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Nayono S.E.,State University of Yogyakarta | Nayono S.E.,Karlsruhe Institute of Technology | Winter J.,Karlsruhe Institute of Technology | Gallert C.,Karlsruhe Institute of Technology
Waste Management | Year: 2010

A highly polluted liquid (" press water" ) was obtained from the pressing facility for the organic fraction of municipal solid waste in a composting plant. Methane productivity of the squeezed-off leachate was investigated in batch assays. To assess the technical feasibility of " press water" as a substrate for anaerobic digestion, a laboratory-scale glass column reactor was operated semi-continuously at 37 °C. A high methane productivity of 270m-3 CH4ton-1 CODadded or 490m-3 CH4ton-1 VSadded was achieved in the batch experiment. The semi-continuously run laboratory-scale reactor was initially operated at an organic loading rate of 10.7kg CODm-3d-1. The loading was increased to finally 27.7kg CODm-3d-1, corresponding to a reduction of the hydraulic retention time from initially 20 to finally 7.7days. During the digestion, a stable elimination of organic material (measured as COD elimination) of approximately 60% was achieved. Linearly with the increment of the OLR, the volumetric methane production of the reactor increased from 2.6m3mreactor-3d-1 to 7.1 m3mreactor-3d-1. The results indicated that " press water" from the organic fraction of municipal solid waste was a suitable substrate for anaerobic digestion which gave a high biogas yield even at very high loading rates. © 2009 Elsevier Ltd.

Nayono S.E.,State University of Yogyakarta | Nayono S.E.,Karlsruhe Institute of Technology | Gallert C.,Karlsruhe Institute of Technology | Winter J.,Karlsruhe Institute of Technology
Bioresource Technology | Year: 2010

Co-digestion of press water from organic municipal wastes and of homogenized food residues with defibered kitchen wastes (food waste) as the main substrate was examined to improve biogas production. Although the biowaste digester was operated already at high organic loading (OLR) of 12.3 kg COD m-3 d-1 during the week, addition of co-substrates not only increased biogas production rates but also improved total biogas production. By feeding the two co-substrates up to 20 kg COD m-3 d-1 gas production followed the increasing OLR linearly. When the OLR was further increased with food waste, not more gas than for 20 kg COD m-3 d-1 OLR was obtained, indicating the maximum metabolic capabilities of the microbes. During weekends (no biowaste available) food waste could substitute for biowaste to maintain biogas production. Addition of press water or food waste to biowaste co-digestion resulted in more buffer capacity, allowing very high loadings without pH control. © 2010 Elsevier Ltd. All rights reserved.

Khairudin M.,State University of Yogyakarta
ICITACEE 2015 - 2nd International Conference on Information Technology, Computer, and Electrical Engineering: Green Technology Strengthening in Information Technology, Electrical and Computer Engineering Implementation, Proceedings | Year: 2016

This study describes the development of robust control design for a spindle of lathe machine. The dynamic of the spindle is uncertain and time variation due to the deepness variation on cutting process. The dynamics model of a spindle were obtained by system identification. To find a linear model of the system based on the nonlinear system using the data of real time system identification. For obtaining a controller synthesis used linear models and its uncertainty bound with real time system identification. Using the selected input signal, the data of output and responses are acquired and then a nonlinear system identification is performed to obtain a linear model. Practical design steps are presented in which compensator and prefilter-based conditions are formulated to obtain a robust control of a spindle. Moreover, effects of the deepness variation on cutting process and the dynamic characteristics of a spindle are studied and discussed. © 2015 IEEE.

Cascarilla N.W.,State University of Yogyakarta | Lestari D.,State University of Yogyakarta
Journal of Physics: Conference Series | Year: 2016

This study aims to explain stability of the spread of AIDS through treatment and vertical transmission model. Human with HIV need a time to positively suffer AIDS. The existence of a time, human with HIV until positively suffer AIDS can be delayed for a time so that the model acquired is the model with time delay. The model form is a nonlinear differential equation with time delay, SIPTA (susceptible-infected-pre AIDS-treatment-AIDS). Based on SIPTA model analysis results the disease free equilibrium point and the endemic equilibrium point. The disease free equilibrium point with and without time delay are local asymptotically stable if the basic reproduction number is less than one. The endemic equilibrium point will be local asymptotically stable if the time delay is less than the critical value of delay, unstable if the time delay is more than the critical value of delay, and bifurcation occurs if the time delay is equal to the critical value of delay. © Published under licence by IOP Publishing Ltd.

The use of information technology to support the business organization's performance is one thing that needs to be done by large-scale industrial sector and small industrial sector (SMEs) to face global competition. As a developing country, the SMES sector in Indonesia is still not fully adopt and utilize information technology (IT) in the business process. Factors of contributors, inhibitors and the effect of the competitive environment and government support will tend to trigger SMEs to adopt IT. This study tries to explore the influence Contributor, Inhibitor, Government Support, and Competitor Pressure, to Technology Readiness (H1, H2, H3, H4), and the Influence of Technology Readiness on Behavioral to Use (H5). The study used 446 valid sample of SMEs of craft industry and being tested using the Partial Least Square (PLS) technique. The testing result shows that the Contributor and Inhibitor have the significant effect on the Technology Readiness with p-value of.000 (<0.05) (H1 and H2 were supported). The testing result of the Technology Readiness on the Behavior to Use also shows the significant result with the p-value 0.00 (<0.05) (H5 was supported). The test of the effect of the Government Support and Competitor Pressure shows the insignificant result with the p-value of 0.81 and 0.53 (>0.05) (H3 and H4 were not supported). Further analysis also found that the Government Support and Competitor Pressure do not affect on the IT users (Behavior to Use) in SMEs. The finding also strengthen the previous claim that the Government Support and the Competitor pressure are not the component which make SMEs ready to adopt and use the IT on their business process. © 2015 The Authors.

