• Journal of the Korean Geotechnical Society
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• v.26 no.4
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• pp.15-26
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• 2010

To determine the frost heave suppressing mechanism of soil mixed with tire powder, we conducted three kinds of laboratory experiments: measurement of unfrozen water, evaluation of thermal conductivity, and a frost heave. In this research, we focused on changes in the coefficient of permeability of the mixed soil, and first found that of the unsaturated soil. Next, in the case of the presence of ice, we took the ice-impeding factor into consideration to derive the coefficient of permeability of the frozen fringe from the area ratio of the soil and tire powder in mixed soil. The results show a positive correlation between the water intake rate and the coefficient of permeability. Moreover, we found that the frost heave decreased thanks to a reduction in the permeability and a fall in the unfrozen water content of the soil mixed with tire powder. We also calculated the weight of the water content of the soil and tire powder void quantitatively using the result of the volumetric ratio of mixed soil.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.77-84
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• 2007

One of the most sensitive design specifications to be considered is infiltration and external pore-water pressures on underground structure construction. Development of pore-water pressure may accelerate leakage and consequently cause deterioration of the lining. In this paper, the development of pore-water pressure due to malfunctioning of drainage system and its potential effect on the linings are investigated using physical model tests. The deterioration procedure was simulated by controlling both permeability and flow rate. Development of pore-water pressure was monitored on the lining using pore pressure measurement cells. Test results identified the mechanism of pore-water pressure development on the tunnel lining. In addition, they showed that controlling flow rate is more effective method fur simulating deterioration procedure than permeability control. The laboratory model tests were reproduced using coupled numerical method, and showed that the effect of deterioration of drainage system can be theoretically expected using coupled numerical modeling method.

• Composites Research
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• v.22 no.6
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• pp.1-6
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• 2009

This paper presents an experimental study on the piezoresistive behavior of nanocomposite strain sensors subjected to various loading modes and their capability to detect structural deformations and damages. The electrically conductive nanocomposites were fabricated in the form of a film using various types of thermoplastic polymers and multi-walled carbon nanotubes (MWNTs) at various loadings. In this study, the nanocomposite strain sensors were bonded to a substrate and subjected to tension, flexure, or compression. In tension and flexure, the resistivity change showed dependence on measurement direction, indicating that the sensors can be used for multi-directional strain sensing. In addition, the sensors exhibited a decreasing behavior in resistivity as the compressive load was applied, suggesting that they can be used for pressure sensing. This study demonstrates that the nanocomposite strain sensors can provide a pathway to affordable, effective, and versatile structural health monitoring.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.181-188
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• 2023

In a typical living space, windows are directly exposed to the external noise environment. The best way to reduce outside noise is to block it from the outside, not the inside. Exterior blinds for blocking sunlight are commercialized in various ways. However, it has not yet been actively utilized in Korea. In the previous study, an experiment was conducted in an accredited laboratory to verify the sound insulation performance of an external motorized blind manufactured for shading. And it was verified that there is a sound insulation performance of 6 dBA compared to the reduction performance of a general window. In this study, we tried to confirm the reduction performance by applying the sound insulation performance of external electric blinds to windows in actual living spaces. In addition, an improvement plan was sought to increase the effective noise reduction performance. As a result of the measurement, the reduction performance of the external motorized blind itself was insufficient at the level of 1 dBA to 3 dBA. However, additional reduction performance of the 2 dBA level was confirmed by filling the gap between the blind slits.

• Smart Structures and Systems
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• v.31 no.1
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• pp.57-68
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• 2023

Bridge hangers, such as those in suspension and cable-stayed bridges, suffer from cumulative fatigue damage caused by dynamic loads (e.g., cyclic traffic and wind loads) in their service condition. Thus, the identification of damage to hangers is important in preserving the service life of the bridge structure. This study develops a new method for condition assessment of bridge hangers. The tension force of the bridge and the damages in the element level can be identified using the Bayesian optimization method. To improve the number of observed data, the additional mass method is combined the Bayesian optimization method. Numerical studies are presented to verify the accuracy and efficiency of the proposed method. The influence of different acquisition functions, which include expected improvement (EI), probability-of-improvement (PI), lower confidence bound (LCB), and expected improvement per second (EIPC), on the identification of damage to the bridge hanger is studied. Results show that the errors identified by the EI acquisition function are smaller than those identified by the other acquisition functions. The identification of the damage to the bridge hanger with various types of boundary conditions and different levels of measurement noise are also studied. Results show that both the severity of the damage and the tension force can be identified via the proposed method, thereby verifying the robustness of the proposed method. Compared to the genetic algorithm (GA), particle swarm optimization (PSO), and nonlinear least-square method (NLS), the Bayesian optimization (BO) performs best in identifying the structural damage and tension force.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.4
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• pp.135-145
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• 2023

