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We discovered unique Anderson localization behaviors of pseudospin systems in a 1D disordered potential. For a pseudospin-1 system, due to the absence of backscattering under normal incidence and the presence of a conical band structure, the wave localization behaviors are entirely different from those of conventional disordered systems. We show that there exists a critical strength of random potential ([Formula: see text]), which is equal to the incident energy ([Formula: see text]), below which the localization length [Formula: see text] decreases with the random strength [Formula: see text] for a fixed incident angle [Formula: see text] But the localization length drops abruptly to a minimum at [Formula: see text] and rises immediately afterward. The incident angle dependence of the localization length has different asymptotic behaviors in the two regions of random strength, with [Formula: see text] when [Formula: see text] and [Formula: see text] when [Formula: see text] The existence of a sharp transition at [Formula: see text] is due to the emergence of evanescent waves in the systems when [Formula: see text] Such localization behavior is unique to pseudospin-1 systems. For pseudospin-1/2 systems, there is also a minimum localization length as randomness increases, but the transition from decreasing to increasing localization length at the minimum is smooth rather than abrupt. In both decreasing and increasing regions, the [Formula: see text] dependence of the localization length has the same asymptotic behavior [Formula: see text].

© 2015 Elsevier Ltd. This study investigates the influence of key biomass parameters on specific oxygen uptake rate (SOUR) in a sponge submerged membrane bioreactor (SSMBR) to develop mathematical models of biomass viability. Extra-cellular polymeric substances (EPS) were considered as a lumped parameter of bound EPS (bEPS) and soluble microbial products (SMP). Statistical analyses of experimental results indicate that the bEPS, SMP, mixed liquor suspended solids and volatile suspended solids (MLSS and MLVSS) have functional relationships with SOUR and their relative influence on SOUR was in the order of EPS. > bEPS. >. SMP. >. MLVSS/MLSS. Based on correlations among biomass parameters and SOUR, two independent empirical models of biomass viability were developed. The models were validated using results of the SSMBR. However, further validation of the models for different operating conditions is suggested.

© 2015 Elsevier Ltd. This study investigates the influence of key biomass parameters on specific oxygen uptake rate (SOUR) in a sponge submerged membrane bioreactor (SSMBR) to develop mathematical models of biomass viability. Extra-cellular polymeric substances (EPS) were considered as a lumped parameter of bound EPS (bEPS) and soluble microbial products (SMP). Statistical analyses of experimental results indicate that the bEPS, SMP, mixed liquor suspended solids and volatile suspended solids (MLSS and MLVSS) have functional relationships with SOUR and their relative influence on SOUR was in the order of EPS. > bEPS. >. SMP. >. MLVSS/MLSS. Based on correlations among biomass parameters and SOUR, two independent empirical models of biomass viability were developed. The models were validated using results of the SSMBR. However, further validation of the models for different operating conditions is suggested.

The production and accumulation of soluble microbial products (SMP), extracellular polymeric substances (EPS) and colloidal inert compounds within a membrane bioreactor (MBR) may greatly affect the biomass viability and subsequently the permeability of the membrane. This paper aims at presenting new mathematical models of biomass viability and membrane fouling that has been conceptually developed through establishing links between these biomass parameters and operating parameters of the MBR. The proposed models can be used to predict the biomass viability and membrane fouling at any state of operation of MBR. Meanwhile, easily measurable parameters of the proposed model can also serve to estimate SMP/EPS concentration in the supernatant of MBR without the tedious and expensive measurement. © 2013 Elsevier Ltd.

The production and accumulation of soluble microbial products (SMP), extracellular polymeric substances (EPS) and colloidal inert compounds within a membrane bioreactor (MBR) may greatly affect the biomass viability and subsequently the permeability of the membrane. This paper aims at presenting new mathematical models of biomass viability and membrane fouling that has been conceptually developed through establishing links between these biomass parameters and operating parameters of the MBR. The proposed models can be used to predict the biomass viability and membrane fouling at any state of operation of MBR. Meanwhile, easily measurable parameters of the proposed model can also serve to estimate SMP/EPS concentration in the supernatant of MBR without the tedious and expensive measurement. © 2013 Elsevier Ltd.

