Miniature Diode Research Articles

Enhanced Dye-Sensitized Mechanosensation Utilizing Pulsed and Digitally Modulated Light.

The generation of pressure perturbations in matter stimulated by pulsed light is a method widely recognized as the photoacoustic or light-induced thermoelastic effect. In a series of psychophysical experiments, the robustness of the tactile perception generated with a variety of light sources is examined: a diverging pulsed laser used for photoacoustic tomography optical parameter oscillation (OPO), a miniature diode laser (MDL), and a commercial digital light processing (DLP) projector. It is demonstrated that participants can accurately detect, categorically describe the sensations, and discern the direction of pulsed light travel. High detection accuracy is reported as follows: (d' = 4.95 (OPO); d' = 2.78 (modulated MDL); d' = 2.99 (DLP)) of the stimulus on glabrous skin coated with a thin layer of dye absorber. For all light sources, the predominant sensation is felt as vibration at the distal phalanx (i.e., fingertip, 55.21-57.29%) and the proximal phalanx (41.67-44.79%). At the fingertip, thermal sensations are perceived less frequently than mechanical ones. Moreover, these haptic effects are preserved under a wide range of pulse widths, spot sizes, optical energies, and wavelengths of the light sources. This form of sensory stimulation demonstrates a generalizable non-contact, non-optogenetic, in situ activation of the mechanosensorysystem.

High Precision Human Skin Temperature Fluctuations Measuring Instrument.

This paper describes the experimental results of testing a prototype of a high precision human skin rapid temperature fluctuations measuring instrument. Based on the author’s work, an original circuit solution on a miniature semiconductor diode sensor has been designed. The proposed circuitry provides operation in the full voltage range with automatic setting and holding the operating point, as well as the necessary slope of the conversion coefficient (up to 2300 mV/°C), which makes it possible to register fast temperature oscillations from the surface of the human body and other biological objects. Simulation results in the Microcap 12 software and laboratory tests have confirmed all declared design specifications: temperature resolution of 0.01 °C, transducer thermal time constant of 0.05 s. An original thermostat and an experimental setup for the simultaneous registration of the electrocardiogram, pulse wave signals from the Biopac polygraph MP36 and a signal of temperature oscillations from the prototype thermometer have been designed for further investigations. The preliminary test results indicates that using the designed measuring instrument gives a possibility to provide an in-depth study of the relationship between micro- and macro-blood circulations manifested in skin temperature fluctuations.

微型化LD泵浦Er 3+ ,Yb 3+ 共掺磷酸盐玻璃被动调Q激光器

A miniature diode pumped passively Q-switched Er3+ and Yb3+ co-doped phosphate glass laser is reported. The center wavelength of pump source is 940 nm. A Co2+: MgAl2O4 crystal is used as a saturable absorber. When the pump energy is 14 mJ, stable Q-switched pulses are obtained at repetition frequency of 10 Hz and pump pulse width of 5 ms. The output pulse energy of laser is 480 J and pulse width is 5 ns . The wavelength of laser is 1535 nm. The peak power is higher than 20 kW and beam quality is 1.2.

Characterization of miniature RAD-HARD silicon diodes as dosimeters for small fields of photon beams used in radiotherapy

The dosimetric response characterization and beam data acquisition performance of a miniature Float Zone (FZ) silicon diode for photon beams was investigated using Novalis TX linear accelerator (Varian Medical Systems®). In all measurements the unbiased diode operated in a short-circuit mode, connected to the input of a Keithley 6517B electrometer using a water phantom. For photon beams of the 6 and 15 MV the results presented good repeatability (coefficient of variation ≤1.6%), measured through switching on/off the photon beams. Moreover, the diode showed a quite linear response, given by the charge versus absorbed dose, with charge sensitivities higher than 6.9 nC/Gy. The output factor, percentage depth dose profile (PDD) and transversal dose profile (TDP) were also measured in a water phantom. For small field sizes, the output factor values using the FZ diode were compared with measurements obtained with a SFD (Stereotactic Field Diode) commercial diode and the differences were 5.4%, 2.5% and 1.3% for the field sizes of 1 × 1, 2 × 2 and 3 × 3 cm². For larger field sizes (≥4 × 4 cm²), the maximum difference found was 0.7% in comparison with values obtained with a CC13 ionization chamber. Thus, the result demonstrates that the unshielded FZ diode has the potential to be used for measuring of, as it performed acceptably well for both small and large field sizes. The TDP experimental results obtained with the FZ diode for field sizes of: 1 × 1 cm2, 2 × 2 cm2 and 4 × 4 cm2 are in agreement with experimental results acquired with several commercial detectors. Through the TDP study, the comparison of the field penumbra size confirmed the excellent spatial resolution of the miniature diode. However, the PDD study, requires further investigation.

