• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.5
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• pp.775-786
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• 2017

Monitoring sediment flux is crucial especially for maintaining river systems to understand morphological behaviors. Recently, hydroacoustic backscatter (or SNR) as a surrogate to empirically estimate suspended sediment concentration has been increasingly highlighted for more efficient acquisition of sediment dataset, which is difficult throughout direct sediment sampling. However, relevant contemporary researches have focused on wide range solution applicable for large natural rivers where H-ADCPs with relatively low acoustic frequency have been widely utilized to seamlessly measure streamflow discharge. In this regard, this study aimed at investigating hydroacoustical characteristics based on a very recently released H-ADCP (SonTek SL-3000) with high acoustic frequency of 3 MHz in order to capitalize its capacity to be applied for suspended sediment monitoring in laboratory conditions. SL-3000 was tested in a laboratory flume to collect SNR in conjunction with LISST-100X for actual sediment concentration and particle distribution in both sand and silt sediment injection in various amount. Conventional algorithms to correct signal attenuations for water and sediment were carefully tested to validate whether they can be applied for SL-3000. As result of analyzing the SNR-SSC correlation trand, through further study in the future, it is confirmed that SSC can be observed indirectly by using the SNR.

• The Journal of the Acoustical Society of Korea
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• v.32 no.2
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• pp.95-103
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• 2013

An underwater acoustic (UWA) communication in shallow water is strongly affected by the water surface and the seabed acoustical properties. Every reflected signal to receiver experiences a time-variant scattering in sea surface roughness and a grazing-angle-dependent reflection loss in bottom. Consequently, the performance of UWA communication systems is degraded, and high-speed digital communication is disrupted. If there is a dominant signal path such as a direct path, the received signal is modeled statistically as Rice fading but if not, it is modeled as Rayleigh fading. However, it has been known to be very difficult to reproduce the statistical estimation by real experimental evaluation in the sea. To give an insight for this scattering and grazing-angle-dependent bottom reflection loss effect in UWA communication, authors conduct experiments to quantify these effects. The image is transmitted using binary frequency shift keying (BFSK) modulation. The quality of the received image is shown to be affected by water surface scattering and grazing-angle-dependent bottom reflection loss. The analysis is based on the transmitter to receiver range and the receiver depth dependent image quality and bit error rate (BER). The results show that the received image quality is highly dependent on the transmitter-receiver range and receiver depth which characterizes the channel coherence bandwidth.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.243-244
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• 2013

Over the past 15 years, several groups have incorporated radio-frequency quadrupole (RFQ) based instruments before the accelerator in accelerator mass spectrometry (AMS) systems for ion-gas interactions at low kinetic energy (＜40 eV). Most AMS systems arebased on a tandem accelerator, which requires negative ions at injection. Typically, AMS sensitivity abundance ratios for radioactive-to-stable isotope are limited to Xr/Xs ＞10^-15, and the range of isotopes that can be analyzed is limited because of theneed to produce rather large negative ion beams and the presence of atomic isobaric interferences after stripping. The potential of using low-kinetic energy ion-gas interactions for isobar suppression before the accelerator has been demonstrated for several negative ion isobar systems with a prototype RFQ system incorporated into the AMS system at IsoTrace Laboratory, Canada (Ontario, Toronto). Requisite for any such RFQ system applied to very rare isotope analysis is large transmission of the analyte ion. This requires proper phase-space matching between the RFQ acceptance and the ion beam phase space (e.g. 35 keV, ${\varphi}3mm$, +-35 mrad), and the ability to control the average ion energy during interactions with the gas. A segmented RFQ instrument is currently being designed at Korea Institute for Science and Technology (한국과학기술연구원, KIST). It will consist of: a) an initial static voltage electrode deceleration region, to lower the ion energy from 35 keV down to ＜40 eV at injection into the first RFQ segment; b) the segmented quadrupole ion-gas interaction region; c) a static voltage electrode re-acceleration region for ion injection into a tandem accelerator. Design considerations and modeling will be discussed. This system should greatly lower the detection limits of the 6 MV AMS system currently being commissioned at KIST. As an example, current detection sensitivity of 41Ca/Ca is limited to the order of 10^-15 while the 41Ca/Ca abundance in modern samples is typically 41Ca/Ca~10^-14 - 10^-15. The major atomic isobaric interference in AMS is 41K. Proof-of-principal work at IsoTrace Lab. has demonstrated that a properly designed system can achieve a relative suppression of KF3-/41CaF3- ＞4 orders of magnitude while maintaining very high transmission of the 41CaF3- ion. This would lower the 41Ca detection limits of the KIST AMS system to at least 41Ca/Ca~10^-19. As Ca is found in bones and shells, this would potentially allow direct dating of valuable anthropological archives and archives relevant to our understanding of the most pronounced climate change events over the past million years that cannot be directly dated with the presently accessible isotopes.

