• Computational Structural Engineering
• /
• v.8 no.3
• /
• pp.113-122
• /
• 1995

The purpose of this study is to evaluate performance and safety of structures designed according to current seismic code or provisions (e.g., Uniform Building Code(UBC), NEHRP provisions, etc.) during lifetime of structures. The performance is represented in terns of reliability in this paper. To perform reliability analyses, a large number of time history response analyses for a given structure are usually required. In this study, to perform reliability analyses ground motions are generated based on nonstationary random process and structures are designed based on UBC. In this paper, responses of structures under a given earthquake is evaluated using dynamic nonlinear time history analyses and also an equivalent nonlinear system (ENS) with response scaling factors. The ENS system is described in the companion paper. Therefore, this paper evaluates the seismic performance of structures and also verify the accuracy of ENS.

• Macromolecular Research
• /
• v.17 no.2
• /
• pp.99-103
• /
• 2009

We evaluated the efficacy of pH-sensitive micelles, formed by methoxy poly(ethylene glycol)-b-poly($\beta$)-amino ester) (PEG-PAE), as carriers for paclitaxel (PIX), a drug currently used to treat various cancers. PTX was successful encapsulated by a film hydration method. Micelles encapsulated more than 70% of the PTX and the size of the PTX-encapsulated micelles (PTX-PM) was less than 150 nm. In vitro experiments indicated that the micelles were unstable below pH 6.5. After encapsulation of PTX within the micelles, dynamic light scattering (DLS) studies indicated that low pH had a similar demicellization effect. An in vitro release study indicated that PTX was slowly released at pH 7.4 (normal body conditions) but rapidly released under weakly acidic conditions (pH 6.0). We demonstrated the safety of micelles from in vitro cytotoxicity tests on HeLa cells and the in vivo anti-tumor activity of PTX-PM in B16F 10 tumor-bearing mice. We concluded that these pH-sensitive micelles have potential as carriers for anti-cancer drugs.

• Korean journal of food and cookery science
• /
• v.33 no.3
• /
• pp.300-306
• /
• 2017

Purpose: This study aimed to prepare sea tangle vinegar and test its applicability as a vinegar-based functional salad dressing in terms of physicochemical properties. Methods: Sea tangle vinegar was prepared by mixing sea tangle with sugar and vinegar and fermenting the mixture at room temperature for 3 months. The resulting sea tangle vinegar was examined for its physicochemical properties and antioxidant activity with brewed vinegar and persimmon vinegar as controls. Results: The sea tangle vinegar showed significantly higher viscosity than control vinegars, and shear thinning behavior that is typical for salad dressing containing polymers. In addition, storage modulus (G′) of sea tangle vinegar was relatively high in dynamic viscosity measurement while that of control vinegars remained negligible. Together with the high soluble solids content of sea tangle vinegar, rheological behavior indicates that sea tangle vinegar had soluble polysaccharides extracted from sea tangle, consequently leading to an increase in viscosity. Titratable acidity (TA) and pH were 2.52% and 3.58, respectively, which satisfies the TA and pH requirements for microbiological safety of a salad dressing. Absorbance at 285 nm and Folin Ciocalteu's reagent method revealed that sea tangle vinegar contained antioxidative phenolic compounds. Conclusion: This study demonstrates that sea tangle vinegar could be potentially developed as a vinegar-based functional salad dressing when combined with sensory evaluation in the future.

