• Journal of Astronomy and Space Sciences
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• v.33 no.4
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• pp.335-344
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• 2016

Scientific CubeSat with Instruments for Global Magnetic Fields and Radiations (SIGMA) is a 3-U size CubeSat that will be operated in low earth orbit (LEO). The SIGMA communication system uses a very high frequency (VHF) band for uplink and an ultra high frequency (UHF) band for downlink. Both frequencies belong to an amateur band. The ground station that communicates with SIGMA is located at Kyung Hee Astronomical Observatory (KHAO). For reliable communication, we carried out a laboratory (LAB) test and far-field tests between the CubeSat and a ground station. In the field test, we considered test parameters such as attenuation, antenna deployment, CubeSat body attitude, and Doppler frequency shift in transmitting commands and receiving data. In this paper, we present a communication performance test of SIGMA, a link budget analysis, and a field test process. We also compare the link budget with the field test results of transmitting commands and receiving data.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.836-842
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• 2011

The lateral stability of bridge foundations against train moving load, emergency stopping load, earthquakes, and so on is very important for a railway bridge foundation. A borehole test is much more accurate than laboratory tests since it is possible to minimize the disturbance of ground conditions on the test site. The representative borehole test methods are Dilatometer, Pressuremeter and Lateral Load Tester, which usually provide force-resistance characteristics in elastic range. In order to estimate P-y curves using those methods, the non-linear characteristics of soil which is one of the most important characteristics of the soil cannot be obtained. Therefore, P-y curves are estimated usually using elastic modulus ($E_O$, $E_R$) of lateral pressure-deformation ratio obtained within the range of elastic behavior. Even though the pile foundation is designed using borehole tests in field to increase design accuracy, it is necessary to use a higher safety factor to improve the reliability of the design. A Large Displacement Borehole Testmeter(LDBT) is developed to measure nonlinear characteristics of the soil in this study. P-y curves can be directly achieved from the developed equipment. Comparisons between measured P-y curves the LDBT developed equipment, theoretical methods based on geotechnical investigations, and back-calculated P-y curves from field tests are shown in this paper. The research result shows that the measured P-y curves using LDBT can be properly matched with back-calculated P-y curves from filed tests by applying scale effects for sand and clay, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.423-426
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• 2001

In this paper a large scale direct tension test of plain concrete is represented. Two independently controlled actuators were used to ensure a homogeneous tensile field and to avoid secondary flexural stresses. Fracture energies evaluated by a classical prediction equation and this test are compared. The result indicated that the classical prediction equation is not adequate to predict the fracture energy of large sized specimens. From this test, it was determined that the fracture energy obtained from large scale direct tension tests is significantly higher than the one obtained in wedge splitting tests on laboratory sized specimens. But the tensile strength was about half the value determined from splitting tensile strength test with cylindrical specimens.

• Korean Journal of Veterinary Service
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• v.41 no.2
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• pp.71-78
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• 2018

Bovine tuberculosis (bTB) is a wide-spread zoonotic disease in cattle, which is casued by Mycobacterium bovis that is a part of Mycobacterium tuberculosis complex (MTC). This study describes a field trial conducted in 42 herds with the history of prevalence bovine tuberculosis. Two cell-mediated immunity tests, the gamma-interferon (${\gamma}-IFN$) assay and the single intradermal tuberculin test (SIT) were applied for the diagnosis of bovine tuberculosis in 5,289 animals. The ${\gamma}-IFN$ assay presented 144 (2.7%) head of cattle with the positive result, and 112 (2.1%) head of cattle were shown to be bTB-positive by the SIT. The positive concordance was 45.5%, and the negative concordance was 98.2%. The ${\gamma}-IFN$ assay showed more positive results in younger cattle, especially between 12 and 23 months of age. It is shown that the strategic combination of both cell-mediated immunity test methods is more efficient for the detection of bTB to reduce the number of false positive individuals which are being slaughtered.

• Computers and Concrete
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• v.17 no.2
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• pp.241-253
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• 2016

Depending on the researcher, the effect of prestressing on the natural frequency of a PSC (prestressed concrete) structure appear to have been interpreted differently. Most laboratory tests on PSC beams available showed that the natural frequency is increased appreciably by prestressing. On the other hand, some other references based on field experience argued that the dynamic response of a PSC structure does not change regardless of the prestressing applied. Therefore, the deduced conclusions are inconsistent. Because an experiment with and without prestressing is a difficult task on a full size PSC bridge, the change in natural frequency of a PSC bridge due to prestressing may not be examined through field measurements. The study examined analytically the effects of prestressing on the natural frequency of PSC bridges. A finite element program for an undamped dynamic motion of a beam-tendon system was developed with additional geometric stiffness. The analytical results confirm that a key parameter in changing the natural frequency due to prestressing is the relative ratio of prestressing to the total weight of the structure rather than the prestressing itself.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.47-59
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• 2023

