92 research outputs found
Photoplethysmography Monitoring with Optical Low Angel Pass Filter Using Slanted Mirror Array
No full textDevelopment of Sol-Gel ferroelectric thin films for photonic applications
No full textIn this thesis, the author has prepared and characterized sol-gel processed ferroelectric thin films, including barium titante, and lithium niobate/tantalate.Doctor of Philosophy (EEE
Development of lead-free thin-film dielectrics for capacitor applications
No full textThis PhD project aims to develop lead-free thin-film dielectric materials for fixed value, voltage tunable and high-k zipping variable capacitors using growth techniques that can be scaled for silicon batch fabrication. The thesis specifically details the growth and characterisation of barium zirconate titanate (BZT) and bismuth zinc niobate (BZN) dielectric thin films. Fixed value and tunable capacitors have been realised through the use of low and high permittivity dielectric thin film materials in both the amorphous and crystalline states. Planar devices fabricated using BZT and BZN dielectric thin films were grown by sol-gel and RF magnetron sputtering, respectively. The effects of different bottom electrodes were also investigated. Capacitors in a metal-insulator-metal (MIM) [metal-ferroelectric-metal (MFM) for BZT] structure have been fabricated to characterise the dielectric films at low frequency to 300 kHz. Cont/d
생체 센서 및 생체 센서를 포함하는 전자 장치
No full textA sensor for sensing biometric information includes a light emitting unit that emits a first light ray, a light receiving unit that receives a second light ray, where the second light ray includes a portion of the first light ray reflected by a body of a user, and an optical layer placed over the light emitting unit and the light receiving unit. The optical layer has a first surface facing the light emitting unit and the light receiving unit and a second surface opposite the first surface. The optical layer further includes an asymmetrical protrusion structure formed on the first surface or the second surface and including a plurality of asymmetrical protrusion units. The optical layer may further include a symmetrical protrusion structure formed on the first surface or the second surface opposite the asymmetrical protrusion structure and including a plurality of symmetrical protrusion units
NMR studies of the chemical additives effect on the sol-gel process
No full textDue to its unique advantages, the sol-gel process has attracted considerable attention from both technical and scientific points of view during the past decade. Compared with the conventional method, the sol-gel process can make very pure and homogeneous ceramic materials at much lower temperatures. More importantly, it not only opens up the possibilities of preparing new multicomponent materials with specific properties but also provides a great deal of convenience in some chemical processings such as coating, thin film and fiber fabrication.Chemical additives have been known to drastically influence the gelation process and the physical properties of the sol-gel derived materials, although the mechanism is still not elucidated. It is the aim of this thesis to study the chemical additives effect and gain a better molecular level understanding of the sol-gel process.It is demonstrated that the gelation process is dramatically accelerated and the polymerization process proceeds through the formation of higher branched species from very early stage in the fluoride catalyzed sol-gel system. In addition, the fluoride catalyzed xerogel is shown to have larger average pore radius and narrower pore size distribution, as a result of the decrease of the amount of micropores in the silica network.We have also studied the additive effect of various amides on the sol-gel process. All the amides studied, except N,N-dimethylformamide and N,N-dimethylacetamide, show some acceleration effect on the gelation and increase the pore size. Both hydroxyl and formamide are demonstrated to drastically increase the initial hydrolysis reaction rate whereas N,N-dimethylformamide shows only minor influence. Dynamic information about the solvent molecules in the catalyzed sol-gel systems is also investigated by measuring the spin-lattice relaxation time and the linewidth of NMR spectrum. It is shown that the rotational motion of water molecule is more restricted by the hydrogen bonding in the hydroxyl and formamide catalyzed sol-gel systems.Made available in DSpace on 2011-05-07T13:08:32Z (GMT). No. of bitstreams: 2
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높은 신호 대 잡음비를 갖는 광용적맥파를 위한 저각도 광학 투과 필터
No full text학위논문(석사) - 한국과학기술원 : 바이오및뇌공학과, 2017.2,[vii, 51 p. :]The photoplethysmography (PPG) signal exhibits the human vascular activity using the parameters extracted from the PPG waveform. However, the reflectance type PPG signal is liable to be distorted by noise. In this work, we present the optical low angle pass filter (OLAPF) for high signal-to-noise ratio photoplethysmography (PPG) monitoring. The highly scattered light, which loses their directionality under the human tissue act as a noise in PPG signal. The OLAPF can cut-off these scattered light using their non-directionality. The OLAPF was designed by the ray-optics analysis and numerical analysis. The fabrication of the OLAPF was done by using guided resist reflow and soft lithography method. To figure out the difference between with and without OLAPF, we made the conventional PPG sensor, which can be changed the glass on the photodetector to the OLAPF. As a result, the in-band noise overlapped the signal bandwidth of 0.5 Hz to 4 Hz with OLAPF is 2 times smaller than without the OLAPF. The low-frequency power spectral density, which has bandwidth of 0 Hz to 0.4 Hz of PPG signal with OLAPF is 3 times smaller than without OLAPF. This device can be applied not only PPG signal but also NIRS to improve the signal resolution.한국과학기술원 :바이오및뇌공학과
New Acid Medium Sol-Gel Synthesis of Metal Phosphates
No full textabstract: New sol-gel routes based on peroxo complexes of early transition metals in a highly acidic medium were developed, to prepare metal oxide phosphates that feature structural protons. A sol-gel synthetic route was chosen because it allows atomic level mixing of precursors and lower heating temperatures, which are preferable in exploring metastable phases. Titanium and molybdenum sol-gel chemistries were the focus of the initial studies and the synthesis of Ti1-xMoxP2O7 (x = 0 – 0.5) and Mo1-yTiyP2O8-y (y = 0 – 0.4) type metal oxide phosphates were explored. For the synthesis of the metal oxide phosphates, hydrogen peroxide was employed to prepare the respective precursor solutions. The peroxide ligand suppressed the immediate precipitation of metal cations in aqueous medium, by coordinating to Ti4+ and Mo6+ ions, and produced a soft wet-gel following polycondensation. Phosphoric acid was used to acidify the reaction medium and to provide protons and phosphate ions as structural components. From this synthetic route, a series of Ti1-xMoxP2O7 (x = 0 – 0.5) and Mo1-yTiyP2O8-y (y = 0 – 0.4) crystalline compounds, with various degrees of purity, were synthesized. For x = 0 and y = 0, the crystalline compounds TiP2O7 and MoP2O8 were produced, respectively, after calcining at 600 °C.
