• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.10a
• /
• pp.400-403
• /
• 2018

The VR / AR market has grown significantly due to the development of Virtual Reality and Augmented Reality, the core technologies of the Fourth Industrial Revolution. According to a report released by the Korea Science and Engineering Corporation (KISTEP), the global VR / AR market will grow to $ 105 billion by 2022. An important key to the growth of the VR / AR market is user immersion. VR is dependent on technology of hardware such as display and sensor for biometric signal recognition. In order to improve user's immersion feeling, it is important to transmit sensor data to display device more accurately and quickly. In this paper, we consider various sensor hardware dependencies of VR, and compare various correction methods and filtering methods to lower the Motion to Photon (MTP) time that user movement is fully reflected on the display using sensor devices.

• Physical Therapy Korea
• /
• v.13 no.1
• /
• pp.9-15
• /
• 2006

Work-related musculoskeletal disorder has been associated with long hours of computer work and prolonged periods of static posture. In clinical settings, postural correction is a common treatment approach for individuals with neck, shoulder, and back pain. This study was designed to identify the effect of Forward Head Posture Correctional Device during computer work. Twelve healthy adults (mean age, 27.4 yrs; mean height, 165.0cm mean weight, 65.8 kg) participated in the study. They had no medical history of neurological or surgical problems with their upper extremity. The subjects were asked to perform Head Forward Posture under the guidance of physical therapists and the measured angles were analyzed using a 3-D motion analysis system. Markers were placed on the C7 spinous process, tragus of the ear and forward head angle was between the line from the tragus to the C7 line and the Y-axis at the C7. The statistical significance of difference between, "without" and "with" correctional device was tested by paired t-test. A level of significance was set at ${\alpha}$=.05. In comparison of the computer work between "without" and "with" correctional device, Forward Head Angle was showed significant difference (p<.05). In conclusion, the range of Forward Head Angle was significantly decreased during computer work with the correctional device. Further research is needed to understand the nature of motor control problems in deep muscles in patients with neck, shoulder, and back pain.

• Steel and Composite Structures
• /
• v.19 no.2
• /
• pp.369-384
• /
• 2015

This work presents a free vibration analysis of functionally graded metal-ceramic (FG) beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. For this purpose, a simple displacement field based on higher order shear deformation theory is implemented. The proposed theory is based on the assumption that the transverse displacements consist of bending and shear components in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. The most interesting feature of this theory is that it accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the beam without using shear correction factors. In addition, it has strong similarities with Euler-Bernoulli beam theory in some aspects such as equations of motion, boundary conditions, and stress resultant expressions. The rule of mixture is modified to describe and approximate material properties of the FG beams with porosity phases. By employing the Hamilton's principle, governing equations of motion for coupled axial-shear-flexural response are determined. The validity of the present theory is investigated by comparing some of the present results with those of the first-order and the other higher-order theories reported in the literature. Illustrative examples are given also to show the effects of varying gradients, porosity volume fraction, aspect ratios, and thickness to length ratios on the free vibration of the FG beams.

• Clinics in Orthopedic Surgery
• /
• v.10 no.4
• /
• pp.479-483
• /
• 2018

Background: We developed a modified proximal scarf osteotomy technique for moderate to severe hallux valgus in an attempt to obtain better correction of the deformity. In addition, we compared the clinical and radiographic results of this modified technique with those of the classic scarf osteotomy reported in other studies. Methods: Between December 2004 and July 2009, 44 cases of modified proximal scarf osteotomy was performed in 35 patients with moderate hallux valgus. The American Orthopedic Foot and Ankle Society (AOFAS) score, visual analogue scale (VAS) score, range of motion of the first metatarsophalangeal joint, and radiographic results were evaluated. Results: The mean hallux valgus angle and the mean first intermetatarsal angle improved from an average of $32.2^{\circ}$ and $14.3^{\circ}$, respectively, to an average of $12.5^{\circ}$ and $8.6^{\circ}$, respectively. The distal metatarsal articular angle improved from an average of $18.7^{\circ}$ to $12.4^{\circ}$. The preoperative mean AOFAS and VAS scores were 47 points and 7 points, respectively, which improved to 86 points and 1 point, respectively, at the final follow-up. Limited range of motion occurred in two cases postoperatively. The height of the first metatarsal-cuneiform joint, which was an average of 15.9 mm preoperatively, did not change. The first metatarsal-talus angle increased from an average of $4.1^{\circ}$ to $7.1^{\circ}$. Conclusions: The modified proximal scarf osteotomy for the treatment of moderate hallux valgus showed similar results with the classic scarf osteotomy with regard to changes in the first intermetatarsal angle and postoperative satisfaction. Therefore, we suggest the modified proximal scarf osteotomy be considered as well as other proximal osteotomy in the treatment of moderate to severe hallux valgus.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.22 no.11
• /
• pp.1413-1420
• /
• 2018

The VR / AR market has grown significantly due to the development of virtual reality and augmented reality in the core technology field of the 4th Industrial Revolution. Since VR is basically focused on space and time, and the human brain is very sensitive to temporal events, it is important to make accurate I / O interface technology, one of the virtual reality technologies, not to affect the brain's cognitive ability. VR depends on the technology of the hardware such as the display and the sensor for biometric signal recognition. In this paper, in order to prevent the sensitive brain from affecting the sensor device in consideration of hardware dependency of VR, it is necessary to make various corrections to lower the motion to photon (MTP) to 20m / s or less experiments on the method and filtering were carried out.

