• Journal of computational fluids engineering
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• v.18 no.3
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• pp.8-13
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• 2013

Drag reduction of a running vehicle is very important issue for the energy savings and emission reduction of its power train. Especially for a solar powered electric vehicle, the drag reduction and weight lightening are two serious problems to be solved to extend its driving distance under the given energy condition. In this study, the ground effect of an airfoil shaped road vehicle was studied for an optimum body design of an ultra-light solar powered electric vehicle. Clark-Y airfoil type was adopted to the body shape of the model vehicle to reduce aerodynamic drag. From the study, it was found that the drag of the model vehicle was reduced as the height(h) between ground and the lower surface of the model vehicle was decreased. It is due to the reduction of the down-wash decreasing the induced drag of the vehicle. The lift was also decreased as the height decreased. It is due to the turbulent boundary layer developed beneath the vehicle body. The drag is classified into two types; the form and friction drag. The fraction of form drag to friction one is 76 to 24 on the model vehicle. As the height(h) of the model vehicle from the ground surface increases the form drag also increases but the friction drag is in reverse.

• Geomechanics and Engineering
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• v.21 no.2
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• pp.187-200
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• 2020

In the current work, a series of three-dimensional finite element analyses have been conducted to investigate the behaviour of pre-existing single piles in response to adjacent tunnelling by considering the tunnel face pressures and the relative locations of the pile tips with respect to the tunnel. Via numerical modelling, the effect of the face pressures on the pile behaviour has been analysed. In addition, the analyses have concentrated on the ground settlements, the pile head settlements and the shear stress transfer mechanism at the pile-soil interface. The settlements of the pile directly above the tunnel crown (with a vertical distance between the pile tip and the tunnel crown of 0.25D, where D is the tunnel diameter) with a face pressure of 50% of the in situ horizontal soil stress at the tunnel springline decreased by approximately 38% compared to the corresponding pile settlements with the minimum face pressure, namely, 25% of the in situ horizontal soil stress at the tunnel springline. Furthermore, the smaller the face pressure is, the larger the tunnelling-induced ground movements, the axial pile forces and the interface shear stresses. The ground settlements and the pile settlements were heavily affected by the face pressures and the positions of the pile tip with respect to the tunnel. When the piles were inside the tunnel influence zone, tensile forces were induced on piles, while compressive pile forces were expected to develop for piles that are outside the influence zone and on the boundary. In addition, the computed results have been compared with relevant previous studies that were reported in the literature. The behaviour of the piles that is triggered by adjacent tunnelling has been extensively examined and analysed by considering the several key features in substantial detail.

• Advances in environmental research
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• v.3 no.3
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• pp.231-251
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• 2014

The present study examines the phosphate adsorption potential and behavior of mixture of Ground Burnt Patties (GBP), a solid waste generated from cooking fuel used in earthen stoves and Red Soil (RS), a natural substance in fixed bed column mode operation. The characterization of adsorbent was done by Proton Induced X-ray Emission (PIXE), and Proton Induced ${\gamma}$-ray Emission (PIGE) methods. The FTIR spectroscopy of spent adsorbent reveals the presence of absorbance peak at $1127cm^{-1}$ which appears due to P = O stretching, thus confirming phosphate adsorption. The effects of bed height (10, 15 and 20 cm), flow rate (2.5, 5 and 7.5 mL/min) and initial phosphate concentration (5 and 15 mg/L) on breakthrough curves were explored. Both the breakthrough and exhaustion time increased with increase in bed depth, decrease in flow rate and influent concentration. Thomas model, Yoon-Nelson model and Modified Dose Response model were used to fit the column adsorption data using nonlinear regression analysis while Bed Depth Service Time model followed linear regression analysis under different experimental condition to evaluate model parameters that are useful in scale up of the process. The values of correlation coefficient ($R^2$) and the Sum of Square Error (SSE) revealed the Modified Dose Response model as the best fitted model to the experimental data. The adsorbent mixture responded effectively to the desorption and reusability experiment. The results of this finding advocated that mixture of GBP and RS can be used as a low cost, highly efficient adsorbent for phosphate removal from aqueous solution.

