Dual Sources Research Articles

Modeling aspects of dual frequency sonochemical reactors

The dual or multi-source irradiation with same or different operating frequency has proved to be a new dimension to the sonochemical reactors. In the present work, the model developed earlier [P.A. Tatake, A.B. Pandit, Modeling and experimental investigation into cavity dynamics and cavitational yield: influence of dual frequency ultrasound sources, Chem. Eng. Sci. 57 (2002) 4987] using Rayleigh-Plesset equation has been made more realistic by incorporating the effect of liquid phase compressibility. The aim has been to study the bubble dynamics under the influence of dual frequency acoustic field and explain the superiority of the same as compared to the single frequency irradiations. The effect of intensity and dual-frequency on the bubble dynamics and the conditions of the cavity collapse has been investigated. The numerical results have been compared with the previous experimental trends under similar operating conditions. The simple model developed in the present work seems to quite satisfactorily explain the experimental results obtained using dual frequency sonication system. Thus, the methodology adapted in the present work is a useful starting point for the modeling and designing large scale multiple frequency reactors. Recommendations have also been made for developing realistic bubble dynamics model which should help in optimization of multiple frequency sonochemical reactors.

Transcutaneous Contrast-Enhanced Sonography of Peripheral Lung Lesions

Transpulmonary sonography contrast agents, in conjunction with contrast-specific imaging techniques, are increasingly accepted in clinical use for diagnostic imaging of several organs. Anatomically, the lung is characterized by dual blood sources, supplied from both the pulmonary and bronchial arteries. Contrast-enhanced sonography enables us to determine whether the pulmonary or the bronchial arteries are the source of blood to lung lesions, depending on the time to enhancement and the extent of enhancement after contrast agent application. This article reports our first experience with transcutaneous contrast-enhanced sonography for the diagnosis and differential diagnosis of peripheral lung lesions.

Structural Characterization of Polycrystalline 3C–SiC Films Prepared at High Rates by Atmospheric Pressure Plasma Chemical Vapor Deposition Using Monomethylsilane

Polycrystalline cubic silicon carbide (3C–SiC) films were deposited at a relatively low temperature of 1070 K on Si(001) substrates by atmospheric pressure plasma chemical vapor deposition. Monomethylsilane (CH3SiH3) was used as the single source. CH4 and SiH4 dual sources were also used to compare deposition characteristics. Under the present deposition conditions, very high deposition rates of more than 3 nm/s were obtained. The structure of the SiC films was evaluated by reflection high-energy electron diffraction, Fourier transform infrared absorption spectroscopy and cross-sectional transmission electron microscopy. In addition, optical emission spectroscopy was employed to study the chemical reactions in the CH4/SiH4 and CH3SiH3 plasmas. The results showed that increasing H2 concentration is essential in forming a high quality 3C–SiC film by enhancing the hydrogen elimination reaction at the film-growing surface. From the optical emission spectra, it was found that atomic hydrogen generated by adding H2 in the plasma increase the amount of principal precursors for the film growth. The utilization of CH3SiH3 also led to a higher concentration of principal precursors in the plasma, enhancing the incorporation of Si–C bonds into the film. As a consequence of simultaneously using a high H2 concentration and the CH3SiH3 single source, the columnar growth of 3C–SiC crystallites was achieved.

Stable isotope evidence of dual (Arabian Sea and Bay of Bengal) vapour sources in monsoonal precipitation over north India

High resolution time series data of hydrogen ( δD) and oxygen ( δ 18O) isotope values of precipitation have been generated for the first time at Kolkata, eastern India where the summer monsoon clouds from Bay of Bengal (BOB) commence their journey over India. Use of a Rayleigh cum two component mixing model and comparison of Kolkata data with the International Atomic Energy Agency (IAEA)–Global Network of Isotopes in Precipitation (GNIP) data base of New Delhi suggest that the precipitation at New Delhi cannot be explained by simple continental effect of a BOB vapour source alone, traveling and raining successively along Kolkata–New Delhi route. It is necessary to invoke an admixture of ∼ 20% vapour originating from the Arabian sea with the vapour coming from BOB and finally causing summer monsoon rains at New Delhi. The findings have major implications to the regional water vapour budget over India.

