• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.353-364
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• 2011

In a previous research performed by the authors, the allowable compressive stress coefficient (K) in pretensioned members with rectangular section at transfer was proposed based on strength design theory. In this study, a subsequent research of an enormous analysis was performed to determine the K factor for Tee and inverted Tee section members, considering the effect of section height (h), section type, amount of tendons ($A_{ps}$), and eccentricity ratio (e/h). Based on the analysis results, the allowable compressive stress coefficients (K) for Tee and inverted Tee section members at transfer were derived, which limit the maximum allowable stresses as 80% and 70% of the compressive strengths at the time of release for Tee section and inverted Tee section, respectively. And these were larger than the allowable stresses specified in domestic and other international codes. In order to verify the proposed equations, they were compared to the test results available in literature and other codes, which showed that the allowable stresses in domestic and international codes are unconservative for the cases with low eccentricity ratios while conservative for those with high eccentricity ratios. The proposed equations, however, estimate the allowable stresses of the Tee and inverted Tee section members reasonably close to test results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.119-126
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• 2005

The objective of this paper is to evaluate the flexural tensile strength of unreinforced concrete masonry wall to ensure the structural safety in out-of-plane behaviors under the wind or earthquake loads. Flexural tensile strength of unreinforced concrete masonry wall has been obtained from the full scale tests of total 327 specimens and the statistical analysis are performed for each of the cases. The flexural tensile strength derived from experiments is classified as 13 groups according to masorny units, mortar ingredients, and the direction of tensile stresses and the mean tensile strength and the variable coefficient are obtained for each case. The uniform and concentrated transverse loads have been applied over the face of the wall specimens. The ultimate mean flexural tensile strengths are distributed from 1,564 kPa to 363 kPa according to masonry units, mortar ingredients, and other factors. The allowable flexural tension stress criteria will be established based on the mean flexural tensile strengths in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.40-48
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• 2016

To observe the rail-slab interaction in continuous welded railway(CWR) bridge when earthquake occurs, additional axial rail stresses and relative longitudinal displacements between rail and bridge deck were calculated with input of various load combinations and 3 different types of seismic loads to an analytical model. As results of analysis, it can be found that standard response spectrum proposed by Korea Rail(KR) network authority for earthquake design showed less additional axial rail stresses than allowable levels, but greater relative longitudinal displacement between rail and bridge deck, which means that adjustment of relative longitudinal displacement within a standard level is much more difficult than axial train stress. Additionally, if a large-scaled earthquake as occurred at Kobe, Japan comes up, then both of additional axial rail stress and relative displacement in rail-bridge deck may exceed allowable levels, which indicates to make proper design guides against sudden earthquake occurrence.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.71-84
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• 2003

The metallic shell of soil-steel structures are so weak in bending moment that it should sustain the applied load by the interaction of the backfill soil around the structures. The shell can be subjected to excessive bending moment during side backfilling or under live-load when the soil cover is less than the minimum value. The current design code specifies the allowable deformation and Duncan(1979) and McGrath et al.(2001) suggested the strength analysis methods to limit the moments by the plastic capacity of the shell. However, the allowable deformation is an empirically determined value and the strength analysis methods are based on the results of FE analysis, hence the experimental verification is necessary. In this study, the full-scale tests were conducted on the high-profile arch to investigate its behaviors during backfilling and under static live-loads. Based on the measurements, the allowable deformation of the tested structure could be estimated to be 1.45% of rise, which is smaller than the specified allowable deformation. The comparison between the measurements and the results of two strength analyses indicate that Duncan underestimates the earth-load moment and overestimates the live-load moment, while McGrath et al. predicts both values close to the actual values. However, as the predicted factors of safeties using two methods coincide with the actual factor of safety, it can be concluded that both methods can predict the structural stability under live-loads adequately when the cover is less than the minimum.

• Journal of Radiation Protection and Research
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• v.31 no.3
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• pp.141-148
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• 2006

Surveys of radioactive contamination were performed for imported foodstuffs in 2003. The following samples among imported foodstuffs were selected from markets and Korea Food and Drug Administration(KFDA); the imported samples from country associated with the Chernobyl nuclear accident, the samples produced around the nuclear power plants or nuclear tests, the foodstuffs reported as radioacitive contamination materials in foreign country. After pretreatments such as drying and homogenization, samples were analyzed. The $^{137}Cs$ radionuclide was only measured among the regulation radionuclides($^{137}Cs,\;^{134}Cs,\;^{131}I$) of food code. All foodstuffs except Inonotus Obliquus(Chaga mushooms) are less than 17.0 Bq/kg or below the minimum detectable activity(MDA). The activity concentrations of Chaga mushrooms from Russia ranged up to 131.25 Bq/ltg which is almost 35 % of the maximum permitted level of food code. The fraction of imported foodstuffs having meaningful radioactivity is small, however, the radioactive contamination survey of imported foodstuffs is still needed.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.115-121
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• 2012