• Geomechanics and Engineering
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• v.38 no.6
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• pp.553-569
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• 2024

In recent tunneling projects, encounters with multi-layered strata have become more frequent as the desired scale of tunneling increases. Despite substantial practical experience, the design of large-diameter shield-driven tunnels often simplifies the surrounding ground as uniform, overlooking the complexities introduced by non-uniform geotechnical factors. This study comparatively analyzed the influence of design factors, particularly segment stiffness and joint parameters, on segmental lining behavior in layered ground conditions using numerical methods. A comprehensive parametric study revealed the significant impact of deformative interaction between the lining and the soft top soil layer on overall tunnel behavior. Permitting lining deformation in the soft soil layer effectively mitigated the induced internal forces but resulted in considerable tunnel lining convergence, adopting a peanut-shaped appearance. From a practical design perspective, application of a soft segment with lower stiffness near the stiff soil layer is an economically advantageous approach, alleviating internal forces within an acceptable convergence level. Notably, around the interfaces between soil layers with different stiffnesses, the induced internal forces in the lining were minimized based on joint rotational stiffness and location. This indicates the possibility of achieving an optimal design for segmental lining joints under layered ground conditions. Additionally, a preliminary design method was proposed, which sequentially optimizes parameters for joints located near soil layer interfaces. Subsequently, a specialized design based on the proposed method for complex multi-layered strata was compared with a conventional design. The results confirmed that the internal force was effectively relieved at an allowable lining deflection level.

• Steel and Composite Structures
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• v.53 no.2
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• pp.155-167
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• 2024

Identifying the location of earthquake-induced damage in buildings and mitigating its impact, especially in low-damage systems such as rocking frames, is a significant challenge for structural engineers. Therefore, it is crucial to investigate the sensitivity and type of damage of buildings exposed to severe earthquakes to concentrate damage in predefined locations that can be repaired easily. This paper explores the seismic responses of a Self-Centering Rocking Steel Braced Frame (SCR-SBF) under far-field and near-field ground motions. This earthquake-resistant system includes components such as post-tensioning cables to provide frame self-centering, eliminate residual drift in the system, and replaceable fuses to concentrate the earthquake-induced damage. While previous studies have examined far and near-field earthquakes, their comparative influence on the seismic behavior of structures with a rocking system remains unexplored. This paper presents a novel investigation into the sensitivity of SCR-SBF structures to far and near-field earthquakes. Considering the critical effects of shock and impulse loads on rocking systems, the study aims to assess the effects of near-field earthquakes and compare them to far-field earthquakes on these systems. For this purpose, different response parameters have been calculated under records of far- and near-field earthquakes at three specific ground acceleration levels by incremental nonlinear dynamic analysis. Additionally, the seismic behavior of the SCR-SBF and Steel-Braced Frame (SBF) are compared for near and far-field ground motions. The results show that SCR-SBF systems have better resilience and reduced local failures compared to SBF systems under far and near-field earthquakes, requiring tailored design strategies.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1631-1636
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• 2003

The purpose of this study is to analyze the phenomena of the thermally-induced vibration for the flexible space structure due to abrupt change of radiation heating circumstance using the numerical analyze and experiment test. In order to verify this structure, numerical approaches on the simplified flexible tube were compared with experimental test results at the ground experimental facility In this analyze, it was found that the thermal deformation occurs firstly due to fast radiation heating of flexible structure and then the thermally-induced vibration would be induced due to small periodic change of temperature. According to comparison of numerical and experimental result, in case of no tip mass, the first mode vibration by the numerical analyze was O.78Hz same as that of the experimental result However in case of increase tip-masses of 8g l6g, 50g and 100g, the first modes vibration theoretical analyze were 1.75Hz, 1.3Hz, 0.87Hz and O.73Hz, in decrease trend respectively and those by experimental test were 234Hz, 1.5Hz, O.78Hz and O.78Hz in decrease trend respectively Although using the simpled equation for the estimation, the estimation results were similar to experimental results.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3641-3648
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• 2013

