Papers by yohanes kristianto
Vaasan yliopisto, 2009
III Julkaisija Julkaisuajankohta Vaasan yliopisto Joulukuu 2009 Tekijä(t) Julkaisun tyyppi Artikk... more III Julkaisija Julkaisuajankohta Vaasan yliopisto Joulukuu 2009 Tekijä(t) Julkaisun tyyppi Artikkelikokoelma Julkaisusarjan nimi, osan numero V Publisher Date of publication Vaasan yliopisto December 2009 Author(s) Type of publication Selection of articles Name and number of series
SSRN Electronic Journal, 2021
This article aims to build sustainability in a biofuel supply chain. Ethanol is chosen to represe... more This article aims to build sustainability in a biofuel supply chain. Ethanol is chosen to represent the biofuel and is assessed in terms of economic, environmental, and societal benefit feasibility. A unified optimization model of product, process and supply chain and life cycle assessment (LCA) is proposed to give the optimal solutions for sustainability. The decision parameters of process synthesis and logistics as well as raw materials production synthesize a closed loop economy. The techno-economic analysis embedded into the LCA so that the supply chain design achieves technical feasibility. The results show that integrated product and process design in the supply chain could achieve sustainability. Therefore it is proposed to extend further the design towards the SC contribution to energy grid of the local community.
Bioresource Technology, 2021
In this study, landfill leachate was pre-treated with NaClO, and then diluted to 5%, 10% and 15% ... more In this study, landfill leachate was pre-treated with NaClO, and then diluted to 5%, 10% and 15% for microalgae growth of Chlorella vulgaris and Scenedesmus dimorphus in the mono- and co-culture modes to investigate the nutrient removal and growth characteristics of microalgae. The results revealed that landfill leachate with the 10% dilution rate was conducive for microalgae growth and exhibited robust biomass growth and the highest nutrient removal efficiency. The co-culture biomass in 10% landfill leachate achieved 0.266 g/L within 10 days and demonstrated the improved nutrient utilisation efficiency of microalgae. In addition, the chemical oxygen demand, ammonia nitrogen, total nitrate and total phosphorus removal efficiencies accordingly reached 81.0%, 80.1%, 72.1% and 86.0% in 10% landfill leachate. Meanwhile, both the enzyme activity and fluorescence parameters proved that the cell activity of co-culture was higher than that of mono-culture.
Biomass and Bioenergy, 2020
Abstract Flocculation is regarded as an effective, convenient and promising means for microalgal ... more Abstract Flocculation is regarded as an effective, convenient and promising means for microalgal harvesting of microalgal biomass. In this study three types of metal sulfates (aluminum sulfate, aluminum potassium sulfate and ferric sulfate) were applied as flocculants to harvest microalgae Chlorella vulgaris biomass. The optimal operating parameters such as dosage, rotation speed, flocculation time and sedimentation time during microalgal biomass harvesting were determined, and the effects of metal sulfate application as flocculants on lipid extraction were investigated. The results showed that the optimal dosage for the three flocculants to harvest microalgal biomass was identically 2.5 g L−1, and the optimal rotation speeds for coagulation and flocculation were 150 and 25 rpm, respectively, while the flocculation time of 10 min was found to be appropriate. The findings also suggested that metal residuals in flocculated biomass would affect lipid extraction, resulting in 5.9%, 4.4% and 3.3% reduction of lipid contents for aluminum sulfate, aluminum potassium sulfate and ferrous sulfate, respectively. The contribution of this study lies in the provision of the optimal operating parameters during the microalgal biomass flocculation, thus potentially offering the technical guidance for the harvesting of microalgal biomass using metal sulfates as flocculants in practice.
Energy Conversion and Management, 2019
Effects of nitrogen source inhomogeneity on nutrient removal and biodiesel production of mono-and... more Effects of nitrogen source inhomogeneity on nutrient removal and biodiesel production of mono-and mixcultured microalgae were investigated in this study. The microalgal growth characteristics, lipid accumulation, biodiesel production and nutrient removal were determined by mono-or co-culturing microalgae Chlorella vulgaris and Scenedesmus dimorphus in media with different nitrogen sources. The results showed that microalgae cultivated in media with different nitrogen sources indicated higher nitrogen removal, biomass increase and productivities of biomass, lipids and biodiesel than media with the sole nitrogen source. As for the microalgae grown in media with the same nitrogen source, the pattern for the lipid content was in the relationship C. vulgaris > mixed culture > S. dimorphus. The fatty acids of microalgae mainly consisted of C16:0, C16:1, C18:0, C18:2 and C18:3, accounting for 79.6-90.6% of the total. The biodiesel production in this study ranged from 8.5 to 11.2 g-biodiesel/100 g-dry weight. This study presents one of the few studies, suggesting that nitrogen source itself can influence the nutrient removal and biodiesel production of mono-and mix-cultured microalgae.