Purpose: The process of the proton treatment is done by comparing the DRR and DIPS anatomic structure to find the correction factor and use the PPS to use this factor in the treatment. For the accuracy of the patient set up, the PPS uses a 6 axis system to move. Therefore, there needs to be an evaluation for the accuracy between the PPS moving materialization and DIPS correction factor. In order to do this, we will use a self made PPS QA Phantom to measure the accuracy of the PPS. Materials and Methods: We set up a PPS QA Phantom at the center to which a lead marker is attached, which will act instead of the patient anatomic structure. We will use random values to create the 6 axis motions and move the PPS QA Phantom. Then we attain a DIPS image and compare with the DRR image in order to evaluate the accuracy of the correction factor. Results: The average correction factor, after moving the PPS QA Phantom's X, Y, Z axis coordinates together from 1~5 cm, 1 cm at a time, and coming back to the center, are 0.04 cm, 0.026 cm, 0.022 cm, $0.22^{\circ}$, $0.24^{\circ}$, $0^{\circ}$ on the PPS 6 axis. The average correction rate when moving the 6way movement coordinates all from 1 to 2 were 0.06 cm, 0.01 cm, 0.02 cm, $0.1^{\circ}$, $0.3^{\circ}$, $0^{\circ}$ when moved 1 and 0.02 cm, 0.04 cm, 0.01 cm, $0.3^{\circ}$, $0.5^{\circ}$, $0^{\circ}$ when moved 2. Conclusion: After evaluating the correction rates when they come back to the center, we could tell that the Lateral, Longitudinal, Vertical were all in the acceptable scope of 0.5 cm and Rotation, Pitch, Roll were all in the acceptable scope of $1^{\circ}$. Still, for a more accurate proton therapy treatment, we must try to further enhance the image of the DIPS matching system, and exercise regular QA on the equipment to reduce the current rate of mechanical errors.

• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.69-89
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• 2019

Design chart solution and table solution were proposed by Choi et al. (2019a), which conducted a parametric numerical study for the bored PHC piles socketed into weathered rocks through sandy soil layers. Based on the Choi et al. (2019a), the new prediction formulae for mobilized capacity components such as total capacity, total skin friction and skin friction of sand at the settlement of 5% pile diameter were proposed in this study. The proposed prediction formulae (EQ-G1) considers pile diameter, relative embedment length and ${\bar{N}}$ (i.e, corrected N) value and their verification results are as follows. The SRF calculated from the new proposed design method was 71~94%, which are greatly improved compared with results by the existing design method. The design efficiency of bearing capacity was in the range of reasonable design except 4 cases, and the design efficiency of the PHC pile was evaluated as 85%. Therefore, it is possible that allowable compressive load (P_all) of PHC pile can be utilized in the resonable design by means of the new proposed method using EQ-G1 equations. And the other new proposed equations of EQ-G2-3 can be utilized approximately in calculation of axial compressive bearing capacity components for prebored PHC pile.

• Journal of the Korea Society for Simulation
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• v.16 no.4
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• pp.57-65
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• 2007

In many sensor network applications, sensor nodes are deployed in open environments, and hence are vulnerable to physical attacks, potentially compromising the node's cryptographic keys. False sensing report can be injected through compromised nodes, which can lead to not only false alarms but also the depletion of limited energy resource in battery powered networks. Fan Ye et al. proposed that statistical en-route filtering scheme(SEF) can do verify the false report during the forwarding process. In this scheme, the choice of a partition value represents a trade off between resilience and energy where the partition value is the total number of partitions which global key pool is divided. If every partition are compromised by an adversary, SEF disables the filtering capability. Also, when an adversary has compromised a very small portion of keys in every partition, the remaining uncompromised keys which take a large portion of the total cannot be used to filter false reports. We propose a fuzzy-based adaptive partitioning method in which a global key pool is adaptively divided into multiple partitions by a fuzzy rule-based system. The fuzzy logic determines a partition value by considering the number of compromised partitions, the energy and density of all nodes. The fuzzy based partition value can conserve energy, while it provides sufficient resilience.

• Journal of Korean Society of Transportation
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• v.20 no.2
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• pp.17-26
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• 2002

Driver's psychophysiological load is one of the key measures for evaluating the safety of the highway. The purpose of this study is to propose and to test the methodology of evaluating the length limit of tangent section using driver's psychophysiological load. Driver's psychophysiological data is represented by the data acquire by frontal and occipital lobe. In order to compare the differences between tangent segments and the orders, real road driving experiments were performed. We collected psychophysiological data during the operation of vehicles. The experimental data were analyzed using FFT (Fast Fourier Transform) and relative power spectrum tools. These routine produces the beta value which is a major factor in consideration of driver's condition. The results in this study are summarized as follows: (1) A new methodology of evaluating the length limit in tangent section of highway using driver's psychophysiological load was proposed. (2) It was observed that driver's work load at tangent section was three times lower than that at the other section types. The beta value at tangent section is 2.219, while that at general section is 0.821. (3) It was observed that the driver's work load was significantly dropped to 0.428 after the continuous driving of 4.2km tangent section. (4) Based on the experimental subjects(from 27 Years to 31). we suggest that 30 times of design speed(3.0 km) could be acceptable as the length limit of tangent section in highway rather than the Previous limit which is 20 times of design speed(2.0km).

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.1118-1123
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• 2009

Ten hospitals from the Gwangju area were used to examine shallow dose to eyes and thyroid from panoramagraphy. Thermoluminescent dosimeter (TLD) and Photoluminescent dosimeter (PLD) were used as measurement devices at each hospital. ICRP 60 and ICRP 73 set standards for acceptability for eyes at 15mSv and thyroid at 1mSv per year. Left eye measures with TLD and PLD resulted in 0.19mSv and 0.24mSv respectively. Right eye measures with TLD and PLD resulted in 0.23mSv and 0.25mSv respectively. Thyroid measures with TLD and PLD resulted in 0.08mSv and 0.25mSv respectively with both measures not exceeding standards for acceptance. There was a significant difference in comparing the left eye and thyroid for TLD and PLD (p<0.01). There was no significant difference with the right eye (p>0.05). The absorbed dose measurements for eyes and thyroid using TLD and PLD in regards to panorama devices at each hospital were within the ICRP 60 recommendations; however, with the possibility of stochastic effect, all dose levels were taken into consideration.