AC-based phosphor LED visible light communication by utilizing novel signal modulation

We propose and demonstrate a new AC-light emitting diode based visible light communication system, in which the message signal is up-converted to 400 kHz frequency band and combine with the 60 Hz AC-power from the outlet. A special design bias-tee circuit is first implemented to combine the message signal and the AC-power for minimizing the signal distortion. Thus, the spectra of both signals are well separated. A special design clock recovery is used to synchronize the AC-power with the message signal; hence the message signal can be correctly applied to the rectified AC-power cycle.     

Low-noise fiber optics receiver with super-beta bipolar transistors

Abstract

A low-noise wideband optical fiber receiver has been successfully designed using super-beta bipolar transistors (BJTs) at the front end. Even with commercially available super-beta devices, which are not optimized for our application, the obtainable input sensitivity for medium- and high-bandwidth optical receivers is comparable or superior to the best FET design. To demonstrate this concept, a 10-MHz analog receiver was built with a super-beta BJT at the input stage. This receiver achieved an expected average input noise current density of less than 0.4 PA/√Hz over the full bandwidth for a transresistance of 500 kΩ. Detailed design procedures are given in this paper. The noise characteristics of a 50-MHz receiver using super-beta BJTs are also obtained.     

A novel immunoassay using platinum nanoparticles,silver enhancement and a flatbed scanner

This study reports a potentially rapid and convenient immunoassay using antibody-platinum nanoparticle (Ab-PtNPs) conjugates as a reporter molecule and a flatbed scanner for detecting immuno-reaction and measuring of the immuno-reaction signal. This study was based on the sandwich immunoassay (three-layer format) which contained a primary antibody, test antigens and a secondary antibody. The results showed that the silver precipitation phenomenon was catalyzed by Ab-PtNPs conjugates. The changing color of reaction could easily be observed by naked eye or scanner. The silver enhancement reaction, a signal amplification method in which silver ions are reduced to silver metal, is introduced to magnify the detection signal. The relationship between sample concentration and detection signal was discussed. And the detection limit (sandwich assay) for the sample antigen was 10^-1 ng/mL. Using a flatbed scanner, Ab-PtNPs conjugates and a silver enhancement reaction, a new immunoassay is constructed.     

Four New Lignans with a Bicyclo[3.3.1]nonadienemethanol Skeleton from Cunninghamia lanceolata

Four unique bicyclo[3.3.1]nonadienemethanol lignans, designated lanceolatanins A ( 1 ), B ( 2 ), C ( 3 ), and D ( 4 ), along with one previously known compound, isolariciresinol ( 5 ), were isolated from the MeOH extracts of the heartwood of Cunninghamia lanceolata. Their structures were elucidated by application of various spectroscopic methods, including 1D‐ and 2D‐NMR techniques, to their acetylated derivatives 1a, 2a, 3a , and 4a . Their possible biosynthetic formations are also discussed.     

Dynamics of refractive-index changes and two-beam coupling in resonant media

The dynamics of light-induced change in the refractive index of a resonant medium are examined. For illumination with weak fields, the two relevant relaxation times are T ₁, the population lifetime and T ₂, the dipole-dephasing time. The response time of the index change is determined by the slower relaxation time of the medium which is usually the time T ₁ taken by the excited system to relax back to its thermal equilibrium value. Illumination with two beams of the same frequency that intersect within the medium leads to the formation of a volume grating in the medium that is spatially local. Hence there is no exchange of energy between the beams that write the grating, each beam merely reducing the absorption experienced by the other beam. Illumination with a moving, spatially periodic intensity pattern leads to gain for one beam and additional absorption for the other beam as they propagate through the medium. A complete set of coupled equations describing the intensities and phases of the beams undergoing non-degenerate two-wave mixing in the resonant media is derived using third-order perturbation theory, and the solutions are studied numerically. In particular, the two-beam coupling constant for intensity is shown to depend on the frequency difference between the two beams and on the pressure-induced collisional relaxations in the system.     

Friction, wear and elasto-plastic stress analysis of rf-sputtered carbon-nitrogen protective coatings for rigid magnetic storage disks

Thin carbon protective coatings were deposited on rigid magnetic disks by rf diode sputtering using a mixture of argon and nitrogen gases. A continuous drag test with thin-film head sliders was used to evaluate the performance of carbon coatings. Results significantly show that the carbon-nitrogen coatings have better wear performance than pure argon-sputtered carbon coatings. In addition, an elasto-plastic analysis of the stress distribution strongly indicates that wear damage should more readily occur in carbon overcoats containing large graphite particles and that a durable carbon coating should have a higher percentage of sp³ bonding.     

Instabilities in coupled photorefractive ring cavities and self-pumped phase conjugators

In the preceding paper, we used the mean-field approximation to formulate the time evolution equations for two coupled unidirectional photorefractive ring resonators. Linear stability analysis based upon the steady-state solutions of the mean-field equations showed that the coupled system may become unstable in the unstable off- and steady-state operation regimes. In this paper, we investigate the temporal behavior and nonlinear dynamics of the coupled system. The results indicate that the coupled system exhibits self-pulsation and chaos in the unstable off-state and steady-state operation regimes. The instability is explained in terms of the competition between the nonlinear gain and loss. Numerical results of the transient equations are presented and discussed. The coupling between unidirectional ring resonators is extended to explain the instability in self-pumped phase conjugators.     

Intramolecular cyclization of ethyl ω-(5-amino-4-aminocarbonylimidazol-1-yl)carboxylates

Attempted elaboration of the title compounds to purines by reaction with ethyl formate leads instead to some novel fused imidazoles by intramolecular cyclization.     

Numerical solutions of Navier-Stokes equations with an integrated compartment method (ICM)

The most common numerical methods that are used by physical scientists to approximate partial differential equations employ finite differences and/or finite elements. In addition, compartment analyses have been adopted by ecological system analysts to simulate the evolution of processes governed by differential equations without spatial derivatives. An integrated compartment method (ICM) is proposed to combine the merits of these three numerical techniques. The basic procedures of the ICM are first to discretize the region of interest into compartments, then to apply three integral theorems of vectors to transform the volume integral to the surface integral, and finally to use interpolation to relate the interfacial values in terms of compartment values to close the system. These procedures are applied to the Navier-Stokes equations to yield the computational algorithm from which computer programs can be coded. The computer code is designed to solve one-, two-, or three-dimensional problems as desired. The program is applied to two simple cases: wake formation behind an obstacle in a channel and circulatory motion of a body of fluid in the square cavity. These preliminary applications have shown promising results.