• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.105-109
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• 1991

A computer aided flatness calibration system has been developed. Rectangular grids based measurement procedure is proposed with closing error technique. giving advantages over conventional diagonal measurement procedures (‘Union Jack’). A new analysis technique has been developed for flatness evaluation called ‘ETT(Enclose Tilt technique)’, enabling minimum separation definition which is acknowledged as standard term for flatness definition. Practical assessment shows the performance of the developed system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.1027-1028
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• 2009

• Smart Structures and Systems
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• v.15 no.2
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• pp.489-503
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• 2015

Response estimation at unmeasured locations using the limited number of measurements is an attractive topic in the field of structural health monitoring (SHM). Because of increasing complexity and size of civil engineering structures, measuring all structural responses from the entire body is intractable for the SHM purpose; the response estimation can be an effective and practical alternative. This paper investigates a response estimation technique based on the Kalman state estimator to combine multi-sensor data under non-zero mean input excitations. The Kalman state estimator, constructed based on the finite element (FE) model of a structure, can efficiently fuse different types of data of acceleration, strain, and tilt responses, minimizing the intrinsic measurement noise. This study focuses on the effects of (a) FE model error and (b) combinations of multi-sensor data on the estimation accuracy in the case of non-zero mean input excitations. The FE model error is purposefully introduced for more realistic performance evaluation of the response estimation using the Kalman state estimator. In addition, four types of measurement combinations are explored in the response estimation: strain only, acceleration only, acceleration and strain, and acceleration and tilt. The performance of the response estimation approach is verified by numerical and experimental tests on a simply-supported beam, showing that it can successfully estimate strain responses at unmeasured locations with the highest performance in the combination of acceleration and tilt.

• Atmosphere
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• v.26 no.3
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• pp.473-482
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• 2016

An accurate determination of turbulent fluxes over an urban area is a challenging task due to its morphological diversity and associated flow complexity. In this study, an eddy covariance (EC) method is applied over a highly heterogeneous urban area in a small city (Gongju), South Korea to investigate the quantitative influence of 'coordinate tilt' in determining the turbulent fluxes of sensible heat, latent heat, momentum, and carbon dioxide mass. Two widely-used coordinate transform methods are adopted and applied to eight directional sections centered on the site to analyze a 1-year period EC measurement obtained from the urban site: double rotation (DR) and planar fit (PF) transform. The results show that mean streamline planes determined by the PF method are distinguished from the sections, representing morphological heterogeneity of the site. The sectional pitch angles determined by the DR method also compare well with those in the PF method. Both the PF and DR methods show large variabilities in the determined streamline planes at each directional section, implying that flow patterns may form in a complicate way due to the surface heterogeneity. Resulting relative differences of the turbulent fluxes, defined by $(F_{DR}-F_{PF})/F_{DR}$, are found on average +13% in sensible heat flux, +21% in latent heat flux, +37% in momentum flux, and +26% in carbon dioxide mass flux, which are larger values than those reported previously for fairly homogeneous natural sites. The fractional differences depend significantly on wind direction, showing larger differences in northerly winds at the measurement site. It is also found that the relative fractional differences are negatively correlated with the mean wind speed at both stable/unstable atmospheric conditions. These results imply that EC turbulent fluxes determined over heterogeneous urban areas should be carefully interpreted with considering the uncertainty due to 'coordinate tilt' effect in their applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.11
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• pp.1364-1370
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• 2019

Tilt sensors are mainly used to measure the collapse of structures such as buildings, bridges and tunnels. Recently, due to the ease of use and low price, many tilt sensors using MEMS sensors have been used, but the measurement angle range is limited, and thus, they do not have high precision for 360 degree. This is due to the inherent offset and scale errors of MEMS sensors. In this paper, we proposed an algorithm for the calculation of precision angles to reduce the mechanical error of MEMS sensors, and produced a MEMS sensor module and a transmission module to compare the angle accuracy of sensor modules before calibration and the angle measurement accuracy after calibration. Experimental results show that the proposed technique has a precision of ± 0.015 degrees for all 360-degree.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.605-613
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• 2009

