• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.105-115
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• 2015

Purpose: The accuracy for measuring the refractive power of hydrogel contact lenses by spectacle lens holder and contact lens holder was evaluated. The accuracy for each sample was also analyzed with water content and diopter categories. Methods: The hydrogel contact lenses used for measurement were classified into three categories in water content (38%, 43%, 58%). Also, three diopter categories of refractive power were used such as -3.000 D, -7.000 D, -10.000 D. And also, the reliability of measurement results were evaluated by measuring refractive power with spectacle lens holder and contact lens holder using an Manual lensmeter. Results: In case of spectacle lens holder method, the average value of refractive power was -3.3273D for -3.0000 D, -7.1306 D for -7.0000 D and -10.2944 D for -10.0000 D, respectively. In case of contact lens holder method, the average value of refractive power was -3.1060 D for -3.0000 D, -7.0028 D for -7.0000 D and -10.2611 D for -10.0000 D, respectively. In measurement of all diopters, the accuracy of contact lens holder method was better than spectacle lens holder method. Conclusions: From these results, it is judged that the refractive power of soft contact lens by manual lensmeter with contact lens holder have a higher accuracy than spectacle lens holder.

• Journal of Broadcast Engineering
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• v.21 no.4
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• pp.506-514
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• 2016

In this study, HEVC over DVB-T2 systems with a bandwidth of 6 MHz is considered, particularly for the terrestrial 4K-UHDTV broadcasting service in the Republic of Korea. The threshold of visibility carrier-to-noise power ratio (ToV C/N) and the receiver minimum required input level (sensitivity) for satisfying the subjective picture failure (SPF) condition are measured in the laboratory. It is observed, for transmitting 26.37 Mbps data stream correctly, that ToV C/N is 18.8 dB on average, and the receiver sensitivity is varied from minimum -84.2 dBm to maximum -80.0 dBm. Based on the results, the receiver noise floor is calculated by -100 dBm on average.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.808-820
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• 2014

In this paper, we fabricated two on-wafer type DUT(Device-Under-Test)s; a 10-dB attenuator and an amplifier using commercially available MMIC and we proposed the measurement method of the noise parameters for the two fabricated DUTs. Since the 10-dB attenuator DUT is a passive device, its noise parameters can be accurately determined when its S-parameters are measured. In the case of the amplifier DUT, its noise parameters are available in the datasheet. Hence, the measured noise parameters using the proposed method can be assessed by comparing with the known noise parameters. The noise parameter measurement method having been presented by the authors requires the S-parameters of the 8-port network used in the measurement and limited to coaxial type DUTs. When on-wafer probes are included in the 8-port network, the 8-port S-parameters requires the measurements with different kinds of connectors. In this paper, we obtained the 8-port S-parameters using the Smart-Cal function in the network analyzer. The measured noise parameters shows about ${\pm}0.2dB$ fluctuations for $NF_{min}$. Other noise parameters with the frequency change show good agreement with the expected results.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.2
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• pp.69-79
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• 1994

The conventional machine vision system which has uniform rectangular grid requires tremendous amount of computation for processing and analysing an image especially in 2-D image transfermations such as scaling, rotation and 3-D reconvery problem typical in robot application environment. In this study, the imaging system with nonuiformly distributed image sensors simulating human visual system, referred to as Ploar Exponential Grid(PEG), is compared with the existing conventional uniform rectangular grid system in terms of image resolution and computational complexity. By mimicking the geometric structure of the PEG sensor cell, we obtained PEG-like images using computer simulation. With the images obtained from the simulation, image resolution of the two systems are compared and some basic image processing tasks such as image scaling and rotation are implemented based on the PEG sensor system to examine its performance. Furthermore Fourier transform of PEG image is described and implemented in image analysis point of view. Also, the range and heading-angle measurement errors usually encountered in 3-D coordinates recovery with stereo camera system are claculated based on the PEG sensor system and compared with those obtained from the uniform rectangular grid system. In fact, the PEC imaging system not only reduces the computational requirements but also has scale and rotational invariance property in Fourier spectrum. Hence the PEG system has more suitable image coordinate system for image scaling, rotation, and image recognition problem. The range and heading-angle measurement errors with PEG system are less than those of uniform rectangular rectangular grid system in practical measurement range.

• The KIPS Transactions:PartD
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• v.14D no.2
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• pp.225-234
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• 2007

Recently, IT Governance has emerged as the new keyword in the IT world. However, the multiple definitions and concepts that exist for this word are causing confusion among observers. Thus, in order to clarify the conceptual meaning behind the term 'IT Governance' once and for all, this study reviews previous literature and defines the sub construct of IT Governance. Then, we develop the measurement instrument for IT Governance, which results in three domains: IT resource and performance management. IT project management, and IT service management.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.532-540
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• 2014

It is necessary to measure the current of rotor for controlling the active and reactive power generated by the stator side of the doubly fed induction generator (DFIG) system. There are offset and scaling errors in the current measurement. The offset and scaling errors cause one and two times current ripples of slip frequency in the synchronous reference frame of vector control, respectively. This paper proposes a compensation method to reduce their ripples. The stator current is variable according to the wind force but the rotor current is almost constant. Therefore input of the rotor current is more useful for a compensation method. The proposed method adopts the synchronous d-axis current of the rotor as the input signal for compensation. The ripples of the measurement errors can be calculated by integrating the synchronous d-axis stator current. The calculated errors are added to the reference current of rotor as input of the current regulator, then the ripples are reduced. Experimental results show the effectiveness of the proposed method.

