• Wind and Structures
• /
• v.28 no.6
• /
• pp.389-404
• /
• 2019

In coastal regions, it is common to witness significant damages on low-rise buildings caused by hurricanes and other extreme wind events. These damages start at high pressure zones or weak building components, and then cascade to other building parts. The state-of-the-art in experimental and numerical aerodynamic load evaluation is to assume buildings with intact envelopes where wind acts only on the external walls and correct for internal pressure through separate aerodynamic studies. This approach fails to explain the effect of openings on (i) the external pressure, (ii) internal partition walls; and (iii) the load sharing between internal and external walls. During extreme events, non-structural components (e.g., windows, doors or rooftiles) could fail allowing the wind flow to enter the building, which can subject the internal walls to lateral loads that potentially can exceed their load capacities. Internal walls are typically designed for lower capacities compared to external walls. In the present work, an anticipated damage development scenario is modelled for a four-story building with a stepped gable roof. LES is used to examine the change in the internal and external wind flows for different level of assumed damages (starting from an intact building up to a case with failure in most windows and doors are observed). This study demonstrates that damages in non-structural components can increase the wind risk on the structural elements due to changes in the loading patterns. It also highlights the load sharing mechanisms in low rise buildings.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.1
• /
• pp.77-87
• /
• 2022

In order to perform the scramejt engine intake ground test using the Scramjet Engine Test Facility(SETF) of the Korea Aerospace Research Institute. we introduced the test availability check procedure that is generally conducted. The design process of the newly manufactured Mach 5 nozzle for the scramjet intake test was summarized, a device for checking the core flow distribution of the nozzle was explained, and the core flow test analysis results were written. Through a series of test results, it was confirmed that the intake was located in the new Mach 5 nozzle core.

• The Journal of Engineering Geology
• /
• v.20 no.3
• /
• pp.231-242
• /
• 2010

In order to assess applicability of debris flow simulation on natural terrain in Korea, this study introduced the DEBRIS-2D program which had been developed by Liu and Huang (2006). For simulation of large debris flows composed of fine and coarse materials, DEBRIS-2D was developed using the constitutive relation proposed by Julien and Lan (1991). Based on the theory of DEBRIS-2D, this study selected a valley where a large debris flow was occurred on July 16th, 2006 at Deoksanri, Inje county, Korea. The simulation results show that all mass were already flowed into the stream at 10 minutes after starting. In 10minutes, the debris flow reached the first geological turn and an open area, resulting in slow velocity and changing its flow direction. After that, debris flow started accelerating again and it reached the village after 40 minutes. The maximum velocity is rather low between 1 m/sec and 2 m/sec. This is the reason why debris flow took 50 minutes to reach the village. The depth change of debris flow shows enormous effect of the valley shape. The simulated result is very similar to what happened in the field. It means that DEBRIS-2D program can be applied to the geologic and topographic conditions in Korea without large modification of analysis algorithm. However, it is necessary to determine optimal reference values of Korean geologic and topographic properties for more reliable simulation of debris flows.

• Journal of Korean Society of Transportation
• /
• v.22 no.3 s.74
• /
• pp.109-125
• /
• 2004

In recent decades, microscopic simulation models have become powerful tools to analyze traffic flow on highways and to assist the investigation of level of service. The existing microscopic simulation models simulate an individual vehicle's speed based on a constant free-flow speed dominantly specified by users and driver's behavior models reflecting vehicle interactions, such as car following and lane changing. They set a single free-flow speed for a single vehicle on a given link and neglect to consider the effects of highway design elements to it in their internal simulation. Due to this, the existing models are limitted to provide with identical simulation results on both curved and tangent sections of highways. This paper presents a model developed to estimate the change of free-flow speeds based on highway design elements. Nine neural network models were trained based on the field data collected from seven different freeway curve sections and three different locations at each section to capture the percent changes of free-flow speeds: 100 m upstream of the point of curve (PC) and the middle of the curve. The model employing seven highway design elements as its input variables was selected as the best : radius of curve, length of curve, superelevation, the number of lanes, grade variations, and the approaching free-flow speed on 100 m upstream of PC. Tests showed that the free-flow speeds estimated by the proposed model were statistically identical to the ones from the field at 95% confidence level at each three different locations described above. The root mean square errors at the starting and the middle of curve section were 6.68 and 10.06, and the R-squares at these points were 0.77 and 0.65, respectively. It was concluded from the study that the proposed model would be one of the potential tools introducing the effects of highway design elements to free-flow speeds in simulation.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.1
• /
• pp.1-9
• /
• 1984

