• Geomechanics and Engineering
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• v.35 no.2
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• pp.195-208
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• 2023

The nodular diaphragm wall (NDW) is a novel type of foundation with favorable engineering characteristics, which has already been utilized in high-rise buildings and high-speed railways. Compared to traditional diaphragm walls, the NDW offers significantly improved vertical bearing capacity due to the presence of nodular parts while reducing construction time and excavation work. Despite its potential, research on the vertical bearing characteristics of NDW requires further study, and the investigation and visualization of its displacement pattern and failure mode are scant. Meanwhile, the measurement of the force component acting on the nodular parts remains challenging. In this paper, the vertical bearing characteristics of NDW are studied in detail through the indoor model test, and the displacement and failure mode of the foundation is analyzed using particle image velocimetry (PIV) technology. The principles and methods for monitoring the force acting on the nodular parts are described in detail. The research results show that the nodular part plays an essential role in the bearing capacity of the NDW, and its maximum load-bearing ratio can reach 30.92%. The existence of the bottom nodular part contributes more to the bearing capacity of the foundation compared to the middle nodular part, and the use of both middle and bottom nodular parts increases the bearing capacity of the foundation by about 9~12% compared to a single nodular part of the NDW. The increase in the number of nodular parts cannot produce a simple superposition effect on the resistance born by the nodular parts since the nodular parts have an insignificant influence on the exertion and distribution of the skin friction of NDW. The existence of the nodular part changes the displacement field of the soil around NDW and increases the displacement influence range of the foundation to a certain extent. For NDWs with three different nodal arrangements, the failure modes of the foundations appear to be local shear failures. Overall, this study provides valuable insights into the performance and behavior of NDWs, which will aid in their effective utilization and further research in the field.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.4
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• pp.257-266
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• 2001

It was set up MCS and MS of ship's distance measuring system in land and ship respectively and ship's track including dropped and hove up anchor was tracked by mean of measurement for ship's position, relative bearing and distance from MCS to MS. Results analyzed for possibility of real time anchoring watch and effectiveness of measuring position are as follow; (1) The elapsed time from dropped anchor to hove up anchor is 4 minutes and the elapsed time to start recording ship's track after set up anchoring state is 10 minutes approximately. (2) Shape of hull's swing during anchoring is mostly 8 figue-like or rarely peanut-like shape. (3) Mean anchoring position during whole measuring time was shifted 49m north and 89m eastly. (4) Ship's track were moved counter-clockwise for $8.1^\circ$ range from relative bearing $186.1^\circ$ to $194.2^\circ$ ellipse-like tracks with the major axis 63m and the minor axis 53m. (5) High frequency of ship's position distribution was shown at relative bearing $187^\circ$ and distance 558m while low frequency was shown at relative bearing $194^\circ$ and distance 556m. (6) The designed ship's distance measuring system by PRTK-GPS was fit very well for anchoring watch as secured necessary area demanded for dragging anchor as well as anchoring by means of real time measurement both in distance and bearing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.585-591
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• 2017

Turbocharging is widely used in diesel and gasoline engines as an effective way to reduce fuel consumption. But turbochargers have turbo-lag due to mechanical friction losses. Bearing friction losses are a major cause of mechanical friction losses and are particularly intensified in the lower speed range of the engine. Current turbochargers mostly use oil bearings (two journal bearings and one thrust bearing). In this study, we focus on the bearing friction in the lower speed range. Experimental equipment was made using a drive motor, load cell, magnetic coupling, and oil control system. We measured the friction losses of the turbocharger while considering the influence of the rotation speed, oil temperature, and pressure. The friction power losses increased exponentially when the turbocharger speed increased.

• Journal of Korean Foot and Ankle Society
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• v.7 no.1
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• pp.7-12
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• 2003

Purpose: To study the relationship of the 1st to 2nd intermetatarsal angle(1-2 IMA) between the intra-operative and weight bearing postoperative anterior-posterior(AP) radiography, and evaluate the intra-operative predictability for the postoperative 1-2 IMA after proximal metatarsal osteotomy(PMO) in the hallux valgus deformity. Materials and Methods: 20 cases of moderate to severe hallux valgus patients were included in this study. After the oblique PMO(Ludloff procedure) was performed and the osteotomy site was fixed temporarily, the AP view was taken intra-operatively. About 10 weeks after surgery, postoperative weight bearing AP view was taken. The pre -. intra -, and postoperative 1-2 IMAs were compared and ana lysed statistically. Results: The 1-2 IMAs of the weight bearing preoperative, non-weight bearing intra-operative and weight bearing postoperative AP view were $15.9^{\circ}{\pm}1.8^{\circ},\;4.7^{\circ}{\pm}2.1^{\circ}$, and $6.8^{\circ}{\pm}2.5^{\circ}$ (Mean${\pm}$SD) respectively. The postoperative 1-2 IMA was greater than intra-operative measurement by $2.1^{\circ}{\pm}1.8^{\circ}$ (range; $-1^{\circ}$ to $6^{\circ}$) which was stastistically significant(p<0.05). To get less than $9^{\circ}$ postoperatively as an average normal, intra-operative 1-2 IMA should be within $3.8^{\circ}$ to $5.2^{\circ}$ (95% confidence interval), and intra-operative 1-2 IMA should be within $3.4^{\circ}{\pm}$to $5.4^{\circ}$(95% confidence interval) to get more than $6^{\circ}$ difference between preoperative and postoperative 1-2 IMA, which is regarded as more than average correction by the distal metatarsal osteotomy. Conclusion: In hallux valgus surgery, it should be considered that intra-operative 1-2 IMA was less than the postoperative. To achieve postoperative 1-2 IMA less than $9^{\circ}$ and more than correction angle of $6^{\circ}$, it is suggested that the intra-operative 1-2 IMA should be measured less than about $5^{\circ}$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.803-809
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• 2018

