• Proceedings of the Korean Geotechical Society Conference
• /
• 2004.03b
• /
• pp.173-180
• /
• 2004

In this study, a consolidometer for radially inward drainage under constant rate of strain (CRS) loading was developed. Theoretical solutions for determining the effective vertical stress and the coefficient of consolidation from the test result were also proposed. Reconstituted kaolinite samples which were consolidated up to 130 kPa were used to verify the developed consolidometer and the theory. Comparative experiments with CRS loading and incremental loading (IL) were carried out in radially in ward drainage as well as vertical and radially outward drainage. The results obtained from the developed CRS loading test agreed consistently with those of the conventional incremental loading test according to drainage directions. And the effect of drainage direction and drain diameter to consolidation characteristics was also evaluated. From the test results the applicability and the reliability of the suggested method were verified.

• Computers and Concrete
• /
• v.14 no.1
• /
• pp.1-18
• /
• 2014

The addition of steel fibers in concrete mixture is recognized as a non-conventional mass reinforcement scheme that improves the torsional, flexural, and shear behavior of structural members. However, the analysis of fiber reinforced concrete beams under combined torsion, bending, and shear is limited because of the complicated nature of the problem. Therefore, nonlinear 3D finite element analysis was conducted using the "ANSYS CivilFEM" program to investigate the behavior of fiber reinforced concrete L-beams. These beams were tested at different reinforcement schemes and loading conditions. The reinforcement case parameters were set as follows: reinforced with longitudinal reinforcement only and reinforced with steel bars and stirrups. All beams were tested under two different combined loading conditions, namely, torsion-to-shear ratio (T/V) = 545 mm (high eccentricity) and T/V = 145 mm (low eccentricity). Eight intermediate L-beams were constructed and tested in a laboratory under combined torsion, bending, and shear to validate the finite element model. Comparisons with the experimental data reveal that the program can accurately predict the behavior of L-beams under different reinforcement cases and combined loading ratios. The ANSYS model accurately predicted the loads and deformations for various types of reinforcements in L-beams and captured the concrete strains of these beams.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.41 no.7
• /
• pp.712-722
• /
• 1992

Several voltage instability/collapse problems that have occurred in the electric utility industry worldwide have gained the attention of engineers and researchers of electric power systems. This paper proposes an effective calculation scheme of the extreme loading point and nose curves(P-V curves) using modified Newton-Raphson(N-R) load flow method and the Continuation Method. This method provides detail and visual information of the power system voltage profile and operating margin ro operators and planners. In this paper, a modified load flow claculation method for ill-conditioned power systems is introduced for the purpose of seeking more precise load flow solutions and nose curves, and the Continuation Method is also used as a part of the solution algorithm for the calculation of extreme loading point and nose curves. The conventional polar coordinate based N-R load flow program is modified to avoid numerical difficulties caused by the singularity of the Jacobian matrix occuring in the vicinity of extreme loading point of heavily loaded systems. Application results of the proposed method to Klos-Kerner 11-bus system and modified IEE-30-bus system are presented to assure the usefulness of the approach.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.68.2-68.2
• /
• 2010

Dye-sensitized solar cells (DSSC) show great promise as an inexpensive alternative to conventional p-n junction solar cells. Investigations into the various factors influencing the photovoltaic efficiency have recently been intensified. The conventional absorber electrode in DSSC is composed of compacted or sintered $TiO_2$ nanopowder that carries an anchored organic dye. The absorbance of incident light in the DSC is realized by specifically engineered dye molecules placed on the semiconductor electrode surface ($TiO_2$). The dye absorbs light at wavelengths up to about 920nm, the energy of the exited state of the molecule should be about 1.35eV above the electronic ground state corresponding to the ideal band gap of a single band gap solar cell. The dye molecules ar adhered onto the nanostrutured $TiO_2$ electrode by immersing the sintered electrode into a dye solution, typically 3mM in alcohol, for a long enough period to fully impregnate the electrode. However, the concentrations of the dye is slightly changed due to the evaporation of the alcohol. The dye is more expensive than other materials in DSSC and related to the efficiency of DSSC. Therefore, the concentrations of the dye should be carefully measured. In this study, we investigated to the dye loading on fired $TiO_2$ powder as a function of temperature by the TG-DTA and the dye solution by UV-visible spectroscopy after the impregnation process. The dye loading is related to the porosity of the nanostructured $TiO_2$ electrode.

• Computers and Concrete
• /
• v.17 no.1
• /
• pp.1-27
• /
• 2016

Final construction project cost is significantly determined by construction rate. The Industrialized Building System (IBS) was promoted to enhance the importance of prefabrication technology rather than conventional methods in construction. Ensuring the stability of a building constructed by using IBS is a challenging issue. Accordingly, the connections in a prefabricated building have a basic, natural, and essential role in providing the best continuity among the members of the building. Deficiencies of conventional precast connections were observed when precast buildings experience a large induced load, such as earthquakes and other disasters. Thus, researchers aim to determine the behavior of precast concrete structure with a specific type of connection. To clarify this problem, this study investigates the capacity behavior of precast concrete panel connections for industrial buildings with a new type of precast wall-to-wall connection (i.e., U-shaped steel channel connection). This capacity behavior is compared with the capacity behavior of precast concrete panel connections for industrial buildings that used a common approach (i.e., loop connection), which is subjected to monotonic loading as in-plane and out-of-plane loading by developing a finite element model. The principal stress distribution, deformation of concrete panels and welded wire mesh (BRC) reinforcements, plastic strain trend in the concrete panels and connections, and crack propagations are investigated for the aforementioned connection. Pushover analysis revealed that loop connections have significant defects in terms of strength for in-plane and out-of-plane loads at three translational degrees of freedom compared with the U-shaped steel channel connection.

