Muhammadiyah University of Yogyakarta

www.umy.ac.id
Yogyakarta, Indonesia
SEARCH FILTERS
Time filter
Source Type

Rahman M.E.,University Malaysia Sarawak | Muntohar A.S.,Muhammadiyah University of Yogyakarta | Pakrashi V.,University College Cork | Nagaratnam B.H.,University Malaysia Sarawak | Sujan D.,University Malaysia Sarawak
Materials and Design | Year: 2014

This paper presents an experimental study on the development of normal strength Self compacting concrete (SCC) from uncontrolled burning of rice husk ash (RHA) as a partial replacement to cement and blended fine aggregate whilst maintaining satisfactory properties of SCC. Experiments on the fresh and hardened state properties have been carried out on RHA based SCC from uncontrolled burning. The dosages of RHA are limited to 0%, 20%, 30% and 40% by mass of the total cementitious material in the concrete. The experiments on fresh state properties investigate the filling ability, the passing ability and the segregation resistance of concrete. The experiments on hardened state properties investigate the compressive and the splitting tensile strengths. The water absorption level of the concrete with changing RHA levels has also been monitored. The experimental studies indicate that RHA based SCC developed from uncontrolled burning has a significant potential for use when normal strength is desired. © 2013 Elsevier Ltd.


Syahputra R.,Muhammadiyah University of Yogyakarta | Soesanti I.,Gadjah Mada University
AIP Conference Proceedings | Year: 2017

This paper proposes an artificial immune system (AIS) algorithm approach for reconfiguring distribution network with the presence distributed generators (DG). The distribution network with high-performance is a network that has a low power loss, better voltage profile, and loading balance among feeders. The task for improving the performance of the distribution network is optimization of network configuration. The optimization has become a necessary study with the presence of DG in entire networks. In this work, optimization of network configuration is based on an AIS algorithm. The methodology has been tested in a model of 33 bus IEEE radial distribution networks with and without DG integration. The results have been showed that the optimal configuration of the distribution network is able to reduce power loss and to improve the voltage profile of the distribution network significantly. © 2017 Author(s).


Muntohar A.S.,Muhammadiyah University of Yogyakarta | Rahman M.E.,University Malaysia Sarawak
Construction and Building Materials | Year: 2014

A large amount of waste produced in the processing of palm oil is one of the main contributors to the environmental problem. This paper presents an experimental study on the development of the shellcrete masonry block that made of oil palm kernel. The study was focused on the physical, compressive strength and flexural strength of shellcrete. The eco-efficiency of the shellcrete was also evaluated by measuring the carbon footprint. The shellcrete was made by mixing the Portland cement (PC), sand, and oil palm kernel shell (PKS). A control specimen made of PC and sand mixture (sandcrete) was also prepared. The specimen size was 220 mm length, 110 mm width and 80 mm in thickness. The maximum strength obtained was 22 MPa by mixing proportion of 1 PC:1 Sand:1 PKS, but the recommended mix proportion of the shellcrete for building materials was 1 PC:1 Sand:2 PKS as an optimum mix design for eco-friendly shellcrete. © 2014 Elsevier Ltd. All rights reserved.


Setyonugroho W.,Muhammadiyah University of Yogyakarta | Kennedy K.M.,National University of Ireland | Kropmans T.J.B.,National University of Ireland
Patient Education and Counseling | Year: 2015

Objectives: To explore inter-rater agreement between reviewers comparing reliability and validity of checklist forms that claim to assess the communication skills of undergraduate medical students in Objective Structured Clinical Examinations (OSCEs). Methods: Papers explaining rubrics of OSCE checklist forms were identified from Pubmed, Embase, PsycINFO, and the ProQuest Education Databases up to 2013. Included were those studies that report empirical validity or reliability values for the communication skills assessment checklists used. Excluded were those papers that did not report reliability or validity. Results: Papers focusing on generic communication skills, history taking, physician-patient communication, interviewing, negotiating treatment, information giving, empathy and 18 other domains (ICC-0.12-1) were identified. Regarding the validity and reliability of the communication skills checklists, agreement between reviewers was 0.45. Conclusions: Heterogeneity in the rubrics used in the assessment of communication skills and a lack of agreement between reviewers makes comparison of student competences within and across institutions difficult. Practice implications: Consideration should be afforded to the adoption of a standardized measurement instrument to assess communication skills in undergraduate medical education. Future research will focus upon evaluating the potential impact of adoption of a standardized measurement instrument. © 2015 Elsevier Ireland Ltd.


Dong C.,Curtin University Australia | Sudarisman,Muhammadiyah University of Yogyakarta | Davies I.J.,Curtin University Australia
Journal of Materials Engineering and Performance | Year: 2013

A study on the flexural properties of E glass and TR50S carbon fiber reinforced hybrid composites is presented in this paper. Specimens were made by the hand lay-up process in an intra-ply configuration with varying degrees of glass fibers added to the surface of a carbon laminate. These specimens were then tested in the three-point bend configuration in accordance with ASTM D790-07 at three span-to-depth ratios: 16, 32, and 64. The failure modes were examined under an optical microscope. The flexural behavior was also simulated by finite element analysis, and the flexural modulus, flexural strength, and strain to failure were calculated. It is shown that although span-to-depth ratio shows an influence on the stress-strain relationship, it has no effect on the failure mode. The majority of specimens failed by either in-plane or out-of-plane local buckling followed by kinking and splitting at the compressive GFRP side and matrix cracking combined with fiber breakage at the CFRP tensile face. It is shown that positive hybrid effects exist for the flexural strengths of most of the hybrid configurations. The hybrid effect is noted to be more obvious when the hybrid ratio is small, which may be attributed to the relative position of the GFRP layer(s) with respect to the neutral plane. In contrast to this, flexural modulus seems to obey the rule of mixtures equation. © 2012 ASM International.


