• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.361-367
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• 2024

Ultrasound in the air is widely used in industry as a measurement technique to prevent abnormalities in the machinery. Recently, the use of airborne ultrasound imaging techniques, which can find the location of abnormalities using an array transducers, is increasing. A beamforming method that uses the phase difference for each sensor is used to visualize the location of the ultrasonic sound source. We exploit a random sparse ultrasonic array and obtain beamforming power distribution on the source in a certain distance away from the array. Conventional beamforming methods inevitably have limited spatial resolution depending on the number of sensors used and the aperture size. A high-resolution ultrasound imaging technique was implemented by applying functional beamforming as a method to overcome the geometric constraints of the array. The functional beamforming method can be expressed as a generalized beam forming method mathematically, and has the advantage of being able to obtain high-resolution imaging by reducing main-lobe width and side lobes. As a result of observation through computer simulation, it was verified that the resolution of the ultrasonic source in the air was successfully increased by functional beamforming using the ultrasonic sparse array.

• Journal of Radiation Industry
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• v.17 no.3
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• pp.275-282
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• 2023

Workers in nuclear power plants are likely to be exposed to radiation from various geometrical sources. In order to evaluate the exposure level, the point-kernel method can be utilized. In order to perform a dose assessment based on this method, the radiation source should be divided into point sources, and the number of divisions should be set by the evaluator. However, for the general public, there may be difficulties in selecting the appropriate number of divisions and performing an evaluation. Therefore, the purpose of this study is to develop an algorithm for dose assessment for arbitrary shaped sources based on the point-kernel method. For this purpose, the point-kernel method was analyzed and the main factors for the dose assessment were selected. Subsequently, based on the analyzed methodology, a dose assessment algorithm for arbitrary shaped sources was developed. Lastly, the developed algorithm was verified using Microshield. The dose assessment procedure of the developed algorithm consisted of 1) boundary space setting step, 2) source grid division step, 3) the set of point sources generation step, and 4) dose assessment step. In the boundary space setting step, the boundaries of the space occupied by the sources are set. In the grid division step, the boundary space is divided into several grids. In the set of point sources generation step, the coordinates of the point sources are set by considering the proportion of sources occupying each grid. Finally, in the dose assessment step, the results of the dose assessments for each point source are summed up to derive the dose rate. In order to verify the developed algorithm, the exposure scenario was established based on the standard exposure scenario presented by the American National Standards Institute. The results of the evaluation with the developed algorithm and Microshield were compare. The results of the evaluation with the developed algorithm showed a range of 1.99×10^-1~9.74×10^-1 μSv hr^-1, depending on the distance and the error between the results of the developed algorithm and Microshield was about 0.48~6.93%. The error was attributed to the difference in the number of point sources and point source distribution between the developed algorithm and the Microshield. The results of this study can be utilized for external exposure radiation dose assessments based on the point-kernel method.

• Journal of Radiation Industry
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• v.18 no.3
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• pp.167-171
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• 2024

Technetium-99 (⁹⁹Tc) is recognized as a critical concern in the disposal of spent nuclear fuel due to its long half-life and remarkable stability, existing predominantly as TcO₄^- in the natural environment. The anionic form of technetium is highly soluble and mobile, posing significant environmental risks from the viewpoint of nuclear waste management. Thus, developing efficient and cost-effective sorbents for aqueous Tc(VII) is essential for mitigating relevant contamination. In the present work, the adsorption characteristics of Re(VII), a chemical analog of Tc(VII), were investigated using the clay mineral bentonite, modified with two different organic cations: hexadecylpyridinium (HDPy) and hexadecyltrimethylammonium (HDTMA). Sorption experiments were conducted at a liquid-to-solid ratio of 1 g/L with Re(VII) solutions prepared at concentrations from 10^-4 mol/L to 10^-6 mol/L. The sorption ratio and distribution coefficients were determined with samples collected at reaction times of 10, 50, 100, and 500 minutes after 0.45 ㎛ syringe filtration. In parallel, the modified bentonite samples were further analyzed using the X-ray diffraction (XRD) method to understand the adsorption mechanism of Re(VII) onto the target minerals. According to the quantification analysis results, a rapid equilibrium reaction of aqueous Re(VII) for all modified bentonite samples was identified. Moreover, near-complete adsorption of Re(VII) was observed when the bentonite was modified at 200-400% of its cation exchange capacity (CEC) for both organic cations. For cases of lower modification, the HDTMA-modified bentonite showed relatively higher adsorption efficiency compared with the one modified with HDPy. This result was inferred to be due to the difference in inter-layer spacing based on the characteristics of the organic cations. It is expected that the results obtained through this study will serve as a preliminary case for the synthesis of adsorbents for the retardation of highly mobile anionic radionuclides, such as I and Tc, in the natural environment.