• Food Science and Preservation
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• v.17 no.5
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• pp.571-580
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• 2010

We sought to define the main motivational factors promoting consumption of Prunus mume products. We surveyed both specialized high-volume consumers and public consumers, and focused on consumption of and preferences for Prunus mume and Prunus mume products. We investigated how products were preferentially consumed, purchase experience, purchase location, purchase price, consumption experience, factors important in a purchase decision, preference factors, dissatisfaction factors, consumption outlook, comments on new processed foods, and activation of consumption. A total of 534 responses were received and data were analyzed using the SAS program (Version 9.1) of the Frequency test; Chi-square test was used to detect significant factors. A greater percentage of high-volume(compared with low-volume) consumers processed personal products at home. The public consumer tended to buy commercial products. However, public consumers who were older, who had higher incomes, and who were heads of households, tended to both buy commercial products and to prepare foods at home. The common purchase methods used by high-volume consumers were internet and direct marketing, but the public consumer frequented department stores and hypermarkets. High-volume consumers observed that commercial products were expensive, and such consumers seemed to be particularly cost-sensitive. The decisive factor triggering purchase decisions in high-volume consumers was the geographical origin of the fruit, whereas the public consumer was more concerned with taste. In public, positive factors were that the product was good for health and had a pleasant taste. Some of those surveyed complained of a lack of variety in Prunus mume products and that the amount of Prunus mume in certain products was low. To promote and increase consumption, convenient-to-eat products with healthy images are needed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.390-395
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• 2019

Hydrogymnastics so that sufficient exercise effect can be obtained using the resistance of water has a positive effect on patients who have to receive arthritis or rehabilitation treatment. However, the studies on the effect are insufficient, and the main cause of their effects has not been unclear yet. In this study, in order to identify the main cause of the effects of Hydrogymnastics, conducted Unsteady fluid flow simulation under the same conditions as the actual environment. The analysis model based on real hands, and the pressure fluctuation applied to the knuckle was analyzed by the computational fluid method. During the underwater movement of the hands, Various sizes of vortices were generated between fingers due to skin surface velocity and flow resistance. Pressure of about -500 Pa to +500 Pa is applied by the vortex flow. Also It was confirmed that the positive pressure and the negative pressure were continuously repeated up to maximum + 2000 Pa at the minimum of -2000 Pa at the portion where the direction was changed. Pressure fluctuations with a frequency of 20 Hz to 70 Hz were added continuously for each knuckle. These continuous pressure fluctuations provide a direct massage effect on the knuckles, an It is judged that the blood circulation at the relevant part is positively affected.

• The Journal of the Acoustical Society of Korea
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• v.42 no.6
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• pp.491-499
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• 2023

Scattering by Sea surface roughness occurs due to sea level roughness, communication performance deteriorates by causing frequency spread in communication signals and time variation in communication channels. In order to compare the difference in time variation of underwater acoustic communication channel according to the surface roughness, an experiment was performed in a tank owned by Hanyang University Ocean Acoustics Lab. Artificial surface roughness was created in the tank and communication signals with three bandwidths were used (8 kHz, 16 kHz, 32 kHz). The measured surface roughness was converted into a Rayleigh parameter and used as a roughness parameter, and statistical analysis was performed on the time-varying channel characteristics of the surface path using Doppler spread and correlation time. For the Doppler spread of the surface path, the Weighted Root Mean Square Doppler spread (w_fσ_ν) that corrected the effect of the carrier frequency and bandwidth of the communication signal was used. Using the correlation time of the surface path and the energy ratio of the direct path and the surface path, the correlation of total channels was simulated and compared with the measured correlation time of total channels. In this study, we propose a method for efficient communication signal design in an arbitrary marine environment by using the time-varying characteristics of the sea surface path according to the sea surface roughness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.678-684
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• 2012

The purpose of this study is to figure out and establish the basic data that can help improve management of oral healthcare for the international marriage migrantwomen. In this sense, we surveyed questions on 237 women out of 1,300 immigrant women, who have participated the program in operation by multi-cultural household supporting center, in a fashion of face-to-face investigation and on-the-spot direct cavity inspection simultaneously from May 1th to October 31th, 2010. Collected data were electro-statistically computerized under SPSS 17.0 program and analyzed with frequency analysis, recurrence analysis and logistic regression analysis respectively. Foundings were revealed as follows; On the nationality base, show the data in the ratio of 38.8% for Vietnamese, 29.1% for Philippine, 12.2% for Chinese and 6.8% for Japanese respectively. Current oral cavity status shows in the ratio of 60% with carious tooth symptoms, 40% without carious tooth symptom. Philippine women have irregular sets of tooth in many a case. (i.e., in short of numbers of teeth, due to removing individual tooth.) Japanese ladies are indicated to have less irregular sets of tooth, in comparison with that of the other immigrants from overseas. And lastly, high-income immigrant women in general were found having less numbers of unhealthy sets of tooth. Getting older, it appears that decayed tooth symptom is on the tendency of getting less in the field of dentistry circles. Immigrant ladies living with husbands under higher education background usually are found living a life in the less ratio of having toothache. A full-time immigrant housewives, however, are living everyday life in more times of suffering with tooth disease.

