was achieved by the 6 wt.% sample which was as high as 4.3 gr/cm3 or 93.5% theoretical density. The latter sample would be a potential material for lithium battery applications when a conductive layer such as carbon is introduced. [ABSTRACT FROM AUTHOR]

Sumatra subduction zone is one of the most seismically active region in the world. In recent years, several large earthquakes occurred along this subduction zone. In February 2, 2019 09.27 (UTC), an earthquake with magnitude Mw ~6.0 occurred in Mentawai islands, western coast of Sumatra island. We investigated source mechanism of this earthquake using regional waveform inversion from IA-net seismic network. The frequency band used for the inversion was selected at 0.01-0.025 Hz. We inferred that the mechanism is estimated to be thrust type mechanism. [ABSTRACT FROM AUTHOR]

The H-κ stacking method has been widely utilized to estimate the crustal thickness and the Vp/Vs ratio using teleseismic receiver functions. The presence of anisotropic layers in the crust can be identified, for example, as systematic pattern of Ps converted wave or reversal amplitude Ps arrival on the radial receiver function as function of backazimuth. These effects cause inaccurate interpretation for the crustal thickness using H-κ stacking method. Thus, by using synthetic data, we demonstrate the possible problems which may arise when using this method for the receiver functions in anisotropic crust. In the test models, we used anisotropic variations in the upper, mid and lower crusts to see the effect of this complex structure to the H-κ stacking results. [ABSTRACT FROM AUTHOR]

In this study, we invert the receiver function beneath GSI seismic station to estimate the crustal structure beneath Nias Island, Sumatra. The receiver function is computed from 24 teleseismic events using a time-domain deconvolution technique and divided into three groups by observations with similar back azimuth namely GSI_NW, GSI_NE, and GSI_SE. The resulted receiver function then stacked to increase the signal-to-noise ratio. The shear wave velocity structures of the crust are obtained by inverting receiver functions using linearized-iterative inversion with A0K-135 for the initial model. The inversion result shows a thick sediment layer ranged from 1 to 3 km with velocities around 2,4 km/s near the surface. The Moho and the top of the subducting oceanic slab are observed around 22-24 km and 32 km depth respectively. The low shear wave velocity above the transition to the subducting slab is suggested as the signature of the serpentinization. [ABSTRACT FROM AUTHOR]

To investigate the ultra-low frequency (ULF) geomagnetic anomalies related to the Lebak earthquake, we have analyzed the three components geomagnetic data observed from January to February 2018. The earthquake occurred on January 23, 2018, in the Lebak regency, Banten Province, Indonesia and caused some losses and casualties. Its magnitude and depth were M6.1 and 46 km, respectively. The distance of the earthquake epicenter from the nearest geomagnetic observation is about 113.99 km. In this study, the energy of the ULF geomagnetic signal at the frequency around 0.02 Hz has been investigated by applying spectral density ratio based on Fast Fourier Transform (FFT). The result demonstrated that the geomagnetic energy enhanced around two weeks before the earthquake. When the unusual geomagnetic energy enhancements occurred, the DST index showed there are no peculiar global geomagnetic activities. It suggested that the geomagnetic anomalies possibly related to the occurrence of the earthquake. [ABSTRACT FROM AUTHOR]

Geotechnical study has been conducted through gravity data acquisition in Bekasi City. This study aims to detect the presence of structures in this area using the ms-svd method. The geological structure in this study is fault. The study was carried out by conducting data acquisition in the study area of 362.79 km2. The acquisition was done at 171 measurement stations with a distance between stations is 1 km in northing and 2 km in easting. Data processing is done by making CBA maps and then carried out upward continuation. The SVD method is then carried out on each map of upward continuation. The MS-SVD graph results can show the magnitude and direction of the dip from the fault by looking at the zero value shift on the graph. The results of the MS-SVD method show there are several faults in Bekasi City with their respective characteristics. Three faults are identified in east-west direction and the other younger fault in northwest-southeast direction. The faults have dip angle for more than 60°. [ABSTRACT FROM AUTHOR]

Monolithic dye-sensitized solar cell (DSSC) is a modification of conventional sandwich DSSC that effectively reduces the production cost because it only uses a single substrate for both of photoelectrode and counter electrode. In this research, monolithic DSSC was prepared on fluorine-doped tin oxide (FTO) glass substrate that contains TiO2 paste layer, ZrO2 layer as spacer and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as conductive layer. To improve the performance of monolithic DSSC, a TiO2 blocking layer was added between FTO and TiO2 layer wherein the blocking layer thickness was varied by changing mesh screen size and printing frequency. The morphology and optical characteristics of the blocking layer was obtained by scanning electron microscopy (SEM) and ultraviolet-visible (UV-Vis) spectroscopy, while the monolithic device performance was analyzed using current-voltage (I-V) measurement. From the results, it was confirmed that the highest performance with photoconversion efficiency of 0.260% was achieved by the monolithic device with the thickest blocking layer. [ABSTRACT FROM AUTHOR]

