• International Journal of Aeronautical and Space Sciences
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• v.11 no.4
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• pp.303-312
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• 2010

This paper introduces the upper stage attitude control system of KSLV-I, which is the first space launch vehicle in Korea. The KSLV-I upper stage attitude control system consists of two electro-hydraulic actuators and a reaction control system using cold nitrogen gas. A proportional, derivative, and integral controller is designed for the electro-hydraulic thrust vectoring system, and Schmidt trigger ON/OFF controllers are designed for the reaction control system. Each attitude controller is designed to have enough stability margins. The stability and performance of KSLV-I upper stage attitude control system is verified via hardware in the loop tests. Hardware in the loop tests are accomplished for perturbed flight conditions as well as nominal flight condition. The test results show that the attitude control loop of KSLV-I upper stage is very stable and the attitude controllers perform well for all flight conditions. Attitude controllers designed in this paper have been successfully applied to the first flight of KSLV-I on August 25, 2009. The flight test results show that all attitude controllers of the KSLV-I upper stage performed well and satisfied the accuracy specifications even during abnormal flight conditions.

• Journal of Soil and Groundwater Environment
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• v.25 no.2
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• pp.1-8
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• 2020

In general, the estimation of optimum yield for the radial collector well is determined by the empirical equation or numerical modeling, in which hydraulic conductivity of the aquifer is a main influence factor. Hydraulic conductivities of 164 soil samples collected from boreholes and horizontal wells (average length: about 50 m) installed during well construction in the Anseong stream were drawn in two-dimensional map by the Kriging method and utilized in this study. Hydraulic conductivity analyses by Representative Elementary Count (REC) indicated the average hydraulic conductivity is similar to that of the pumping test when the number of samples reaches about 1,000, which correspond to 1,000 ㎡. Pumping test was also conducted at 1 pumping well and 13 observation wells to estimate hydraulic conductivities at each observation well. REC analysis indicated that the average value of hydraulic conductivity calculated from at least four observation wells is valid as a representative value. The overall result suggested that multiple observation wells or multiple pumping-observation well systems that are located within the range of horizontal wells should be utilized to properly estimate the representative hydraulic conductivity values and the yield of a radial collector well.

• Geotechnical Engineering
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• v.3 no.4
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• pp.31-40
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• 1987

A helical probe test (HPT) suitable for in.situ soil exploration to a shallow depth and compaction control were developed and tested in different soils alongside traditional in-situ tests, including Standard Penetration Test (SPT), Cone Penetration Test (CPT) and in-situ density test. The helical probe test is economical and can be performed by a single person. The torque necessary to insert the probe Is used as a measure of soil characteristics. It was found that: the HPT test correlates well with the SPT test and the correlation is not sensitive to the soil type; the HPT test correlates well with the CPT test, but the correlation is sensitive to the soil type; the HPT torque provides a sensitive measure of relative compaction rind in-situ dry density of compacted soils; the reverse torque ratio decreases with increasing average grain sloe.

• Ocean Science Journal
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• v.40 no.1
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• pp.17-24
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• 2005

A series of experiments were conducted to develop standard test organisms and test protocols for measuring sediment toxicity using candidate amphipods such as Mandibulophoxus mai, Monocorophium acherusicum, Haustorioides indivisus, and Haustorioides koreanus, which are indigenous to Korea. The relevant association of test species with sediment substrates was one of the important factors in sediment bioassay. The indigenous amphipods M mai and M. acherusicum were well associated with test sediments when they were exposed to various sediment substrates from sand to mud. The tolerant limits to various physico-chemical factors affecting bioassay results such as temperature, salinity and ammonia, as well as sensitivities to reference toxicant and contaminated sediments, were investigated using M. mai and M. acherusicum in the present study. These amphipods were tolerant to relatively wide ranges of salinity $(10{\sim}30\;psu)$ and ammonia (<50 ppm), and displayed relevant sensitivity to temperature as well. They are more sensitive to Cd, the reference toxicant, when compared to the standard test species used in other countries. Field-sediment toxicity tests revealed that M. mai would be more sensitive to sediment-associated pollutants than M. acherusicum, while the sensitivity of M. acherusicum was comparable to that of Leptocheirus plumulosus, which has been used as a standard test species in the United States of America. Overall results of this first attempt to develop an amphipod sediment toxicity test protocol in Korea indicated that M. mai and M. acherusicum would be applicable in the toxicity assessment of contaminated sediments, following the further evaluation encompassing various ecological and toxicological studies in addition to test method standardization.