Capacitively coupled microplasma for on-column detection of chromatographically separated inorganic gases by optical emission spectrometry

Two tubular electrodes placed on a capillary tubing are used to couple an electrical ac field of high voltage (20 kV) but low frequency (20 kHz) and about 8 W power inside for generation of the plasma. The emitted radiation is passed to a spectrometer via an optical fibre butted to the side of the capillary. The excitation temperature of the plasma determined from helium emission lines is about 4000 K. It was found possible to detect oxygen from its emission at 777 and 845 nm, hydrogen at 656 nm and sulfur containing species from emission at 923 nm. The carbon-containing species CH 4, CO, and CO 2 could be determined from an emission band at 385 nm due to CN. Detection limits in the range between about 1 and 10 ng were obtained using a miniature diode array spectrometer.

A miniature biochip system for detection of aerosolized Bacillus globigii spores.

The feasibility of using a novel detection scheme for the analysis of biological warfare agents is demonstrated using Bacillus globigii spores, a surrogate species for Bacillus anthracis. In this paper, a sensitive and selective enzyme-linked immunosorbent assay using a novel fluorogenic alkaline phosphatase substrate (dimethylacridinone phosphate) is combined with a compact biochip detection system, which includes a miniature diode laser for excitation. Detection of aerosolized spores was achieved by coupling the miniature system to a portable bioaerosol sampler, and the performance of the antibody-based recognition and enzyme amplification method was evaluated. The bioassay performance was found to be compatible with the air sampling device, and the enzymatic amplification was found to be an attractive amplification method for detection of low spore concentrations. The combined portable bioaerosol sampler and miniature biochip system detected 100 B. globigii spores, corresponding to 17 aerosolized spores/L of air. Moreover, the incorporation of the miniature diode laser with the self-contained biochip design allows for a compact system that is readily adaptable to field use. In addition, these studies have included investigations into the tradeoff between assay time and sensitivity.

Using miniature diode array NIR spectrometers for analysing wood chips and bark samples in motion

The chemical and physical properties of the wood chips entering the Kraft pulping process are of high interest for many different reasons. The most important one is the possibility to establish an effective and dynamic forward process control. The same is valid for one of the by-products, bark, which is burned in a solid fuel furnace for energy recovery. In the present study, NIR (near-infrared) reflectance measurements with an inexpensive silicon diode array spectrometer operating in the 800–1100 nm range are evaluated as a tool for on-line analysis of wood chips and bark transported on a conveyor belt moving at 1 m s−1. The objective of this work was to investigate the determination of water content, extractive content, Klason lignin, carbohydrate monomers and size distribution of wood chips together with water content, wood content and coarseness of bark. All these parameters could be measured with the exception of the carbohydrates, for which it was only possible to satisfactorily measure the sum of pentoses (arabinose + xylose) and the sum of hexoses (glucose + galactose + mannose). FWEFA (fixed window evolving factor analysis) was used for automatic identification of outliers. Copyright © 2000 John Wiley & Sons, Ltd.