Biofuels, Bioproducts and Biorefining, 2019
This paper studies an integration model of production planning, scheduling, and order-based inven... more This paper studies an integration model of production planning, scheduling, and order-based inventory distribution control systems. It models supply-chain and production dynamics and employs process control to supply-chain operations and the production process and scheduling. It embeds generalized disjunctive programming (GDP) and branch-and-reduce algorithms to obtain an optimal solution. Generalized disjunctive programming reformulates the original mixed integer nonlinear programming (MINLP) model and solves the new model with a lower number of integer variables. Afterwards, the branch and reduce algorithm, which is strengthened with outer approximation (OA) cutting planes, is able to find optimal solutions with permissible optimality gaps. The results show that supply network size does not affect forecast accuracy; there is a forecast error rate of 12.9%. Similar figures are also shown for the inventory level, which is expected to be 32% of demand level, production changeover time at 0.58 days, inventory ramp-up period to meet the expected raw materials and final products inventory at 0.02 and 0.04 days respectively, and extra delivery time to meet a certain level of demand change at 1.1 days. The results show that the model is capable of controlling demand forecast, inventory level, and delivery quantity, so that the supply chain can avoid stock out at a minimal level of inventory, regardless of the size of supply-chain networks.
Renewable Energy, 2019
Sustainable biofuel supply chain is a key to sustainable manufacturing and the future of producti... more Sustainable biofuel supply chain is a key to sustainable manufacturing and the future of production. Greener production is now becoming an order qualifier for the global competition. Modeling biofuel supply chains that achieve economic, social, and environmental feasibility is a challenge. This article develops biofuel platform planning and optimization that unifies biofuel product, production process and networks design into an umbrella of sustainable supply chain planning. A design of biofuel supply chain networks under various production paths is considered. The modeling results show that an optimum region of composition ratio between rice straws and waste cooking oils can be set within the range from 0% to 50%. Bio-diesel is favored over ethanol by occupying over 40% of the total biofuel outputs. However, ethanol yield is 99.1% and therefore it is sufficient to be directly mixed with gasoline at final depots. In terms of social contribution, it is estimated that the supply chain contribution to the case country GDP is about 0.17%. Looking at the above statistics, future research on global economic impacts and competitiveness of biofuel production is suggested.
Industrial & Engineering Chemistry Research, 2019
Biomass feedstock is a potential solution to future source of biofuels and fine chemicals. A majo... more Biomass feedstock is a potential solution to future source of biofuels and fine chemicals. A major challenge of its availability to meet energy demands extend the scope of production planning from single to multi locations. However, multi-location production planning needs an integrated production scheduling to minimize idle times and over-stocks and process control to hedge against any change in production planning. This article models an integration of production planning, scheduling and process control system, and formulates the model as a bi-level generalized disjunctive programming (GDP). We use a reformulation technique that coverts bi-level into a single level programming. We solve the model by using Branch and Reduce method, and add outer approximation (OA) cutting plane at each lower bounding iteration. The computational result shows that the supply chain can mitigate stock out or over stock, and generate no delivery delay. In terms of computational results, we find that the algorithm is capable of minimizing optimality gaps within the range of allowable error.
The TQM Journal, 2012
PurposeThe purpose of this paper is to present the results of a survey of customer satisfaction w... more PurposeThe purpose of this paper is to present the results of a survey of customer satisfaction with regard to the strategy of total quality management (TQM) adopted in a wheat flour milling company.Design/methodology/approachA survey was conducted to learn more about customer expectations and satisfaction. The respondents were all customers of a flour‐based food processor. Quality function deployment (QFD) was applied to improve customer service performance by focusing on customer satisfaction, value and retention.FindingsThe results show that customer satisfaction has increased steadily over a period of three years. The QFD approach helped to design a competitive product by aligning the company resources to customers’ needs.Research limitations/implicationsThe findings are limited to a specific food manufacturing company and for this reason they cannot be generalized to the whole in service sector. Further research is needed for other service companies.Practical implicationsThe fi...
Journal of Modelling in Management, 2013
Purpose – This paper aims to focus on duopolistic competition under dynamic price and production ... more Purpose – This paper aims to focus on duopolistic competition under dynamic price and production postponement for two differentiable products that share common product platform at a certain degree of product commonality.Design/methodology/approach – Both price and production postponement modelling are benchmarked according to their profit in order to investigate the product substitutability effect to the profit and also their appropriateness to different competition situations. In addition, dynamic property is applied to show the demand changes effect of both strategic decisions (price and production) against demand uncertainty.Findings – The results show that the pure price postponement is appropriate to be applied into highly customized products while pure production postponement to configurable products.Research limitations/implications – Price and production postponement decisions help managers to optimize product development as well as production strategy by considering demand and supply sides.Practi...
