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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Kusmaryono I.,Islamic University of Sultan Agung | Suyitno H.,State University of Semarang
Journal of Physics: Conference Series | Year: 2016

This study used a model of Concurrent Embedded with the aim of: (1) determine the difference between the conceptual understanding and mathematical power of students grade fourth who take the constructivist learning using scientific approach and direct learning, (2) determine the interaction between learning approaches and initial competence on the mathematical power and conceptual of understanding, and (3) describe the mathematical power of students grade fourth. This research was conducted in the fourth grade elementary school early 2015. Data initial competence and mathematical power obtained through tests, and analyzed using statistical tests multivariate and univariate. Statistical analysis of the results showed that: (1) There are differences in the concept of understanding and mathematical power among the students who follow the scientifically-based constructivist learning than students who take the Direct Learning in terms of students initial competency (F = 5.550; p = 0.007 < 0.05), and (2) There is an interaction between the scientific-based constructivist learning approach with an initial competence (high and low) on the ability of concept of understanding and mathematical power (F = 5.259; p =0.033 < 0,05). Observations and in-depth interviews with students, shows that the construction of mathematical power of students have influenced the thinking of students in problem solving and contributes tremendous increase students' math skills. Researcher suggested that the learning of mathematics in schools using scientifically- based constructivist approach to improve the mathematical power of students and conceptual understanding. © 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
Bioresource Technology | Year: 2013

This study focused on improving the producer gas quality using radio frequency (RF) tar thermocatalytic treatment reactor. The producer gas containing tar, particles and water was directly passed at a particular flow rate into the RF reactor at various temperatures for catalytic and thermal treatments. Thermal treatment generates higher heating value of 5.76MJNm-3 at 1200°C. Catalytic treatments using both dolomite and Y-zeolite provide high tar and particles conversion efficiencies of about 97% on average. The result also showed that light poly-aromatic hydrocarbons especially naphthalene and aromatic compounds particularly benzene and toluene were still found even at higher reaction temperatures. Low energy intensive RF tar thermocatalytic treatment was found to be effective for upgrading the producer gas quality to meet the end user requirements and increasing its energy content. © 2013 Elsevier Ltd.

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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