Sekaran, Indonesia
Sekaran, Indonesia

The State University of Semarang is a public university in the city of Semarang, Central Java, Indonesia. The university is located in Gunungpati, a highland area of Semarang, Central Java.Unnes has eight faculties: Education, Language and Arts, Social science, Mathematics and Science, Engineering, Sport Science, Economics, and Law. Wikipedia.

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Wahyuni S.,State University of Semarang | Prasetya A.T.,State University of Semarang
IOP Conference Series: Materials Science and Engineering | Year: 2017

The aim of this research is to develop nanomaterials for coating applications. This research studied the effect of various TiO2-SiO2 composites in acrylic paint to enhance the hydrophobic properties of the substrate. Titanium dioxide containing silica in the range 20-35 mol% has been synthesized using sol-gel route. The XRD's spectra show that increasing SiO2 content in the composite, decreasing its crystalline properties but increasing the surface area. TiO2-SiO2 composite was dispersed in acrylic paint in 2% composition by weight. The largest contact angle was 70, which produced by the substrate coated with TS-35-modified acrylic paint. This study also investigated the enhanced photo-activity of TiO2-SiO2 modified with poly-aniline. The XRD spectra show that the treatment does not change the crystal structure of TiO2. The photo-activity of the composite was evaluated by degradation of Rhodamine-B with visible light. The best performance of the degradation process was handled by the composite treated with 0.1mL anilines per gram of TiO2-SiO2 composite (TSP-A). On the other side, the contact angle 70 has not shown an excellent hydrophobic activity. However, the AFM spectra showed that nanoroughness has started to form on the surface of acrylic paint modified with TiO2-SiO2 than acrylic alone. © Published under licence by IOP Publishing Ltd.

Mursiti S.,State University of Semarang | Supartono,State University of Semarang
IOP Conference Series: Materials Science and Engineering | Year: 2017

Flavonoid is one of the secondary metabolites compounds in mahogany seeds. Mahogany seeds can be used as an antimicrobial. This study aims to determine the antimicrobial activity of flavonoid compounds from mahogany seeds against Escherichia coli (E.coli) and Bacillus cereus (B.cereus). Isolation of flavonoid compounds done step by step. First, the maceration using n-hexane, then with methanol. The methanol extract was dissolved in ethyl acetate and aquadest, then separated. Ethyl acetate extract evaporated Flavonoid compounds were. The testing of antimicrobial activity of flavonoid compounds using the absorption method. The results showed that the antimicrobial activity of flavonoid compounds from mahogany seeds shows the inhibitory activity and provide clear zone against bacteria E.coli with value Inhibitory Regional Diameter 18.50 mm respectively, and 14.50 mm to the bacteria. Based on the results of the study, it can be concluded that flavonoid compounds from mahogany seeds have antimicrobial activity against E.coli and B.cereus. © Published under licence by IOP Publishing Ltd.

Kusumawardaningsih Y.,State University of Semarang | Hadi M.N.S.,University of Wollongong
Composite Structures | Year: 2010

Confining columns with fibre reinforced polymer (FRP) composites have been investigated in the last few decades to address the problem of upgrading and retrofitting reinforced concrete (RC) columns; however, most studies have concentrated on solid columns. This paper investigates the comparative behaviour of FRP confined hollow RC columns subjected to concentric loading. A total of twelve RC columns made from high strength concrete (HSC) were cast and tested. Six of the columns had a circular cross section (two solid columns, two hollow columns each having a circular hole, and two hollow columns each having a square hole) and the remainder columns had a square cross section (two solid columns, two hollow columns each having a circular hole, and two hollow columns each having a square hole). Six columns in total, three from each configuration were left unconfined as control specimens, while the others were confined with FRP. It was found that FRP confinement increased hollow RC columns' axial load and ductility capacities; and hollow columns having circular holes had better performance compared to hollow columns having square holes. © 2010 Elsevier Ltd.

Solikhah B.,State University of Semarang
International Journal of Applied Business and Economic Research | Year: 2016

The issue about CSR disclosure increases rapidly, while the research related to CSR disclosure found dissimilar results. The purpose of this study was to analyze the effect of industry sensitivity and company's size on CSR disclosure based on legitimacy theory. The 117 manufacturing companies listed in Indonesian Stock Exchange were used as the sample. CSR disclosure was measured by using the Global Reporting Initiative (GRI) index 4.0 version, which has not been widely used in previous studies. The methods used in this study were descriptive analysis and multiple regression analysis. The results support legitimacy theory that states there is a social contract between the company and the society. More specifically, high profile industry (oil and gas, agriculture, mining, fisheries, chemical, automotive, consumer goods, food and beverage, paper, pharmaceuticals, plastics and construction) disclose CSR broader than low profile industry. The larger companies will encourage them to expand their disclosure of social responsibility. Further research can use more varied measurement for CSR Disclosure because this paper uses only a score of 0 and 1. Weighting scale which can be used for each item of criteria such as 0 (undisclosed), 1 (otherwise disclosed in this narrative), 2 (if expressed in narrative and numbers).

Anis S.,Universiti Sains Malaysia | Anis S.,State University of Semarang | Zainal Z.A.,Universiti Sains Malaysia | Bakar M.Z.A.,Universiti Sains Malaysia
Bioresource Technology | Year: 2013

A new effective RF tar thermocatalytic treatment process with low energy intensive has been proposed to remove tar from biomass gasification. Toluene and naphthalene as biomass tar model compounds were removed via both thermal and catalytic treatment over a wide temperature range from 850. °C to 1200. °C and 450. °C to 900. °C, respectively at residence time of 0-0.7. s. Thermal characteristics of the new technique are also described in this paper. This study clearly clarified that toluene was much easier to be removed than naphthalene. Soot was found as the final product of thermal treatment of the tar model and completely removed during catalytic treatment. Radical reactions generated by RF non-thermal effect improve the tar removal. The study showed that Y-zeolite has better catalytic activity compared to dolomite on toluene and naphthalene removal due to its acidic nature and large surface area, even at lower reaction temperature of about 550. °C. © 2013 Elsevier Ltd.

