• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.2
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• pp.137-141
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• 1990

When the relative humidity is measured with an aspirated psychrometer, three factors, which affect the measurement of relative humidity, are atmospheric pressure, the size of wet element and the wind velocity. This paper investigated the effects of the above three factors, and the computer code was developed in order to enhance the accuracy of the relative humidity measurement. As results, it is found that the relative humidity decreases by 6%RH with increasing atmospheric pressure from 650 mbar to 1100 mbar. It is found that the relative humidity drops down when the size of the wet element increases, though the effect of the size of the wet element is not significant. Finally, relative humidity increases with the increasing wind velocity. The difference between the psychrometic table in the present KS and the present results is about 2%RH maximum. As a conclusion, the three factors mentioned above should be considered in order to secure accurate measurement of relative humidity.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2537-2539
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• 2002

This paper presents an in-process measurement system for shaft radius measurement during grinding process. This system does not require to stop the grinding process, which can enhance productivity and quality. For data analysis, the measurement system is modeled as a linearized discrete form where the states with noise are estimated by an extended Kalman filter. This system has been validated through simulations and experiments.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.115-116
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• 2002

This study aimed to investigate flow measurement by using a 'bucket and stop-watch' method of flow measurement. Most flow measurement systems measure pressure or other fluid properties to infer flow rate, though time is a variable which can be easily and very accurately measured. The main principle behind the method was to fill up a reservoir until a set pressure had been reached. This reservoir would then be emptied and the cycle would repeat itself. The prototype was designed to control flow rate using the method. It made use of computer control with an analogue digital converter and fast acting solenoid valves which controlled the flow into a reservoir. Reservoirs were available with internal diameter of 1mm up to 5.5mm to cope with a range of flow rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1307-1312
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• 2007

The flow characteristics of R-134a in a small diameter tube was investigated experimentally. An experimental apparatus was consisted of a magnetic gear pump, an evaporator, a sight-glass, a condenser and a measurement instruments. The sight-glass for flow pattern observations was located at the inlet and outlet of the evaporator. The experiment was carried out to show the flow characteristics of R-134a in a small diameter tube. Mass flux of refrigerants was ranged from 100 to 1000 $kg/m^2s$, the saturation temperature was $30^{\circ}C$. In the flow patterns during evaporation, the annular flow in a 2 mm inner diameter tube occurred at a relatively lower quality and mass velocity, compared to that in a 8 mm inner diameter tube. The evaporation flow pattern in a small diameter tube has been shown major deviations with the Baker, Mandhane and Taitel-Dutler's flow pattern maps but it was similar to the Dobson's flow pattern map.

• The Journal of Advanced Prosthodontics
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• v.15 no.6
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• pp.302-314
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• 2023

PURPOSE. The aim of this study was to classify the shapes of retromolar pads and assess their morphometric differences using a 3D model. MATERIALS AND METHODS. Two hundred fully edentulous or Kennedy Class I partially edentulous patients (400 retromolar pads) were enrolled. Scan data of the definitive mandibular casts produced through functional impressions were obtained using a 3D laser scanner. Seven parameters (transverse diameter, longitudinal diameter, transverse-contour length, longitudinal-contour length, longitudinal/transverse diameter ratio, longitudinal/transverse-contour length ratio, and angle of the retromolar pad line to the residual alveolar ridge line) were measured using image analysis software. Subsequently, the pads were classified according to the shape. Statistical analyses were performed using 95% confidence intervals. RESULTS. Classifying the retromolar pads into three shapes led to high intra-examiner reliability (Cronbach's alpha = 0.933). The pear shape was the most common (56.5%), followed by oval/round (27.7%) and triangular (15.8%) shapes. There were no significant differences between the left and right sides according to the shape and no significant differences in any parameter according to age. The transverse diameter and longitudinal/transverse diameter ratio differed between sexes (P < .05). The triangular shape had a significantly different transverse diameter, transverse-contour length, longitudinal/transverse diameter ratio, and longitudinal/transverse-contour length ratio compared with the pear and oval/round shapes (P < .05). CONCLUSION. From a clinical reliability standpoint, classifying retromolar pads into three shapes (oval/round, pear-shaped, and triangular) is effective. The differences in the sizes among the shapes were attributed to the transverse measurement values.

• Journal of Magnetics
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• v.20 no.1
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• pp.40-46
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• 2015

This study investigated the accuracy of magnetic resonance angiography (MRA) and computed tomography angiography (CTA) in terms of reflecting the actual vascular length. Three-dimensional time of flight (3D TOF) MRA, 3D contrast-enhanced (CE) MRA, volume-rendering after CTA and maximum intensity projection were investigated using a flow model phantom with a diameter of 2.11 mm and area of $0.26cm^2$. 1.5 and 3.0 Tesla devices were used for 3D TOF MRA and 3D CE MRA. CTA was investigated using 16 and 64 channel CT scanners, and the images were transmitted and reconstructed by volume-rendering and maximum intensity projection, followed by conduit length measurement as described above. The smallest 3D TOF MRA measure was $2.51{\pm}0.12mm$ with a flow velocity of 40 cm/s using the 3.0 Tesla apparatus, and $2.57{\pm}0.07mm$ with a velocity of 71.5 cm/s using the 1.5 Tesla apparatus; both images were magnified from the actual measurement of 2.11 mm. The measurement with the 16 channel CT scanner was smaller ($3.83{\pm}0.37mm$) than the reconstructed image on maximum intensity projection. The images from CTA from examination apparatus and reconstruction technique were all larger than the actual measurement.

