• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.521-527
• /
• 2011

Korea announced GHG reduction goal, 30% reduction compare with 2020 BAU and reduction target for each industry sector is planning. Transportation sector also trying to make effective technical and political counterplan of allocated GHG reduction target such as material lightening, energy efficiency improvement and Modal shift technology and so on. Modal Shift is shifting low energy efficiency vehicle to high energy efficiency vehicle which is economically meaningful under current market conditions. We can get not only energy efficiency improvement but also GHG reduction effect through modal shift. Modal Shift is effectively applying and studied in logistics field in Europe and Japan and one of the Indian companies has been registered CDM project activity involving modal shift from roadways to railways for finished goods. In this study, the scenarios are developed with detail modal shift ratio and fuel type base on state of road and rail use and GHG emission factor for each fuel type from MLTM. This result can be used as basic information to improve policies and promote increasing use of train which is more environment friendly transportation vehicle.

• Structural Engineering and Mechanics
• /
• v.33 no.2
• /
• pp.215-238
• /
• 2009

This paper introduces an improved modal pushover analysis (IMPA) which can effectively evaluate the seismic response of multi-span continuous bridge structures on the basis of modal pushover analysis (MPA). Differently from previous modal pushover analyses which cause the numerical unstability because of the occurrence of reversed relation between the pushover load and displacement, the proposed method eliminates this numerical instability and, in advance the coupling effects induced from the direct application of modal decomposition by introducing an identical stiffness ratio for each dynamic mode at the post-yielding stage together with an approximate elastic deformation. In addition to these two introductions, the use of an effective seismic load, calculated from the modal spatial force and applied as the distributed load, makes it possible to predict the dynamic responses of all bridge structures through a simpler analysis procedure than those in conventional modal pushover analyses. Finally, in order to establish validity and applicability of the proposed method, correlation studies between a rigorous nonlinear time history analysis and the proposed method were conducted for multi-span continuous bridges.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.409-416
• /
• 2004

An active modal-fuzzy control method using hydraulic actuators is presented for seismic response reduction. In the proposed control system, a new fuzzy controller designed in the modal space produces the desired active control force. This type controller has all advantages of the fuzzy control algorithm and modal approach. Since it is very difficult to select input variables used in fuzzy controller among an amount of state variables in the active fuzzy control system the presented algorithm adopts the modal control algorithm which is able to consider more easily information of all state variables in civil structures that are usually dominated by first few modes. In other words, all information of the whole structure can be considered in the control algorithm evaluated to reduce seismic responses and it can be efficient for especially civil structures. In addition, the presented algorithm is expected to magnify utility and performance caused by efficiency that the fuzzy algorithm can handle complex model more easily. An active modal-fuzzy control scheme is applied together with a Kalman filter and a low-pass filter to be applicable to real civil structures. A Kalman filter is considered to estimate modal states and a low-pass filter was used to eliminate spillover problem. The results of the numerical simulations far a wide amplitude range o f loading conditions and for historic earthquakes having various frequency components show that the proposed active modal-fuzzy control system can be beneficial in reducing seismic responses of civil structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.1467-1475
• /
• 2007

This paper investigates the modal acoustic power by a cascade of flat-plate airfoils interacting with homogeneous, isotropic turbulence. Basic formulation for the acoustic power upstream and downstream is based on the analytical theory of Smith and its generalization due to Cheong et al. The acoustic power spectrum has been expressed as the sum of cut-on acoustic modes, whose modal power is the product of three terms: a turbulence series, an upstream or downstream power factor and an upstream or downstream acoustic response function. The effect of these terms in the modal acoustic power has been examined. For isotropic turbulence gust, the turbulent series are only reducing factor of the modal acoustic power. The power factor tends to reduce the modal acoustic power in the upstream direction, although the power factor is liable to increase the modal acoustic power in the downstream direction. The modes close to cut-off are decreasing strongly, especially in the downstream direction. Therefore the modes close to cut-off don't contribute highly to the radiated acoustic power in the downstream direction, although the modal acoustic pressure is high for these modes.

• Earthquakes and Structures
• /
• v.10 no.5
• /
• pp.1067-1087
• /
• 2016

In this paper, a decoupled proportional-integral-derivative (PID) control approach for seismic control of smart structures is presented. First, the state space equation of a structure is transformed into modal coordinates and parameters of the modal PID control are separately designed in a reduced modal space. Then, the feedback gain matrix of the controller is obtained based on the contribution of modal responses to the structural responses. The performance of the controller is investigated to adjust control force of piezoelectric friction dampers (PFDs) in a benchmark base isolated building. In order to tune the modal feedback gain of the controller, a suitable trade-off among the conflicting objectives, i.e., the reduction of maximum modal base displacement and the maximum modal floor acceleration of the smart base isolated structure, as well as the maximum modal control force, is created using a multi-objective cuckoo search (MOCS) algorithm. In terms of reduction of maximum base displacement and story acceleration, numerical simulations show that the proposed method performs better than other reported controllers in the literature. Moreover, simulation results show that the PFDs are able to efficiently dissipate the input excitation energy and reduce the damage energy of the structure. Overall, the proposed control strategy provides a simple strategy to tune the control forces and reduces the number of sensors of the control system to the number of controlled stories.

