• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.6 s.52
• /
• pp.93-102
• /
• 2006

Control input's saturation of active control devices for large structures under large external disturbances are often occurred. It is more difficult to obtain the exact values of mass and stiffness as structures are higher. The modelling errors between mathematical models and real structures must be also included as parameter uncertainties. Therefore, in active vibration control of civil engineering structures like buildings and bridges, the robust saturation controller design method considering both control input's saturation and parameter uncertainties of system is needed. In this paper, stabilities of linear optimal controller LQR, modified bang-bang controller, saturated sliding mode controller, and robust saturation controller among various controllers which have been studied and applied to active vibration control of buildings are investigated. Especially, unstable phenomena of the LQR, the modified bang-bang controller and the saturated sliding mode controller when the control input is saturated or parameter uncertainties exist are presented to show the necessity of the robust saturation controller. The robust stability of the robust saturation controller are shown through a numerical example of a 2DOF linear vibrating system and an experimental test of the two-story structure with an active mass damper (AMD).

• Journal of Korea Spatial Information System Society
• /
• v.11 no.1
• /
• pp.145-156
• /
• 2009

Ubiquitous City(U-City) in Korea is not a fantastic wonderland but an on-going real phenomenon. Many researchers so far have mainly dealt with a rosy future where U-City would potentially promise the high Quality of Life and positive economic effects. However, a suspicion of unexpected disadvantages can be able to take place in the bright future of U-City : the running cost of U-City. Without full consideration of it, descendants living in the U-City in near future will suffer from the heavy burden in operating the U-City. Given this circumstantial background, the aim of this study is to indicate potential solutions to address a sustainable U-City controlled by the virtuous cycled mechanism toward a self-sufficient city, which will illuminate a new paradigm of the city history. Solutions were sought from the several viewpoints, which were behavioral and institutional aspects, developing profitable business models and core technologies applicable to U-City, and building self-owned networks. Based on this preliminary study, further efforts and devotion to seeking virtuous-cycled U-City model will contribute to bringing a prominent future of U-City whose belongings will be able to manage to enjoy better quality of life.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.2
• /
• pp.79-86
• /
• 2014

This paper describes an integrity evaluation method for emergency diesel generator(EDG) and rotor part of EDG. EDG is a very important equipment in the nuclear power plant(NPP). EDG supplies electricity to the safety-related equipments for the safety shut down of NPP in an emergency situation of earthquake. The safety of the rotor part of EDG is also important during seismic impact from earthquake. The finite element modelling of the EDG including rotor part was constructed. The modal analysis of EDG was firstly performed. The first natural frequency was calculated and revealed higher than the cutoff frequency of seismic spectrum. Then the stress analysis was done to compare with the allowable stress. The safety of the rotor part was investigated by the finite element analysis of the rotor and journal bearing interaction to find film thickness and critical speed. The seismic load was applied to rotor part in a manner that the load was a weighted static load. Analysis results showed that the maximum stress was within the range of allowable stress and the film thickness is larger than the permissible minimum thickness, and the critical speed was out of the operating speed. Hence, the structural and dynamic integrity of EDG could be confirmed by the numerical analysis method used in this paper. However, dynamic analysis of a rotating rotor and supporting bearing with the seismic impact needs to be investigated in a more rigorous method since the seismic load to the rotating part complicates the behavior of rotating system.

• Journal of Yeungnam Medical Science
• /
• v.20 no.2
• /
• pp.160-168
• /
• 2003

Background: Confirm the stability of intervertebral disc sustaining each fused lumbar spine cases, comparing vertical compression, A-P shear force and rotational moment on intervertebral disc of instrumented lumbar spine with simple vertical compression load and follower load using finite element analysis. Materials and Methods: We analyze the stability of intervertebral disc L4-5 supporting fused lumbar spine segments. After performing finite element modelling about L1-L5 lumbar vertebral column and L1-L4 each fusion level pedicle screw system for fused lumbar spine fine element model. Intervertebral discs with complex structure and mechanical properties was modeled using spring element that compensate stiffness and tube-to-tube contact element was employed to give follower load. Performing geometrical non-linear analysis. Results: The differences of intervertebral disc L4-5 behavior under the follower compression load in comparision with vertical compression load are as follows. Conclusion: As a result of finite element interpretation of instrumented lumbar spine, the stability of L4-5 sustaining fused lumbar segment, the long level fused lumbar spine observed hing stability under follower load. This research method can be the basis tool of effects prediction for instrumentation, a invention of a more precious finite element interpretation model which consider the role of muscle around the spine is loaded.

• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.12
• /
• pp.821-827
• /
• 2014

The 4major river project has caused changes in flow and water quality patterns in major rivers in Korea including the Nakdong River where several toxicant release accidents have had occurred. Three dimensional hydrodynamic model, the Environmental Fluid Dynamics Code (EFDC), was applied to evaluate the effect of geomorphological change of the river on the advection and dispersion patterns of a conservative toxic pollutant. A hypothetical scenario was developed using historical data by assuming a toxic release from an upstream location. If there is a toxic release at the Gumi Industrial Complex, the toxic material would be detected after 2.22 and 9.83 days at Chilgok and Gangjung weir, respectively, in the new river system. It was estimated that they took at least 12 times longer than those with the river conditions before the project. Effect of relocation of intake towers for Daegu Metro City to upstream of Gumi City was also evaluated using the developed modeling system. It was observed that hydraulic residence time would be increased due to decreased flow rate and thus due to lowered water level. However, peak concentration differences were found to be about 2% lower in both places due to increased dispersion effect after the relocation.

• Journal of the Korean Geotechnical Society
• /
• v.33 no.3
• /
• pp.29-36
• /
• 2017

It has been known that rockbolt is one of important supports improving the support capacity with shotcrete in NATM tunnel. Also, it is necessary for the inclined system bolting to enhance the efficiency of installation in case of a narrow space such as cross passage and enlargement tunnel. However, there is no profound technical study for the effect of inclined rockbolt of systematic installation on the support mechanism and ground behaviour in NATM tunnel. In this study, the effects of the length and installation angle of rockbolt on the characteristics of support and ground reinforcement were analyzed by using 3D finite element numerical study. Through the numerical results for the parametric modelling of inclined rockbolt, the characteristics of mechanical behaviors between the axial force of rockbolt and the effect of ground reinforcement in regard to the various factors of the length and installation angle of rockbolt were verified and reviewed thoroughly. Also, it was shown that the installation angle of rockbolt for enhancing the arching effect in NATM tunnel was $45^{\circ}$, and the difference of the reinforcing effect for support between the installation angles of $75^{\circ}$ and $90^{\circ}$ was insignificant. The additional numerical studies for various condition would be carried out for practical design guideline of inclined rockbolt.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.20 no.2
• /
• pp.75-88
• /
• 2017

This study analyzed wind flows based on spatial and geomorphological characteristics of Daegu Metropolitan City. A three-stage analysis was performed, starting with a comparison of meteorological relationships between local wind direction (synoptic wind) and local wind flow. In the second stage the study area was subdivided into districts and suburban districts to analyze the relative change of local wind flow. In stage three, the formation of wind corridor for local wind flow, wind flow for the entire urban space, and spatial relationships between flows were verified comparatively using KLAM_21. Three results are notable, the first of which is a low correlation between synoptic wind of a region, and local wind, flow in terms of meteorology. Secondly, observations of local wind flow at five downtown districts and two suburban districts showed that there were diverse wind directions at each measurement point. This indicates that the spatial and geomorphological characteristics of areas neighboring the measurement points could affect the local wind flow. Thirdly, verifying the results analyzed using KLAM_21, compared to Atomatic Weather System(AWS) measurement data, confirmed the reliability of the numerical modelling analysis. It was determined that local wind flow in a city performs a spatial function and role in ameliorating the urban heat island phenomena. This indicates that, when an urban planning project is designed, the urban heat island phenomena could be ameliorated effectively and sustainably if local wind flow caused by immediate spatial and geomorphological characteristics is confirmed systematically and techniques are intentionally applied to connect the flows spatially within areas where urban heat islands occur.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.20 no.2
• /
• pp.166-174
• /
• 2018

