• Journal of Environmental Science International
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• v.21 no.5
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• pp.613-622
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• 2012

A pilot-scale pulse-jet bagfilter was designed, built and tested for the effects of four operating conditions (filtration velocity, inlet dust concentration, pulse pressure, and pulse interval time) on the total system pressure drop, using coke dust from a steel mill factory. Two models were used to predict the total pressure drop according to the operating conditions. These model parameters were estimated from the 180 experimental data points. The empirical model (EM) with filtration velocity, areal density, inlet dust concentration, pulse interval time and pulse pressure shows the best correlation coefficient (R=0.971) between experimental data and model predictions. The empirical model was used as it showed higher correlation coefficient (R=0.971) compared to that of the Multivariate linear regression(MLR) (R=0.961). The minimum pulse pressure predicted by empirical model (EM) was 5kg/$cm^2$.

• Geotechnical Engineering
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• v.13 no.5
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• pp.19-34
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• 1997

Classical earth pressure theories normally assume that ground condition remains uniform for considerable distance from the wall, and that the movement of the wall is enough to result in the development of an active pressure distribution. In the case of many low gravity walls in cut, constructed, for example, by using gabions or cribs, this is not commonly the case. In strong ground a steep temporary face will be excavated for reasons of economy, and a thin wedge of backfill will be placed behind the wall following its construetion. A designer then has the difficulty of selecting appropriate soil parameters and a reasonable method of calculating the earth pressure on the w리1. This paper starts by reviewing the existing solutions applicable to such geometry. A new silo and a wedge methods are developed for static and dynamic cases, and the results obtained from these are compared with two experimental results which more correctly mod el the geometry and strength of the wall, the fill, and the soil condition. Conclusions are drawn concerning both the magnitute and distribution of earth pressures to be supported by such walls.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.662-669
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• 2016

In this work, nonlinear control of a three-phase shunt active power filter (SAPF) has been studied and compared to classical control based on proportional integral regulator. The control strategy is based on the direct current method using sliding mode control (SMC), where the aim is to regulate the average voltage across the dc bus of the inverter. Details are given for the control algorithm; the controller is comprised of a current loop which utilizes a hysteresis controller to generate the gating signals for the switching devices, and a nonlinear controller based on SMC law which is different from classical laws based on error between reference and measured output voltage of the inverter. Sliding surface applied in this work contains the whole of state variables, in order to ensure full control of the system behavior in the presence of disturbances that affect the supply source, the load parameters or the reference value. The designed controller offers advantage that it can gives the improvement of dynamic and static performances in cases of large disturbances. A comparison of the effects of PI control and SMC on the APF response in steady stat, under line variations, load variations, and different component variations is performed.

• Earthquakes and Structures
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• v.6 no.6
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• pp.689-713
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• 2014

The seismic vulnerability of stone masonry buildings is studied on the basis of their fragility curves. In order to account for out-of-plane failure modes, normally disregarded in past studies, linear static Finite Element analysis in 3D of prototype regular buildings is performed using a nonlinear biaxial failure criterion for masonry. More than 1100 analyses are carried out, so as to cover the practical range of the most important parameters, namely the number of storeys, percentage of side length in exterior walls taken up by openings, wall thickness, plan dimensions and number of interior walls, type of floor and pier height-to-length ratio. Results are presented in the form of damage and fragility curves. The fragility curves correspond well to the damage observed in masonry buildings after strong earthquakes and are in good agreement with other fragility curves in the literature. They confirm what is already known, namely that buildings with stiff floors or higher percentage of load-bearing walls are less vulnerable, and that large openings, taller storeys, larger number of storeys, higher wall slenderness and higher ratio of clear height to horizontal length of walls increase the vulnerability, but show also by how much.

• Earthquakes and Structures
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• v.6 no.6
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• pp.627-646
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• 2014

Adobe is one of the oldest construction materials that is still used in many seismic countries, and different construction techniques are found around the world. The adobe material is characterized as a brittle material; it has acceptable compression strength but it has poor performance under tensile and shear loading conditions. Numerical modelling is an alternative approach for studying the nonlinear behaviour of masonry structures such as adobe. The lack of a comprehensive experimental database on the adobe material properties motivated the study developed here. A set of a reference material parameters for the adobe were obtained from a calibration of numerical models based on a quasi-static cyclic in-plane test on full-scale adobe wall representative of the typical Peruvian adobe constructions. The numerical modelling, within the micro and macro modelling approach, lead to a good prediction of the in-plane seismic capacity and of the damage evolution in the adobe wall considered.