In pursuit of new metastable molybdenum oxide phosphate compounds, peroxo-molybdenum precursor mixtures with different molar ratios were treated gently by low-temperature heating. After controlled drying in a lab oven, MoO2(H2O)(HPO4) crystals were obtained as a highly crystalline pure product instead of a gel. The dissolution of MoO2(H2O)(HPO4) in water and precipitation with a CsCl solution produced a new crystalline compound with a cubic unit cell (a = 11.8(2) Å). Further studies will lead to crystal structure determination and elucidation of the aqueous chemistry of MoO2(H2O)(HPO4).Dissertation/ThesisMasters Thesis Chemistry 201
Development of optical devices in a flat-fibre platform
No full textThis thesis describes the development of optical devices in a novel flat-fibre platform. Device fabrication is achieved using direct grating writing and physical micromachining techniques.A series of experimental studies have been undertaken in order to optimise the fabrication of UV-written waveguides and Bragg gratings in the flat-fibre geometry. The UV-writing parameters have been investigated including fluence and duty cycle, together with hydrogen loading and alignment factors. Loss measurements have been performed on a variety of passive and active structures using a novel distributed Bragg grating technique. The measured propagation loss of a channel waveguide based UV-written was 0.13 dB/cm ± 0.03 dB/cm.Flat-fibre devices have been used as physical and refractive index sensors on a wedge flat-fibre structure. Through using UV-written Bragg gratings in series and parallel arrangement, it provides the capability of sensing two-dimensional bending and external refractive index variation in a single device.Another passive device that has been developed in flat-fibre is the multimode interference (MMI) device. The concept of using two micro-machined trenches to fabricate the MMI device has also been discussed. In this work, a successful 1x3 MMI device has been fabricated by using a high precision dicing saw and the excess loss was measured as 1.89 dB.Finally, the spectroscopy study of an erbium doped flat-fibre was performed. Absorption to about 0.32 dB/cm at 976 nm wavelength has been achieved in the erbium-doped flat-fibre. The first demonstration of signal amplification at wavelength of 1530 nm has been carried out where showing that the relative gain was 0.74 dB
Tropical Cyclone Activity in the Northwest Pacific in Relation to the El Niño/Southern Oscillation Phenomenon
No full textThe interannual variations in tropical cyclone activity in the northwest Pacific (NWPAC) and their
relationships with the EI Nino/Southern Oscillation (ENSO) phenomenon were studied using the method of
spectral analyses. Time series of a Southern Oscillation Index (SOl, defined as the sea-level pressure difference
between Easter Island and Darwin) and tropical cyclone activity in the entire (NWPAC) ocean basin as well
as in different regions of the NWPAC were analyzed. Two spectral peaks are apparent in all these time series.
One corresponds to the generally accepted Southern Oscillation with a period of - 3 to 3.5 years and another
at the quasi-biennial oscillation (QBO) frequency. Cross-spectral analyses between the SOl and tropical
cyclone activity show significant coherence in these two spectral peaks. The dominant peak is at the Southern
Oscillation frequency with the SOl leading typhoon activity by almost a year. At the QBO frequency, the
two series are almost in phase. Cyclone activity in the eastern part of NWPAC, however, is -180' out of
phase with the SOl series at the Southern Oscillation frequency. It appears that fluctuations of cyclone activity at the dominant Southern Oscillation frequency may be
explained in terms of the change in the horizontal and vertical circulations in the atmosphere during periods
of low SOl. The establishment of an anomalous Walker Circulation shifts areas of enhanced or suppressed
convection, leading to the observed variations in cyclone activity.The author, a National Research Council Research Associate during the period of this study, acknowledges support by the Foundation Research Program at the Naval Postgraduate School
Digestibility of amino acids in pigs fed distillers dried grains with solubles derived from corn, sorghum, and triticale
No full textAn experiment was conducted to determine the standardized ileal digestibility (SID) of amino acids (AA) in distillers dried grains with solubles derived from corn (C-DDGS), sorghum (S-DDGS), and triticale (T-DDGS) fed to growing pigs. A total of 16 barrows (initial body weight = 23.1 2.03 kg) surgically fitted with T-cannulas at the distal ileum were divided into 4 groups based on body weight and assigned to a quadruplicated 4 2 incomplete Latin Square design with 4 dietary treatments and 2 experimental periods. Three diets containing C-DDGS, S-DDGS, or T-DDGS and a nitrogen-free diet were fed in each experimental period consisting of 5-d adaptation and 2-d ileal digesta collection. Pigs fed S-DDGS had less (PThe presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
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