Potato(Solanum tuberosum L.) is one of the major food crop in the world following rice, wheat, and maize. It is thus important to project yield predict of potato under climate change conditions for assessment of food security. A crop growth modelling is widely used to simulate crop growth condition and total yield of various crops under a given climate condition. The decision support system for agrotechnology transfer (DSSAT) cropping system model, which was developed by U.S. which package integrating several models of 27 different crops, have been used to project crop yield for the impact assessment of climate change on crop production. In this study, we simulated potato yield using RCP 8.5 climate change scenario data, as inputs to the DSSAT model in five regions of Korea. The genetic coefficients of potato cultivar for 'superior', which is one of the most widely cultivated potato variety in Korea were determined. The GenCalc program, which is a submodule of the DSSAT package, was used to determine the genetic coefficients for the superior cultivar. The values of genetic coefficients were validated using results of 39 experiments performed over seven years in five regions. As a case study, the potato yield was projected that total yields of potato across five regions would increase by 26% in 2050s but decrease by 17% in 2090s, compared with 2010s. These results suggested that the needs for cultivation and irrigation technologies would be considerably large for planning and implementation of climate change adaptation for potato production in Korea.

• Fire Science and Engineering
• /
• v.30 no.5
• /
• pp.74-81
• /
• 2016

This study evaluated the habitability of operators for main control room fires in nuclear power plants. Fire modeling (FDS v.6.0) was utilized for a fire safety assessment so that it could determine the performance of the smoke ventilation and operator habitability with the main control room. For this study, it categorized fire scenarios into three cases depending on the conditions in the HVAC system. As a result of fire modelling, it showed that Case 1 (with HVAC) would give rise to the worst situation associated with the absolute temperature, radiative heat flux, optical density, and smoke layer height as deliberating the habitability and smoke ventilation. On the other hand, it showed that Cases 2 (w/o HVAC) and 3 can maintain much safer situations than Case 1. In the case of temperature at 820 s, Cases 2 and 3 were up to approximately 63% greater than Case 1 in the wake of ignition. In addition, the influence of radiative heat flux of Case 1 was even larger than Cases 2 and 3. That is, the radiative heat fluxes of Cases 2 and 3 were approximately 68% higher than Case 1. Furthermore, when it comes to considering the optical density, Case 1 was approximately 93% greater than Cases 2 and 3. Accordingly, it expected that the HVAC system can influence a the performance on the smoke ventilation that can be sustainable for operator habitability. On the other hand, it revealed an inconsecutive pattern for the smoke layer height of Cases 2 and 3 because supply vents and exhaust vents were installed within the same surface.

• Journal of Korean Society for Geospatial Information Science
• /
• v.1 no.1 s.1
• /
• pp.141-152
• /
• 1993

This study aims to generate digital elevation model from digital satellite imagery. Digital elevation model is being increasingly used for geo-spatial information system database development and for digital map production. Image matching technique was applied to acquire conjugate image coordinates and the algorithm for digital elevation model generation is presented in this study The exterior orientation parameters of the satellite imagery is determined by bundle adjustment and standard correlation was applied for image matching conjugate of image points. The window as well as the searching area have to be defined in image matching. Different sizes of searching area were tested to study the appropriate size of the searching area. Various coordinate transformation methods were applied to improve the computation speed as well as the geometric accuracy. The results were then statistically analysed after which the searching area is determined with the safety factor. To evaluate the accuracy of digital elevation model, 3-D coordinates were extracted from 1/5000 scale topographic map and this was compared to the digital elevation model generated from satellite imagery. The algorithm for generation of digital elevation model generated from satellite imagery is presented in this study which will prove effective in the database development of geo-spatial information system and in digital elevation modelling of large areas.