• Journal of IKEEE
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• v.28 no.3
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• pp.458-464
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• 2024

This study proposes a fault-tolerant caching system to address the issue of caching content imbalance caused by the dynamic departure and participation of cache servers in a heterogeneous cache server network, and validates it in both real and virtual environments. With the increase of large-scale media content requiring various types and resolutions, the necessity of cache servers as key components to reduce response time to user requests and alleviate network load has been growing. In particular, research on heterogeneous cache server networks utilizing edge computing and low-power devices has been actively conducted recently. However, in such environments, the irregular departure and participation of cache servers can occur frequently, leading to content imbalance among the cache servers deployed in the network, which can degrade the performance of the cache server network. The fault-tolerant caching algorithm proposed in this study ensures stable service quality by maintaining balance among media contents even when cache servers depart. Experimental results confirmed that the proposed algorithm effectively maintains content distribution despite the departure of cache servers. Additionally, we built a network composed of seven heterogeneous cache servers to verify the practicality of the proposed caching system and demonstrated its performance and scalability through a large-scale cache server network in a virtual environment.

• Journal of Distribution Science
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• v.8 no.3
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• pp.27-35
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• 2010

As the population, buying power, and intensity of self-expression of the elderly generation increase, its importance as a market segment is also growing. Therefore, the mass marketing strategy for the elderly generation must be changed to a micro-marketing strategy based on the results of sub-segmentation that suitably captures the characteristics of this generation. Furthermore, as a customer access strategy is decided by sub-segmentation, proper segmentation is one of the key success factors for micro-marketing. Segments or sub-segments are different from sectors, because segmentation or sub-segmentation for micro-marketing is based on the homogeneity of customer needs. Theoretically, complete segmentation would reveal a single voice. However, it is impossible to achieve complete segmentation because of economic factors, factors that affect effectiveness, etc. To obtain a single voice from a segment, we sometimes need to divide it into many individual cases. In such a case, there would be a many segments to deal with. On the other hand, to maximize market access performance, fewer segments are preferred. In this paper, we use the term "sub-segmentation" instead of "segmentation," because we divide a specific segment into more detailed segments. To sub-segment the elderly generation, this paper takes their lifestyles and life stages into consideration. In order to reflect these aspects, various surveys and several rounds of expert interviews and focused group interviews (FGIs) were performed. Using the results of these qualitative surveys, we can define six sub-segments of the elderly generation. This paper uses five rules to divide the elderly generation. The five rules are (1) mutually exclusive and collectively exhaustive (MECE) sub-segmentation, (2) important life stages, (3) notable lifestyles, (4) minimum number of and easy classifiable sub-segments, and (5) significant difference in voices among the sub-segments. The most critical point for dividing the elderly market is whether children are married. The other points are source of income, gender, and occupation. In this paper, the elderly market is divided into six sub-segments. As mentioned, the number of sub-segments is a very key point for a successful marketing approach. Too many sub-segments would lead to narrow substantiality or lack of actionability. On the other hand, too few sub-segments would have no effects. Therefore, the creation of the optimum number of sub-segments is a critical problem faced by marketers. This paper presents a method of evaluating the fitness of sub-segments that was deduced from the preceding surveys. The presented method uses the degree of homogeneity (DoH) to measure the adequacy of sub-segments. This measure uses quantitative survey questions to calculate adequacy. The ratio of significantly homogeneous questions to the total numbers of survey questions indicates the DoH. A significantly homogeneous question is defined as a question in which one case is selected significantly more often than others. To show whether a case is selected significantly more often than others, we use a hypothesis test. In this case, the null hypothesis (H0) would be that there is no significant difference between the selection of one case and that of the others. Thus, the total number of significantly homogeneous questions is the total number of cases in which the null hypothesis is rejected. To calculate the DoH, we conducted a quantitative survey (total sample size was 400, 60 questions, 4~5 cases for each question). The sample size of the first sub-segment-has no unmarried offspring and earns a living independently-is 113. The sample size of the second sub-segment-has no unmarried offspring and is economically supported by its offspring-is 57. The sample size of the third sub-segment-has unmarried offspring and is employed and male-is 70. The sample size of the fourth sub-segment-has unmarried offspring and is not employed and male-is 45. The sample size of the fifth sub-segment-has unmarried offspring and is female and employed (either the female herself or her husband)-is 63. The sample size of the last sub-segment-has unmarried offspring and is female and not employed (not even the husband)-is 52. Statistically, the sample size of each sub-segment is sufficiently large. Therefore, we use the z-test for testing hypotheses. When the significance level is 0.05, the DoHs of the six sub-segments are 1.00, 0.95, 0.95, 0.87, 0.93, and 1.00, respectively. When the significance level is 0.01, the DoHs of the six sub-segments are 0.95, 0.87, 0.85, 0.80, 0.88, and 0.87, respectively. These results show that the first sub-segment is the most homogeneous category, while the fourth has more variety in terms of its needs. If the sample size is sufficiently large, more segmentation would be better in a given sub-segment. However, as the fourth sub-segment is smaller than the others, more detailed segmentation is not proceeded. A very critical point for a successful micro-marketing strategy is measuring the fit of a sub-segment. However, until now, there have been no robust rules for measuring fit. This paper presents a method of evaluating the fit of sub-segments. This method will be very helpful for deciding the adequacy of sub-segmentation. However, it has some limitations that prevent it from being robust. These limitations include the following: (1) the method is restricted to only quantitative questions; (2) the type of questions that must be involved in calculation pose difficulties; (3) DoH values depend on content formation. Despite these limitations, this paper has presented a useful method for conducting adequate sub-segmentation. We believe that the present method can be applied widely in many areas. Furthermore, the results of the sub-segmentation of the elderly generation can serve as a reference for mature marketing.

