• Journal of Internet of Things and Convergence
• /
• v.9 no.6
• /
• pp.111-117
• /
• 2023

There is a lot of research on using a combination of graph neural networks and recurrent neural networks as a way to account for both temporal and spatial dependencies. In particular, graph neural networks are an emerging area of research. Seoul's bicycle rental service (aka Daereungi) has rental stations all over the city of Seoul, and the rental information at each station is a time series that is faithfully recorded. The rental information of each rental station has temporal characteristics that show periodicity over time, and regional characteristics are also thought to have important effects on the rental status. Regional correlations can be well understood using graph neural networks. In this study, we reconstructed the time series data of Seoul's bicycle rental service into a graph and developed a rental prediction model that combines a graph neural network and a recurrent neural network. We considered temporal characteristics such as periodicity over time, regional characteristics, and the degree importance of each rental station.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.6
• /
• pp.658-662
• /
• 2001

The classification of surface flaw types was performed on the basis of angular dependence of backscattered ultrasound. The copper line adhered on the surface, cower line filled in groove, pure groove and the normal edge were adopted as various surface flaw patterns of glass specimen. A backward longitudinal profile was formed probably by the longitudinal wane scattering at and near 1st critical angle. The wave trains at the peak angles of the backward radiation profiles showed different shapes according to the superposition ratio of scattered and leaky waves. The asymmetry of the backward radiation profile arose due to the scattering effect of flaw. The additive resonance effect of copper line appeared in the left side of the profile. The peak angles of both the longitudinal and radiation profiles were shifted toward small angle by the scattering effect.

• Korean Journal of Optics and Photonics
• /
• v.5 no.1
• /
• pp.100-105
• /
• 1994

We have reduced the oscillating linewidth of the commercial single mode InGaAsP visible laser diodes which emits in the 657 nm region of the spectrum down to 10 MHz by making a extended cavity employing the Littrow-type grating. The wavelength tuning characteristics of the commercial visible laser diode (CQL820D, Philips Co.) for the grating angle, laser temperature, and injection currents were measured by using the wavemeter. The proportional coefficients of the laser were found to be 1 THzlmrad, 32.4 GHz/K, and 6.14 GHz/mA, respectively.tively.

• Journal of Korea Multimedia Society
• /
• v.7 no.11
• /
• pp.1571-1579
• /
• 2004

Recently, FD(Frame Dropping)-CD(Coefficient Dropping) transcoding is considered mainly due to the low computational complexity and simple implementation. But, CD errors in the FD-CD transtoding scheme tend to be propagated and they have a significant effect on the qualities of decoded images. In this paper, we derive the error characteristics incurred by the CD operations and propose an effective estimation model that adaptively describes well the characteristics of propagation/accumulation errors in compressed domain. Furthermore, we apply the proposed model to distortion control achieving nearly constant distortion allocation among frames. Simulation results show that the proposed model is quite accurate in estimating the overall distortions and is effectively applied to distortion control over a range of sequences with varying scene types.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.1
• /
• pp.9-14
• /
• 2005

The angular dependence(profile) of backward radiated ultrasound was measured for glass specimens with random surface roughness using ultrasonic goniometer that ran changes the incident angle continuously. It was concluded that the roughened region had greater acoustic impedance than the unperturbed region. The comparison of backward radiations showed that the amplitude of peak and the area of radiation profile were increased with surface roughness. It was suggested from the sensitive dependence of the profile area that the profile of backward radiation could be applied to in the nondestructive evaluation of sulfate region. Inclined C-scan technique with the transducer inclined at Rayleigh angle showed the reverse of luminosity and the high signal to noise ratio so that it provided high resolution.

• Korean Journal of Materials Research
• /
• v.7 no.7
• /
• pp.559-563
• /
• 1997

Ta을 2MeV의 에너지로 가속시켜 1x$10^{17}$atoms/$\textrm{cm}^2$의 농도로 TiC(001)면에 이온 주입시킨 후 비행시간형 직충돌이온산란 분광법(time-of-flight impact-collision ion scattering spectroscopy; TOF-ICISS)을 사용하여 TiC(001)면의 Ta표면 편석을 연구하였다. TOF-ICISS는 표면 수층 깊이까지 원자구조를 측정할 수 있는 수법으로, 이온주입된 시편을 1$600^{\circ}C$에서 300sec동안 진공 가열하여 Ta 원자를 편석시킨 후 스펙트럼의 입사각도 의존성을 구함으로써 Ta원자의 편석 위치 및 농도구배를 조사하였다. [110]및 [100]방위에서 Ta과 Ti의 focusing peak가 서로 같은 입사각도에서 나타나며 편석된 Ta원자는 TiC의 Ti-site에 위치한다. Ta원자는 표면 최외층에만 편석되는 것이 아니라 수층에 걸쳐 Ti-site에 자리하고 있으며, Ta 원자의 농도는 표면 최외층에서 내부 층으로 깊어질수록 작아진다. 이온주입시 생성된 표면층의 탄소 격자 결함은 시편 가열시 벌크에 자리하는 탄소가 확산되어 없어진다.다.