In this paper, we studied for the real-time azimuthal measurement of HMD (Head Mounted Display) to control the tele-operated vision system on the mobile robot. In the preexistence tele-operated vision system, a joystick was used to control the pan-tilt unit of the remote camera system. To give the sense of presence to the tele-operator, we used a HMD to display the remote scene, measured the rotation angle of the HMD on a real time basis, and transmitted the measured rotation angles to the mobile robot controller to synchronize the pan-tilt angles of remote camera with the HMD. In this paper, we suggest an algorithm for the real-time estimation of the HMD rotation angles using feature points extraction from pc-camera image. The simple experiment is conducted to demonstrate the feasibility.

• Imaging Science in Dentistry
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• v.43 no.3
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• pp.191-196
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• 2013

Purpose: This study assessed the accuracy of linear and angular measurements on panoramic radiographs taken at different positions in vitro. Materials and Methods: Two acrylic models were fabricated from a cast with normal occlusion. Straight and $75^{\circ}$ mesially and lingually angulated pins were placed, and standardized panoramic radiographs were taken at standard position, at an $8^{\circ}$ downward tilt of the occlusal plane compared to the standard position, at an $8^{\circ}$ upward tilt of the anterior occlusal plane, and at a $10^{\circ}$ downward tilt of the right and left sides of the model. On the radiographs, the length of the pins above (crown) and below (root) the occlusal plane, total pin length, crown-to-root ratio, and angulation of pins relative to the occlusal plane were calculated. The data were subjected to repeated measures ANOVA and LSD multiple comparisons tests. Results: Significant differences were noted between the radiographic measurements and true values in different positions on both models with linear (P<0.001) and those with angulated pins (P<0.005). No statistically significant differences were observed between the angular measurements and baselines of the natural head posture at different positions for the linear and angulated pins. Conclusion: Angular measurements on panoramic radiographs were sufficiently accurate and changes in the position of the occlusal plane equal to or less than $10^{\circ}$ had no significant effect on them. Some variations could exist in the pin positioning (head positioning), and they were tolerable while taking panoramic radiographs. Linear measurements showed the least errors in the standard position and $8^{\circ}$ upward tilt of the anterior part of the occlusal plane compared to other positions.

• Journal of the Korean Society of Physical Medicine
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• v.1 no.1
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• pp.23-36
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• 2006

Purpose : The purpose of this study was to evaluate the effects of back muscle stretching on the flexibility of spinal column. Methods : The subjects were consisted of healthy adults (18 of females, 22 males ; mean aged 21.83) from 18 to 29. All subjects randomly assigned to the control group, back muscle stretching group. back muscle stretching group received back muscles stretching for 20 minutes per day and 3 times a week during 3 week period. Spine motion analyzer (Spinal Mouse) was used to measure the flexibility of spinal column. All measurement of each subjects were measured at pre-experiment, after 10 days, and after 21 days. Results : The results of this study were summarized below 1. The sacral tilt angle of the hip joint of control group, back muscle stretching group was no significantly differences at pre-experiment and after 10 days(p>0.5), but differency of each group occurred at after 21 days(p<0.5). the sacral tilt angle significantly increased at the back muscle stretching group rather than the control group. 2. The thoracic vertebral tilt angle of the control group, back muscle stretching group was no significantly differences at pre-experiment, after 10 days, after 21 days(p>0.5). 3. The lumbar vertebral tilt angle of the control group, back muscle stretching group was no significantly differences at pre-experiment, after 10 days, after 21 days(p>0.5). 4. The spinal tilt angle of control group, back muscle stretching group was no significantly differences at pre-experiment and after 10 days(p>0.5), but differency of each group occurred at after 21 days(p<0.5). the spinal tilt angle significantly increased at the back muscle stretching group rather than the control group(p>0.5). 5. The length of the spinal column of control group, back muscle stretching group was no significantly differences at pre-experiment and after 10 days (p>0.5), but differency of each group occurred at after 21 days(p<0.5). the length of the spinal column significantly increased at the back muscle stretching group rather than the control group(p<0.5). Conclusion : These data suggests that 3-week back muscle stretching improved the flexibility of sacrum, spinal column, and also improved spinal column lengthening. Additional randomized controlled trials to more fully investigate treatment effects and factors that may mediate these effects are needed.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.12 no.1
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• pp.1-15
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• 2006