• Ocean Systems Engineering
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• v.8 no.3
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• pp.247-279
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• 2018

This study aims to investigate the behavioral characteristics of the LWSCR (lazy-wave steel catenary riser) for a turret-moored FPSO (Floating Production Storage Offloading) by using fully-coupled hull-mooring-riser dynamic simulation program in time domain. In particular, the effects of initial geometric profile on the global performance and structural behavior are investigated in depth to have an insight for optimal design. In this regard, a systematic parametric study with varying the initial curvature of sag and arch bend and initial position of touch down point (TDP) is conducted for 100-yr wind-wave-current (WWC) hurricane condition. The FPSO motions, riser dynamics, constituent structural stress results, accumulated fatigue damage of the LWSCR are presented and analyzed to draw a general trend of the relationship between the LWSCR geometric parameters and the resulting dynamic/structural performance. According to this study, the initial curvature of the sag and arch bend plays an important role in absorbing transferred platform motions, while the position of TDP mainly affects the change of static-stress level.

• Journal of computational fluids engineering
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• v.20 no.4
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• pp.7-13
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• 2015

Vortex tube is a thermal static device that separates compressed air into hot and cold streams. In general, the cooling efficiency of vortex tubes is lower than that of traditional air conditioning equipment and vortex tubes are mainly used for industrial spot cooling applications because of their quick responses. In this study, conical frustums are employed in the nozzle chamber to improve the cooling performance. Conical frustums can be used to decrease the ineffective mass fraction that directly passes through the cold exit without energy separation. The shape optimization of conical frustums has been performed using full factorial design. It is found that the height of frustums has the largest main effects on the cooling performance. Computational results show that the cooling performance can be increased by about 10% within the considered range of the design parameters. This is because the ineffective mass fraction toward the cold exit is decreased by about 20%.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.97-100
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• 2008

Various flyers in nature have attracted great interests with a recent need for developing versatile and small-size flight vehicles. In the present study, we focus on the flying fish which has been observed to glide a long distance just above a seawater surface. Since previous studies have depended on the field observation or measurement of the physical parameters only, quantitative data of the flying fish flight has not been provided so far. Therefore, we evaluate the wing performance of the flying fish in gliding flight by directly measuring the lift, drag and pitching moment on real flying fish models (Cypselurus hiraii) in a wind tunnel. In addition, we investigate the roles of wing morphology like the enlarged pectoral and pelvic fins, and lateral dihedral angle of pectoral fins. With both the pectoral and pelvic fins spread, the lift-to-drag ratio is larger and the longitudinal static stability is enhanced than those with the pelvic fins folded. From the glide polar, we find that the wing performance of flying fish is equivalent to those of medium-size birds like the petrel, hawk and wood duck. Finally, we examine the effect of water surface underneath the flying fish and find that the water surface reduces the drag and increases the lift-to-drag ratio.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.2
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• pp.103-109
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• 1986

The distributions of fatigue life of concrete for various applied fatigue stress levels are investigated. The concrete beam specimens are tested in four-point flexural loading conditions. Three different levels of applied fatigue stresses are considered. They are 85%. 75%. 65%, respectively, of the static flexural strength of concrete. The present study indicates that the shapes of the probability distribution of fatigue lives are rather different for different levels of applied fatigue stress. This necessitates the consideration of the effects of applied fatigue stress levels on fatigue life distributions of concrete in order to conduct a realistic fatigue reliability analysis. The graphical method, the method of moments, and the method of maximum likelihood estimation are used to evaluate the distribution parameters of fatigue lives. It was found that the shape parameter of Weibull distribution for the fatigue life of concrete ranges from 2.0 to 4.0 according to the level of applied fatigue stress.

• Advances in materials Research
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• v.5 no.3
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• pp.193-203
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• 2016

Compared to metal-to-metal tribology, polymer tribology presents further complexity as it is more prone to be influenced by operating conditions. Over the past two decades, progress in the field of wear of polymers has led to the establishment of more refined wear mechanisms. The current paper establishes the link between different load parameters and the wear rate of polymers, based on experimental investigations. A pin-on-plate reciprocating tribometer was used to examine the wear behaviour of polyamide sliding against a steel counterface, under constant and fluctuating loads, in dry conditions. In addition, the influence of controlled imperfections in the polymer surface upon its wear rate were examined, under cyclic and steady loading, in order to better understand surface fatigue wear of polymers. The imposed imperfections consisted of vertical artificial deep crack (slit) perpendicular or parallel to the direction of sliding. The study concludes with the followings findings; in general, wear of polymers shows a significant tendency to the type of applied load. Under cyclic loads, polymers show an increase in wear rate compared to those tested under static loads. Such increase was found to increase with the increase in cyclic load frequency. It is also demonstrated that surface cracks results in higher wear rates, particularly under cyclic loads.