• Journal of Nuclear Fuel Cycle and Waste Technology
• /
• v.1 no.1
• /
• pp.65-73
• /
• 2013

Temperature-dependent hydrolysis behaviors of aqueous U(VI) species were investigated with time-resolved laser fluorescence spectroscopy (TRLFS) in the temperature range from 15 to $75^{\circ}C$. The formation of four different U(VI) hydrolysis species was measured at pHs from 1 to 7. The predominant presence of $UO{_2}^{2+}$, $(UO_2)_2(OH){_2}^{2+}$, $(UO_2)_3(OH){_5}^+$, and $(UO_2)_3(OH){_7}^-$ species were identified based on the spectroscopic properties such as fluorescence wavelengths and fluorescence lifetimes. With an increasing temperature, a remarkable decrement in the fluorescence lifetime for all U(VI) hydrolysis species was observed, representing the dynamic quenching behavior. Furthermore, the increase in the fluorescence intensity of the further hydrolyzed U(VI) species was clearly observed at an elevated temperature, showing stronger hydrolysis reactions with increasing temperatures. The formation constants of the U(VI) hydrolysis species were calculated to be $log\;K{^0}_{2,2}=-4.0{\pm}0.6$ for $(UO_2)_2(OH){_2}^{2+}$, $log\;K{^0}_{3,5}=-15.0{\pm}0.3$ for $(UO_2)_3(OH){_5}^+$, and $log\;K{^0}_{3,7}=-27.7{\pm}0.7$ for $(UO_2)_3(OH){_7}^-$ at $25^{\circ}C$ and I = 0 M. The specific ion interaction theory (SIT) was applied for the extrapolation of the formation constants to infinitely diluted solution. The results of temperature-dependent hydrolysis behavior in terms of the U(VI) fluorescence were compared and validated with those obtained using computational methods (DQUANT and constant enthalpy equation). Both results matched well with each other. The reaction enthalpies and entropies that are vital for the computational methods were determined by a combination of the van't Hoff equation and the Gibbs free energy equation. The temperature-dependent hydrolysis reaction of the U(VI) species indicates the transition of a major U(VI) species by means of geothermal gradient and decay heat from the radioactive isotopes, representing the necessity of deeper consideration in the safety assessment of geologic repository.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2001.05a
• /
• pp.119-126
• /
• 2001

The potential pollution problems resulting from tanker collision necessitate the requirement for an effective structural design and the development of relevant safety regulation. During a few decades, the great effort has been made by International Maritime Organization and the Administration, etc, to reduce oil spillage from collision accidents. However there is still a need for investigation in the light of structural evaluation method for the experiments and rational analysis, and design development for an operational purpose of ships. This study is aimed at investigating a complicated structural response of bow structures of oil carriers for assessing the energy dissipation and crushing mechanics of striking vessel through a methodology of the numerical analysts for the various models and its design changes. Through this study an optimal bow construction absorbing great portion of kinetic energy in the least penetration depth prior to reach to the cargo area and an effective location of collision bulkhead are investigated. In order to obtain a rational results in this study, three stages of response analysis procedures are performed as follows; 1). 16 simplified ship models are used to investigate the structural response against bow collision with variation of primary and secondary members. Mass and speed are also varied in two conditions. 2). 21 models conisted of 5 size of full scaled oil carriers are used to perform the collision simulation with the various sizes and deadweight delivered in a recent which are complied with SOLAS and MARPOL. 3). 36 models of 100k oil carrier are used to investigate the structural response and its influence to the collision bulkhead against bow collision in variation with location of collision bulkhead, primary mombers, framing system and colliding conditions, etc.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.2
• /
• pp.113-120
• /
• 2014

This paper showed the behavior of the material four members under blast load, and are trying to demonstrate the effectiveness of the prestress. The prestressed concrete structures are on the rise, but there is little research in this regard explosion. Concrete panels, Reinforced concrete panels, the prestressed concrete panels, and the prestressed reinforced concrete panels was set variables. TNT 500 kg was an explosion in the distance 3m. Analysis, concrete and reinforced concrete members after an explosion occurred continuously deformed, but the including prestressed panel deformation occurs only at the beginning of the explosion were able to see the results. That is, the including prestressed member is prestressed against blast load cracking and destruction can be seen that control.