Purpose: The purpose of this study was to evaluate the effects of abdominal muscle strengthening exercises and back muscle stretching on the flexibility of spinal column. Methods: The subjects were consisted of healthy adults ( 28 of females, 32 males; mean aged 21.6) from 18 to 29. All subjects randomly assigned to the control group, back muscle stretching group, abdominal muscle strengthening exercises group. back muscle stretching group received back muscles stretching for 20 minutes, abdominal muscle strengthening exercises group received abdominal muscle strengthening exercises for 30 minutes per day and 3 times a week during 3 week period. Spine motion analyzer (Spinal Mouse) was used to measure the flexibility of spinal column. All measurement of each subjects were measured at pre-experiment, after 10 days, and after 21 days. Results: The results of this study were summarized below 1. The sacral tilt angle of the hip joint of control group, back muscle stretching group, abdominal strengthening exercises group was no significantly differences at pre-experiment and after 10 days(p>0.5), but differency of each group occurred at after 21 days(p<0.5). the sacral tilt angle significantly increased at the back muscle stretching group, abdominal muscle strengthening exercises group, rather than the control group. 2. The thoracic vertebral tilt angle of the control group, back muscle stretching group, abdominal muscle strengthening exercises group was no significantly differences at pre-experiment, after 10 days, after 21 days(p>0.5). 3. The lumbar vertebral tilt angle of the control group, back muscle stretching group, abdominal muscle strengthening exercises group was no significantly differences at pre-experiment, after 10 days, after 21 days(p>0.5). 4. The spinal tilt angle of control group, back muscle stretching group, abdominal muscle strengthening exercises group was no significantly differences at pre-experiment and after 10 days(p>0.5), but differency of each group occurred at after 21 days(p<0.5). the spinal tilt angle significantly increased at the back muscle stretching group, abdominal muscle strengthening exercises group, rather than the control group(p<0.5). 5. The length of the spinal column of control group, back muscle stretching group, abdominal muscle strengthening exercises group was no significantly differences at pre-experiment and after 10 days (p>0.5), but differency of each group occurred at after 21 days(p<0.5). the length of the spinal column significantly increased at the back muscle stretching group, abdominal muscle strengthening exercises group, rather than the control group(p<0.5). Conclusion: these data suggests that 3-week abdominal muscle strengthening exercises and back muscle stretching improved the flexibility of sacrum, spinal column, and also improved spinal column lengthening. Additional randomized controlled trials to more fully investigate treatment effects and factors that may mediate these effects are needed.

• PNF and Movement
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• v.19 no.3
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• pp.303-310
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• 2021

Purpose: The purpose of the present study was to investigate the effects of the contact-relax (CR) intervention on pelvic alignment in subjects with habitual poor posture. Methods: Fifteen subjects who have habitual poor posture participated in this study. The subjects received an intervention inducing pelvic posterior depression with the elevated pelvic side. Pre- and post-intervention, and two weeks after intervention, the pelvic alignment was measured with a palpation meter (PALM) and a three-dimensional diagnostic imaging system. Results: Measuring with PALM, the pelvic height and anterior tilt angle were significantly decreased immediately after and were still decreased two weeks after intervention, compared to the pre-measurement (p<0.05). Three-dimensional pelvic alignment was also significantly different between measurement points, while the pelvic position (pelvic lateral tilt) was significantly decreased after intervention (p<0.05). Conclusion: By applying the intervention generating CR on an elevated pelvis, frontal pelvic alignment can be improved.