• Computers and Concrete
• /
• v.33 no.2
• /
• pp.205-216
• /
• 2024

Self-Curing Self Compacting Concrete (SCSCC), is a special concrete in contemporary construction practice aimed at enhancing the performance of structural concrete. Its primary function is to ensure a sufficient moisture supply that facilitates hydration along with flow, particularly in the context of high-rise buildings and tall structures. This innovative concrete addresses the challenges of maintaining adequate curing conditions in large-scale projects, maintaining requisite workability, contributing to the overall durability and longevity of concrete structures. For implementing such a versatile material in construction, it is imperative to understand the stress-strain (S-S) behaviour. The primary aim of this study is to develop the S-S curves for TCSCSCC and compare through experimental results. Finite element (FE) analysis based ATENA-GiD was employed for the numerical simulation and develop the analytical stress-strain curves by introducing parameters viz., grade of concrete, tie diameter, tie spacing and yield strength. The stress ratio and the strain ratios are evaluated and compared with experimental values. The mean error is 1.2% with respect to stresses and 2.2% in case of strain. Finally, the stress block parameters for tie confined SCSCC are evaluated and equations are proposed for the same in terms of confinement index.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.2
• /
• pp.91-101
• /
• 2006

Lately, massive concrete structures are increasingly built. In such massive structures, the heat of hydration of mass concrete causes thermal cracks. To avoid thermal crack, methods widely acceptable for practical use are pre-cooling, pipe cooling and control of placing height. Thermal stress analysis is performed to find the way of controlling the thermal crack of pier footing mat in this paper. The footing mat model for the analysis is $12m{\times}14m$area and 3m height. The analysis results are compared with method of control of lift height and method of pipe cooling. The analysis results show that thermal crack can be removed by method of placing control and pipe cooling at footing mat placed on the ground.

• Korean Journal of Environmental Agriculture
• /
• v.23 no.2
• /
• pp.111-116
• /
• 2004

Salt occlusion in Zeolite is a unique phenomenon that takes place only when the salt size is similar to the window size of host zeolite. $KCIO_3$-occluded Zeolite, as an environment-friendly oxidant, has a high potential for effective removal of various organic pollutants. This study was carried to investigate the characteristics and the removal kinetics of fungicide chlorothalonil by zeolite-$KCIO_3$ complex. About 10% of $KCIO_3$ was occluded in zeolite pores synthesized by salt-thermal method from fly ash, although the occlusion amount was relatively less compared to that of nitrate salts. By occlusion with $KCIO_3$, no remarkable changes were found in X-ray diffraction patterns of cancrinite, whereas some decrease of overall peak intensities was found with those of sodalite. Different releasing kinetics of $CIO_3^-$ ion were observed in distilled water and soil solution from zeolite-$KCIO_3$ complex. Two reactions, hydration and diffusion, seem to be related with the release of $KCIO_3$. Therefore, the release isotherm of $CIO_3^-$ ion well fitted to the power function model which indicate the release was made by hydration and diffusion. The removal of chlorothalonil by zeolite and $KCIO_3$ reached at reaction equilibrium within 6 hours by 18% and 47% respectively. However, the chlorothalonil removal by the zeolite-$KCIO_3$ complex increased slowly and steadily up to 92% in 96 hours. These findings suggested that zeolite-$KCIO_3$ complex could be applied for effective removal of organic contaminants in the soil and aqueous environment.

