Surabaya, Indonesia
Surabaya, Indonesia

Petra Christian University is a major private Christian university in Surabaya, Indonesia, established in 1961. It has about 9,900 students and 6 faculties. Wikipedia.


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Tumbelaka H.H.,Petra Christian University | Miyatake M.,Sophia University
ISIEA 2010 - 2010 IEEE Symposium on Industrial Electronics and Applications | Year: 2010

This paper proposes a three-phase four wire current-controlled Voltage Source Inverter (CC-VSI) for both harmonic mitigation and PV energy extraction. For harmonic mitigation, the CC-VSI works as a grid current-controlling shunt active power filter. Then, the PV array is coupled to the DC bus of the CC-VSI. The MPPT controller employs the Fibonacci search method. The output of MPPT controller is a DC voltage that determines the DC-bus voltage according to the PV maximum power. From computer simulation, the CC-VSI can effectively compensate for harmonics as well as deliver PV power to the grid. ©2010 IEEE.


Intan R.,Petra Christian University
Communications in Computer and Information Science | Year: 2015

Since the appearance of the first paper on fuzzy sets proposed by Zadeh in 1965, the relationship between probability and fuzziness in the representation of uncertainty has been discussed among many people. The question is whether probability theory itself is sufficient to deal with uncertainty. In this paper the relationship between probability and fuzziness is analyzed by the process of perception to simply understand the relationship between them. It is clear that probability and fuzziness work in different areas of uncertainty. Here, fuzzy event in the presence of probability theory provides probability of fuzzy event in which fuzzy event could be regarded as a generalization of crisp event. Moreover, in rough set theory, a rough event is proposed representing two approximate events, namely lower approximate event and upper approximate event. Similarly, in the presence of probability theory, rough event can be extended to be probability of rough event. Finally, the paper shows and discusses relation among lower-upper approximate probability (probability of rough events), belief-plausibility measures (evidence theory), classical probability measures, probability of generalized fuzzy-rough events and probability of fuzzy events. © Springer-Verlag Berlin Heidelberg 2015.


Purba K.R.,Petra Christian University
Communications in Computer and Information Science | Year: 2015

Genetic algorithm is a well-known optimization solution for an unknown, complex case that cannot be solved using conventional methods. In Role-Playing Games (RPG), usually the main features are character's stats and equip items. Character has stats, namely strength, defense, speed, agility, life. Also, equip items that can boost character's stats. These items retrieved randomly when an enemy dead.A problem arise when the player have so many items that we cannot choose the best. Latest items doesn't always mean best, because usually in RPGs, items don't always boost all stats equally, but often it reduces certain stat while increasing the other.Based on this, a function is built in this research, to auto equip all items, based on the standard deviation of character's stats after equipping. The genetic algorithm will evaluate the best combination of gloves, armors and shoes. This algorithm involves the process of evaluating initial population (items combination), selection, crossover, mutation, elitism, creating new population. The algorithm stops when the best fitness is getting stable in successive 3 generations.After the auto equip process, the character is getting significantly stronger compared to using default equip items, measured by the remaining life after fighting with several enemies. © Springer-Verlag Berlin Heidelberg 2015.


Wee H.M.,Chung Yuan Christian University | Widyadana G.A.,Petra Christian University
International Journal of Production Economics | Year: 2013

Integrated single-vendor single-buyer inventory model with multiple deliveries has proved to result in less inventory cost. However, many researchers assumed that the production run is perfect and there is no production delay. In reality, production delay is prevalent due to random machine unavailability and shortages. This study considers lost sales, and two kinds of machine unavailability distributions - uniformly and exponentially distributed. A classical optimization technique is used to derive an optimal solution and a numerical example is provided to illustrate the theory. The results show that delivery frequency has significant effect on the optimal total cost, and a higher lost sales cost will result in a higher delivery frequency. © 2012 Elsevier B.V. All rights reserved.


Chandra H.P.,Petra Christian University
Procedia Engineering | Year: 2015

A great deal of literature has pointed to the importance of understanding the construction project risk. Risks inherent in every construction project that can affect of project success. Risk is present in all situations that can be identified such as natural risks, design risks, resources risks, financial risks, legal and regulatory risks, and construction risks. The objectives of this paper are to identify the factors that causes of risks, to identify the factors of project success, and to represent the model of risk factors that affecting the project success. The data collected from the questionnaire survey carried out to 180 valid responses were analyzed with the assistance of structural equation modeling (SEM) to predict the project success. The results of the structural equation modeling suggest that the relationship between risk factors and project success in Surabaya projects can be explained by standardized coefficient of 0.442 for natural risks; -0, 499 for design risks; 0, 257 for resources risks; 0.651 for financial risks; 0.166 for legal and regulation risks; and -0.197 for construction risks. Project success is significantly related to cost (standardized coefficient of 0.878), quality (standardized coefficient of 0.873), time (standardized coefficient of 0.804), customer satisfaction (standardized coefficient of 0.884), and profit (standardized coefficient of 0.850). In order to achieve project success, suggestions are made for preparing financial risks related to inflation rate. © 2015 The Authors. Published by Elsevier Ltd.


