• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.638-643
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• 2013

Chaos communication system has a sensitive characteristic to initial conditions, because completely another signal is generated when initial condition of chaos equation is changed subtly. Also, chaos communication systems have the characteristics of non-periodic, non-predictability, the broadband signal, such as ease of implementation. Due to these characteristics, security of chaos communication system generally is evaluated better than other systems. However, BER(Bit Error Rate) performance is evaluated worse than other digital system, because existing chaos communication system's transmitter and receiver are strong influence by interference signal and noise. So, research to improve the BER performance of the chaotic communication system is performed continuously. In this paper, We will propose a new CDSK(Correlation Delay Shift Keying) receiver for BER performance improvement. After we compare to the performance of existing CDSK receiver and proposed CDSK receiver, BER performance of proposed CDSK receiver evaluate. Also, when using the new CDSK receiver, we evaluate the BER performance according to the spreading factors and find an optimum spreading factor. If chaos communication system use a new CDSK receiver, BER performance is improved than existing CDSK receiver. Also, if spreading factor's value is increased, BER performance is improved, because it is not nearly affected by interference signal and noise.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.916-922
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• 1986

This paper presents the preliminary results of an experimental study on surface crack growth under fatigue loadings. The objective of this paper is to assess the effect of the initial crack size on crack propagation behaviors. Transparent PMMA plate speciments with shallow circular arc notch were used. Crack growth behaviors were observed and measured in two directions by travelling microscopes. The fatigue crack initiated at the deepest part on the initial arc shaped notch and then propagated to depth direction as well as spreading gradually along the notch tip. A considerable number of cycles was needed until the depth crack spreaded to the surface notch tip. When the fatigue crack reached the surface notch tip the crack front became an approximate semi-ellipse, primary semi-elliptical crack. Test results suggest that the relationships between fatigue crack growth rate and stress intensity factor range in both directions can be expressed by power law (Paris) and that relationship in width direction depends upon the crack ratios a$_{1}$/b$_{1}$, of the primary semi-elliptical crack. The relationship between the nondimensional crack lengths in both directions can be represented as the formula: (a/t)$^{n}$ =B(2b/W+A) where n and A are constants and B is seems to be depended upon the crack ratio a$_{1}$/b$_{1}$.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.36-48
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• 2021

As the material aging of nuclear power plants has been progressing in domestic and overseas, crack growth becomes one of the most important issues. In this respect, the crack growth assessment has been considered an essential part of structural integrity. The crack growth assessment for nuclear power plants has been generally performed based on ASME B&PV Code, Sec. XI but the idealization of crack shape and the conservative solutions of stress intensity factor (SIF) are used. Although finite element analysis (FEA) based on iterative crack growth analysis is considered as an alternative method to simulate crack growth, there are yet no guidelines to model the crack-tip spider-web mesh for such analysis. In this study, effects of various meshing factors on FE SIF calculation are systematically examined. Based on FEA results, proper criteria for spider-web mesh in crack-tip are suggested. The validation of SIF calculation method through mapping initial stress field is investigated to consider initial residual stress on crack growth. The iterative crack-tip modeling program to simulate crack growth is developed using the proposed criteria for spider-web mesh design. The SIF results from the developed program are validated by comparing with those from technical reports of other institutes.

• Journal of Microbiology and Biotechnology
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• v.30 no.7
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• pp.1067-1071
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• 2020