In the utilization of solar energy most often a flat solar collector is used for solar heating, system. Since solar energy is absorbed through this solar collector, it is considered to be a most important part in the whole solar heating system. The purpose of the present investigation is to evaluate the influence of varying design parameters for thermal performances of flat-plate solar collector. By analysing these parameters, optimum design of solar collector would become possible. Specification of the existing solar collector are utilized in calculation as a starting point. Analysis is carried out numerically for "Unit Solar Collector" which is composed of fin and tube. Among design parameters. such parameters as mass flow rate per unit area, tube spacing and fin thickness are selected as variables in the computer simulation model. Results are presented for thermal performances of flat-plate solar collector for each important design parameters, so that predictions become possible through numerical analysis without performing experiments whenever it is required. required.

• Proceedings of the KIEE Conference
• /
• 1991.11a
• /
• pp.304-306
• /
• 1991

A new gas-flow type reactor for plasma polymerization was developed to symthesize functional polymer, which enhances the reaction of radicals activated in discharge. $\alpha$-Methylstyrene was used for the polymerization, which are known as starting monomers for the polymer with degradating characteristics. The molecular structure and molecular weight distribution of the polymers were studied.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.1
• /
• pp.25-32
• /
• 1988

Vehicle platoons starting a stopline are dispersed while travelling along the street and the delay at the next intersection depends on the arrival pattern of dispersed traffic flow. In this paper, the platoon dispersion charactiristics of our country, especially the time gap between passenger cars and buses caused by the dwell time at bus stops, were investigated through travel time surveys. Based on the survey results, on improved analysis method of intersection delay is proposed.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 1993.10a
• /
• pp.779-790
• /
• 1993

A prototype of the feeding-milking robot was developed in the Hungarian Institute of Agricultural Engineering in 1988-89. Before starting with the operation tests the cleaning system had to be elaborated . The cleaning system has two parts. Those are the complete cleaning of the system, producing a practically sterile state, as well as flushing through the milking device between milking of two cows. Separate electronic sensor development was necessary for both system which can connect to the control system of the robot. To clean the system pneumatic air input was applied. As an effect of the local adjustment of the electronic control system optimal flow conditions can be formed what is more favourable comparing to the earlier solutions of cleaning due to the mechanical effect. In the flushing through overpressure air is applied. The air and the cleaning liquid input duration can be adjusted to the local conditions. The electronic control unit can be connected to the electric ircuits of robot.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.54 no.10
• /
• pp.470-476
• /
• 2005

In this paper PU control scheme is presented. The proposed scheme has following features. The one is oft-starting method which is used for preventing to flow large current in motor phase winding when motor starts. The ther is the selection of the level of the over current. The first feature is implemented by increasing the PWM duty lowly, the second feature is implemented by limiting the magnitude of the phase current level by which the over heat f motor by copper losses and magnetic saturation decreases. By the analysis using FEM considering load condition, the peed of mode transition from PW to single pulse control is selected and confirmed by simulation that there is no ver current occurs during the mode transition. For the verification of proposed scheme, the simulation using MATLAB Simulink with considering non-linearity of inductance profile from FEM analysis is performed and the experiment with SRM drive system which has the DSP controller and single Phase SRM are peformed.

• Proceedings of the Korea Society for Simulation Conference
• /
• 2001.10a
• /
• pp.269-273
• /
• 2001

Semiconductor wafer fabrication is a business of high capital investment and fast changing nature. To be competitive, the production in a fab needs to be effectively planned and scheduled starting from the ramping up phase, so that the business goals such as on-time delivery, high output volume and effective use of capital intensive equipment can be achieved. In this paper, we propose Stand Alone layout and In-Line layout are analyzed and compared while varying number of device variable changes. The comparison is performed through simulation using ProSys; a window 98 based discrete system simulation software, as a tool for comparing performance of two proposed layouts. The comparison demonstrates that when the number of device variable change is small, In-Line layout is more efficient in terms of production quantity. However, as the number of device variable change is more than 14 titles, Stand Alone layout prevails over In-Line layout.