By using only one pump beam, we show theoretically that both forward and backward phase conjugations can be generated simultaneously and efficiently in one-dimensional chi((3))-nonlinear photonic crystals of only a few micrometers in size. The photonic crystal considered here is a CdS/SiO2 superlattice. By using realistic optical parameters in our calculations, we find that the phase-conjugate generation efficiency can be enhanced by four to five orders of magnitude as compared with that in a homogeneous CdS medium of the same nonlinearity and length. The enhancement is caused by multiple reflections as well as strong field localization introduced by the shifted band-edge state, the gap localized state, or the shifted defect state. (C) 2006 American Institute of Physics.

We report on observation of simultaneous strong enhancements of second-harmonic generation (SHG) and third-harmonic generation (THG) in visible spectra region in a one-dimensional ZnSe-ZnMgS semiconductor photonic crystal. These enhancements come from phase matching and a high density of modes near the photonic band edge. Our result shows that the THG is due to direct X-(3) process instead of the cascaded two-step X-(2) process. Measured forward SH conversion efficiency close to 1\% for only a few microns thick film demonstrates potential device applications. Theoretical calculations are in good agreement with the experimental measurements.

By using only one pump beam, we show theoretically that both forward and backward phase conjugations can be generated simultaneously and efficiently in one-dimensional chi((3))-nonlinear photonic crystals of only a few micrometers in size. The photonic crystal considered here is a CdS/SiO2 superlattice. By using realistic optical parameters in our calculations, we find that the phase-conjugate generation efficiency can be enhanced by four to five orders of magnitude as compared with that in a homogeneous CdS medium of the same nonlinearity and length. The enhancement is caused by multiple reflections as well as strong field localization introduced by the shifted band-edge state, the gap localized state, or the shifted defect state. (C) 2006 American Institute of Physics.

We report on observation of simultaneous strong enhancements of second-harmonic generation (SHG) and third-harmonic generation (THG) in visible spectra region in a one-dimensional ZnSe-ZnMgS semiconductor photonic crystal. These enhancements come from phase matching and a high density of modes near the photonic band edge. Our result shows that the THG is due to direct X-(3) process instead of the cascaded two-step X-(2) process. Measured forward SH conversion efficiency close to 1\% for only a few microns thick film demonstrates potential device applications. Theoretical calculations are in good agreement with the experimental measurements.

By using only one pump beam, we show theoretically that both forward and backward phase conjugations can be generated simultaneously and efficiently in one-dimensional chi((3))-nonlinear photonic crystals of only a few micrometers in size. The photonic crystal considered here is a CdS/SiO2 superlattice. By using realistic optical parameters in our calculations, we find that the phase-conjugate generation efficiency can be enhanced by four to five orders of magnitude as compared with that in a homogeneous CdS medium of the same nonlinearity and length. The enhancement is caused by multiple reflections as well as strong field localization introduced by the shifted band-edge state, the gap localized state, or the shifted defect state. (C) 2006 American Institute of Physics.

We report on observation of simultaneous strong enhancements of second-harmonic generation (SHG) and third-harmonic generation (THG) in visible spectra region in a one-dimensional ZnSe-ZnMgS semiconductor photonic crystal. These enhancements come from phase matching and a high density of modes near the photonic band edge. Our result shows that the THG is due to direct X-(3) process instead of the cascaded two-step X-(2) process. Measured forward SH conversion efficiency close to 1\% for only a few microns thick film demonstrates potential device applications. Theoretical calculations are in good agreement with the experimental measurements.

We find that a phononic gap in a periodic or quasiperiodic elastic composite can be significantly enhanced by inserting air inclusions into the systems. The positions of the insertion are chosen to suppress the shear potential energy of the acoustical branches and lower their frequencies. This is demonstrated in two dimensions. Gap positions and sizes as functions of the radii of the air cylinders for systems of aluminum cylinders in epoxy and steel cylinders in epoxy are presented for both triangular and 12-fold quasiperiodic lattices.