Optimal biostimulation strategy for phenol degradation with indigenous rhizobium Ralstonia taiwanensis

This study provides a first attempt from a perspective of Gaden's classification of fermentation and phase–plane to put forward phenol degradation using various augmented nutrient media for biostimulation. It aimed to identify the most promising nutrient source(s) to attenuate synergistic interactions with phenol for optimal phenol degradation. Therefore, the growth association of phenol degradation using various nutrient media in place of combined toxic interactions was established via Gaden's classification scheme of fermentation and phase–plane analysis. In cultures grown on medium bearing dual carbon sources (glycerol and phenol) or phenol alone, phenol was found to be firstly biodegraded for microbial growth (i.e., growth-associated degradation). In contrast, when yeast extract or acetate was supplemented, a diauxic growth behavior was observed as the augmented nutrient was primarily utilized while phenol degradation was repressed. Moreover, using glycerol as the nutrient source, phenol degradation seemed to be enhanced simultaneously during the consumption of glycerol for cellular growth after ca. 2 h response lag in growth. Although gluconic acid could enhance cell growth as well as phenol degradation, the phenol degradation performance was still not as good as that of glycerol. Thus, biostimulation with glycerol appeared to show the most favorable metabolic characteristics against phenol toxicity on Ralstonia taiwanensis, leading to better degradation efficiency of the toxic pollutant. Phase–plane trajectories also clearly confirmed that glycerol was the optimal biostimulating nutrient source for phenol degradation.

ANALYSIS OF DUAL FREQUENCY CONFINED CAPACITIVELY COUPLED PLASMA AT LOW POWER

Confined dual frequency hydrogen plasma discharge has been investigated with microwave interferometer method and radial profiles are taken by Abel inversion technique. Dual radio-frequency sources, operating at 27.12MHz and 1.94MHz, are coupled to each other through the plasma. 27.12MHz RF power is used to enhance plasma density and 1.94MHz power is used to enhance ion acceleration energy to the electrode. Radial density profiles has been taken for comparing the effects of low frequency source that the secondary RF source causes reduction in plasma density due to the sheath expansion. Instead radial density profile is assumed as flat by most of the models, there is about 2.5eV of potential drop occurs from centre to boundary at 40W of primary source power. It has been observed that increasing sheath width (increasing the secondary source power to primary source power) reduces the bulk plasma volume and makes potential profile flattening in y direction. While the high frequency power is dissipated by electrons in the bulk plasma; low frequency power is mostly dissipated by ions in the sheath region. Using both high and low frequency power, we may control plasma density and ion acceleration energy to the electrode simultaneously.

Dual sand sources on Farewell Spit intertidal sand flats, New Zealand: Partitioning during redistribution

Extensive intertidal sand flats (c.10000 ha, c. 100 km2) on the sheltered southern side of Farewell Spit, a 30 km long sand spit located at the northern tip of South Island, New Zealand, extend for up to 8 km into Golden Bay. They consist primarily of fine sand with an upper size limit of 0.36 mm, blown from the spit during northerly storms. In parts of the flats fine sand is supplemented by significant but highly variable amounts of coarse sand, with rare stones up to 40 cm long. Tree trunks with tangled root masses, stranded on the flats, suggest that the coarse sediment is being delivered in the root masses of trees which are washed out of rivers discharging into Golden Bay from the mountainous southern hinterland. The greatest concentrations of coarse sediment are located northeast of the Aorere and Takaka Rivers, the two largest rivers discharging into Golden Bay. We propose that some trees are blown by prevailing southwesterly winds from the river mouths to the sand flat, and that a clockwise tidal current gyre carries trees from all rivers onto the flats in the northwestern corner of the bay. The patchy distribution of coarse sand on the intertidal flats indicates that redistribution of sand across the flats is partitioned: coarse sand (>0.5 mm) is not widely mixed with fine sand by surface processes, while fine sand is widely distributed. The sand flat extends subtidally to the 10 m bathymetric contour, giving the system a total area of c. 200 km2. An estimated volume of Holocene age sand in the spit and the sand flats of c. 5.7 km3 represents only c. 10% of the sand delivered to the northern tip of the South Island by longshore movement up the West Coast. The bulk of the sand may be accumulating on the continental shelf.

Accurate polarization measurements with a dual photoelastic modulator

Measurements of the polarization effects in multimirror experiments by using a dual photoelastic modulator are described. The effect of single and multiple mirrors in polarization measurements in two and three dimensions is discussed, and experimental results show how symmetrical placement of mirrors in three-dimensional geometry can eliminate changes in the polarization. Calibration procedures for a dual photoelastic modulator and potential error sources such as misalignment of analyzer, signal dc offset, and neglect of aperture size are presented. Mirror-surface evolution and how it can disturb the polarization measurement are also addressed.

Scaling laws for dual radio-frequency capacitively coupled discharges

The characteristics of dual radio-frequency capacitively coupled discharges are studied based on a homogeneous analytic model. We are considering a planar plasma device that can be approximated using a one-dimensional model. A set of equations describing the dynamics of the system are presented and used to give the analytic scaling laws. Scaling laws relating the drive frequencies and the applied voltages of dual radio-frequency sources to operating functions such as plasma density and plasma potential are examined and compared with numerical simulations.

