• Journal of Fisheries and Marine Sciences Education
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• v.28 no.2
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• pp.384-390
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• 2016

The purpose of this paper is to improve the availability of underwater sound by the fundamental data on the hearing ability of Redlip croaker Pseudosciaena polyactis, which is cultured according to the cultivation technology, recently. The auditory thresholds of Redlip croaker were determined at 6 frequencies from 80Hz to 800Hz by heartbeat conditioning method using pure tones coupled with a delayed electric shock. The audible range of the Redlip croaker extended from 80Hz to 800Hz with the best sensitive frequency range including little difference in hearing ability from 80Hz to 500Hz. In addition, the auditory thresholds over 800Hz increased rapidly. The mean auditory thresholds of the Redlip croaker at the test frequencies from 80Hz to 800Hz were 90.7dB, 93.4dB, 92.9dB, 94.4dB, 95.5dB and 108dB, respectively. Auditory masking for the redlip croaker was measured using masking stimuli with the spectrum level range of about 66, 71, 75dB (0dB re $1{\mu}Pa/{\sqrt{Hz}}$). According to white noise level, the auditory thresholds increased as compared with thresholds in a quiet background noise. The Auditory masking by the white noise spectrum level was stared over about 70dB within 80~500Hz. Critical ratio ranged from minimum 20.7dB to maximum 25.5dB at test frequencies of 80Hz~500Hz.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.549-555
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• 2004

Cement of three alkalinities (equivalent alkalinities of 0.36,0.52 and 0.97) was employed in fabricating a set of classical G109 type specimens. To-date, these have been subjected to a one week wet-one week dry cyclic pending using 15 w/o NaCl solution. At the end of the dry period, potential and macro-cell current were measured to indicate whether the top reinforcing steel was in the passive or active state. Once this bar became active, the specimen was autopsied and the extent of corrosion was documented. Subsequent to visual inspection, concrete powder samples were collected from the upper region of the top rebar trace; and at a certain times concrete cores were taken from non-reinforced specimens. Using these, determinations were made of (1) critical chloride concentration for corrosion initiation ($Cl_{th}^-$), (2) effective chloride diffusion coefficient ($D_e$), and (3) pore water alkalinity ($[OH^-]$). The pore water alkalinity was strongly related to the alkali content of cement that was used in the mix. The chloride concentration, ($Cl^-$), was greater at active than at passive sites, presumably as a consequence of electro migration and accumulation of these species at active site subsequent to corrosion initiation. Accordingly, ($Cl^-$) at passive sites was considered indicative of the threshold concentration fur corrosion initiation. The $Cl_{th}^-$ was increased with increasing Time-to-corrosion ($T_i$). Consequently, the HA(High Alkalinity) specimens exhibited the highest $Cl_{th}^-$ and the NA(Normal Alkalinity) was the least. This range exceeds what has previously been reported in North America. In addition, the effective diffusion coefficient, $D_e$, was about 40 percent lower for concrete prepared with the HA cement compared to the NA and LA(Low Alkalinity) ones.

• Corrosion Science and Technology
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• v.8 no.5
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• pp.171-176
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• 2009

The chloride threshold level (CTL) in mixed concrete containing, ordinary Portland cement (OPC), pulverized fuel ash (PFA) ground granulated blast furnace slag (GGBS), and silica fume (SF) is important for study on corrosion of reinforced concrete structures. The CTL is defined as a critical content of chloride at the steel depth of the steel which causes the breakdown of the passive film. The criterion of the CTL represented by total chloride content has been used due to convenience and practicality. In order to demonstrate a relationship between the CTL by total chloride content and the CTL by free chloride content, corrosion test and chloride binding capacity test were carried out. In corrosion test, Mortar specimens were cast using OPC, PFA, GGBS and SF, chlorides were admixed ranging 0.0, 0.2, 0.4, 0.8, 1.0, 1.5, 2.0, 2.5 and 3.0% by weight of binder. All specimens were cured 28 days, and then the corrosion rate was measured by the Tafel's extrapolation method. In chloride binding capacity, paste specimens were casting using OPC, PFA, GGBS and SF, chlorides were admixed ranging 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0% by weight of binders. At 28days, solution mixed with the powder of ground specimens was used to measure binding capacity. All specimens of both experiments were wrapped in polythene film to avoid leaching out of chloride and hydroxyl ions. As a result, the CTL by total chloride content ranged from 0.36-1.44% by weight of binders and the CTL by free chloride content ranged from 0.14-0.96%. Accordingly, the difference was ranging, from 0.22 to 0.48% by weight of binder. The order of difference for binder is OPC > 10% SF > 30% PFA > 60% GGBS.