Generally, the gap-and-sag method is used in the shipbuilding stage before coupling the shafts to check whether they are installed at the same position as designed and derived from shaft alignment calculation. The primary installed propeller shaft becomes a reference point, the position of the remaining shafts are sequentially determined through the gap-and-sag value derived from the deflection and deflection angle at each shaft flange by own weight. If the reference point varies against the design value, it would have a series of effects on the installation of the remaining shafts. Moreover, after coupling the shafts, even if the bearing reaction forces derived from measurement are satisfied by the allowable limit range, consequently it might have an adverse effect on the stability of the shafting system by not being able to estimate the relative slope angle between the propeller shaft and the after-stern tube bearing. In this paper, to deal with above-mentioned phenomenon, the theoretical calculations related to designing an effective support point of the aft stern tube bearing and analysis by measurement is conducted through a case of open-up inspections. Based on this, a shaft installation guideline is proposed to minimize the misalignment related to preventing wiping damage of the after-stern tube bearing.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.109-117
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• 2009

This paper presents a linear air bearing stage with compensated motion errors by active control of preloads generated by magnetic actuators with combination of permanent and electromagnets. A 1-axis linear stage motorized with a linear motor with 240mm of travel range is built for verifying this design concept and tested its performances. The three motions of the table are controlled with four magnetic actuators driven by current amplifiers and a DSP based digital controller. Three motion errors were measured combined method with laser interferometer and two-probe method with $0.085{\mu}m$ of repeatability for straightness error. The measured motion errors were modeled as functions of the stage position, and compensation were carried out with feedforward control because the characteristics of the motion control with magnetic actuators are linear and independent for each degree-of-freedoms. As the results, the errors were reduced from $1.09{\mu}m$ to $0.11{\mu}m$ for the vertical motion, from 9.42 sec to 0.18 sec for the pitch motion and from 2.42 sec to 0.18 sec for roll motion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.71-78
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• 2006

When a tracking filter may be designed in the Cartesian coordinate, the covariance of the measurement errors varies according to the range and the bearing of an interested target. In this paper, interacting multiple model based tracking filter is formulated in the Cartesian coordinate utilizing the analytic solution of the steady state Kalman filter, which can be able to consider the variation of the measurement error covariance. 100 Monte Carlo runs performed to verify the proposed method. The performance of the proposed method is compared with the conventional fixed gain and Kalman filter based IMM tracking filter in terms of the root mean square error. The simulation results show that the proposed approach meaningfully reduces the computation time and provides a similar tracking performance in comparison with the conventional Kalman filter based IMM tracking filter.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.9
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• pp.723-732
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• 2016

This paper proposes an approach to fused navigation of an unmanned surface vehicle(USV) and to detection of the outlier or interference of global positioning system(GPS). The method fuses available sensor measurements through extended Kalman filter(EKF) to find the location and attitude of the USV. The method uses error covariance of EKF for detection of GPS outlier or interference. When outlier or interference of the GPS is detected, the method excludes GPS data from navigation process. The measurements to be fused for the navigation are GPS, acceleration, angular rate, magnetic field, linear velocity, range and bearing to acoustic beacons. The method is tested through simulated data and measurement data produced through ground navigation. The results show that the method detects GPS outlier or interference as well as the GPS recovery, which frees navigation from the problem of GPS abnormality.

• Economic and Environmental Geology
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• v.22 no.2
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• pp.129-139
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• 1989

The anthracite coalfields of Korea are confined to the areas where sedimentary rocks of Permian and Jurassic are preserved. The Chungnam coalfield lies in the sedimentary rocks of Jurassic which belongs to the Daedong Supergroup (the Nampo group). For the property analysis of each coal seam interbeded in Daedong Supergroup, Seongju area is chosen and twelve coalseams are taken. Many standard tests have been established for optical analysis (maceral analysis, coalification degree measurement), chemical analysis (proximate, ultimate analysis) and physical analysis (ignition temperature, ash fusion temperature, hardgrove grindability index and X-ray diffraction). The Jurassic anthracite mainly consist of vitrinite and macrinite and the range of the reflectance is $R_{max}$ 5.0-6.5 which means metaanthracite rank. By the chemical composition analysis, it shows low H/C and high O/C value compare with international average value. By the physical analysis, it has very high ignition temperature ($531-584^{\circ}C$) and ash fusion temperature ($1510-1700^{\circ}C$) and very low combustion velocity (0.2-1.9 mg/min). The very wide range of the hardgrove grindability index (46-132) means that the grindability controlled mainly by the structural conditions of coal bearing strata.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.1
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• pp.31-40
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• 2006

The entrance and the exit structures of tunnels are often constructed on unfavorably soft soils (colluvial soils) as a result of environment-friendly design highlighted in recent years. For construction of such a tunnel, it is essential to secure sufficient bearing capacity of the lining supports as well as that of the surrounding soils. In this regard, H-shape steel-ribs with high stiffness are commonly used for lining supports. However, it was the past convention to ignore the effect of the steel-ribs in numerical evaluation of the structural safety. This study is intended to show how the shotcrete stresses are relieved by the steelribs, on the basis of numerical data obtained from 3-dimensional finite element analysis. The effect of steel ribs to shotcrete stresses is examined at different levels of application rates, i.e., 0%, 50%, 75% and 100% of the total stiffness. The data obtained from numerical analysis was compared with in-situ measurement. The effect of st eel ribs to shotcrete stresses was verified and appropriate total stiffness was proposed in the range of 50%~75%.