• 천문학회보
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• 제37권2호
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• pp.160.1-160.1
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• 2012

We present an alternative approach for satellite formation reconfiguration by an optimal impulsive-thrust strategy to minimize the total characteristic velocity in a near-circular-orbit. Linear transformation decouples the Hill-Clohessy-Wiltshire(HCW) dynamics into a new block-diagonal system matrix consisting of 1-dimensional harmonic oscillator and 2-dimensional subsystem. In contrast to a solution based on the conventional primer vector theory, the optimal solution and the necessary conditions are represented as times and directions of impulses. New analytical expression of the total characteristic velocity is found for each sub systems under general boundary conditions including transfer time constraint. To minimize the total characteristic velocity, necessary conditions for times and directions of impulses are analytically solved. While the solution to the 1-dimensional harmonic oscillator has been found, the solution to the 2-dimensional subsystem is currently under construction. Our approach is expected to be applicable to more challenging problems.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.601-604
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• 2004

Precise position and attitude control of pico-satellite requires huge number of impulses of the order of 10$^{-6}$ Ns. MEMS solid rocket array is a promising propulsion system but the higher degree of miniaturization causes unreliable operation mainly due to quenching. In order to breakthrough this situation, a novel design of solid micro-rocket is proposed, which generates tiny impulses repetitively from a single rocket not from array. This unique micro-rocket is based on the utilization of quenching, which causes propellant reaction to sustain only in a small area. A test chip of a micro solid propellant tank and micro heater array is fabricated and ignition test is conducted. Obtained results show the feasibility of this concept and future direction of this quenching-based propulsion is discussed.

• 대한수학회논문집
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• 제26권2호
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• pp.197-205
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• 2011

Explicit sufficient conditions are established for the oscillation of the one order neutral differential equations with impulsive $(x(t)+{\sum\limits^n_{i=1}}c_ix(t-{\sigma}_i))'+px(t-{\tau})=0$, $t{\neq}t_{\kappa}$, ${\Delta}(x(t_{\kappa})+{\sum\limits^n_{i=1}}c_ix(t_{\kappa}-{\sigma}_i))+p_0x(t_{\kappa}-{\tau})=0$, $c_i{\geq}0$, $i=1,2,{\ldots}n$, $p{\tau}$>0, $p_0{\tau}$>0, ${\Delta}(x_{\kappa})=x(t^+_{\kappa})-x(t_{\kappa})$. Explicit sufficient and necessary condition are established when $c_i$ = 0, i = 1, 2, ${\ldots}$, n.

• The Korean Journal of Physiology
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• 제21권1호
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• pp.59-66
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• 1987

This study was aimed to investigate whether the conduction velocity of nerve impulses through the ventral afferent fibers is constant along their entire courses in dorsal as well as in ventral roots. Cats were anesthetized with ${\alpha}-chloralose$ (60 mg/kg, i.p.) and artificially ventilated. Laminectomies were done on L4-S1 spinal vertebrae to expose the lumbosacral spiral cord. Both ventral and dorsal roots of L7 or S1 spinal segments were isolated and cut near the spinal cord. Ventral roots were placed on 6-lead stimulating electrodes and stimulated with supra C-threshold intensity. Divided dorsal root fascicles were placed on bipolar recording electrodes and single fiber units activated by the stimulation of the ventral roots were identified. Followings are the results obtained: 1) A total of 27 VRA units were identified. 10 units of them conducted impulses slower than 2 m/sec. Conduction velocities of the remaining units were in the range of 3.11-20.91 m/sec. 2) In 12 Units conduction velocities Of the VRA units through dorsal$(CV_{DR})$ and venral root$(CV_{DR})$ were determined respectively. There was a tendency to conduct impulses faster through dorsal roots$(CV_{DR}=8.19{\pm}3.26\;m/sec)$ than ventral roots$(CV_{DR}=3.46{\pm}1.02\;m/sec)$. From the above results we confirmed that there exist nerve fibers in continuity between the spinal ventral and dorsal roots but we could not ascertain whether there is a change in conduction velocity through the entire course of ventral afferent unit.

• The Journal of Korean Physical Therapy
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• 제21권3호
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• pp.61-68
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• 2009