• Computers and Concrete
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• v.19 no.3
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• pp.305-313
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• 2017

A robust finite element based reinforced concrete bridge deck corrosion initiation model is applied for time-dependent probabilistic sensitivity analysis. The model is focused on uncertainties in the governing parameters that include variation of high performance concrete (HPC) diffusion coefficients, concrete cover depth, surface chloride concentration, holidays in reinforcements, coatings and critical chloride threshold level in several steel reinforcements. The corrosion initiation risk is expressed in the form of probability over intended life span of the bridge deck. Conducted study shows the time-dependent sensitivity analysis to evaluate the significance of governing parameters on chloride ingress rate, various steel reinforcement protection and the corrosion initiation likelihood. Results from this probabilistic analysis provide better insight into the effect of input parameters variation on the estimate of the corrosion initiation risk for the design of concrete structures in harsh chloride environments.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.955-956
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• 2006

Fe-doped $TiO_2$ nanopowders were prepared by mechanical alloying (MA) varying Fe contents up to 8.0 wt.%. The UV-vis absorption showed that the UV absorption for the Fe-doped powder shifted to a longer wavelength (red shift). The absorption threshold depends on the concentration of nano-size Fe dopant. As the Fe concentration increased up to 4 wt.%, the UV-vis absorption and the magnetization were increased. The benefical effect of Fe doping for photocatalysis and ferromagnetism had the critical dopant concentration of 4 wt.%. Based on the UV absorption and magnetization, the dopant level is localized to the valence band of $TiO_2$.

• Journal of Periodontal and Implant Science
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• v.41 no.5
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• pp.218-226
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• 2011

Purpose: Micro-computed tomography (micro-CT) has been widely used in the evaluation of regenerated bone tissue but the reliability of micro-CT has not yet been established. This study evaluated the correlation between histomorphometric analysis and micro-CT analysis in performing new bone formation measurement. Methods: Critical-size calvarial defects were created using a 8 mm trephine bur in a total of 24 Sprague-Dawley rats, and collagen gel mixed with autogenous rat bone marrow stromal cells (BMSCs) or autogenous rat BMSCs transduced by adenovirus containing bone morphogenic protein-2 (BMP-2) genes was loaded into the defect site. In the control group, collagen gel alone was loaded into the defect. After 2 and 4 weeks, the animals were euthanized and calvaria containing defects were harvested. Micro-CT analysis and histomorphometric analysis of each sample were accomplished and the statistical evaluation about the correlation between both analyses was performed. Results: New bone formation of the BMP-2 group was greater than that of the other groups at 2 and 4 weeks in both histomorphometric analysis and micro-CT analysis (P=0.026, P=0.034). Histomorphometric analysis of representative sections showed similar results to histomorphometric analysis with a mean value of 3 sections. Measurement of new bone formation was highly correlated between histomorphometric analysis and micro-CT analysis, especially at the low lower threshold level at 2 weeks (adjusted $r^2=0.907$, P<0.001). New bone formation of the BMP-2 group analyzed by micro-CT tended to decline sharply with an increasing lower threshold level, and it was statistically significant (P<0.001). Conclusions: Both histomorphometric analysis and micro-CT analysis were valid methods for measurement of the new bone in rat calvarial defects and the ability to detect the new bone in micro-CT analysis was highly influenced by the threshold level in the BMP-2 group at early stage.

