• Structural Engineering and Mechanics
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• 제38권5호
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• pp.593-618
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• 2011

This paper deals with the problem of the determination of the response of a viscoelastic Bernoulli-Navier beam, which is resting on an elastic medium. Assuming uniaxial bending, the displacement of the beam axis is governed by an integro-differential equation. The compatibility of the displacements between the beam and the elastic medium is imposed through an integral equation. In general and in particular in the case of a Boussinesq medium, the solution has to be pursued numerically. On the contrary, in the case of a Winkler's medium the compatibility equation becomes a linear finite relationship, which allows finding an original analytical solution of the problem for both hereditary and aging behavior of the beam. Some numerical examples complete the paper, in which a comparison is made between the hereditary and the aging model for the creep of the beam.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2415-2418
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• 2008

Polydiacetylenes (PDAs) are very attractive chemical substances which have distinctive features of color change and fluorescence emission by thermal or chemical stress. Especially, when PDAs contact with solutions of a particular pH, such as a strong alkaline sodium hydroxide (NaOH) solution or a strong acidic hydrogen chloride (HCl) solution, PDAs change their color from non-fluorescent blue to fluorescent red. In this study, we propose a novel method to detect alkaline pH using PDAs and NaOH solutions by hydrodynamic focusing on a microfluidic chip. Preliminary results indicate that the fluorescent intensity of PDAs increases in respond to the NaOH solution concentrations. Also, the fluorescence is quenched back when the PDAs are in contact with a HCl solution. These results are useful in a microfluidic PDA sensor chip design for pH detection.

• Structural Engineering and Mechanics
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• 제34권1호
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• pp.85-95
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• 2010

In this paper, numerical solution of the singular integral equation for the multiple curved branch-cracks is investigated. If some quadrature rule is used, one difficult point in the problem is to balance the number of unknowns and equations in the solution. This difficult point was overcome by taking the following steps: (a) to place a point dislocation at the intersecting point of branches, (b) to use the curve length method to covert the integral on the curve to an integral on the real axis, (c) to use the semi-open quadrature rule in the integration. After taking these steps, the number of the unknowns is equal to the number of the resulting algebraic equations. This is a particular advantage of the suggested method. In addition, accurate results for the stress intensity factors (SIFs) at crack tips have been found in a numerical example. Finally, several numerical examples are given to illustrate the efficiency of the method presented.

• Journal of Microbiology
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• 제43권1호
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• pp.54-61
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• 2005

In this study, we attempted to determine the effects of iron-availability and the activity of the bacterial iron-uptake system (IUS) on the growth of Staphylococcus aureus in human peritoneal dialysate (HPD) solution. A streptonigrin-resistant S. aureus (SRSA) strain, isolated from S. aureus ATCC 6538, exhibited defective siderophore production, thereby resulting in ineffective uptake of iron from low iron-saturated transferrin. The growth of both strains was stimulated in HPD solution supplemented with FeCl_3 and holotransferrin, but growth was inhibited in HPD solution which had been supplemented with apotransferrin and dipyridyl. The SRSA strain grew less robustly than did its parental strain in both iron-supplemented HPD solution and regular HPD solution. These results indicate that iron-availability and siderophore-mediated IUS activity in particular, the ability to produce siderophores and thus capture iron from low iron-saturated transferrin play critical roles in the growth of S. aureus in HPD solution. Our results also indicated that the possibility of using iron chelators as therapeutic or preventive agents warrants further evaluation.

• Preventive Nutrition and Food Science
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• 제15권4호
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• pp.297-303
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• 2010

The present study compared the Maillard reaction products (MRPs) derived from aqueous and ethanolic fructoseglycine and its oligomer (dimer and trimer) solutions. The pH was lower in glycine (G) than in diglycine (DG) and triglycine (TG) in both aqueous and ethanolic solutions, but the pH difference between the DG and TG was not significant. MRPs derived from the DG had a greater absorbance at 294 and 420 nm in ethanolic solution than in an aqueous solution. In particular, the loss of sugar was higher in ethanolic solution than in aqueous solution. Enolization of fructose was observed in both aqueous and ethanolic MRP solutions; however, enolization was not observed for the G in aqueous MRP solutions. The glycine oligomer content in ethanolic MRP solutions remained higher than that in aqueous MRP solutions. Furthermore, neither diglycine nor triglycine were detected in the G aqueous or ethanolic MRP solutions, while triglycine was detected in both the DG aqueous and ethanolic MRP solutions. Absorption in the ultraviolet-visible (UV-Vis) spectra was higher with MRPs derived from the ethanolic solution than with those derived from the aqueous solution. MRPs derived from the DG in an ethanolic solution showed the highest absorption intensity.

• 한국멀티미디어학회논문지
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• 제17권10호
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• pp.1198-1204
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• 2014

Most of vaccine type security solutions detect intrusion of computer virus or malicious code. However, they almost don't have functionalities of the information leakage detection. In particular, information leakage through keylogging attact cannot be detected. In this paper, we design and implement a solution to detect the leakage of information through keylogging attact. Proposed solution detects the user-specified information in real time. To detect the leakage of user-specified information, the solution extracts the payload field from each outbound packet and compares with user-specified information. We design the solution to reduce the effect on the packet transmission delay time due to packet monitoring operation. And we design a simple user interface. By proposed solution, user can response to intrusion or information leakage immediately because he or she can perceives a leakage of information in real time.

• 제어로봇시스템학회논문지
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• 제19권7호
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• pp.633-639
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• 2013

Several estimation methods used in the range measurement based wireless localization area have individual problems. These problems may not occur according to certain application areas. However, these problems may give rise to serious problems in particular applications. In this paper, three methods, ILS (Iterative Least Squares), DS (Direct Solution), and DSRM (Difference of Squared Range Measurements) methods are considered. Problems that can occur in these methods are defined and a simple hybrid solution is presented to solve them. The ILS method is the most frequently used method in wireless localization and has local minimum problems and a large computational burden compared with closed-form solutions. The DS method requires less processing time than the ILS method. However, a solution for this method may include a complex number caused by the relations between the location of reference nodes and range measurement errors. In the near-field region of the complex solution, large estimation errors occur. In the DSRM method, large measurement errors occur when the mobile node is far from the reference nodes due to the combination of range measurement error and range data. This creates the problem of large localization errors. In this paper, these problems are defined and a hybrid localization method is presented to avoid them by integrating the DS and DSRM methods. The defined problems are confirmed and the performance of the presented method is verified by a Monte-Carlo simulation.

• 대한기계학회논문집B
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• 제21권12호
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• pp.1710-1719
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• 1997

An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated flat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form depending on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity oft the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result. A simple approximate method for estimating the effect of convection on heat transfer across the liquid film is also proposed.

• 대한수학회논문집
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• 제29권1호
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• pp.195-204
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• 2014

We consider a functional difference equation and use fixed point theory to analyze the stability of its zero solution. In particular, our study focuses on the nonlinear delay functional difference equation x(t + 1) = a(t)g(x(t - r)).

• 대한수학회보
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• 제51권4호
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• pp.1211-1216
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• 2014

In this paper, we study the structure of m-quasi Einstein manifolds when there exists another distinct solution to the (${\lambda}$, n + m)-Einstein equation. In particular, we derive sufficient conditions for the non-existence of such solutions.