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We report on a master and slave configuration consisting of two optically pumped spin-vertical-cavity surface-emitting lasers for chaos synchronization and secure communication. Under appropriate conditions, high-quality chaos synchronization is achieved. We propose two encryption schemes, where either the pump magnitude or polarization is modulated. The results show that these allow for Gb/s transmission of secure data, but exhibit different features: one indicates that the message can be recovered by the total intensity, but not the polarization components, whereas the other shows that the message can be better or exclusively retrieved from the polarization components at high bit rates. more...

Sustained, large amplitude and tunable birefringence-induced oscillations are obtained in a spin-vertical cavity surface-emitting laser (spin-VCSEL). Experimental evidence is provided using a spin-VCSEL operating at 1300 nm, under continuous-wave optical pumping and at room temperature. Numerical and stability analyses are performed to interpret the experiments and to identify the combined effects of pump ellipticity, spin relaxation rate, and cavity birefringence. Importantly, the frequency of the induced oscillations is determined by the device’s birefringence rate, which can be tuned to very large values. This opens the path for ultrafast spin-lasers operating at record frequencies exceeding those possible in traditional semiconductor lasers and with ample expected impact in disparate disciplines (e.g., datacomms, spectroscopy). more...

We study numerically a parametrically driven discrete nonlinear Schrödinger equation modeling periodically curved waveguide arrays. We show that discrete surface solitons persist, but their threshold power is altered by the drive. There are critical drives at which the threshold values vanish. We also show that parametric drives can create resonance with a phonon making a barrier for discrete solitons. By calculating the corresponding Floquet multipliers, we find that the stability of symmetric and antisymmetric off-side discrete surface solitons switches approximately at the critical drives for thresholdless solitons. more...

We observe dipole-like gap solitons in two-dimensional waveguide lattices optically induced with a self-defocusing nonlinearity. Under appropriate conditions, two mutually coherent input beams excited in neighboring lattice sites evolve into a self-trapped state, whose spatial power spectrum and stability depend strongly on the initial excitation conditions. Our experimental observations are compared with numerical simulations. more...

Application of ultrafiltration membrane in the separation of oil-in-water emulsion has a consequence of fouling formation and relate to significantly flux reduction. Filtration of oil-in-water emulsions is challenging since both oil and surfactant have interaction with the membranes. In addition, there is a possibility of droplet deformation to enter the membrane pores. This research was focused on the effect of surfactant type on the ultrafiltration performance. Models of oil-in-water emulsion consisted of crude oil, diesel oil and lubricant oil as dispersed phase and mixture of distilled water with the addition of 0.1% of Tween 80 or Alkyl Benzene Sulfonate as the continuous phase. Flat-sheet Polyethersulfone having 10 kDa molecular weight cut-off was selected as the membrane. The result showed that there were fluxes decline during 2 hours of operation in ultrafiltration of oil-in-water emulsion stabilized with a non-ionic surfactant (Tween 80). On the other hand, when oil-in-water emulsion was stabilized with anionic surfactant (Alkyl Benzene Sulfonate), the fluxes were relatively constant during 2 hours filtration. The COD rejection was in the range of 98-97%, 94-96% and 90-94% for oil types of crude oil, diesel oil and lubricant oil respectively. Total oil content rejection was found as 98-99% for both crude oil and lubricant oil and 98-97% for the diesel oil. Based on Scanning Electron Microscopy, images of the membrane after filtration of oil-in-water emulsion stabilized with Tween 80 showed foulant deposit which was predicted as oil and surfactant. However, when filtering oil-in-water stabilized surfactant only less deposit on the membrane surface was observed. more...

