• Journal of Navigation and Port Research
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• v.48 no.3
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• pp.192-199
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• 2024

Wave overtopping is a significant natural hazard that occurs in coastal areas, primarily driven by high waves, particularly those generated during typhoons, which can cause coastal flooding. The development of residential and commercial areas along the coast, driven by increasing social and economic demands, has led to a concentration of people and assets in these vulnerable areas. This, coupled with long-term sea level rise and an increase in typhoon frequency, has heightened the risk of coastal hazards. Traditionally, the evaluation of wave overtopping volumes has relied on directly measuring the collected volume of water that exceeds the crest height of structures through hydraulic model experiments. These experiments are averaged over a specific measurement period. However, in this study, we propose a new method for estimating individual wave overtopping volumes. We utilize the temporal variation of wave overtopping heights to develop an observation system that can quantitatively assess wave overtopping volumes in actual coastal areas. To test our method, we conducted hydraulic model experiments on rubble mound breakwaters, which are commonly installed along the Korean coast. We introduce wave overtopping discharge coefficients, assuming that the inundation velocity from the structure's crest is the long-wave velocity. We then predict overtopping volumes based on wave overtopping heights and compare and review the results with experimental data. The findings of our study confirm the feasibility of estimating wave overtopping volumes by applying the overtopping discharge coefficients derived in this study to wave overtopping heights.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.32-38
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• 2024

In the case of apartment building, it is difficult to conduct non-destructive testing due to the actual presence of people and the dust and noise generated during the core test, so inspections are performed each time in the common area and underground parking lot, and the tests are conducted on the finishing material rather than on the concrete surface due to low-cost orders. As the process progresses, poor inspection is inevitable. In addition, the proposed formulas for strength estimation have large fluctuations depending on the differences in test conditions and environments, and even if they show the same measured value, the deviation between each proposed formula is large, making it difficult to accurately estimate strength, making it difficult to use. Accordingly, we would like to select finishing materials mainly used in apartment complexes and compare and evaluate the compressive strength of concrete according to the type of finishing material by using non-destructive testing methods directly on the finishing materials without removing the finishing materials. The reliability evaluation results of the estimated compressive strength of concrete using the ultrasonic velocity method according to the type of finishing material are as follows. The error rate between the estimated compressive strength and compressive strength derived through the ultrasonic velocity method shows a wide range of variation, ranging from 21.83% to 58.89%. The effect of the presence or absence of finishing materials on the estimated compressive strength was found to be insignificant. Accordingly, it is necessary to select more types of finishing materials and study ultrasonic velocity methods according to the presence or absence of finishing materials, and to study estimation techniques that can increase reliability.

• The Journal of the Acoustical Society of Korea
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• v.26 no.6
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• pp.250-258
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• 2007

Current speech recognition technology s achieved high performance with the development of hardware devices, however it is insufficient for some applications where high reliability is required, such as voice control of powered wheelchairs for disabled persons. For the system which aims to operate powered wheelchairs safely by voice in real environment, we need to consider that non-voice commands such as user s coughing, breathing, and spark-like mechanical noise should be rejected and the wheelchair system need to recognize the speech commands affected by disability, which contains specific pronunciation speed and frequency. In this paper, we propose non-voice rejection method to perform voice/non-voice classification using both YIN based fundamental frequency(F0) extraction and reliability in preprocessing. We adopted a multi-template dictionary and acoustic modeling based speaker adaptation to cope with the pronunciation variation of inarticulately uttered speech. From the recognition tests conducted with the data collected in real environment, proposed YIN based fundamental extraction showed recall-precision rate of 95.1% better than that of 62% by cepstrum based method. Recognition test by a new system applied with multi-template dictionary and MAP adaptation also showed much higher accuracy of 99.5% than that of 78.6% by baseline system.