This article discussed the behavior of rice husk ash as fillers in polyester-fiber glass bi-panel composites to withstand the high-impact projectile impacts. This composite bi-panel consists of unsaturated polyester resin BQTN 157 and S-glass woven reinforced with rice husk ash. Specimens were prepared by varying the volume fraction of rice husk ash as fillers (3, 5, 7, and 9 %v) into the polyester resin. Composite panel manufacturing was fabricated using a hand lay-up method. Each panel has a size of 20 × 20 × 0.4 cm. Then the ballistic test was carried out using a 9 mm FN ammunition pistol with a velocity of 380 m/s projectile at a distance of 5 m. Characterizations were conducted using a Simultaneous Thermal Analyzers (STA) and a Differential Scanning Calorimeter (DSC). The optimum ballistic result is obtained on the bi-panel composites with the addition of 9 %v rice husk ash as fillers with a density of 1.604 g/cm3. This can be seen in the TGA and DSC analysis showing the changes in the panel decomposition temperature with the addition of rice husk ash. This decomposition temperature has contributed to better material characteristics. Rice husk ash increases the ability of the bi-panel composite to withstand the impact of a high-speed projectile. [ABSTRACT FROM AUTHOR]

One of the necessary parameters in battery management systems is characteristic of correlation between state of charge (SOC) and open circuit voltage (OCV). Correlation of SOC-OCV can be obtained by one of the characterization methods that implement a certain incremental charge-discharge procedure. Characterization using this method takes a lot of time caused by a long waiting time of OCV measurement. Another method is an injection of pulse currents. This method is claimed to be able to reduce battery relaxation time. This paper tries to relate an experimental analysis of a current pulse injection in battery relaxation. The experiments are intended for getting information about how big the contribution of the current pulse in reducing the battery's relaxation time. Besides, this paper proposed a new modified pulse current to reduce the polarization effect of the battery voltage that was successful in reducing relaxation time by up to 80% of its normal relaxation time. [ABSTRACT FROM AUTHOR]

A paper battery is a 6 cm × 4 cm × 1 mm dimension battery that uses CuCl as a cathode, magnesium as an anode, and urine as an electrolyte. CuCl2 dan CuSO4 as used to synthesis CuCl was analyzed. A simple and cheap sandwiched fabrication model has been identified using the low-cost CuCl synthesis process. This paper battery has passed experimental testing and delivers the best power generation at 169,588 mW and continuously up to 4 hours. Voltage also measured and provided a stable voltage at least for 6 hours at 582.667 mV. Method 2 of using CuSO4, which has price lower than CuCl2 showed better power generation and stability. [ABSTRACT FROM AUTHOR]

Asiaticoside is the most active component of gotu kola plant (Centella asiatica L) which has been proven efficacious in the process of wound healing by increasing fibroblasts and collagen synthesis. Conventional drug form for treating wounds such as ointments, gels and plasters have many disadvantages including not penetrating and optimally absorbing into the tissues and relatively long healing process. Wounds treatments need carriers that can deliver asiaticoside with a good release profile so the effectiveness of wound healing can be optimal. Membrane nano-composite is a drug form that is similar to the body's extracellular tissue. It can help the wound healing process. This research is carried out to study the characteristics of membrane nano-composite made from PVA-chitosan mixtures as polymers and asiaticosides as active ingredients. Comparison of PVA-chitosan-asiaticoside mixture used is FI (5:0:1), FII (5:0.2:1), F3 (5:0.4:1) and F4 (5:0.5:1). The electrospinning parameters used include; collector distance is 10 cm, the flow rate is 0.3 mL/hr, the voltage used is 20 kV and the diameter of the needle used is 21 G. Then an evaluation of formula solution (pH, Viscosity and Conductivity) and evaluation for membrane nano-composite includes measurement of shape and morphology (FESEM). Membrane nano-composite that have been formed are then tested for the effectiveness of wound healing in vivo using rabbits. The results showed the increasing concentration of chitosan in the formula showed a difference in the morphology of the membrane nano-composite produced and the effectiveness of wound healing process. [ABSTRACT FROM AUTHOR]