• Journal of Distribution Research
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• v.17 no.1
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• pp.87-115
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• 2012

Introduction: In these days, a loyalty program is one of the most common marketing mechanisms (Lacey & Sneath, 2006; Nues & Dreze, 2006; Uncles et al., 20003). In recent years, Coalition Loyalty Program is more noticeable as one of progressed forms. In the past, loyalty program was operating independently by single product brand or single retail channel brand. Now, companies using Coalition Loyalty Program share their programs as one single service and companies to participate to this program continue to have benefits from their existing program as well as positive spillover effect from the other participating network companies. Instead of consumers to earn or spend points from single retail channel or brand, consumers will have more opportunities to utilize their points and be able to purchase other participating companies products. Issues that are related to form of loyalty programs are essentially connected with consumers' perceived view on convenience of using its program. This can be a problem for distribution companies' strategic marketing plan. Although Coalition Loyalty Program is popular corporate marketing strategy to most companies, only few researches have been published. However, compared to independent loyalty program, coalition loyalty program operated by third parties of partnership has following conditions: Companies cannot autonomously modify structures of program for individual companies' benefits, and there is no guarantee to operate and to participate its program continuously by signing a contract. Thus, it is important to conduct the study on how coalition loyalty program affects companies' success and its process as much as conducting the study on effects of independent program. This study will complement the lack of coalition loyalty program study. The purpose of this study is to find out how consumer loyalty affects affiliated brands, its cause and mechanism. The past study about loyalty program only provided the variation of performance analysis, but this study will specifically focus on causes of results. In order to do these, this study is designed and to verify three primary objects as following; First, based on opinions of Switching Barriers (Fornell, 1992; Ping, 1993; Jones, et at., 2000) about causes of loyalty of coalition brand, 'brand attractiveness' and 'brand switching cost' are antecedents and causes of change in 'brand loyalty' will be investigated. Second, influence of consumers' perception and attitude prior to joining coalition loyalty program, influence of program in retail brands, brand attractiveness and spillover effect of switching cost after joining coalition program will be verified. Finally, the study will apply 'prior brand preference' as a variable and will provide a relationship between effects of coalition loyalty program and prior preference level. Hypothesis Hypothesis 1. After joining coalition loyalty program, more preferred brand (compared to less preferred brand) will increase influence on brand attractiveness to brand loyalty. Hypothesis 2. After joining coalition loyalty program, less preferred brand (compared to more preferred brand) will increase influence on brand switching cost to brand loyalty. Hypothesis 3. (1)Brand attractiveness and (2)brand switching cost of more preferred brand (before joining the coalition loyalty program) will influence more positive effects from (1)program attractiveness and (2)program switching cost of coalition loyalty program (after joining) than less preferred brand. Hypothesis 4. After joining coalition loyalty program, (1)brand attractiveness and (2)brand switching cost of more preferred brand will receive more positive impacts from (1)program attractiveness and (2)program switching cost of coalition loyalty program than less preferred brand. Hypothesis 5. After joining coalition loyalty program, (1)brand attractiveness and (2)brand switching cost of more preferred brand will receive less impacts from (1)brand attractiveness and (2)brand switching cost of different brands (having different preference level), which joined simultaneously, than less preferred brand. Method : In order to validate hypotheses, this study will apply experimental method throughout virtual scenario of coalition loyalty program if consumers have used or available for the actual brands. The experiment is conducted twice to participants. In a first experiment, the study will provide six coalition brands which are already selected based on prior research. The survey asked each brand attractiveness, switching cost, and loyalty after they choose high preference brand and low preference brand. One hour break was provided prior to the second experiment. In a second experiment, virtual coalition loyalty program "SaveBag" was introduced to participants. Participants were informed that "SaveBag" will be new alliance with six coalition brands from the first experiment. Brand attractiveness and switching cost about coalition program were measured and brand attractiveness and switching cost of high preference brand and low preference brand were measured as same method of first experiment. Limitation and future research This study shows limitations of effects of coalition loyalty program by using virtual scenario instead of actual research. Thus, future study should compare and analyze CLP panel data to provide more in-depth information. In addition, this study only proved the effectiveness of coalition loyalty program. However, there are two types of loyalty program, which are Single and Coalition, and success of coalition loyalty program will be dependent on market brand power and prior customer attitude. Therefore, it will be interesting to compare effects of two programs in the future.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.487-502
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• 2012

