• 한국의류학회지
• /
• 제39권1호
• /
• pp.63-76
• /
• 2015

This study conducted a survey to gauge the buying and wearing propensities of wearers of leg guards made for baseball catchers, as well as product characteristics of preferred leg guards. Data from the survey were analyzed to obtain basic data for the development of an advanced leg guard design. Degree of compression, horizontal distance, cross section view and outline 3D sketch were also analyzed from the 3D data of leg guards; in addition, mobility and kinematic analysis were conducted through a wearing test. The survey indicated that imported products dominate the current retail market because they are appreciated by customers in terms of fit, price, brand, and protection. Representative complaints of products were discomfort, pressure, and the heavy-weight of the leg guards in general attributed to overall structure and 3D shape. When the pressure was lower on the front area of knee, it feels better to wear and the average knee angular velocity during the up and down motion increased, which suggests a better design from a kinematic point of view. The knee is the primary part of the body responsible for any movement of the lower limbs; consequently, the degree of compression and support stability of the leg guards near the knee area are important factors to evaluate the performance of leg guards. The results of our study indicate significant opportunities for improvement in product design and the development of baseball leg guards along with an ergonomic design that considers the mobility of the knee, skin deformations is necessary to improve performance. The process followed in this study will be applicable to studies on other personal protective equipment for sports.

• 천문학회보
• /
• 제43권1호
• /
• pp.44.1-44.1
• /
• 2018

We present a spectroscopic study of the Galactic supernova remnant (SNR) Cygnus Loop using the fifth Data Release (DR5) of LAMOST. The LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) features both a large field-of-view (about 20 deg2) and a large aperture (~4 m in diameter), which allow us to obtain 4000 spectra simultaneously. Its wavelength coverage ranges from ${\sim}3700{\AA}$ to $9000{\AA}$ with a spectral resolution of $R{\approx}1800$. The Cygnus Loop is a prototype of middle-aged SNRs, which has advantages of being bright, large in angular size (${\sim}3.8^{\circ}{\times}3^{\circ}$), and relatively unobscured by dust. Along the line of sight of the Cygnus Loop, 2747 LAMOST DR5 spectra are found in total, which are spatially distributed over the entire remnant. Among them, 778 spectra are selected based on the presence of emission lines (i.e., [O III]${\lambda}5007$, Ha, and [S II]${\lambda}{\lambda}$ 6717, 6731) for further visual inspection. About half of them (336 spectra) show clear spectral features to confirm their association with the remnant, 370 spectra show stellar features only, and 72 spectra are ambiguous and need further investigation. For those associated with the remnant, we identify emission lines and measure their intensities. Spectral properties considerably vary within the remnant, and we compare them with theoretical models to derive physical properties of the SNR such as electron density and temperature, and shock velocity. While some line ratios are in good agreement with model prediction, others cannot be explained by simple shock models with a range of shock velocities. We discuss these discrepancies between model predictions and the observations and finally highlight the powerfulness of the LAMOST data to investigate spatial variations of physical properties of the Cygnus Loop.

• 제어로봇시스템학회논문지
• /
• 제19권6호
• /
• pp.569-575
• /
• 2013

This paper proposes a method for PDR (Pedestrian Dead-Reckoning) using a low cost IMU. Generally, GPS has been widely used for localization of pedestrians. However, GPS is disabled in the indoor environment such as in buildings. To solve this problem, this research suggests the PDR scheme with an IMU attached to the pedestrian's waist. However, despite the fact many methods have been proposed to estimate the pedestrian's position, but their results are not sufficient. One of the most important factors to improve performance is, a new calibration method that has been proposed to obtain the reliable sensor data. In addition to this calibration, the PDR method is also proposed to detect steps, where estimation schemes of step length, attitude, and heading angles are developed. Peak and zero crossings are detected to count the steps from 3-axis acceleration values. For the estimation of step length, a nonlinear step model is adopted to take advantage of using one parameter. Complementary filter and zero angular velocity are utilized to estimate the attitude of the IMU module and to minimize the heading angle drift. To verify the effectiveness of this scheme, a real-time system is implemented and demonstrated. Experimental results show an accuracy of below 1% and below 3% in distance and position errors, respectively, which can be achievable using a high cost IMU.