This paper presents the effect of hot isostatic pressure post-treatment on tin powder particle under elevated temperature in order to obtain the spherical particle shape. The tin powder particle obtained from the gas atomization as used as a precursor. The powder was placed in the liquid olive oil within the Teflon-lined autoclave, which was then subjected to the hot isostatic pressure post-treatment at five type temperature for specified time. The as-treated powder was rinsed, dried, and observed morphologically using high resolution digital microscope. It is found that the ratio of spherical particle shape is increased by 2.4 - 3 times, relative to the untreated powder particle, which can be achieved after 210 minutes post-treatment at temperature of 90% of its melting point. The density of the post-treated powder is increased by 1.05 - 1.15 times, and the porosity is increased by 5.7 – 8.0 times. These results offer another possible method to obtain spherical and enhance density metal powder particle for specific purposes. [ABSTRACT FROM AUTHOR]

CoFe2O4/SiO2 magnetic nanoparticles have been prepared by co-precipitation methods. The structure, morphology and magnetic properties were analyzed using various characterization such as XRD, FTIR, TEM, and VSM respectively. The surface was modified using silica in order to create new active sites as a potential adsorbent to remove Ni and Cu ions from wastewater. The result obtained that the crystal size of CoFe2O4/SiO2 increased compared to uncoated magnetic nanoparticles. The size of crystal before and after coated using silica was found about 8 nm and 11 nm, respectively. The FTIR results suggested that stretching vibration of Fe/Co-O occurs at a wavenumber of 470.63 cm−1 and 399.47 cm-1, and wavenumber of 1033.85cm-1 indicate bending vibration of Si-O-H. It confirmed that SiO2 was successfully coated the nanoparticles. The magnetic properties of coated material were found decreased after the silica addition is about 22.34 emu/g, while the magnetic saturation (Ms) of uncoated cobalt ferrite is about 37.56 emu/g. The decrease of the value is due to the presence of silica properties as non-magnetic materials and the presence of impurity (α-Fe3O4) on the core material. In the adsorption process, the other factors were also observed (e.g. the effect of particles size and magnetic properties). The adsorption capacity of silica-coated CoFe2O4 reaches about 77.48 mg/g and 74.46 mg/g for Ni and Cu ions, respectively. The smallest particles size has a wide surface area and the highest magnetic saturation gives the greatest influence on the adsorption capacity of Ni and Cu ions. The results confirm that the silica-coated CoFe2O4 magnetic nanoparticles could be a potential adsorbent for the effective removal of heavy metals from aqueous solutions. [ABSTRACT FROM AUTHOR]

Increasing of demand for implant material especially for hip bone is caused by the increasing of elder who are prone to osteoporosis. Several studies have reported that elements of Al and V in Ti-6Al-4V can decompose and result in adverse effects in the form of health problems, allergies, neurological disorders and Alzheimer's disease. In addition, Ti- 6Al-4V has a problem, the difference of young's modulus with human bones can cause stress shielding phenomena. The cost of replacing hip bones is quite expensive because it uses valuable alloy elements. The novelty carried out in this study was the design of a new titanium type β (beta) composition with a composition of the weight of Ti-6%Nb-6%Mo with the addition of Mn 8%, 10%, 12% and continued with heat treatment at 1100°C with variations of heat treatment time 3 hours, 6 hours and 12 hours with water quench which aims to increase beta phase volume. The material characterization was performed using XRF, XRD, metallographic test, micro Vickers hardness test and ultrasonic test to calculate the magnitude of young's modulus. The results obtained show that the addition of manganese will increase beta phase. The most optimal duration for heat treatment is 6 hours because the Ti-6Mo-6Nb microstructure with the addition of 12% manganese and heat treatment for 6 hours has higher beta phase volume than others. [ABSTRACT FROM AUTHOR]

We theoretically study electronic and thermoelectric properties of two-dimensional hydrogenated borophene ("boro-phane"). We show that, according to the first-principles calculation, hydrogenated borophene is semimetallic, with two bands meeting at a single point at the Fermi level. The thermoelectric properties evaluated by using the Boltzmann equation with a constant relaxation time approximation (CRTA). At room temperature, we obtain large power factor for electron doping regime. Therefore, appropriate doping to this material can enhance its thermoelectric efficiency. [ABSTRACT FROM AUTHOR]

The double perovskite La2FeMnO6 (LFMO) has been synthesized with variation of calcination temperature (900 °C and 750 °C) using sol-gel method. The structure of compound was characterized by X-ray Diffraction (XRD) and X-ray Fluorescence (XRF). The X-ray diffraction pattern confirmed that La2FeMnO6 has a cubic structure with space group Pm-3m and difference phase due to calcination temperature. XRF showed the weight and atomic ratio of compound are suitable with double perovskite stoichiometric, respectively. The electrical properties were characterized by impedance spectroscopy method with range frequency of 100 Hz- 1 MHz at room temperature. The Nyquist plot shows that decrement of semi-circle diameter with decreasing calcination temperature. The value of dielectric constant (Ԑ') was decreased with the increasing calcination temperature. [ABSTRACT FROM AUTHOR]