This paper is focused on mineral compositions, microstructures and distributional characters of remained grains in the fault rocks collected from a fault developed in Yongdang-ri, Yangbuk-myeon, Gyeongju City, Korea, using X-ray diffraction (XRD), optical microscope, laser grain size analysis and fractal dimension analysis methods. The exposed fault core zone is about 1.5 meter thick. On the average, the breccia zone is 1.2 meter and the gouge zone is 20cm thick, respectively. XRD results show that the breccia zone consists predominantly of rock-forming minerals including quartz and feldspar, but the gouge zone consists of abundant clay minerals such as chlorite, illite and kaolinite. Mineral vein, pyrite and altered minerals commonly observed in the fault rock support evidence of fault activity associated with hydrothermal alteration. Fractal dimensions based on box counting, image analysis and laser particle analysis suggest that mineral grains in the fault rock underwent fracturing process as well as abrasion that gave rise to diminution of grains during the fault activity. Fractal dimensions(D-values) calculated by three methods gradually increase from the breccia zone to the gouge zone which has commonly high D-values. There are no noticeable changes in D-values in the gouge zone with trend being constant. It means that the bulk-crushing process of mineral grains in the breccia zone was predominant, whereas abrasion of mineral grains in the gouge zone took place by continuous fault activity. It means that the bulk-crushing process of mineral grains in the breccia zone was predominant, whereas abrasion of mineral grains in the gouge zone took place by continuous fault activity. Mineral compositions in the fault zone and peculiar trends in grain distribution indicate that multiple fault activity had a considerable influence on the evolution of fault zones, together with hydrothermal alteration. Meanwhile, fractal dimension values(D) in the fault rock should be used with caution because there is possibility that different values are unexpectedly obtained depending on the measurement methods available even in the same sample.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.4
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• pp.319-327
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• 2010

A nuclear plant ESF ACS simulator was designed, built, and verified to perform experiment related to ESF ACS of nuclear power plants. The dimension of 3D CAD model was based on drawings of the main control room(MCR) of Yonggwang units 5 and 6. The CFD analysis was performed based on the measurement of the actual flow rate of ESF ACS. The air flowing in ACS was assumed to have $30^{\circ}C$ and uniform flow. The flow rate across the HEPA filter was estimated to be 1.83 m/s based on the MCR ACS flow rate of 12,986 CFM and HEPA filter area of 9 filters having effective area of $610{\times}610mm^2$ each. When MCR ACS was modeled, air flow blocking filter frames were considered for better simulation of the real ACS. In CFD analysis, the air flow rate in the lower part of the active carbon adsorber was simulated separately at higher than 7 m/s to reflect the measured value of 8 m/s. Through the CFD analyses of the ACSes of fuel building emergency ventilation system, emergency core cooling system equipment room ventilation cleanup system, it was confirmed that all three EFS ACSes can be simulated by controlling the flow rate of the simulator. After the CFD analysis, the simulator was built in nuclear grade and its reliability was verified through air flow distribution tests before it was used in main tests. The verification result showed that distribution of the internal flow was uniform except near the filter frames when medium filter was installed. The simulator was used in the tests to confirm the revised contents in Reg. Guide 1.52 (Rev. 3).

