Su-Young Han

Fabrication of nanocrystalline Fe–Co–Ta–N magnetic films with high saturation magnetization and excellent high-frequency characteristics

As-deposited Fe–Co–Ta–N soft magnetic thin films with a thickness of 250 nm were fabricated to achieve high saturation magnetization and excellent high-frequency characteristics. During sputtering, the input power was fixed at 450 W and the nitrogen partial pressure varied from 0% to 10%. In these films, the values of saturation magnetization and coercivity that were obtained were 17–23 kG and 3–6 Oe, respectively. The Fe78Co8Ta9N5 (4% PN2) film exhibits excellent high-frequency characteristics with an effective permeability of about 2000, which is maintained up to 700 MHz. Also, this film has Bs=21u2009kG, Hc-hard=3u2009Oe, ρ=100u2009μΩu200acm, and Hk=20u2009Oe. These high-frequency characteristics could result from the high values of the electrical resistivity and the magnetic anisotropy field. Furthermore, the corrosion resistance of these films was improved by the addition of nitrogen to give characteristics better than those of Co–Ni–Fe and Fe–Hf–N films.

Structural, photoluminescence and photoelectrochemical properties of electrosynthesized ZnSe spheres

Zinc selenide (ZnSe) spheres have been successfully synthesized by a simple galvanostatic mode of electrodeposition method for the photoelectrochemical properties. These spheres are characterized for their structural and morphological features using X-ray diffraction studies, scanning electron microscopy techniques. The growth mechanism of the ZnSe spheres have been discussed in detail, which can be addressed as the 2H+ gas trap and cation exchange reaction. UV–vis absorption spectra revealed that an absorbance peak at 380xa0nm and its band gap energy was found to be ~2.57xa0eV. Photoluminescence measurement spectra revealed that, the spheres exhibit strong emission at 675.94xa0nm. The photoelectrochemical measurement of ZnSe spheres was studied and the calculated efficiency was found to be ~0.05xa0%. In the electrodeposition galvanostatic mode is good technique applicable for controlling the film thickness. Hence, these galvanostatically electrosynthesized ZnSe spheres could be used as a buffer layer in the photoelectrochemical solar cells.

The effects of electron irradiation on the optical properties of the organic semiconductor polypyrrole

The optical properties of polypyrrole (Ppy) thin films upon 2 MeV electron beam irradiation changes with different doses. The induced changes in the optical properties for Ppy thin films were studied in the visible range 300 to 800 nm at room temperature. The optical band gap of the pristine Ppy was found to be 2.19 eV and it decreases up to 1.97 eV for a 50 kGy dose of 2 MeV electron beam. The refractive index dispersion of the samples obeys the single oscillator model. The obtained results suggest that electron beam irradiation changes the optical parameters of Ppy thin films.

A robust digital watermarking adopting 2d barcode

In this paper, a new watermarking algorithm using 2D barcode is proposed. The 2D barcode means 2-dimensional barcode that contains more information than conventional 1-dimensional barcodes. For error correction, 2D barcode allow the recognition of barcodes that are up 60% damaged. Therefore, the 2D barcode as watermark can be survived when it used in highly noisy environment. In this paper, a new wavelet based watermarking algorithm using 2D barcode as watermark is proposed. Dynamically generated 2D barcode is inserted as watermark in wavelet domain. From the experimental result, the proposed algorithm shows better invisibility and robustness comparing with the conventional methods using plain image as watermark.

The Study on the Structural relations among the visitor satisfaction, it`s antecedents and the modification of images of Korea perceived by Chinese and Russian Tourists after their visits to Korea

The purpose of this study is to examine the impact relation among the visitor satisfaction, it`s antecedents and the modification of images of Korea perceived by Chinese and Russian Tourists after their visits to Korea. According to the data analysis, the satisfaction of Russian tourists is higher than that of Chinese tourists within statistical significance. The result produced by structural equation model shows that the satisfaction of Chinese tourists is affected by destination attractiveness, public order, shopping, food and accommodations positively. Especially the public order and shopping of Korea are relative major attributes. In comparison, the satisfaction of Russian tourists is affected by only destination attractiveness, public order and food positively. Then again, the impact relation between overall satisfaction and the modification of images of Korea perceived by tourist visited Korea is affected positively within statistical significance.