To understand the formation of initial gut microbiota, three initial fecal samples were collected from two groups of two breast milk-fed (BM1) and seven formula milk-fed (FM1) infants, and the compositional changes in gut microbiota were determined using metagenomics. Compositional change analysis during week one showed that Bifidobacterium increased from the first to the third fecal samples in the BM1 group (1.3% to 35.1%), while Klebsiella and Serratia were detected in the third fecal sample of the FM1 group (4.4% and 34.2%, respectively), suggesting the beneficial effect of breast milk intake. To further understand the compositional changes during progression from infancy to childhood (i.e., from three weeks to five years of age), additional fecal samples were collected from four groups of two breast milk-fed infants (BM2), one formula milk-fed toddler (FM2), three weaning food-fed toddlers (WF), and three solid food-fed children (SF). Subsequent compositional change analysis and principal coordinates analysis (PCoA) revealed that the composition of the gut microbiota changed from an infant-like composition to an adult-like one in conjunction with dietary changes. Interestingly, overall gut microbiota composition analyses during the period of progression from infancy to childhood suggested increasing complexity of gut microbiota as well as emergence of a new species of bacteria capable of digesting complex carbohydrates in WF and SF groups, substantiating that diet type is a key factor in determining the composition of gut microbiota. Consequently, this study may be useful as a guide to understanding the development of initial gut microbiota based on diet.

• Journal of Korean Neurosurgical Society
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• v.55 no.1
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• pp.1-4
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• 2014

Objective : The case fatality rate of nonlesional intracerebral hemorrhage (n-ICH) was high and not changed. Knowing the causes is important to their prevention; however, the reasons have not been studied. The aims of this study were to determine the cause of death, to improve the clinical outcomes. Methods : We retrospectively analyzed consecutive cases of nonlesional intracerebral hemorrhage in a prospective stroke registry from January 2010 to December 2010. Results : Among 174 patients ($61.83{\pm}13.36$, 28-90 years), 29 patients (16.7%) died during hospitalization. Most common cause of death was initial neurological damage (41.4%, 12/29). Seventeen patients who survived the initial damage may then develop various potentially fatal complications. Except for death due to the initial neurological sequelae, death associated with immobilization (such as pneumonia or thromboembolic complication) was the most common in eight cases (8/17, 47.1%). However, death due to early rebleeding was not common and occurred in only 2 cases (2/17, 11.8%). Age, initial Glasgow Coma Scale, and diabetes mellitus were statistically significant factors influencing mortality (p<0.05). Conclusion : Mortality of n-ICH is still high. Initial neurological damage is the most important factor; however, non-neurological medical complications are a large part of case fatality. Most cases of death of patients who survived from the first bleeding were due to complications of immobilization. These findings have implications for clinical practice and planning of clinical trials. In addition, future conduct of a randomized study will be necessary in order to evaluate the benefits of early mobilization for prevention of immobilization related complications.

• Journal of Advanced Navigation Technology
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• v.19 no.5
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• pp.440-445
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• 2015

An app that users can conveniently use has been an explosive increase in the emergence of smart devices, including smart phones. However, the advent of various smart appliances operating systems, acting as an inhibitory factor to the development of the application. Accordingly, there has been a growing interest in HTML5 that can simultaneously support various platforms. HTML5 using the browser is used in the most innovative way of cross-platform. However, it does not show the complete compatibility for now. Depending on the browser of the environment, the difference between the initial load time of Web pages out. Therefore, to understand the cause of slowing down the browser-specific initial load time through the analysis of HTML5, JavaScript and CSS. Look for ways that can further improve the initial load rate.

• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.68-74
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• 2012

Investigation of the effective soil thermal conductivity($k$) is the first step in designing the ground loop heat exchanger(borehole) of a geothermal heat pump system. Another important factor is the borehole thermal resistance($R_b$). Thermal response tests offer a good method to determine the ground thermal properties for the total heat transport in the ground. The first step is measured for initial soil temperature. This is done by supplying a only pump power into a borehole heat exchanger. They need to supply into water unload heat power more than 30 minutes. In this study, the initial soil temperature was found to analysis $14.1{\sim}16.0^{\circ}C$,the ratio was 68.7% represented. In this case of $k$, was 2.1~3.0 $W/m{\cdot}k$, $R_b$ was 0.11~0.20 $m{\cdot}K/W$. In this work, it is also shown that the distribution of a soil thermal conductivity and borehole thermal resistance were on the influence of initial soil temperature. And soil thermal conductivity was related with factors of equation by linear least square method, borehole thermal resistance was on the influence of composite factors.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.6
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• pp.435-443
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• 2015

