• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.77-85
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• 2009

This paper describes the findings obtained from a research project aimed at investigating, via 1 g laboratory model tests, the ground movements caused by multiple side-by-side (sbs) tunnel construction in clay. The ground movements above a second tunnel showed different trends from those observed above a first tunnel. These trends include an increase in the overall volume loss, and a widening of the settlement troughs on the near limb of the trough accompanied by a shift of the maximum settlement towards existing tunnel. This would suggest that the use of simple predictive methods of adopting a Gaussian curve for analysing the ground settlements associated with twin (sbs) tunnel construction is not appropriate. Therefore the current paper adopts a method that modifies the Gaussian curve approach in order to improve the predictions. This paper comments on the parameter selection involved with adopting this new method to apply it to full-scale field situations, and also discusses its limitations.

• Journal of KIBIM
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• v.13 no.1
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• pp.1-12
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• 2023

The number of old buildings in Korea is increasing. According to a report from the Ministry of Land, Infrastructure and Transport, the proportion of old buildings increased from 29.0% in 2005 to 37.8% in 2009. However, the ratio of repairs to improve usability and improve the environment through problem improvement The proportion of old buildings was 72% in 2010, but decreased to 38% in 2020 and does not exceed 40%. The reason is that the difficulty of remodeling old buildings is more difficult than repairing new ones, and business estimates are difficult to predict. Accurately reflecting the current condition of a building in a repair project has a huge impact on time and budget. Accurate and detailed measurements are essential. Current repair methodologies require a lot of manpower, time and money to remodel an old building. Therefore, it is necessary to improve the remodeling methodology applied in the field. In this study proposed a Digital-Twin-based remodeling process that introduced various digital technologies such as 3D Scanning, BIM, Reverse Engineering, and Digital Fabrictation in consideration of the latest technologies used in recent construction projects. In addition, the process proposed in this study was applied to an actual small-scale building remodeling project and the results were analyzed. In addition, useful basic data were provided for the establishment of plans related to the repair process of buildings in the future.

• Smart Structures and Systems
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• v.23 no.6
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• pp.669-682
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• 2019

Vibration mitigation of cables or hangers is one of the crucial problems for cable supported bridges. Previous research focused on the behaviors of cable with dampers or crossties, which could help engineering community apply these mitigation devices more efficiently. However, less studies are available for hybrid applied cross-ties and dampers, especially lack of both analytical and experimental verifications. This paper studied damping and frequency of two parallel identical cables with a connection cross-tie and an attached damper. The characteristic equation of system was derived based on transfer matrix method. The complex characteristic equation was numerically solved to find the solutions. Effects of non-dimensional spring stiffness and location on the maximum cable damping, the corresponding optimum damper constant and the corresponding frequency of lower vibration mode were further addressed. System with twin small-scale cables with a cross-link and a viscous damper were tested. The damping and frequency from the test were very close to the analytical ones. The two branches of solutions: in-phase modes and the out-of-phase modes, were identified; and the two branches of solutions were different for damping and frequency behaviors.

• Journal of ILASS-Korea
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• v.23 no.4
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• pp.205-211
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• 2018

Y-jet nozzle has various advantages over other twin-fluid nozzles and are used in industrial boilers. However, it costs large energy consumption because of assisted air and its design is complex. The Y-jet nozzle is consisted of a liquid and gas port and a mixing chamber. The diameter of the port and the length of the mixing chamber greatly affect spray and atomization characteristics, therefore, they are the most important factors in nozzle design. In this study, The experimental setup is consisted of a laboratory scale spray system. The characteristics of the Y-jet nozzle according to the design parameters were observed. As a result, it was found that the length of the mixing chamber did not have effect on the flow rate and the choking condition. The droplet size was measured using a Malvern type measuring device. In addition, measurements were conducted in the front and the right directions of the nozzles. Based on the results, the SMD View Ratio is defined. It is the asymmetrical design characteristics of the Y-jet nozzle.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.969-977
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• 2016

In this paper, the static load test of long span PSC deck used in the twin steel plate girder bridge was conducted. To evaluate the structural behavior of long span deck, longitudinally sufficient length of deck is needed, but it is difficult to test the full-scale long span deck due to limit of transportation, setting and laboratory space. Therefore, this study proposed a method to apply longitudinal stiffness of the full-scale deck to the test specimen of longitudinally short length, and it was reinforced with the steel beam. The failure behavior and structural performance of the long span deck were evaluated by the proposed test specimen deck.

