Witono J.R.,Parahyangan Catholic University |
Noordergraaf I.W.,University of Groningen |
Heeres H.J.,University of Groningen |
Janssen L.P.B.M.,University of Groningen
Carbohydrate Polymers | Year: 2012
The graft copolymerization of cassava starch with acrylic acid was investigated using a free radical initiator system (Fe2+/H 2O2 redox system) in water. A comprehensive understanding of the important variables and their interaction has been obtained by applying an experimental design method. In this approach, two ('high' and 'low') values of selected variables are considered. Important result parameters are add-on and the grafting efficiency. Out of eight reaction variables, it was found that only temperature, starch concentration and the starch to monomer ratio have a pronounced influence on these response parameters. Moderate reaction temperature (40 °C) and high starch concentration (10%) give relatively good results of add-on and grafting efficiency. A low starch to monomer ratio favors add-on but decreases grafting efficiency. These findings can be used to optimize the production of cassava starch-acrylate copolymers and to gain insight in the process-product property interactions, for various applications. © 2012 Elsevier Ltd. All rights reserved.
Wibowo A.,Parahyangan Catholic University |
Mohamed S.,Griffith University
International Journal of Project Management | Year: 2010
Public-private-partnership (PPP) infrastructure projects typically involve a plethora of risks. Given that many risks which are traditionally borne by the government get transferred to the private sector, careful risk allocation is considered to be the key to successful PPP projects. This paper focuses on the current risk allocation practice within Indonesia's water supply projects. The paper captures, presents and discusses the perceptions of both regulators and operators in the context of project risk criticality and allocation. Both parties consider non-availability of raw water is of paramount concern. However, survey findings highlight low-to-moderate levels of intra-group and inter-group agreement regarding the allocation of specific project risk factors. Thus, asserting that the issue of optimal risk allocation remains elusive. © 2009 Elsevier Ltd and IPMA.
Siahaan H.M.,Parahyangan Catholic University
Modern Physics Letters A | Year: 2011
We calculate the static Wilson loop from string/gauge correspondence to obtain the QQ̄ potential in nonrelativistic quantum field theory, i.e. CFT with Galilean symmetry. We analyze the convexity conditions13 for QQ̄ potential in this theory, and obtain restrictions for the acceptable dynamical exponent z. © 2011 World Scientific Publishing Company.
Susanto S.,Parahyangan Catholic University |
Bhattacharya A.,Dublin City University
Computers and Industrial Engineering | Year: 2011
This paper models a crisp Linear Programming (LP) as a Compromise Fuzzy Multi-Objective LP (CFMOLP). The application of CFMOLP has been focused on an industrial engineering problem that seeks profit maximisation by optimising product-mix. Imprecision of the large volume of industrial data and the conglomerated decision from all levels of management lead fuzzication of the identified constraints and the objective functions as well. The crisp model described is in the form of crisp-Multi-Objective Linear Programming (MOLP) with objective functions, functional constraints and non-negativity constraints. This model is formulated as a fuzzy-MOLP and subsequently converted into an equivalent compromise-MOLP model. The paper describes the development process for the CFMOLP model and its application along with appropriate interpretation. © 2011 Elsevier Ltd. All rights reserved.
Siahaan H.M.,Parahyangan Catholic University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016
By neglecting the self-force, self-energy, and radiative effects, it has been shown that an extremal or near-extremal Kerr-Newman black hole can turn into a naked singularity when it captures charged and spinning massive particles. A straightforward question then arises: do charged and rotating black holes in string theory possess the same property? In this paper we apply Wald's gedanken experiment, in his study on the possibility of destroying extremal Kerr-Newman black holes, to the case of (near-)extremal Kerr-Sen black holes. We find that feeding a test particle into a (near-)extremal Kerr-Sen black hole could lead to a violation of the extremal bound for the black hole. © 2016 American Physical Society.