• Journal of the Korean GEO-environmental Society
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• v.14 no.1
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• pp.5-13
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• 2013

Soils around a pile are highly constrained when the vertical load is applied to the pile. However, the conventional direct shear test cannot evaluate the shear strength of the soils under the normal confinement condition. The goal of this study is to evaluate the shear behaviors according to the normal displacement confinement condition including free normal displacement (FND) and constrained normal displacement (CND) during direct shearing. Jumunjin sands were prepared at the different relative densities and loaded at the different normal stresses. The specimens were sheared according to the normal confinement conditions. Experimental results show that shear strengths obtained by the CND tests are higher than those obtained by the FND tests. In addition, for the constrained normal displacement condition, the increment of shear strength increases with the increase of relative density, while the increment of shear strength decreases with the initial normal stress. This study suggests that the effect of confinement condition on the shear strength should be considered when the stability of constrained soils is analyzed.

• The Journal of Korean Physical Therapy
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• v.23 no.1
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• pp.53-58
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• 2011

Purpose: The purpose of this study was to determine the effect of direct functional magnetic stimulation (FMS) of affected spinal cord on motor recovery following spinal cord injury in rats. Methods: After a contusion injury at the spinal level T9 using an NYU Impactor, functional magnetic stimulation was delivered by a magnetic stimulator through a round prototype coil (7 cm in diameter). Stimulation parameters were set as follows: repetition rate = 50 Hz (stimulus intensity 100% = 0.18 T), stimulation time = 20 min. Functional magnetic stimulation was administered twice a day, 5 days per week for 8 weeks starting 4 days after spinal cord injury. Functional magnetic stimulationwas delivered directly to the affected spinal cord. Outcomes of locomotor performance were assessed by the Basso Beattie Bresnahan (BBB) locomotor rating scale and by an inclined plane test weekly for 8 weeks. Results: In the BBB test, hindlimb motor function in the Functional magnetic stimulation group improved significantly more compared to the control group at 3, 4, 6, 7, and 8 weeks (p<0.05). In the inclined plane test, the angle of the plane in the functional magnetic stimulation group increased significantly more compared to the control group at 4, 5, 7, and 8 weeks (p<0.05). Conclusion: Our results demonstrate that direct Functional magnetic stimulation of the lesional site may have beneficial effects on motor improvement after spinal cord injury.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.9
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• pp.531-538
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• 2005

This paper proposes an expert system which is able to enhance the accuracy and productivity by determining the test strategy based on heuristic rules for test of the hybrid electronic circuit board producted massively in production line. The test heuristic rules are obtained from test system designer, test experts and experimental results. The guarding method separating the tested device with circumference circuit of the device is adopted to enhance the accuracy of measurements in the test of analog devices. This guarding method can reduce the error occurring due to the voltage drop in both the signal input line and the measuring line by utilizing heuristic rules considering the device impedance and the parallel impedance. Also, PSA(Parallel Signature Analysis) technique Is applied for test of the digital devices and circuits. In the PSA technique, the real-time test of the high integrated device is possible by minimizing the test time forcing n bit output stream from the tested device to LFSR continuously. It is implemented in Visual C++ computer language for the purpose of the implementation of the inference engine using the dynamic memory allocation technique, the interface with the electronic circuit database and the hardware direct control. Finally, the effectiveness of the builded expert system is proved by simulating the several faults occurring in the mounting process the electronic devices to the surface of PCB for a typical hybrid electronic board and by identifying the results.

• Membrane Journal
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• v.32 no.4
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• pp.253-263
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• 2022

