2,965 research outputs found
Fully integrated low phase-noise VCOs with on-chip MEMS inductors
No full textWe present fully integrated high-performance voltage-controlled oscillators (VCOs) with on-chip microelectromechanical system (MEMS) inductors for the first time. MEMS inductors have been realized from the unique CMOS-compatible MEMS process that we have developed to provide suspended thick metal structures for high-quality (Q) factors. Fully integrated CMOS VCOs have been fabricated by monolithically integrating these MEMS inductors on the top of the CMOS active circuits realized by the TSMC 0.18-mum mixed-mode CMOS process. Low phase noise has been achieved as -124 and -117 dBc/Hz at 300-kHz offset from carrier frequencies of 1 and 2.6 GHz, respectively, in the fabricated single-chip VCOs.This work was performed as part of the National Research
Laboratory Program of the Ministry of Science and Technology
On unitary convex decompositions of vectors in a -algebra
No full textsummary:By exploiting his recent results, the author further investigates the extent to which variation in the coefficients of a unitary convex decomposition of a vector in a unital -algebra permits the vector decomposable as convex combination of fewer unitaries; certain -algebra results due to M. Rørdam have been extended to the general setting of -algebras
Photo-crosslinkable, thermo-sensitive and biodegradable Pluronic hydrogels for sustained release of protein
No full textThermo-sensitive and biodegradable hydrogels based on Pluronic tri-block copolymers were prepared by a photo-polymerization method. Two terminal hydroxyl groups in Pluronic F-127 were acrylated to form a Pluronic macromer. Photo-cross-linked Pluronic hydrogels prepared by UV radiation showed a gradually decreased swelling ratio with increasing temperature and exhibited a thermally-responsive change in the swelling ratio when the temperature was cycled between 10degreesC and 37degreesC. These hydrogels degraded slowly due to the cleavage of ester linkage in the acrylated Pluronic terminal end. When lysozyme, a model protein drug, was loaded in the hydrogels, bi-phasic protein release profiles were attained: a burst-free and rapid controlled release profile was initially observed for a one week period and a much slower sustained release was followed thereafter. The release rates could be controlled by varying the amount of Pluronic macromer for photo-polymerization.the Korea Science and Engineering Foundation,
Kore
Phase sensitive detection for mode-locked fiber laser gyroscope
No full textWe demonstrate a significant improvement in the performance of a mode-locked fiber laser gyroscope by using a lock-in amplifier. We show that the direct output of the lock-in amplifier has a desirable linear dependence on the rotation rate and is insensitive to the intensity difference between two pulses that causes phase error in the time interval measurement. Two orders of magnitude improvement is demonstrated in the longterm stability compared to that from previously reported time interval measurement
The effect of plastic anisotropy on compressive instability in sheet metal forming
No full textThe wrinkling behavior of a thin sheet with perfect geometry is associated with compressive instability. The compressive instability is influenced by many factors such as stress state, mechanical properties of the sheet material, geometry of the body, contact conditions and plastic anisotropy. The analysis of compressive instability in a plastically deforming body is difficult considering all the factors because the effects of the factors are very complex and the instability behavior may show a wide variation for a small deviation of the factors. In this study, the bifurcation theory is introduced for the finite element analysis of puckering initiation and growth of a thin sheet with perfect geometry. All the above mentioned factors are conveniently considered by the finite-element method. The instability limit is found by the incremental analysis and the post-bifurcation behavior is analyzed by introducing the branching scheme proposed by Riks, The finite-element formulation is based on the incremental deformation theory and elastic-plastic material modeling. The finite-element analysis is carried out using the continuum-based resultant shell elements considering the anisotropy of the sheet metal. In order to investigate the effect of plastic anisotropy on the compressive instability, a square plate that is subjected to compression in one direction and tension in the other direction is analyzed by the above-mentioned finite-element analysis. The critical stress ratios above which buckling does not take place are found for various plastic anisotropic modeling methods and discussed. Finally, the effect of plastic anisotropy on the puckering behavior in the spherical cup deep drawing process is investigated. From the results of the finite-element analysis, it is shown that puckering behavior of sheet metal is largely affected by plastic anisotropy. (C) 2000 Elsevier Science Ltd. All rights reserved
An analysis of springback with bifurcation behavior and its application to die design
No full textSpringback in sheet metal product makes difficulties in die design because small strain causes large displacement. Especially for the sheet metal product having small geometric constraints, springback displacement may become severe. After stamping of outer case of washing machine, a large amount of springback is observed with small geometric constraints. Also, a bifurcation takes place during the springback analysis. Figure 2 shows the springback shape of the outer case of washing machine. In order to reduce the springback displacement, the effect of tooling dimensions on bifurcation behaviour and springback displacement are investigated
Investigation into wrinkling behavior in the elliptical cup deep drawing process by finite element analysis using bifurcation theory
No full textThe initiation and growth of wrinkles in sheet metal forming processes are influenced by many factors such as the stress state, the mechanical properties of the sheet material, the geometry of the body, and the contact conditions. It is difficult to analyze wrinkling initiation and growth considering these factors, because the effects of the factors are very complex and the wrinkling behavior may show a wide variation for small deviation of the, factors. In this study, bifurcation theory: is introduced for the finite element analysis of wrinkling initiation and growth. All the above mentioned factors are conveniently considered by the finite element method. The wrinkling initiation is determined by checking the determinant of the stiffness matrix at each iteration and the wrinkling behavior is analyzed by successive iteration with the perturbed guess along the eigenvector. The finite element formulation is based on the incremental deformation theory and elastic-plastic material modeling. The finite element analysis is carried out using continuum-based resultant shell elements. The initiation and growth of wrinkling in the elliptical cup deep drawing process are analyzed by the proposed algorithm. The effect of the aspect ratio of a punch on the wrinkling behavior in the elliptical cup deep drawing process is investigated. (C) 2001 Elsevier Science B.V. All rights reserved
Fabrication of polymeric large-core waveguides for optical interconnects using a rubber molding process
No full textPolymeric large-core (47 mu m x 41 mu m) optical waveguides for optical interconnects have been fabricated by using a rubber molding process. For low-cost low-loss large-core waveguides, our newly developed thick-photoresist patterning process is used for a master fabrication. Also a low-loss thermocurable polymer, perfluorocyclobutane (PFCB), is used in fabricating optical waveguides by rubber molding for the first time. The propagation loss is measured to be 0.4 dB/cm at the wavelength of 1.3 mu m, and 0.7 dB/cm at the wavelength of 1.55 mu m
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