• Smart Structures and Systems
• /
• v.17 no.6
• /
• pp.917-933
• /
• 2016

In a prestressed concrete bridge, the magnitude of the prestress force (PF) decreases with time. This unexpected loss can cause failure of a bridge which makes prestress force identification (PFI) critical to evaluate bridge safety. However, it has been difficult to identify the PF non-destructively. Although some research has shown the feasibility of vibration based methods in PFI, the requirement of having a determinate exciting force in these methods hinders applications onto in-service bridges. Ideally, it will be efficient if the normal traffic could be treated as an excitation, but the load caused by vehicles is difficult to measure. Hence it prompts the need to investigate whether PF and moving load could be identified together. This paper presents a synergic identification method to determine PF and moving load applied on a simply supported prestressed concrete beam via the dynamic responses caused by this unknown moving load. This method consists of three parts: (i) the PF is transformed into an external pseudo-load localized in each beam element via virtual distortion method (VDM); (ii) then these pseudo-loads are identified simultaneously with the moving load via Duhamel Integral; (iii) the time consuming problem during the inversion of Duhamel Integral is overcome by the load-shape function (LSF). The method is examined against different cases of PFs, vehicle speeds and noise levels by means of simulations. Results show that this method attains a good degree of accuracy and efficiency, as well as robustness to noise.

• Geomechanics and Engineering
• /
• v.9 no.5
• /
• pp.645-667
• /
• 2015

Single treatment and staged treatments in vertical wells are widely applied in sandstone and mudstone thin interbedded (SMTI) reservoir to stimulate the reservoir. The keys and difficulties of stimulating this category of formations are to avoid hydraulic fracture propagating through the interface between shale and sand as well as control the fracture height. In this paper, the cohesive zone method was utilized to build the 3-dimensional fracture dynamic propagation model in shale and sand interbedded formation based on the cohesive damage element. Staged treatments and single treatment were simulated by single fracture propagation model and double fractures propagation model respectively. Study on the changes of fracture vicinity stress field during propagation is to compare and analyze the parameters which influence the interfacial induced stresses between two different fracturing methods. As a result, we can prejudge how difficult it is that the fracture propagates along its height direction. The induced stress increases as the pumping rate increasing and it changes as a parabolic function of the fluid viscosity. The optimized pump rate is $4.8m^3/min$ and fluid viscosity is $0.1Pa{\cdot}s$ to avoid the over extending of hydraulic fracture in height direction. The simulation outcomes were applied in the field to optimize the treatment parameters and the staged treatments was suggested to get a better production than single treatment.

• Journal of the Korean Society for Railway
• /
• v.20 no.5
• /
• pp.577-587
• /
• 2017

In the design process of dynamic characteristics of a railway vehicle, demand for analysis, testing and estimation methods of running stability are increasing as railway vehicle speed is increasing. Critical speed tests and estimation have been carried out using computer simulation or special test facilities, like roller rigs, because real track testing at critical speed is very dangerous. This paper introduces a test and assessment method for critical speed and estimates the validity using several roller rig tests. The test results show that it is difficult to estimate the critical speed using safety and instability assessment method in UIC 518, but that there is good agreement between the reduction of the equivalent damping ratio and the critical speed.

• Journal of Institute of Control, Robotics and Systems
• /
• v.4 no.3
• /
• pp.392-399
• /
• 1998

A full-scope replica type simulator whose MCR(main control room) has the same features and operation functions as MCR of the reference power plant has been developed for a fossil power plant. This simulator was developed with the model of Poryung Fossil Power Plant #3,4 which is the standard model of the Korean fossil power plant. It is the first localized simulator for the supercritical, variable boiler pressure type fossil power plant. The simulator provides various kinds of accidents which are in normal plant operation and thus enables operators to recover or reduce possible damages. To design and develop this kind of simulator, we need to integrate high technologies such as system analysis, plant operation and system integration of mechanics, physics, computer science. CASE(Computer Aided Software Engineering) tools were used to develop the dynamic model. This simulator will greatly contribute to the improvement of the safety and efficiency of the fossil power plant by implementing operator training. In this paper, the outline of software and hardware configuration and characteristics of the simulator are described, and the results of 30%, 50%, 75%, 100% load operation test will be discussed.