Non-Invasive Fermentation Analysis Using an Artificial Neural Network Algorithm for Processing near Infrared Spectra

The feasibility of using Artificial Neural Networks (ANN) to improve the performance of a fibre optic, near infrared (NIR) spectroscopic probe for monitoring fermentation processes was investigated. A miniature diode array spectrometer, operating between 1100 and 1450 nm, was used for on-line, in situ fermentation monitoring by placing a bifurcated fibre bundle inside a fermentation vessel. Non-linearities in the spectral response were complicated by the combined effects of spectral variations in the OH vibrational bands due to temperature fluctuations and pH variation. As the fermentation proceeds interferences from other absorbing molecules and cell masses increase at an exponential rate. The feasibility of accurately predicting both glucose and ethanol concentrations simultaneously during a fermentation process were assessed by applying Partial Least Squares (PLS) and Artificial Neural Networks (ANN) to the NIR spectral data. For a 5% glucose fermentation, a PLS model was able to predict “on-line” concentrations with standard errors of prediction ( SEP) of 0.19% for glucose and 0.11% for ethanol. Three separate on-line fermentation experiments were performed in order to determine the possibility of using a model developed from one experiment to predict the concentrations of another experiment. PLS models produced an average SEP of 0.21% when used to predict different fermentation experiments. The ANN algorithm produced an average SEP of 0.13% on the same data.

MeasureNet: Electronic Measurement Network for the Freshman Chemistry Laboratory

All of the students in our freshman chemistry laboratory program now have routine access to a range of high-quality electronic measurements. This has been accomplished by means of a newly-designed network system, based on network technology developed by the automotive industry. Each individual network serves 20 students working in pairs, but requires only 1 PC with printer, since much of the data observation and manipulation take place on the graphical displays of the individual measurement and display stations. In addition to the expected types of measurement (pH, temperature, pressure, voltage, etc.), a miniature diode array spectrometer has now been added to the system, providing easy access to visible emission and absorption spectroscopy. This networked spectrometer greatly extends the capabilities provided for routine student use. The system makes it easy for groups to share and combine data. For instance, all 20 students on one system can divide up the experimental work and then combine and discuss ...

Advances in the development of the interferometric otoscope.

Present measurement techniques for middle ear function have inherent limitations because they are either spatially insensitive (acoustic immittance) or descriptive and qualitative in nature (otoscopy). By integrating advances in electrooptic technology (fiber optics, miniature diode lasers, solid-state detector arrays) and digital processing, further advances are possible. On the basis of measurements taken with electronic speckle-pattern interferometry on human temporal bones and models, we demonstrate quantitative static and dynamic vibration/displacement characteristics of the tympanic membrane with high spatial resolution. Our presentation emphasizes advantages of optically based methods and demonstrates computerized signal processing capable of fringe localization, enhancement, and counting. Miniaturization and real-time digital image processing in the clinical setting is the goal of this research.

Experimental relative frequency stabilization of a set of lasers using optical phase-locked loops

A relative frequency stabilization technique using optical phase locking of miniature diode pumped Nd:YAG ring lasers is described. The master laser is RF phase modulated with a modulation index up to 7.4, and slave lasers are locked up to 21 master laser sidebands with a frequency stability better than 3 kHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An evaluation of microwave diathermy applicators using free space electric field mapping

An electric field mapping study is described which was designed and executed to study the performance characteristics of various prototype and currently used microwave diathermy applicators operating at 2450 MHz. A miniature diode detector/dipole probe, developed by the Bureau of Radiological Health, was used to map the 'near' electric fields in the aperture plane of each applicator. From the field mapping results, parameters for use in the evaluation of the radiation safety of various applicators are developed. A thermographic camera was used to determine heating characteristics of the applicators in simulated biological material. The thermal effectiveness of these applicators was also investigated by determining their Specific Absorption Rate, a recently developed parameter. The superiority of a specially designed prototype applicator (in terms of uniformity and effectiveness of energy deposition, and minimal leakage radiation) compared with currently used applicators is demonstrated.

Miniature tunnel diode transducers

Miniature tunnel diode transducers having operation related to controllable band gap modulation mechanism

Direct Measurement of Generator Winding Temperature Using a Miniature Transmitter

The direct measurement of stator winding copper temperatures in large electric machines is made possible with a miniature tunnel diode oscillator, mounted directly on the current-carrying conductor. A temperature-sensitive capacitor in the oscillator's resonant circuit causes the radiated signal frequency to change as copper temperature changes. This signal, radiated through the thickness of the winding ground insulation, reaches an antenna external to the ground insulation. Then this signal is compared with one from a calibrated external oscillator, using a standard AM (amplitude modulated) radio circuit which will indicate changes in transmitted frequency. Calibration curves of frequency vs. temperature will reveal the copper temperature at the transmitter.