• Journal of the Korean Geotechnical Society
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• v.28 no.11
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• pp.17-31
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• 2012

No analytical solution exists for evaluating in-situ hydraulic conductivity of vertical cutoff walls by analyzing slug test results with consideration of transient flow. There is an analytical solution proposed to interpret a slug test performed in a partially penetrated well within an aquifer. However, this analytical solution cannot be directly applied to the cutoff wall because the solution has been developed exclusively for an infinite aquifer instead of a narrow cutoff wall. To consider the cutoff wall boundary conditions (i.e, constant head boundary and no flux boundary condition), the analytical solution has been modified in this study to take into account the narrow boundaries by introducing the imaginary well theory. Type curves are constructed from the currently derived analytical solution and compared with those of a partially penetrated well within an aquifer. The constant head boundary condition provides faster hydraulic head recovery curve than the aquifer case. On the other hand, no flux boundary condition leads to slower hydraulic head recovery. The bigger the shape factor and deviation of the well and the smaller the width of the vertical cutoff wall are, the more effect of boundary condition was observed. The type curves obtained from the analytical solution for a cutoff wall are similar to those made by the numerical method in the literature.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.2
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• pp.211-217
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• 2010

In order to suggest the methodology for achieving anti-vortex within multi pump intake well, the field test and CFD(Computational Fluid Dynamics) simulation were conducted. The filed test were carried out for domestic W_multi pump intake well according to usual operation condition through the naked observation. From the results, operating #4, #5, #8 and 9# pumps, the vortex and swirl occurred above #4 and #9 intake pipe within two wells. For qualitative analysis, a commercial CFD code, using sump model, was used to predict the vortex generation within the selected pump intake facility accurately. The analysed results by CFD show that the vortex structure and location are in accordance with the results of the field test.

• Journal of the Korean Society of School Health
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• v.24 no.1
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• pp.71-80
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• 2011

Purpose: This study was conducted to compare the level of depressive symptom, spiritual well-being and faith maturity between college freshmen and seniors and to investigate the affecting factors on their depressive symptom. Methods: The study was cross-sectional descriptive survey. A self-report questionnaire were used to collect data from 335 college students during June to July, 2010. Data were analyzed by ${\chi}^2$-test, t-test, ANOVA, Scheffe's test, pearson correlation coefficient, and stepwise multiple regression using the SPSS/WIN 14.0 program. Results: The mean score of depressive symptom was $17.55{\pm}11.24$ and prevalence of depression was 26.5% in college freshmen. And those in college seniors were $14.18{\pm}14.17$ and 17.4%. And those were significantly higher in college freshmen than in seniors. The depressive symptom was a significant negative correlation with spiritual well-being, existential spiritual well-being, religious spiritual well-being, and faith maturity. Factors significantly influencing on depression in college freshmen included existential spiritual well-being, subjective health status, age, and confidence of salvation ($R^2$=49.7%). And those in college seniors included existential spiritual well-being and life satisfaction ($R^2$=53.3%). Conclusion: The counseling program and spirituality development program for preventing depression considering these affecting factors for especially college freshmen are necessary.

• Geomechanics and Engineering
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• v.24 no.1
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• pp.15-28
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• 2021

Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. However, there is still a lack of knowledge of lateral behavior of digging well foundation considering the soil-foundation interaction. In this study, scaled models of bridge pier-digging well foundation system are constructed for quasi-static test to investigate their lateral behaviors. The failure mechanism and responses of the soil-foundation-pier interaction system are analyzed. The testing results indicate that the digging foundations tend to rotate as a rigid body under cyclic lateral load. Moreover, the depth-width ratio of digging well foundation has a significant influence on the failure mode of the interaction system, especially on the distribution of foundation displacement and the failure of pier. The energy dissipation capacity of the interaction system is discussed by using index of the equivalent viscous damping ratio. The damping varies with the depth-width ratio changing. The equivalent stiffness of soil-digging well foundation-pier interaction system decreases with the increase of loading displacement in a nonlinear manner. The absolute values of the interaction system stiffness are significantly influenced by the depth-width ratio of the foundation.

• Journal of the Korean Society of Physical Medicine
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• v.19 no.1
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• pp.1-10
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• 2024

PURPOSE: This pre-post intervention study aimed to examine the effects of a 12-week supervised modified Taekwondo exercise program on the functional fitness of community-dwelling older adults. METHODS: 10 participants (mean age: 72.3 ± 4.6 years) completed the program over a 12-week period. The intervention consisted of Taekwondo-based exercises modified for older persons. Changes to functional fitness were measured using the finger-to-nose test, functional reach test, timed up and go test, 30-second sit-to-stand test, 30-second arm curl test, Chester step test, chair sit-and-reach test, and back scratch test. Participants were assessed prior to the training and after the final training session, changes were measured using descriptive statistics and paired sample 't' tests. RESULTS: Effect sizes ranged from small to large (Cohen's d = .22 to 1.23). The exercise program was well- tolerated by participants, with a high level of engagement and no attrition for the duration of the program. Results showed significant improvements in most measures of functional fitness (p < .05) except for the back scratch test (p = .051). CONCLUSION: These findings suggest a well-designed, supervised, modified Taekwondo exercise program can significantly improve functional fitness in older adults.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.1
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• pp.20-23
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• 2000

A general solution for determining the storage coefficient from multi-step pumping test recovery data is suggested. This solution is essentially based on the method of Banton and Bangoy (1996), which used single-step pumping test recovery data. The suggested solution can be applied to any-step pumping test recovery data. We have demonstrated the applicability of the general solution to single-, double-, and triple-step pumping and/or step-drawdown test data partially described in Lee and Lee (1999). The estimates of storage coefficient as well as transmissivity are well consistent with the values from other methods for pumping phase data.