• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.573-579
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• 2004

Electroflotation, which is used as an alternative to sedimentation, is a separation treatment process that uses small bubbles to remove low-density particulates. Making allowances for recent collision efficiency diagram based on trajectory analysis, it is necessary to tailor zeta potential of bubbles that collide with negatively charged particles. In this paper, the study was performed to investigate the effects of magnesium and aluminium ions on zeta potential of bubbles. And, it was studied to find out factors which could affect the positively charged bubbles. Consequently, zeta potential of bubbles increased both with higher concentration of metal ions and in the acidic pH value. And, a probable principle that explained the procedure of charge reversal could be a combined mechanism with both specific adsorption of hydroxylated species and laying down of hydroxide precipitate. It also depended on the metal ion concentration in the solution to display its capacity to control the bubble surface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.722-725
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• 2014

The spatial focusing of time reversal Lamb waves on a plate has attracted considerable attention for identifying the location of an input source. This study investigates the spatial focusing performance on a plate with respect to the number of piezoelectric (PZT) sensors for varying locations of input sources. In particular, a small number of PZT sensors produce spatial focusing through the virtual sensor effect due to reflection of Lamb waves at plate edges. The spatial focusing performance with respect to the number of PZT sensors is quantified in terms of signal to noise ratio through numerical simulation and its implication is discussed.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2008.10a
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• pp.520-524
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• 2008

This research verifies the phenomenon of which the Momentum and Reversal effect of stock price would depend on the subject of investment in the point of view of the Behavior Finance hypothesis. For the experiment, this paper uses the KOSPI200 daily data and Net Investment Flow from Jan. 1999 to Dec. 2006. And we analyze the marginal profit and loss with foreigners, individual investors, and institutions. We verify the response of the subjects of investment based on the CAR for 3 days after more than 3 percent rising or drop. We also verify the response with respect to the ascending and descending trend based on the profit trend and subjects' behaviors a week before the drop.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.162-166
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• 2003

In combined forward-backward extrusion with controlled forward speed by a counter punch, accurate parts with forward rod can be formed. As an extension of this method, reverse extrusion is proposed, in which the extruded forward rod is pushed back while the main punch is kept at the final position after the forward-backward extrusion process. The experiment is carried out using lead as a model material. With the reverse extrusion method, longer forward rods can be formed without under-filling defect than that by combined extrusion with controlling extrusion speed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.715-722
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• 2012

A structural health monitoring (SHM) technique for locating impact position in a composite plate is presented in this paper. The technique employs a single sensor and spatial focusing properties of time reversal (TR) and inverse filtering (IF). We first examine the focusing effect of back-propagated signal at the impact position and its surroundings through simulation. Impact experiments are then carried out and the localization images are found using the TR and IF signal processing, respectively. Both techniques provide accurate impact location results. Compared to existing techniques for locating impact or acoustic emission source, the proposed methods have the benefits of using a single sensor and not requiring knowledge of material properties and geometry of structures. Furthermore, it does not depend on a particular mode of dispersive Lamb waves that is frequently used in the SHM of plate-like structures.

• Journal of Magnetics
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• v.5 no.1
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• pp.4-8
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• 2000

Local coercivity variation of Co/Pd nanomultilayers has been investigated by measuring the polar Kerr hysteresis loops of local areas of submicron size using a magnetooptic Kerr microscope system. Interestingly, the local coercivity distribution is very sensitive to an increase in the number of repeats: the $(2-{\AA}\;Co/ll-{\AA} Pd)_10$ sample showed a smooth variation of the local coercivity, while $(2-{\AA}\;Co/ll-{\AA} Pd)_18$ showed a large fluctuation. From micromagnetic considerations based on a thermally activated relaxation odel, we have found that this local coercivity variation has a crucial effect on the contrasting magnetization reversal behavior observed in those samples: dominant wall-motion far the former sample and dominant nucleation for the latter one.

• Proceedings of the Korean Magnestics Society Conference
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• 2001.04a
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• pp.108-109
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• 2001

• The Journal of Asian Finance, Economics and Business
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• v.5 no.4
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• pp.21-34
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• 2018

The study tests the Fama and French three-factor model by using the newly created Islamic equity style indices. Based on a dataset from May 2006 to April 2011, the three-factor model is tested based on returns of Islamic unit trust funds using the Generalized Method of Moments (GMM) methodology. The sample period is also divided between periods before and after the Global Financial Crisis in August 2008 to test for robustness, and the Bai and Perron (2003) multiple structural break test was used to determine the structural break in the series. The analysis shows that the Fama and French model is valid for Islamic unit trust funds before and after the collapse of Lehman Brothers. The result further indicates the reversal of size effect. As for trading strategies, value funds outperform growth funds by annualized 3.13 percent for the full period. During pre-crisis period, value funds perform better than growth funds while in post-crisis, size factor yields better return than other strategies. As policy suggestion, fund managers need to be aware of the reversal of size effect, and they need to ensure a more transparent stock selection process so that investors can make an informed decision in their asset allocation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.347-356
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• 2006

In this paper, practical nonlinear inelastic analysis method of 3-dimensional steel structures accounting for gradual yielding with fibers on a section is developed. Geometric nonlinearities of member(p-$\delta$) and frame(p-$\Delta$) are accounted for by using stability functions. Residual stresses are considered by assigning initial stresses to the fiber on the section. The elastic core in a section is investigated at every loading step to determine the axial and bending stiffness reduction. The strain reversal effect is captured by investigating the stress change of each fiber. The proposed analysis proves to be useful in applying for practical analysis and design of three-dimensional steel frames.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.251-260
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• 1995

It has been reported that Co-based amorphous ferromagnetic alloys annealed in a small magnetic field develop a reproducible, asymmetric hysteresis loop. If the direction of the field during annealing is regarded as +, the magnetization reversal from - to + is smooth and reversible, with its slope determined by the demagnetizing field of the sample. This phenomenon is called the asymmetric magnetization reversal (AMR). The shape of the hyster-esis loop depends sensitively on the condition during the anneal and the alloy composition. Here, we report on the effect of the annealing temperature and time on AMR in a zero magnetostrictive ferromagnetic amorphous alloy. The AMR effect develops in a very short time at a reasonably high temperature, but is stabilized by annealing for a prolonged time.