• Progress in Medical Physics
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• v.33 no.1
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• pp.1-9
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• 2022

Purpose: To evaluate the effective volume of the Korea Research Institute of Standards and Science free air chamber (KRISS FAC) L1 used for the primary standard device of the low-energy X-ray air kerma. Methods: The mechanical dimensions were measured using a 3-dimensional coordinate measuring machine (3-d CMM, Model UMM 500, Carl Zeiss). The diameter of the diaphragm was measured by a ring gauge calibrator (Model KRISS-DM1, KRISS). The elongation of the collector length due to electric field distortion was determined from the capacitance measurement of the KRISS FAC considering the result of the finite element method (FEM) analysis using the code QuickField v6.4. Results: The measured length of the collector was 15.8003±0.0014 mm with a 68% confidence level (k=1). The aperture diameter of the diaphragm was 10.0021±0.0002 mm (k=1). The mechanical measurement volume of the KRISS FAC L1 was 1.2415±0.0006 cm³ (k=1). The elongated length of the collector due to the electric field distortion was 0.170±0.021 mm. Considering the elongated length, the effective measurement volume of the KRISS FAC L1 was 1.2548±0.0019 cm³(k=1). Conclusions: The effective volume of the KRISS FAC L1 was determined from the mechanically measured value by adding the elongated volume due to the electric field distortion in the FAC. The effective volume will replace the existing mechanically determined volume in establishing and maintaining the primary standard of the low-energy X-ray.

• Journal of the Korean Society of Visualization
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• v.9 no.4
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• pp.41-46
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• 2011

Oxygen sensitive functional particles(OSParticle) were fabricated by three different methods for using the particles as oxygen sensors and PIV tracers. The used methods were a physical coating method, an ion-exchange method and a dispersion polymerization method. The physical coating method is dipping $SiO_2$ hollow particles into dye solution then drying. This method is very simple, but particles are not uniform in diameter and luminescence. The particles fabricated by the ion-exchange method have very uniform diameter and well doped. However, it can not be used in water since the particles are hydrophobic. In case of the dispersion polymerization method, the diameter of OSParticles is quite uniform. The diameter of OSParticles can be changed by controlling the quantity of AIBN (2,2'-azobis isobutyronitrile). For the purpose of dissolved oxygen concentration measurement in micro scale water flows, the dispersion polymerized OSParticles turn out to be the most superior functional particles. The luminescent intensity of OSParticles was tested with the variation of dissolved oxygen concentration in water samples. As a result, the luminescent intensity of OSParticles is monotonically decreased with increasing DO (Dissolved oxygen) concentration of water.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.10
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• pp.1387-1393
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• 2002

The measurement of velocity and stain rate field has been conducted in opposed impinging jet combustion. When a smaller diameter (5mm) orifice of pre-chamber was used, previous studies had reported that the combustion phase showed a shift from weak turbulent combustion to moderate turbulent combustion in the modified Borghi Diagram. In the case with smaller orifice diameter (5mm), NOx emission was substantially reduced by a factor 1/2 while the combustion pressure remains at the same as that in the conventional combustion. Hence, in this study, the experiment setup using PIV technique was designed to identify the relation of the strain rate distribution and NOx reduction associated with moderate turbulent combustion. As a result, it was found that the highly strained pockets are widely distributed during the combustion in the middle of chamber when the orifice diameter is 5mm. And the corresponding PDF distribution of strain rates she was the smoothly distributed strain .ate within the range of ｜$\pm$1000｜ (1/sec) rather than a spike shape about zero point. This is the unique feature observed in the combustion with 5mm orifice diameter. Therefore, it can be concluded that the substantial NOx reduction in opposed impinging combustor is mainly attributed to the strain rate distribution within the range of ｜$\pm$1000｜resulting in the combustion phase shift to moderate turbulent combustion.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1-6
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• 2008

When a saturated clay is sampled in an undisturbed manner from a bore hole, the sample extends vertically and shrinks horizontally under undrained conditions due to stress release. The conventional consolidation test specimen is trimmed from the expanded sample so that its diameter is equal to the inner diameter of the consolidation test ring, this test procedure does not reproduce the actual consolidation behavior. The measurement of sample extension was conducted by means of overcoring method found that the extension strains were 1 to 2%. To simulate the in-situ consolidation behavior, the consolidation test method that uses a specimen with a slightly smaller diameter than the inside diameter of consolidometer so that the specimen expands laterally to the inside of the ring.