• Communications of the Korean Mathematical Society
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• v.34 no.2
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• pp.633-635
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• 2019

In this note we show that Lorentzian Concircular Structure manifolds $(LCS)_n$ coincide with Generalized Robertson-Walker space-times.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.522-528
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• 2012

It is the aim of this paper to propose the empirical fatigue crack propagation model fit to describe a crack growth behavior of AZ31 magnesium alloys. The statistical data of a crack growth for an estimation are obtained by fatigue crack propagation tests under the three cases of maximum load. The empirical models estimated are Paris-Erdogan model, Walker model, Forman model, and modified-Forman model. It is found that the empirical model fit to describe a crack growth behavior of AZ31 magnesium alloys is Paris-Erdogan model and Walker model. It is also verified that a fatigue crack growth rate exponent of a empirical model is to be a material constant.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.9
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• pp.823-826
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• 2010

In this study, the control method of assistive robot was developed for the elderly. The control method of gait-assistant-robot was proposed considering the change of COP (Center of Pelves), BOS (Base of Support) and comparative analysis of the moving velocity for the elderly. We analyzed the movement of COP of the body and its velocity of the elderly equipped with manual walker and gait-assistant-robot. As a result, change in COP was greater from left to right than from anterior to posterior; also, the average velocity of the movement of COP and manual walker for manual walker gait was 0.7(m/s). Therefore, it is necessary to concern more on the left-right balance and synchronization of the velocity of COP.

• Korean journal of applied entomology
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• v.44 no.1 s.138
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• pp.13-20
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• 2005

Thirty-four species of the subfamily Plusiinae were recognized from the lepidopteran expeditions to Mt. Changbai during 2000-2004. Among them, six species (Abrostola ussuriensis Dufay, Polychrysia aurata (Staudinger), P. splendida (Butler), Lamprotes mikadina (Butler), Autographa amurica (Staudinger), and A. v-minus (Oberthur)) are reported for the first time from China. Three previously reported species Antoculeora ornatissima (Walker), Autographa nigrisigna (Walker), and Syngrapha hochenwarthi (Hochenwarth) were not found in this study, Photographic images of adults of the newly known species from China and their male or female genitalia are given, with a check list of the 37 known species of the subfamily in Mt Changbai.

• Korean journal of applied entomology
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• v.51 no.4
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• pp.439-442
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• 2012

Two species, Daulia afralis Walker and Herpetogramma cynaralis Walker, belonging to the family Crambidae, Lepdidoptera, are reported for the first time from Korea, based on the materials collected from Jeju Islands located in the southern part of the Korean peninsula. Both male and female genitalia were dissected and examined. Also, the photos of the external morphology, including the wing patterns, and genitalic characteristics of the two species are taken and redescribed briefly, including distributional ranges and available information. Taxonomic information and synonymies for the species were given and discussed.

• Korean journal of applied entomology
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• v.61 no.3
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• pp.497-502
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• 2022

The genus Ippa Walker, 1864 is reported for the first time from Korea, with a species I. conspersa (Matsumura, 1931). I. conspersa is generally known as myrmecophiles having ecological relationships with some ant species such as Lasius spp. Photographs of adults, immature stages, and the genitalia of I. conspersa are provided.

• Journal of Korean Physical Therapy Science
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• v.30 no.4
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• pp.1-8
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• 2023

Background: This study evaluates the usability of the Motion-Tracking Gait Assistive Walker (MTGAW) designed for elderly individuals and those with disabilities, identifying areas for improvement through interviews with physical and occupational therapists. Design: A survey study involves the usability test for MTGAW. Methods: Usability evaluations were conducted with 37 physical therapists and occupational therapists. The process included explanation, product usage, satisfaction surveys, and interviews. A satisfaction survey covering 19 items across safety, maneuverability, usability, and management areas was administered. Individual interviews identified areas for improvement. Results: Overall, high satisfaction was reported across the four areas, but interviews highlighted the need for improvements, such as addressing discomfort due to slow speed and enhancing safety measures to prevent rear-end falls. Adjusting the walker's height and width to suit the user's physique was also suggested. Conclusion: MTGAW enhances walking support and hand movement freedom but needs refinement in speed control, fall prevention, and customization based on the user physique. Future efforts should focus on developing an improved MTGAW, considering recommendations from physical therapy experts, and conducting studies to analyze its clinical effectiveness for commercialization.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.379-386
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• 2012

