• Korean Journal of Agricultural Science
• /
• v.38 no.2
• /
• pp.325-330
• /
• 2011

In order to revive the ecological function of degraded rivers, a total restoration plan for riverbeds and riparians needs to be developed. Previous evaluations for rivers were mainly focused on the river's physical structures. Therefore, this research has developed indicators to evaluate a riparian restoration considering biodiversity. Through literature and previous cases review, 4 fields and 13 indicators are selected for the evaluation. Four fields are biodiversity, habitat diversity, connectivity and habitat functionality. In the biodiversity field, 4 indicators of the exuberant extent of herbaceous vegetation and their diversity, the exuberant extent of shrub and woody plants and their diversity, the number of plant communities and naturalized plants are included. Habitat diversity are comprised of 4 indicators of the longitudinal continuity of vegetation, the mixture of plant communities, the extent of plant type color fruit abundance and the distribution of vegetation. Connectivity includes 3 indicators of target distribution, the shore slope of low water channels and the extent of artificial embankment materials. Habitat functionality has 2 indicators of the status of food supply plants and the habitat functionality. The value weighting for the fields and indicators has been calculated based on the AHP(Analytic Hierarchy Process) method. 50 experts were surveyed with quantifiable questionnaire, among them 43 experts have more than 10 yesrs experiences in the nature restoration field. The selected and weighted indicators have been tested to the 12 sections in Gap stream located in Daejeon. In conclusion, the indicators are feasible and the selected indicators could be used to establish the direction and objectives of riparian restoration.

• Korean Journal of Social Welfare
• /
• v.64 no.1
• /
• pp.101-124
• /
• 2012

This study examined the longitudinal changes of self-perceptions of own aging among middle-aged and elderly adults, using the latent growth modeling with the three waves of the "Aging and the Quality of Life of the Elderly in Korea", which sampled adults aged over 45 living in Seoul and Chuncheon. The dependent variable is attitudes toward own aging, the sub-scale of the Philadelphia Geriatric Center Morale Scale developed by Lawton (1975). The results showed that the research participants' attitudes of their own aging deteriorated over time. In addition, the lower initial status of the research participants' attitudes of their own aging was associated with being older, being non-married, living in rural areas, attaining the lower level of education, having the fewer social activities, reporting the worse subjective economic status, and reporting the worse subjective health status. The slope of the research participants' attitudes of their own aging differed by the residence areas, educational attainments, subjective economic status and subjective health status. In particular, the difference of the initial status by educational attainments grew over time. Social welfare policy and practice implications are discussed for middle-aged and elderly adults to improve attitudes toward their own aging.

• Journal of Families and Better Life
• /
• v.34 no.3
• /
• pp.65-84
• /
• 2016

This study examined the factors that were associated with longitudinal changes for ten years from 2004 to 2014 in time spent on housework by married couples who had a preschooler as their first-born child. It also sought to figure out how much of such temporal changes were attributable to differences in the means on associated factors as well as to differences in the influence or slope of such factors. A total of 9,668 time diaries from the Korean Time Use Survey were used to analyze the influence of couple's weekly work hours, wife's relative income, couple's education and gender role attitudes on the time spent on housework of husbands and wives. Results from descriptive statistics, regression and decomposition analysis were as follows. First, women decreased, while men increased their time doing housework. Second, weekly work hours of husband and wife were related to their time doing housework in every year surveyed. Third, wife's relative earnings and couple's gender role attitudes affected wife's time doing housework more than husbands', whereas couple's education had stronger effects on husbands than wives. However, such influence was apparent on a certain survey year, and then disappeared in another, or became stronger or weaker longitudinally. Fourth, the temporal decrease in wife's housework time and increase in husband's housework time were attributable to social and cultural changes such as reduced working hours, rising female income, higher educational background, and prevalence of egalitarian gender role attitudes. Findings suggest that the trend in spending time on housework is expected to continue, and provide a timely policy implications to facilitate the change.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.5
• /
• pp.567-573
• /
• 2008