This study suggests a guideline for designing unit process of wastewater reuse in terms of a maintenance of the process based on critical parameters to draw a high quality performance of RO unit. Defining the parameters was done by applying membrane integrity test (MIT) in pretreatment process utilizing lab-scale MF. SDI is utilized for judging whether permeate is suitable to RO unit. However, result said TOC concentration matching with particle count analysis is better for judging the permeate condition. When membrane test pressure (P_test) was measured to derive log removal value in PDT, virgin state of membrane fiber was used to measure dynamic contact angle utilizing surface tension of the membrane fiber. Actually, foulant affects to the state of membrane surface, and it decreases the P_test value along with time elapsed. Consequently, LRV_DIT is also affected by P_test value. Thus, sensitivity of direct integrity test descends with result of P_test value change, so P_test value should be considered not the virgin state of the membrane but its current state. Overall, this study focuses on defining design parameters suitable to MF pretreatment for RO process in wastewater reuse by assessing its impact. Therefore, utilities can acknowledge that the membrane surface condition must be considered when users conduct the direct integrity test so that P_test and other relative parameter used to calculate LRV_DIT are adequately measured.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.5-12
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• 2012

Geotextile tube method is the latest application process to construct a variety of civil structures such as river and coastal structures by using geotextile which is a high polymer synthetic fiber. In this paper, laboratory tests and field tests were conducted in order to identify the behavior, stability and application possibility of geotextile tube which prevents the erosion of coastal sand. As a result of large-scale direct shear test, which is one of laboratory tests, the increase in friction angle was shown as the relative density increased, and friction angle of sand/geotextile was larger than that of sand/sand. As a result of field test, the behavior and stability during construction and after construction were identified through measurement, and the effect of preventing erosion was confirmed.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.285-298
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• 2003

Shear properies of geosynthetic/geosynthetic and geosynthetic/soil interfaces which are widely met in landfill sites were evaluated from the inclined board tests. The inclined board testing apparatus is known to reproduce the shear behavior on the low normal stress most accurately. In this study, the friction angle of each interface was estimated and the tensile force mobilized at the geosynthetic was measured as well. The test results showed that the friction angle of each interface and the tensile force of the geosynthetics depended on the amount of normal stress, the type of the geosynthetics used, and the combinations of geosynthetics and soils. In addition, the sand/geotextile/geomembrane interface system was simulated in this study, and it was observed that the tensile force developed at the geomembrane decreased due to the protection effect of the geotextile located above the geomembrane. The test results of this research was compared with those of direct shear tests published, too. Finally, by comparing the measured tensile force of the geosynthetics when the initial displacement of the box occurs, when the slope is called as the critical slope, with suggested analytic solution, the accuracy of analytic solution and the applicability to design were identified.

• International Journal of Highway Engineering
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• v.17 no.1
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• pp.43-49
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• 2015

PURPOSES : The objective of this study is to develop new pothole repair materials using polyurethane-modified asphalt binder, and to evaluate them relative to current pothole repair materials in order to improve the performance of repaired asphalt pavement. METHODS : In the laboratory, polyurethane-modified asphalt binder is developed, and then asphalt binder is added to produce pothole repair materials. In order to evaluate the properties of this new pothole repair material, both an indirect tension strength test and a direct tension strength test are performed to measure the material strength and bond strength, respectively. Additionally, the basic material properties are evaluated using the asphalt cold mix manual. The strength characteristics based on curing times are evaluated using a total of 7 types of materials (3 types of current materials, 2 types of new materials, and 2 types of moisture conditioned new materials). The indirect tension strength tests are conducted at 1, 2, 4, 8, 16, and 32 days of curing time. The bond strength between current HMA(Hot Mix Asphalt) and the new materials is evaluated by the direct tension strength test. RESULTS AND CONCLUSIONS : Overall, the new materials show better properties than current materials. Based on the test results, the new materials demonstrate less susceptibility to moisture, faster curing times, and an improved bond strength between HMA and the new materials. Therefore, the use of the new materials reported in this study may lead to enhanced performance of repairs made to asphalt pavement potholes.

• KCI Concrete Journal
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• v.12 no.2
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• pp.85-93
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• 2000