High growth rate deposition of oriented InN pillar crystals

High growth rate deposition of highly oriented indium nitride (InN) pillar crystals were successfully grown on Si(100) substrate prepared under atmospheric pressure using a halide CVD method (AP-HCVD). The growth rate of InN pillar crystal can be enhanced threefold by AP-HCVD system with metal halide dual sources zone, and the maximum growth rate of 8.33 nm/s was achieved. X-ray diffraction and X-ray pole-figure analyses showed that the each InN pillar crystal grows with a different rotation angle around the 〈001〉 axis. Selected area transmission electron diffraction showed that that they are of high crystal quality.

Ion energy distribution control in single and dual frequency capacitive plasma sources

Particle-in-cell/Monte Carlo simulations are used to study the possibility of ion energy distribution function (IEDF) control on the powered electrode in asymmetric single and double frequency capacitive discharges in argon. The possibility of IEDF control is demonstrated. It is shown that the IEDF shape and spread on the cathode can be controlled by the driven voltage in a single frequency discharge and by the low frequency voltage in a dual frequency capacitive discharge. It is shown that the IEDF shape on the powered electrode can be controlled by the driven frequency in single frequency capacitively coupled plasmas. It is shown that the density of plasma decreases, and the sheath width, the plasma potential and the self-bias voltage increase, with growth of the low frequency voltage in the dual frequency capacitive discharge.

The mammary pheromone of the rabbit: from where does it come?

Newborn rabbits, Oryctolagus cuniculus, are directed to their mother's nipples by specialized odour cues. Previous investigations have suggested that these cues are released from the doe's abdominal surface from structures located around the nipple. We tested pups with samples of various cutaneous tissues or fluids collected from lactating females to determine the location of the source of the odour cues. After finding that the nipples from lactating does were more attractive than those of virgin females, we conducted three experiments using skin samples collected at increasing distance from the nipples, dermal and mammary tissues taken below the nipples, and milk collected at different levels of the mammary pathway. These different substrates were assessed for their ability to elicit searching/grasping responses in pups. Efficient odour cues were released only from the nipples, whereas the dermal or mammary tissues sampled beneath the nipples were behaviourally inefficient, and milk became behaviourally active only after it had flown through the nipple. These results suggest dual exocrine sources of active factors from the nipple of lactating rabbits: cues released within the nipple that render milk behaviourally active and cues distributed over the nipple epidermis.

Heat-pipe enhanced solar-assisted heat pump water heater

A heat-pipe enhanced solar-assisted heat pump water heater (HPSAHP) is studied. HPSAHP is a heat pump with dual heat sources that combines the performance of conventional heat pump and solar heat pipe collector. HPSAHP operates in heat-pump mode when solar radiation is low and in heat-pipe mode without electricity consumption when solar radiation is high. HPSAHP can thus achieve high energy efficiency. A prototype was designed and built in the present study. An outdoor test for a HPSAHP in the present study has shown that COP of the hybrid-mode operation can reach 3.32, an increase of 28.7% as compared to the heat-pump mode COP (2.58).

Dual sources of ensimatic magmas, Hearne domain, Western Churchill Province, Nunavut, Canada: Neorchean “infant arc” processes?

In the Henik segment of the Central Hearne supracrustal belt, Neoarchean supracrustal rocks accumulated in deep-water depositional systems that were well removed from a continental influence. Repeated in time and space, these systems consisted of mafic lava plain, slope, and apron subenvironments, with local emergent to near-emergent felsic volcanic centres. Volcanic and plutonic rocks are subalkaline, and range in composition from basalt to rhyolite. Consistent with field relationships, the volcanic rocks are juvenile and, with predominantly positive values that are independent of compositional variation, display little evidence of contamination by continental crust. However, despite primary interlayering on scales of 10s of metres, mafic and felsic rocks display markedly different rare earth element (REE) characteristics. The mafic volcanic rocks are MORB-like and display a tholeiitic magma evolution trend, flat REE patterns, and positive values, suggesting that they were derived from partial melting of depleted mantle. In marked contrast, the felsic rocks display steeply sloping REE patterns with significantly lower heavy REE abundances, negative Nb anomalies, and positive Zr and Hf anomalies suggesting derivation from partial melting of slightly older basaltic crust. This duality of magma sources supports a generalized model for the Central Hearne supracrustal belt that draws analogies from Eocene intraoceanic “infant arc” processes described from the southwestern Pacific Ocean, rather than from those normally associated with fully developed Phanerozoic subduction.