Bismuth ferrite (BiFeO3 or BFO) is the most promising single-phase multiferroic material exhibiting ferroelectric and antiferromagnetism at room temperature. It has attracted the interest of researchers because it could be widely used in microelectronic devices such as multiple state memory storage devices, data storage, spintronics, optical, and sensors magnetic. But along with these potentials, this material has serious drawbacks and some of them are the large dielectric loss and high leakage current. Since the ferroelectricity property of BFO mainly originates from a lone pair of Bi3+ ion electrons, it is very important to dope from A-site to improve its characteristics. Hence Zirconium doped Bi-site in BiFeO3 has been synthesized by the sol-gel method to study its structural and electrical properties using impedance analysis at room temperature. Structural characteristics were studied by XRD and XRF. Based on the pattern of X-Ray Diffraction, it is found that the material has a hexagonal structure with R3c space group. The electrical properties were carried out using LRC-meters in the frequency range of 1MHz-100Hz at room temperature and were analyzed by impedance spectroscopy analysis. We obtained constant dielectric and tan loss from BZFO has increased with the increasing Zr concentration. [ABSTRACT FROM AUTHOR]

Requirement for safer and more flexible energy storage has encouraged research in all solid state battery, employing conductive polymer membrane as electrolyte-cum-separator. Solid polymer electrolyte employs polymer as a matrix, with electrolyte salt dissolved in it. In this research, solid polymer electrolyte for lithium-ion battery application has been prepared using solution cast technique. LiBOB and PVDF-HFP were used as electrolyte salt and polymer matrix, respectively. Fillers were added in the solution mainly in the mission of reducing crystallinity allowing ion lithium to move more efficiently between electrodes, therefore increasing its ionic conductivity. In this experiment, we utilized SN, TiO2, and Al2O3 filler. Resulting free-standing membranes were characterized using FT-IR and SEM to observe its morphology and interaction between functional groups. The performance was tested using EIS against stainless steel plate to obtain bulk resistivity, which was then utilized to measure ionic conductivity. Amongst the three fillers, the most optimum performance was found in the SN-embedded solid polymer electrolyte with ionic conductivity of 7.77×10−9 S/cm. [ABSTRACT FROM AUTHOR]

La0.8Ba0.2MnO3 (LBMO) perovskite nanoparticles were prepared by a solid-state reaction technique with elaborating each of the parental compounds of LaMnO3 (LMO) and BaMnO3 (BMO); both of the latter compounds had been previously synthesized by the sol-gel method. Single-phase compound formation of the parental compounds was confirmed by initial X-ray structural analysis and LaMnO3 and BaMnO3 crystallized in the rhombohedral and hexagonal systems with R-3c and P63/mmc space groups, respectively. X-ray diffraction (XRD) disclose that another phase of LBMO had been identified, suggesting that La0.8Ba0.2MnO3 was not fully formed. Field emission scanning electron microscopy with electron disperse X-ray spectroscopy (FESEM-EDXS) display that LBMO has low homogeneity compared to that of its parental compounds. From the morphology, the average crystallite size of the LBMO sample is significantly larger than that of the LMO compound. Fourier transform infrared spectrometry (FT-IR) suggested the occurrence of Mn–O bonds, denoting that despite the inhomogeneity, LBMO was able to form by incorporating LMO and BMO compounds. The obtained results indicate that sol-gel based synthesis is likely to have higher success rate in producing homogenous compounds in comparison with solid state reaction method. This preliminary study shows that LBMO fabricated from single phase LMO and BMO compounds may have created a multiphase LBMO compound. The combination of sol-gel and solid-state reaction methods provided a different kind of approach into properties of rare earth perovskite manganites. [ABSTRACT FROM AUTHOR]

We report the study of lithium-ion diffusion in LiTi2O4 battery material by the analysis of muon spin polarization function at the muon site by DFT calculation. The important parameters which explain the lithium-ion diffusion will be derived from the function, including the field fluctuation rate and the local field distribution. The calculated results are shown in good agreement with the previously measured field distribution and the field fluctuation rate in LiTi2O4 at the ground state temperature. This method, therefore, may apply to the study of other battery materials. [ABSTRACT FROM AUTHOR]