• Journal of Veterinary Clinics
• /
• v.31 no.3
• /
• pp.180-193
• /
• 2014

Allergic contact dermatitis (ACD) is an inflammatory skin disease and regarded as a prototype of T-cell mediated delayed-type hypersensitivity reactions. Aroma Oil Complex (AOC) is composed of lavender true oil, chamomile roman oil and tea tree oil. This study was performed to assess the effects of AOC in a canine model of ACD. ACD was induced on the back of dogs induced by sensitization and repeated application by 2,4-dinitro-1-chlorobenzene (DNCB). Topical treatment of AOC was applied once a day for 8 days and skin biophysical parameters including transepidermal water loss (TEWL), skin hydration, skin thickness and erythema index, were measured every two days during experimental periods. Histopathology and immunohistochemistry were performed to evaluate the anti-inflammatory effect. In skin biophysical parameters, TEWL, skin hydration, skin thickness and erythema index were significantly increased, with a maximum increase appeared on day 2 (p<0.05). After the completion of AOC treatment, skin biophysical parameters were significantly reached those of baseline in a time-dependent manner (p<0.05). In histopathology, marked increases of epidermal thicknesses were induced after DNCB challenge with numerous inflammatory cell infiltrations and edematous changes, decreases of connective tissue occupied regions in dermis. In addition, marked increases of cytokine - tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) and interferon-${\gamma}$ (IFN-${\gamma}$)-immunoreactivities in the dermis and of apoptotic markers - caspase-3 and PARP-immunoreactivities in the epidermis were observed in DNCB control as compared with intact control, respectively (p<0.01). The decrease of infiltrated inflammatory cells and related decreases of pro-inflammatory cytokine immunoreactivities were observed in AOC treated skin (p<0.01). Based on these findings, AOC may have anti-inflammatory and alleviatory effects in the allergic contact dermatitis.

• Investigative Magnetic Resonance Imaging
• /
• v.3 no.2
• /
• pp.159-166
• /
• 1999

Purpose : To evaluate the effect of rotational correlation time (${\tau}_R$) and the possible related changes of other parameters, ${\tau}_M,{\;}{\tau}_S,{\;}and{\;}(\tau}_V$ of gadolinium (Gd) chelate on T1 relaxation enhancement in two pool model. Materials and Methods : The NMRD (Nuclear Magnetic Relaxation Dispersion) profiles were simulated from 0.02 MHz to 800 MHz proton Larmor frequency for different values of rotational correlation times based on Solomon-Bloembergen equation for inner-sphere relaxation enhancement. To include both unbound pool (pool A) and bound pool (pool B), the relaxivity was divided by contribution from unbound pool and bound pool. The rotational correlation time for pool A was fixed at the value of 0.1 ns, which is a typical value for low molecular weight complexes such as Gd-DTPA in solution and ${\tau}_R$ for pool B was changed from 0.1 ns to 20 ns to allow the slower rotation by binding to macromolecule. The fractional factor of was also adjusted from 0 to 1.0 to simulate different binding ratios to macromolecule. Since the binding of Gd-chelate to macromolecule cab alter the electronic environment of Gd ion and also the degree of bulk water access to hydration site of Gd-chelate, the effects of these parameters were also included. Results : The result shows that low field profiles, ranged from 0.02 to 40 MHz, and dominated by contribution from bound pool, which is bound to macromolecule regardless of binding ratios. In addition, as more Gd-chelate bound to macromolecule, sharp increase of relaxivity at higher field occurs. The NMRD profiles for different values of ${\tau}_S$ show the enormous increase of low field profile whereas relaxivity at high field is not affected by ${\tau}_S$. On the other hand, the change in ${\tau}$V does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The results shows a fluences on both inflection field and the maximum relaxivity value. The results shows a parabolic dependence of relaxivity on ${\tau}_M$. Conclusion : Binding of Gd-chelate to a macromolecule causes slower rotational tumbling of Gd-chelate and would result in relaxation enhancement, especially in clinical imaging field. However, binding to macromolecule can change water enchange rate (${\tau}_M$) and electronic relaxation ($T_le$) vis structural deformation of electron environment and the access of bulk water to hydration site of metal-chelate. The clinical utilities of Gd-chelate bound to macromolecule are the less dose requirement, the tissue specificity, and the better perfusion and intravascular agents.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.6
• /
• pp.505-512
• /
• 2016

Even though high performance concrete was developed according to the trend of bigger and higher of reinforced concrete building, the rheological evaluations such as viscosity, yield stress are not enough to use as input data to accomplish the numerical analysis for the construction design. So there are many problems in the harden concrete such as poor compaction, rock pocket and crack, etc. in the field. In this study, consistency curves were measured by the viscometer as hydration reaction time passed. At the same time the slump flow test and Vicat setting test were carried out for comparing with the results of rheological properties. The fluidity of the W/B 30% decreased as the increase of replacement ratio of blast furnace slag. But in case of W/B 40%, the replacement ration did not significantly influenced to the slump flow value with the passage of hydration time. By the replacement of blast furnace slag to cement, initial setting was delayed and the time gap between initial and final setting became shorten. Through the regression analysis using Bingham model, there are a sudden changes of viscosity and yield stress around initial setting in case of low W/B 30%. The increase of workability by the change of free water in cement paste was offset by the coating effect of impermeable layer in case of W/B 40%.