Anis S.,Universiti Sains Malaysia | Anis S.,State University of Semarang | Zainal Z.A.,Universiti Sains Malaysia
Renewable and Sustainable Energy Reviews | Year: 2011

Biomass gasification presents highly interesting possibilities for expanding the utilization of biomass as power generation using internal combustion engines or turbines. However, the need to reduce the tar in the producer gas is very important. The successful application of producer gas depends not only on the quantity of tar, but also on its properties and compositions, which is associated with the dew-point of tar components. Class 5, 4, and 2 tar become a major cause of condensation which can foul the engines and turbines. Hence, the selectivity of tar treatment method to remove or convert class 5, 4, and 2 tar is a challenge in producer gas utilization. This review was conducted to present the recent studies in tar treatment from biomass gasification. The new technologies with their strengths and the weaknesses in term of tar reduction are discussed. © 2011 Elsevier Ltd. All rights reserved.

Megawati,State University of Semarang | Sediawan W.B.,Gadjah Mada University | Sulistyo H.,Gadjah Mada University | Hidayat M.,Gadjah Mada University
Bioresource Technology | Year: 2011

This study focuses on kinetics of rice husk hydrolysis using sulfuric acid catalyst to produce sugars. The experiments were conducted at various catalyst concentrations. It turned out that during hydrolysis, degradation of sugars was encountered. The kinetics was expressed with both homogeneous and heterogeneous models. At catalyst concentration of higher than 0.44N, heterogeneous model works better than homogeneous model, while at the lower, both models work well. In the heterogeneous model, it is observed that the mass transfer of sulfuric acid in the particles and the hydrolysis reaction control the rate of hydrolysis. The mass transfer can be described by Fick's law with the effective diffusivity of 1.4×10-11cm2/s, while the hydrolysis and sugar degradation rate constants follow Arrhenius equations. In addition, it was experimentally observed that the sugars produced can be converted to ethanol by fermentation using yeast. © 2010 Elsevier Ltd.

Sutikno M.,State University of Semarang | Marwoto P.,State University of Semarang | Rustad S.,State University of Semarang
Carbon | Year: 2010

Carbonized coconut char powder-based friction materials for automotive brakes were produced using hot isostatic pressing machine at 190 °C for 3 h. The amounts of coconut char and magnesium oxide powders used in the mixing were optimized while fixing the compositions of other ingredients (styrene butadiene rubber, stearic acid, sulphur, zinc oxide, bakelite, calcium carbonate, brass, bronze and stainless steel), and effects on microstructure, surface roughness, hardness, wear resistance, and tensile strength were investigated. The powders were used as substitutes for graphite or coal powders. The amount of char used varied between 7-14% of total volume and its chemical analysis was determined using energy dispersive X-ray spectroscopy. The surface roughness, Rockwell hardness number, maximum tensile strength, and specific wear resistance of the materials fabricated are in the range of 1.98-5.16 μm, 34.67-76.06, 0.63-1.67 MPa and 4.13exp-14 to 10.27exp-14 m2/N, respectively. © 2010 Elsevier Ltd. All rights reserved.

Prajanti S.D.W.,State University of Semarang
Management of Environmental Quality | Year: 2014

Purpose: The purpose of this paper is to determine strategies in controlling over the function of paddy field in Central Java. Design/methodology/approach: Purposive sampling was employed by having 12 people interviewed. Analytical hierarchy process was used to determine a strategy related to policy control toward agricultural land conversion. Findings: The results indicated priorities which are recommended to include in the policy toward the function of the land conversion in Central Java. They are: first, the application of laws that regulate land conversion mechanism; second, tightening or restricting and prohibiting rules for anyone who wants to change the function of agricultural land; and finally, zoning or clustering region based on urban spatial and land use. Research limitations/implications: This study suggests that the government is expected to invest directly for agriculture and plantation by avoiding the use of existing rice field. Practical implications: It is also advisable for government to utilize the available unused land. Originality/value: This paper captures factual condition of the decrease of the land use for agriculture which has been very critical issues in any agrarian countries. This is essential to know the core of the problem and possible solutions for similar case in other typical nations. © 2014, Emerald Group Publishing Limited.

Ahmad A.L.,Universiti Sains Malaysia | Kusumastuti A.,Universiti Sains Malaysia | Kusumastuti A.,State University of Semarang | Derek C.J.C.,Universiti Sains Malaysia | Ooi B.S.,Universiti Sains Malaysia
Desalination | Year: 2012

This paper presents a comprehensive study on emulsion diameter and removal capacity of Cd(II) from aqueous solution using emulsion liquid membrane (ELM). The liquid membrane consists of trioctylamine (TOA) as a carrier, kerosene as an organic diluent, ammonia as a stripping solution and Span 80 (sorbitan monooleate) as an emulsifying agent, prepared using ultrasonic. The important parameters affecting the emulsion diameter for recovery of Cd(II) including emulsification time, surfactant concentration, carrier concentration, and volume ratio of membrane to internal phase were systematically studied. The effects to membrane breakage were also investigated. The effect of emulsion diameter on the removal capacity of Cd(II) was also studied as its important role in the permeation process. The results showed that the emulsion diameter ranging from 0.878 up to 2.46 μm. The highest removal capacity was 0.493. mg Cd/ml emulsion while the lowest membrane breakage was 0.117% were obtained at the smallest emulsion droplets diameter. © 2011 Elsevier B.V.

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