• Clinics in Shoulder and Elbow
• /
• v.22 no.3
• /
• pp.128-134
• /
• 2019

Background: Patients with rotator cuff tears are usually afflicted with shoulder pain and disability. However, it is unclear which factors are related to shoulder pain in patients with rotator cuff tears. This study was therefore undertaken to determine the factors correlated with shoulder pain in patients with painful rotator cuff tears, but without any history of trauma. Methods: We evaluated a cohort of 745 patients with painful rotator cuff tears having no trauma history, and analyzed the relationship between pain and multiple factors including demographic data, tear characteristics, and passive range of motion. Pain was analyzed with a questionnaire concerning the visual analogue scale (VAS) for pain. Tear characteristics were determined by evaluating tear size, muscle atrophy, number of torn tendons, and presence of arthritis. Multivariate linear regression analysis and chi-squared test were applied to evaluate the relationship between the VAS for pain and variable factors. Results: Shoulder pain was associated with young age (p=0.01), male sex (p=0.01) and the presence of diabetes mellitus (p<0.001). Measurements of rotator cuff tear characteristics including tear size (p=0.53), muscle atrophy (p=0.16) and the number of torn tendons (p=0.34) did not correlate with shoulder pain. Symptom duration (p=0.60) and range of motion (p>0.05) also showed no correlation with VAS for pain. Conclusions: Young age, male sex and the presence of diabetes mellitus correlated positively with preoperative shoulder pain in patients with painful rotator cuff tears without a trauma history. Combined treatment of pain management and risk factor correction could be helpful to control preoperative shoulder pain.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2022.05a
• /
• pp.587-588
• /
• 2022

In this paper, we propose a rigid body tracking method in 3D space using 2D passive marker images from multiple motion capture cameras. First, a calibration process using a chess board is performed to obtain the internal variables of individual cameras, and in the second calibration process, the triangular structure with three markers is moved so that all cameras can observe it, and then the accumulated data for each frame is calculated. Correction and update of relative position information between cameras. After that, the three-dimensional coordinates of the three markers were restored through the process of converting the coordinate system of each camera into the 3D world coordinate system, the distance between each marker was calculated, and the difference with the actual distance was compared. As a result, an error within an average of 2mm was measured.

• Korean Journal of Optics and Photonics
• /
• v.33 no.4
• /
• pp.146-158
• /
• 2022

The detector of a focal-plane-array mid-wave infrared (MWIR) camera has different response characteristics for each detector pixel, resulting in nonuniformity between detector pixels. In addition, image nonuniformity occurs due to heat generation inside the camera during operation. To solve this problem, in the process of camera manufacturing it is common to use a gain-and-offset table generated from a blackbody to correct the difference between detector pixels. One method of correcting nonuniformity due to internal heat generation during the operation of the camera generates a new offset value based on input frame images. This paper proposes a technique for dividing an input image into block image patches and generating offset values using only homogeneous patches, to correct the nonuniformity that occurs during camera operation. The proposed technique may not only generate a nonuniformity-correction offset that can prevent motion marks due to camera-gaze movement of the acquired image, but may also improve nonuniformity-correction performance with a small number of input images. Experimental results show that distortion such as flow marks does not occur, and good correction performance can be confirmed even with half the number of input images or fewer, compared to the traditional method.

• Structural Engineering and Mechanics
• /
• v.18 no.3
• /
• pp.343-362
• /
• 2004

Rocking response of rigid bodies with rectangular footprint, freely standing on horizontal rigid plane is studied analytically. Bodies are subjected to simulated single component of horizontal earthquakes. The effect of baseline correction, applied to simulated excitations, on the rocking response is first examined. The sensitiveness of rocking motion to the details of earthquakes and geometric properties of rigid bodies is investigated. Due to the demonstrated sensitivity of rocking response to these factors, prediction of rocking stability must be made in the framework of probability theory. Therefore, using a large number of simulated earthquakes, the effects of duration and shape of intensity function of simulated earthquakes on overturning probability of rigid bodies are studied. In the case when a rigid body is placed on any floor of a building, the corresponding probability is compared to that of a body placed on the ground. For this purpose, several shear frames are employed. Finally, the viability of the energy balance equation, which was introduced by Housner in 1963 and widely used by nuclear power industry to estimate the rocking stability of bodies, is evaluated. It is found that the equation is robust. Examples are also given to show how this equation can be used.

• Advances in materials Research
• /
• v.6 no.1
• /
• pp.13-26
• /
• 2017

In this work we introduce a higher-order hyperbolic shear deformation model for bending and frees vibration analysis of functionally graded beams. In this theory and by making a further supposition, the axial displacement accounts for a refined hyperbolic distribution, and the transverse shear stress satisfies the traction-free boundary conditions on the beam boundary surfaces, so no need of any shear correction factors (SCFs). The material properties are continuously varied through the beam thickness by the power-law distribution of the volume fraction of the constituents. Based on the present refined hyperbolic shear deformation beam model, the governing equations of motion are obtained from the Hamilton's principle. Analytical solutions for simply-supported beams are developed to solve the problem. To verify the precision and validity of the present theory some numerical results are compared with the existing ones in the literature and a good agreement is showed.