The ANNIGMA-wrapper approach to fast feature selection for neuralnets

This paper presents a novel feature selection approach for backpropagation neural networks (NNs). Previously, a feature selection technique known as the wrapper model was shown effective for decision trees induction. However, it is prohibitively expensive when applied to real-world neural net training characterized by large volumes of data and many feature choices. Our approach incorporates a weight analysis-based heuristic called artificial neural net input gain measurement approximation (ANNIGMA) to direct the search in the wrapper model and allows effective feature selection feasible for neural net applications. Experimental results on standard datasets show that this approach can efficiently reduce the number of features while maintaining or even improving the accuracy. We also report two successful applications of our approach in the helicopter maintenance applications.     

Bayesian classification for data from the same unknown class

In this paper, we address the problem of how to classify a set of query vectors that belong to the same unknown class. Sets of data known to be sampled from the same class are naturally available in many application domains, such as speaker recognition. We refer to these sets as homologous sets. We show how to take advantage of homologous sets in classification to obtain improved accuracy over classifying each query vector individually. Our method, called homologous naive Bayes (HNB), is based on the naive Bayes classifier, a simple algorithm shown to be effective in many application domains. RNB uses a modified classification procedure that classifies multiple instances as a single unit. Compared with a voting method and several other variants of naive Bayes classification, HNB significantly outperforms these methods in a variety of test data sets, even when the number of query vectors in the homologous sets is small. We also report a successful application of HNB to speaker recognition. Experimental results show that HNB can achieve classification accuracy comparable to the Gaussian mixture model (GMM), the most widely used speaker recognition approach, while using less time for both training and classification.     

Application of VUV irradiation to promote the wet etch resistance of PSZ-SOG film inside the gap

In this paper, we demonstrate that vacuum ultraviolet (VUV) irradiation was effective to promote the wet etch resistance of perhydro-polysilazane-based inorganic spin-on-glass (PSZ-SOG) film inside the gap. The baking condition of VUV irradiation was chosen at 150 °C in 0.2 Pa before furnace curing process. Observed the densification characteristics of various trench sizes (aspect ratio (AR) = 3.1-0.13), all densification coefficient (D_eff) of the samples with VUV irradiation were larger than 0.90. On the contrary, for the sample without VUV irradiation, a remarkable reduction of D_eff values from 0.99 to 0.58 was found while the AR increasing from 0.13 to 3.1. The better densification characteristics of PSZ-SOG films were mainly contributed to the VUV photon. Compared with the reaction mechanisms during VUV irradiation and furnace curing, VUV photon is responsible for triggering the Si-N bond dissociation and accelerating the conversion rate of PSZ. Finally, the new reaction mechanism makes SOG films denser at STI region without additional thermal budget.     

A study on the circumferential groove effects on the minimum oil film thickness in engine bearings

This paper presents the effects of circumferential groove on the minimum oil film thickness in engine bearings. The fluid film pressures are calculated by using the infinitely short bearing theory for the convenience of analysis. Journal locus analysis is performed by using the mobility method. A comparison of minimum oil film thickness of grooved and ungrooved bearing is presented. It is found that circumferential 360° groove only reduces the absolute magnitude of the oil film thickness, but 180° half groove affects the shape of film thickness curve and position of minimum oil film thickness.     

Synthesis and photophysical properties of novel organo-soluble polyarylates bearing triphenylamine moieties

Two series of new blue photoluminescent aromatic polyesters (polyarylates) were synthesized from 4,4′-dicarboxytriphenylamine and 4,4′-dicarboxy-4″-methyltriphenylamine with various bisphenols by the diphenylchlorophosphate (DPCP) activated direct polycondensation in a medium of pyridine and lithium chloride. These polymers were amorphous and readily soluble in various common organic solvents including DMAc, THF, and chloroform, and could be cast from their chloroform solutions into transparent films due to their excellent solubility. These polyarylates exhibited moderately high T _g values (186–264 °C) and thermal stability. In THF solution, these triphenylamine-containing polyarylates showed UV-Vis absorption bands at 359–365 nm and photoluminescence peaks around 427–451 nm in the blue region. Figure Two series of new blue photoluminescent aromatic polyesters (polyarylates) were synthesized from 4,4’-dicarboxytriphenylamine and 4,4’-dicarboxy-4”-methyltriphenylamine with various bisphenols by the diphenylchlorophosphate (DPCP) activated direct polycondensation in a medium of pyridine and lithium chloride. These polymers were amorphous and readily soluble in various common organic solvents including DMAc, THF, and chloroform, and could be cast from their chloroform solutions into transparent films due to their excellent solubility. These polyarylates exhibited moderately high Tg values (186-264 oC) and thermal stability. All the PL spectra of these polymers showed a blue shift when the solvent was changed from NMP to THF or chloroform. Solvation should increase the interaction between polymer chain and solvent, which may consume certain excitation energy and lead to increase on the emission wavelength.     

