On the Dual-Tree Complex Wavelet Packet and $M$-Band Transforms

The two-band discrete wavelet transform (DWT) provides an octave-band analysis in the frequency domain, but this might not be ldquooptimalrdquo for a given signal. The discrete wavelet packet transform (DWPT) provides a dictionary of bases over which one can search for an optimal representation (without constraining the analysis to an octave-band one) for the signal at hand. However, it is well known that both the DWT and the DWPT are shift-varying. Also, when these transforms are extended to 2-D and higher dimensions using tensor products, they do not provide a geometrically oriented analysis. The dual-tree complex wavelet transform , introduced by Kingsbury, is approximately shift-invariant and provides directional analysis in 2-D and higher dimensions. In this paper, we propose a method to implement a dual-tree complex wavelet packet transform , extending the as the DWPT extends the DWT. To find the best complex wavelet packet frame for a given signal, we adapt the basis selection algorithm by Coifman and Wickerhauser, providing a solution to the basis selection problem for the . Lastly, we show how to extend the two-band to an -band (provided that ) using the same method.     

Composition-Dependent Photoluminescence Properties and Anti-Counterfeiting Applications of A2AgX3 (A = Rb,Cs; X = Cl,Br, I)

Copper(I) halides are emerging as attractive alternatives to lead halide perovskites for optical and electronic applications. However, blue-emitting all-inorganic copper(I) halides suffer from poor stability and lack of tunability of their photoluminescence (PL) properties. Here, the preparation of silver(I) halides A₂AgX₃ (A = Rb, Cs; X = Cl, Br, I) through solid-state synthesis is reported. In contrast to the Cu(I) analogs, A₂AgX₃ are broad-band emitters sensitive to A and X site substitutions. First-principle calculations show that defect-bound excitons are responsible for the observed main PL peaks in Rb₂AgX₃ and that self-trapped excitons (STEs) contribute to a minor PL peak in Rb₂AgBr₃. This is in sharp contrast to Rb₂CuX₃, in which the PL is dominated by the emission by STEs. Moreover, the replacement of Cu(I) with Ag(I) in A₂AgX₃ significantly improves photostability and stability in the air under ambient conditions, which enables their consideration for practical applications. Thus, luminescent inks based on A₂AgX₃ are prepared and successfully used in anti-counterfeiting applications. The excellent light emission properties, significantly improved stability, simple preparation method, and tunable light emission properties demonstrated by A₂AgX₃ suggest that silver(I) halides may be attractive alternatives to toxic lead halide perovskites and unstable copper(I) halides for optical applications.     

A Hybrid Electromagnetic-Circuit Method for Electromagnetic Interference Onto Mass Wires

A current decomposition method is proposed for the analysis of field coupling to mass wires near complex structures. The foremost attribute of the method is the decomposition of the current on each wire into push-pull and push-push mode currents. The former refers to the perturbation current accounting for the interactions among the wires within the bundle, whereas the latter represents the interactions between the mass wire bundle and the surrounding structure. Multiconductor transmission line theory is employed to compute the push-pull mode current by using one of the wires in the bundle as the return/reference conductor. Current induced on a test wire located along the reference line is used to compute the push-push mode. For this analysis, we employed the method of moments for the electromagnetic analysis of surrounding structure and simulation program with integrated circuit emphasis (SPICE)-like simulators for the analysis of a circuit model of the transmission lines extracted via the partial element equivalent circuit method. Several validation examples (including transmission lines inside an automobile) are presented. It is also shown that the traditional transmission line theory based on quasi-static analysis fails with increasing complexity of the surrounding structure.     

An on-line, business-oriented optimization of performance and availability for utility computing

Utility computing provides a pay-as-you-go approach to information systems in which application providers (e.g., web sites) can better manage their costs by adding capacity in response to increased demands and shedding capacity when it is no longer needed. This paper addresses application providers who use clusters of servers. Our work develops a framework to determine the number of servers that minimizes the sum of quality-of-service (QoS) costs resulting from service level penalties and server holding costs for the server cluster. The server characteristics considered are service rate, failure rates, repair rates, and costs. The contributions of this paper are: 1) a model for the performance and availability of an e-Commerce system that is consistent with data from a multisystem testbed with an e-Commerce workload; 2) a business-oriented cost model for resource allocation for application providers; 3) a closed form approximation for the optimal allocation of servers for an application provider based on the performance model in 1) and the cost model in 2); and 4) a simple criteria for utility owners and server manufacturers to make tradeoffs between server characteristics.     

Cubic Phase GaN on Nano‐grooved Si (100) via Maskless Selective Area Epitaxy

A method of forming cubic phase (zinc blende) GaN (referred as c‐GaN) on a CMOS‐compatible on‐axis Si (100) substrate is reported. Conventional GaN materials are hexagonal phase (wurtzite) (referred as h‐GaN) and possess very high polarization fields (～MV/cm) along the common growth direction of <0001>. Such large polarization fields lead to undesired shifts (e.g., wavelength and current) in the performance of photonic and vertical transport electronic devices. The cubic phase of GaN materials is polarization‐free along the common growth direction of <001>, however, this phase is thermodynamically unstable, requiring low‐temperature deposition conditions and unconventional substrates (e.g., GaAs). Here, novel nano‐groove patterning and maskless selective area epitaxy processes are employed to integrate thermodynamically stable, stress‐free, and low‐defectivity c‐GaN on CMOS‐compatible on‐axis Si. These results suggest that epitaxial growth conditions and nano‐groove pattern parameters are critical to obtain such high quality c‐GaN. InGaN/GaN multi‐quantum‐well structures grown on c‐GaN/Si (100) show strong room temperature luminescence in the visible spectrum, promising visible emitter applications for this technology.     

