One-dimensional antireflection gratings in (100) silicon: a numerical study

The antireflection properties of V-grooved gratings in (100)crystalline silicon are studied numerically by use of rigorouselectromagnetic theory. This study shows that these gratings canexhibit antireflective behavior only for TM-polarizedradiation. The V-grooved structures are analyzed as a function ofgrating period, duty cycle, and depth of a SiO(2) mask layerthat is added to the tops of the V-grooved mesas. Specificantireflection grating designs (the duty cycle and depth versus theperiod) are presented that illustrate TM-polarized reflectivity muchless than 10(-3) with periods as high as 80% the wavelengthof incident radiation. These designs exhibit good tolerance tofabrication errors and grating's plane deviations in aplanar-diffraction mounting.     

Usage of bioactivated PCL nanofiber as a fluoxetine capturing matrix in milk

ABSTRACT

In this study, for the first time, polycaprolactone (PCL) nanofiber matrix was bioactivated for the removal of fluoxetine from milk. Bioactivated nanofiber was prepared by immobilizing fluoxetine antibody on PCL nanofiber matrix. The fluoxetine removal efficiency of bioactivated nanofiber in milk was found to be approximately 93.6%. This removal did not significantly change the biochemical composition of milk. In conclusion, as a novel product, bioactivated nanofibrous PCL matrix can be used for the removal of drugs or unwanted chemicals from breast milk or from other fluids.     

A modified C-dump converter for variable-reluctance machines

A new type of converter for variable-reluctance-machine (VRM) drives is described. In this converter topology, the energy extracted from an ongoing phase is stored in a dump capacitor. The energy stored is consequently used either to quickly turn on the next ongoing phase or to energize the conducting phase frequently during the conduction interval instead of being returned to the supply as for a conventional C-dump circuit. Since, the additional switch used to pass the energy to the C-dump capacitor is switched under a relatively-low-voltage condition and its switching frequency is relatively low, the rating of the additional switch is modest. The major advantage os this converter is that it uses a low-switching device/phase ratio while achieving better performance characteristics than the other topologies     

Probability‐Generated Aggregators

The paper addresses a relation between logical reasoning and probability and presents probability‐generated aggregators. The obtained aggregators implement probability distributions for specification of generator functions; as it was proven in the paper, such implementation is always possible. In the paper, the relation between neutral element of the probabilistic uninorm and parameters of the underlying probability distribution is demonstrated, and a method for specification of the probabilistic uninorm, and thus—of the probability distribution using t‐norm and t‐conorm—is constructed. In addition, the obtained probabilistic uninorm and probabilistic absorbing norm or nullnorm are briefly considered as algebraic operations on the open unit interval. In is demonstrated, that, in general, the obtained algebra is nondistributive and depends on the distributions, which are used for generating probabilistic uninorm and absorbing norm. The obtained results bridge several gaps between fuzzy and probabilistic logics and provide a basis both for theoretical studies in the field and for practical techniques of digital/analog schemes synthesis and analysis.     

Simple analytical and graphical methods for carrier-based PWM-VSIdrives

This paper provides analytical and graphical methods for the study, performance evaluation and design of the modern carrier-based pulse width modulators (PWMs), which are widely employed in PWM voltage-source inverter (VSI) drives. Simple techniques for generating the modulation waves of the high-performance PWM methods are described. The two most important modulator characteristics-the current ripple and the switching losses-are analytically modeled. The graphical illustration of these often complex multivariable functions accelerate the learning process and help one understand the microscopic (per-carrier cycle) and macroscopic (per fundamental cycle) behavior of all the modern PWM methods. The analytical formulae and graphics are valuable educational tools. They also aid the design and implementation of the high-performance PWM methods     

Economic evaluation of energy conservation projects with an emphasis on initiation time

A procedure for assessing the economic viability of an energy conservation project integrated with building installation has been investigated in previous works. In the present work, a method is developed for economic evaluation of energy conservation projects, which may initiate independence of building construction. A model for optimization of the initiation time has been developed, and the conditions to determine economic feasibility are derived. It was found that the break-even value of the annual energy saved for $1 investment may significantly increase with even a moderate decrease in the expected real investment cost. This break-even value is always greater than the corresponding one found in the building integrated case. The difference increased with an increase in expected fuel inflation rate and also with a decrease in expected investment cost.     

Donor-acceptor-donor type conjugated polymers for electrochromic applications: benzimidazole as the acceptor unit

Donor-acceptor-donor (DAD) type benzimidazole (BIm) and 3,4 ethylenedioxythiophene (EDOT) bearing monomers were synthesized and electrochemically polymerized. Pendant group at 2-C position of the imidazole ring was functionalized with phenyl (P1), EDOT (P2) and ferrocene (P3) in order to observe substituent effect on electrochemical and electrochromic properties of corresponding polymers. Spectroelectrochemical results showed that different pendant groups resulted in polymers with slightly different optical band gaps (1.75, 1.69 and 1.77 eV respectively) and different number of achievable colored states. Optoelectronic performance and comparison of results with other well known π-accepting benzazole bearing DAD type polymers were reported in detail.     

Design and analysis of low-reflection grating microstructures for a solar energy absorber

The problem of calculating the photo-induced current in an n⁺p junction solar cell with a microstructure grating on the top is formulated. For the case where useful absorption regions lie below the grating a closed solution of the problem is obtained, in which the carrier photo-generation rate is calculated using a full-vector electromagnetic simulation technique. Two structures: filled lamellae grating and overlayer, and filled V-groove grating and overlayer are considered. The first structure is optimized with respect to the integral photo-current and the second with respect to reflection loss. Both optimized structures are much less reflective and more efficient than an optimized flat-surface Si–SiO₂ layer cell.     

Spectral tuning and linewidth narrowing of shallow-junction surface emitting GaAs LED́s through γ-ray irradiation

Alterations of device characteristics as a result of γ-ray irradiation of shallow-junction surface emitting devices are different from those of deep-junction devices with respect to LED emission intensity reduction, I-V curve, line shape, and spectral shift. In particular, much larger spectral shifts in the opposite direction-toward longer wavelengths-are reported here than those found in the literature for deep-junction devices. A qualitative model based upon photochemical doping and changes in surface band bending is proposed to explain these phenomena. Changes in surface emitting shallow-junction optical radiation source device characteristics brought about by γ-ray irradiation are desirable ones for utilization in most optical fiber communication systems. These changes include linewidth narrowing, decreased time response, and decreased material dispersion because of the emission wavelength change.     

Gamma ray irradiated LED's: Surface emission and significant wavelength tuning via surface states

Wavelength tuning via shallow junction GaAs LED's as a result of gamma irradiation is increased significantly when the irradiated LED's are operated in vacuum. Vacuum operation is seen to be essentially equivalent to increased gamma ray dosage for low irradiation levels as a result of desorptive processes common to both phenomena. They give rise to decreased nonradiative and increased radiative components of surface recombination photon emission. It is this spectrum which is shifted according to changes in surface potential and forward voltage deriving from alterations in surface state populations. A mathematical model is developed to relate wavelength tuning with surface potential and forward voltage shift. This technique is, in principle, a general technique independent of semiconductor material. It suggests the possibility of wavelength tuning via surface band-bending changes deriving from surface electric field changes, as is done with MIS devices. Examination of irradiated diode properties in vacuum and under pressure permits greater insight into the basic nature of surface phenomena long suspected to play a significant role in the diode electronic property changes brought about by nuclear irradiation.