• PNF and Movement
• /
• 제19권2호
• /
• pp.261-267
• /
• 2021

Purpose: This study aimed to investigate changes in gait variables depending on whether a task was performed using a smartphone while walking on a ramp. Methods: The participants of this study were 41 college students attending U University located in Gyeongju City, Gyeongsangbuk-do. In this study, gait variables were measured during ramp gait while using a smartphone to perform a task and during ramp gait without performing such tasks. In other words, four walking conditions were used: 1) walking up a ramp, 2) walking up a ramp while using a smartphone to perform a task, 3) walking down a ramp, and 4) walking down a ramp while using a smart phone to perform a task. Gait variables were measured using a gait analysis tool (Legsys; BioSensics, USA), and stride time, stride length, stride velocity, cadence, and double support were analyzed. The order of measurements was randomized to control for order effects due to repeated measurements. Results: The comparative analysis of gait variables according to the presence or absence of smartphone use during ramp gait showed that there were significant differences in stride time, stride length, and stride velocity during both ramp ascent and ramp descent (p < 0.05). In both ramp ascent and ramp descent, stride time increased when walking using a smartphone, compared to when walking without using a smartphone (p < 0.05). However, in both ramp ascent and ramp descent, stride length and stride velocity were decreased when walking using a smartphone compared to when walking without using a smartphone (p < 0.05). Conclusion: The study results showed that the use of a smartphone during walking can affect safety. Therefore, it is necessary to improve the awareness of risks associated with walking while using a smartphone, and further research needs to be conducted in various environments and with different ramps.

• 반도체디스플레이기술학회지
• /
• 제5권2호
• /
• pp.11-14
• /
• 2006

A new reset waveform with negative ramp pulse is proposed. Conventional reset waveform applied to the commercial PDP uses a positive ramp pulse. The reset waveforms, especially focused on ramp area, were examined with 2 dimensional fluid code. The proposed negative reset waveform showed much lower ignition voltage ($\sim$70V) as compared with the conventional reset waveform. When the negative ramp pulse was applied, all of the positive-charged ions are collected on the scan electrode. It is found that the ignition voltage of reset discharge due to the negative ramp pulse became lower than that of positive ramp discharge.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
• /
• pp.1258-1261
• /
• 2005

The ramp type bias voltage applied to the common electrode during a reset-period is newly proposed to lower the background luminance and to improve the address discharge characteristics in AC-PDP. The positive ramp bias voltage is applied during the ramp-up period, whereas the negative ramp bias voltage is applied during the ramp-down period. The effects of the voltage slopes in both the positive and negative ramp bias voltages on the background luminance and address voltage characteristics are examined intensively. It is observed that the optimized positive and negative ramp bias voltages applied to the common electrode during the ramp-period can lower the background luminance and also enhance the address discharge characteristics of the AC-PDP.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.384-387
• /
• 2006

Vertical L/UL (Load/Unload) velocity is very important parameter to determine the L/UL performance, and the vertical velocity is determined by the actuator velocity and the ramp profile. However, it is not easy to precisely control the actuator rotating velocity during the L/UL process. Especially in emergency parking, servo system doesn't operate, it is impossible to control an actuator velocity. Then, the vertical unloading velocity depends on only ramp profile. The ramp height and the sliding length for L/UL process in SFF (Small Form Factor) HDD are restricted due to slimness and small media. For these reasons, it is very difficult to design the ramp profile in SFF HDD. Therefore, this study analyzes the unloading dynamic characteristics for various ramp profiles and makes the thesis for ramp profile design.

• 정보저장시스템학회논문집
• /
• 제2권2호
• /
• pp.150-155
• /
• 2006

Vertical L/UL (Load/Unload) velocity is very important parameter to determine the L/UL performance, and the vertical velocity is determined by the actuator velocity and the ramp profile. However, it is not easy to precisely control the actuator rotating velocity during the L/UL process. Especially in emergency parking, servo system doesn't operate, it is impossible to control an actuator velocity. Then, the vertical unloading velocity depends on only ramp profile. The ramp height and the sliding length for L/UL process in SFF (Small Form Factor) HDD are restricted due to slimness and small media. For these reasons, it is very difficult to design the ramp profile in SFF HDD. Therefore, this study analyzes the unloading dynamic characteristics for various ramp profiles and makes the thesis for ramp profile design.

• Journal of Biosystems Engineering
• /
• 제26권6호
• /
• pp.517-524
• /
• 2001

Steep and narrow ramp installed in the paddy field makes it difficult and sometimes dangerous to drive agricultural machines on it. Because agricultural machinery become larger and heavier, it is necessary to revise design standard for ramp to provide safe travel. This study was conducted to revise the design standard fur paddy field ramp, especially for its width and slope. A mathematical model predicting travelling path of a tractor on paddy field ramp and farm road was developed and simulated. To verify this model, field tests were carried out. The model could predict trvelling path with RMS Error of 12.5cm and 8.2cm, which were judged to be adoptable fur determining the width of paddy field ramp. By applying this model to 110ps tractor, which was assumed to be the largest tractor in Korea, width of paddy field ramp was determined as over 3.6m. The slope of paddy field ramp, which provided tractor with 10% of the total weight of the tractor and the mounted implement as reaction force at front wheel against ground was analyzed by considering weight transfer effect on a ramp. The result showed that adequate slope of paddy field ramp was 14°.