The purpose of this research is to identify which aspects of the communication skills and mathematics connections of the prospective mathematics teacher that need to be improved. The subjects of the research were 34 fourth-semester students of Mathematics Education Study Program, State University of Yogyakarta, Indonesia, who took Discrete Mathematics course from February to May 2012. The identifications are done through 6 times by quizzes/tests. The aspect of mathematical communication that had been studied was the ability of students in: (1) writing the statements, reasons, or explanations, and (2) using terms, notations, tables, diagrams, charts, drawings, illustrations, mathematical models, or formulas. While the aspect of mathematical connections that had been examined was the ability of students in: (1) stating the relationship between facts, concepts, or mathematics principles, (2) developing a mathematical model of the daily life problems, and (3) mentioning the concept underlying the solution from the given mathematical problems. Results shows that the students tend to be weak in: (1) writing down the reasons, (2) using charts, pictures, and illustrations, and (3) developing a mathematical model. © 2013 Penerbit UTM Press. All rights reserved.

Dwandaru W.S.B.,State University of Yogyakarta | Darmawan D.,State University of Yogyakarta
Advanced Studies in Theoretical Physics | Year: 2016

The advancement of nanotechnology opens exciting opportunities in the creation of semiconductor fabrication technology. It offers the production of small nano scale systems which consists of only one electron, i.e. quantum dot. The main idea behind a quantum dot is the Coulomb blockade. The dynamical mechanism of the Coulomb blockade can be studied by coupling the quantum dot to two reservoirs, viz. source and drain, at each end of the quantum dot. A potential difference of Vsd between the source and the drain is specified such that an electron asymmetrically tunnels from the source into the dot and out to the drain. The tunneling of the electron also depends on the gate potential, Vg, which is the potential applied to the dot. Based on the aforementioned description, a dynamical model is put forward to capture the qualitative and quantitative physical aspects of the quantum dot. The model is the totally asymmetric simple exclusion process or the TASEP. Here, a connection between the quantum dot and the TASEP in one dimension with a single site is put forward. The hopping rate is connected to the gate potential and the source-drain potential. The dot is the single site lattice, whereas the source and the drain are the reservoirs. From this connection the density and current density of particles may be obtained. © 2015 Wipsar Sunu Brams Dwandaru and Denny Darmawan.

Sugiman,State University of Yogyakarta
Jurnal Teknologi (Sciences and Engineering) | Year: 2013

Student as a mathematics teacher candidate must have competence in solving and creating mathematical problems. This paper describes how the two competencies are mastered by students. On the one competence, problem solving ability is reviewed by using four aspects: (1) conceptual and procedural understanding, (2) strategy knowledge, (3) mathematical communication ability and (4) accuracy. On the other competence, student's creativity in developing mathematical problem is evaluated based on: (1) fluency, (2) flexibility and (3) novelty. Research subjects are students who take Integral Calculus course in the academic year of 2012. Data are collected through documentation, observation and interview and then analyzed quantitatively and qualitatively. Students show their abilities and some difficulties in both solving and creating mathematical problem. © 2013 Penerbit UTM Press. All rights reserved.

Ariswan,State University of Yogyakarta
Advanced Materials Research | Year: 2014

CdTe polycrystalline thin films had been fabricated using vacuum evaporation technique. Their properties had been investigated using X-ray diffraction, energy dispersive spectroscopy (EDS), scanning electron microscope (SEM) and uv-vis spectroscopy. The results showed that the CdTe thin films crystalized at hexagonal structure with lattice parameters a = 6.45 Å and c =7.66 Å. The EDS results showed that the chemical composition was non stoichiometry, slightly rich of Tellerium with Cd/Te of 0.9. It had a uniform shape with color homogenity and an optical band gap at room temperature about 1.47eV. © (2014) Trans Tech Publications, Switzerland.

Dwandaru W.S.B.,University of Bristol | Dwandaru W.S.B.,State University of Yogyakarta | Schmidt M.,University of Bristol | Schmidt M.,University of Bayreuth
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

We show that classical density functional theory can be based on the constrained search method. From the Gibbs inequality one first derives a variational principle for the grand potential as a functional of a trial many-body distribution. This functional is minimized in two stages. The first step consists of a constrained search of all many-body distributions that generate a given one-body density. The result can be split into internal and external contributions to the total grand potential. In contrast to the original approach by Mermin and Evans, here the intrinsic Helmholtz free-energy functional is defined by an explicit expression that does not refer to an external potential in order to generate the given one-body density. The second step consists of minimizing with respect to the one-body density. We show that this framework can be applied in a straightforward way to the canonical ensemble. © 2011 American Physical Society.

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