• 한국정밀공학회지
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• 제28권3호
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• pp.323-329
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• 2011

Certified reference materials (CRMs) have been used to calibrate surface profilers for reliable measurements. In this paper, we present a newly designed step height CRM which has a step height pattern with two different widths and various special patterns for checking radial magnification, distortion of optical viewing systems, etc. Especially, it could be useful for multi-probe inspection instruments in the manufacturing lines. The fabrication was done by conventional optical lithography and dry etching process with optimized conditions. To verify the step height values, a white-light scanning interferometer was used with objective lenses having magnification of $10{\times}$ and $100{\times}$. CRMs with nominal step heights of $0.5\;{\mu}m$, $1\;{\mu}m$, $3\;{\mu}m$, $5\;{\mu}m$, $7\;{\mu}m$, and $10\;{\mu}m$ were fabricated and the uniformity of these CRMs was evaluated to be less than 3 nm ($1{\sigma}$).

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2142-2148
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• 2015

This paper proposes novel real-time footstep planning and following methods for the navigation of humanoid robots. A footstep command is defined by a walking direction and step lengths for footstep planning. The walking direction is determined by a uni-vector field navigation method, and the allowable yawing range caused by hardware limitation is considered. The lateral step length is determined to avoid collisions between the two legs while walking. The sagittal step length is modified by a binary search algorithm when collision occurs between the robot body and obstacles in a narrow space. If the robot body still collides with obstacles despite the modification of the sagittal step length, the lateral step length is shifted at the next footstep. For footstep following, a walking pattern generator based on a 3-D linear inverted pendulum model is utilized, which can generate modifiable walking patterns using the zero-moment point variation scheme. Therefore, it enables a humanoid robot to follow the footstep command planned for each footstep. The effectiveness of the proposed method is verified through simulation and experiment.

• Structural Engineering and Mechanics
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• 제65권4호
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• pp.415-422
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• 2018

The Conjugate Finite-Step Length" (CFSL) algorithm is proposed to improve the efficiency and robustness of first order reliability method (FORM) for reliability analysis of highly nonlinear problems. The conjugate FORM-based CFSL is formulated using the adaptive conjugate search direction based on the finite-step size with simple adjusting condition, gradient vector of performance function and previous iterative results including the conjugate gradient vector and converged point. The efficiency and robustness of the CFSL algorithm are compared through several nonlinear mathematical and structural/mechanical examples with the HL-RF and "Finite-Step-Length" (FSL) algorithms. Numerical results illustrated that the CFSL algorithm performs better than the HL-RF for both robust and efficient results while the CFLS is as robust as the FSL for structural reliability analysis but is more efficient.

• 한국전문물리치료학회지
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• 제15권3호
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• pp.35-43
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• 2008

The purpose of this study was to compare spatio-temporal parameters during walking between patients with idiopathic Parkinson's disease and a control group matched for age, height, and weight. Thirty-three subjects were included in this study. Fifteen normal subjects (age, $63.3{\pm}5.8$ yrs; height, $164.1{\pm}8.7$ cm; weight, $60.7{\pm}17.5$ kg) and eighteen patients (age, $64.0{\pm}7.7$ yrs; height, $164.7{\pm}7.3$ cm; weight, $63.6{\pm}7.7$ kg) participated in the study. The Vicon 512 Motion analysis system was used for gait analysis in each group during walking, with and without an obstacle. The measured spatio-temporal parameters were cadence, walking speed, stride time, step time, single limb support time, double limb support time, stride length, and step length. Results in stride length and step length, when walking without an obstacle, showed a significantly greater decrease in the patient group compared to the control group. During walking with an obstacle, the patient group showed a significantly greater decrease in the step length as compared to the control group. For the control group, there were significant decreases in parameters of cadence and walking speed and increases in parameters of stride time, step time, and single limb support time when walking with an obstacle. The patient group had lower cadence and walking speed and higher stride time, step time, and single limb support time during walking with an obstacle than in walking without an obstacle. These results suggest that patients with Parkinson's disease who walk over an obstacle can decrease cadence, stride length, and step length. Further study is needed, performed with more obstacles and combined with other external cues, such as visual or acoustic guides.

• 대한한방내과학회지
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• 제37권6호
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• pp.990-997
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• 2016

Objectives: This study observed changes in gait pattern according to the motor grade of the paretic lower limb in patients with basal ganglia stroke who are in the subacute phase. Methods: We used the Manual Muscle Test (MMT) to evaluate the motor grade of the paretic lower limb of 21 patients with subacute basal ganglia stroke and then divided them into two groups based on the MMT results. Stroke patients with a motor grade above Gr. III were put in group I (15 people) and those with a grade less than Gr. III in group II (6 people). We also estimated spatiotemporal factors using treadmill gait analysis equipment. The values were gait velocity, step length, step time, double support phase, and cadence. The first measure was conducted during the early period of admission and the second was between four and five weeks after admission. Results: In Group I, the gait velocity and step length of both legs significantly increased. In Group II, the step length and step time of the paretic side and the gait velocity tended to decrease, but not significantly. The step length of the paretic side in Group II was significantly longer than that in Group I at the first measure. The step time of the paretic side in Group I was significantly shorter than that in Group II and gait velocity and cadence in Group I were significantly higher than in Group II at the second measure. Conclusions: The gait parameters of all stroke patients improved in terms of time. In addition, the changes in gait pattern were different depending on the motor grade of the paretic lower limb.