In this research, laboratory tests were conducted on clayey sand (SC) to analyze its physical properties, compaction/permeability characteristics, and stress-strain behavior. The main objective was to determine the transitional fines content at which the mechanical properties of sand transition to those of clay, resulting in a change in the geotechnical behavior of the material. Additionally, to assess the practical applicability of SC soil, field data from a soft ground improvement site with significant settlement issues were collected. The settlement characteristics derived from laboratory tests and numerical simulations were then compared and analyzed in relation to the actual settlement data obtained from the field, aiming to evaluate the suitability of the SC soil as a compaction target layer. The laboratory tests and compaction analysis showed that the SC soil exhibited a distinct change in mechanical properties, shifting from sandy behavior to clayey behavior when the fines content exceeded 25%. This transition in mechanical behavior was found to be closely correlated with the content of clay particles within the material. Through numerical simulations of the soft ground site, it was verified that the use of clayey sand with a fines content exceeding the transitional level as a compaction target layer resulted in settlements that closely aligned with the measured settlements, with an average agreement of 91.2%. Based on these findings, it is deemed advisable to incorporate clayey sand with a fines content exceeding the transitional level as part of the compaction target layer in the design of soft ground improvements.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.67-79
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• 2005

The field plate load test has a good potential for determining modulus since it measures both plate pressure and settlement. Conventionally the modulus has been assumed to be a constant secant value defined from the settlement of the plate at a given load intensity. A constant modulus (modulus of subgrade reaction, k), however, may not be a representative value of subgrade soil under working load. Field strain(o. stress)-dependent modulus characteristics of subgrade soils, at relatively low to intermediate strains, are important in the pavement design. In this study, the field strain dependent moduli of subgrade soils were obtained using cyclic plate load test. Testing procedure and data reduction method are proposed. The field crosshole and laboratory resonant column tests were also performed to determine field nonlinear modulus at $0.001\%\;to\;0.1\%$ strains, and the modulus values and nonlinear trends are compared to those obtained by cyclic plate load tests. Both modulus values match relatively well when the different state of stress between two tests was considered, and the applicability of field cyclic plate load test for determining nonlinear modulus values of subgrade soils is verified.

• Geomechanics and Engineering
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• v.23 no.1
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• pp.61-69
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• 2020

The uniaxial compressive strength (UCS) of rock is a basic parameter in underground engineering design. The disadvantages of this commonly employed laboratory testing method are untimely testing, difficulty in performing core testing of broken rock mass and long and complicated onsite testing processes. Therefore, the development of a fast and simple in situ rock UCS testing method for field use is urgent. In this study, a multi-function digital rock drilling and testing system and a digital core bit dedicated to the system are independently developed and employed in digital drilling tests on rock specimens with different strengths. The energy analysis is performed during rock cutting to estimate the energy consumed by the drill bit to remove a unit volume of rock. Two quantitative relationship models of energy analysis-based core drilling parameters (ECD) and rock UCS (ECD-UCS models) are established in this manuscript by the methods of regression analysis and support vector machine (SVM). The predictive abilities of the two models are comparatively analysed. The results show that the mean value of relative difference between the predicted rock UCS values and the UCS values measured by the laboratory uniaxial compression test in the prediction set are 3.76 MPa and 4.30 MPa, respectively, and the standard deviations are 2.08 MPa and 4.14 MPa, respectively. The regression analysis-based ECD-UCS model has a more stable predictive ability. The energy analysis-based rock drilling method for the prediction of UCS is proposed. This method realized the quick and convenient in situ test of rock UCS.

• Tunnel and Underground Space
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• v.3 no.2
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• pp.132-141
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• 1993

Laboratory and field tests were performed to find out the effectiveness of ground improvement by grouting for an urban subway tunnel that was excavated in weak rock by the NATM. Field measurements were carried out to monitor the behavior of rock mass around the tunnel and to ensure the validity of the current design of the distance form the measuring points to the tunnel face. The final converged displacement and the peroid were predicted using the gamma function. It was found that the ground improvement in terms of reduced permeability and increased stength in the self-supportability of the excavation face enabled the NATM applied in poor gorund. As the result of applying the gamma function to the predicting of displacement, the final displacement including the preceding one and the converged period could be approximately predicted at the early excavation stage.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.743-749
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• 2009

In this study, the field test for suction drain method which does not require a surcharge load and a sealing sheet was performed at west seashore's site constructed by the dredged and reclaimed clay. The improvements of soft ground by suction drain method was analyzed by the results of real-time field measurement, SPT(Standard Penetration Test) and laboratory tests. The results indicated that the soft ground improvement is effective the vertical drain method used with vacuum pressure rather than surcharge load with considering settlements, dissipation of pore water pressure and shear strength.