Papers by Gunawan Gunawan
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Bulletin of Indonesian Economic Studies, 1982
... There was an acceleration of land sales from mar-ginal farmers, often to those outside the ..... more ... There was an acceleration of land sales from mar-ginal farmers, often to those outside the ... wages: a change in the present favour-able weather conditions, a slowdown in construction if the ... Real wages = nominal wage divided by price of milled rice (berm) in the village at the ...
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Computing Research Repository, 2010
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A Rate-Compatible Punctured Convolutional (RCPC)-encoded Vertical Bell Laboratories Layered Space... more A Rate-Compatible Punctured Convolutional (RCPC)-encoded Vertical Bell Laboratories Layered Space-Time (V-BLAST) MIMO system to provide a robust wireless communication link is proposed. The V-BLAST detection is based on Minimum Mean-Squared Error (MMSE) criterion, to alleviate the noise enhancement commonly found in the original V-BLAST scheme based on Zero Forcing criterion. Different code rates and transmit powers are allocated to data streams emitted from the multiple transmit antennas, according to the attenuation levels of the subchannels. This scheme is efficient in terms of transmit power and bandwidth usage, as the data stream entering a destructive subchannel is given low transmit power and high code rate. Simulations show that the proposed system can attain good performance at a reasonably low Eb/No.
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Journal of Wood Chemistry and Technology, 2011
Metal/carbon nanocomposites find use in many potential applications, in areas such as batteries, ... more Metal/carbon nanocomposites find use in many potential applications, in areas such as batteries, catalysts, inks, polymer additives, and solar cells. Nickel/carbon nanocomposites are widely used as heterogeneous catalysts in oil processing and other catalytic reactions. Here we describe a novel microwave-assisted synthesis of nickel/carbon nanocomposites, achieved within a few minutes, starting from nickel salts and a renewable high-content carbon source, tannin. The carbon precursor is Quebracho tannin, which is a renewable-resource material obtained from the hot-water extraction of Schinopsis lorentzii and Schinopsis balansae, which are indigenous to Argentina and Paraguay. The process involves a simultaneous carbonization of the carbon precursor as well as the reduction of nickel ions to elemental nickel nanoparticles in an ambient atmosphere. Thus, this technique provides a fast, easy, and economical way to produce nickel/carbon nanocomposites without requiring the need for hydrogen or inert gas during the transformation. This technique could be used to synthesize a wide range of other metal/carbon nanocomposites and therefore holds tremendous economic promise. The nanocomposites have a high surface area and may be suitable as high efficiency catalysts.
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Journal of Macromolecular Science, Part A, 2011
High arsenic concentration in groundwater is found in many countries, including Bangladesh, India... more High arsenic concentration in groundwater is found in many countries, including Bangladesh, India, Vietnam, Thailand and United States. In these countries, the arsenic concentrations have reached dangerous levels for human consumption, especially where the main source of drinking water is from groundwater. Many techniques have been developed for arsenic removal, one being the use of iron oxide or magnetite nanoparticles for heavy metal removal. In this study, a novel tannin-based carbon-iron oxide composite has been developed by us for arsenic removal and results show that a concentration of 100 ppb As in water could be brought down to <10 ppb with the maximum capacity of the arsenic removal calculated to be 1.5 mg As/g Fe in the nanocomposite. The characterization of the nanocomposite and the advantages of using this renewable resource-based nanocomposite are also discussed.
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Phosphorus Sulfur and Silicon and The Related Elements, 2012
A novel, fast, and easy method for synthesizing a carbon-supported Ni2P nanocomposite (C/Ni2P) is... more A novel, fast, and easy method for synthesizing a carbon-supported Ni2P nanocomposite (C/Ni2P) is described. The process involves a reaction between a nickel salt, phosphoric acid, and a carbon source by utilizing microwave irradiation. The carbon source for the nanocomposite is from renewable supplies, namely, tannin and lignin. The method has successfully synthesized Ni2P nanoparticles dispersed in a carbon matrix with a particle size ranging from 20 to 50 nm in diameter. During the microwave process, tannin and lignin provided a reducing environment in the microwave irradiation process. The synthesized products are characterized by several characterization methods. The method showed that phosphoric acid, which is a nontoxic compound, could be used as an alternative P source for synthesizing Ni2P. The method is fast, easy, and an economical process to synthesize the carbon-coated Ni2P nanocomposite.
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Journal of Wood Chemistry and Technology, 2012
Magnetic carbon-iron oxide nanoparticles have been synthesized using tannin, a renewable resource... more Magnetic carbon-iron oxide nanoparticles have been synthesized using tannin, a renewable resource material, in combination with a microwave-based thermolytic process without the addition of any inert or reducing gas during the synthesis. The predominant iron oxide species present in these particles has been determined by XRD and FT-IR to be magnetite (Fe3O4). These iron oxide nanoparticles are embedded within a carbon matrix in small clusters generally ≤100 nm in size. The resulting powder is approximately 48% (w/w) magnetite, and has been characterized by magnetic susceptibility and SQUID analysis.
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Papers by Gunawan Gunawan