• Journal of Powder Materials
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• v.16 no.4
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• pp.291-295
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• 2009

The electromagnetic wave absorption sheets were fabricated by mixing of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHz$\sim$10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHz$\sim$1 GHz.

• Applied Biological Chemistry
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• v.37 no.4
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• pp.287-294
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• 1994

New 3-phenyl-1-(2-furyl)propenones, 1 and 3-phenyl-1-(2-furyl)-3-thiophenyl-propanone, 2 derivatives were synthesized, and their fungicidal activities in vitro against Botrytis cineria (BC), Valsa ceratosperma (VC), Scelerotium cepivorum (SC) and Phytophthora capsici (PC) were investigated using a generalized structure-activity relationship (SAR). The activity of 1 was superior to those of 2, and nonsubstituent, 1a and chloro group substituent, 1d of E (Syn) conformer were the most effective $(EC_{50}=10{\sim}12\;ppm)$ compound to BC. Antifungal activities were able to predict to depend essentially on the ${\beta}$ carbon and their positive charge from the results that the good correlation $(r^2=0.90)$ was observed between hydrolysis rate constant (logk) of 1 and the electronic parameter $({\sigma})$ of X-substituent on the ${\beta}-phenyl$ ring.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.3
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• pp.302-309
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• 2016

Urea-SCR system is currently regarded as promising NOx reduction technology for diesel engines. SCR system has to achieve maximal NOx conversion in combination with minimal $NH_3$ slip. In this study, model based open loop control for urea injection was developed and assessed in the European Transient Cycle (ETC) for heavy duty diesel engine. On the basis of the transient modeling, the kinetic parameters of the $NH_3$ adsorption and desorption are calibrated with the experimental results performed over the zeolite based catalyst. $NH_3$ storage or surface coverage of SCR catalyst can not be measured directly and has to be calculated, which is taken into account as a control parameter in this model. In order to reduce $NH_3$ slip while maintaining NOx reduction, $NH_3$ storage control algorithm was applied to correct the basic urea quantity. If the actual $NH_3$ surface coverage is higher than the maximal $NH_3$ surface coverage, the urea injection quantity is significantly reduced in the ETC cycle. By applying this logic, the resulting $NH_3$ slip peak can be avoided effectively. With optimizing the kinetic parameters based on standard SCR reaction, it suggests that a simplified, less accurate model can be effective to evaluate the capability of model based control in the ETC cycle.

• Journal of Broadcast Engineering
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• v.8 no.3
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• pp.268-277
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• 2003

In this paper, we propose a new video watermarking method exploiting the human visual system (HVS) to find effective locations. in the video frames which make the watermark robust and imperceptible simultaneously. In particular, we propose a new HVS-optimized weighting map for hiding the watermark by considering HVS in three different aspects : frequency, spatial, and motion masking effects. The global masking map is modeled by combining the frequency masking, the spatial masking, and the motion masking. In this paper, we use a watermark which is generated by the bitwise exclusive-OR operation between a logo image and a random sequence. The amount of watermarks is weighted by a control parameter. Furthermore, we embed the watermark in the uncompressed video sequence for the general watermarking method available to various coding schemes. Simulation results show that the watermark is imperceptible and the proposed method is good for watermark capacity. It is also demonstrated that the proposed method is robust against various attacks, such as MPEG coding, MPEG re-encoding, and frame attacks.

• The Journal of Engineering Geology
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• v.28 no.3
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• pp.455-463
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• 2018

This study developed a method to quantitatively measure the size of cracks in concrete using X-ray CT images. We prepared samples with a diameter of 50 mm and a length of 100 mm by coring cracked concrete block that was obtained by chipping. We used a micro-focus X-ray CT, then applied the 3DMA method (3 Dimensional Medial axis Analysis) to the 3D CT images to find effective parameters for damage assessment. Finally, we quantitatively assessed the damage based on sample locations, using the damage assessment parameter. Results clearly show that the area near the chipping surface was damaged to a depth of 3 cm. Furthermore, X-ray methods can be used to evaluate the porosity index, burn number, and medial axis, which are used to estimate the damage to the area near the chipping surface.