Chandra H.P.,Petra Christian University
Procedia Engineering | Year: 2015

The sustainable construction safety and health is an integral aspect of sustainable and green building efforts. Sustainable construction is defined as the creation and responsible management of a healthy built environment based on resource efficiency and ecological principles. Therefore, the important thing is to know the potential motivators to achieve sustainable construction safety and health. The aims of this paper are to investigate the potential motivators, to determine the important factors in successful sustainable construction safety and health, and to suggest the model of initial investigation for potential motivators due to sustainable construction safety and health. High potential motivators can be identified such as project organization, leadership, and company support. In addition, the elements of the sustainable construction safety and health can be measured by on-site renewable energy and optimized energy performance; construction waste management; stormwater quality control; heat-island effect roof, indoor chemical and pollutant source control and outdoor air delivery monitoring; controllability of system-lighting and daylight 75% of spaces.The data collected from the questionnaire survey carried out from contractors, Selection of the indicators is highly significant in the context of a true measure of the representative practices across the latent or unmeasured variables for use in Partial Least Square (PLS). The results of this research suggest that the relationship between potential motivators and sustainable construction safety and health in which standardized coefficient of 0.429 for project organization, 0.424 for leadership, and 0.317 for company support. Moreover, the potential motivators was found to have influence on sustainable construction safety and health with standardized coefficient of 0.567. The results also show that the sustainable construction safety and health has a significant indicator in term of on-site renewable energy and optimized energy performance for standardized coefficient of 0.796. © 2015 The Authors. Published by Elsevier Ltd.


Kwanda T.,Petra Christian University
Procedia Engineering | Year: 2015

This paper aims to discuss the application of the notion of authenticity principle in the conservation work of De Javasche Bank building in Surabaya in term of form, materials and substance. This heritage building was built in 1910, and it has been unoccupied and dilapidated for decades, subsequently in 2010, the owner, Bank Indonesia began the conservation wok of the building. Data regarding form, materials and substance of the building were collected from field observation during the conservation work from 2011 to 2012, and collected from the Conservation Plan prepared in 2009. Based on the data, the principle of tangible authenticity is tested based upon scientific method to test material authenticity, and through a good knowledge of the typology of objects such as form of the building and elements of the building, materials and substance of the roof and floor tiles, plasters and paints, and the ornaments. The results show that to achieve the principle of authenticity in the conservation work, action taken should follow the ascending degrees of intervention dealing with preservation of the existing state and the original form, material and substance; consolidation of the fabric; restoration of the original building form; rehabilitation of all decay building elements; reproduction of the broken materials with replica such as floor tiles; reconstruction the missing section such as the original name of De Javasche Bank, and adaptation, as new elements such as new lighting systems, air condition, sound system were added to meet the adaptive reuse of the building as multi-purpose hall. In addition, to achieve the principle of authenticity in the conservation work, action taken should follow the principles namely the principle of minimum intervention preserving the original form, material and substance; recognizable as a new when introduce new materials and techniques; and the principle of reversible when in the future if all of the new elements will be detached they will not displace the original elements. © 2015 The Authors. Published by Elsevier Ltd. Published by Elsevier Ltd.


Widyadana G.A.,Chung Yuan Christian University | Widyadana G.A.,Petra Christian University | Wee H.M.,Chung Yuan Christian University
International Journal of Systems Science | Year: 2012

In recent years, many researches on economic production quantity (EPQ) models with machine breakdown and preventive maintenance have been developed, but few of them have developed integrated models for deteriorating items. In this study, we develop EPQ models for deteriorating items with preventive maintenance, random machine breakdown and immediate corrective action. Corrective and preventive maintenance times are assumed to be stochastic and the unfulfilled demands are lost sales. Two EPQ models of uniform distribution and exponential distribution of corrective and maintenance times are developed. An example and sensitivity analysis is given to illustrate the models. For the exponential distribution model, it is shown that the corrective time parameter is one of the most sensitive parameters to the optimal total cost. © 2012 Copyright Taylor and Francis Group, LLC.


Widyadana G.A.,Petra Christian University | Wee H.M.,Chung Yuan Christian University
International Journal of Production Economics | Year: 2012

Rework is one of the main issues in reverse logistic and green supply chain, since it can reduce production cost and environmental problem. Many researchers focus on developing rework model, but few of them developed model for deteriorating items. In this paper, we develop an economic production quantity (EPQ) model for deteriorating items with rework. In one cycle, production facility can produce items in m production setups and one rework setup, (m, 1) policy. An example and sensitivity analysis is shown to illustrate the model. The results show that the deteriorating rate affects the optimal cost per unit time, but the effect is not significant. The parameters that significantly affect the optimal total cost per unit time are the serviceable holding cost, the production setup cost and the demand rate. © 2012 Elsevier B.V. All rights reserved.


Wee H.M.,Chung Yuan Christian University | Widyadana G.A.,Chung Yuan Christian University | Widyadana G.A.,Petra Christian University
International Journal of Production Research | Year: 2012

Economic production quantity (EPQ) models for deteriorating inventory have been investigated by many researchers in recent years. In this paper, we develop EPQ models for deteriorating items with rework and stochastic preventive maintenance time. The models are solved using a search method, since a closed form solution cannot be derived. A numerical example and sensitivity analysis are provided to evaluate the models. The sensitivity analysis shows that the deteriorating cost has a significant effect on the optimal inventory cost; however, the production and the demand rate have the most significant effect on the optimal total cost and the optimal production up-time period. © 2012 Copyright Taylor and Francis Group, LLC.

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