• Journal of the Korean Geotechnical Society
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• v.39 no.6
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• pp.21-30
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• 2023

One of the methods for calculating unit skin friction of soft-rock-socket parts for cast-in-place piles involves the roughness measurement of the parts. The measurements are conducted during the excavation stage. A roughness measuring device is installed in the excavation hole and the unit skin friction is calculated from the measured surface roughness of the rock socket. Herein, the results of roughness measurement of rock-socket parts in cast-in-place piles and that of load transfer tests are analyzed and compared. The unit skin friction from the roughness measurements can be converted into unit skin friction corresponding to the displacement of a pile generated in a load transfer test. A reduction factor is given as R_f = -0.14n + 1.48.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.3
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• pp.234-239
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• 2010

The utilization of micro-electro-mechanical system (MEMS) gyros and accelerometers in low-level inertial measurement unit (IMU) influences cost effectiveness in a positive way under the condition that device error characteristics are fully calibrated. The conventional calibration process utilizes a rate table; however, this paper proposes a new method for achieving reference calibration data from the natural motion of pendulum to which the IMU undergoing calibration is attached. This concept was validated with experimental data. The pendulum angle measurements correlate extremely well with the solutions acquired from the pendulum equation of motion. The calibration data were computed using the regression method. The whole process was validated by comparing the measurement from the 6 sensor components with the measurements reconstructed using the identified calibration data.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.92-94
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• 2001

This paper investigated the real-time generator swing prediction by some researchers. And the first swing stability assessment based on EAC(Equal-Area Criterion) by using phasor measurement unit is proposed. Also we proposed the multi-swing prediction techniques, which is to estimate system parameters by using least square method / extrapolation with phasor measurement units. And the multi-swing prediction is performed with the estimated parameters. Future works are necessary to verify the proposed approaches in this paper.

• Annals of Hepato-Biliary-Pancreatic Surgery
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• v.27 no.2
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• pp.189-194
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• 2023

Backgrounds/Aims: Postoperative pancreatic fistula (POPF) after pancreaticoduodenectomy (PD) is a source of major morbidity and mortality. Early diagnosis and treatment of POPF is mandatory to improve patient outcomes and clinical risk scores may be ombined with postoperative drain fluid amylase (DFA) values to stratify patients. The aim of this pilot study was to etermine if intraoperative fluid amylase (IFA) values correlate with DFA1 and POPF. Methods: In patients undergoing PD from February to November 2020, intraoperative samples of intra-abdominal fluid adjacent to the pancreatic anastomosis were taken and sent for fluid amylase measurement prior to abdominal closure. Data regarding patient demographics, postoperative DFA values, complications, and mortality were prospectively collected. Results: Data were obtained for 52 patients with a median alternative Fistula Risk Score (aFRS) of 9.9. Postoperative complications occurred in 20 (38.5%) patients (five Clavien grade ≥ 3). There were eight POPFs and two patients died (pneumonia/sepsis). There was a significant correlation between IFA and DFA1 (R² = 0.713; p < 0.001) and DFA3 (p < 0.001), and the median IFA was higher in patients with POPF than patients without (1,232.5 vs. 122; p = 0.0003). IFA > 260 U/L predicted POPF with sensitivity, specificity, positive and negative predictive values of 88.0%, 75.0%, 39.0%, and 97.0%, respectively. The incidence of POPF was 43.0% in high-risk (high aFRS/IFA) and 0% in lowrisk patients (low aFRS/IFA). Conclusions: IFA correlated with POPF and may be a useful adjunct to clinical risk scores to stratify patients during PD. Larger, prospective studies are needed to determine whether IFA has clinical utility.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.34-41
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• 1997

The dimension measurement problem of products has been a major concern in the quality control in the industrial fields. A non-contacting measurement system using the vision sensor is proposed in this paper. The system consists of a CCD camera for the image capture, a frame grabber for the acquired image processing, a laser unit for the illumination, scanning unit for the measurement, and a personal computer for the geometry computation. The slit beam which is generated by passing the laser beam through a cylin- drical lens is fired to the axial-symmetric object on the rotating plate. The image of objects reflected by the laser slit beam, acquired by the CCD camera, becomes much brighter than the other parts of objects. After the histogram of brightness for the captured image is calculated, low intensity pixels are filtered out by threshold method. The performance of proposed measurement system is obtained for several different axial symmetric objects. The proposed system is verified as a good tool for measuring axial-symmetric parts in a limited condition with a minor investment cost.