• Journal of the Korea Concrete Institute
• /
• v.22 no.3
• /
• pp.427-435
• /
• 2010

One of the most vulnerable properties in concrete is tensile cracking, which usually happens at early ages due to hydration heat and shrinkage. In order to accurately predict the early age cracking, it needs to find out how stress-crack opening relation is varying over time. In this study, inverse analyses were performed with the existing experimental data for wedge-splitting tests, and the parameters of the softening curve for the stress-crack opening relation were determined from the best fits of the measured load-CMOD curves. Based on the optimized softening curve, variation of fracture energy over time was first examined, and a model for the stress-crack opening relation at early ages was suggested considering the found feature of the fracture energy. The model was verified by comparisons of the peak loads, CMODs at peak loads, and fracture energies obtained from the experiments and the inverse analysis.

• Biomolecules & Therapeutics
• /
• v.28 no.6
• /
• pp.542-548
• /
• 2020

Naturally derived diosmetin and its glycoside diosmin are known to be effective in treating inflammatory disease. This study was performed to determine whether diosmin and diosmetin have the effect of improving atopic dermatitis in a 2,4-dinitrochlorobenzen (DNCB)-induced atopic dermatitis (AD) model. DNCB was used to establish AD model in hairless mice. Skin moisture, serum immunoglobulin E (IgE), interleukin 4 (IL-4), and histological analysis were performed to measure the effectiveness of diosmin and diosmetine to improve AD. IL-4 levels were also measured in RBL-2H3 cells. Administration of diosmetin or diosmin orally inhibited the progress of DNCB-induced AD-like lesions in murine models by inhibiting transdermal water loss (TEWL) and increasing skin hydration. Diosmetin or diosmin treatment also reduced IgE and IL-4 levels in AD-induced hairless mouse serum samples. However, in the in vitro assay, only diosmetin, not diosmin, reduced the expression level of IL-4 mRNA in RBL-2H3 cells. Diosmin and diosmetine alleviated the altered epidermal thickness and immune cell infiltration in AD. Diosmin is considered effective in the cure of AD and skin inflammatory diseases by being converted into diosmetin in the body by pharmacokinetic metabolism. Thus, oral administration of diosmetin and diosmin might be a useful agent for the treatment of AD and cutaneous inflammatory diseases.

• Polymer(Korea)
• /
• v.33 no.5
• /
• pp.485-489
• /
• 2009

The temperature dependence of the structure of micelles formed by a deuterated polystyrene-poly(ethylene oxide) diblock copolymer (dPS-PEO) in heavy water were investigated with small-angle neutron scattering (SANS). SANS data were analyzed using the hard-sphere structure factor in combination with the form factor of a core-shell model. The micelle aggregation number and corona radius were obtained from the fits to the SANS data. The micelle aggregation numbers varied with temperature from 229 at $25^{\circ}C$ to 240 at $45^{\circ}C$, with a corresponding increase in the core radius. However, the shell thickness of micelles decreased with increasing temperature from 6.2 to 5.8 nm. These structural changes of micelles might be ascribed to the decrease in the hydration volume per hydrophilic group in the corona because of the increase in hydrophobicity of the PEO block with increasing temperature.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.10 no.1
• /
• pp.15-22
• /
• 2010

Chloride-induced corrosion of steel bars in concrete exposed to marine environments has become one of the major causes of deterioration in many important facilities made of reinforced concrete. A study on chloride penetration in concrete has developed through long period exposure test along seawater, assesment of chloride ion diffusion by electrochemical techniques and so on. However, reasonable and exclusive chloride penetration model considering concrete material properties with mixture, degree of hydration, binding capacity has not been established. Therefore, in this paper, chloride penetration analysis of non-steady state is accomplished with material properties of concrete. Comparing with the results of analysis and chloride ponding test, we could accept the effect of binding capacity on chloride penetration in concrete and these results could be applied to a service life prediction of R.C. structures submerged in seawater. Therefore, there are 20~40% differences of service life to SHRP prediction.