• Advances in biomechanics and applications
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• v.1 no.1
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• pp.15-22
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• 2014

Computed tomography (CT) is being utilized in orthopaedics and related research to estimate bone strength. These applications benefit from calibration of Hounsfield units to mineral density typical of long bone, up to $1750mg/cm^3$. This study describes a method for establishing repeatable calibration of Hounsfield units to density, and determines the effects of imaging medium on calibration accuracy. Four hydroxyapatite standards were imaged in air on 7 occasions over 19 weeks using a helical multi-slice CT scanner. Each standard was scanned 5 times in different media: porcine soft tissue, water, and air. Calibrated densities were highly repeatable (CV<3.5%). No difference in density was observed between water and soft tissue conditions (p>0.08). This work provides a model for determining repeatable scanner-specific density calibration, demonstrates that the linear relationship between Hounsfield units and density extends to values typical of cortical bone, and supports the practice of imaging calibration standards in an environment similar to that of the target bone.

• Journal of the Korean Geophysical Society
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• v.7 no.4
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• pp.237-245
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• 2004

Series of basic experiments for current density calibration by user process and for density calibration using geophysical model borehole were made. We tried to find the sonde response characteristics for current calibration using water and aluminium field jig, and using the equation of half life of 137Cs source. The result of calibration test made in a geophysical model borehole built first in Korea shows a perfect linear calibration equation. By adopting this calibration equation we could estimate the limitation as well as possibility of current density calibration by user process.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.23-29
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• 2009

A sand-cone method is commonly used to determine the density of the compacted soils. This method uses a calibration container to determine the bulk-density of the sand for use in the test. The density of the test or compacted soil is computed on the assumption that the calibration container has approximately the same size or volume and allows the sand to fall approximately the same height as a test hole in the field. However, in most cases the size or shape of test hole is not exactly the same as the calibration container. There is certain discrepancy between sand particle settlement or arrangement in the laboratory calibration and in the field testing, which may cause an erroneous determination of in-situ density. The sand filling process is simulated in the laboratory and its effect on the determination of density is investigated. Artificially-made holes with different heights and bottom shapes are prepared to simulate various shapes of the test hole in the field. The sands with different gradations are used in the testing to examine how sand grain size influences the determination of density in the field.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.09a
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• pp.73-82
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• 2005

We constructed a series of calibration models in the campus of Kangwon National University. A series of experiment for calibrating sonde response as well as casing effect in field measurement. Here we explained the process of construction of calibrating facility which consists of three model holes of different density and three model holes of different diameter. It was discussed the calibration equations obtained from its sonde response calibration test. A density correction chart for different separation of detector from hole wall was suggested, and verified the possibility of determining true density from measurements in cased hole.

• Journal of the Korean Geosynthetics Society
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• v.14 no.1
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• pp.59-65
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• 2015

The objective of the study is to verify a new calibration equation of dry density and water contents with TDR. Since the traditional calibration equation was proposed, some research to develop a new calibration equation has been conducted by several researchers. As traditional calibration equation is difficult to be applied for loose soil and fine-grained soil at high water contents, this study developed a new calibration equation. Thus, this study introduces a new calibration equation and its applicability by comparing TDR test results with conventional test results. Based on the analyses, the calibration equation for water content has large error. A new calibration equation was proposed and it showed more than 95% accuracy for estimating water content of soil.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1452-1461
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• 2020

A triple bubbler sensor was tested in LiCl-KCl molten salt from 450 to 525 ℃ in a transparent furnace to validate thermal-expansion corrections and provide additional molten salt data sets for calibration and validation of the sensor. In addition to these tests, a model was identified and further developed to accurately determine the density, surface tension, and depth from the measured bubble pressures. A unique feature of the model is that calibration constants can be estimated using independent depth measurements, which allow calibration and validation of the sensor in an electrorefiner where the salt density and surface tension are largely unknown. This model and approach were tested using the current and previous triple bubbler data sets, and results indicate that accuracies are as high as 0.03%, 4.6%, and 0.15% for density, surface tension, and depth, respectively.

• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1017-1023
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• 2023

The purpose of this study was to improve the accuracy of effective atomic number (EAN) and relative electron density (RED) using a polynomial-based calibration method using dual-energy CT images. A phantom composed of 11 tissue-equivalent materials was acquired with dual-energy CT to obtain low- and high-energy images. Using the acquired dual-energy images, the ratio of attenuation of low- and high-energy images for EAN was calibrated based on Stoichiometric, Quadratic, Cubic, Quartic polynomials. EAN and RED were extracted using each calibration method. As a result of the experiment, the average error of EAN using Cubic polynomial-based calibration was minimum. Even in the RED image extracted using EAN, the error of the Cubic polynomial-based RED was minimum. Cubic polynomial-based calibration contributes to improving the accuracy of EAN and RED, and would like to contribute to accurate diagnosis of lesions in CT examinations or quantification of various materials in the human body.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.90-96
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• 1999

In contracts for sales of natural gas between sellers and buyers, it is not suncient to only measure a volumetric quantity of gas in flowing conditions in metering station. Therefore the measured volumetric quantity must be converted to that of reference conditions. The density of the natural gas required in such a calculation can be measured directly or estimated from the equation of sate or any other experimental methods. The specific gravity meter is the apparatus used to measure the density of fluids under the reference conditions and it can be widely used in industrial areas, especially in massive flow rate natural gas industry. This study has been carried out in an attempt to improve measurement accuracy of natural gas flow rate calculation, providing the adequate installation and proper operation conditions of specific gravity meter. The test results are 1) the density measurement errors in case of using methane and standard gas as calibration gases are smaller than using methane and nitrogen gas, 2) the periodical calibration to maintain accurate density measurements is essential, and 3) the specific gravity meter is sensitive to changes of environmental conditions, especially environmental temperature surrounding the specific gravity meter.

• International Journal of Highway Engineering
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• v.16 no.4
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• pp.119-126
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• 2014

PURPOSES: Used in transportation planning and traffic engineering, almost traffic simulation tools have input variable values optimized by overseas traffic flow attribution because they are almost developed in overseas country. Thus, model calibration appropriated for internal traffic flow attribution is needed to improve reliability of simulation method. METHODS : In this study, the traffic flow model calibration is based on expressways. For model calibration, it needs to define each expressway link according to attribution, thus it is classified by design speed, geometric conditions and number of lanes. And modified greenshield model is used as traffic flow model. RESULTS : The result of the traffic model calibration indicates that internal congested density is lower than overseas. And the result of analysis according to the link attribution indicates that the more design speed and number of lanes increase, the lower the minimum speed, the higher the congested density. CONCLUSIONS: In the traffic simulation tool developed in overseas, the traffic flow is different as design speed and number of lanes, but road segment don't affect traffic flow. Therefore, these results need to apply reasonably to internal traffic simulation method.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.178-184
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• 2014

In this study, we develop liquid density sensor by measuring of balanced position between gravity and bouyancy, corresponding to liquid density, using distance measuring by magnetostriction technology. For improvement of accuracy of liquid density sensor system. And we derive the related equation between liquid density and moving distance of density sensor, and make the calibration method for liquid density sensor by magnetostriction technology. Using fabricated liquid density sensing system and derived equation, have measured the density of several liquids. And compare it to measuring results using Oscillating U-tube type high accuracy density meter, having 0.000001 g/cc resolution. The deviation of results between two density measuring systems was less than 0.001 g/cc.