This research determines the optimal investment timing using real options valuation to support decision-making for economic sustainability assessment. This paper illustrates an option pricing model using the Black-Scholes model applied to a case project to understand the model performance. Applicability of the project to the model requires two Monte Carlo simulations to satisfy a Markov process and a Wiener process. The position of project developers is not only the seller of products, but it is also the buyer of raw materials. Real options valuation can be influenced by the volatility of cash outflow, as well as the volatility of cash inflow. This study suggests two-color rainbow options valuation to overcome this issue, which is demonstrated for a steel plant project. The asymmetric results of the case study show that cash outflow (put option) influences the value of the steel plant project more than cash inflow (call option) does of which the discussion of the results is referred to a sensitivity analysis. The real options valuation method proposed in this study contributes to the literature on applying the new model, taking into consideration that investors maximize project profitability for economic sustainable development.
The present research work studies the direct synthesis of hydroxyapatite (Ca10(PO4)6(OH)2), via a heat-assisted precipitation technique based on the reaction between Ca2+, phosphate (PO4)3–, and (OH)− ions under highly alkaline conditions. An assessment carried out on the thermodynamics involved in the formation of hydroxyapatite (HAP) via precipitation reactions highlighted the favorability of using a high pH to perform HAP synthesis in terms of ΔG Reaction and element speciation. On the basis of these results, laboratory experiments performing the synthesis of hydroxyapatite at pH 11 using four different chemical reactions and different ripening times suggested that HAP nanocrystals are formed through the route of amorphous calcium phosphate (ACP) toward hydroxyapatite. Our results pointed out that the product obtained was a nonstoichiometric hydroxyapatite with a calcium to phosphorus molar ratio in the range Ca/P = 1.40 to Ca/P = 1.95, with carbonate ions (CO3)2– being present in the HAP crystals obtained under these experimental settings. In addition, XRD characterization suggested that the reagent used to achieve a high pH exerts an influence on the arrangement of HAP, as the reflection of the (300) plane was more prominent when alkali metal hydroxides were used as the source of (OH)− ions. Lastly, SEM imaging confirmed that carrying out the synthesis under highly alkaline conditions consistently yields agglomerated clusters of primary HAP nanoparticles, irrespective of the ripening time or the particular reaction used.
The construction of most apartment underground parking lots utilizes reinforced concrete (RC) structures composed mainly of rebar work and formwork. RC structures lower construction efficiency and significantly delay the construction because they require a large number of temporary materials and wooden formwork. In this study, a precast concrete double wall (PCDW) system was developed to address the existing problems of RC structures and to improve the productivity of retaining wall construction. PCDW is a precast concrete (PC) wall in which two thin concrete panels are connected parallel to each other with truss-shaped reinforcement between them. PCDW can contribute to securing integrity, reducing the delay in construction, and improving quality. An overall process for the member design and construction stage of the PCDW system was proposed, and its improvement effects were examined regarding various aspects in comparison to the RC method.Sustainability 2020, 12, 3454 2 of 12 various methods, including joining methods and performance verification, to be applied to special members involving difficult construction such as apartment framework, balconies, stairs, railings, and underground parking lots [12][13][14][15][16].Ji and Choi [17] researched a method of manufacturing an integrated wall by installing a link beam on the inside and outside walls of a PC and applied the method to common and reservoir walls. Furthermore, Park [18] proposed a method of forming a wall by fastening a PC panel and a panel with anchor bolts, while Oh et al. [19] conducted a study to confirm the advantages of the corresponding wall in the area of air shortening. In addition, Yang et al.[20] produced a double-synthetic precast wall with a double T-shaped PC panel facing each other to secure the economy and safety of the basement wall construction and then conducted experiments on the bending and shear behavior of the specimen. The method of pouring topping concrete after PC installation was applied also to slabs and columns. For slabs, double tee slabs, hollow slabs, and half PC slabs were identified [21]. In the case of columns, the hollowed precast concrete (HPC) column was produced by centrifugally molding a hollow PC part in the factory and pouring concrete into the field [22]. It was confirmed that the difference in performance between the existing RC structure and the HPC column was applicable to the seismic structure system. In addition, Roh and Hashlamon [23] and Kim and Kang [24] presented a development for piers and bridge columns through pouring concrete in the hollow precast and further conducted a study to analyze the seismic performance. In the case of a typical PC method, stress discontinuity due to inter-component disconnection is formed at the joint; thus, it is not easy to achieve the same performance as that of the RC structure. Furthermore, such a method may fail if the external wall support is insufficient, and there is risk of a safety accident. Therefore, the composite method of combining PC and topping concrete i...
Various studies have confirmed that the increasing quality of safety climate has a positive influence on reducing the occurrence of accidents. The quality of safety climate is comprehensively affected in three domains: management, site, and enterprise. At the company level, it is challenging to manage all areas at a high level due to limited managerial resources. Therefore, it is necessary to establish a strategy that improves the safety climate step by step. For the efficient execution of the strategy, it is necessary to analyze the relative importance of each evaluation factor of the safety climate and allocate managerial resources accordingly. Therefore, this study aims to analyze the relative importance of safety climate evaluation factors using the analytical hierarchical process (AHP) technique. For this study, AHP questionnaire and analysis are conducted, and the relative priorities of safety climate evaluation factors are derived. As a result, (E) workers’ safety priority and risk non-acceptance is the most important dimension among seven dimensions as the weight is 0.1900. In addition, (E1) compliance with safety regulations, even if the process is tight, is the most important one between items as the weight 0.6663. The results of this study will be used as basic data for institutional improvement and policy making for a high-quality safety climate at construction sites.
This paper focuses on an investment decision-making process for sustainable development based on the profitability impact factors for overseas projects. Investors prefer to use the discounted cash-flow method. Although this method is simple and straightforward, its critical weakness is its inability to reflect the factor volatility associated with the project evaluation. To overcome this weakness, the Value-at-Risk method is used to apply the volatility of the profitability impact factors, thereby reflecting the risks and establishing decision-making criteria for risk-averse investors. Risk-averse investors can lose relatively acceptable investment opportunities to risk-neutral or risk-amenable investors due to strict investment decision-making criteria. To overcome this problem, critical factors are selected through a Monte Carlo simulation and a sensitivity analysis, and solutions to the critical-factor problems are then found by using the Theory of Inventive Problem Solving and a business version of the Project Definition Rating Index. This study examines the process of recovering investment opportunities with projects that are investment feasible and that have been rejected when applying the criterion of the Value-at-Risk method. To do this, a probabilistic alternative approach is taken. To validate this methodology, the proposed framework for an improved decision-making process is demonstrated using two actual overseas projects of a Korean steel-making company.
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