Empty fruit bunch (EFB) is not yet utilized as a solid fuel for boiler due to their physical characteristics such as very bulky, high moisture and potassium contents. The hydrothermal treatment (HT) has been conducted in our research to overcome those problems. HT experiments were conducted in a 2 L digester, with 100 grams of EFB. The liquid to solid ratio was 5:1 mL/g. HT were conducted at temperature of 120, 150, 180, 200, and 220degC, and holding time of 60 minutes. The results indicated that the properties on solid products could be improved using HT, particularly its higher heating value (HHV) of 20.1 MJ/kg (obtained from HT at 180degC) compared to feedstock of 19.68 MJ/kg and commercial pellet of EFB of 13.03 MJ/kg. Pellets made of solid product from HT at 150degC and pelletized at 200 bar were considered to meet the characteristic of commercial pellets. more...

The increase of Liquid Petroleum Gas (LPG) import in Indonesia made the government promote Dimethyl Ether (DME) as partial substitution of LPG as written in the General Planning of National Energy (RUEN) 2017. DME can be produced from biomass which abundantly exists in Indonesia. Such biomass is especially oil palm empty fruit bunches (EFB) that consist of 49.07% C, 6.48% H, 0.70% N, 38.29% O, and 5.36% Ash. Techno-economic analysis of this bio-DME production plant was conducted based on literature data. The direct synthesis of DME was applied in this study, instead of using methanol as an intermediate product. Result calculated from mass and energy balance simulation was 4.1 EFB/DME. Thus, 1,090 ton per day of DME can be produced from EFB with a collecting radius of 100 km in Riau Province. Assuming 20 years plant operation with DME selling price of IDR 145,000/12-kg-LPG-equivalent and EFB price of 300 IDR/kg, economic evaluation showed that this business was economically feasible with 10.08% IRR generated. The CAPEX of this plant was 990.4 million USD and the OPEX was IDR 7,143 IDR/kg-LPG-equivalent. DME production from EFB will give the positive economics and environmental effects. Therefore, support and synergy from government, industries, and academics are needed to realize this business. more...

Direct synthesis of DME catalyst was prepared using the co-precipitation method. The catalyst contained CuO/ZnO/Al2O3 about 40/27/33 (%-wt). Two types of catalyst were prepared, i.e. CZMA0 (Mg 0%-wt) and CZMA20 (Mg 20%-wt). Both of catalysts were activated using reducing gas (5% H2 and N2). The activity test was conducted by syngas model which contained (%-mole) 65% H2, 28% CO and 7% N2. The reaction was carried out in a fixed bed reactor at 5 bar, and temperature of 240, 250 and 260degC. Synthesis shown CZMA20 catalyst gave the highest catalytic activity with 73% of CO conversion and 66% of H2 conversion (5 bar and 260degC). Direct synthesis of DME was also carried out using a dual-catalyst, i.e. catalyst for methanol synthesis (M151, the commercial catalyst of methanol synthesis) and methanol dehydration (g-Al2O3-ITB). The activity of dual catalyst shown 93% of CO conversion and 91% of H2 conversion. This activity was more stable than two other catalysts (CZMA0 and CZMA20). more...

Road map of land for agricultural commodities in West Aceh is prioritized for rubber plantations. This commodity is the main source of livelihood and employment for the commodity. Furthermore, it is very difficult for a novice tap to be able to control the depth, thickness, and slope of tapping angle. Therefore, rubber tapping is created to increase the productivity of rubber crops in this region. This research conducted using software where the selection of component materials and manufacturing are tested on 9 rubber trees. The treatment is carried out according to the design plan; controlling the depth between 1-1.5 mm of cambium, tapping the thickness 1.5-2 mm, and tilting the angles of 350-600. Thus, the result of the functional testing shows that rubber tapping can function properly and the test data at interval 09:00-10:00 WIB for slope 60deg, 45deg, 35deg obtained the average latex amount of 1.83 grams, 1.11 grams, and 0.74 grams. In addition, the rubber tapping capacity of 5-6 seconds per tree is better when compared to conventional rubber tapping between 6-8 seconds with 5.32 cm3 rubber bark consumption. more...