• Journal of the Korean Geosynthetics Society
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• v.23 no.1
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• pp.9-16
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• 2024

In order to evaluate the relationship between the ground confining pressure and the shear characteristics of the pile-soil interface, this study described the comparative results of the existing experimental results and the FEA results using the strength reduction factor. The strength reduction factor was applied to simulate the shear behavior of the pile-soil interface in finite element analysis(FEA). The analysis results showed that the maximum pullout resistance decreased due to the influence of low confining pressure, as the fines content increased. This trend was similar to the previous experimental research, and this FEA model simulated with the interface strength reduction factor was evaluated as reasonable. The analysis results of the variation in the interface strength reduction factor clearly showed that the interface strength reduction factor clearly increased at a high fines content when the confining pressure was 50kPa. However, it was found that the increase rate was low when the confining pressure was 100kPa and 150kPa. Therefore, confining pressure and fines content need to be considered in FEA to evaluate the shear behavior of the pile-soil interface.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.2
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• pp.99-106
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• 2013

Purpose: The aim of this research was to establish the effect and variation in differing convergence angle and length of abutment on the retention of full veneer casted gold crown. Materials and methods: Two different length,5 mm and 10 mm in height with convergence angles of 5, 10, 15 and 25 degrees crowns were fabricated. Cementation was done using cements; zinc phosphate cement (Fleck's zinc phosphate cement), resin-modified glass ionomer cement (Vitremer) and resin cement (Panavia 21). These were tested for tensile force at the point of separation by using Instron Universal Testing Machine. Statistical analysis was done by SAS 6.04 package. Results: In all cements the mean retention decreased with significant difference on increase of convergence angle (P<.05). Increase in every 5 degree-convergence angel the retention rate decreased with resin-modified glass ionomer cement of 15.9% and resin cement of 14.8%. With zinc phosphate cement, there was largest decreasing rate of mean retention of 25.5% between convergence angles from 5 degree to 10 degree. When the crown length increased from 5 mm to 10 mm, the retention increased with the significant difference in the same convergence angle and in all types of cement used (P<.05). Conclusion: The retention was strongly dependent on geometric factors of abutment. Much care is required in choosing cements for an optimal retention in abutments with different convergence angles and crown lengths.

• Journal of Korean Society of Forest Science
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• v.46 no.1
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• pp.29-43
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• 1980

The sampling methods selected for this area was (1) Simple random sampling (2) Systematic sampling and (3) Sub-sampling. For the calculation of the number of sampling plot, 10 % coefficient of variation was adapted. As a result, 57 plots each for simple random sampling and systematic sampling was calculated. In the sub-sampling method, however, total of 40 plots, which were consisted of 5 Blocks, secondary 4 major units and tertiary 2 minor units, were examined. The reuslts obtained are summarized as follows : 1. The rate of expected error was 9.24% for simple random sampling, 8.36% for systematic sampling and 7.54% for sub-sampling, respectively. Therefore, the sub-sampling was proved to be the most accurate method among the test. 2. The volume calculated by each sampling method was compared to the volume of all stand. The rate of expected error was also lowest in the sub-sampling (0.39%), followed by systematic sampling (4.18%) and simple random sampling (7.92%). 3. Comparing the various reuslts and analysis of these results, the sub-sampling was regarded as the most rapid and economical method because this method had not only the least number of plots but also the least expected error among the tested sampling methods Therefore the sub-sampling is proved to be an ideal sampling method for forest survey.

• The Korean Journal of Pesticide Science
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• v.17 no.3
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• pp.145-154
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• 2013

Flonicamid was a water-soluble and systemic insecticide. It was applied to control neonicotinod pesticide-resistant cotton aphid in sweet peppers. However, the residue levels of total flonicamid in sweet pepper exported to Japan in 2009 were exceeded the maximum residue limit (MRL). This study was conducted to elucidate residual properties of flonicamid parent compound and its metabolites in sweet peppers. It was carried out to compare the variation of residues in sweet pepper in three different greenhouses for 21 days after 3 times application with 7 days interval. The mean residues were 0.176, 0.152 and 0.108 mg $kg^{-1}$ and the residue levels in sweet pepper among three greenhouses show significant difference. The maximum residue levels were detected 10 days later after last treatments. The overall residue levels were lower than MRL 2.0 mg $kg^{-1}$ (by Korea) and 0.4 mg $kg^{-1}$ (by Japan in 2009 but now revised MRL is 2.0 mg $kg^{-1}$). But the residue level of total flonicamid at the 21th day after 3 times treatment with 7 days interval was 0.429 mg $kg^{-1}$ restricted by the application of double rate than recommended rate. The amounts of metabolites, TFNA, 4-Trifluoro methyl nicotinic acid and TFNG, N-(4-trifluoro methyl nicotinoyl) glycine were increased while flonicamid parent compound was decreased over time. Therefore the longer trial period should be needed for flonicamid in sweet peppers.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.664-668
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• 2011