• Korean Journal of Social Welfare
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• v.55
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• pp.255-281
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• 2003

This study sought to explore factors affecting the adjustment of children living in shelters for battered women. Specifically, the impact of domestic violence on children's internal and external adjustment was examined using data from two samples: children who were exposed to marital violence and those who did not have violent experience. Likewise, this study identified the variables that distinguished the "resilient" children from the maladjusted group. The pathways by which protective factors considerably affected children's adjustment were also investigated. A total of 72 children in a women's shelter and their mothers and 76 children in nonviolent homes and their mothers were considered. ANOVA, logistic regression models, and path analysis were employed to process the data. Results revealed that children of battered women demonstrated a high frequency of aggressive and delinquent behaviors and had poor academic achievement and depressive mood compared to children coming from nonviolent homes. Likewise, children who were exposed to marital violence and were physically abused themselves were more likely show aggressive or delinquent behaviors compared to those who only witnessed marital violence. In addition, social support was found to be a protective factor in academic achievement. Predictors of delinquent behavior included the mother's education and income as well as the children's age and social support. Factors related to children's self-esteem included the social support and the mother's self-esteem. Moreover, woman battering has a direct effect on children's adjustment as well as indirect effect through children's academic achievement and self-esteem. Finally, woman battering indirectly affected children's academic achievement through the mother's depression or the child's social support. Based on these findings, practical implications of enhancing children's adjustment were discussed.

• Culinary science and hospitality research
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• v.15 no.2
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• pp.205-218
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• 2009

The purpose of this study was to analyze what effects the service quality of the food and beverage section have on its organization value in the value-oriented hotel business, how the organization value influence work performance, and what causal relationships exist among variable factors such as service quality, organization value, and work performance for helping get the hotel business more profitable through guiding service improvements. For conducting the study, full-time staff working at the restaurants of premium hotels in Seoul participated in the test as samples from January 10th to January 22nd, 2009. The statistical data analyses were completed using the SPSS 12.0 program, and frequency analyses, reliability analysis, factor analysis, multiple regression analysis were conducted. The main results of this study were as follows. First, service quality of the food and beverage section in the hotel business caused positive effects on organization values. Second, it was found that the organization value and service quality also positively influenced work performance. Third, among service quality, organization value, and work performance, service quality had a direct effect on business performance, and organization value played an indirect role to cause effects on work performance through service quality. Accordingly, all of the workers engaging in the hotel business, including board of directors, ordinary managers and staff working at the food and beverage section, are highly required to recognize how keenly important service quality is for the hotel business.

• Investigative Magnetic Resonance Imaging
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• v.2 no.1
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• pp.73-82
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• 1998

Purpose : A precise NMR technique for measuring the rate of water exchange and cell membrane permeability across the hepatocyte membrane using liver-specific MR contrast agent is described. Materials and Methods : The rat hepatocytes isolated by perfusion of the livers were used for the NMR measurements. All experiments were performed on an IBM field cycling relaxometer operating from 0.02MHz to 60 MHz proton Larmor frequency. spin-echo pulse sequence was empolyed to measure spin-lattice relaxation time, T1. The continuous distribution analysis of water proton T1 data from rat hepatocytes containing low concentrations of the liver specific contrast agent, Gd-EOB-DTPA, modeled by a general two compartment exchange model. Results : The mean residence time of water molecule inside the hepatocyte was approximately 250 msec. The lower limit for the permeability of the hepatocyte membrane was $(1.3{\pm}0.1){\;}{\times}{\;}10^{-3}cm/sec$. The CONTIN analysis, which seeks the natural distribution of relaxation times, reveals direct evidence of the effect of diffusive exchange. the diffusive water exchange is not small in the intracellular space in the case of hepatocytes. Conclusions : Gd-EOB-DTPA, when combined with continuous distribution analysis, provides a robust method to study water exchange and membrane permeability in hepatocytes. Water exchange in hepatocyte is much slower thatn that in red blood cells. Therefore, tissue-specific contrast agent may be used as a functional agent to give physiological information such as cell membrane permeability.