Offshore structure may be considerably vulnerable to fatigue failure while initial flaw propagates under cyclic loading, so crack propagation analysis/fracture/yield assessments about initial flaw detected by NDT are necessarily required. In this paper, case studies have been conducted by flaw assessment program using engineering criticality analysis (ECA) approach. Variables such as flaw geometry, flaw size, structure geometry, dynamic stress, static stress, toughness, crack growth rate, stress concentration factor (SCF) affected by weld are considered as analysis conditions. As a result, the safety of structure was examined during fatigue loading life. Also, critical initial flaw size was calculated by sensitivity module in the developed program. The flaw assessments analysis using ECA approach can be very useful in offshore industries owing to the increasing demand on the engineering criticality analysis of potential initial flaws.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.888-893
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• 2016

In this study, the solution plasma process was utilized with the aim of degrading synthetic dyes in water at atmospheric pressure. The experiments were conducted in a batch-type reactor consisting of a symmetric wire-wire electrode configuration with rhodamine B (RhB) as the target synthetic dye. The effects of the plasma treatment time and initial dye concentration on the RhB degradation were investigated by monitoring the change in absorbance of RhB solutions. The RhB solutions turned lighter in color and finally colorless with prolonged plasma treatment time, indicating the destruction of dye molecules. The RhB solutions were found to have degraded, following the first-order kinetic process. However, for high initial RhB concentrations, another kinetic process or factor seems to play a dominant role at the initial degradation stage. The fitted first-order rate constant decreased as the initial concentration increased. This result suggests that the degradation behavior and kinetic process of the RhB solution strongly depends on its initial concentration. The RhB degradation is considered to be due to a combination of factors, including the formation of chemically oxidative species, as well as the emission of intense UV radiation and high-energy electrons from the plasma. We believe that the solution plasma process may prove to be an effective and environment-friendly method for the degradation or remediation of synthetic dye in wastewater.

• The Korean Journal of Franchise Management
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• v.10 no.4
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• pp.7-18
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• 2019

Purpose: This study identifies the relative importance of the sub - factors of initial services and continuous services using AHP (Analytic Hierarchy Process) method, and calculates the competitive index for the detailed factors. The purpose of this paper is to propose the establishment of long - term and short - term management strategy for expansion of business of food service franchise, franchisors, long - term and win - win relationship with franchisees, and rationalization of operating system. Research design, data, and methodology: The population for the survey is 92 franchisees in 46 foreign brands and 46 domestic brands in the Seoul metropolitan area (Seoul / Gyeonggi / Incheon). The survey was conducted from July 1 to August 31, 2018 through the survey agency with a telephone interview and a surveyor's direct visit. A total of 100 questionnaires were collected, but a total of 92 parts were used for analysis except 8 parts that were considered to contain false information. Using the AHP method, relative importance and competitiveness index were calculated for the details of initial services and continuous services. Results: The results shows continuous services were significantly higher for both foreign brand franchises, domestic brand franchises, and overall than initial services, This suggests that the continuous services of the affiliated franchisors has a higher relative importance than the initial services. Among the continuous services, brand reinforcement and promotion were significantly higher for both foreign brand merchants and domestic brand franchises. This can be regarded as the most important factor in brand reinforcement and promotion when selecting a food service franchisors. Conclusions: In the Standard Terms and Conditions governed by the Fair Trade Commission, the franchisors should increase the fairness by creating manuals for supporting services, especially after opening, and regularly checking whether the supporting services have been carried out like manuals since the establishment of franchisees. In addition, the Brand Strengthening and Public Relations Committee (tentative name) jointly participated by the franchisors and franchisees for the purpose of strengthening and promoting the brand, suggesting a system for transparent and efficient execution of the brand reinforcement and promotion budget and monitoring afterwards.