• Structural Engineering and Mechanics
• /
• v.52 no.2
• /
• pp.275-290
• /
• 2014

In this paper, Simple Adaptive Control (SAC) method is used to mitigate the detrimental effects of earthquakes on MR-damper equipped structures. Acceleration Feedback (AF) is utilized since measuring the acceleration response of structures is known to be reliable and inexpensive. The SAC is simple, fast and as an adaptive control scheme, is immune against the effects of plant and environmental uncertainties. In the present study, in order to translate the desired control force into an applicable MR damper command voltage, a neural network inverse model is trained, validated and used through the simulations. The effectiveness of the proposed AF-based SAC control system is compared with optimal H2/LQG controllers through numerical investigation of a three-story model building. The results indicate that the SAC controller is substantially effective and reliable in both undamaged and damaged structural states, specifically in reducing acceleration responses of seismically excited buildings.

• ETRI Journal
• /
• v.15 no.3
• /
• pp.1-26
• /
• 1994

Simulated annealing is an attractive, but expensive, heuristic method for approximating the solution to combinatorial optimization problems. Attempts to parallel simulated annealing, particularly on distributed memory multicomputers, are hampered by the algorithm's requirement of a globally consistent system state. In a multicomputer, maintaining the global state S involves explicit message traffic and is a critical performance bottleneck. To mitigate this bottleneck, it becomes necessary to amortize the overhead of these state updates over as many parallel state changes as possible. By using this technique, errors in the actual cost C(S) of a particular state S will be introduced into the annealing process. This paper places analytically derived bounds on this error in order to assure convergence to the correct optimal result. The resulting parallel simulated annealing algorithm dynamically changes the frequency of global updates as a function of the annealing control parameter, i.e. temperature. Implementation results on an Intel iPSC/2 are reported.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.10a
• /
• pp.490-495
• /
• 2000

This paper presents the dynamic behavior of stay cable with Lead-Shear damper( LSD) near the support. This kind of research about the dynamic behavior of LSD is essential to design LSD in order to mitigate the ambient vibration of stay cable. The hysteresis curve of LSD was assumed to be perfect elasto-plastic behavior based on the real hysteretic behavior of such lead-based dampers. Mechanical model of LSD was equivalent Kelvin model and sag effect of stay cable was considered. Yielding force (also referred as size) of LSD was selected as a design parameter. Effects of tension of stay cable and installation point of LSD were studied. It was found that optimal size of LSD exists for each case of stay cable.

• Korean Journal of Optics and Photonics
• /
• v.11 no.6
• /
• pp.447-451
• /
• 2000

In this paper, an adaptive equalizer which has been widely used in communication channel and high-density storage system was adopted to mitigate ISI and improve BER generated during storage and retrieval process of the digital holographic memory system. Our experimental results show that the BER performance with an adaptive equalizer is improved about 19.6% on average compared to the binary-decision process by global thresholding. lding.

• Journal of Navigation and Port Research
• /
• v.36 no.4
• /
• pp.321-327
• /
• 2012

Logistics in a supply chain network has become an important operational strategy in a competitive market. A number of internal and external risks involved in the logistics operations in a company tend to create problems in fulfilling customer orders. This research presents how ERM (enterprise risk management) can be used to identify, assess, and control logistics risks. An electronic company's logistics activities were used as an industry case to demonstrate a way to identify and assess risks surrounding global logistics function. This paper has further presented action plans to mitigate the impact of the risks that occur.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.515-520
• /
• 2011

The Climate Change has been emerged as one of the most important social and economic issues and is affecting our daily life. The Post-Kyoto Protocol aims to reduce GHG(Greenhouse Gas) emission and mitigate climate change. Under this protocol, developed countries which are classified as Annex I implements programmes and strategies confronting against the climate change. South Korea has set voluntary GHG reduction goal of 30% reduction compared to BAU(Business As Usual) in 2020 and prepares National GHG inventory system and Negotiated Agreements(NA) with industries. It will affect seriously to industry and transport sector and its obligation to reduce GHG emission will be strengthened gradually. Therefore, there will be large impact on industry structure. In Korea, various strategies against climate change are being prepared as researches of development of GHG emission reduction technologies and integrated GHG emission management system in transport sector. In this study, strategy on climate change in transport sector is proposed by being based on developed countries' respond to climate change in transport sector.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.232-238
• /
• 2011

Hazard analysis provides the basic foundation for system safety. Hazard analysis is performed to identify hazards, hazard effects, and hazard causal factors. Hazard analysis is used to determine system risk, to determine the significance of hazards, and to establish design measures that will eliminate or mitigate the identified hazards. Hazard analysis is used to systematically examine systems, subsystems, facilities, components, software, personnel, and their interrelationships, with consideration given to logistics, training, maintenance, test, modification, and operational environments. This paper present hazard analysis techniques which is commonly used in railway signalling, comparised their benefits and limitations.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.2838-2843
• /
• 2011

Recently, the floating slab track that can effectively mitigate the vibration and structure-borne noise is being discussed to be adopted. The floating slab track which is a track system isolated from the sub-structure by vibration isolators. Unsimilarly to conventional track and the slab deflection is large. Therefore, the running safety and ride comfort should be investigated. Especially at slab joint since the load cannot be transferred, the possibility that the dynamic behavior of track and train became unstable is high. Thus, in general dowel bar are often installed at slab joints. To determine the appropriate dowel ratio the load transfer characteristics should be investigated. In this study, dowel bar joint is modeled by equivalent shear spring and this model is verified by comparison with experimental results. Using the proven model, the load transfer efficiency and deflection at slab joint according to dowel ratio, and stiffness and spacing of vibration isolator were examined.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.1624-1630
• /
• 2011

Currently the train operating environment to affect track irregularity is changed rapidly such as speed-up, linear improvement and rolling stack upgrade. The recent track maintenance criteria of track irregularity was quoted from past Japan's, and the needs of revision of criteria are increased because of the rapid change in train operating environment. In case of enhance the track irregularity criteria, it secure driving safety and riding comfort but maintenance cost are increase. And also decrease ballast durability by frequent corrective work. In case of mitigate the criteria, it decrease driving safety and riding comfort, but save the maintenance cost. The study for enacting rational criteria did not carry out so far. In this study, survey the domestic and international track irregularity and case study for track irregularity inspection results and maintenance history for guideline of enacting irregularity criteria study.

• The KSFM Journal of Fluid Machinery
• /
• v.15 no.3
• /
• pp.51-56
• /
• 2012

This study analyzed the influence of firing biogas on the performance and operation of a gas/steam turbine combined system. A reference gas/steam turbine combined system, designed with biogas fuel(57% volumetric methane) was set up and off-design simulation was made to investigate operating characteristics when a couple of operating schemes to mitigate turbine blade overheating were applied. Performance at base-load operation using each scheme was compared and part load operation using the variable inlet guide vane was analysed. Also, differences in operating characteristics and performance caused by changes in the methane content of biogas and ambient temperature were examined.