• Journal of Navigation and Port Research
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• v.35 no.10
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• pp.785-791
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• 2011

This paper describes the evaluation and selection of MEMS(Micro-Elect Mechanical System) based inertial sensor to fit to implement the Inertial Measurement Unit(IMU) for a small-sized vessel at sea. At first, the error model and the noise model of the inertial sensors are defined with Euler's equations and then, the inertial sensor evaluation is carried out with Allan Variance techniques and Monte Carlo simulation. As evaluation results for the five sensors, ADIS16405, SAR10Z, SAR100Grade100, LIS344ALH and ADXL103, the combination of gyroscope and accelerometer of ADIS16405 is shown minimum error having around 160 m/s standard deviation of velocity error and around 35 km standard deviation of position error after 600 seconds. Thus, we select the ADIS16405 inertial sensor as a MEMS-based inertial sensor to implement IMU and, the error reducing method is also considered with the search for reference papers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.4
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• pp.97-103
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• 2009

Since a demand for an extensive range of earthmoving equipment like a hydraulic excavator with a capacity of 85tons has been asked in construction fields, a performance of its track drive unit has to be verified experimentally. Among the verification of the performances, a torque measurement is at issue, in which a torque meter is utilized widely. However, the very large scaled torque meter is necessary when a discharged torque from the track drive unit is increased significantly. In addition, the price for experimental set-up of a torque meter is too high due to its limitation of the geometry such as long length, and a break down in operation occurs frequently. In this study, to measure a high torque up to 200,000Nm, a new technique was proposed as an alternative of conventional measurement by using a torque meter. The new technique enables to measure the high torque stably in a compact space via a torque arm and two load cells. The experimental results showed a propriety of the proposed torque measuring technique for a track drive unit with very large capacity.

• Journal of Educational Research in Mathematics
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• v.20 no.3
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• pp.305-322
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• 2010

The epistemological obstacles in the area learning of plane figure can be categorized into two types that is closely related to an attribute of measurement and is strongly connected with unit square. First, reasons for the obstacle related to an attribute of measurement are that 'area' is in conflict. with 'length' and the definition of 'plane figure' is not accordance with that of 'measurement'. Second, the causes of epistemological obstacles related to unit square are that unit square is not a basic unit to students and students have little understanding of the conception of the two dimensions. Thus, To overcome the obstacle related to an attribute of measurement, students must be able to distinguish between 'area' and 'length' through a variety of measurement activities. And, the definition of area needs to be redefined with the conception of measurement. Also, the textbook should make it possible to help students to induce the formula with the conception of 'array' and facilitate the application of formula in an integrated way. Meanwhile, To overcome obstacles related to unit square, authentic subject matter of real life and the various shapes of area need to be introduced in order for students to practice sufficient activities of each measure stage. Furthermore, teachers should seek for the pedagogical ways such as concrete manipulable activities to help them to grasp the continuous feature of the conception of area. Finally, it must be study on epistemological obstacles for good understanding. As present the cause and the teaching implication of epistemological obstacles through the research of epistemological obstacles, it must be solved.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.78-84
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• 2014

The rotation of a spindle unit must be accurate for high-quality machining and to improve the quality of the machine tools.Therefore, the proper measurement of the rotation accuracy and ensuring a proper analysis are very important. Separate processes are necessary because spindle errors and roundness errors associated with the test balls can both factor into the measured rotation error values. We used three methods to discern test ball errors and analyzed which could be deemed as the most proper technique in a test of the rotation accuracy of the main spindle of a machine tool.

• Journal of Ocean Engineering and Technology
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• v.11 no.1
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• pp.95-105
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• 1997

This paper presents a Inertial Measuring Unit(IMU) for motion measurement of an AUV. The IMU is composed of three parts: inertial sensors with three servo accelerometers and three rate gyros, an analog/digital interface board, and a signal processing board with TMS320C31 DSP processor. The IMU is a class of strap-down inwetial navigation system does not applicable directly to the navigation system in consequence of the AUV and integrated sensors for an integrated navigation system of the AUV. Fast calculstion of direction cosine matrix for the coordinate transformation body to reference is obtained through the DSP processor. A switching algotrithm is used to lessen the low frequency drift effect of the gyros in the vertical plane with use of low pass filtering of the signal of the accelerometers.