Water quality in the longitudinal and cross section was measured and analyzed at Dal stream. The change of water quality was compared with the change of discharge at the important points. When discharge was increased by rainfall, the concentration of BOD was decreased and the concentrations of TN and TP were increased. The correlation coefficient of BOD, TN, TP showed large with the water velocity and depth in the Case 2 that discharge was increased. Rainfall had much influenced in water quality because of moving the nonpoint source to the channel. Water velocity was analyzed by numerical model(Surface water Modeling System). Velocity was comparatively fast in the upstream that had a steep slope and narrow channel. The characteristics of pollution transfer was simulated in 2-dimensional channel, the pollution diffused rapidly to the center of flow in the main channel. Flow had much influenced in diffusion of pollution.

• International Journal of Aeronautical and Space Sciences
• /
• v.18 no.2
• /
• pp.197-205
• /
• 2017

We investigate the slat noise generation mechanism by using large-eddy simulation (LES) and simple source modeling based on linearized Euler equations. An incompressible LES of an MD 30P30N three-element airfoil in the high-lift configuration is conducted at $Re_c=1.7{\times}10^6$. Using the total derivative of the hydrodynamic pressure (DP/Dt) acquired from the incompressible LES, representative noise sources in the slat cove region are characterized in terms of simple sources such as frequency-specific monopoles and dipoles. Acoustic radiation around the 30P30N multi-element airfoil is effectively computed using the Brinkman penalization method incorporated with the linearized Euler equation. The directivity pattern of $p^{\prime}_{rms}$ at $r=20c_{slat}$ in the multiple sources is closely compared to that obtained by the application of the LES/Ffowcs-Williams and Hawking's methods to the entire flow field. The power spectrum of p' at ${\theta}=290^{\circ}$ is in good agreement with the data reported in BANC-III, especially the broadband part of the spectrum with a decaying slope ${\propto}f^{-3}$.

• Journal of Korea Water Resources Association
• /
• v.48 no.8
• /
• pp.635-645
• /
• 2015

The objective of this study is to examine the three-dimensional turbulent flows occurring in the meandering channel with presence of a groyne. A series of laboratory experiments are carried out in a meandering channel with trapezoidal cross sections. The channel is a 24.4 m long, 1.5 m wide, and the bottom slope in the longitudinal direction is 0.02. Two cases with and without the groyne are considered in the experiment. Three-dimensional velocity fields are measured using an acoustic Doppler velocimetry (ADV) at approximately sixty locations in each cross section. The measured velocity fields are averaged in time, and the time-averaged flow revealed that the mean velocity magnitude along the outer bank of the channel was reduced significantly and the direction of the primary flow was directed toward the center of the channel due to the presence of the groyne.

• Journal of Ecology and Environment
• /
• v.39 no.1
• /
• pp.43-49
• /
• 2016

Fishways are constructed to provide longitudinal connectivity of streams or rivers where their flow has been altered by in-stream structures such as dams or weirs. Nature-like fishways have an additional function of providing fish habitats. In the study, we estimated the role of a nature-like fishway (length: 700 m, slope: 1/100) for fish habitat by using two dominant species in the Sangju Weir, Nakdong River, to calculate the optimal ecological flow rate using Physical HABitat SIMulation (PHABSIM). To identify the dominant species that used the fishway, we conducted trap monitoring from August to November 2012 at the fishway exit. The dominant species were Zacco platypus and Opsariichthys uncirostric amurensis with a relative abundance of 62.1% and 35.9%, respectively. Optimal habitat suitability indices (HSIs) for Z. platypus and O. u. amurensis were calculated as 0.6-0.8 m/s (water velocity) and 0.2-0.4 m (water depth), and 0.5-0.7 m/s (water velocity) and 0.1-0.3 m (water depth), respectively. The optimal ecological flow rates (OEFs) for Z. platypus and O. u. amurensis were 1.6 and 1.7 cubic meter per second (CMS), respectively. The results of the study can be used in a management plan to increase the habitat function of nature-like fishways in the Sangju Weir. This methodology can be utilized as an appropriate tool that can determine the habitat function of all nature-like fishways.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.19 no.2
• /
• pp.110-117
• /
• 1999