Electrically bistable digital memory behaviors of thin films of polyimides based on conjugated bis(triphenylamine) derivatives

Three functional polyimides (PIs) bearing conjugated bis(triphenylamine) (2TPA) derivatives with electron-donating and accepting groups were synthesized with reasonably high molecular weights. The PIs exhibited high thermal and dimensional stabilities and furthermore produced high-quality nanoscale thin films via conventional solution coating process. All of the PIs in the films were found to be amorphous, but they were oriented somewhat preferentially in the film plane, rather than randomly. Their film densities and interchain distances were measured, and the optical and electrochemical properties were determined. All of the PIs in the devices with aluminum top and bottom electrodes initially revealed a high resistance (OFF-state). However, under positive and negative voltage sweeps, the PIs demonstrated volatile or nonvolatile digital memory behavior, depending on the substituents of the 2TPA unit. The 2TPA-based PI, as well as the PI bearing 2TPA with electron-donating methoxy substituents showed unipolar write-once-read-many-times (WORM) memory behavior, whereas the 2TPA-based PI containing electron-accepting cyano groups exhibited unipolar dynamic random access memory (DRAM) behavior. All of the PI films revealed excellent retention abilities in both the OFF- and ON-state, even under ambient air conditions. Moreover, they all revealed high ON/OFF current ratios (10⁶–10¹⁰). All of the memory behaviors were found to be governed by a mechanism involving trap-limited space-charge limited conduction and local filament formation. Such memory behaviors were further investigated in detail with taking into consideration the PI components' chemical nature and molecular orbital levels, possible trapping sites, substituents' effect, and the metal electrodes' work function. Overall, this study demonstrated that the thermally, dimensionally stable PIs are highly suitable for the low-cost mass production of high performance, polarity-free digital memory devices that can be operated with very low power consumption. Moreover, the memory mode can be tuned by changing the substituent in the 2TPA unit.     

K-Band CMOS Sub-Harmonic Resistive Mixer With a Miniature Marchand Balun on Lossy Silicon Substrate

A K-band sub-harmonically pumped resistive mixer is demonstrated using standard 0.13 mum CMOS technology. A miniature Marchand Balun is integrated with the resistive mixer to generate equal amplitude and out-of-phase signals for mixer's local oscillation (LO) port directly on the lossy silicon substrate. The sub-harmonic resistive mixer with the integrated Marchand balun has conversion loss of 11-12 dB at f_IF = 100 MHz and P_LO = 7 dBm for RF frequencies from 18 to 26 GHz. The LO-RF and LO-IF isolations are approximately 30 and 33 dB, respectively.     

Measurement and simulation of residual stress in type 304 weld overlay stainless steel pipe

Repair by welding overlay is a commonly used method mainly employed to rebuild piping systems suffering from intergranular stress corrosion cracking (IGSCC). It is desirable that the overlay welding technique, by attaching an overlay weld to the pipe and sustaining a heat sink of flowing water inside the pipe, induces a compressive residual stress at the inner surface of the welded pipe for prevention of IGSCC. A better understanding of the effect of a welding overlay repair on the residual stresses at the inner and outer surfaces of weld overlay is thus required. To obtain this understanding, it is necessary to investigate the distribution of residual stresses on the welded pipe.

In this study, the hole-drilling strain-gauge method was adopted to determine the residual stresses at the inner and outer surfaces of the weld overlay pipe. The incremental drilling technique was used on pipes with outside diameters of 267 mm. In addition, the Weld 3 code was applied to simulate the residual stress distribution for comparison and verification with the measured results.

The results obtained from the experimental and from the computational methods are in good agreement. The residual stress at the inner surface of the pipe is compressive with a magnitude approaching the yield stress of the material; that at the outer surface is tensile, also with a magnitude close to yield stress but smaller than the compressive stress. The experimental residual stress magnitude is generally greater than that from computation. This observation can be attributed to several factors including applied mechanics, temperature distribution, original residual stress, strain gauge location, mechanical grinding and the oxidation layer.     

Improvement of silicon solar cell efficiency by ion beam sputtered deposition of AlOxNy thin films

Negative charge material, AlOxNy, has been fabricated to passivate the surface of p-type silicon. The fabrication of AlOxNy was possible by using ion beam sputtering deposition to deposit AlN thin film on the surface of a p-type silicon wafer and following annealing in oxygen ambient. Capacitance-voltage analysis shows the fixed charge density has increased from 10(11)?cm(-2) to 2.26×10(12)?cm(-2) after annealing. The solar cell efficiency increased from 15.9% to 17.3%, which is also equivalent to the reduction of surface recombination velocity from 1×10(5) to 32 cm/s.