Epitaxial growth of ZnO/ZnAl 2 O 4 (core/shell) nanotubes from Al 2 O 3 coated ZnO nanorods were synthesized using a three-step reaction. In the first step we synthesized ZnO nanorod on Si(100) wafers using chemical vapor deposition, followed by Al 2 O 3 deposition on synthesized ZnO nanorod with the help of atomic-layer deposition. Finally in the last step, the resultant sample (i.e. Al 2 O 3 deposited ZnO nanorod) was calcined at 500 C for 1 h. Hexagonally well-faceted ZnO nanorod arrays were aligned to Si(100) wafers without metal-catalyst at 500 C for 1 h. Thereafter it was transformed to spinel-type ZnAl 2 O 4 nanotubes, which still have ZnO nanotube as a core, by interfacial solid-state reaction in Al 2 O 3 coated ZnO nanorods. XRD and Raman analysis demonstrated that single crystallites of both nanotubes co-exist. The photoluminescence spectra show that ZnO nanorod, Al 2 O 3 coated ZnO nanorod, ZnO/ZnAl 2 O 4 (core/shell) nanotube indicated different luminescence bands with different intensity at He-Cd laser excitation (325 nm line).The controlled preparation of nanomaterials plays a central role in nanoscience and nanotechnology. 1,2 Without controllability, devices based on these nanomaterials are extravagant hopes in most cases. Controllability mainly consists of three parts: composition, morphology, and structure control. Morphology, composition, and structure together govern the chemical, gas sensors, mechanical, electrical, magnetic, and optical properties of the materials that are used to functionalize the devices. [3][4][5][6][7][8] Especially, the one-dimensional nanostructures, such as nanorods, nanowires, nanobelts, nanotubes etc., have attracted considerable attention for their exceptional, unique, electronic, electrical, optical, and mechanical properties and their potential uses in both fundamental and practical studies.
The viscosity and mechanical property of HTPB/AP composite solid propellant are profoundly affected by particle size of AP. In HTPB/AP propellant formulated by two mode of AP size such as 190 μm and 7 μm, the propellant was found to be much less viscose at end of mix when coarse/fine AP ratio is ranged from 70/30 to 60/40 due to high solid packing fraction. It was shown that the toughness of tensile strength test for HTPB/AP propellant increased with the increase in coarse AP.Considering both lower viscosity and better tensile strength, the optimum ratio of AP coarse/fine was estimated to be 70/30.
Noncontact electrocardiogram (ECG) measurement using capacitive-coupled technique is a very reliable long-term noninvasive health-care remote monitoring system. It can be used continuously without interrupting the daily activities of the user and is one of the most promising developments in health-care technology. However, ECG signal is a very small electric signal. A robust system is needed to separate the clean ECG signal from noise in the measurement environment. Noise may come from many sources around the system, for example, bad contact between the sensor and body, common-mode electrical noise, movement artifacts, and triboelectric effect. Thus, in this paper, the extended Kalman filter (EKF) is applied to denoise a real-time ECG signal in capacitive-coupled sensors. The ECG signal becomes highly stable and noise-free by combining the common analog signal processing and the digital EKF in the processing step. Furthermore, to achieve ubiquitous monitoring, android-based application is developed to process the heart rate in a realtime ECG measurement.
Trivalent terbium-doped lutetium-aluminate nano-garnet (Lu3Al5O12:Tb 3+ ) powder was prepared by using the Pechini sol-gel process. The structure and crystallinity of the Lu3Al5O12:Tb 3+ nano-garnet were characterized by using X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy. The green emission of Tb 3+ ions is observed at 545 nm corresponding to the 5 D4 → 7 F5 transition under the 271-nm excitation. The temperature dependent luminescence properties of the Lu3Al5O12:Tb 3+ nano-garnet are investigated. The results show that the present garnet exhibits better thermal stability than the other green emitting phosphors, hence, the Lu3Al5O12:Tb 3+ phosphor is a promising candidate for light-emitting devices. PACS numbers: 78.55.-m
LED(Light Emitting Diode) is an emitting device which energy is same to the bandgap energy of p-type and n-type semiconductor junction. Recently high brightness LED is used in fish-luring light and traffic signal light alternative of normal light bulb, and widely used in the area of display pannel. Moreover nowadays LED has been used as a back light of LCD display.Recently, visible light communication(VLC) using LED, that allow two-way serial data communication between LEDs over a distance of sveral centimeters or meters, has been widely studied in the area of digital information transmission along with illumination and display. In this paper, we present LED communication system and their applications. 키워드LED 가시광 통신, LED, VLC, 통신시스템
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