• Smart Structures and Systems
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• v.22 no.5
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• pp.547-560
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• 2018

This paper investigates the operation of the $H_{\infty}$ static output-feedback controller to reduce dynamic responses under seismic excitation on the five-story and benchmark 20 story building with parametric uncertainties. Linear matrix inequality (LMI) control theory is applied in this system and then to achieve the desired LMI formulations, some transformations of the LMI variables is used. Conversely uncertainties due to material properties, environmental loads such as earthquake and wind hazards make the uncertain system. This problem and its effects are studied in this research. Also to decrease the transition of large amount of data between sensors and controller, avoiding the disruption of whole control system and economy problems, the operation of the decentralized controllers is investigated in this paper. For this purpose the comparison between the performance of the centralized, fully decentralized and partial decentralized controllers in uncoupled and coupled cases is performed. Also, the effect of the changing the number of stories in substructures is considered. Based on the numerical results, the used control algorithm is very robust against the parametric uncertainties and structural responses are decreased considerably in all the control cases but partial decentralized controller in coupled form gets the closest results to the centralized case. The results indicate the high applicability of the used control algorithm in the tall shear buildings to reduce the structural responses and its robustness against the uncertainties.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.92-98
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• 2005

The learning control develops controllers that learn to improve their performance at executing a given task, based on experience performing this specific task. In a previous work, the authors presented an iterative precision of linear decentralized learning control based on p-integrated learning method for the vertical dynamic multiple systems. This paper develops an indirect decentralized teaming control based on adaptive control method. The original motivation of the teaming control field was loaming in robots doing repetitive tasks such as on an assembly line. This paper starts with decentralized discrete time systems, and progresses to the robot application, modeling the robot as a time varying linear system in the neighborhood of the nominal trajectory, and using the usual robot controllers that are decentralized, treating each link as if it is independent of any coupling with other links. Some techniques will show up in the numerical simulation for vertical dynamic robot. The methods of learning system are shown up for the iterative precision of each link.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.111-124
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• 2014

Decentralized water supply systems, treating the water in users'vicinity, cutting down the distribution system, utilizing the alternative water resources(rainwater harvesting, water reclamation and reuse and so on.) and saving energy and other resources, could be categorized into POU(Point-Of-Use), POE(Point-Of-Entry) and community small scale system. From the literature review, we could thought that decentralized water supply system and hybrid system(integrating centralized and decentralized water supply system within urban water management) might have strengthening comparative advantages to centralized system with respect to: (1) water security, (2) sustainability, (3) economical affordability. Even though it is difficult to derive and quantify direct benefit advantages from decentralized and hybrid system in comparison with centralized system, (1) operational cost reduction, (2) assurance for safe and stability water supply and (3) greenhouse gas reduction can be expected from successful establishment of the former.

• KIEAE Journal
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• v.5 no.3
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• pp.17-24
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• 2005

Until today, rainwater management was processed without disposing the peak discharge, which was due to rainfall, to provide stability against flood damage. In this process, the natural hydrologic cycle changed quickly, and because of this, some problems that could harm human beings and the environment arose. These problems need to be addressed accordingly. One of the proposals was to carry out decentralized rainwater management through a natural hydrologic cycle on site, including utilization, infiltration, detention, and retention of rainwater. This study aims to set the direction of applicable decentralized rainwater management to housing complex in Korea. Therefore, spacial properties in urban housing complexes were analysed such as the impervious area-to-land ratio, the green area-to-land ratio, artificial land-to-land ratio etc. As the result of this study, when a housing complex was small and developed by reconstruction, the impervious area, artificial land, the green area in the artificial land-to-land ratio were high. So, direction of decentralized rainwater management of these housing complexes is available to utilize and detain rainwater. On the other hand, those of big housing complexes in land development district were low relatively. So, direction of decentralized rainwater management of these housing complexes is available to infiltrate and evaporate rainwater.

• KIEAE Journal
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• v.11 no.2
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• pp.59-65
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• 2011

To analyze changes in the water-balance before and after using decentralized rainwater management facilities, this study carried out hydrologic modeling based on data including roof planting, rainwater use, infiltration and detention facilities applied to the sites. The results of the analysis are as follows: First, the total runoff quantity after facility installation was about 24% less than before. In particular, it showed that the surface runoff declined significantly. Second, the analysis of the effects of different decentralized rainwater management facilities revealed that the rooftop planting contributed to about a 3.5 times increase in actual evaporation than before. Third, the analysis of the effect of decentralized management facilities by different rainfall events showed that it turned to have about a 30% decreasing effect after facility installation for a monthly rainfall over 500mm or so and about 50% declining effect for a monthly rainfall about 200mm. As discussed above, the study confirmed that it is important to implement decentralized rainwater management facilities to improve inevitable changes in water-balance arising from development as it would be a significant alternative for sustainable urban development.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.12
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• pp.321-332
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• 2020