• Journal of Labour Economics
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• v.25 no.3
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• pp.1-34
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• 2002

This paper investigates the effects of hours reduction on growth, investment, and consumption as well as employment. We adopt the basic framework of the indivisibility of labor developed by Hansen (1985) and Rogerson (1988) and extend it by allowing heterogeneity of workers in productive efficiency. On the basis of monthly panel data constructed from Economically Active Population Surveys and Household Income and Expenditure Surveys, we estimate the value of productive efficiency parameter of newly hired workers relative to existing workers by considering differences between the two groups in unobservable as well as observable worker characteristics. Numerical simulation of steady states demonstrates that reduction of statutory weekly hours from 44 to 40 leads to a rise in employees by 4.9 percent. However, GNP, investment, and consumption are all reduced by 2.03 percent, which is attributed to reduction in the amount of effective labor input, which in turn comes from reduction of actual average hours and productivity differences between exiting and newly hired workers.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.415-424
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• 2020

Recently, many structural damage detection (SDD) methods have been proposed to monitor the safety of structures. As an important modal parameter, mode shape has been widely used in SDD, and the difference of vectors was adopted based on sensitivity analysis and mode shapes in the existing studies. However, amplitudes of mode shapes in different measured points are relative values. Therefore, the difference of mode shapes will be influenced by their amplitudes, and the SDD results may be inaccurate. Focus on this deficiency, a multi-strategy SDD method is proposed based on the included angle of vectors and sparse regularization in this study. Firstly, inspired by modal assurance criterion (MAC), a relationship between mode shapes and changes in damage coefficients is established based on the included angle of vectors. Then, frequencies are introduced for multi-strategy SDD by a weighted coefficient. Meanwhile, sparse regularization is applied to improve the ill-posedness of the SDD problem. As a result, a novel convex optimization problem is proposed for effective SDD. To evaluate the effectiveness of the proposed method, numerical simulations in a planar truss and experimental studies in a six-story aluminum alloy frame in laboratory are conducted. The identified results indicate that the proposed method can effectively reduce the influence of noises, and it has good ability in locating structural damages and quantifying damage degrees.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.495-502
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• 2012

Using the Sedimentation method it's possible to get $TiO_2$ particle from which by this research, $TiO_2$ particle was produced. The parameter in the kind of the temperature and the alcohol solvent used $TiO_2$ particle production investigated crystal structure of $TiO_2$ particle and the influence exerted on the size of the particle and the form. After scanning electron microscope (SEM) analyzed methyl alcohol, iso-propylalcohol and tert-butylalcohol used by a solvent at the $TiO_2$ particle production, iso-propylalcohol was most effective. And after an thermogravimetric analyzer method was used, the anatase structure was maintained $500^{\circ}C$ by $200^{\circ}C$, but it was converted by the rutile structure by $800^{\circ}C$.

• Journal of Biomedical Engineering Research
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• v.34 no.3
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• pp.111-116
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• 2013

Finite element analysis(FEA) has been extensively applied in the analyses of biomechanical properties of stents. Geometrically, a closed-cell stent is an assembly of a number of repeated unit cells and exhibits periodicity in both longitudinal and circumferential directions. This study concentrates on various parameters of the FEA models for the analysis of drug-eluting biodegradable polymeric stents for application to the treatment of coronary artery disease. In order to determine the mechanical characteristics of biodegradable polymeric stents, FEA was used to model two different types of stents: tubular stents(TS) and helicoidal stents(HS). For this modeling, epigallocatechin-3-O-gallate (EGCG)-eluting poly[(L-lactide-co-${\varepsilon}$-caprolactone), PLCL] (E-PLCL) was chosen as drug-eluting stent materials. E-PLCL was prepared by blending PLCL with 5% EGCG as previously described. In addition, the effects of EGCG blending on the mechanical properties of PLCL were investigated for both types of stent models. EGCG did not affect tensile strength at break, but significantly increased elastic modulus of PLCL. It is suggested that FEA is a cost-effective method to improve the design of drug-eluting biodegradable polymeric stents.

• Journal of Biomedical Engineering Research
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• v.34 no.3
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• pp.105-110
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• 2013

Respiratory signal is one of the important physiological information indicating the status and function of the body. Recent studies have provided the possibility of being able to estimate the respiratory signal by using a change of PWV(pulse width variability), PRV(pulse rate variability) and PAV(pulse amplitude variability) in the PPG (photoplethysmography) signal during daily life. But, it is not clear whether the respiratory monitoring is possible even during sleep. Therefore, in this paper, we estimated the respiration from PWV, PRV and PAV of PPG signals during sleep. In addition, respiration rates of the estimated respiration signal were calculated through a time-frequency analysis, and errors between respiration rates calculated from each parameter and from reference signal were evaluated in terms of 1 sec, 10 sec and 1 min. As a result, it showed the errors in PWV(1s: $36.38{\pm}37.69$ mHz, 10s: $36.53{\pm}38.16$ mHz, 60s: $30.35{\pm}38.72$ mHz), in PRV(1s: $1.45{\pm}1.38$ mHz, 10s: $1.44{\pm}1.37$ mHz, 60s: $0.45{\pm}0.56$ mHz), and in PAV(1s: $1.05{\pm}0.81$ mHz, 10s: $1.05{\pm}0.79$ mHz, 60s: $0.56{\pm}0.93$ mHz). The errors in PRV and PAV are lower than that of PWV. Finally, we concluded that PRV and PAV are more effective than PWV in monitoring the respiration in daily life as well as during sleep.