• 한국운동역학회지
• /
• 제31권2호
• /
• pp.113-118
• /
• 2021

Objective: The purpose of this study was to investigate differences of landing strategy between people with or without chronic ankle instability (CAI) during double-leg drop landing. Method: 34 male adults participated in this study (CAI = 16, Normal = 18). Participants performed double-leg drop landing task on a 30 cm height and 20 cm horizontal distance away from the force plate. Lower Extremities Kinetic and Kinematic data were obtained using 8 motion capture cameras and 2 force plates and loading rate was calculated. Independent samples t-test were used to identify differences between groups. Results: Compared with normal group, CAI group exhibits significantly less hip internal rotation angle (CAI = 1.52±8.12, Normal = 10.63±8.44, p = 0.003), greater knee valgus angle (CAI = -6.78±5.03, Normal = -12.38 ±6.78, p = 0.011), greater ankle eversion moment (CAI = 0.0001±0.02, Normal = -0.03±0.05, p = 0.043), greater loading Rate (CAI = 32.65±15.52, Normal = 18.43±10.87, p = 0.003) on their affected limb during maximum vertical Ground Reaction Force moment. Conclusion: Our results demonstrated that CAI group exhibits compensatory movement to avoid ankle inversion during double-leg drop landing compared with normal group. Further study about how changed kinetic and kinematic affect shock absorption ability and injury risk in participants with CAI is needed.

• 자동차안전학회지
• /
• 제16권2호
• /
• pp.20-26
• /
• 2024

The delivery using drones has been attracting attention because it can innovatively reduce the delivery time from the time of order to completion of delivery compared to the current delivery system, and there have been pilot projects conducted for safe drone delivery. However, the current drone delivery system has the disadvantage of limiting the operational efficiency offered by fully autonomous delivery drones in that drones mainly deliver goods to pre-set landing sites or delivery bases, and the final delivery is still made by humans. In this paper, to overcome these limitations, we propose obstacle detection and landing site selection algorithm based on a vision sensor that enables safe drone landing at the delivery location of the product orderer, and experimentally prove the possibility of station-to-door delivery. The proposed algorithm forms a 3D map of point cloud based on simultaneous localization and mapping (SLAM) technology and presents a grid segmentation technique, allowing drones to stably find a landing site even in places without prior information. We aims to verify the performance of the proposed algorithm through streaming data received from the drone.

• 한국운동역학회지
• /
• 제21권1호
• /
• pp.31-38
• /
• 2011

This study aimed to determine the effects of the blockage of visual feedback on joint dynamics of the lower extremity. Fifteen healthy male subjects(age: $24.1{\pm}2.3\;yr$, height: $178.7{\pm}5.2\;cm$, weight: $73.6{\pm}6.6\;kg$) participated in this study. Each subject performed single-legged landing from a 45 cm-platform with the eyes open or closed. During the landing performance, three-dimensional kinematics of the lower extremity and ground reaction force(GRF) were recorded using a 8 infrared camera motion analysis system (Vicon MX-F20, Oxford Metric Ltd, Oxford, UK) with a force platform(ORG-6, AMTI, Watertown, MA). The results showed that at 50 ms prior to foot contact and at the time of foot contact, ankle plantar-flexion angle was smaller(p<.05) but the knee joint valgus and the hip flexion angles were greater with the eyes closed as compared to with the eyes open(p<.05). An increase in anterior GRF was observed during single-legged landing with the eyes closed as compared to with the eyes open(p<.05). Time to peak GRF in the medial, vertical and posterior directions occurred significantly earlier when the eyes were closed as compared to when the eyes were open(p<.05). Landing with the eyes closed resulted in a higher peak vertical loading rate(p<.05). In addition, the shock-absorbing power decreased at the ankle joint(p<.05) but increased at the hip joints when landing with the eyes closed(p<.05). When the eyes were closed, landing could be characterized by a less plantarflexed ankle joint and more flexed hip joint, with a faster time to peak GRF. These results imply that subjects are able to adapt the control of landing to different feedback conditions. Therefore, we suggest that training programs be introduced to reduce these injury risk factors.

• 한국컴퓨터정보학회논문지
• /
• 제19권9호
• /
• pp.161-168
• /
• 2014

공항에 불규칙한 시간간격으로 접근하는 항공기들을 최소의 비용으로 착륙시키는 항공기 착륙 문제 (ALP)는 최적 해를 구하기 어려워 다양한 메타휴리스틱 방법들이 제안되고 있다. 본 논문에서는 ALP에 대해 O(nlog n)의 다항시간으로 최적 해를 구하는 휴리스틱 알고리즘을 제안한다. 제안된 알고리즘은 착륙 목표시간 오름차순으로 정렬시키고, 항공기들 간의 분리 시간과 착륙 비용을 고려하여 착륙순서를 변경시킨 최적화 과정을 수행하는 방법을 적용하였다. ALP에 대한 예제 데이터인 Airland1 ~ Airland8에 대해 소요비용이 0이 되는 활주로 개수 m까지 25개 데이터를 실험한 결과 모든 데이터에 대해 최적 해를 구하였다. 특히, Airland8의 m = 1 데이터에 대해서는 기존에 알려진 최적 해를 개선하였다.

