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Manila, Philippines

Functionalization of zigzag graphene nanoribbon (ZGNR) segment containing 120 C atoms with pyridine (3NV-ZGNR) defects was investigated on the basis of density-functional theory (DFT) calculations, results show that edge-modified ZGNRs by Sc can adsorb multiple hydrogen molecules in a quasi-molecular fashion, thereby can be a potential candidate for hydrogen storage. The stability of Sc functionalization is dictated by a strong binding energy, suggesting a reduction of clustering of metal atoms over the metal-decorated ZGNR. Source

Tan R.R.,De La Salle University - Manila
Applied Energy | Year: 2011

The concept of inoperability was originally introduced as a means of quantifying risk in systems comprised of interdependent subsystems, using a modified input-output framework. This paper describes a novel robust optimization model for energy planning with inoperability constraints. The formulation is based on the established source-sink framework, which has been used extensively for energy planning applications under various environmental footprint constraints. The proposed model determines the optimal allocation of various energy sources within a system to corresponding energy sinks or demands, while ensuring that inoperability limits of the latter are satisfied for multiple enumerated scenarios. The basic formulation results in a linear program (LP), while a mixed integer linear programming (MILP) extension is also described. In either case, a globally optimal solution can be easily determined if one exists. Illustrative case studies are then given to demonstrate this new method. © 2011. Source

Tseng M.-L.,University of Business and Technology | Chiu A.S.F.,De La Salle University - Manila
Journal of Cleaner Production | Year: 2013

There has been an increasing interest towards firms' environmental sustainability activities to improve practices in their supply chain. Stringent environmental regulations in Europe and US challenge manufacturers to comply with these without losing their competitiveness. This study illustrates the case of a printed circuit board manufacturer in Taiwan that seeks to implement green supply chain management (GSCM) and selects a green supplier to meet its requirements. Choosing the suitable supplier is a key strategic direction in eliminating environmental impact on supply chain management for manufacturing firms. The firm's criteria and supplier selection need to be unified as a system to improve the firm's performance. This study identified the appropriate environmental and non-environmental GSCM criteria for the case firm and developed the following selection method: (i) evaluate the weights of criteria and alternatives as described both by qualitative and quantitative information; and (ii) rank alternative suppliers using a grey relational analysis. The result shows Alternative 3 ranks first among the four evaluated suppliers and demonstrated strong performance in the top three important criteria, namely, environmental management systems, profitability of supplier and relationship supplier closeness. Additionally, the perception weights on criteria itself are same as the most top five in weighted alternative. © 2010 Elsevier Ltd. All rights reserved. Source

Ooi R.E.H.,University of Selangor | Foo D.C.Y.,University of Selangor | Tan R.R.,De La Salle University - Manila
Applied Energy | Year: 2014

Carbon constrained energy planning (CCEP) is useful to ensure that the CO2 emissions limit for a region is met through deployment of low-carbon technologies. The increased demand in energy consumption due to economic growth requires additional energy supply and generation which would subsequently increase the carbon emissions. Nevertheless, most countries are now committed to reduce carbon emission to achieve long term sustainability goals. However, the development of alternative energy sources or carbon capture and storage (CCS) initiatives for power plants entails major capital investments. This paper demonstrates how these issues may be handled using CCEP with insight- and optimisation-based targeting techniques for multi-period scenarios. Both approaches were developed recently for CCEP problems, but previous techniques were limited to single-period planning. The extensions to multi-period scenarios are demonstrated in this work with hypothetical illustrative examples, as well as a Malaysian case study. © 2013 Elsevier Ltd. Source

Tan R.R.,De La Salle University - Manila
Industrial and Engineering Chemistry Research | Year: 2011

Source-sink problems occur in various process systems engineering applications, such as the design of water reuse systems and resource conservation networks. Such problems may be solved using alternative approaches, including graphical pinch analysis and linear programming. In most cases, it is normally assumed that the stream flow rates and quality levels are deterministic. This paper presents a fuzzy mathematical programming model for the synthesis of water networks when the model parameters exhibit fuzzy uncertainties. The modeling approach is illustrated for three water network case studies adapted from literature. These illustrative examples cover concentration- and property-based stream quality indices, as well as single- and multiple-plant water integration. © 2010 American Chemical Society. Source

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