• Korean Journal of Food Science and Technology
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• v.22 no.1
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• pp.105-109
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• 1990

A laboratory scale co-rotating twin-screw extruder (D24 mm, L/D=14) was used for the extrusion of rice, which could be used for a puffed rice snack. As screw speed of the extrusion cooker was increased from 200 to 360 rpm, air cells structure of the extrudate from glutinous rice powder was improved to small and uniform air cells, and the moisture conetent of rice powder should be maintained to 15-17.5% for better texture of the extrudate. Objective and sensory texture of the extrudate from powder was better than those from grits, and there was no significant difference in textural properties between extrusion made with rice and glutinous rice.

• Journal of Broadcast Engineering
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• v.26 no.4
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• pp.390-397
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• 2021

As digital twin technology is applied to various industrial fields, technologies to effectively process large amounts of data are required. In this paper, we discuss a customized service method for fast search and effective delivery of large-scale data for underground facility for public utilities management. The proposed schemes are divided into two ways: a fast search data generation method and a customized information service segmentation method to efficiently search and abbreviate vast amounts of data. In the high-speed search data generation, we discuss the configuration of the synchronization process for the time series analysis of the sensors collected in the underground facility and the additional information method according to the data reduction. In the user-customized service method, we define the types of users in normal and disaster situations, and discuss how to service them accordingly. Through this study, it is expected to be able to develop a systematic data generation and service model for the management of underground utilities that can effectively search and receive large-scale data in a disaster situation.

• Polymer(Korea)
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• v.37 no.1
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• pp.113-120
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• 2013

The melt intercalation to commercialize nanocomposites in a pilot scale was applied and the water absorption characteristics for polyamide/MMT nanocomposites manufactured by twin screw extruder was studied. As a result, water absorption decreased with the introduction of MMT and dimensional stability was improved. However, as water absorption increased, flexural strength and modulus were reduced. Therefore, the effect of MMT introduction on mechanical properties of nanocomposites was clearly observed, which may increase the level of strength by maintaining anti-water absorption property of nanocomposite.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2292-2314
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• 2006

Efficient numerical method is developed for the prediction of aerodynamic noise generation and propagation in low Mach number flows such as aeolian tone noise. The proposed numerical method is based on acoustic/viscous splitting techniques of which acoustic solvers use simplified linearised Euler equations, full linearised Euler equations and nonlinear perturbation equations as acoustic governing equations. All of acoustic equations are forced with immersed surface dipole model which is developed for the efficient computation of aerodynamic noise generation and propagation in low Mach number flows in which dipole source, originating from unsteady pressure fluctuation on a solid surface, is known to be more efficient than quadrupole sources. Multi-scale overset grid technique is also utilized to resolve the complex geometries. Initially, aeolian tone from single cylinder is considered to examine the effects that the immersed surface dipole models combined with the different acoustic governing equations have on the overall accuracy of the method. Then, the current numerical method is applied to the simulation of the aeolian tones from twin cylinders aligned perpendicularly to the mean flow and separated 3 diameters between their centers. In this configuration, symmetric vortices are shed from twin cylinders, which leads to the anti-phase of the lift dipoles and the in-phase of the drag dipoles. Due to these phase differences, the directivity of the fluctuating pressure from the lift dipoles shows the comparable magnitude with that from the drag dipoles at 10 diameters apart from the origin. However, the directivity at 100 diameters shows that the lift-dipole originated noise has larger magnitude than, but still comparable to, that of the drag-dipole one. Comparison of the numerical results with and without mean flow effects on the acoustic wave emphasizes the effects of the sheared background flows around the cylinders on the propagating acoustic waves, which is not generally considered by the classic acoustic analogy methods. Through the comparison of the results using the immersed surface dipole models with those using point sources, it is demonstrated that the current methods can allow for the complex interactions between the acoustic wave and the solid wall and the effects of the mean flow on the acoustic waves.

• Tunnel and Underground Space
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• v.23 no.2
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• pp.130-140
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• 2013

In this study, scaled model tests were performed to investigate the stability of twin tunnels with small clearance, where the pillar widths were 0.5D and 0.25D, respectively. The tunnels were supposed to be constructed in anisotropic weathered rocks with $30^{\circ}$ inclined bedding planes, and the model tests were conducted under the condition of lateral pressure ratio, 1. Six types of test models which had respectively different pillar widths and support conditions were experimented, where crack initiating pressures, maximum pressures, failure modes of pillar and deformation behaviors around tunnels were investigated. The models with wider pillar were cracked under higher pressure than the models with shallower pillar. The models with lining support were cracked under higher pressure and showed less tunnel convergence than the unsupported models. The models with both lining and pillar reinforcement were proved to be most stable among the tested models. In particular, as the model of 0.25D pillar width with only lining support showed shear failure of pillar according to the existing bedding planes, so both lining and pillar reinforcement were thought to be indispensable in that case of tunnel.