• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.989-999
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• 2021

The sound of finless porpoises Neophocaena asiaeorientalis was recorded with an acoustic recorder to confirm their emergence in the South Sea of South Korea in February, June, and November 2020. Sea water temperature and salinity were also measured. In addition, a sighting survey was conducted to observe the behavior of the finless porpoises and the marine environment, and the clicks of the finless porpoises were recorded every day. The results showed that they always emerged in the survey area. The finless porpoises mainly foraged, whereas some played or rested. The water temperature range of areas where the finless porpoises emerged was 7.5-23.5℃. Assuming that the number of clicks corresponds to the number of finless porpoises, the finless porpoises emerged the most during spring. The emergence decreased during winter and was the lowest during autumn. The finless porpoises emerged more during the daytime than during the nighttime in all seasons, indicating a temporal difference in the usage of the survey area. This might be due to the movement of prey organisms according to regional characteristics. A long-term survey and research on habitat use and environment is needed to manage and conserve the finless porpoises.

• Steel and Composite Structures
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• v.43 no.2
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• pp.271-278
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• 2022

Buckling is one of the most critical phoneme in the design of steel structures. Lateral torsional buckling (LTB) is particularly significant for slender beams generally subjected to loading in plane. The web distortion effects on LTB are not addressed explicitly in standards for flexural design of steel I-section members. Hence, the present study is focused to predict the influence of the web distortion on the elastic (L_r) limiting lengths given in American Institute of Steel Construction (AISC) code for the lateral torsional buckling (LTB) behavior of steel beams due to no provision in the code for consideration of web distortion. For this aim, the W44x335 beam is adopted in the buckling analysis carried out by the ABAQUS finite element (FE) program since it is one of the most critical sections in terms of lateral torsional buckling (LTB). The strain results at mid-height of the web at mid-span of the beam are taken into account as the monitoring parameters. The web strain results are found to be relatively greater than the yield strain value when L/L_r is equal to 1.0. In other words, the ratio of L/L_r is estimated from the numerical analysis to be about 1.5 when the beam reaches its first yielding at mid-span of the beam at mid-height of the section. Due to the effect of web distortion, the elastic limiting length (L_r) from the numerical analysis is obtained to be considered as greater than the calculated length from the code formulation. It is suggested that the formulations of the limiting length proposed in the code can be corrected considering the influence of the web distortion. This correction can be a modification factor or a shape factor that reduces sectional slenderness for the LTB formulation in the code.

• Journal of the Korean Geotechnical Society
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• v.26 no.4
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• pp.37-45
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• 2010

Salt cementation, a typical naturally-cemented phenomenon, may occur due to water evaporation under the change of climate. Capillary force may influence the distribution of cement in granular soils. This study addresses the effect of capillary force on salt cementation using five different techniques: cone penetration test, electrical conductivity measurement, photographic imaging technique, nondestructive imaging technique, and process monitoring by elastic wave. Glass beads modeling a particulate media was mixed with salt water and then dried in an oven to create the cementation condition. Experimental results show that salt cementation highly concentrates at the top of the small particle size specimens and at the middle or the bottom of the large particle specimens. The predicted capillary heights are similar to the locations of high salt concentration in the cemented specimens. Five suggested methods show that the behavior of salt-cemented granular media heavily depends on the capillary force.

• Journal of the Korean Geotechnical Society
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• v.26 no.11
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• pp.99-110
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• 2010

A fundamental study of the pile-soil systems subjected to negative skin friction in soft soil was conducted using the long-term field measurements. The emphasis was on the identification of the magnitude and distribution of skin frictions ($\alpha$ and $\beta$ coefficients) in bitumen coated and uncoated piles. A skin friction coefficient of instrumented piles is back-calculated by varying degrees of consolidation (U) of surrounding soils. It is shown that the bitumen coated pile is capable of reducing the negative skin friction up to almost 50 to 90 percents. Through comparisons with the existing friction coefficient values ($\alpha$ and $\beta$ coefficients), the calculated coefficients are within the appropriate range, and thus we can suggest basic materials to estimate the realistic pile behavior in the short-term and long-term analysis.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.85-93
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• 2008

For long piles driven in deep clay deposits, it is difficult to estimate the ultimate bearing capacity due to large resistance induced by long embedded depth, and also the load transfer curve due to large residual load induced by negative skin friction, even with the performance of pile load tests. In this research, a hi-directional load test on a PHC pile driven in deep soft deposit was performed in order to evaluate the tip and shaft resistances separately, which are feasible to estimate the ultimate bearing capacity of the pile. Residual load of the pile was determined by continuous monitoring of pile strains after the pile installation. The true resistance and true load-movement curve of the pile were properly estimated by taking account of the residual load. A model far behavior of the shaft resistance vs. movement was also proposed, which includes the effects of residual load based on the experiment. Consequently, it was proved that the residual load should be taken into consideration for correctly analyzing load test results of piles in deep clay deposits.