• Journal of Magnetics
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• 제20권2호
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• pp.133-137
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• 2015

This study was conducted to determine the effects of repetitive transcranial magnetic stimulation (rTMS) integrated mirror therapy on the gait of post-stroke patients. Thirty patients who were six months post-stroke were assigned to either the experimental group (n = 15) or the control group (n = 15). Stroke patients in the experimental group underwent rTMS and mirror therapy for the lower limbs, while those in the control group underwent rTMS and sham therapy. Participants in both groups received therapy five days per week for four weeks. A significant difference in post-training gains for the single support phase, step length, stride length and velocity was observed between the experimental group and the control group (p < 0.05). The experimental group showed a significant increment in the single support phase, step length, stride length, swing phase, velocity, cadence, double support phase and step width as compared to pre-intervention (p < 0.05). The control group showed a significant increment in step length, velocity, cadence and step width compared to preintervention (p < 0.05). Further investigation of the availability and feasibility of rTMS integrated mirror therapy for post-stroke patients as a therapeutic approach for gait rehabilitation is warranted.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.60-60
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• 2021

Investigating Backward-Facing Step(BFS) flow is important in that it is a representative case for separation flows in various engineering flow systems. There have been a wide range of experimental, theoretical, and numerical studies to investigate the flow characteristics over BFS, such as flow separation, reattachment length and recirculation zone. However, most of such previous studies were concentrated only on the perpendicular step angle. In this study, several numerical investigations on the flow pattern over BFS with various step angles (10° ~ 90°) and expansion ratios (1.48, 2 and 3.27) under different Reynolds numbers (5000 ~ 64000) were carried out, mainly focused on the reattachment length. The numerical simulations were performed using an open source 3D CFD software, OpenFOAM, in which the velocity profiles and turbulence intensities are calculated by RANS (Reynolds Averaged Navier-Stokes equation) and 3D LES (Large Eddy Simulation) turbulence models. Overall, it shows a good agreement between simulations and the experimental data by Ruck and Makiola (1993). In comparison with the results obtained from RANS and 3D LES, it was shown that 3D LES model can capture much better and more details on the velocity profiles, turbulence intensities, and reattachment length behind the step for relatively low Reynolds number(Re < 11000) cases. However, the simulation results by both of RANS and 3D LES showed very good agreement with the experimental data for the high Reynolds number cases(Re > 11000). For Re > 11000, the reattachment length is no longer dependent on the Reynolds number, and it tends to be nearly constant for the step angles larger than 30°.) Based on the calibrated and validated numerical simulations, several additional numerical simulations were also conducted with higher Reynolds number and another expansion ratio which were not considered in the experiments by Ruck and Makiola (1993).

• 대한물리의학회지
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• 제6권2호
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• pp.199-205
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• 2011

Purpose: The purpose of this study was to investigate the effect of 0cm, 2.5cm, 5cm height increase elevator shoes insole on gait and foot pressure Methods: Fifteen young adult were recruited this study. Gait and foot was measured by Gait AnalyzerTM(Tech Storm Inc. korea). Statistical analysis was used one-way ANOVA to know difference between 0cm, 2.5cm insole and 5cm insole Results: There was no significantly difference on foot length, foot width, foot angle, step time during gait. But step length and step width was significantly difference during gait. There was no significantly difference on gait ratio during stance phase. There was significantly difference on forefoot pressure and rearfoot pressure ratio. Conclusion: These results indicate that height increase elevator shoes insole may be caused step length, step width decreaseed during gait. It caused forefoot pressure increased and rearfoot pressure decreased on foot.

• 융복합기술연구소 논문집
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• 제4권1호
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• pp.33-35
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• 2014

Investigation of flow characteristics behind a edged backward facing step is important for selecting appropriate positions of building constructions in the desert area. In the present study, the effect of edge angles on the flow characteristics is investigated using a commercial software CFD-ACE+. When the edge angle is less than 30 degree, reattachment length decreases, whereas when the edge angle is larger than 30 degrees, reattachment angle increases. It can be concluded that the flow patterns behind an edged backward facing step is classified as the two, streamlined and bluffed bodies. Appropriate edge angles have an effect of increasing the momentum toward the wall, which can reduce the reattachment length. It can be said that present results can be utilized for diverse industrial applications that includes the backward facing step.

• 한국정밀공학회지
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• 제30권4호
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• pp.450-458
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• 2013

The aim of this study was to develop and verify gait training system for post-stroke hemiplegia patients with step length asymmetry. Most post-stroke hemiplegic patients show gait asymmetry and weight shifting training has been suggested as a useful method for improving the walking ability. However, verbal cue by physical therapist may be not effective. Therefore, our weight shift training system was designed to give a feedback to patients through precise plantar pressure and center of pressure (COP) measurement. This weight shifting biofeedback training system is composed of F-Scan plantar pressure measurement system and software development kit (SDK) for Windows operating system. Two post-stroke patients with step length asymmetry were enrolled in this study. After training for six weeks, the weight shift score and step length ratio of two all patients were improved and approached to them of non-disabled. This system developed in this study may improve the step length asymmetry, and therefore this system is also expected to improve a walking ability in hemiplegic patients.