• Tuberculosis and Respiratory Diseases
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• v.41 no.5
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• pp.484-488
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• 1994

Background : The antigen-specific receptor on the surface of most peripheral T lymphocytes is a disulfide-linked heterodimer composed of $\alpha$ and $\gamma$ subunits, noncovalently associated with CD3 polypeptides. Recently, a novel type of CD3-associated heterodimer was described on a T cell subset that does not express CD4 or CD8 molecules. This second type of TCR dimer is composed of chains encoded for by the $\gamma$- and $\delta$-TCR genes. These cells may exert both cytotoxic and lymphokine producing functions. Although it was reported that some ${\gamma}{\delta}$-TCR might recognize an MHC-linked determinant, the funεtion or physiologic ligand for this new receptor is not yet clear. It was found that ${\gamma}{\delta}$-TCR can react with 65 kD heat shock protein of M. tuberculosis, which suggests the possible protective role of ${\gamma}{\delta}$ T lymphocytes against tuberculosis. In our previous study, there was neither the increase in number nor the functional activation of ${\gamma}{\delta}$ T cells in the peripheral blood from patients with pulmonary tuberculosis. Now we report the distribution of ${\gamma}{\delta}$ T cells in the regional sites of M. tuberculosis infection, especial1y tuberculous lymphadenitis. Methods : Lymph nodes from patients with pathologically-proven tuberculous lymphadenopathy (n=5) and reactive hyperplasia (n=3) were used. Tissues were frozen in liquid nitrogen immediately after removal and stored below $-70^{\circ}C$. The cryostat sections of these frozen specimens were stained with anti-Leu-4 Ab, Identi-T TCR ${\delta}1$, and Identi-T ${\beta}F1$. The number of positively stained cells were counted at high power field. Results : The infiltration of ${\gamma}{\delta}$ T cells was significantly higher in the lymph nodes from patients with tuberculous lymphadenopathy than that with reactive hyperplasia ($16.3{\pm}10.3%$ vs. $1.7{\pm}1.5%$). Conclusion : These results suggest that ${\gamma}{\delta}$) T cells may play a role in the defense against M. tuberculosis infection, especially in the regional sites of infection.

• Journal of Bio-Environment Control
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• v.23 no.1
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• pp.1-10
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• 2014

This study analyzed the efficiency and uniformity by measuring the temperature change depending on the position in the chamber with the use of QRD (quadratic residue diffusor) microwave capable of inducing even sterilization by changing wavelength phase difference and enhancing the effect on low power. The results are summarized as follows: When irradiating 7 kW of QRD microwave, the highest efficiency was obtained at 35 cm height and in the center of the chamber. When irradiating 5 kW of QRD microwave, high efficiency was obtained on the sides of the chamber. When irradiating 3 kW of QRD microwave to Magnetrons 1, 2 and 3, the temperature uniformity according to the position of the bars was similar in the position of Bar 1 and 2. When irradiating 3 kW of QRD microwave to Magnetrons 3, 4 and 5, the temperature increased by approximately 10 to 20% in Bar 3. When irradiating 5, 7 and 9 kW of magnetron, the average temperature during the irradiation time increased in a similar form independently of the position of the bars. On the other hand, the efficiency of the chamber's proper internal volume was not necessarily proportional to the irradiation dose. When irradiating 3 kW of magnetron for 60 120 and 180 seconds, the temperature increased by approximately 5 to 10 at the edge of the chamber according to the irradiation position of magnetron. The temperature distribution for each position in the horizontal plane was relatively uniform, and the temperature had a tendency to slightly increase at the edge. When irradiating 5, 7 and 9 kW of magnetron, the temperature relatively evenly increased independently of the position of the bars. It was thought necessary to increase the irradiation dose by approximately 10 to 20% by considering the difference in temperature rise according to the position of magnetron.