• Composites Research
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• v.22 no.6
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• pp.45-51
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• 2009

The marginal integrity at the composite resin-tooth interface has been analyzed in real time through acoustic emission (AE) monitoring during the polymerization shrinkage of composite resin subjected to the light exposure. It was found that AE signals were generated by the polymerization shrinkage. Most AE hit events showed a blast type signal having the principal frequency band of 100-200kHz. Bad bonding states were indicated by many hit events in the initial curing period of 1 minute with high contraction rate. The quantity of hit events for the human molar dentin specimen was much less than that for the steel ring specimen but more than that for the PMMA ring specimen. The better the bonding state, the less the AE hit events. The AE characteristics were related with the tensile crack propagation occurring in the adhesive region between the composite resin and the ring substrate as well as the compressive behavior of the ring substrate, which could be used for a nondestructive characterization of the marginal disintegrative fracture of the dental restoration.

• Structural Monitoring and Maintenance
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• v.10 no.1
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• pp.1-23
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• 2023

Various efforts have been made to reduce the weight of concrete slabs while preserving their flexural strength. This will result in reducing deflection and allows the utilization of longer spans. The top zone of the slab requires concrete to create the compression block for flexural strength, and the tension zone needs concrete to join with reinforcing for flexural strength. Also, the top and bottom slab faces must be linked to transmit stresses. Voided slab systems were and are still used to make long-span slab buildings lighter. Eight slab specimens of (1000^*1000 (1000^*1000 mm²) were cast and tested as two-way simply supported slabs in this research. The tested specimens consist of one solid slab and seven voided slabs with the following variables (type of slab solid and voided), thickness of slab (100 and 125 mm), presence of steel fibers (0% and 1%), and the number of GFRP layers). The voids in slabs were made using high-density polystyrene of dimensions (200^*200^*50 mm) with a central hole of dimensions (50^*50^*50 mm) at the ineffective concrete zones to give a reduction in weight by (34% to 38%). The slabs were tested as simply supported slabs under partial uniform loading. The results of specimens subjected to monotonic loading show that the combined strengthening by steel fibers and GFRP sheets of the concrete specimen (V-125-2GF-1%) shows the least deflection, deflection (4.6 mm), good ultimate loading capacity (192 MPa), large stiffness at cracking and at ultimate (57 and 41.74) respectively, more ductility (1.44), and high energy absorption (1344.83 kN.mm); so it's the best specimen that can be used as a voided slab under this type of loading.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.3
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• pp.889-899
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• 2017

Various efforts and technical development for integrating the ICT technologies to the area of special needs education have been continuing. In this paper we have studied and implemented various ICT-based disability evaluation websites and mobile applications for special needs education and also verified their usefulness from the field test at disability schools. The valuer can access the websites and mobile applications for autistic behavior or learning disability evaluation at the any places and by any devices such as laptop, PC, smartphone and tablet PC. And all the evalation results are stored into and managed at the server database and shared with websites and mobile applications to integrate together easily. From the study about disability evaluation and implementation results we have a confidence that they will be useful to support the seamless evaluation and the continuous monitoring services for the disabled at the special needs education fields.

• Journal of Auto-vehicle Safety Association
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• v.15 no.2
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• pp.35-41
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• 2023

On December 19, 2015, as Article 29-3 (Installation of Accident Recording Devices and Provision of Information) of Motor Vehicle Management Act came into force, In Korea, the EDR (Event Data Recorder) reports are often used for the analysis of various traffic accident cases such as multiple collisions, traffic insurance crimes, and sudden unintended acceleration (SUA), and the others. So many investigators have analyzed the driver's behavior and vehicle situation by comparing the time zero in the EDR report to the actual crash time in dash-cam (or CCTV). Time zero (T0) is defined as the reference time for the record interval or time interval when recording an accident in Article 56-2, Enforcement rule of Performance and Standard for Automobile and Automotive parts. Also in the EDR report, time zero (T0) is defined as whichever of the following occurs first; 1. "wake-up" by an air-bag control system, 2. Continuously running algorithms (by monitoring of longitudinal or lateral delta-V), 3. Deployment of a non-reversible deployment restraint. We have already proposed the "Flowchart & Checklist" to adopt the EDR report for traffic accident investigation and the necessity of specialized institutions or courses to systematically educate or analyze the EDR data. Therefore, in this paper, we report to traffic accident investigators notable points and analysis methods based on some real-world traffic accidents that can be misjudged in specifying time zero (T0).

• Analytical Science and Technology
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• v.21 no.5
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• pp.403-411
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• 2008

Dimethyldibutyltetradecylmalonamide (DMDBTDMA) extractant was used in a solvent extraction process for a radioactive liquid waste treatment. For the study of radiolysis phenomena, DMDBTDMA was synthesized and the degradation compounds (n-methylbutylamine, tetradecane, 1-tetradecanol) in the DMDBTDMA extractant, irradiated with $^{60}Co$ gamma ray, were identified and determined as radiolysis products by a Fourier transform infrared (FT-IR), gas chromatograph/mass spectrometer (GC/MS) analysis and GC/MS with selected ion monitoring (SIM) mode. Retention behavior of n-methylbutylamine, n-dodecane, tetradecane and 1-tetradecanol in the total ion chromatogram with the standard materials and n-dodecane as the internal standard (ISTD) were 2.35 min., 8.83 min., 10.68 min. and 12.75 min., respectively. In the case of tetradecane, there was a linear relationship between the concentration of the tetradecane and the absorbed dose of the ${\gamma}$-ray irradiated DMDBTDMA.