• 한국항공운항학회지
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• 제19권2호
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• pp.58-63
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• 2011

A Continuous Descent Approach(CDA) is defined as a simple, cost-effective, noise and emission abatement technique for any powered aircraft on approach. CDA also can be optimised within energy, speed and safety constraints by avoiding unnecessary flap, air brake and engine thrust. This study includes comparison on fuel consumption between Continuous Descent type and Step Down type by using flight data. In particular, we investigated fuel flow per hour, calibrated airspeed and pressure altitude for all flight time. During descent flight, the fuel consumption of Continuous Descent type was less than the fuel consumption of Step Down type.

• Journal of applied mathematics & informatics
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• 제20권1_2호
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• pp.239-254
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• 2006

An efficient descent method for unconstrained optimization problems is line search method in which the step size is required to choose at each iteration after a descent direction is determined. There are many ways to choose the step sizes, such as the exact line search, Armijo line search, Goldstein line search, and Wolfe line search, etc. In this paper we propose a new inexact line search for a general descent method and establish some global convergence properties. This new line search has many advantages comparing with other similar inexact line searches. Moreover, we analyze the global convergence and local convergence rate of some special descent methods with the new line search. Preliminary numerical results show that the new line search is available and efficient in practical computation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.823-828
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• 1992

A novel steepest descent adaptive filter algorithm, which uses the instantaneous stochastic gradient for the steepest descent direction, is derived from a newly devised performance index function. The performance function for the new algorithm is improved from that for the LMS in consideration that the stochastic steepest descent method is utilized to minimize the performance index iterativly. Through mathematical analysis and computer simulations, it is verified that there are substantial improvements in convergence and misadjustments even though the computational simplicity and the robustness of the LMS algorithm are hardly sacrificed. On the other hand, the new algorithm can be interpreted as a variable step size adaptive filter, and in this respect a heuristic method is proposed in order to reduce the noise caused by the step size fluctuation.

• 한국운동역학회지
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• 제16권4호
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• pp.31-38
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• 2006

The purpose of this study was to investigate the effect of changing the steps height on the joint moment of lower extremity in stair-descent activity of elderly persons. Data were collected by 3-D cinematography and force platform. 9 male elderly subjects in the 60s and 70s participated in this study. All subjects performed a stair-descent in four different heights of stairs (10, 14, 18, 22cm) having 5 step staircase. The results were as follows. 1. For the step height of 22cm the maximum. plantarflexion moment was the smallest and the largest for the step height of 14cm. 2. There was not a statistical difference shown for the extension moment of the knee joint for the different height of steps. 3. There was not a statistical difference shown for the flexion moment of the hip joint for the varying height of steps but on average for the 18cm step this increased rapidly. 4. The smallest maximum. value for inversion moment was revealed for the step height of 10cm and this increased significantly for the step height of 22cm. 5. The smallest maximum. value for abduction moment of the hip joint was revealed for the step height of 10cm and this increased significantly for the step height of 22cm. 6. There was no significant difference shown for the maximum. abduction moment for the hip joint. The main conclusion is that there is a huge difference in the moment of the lower extremities for the elderly while walking down a stairs with a step height above 18 cm and that this moment increased or decreased rapidly under a condition of step height being 22cm. With the results from this research and related research of elderly walking upstairs it can be shown that the step height has a large role in the safety for the elderly.

• The Journal of Korean Physical Therapy
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• 제18권1호
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• pp.95-106
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• 2006

Purpose: The aim of this study was to investigate the kinematics of young adults during ramp climbing at different inclinations. Methods: Twenty-three subjects ascended and descended four steps at four different inclinations(level, $8^{\circ},\;16^{\circ},\;24^{\circ}$). Temporal-spatial parameters were measured by GaitRite system(standard mat). Groups difference was analysed with on-way ANOVA and Student-Newman-Keuls test. Results: The different kinematics of ramp ascent and descent were analysed and compared to level walking patterns. In ascending ramps, step length and stride length decreased with $24^{\circ}$ inclination (p<.000). Stance duration increased with $24^{\circ}$, but swing duration decreased with $24^{\circ}$ inclination (p<.000). Step time and velocity decreased with $16^{\circ}C,\;24^{\circ}$ inclination (p<.000). Cadence decreased with all inclination($8^{\circ},\;16^{\circ},\;24^{\circ}$)(p<.000). In descending ramps, step length and stride length, velocity decreased with all inclination($8^{\circ},\;16^{\circ},\;-24^{\circ}$)(p<.000). Stance duration increased with all inclination($8^{\circ},\;-16^{\circ},\;-24^{\circ}$) and swing duration decreased with all inclination($-8^{\circ},\;-16^{\circ},\;-24^{\circ}$)(p<.000). But Step time was not differentiated with different inclinations. Cadence decreased with only. $8^{\circ}$ inclination(p<.05). Conclusion: These results suggest that there is a certain inclination angle or angular range where subjects do switch between level walking and ramp walking gait pattern. This shows their motor control strategy between level and ramp walking. Further studies are necessary to confirm and detect the ascent and descent ramp gait patterns.