Dramatic enhancement of second harmonic generation (SHG) near the photonic band edge was observed in a one-dimensional ZnSe/ZnMgS semiconductor photonic crystal (PC) structure. Over two orders of magnitude increase in SHG intensity was observed at the photonic band edge at similar to 1400 nm compared to the nonphase matching region. The maximum SHG conversion efficiency of 0.8\% is observed in only seven micrometers length of crystal. This enhancement came from a combination of large ZnSe second order susceptibility coefficient (chi((2))), high density of optical modes and phase matching of the fundamental and second harmonic waves near the photonic band edge due to modification of the dispersion curve by the PC structure. (C) 2005 American Institute of Physics.

We find that a phononic gap in a periodic or quasiperiodic elastic composite can be significantly enhanced by inserting air inclusions into the systems. The positions of the insertion are chosen to suppress the shear potential energy of the acoustical branches and lower their frequencies. This is demonstrated in two dimensions. Gap positions and sizes as functions of the radii of the air cylinders for systems of aluminum cylinders in epoxy and steel cylinders in epoxy are presented for both triangular and 12-fold quasiperiodic lattices.

Dramatic enhancement of second harmonic generation (SHG) near the photonic band edge was observed in a one-dimensional ZnSe/ZnMgS semiconductor photonic crystal (PC) structure. Over two orders of magnitude increase in SHG intensity was observed at the photonic band edge at similar to 1400 nm compared to the nonphase matching region. The maximum SHG conversion efficiency of 0.8\% is observed in only seven micrometers length of crystal. This enhancement came from a combination of large ZnSe second order susceptibility coefficient (chi((2))), high density of optical modes and phase matching of the fundamental and second harmonic waves near the photonic band edge due to modification of the dispersion curve by the PC structure. (C) 2005 American Institute of Physics.

We find that a phononic gap in a periodic or quasiperiodic elastic composite can be significantly enhanced by inserting air inclusions into the systems. The positions of the insertion are chosen to suppress the shear potential energy of the acoustical branches and lower their frequencies. This is demonstrated in two dimensions. Gap positions and sizes as functions of the radii of the air cylinders for systems of aluminum cylinders in epoxy and steel cylinders in epoxy are presented for both triangular and 12-fold quasiperiodic lattices.

We propose that, by applying an electric field to a Kerr nonlinear photonic crystal, we can tune its photonic band gap and dynamically control the light propagation. The method is efficient and easy to implement in practice. The transmission behavior of the light caused by nonlinear effects induced by both the external electric field and the light is numerically studied in detail in a one-dimensional superlattice. The dynamical control of light propagation can also be made possible in a Pockels photonic crystal by applying an electric field. (C) 2004 American Institute of Physics.

We propose that, by applying an electric field to a Kerr nonlinear photonic crystal, we can tune its photonic band gap and dynamically control the light propagation. The method is efficient and easy to implement in practice. The transmission behavior of the light caused by nonlinear effects induced by both the external electric field and the light is numerically studied in detail in a one-dimensional superlattice. The dynamical control of light propagation can also be made possible in a Pockels photonic crystal by applying an electric field. (C) 2004 American Institute of Physics.

We propose that, by applying an electric field to a Kerr nonlinear photonic crystal, we can tune its photonic band gap and dynamically control the light propagation. The method is efficient and easy to implement in practice. The transmission behavior of the light caused by nonlinear effects induced by both the external electric field and the light is numerically studied in detail in a one-dimensional superlattice. The dynamical control of light propagation can also be made possible in a Pockels photonic crystal by applying an electric field. (C) 2004 American Institute of Physics.