Decentralized approaches are extensively researched by academia and industry in order to cover up the flaws of existing systems in terms of data privacy. Blockchain and decentralized learning are prominent representatives of a deconcentrated approach. Blockchain is secure by design since the data record is irrevocable, tamper-resistant, consensus-based decision making, and inexpensive of overall transactions. On the other hand, decentralized learning empowers a number of devices collectively in improving a deep learning model without exposing the dataset publicly. To motivate participants to use their resources in building models, a decent and proportional incentive system is a necessity. A centralized incentive mechanism is likely inconvenient to be adopted in decentralized learning since it relies on the middleman that still suffers from bottleneck issues. Therefore, we design an incentive model for decentralized learning applications by leveraging the Ethereum smart contract. The simulation results satisfy the design goals. We also outline the concerns in implementing the presented scheme for sensitive data regarding privacy and data leakage.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.501-508
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• 2022

The flow of global digitalization is leading to the emergence of a decentralized system environment based on blockchain or distributed ledger technology in the fields of economy, identity authentication, and logistics. Accordingly, a requirement that public services be searchable from several decentralized maritime service registries (MSRs) has been derived in terms of the discoverability of e-navigation services. This study describes a decentralized MSR environment composed of the MSR ledger and multiple local MSRs, and it has implemented a service search system that can search global e-navigation services in the environment through a web browser. This system is a decentralized application that dynamically generates service attributes, geometry information, and free text queries, and that provides users with relevant MSR and service access information from search results that are registered in the MSR ledger. In this study, we tested the established decentralized MSR environment and the system that performs service search within that environment, and we discussed its advantages and limitations.

• Proceedings of the Korea Association of Information Systems Conference
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• 1996.11a
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• pp.217-227
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• 1996

The new field of learning control develops controllers that learn to improve their performance at executing a given task, based on experience performin this specific task. In a previous work［6］, the authors presented a theory of indirect learning control based on use of indirect adaptive control concepts employing simultaneous identification ad control. This paper develops improved indirect learning control algorithms, and studies the use of such controllers in decentralized systems. The original motivation of the learning control field was learning in robots doing repetitive tasks such as on an assembly line. This paper starts with decentralized discrete time systems, and progresses to the robot application, modeling the robot as a time varying linear system in the neighborhood of the nominal trajectory, and using the usual robot controllers that are decentralized, treating each link as if it is independent of any coupling with other links. The basic result of the paper is to show that stability of the indirect learning controllers for all subsystems when the coupling between subsystems is turned off, assures convergence to zero tracking error of the decentralized indirect learning control of the coupled system, provided that the sample time in the digital learning controller is sufficiently short.

• Journal of Environmental Health Sciences
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• v.39 no.5
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• pp.474-481
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• 2013

Objectives: This study was conducted to investigate the application of microbial fuel cells (MFCs) to the wastewater treatment systems employed in the Living Building Challenge. Methods: I reviewed a range of information on decentralized wastewater treatment technologies such as composting toilets, constructed wetlands, recirculating biofilters, membrane bioreactors, and MFCs. Results: The Living Building Challenge is a set of standards to make buildings more eco-friendly using renewable resources and self-treating water systems. Although there are various decentralized wastewater treatment technologies available, MFCs have been considered an attractive future option for a decentralized system as used in the Living Building Challenge. MFCs can directly convert substrate energy to electricity with high conversion efficiency at ambient and even at low temperatures. MFCs do not require energy input for aeration if using open-air cathodes. Moreover, MFCs have the potential for widespread application in locations lacking water and electrical infrastructure Conclusions: This paper demonstrated the feasibility of MFCs as a novel decentralized wastewater treatment system employed in the Living Building Challenge.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.2
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• pp.195-203
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• 2017

This paper is concerned with the active vibration control of shell structure that is subjected to internal unbalanced excitation by using active mounts and accelerometers. The unbalanced excitation is caused by a rotating unbalanced mass. The control algorithm considered in this study is the negative acceleration feedback (NAF) control. A simplified dynamic model was derived to verify the effectiveness of the NAF control. Four actuators and four accelerometers were mounted on the shell structure, so that the multiple-input and multiple-output (MIMO) NAF controller was designed by both centralized and decentralized ways. Numerical results show that both the decentralized and centralized NAF controllers are effective. Based on the numerical simulation, the proposed decentralized NAF controller was applied to the real shell structure. Experimental results show that the proposed decentralized NAF controller can effectively suppress vibrations of the shell structure.