• 전기학회논문지
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• 제62권12호
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• pp.1798-1802
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• 2013

We present a technique for measuring low resistance ranges of a decade resistor with a 4-Terminal connection. With the technique the accuracy of 0.8 % was obtained for a 1 $m{\Omega}$ resistance of the decade resistor. We suggested a proper pattern 4-Terminal measurement results with several 4-Terminal pattern and adapters. Additionally, we should that precise measurements for low resistance can be made usung a digital multimeter(DMM) only.

• 한국전기전자재료학회논문지
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• 제32권2호
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• pp.151-156
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• 2019

The aim of this investigation is to detect specific waveforms in a distribution line prior to the occurrence of a fault. Conditions were introduced such that a feeder remote terminal unit (FRTU) of the distribution automation system selects and stores fault waveforms from the different waveforms detected in the distribution line. In addition, an algorithm was developed to detect specific waveforms from the fault waveforms stored using the FRTU. This algorithm exploits the duration and periodicity of harmonic changes in voltage and current. The efficacy of the algorithm was confirmed based on the measurements of fault waveforms in an actual distribution line. The results indicated that faults in a distribution line can be predicted via experimental measurements.

• 한국정보통신학회논문지
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• 제13권12호
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• pp.2719-2730
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• 2009

본 논문에서는 EDGE (Enhanced Data Rates for GSM Evolution) 단말의 성능을 측정하기 위한 측정 알고리즘을 소프트웨어로 구현하고 EDGE 신호 발생기를 통해 발생된 신호를 이용해 구현된 소프트웨어 측정 알고리즘의 성능을 평가해본다. 일반적으로 통신신호 측정기는 매우 정밀한 정확도를 필요로 하므로 정확도가 충분히 높지 않은 일반 통신모뎀 수준의 수신 알고리즘을 직접적으로 측정기에 적용할 수는 없다. 본 논문에서는 EDGE 신호의 정밀한 측정을 위한 새로운 EDGE 신호의 수신 알고리즘을 제안한다. 제안된 EDGE 수신 알고리즘에는 2단계(개략적 단계, 미세 단계)의 파라미터(심볼타이밍, 주파수오프셋, 반송파위상) 추정방식을 사용하였다. 또한 수신신호의 보간을 이용하여 수신 신호 샘플의 개수를 증가시킴으로서 측정의 정확도를 향상시켰다. 본 논문에서 제안된 EDGE 신호 측정방식은 하드웨어를 구현하기 전에 소프트웨어를 이용하여 사전에 측정 성능을 검증하는데 사용될수 있다. 또한 구현된 소프트웨어 알고리즘을 속도측면에서 최적화함으로서 직접 EDGE 신호 측정을 위한 상용 시스템으로도 이용할 수 있다.

• The Journal of Advanced Prosthodontics
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• 제14권1호
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• pp.22-31
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• 2022

PURPOSE. The purpose of this study was to investigate the misfit and screw preload at the implant abutment connection of implant supported fixed dental prosthesis with cantilever (ICFDP) manufactured using different digital manufacturing techniques and to compare the screw preload before and after cyclic loading. MATERIALS AND METHODS. Mandibular jaw model with four intra-foraminal implants was scanned using digital scanner. Stereolithography file was used to design a framework with nonengaging (NE) abutments and 10 mm cantilever distal to one terminal implant. Five frameworks were constructed using combined digital-conventional techniques (CAD-cast), and five frameworks were constructed using three-dimensional printing (3DP). Additional CAD-cast framework was constructed in a way that ensures passive fit (PF) to use as control. Scanning electron microscope (SEM) measured the implant abutment connection misfit. Sixty screws were used on the corresponding frameworks. Screws were torqued and pre-cyclic loading reverse torque value (RTV) was recorded. Frameworks were subjected to 200,000 loading cycles with a loading point 9 mm from the center of terminal implants adjacent to the cantilever and post-cyclic loading RTVs were recorded. RESULTS. Microscopic readings showed significant differences between frameworks. PF demonstrated the lowest measurements of 16.04 (2.6) ㎛ while CAD-cast demonstrated the highest measurements of 29.2 (3.1) ㎛. In all groups, RTVs were significantly lower than the applied torque. Post-cyclic loading RTV was significantly lower than pre-cyclic loading RTV in PF and 3DP frameworks. Differences in RTVs between the three manufacturing techniques were insignificant. CONCLUSION. Although CAD-cast and three-dimensionally printed (3DP) both produce frameworks with clinically acceptable misfit, 3DP might not be the technique of choice for maintaining screw's preload stability under an aggressive loading situation.