• Journal of Service Research and Studies
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• v.7 no.4
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• pp.109-126
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• 2017

Designing cost-effective service recovery strategies mix has been recognized one of important issues by both service researchers and practitioners. In spite of the rising interest in them, there has been scarce studies on them. In this paper, we try to find cost-effective service recovery strategies mix via game-theoretic modeling. Especially, we focus on the possible incentives such as voucher type reward and service re-performance which have different cost structure. We investigated three questions about the topics as follows:(1) Should the service firm use the possible incentive scheme such as voucher and service re-performance for service recovery?, (2) How much voucher and service re-performance is adequate for service recovery under diverse service failure severity level?, (3) How much voucher and service re-performance is adequate for service recovery under diverse threshold level to make the customer repurchase? The results are as follows:(1) The use of both voucher and service re-performance for service recovery results in greater surplus for the service firm. (2) The higher gets the service failure severity level, the higher total incentives are required in the equilibrium. As service failure severity level gets higher, higher level of discount might be more useful to the service firm. However, service re-performance should be cut down above some critical level of service failure severity in the equilibrium. (3) The higher gets the threshold level to make the customer repurchase, the higher incentives are required in the equilibrium, and the higher portion of voucher incentive is required relative to that of service re-performance in the equilibrium.

• Korean Institute of Interior Design Journal
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• v.25 no.1
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• pp.132-141
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• 2016

For those with disabilities, the residential area is the primary place to adapt the disabilities. Since the quality of the area gives a critical impact on their quality of life, it is essential to finding the measures to create the residential environment that supports their independence. In this regard, this study aimed to compare and analyze the interior elements of the houses that hinder the independence of the physically handicapped in the rural and urban areas, and conducted a survey on a total of 80 physically challenged in Seoul and Yeongwol (40 for each area). As a result, the respondents answered that the houses where they are currently living are hindering their independence regardless of area, and there were regional differences in the level of inconvenience with the size of living room, size of utility room, location of room, lighting and heating environment, ventilation system, deteriorated wallpapers and finishing materials, threshold and floor level difference and humidity control. This study has significance by providing the realistic measures to improve the housing environment of the physically challenged living in the rural and urban areas to be customized to them to increase their quality of life.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.6
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• pp.7-16
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• 2011

This study discussed the applicability of satellite SAR (Synthetic Aperture Radar) imagery with regard to reservoir monitoring, and tried the extraction of reservoir storage from multi-temporal C-band RADARSAT-1 SAR backscattering images of Yedang and Goongpyeong agricultural reservoirs, acquired from May to October 2005. SAR technology has been advanced as a complementary and alternative approach to optical remote sensing and in-situ measurement. Water bodies in SAR imagery represent low brightness induced by low backscattering, and reservoir storage can be derived from the backscatter contrast with the level-area-volume relationship of each reservoir. The threshold segmentation over the routine preprocessing of SAR images such as speckle reduction and low-pass filtering concluded a significant correlation between the SAR-derived reservoir storage and the observation record in spite of the considerable disagreement. The result showed up critical limitations for adopting SAR data to reservoir monitoring as follows: the inappropriate specifications of SAR data, the unreliable rating curve of reservoir, the lack of climatic information such as wind and precipitation, the interruption of inside and neighboring land cover, and so on. Furthermore, better accuracy of SAR-based reservoir monitoring could be expected through different alternatives such as multi-sensor image fusion, water level measurement with altimeters or interferometry, etc.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.3
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• pp.234-240
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• 2011

In order to obtain the fundamental data about the behavior of sharks by underwater audible sound, this experiment was carried out to investigate the auditory characteristics of tiger shark Scyliorhinus torazame which was caught in the coast of Jeju Island by heart rate conditioning method using pure tones coupled with a delayed electric shock. The audible range of tiger shark extended from 80Hz to 300Hz with a peak sensitivity at 80Hz including less sensitivity at 300Hz. The mean auditory thresholds of tiger shark at the frequencies of 80Hz, 100Hz, 200Hz and 300Hz were 90dB, 103dB, 94dB and 115dB, respectively. The positive response of tiger shark was not evident after the sound projection of over 300Hz. At the results, the sensitive frequency range of tiger shark is narrower than that of fish that has swim bladder. In addition, it is assumed that the most sensitive frequency in auditory thresholds of Chondrichthyes is lower than that of Osteichthyes. Critical ratios of tiger shark measured in the presence of masking noise in the spectrum level range of about 60-70dB (0dB re $1{\mu}Pa/\sqrt{Hz}$) increased from minimum 27dB to maximum 39dB at test frequencies of 80-200Hz. The noise spectrum level at the start of masking was distributed at the range of about 65dB within 80-200Hz.