Magnetite (Fe3O4) nanoparticles has been successfully synthesized using the co-precipitation method with various pHs. The magnetites were derived from natural ironstone Kalimantan, Indonesia. The synthesis was carried out with 4 variations of precipitation pHs, i.e., 8.00; 9.06; 10.00; and 11.00. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM), and Particle Size Analyzer (PSA) were utilized to examined the crystal structure, micro and nanostructures, and particles size distribution, respectively. The XRD results revealed that the magnetite is the dominant phase of all samples and the single phase of magnetite can be achieved with the precipitation pH > 9.06. Moreover, the particle sizes of the magnetite nanoparticles are 11, 10 and 7 nm for 9.06, 10.00, and 11.00 precipitation pH, respectively. The SEM and HRTEM images show that the particle size of ironstone and magnetite precipitates is in micro and nanoscales. The PSA results show that the particle size distribution of the magnetite nanoparticles tend to decrease with the increasing level of pH. Meanwhile, the average particle size tend to decrease with the increasing of precipitation pH,+ from 153 nm (8.00), 315 nm (9.06), 190 nm (10.00), and 153 nm (11.00). HRTEM images show that particles of Fe3O4 is spherical in shape and tend to agglomerate. [ABSTRACT FROM AUTHOR]

The composite of hybrid magnet consists of a combination of NdFeB magnetic particles with SrFe12O19 (Sr-ferrite) and uses epoxy resin as binder. This study was done to analyse the physical, mechanical (compressive strength) and magnetic properties of composite of hybrid magnets. The composition ratio Sr-ferrite–NdFeB in weight % was varied into several values: 90% : 10%, 80% : 20%, 70% : 30% and 60% : 40%, while the epoxy resin composition was 3% of total mass of magnetic particles. The process of forming pellet samples were done by cold compression using a 10 tonf force. Sample hybrid composite magnet systems Sr-ferrite–NdFeB with 30% and 40% NdFeB contents have the highest density (5.65–6.02 g/cm3) and magnetic flux (710–820 gauss). The composition ratio Sr-ferrite–NdFeB strongly affects the bulk density and magnetic flux, but it gives small influence on shore hardness, remanence, and coercivity. [ABSTRACT FROM AUTHOR]

We performed Boltzmann transport calculation to obtain the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and thermoelectric figure of merit (ZT) for Dirac systems. We found an enhancement of ZT due to the gap opening. When the phonon thermal conductivity is small enough, the optimum ZT in gapped Dirac system can be larger than 1, which is preferable for thermoelectric applications. [ABSTRACT FROM AUTHOR]

In order to understand the dependability of the crystal structure and the magnetic properties of the nanoparticles as adsorbent of Pb ions, magnesium ferrite (MgFe2O4) based on natural iron sand with various concentrations of ammonia solutions (0.5, 1, 1.5 and 2 M) have been synthesized using a co-precipitation method. X-ray diffraction analysis revealed that MgFe2O4 formed a single phase, in which the size of the crystal decreased by increasing the ammonia concentrations. The smallest crystal size was obtained at 2 M of NH4OH addition. On the other hand, the VSM analysis showed that the magnetization saturation (Ms) increased by increasing the ammonia concentration, while the coercivity decreased. The highest value of Ms was achieved at 48.2 emu/g by adding 2 M of NH4OH. This result affected the ability of the nanoparticles to adsorb Pb ions. The large surface area due to small particles size and its high saturation can adsorb Pb ions up to 92.65 mg/g, with an efficiency of 84.23%. Therefore, these nanoparticles have a potential application to be used as heavy metal adsorbent in waste-water. [ABSTRACT FROM AUTHOR]

In this study, we have investigated the relaxed domain structure of square-shaped ferromagnets by micromagnetic simulation. The simulation was performed to some basic ferromagnetic materials such as Cobalt (Co), Iron (Fe), Nickel (Ni), and Permalloy (Py). The side length of square-shaped ferromagnets was varied from 100 to 500 nm and the thickness were 5, 10, and 15 nm. The cell size was 2.5×2.5×2.5 nm3 and the damping factor α was 0.05. The initial magnetization state was random configuration. The domain structure was observed after the system reached equilibrium. We observed that there are two pattern of domain configuration, single domain (SD) and multi-domain (MD) structures. For all materials, the domain tended to form multi-domain structure as the side length and thickness increased. By analyzing the energy profiles, it was found that the SD structure exhibited the higher demagnetization energy than the exchange energy, while the MD structure showed the opposite. [ABSTRACT FROM AUTHOR]