In order to ultrasonically evaluate creep cavities pure copper samples were subjected to creep test and their microstructures were examined. Ultrasonic velocities. frequency-dependent magnitude spectra and attenuations were measured on a series of copper samples obtained from the different stages of creep test. Velocities measured in three directions with respect to the loading axis decreased and their anisotropy increased as a function of the creep-induced porosity. The anisotropic behavior could be attributed to the progressive change of pore shape and preferred orientation as the creep advanced. The 2% porosity by volume decreased the longitudinal and shear wave velocities by 11% and 4%, respectively. Furthermore, both velocities decreased nonlinearly with the porosity. As the creep damage developed, the magnitude spectra lost high frequency components and their central frequencies shifted to lower values. The attenuation showed almost linear behavior in the frequency range used. Normalized velocity, central frequency shift and attenuation slope were selected as nondestructive evaluation parameters. These results were presented and showed good relations with the porosity content.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.394-394
• /
• 2013

The spin-orbit interaction has received great attention in the field of spintronics, because of its property and applicability. For instance, the spin-orbit interaction induces spin precession which is the key element of spin transistor proposed by Datta and Das, since frequency of precession can be controlled by electric field. The spin-orbit interaction is classified according to its origin, Dresselhaus and Rashba spin-orbit interaction. In particular, the Rashba spin-orbit interaction is induced by inversion asymmetry of quantum well structure and the slope of conduction band represents the strength of Rashba spin-orbit interaction. The strength of spin-orbit interaction is experimentally obtained from the Shubnikov de Hass (SdH) oscillation. The SdH oscillation is resistance change of channel for perpendicular magnetic field as a result of Zeeman spin splitting of Landau level, quantization of cyclotron motion by applied magnetic field. The frequency of oscillation is different for spin up and down due to the Rashba spin-orbit interaction. Consequently, the SdH oscillation shows the beat patterns. In many research studies, the spin-orbit interaction was treated as a tool for electrical manipulation of spin. On the other hands, it can be considered that the Rashba field, effective magnetic field induced by Rashba effect, may interact with external magnetic field. In order to investigate this issue, we utilized InAs quantum well layer, sandwiched by InGaAs/InAlAs as cladding layer. Then, the SdH oscillation was observed with tilted magnetic field in y-z plane. The y-component (longitudinal term) of applied magnetic field will interact with the Rashba field and the z-component (perpendicular term) will induce the Zeeman effect. As a result, the strength of spin-orbit interaction was increased (decreased), when applied magnetic field is parallel (anti-parallel) to the Rashba field. We found a possibility to control the spin precession with magnetic field.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.60 no.1
• /
• pp.1-10
• /
• 2018

This study analyzed pore water pressure, seepage and leakage quantity, height of seepage and critical hydraulic gradient in order to suggest the seepage characteristics of agricultural reservoir embankment considering filter interval. The seepage characteristics of a deteriorated reservoir embankments were conducted according to the horizontal filter intervals range using three- dimensional finite element analysis. The wider the horizontal filter interval, the higher the pore water pressure increased, and the pore water pressure ratio in the center of the core has a greater effect than the base part. The seepage and leakage quantity appeared largely in the two-dimensional analysis conditions (case 1), where the filter was constructed totally in the longitudinal direction of the embankment, the wider the horizontal filter interval was gradually reduced. The reasonable filter intervals to yield efficient seepage characteristics were within 30 m for the pore water pressure of the core and the height of the seepage line. The stability of the filter installation was able to evaluate the stability of the piping by the critical hydraulic gradient method. The deteriorated reservoir with no filters or decreased functionality can significantly reduce the possibility of piping by simply installing a filter on the downstream slope. In the future, the deteriorated reservoir embankment should be checked for the reservoir remodeling because the core and filter functions have been lost or decreased significantly. In the case of a new installation, the seepage characteristic behavior due to the core and filter changes should be applied to the field after obtaining a reasonable horizontal filter interval that satisfies the safety factor by a three-dimensional analysis.