• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.10
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• pp.848-855
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• 1989

The asymptotic properties of the Overdetermined Yule-Walker (OYW) estimators were studied. A formula was derived for the asymptotic covariance matrix of the estimation errors. It verified the experimentally observed fact that the frequency estimation accuracy is generally improved as the number of Yule-Walker equations is increased. The asymptotic estimation accuracies of the OYW method were compared with the Cramer-Rao low bound.

• Radiation Oncology Journal
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• v.5 no.2
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• pp.75-82
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• 1987

For evaluation of biological effect of $p^+(50.5MeV)$ Be neutron beam produced by Korea Cancer Center Hospital (KCCH) cyclotron the RBE had been measured in experimental tumor Walker 256 carcinosarcoma as well as normal tissue, mouse intestine and bone marrow, in single and fractionated irradiation. As pilot study, the RBE had been measured for the mouse jejunal crypt cells in single whole body irradiation of which the result was 2.8. The obtained RBE values of TCD 50 of Walker 256 tumor, bone marrow and intestine En single irraiation were 1.9, 1.9 and 1.5 respectively. In fractionated irradiation, the RBE value of tumor Walker 256 was decreased as increasing of fraction number and increased as increaing of fraction size.

• Journal of Korean Academy of Nursing
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• v.29 no.2
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• pp.361-370
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• 1999

Baby walkers have been a major cause of injuries in young children. The main purpose of this study is to identify the pattern of injuries associated with baby walker. The data ore collected from May 13 to June 15, 1998 from 438 mothers who have used or are using baby walkers for their children aged average 6 month old(range 1-33 month). It was founded that 19.2%(84 infants) of these children had walker-related accidents. The types of injuries included ‘falling down’(52.4%), ‘tiping over’(21.4%), ‘being crashed into the wall’(17.9%), and burns(1.2%). These injuries predominantly involved the head and neck region(88%). The majority of injuries were minor, and most injuries occured at home with the mother present. The most common reason to use the baby walker was to keep the infant happy and occupied. Although many parents used walker to promote walking, there was no supportive evidence that walkers helped babies learn to walk sooner. In conclusion, injuries among infants who use walkers are minor, but common. Also, baby walkers may cause a fatal min to some infants. Therefore, child safety warning label policies, anticipatory safety guidance and quality control of infant walkers are needed to prevent injuries associated with a infant walker.

• Journal of the Korean Statistical Society
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• v.26 no.1
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• pp.47-56
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• 1997

The asymptotic distribution of the extended Yule-Walker estimates of a mixed ARMA process is derived. Also, a recursive algorithm is derived to calculate the extended Yule-Walker estimates recursively, which is a generalization of the Levinson-Durbin algorithm.

• Korean journal of applied entomology
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• v.33 no.4
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• pp.257-262
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• 1994

Nine species of aphid-hypelparasitoids are listed in Korea. Prev~ous reports about the dihibution of the two species, Ardileo conuexa (Walker, 1833) and Asaphes uulgaris Walker, 1834 are doubtful in Korea.

• Journal of Korean Neurosurgical Society
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• v.50 no.5
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• pp.475-477
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• 2011

Neurocutaneous melanosis associated with Dandy-Walker malformation is a rare dysmorphogenesis that is associated with single or multiple giant pigmented cutaneous nevi and diffuse involvement of the central nervous system. In this article, we present a 2-month-old patient with neurocutaneous melanosis associated with Dandy-Walker malformation. In addition, we reviewed the literature and discussed the pathogenesis based on the preferred hypotheses.

• Honam Mathematical Journal
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• v.41 no.1
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• pp.153-161
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• 2019

In practical applications play an new important role timelike biharmonic particle by Fermi-Walker derivative. In this article, we get a innovative interpretation about timelike biharmonic particle by means of Fermi-Walker derivative and parallelism in Heisenberg spacetime. With this new representation, we derive necessary and sufficient condition of the given particle to be the inextensible flow. Moreover, we provide several characterizations designed for this particles in Heisenberg spacetime.

• Communications of the Korean Mathematical Society
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• v.39 no.1
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• pp.201-210
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• 2024

This paper is concerned with the study of spacetimes satisfying div 𝓜 = 0, where "div" denotes the divergence and 𝓜 is the m-projective curvature tensor. We establish that a perfect fluid spacetime with div 𝓜 = 0 is a generalized Robertson-Walker spacetime and vorticity free; whereas a four-dimensional perfect fluid spacetime becomes a Robertson-Walker spacetime. Moreover, we establish that a Ricci recurrent spacetime with div 𝓜 = 0 represents a generalized Robertson-Walker spacetime.

• The Journal of Korean Physical Therapy
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• v.25 no.5
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• pp.239-245
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• 2013

Purpose: Osteoarthritis occurs in many different joints of the body, causing pain, stiffness, and decreased function. The knee is the most frequently affected joint of the lower limb. The aim of this study was to investigate the differences of biomechanics between independent gait and anterior walker dependent gait of patients with osteoarthritis of the knee. Methods: Lower limb joint kinematics and kinetics were evaluated in 15 patients with knee osteoarthritis when walking independently and when walking with an anterior walker. Participants were evaluated in a gait laboratory, with self-selected gait speed and natural arm swing. Results: When walking with a dependent anterior walker, participants walked significantly faster (p<0.01), using a longer stride length (p<0.01), compared to independent gait. When walking with a dependent anterior walker, participants exhibited significantly greater knee flexion/extension motion (p<0.01) and lower knee flexion moment (p<0.05) compared to independent gait. When walking with a dependent anterior walker, participants showed significantly greater peak ankle motion (p<0.01), ankle dorsiflexion/plantarflexion moments (p<0.01), and ankle power generation (p<0.05) compared to independent gait. Conclusion: These biomechanical properties of gait, observed when participants walked with a dependent anterior walker, may be a compensatory response to impaired knee function to allow sufficient power generation for propulsion. Therefore, rehabilitative strategies for patients with osteoarthritis of the knee are needed in order to improve not only knee function but also hip and ankle function.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.3
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• pp.187-196
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• 2014

This paper suggests linearity enhancement algorithm to Ensure safety of Mobile Walker on Slope. Mobile Walker happens to get off track due to external forces from Walker's weight and the degree of the slope while slope driving. In order to compensate this, this research used the controller that estimates the external forces according to the slope of road surface and adjusts it to the motor output. Also, through comparisons between targeted rotational angular velocity which the user inputs and its velocity of the robot, algorithm was applied which applies a weight to each shaft. As a result of applying the proposed correction controller, it diverges in case of non-compensation experiments that deviates when moving, but it case of applying the ramp calibration algorithm, the deviation distance at max was within 10cm that it keeps safe driving, and change rate of deviation distance was also stabilized after 1m where no more changes occurred.