We have synthesized copper-doped Ba0.5Sr0.5FeO3-δ using sol-gel combustion method. The Ba0.5Sr0.5Fe0.9Cu0.1O3-δ (BSFCu-91) and Ba0.5Sr0.5Fe0.8Cu0.2O3-δ (BSFCu-82) powder calcined at 850°C and sintered at 1100°C for 6 hours respectively. Neutron diffraction technique were used to identify the crystal parameter and oxygen stoichiometry in the sample. The HRPD data was analyzed using the Rietveld method to determine the crystal structure. The results of structural analysis show that Ba0.5Sr0.5Fe1-xCuxO3-δ (x = 0.1 - 0.2) has a space group P m -3 m with cubic crystal system. The lattice parameter for BSFCu-91 a=b=c=3.9301 Å; and for BSFCu-82 a = b = c = 3.9383. The oxygen stoichiometry for x=0.1 is 2,8; x=0.2 is 2.6. [ABSTRACT FROM AUTHOR]

In this work, we study the structural and optical analysis of La1-xMgxFeO3 with x = 0.0, 0.1, 0.2, and 0.3 perovskite material. The (La,Mg)FeO3 material were synthesized by sol-gel method. The structural properties were characterized by X-Ray diffraction (XRD) while the optical properties were characterized by Fourier Transform Infrared spectroscopy (FTIR), Raman spectroscopy and UV-Vis spectrophotometry. The band gap energy was analyzed using the Kubelka-Munk (KM) method from UV-Vis spectrum. XRD analysis revealed the single phase of (La,Mg)FeO3 orthorhombic crystal structure with Pnma space group which is also confirmed by identical Raman spectrum. The crystallite size decreases with increasing Mg-content. The FTIR spectrum confirmed the La/Mg-O stretching, Fe-O stretching and Fe-O-Fe bending vibration modes. The vibration modes of (La,Mg)FeO3 material were analyzed by Raman spectroscopy and assigned to some specific Raman phonon modes. UV-Vis analysis shows decreasing band gap energy from 2.14 eV to 2.05 eV with increasing Mg-content. [ABSTRACT FROM AUTHOR]

The structure of the alloy plays a significant role in determining its properties. In the present study, the Fe-Mn-Si alloys were synthesized using ferromanganese (FeMn) and ferrosilicon (FeSi) lumps. The lump materials were crushed and sieved to obtain small granules. It was then wet-milled into a fine powder using a shaker mill for 4h. In order to obtain a homogeneous mixture, the FeMn and FeSi powders with the composition of 50(FeMn)-50(FeSi), 75(FeMn)-25(FeSi) and 87.5(FeMn)-12.5(FeSi) were mechanically alloyed for 2h. The mixed powder was compacted at 8 ton in load and then sintered in a vacuum furnace at 1100°C for 2h. The shrinkage and density of sintered alloy increase with the increase of Mn and the decrease of Si content in the alloy. The results also show that pores and oxide are formed in the alloy. Their fraction is likely to decrease with decreasing Si concentration. According to the results of hardness measurement, the 75(FeMn) alloy with 25(FeSi) content show the highest hardness among the other compositions. The obtained results were intensively discussed in this paper. [ABSTRACT FROM AUTHOR]

Gold (Au) and silver (Ag) nanoparticles had been successfully synthesized using a laser ablation method in distilled water. Ascorbic acid was used as the analyte to test the character of their surface enhanced Raman scattering (SERS). The concentrations of ascorbic acid were varied to study the detection limit and the incubation time effect. The size of synthesized Au and Ag nanoparticles was measured by UV-Vis spectrophotometer. The Raman scattering spectra were analyzed on 3 mL Au colloidal nanoparticles with addition of ascorbic acid in various concentrations of 0.25, 0.5 and 1 wt%. The solutions were incubated for 3 hour in room temperature prior to the Raman spectroscopy for ensuring good adsorption of ascorbic acid into the nanoparticles surface. The results were then compared with the sample using Au/Ag colloidal mixture nanoparticles incubated for same length time. The experimental results showed that the Au/Ag colloidal substrate shows more SERS sensitive for ascorbic acid signal detection compared to the Au colloidal substrate without Ag colloidal nanoparticle addition. [ABSTRACT FROM AUTHOR]