• 한국항행학회논문지
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• 제2권2호
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• pp.84-99
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• 1998

탄도탄 요격용 유도무기의 closed-loop 유도기법으로 종말유도의 효율성을 증대시키기 위해 산정된 비행자세 각으로 표적을 요격하기 위한 중기유도 법칙을 제시한다. 제시된 유도법칙은 잡음환경하에서의 비선형 레이더 측정치를 사용하는 확장칼만필터(EKF) 알고리즘을 사용하여 추정된 표적의 상태변수를 이용하고 표적의 운동을 간략화 하여 구한 추정된 표적의 위치를 기반으로 한다. 제시된 중기유도법칙의 3차원 공간으로의 확장에 대해서도 연구한다. 제시된 중기유도법칙을 적용하고, 종말유도법칙으로 비례항법유도(PNG)을 사용하는 일련의 시뮬레이션을 통해 유도성능을 확인한다.

• 한국전문물리치료학회지
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• 제28권2호
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• pp.117-122
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• 2021

Background: Flat-back posture refers to a posture in which the pelvis is tilted backward, the lumbar spine is bent, the upper thoracic spine is increasingly bent, and the lower thoracic spine is straight. Given that most of the day is spent sitting, we need to develop exercise programs and devices that are suitable for people who spend less time exercising than sitting. Objects: This study investigated the effects of resistance footrest exercise on spine posture angles in visual display terminal (VDT) workers with flat back. Methods: We measured the upper lumbar angle (ULA) and lower lumbar angle (LLA) using a flexible ruler for the ULA and LLA. Then, after 1 week of resistance footrest exercise designed to strengthen the lumbar spine musculature, we measured these angles again. We measured each angle three times and then compared measurements from before and after exercise. Results: There were no significant differences in the ULA following the strengthening exercise, but significant differences were observed in LLA. Conclusion: The resistance footrest exercise strengthened the muscles affecting the pelvic and lumbar lordotic angles, and increases in the LLA were changed. This suggests that the role of the lower lumbar spine in the lumbar lordotic curve is greater than that of the upper lumbar spine. In addition, considering the contemporary tendency to lead fairly sedentary lives, these results indicate that exercising while seated can be effective.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.83-88
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• 2006

Many applications in the area of location-based services and personal navigation require nowadays the location determination of a user not only in outdoor environment but also indoor. To locate a person or object in a building, systems that use either infrared, ultrasonic or radio signals, and visible light for optical tracking have been developed. The use of WiFi for location determination has the advantage that no transmitters or receivers have to be installed in the building like in the case of infrared and ultrasonic based location systems. WiFi positioning technology adopts IEEE802.11x standard, by observing the radio signals from access points installed inside a building. These access points can be found nowadays in our daily environment, e.g. in many office buildings, public spaces and in urban areas. The principle of operation of location determination using WiFi signals is based on the measurement of the signal strengths to the surrounding available access points at a mobile terminal (e.g. PDA, notebook PC). An estimate of the location of the terminal is then obtained on the basis of these measurements and a signal propagation model inside the building. The signal propagation model can be obtained using simulations or with prior calibration measurements at known locations in an offline phase. The most common location determination approach is based on signal propagation patterns, namely WiFi fingerprinting. In this paper the underlying technology is briefly reviewed followed by an investigation of two WiFi positioning systems. Testing of the system is performed in two localization test beds, one at the Vienna University of Technology and the second at the Hong Kong Polytechnic University. First test showed that the trajectory of a moving user could be obtained with a standard deviation of about ${\pm}$ 3 m.

