Thermoelectric Generation Using Water Lenses

A solar light concentrator composed of water and plastic transparent film has been designed. This flexible lens design can trace the solar movement through control of the tensile stress and amount of water, and concentrate the solar energy onto the thermoelectric (TE) module surface. An experimental water lens was constructed, and the concentrated intensity was monitored by a photodiode as a function of x–z position; For example, when 3.0 kg water was filled and tension of 69.0 N/m was applied to the transparent vinyl sheet, the concentration ratio was evaluated as the maximum of 28.0 at a depth of 657 mm from the water lens bottom surface. TE generation was tested to show the validity of the water lens. The surface condition of the receiver was found to be critical.     

Ocular Effects of Exposure to 40, 75, and 95 GHz Millimeter Waves

The objective of this study was to develop a model of ocular damage induced by 40, 75, and 95 GHz continuous millimeter waves (MMW), thereby allowing assessment of the clinical course of ocular damage resulting from exposure to thermal damage-inducing MMW. This study also examined the dependence of ocular damage on incident power density. Pigmented rabbit eyes were exposed to 40, 75, and 95 GHz MMW from a spot-focus-type lens antenna. Slight ocular damage was observed 10 min after MMW exposure, including reduced cornea thickness and reduced transparency. Diffuse fluorescein staining around the pupillary area indicated corneal epithelial injury. Slit-lamp examination 1 day after MMW exposure revealed a round area of opacity, accompanied by fluorescence staining, in the central pupillary zone. Corneal edema, indicative of corneal stromal damage, peaked 1 day after MMW exposure, with thickness gradually subsiding to normal. Three days after exposure, ocular conditions had almost normalized, though corneal thickness was slightly greater than that before exposure. The 50% probability of ocular damage (DD₅₀) was in the order 40?>?95?≈?75 GHz at the same incident power densities.     

Pipelined delay-sum architecture based on bucket-brigade devices for on-chip ultrasound beamforming

A pipelined delay-sum architecture based on bucket-brigade devices is proposed as an analog beamformer for integrated far-field steering scanning of a micromachined piezoelectric ultrasonic sensor phased array. The prototype beamformer, fabricated with an 8-/spl mu/m standard CMOS process, exhibits a total harmonic distortion of -45 dB, dynamic range of more than 65 dB, and beamforming imperfection of less than -50 dB using a 100-kHz input signal with peak voltage of 400 mV.     

Extending transmission bandwidth of air-core photonic bandgap fibers

Air-core photonic bandgap fibers offer many unique properties and are critical to many emerging applications. A notable property is the high nonlinear threshold which provides a foundation for applications at high peak powers. The strong interaction of light and air is also essential for a number of emerging applications, especially those based on nonlinear interactions and spectroscopy. For many of those applications, much wider transmission bandwidths are desired to accommodate a wider tuning range or the large number of optical wavelengths involved. Presently, air-core photonic bandgap fibers have a cladding of hexagonal lattice. The densely packed geometry of hexagonal stacking does not allow large nodes in the cladding, which would provide a further increase of photonic bandgaps. On the other hand, a photonic cladding with a square lattice can potentially provide much larger nodes and consequently wider bandgap. In this work, the potentials of much wider bandgap with square lattice cladding is theoretically studied and experimentally demonstrated.     

Monolithic 2.1 Gbit/s decision circuit with a decision threshold ambiguity width of less than 10 mV

An Si bipolar monolithic decision circuit for practical use is developed using an improved circuit technique and super self-aligned process technology with the reliable 1.25 ?m rule. The circuit consists of a slice amplifier, a master-slave D flip-flop and an output buffer. This circuit is capable of operating up to 2.1 Gbit/s with a decision threshold ambiguity width of less than 10 mV. In addition, a clock phase margin of 250 degrees and power dissipation of 640 mW at VEE=?6 V can be achieved.     

Heat Transfer & Thermal Stress Analysis of Plastic-Encapsulated ICs

Analytic approaches of thermal stress in plastic-encapslated ICs reliability have been studied using a simple, 2-dimensional model of the cross section of ICs by the finite-element method. To test the validity of the model, the actual stress within the silicon chip was measured using piezoresistive devices. The calculated stress in the silicon chip agreed with the experimental values. The stress distributions were changed by lead-frame properties. Package cracking, and delamination between the molding plastic and the lead-frame were qualitatively explained. We estimated the effect of the plastic properties on stress quantitatively. Furthermore, to test the validity of this model, the temperature change at the silicon chip was measured using the Vf temperature dependency of a diode. The calculated temperature change at the silicon chip agreed with the observed values. A very high temperature gradient was observed near the surface of the plastic immediately after solder dipping. The non-uniform temperature distributions produced different thermal stress distributions than those observed in the steady-state. This result indicated that rapid thermal shock could delaminate the plastic from the lead-frame. We believe that these results can guide the development of an optimum low-stress plastic.     

InP/InGaAsP p-type substrate and mass transported doubly buried heterostructure laser

A novel InP/InGaAsP buried heterostructure laser diode on p-type InP substrate has been developed. The laser has achieved a threshold current as low as 20 mA DC with high power output of 50 mW under CW operation in the fundamental transverse mode.     

Electronic scanning by ferrite-loaded corner reflector antennas

The measured performances of the antennas which consist of a90degcorner reflector, a horn, a core wire of a coaxial line, two or three ferrite rods, and electromagnets magnetizing the respective ferrites are presented. The following are made clear for the antenna with two ferrite rods. The load of the ferrites yields the asymmetric power pattern owing to the anisotropy of the ferrites, though the antenna geometry and the magnetization of the ferrites are symmetric. Moreover, the remarkably sharper main lobe and the higher gain are obtained by loading the ferrites. The main lobe can be turned to the direction reflected about the symmetric plane of the antenna by reversing all the dc magnetic fields applied to the ferrites, that is, electronic lobe switching in theH-plane is realized. It is shown that the antenna loaded with three ferrite rods makes the continuous scan of the main lobe possible by applying the suitable magnetic fields to the ferrites. The direction of the main lobe of these antennas is turned by electronically changing the currents of the electromagnets, that is, by changing the tensor permeabilities of the ferrites. The reciprocity for antennas composed of isotropic media does not hold for these antennas. The receiving power pattern coincides with the transmitting pattern reflected about the symmetric plane when the same dc magnetic fields are applied for both cases. Hence, these antennas permit us to receive from a direction and simultaneously to transmit in the direction reflected about the symmetric plane.     

Long-range OTDR for single-mode optical fibre using a P2O5 highly doped fibre Raman laser

A wide-dynamic-range single-mode optical time-domain reflectometer using a P2O5 highly doped fibre Raman laser and a cooled Ge-PIN photodiode has been realised for the first time. The maximum detectable one-way loss was improved to 35dB in the 1.5 ?m wavelength band.     

Preparation of silica fibers and non-woven cloth by electrospinning

Silica fibers, which can potentially be used as filters and media for catalysts immobilization, were successfully spun via electrospinning process with precursor prepared through the sol–gel synthesis. Spinnable sols can be obtained only when the molar ratio of water to TEOS is less than 2 which is consistent with the retrospective results derived for other spinning methods. It was confirmed for the first time that the reaction time can be drastically reduced by introducing humidified air, controlled by KCl saturated aqueous solution, during sol–gel process. The size of obtained silica fibers is about 4.5 μm and has a certain degree of flexibility and mechanical strength. Although the specific surface area of as spun fiber was 7.7 m²/g, which is apparently small comparing to generic silica, treatment by boiling water only for 5 min could increase the specific surface area to be about 500 m²/g.