• The Journal of Advanced Prosthodontics
• /
• v.10 no.2
• /
• pp.85-92
• /
• 2018

PURPOSE. This research evaluated clinical outcomes of two types of hydroxyapatite (HA)-coated implants: OT (Osstem TS III-HA, Osstem implant Co., Busan, Korea) and ZM (Zimmer TSV-HA, Zimmer dental, Carlsbad, USA). MATERIALS AND METHODS. The research was conducted on 303 implants (89 of OT, 214 of ZM), which were placed from January 16, 2010 to December 20, 2012. The prognosis was evaluated in terms of success rates, survival rates, annual marginal bone loss, and implant stability quotients (ISQ). The samples were classified into immediate, early, conventional, and delayed groups according to the loading time. RESULTS. Overall, there were no significant differences between OT and ZM in success rates, survival rates, and annual marginal bone loss, except for the result of secondary stability. OT showed $77.83{\pm}8.23ISQ$, which was marginally higher than $76.09{\pm}6.90ISQ$ of ZM (P<.05). In terms of healing periods, only immediate loading showed statistically significant differences (P<.05). Differences between OT and ZM were observed in terms of two indices, the annual marginal bone loss ($0.17{\pm}0.58mm/year$ < $0.45{\pm}0.80mm/year$) and secondary stability ($84.36{\pm}3.80ISQ$ > $82.48{\pm}3.69ISQ$) (P<.05). OT and ZM did not have any statistically significant differences in early, conventional, and delayed loading (P>.05). CONCLUSION. OT (97.75%) and ZM (98.50%) showed relatively good outcomes in terms of survival rates. In general, OT and ZM did not show statistically significant differences in most indices (P>.05), although OT performed marginally better than ZM in the immediate loading and 1-stage surgery (P<.05).

• Journal of the Korean Electrochemical Society
• /
• v.24 no.2
• /
• pp.28-33
• /
• 2021

Many researchers have increased the loading level of electrodes to improve the energy density of secondary batteries. In this study, high-loading NCM523 (LiNi_0.5Co_0.2Mn_0.3O₂) positive electrode is manufactured using a polytetrafluoroethylene (PTFE) binder, not the conventional polyvinylidene fluoride (PVdF) binder, which has been commonly used in lithium-ion batteries. Through the kneading process using PTFE suspension, not the conventional slurry process using PVdF solution in N-methyl-2-pyrrolidinone (NMP), thick electrodes with high loading are easily manufactured. When the PTFE and PVdF-based electrodes are prepared at a loading level of 5.0 mAh/cm², respectively, the PTFE-based electrode shows better cycle performance and rate capability than those of PVdF-based electrodes. The electrode manufactured by the kneading process using a PTFE binder has high electrode porosity due to insufficient roll-press, but the porosity can be lowered by high temperature roll-press over 120℃. However, there is no significant difference in cycle performance according to the roll press temperature. In addition, the cycle performance of the high loading electrode is slightly improved by increasing the content of the conductive material. Overall, the PTFE binder can improve the performance of the high loading electrode, but additional solutions will be needed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.367-372
• /
• 2002

In these days, The base isolation system is often used to improve the seismic capacity of the structures instead of conventional techniques of strengthening the structural members. The purpose of this study is to evaluate dynamic properties and mechanical characteristics of the 10tonf-LRB(Lead-Rubber Bearing). Experimental studies were performed to obtain the hysteretic behavior, effective shear stiffness( $K_{eff}$), equivalent damping( $H_{eq}$ ), capacity of energy dissipation( $W_{D}$) of six 10tonf-LRB. Especially, in this study, the response of the LRB for high loading frequency(0.5Hz~3.0Hz) was estimated. The effective shear stiffness of the LRB decreases and the capacity of energy dissipation increases as the shear strain amplitude increases. But the shear behavior of the LRB is not affected sensitively by loading frequency.y.y.

• Journal of Energy Engineering
• /
• v.11 no.1
• /
• pp.47-58
• /
• 2002

This paper presents a new method for the evaluation of avoided generation costs. Unlike conventional load decrement method, it exactly considers forced outage rate and economic loading order of IPPs (Independent Power Producers). Therefore we can provide exact generation avoided costs of IPPs by the developed method. Because probabilistic simulation is conducted in this method, effects on the costs of IPPs are exactly considered. Also we suggest an allocation method of avoided generation costs by participation factor. In the case studies we have shown avoided generation costs considering loading order and forced out-age rate by using this method.

• Tribology and Lubricants
• /
• v.29 no.2
• /
• pp.91-97
• /
• 2013

Quantifying the nanoscale force between the atomic force microscopy (AFM) probe of a force-sensing cantilever and the sample is one of the challenges faced by AFM researchers. The normal force calibration is straightforward; however, the lateral force is complicated due to the twisting motion of the cantilever. Force measurement in a liquid environment is often needed for biological applications; however, calibrating the force of the AFM probes for those applications is more difficult owing to the limitations of conventional calibration methods. In this work, an accurate nondestructive lateral force calibration method using multiple pivot loading was proposed for liquid environment. The torque sensitivity at the location of the integrated probe was extrapolated based on accurately measured torque sensitivities across the cantilever width along a few cantilever lengths. The uncertainty of the torque sensitivity at the location of the integrated tip was about 13%, which is significantly smaller than those for other calibration methods in a liquid environment.