Purpose: The purpose of this study was to analyze the changes of the relative impulse of the foot when carrying 5 types of schoolbag during level walking. Methods: Forty-four normal subjects were divided into 5 groups according to the method of carrying a bag: carrying no bag (condition 1), a backpack (condition 2), a shoulder bag (condition 3), a cross bag (condition 4) and a one-hand bag (condition 5). To evaluate the partial relative impulse, 7 areas were measured on the sole of a foot: the hallux, toe, 1st metatarsal head (Met1) and the 2nd & 3rd metatarsal heads (Met2/3), the 4th & 5th metatarsal heads (Met4/5), mid foot and heel. Repeated one-way analysis of variance (ANOVA) and independent t-tests were used to analyze the statistical data. Results: In the right foot, the relative impulses in every areas revealed no significant difference (p>0.05), however, the relative impulses at Met1, Met2/3, Met4/5 and heel were significantly different between the different conditions (p<0.05). There were significant differences on comparing the relative impulse between left and right foot within one condition, the mid foot in condition 2, as well as the hallux and Met1 in condition 3 (p<0.05). In condition 4, the toe, Met1, Met4/5 and mid foot were significantly different (p<0.05). The values at the hallux, toe and Met1 in condition 5 also were significantly different (p<0.05). Conclusion: These findings showed that the symmetrical relative impulse of the foot was present in the case of carrying a backpack, but there was an extra load on specific regions and asymmetrical relative impulses in the case of carrying a shoulder bag, a across bag and a one-hand bag. (ED note: this abstract is not clear. You need to work on it.)

• The Korean Journal of Pain
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• 제14권1호
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• pp.7-11
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• 2001

Background: Although several mechanisms of causalgia, which results from a partial injury to the peripheral nerve trunk, have been proposed, whether or not antidromic impulses from the injured neurons contribute to the development of the mechanical hyperalgesia has not been studied. The purpose of this experiment is was to investigate the role of antidromic impulses to the peripheral sensory receptor site on the development of mechanical hyperalgesia in a rat model of peripheral neuropathy. Methods: Rats were prepared with tight ligation of by tightly ligating the left fifth and sixth lumbar spinal nerves. The effect of bupivacaine pretreatment on the development of mechanical hyperalgesia was evaluated by injecting 0.5% bupivacaine (0.3 ml) into the plantar surface of the left hind paw before the skin incision was made. For the control group, normal saline (0.3 ml) was injected instead of bupivacaine. To measure the mechanical hyperalgesia, paw withdrawal thresholds were measured using a series of von Frey hairs. Mechanical hyperalgesia was measured a the day before, and 1, 2, 3, 4, 7, and 14 days after the surgery. Results: The control group showed decreased withdrawal thresholds from the day after the surgery (the values were $14.0{\pm}0.5$, $8.9{\pm}1.3$, $8.4{\pm}1.6$, $6.9{\pm}1.2$, $8.8{\pm}1.5$, $10.5{\pm}1.3$, and $8.6{\pm}1.3$ g; at -1, 1, 2, 3, 4, 7, and 14 days after the surgery, respectively). However, withdrawal thresholds of the bupivacaine-pretreated group showed increased withdrawal thresholds for three days after the surgery ($14.5{\pm}0.3$, $12.6{\pm}1.4$, $12.7{\pm}1.1$, $10.5{\pm}1.3$ g; at 1, 1, 2, 3 days after the surgery). Conclusions: Our result suggests that antidromic impulses to the peripheral sensory receptors are at least partly responsible for the initial development of mechanical hyperalgesia in a rat model of peripheral neuropathy.

• 한국콘텐츠학회논문지
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• 제16권1호
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• pp.263-273
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• 2016

본 연구의 목적은 노인의 사회적 배제가 자살에 미치는 영향에 대한 적응유연성의 조절효과를 검증하는 것이며, 연구결과는 다음과 같다. 첫째, 인구사회학적 특성에 따른 자살 생각에 영향을 미치는 요인으로 연령, 교육수준, 혼인상태, 자녀와의 동거유무가 차이가 있는 것으로 나타났다. 연령은 75세 이상 80세 미만이 자살 생각을 가장 많이 갖는 것으로 나타났으며, 교육수준은 학력이 낮아질수록 자살 생각이 증가하는 것으로 나타났다. 그리고, 이혼, 사별, 별거 등으로 혼자된 노인과 자녀와 비 동거 상태인 노인일수록 자살생각을 많이 갖는 것으로 나타났다. 둘째, 노인의 사회적 배제가 높을수록 자살생각이 높은 것으로 나타났다. 셋째, 노인의 사회적 배제가 자살생각에 미치는 영향에 대한 적응유연성의 조절효과가 있는 것으로 나타났다. 마지막으로 기울기 검정 결과는 사회적 배제가 높은 집단의 적응유연성이 낮은 것으로 나타났다. 본 연구결과 노인의 자살생각이 자살행위로 이전되기 전 예방을 위한 사회적 차원의 정책적 방향성을 제시하고자 함이며, 보호요인인 적응유연성에 대한 실천적 함의를 후속연구로 제언하고자 한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1986년도 하계학술대회논문집
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• pp.459-462
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• 1986

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제13권2호
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• pp.121-136
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• 2006

We formulate and analyze a hybrid system model that involves Volterra integral operators with multiple integrals and two types of impulsive terms. We give a constructive proof, via an iteration method, of existence and uniqueness of solutions.

• Journal of applied mathematics & informatics
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• 제13권1_2호
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• pp.165-182
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• 2003

Sufficient conditions for oscillation of all solutions of a class of second-order quasilinear delay differential equations with fixed moments of impulse effect are found.