Syahputra R.,Muhammadiyah University of Yogyakarta
Journal of Theoretical and Applied Information Technology | Year: 2016

This paper presents the application of neuro-fuzzy method for prediction of vehicle fuel consumption prediction. Prediction motor vehicle fuel consumption has become a strategic issue, because it is not only related to the issue of availability of fuel but also the problem of the environmental impact caused. This study used automobile data, i.e. number of cylinders, displacement, horsepower, weight, acceleration, and model year, while the output variable to be predicted is the fuel consumption in MPG (miles per gallon). 'Weight' and 'Year' are selected as the best two input variables. The training and checking errors are getting distinguished, indicating the outset of overfitting. The results of this research are expressed in three dimension input-output surface graph of the best two-input ANFIS model for MPG prediction. It is a nonlinear and monotonic surface, in which the predicted MPG increases with the increase in 'Weight' and decrease in 'Year'. The training RMSE is 2.767; the checking RMSE is 2.996. The greater the weight of the motor vehicle, the greater the amount of fuel needed to travel the same distance. In comparison, a simple linear regression using all input candidates results in a training RMSE of 3.453, and a checking RMSE of 3.445. © 2005 -2016 JATIT & LLS. All rights reserved.


Syahputra R.,Muhammadiyah University of Yogyakarta | Soesanti I.,Gadjah Mada University
International Journal of Applied Engineering Research | Year: 2016

This paper presents the control scheme of doubly-fed induction generator (DFIG) using ANFIS method. The scheme is a part of wind power in order to on-grid to electrical power grid system. In this work, wind turbine driven is by DFIG which feeds ac power to distribution network. The system is modeled and simulated in the Simulink-Matlab software in such a way that it can be suited for modeling of induction generator configurations. The system model makes use of rotor reference frame using dynamic vector control approach for machine reference model. ANFIS controller is applied to rotor side converter for controlling active power and regulating voltage of wind power. In order to studying the performance of theANFIS controller, the different abnormal conditions are examined even the worst case. Simulation results prove the good performance of ANFIS control unit as improving power quality and stability of wind power system. © Research India Publications.


Muntohar A.S.,Muhammadiyah University of Yogyakarta | Liao H.-J.,National Taiwan University of Science and Technology
Natural Hazards | Year: 2010

Shallow slope failure due to heavy rainfall during rainstorm and typhoon is common in mountain areas. Among the models used for analyzing the slope stability, the rainwater infiltration model integrated with slope stability model can be an effective way to evaluate the stability of slopes during rainstorm. This paper will propose an integrated Green-Ampt infiltration model and infinite slope stability model for the analysis of shallow type slope failure. To verify the suitability of the proposed model, seven landslide cases occurred in Italy and Hong Kong are adopted in this paper. The results indicate that the proposed model can be used to distinguish failed and not-yet failed slopes. In addition, the proposed model can be used as the first approximation for estimating the occurrence time of a rainfall-induced shallow landslide and its depth of sliding. © 2010 Springer Science+Business Media B.V.


Rosyidi S.A.P.,Muhammadiyah University of Yogyakarta
Procedia Engineering | Year: 2015

Non-destructive testing (NDT) has been developed as a effective tool in road evaluation system in order to in-situ assess the stiffness parameter of pavement layer, partcularly in conducting a quick assessment on soil subgrade layer. The NDT method based on the seismic surface wave measurement has been recently developed and applied for material evaluation of roadpavement, i.e. The shear wave velocity, Poisson's ratio and dynamic elastic modulus. In this paper, an improved technique of tomography surface waves measurement for simultaneously evaluation of stiffness and anomalies of pavement soil-subgrade is presented. The method performs the time-frequency spectrum analysis on recorded seismic wave data, which is non-destructively sampling the subgrade layers properties. An interactive wavelet analysis is used in the spectrum analysis to produce the real phase velocity and its corresponding shear wave velocity. Using principal of stress-strain material in elastic behavior, the elastic modulus parameter of soil-subgrade layers is then generated. This method is improved for producing the 2-D elastic modulus profile and at the same time, it shows the structure anomalies in the investigated subgrade layers. The higher elastic modulus values can be found in the subgrade layer with more homogeneous soil densities that may be produced from a good degree of compaction. While the lower elastic modulus can be identified in the subgrade layers which are having many structural anomalies. From this study, it can be shown that the tomography seismic surface wave technique is able to simultaneously determine the stiffness and structure anomalies within existing road pavement. Thus, this method can be potentially advanced and developed as an innovative material evaluation device for pavement structures. © 2015 The Authors. Published by Elsevier Ltd.


Muntohar A.S.,Muhammadiyah University of Yogyakarta
Construction and Building Materials | Year: 2011

Utilization of lime and rice husk ash for soil stabilization produced considerable strength gain and other geotechnical properties of the stabilized soils. Its application could be also superior for construction materials as compressed-stabilized earth (CSE) or unfired-brick. This paper presents the investigation result of the application of lime and rice husk for unfired brick or compressed stabilized earth. The compressive and three-point flexural strength tests including compressive strength after water submersion were carried out in this present study. The investigation results show that compressive and flexural strength of clay brick are improved by adding of lime and RHA. The best quantity of lime and RHA in this study, is obtained by ratio 1:1 of lime and RHA. The addition of sand in stabilized clay resulted in more improvement in the water retention ability. © 2011 Elsevier Ltd. All rights reserved.

Loading Muhammadiyah University of Yogyakarta collaborators
Loading Muhammadiyah University of Yogyakarta collaborators