This article presents a review of the lasing and photonic properties of periodic one-dimensional anisotropic structures with the symmetry of a double helix. Examples are self-organized cholesteric liquid crystals (CLCs) and sculptured thin films created by vapor deposition. A reflection band with sharp, closely spaced transmission peaks at its edges occurs for circularly polarized light with the same handedness as the helical structure. Within the reflection band, this wave is evanescent, corresponding to a vanishing density of states (DOS). Oppositely polarized light is uniformly transmitted. Since optical emission is proportional to the DOS, it is suppressed within the reflection band. However, it is enhanced at the band edge, where a series of narrow long-lived transmission modes are found. For this reason lasing in dye-doped CLCs occurs at the edge of the stop band rather than at its center, where reflection is highest. Introducing an additional rotation or an isotropic layer within a chiral structure creates a single circularly polarized localized mode with the same handedness as the structure. A resonance appears in the transmission of light of this polarization in thin samples. In thicker samples, the resonance appears instead in the reflection for oppositely polarized light. In contrast to strong modulation of the intensity within the sample on a wavelength scale, a characteristic of layered dielectric medium, the intensity within a chiral medium varies slowly when the sample is excited either at the band edge or at a localized mode. A transverse coherence is created in emission over a length scale proportional to the square root of the photon dwell time at resonance with long-lived modes. This makes possible spatially coherent lasing over a large area in thin films. The photonic properties of chiral thin films make them promising candidates for a variety of filter and laser applications. (C) 2003 Elsevier Ltd. All rights reserved.

We find that a large absolute band gap can be created by inserting air inclusions in a two-component elastic phononic crystal with small density contrast and filling fraction. The positions of the insertion are chosen to suppress the shear potential energy of the first optical band and lower their frequencies. This is demonstrated in a two-dimensional system consisting of aluminum cylinders in a triangular lattice with a filling fraction of 0.145 embedded in an epoxy host. Both the band structure and the transmission calculations show that the insertion of air cylinders in the earlier system is capable of creating a large elastic band gap with gap/midgap ratio Deltaomega/omega(c)=0.53. Such a system makes the realization of a light and effective sonic insulator possible. (C) 2003 American Institute of Physics.

In recent years, the study of acoustic and elastic waves propagation in periodic materials, known as "phononic crystals", has received increasing amount of attention. Analogous to photonic crystals, a large and robust band gaps is essential to all applications of phononic crystals. In this work, a perturbative approach is applied to phononic crystals and two main results are obtained. Firstly, we show that a perturbation analysis can provide us an efficient method to enlarge an existing acoustic band gap. Secondly, by extending the perturbative analysis to disordered phononic crystals, we can quantitatively estimate the effect of the disorder on the size of an acoustic band gap. Due to the difference in the mathematical structures between Maxwell equations in a photonic crystal and acoustic wave equation in a phononic crystal, we find that it is much more efficient to enlarge an acoustic band gap than a photonic band gap. Numerical simulations using the Multiple Scattering Method verify all the conclusions above.

This article presents a review of the lasing and photonic properties of periodic one-dimensional anisotropic structures with the symmetry of a double helix. Examples are self-organized cholesteric liquid crystals (CLCs) and sculptured thin films created by vapor deposition. A reflection band with sharp, closely spaced transmission peaks at its edges occurs for circularly polarized light with the same handedness as the helical structure. Within the reflection band, this wave is evanescent, corresponding to a vanishing density of states (DOS). Oppositely polarized light is uniformly transmitted. Since optical emission is proportional to the DOS, it is suppressed within the reflection band. However, it is enhanced at the band edge, where a series of narrow long-lived transmission modes are found. For this reason lasing in dye-doped CLCs occurs at the edge of the stop band rather than at its center, where reflection is highest. Introducing an additional rotation or an isotropic layer within a chiral structure creates a single circularly polarized localized mode with the same handedness as the structure. A resonance appears in the transmission of light of this polarization in thin samples. In thicker samples, the resonance appears instead in the reflection for oppositely polarized light. In contrast to strong modulation of the intensity within the sample on a wavelength scale, a characteristic of layered dielectric medium, the intensity within a chiral medium varies slowly when the sample is excited either at the band edge or at a localized mode. A transverse coherence is created in emission over a length scale proportional to the square root of the photon dwell time at resonance with long-lived modes. This makes possible spatially coherent lasing over a large area in thin films. The photonic properties of chiral thin films make them promising candidates for a variety of filter and laser applications. (C) 2003 Elsevier Ltd. All rights reserved.