Spherical alumina precursors represented by $AlO_xCl_y(OH)_z$, 30~200 nm in particle diameter, were prepared by partial hydrolysis of $AlCl_3$ vapor in a 500 ml reactor. Investigated on the particle morphology and size were the effects of the reaction time, the stirring speed and the reaction temperature. The particle morphology and size was insensitive to the reaction time in the range 20 to 300 s. The variation of the stirring speed from 0 to 300 and 800 rpm showed that the particle size was the largest at 0 rpm. As the temperature was varied from 180 to 190, 200, $140^{\circ}C$, the particle size showed a maximum at $190^{\circ}C$. By calcination of the as-produced particles at $1,200^{\circ}C$ for 6h with a heating rate of $10^{\circ}C$/min, ${\alpha}$-alumina particles 45 nm in surface area equivalent diameter were obtained. The particle shape after calcination turned wormlike due to sintering between neighboring particles. A rapid calcination at $1400^{\circ}C$ for 0.5 h with a higher heating rate of $50^{\circ}C$/min reduced the sintering considerably. An addition of $SiCl_4$ or TMCTS(2,4,6,8-tetramethylcyclosiloxane) to the $AlCl_3$ reduced the sintering effectively in the calcination step; however, peaks of ${\gamma}$ or mullite phase appeared. An addition of $AlF_3$ to the particles obtained from the hydrolysis resulted in a hexagonal disc shaped alumina particles.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.5
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• pp.137-145
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• 2008

In this study, to reduce the flood damage caused by flood discharge exceeding project flood, the primary technology was applied to determining the optimal location and size for underground sluiceway. The Jungrang Stream was selected for this study because the stream was overflowed and the embankment section of the stream was destroyed owing to localized torrential rainfall in 1998 and 2001. Considering 200-year frequency storm, the inlets of the underground discharge channel were located at Seoul City limits, the confluence of Danghyun Stream, Wolgye 1-gyo, and the confluence of Mukdong Stream. The outlets were located at the estuary of Jungrang Stream and rightbank of Banpo Bridge in Han River. The transverse discharge according to the variation of overflow depth at the inlet of underground discharge channel was estimated and the effect of inundation reduction was analyzed. To examine the appropriate scale of the underground discharge channel, the 8 operation methods for the management of outlet discharge were compared considering four rules (only storage, the constant discharge rate, the constant discharge volume, and the mixture of the constant discharge rate and discharge volume). As a result, the effect of inundation reduction was most significantly improved when the inlet was located at the confluence of Danghyun Stream. The appropriate size of underground sluiceway for 200-year frequency storm was studied, and as a result, the appropriate diameters of the underground discharge channel were 12 m in case of only storage(Rule D), 9m in 50% of discharge(Rule E), 8 m in constant discharge volume(Rule F), and 7 m in mixture method(Rule G). This investigation process can be applied to design the underground discharge channel when the inundation damage is significant in coastal area due to embankment overflow. The underground discharge channel in Jungrang Stream can also be used as an underground road to link Seoul City to Uijeongbu City during dry season.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.599-604
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• 1998

We have investigated Pt and $RuO_2$ as a bottom electrode for ferroelectric capacitor applications. The bottom electrodes were prepared by using an RF magnetron sputtering method. Some of the investigated parameters were a substrate temperature, gas flow rate, RF power for the film growth, and post annealing effect. The substrate temperature strongly influenced the surface morphology and resistivity of the bottom electrodes as well as the film crystallographic structure. XRD results on Pt films showed a mixed phase of (111) and (200) peak for the substrate temperature ranged from RT to $200^{\circ}C$, and a preferred (111) orientation for $300^{\circ}C$. From the XRD and AFM results, we recommend the substrate temperature of $300^{\circ}C$ and RF power 80W for the Pt bottom electrode growth. With the variation of an oxygen partial pressure from 0 to 50%, we learned that only Ru metal was grown with 0~5% of $O_2$ gas, mixed phase of Ru and $RuO_2$ for $O_ 2$ partial pressure between 10~40%, and a pure $RuO_2$ phase with $O_2$ partial pressure of 50%. This result indicates that a double layer of $RuO_2/Ru$ can be grown in a process with the modulation of gas flow rate. Double layer structure is expected to reduce the fatigue problem while keeping a low electrical resistivity. As post anneal temperature was increased from RT to $700^{\circ}C$, the resistivity of Pt and $RuO_2$ was decreased linearly. This paper presents the optimized process conditions of the bottom electrodes for memory device applications.