• Journal of the Korea Society of Computer and Information
• /
• v.19 no.5
• /
• pp.43-52
• /
• 2014

In this paper, we propose Gravity Removal and Vector Rotation algorithm for counting steps of wearable device, and we evaluated the proposed GRVR algorithm with Micro-Electro-Mechanical (MEMS) 3-axis accelerometer equipped in low-power wearable device while the device is mounted on various positions of a walking or running person. By applying low-pass filter, the gravity elements are canceled from acceleration on each axis of yaw, pitch and roll. In addition to DC-bias removal and the low-pass filtering, the proposed GRVR calculates acceleration only on the yaw-axis while a person is walking or running thus we count the step even if the wearable device's axis are rotated during walking or running. The experimental result shows 99.4% accuracies for the cases where the wearable device is mounted in the middle and on the right of the belt, and 91.1% accuracy which is more accurate than 83% of commercial 3-axis pedometer when worn on wrist for the case of axis-rotation.

• Korean Journal of Applied Biomechanics
• /
• v.21 no.3
• /
• pp.269-279
• /
• 2011

This study was analyzed the characteristics on the stability of posture while conducting a through two and half rotation technic of pench$\acute{e}$ in rhythmic gymnastics. Two rhythmical gymnastics player(LKH and SSJ) who is a member of the national team were selected, and for obtain the kinematic and kinetic variables were used a ProReflex MCU 240 infrared camera(Qualisys, Sweden) and a Type9286A force platform(Kistler, Switzerland). The mechanical factors were computed by using Visual3D program and Matlab R2009a. During the landing and rotation phase the results showed following characteristics; 1) In medial-lateral and horizontal displacement of the support foot, LKH showed smaller movement than SSJ, but SSJ showed smaller movement than LKH in swing foot. LKH showed bigger movement in medial-lateral axis of COP and vertical axis of COG, but SSJ showed bigger movement in horizontal axis of COP and medial-lateral axis of COG. 2) SSJ showed bigger maximum horizontal and vertical velocity at P1 and P2 than LKH. 3) In the inclination angle of COP and COG, SSJ showed smaller change than LKH, but within medial-lateral tilt of the shoulder, LKH performed rotation motion in horizontal position than SSJ. There was no differences in each force components during rotation, but on landing phase, the results showed a characteristic that SSJ exerted bigger breaking force and vertical force than LKH.

• The Journal of Korean Academy of Prosthodontics
• /
• v.25 no.1
• /
• pp.119-135
• /
• 1987

For the determination of instantaneous centre of rotation in the mandibular movement, the habitual opening path was recorded on the sagittal tracing plate by a Gnathorecorder attached on the lower anterior teeth which was designed for this study. The opening path was demonstrated mathematically and the instantaneous centre of rotation in the opening path were calculated and plotted by computer programs, and then a computer graphic movement of the mandible was obtained according to the opening path. The hinge path of posterior border movement was graphied by the Gnathorecorder as well and demonstated mathematically. This hinge path was compared with the same obtained by Visitrainer to prove a reliability of the Gnathorecorder. The results obtained from this study were as follows. 1. The habitual opening path and hinge path obtained from the Gnathorecorder movement were expressed mathematically as follows: $y=0.11x^2-0.66x+3.09$ (equation of opening path), $y=0.04x^2+0.21x+3.71$ (equation of hinge path), and a kinematic hinge axis was not shown in the equation of kings path. 2. The early habitual opening movement of the mandible demonstrated almost a straight opening path or an arc motion with the larger radius and it's centre of rotation moved parallelly in the more rear and lower position than a kinematic hinge axis. 3. Instantaneous centre of rotation occured along with the translation of the condyle, and mandible was rotated around an axis in the close to the maximum opening and then moved toward the forward and upward position. 4. There were some similarities between the articular eminence and the movement pattern of a special point which was the kinematic hinge axis.

• Korean Journal of Applied Biomechanics
• /
• v.29 no.2
• /
• pp.61-70
• /
• 2019

Objective: This study aimed to investigate the characteristics of the declination of the subtalar joint rotation axis and the structural features of the ankle joint complex such as rear-foot angle alignment and ligament laxity test between chronic ankle instability (CAI) patients and healthy control. Method: A total of 76 subjects and CAI group (N=38, age: $23.11{\pm}7.63yrs$, height: $165.67{\pm}9.54cm$, weight: $60.13{\pm}11.71kg$) and healthy control (N=38, age: $23.55{\pm}7.03yrs$, height: $167.92{\pm}9.22cm$, weight: $64.58{\pm}13.40kg$) participated in this study. Results: The declination of the subtalar joint rotation axis of the CAI group was statistically different from healthy control in both sagittal slope and transverse slope. The rear-foot angle of CAI group was different from a healthy control. Compared to healthy control, they had the structure of rear-foot varus that could have a high occurrence rate of ankle varus sprain. CAI group had loose ATFL and CFL compared to the healthy control. Conclusion: The results of this study showed that the deviation of the subtalar joint rotation axis and the structural features of the ankle joint complex were different between the CAI group and the healthy control and this difference is a meaningful factor in the occurrence of lateral ankle sprains.