• Smart Structures and Systems
• /
• v.19 no.6
• /
• pp.653-663
• /
• 2017

The modal parameters of the deck of Runyang Suspension Bridge (RSB) as well as their relationships with wind and temperature are studied based on the data recorded by its Structural Health Monitoring System (SHMS). Firstly, frequency analysis on the vertical responses at the two sides of the deck is carried out to distinguish the vertical and torsional vibration modes. Then, the vertical, torsional and lateral modal parameters of the deck of RSB are identified using Hilbert-Huang Transform (HHT) and validated by the identified results before RSB was opened to traffic. On the basis of this, the modal frequencies and damping ratios of RSB during the whole process of Typhoon Masta are obtained. And the correlation analysis on the modal parameters and wind environmental factors is then conducted. Results show that the HHT can achieve an accurate modal identification of RSB and the damping ratios show an obvious decay trend as the frequencies increase. Besides, compared to frequencies, the damping ratios are more sensitive to the environmental factors, in particular, the wind speed. Further study on configuring the variation law of modal parameters related with environmental factors should be continued.

• Korean Journal of Child Studies
• /
• v.7 no.1
• /
• pp.67-84
• /
• 1986

The purpose of the present research was to investigate cross-modal transfer, especially tactual-to-visual transfer in infancy and to study the relation between failure of cross-modal transfer performance and length of familiarization period. The subjects of this study were 60 infants, 10 boys and 10 girls at each level: six, nine, and twelve months of age. All were normal, healthy, full-term babies. The mothers' educational achievement was controlled at more than 12 years of schooling. There were two separate experimental conditions, one 30-sec and one 60-sec familiarization period. Each experimental condition consisted of a tactual familiarization and a visual recognition memory test. Each child was presented with these 2 sets of cross-modal stimuli in one of the 2 experimental conditions. Infants' visual responses in the visual recognition memory test were videotaped for 20 seconds. Visual fixation time to novel and familiar stimuli was observed throughout the test. The data was analyzed with t-test, percentage of total fixation time to novel stimuli, and ANOVA. The results showed that: 1) Significant differences were found in the cross-modal transfer performance from touch to vision between the 3 age groups. This is, 6 and 9 month old infants didn't show cross-modal transfer in the 30-sec condition, but 12 month old infants did show cross-modal transfer in the 30-second. 2) In all 3 age groups, no significant differences were found in cross-modal transfer performance between the two conditions.

• Structural Engineering and Mechanics
• /
• v.65 no.1
• /
• pp.43-51
• /
• 2018

Structural modal parameters i.e. natural frequencies, damping ratios and mode shapes are dynamic features obtained either by measuring the vibration responses of a structure or by means of finite elements models. Over the past two decades, modal parameters have been used to detect damage in structures by observing its variations over time. However, such variations can also be caused by environmental factors such as humidity, wind and, more importantly, temperature. In so doing, the use of modal parameters as damage indicators can be seriously compromised if these effects are not properly tackled. Many researchers around the world have found numerous methods to mitigate the influence of such environmental factors from modal parameters and many advanced damage indicators have been developed and proposed to improve the reliability of structural health monitoring. In this paper, several vibration tests are performed on a simply supported steel beam subjected to different damage scenarios and temperature conditions, aiming to describe the variation in modal parameters due to temperature changes. Moreover, four statistical methodologies are proposed to identify damage. Results show a slightly linear decrease in the modal parameters due to temperature increase, although it is not possible to establish an empirical equation to describe this tendency.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.778-785
• /
• 2006

In this paper, two possible ways for mode shape expansion are proposed and opened for discussion for future use. The first method minimizes the modal flexibility error between the experimental and analytical mode shapes corresponding to the measured DOFs to find the multiplication matrix which can be treated as the least-squares minimization problem. In the second method, Normalized Modal Difference (NMD) is used to calculate multiplication matrix using the analytical DOFs corresponding to measured DOfs. This matrix is then used to expand the measured mode shape to unmeasured DOFs. A simulated simply supported beam is used to demonstrate the performance of the methods. These methods are then compared with two most promising existing methods namely Kidder dynamic expansion and Modal expansion methods. It is observed that the performance of the modal flexibility method is comparable with existing methods. NMD also have the potential to expand the mode shapes though it is seen more sensitive to the distribution of error between FEM and actual test data.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2005.03a
• /
• pp.513-520
• /
• 2005

An active modal-fuzzy control method using hydraulic actuators is presented for seismic response reduction. In the proposed control system, a new fuzzy controller designed in the modal space produces the desired active control force. This type controller has all advantages of the fuzzy control algorithm and modal approach. Since it is very difficult to select input variables used in fuzzy controller among an amount of state variables in the active fuzzy control system, the presented algorithm adopts the modal control algorithm which is able to consider more easily information of all state variables in civil structures that are usually dominated by first few modes. In other words, all information of the whole structure can be considered in the control algorithm evaluated to reduce seismic responses and it can be efficient for especially civil structures. In addition, the presented algorithm is expected to magnify utility and performance caused by efficiency that the fuzzy algorithm can handle complex model more easily. An active modal-fuzzy control scheme is applied together with a Kalman filter and a low-pass filter to be applicable to real civil structures. A Kalman filter is considered to estimate modal states and a low-pass filter was used to eliminate spillover problem. The results of the numerical simulations for a wide amplitude range of loading conditions show that the proposed active modal-fuzzy control system can be beneficial in reducing seismic responses of civil structures.