The gaseous fuel from biomass gasification might reduce the consumption of diesel fuel by 70%. The investment cost of the whole unit with a capacity of 45 kWe was about IDR 220 million in 2008 comprised of 24% for gasification unit, 54% for diesel engine and electric generator, 22% for transportation of the whole unit from Bandung to the site in South Borneo. The gasification unit was made in local workshop in Bandung, while the diesel-generator was purchased also in a local market. To anticipate the development of biomass based electricity in remote areas, an economic analysis has been made for implementations in 2019. A specific investment cost of 600 USD/kW has been estimated taking account to the escalation and capacity factors. Using a discounted factor of 11% and biomass cost in the range of 0.03-0.07 USD/kg, the production cost of electricity would be in the range of 0.09-0.16 USD/kWh. This production cost was lower than that of diesel engine fueled with full oil commonly implemented in many remote areas in Indonesia at this moment. This production cost was also lower than the Feed in Tariff in some regions established by Indonesian government in 2017. more...

The objective of this study is to optimize the performance of the tread compound, by mixing of specified ingredients, such as Natural Rubber (NR) and Butadiene Rubber (BR) at various compositions, and also the type of carbon black as filler. The composition of NR and BR are used as follows 100:0; 95:5 and 85:15. Other materials used as rubber additives are peptizer, ZnO, stearic acid, additives, processing oil, and curatives. Two types of carbon black namely N220 and N234 are used in this research. The un-vulcanized rubber from each formula was characterized of curing characteristics and Mooney viscosity. The vulcanized rubber was then characterized its mechanical and thermal properties. It is clear from the research that, the addition of BR into the NR compound increases the abrasion resistance, rebound resilience and hardness, yet the glass transition temperature of the rubber compounds decreases. On the other hand, it seems that the rubber compound reinforced N220 or N234 gives comparable results on both mechanical and thermal properties. more...

The Membranes Polymer Gel Electrolyte (MPGEs) based poly (vinylidene fluoride) (PVDF) was prepared by a phase inversion method using polyvinyl pyrrolidone (PVP) as a pore-forming agent and N, N-dimethyl acetamide (DMAc) as a solvent and water as non solvet. The membranes were then soaked in 1 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate (EC) / dimethyl carbonate (DMC) / Diethyl carbonate (DEC) (4:2:4 %vol) solution in order to prepare polymer electrolyte membranes. The MPEGs PVDF/PVP/Nanoclay was applied using central composite design (CCD) experimental design to obtain a quantitative relationship between selected membranes prepared parameters namely (PVDF, PVP as pore forming agent and nanoclay filler concentration) and Ionic conductivity MPEGs. The model was used to find the optimum ionic conductivity from polymer electrolyte membranes. The polymer electrolyte membranes show good ionic conductivity on the order of 6.3 - 8.7 x 10-3 S cm-1 at the ambient temperatures. The ionic conductivity tended to increase with PVP and nanoclay concentration and decrease with PVDF composition. The model predicted the maximum ionic conductivity of 8.47 x 10-3 S cm-1 when the PVDF, PVP and nanoclay concentration were set at 8.01 %, 8.04 % and 10.12%, respectively. The first section in your paper. more...

This paper presents preparation of low fouling PES membranes by non solvent induced phase separation (NIPS) coupled with redox polymerization. The membrane characterization included water permeability, morphology structure (by SEM) and surface chemistry (by FTIR). Water permeability measurements showed thatthe membranes have water permeability within the range 10-50 L/h.m2.bar. Addition of PEG dan PEGMA intopolymer solution increased water permeability, whereas blending redox initiator and crosslinker, MBAA in polymer solution decreased water permeability. Surface morfology of membranes by SEM showed that unmodified PES membrane had smaller pore size than PEG or PEGMA modified PES membranes. Furthermore, PES-PEG or PES-PEGMA membranes modified by blending with redox initiator and MBAA as crosslinker showed smaller pore size than unmodified membrane. FTIR analysis showed that all membranes have typical spectraof PES polymer; however no additional peak was observed forthe membranes prepared with addition of PEG/PEGMA, initiator redox and also crosslinker. The addition of PEG/PEGMA, redox initiator and crosslinker resulted in membranes with high rejection and an acceptable flux as well as more stable due to relatively high fouling resistance. more...