Suspended Configuration Research Articles

Low Profile Suspended Microstrip Antennas for Wideband Applications

In this paper, design of a coplanar capacitive coupled probe fed microstrip antenna suspended above the ground plane is presented. It is demonstrated that the proposed approach can be used for designing suspended microstrip antennas with impedance bandwidth of about 50% and a good gain to operate in various microwave bands. The bandwidth improvement achieved is from the well-known fact that air gap reduces the effective dielectric constant close to unity and increases the thickness of the mixed substrate. However, suspended configurations increase the overall height/volume of the antenna which limits the use of these antennas in compact applications. Therefore, in this work an effort has been made to reduce the overall height (about 55 to 73% keeping adequate impedance bandwidth (> 30%)) of the antenna significantly which is one of the key of design aspects of compact wideband antennas. It is demonstrated that the gain and radiation patterns of the proposed low profile antenna remain nearly unchanged.

SIMULATED ACID AZO DYE WASTEWATER TREATMENT USING SUSPENDED GROW TH CONFIGURED SEQUENCING BATCH REACTOR (SBR) UNDER ANOXIC-AEROBIC-ANOXIC MICROENVIRONMENT

Studies on the treatment of simulated acid metal complex azo dye (C.I.Acid black 210) wastewater was carried out in anoxic-aerobic-anoxic microenvironment using a periodically operated sequencing batch reactor (SBR) with suspended growth configuration at two organic loading rates (0.56 Kg COD/cum-day and 0.75 Kg COD/cum-day). The experimental data revealed the effective performance of the SBR system in the process of azo dye minerilazation, which may be attributed to the prevailing anoxic microenvironment present during the cycle operation. The reactor showed rapid startup (within 22 days) and stabilization (within 6 days after loading) compared to conventional continuously operated systems. Organic loading (shock loads) rates have shown relatively less effect on the performance.

Influence of reactor configuration on fermentative hydrogen production during wastewater treatment

Abstract Influence of reactor configuration [biofilm/suspended growth] on fermentative hydrogen (H 2 ) production and substrate degradation was evaluated employing anaerobic mixed consortia. Reactors were operated at acidophilic (pH 6.0) condition employing designed synthetic wastewater as substrate at an organic loading rate of 3.4 Kg COD/m 3 -day with a retention time of 24 h at 28 ± 2 °C. Experimental data enumerated the influence of reactor configuration on both H 2 production and wastewater treatment. Biofilm reactor (28.98 mmol H 2 /day; 1.25 Kg COD/m 3 -day) showed relatively efficient performance over the corresponding suspended growth configuration (20.93 mmol H 2 /day; 1.08 Kg COD/m 3 -day). Specific H 2 yields of 6.96 mmol H 2 /g-COD L -day (19.32 mmol H 2 /g-COD R -day) and 5.03 mmol H 2 /g-COD L -day (16.10 mmol H 2 /g-COD R -day) were observed during stabilized phase of operation of biofilm and suspended growth reactors respectively. Higher concentration of VFA generation was observed in the biofilm reactor. Both the configurations recorded higher acetate concentration over other soluble metabolites indicating the dominance of acid-forming metabolic pathway during the H 2 production process.

Simulated acid azo dye (Acid black 210) wastewater treatment by periodic discontinuous batch mode operation under anoxic–aerobic–anoxic microenvironment conditions

Treatment of simulated acid azo dye (C.I. Acid black 210) wastewater was studied in periodic discontinuous batch mode operation employing sequencing batch reactor (SBR) with suspended growth configuration under anoxic–aerobic–anoxic microenvironment. The performance of the reactor was evaluated at two organic loading rates (0.56 kg COD/m 3-day and 0.75 kg COD/m 3-day) with a total cycle period of 24 h [fill phase: 30 min; react phase: 23 h; settle phase: 15 min; decant phase: 15 min] at room temperature. The performance of SBR was assessed by monitoring both COD and colour (OD-617 nm) concentrations. Periodic discontinuous batch mode operation feasibility for dye colour removal along with simultaneous substrate (COD) removal. The performance efficiency of the system was found to depend on the operating organic loading rate. Induced anoxic microenvironment during cycle operation and persistent anoxic microenvironment in the internal layer of suspended biomass may be probable reasons for dye mineralization/reduction. Rapid startup period and non-inhibited performance at higher loading rate are some of the advantages observed in the SBR operation.