A copper-nickel alloy-based thermoelectric material has been synthesized by powder metallurgy and conventional sintering using 70% Cu and 30% Ni. This study is conducted to determine the effect of compaction pressure on the mechanical and thermoelectric properties of the Cu0.7Ni0.3 alloy. The samples are compacted with the compaction pressure of 60 kg/cm2, 70 kg/cm2 and 80 kg/cm2. All compacted samples are sintered at 900°C for 5 hours in conventional muffle furnace. The sintered samples are characterized to determine density by Archimedes method, metallography by micro-Vickers, morphology by SEM-EDS, and thermoelectric properties by LSR-4. The maximum density of about 80 kg/cm2 was obtained at compacting pressure of 8.71 g/cm3. The maximum absolute Seebeck coefficent value of -46.28 µV/K and power factor of 4.969 ×10-3W/mK2 for that maximum density were obtained at a temperature of 390 K. The Seebeck coefficient and power factor for the maximum density is also larger than those for 60 kg/cm2 and 70 kg/cm2. On the other hand, the microstructure shows the porosity at compaction pressure of 80 kg/cm2 is less than that at 60 kg/cm2 and 70 kg/cm2. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulation of diffusion welding between aluminum and nickel has been performed and the tensile behavior of the as-welded material has been examined. Two slabs Al-Ni are being contacted directly to introduce diffusion between the two with certain parameters. Diffusion welding was performed at a temperature of 500 K, at the pressure of 10 MPa in the x-direction, and a holding time of 200 ps. The tensile test is performed at a strain value of 2.64e9/s. The results have shown that the displacement of atoms during diffusion welding significantly occurs from the beginning until it reaches about 10 ps. However, the movement of atoms experiencing a plateau stage and less atomic exchange is occurring afterward. nickel slab that has a better strength was able to maintain its fcc crystalline structure during diffusion welding and tensile test than aluminum which has lower strength. The higher melting point of Ni promoting better resistance in the interface to be deformed, while the lower melting point of Al has been promoting better bonding between the two that is promoted by the defects that occur at the interface. During the tensile test, the lower strength of Al made it randomly deformed and crack seems to occur. However, failure of the diffusion-welded Al-Ni has occurred around the interface. The ultimate tensile strength of the diffusion-welded Al-Ni reaches up to 4.166 GPa at a strain value of 0.07128. [ABSTRACT FROM AUTHOR]

Laser has a special characteristic to be developed as Optical Wireless Power Transmission (OWPT) for long-distance. It provides a coherent almost non-divergent beam with high energy density in a small beam size of diameter. This condition makes the direction of the laser beam to the appropriate target using laser beam tracking system is needed. In this research, we developed a beam tracking system to track a high-speed object movement by using the Galvano mirror and CMOS camera. Color filtering method was chosen to recognize the object. As a result, the beam tracking system can be used to track the beam to follow object movement speed up to 52°/s. Error position between the central point of area recognition with the laser beam spot tends to increase when the object speed was increased. The prediction method was added in the control system to reduce it, the delay factor was attached to the calculation of 128 ms. This method can minimize the error position less than 2°/s. [ABSTRACT FROM AUTHOR]

PUSPIPTEK is a science and technology park, situated in Tangerang Selatan, Banten-Indonesia. Due to its location in a tropical country, the tendency of PUSPIPTEK to be exposed by solar radiation is bigger than other areas in subtropical, temperate and polar regions. In order to ensure the health security level affected by solar radiation, a preliminary solar radiation measurement, by measuring ultraviolet index (UVI), is needed. The measurement was carried out in July and August, 2018. The measurement data revealed that the highest UVI value was obtained at noon time, especially at 11 AM. Hence, the UVI level of PUSPIPTEK was categorized moderate (it was safe to go outdoor but the protection usage was required). The UVB dose of PUSPIPTEK was also safe (it was not more than the UVB MED with maximum exposure time was 17.433 minutes at noon). [ABSTRACT FROM AUTHOR]

Load sensor based on fiber optic has been developed to solve conventional sensor problems. Most of these sensors use intensity loss as their principle of operation. The intensity loss shows specific correlation with the load. In order to optimize the intensity loss's correlation, various configurations are applied. In this paper, the effect of bending radius variation in optical fiber load sensor with sinusoidal configuration is observed. By using sinusoidal bending radius variations and adding a deformer, the load sensor's response is obtained. The proposed sensor showed good response both in sensitivity and linearity. The sensor without deformer showed maximum sensitivity of 0.0447 mV.N−1 and maximum linearity of 0.9599 with maximum measurement range from 0 N to 14 kN. The addition of deformer enhanced the sensor's sensitivity to 0.2272 mV.N−1, however it shortened the measurement range to 5.184 kN. [ABSTRACT FROM AUTHOR]

This paper describes a fiber extensometer system that utilizes pulse width modulation in its light source for power efficiency reason. The fiber extensometer was used to monitor displacement by intensity modulation techniques based on macro bending effects. The fiber extensometer consisted of an Arduino microcontroller; to modulate laser sources into optical pulses and to regulate data transmission; a bent fiber for displacement sensor, detector and amplifier, GSM module, antennas and power supply system which was solar cell based. The ON - OFF pulse timer from the programming using the C + language in the Arduino sets the pulse time difference ON - OFF of laser light. The modulated light was then launched to the sensor fiber, received and amplified by detector system. When displacement occurs, the diameter of the fiber bent will change as well as the sensor output. Furthermore, the microcontroller instructed the GSM module to send the output signals contain information about displacement to the user's mobile phone in the form of short message service (SMS). It was obtained that power savings that can be achieved using pulse width modulation techniques on this fiber extensometer system reached 30%, compared to that of fiber extensometers that used continuous laser. [ABSTRACT FROM AUTHOR]