• 수산경영론집
• /
• 제31권1호
• /
• pp.33-54
• /
• 2000

This study intends to examine the distribution channel of the most popular ten species caught in Korean coastal and off-shore fisheries with the aid of interviewing fish brokers and cooperative staffs in fish landing markets. This paper finds and emphasizes the following three suggestions, in order to improve the present scheme of fish distribution system. Firstly, annual catch of 10 kinds of fishes is successively decreasing in quantity from 1994 to 1998. Moreover annual catch shows larger variations than fish price and cooperative sales quantity. Except sea eel and sole, cooperative sales accommodates more than 90% of the fish landed, accounting for the small variation in cooperative sales, which invalidates the effectiveness of the free distribution system adopted by the government. Secondly, diversified distribution channels are exposed according to the nature of the fish, the method to harvest, and the quantity caught. Large retailers such as discount stores, super chains and home shopping institutions are actively involving themselves in direct purchase in fish landing markets. Through the analysis of distribution routes, the general distribution channel of fresh fish has been found such as producers longrightarrow fish brokers in landing markets longrightarrow fish brokers in central wholesale markets longrightarrow wholesalers longrightarrow retailers longrightarrow consumers. In order to reduce distribution margin through the analysis of distribution function and distribution margin, this paper presents a new distribution channel such as producers longrightarrow fish brokers in landing markets longrightarrow wholesalers longrightarrow retailers longrightarrow consumers. Thirdly, to improve the fish landing markets, this paper suggests the M&A of uneconomical fish landing markets or renovating toward wholesalers, introduction of processing services and improvement of processing facilities, subsidizing fish brokers in landing markets, revitalization of marketing divisions in cooperatives and improvement in fish auction system.

• 한국운동역학회지
• /
• 제25권1호
• /
• pp.49-56
• /
• 2015

Objectives : The purpose of this study was to present quantitative data and basic references to decrease the accident risk of soccer instructors. Methods : To obtain data, we conducted an investigation on how H/Q ratio affects the dynamic stability of the lower extremity at the time of drop landing. The study targeted 13 soccer players from C University who have not had any injuries or wounds in the lower extremity joints and in any other parts of their bodies over the last 6 months. By using CMIS (USA), the players were divided into two groups according to H/Q ratios higher and lower than 69%, respectively. The subjects in each group were instructed to perform a drop landing. Results : The H/Q ratio did not affect the maximal flexion angle of the knee joints at the time of drop landing. In addition the dominant group with a relatively high H/Q ratio was observed to have increased time to reduce shock and to efficiently absorb the ground reaction force during drop landing. Also, the dominant group with a relatively high H/Q ratio utilized the strong performances of the antagonistic muscles around the hamstrings and the controlled rotatory powers of the thighs that were applied to the tibias supported by the ground. Finally, H/Q ratio, load factors, and mean and maximum EMG were significantly negatively related, whereas GRFx showed a positive relationship. In fact, these factors all affected the impact of the load from the H/Q ratio to the knee joints. Conclusion : From these findings it can be concluded that unbalanced H/Q ratio can be considered as a predictor of knee joint injury at the time of drop landing.

• 한국운동역학회지
• /
• 제25권2호
• /
• pp.141-147
• /
• 2015

Objective : This study aimed to understand how increased heart rates at the time of drop landing during a step test would affect biomechanical variables of the lower extremity limbs. Background : Ballet performers do more than 200 landings in a daily training. This training raises the heart rate and the fatigability of the lower extremity limbs. Ballet performance high heart rate can trigger lower extremity limb injury. Method : We instructed eight female ballet dancers with no instability in their ankle joints(mean ${\pm}$ SD: age, $20.7{\pm}0.7yr$; body mass index, $19.5{\pm}1.2kg/m^2$, career duration, $8.7{\pm}2.0yr$) to perform the drop landing under the following conditions: rest, 60% heart rate reserve (HRR) and 80% HRR. Results : First, the study confirmed that the increased heart rates of the female ballet dancers did not affect the working ranges of the knee joints during drop landing but only increased angular speeds, which was considered a negative shock-absorption strategy. Second, 80% HRR, which was increased through the step tests, led to severe fatigue among the female ballet dancers, which made them unable to perform a lower extremity limb-neutral position. Hence, their drop landing was unstable, with increased introversion and extroversion moments. Third, we observed that the increasing 80% HRR failed to help the dancers effectively control ground reaction forces but improved the muscular activities of the rectus femoris and vastus medialis oblique muscles. Fourth, the increasing heart rates were positively related to the muscular activities of the vastus medialis oblique and rectus femoris muscles, and the extroversion and introversion moments. Conclusion/Application : Our results prove that increased HRR during a step test negatively affects the biomechanical variables of the lower extremity limbs at the time of drop landing.