• Journal of Korean Association for Spatial Structures
• /
• v.22 no.1
• /
• pp.33-40
• /
• 2022

When the center of stiffness and the center of mass of the structure differ under the seismic load, torsion is caused by eccentricity. In this study, an analysis model was modeled in which the positions of the core and the plane rotation axis of a 60-story torsional atypical structure with a plane rotation angle of 1 degree per floor were different. The structural behavior of the analysis model was analyzed, and the earthquake response behavior of the structure was analyzed based on the time history analysis results. As a result, as the eccentricity of the structure increased, the eccentricity response was amplified in the high-rise part, and the bending and torsional behavior responses were complex in the low-order vibration mode. As a result of the analysis, the maximum displacement and story drift ratio increased due to the torsional behavior. The maximum story shear force and the story absolute maximum acceleration showed similarities for each analysis model according to the shape of the vibration mode of the analysis model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.817-825
• /
• 2001

The natural frequencies of a flexible spinning disk misaligned with the axis of rotation are studied in an analytic manner. The effects of misalignment on the natural frequency need to be investigated, because the misalignment between the axis of symmetry and the axis of rotation cannot be avoided in the removable disks such as CD-R, CD-RW or DVD disks. Assuming that the in-plane displacements are in steady state and the out-of-plane displacement is in dynamic state, the equations of motion are derived for the misaligned spinning disk. After the exact solutions are obtained for the steady-state in-plane displacements, they are plugged into the equation for the dynamic-state out-of-plane motion. The resultant equation is a linear equation for the out-of-plane displacement, which is discretized by the Galerkin method. Based on the discretized equations, the effects of the misalignment are analyzed on the vibration characteristics of the spinning disk, i.e., the natural frequencies and the critical speed

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1994.10a
• /
• pp.33-43
• /
• 1994

A series of tensile tests have been performed to investigate the hardening behavior of rolled steel sheets. Tensile tests consist of three stages. At the 1st stage, full size tensile specimens were prestrained in the direction of rolling, then mid-sized tensile specimens were cut from the gauge sections of the full size specimens at angles to the rolling direction. At the 2nd stage, mid-sized specimens were prestrained by predetermined magnitudes of strains and miniature tensile specimens were prepared from each of the mid-sized specimens at every 10 degrees. At the final stage, from tests on miniature tensile specimens the hardening behavior of the prestrained sheets has been investigated. According to the experimental results, orthotropic symmetry is reserved during tensile elongation, and one of the orthotropy axes is continuously rotated to specimen axis. Existing theories seem to fail to explain the rotation of orthotropy axis. A new phenomenological model is proposed to explain the strain induced rotation of orthotropy axes.

• Korean Journal of Remote Sensing
• /
• v.24 no.6
• /
• pp.641-644
• /
• 2008

In order to improve a camera rotation calculation based on the bundle adjustment in Chon's camera motion (Chon and Shankar, 2007, 2008), this paper introduces a method calculating the camera rotation. It estimates a unit vector in the optical axis of a camera through the angles between the optical axis and vectors passing a camera position and ground control points (GCP). The camera position is estimated by using the inner product method proposed by Chon. The horizontal and vertical unit vectors of the camera are determined by using Yakimovsky and Cunningham's camera model (CAHV) (1978).

• Journal of Korean Ophthalmic Optics Society
• /
• v.15 no.3
• /
• pp.213-217
• /
• 2010

Purpose: To emphasize the necessity of post-fitting by follow-up test, the mis-alignment was analyzed after initial wearing of toric soft contact lenses (TSCL). Methods: After trial contact lenses were worn to 87 eyes with myopic astigmatism for 1 week, we observed the alignment of axis mark on trial contact lenses using slit lamp and corrected the rotated axis by method of LARS. After final fitting, rotation ratio, rotation degree and rotation position were analyzed compared to initial prescription divided to amount of cylinderical and spherical powers. Results: Rotation ratio of TSCL's axis was increased as increment of both cylinderical powers and (-)spherical powers. An average of rotation degree was $10^{\circ}{\sim}13^{\circ}$ which was not related to amount of their powers. Rotation position of TSCL's axis was more to temporal than to nasal. Conclusions: Because mis-alignment of axis after TSCL wearing induce the poor sight, adjustment of axial alignment as a result of follow-up must be performed.

• Clinics in Shoulder and Elbow
• /
• v.17 no.1
• /
• pp.25-30
• /
• 2014

Background: Normal elbow joint kinematics has been widely studied in cadaver, whilst in vivo study, especially of the forearm, is rare. Our study analyses, in vivo, the kinematics of normal forearm and of malunited forearm using a three-dimensional computerized simulation system. Methods: We examined 8 patients with malunited Monteggia fracture and 4 controls with normal elbow joint. The ulna and radius were reconstructed from CT data placing the forearm in three different positions; full pronation, neutral, and full supination using computer bone models. We analyzed the axis of rotation 3-dimentionally based on the axes during forearm rotation from full pronation to full supination. Results: Axis of rotation of normal forearm was pitch line, with a mean range of 2 mm, from full pronation to full supination, connecting the radial head center proximally and ulnar fovea distally. In normal forearm, the mean range was 1.32 mm at the proximal radioulnar joint and 1.51 mm at the distal radioulnar joint. However in Monteggia fracture patients, this range changed to 7.65 mm at proximal and 4.99 mm at distal radoulnar joint. Conclusions: During forearm rotation, the axis of rotation was constant in normal elbow joint but unstable in malunited Monteggia fracture patients as seen with radial head instability. Therefore, consideration should be given not only to correcting deformity but also to restoring AOR by 3D kinematics analysis before surgical treatment of such fractures.