• Journal of Periodontal and Implant Science
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• 제24권2호
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• pp.261-270
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• 1994

The purpose of this study was to evaluate relationship of probing attachment levels, radiographic measurements and surgical measurements according to gingival inflammatory condition. Patients with incipient to moderate periodontitis were selected. Upper and lower premolar and molar teeth excluding third molars were measured. At first visit, gingival index and bleeding on probing were taken, and subjects were grouped into 4 categories as follows : Experimental group I : gingival index 1 and no bleeding on probing. Experimental group II : gingival index 2 and no bleeding on probing absent. Experimental group III : gingival index 1 and bleeding on probing present. Experimental group IV : gingival index 2 and bleeding on probing present. Probing attachment levels were measured with manual probe on mesial and distal surfaces from cementoenamel junctions to terminal ends of probe. Radiographic measurements were made to assess bone loss by measuring the distance from cementoenamel junction to the alveolar crest. After thorough scating, a flap was raised exposing the alveolar bone and surgical measurements were made from cementoenamel junction to alveolar bone. The results were as follows: 1. Differences between probing attachment level and radiographic measurements showed $1.01{\pm}0.73mm$ for experimental group I, $0.98{\pm}0.48mm$ for experimental group II, $0.59{\pm}0.66mm$ for experimental group III, $0.98{\pm}0.38mm$ for experimental group IV and with no significant difference between groups. 2. Differences between probing attachment level and surgical measurements showed $1.36{\pm}0.80mm$ for experimental group I, $1.47{\pm}0.54mm$ for experimental group II, $1.06{\pm}0.39mm$ for experimental group III, $1.41{\pm}0.40mm$ for experimental group IV and with no significant difference between groups. 3. Differences between surgical and radiographic measurements showed $0.36{\pm}0.48mm$ for experimental group I, $0.51{\pm}0.54mm$ for experimental group II, $0.57{\pm}0.72mm$ for experimental group III, $0.41{\pm}0.49mm$ for experimental group IV and with significant difference between experimental group I and experimental group II, III, IV(P<0.05).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1824-1827
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• 2003

During normal machine operation, partial discharge(PD) measurements were performed with turbine generator analyzer(TGA) in two high voltage motors. Two 6.6kV motors were installed with 80pF capacitive couplers at the terminal box. The PD patterns were displayed two dimensional and three dimensional. TGA summarizes each plot with two quantifies such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). Off-line PD measurements were conducted on one 4.16kV motor. The motor was energized to 2.4kV, 3.0kV, 3.5kV and 4.16kV, respectively. The PD levels in pC were measured with a conventional digital PD detector. The comparison of positive to negative PD indicates whether the defect elements of PD are within the insulation or on the insulation surface. Discharge at conductor surface was discovered in No. 1 motor. Internal discharges were generated in phase A, B and C of No. 2 motor, Slot discharges occurred in three phases of No. 3 motor.

• 한국대기환경학회지
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• 제17권1호
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• pp.39-50
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• 2001

The spatial distribution characteristics of airborbe mercury(Hg) were investigated used its concentration data from six measurement sites selected to represent:(1) three terminal sites with heavy traffic loads in urban area, (2) one urban residential site and (3) two mountainous sites in Korea. The measurement data obtained during September 1997 through May 1998 indicated that the mean concentration of Hg from different study sites were comparably high with the mean values spanning from 5-9ng./㎥. The concentration from all those sites were systmatically high compared to those of most background sites around world or to other Korean sites investigaed previously. When results of correlation analysis between Hg and relevant parameters were compared among different study sites. temperature was most frequently found out to be in strong correlation with Hg concentrations. Results of factor analysis also indicated that Hg concentrations could be affected simultaneously by th factors affecting such parameters as ozone, temperature, ozone, carbon monoxide, and PM. The findings of enhanced Hg levels from Ji-Ri Mountain relative to terminal site suggest that is distributions may be rather homogeneous not enough to clearly distinguish areal differences and the associated source signatures between urban and rural area. The existence of systmatically high concentrations from all investigated sites also indicate that the impact of its source processes should be quite ubiquitous, while highly variable in relatively long term scale.