• Journal of the Korean Society of Clothing and Textiles
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• v.48 no.2
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• pp.233-253
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• 2024

This study analyzed differences between three-dimensional (3D) body scanning and manual measurements, aiming to assess whether 3D scanning can replace traditional anthropometric tools, such as tape measures and calipers. Data from 4,478 participants in the 8th Size Korea Project were analyzed, covering 43 measurement items. Since Given that the 3D and manual measurements were performed on the same subjects in the 8th Size Korea Project, it was possible to determine the correlation more accurately between the two measurement methods more accurately. Using Applying ISO 20685-1(2018) standards, 15 out of the 43 items fell within allowable error limits. When classified into six types, "small circumferences" and "segment lengths" showed averages of 3.35 mm and 3.10 mm, respectively, within acceptable range. "Body heights" and "body depths" slightly exceeded the limit, with averages of 5.28 mm and 6.58 mm. "Body widths" and "large circumferences" surpassed the limit, with means of 16.77 mm and 16.18 mm. The study offers an objective basis to for validate validating 3D measurements' measurements' reliability and accuracy, addressing various industries' needs for information on the human body's dimensions information.

• Progress in Medical Physics
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• v.26 no.1
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• pp.42-51
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• 2015

In proton therapy, verification of proton dose distribution is important to treat cancer precisely and to enhance patients' safety. To verify proton dose distribution, in a previous study, our team incorporated a vertically-aligned one-dimensional array detection system. We measured 2D prompt-gamma distribution moving the developed detection system in the longitudinal direction and verified similarity between 2D prompt-gamma distribution and 2D proton dose distribution. In the present, we have developed two-dimension prompt-gamma measurement system consisted of a 2D parallel-hole collimator, 2D array-type NaI(Tl) scintillators, and multi-anode PMT (MA-PMT) to measure 2D prompt-gamma distribution in real time. The developed measurement system was tested with $^{22}Na$ (0.511 and 1.275 MeV) and $^{137}Cs$ (0.662 MeV) gamma sources, and the energy resolutions of 0.511, 0.662 and 1.275 MeV were $10.9%{\pm}0.23p%$, $9.8%{\pm}0.18p%$ and $6.4%{\pm}0.24p%$, respectively. Further, the energy resolution of the high gamma energy (3.416 MeV) of double escape peak from Am-Be source was $11.4%{\pm}3.6p%$. To estimate the performance of the developed measurement system, we measured 2D prompt-gamma distribution generated by PMMA phantom irradiated with 45 MeV proton beam of 0.5 nA. As a result of comparing a EBT film result, 2D prompt-gamma distribution measured for $9{\times}10^9$ protons is similar to 2D proton dose distribution. In addition, the 45 MeV estimated beam range by profile distribution of 2D prompt gamma distribution was $17.0{\pm}0.4mm$ and was intimately related with the proton beam range of 17.4 mm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.181-181
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• 2004

3 차원 형상측정기술(3-D Profile Measurement Method)은 가공품의 치수검사 및 형상측정 등의 공학분야뿐만 아니라 최근에는 의류산업 및 의학산업은 물론 오락산업의 가상현실 구현 등 여러 분야로 점차 사용이 확대되고 있다. 이러한 요구를 만족시킬 수 있는 광학을 바탕으로 한 비접촉 3 차원 형상측정방법(Non-contacting 3-D Profile Measuring Method)은 고속, 고정밀도 측정이 가능하기 때문에 활발히 연구되고 있다. 광학을 이용한 대표적인 3 차원 비접촉 측정방법의 하나인 영사식 무아레는 그림자식 무아레의 단점인 격자의 크기가 측정물체보다 커야 한다는 점과 측정물체와 격자사이의 거리 제한 문제를 해결하였으며, 위상이동법을 사용함으로서, 무아레 무늬 형태의 영향을 받지 않고 측정이 가능해졌다.(중략)

• Progress in Superconductivity and Cryogenics
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• v.13 no.2
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• pp.29-32
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• 2011

The thermal properties of insulation material are essential to develop a high-temperature superconducting (HTS) power cable to be operated at around liquid nitrogen temperature. Unlike metallic materials, nonmetallic materials have a high thermal resistance; therefore special attention needs to be paid to estimate heat flow correctly. Thus, we have developed a precise instrument for measuring the thermal conductivity of insulating materials over a temperature range from 40 K to near room temperature using a cryocooler. Firstly, the measurement of thermal conductivity for Teflon is carried out for accuracy confirmation. For a supplied heat flux, the temperature difference between warm and cold side is measured in steady state, from which the thermal conductivity of Teflon is calculated and compared with published result of NIST. In addition, the apparent thermal conductivity of Polypropylene laminated paper (PPLP) is presented and its temperature dependency is discussed.