Potentially significant mechanical improvements in tension can be achieved by the incorporation of randomly distributed, short discrete fibers in concrete. The improvements due to the incorporation fibers significantly influence the composite stress - strain ($\sigma$-$\varepsilon$) characteristics. In general incorporating fibers in a plain concrete has relatively small effect on its precracking behavior. It, however, alters its post-cracking behavior quite significantly, resulting in greatly improved ductility, crack controls, and energy absorption capacity (or toughness). Therefore, a thorough understanding the complete tensile stress - strain ($\sigma$-$\varepsilon$) response of fiber reinforced concrete is necessary for proper analysis while using structural components made with fiber reinforced concrete. Direct tensile stress applied to a specimen is in principle the simplest configuration for determining the tensile response of concrete. However, problems associated with testing brittle materials in tension include (i) the problem related to gripping of the specimen and (ii) the problem of ensuring centric loading. Routinely, indirect tension tests for plain concrete, flexural and split-cylinder tests, have been used as simpler alternatives to direct uniaxial tension test. They are assumed to suitable for fiber reinforced concrete since typically such composites comprise 98% by volume of plain concrete. Clearly since the post-cracking characteristics are significantly influenced by the reinforcing parameters and interface characteristics, it would be fundamentally incorrect to use indirect tensile tests for determining the tensile properties of fiber reinforced concrete. The present investigation represents a systematic look at the failure and toughening mechanisms and macroscopic stress - strain ($\sigma$-$\varepsilon$) characteristics of fiber reinforced concrete in the uniaxial tension test. Results from an experimental parametric study involving used fiber quantity, type, and mechanical properties in the uniaxial tension test are presented and discussed.

• International Journal of Highway Engineering
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• v.17 no.5
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• pp.25-31
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• 2015

PURPOSES: The objective of this study is to analyze the relationship between the FWD back-calculated modulus and dynamic modulus of asphalt layers for existing asphalt pavements. METHODS: To evaluate the dynamic modulus of the asphalt mixture in the existing and new asphalt layers, the uniaxial direct tension test was conducted on small asphalt specimens obtained from the existing asphalt-covered pavements. A dynamic modulus master curve was estimated by using the uniaxial direct tension test for each asphalt layer. The falling weight deflectometer (FWD) testing was conducted on the test sections, and the modulus values of pavement layers were back-calculated using the genetic algorithm and the finite element method based back-calculation program. The relationship between measured and back-calculated asphalt layer moduli was examined in this study. The normalized dynamic modulus was adopted to predict the stiffness characteristics of asphalt layers more accurately. RESULTS: From this study, we can conclude that there is no close relationship between dynamic modulus of first layer and back-calculated asphalt modulus. The dynamic moduli of second and third asphalt layers have some relation with asphalt stiffness. Test results also showed that the normalized dynamic modulus of the asphalt mixture is closely related to the FWD back-calculated modulus with 0.73 of R square value. CONCLUSIONS: The back-calculated modulus of asphalt layer can be used as an indicator of the stiffness characteristics of asphalt layers in the asphalt-covered pavements.

• Journal of the Korean Home Economics Association
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• v.45 no.2
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• pp.1-22
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• 2007

The purpose of this study was to investigate the effect of mother's characteristics, mediated by disciplinary methods and young children's emotional regulation, on young children's aggression. Subjects of this study consisted of 342 young children drawn from seven preschools in Cheongju city. The pilot study was used to examine the applicability of survey instrument. Data were analyzed by the method of frequency, percentage, Cronbach' ${\alpha}$, factor analysis, T-test. F-test, and Duncan post-hoc test using SPSSWIN program. The test of model was done with analysis of correlational matrix in LISREL VII package using a maximum likehood estimation. The results of this research were as follows: First, there were statistically significant differences in mother's characteristics consisting of neurosis symptom and extroversions, disciplinary methods consisting of coercive-punishment and indifferent-irresponsibility, young children's emotional regulation, and young children's aggression consisting of relation and overtness according to some socio-demographic variables. Girls had the higher emotional regulation than boys. Second, the direct effects of disciplinary methods and emotional regulation on boys' aggression were different in between relational and overt aggression. Third, the variables predicting boys' emotional regulation directly were the same in both relational and overt aggression. Forth, the direct effect of mother's characteristics on disciplinary methods was different in between coercive-punishment and indifferent-irresponsibility. Fifth, the indirect effects of mother's characteristics, mediated by disciplinary methods and young children's emotional regulation, on young children's aggression were partly supported in this study. Sixth, the theoretical model of the impact of mother's characteristics, disciplinary methods, and young children's emotional regulation on young children's aggression was different according to gender.