• 자동차안전학회지
• /
• 제8권4호
• /
• pp.12-17
• /
• 2016

NHTSA (National Highway Traffic Safety Administration) has offered consumers the vehicle safety information on their car since 1978. NHTSA believes that they contribute auto makers to develop safer vehicle for customers, which will result in even lower numbers of deaths and injuries resulting from motor vehicle crashes. NHTSA has been studied why people are still dying in frontal test despite of the use of many restraints system and they understand that current test does not reflect real world crash data such as oblique and corner impact test. As a result, NHTSA announced that a new test method will be introduced to use of enhanced biofidelic dummy and new crash avoidance technology evaluation from 2019. New and refined injury criteria will be applied to Head / Neck / Chest / Lower Leg. BrIC(Brain Injury Criterion)value in NHTSA test results using THOR dummy from 2014 to 2015 was average 0.91 and 1.24 in driver and passenger dummies. IIHS 64kph SOF test is the most likely to new frontal oblique test in an aspect of offset impact which is being studied by NHTSA. In this paper, we focused on head injury, especially brain injury - BrIC and conducted IIHS 64kph SOF (Small Offset Front) test with Hybrid III dummy to evaluate the injury for BrIC. Based on the test results, these data can be predicted BrIC level and US NCAP rating with current vehicle.

• 한국항공우주학회지
• /
• 제47권11호
• /
• pp.795-802
• /
• 2019

본 논문에서는 인공위성의 근접운용에서 발생할 수 있는 위치-자세 결합운동을 정의하고, 이를 듀얼 쿼터니언 기반의 운동방정식을 통해 접근한다. 인공위성의 위치-자세 결합운동은 두 위성의 상대운동에서 목표 지점이 무게 중심이 아닌 위성체 위의 임의의 점에 위치할 때 발생하며, 특히 근거리 운용에서 명확히 보여진다. 듀얼 쿼터니언 기반의 운동방정식은 각속도 상태를 직접 반영하여, 자세의 변화가 위치에 영향을 미치는 위치-자세 결합운동을 간결하게 정의할 수 있다. 여기에서는 위치-자세 결합운동의 해결을 위해 기존의 접근방법과 함께 듀얼 쿼터니언 기반의 운동방정식을 새롭게 제시한다. 수치 시뮬레이션에서는 두 위성의 상대운동에서 위치-자세 결합운동으로 목표 지점에 대한 위치 오차가 발생함을 보이고, 듀얼 쿼터니언 기반의 운동방정식이 이를 해결할 수 있음을 검증한다.

• 대한기계학회논문집B
• /
• 제25권9호
• /
• pp.1157-1164
• /
• 2001

Centrifugal fans are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few research have been carried out on predicting the noise because of the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to understand the generation mechanism of sound and to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan. We assume that the impeller rotates with a constant angular velocity and the flow field of the impeller is incompressible and inviscid. So, a discrete vortex method(DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowsons method is used to predict the acoustic source. In order to compare the experimental data, a centrifugal impeller and wedge introduced by Weidemann are used in the numerical calculation and the results are compared with the experimental data. Reasonable results are obtained not only for the peak frequencies but also for the amplitudes of the tonal.

• 한국항공우주학회지
• /
• 제44권3호
• /
• pp.228-239
• /
• 2016

CNUSAIL-1은 $4m^2$ 크기의 태양돛을 탑재한 3U 크기의 큐브위성이며, 주 임무는 지구 저궤도에서 태양돛을 성공적으로 전개하고 태양돛을 이용해 Drag Sail을 실현하는 것이다. 또한, 이에 따른 자세와 궤도에 대한 영향을 확인하는 임무를 수행한다. 본 논문에서는 CNUSAIL-1의 태양돛에 사용되는 박막과 붐의 재질과 물성치에 관련된 실험을 수행하며, 이를 통해 태양돛 박막의 반사율/투과율 요구도를 확인하고, 박막과 붐의 인장강도를 측정함으로서 지구 저궤도 환경에서의 돛 전개 시 발생가능 응력에 대한 안전성을 확인한다. 또한, 태양돛의 전개장치를 개발 제작하여 우주환경을 모사한 지상시험을 수행함으로서 태양돛 전개의 가능성을 검증하였으며, 태양돛의 탑재와 접기 방법에 따라 비교 전개하는 실험을 통하여 접기방법을 결정하고, Spiral spring 두께에 따른 전개실험과 각속도 시험을 수행하여 실제 전개 시에 생길 수 있는 위성체에 대한 영향성 등을 살펴보았다.