• 수산경영론집
• /
• 제5권1호
• /
• pp.9-42
• /
• 1974

Korea is a peninsular country surrounded by seas on three sides, and the fishing industry has carried out the service of suppling to the people with important anima protein. The distribution of fishery products has very complicated structures, because the production is in charge of small producers scattering along the coast all over the country, while consumpstion is made by separate homes in areas away from producing district. The relation between these two factors the structures make very complicated. The most typical and special structures of fishery distridution are distinguished in two, that is, one is landing market, the other is inland market. Landing markets have been monopolized by fishermen's cooperatives, providing with landing facilities and building sites. Fish markets played not only an important role in the landing, but distribution and price determination of catches by auction or tender. Inland markets are two types of wholesale market in consuming center, one is the terminal market for urban consumers, the other type is the local market for rural consumers. Fundamental functions of landing markets are gathering, assessment, and distribution functions. Gathering function is in charge of wholesaler in fishery cooperative. Gathering amounts are equal to gathering capacity of wholesaler and transact ability of licensed dealers as shown below model. Gathering amount=f.gathering capacity(=pre price.landing facility.account of wholesaler.distance of fishing ground.conveniency purchasing.home port)=fㆍ transact ability of licensed dealers≒f.population or port, and table 1 indicates these relationship. Assessment and distribution functions are in charge of licensed dealers in consumption side. Assessment function should bring the value in production activity through the auction between the cooperative seller and the licensed dealer as buyer. For fair trade transaction in auction, the free competition is supposed to be a prerequisite among the licensed dealers. The ideal condition for free competition is sameness in the scale of buying amount by licensed delaers, but it is almost impossible to attain its goal in actual marketing.

• 한국운동역학회지
• /
• 제22권3호
• /
• pp.315-324
• /
• 2012

The purpose of current study was to investigate the effects of the heights on the lower extremities, torso and neck segments for energy dissipation during single-leg drop landing from different heights. Twenty eight young healthy male subjects(age: $23.21{\pm}1.66yr$, height: $176.03{\pm}4.22cm$, weight: $68.93{\pm}5.36kg$) were participated in this study. The subjects performed the single-leg drop landing from the various height(30, 45 & 60 cm). Force plates and motion-capture system were used to capture ground reaction force and kinematics data, respectively. The results were as follows. First, the ROM at the ankle, knee, hip and trunk was increased with the increased heights but the ROM at the neck was increased in the 60cm. Second, the angular velocity, moment and eccentric work at the ankle, knee, hip, trunk, and neck was increased with the increased heights. Third, the contribution to total work at the knee joint was not significantly different, while the ankle joint rate was decreased and hip and neck rate was increased in the 60cm, and trunk rate was increased with the increased heights. Lastly, the increase in landing height was able to augment the level of energy dissipation not only at the lower extremities but also at the trunk and neck. The findings showed that drop landing affect trunk and neck with lower extremity joints. Therefore, we need to consider that trunk and neck strengthening including stability should be added to reduce sports injury during prevention training.

• 한국항공우주학회지
• /
• 제41권6호
• /
• pp.465-472
• /
• 2013

본 논문에서는 요구 위치에 정밀 착륙을 위한 낙하산 전개지점 선정 기법을 제안한다. 무인기-낙하산 시스템을 위해 9-DOF 운동 모델을 구성하였고, 신경회로망을 학습시키기 위한 입출력 데이터 셋을 구성하였다. 입력 데이터 셋은 현재 항공기 위치, 속도정보 및 바람 정보로 구성되어 있고, 출력 데이터 셋은 9-DOF 운동 모델을 시뮬레이션 하여 획득한 착륙 위치 정보이다. 이를 이용하여 nonlinear function approximator를 구성함으로써 현재 위치로부터 상대적인 착륙 지점을 예측할 수 있고, 예측된 착륙 지점과 요구 착륙 지점과의 상대적인 거리 오차를 계산하여 이를 보상해줌으로써 낙하산 전개 지점을 결정할 수 있다.