Orthonormal FBs With Rational Sampling Factors and Oversampled DFT-Modulated FBs: A Connection and Filter Design

Methods widely used to design filters for uniformly sampled filter banks (FBs) are not applicable for FBs with rational sampling factors and oversampled discrete Fourier transform (DFT)-modulated FBs. In this paper, we show that the filter design problem (with regularity factors/vanishing moments) for these two types of FBs is the same. Following this, we propose two finite-impulse-response (FIR) filter design methods for these FBs. The first method describes a parameterization of FBs with a single regularity factor/vanishing moment. The second method, which can be used to design FBs with an arbitrary number of regularity factors/vanishing moments, uses results from frame theory. We also describe how to modify this method so as to obtain linear phase filters. Finally, we discuss and provide a motivation for iterated DFT-modulated FBs.     

Efficacy of various plant hydrosols as natural food sanitizers in reducing Escherichia coli O157:H7 and Salmonella Typhimurium on fresh cut carrots and apples

In the present study, inhibitory effects of the hydrosols of thyme, black cumin, sage, rosemary and bay leaf were investigated against Salmonella Typhimurium and Escherichia coli O157:H7 inoculated to apple and carrots (at the ratio of 5.81 and 5.81 log cfu/g for S. Typhimurium, and 5.90 and 5.70 log cfu/g for E. coli O157:H7 on to apple and carrot, respectively). After the inoculation of S. Typhimurium or E. coli O157:H7, shredded apple and carrot samples were washed with the hydrosols and sterile tap water (as control) for 0, 20, 40 and 60 min. While the sterile tap water was ineffective in reducing (P > 0.05) S. Typhimurium and E. coli O157:H7, 20 min hydrosol treatment caused a significant (P < 0.05) reduction compared to the control group. On the other hand, thyme and rosemary hydrosol treatments for 20 min produced a reduction of 1.42 and 1.33 log cfu/g respectively in the E. coli O157:H7 population on apples. Additional reductions were not always observed with increasing treatment time. Moreover, thyme hydrosol showed the highest antibacterial effect on both S. Typhimurium and E. coli O157:H7 counts. Inhibitory effect of thyme hydrosol on S. Typhimurium was higher than that for E. coli O157:H7. Bay leaf hydrosol treatments for 60 min reduced significantly (P < 0.05) E. coli O157:H7 population on apple and carrot samples. In conclusion, it was shown that plant hydrosols, especially thyme hydrosol, could be used as a convenient sanitizing agent during the washing of fresh-cut fruits and vegetables.     

Porous polyurethane film fabricated via the breath figure approach for sustained drug release

The breath figure (BF) method is an effective process for fabricating porous polymeric films. In this study, we fabricated porous polymer films from thermoplastic polyurethane (PU) through static BF with CHCl₃ as a solvent under 55–80% relative humidity. The porous PU films were prepared within various pore structures and sizes, which were adjustable, depending on the fabrication conditions. The humidity and exposure time were examined as variable parameters affecting the surface morphology, wettability, and cytotoxicity. Atorvastatin calcium, a hyperlipidemic agent, was loaded into the porous films during the casting process, and the drug-loading and drug-releasing behaviors of the porous PU membranes were evaluated. Approximately 60–80% of the drug was released in 14 days. The films exhibited sustained drug-release performances because of the hydrophobicity and nonbiodegradable nature of PU for perivascular drug administration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47658.     

Microfabrication of vacuum-sealed cavities with nanocrystalline and ultrananocrystalline diamond membranes and their characteristics

Vacuum-sealed cavities featuring diamond membranes are fabricated using plasma-activated direct bonding technology. A chemical mechanical polished (CMP) silicon dioxide interlayer, deposited on diamond with a high temperature oxide (HTO) process at 850 °C in a low pressure chemical vapor deposition (LPCVD) furnace, is employed for successful direct bonding and vacuum cavity formation. The circular cavities are defined on the thermally grown oxide of the phosphorus-doped Si wafer (4-in, < 100>, 1.2 Ω/sq) using reactive ion etching (RIE). The same microfabrication steps are applied for low residual stress (i.e. < 50 MPa) nanocrystalline (NCD) and ultrananocrystalline (UNCD) diamonds to determine and compare membrane characteristics. For both diamond types, successful microfabrication of membranes is demonstrated using the optimized process flow. Profilometer measurements of membrane deflection are compared with finite element modeling (FEM), and indicate a Young's modulus of 1000 GPa for NCD and 850 GPa for UNCD. Furthermore, FEM analysis suggests the residual stress of UNCD membrane is approximately 100 MPa tensile, whereas NCD one does not show any significant residual stress (< 50 MPa). Our results show that NCD is a more promising choice than UNCD as a membrane material for electromechanical transducers.