Energy transfer and bond dissociation of $C-H_{methyl}$ and $C-H_{ring}$ in excited toluene in the collision with $H_2$ and $D_2$ have been studied by use of classical trajectory procedures at 300 K. Energy lost by the vibrationally excited toluene to the ground-state $H_2/D_2$ is not large, but the amount increases with increasing vibrational excitation from 5000 and $40,000cm^{-1}$. The principal energy transfer pathway is vibration to translation (V-T) in both systems. The vibration to vibration (V-V) step is important in toluene + $D_2$, but plays a minor role in toluene + $H_2$. When the incident molecule is also vibrationally excited, toluene loses energy to $D_2$, whereas it gains energy from $H_2$ instead. The overall extent of energy loss is greater in toluene + $D_2$ than that in toluene + $H_2$. The different efficiency of the energy transfer pathways in two collisions is mainly due to the near-resonant condition between $D_2$ and C-H vibrations. Collision-induced dissociation of $C-H_{methyl}$ and $C-H_{ring}$ bonds occurs when highly excited toluene ($55,000-70,400cm^{-1}$) interacts with the ground-state $H_2/D_2$. Dissociation probabilities are low ($10^{-5}{\sim}10^{-2}$) but increase exponentially with rising vibrational excitation. Intramolecular energy flow between the excited C-H bonds occurring on a subpicosecond timescale is responsible for the bond dissociation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.2
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• pp.135-146
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• 2003

This paper presents the effect of ground vibration induced by vibrohammer and RCD on adjancent subway tunnel performance using FDM program. Firstly, the stability criteria for structures near vibration source were proposed according to existing data, then peak particle velocity around tunnel was estimated based on detailed information of vibrohammer and existing formula for dynamic loads through numerical analysis. The peak particle velocity induced by RCD bit rotation was also estimated using surveyed data and formula. Consequently, displacement and stress responses were obtained at crown, shoulder and spring line and compared with the criteria to check stability of tunnel.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.435-443
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• 2014

The purposes of this study was to investigate the physical compensation for gait on induced equinus in normal subjects. Ten subjects were participate in the experiment (age: $23.8{\pm}2.8yrs$, height: $177.3{\pm}4.3cm$, weight: $70.8{\pm}4.6kg$). The study method adopted 3D analysis with six cameras and ground reaction force with two force-plate. Induced equinus were classify as gait pattern on unilateral and bilateral equinus. The results were as follows; In displacement of COM, medio-lateral and anterior-posterior COM were no significant, but in vertical COM, unilateral equinus gait was higher than bilateral equinus gait. In displacement hip joint, left hip joint was more extended in FC1 and FC2 during unilateral equinus gait. In displacement knee joint, left knee joint was more extended in FC2, right knee joint was more extended in all event during unilateral equinus gait. In trunk tilt, unilateral equinus gait was more forward tilt in TO1 and TO2. ROM of each joint was no significant. In Displacement of pelvic tilt angle, X axis of unilateral equinus gait was more increase than bilateral equinus gait at FC2, TO2 and MS2. Y axis of unilateral equinus gait was more increase than bilateral equinus gait at MS1, FC2 and MS2. Z axis was no significant in both equinus gait. In GRF, right Fx and Fy were no significant in both equinus gait, Fz was more bigger vertical force in bilateral equinus gait. Left Fx was more bigger internal force in unilateral equinus gait, Fy and Fz were no significant in both equinus gait.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.83-97
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• 2018

Tunnels are widely used for special purposes including roads, railways and culvert for power transmission, etc. Its cross-section shape is determined by uses, ground condition, environmental or economic factor. Many papers with respect to behaviours of adjacent ground and existing structure tunnelling-induced have been published by many researchers, but tunnel cross-section have rarely been considered. A collapse of tunnel causes vaster human and property damage than structures on the ground. Thus, it is very important to understand and analyse the relationship between behavoiurs of ground and cross-section type of tunnel. In this study, the behaviour of ground due to tunnel excavation for underground station below the grouped pile supported existing structure was analysed through laboratory model test using a trap-door device. Not only two cross-section types, 2-arch and box, as station for tunnel, but also, offset between tunnel and grouped pile centre (0.1B, 0.25B, 0.4B) are considered as variable of this study. In order to measure underground deformation tunnelling-induced, Close Range Photogrammetry technique was applied with laboratory model test, and results are compared to numerical analysis.