• Journal of the Korean Magnetics Society
• /
• v.12 no.5
• /
• pp.163-167
• /
• 2002

In order to study the temperature dependence of the magnetostatic wave modes for an YIG thin film, grown by a liquid phase epitaxy method, The ferromagnetic resonance was performed by an FMR spectrometer in the temperature range -140$\^{C}$∼200$\^{C}$. The magnetostatic surface wave and backward volume wave modes show periodic excitations in parallel configuration. The resonance fields of all modes and intensities decreased with decreasing the temperature. All magnetostatic modes can be well explained by the Walker and Damon-Eshbach theory. The calculated saturation magnetization Ms of the YIG thin film was increased with decreasing the temperature. The line widths of magnetostatic modes changed in various trends with decreasing the temperature.

• Korean Journal of Optics and Photonics
• /
• v.20 no.5
• /
• pp.288-293
• /
• 2009

Polarization characteristics of a composite film composed of two optically anisotropic films are analyzed. The procedure to determine the effective optics axis and the equivalent retardation of the composite film is suggested in conjuction with the related ellipsometric expressions. The explicit expressions of the effective optic axis and the equivalent retardation of a non-uniform anisotropic film are derived when all optic axes are parallel. Those expressions of the composite film where optic axes of two constituting anisotropic films are not parallel are also derived. Dependence of those expressions on the polarization state of the incident light or the azimuth angle of the linearly polarized light and their limit when applied to practical use are discussed.

• Journal of Food Hygiene and Safety
• /
• v.13 no.4
• /
• pp.355-359
• /
• 1998

Platelet activation is originated by the intracellular or/and extracellular $Ca^{2+}$. Agonist-induced $Ca^{2+}$ entry through a plasma-membrane pathway has been reported repeatedly, but the mechanisms has proven harder to elucidate. Recently, a number of natural products have been isolated from medicinal plants and marine organisms and have proved to be useful chemical tools for resolving the mechanism of cellular functions. In an attempt to understand the mechanism of platelet activation in Bupleuri Radix, we have studied some aspects of the isolation of active components and their dependence of external $Ca^{2+}$> on platelet activation. Acetone extract of Bupleuri Radix has the most activity on platelet activation and it's active components were identified as saikosaponin a and d. Their optimal concentration was respectively $20\;\mu\textrm{g}/ml$ and $5\;\mu\textrm{g}/ml$ and their platelet activation was not dependent on external $Ca^{2+}$>, whereas optimal concentration of each agonist was arachidonic acid ($10\;\mu\textrm{M}$), collagen ($10\;\mu\textrm{M}/ml$), thrombin (0.1 unit/mi), PAF (5 nM), PMA ($5\;\mu\textrm{M}$), ionophore A23187 ($2\;\mu\textrm{g}$) and their dependence of external $Ca^{2+}$> on platelet activation appeared to thrombin > collagen $\geq$ PAF > PMA > arachdonic acid> ionophore A23187. These results suggest that saikosaponin is different from each agonists in the dependence of external $Ca^{2+}$ on platelet activation.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.4
• /
• pp.52-59
• /
• 2018

To control chloride attacks which is a representative deterioration in RC(Reinforced Concrete) structures, many studies have been conducted. Above all, a method using mineral admixture was known to be effective for corrosion protection. In this study, durability test about chloride attacks was carried out for concrete specimens containing FA(Fly Ash)-representative concrete mineral admixture and OPC concrete specimens considering 3 different levels of W/B(Water to Binder). Accelerated chloride diffusion coefficient tests referred to Tang's method, total passed charge tests referred to ASTM C 1202, and compressive strength tests based on KS F 2405 were performed at each target age day. Also, based on previous studies of 28 days, time-parameter which is a key parameter for diffusion behavior is evaluated and its relations with compressive strength at the age of 365 days is evaluated. After the age of 49 days, chloride resistance of FA concrete is much improved than that of OPC concrete, which arose out of stable hydrates due to pozzolan reaction of fly ash. Time-parameter of FA concrete is evaluated to be about 1.5 times larger than that of OPC concrete. Also, time-parameter of FA concrete has a linearly decreasing relation while that of OPC concrete has a linearly increasing relation with compressive strength development.