The influence of monomer concentration on the optical properties of electrochemically synthesized polypyrrole thin films

Polypyrrole (PPy) thin films were deposited on stainless steel and ITO coated glass substrate at a constant deposition potential of 0.8 V versus saturated calomel electrode (SCE) by using the electrochemical polymerization method. The PPy thin films were deposited at room temperature at various monomer concentrations ranging from 0.1 M to 0.3 M pyrrole. The structural and optical properties of the polypyrrole thin films were investigated using an X-ray diffractometer (XRD), FTIR spectroscopy, scanning electron microscopy (SEM), and ultraviolet—visible (UV—vis) spectroscopy. The XRD results show that polypyrrole thin films have a semi crystalline structure. Higher monomer concentration results in a slight increase of crystallinity. The polypyrrole thin films deposited at higher monomer concentration exhibit high visible absorbance. The refractive indexes of the polypyrrole thin films are found to be in the range of 1 to 1.3 and vary with monomer concentration as well as wavelength. The extinction coefficient decreases slightly with monomer concentration. The electrochemically synthesized polypyrrole thin film shows optical band gap energy of 2.14 eV.

Wavelet Packet Image Coder Using Coefficients Partitioning for Remote Sensing Images

In this paper, a new embedded wavelet packet image coder algorithm is proposed for an effective image coder using correlation between partitioned coefficients. This new algorithm presents parent-child relationship for reducing image reconstruction error using relations between individual frequency sub-bands. By parent-child relationships, every coefficient is partitioned and encoded for the zerotree data structure. It is shown that the proposed wavelet packet image coder algorithm achieves lower bit rates than SPIHT. It also demonstrates higher PSNR under the same bit rate. The perfect rate control is compared with the conventional methods. These results show that the encoding and decoding processes of the proposed coder are simpler and more accurate than the conventional ones for texture images that include many mid and high-frequency elements such as aerial and satellite photograph images. The experimental results imply the possibility that the proposed method can be applied to real-time vision system, on-line image processing and image fusion which require smaller file size and better resolution.

Embedded wavelet packet image coder using set partitioning

In this paper, we propose an embedded wavelet packet image coder in which a new model for parent-child relationships using set partitioning is considered. By the wavelet packet transform, energy compaction of the image is achieved, and an embedding approach on set partitioning in packet trees is then adopted for the coding of the wavelet packet transform coefficients. It is shown that the proposed technique achieves good compression results and allows a perfect rate control.

A Generalizable Top‐Down Nanostructuring Method of Bulk Oxides: Sequential Oxygen–Nitrogen Exchange Reaction

A thermal reaction route that induces grain fracture instead of grain growth is devised and developed as a top-down approach to prepare nanostructured oxides from bulk solids. This novel synthesis approach, referred to as the sequential oxygen-nitrogen exchange (SONE) reaction, exploits the reversible anion exchange between oxygen and nitrogen in oxides that is driven by a simple two-step thermal treatment in ammonia and air. Internal stress developed by significant structural rearrangement via the formation of (oxy)nitride and the creation of oxygen vacancies and their subsequent combination into nanopores transforms bulk solid oxides into nanostructured oxides. The SONE reaction can be applicable to most transition metal oxides, and when utilized in a lithium-ion battery, the produced nanostructured materials are superior to their bulk counterparts and even comparable to those produced by conventional bottom-up approaches. Given its simplicity and scalability, this synthesis method could open a new avenue to the development of high-performance nanostructured electrode materials that can meet the industrial demand of cost-effectiveness for mass production.

A smart sensor overlay network for ubiquitous computing

Sensor networks have been considered as a base technology for constructing ubiquitous computing environment. However, most researches about sensor networks have not focused on ubiquitous computing but mainly focused on efficiency of sensor networks itself. Ubiquitous computing requires sensor networks to be accessed in a transparent and abstract manner from the outer world. However the requirements cannot be easily achieved because of physical restrictions of sensor networks and centralized data processing scheme. In this paper, we have designed a sensor overlay network that enables ubiquitous computing applications to consider sensor networks as an ordinary component of ubiquitous computing environment. Virtual sensors and actuators on the overlay network cooperate with each other and provide intelligent decision that was impossible to be implemented with current physical sensor networks. The proposed overlay network also provides dynamic service composition and device integration essential to ubiquitous computing. To evaluate the usefulness of the designed system, the overlay network is implemented and simulated on J-Sim simulator.