Multichannel sampling schemes for optical imaging systems

We introduce a framework of focal-plane coding schemes for multichannel sampling in optical systems. A particular objective is to develop an ultrathin imager without compromising image resolution. We present a complete f/2.1 optical system with a thickness of 2.2 mm. The resolution is maintained in the thin optical system by an integrated design of the encoding scheme, the process of making the coding elements, and the decoding algorithms.     

Effect of Modes of Heterogenizing Annealing Before Cold Rolling on the Structure and Properties of Sheets from Alloy 1565ch

Metal Science and Heat Treatment - The effect of modes of heterogenizing annealing (in the temperature range of 130 – 230°C with exposure of 6 – 24 h) before cold rolling on the...     

Analysis of softening alloys of the Al-Ni system containing particles of variable dispersity

Regularities of the deformation strengthening and softening of aluminum alloys containing second-phase Al₃Ni particles 0.3 to 2.2 μm in size with a volume fraction from 0.03 to 0.1 are investigated during cold deformation and subsequent annealing at 0.6t _m. It is shown that the largest hardness increment is observed for alloys with a maximal fraction of fine particles (d = 0.3 μm) after rolling deformation larger than 0.4. Fine particles prevent the development of crystallization upon true deformation up to 2.3, thereby effectively inhibiting softening. An increase in the particle size to 1.2–2.2 μm stimulates nucleation during recrystallization, substantially accelerating this process. For example, in order to ensure recrystallization uniformly over the entire sheet volume at d = 2.2 μm, cold deformation with ? = 0.4 is sufficient.     

Hydrodynamics of shunt valves

A study of differential pressure valves (DPV) used in the treatment of hydrocephalus was undertaken to determine their pressure-flow characteristics and compatability with the antisiphon valve (ASV). DPV could be classified into two groups: low resistance valves (LRV) and high resistance valves (HRV). The LRV maintains intraventricular pressure (IVP) near the closing pressure (CP) of the valve by permitting a high flow whenever CP is exceeded. The HRV regulates IVP by attempting to match inflow with some point on the pressure-flow curve of the valve. These characteristics were lost unless valve outlet pressure was maintained at atmospheric pressure. This could be accomplished by using a proximal DPV with an ASV at the DPV outlet, thus converting the DPV into a gauge pressure valve and preventing the 'siphon effect' seen with the use of a DPV alone.     

Optimal selection of IC fabrication parameters

A procedure is described in which the output characteristics of an integrated circuit are optimized with respect to a set of variable fabrication parameters. A simple RC coupled audio amplifier is used as an example. The gain–bandwidth product is obtained as a function of oxidation and diffusion times and temperatures, and the optimization is performed by way of a line search using these variables as the parameters of the optimization. The values established for the process parameters are consistent with those employed for conventional fabrication, and desired changes in performance can be obtained, in general, by a straightforward readjustment of the values of the process variables. Although limited by certain assumptions and a relatively primitive circuit, the results demonstrate the validity of the procedure.     

Role of the amplifying gate in the turn-on process of involutestructure thyristors

The switching characteristics of involute thyristors with and without the amplifying gate structure are discussed. The effects of peak gate currents (10-100 A) on the anode current di/dt, switching delay, and energy loss in both types of devices are presented. The performance of the devices without the amplifying gate was far superior than that of the devices with the amplifying gate. A model is presented to explain this difference. Thyristors without the amplifying gate successfully switched anode currents on the order of 12.6 kA, at a di/dt of 100000 A/μs, from an anode voltage of 2 kV on a single-shot basis     

Quantile regression with doubly censored data

Quantile regression offers a semiparametric approach to modeling data with possible heterogeneity. It is particularly attractive for censored responses, where the conditional mean functions are unidentifiable without parametric assumptions on the distributions. A new algorithm is proposed to estimate the regression quantile process when the response variable is subject to double censoring. The algorithm distributes the probability mass of each censored point to its left or right appropriately, and iterates towards self-consistent solutions. Numerical results on simulated data and an unemployment duration study are given to demonstrate the merits of the proposed method.     

MOS-gated thyristors (MCTs) for repetitive high power switching

Certain applications for pulse power require narrow, high current pulses for their implementation. This work was performed to determine if MOS controlled thyristors (MCTs) could be used for these applications. The MCTs were tested as discharge switches in a low inductance circuit delivering 1 μs pulses at currents between roughly 3 kA and 11 kA, single shot and repetitively at 1, 10, and 50 Hz. Although up to 9000 switching events could be obtained, all the devices failed at some combination of current and repetition rate. Failure was attributed to temperature increases caused by average power dissipated in the thyristor during the switching sequence. A simulation was performed to confirm that the temperature rise was sufficient to account for failure. Considerable heat sinking, and perhaps a better thermal package, would be required before the MCT could be considered for pulse power applications     

Friction of copolymers of methyl α-n-alkylacrylates (alkyl ⩾ C16H33) and n-octadecyl methacrylate with methyl methacrylate

A comparative study was made of the friction and wear properties of homopolymers and copolymers (with methyl methacrylate (MMA)) of methyl α-n-hexadecylacrylate (MHDA), methyl α-n-octadecylacrylate (MODA) and n-octadecyl methacrylate (ODMA). In the first two compounds the long alkyl side chain is attached to the polymer backbone, whereas in the last it is adjacent to the carboxyl group that is attached to the polymer backbone. The friction data obtained for homopolymers and copolymers (thin films on glass or steel) of MHDA, MODA and ODMA were similar. The coefficient of friction μ decreased rapidly at a low concentration of MHDA, MODA or ODMA in the copolymers, then decreased more slowly. At about 50 mol.% μ (copolymer) ≈ μ(homopolymer) and further increases in the concentrations of these monomers in the copolymer led to a slight decrease in μ to the limit of the μ value for the homopolymer (μ ≈ 0.10). The durability of thin films (about 3700–4100 Å thick) of the copolymers increased with the concentration of MHDA, MODA or ODMA up to 21–25 mol.%. However, 100% MHDA and MODA have lower durabilities than some of the copolymers. All homopolymers and copolymers show higher durabilities than poly-MMA and the durabilities of some of the copolymers approach that of poly-ODMA, which has the highest durability in the series of polymers studied. The lower durabilities of poly-MHDA and poly-MODA ($\text{M}\text{?}{}_{\mathrm{n}}$ values 7083 and 1320) compared with that of poly-ODMA ($\text{M}\text{?}{}_{\mathrm{n}}\text{= 1.9 × 10}{}^5$) may be related to their low molecular weights. In all cases the durability of the homopolymers and copolymers was greater on glass than on steel. Available evidence indicates that the decrease in μ and the increase in durability of the copolymers studied is attributable to the long alkyl side chain and not to the polymer backbone. Further, the effect of the long alkyl side chain on μ and on durability is related to its flexibility and capability of orientation during the rubbing process.