The primary aim of this paper was to evaluate several probabilistic fatigue crack propagation models using the residual of a random variable, and to present the model fit for probabilistic fatigue behavior in Mg-Al-Zn alloys. The proposed probabilistic models are the probabilistic Paris-Erdogan model, probabilistic Walker model, probabilistic Forman model, and probabilistic modified Forman models. These models were prepared by applying a random variable to the empirical fatigue crack propagation models with these names. The best models for describing fatigue crack propagation behavior in Mg-Al-Zn alloys were generally the probabilistic Paris-Erdogan and probabilistic Walker models. The probabilistic Forman model was a good model only for a specimen with a thickness of 9.45 mm.

• Journal of the Korean earth science society
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• v.37 no.6
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• pp.359-372
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• 2016

The time-series of Walker circulation index (WCI) in this study shows the strengthening of the Walker circulation in recent years. To further understand the large-scale features related to the WCI strengthening, a difference between the averaged meteorological variables in two time periods 1999-2013 and 1984-1998 is analyzed. The difference in 850 hPa stream flows between the two periods shows that the anomalous easterlies (anomalous trade wind) are dominant due to the strengthening of anomalous anticyclonic circulations at the subtropical Pacific of both hemispheres. The difference between the averaged zonal atmospheric circulations over $5^oS-5^oN$ in the two periods confirms that upward flows are strengthened at the tropical western Pacific and downward flows are strengthened at the tropical central and eastern Pacific in recent years. It matches the WCI strengthening in recent years. The time-series of tropical cyclone (TC) genesis frequency from July to September shows that a mean TC genesis frequency from 1999-2013 decreases compared to that of the time period 1984-1998. The monsoon trough in the period 1984-1998 was located in the further east direction and stronger than that in the period 1999-2013. TCs in the recent period that are generated in further west than TCs in the past period moved from the west. Thus, the TC intensity along the coasts in East Asia becomes weaker in recent period. The intensification of Walker circulation in recent years is related to the weaker TC intensity in East Asia through strengthened anomalous anticyclones at the subtropical western Pacific.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.1-10
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• 2012

Throughout much of the world, many ecological problems have arisen in watersheds where a significant portion of stream flows are diverted to support agriculture production. Within endorheic watersheds (watersheds whose terminus is a terminal lake) these problems are magnified due to the cumulative effect that reduced stream flows have on the condition of the lake at the stream's terminus. Within an endorheic watershed, any diversion of stream flows will cause an imbalance in the terminal lake's water balance, causing the lake to transition to a new equilibrium level that has a smaller volume and surface area. However, the total mass of Total Dissolved Solids within the lake will continue to grow; resulting in a significant increase in the lake's TDS concentration over time. The ecological consequences of increased TDS concentrations can be as limited as the intermittent disruption of productive fisheries, or as drastic as a complete collapse of a lake's ecosystem. A watershed where increasing TDS concentrations have reached critical levels is the Walker Lake watershed, located on the eastern slope of the central Sierra Nevada range in Nevada, USA. The watershed has an area of 10,400 sq. km, with average annual headwater flows and stream flow diversions of 376 million $m^3/yr$ and 370 million $m^3/yr$, respectively. These diversions have resulted in the volume of Walker Lake decreasing from 11.1 billion m3 in 1882 to less than 2.0 billion $m^3$ at the present time. The resulting rise in TDS concentration has been from 2,560 mg/l in 1882 to nearly 15,000 mg/l at the current time. Changes in water management practices over the last century, as well as climate change, have contributed to this problem in varying degrees. These changes include the construction of reservoirs in the 1920s, the pumpage of shallow groundwater for irrigation in the 1960s and the implementation of high efficiency agricultural practices in the 1980s. This paper will examine the impacts that each of these actions, along with changes in the region's climate, has had on stream flow in the Walker River, and ultimately the TDS concentration in Walker Lake.