Overlap integral analysis for second-harmonic generation within inverted waveguide using mode dispersion phase match

We have discussed the design of a multilayer waveguide toward an efficient nonlinear interaction. We have investigated five- and seven-layer inverted waveguides. The effect of the interlayer thickness and refractive index on the waveguide overlap integral and phase match thickness has been described. A simple approach for improving the nonlinear interaction within an inverted waveguide through maximization of the overlap integral is presented.     

Parallel-cascaded semiconductor microring resonators for high-order and wide-FSR filters

We demonstrate an optical channel dropping filter (OCDF) using three parallel-cascaded vertically coupled microrings with improved rolloff, bandpass flattening, and wide free spectral range (FSR) compared to a single-ring OCDF using single-mode tightly confined waveguides in both GaAs-AlGaAs and GaInAsP-InP. We achieve FSRs of 30 nm for GaAs-AlGaAs and 40 nm for GaInAsP-InP devices, which are three and four times greater, respectively, than those for single rings. The rolloff is 2.8 times faster than that for a single ring.     

Suspended microchannel resonators for ultralow volume universal detection

Universal detectors that maintain high sensitivity as the detection volume is reduced to the subnanoliter scale can enhance the utility of miniaturized total analysis systems (mu-TAS). Here the unique scaling properties of the suspended microchannel resonator (SMR) are exploited to show universal detection in a 10 pL analysis volume with a density detection limit of approximately 1 microg/cm (3) (10 Hz bandwidth) and a dynamic range of 6 decades. Analytes with low UV extinction coefficients such as polyethylene glycol (PEG) 8 kDa, glucose, and glycine are measured with molar detection limits of 0.66, 13.5, and 31.6 microM, respectively. To demonstrate the potential for real-time monitoring, gel filtration chromatography was used to separate different molecular weights of PEG as the SMR acquired a chromatogram by measuring the eluate density. This work suggests that the SMR could offer a simple and sensitive universal detector for various separation systems from liquid chromatography to capillary electrophoresis. Moreover, since the SMR is itself a microfluidic channel, it can be directly integrated into mu-TAS without compromising overall performance.     

Motor vehicle driver death and high state maximum speed limits: 1991-1993

OBJECTIVE: To measure the association between motor vehicle crash (MVC) driver death and high state maximum speed limits. METHODS: This study used a case-control design and assessed driver deaths from three major types of MVCs: non-collision; collision with motor vehicles in transit; and collision with stationary objects. The study period was 1991-1993. For each type of crash, case subject populations of fatally injured drivers were obtained from the U.S. Department of Transportation Fatality Analysis Reporting System. Four control subject populations, each associated with a different cause of death, were obtained from a U.S. national death certificate database (the causes of death were unintentional poisoning, non-Hodgkin lymphoma, drowning, and diabetes mellitus). Subjects were considered exposed if the state in which they crashed (for cases) or died (for controls) had a maximum speed limit greater than 55mph. Each of the three case subject populations was compared against each of the four control subject populations. Odds ratios (ORs) were adjusted for age and gender. RESULTS: For non-collision driver death, ORs ranged from 3.06 to 6.56, depending on the year and control group; all the ORs were significant. For collision with motor vehicles in transit driver death, ORs ranged from 1.12 to 2.22; all the ORs were significant. For collision with stationary objects driver death, ORs ranged from 0.87 to 1.83. CONCLUSIONS: There was a moderately strong and significant association between non-collision driver death and high state maximum speed limits. For collision with motor vehicles in transit driver death, the association was somewhat milder but still consistent. For collision with stationary objects driver death, the presence of an association was unclear. During 1991-1993, the effects of high state maximum speed limits may have been different for different types of MVCs.     

TiN Coatings Modified by an Interlayer of Electroplated Chromium on Mild Steel

TiN films on mild steel were deposited by reactive d.c. magnetron sputtering: electroplated chromium was incorporated as an interlayer. Surface hardness, measured by the Knoop indentation method under a load of 25 gf, phase analysis by the X-ray diffraction method and corrosion behaviour by the potentiodynamic measurement technique of these coatings have been evaluated. Surface hardness values were found to increase from about 1000–1100 for TiN coatings on mild steel to about 1800–1900 (HK₂₅) for TiN coatings with chromium as interlayer. Potentiodynamic corrosion tests, performed in IN H₂SO₄ solutions, have shown that with a chromium interlayer the corrosion resistance increases significantly as compared to TiN only sputtered coatings on mild steel samples. No spoiling of TiN coatings was observed during full sweep voltage of -1000 mV to +1000 mV when they were tested with a chromium interlayer.     