We find that a large absolute band gap can be created by inserting air inclusions in a two-component elastic phononic crystal with small density contrast and filling fraction. The positions of the insertion are chosen to suppress the shear potential energy of the first optical band and lower their frequencies. This is demonstrated in a two-dimensional system consisting of aluminum cylinders in a triangular lattice with a filling fraction of 0.145 embedded in an epoxy host. Both the band structure and the transmission calculations show that the insertion of air cylinders in the earlier system is capable of creating a large elastic band gap with gap/midgap ratio Deltaomega/omega(c)=0.53. Such a system makes the realization of a light and effective sonic insulator possible. (C) 2003 American Institute of Physics.

In recent years, the study of acoustic and elastic waves propagation in periodic materials, known as "phononic crystals", has received increasing amount of attention. Analogous to photonic crystals, a large and robust band gaps is essential to all applications of phononic crystals. In this work, a perturbative approach is applied to phononic crystals and two main results are obtained. Firstly, we show that a perturbation analysis can provide us an efficient method to enlarge an existing acoustic band gap. Secondly, by extending the perturbative analysis to disordered phononic crystals, we can quantitatively estimate the effect of the disorder on the size of an acoustic band gap. Due to the difference in the mathematical structures between Maxwell equations in a photonic crystal and acoustic wave equation in a phononic crystal, we find that it is much more efficient to enlarge an acoustic band gap than a photonic band gap. Numerical simulations using the Multiple Scattering Method verify all the conclusions above.

This article presents a review of the lasing and photonic properties of periodic one-dimensional anisotropic structures with the symmetry of a double helix. Examples are self-organized cholesteric liquid crystals (CLCs) and sculptured thin films created by vapor deposition. A reflection band with sharp, closely spaced transmission peaks at its edges occurs for circularly polarized light with the same handedness as the helical structure. Within the reflection band, this wave is evanescent, corresponding to a vanishing density of states (DOS). Oppositely polarized light is uniformly transmitted. Since optical emission is proportional to the DOS, it is suppressed within the reflection band. However, it is enhanced at the band edge, where a series of narrow long-lived transmission modes are found. For this reason lasing in dye-doped CLCs occurs at the edge of the stop band rather than at its center, where reflection is highest. Introducing an additional rotation or an isotropic layer within a chiral structure creates a single circularly polarized localized mode with the same handedness as the structure. A resonance appears in the transmission of light of this polarization in thin samples. In thicker samples, the resonance appears instead in the reflection for oppositely polarized light. In contrast to strong modulation of the intensity within the sample on a wavelength scale, a characteristic of layered dielectric medium, the intensity within a chiral medium varies slowly when the sample is excited either at the band edge or at a localized mode. A transverse coherence is created in emission over a length scale proportional to the square root of the photon dwell time at resonance with long-lived modes. This makes possible spatially coherent lasing over a large area in thin films. The photonic properties of chiral thin films make them promising candidates for a variety of filter and laser applications. (C) 2003 Elsevier Ltd. All rights reserved.

We find that a large absolute band gap can be created by inserting air inclusions in a two-component elastic phononic crystal with small density contrast and filling fraction. The positions of the insertion are chosen to suppress the shear potential energy of the first optical band and lower their frequencies. This is demonstrated in a two-dimensional system consisting of aluminum cylinders in a triangular lattice with a filling fraction of 0.145 embedded in an epoxy host. Both the band structure and the transmission calculations show that the insertion of air cylinders in the earlier system is capable of creating a large elastic band gap with gap/midgap ratio Deltaomega/omega(c)=0.53. Such a system makes the realization of a light and effective sonic insulator possible. (C) 2003 American Institute of Physics.