Purpose : The purpose of this study was to discover which breathing technique is more effective in improving respiratory function by applying different breathing techniques-the chest expansion respiratory technique and the abdominal expansion respiratory technique-to adults in the same aerobic exercise situation. Methods : In this study, 30 people were randomly assigned to two groups: chest expansion respiratory technique with aerobic exercise (A group) and abdominal expansion respiratory technique with aerobic exercise (B group). Group A was asked to breathe after wrapping their rib cage with an elastic band, and Group B was asked to breathe after wrapping their abdomen with an elastic band. A total of 3 sets of 30 breaths were performed, 3 times a week for 6 weeks. For statistical processing, an independent t-test was used to verify homogeneity between the two groups, and a repeated measure analysis of variance (ANOVA) was used to compare differences according to the period for each group. Results : The changes in FVC and FEV₁ for each group following 6 weeks of intervention are as follows. In comparison according to the intervention period, there was a significant increase in all groups depending on the timing of measurement (p<.05), and as a result of the inter-subject effect test, there was no significant difference between groups (p>.05). In addition, there was no interaction effect between period and group (p>.05). Conclusion : The conclusion of this study is that FVC and FEV₁ values increased according to the intervention period in both groups; therefore, it can be suggested that flexible breathing techniques can be applied depending on the patient's physical situation when applying a breathing program to improve respiratory function.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.526-534
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• 2023

To evaluate the risk of leakage when using liquid hydrogen, a leakage test was conducted using liquid nitrogen in an outdoor environment rather than a laboratory environment. To assume a real-scale continuous leak, liquid nitrogen was allowed to leak for 5 minutes through a pipe with a diameter of 25.4 mm at a design spill rate of 60 L/min. The measurement system consisted of devices for climate conditions, LN2 spread and vapor clouds. The main experimental results are the liquid pool radius and the concentration of vapor cloud, and the radius of the liquid pool was compared with the numerical analysis results.

• Current Optics and Photonics
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• v.8 no.1
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• pp.45-55
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• 2024

A fiber spool with ultra-low vibration sensitivity has been demonstrated for the ultra-narrow-linewidth fiber-stabilized laser by the multi-object orthogonal experimental design method, which can achieve the optimization object and analysis of influence levels without extensive computation. According to a test of 4 levels and 4 factors, an L₁₆ (4⁴) orthogonal table is established to design orthogonal experiments. The vibration sensitivities along the axial and radial directions and the normalized sums of the vibration sensitivities are determined as single objects and comprehensive objects, respectively. We adopt the range analysis of object values to obtain the influence levels of the four design parameters on the single objects and the comprehensive object. The optimal parameter combinations are determined by both methods of comprehensive balance and evaluation. Based on the corresponding fractional frequency stability of ultra-narrow-linewidth fiber-stabilized lasers, we obtain the final optimal parameter combination A3B1C2D1, which can achieve the fiber spool with vibration sensitivities of 10^-12/g magnitude. This work is the first time to use an orthogonal experimental design method to optimize the vibration sensitivities of fiber spools, providing an approach to design the fiber spool with ultra-low vibration sensitivity.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.142-146
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• 2007

Ambient noise was measured for 3 hours on May, 2001 at a site of 20 m water depth in the Korean coast of the Yellow Sea. During the measurement, the strong underwater sound assuming by marine life was continually observed. The spectrum level of this sound was very high compared to that of underwater ambient noise over the frequency range from 1 to 20 kHz. Therefore, this underwater sound can continually affect the ambient noise level. In this study, the source of the underwater sound was investigated. The snapping shrimp was estimated as reliable source. It was confirmed through comparison with experimental results described in previously literatures. It was also confirmed through analysis of snapping shrimp sound measured under laboratory conditions.

• Journal of Veterinary Science
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• v.25 no.3
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• pp.48.1-48.12
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• 2024

Importance: Early diagnosis of canine pancreatitis is challenging due to non-specific clinical signs. Currently, abdominal ultrasonography and measurement of canine pancreatic lipase (cPL) have been employed for the diagnosis of pancreatitis. Objective: Many qualitative and quantitative commercial cPL tests have been developed and used in veterinary clinics. This study aimed to compare three different methodologies SNAP cPL, Spec cPL, and Vcheck cPL tests to assess the concordance of these assays. Methods: Fifty serum samples were collected from 36 dogs with or without pancreatitis and subjected to SNAP cPL, Spec cPL, and Vcheck cPL tests. Agreement and correlation coefficients were calculated between the test results, and correlations were determined during the management of the patients. Results: The results of the three cPL assays were strongly correlated in 47/50 serum samples (94%). Cohen's kappa analysis between the Spec cPL and Vcheck cPL showed near perfect agreement (κ = 0.960, p < 0.001), SNAP cPL and Vcheck cPL (κ = 0.920, p < 0.001), and Spec cPL and SNAP cPL (κ = 0.880, p < 0.001). The correlation coefficients (r) between data from Spec cPL and Vcheck cPL tests was calculated by Spearman's correlation test (r = 0.958, p < 0.001). Furthermore, the patterns of change in serum cPL concentrations determined using Spec cPL and Vcheck cPL were significantly consistent during the monitoring period in 11 patients. Conclusions and Relevance: Our data illustrated that Spec cPL and Vcheck cPL tests are compatible for clinical use in the diagnosis and monitoring of canine pancreatitis.