International Journal of Information Systems and Supply Chain Management, 2010
This paper studies duopolistic competition under dynamic price and production quantity postponeme... more This paper studies duopolistic competition under dynamic price and production quantity postponement for two differentiable products, which share common components from one supplier at a certain degree of substitution. Both price and quantity postponement is benchmarked according to the Bertrand and Cournot Stackelberg game. In addition, system dynamic is applied to show the long term effect of both strategic decisions (price and production quantity) on profit and against demand uncertainty. The results show that price postponement is appropriate for high modular products (make-to-stock) and production quantity postponement for special orders (make-to-order). The final part of the paper concludes with results and outlines future research directions.
Journal of Advances in Management Research, 2010
PurposeThis paper focuses on decision making related to the use of strategic inventory allocation... more PurposeThis paper focuses on decision making related to the use of strategic inventory allocation in product platform design. The purpose of the paper is to present a novel approach to managing product variety by considering product and manufacturing strategy, and considering the supply chain benefits.Design/methodology/approachDiscrete event simulation is used for analyzing product platform performance in terms of inventory level and throughput. Simulation parameters such as lead times and safety stock allocation are optimized by using an analytical model of strategic safety stock allocation.FindingsThe results show that strategic safety stock allocation supports product platform strategy by increasing production output, and reducing inventory level and customer order queues at a higher level of product variety.Research limitations/implicationsLinking the safety stock allocation and product platform strategy facilitates simultaneous product and process design by providing the most ...
International Workshop of "Stochastic Programming for Implementation and Advanced Applications", 2012
International Journal of Strategic Decision Sciences, 2010
This paper examines knowledge sharing in supply chain by developing analytical models to minimize... more This paper examines knowledge sharing in supply chain by developing analytical models to minimize knowledge sharing uncertainty. Analogies from thermodynamics are used to describe the phenomenon in supply chain knowledge sharing. The study finds that distance and sender capacity are important to reduce knowledge sharing uncertainty. Furthermore, higher contact frequency between the sender and the receiver without considering sender capacity is proven to be insignificant to reduce uncertainty. This mechanism provides a new approach to explicate knowledge sharing in supply networks. It also serves as a deep-rooted opening point for supplementary empirical assessment. The mechanism facilitates managers to expand their understanding of composite circumstances embedded into global supply networks to share their knowledge. With enhanced understanding, managers can spotlight their actions, increasing their firms’ competitiveness. This study provides a deeper theoretical understanding of kn...
Journal of Power Sources, 2003
Journal of Manufacturing Technology Management, 2012
PurposeThe purpose of this paper is to study the effect of technology adoption on operational com... more PurposeThe purpose of this paper is to study the effect of technology adoption on operational competitiveness by taking an example from international manufacturing companies.Design/methodology/approachThis paper develops a conceptual model to generate strategic flexibility and benefit for a manufacturing firm by managing manufacturing strategy and technology adoption with different leadership roles.FindingsThe results show that the leadership role is a significant factor to motivate strategic flexibility and generate higher benefit. For intellectuals, the mechanism provides a new approach to explicate technology adoption in a manufacturing company. Besides, it provides a deep‐rooted preliminary point for supplementary empirical assessment. The mechanism facilitates managers to expand their understanding of the leadership role for trust building and knowledge sharing in manufacturing firms.Practical implicationsWith that enhanced understanding, the managers can spotlight their action...
International Journal of Procurement Management, 2010
This paper focuses on control systems modelling built-to-order buyers facing customised demand. T... more This paper focuses on control systems modelling built-to-order buyers facing customised demand. The general purpose is to present a novel approach to managing collaboration, by considering information exchange between the buyer and the supplier. The methodology applies feedback control mechanism to analyse supplier responsiveness and product platform commonality degree to represent the need for product platform standardisation. A two stage game is applied ahead of control system application to optimise the production rate decision and supply contract, with the ultimate goal being profit maximisation and stabilisation. The results show that a higher product commonality degree gives more opportunity for quick response built-to-order supply chains at minimum shop floor operations changes, which are managed by feedback control. Furthermore, a contribution to collaborative supply chains is shown by applying a synchronised supply model to represent supplier and the buyer communication.
International Journal of Industrial and Systems Engineering, 2010
Segregation of product development and manufacturing process creates an engineering problem in co... more Segregation of product development and manufacturing process creates an engineering problem in concurrent engineering application. Commonality analysis has never been used for solving this problem, but rather solely as a product development tool. This paper focuses on coordinating the manufacturing and product development process to produce supply chain agility. The purpose of this paper is to present a novel approach to managing the product development process by considering strategic safety stock allocation to decide on ...
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Papers by yohanes kristianto