Au-Ag nanoalloys have been successfully synthesized using femtosecond laser from the colloidal mixture of gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs). In the formation of Au-Ag nanoalloys, there was a phenomenon of laser melting and alloying. Au nanoparticles and Ag nanoparticles were prepared and were mixed with different compositions: Au20Ag80, Au30Ag70, Au50Ag50, Au70Ag30 and Au80Ag20. Each of the mixed colloid of Au NPs and Ag NPs was irradiated with laser femtosecond until Au-Ag nanoalloys were formed. The shifting of surface plasmon during alloying was observed using real-time monitoring with UV-Vis spectrophotometer every 5 min. The results showed that Au20Ag80, Au30Ag70, Au50Ag50 formed into Au-Ag nanoalloys in 15 min, while Au70Ag30 and Au80Ag20 formed into Au-Ag nanoalloys in 20 min. [ABSTRACT FROM AUTHOR]

We theoretically investigate how coherent phonon amplitudes in low dimensional materials can be modulated by ultrafast laser pulse trains. Important laser parameters for the modulation of coherent phonon amplitudes are the pulse width, repetition period, and number of pulses in the pulse train. We find that it is possible to switch on or switch off the radial breathing mode (RBM) and the G-band phonons in a single wall carbon nanotube (SWNT), as a typical model of low-dimensional materials. In particular, if the repetition period matches with integer multiple of the RBM phonon period, the RBM phonon could be switched on, while the other modes are switched off. On the other hand, for the G-band, which has a higher frequency (shorter period) than the RBM, the number of pulses in the pulse train also affects the switching process. The ratios of the G-band and RBM amplitudes are found to be significantly enhanced at certain integer multiples of pulse number as a function of SWNT diameter. Such a "magic number" phenomenon in ultrafast spectroscopy can be extended to other low-dimensional materials, in which we may realize a phonon switch in the future. [ABSTRACT FROM AUTHOR]

The purpose of this study was to find the most optimal configuration of multipath optical ring resonator (MpORR) based on silicon on insulator (SOI). Two important indicators of MpORR are free spectral range (FSR) and Q factor. The greater the FSR and Q factor, the greater the ability of the MpORR to distinguish each resonance signal so that the sensor is more selective and can detect substances with small concentrations. Finite-difference time-domain (FDTD) simulations was used to optimize and analyze the design of MpORR. Several parameters that can affect the FSR and Q factors of the MpORR were investigated, including the ring resonator radius, the gap separation distance between the waveguide and the ring resonator, and the gap separator distance between resonator rings of MpORR. Based on the simulation, the most optimal configuration for MpORR are 3 µm, 200 nm, and 160 nm, that correspond to the ring resonator radius, the gap separation distance between the waveguide and the ring resonator, and the gap separator distance between resonator rings, respectively. From the simulation, 28 nm wide FSR and 1495 of Q Factor were obtained. With a wide FSR and a high Q factor, the design can be used to detect various analytes with high sensitivity. [ABSTRACT FROM AUTHOR]

Noble metals (Au and Ag) are the primary raw materials which have vast potential application ranging from across biosensor, biomedicine, science, and engineering fundamental. However, alloying them will enhance the efficiency and applicability of noble metals. Employing the linear-weight (LW) technique to construct a dielectric function of a binary solution is still disputed. However, this method is still widely used to examine Localized Surface Plasmon Resonance (LSPR) of Au-Ag binary solution. In this work, the calculation of electromagnetic response such as Localized Surface Plasmon Resonance (LSPR) of bimetallic Au-Ag nanorod was performed by means of MNPBEM package. We utilized nanorod-shaped with two different excitation modes, namely, Transverse Mode (TM) and Longitudinal Mode (LM), and various compositions to investigate their LSPR shifting anomalies. Moreover, we employed the LW technique to construct their dielectric function and analyze the LSPR anomalies. Interestingly, we found that using LW approximation, the resonance peak of TM is separate into two peaks. These peaks originated from the free electron of Au and Ag respectively, however, some of LSPRs peak did not occur amongst peak of pure Au and Ag. Practically, using LW method the resonance peak should be located amongst their individual elements. This work has provided the limitation of using silver fraction and the related aspect ratios to predict the LSPR spectra of Au and Ag on nanorod-shaped. [ABSTRACT FROM AUTHOR]