• Physical Therapy Rehabilitation Science
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• 제3권1호
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• pp.43-48
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• 2014

Objective: The purpose of this study was to examine the influences on gait features during mobile phone use while ramp walking. Design: Cross-sectional study. Methods: Thirty-three healthy adult subjects performed four walking conditions on an outside ramp with a 5 m length, 1.5 m width, and a $5^{\circ}$ angle. All participants were touch screen mobile phone users. Four walking conditions were used: 1) ramp ascent, 2) ramp descent, 3) texting during ramp ascent, and 4) texting during ramp descent. In conditions 3) and 4), subjects texted the words of "Aegukga"-the song of patriotism-while walking. Upon the signal of start, the subjects walked the ramp during texting. Gait parameters were measured at the length of 3 m excluding 1 m of the start and end of the total length. Each situation was repeated three times for each subject, and mean values were calculated. For gait examination, a gait analyzer was used (OptoGait). Results: Subjects ranged in age from 23 to 38 years (mean age, 27.73). Eighty-three percent of subjects in our study had experienced an accident during mobile phone use. Texting on a mobile phone while walking significantly decreased ramp gait, speed, cadence, stride length, step length, and single support (p<0.05) and significantly increased stride time, step time, gait cycle, and double support (p<0.05). There was a significant difference in cadence, step length, stride time, step time, and single support during ramp ascent and descent (p<0.05). Conclusions: Texting on a mobile phone while walking significantly decreased gait quality.

• ETRI Journal
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• 제45권1호
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• pp.119-130
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• 2023

We propose a quantized gradient search algorithm that can achieve global optimization by monotonically reducing the quantization step with respect to time when quantization is composed of integer or fixed-point fractional values applied to an optimization algorithm. According to the white noise hypothesis states, a quantization step is sufficiently small and the quantization is well defined, the round-off error caused by quantization can be regarded as a random variable with identically independent distribution. Thus, we rewrite the searching equation based on a gradient descent as a stochastic differential equation and obtain the monotonically decreasing rate of the quantization step, enabling the global optimization by stochastic analysis for deriving an objective function. Consequently, when the search equation is quantized by a monotonically decreasing quantization step, which suitably reduces the round-off error, we can derive the searching algorithm evolving from an optimization algorithm. Numerical simulations indicate that due to the property of quantization-based global optimization, the proposed algorithm shows better optimization performance on a search space to each iteration than the conventional algorithm with a higher success rate and fewer iterations.

• 한국항공운항학회지
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• 제19권2호
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• pp.52-57
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• 2011

The procedures of Continuous Descent Approach(CDA) is designed to minimize the thrust required during landing, thereby reducing fuel consumption, noise and emissions compared to conventional approach procedures. Widespread implementation of CDA would result in significant reductions in the environmental impact and aircraft operation costs. This paper estimated the possible economic effects from the perspective of airliners through cost-benefit analysis, provided that the CDA is introduced. It is now proposed that a more comprehensive analysis model, which includes the reduced ATC communication burden between controllers and pilots, not to mention the economic aspect, should be established for the improvement.

• Journal of applied mathematics & informatics
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• 제11권1_2호
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• pp.201-213
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• 2003

In this paper we present a second order PVT (parallel variable transformation) algorithm converging to second order stationary points for minimizing smooth functions, based on the first order PVT algorithm due to Fukushima (1998). The corresponding stopping criterion, descent condition and descent step for the second order PVT algorithm are given.

• 한국인터넷방송통신학회논문지
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• 제23권1호
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• pp.109-116
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• 2023

이 연구의 목적은 계단 내리기 시 성별과 중량차이가 하지역학에 미치는 영향을 분석하는 것이다. 건강한 남성 10 명과 여성 10 명이 참여하였다. 계단 내리기 동작은 중량 변화(체중의 0%, 10%, 20%, 30%)에 따라 영상분석법과 지면반력 시스템을 이용해 분석하였다. 골반의 최대 합성속도에서 성별(남성>여성)과 중량변화(30%, 20%, 10%> 0%)에 따라 서로 차이가 있는 것으로 나타났으며, 성별과 중량 간 상호작용이 나타났다(중량>성별). 계단 내리기 동안 성별의 주효과는 초기 접촉 단계에서 남성보다 여성이 더 감소된 다리길이를 보였다. 또한, 남성보다 여성에게서 더 굴곡된 엉덩, 무릎관절 각도와 발목관절 각도의 저측 굴곡형태가 나타났다. 운동역학 변인에서, 계단 내리기 시 성별의 주효과는 남성보다 여성이 더 증가된 좌우 지면반력과 다리강성을 보였다. 결론적으로 여성들이 계단 내리기 동안 엉덩 관절의 운동 범위와 함께 합성이동속도를 감소시켜 중량을 성공적으로 수용한다는 것을 발견하였다. 반면 남성들은 중량수용과 운동량을 제어하기 위해 좌우 및 수직지면반력, 그리고 다리강성을 더 증가시킨다.