Microfinance Programs in Uganda: An Analysis of Household Participation and Investment Behavior

This paper identifies a model of low-income household participation in microfinance credit programs and the effects on investment behavior from repeated access to these institutions using evidence from household survey data. The primary focus is on changes in household investment behavior, not the assessment of changes in welfare per se. The results for a representative sample of households in Uganda indicate that the most significant factors influencing the decision of a household to participate are proximity to microfinance institutions (MFIs), dual sources of household income, and income stability. This paper shows that once the decision has been made to participate, repeated use of the financial services of MFIs has a positive impact on household investment in health, education, and consumption. Repeated access to credit from an MFI significantly raises the likelihood that a household will invest more in nutrition, health and education, ceteris paribus. Through repeated access to credit, income and wealth effects are generated that may reduce vulnerability to poverty. Keywords: microfinance credit, household investment and consumption, participation Eastern African Journal of Rural Development

S/S+ band tunable thulium-doped fiber laser anchored on 50-GHz ITU-T grid

We, for the first time, demonstrate a S/S+ band tunable thulium-doped fiber laser (TTDFL) anchored on 50-GHz ITU-T grid. The laser has a ring-type cavity where the gain medium (TDF) was pumped by dual wavelength light sources (1.4 and 1.5 μm). A fiber-pigtailed Fabry–Perot filter was introduced into the cavity to fit the laser wavelengths into 50 GHz grid. The tuning range was more than 57 nm (1454.9–1512.0 nm) covering most of the thulium bandwidth. The laser shows sufficient output power (higher than 0 dB) over the entire tuning range and SMSR of the lasing peak was measured to be more than 55 dB at 0.02 nm resolution bandwidth. The potential applications of this newly developed laser include the wavelength reference sources for S/S+ band DWDM in industries and laboratories.

Fluorescence-enhanced optical imaging of large phantoms using single and simultaneous dual point illumination geometries.

Fluorescence-enhanced optical tomography is typically performed using single point illumination and multiple point collection measurement geometry. Single point illumination is often insufficient to illuminate greater volumes of large phantoms and results in an inadequate fluorescent signal to noise ratio (SNR) for the majority of measurements. In this work, the use of simultaneous multiple point illumination geometry is proposed for acquiring a large number of fluorescent measurements with a sufficiently high SNR. As a feasibility study, dual point excitation sources, which are in-phase, were used in order to acquire surface measurements and perform three-dimensional reconstructions on phantoms of large volume and/or significant penetration depth. Measurements were acquired in the frequency-domain using a modulated intensified CCD imaging system under different experimental conditions of target depth (1.4-2.8 cm deep) with a perfect uptake optical contrast. Three-dimensional reconstructions of the fluorescence absorption from the dual point illumination geometry compare well with the reconstructions from the single point illumination geometry. Targets located up to 2 cm deep were located successfully, establishing the feasibility of reconstructions from simultaneous multiple point excitation sources. With improved excitation light rejection, multiple point illumination geometry may prove useful in reconstructing more challenging domains containing deeply embedded targets. Image quality assessment tools are required to determine the optimal measurement geometry for the largest set off imaging tasks.

A temporal window for the central inhibition of stuttering via exogenous speech signals in adults

We explored a possible temporal window for central stuttering inhibition via exogenously presented speech signals. Thirteen adults who stutter were asked to read while listening to a continuous vowel /a/, or a repeating 1 s vowel /a/ followed by 1, 3 and 5 s silences. In all conditions, stuttering was significantly reduced. However, the continuous and 1 s repeating conditions showed the greatest reduction in stuttering relative to all other conditions. Furthermore, these conditions did not differ significantly from each other, suggesting a temporal window of at least 1 s for stuttering inhibition induced by a 1 s stimulus. We propose that exogenous speech signals provide an additional speech source that engages mirror neurons for ‘on-line’ stuttering inhibition during continous speech. Employing dual speech sources results in ‘on-line’ stuttering inhibition and continuous speech flow. In contrast, endogenous (single source) inhibitory techniques require speech flow to be interrupted and go ‘off-line’ to derive the mirror neuronal.

Dual radio frequency sources in a magnetized capacitively coupled plasma discharge

Nonlinear interaction of two radio frequency (RF) sources in a magnetized Ar/C/sub 2/F/sub 6/ capacitively coupled plasma discharge is investigated using a computational model. Results show that application of a radial magnetic field enhances charged and neutral species densities in the plasma reactor due to reduction in electron loss to surfaces and trapping of secondary electron emission generated electrons. Amplitude of RF currents at electrodes also increases with magnetic field strength and source frequency for a given RF voltage. Due to nonlinear nature of plasma sheath, higher harmonics of applied frequencies and source interaction generated harmonics can be observed in electrode currents. Application of magnetic field decreases electron mobility and makes the system less nonlinear, which reduces higher harmonics relative to primary components. Magnetic field also tends to make the RF sources more isolated. Increase in source frequency moves the plasma from electrode edge to the center of the chamber, which redistributes current through the electrodes. If frequencies of the two RF sources are commensurate, nonlinear interaction of RF sources generates subharmonics of primary frequencies.

A novel indexing mechanism for paper cutting machines

This article describes a novel indexing mechanism to improve the productivity of the paper cutting machines. The mechanism is based on dual light sources and an optical detector.