Digraph and matrix method for the performance evaluation of carbide compacting die manufactured by wire EDM

This paper presents a methodology to evaluate the performance of carbide compacting die using graph theoretic approach (GTA). Factors affecting the die performance and their interactions are analysed by developing a mathematical model using digraph and matrix method. Permanent function or die performance index is obtained from the matrix model developed from the digraphs. This permanent function/index value compares and ranks the factors affecting the die performance. It helps in selection of optimum process parameters during die manufacturing. Hence, process output errors such as dimensional inaccuracy, large surface craters, deep recast layers, etc. will be minimised during die manufacturing which helps to achieve better die performance. In present illustration, factors affecting the performance of carbide compacting die are grouped into five main factors namely work material, machine tool, tool electrode, geometry of die and machining operation. GTA methodology reveals that the machine tool has highest index value. Therefore, it is the most influencing factor affecting the die performance. In case of die material low cobalt concentration and small grain size yields good surface finish, while in machine tool low discharge energy (i.e. low values of peak current, pulse-on time, servo voltage and high value of pulse-off time) and high dielectric flow rate yields good surface finish and, hence, favours the good die performance. In case of die geometry, large work piece thickness and small taper angles results in lesser geometrical deviations and hence helps to achieve better die performance.     

Structural and Magnetic Properties of Co(Cr1−y Al y )2O4 (y=0.0–0.2) Compounds

We present the structural and magnetic properties of Co(Cr_1?y Al _y )₂O₄ compounds prepared by the sol-gel technique for y=0.00,0.025,0.05,0.075,0.10,0.15 and 0.20. It has been observed that non-magnetic Al⁺³ substitution for Cr⁺³ enhances the magnetization at low temperatures compared to that of the parent compound. With increase in Al concentration spiral magnetic transition observed at around 24 K becomes less prominent, without affecting the ferrimagnetic transition temperature at around 97 K. The saturation magnetization values after subtracting the paramagnetic contribution vary from 0.036 μ_B/f.u to 0.376 μ_B/f.u. The enhanced ferromagnetic interaction and resultant magnetization could be explained in terms of decrease in Cr⁺³–O–Cr⁺³ bond angle with increase in doping concentration.     

Optimization of a smooth flat plate solar air heater using stochastic iterative perturbation technique

Due to low heat transfer capability, the thermal efficiency of solar collectors is very low and various techniques are implemented to increase the performance of solar air heaters. There is a need for optimization of design and operating parameters for maximizing the thermal gain from the solar air heating systems. In this paper a stochastic iterative perturbation technique (SIPT) is implemented to obtain the optimized set of different system and operating parameters i.e. the number of glass cover plate, emissivity of the plate, mean plate temperature, rise in temperature, tilt angle and solar radiation intensity for different Reynolds number. The results obtained have also been compared with the results obtained from genetic algorithm and random search global optimization technique for smooth flat plate solar air heater.     

Highly efficient luminescence from hybrid structures of ZnO/multi-walled carbon nanotubes for high performance display applications

We report an interesting observation on strong enhancement in green luminescence from hybrid ZnO/multi-walled carbon nanotubes (MWCNTs). The hybrid structures were synthesized via a high temperature sintering method. The strong green emission at 510 nm has been attributed to surface defects of ZnO, originating from interactions between ZnO and the MWCNT surface, which has been confirmed by high resolution transmission electron microscopy and x-ray photoelectron spectroscopy. Furthermore, the two-dimensional (2D) layer of this hybrid material shows a high degree of homogeneity and 82% transparency. Time resolved emission spectroscopy measurement shows a photoluminescence decay time in microseconds, which is suitable for making optoelectronic devices.     

A Multidisciplinary Engineering Laboratory Course

The Colorado School of Mines (CSM) curriculum was recently modified by replacing laboratory courses in electrical circuits, fluid mechanics and stress analysis with a sequence of Multidisciplinary Engineering Laboratory courses (MEL I, II, and III). The MEL sequence prepares students for their professional careers by integrating discipline-specific components into systems and building subject-matter depth through a vertical sequence. The experiments move beyond basic theory verification by requiring students to practice higher level thinking. In addition, the systems experiments encourage students to reorganize knowledge and discover the connections among concepts in several courses. The MEL sequence helps students understand relationships among science, engineering science, and engineering design. The MEL experiments develop life-long learning skills by encouraging higher levels of thinking on the Perry scale and requiring students to use a variety of Kolb's learning styles. This paper describes the educational objectives and experiments for the MEL I course. The paper gives assessment results for MEL I and compares it with traditional laboratories.