• 한국운동역학회지
• /
• 제22권1호
• /
• pp.105-111
• /
• 2012

The purpose of this study was to investigate the effect that difference in forefoot of shoe flexibility during the quick lunge from a jump smashing on the lower limbs and the plantar pressure distribution. For this 10 elite badminton players with over 10 years experience and right handed participated. Two kinds of badminton shoes were selected and tested mechanical testing for the forefoot flexibility. Motion analysis, ground reaction forces and plantar pressure distribution were recorded. It was required to conduct lunge movement after jumping smashing as possible as high. Photo sensor was located in 3 meter away from standing position and its height was 40 cm. Subjects were conducted to return original position after touching the sensor as under clear movement as possible as fast. Forefoot stiffness had an effect on shoe peak bending degree and peak bending angular velocity in propulsion phase. Forefoot flexibility had an effect on ankle plantar flexion and knee flexion moment. It appears that joint power on lower limb and peak plantar pressure were not influenced by the flexibility of shoes.

• 한국운동역학회지
• /
• 제22권1호
• /
• pp.65-73
• /
• 2012

The purpose of this study was to identify the saddle to pedal length contributing to successful performance in kayak using a kayak ergometer. Ten male elite kayak players participated in this study. players were tested on the kayak ergometer which was varied saddle to pedal length by the knee flexion angle(90deg; 120deg; 150deg) to measure stroke frequency, paddling amplitude, joint angle, RoM and angular velocity, foot pressure and force, iEMG using the 3D motion system, foot pressure system and EMG wireless system. At a results, rowing at 120deg on knee flexion angle showed higher stroke frequency and paddling amplitude than other knee flexion angles. RoM at upper extremity showed not significant difference between knee flexion angles. But there were significant differences in thorax and pelvis rotation RoM, knee flexion-extension RoM in each condition. In addition, foot pressure, force and iEMG were significantly different in knee flexion angles. Study showed that changed of saddle to pedal length affected rowing performance kinds of stroke frequency, paddling amplitude. The most important thing, increased range of motion in pelvic and thorax has occurred by force that generated foot-bar to seat. Not only that, but it seems to be attributed to a technical adaptation developed to maximum rowing performance.

• 한국운동역학회지
• /
• 제19권3호
• /
• pp.499-508
• /
• 2009

본 연구의 목적은 필드하키 페널티 코너 시 고등학교 선수와 국가대표 선수간의 플릭 슈팅 동작을 비교 분석하여 페널티 코너 지도 시 운동학적 지침을 제시하는 것이다. 이러한 목적을 위하여 전문 슈터 남자 고등학교 선수 5명과 국가대표 선수 6명을 피험자로 선정하여 페널티 코너 시 플릭 슈팅 동작을 비교 분석하였다. 국가 대표 선수들은 고등학교 선수에 비하여 스틱헤드 속도와 볼 속도가 빠른 것으로 나타났다. 국가 대표 선수들은 고등학교 선수에 비하여 스틱으로 볼을 캐치하는 단계에서 오른발을 볼보다 앞쪽에 많이 내딛고, 볼을 앞쪽으로 길게 드래그하여 목표 방향으로 빠르게 보내고 있다. 고등학교 선수들은 국가대표 선수들에 비하여 볼을 캐치하는 단계에서 어깨의 각속도와 손목의 각속도 변화가 크고 동작 시간도 짧게 나타났다. 국가 대표 선수들은 신체 무게 중심의 상하편차가 적으며 폴로스루 단계에서도 릴리즈 단계의 몸 숙임 각도를 일정하게 유지하였으며 릴리즈 시점에서는 손과 전완의 각운동량이 고등학교 선수에 비하여 큰 것으로 나타났다.