In recent years, the study of acoustic and elastic waves propagation in periodic materials, known as "phononic crystals", has received increasing amount of attention. Analogous to photonic crystals, a large and robust band gaps is essential to all applications of phononic crystals. In this work, a perturbative approach is applied to phononic crystals and two main results are obtained. Firstly, we show that a perturbation analysis can provide us an efficient method to enlarge an existing acoustic band gap. Secondly, by extending the perturbative analysis to disordered phononic crystals, we can quantitatively estimate the effect of the disorder on the size of an acoustic band gap. Due to the difference in the mathematical structures between Maxwell equations in a photonic crystal and acoustic wave equation in a phononic crystal, we find that it is much more efficient to enlarge an acoustic band gap than a photonic band gap. Numerical simulations using the Multiple Scattering Method verify all the conclusions above.

The sonic band-gap structures of 12-fold symmetry quasicrystals consisting of rigid cylinders in air are investigated by using the multiple scattering method. Large full gaps are found in this system owing to its high symmetry. At filling fractions between 0.2 and 0.4, this 12-fold square-triangle tiling is much better for the realization of sonic band gaps than the square or triangular lattice. This makes the 12-fold quasicrystal a promising structure for acoustic-wave band-gap materials. (C) 2002 American Institute of Physics.

We investigate the lateral wave transport in quasiperiodically ordered layer media with isotropic randomness. As an example, we consider the case of the Fibonacci sequence and study the ergodic proper-ties in such systems. From the results of the channel occupation number of nine generations, we find that the wave transport in such systems falls between the transport of anisotropic hopping systems and that of randomly layered media and can be associated with a fractal dimension that can be tuned according to the strength of the layer coupling. The origin of this fractal dimensionality is attributed to the interplay between the quasiperiodic ordering in the layer direction and the presence of isotropic randomness in the system.

The sonic band-gap structures of 12-fold symmetry quasicrystals consisting of rigid cylinders in air are investigated by using the multiple scattering method. Large full gaps are found in this system owing to its high symmetry. At filling fractions between 0.2 and 0.4, this 12-fold square-triangle tiling is much better for the realization of sonic band gaps than the square or triangular lattice. This makes the 12-fold quasicrystal a promising structure for acoustic-wave band-gap materials. (C) 2002 American Institute of Physics.

We investigate the lateral wave transport in quasiperiodically ordered layer media with isotropic randomness. As an example, we consider the case of the Fibonacci sequence and study the ergodic proper-ties in such systems. From the results of the channel occupation number of nine generations, we find that the wave transport in such systems falls between the transport of anisotropic hopping systems and that of randomly layered media and can be associated with a fractal dimension that can be tuned according to the strength of the layer coupling. The origin of this fractal dimensionality is attributed to the interplay between the quasiperiodic ordering in the layer direction and the presence of isotropic randomness in the system.

The sonic band-gap structures of 12-fold symmetry quasicrystals consisting of rigid cylinders in air are investigated by using the multiple scattering method. Large full gaps are found in this system owing to its high symmetry. At filling fractions between 0.2 and 0.4, this 12-fold square-triangle tiling is much better for the realization of sonic band gaps than the square or triangular lattice. This makes the 12-fold quasicrystal a promising structure for acoustic-wave band-gap materials. (C) 2002 American Institute of Physics.

We investigate the lateral wave transport in quasiperiodically ordered layer media with isotropic randomness. As an example, we consider the case of the Fibonacci sequence and study the ergodic proper-ties in such systems. From the results of the channel occupation number of nine generations, we find that the wave transport in such systems falls between the transport of anisotropic hopping systems and that of randomly layered media and can be associated with a fractal dimension that can be tuned according to the strength of the layer coupling. The origin of this fractal dimensionality is attributed to the interplay between the quasiperiodic ordering in the layer direction and the presence of isotropic randomness in the system.

Three-dimensional photonic crystals with fall bandgaps at optical wavelengths can be fabricated with inverse-opal techniques. We have shown that the bandgap is extremely sensitive to the presence of geometric disorder in the crystals (see Figure). The bandgap closes completely with a disorder strength as small as under two percent of the lattice constant. This fragility persists even at very high refractive index contrasts and is attributed to the creation of a bandgap at high frequency bands (8-9 bands) in inverse-opal crystals. This should impost severe demand on the quality of lattice uniformity.