• 정보저장시스템학회논문집
• /
• 제5권2호
• /
• pp.70-75
• /
• 2009

Most hard disk drives uses load/unload technology because of benefits as like an increased areal density, a reduced power consumption and an improved shock resistance. However, ramp tilt induced by ramp manufacture and assembly causes mechanical problems such as unload fail in case of exceeding ramp tolerance. In this paper, we focus on experimental analysis for unloading characteristics affected by ramp tilt. We repeatedly perform load/unload test as 500,000 cycles for original model and ramp tilt model. This paper shows that it is possible to analyze unload characteristics through measuring scratch and wear of suspension lift-tab, ramp, suspension dimple-flexure and disk. We also identify structural relation between suspension lift-tab and ramp through scratch and wear of suspension lift-tab and ramp. As the result of measurement and analysis, we can investigate decrease of unloading performance in ramp tilt model.

• 한국조경학회지
• /
• 제23권2호
• /
• pp.157-166
• /
• 1995

To investigate walkability of ramps, walking patterns of 18 healthy adults,12 aged 20 to 26 and 6 aged 68 to 76,were studied at free,rhythm constrained walking up or down ramp using goniometer and footswitch Ramp inclinations were set 4,8,12,16,20 degrees. The results were as follows. 1)The step length of subjects were decreased significantly in12$^{\circ}C$′or 16′free downramp walking. With regard to step length, some subject groups walked abnormally in 16" or 20" ramp walking 2) The step width of subjects were increased significantly in 12" or 16" ramp walking. 3) The cadence duration of some subject groups were increased in 12" upramp walking. 4) The double stance duration and double stance ratio of some subject groups were increased significantly in 8",12", or 16"upramp walking. 5) The maximum knee flexion angle of stance phase were increased in 12" ramp walking. 6)Most temporal parameters and spatial parameters of gait were increased or decreassd greatly between 4" ramp and 8" ramp or between 8′ramp and 12′ramp. But statistics significancy were not recognized 7) The results suggest that ramp inclination less than 8′(14%) -12′(21%) is desirable for the normal gait the ramp inclination must not exceed 16" -20" in unavoidable circumstances.

• The Journal of Korean Physical Therapy
• /
• 제29권4호
• /
• pp.223-226
• /
• 2017

Purpose: This study examined two trunk strategies - medio-lateral ramp and anterior-posterior ram - and their effects on pelvis and trunk movements, providing basic material for safe ramp utilization. Methods: The present study included 20 asymptomatic males recruited from a local university. Participants were asked to stand with their feet shoulder-width apart. Their dorsal side faced the camera, and measurements were performed while standing in a neutral double stance, one leg stance, $15^{\circ}$ of medial and lateral ramp, and $15^{\circ}$ of anterior and posterior ramp. Participants were allowed to practice for 3 minutes, and each participant had a 30 seconds rest between the two ramp conditions. One-way repeated measures analysis of variance was used to determine the effects the ramp conditions on spinal alignment. In all analyses, p<0.05 was used to indicate statistical significance. Results: The trunk-inclination angle on the posterior ramp was significantly lower than that of the double stance position (p<0.05). The trunk imbalance angle was significantly higher on the medial ramp, than that on the double stance position (p<0.05). The pelvic position and pelvic torsion angles were significantly higher in the medial, lateral, and anterior ramp positions than that of the double stance position (p<0.05). The pelvic rotation angles on the medial, lateral, and anterior ramps were significantly lower than that of the double stance position (p<0.05). Conclusion: These findings suggest that when people are exposed to the same form of ramp for an extended period, posture modifications may be triggered.

• 한국안전학회지
• /
• 제27권3호
• /
• pp.9-14
• /
• 2012

The objectives of this study were to compare the results of HSL (Health and Safety Laboratory) ramp test with perceived sense of slip onto the several different floor surfaces under contaminated conditions. There are a variety of approaches from biomechanical measurements to psychophysical test and human perception. However, controversies over these approaches still remain. Some widely accepted methods need to be improved. AHP (Analytic Hierarchy Process) was used to evaluate the perception of slipperiness of seven different floor surfaces under the contaminated condition with glycerol solution. Twelve subjects worn same footwear and walked with self-selected step and cadence along the test floors. The angle of inclination obtained for water wet condition using 5 l/min with HSL ramp test was compared to perception of slipperiness. The surface roughness ($R_z$) related very well both AHP (r=0.95) and ramp test (r=0.92). The high significant correlation (r=0.90) was found between AHP and HSL ramp test.The HSL ramp test values (Coefficient of Friction, COF) according to subjective evaluation were divided into two categories. There were high correlations between test results (subjective evaluation, HSL ramp test) and surface roughness in Rz. Perception rating obtained with AHP showed a high correlation with COF obtained with HSL ramp test.