By using a perturbative approach, we propose a simple, systematic, and efficient method to engineer acoustic band gaps. A gap can be enlarged or reduced by altering the microstructure according to the field-energy distributions of the Bloch states at the band edges as well as their derivatives. Due to the structure of the acoustic wave equation, the engineering of acoustic band gaps is much more efficient than that of photonic band gaps. The validity of the proposed method is supported by multiple-scattering calculations. Our method makes the acoustic band gap "designable." (C) 2001 American Institute of Physics.

By using a perturbative approach, we propose a simple, systematic, and efficient method to engineer acoustic band gaps. A gap can be enlarged or reduced by altering the microstructure according to the field-energy distributions of the Bloch states at the band edges as well as their derivatives. Due to the structure of the acoustic wave equation, the engineering of acoustic band gaps is much more efficient than that of photonic band gaps. The validity of the proposed method is supported by multiple-scattering calculations. Our method makes the acoustic band gap "designable." (C) 2001 American Institute of Physics.

Three-dimensional photonic crystals with fall bandgaps at optical wavelengths can be fabricated with inverse-opal techniques. We have shown that the bandgap is extremely sensitive to the presence of geometric disorder in the crystals (see Figure). The bandgap closes completely with a disorder strength as small as under two percent of the lattice constant. This fragility persists even at very high refractive index contrasts and is attributed to the creation of a bandgap at high frequency bands (8-9 bands) in inverse-opal crystals. This should impost severe demand on the quality of lattice uniformity.

By using a perturbative approach, we propose a simple, systematic, and efficient method to engineer acoustic band gaps. A gap can be enlarged or reduced by altering the microstructure according to the field-energy distributions of the Bloch states at the band edges as well as their derivatives. Due to the structure of the acoustic wave equation, the engineering of acoustic band gaps is much more efficient than that of photonic band gaps. The validity of the proposed method is supported by multiple-scattering calculations. Our method makes the acoustic band gap

We have studied the shape of the distribution F(G) for the conductance G between points on the surface of a metal-insulator nanocomposite film and the conducting substrate by Conducting Atomic Force Microscopy and computer simulation. Random resistor networks with both metallic and tunneling bonds included are used to model the nanocomposite films. The shape of F(G) is determined mainly by the connectivity of metal particles and the maximum tunneling distance in the composite. By qualitatively comparing the simulation results with the experimental data on granular NiFe-SiO2 films near the metal-insulator transition we find important implications for the understanding of microscopic conduction mechanisms near the metal-insulator transition. (C) 2000 Elsevier Science B.V. All rights reserved.

We study the shape of distribution F(G) for the conductance G between a point on the surface of a metal-insulator nanocomposite film and the conducting substrate. Random resistor networks with both metallic and tunneling bonds included are used to model nanocomposite films. Our simulation results show explicitly that the shape of F(G) is determined mainly by the connectivity of metal particles and the maximum tunneling distance in the composite. By applying our results to the available experimental data on granular NiFe-SiO2, we find important implications for the understanding of microscopic conduction mechanisms near the metal-insulator transition. (C) 2000 American Institute of Physics. [S0021-8979(00)02903-0].

High-temperature dependence, up to 150 degrees C, of the photoresponsivity of ZnS, ZnSTe, and ZnSSe photodiodes was investigated in this study. It was found that, in general, the responsivity at higher temperatures will shift to longer wavelengths because of band-gap narrowing. A remarkable observation is that the near-band-edge responsivities of these diodes increase at higher temperature. We believe that this observation is attributed to the change of the density-of-state distribution due to lattice expansion at high temperatures, and a simplified model is used to illustrate this hypothesis. (C) 2000 American Institute of Physics. [S0003-6951(00)04009-2].

This work focused on the studies of the high-temperature dependence of the responsivity of ZnS, ZnSTe and ZnSSe photodiodes. It was found that in general the responsivity at higher temperatures will shift to longer wavelengths because of band gap narrowing. A remarkable observation is that the near-band-edge responsivities of these diodes increase at higher temperature. We believe that this observation is attributed to the change of the density of state distribution due to lattice expansion at high temperature and a simplified model is used to illustrate this hypothesis. (C) 2000 Elsevier Science B.V. All rights reserved.

This work focused on the studies of the high-temperature dependence of the responsivity of ZnS, ZnSTe and ZnSSe photodiodes. It was found that in general the responsivity at higher temperatures will shift to longer wavelengths because of band gap narrowing. A remarkable observation is that the near-band-edge responsivities of these diodes increase at higher temperature. We believe that this observation is attributed to the change of the density of state distribution due to lattice expansion at high temperature and a simplified model is used to illustrate this hypothesis. (C) 2000 Elsevier Science B.V. All rights reserved.

We have studied the shape of the distribution F(G) for the conductance G between points on the surface of a metal-insulator nanocomposite film and the conducting substrate by Conducting Atomic Force Microscopy and computer simulation. Random resistor networks with both metallic and tunneling bonds included are used to model the nanocomposite films. The shape of F(G) is determined mainly by the connectivity of metal particles and the maximum tunneling distance in the composite. By qualitatively comparing the simulation results with the experimental data on granular NiFe-SiO2 films near the metal-insulator transition we find important implications for the understanding of microscopic conduction mechanisms near the metal-insulator transition. (C) 2000 Elsevier Science B.V. All rights reserved.

We study the shape of distribution F(G) for the conductance G between a point on the surface of a metal-insulator nanocomposite film and the conducting substrate. Random resistor networks with both metallic and tunneling bonds included are used to model nanocomposite films. Our simulation results show explicitly that the shape of F(G) is determined mainly by the connectivity of metal particles and the maximum tunneling distance in the composite. By applying our results to the available experimental data on granular NiFe-SiO2, we find important implications for the understanding of microscopic conduction mechanisms near the metal-insulator transition. (C) 2000 American Institute of Physics. [S0021-8979(00)02903-0].

High-temperature dependence, up to 150 degrees C, of the photoresponsivity of ZnS, ZnSTe, and ZnSSe photodiodes was investigated in this study. It was found that, in general, the responsivity at higher temperatures will shift to longer wavelengths because of band-gap narrowing. A remarkable observation is that the near-band-edge responsivities of these diodes increase at higher temperature. We believe that this observation is attributed to the change of the density-of-state distribution due to lattice expansion at high temperatures, and a simplified model is used to illustrate this hypothesis. (C) 2000 American Institute of Physics. [S0003-6951(00)04009-2].

This work focused on the studies of the high-temperature dependence of the responsivity of ZnS, ZnSTe and ZnSSe photodiodes. It was found that in general the responsivity at higher temperatures will shift to longer wavelengths because of band gap narrowing. A remarkable observation is that the near-band-edge responsivities of these diodes increase at higher temperature. We believe that this observation is attributed to the change of the density of state distribution due to lattice expansion at high temperature and a simplified model is used to illustrate this hypothesis. (C) 2000 Elsevier Science B.V. All rights reserved.

We have studied the shape of the distribution F(G) for the conductance G between points on the surface of a metal-insulator nanocomposite film and the conducting substrate by Conducting Atomic Force Microscopy and computer simulation. Random resistor networks with both metallic and tunneling bonds included are used to model the nanocomposite films. The shape of F(G) is determined mainly by the connectivity of metal particles and the maximum tunneling distance in the composite. By qualitatively comparing the simulation results with the experimental data on granular NiFe-SiO2 films near the metal-insulator transition we find important implications for the understanding of microscopic conduction mechanisms near the metal-insulator transition. (C) 2000 Elsevier Science B.V. All rights reserved.

High-temperature dependence, up to 150 degrees C, of the photoresponsivity of ZnS, ZnSTe, and ZnSSe photodiodes was investigated in this study. It was found that, in general, the responsivity at higher temperatures will shift to longer wavelengths because of band-gap narrowing. A remarkable observation is that the near-band-edge responsivities of these diodes increase at higher temperature. We believe that this observation is attributed to the change of the density-of-state distribution due to lattice expansion at high temperatures, and a simplified model is used to illustrate this hypothesis. (C) 2000 American Institute of Physics. [S0003-6951(00)04009-2].