Nanoscale Calorimetry Using a Suspended Bridge Configuration

Abstract A new setup for small-scale differential scanning calorimetry (DSC) studies based on a suspended bridge configuration is presented. The new setup has three major advantages over previously reported DSC setups: 1) superior temperature uniformity in the bridge cross section; 2) less heat loss to the surroundings by at least two orders of magnitude; and 3) a faster transient response by three orders of magnitude. This paper includes a thermal analysis to support these improvements. A major contribution of the new thermal analysis over previous reports is the inclusion of the thermal mass of the substrate in calculations, which makes thermal design more detailed, dramatically affecting accuracy and sensitivity in measurements. Furthermore, the new thermal analysis more accurately accounts for heat loss to the substrate and the surroundings in efforts to resolve suspected inconsistencies in previously reported data. Experimental validation of the new setup is presented by measuring the specific heat of thin layers of Si02 and CoFe. The specific heat of Si02 was found to be 2.2 times 106 Jm -3 K-1 which is nearly 10% different from the literature values of bulk specimens. For CoFe, the specific heat value of 3.16 x 106 Jm -3 K-1 is obtained using differential Cu/Si02 and Cu/Si02/CoFe structures compared to the value of 3.5 times 106 Jm -3 K-1 obtained using single CoFe suspended structure.

Optically-pumped long-wavelength vertical-cavity surface-emitting laser with high modulation bandwidth

Optically-pumped long-wavelength vertical-cavity surface-emitting lasers (VCSELs) have been fabricated exhibiting more than 2mW over 20–70°C, and 1.25mW at 85°C. Small-signal modulation measurements on the VCSEL at 20°C indicate a 3dB bandwidth of 14.8GHz at an output power of 2mW. The VCSELs have a narrow spectral width suitable for data transmission over single-mode fiber. The good temperature performance of the VCSEL is maintained in a suspended configuration that would allow monolithic integration.

Treatment of complex chemical wastewater in a sequencing batch reactor (SBR) with an aerobic suspended growth configuration

A sequencing batch reactor (SBR) has certain advantages over conventional activated sludge processes (ASP) for the treatment of complex wastewater. The performance of a sequencing batch reactor in treating complex chemical effluents was investigated with a suspended biomass configuration and operating under aerobic conditions. A total sequence of 24 h (15 min: filling phase; 23 h: reaction phase (aeration with recirculation); 30 min: setting; and 15 min: withdrawal) was employed and studied with various organic loading rates (1.0 kg COD/m 3/day: 1.7 kg COD/m 3/day and 3.5 kg COD/m 3/day). The SBR performance was assessed by means of carbon removal and operational parameters such as pH, oxidation–reduction potential (ORP), sludge volume (SV), sludge volume index (SVI), suspended solids (SS) and volatile suspended solids (VSS), which were monitored during reactor operation. The SBR showed relatively more efficient performance over conventional suspended growth systems. About 8% sulphate was removed under anoxic conditions at all the studied organic loading rates. Enhanced performance with SBR over conventional ASP may be due to enforced short term unsteady state conditions coupled with periodic exposure of the microorganisms (physiological state) to defined process conditions which facilitate the required metabolic conditions for treating complex chemical effluents.

Simple method to prepare individual suspended nanofibers

A simple and general technique for producing a suspended nanofiber has been developed using coordinate markers and a sacrificial layer of poly(methylmethacrylate). The simple procedure does not involve etching processes or chemical vapor deposition and makes it easier to investigate the physical properties of nanofibers in a suspended configuration. As a demonstration, a suspended carbon nanotube rope was fabricated and Young’s modulus was determined to be 0.4 TPa from the force calibration of an atomic force microscope.

The influence of mandibular deformation, implant numbers, and loading position on detected forces in abutments supporting fixed implant superstructures

Statement of problem. Forces may arise in association with the use of implant stabilized mandibular fixed partial dentures as a result of functional jaw deformation, yet the phenomenon has received little attention and is rarely included as a variable when investigating implant biomechanics. Purpose. This in vitro investigation tested the hypothesis that functional mandibular deformation influences force distribution in the jaw/implant/superstructure complex. Material and methods. Six Brånemark implants were mounted in an acrylic resin replica of an edentulous human mandible. Applied forces were measured with 4-element resistance strain gauges mounted on each of 6 standard titanium abutments. The mandible was supported either on its lower border or suspended in a frame that simulated the natural situation. A cast gold superstructure was mounted on varying combinations of implants, loaded occlusally in different locations, and the resultant forces at each supporting transmucosal abutment measured. Results. The suspended (“natural”) support configuration was associated with considerable differences in patterns of force transmission as compared with bench support. Loads were more widely spread, and large extrusion forces were detected, particularly where several implants were connected. Conclusions. Functional mandibular deformation is a significant factor in the design of mandibular implant stabilized prostheses, and calls into doubt the value of modeling techniques that do not allow for this phenomenon. (J Prosthet Dent 1998;80:169-74.)

Analysis of the suspended strip in elliptical cross section by separation of variables

The coaxial suspended strip configuration in elliptical cross section is often found in transitions from ordinary coax to planar circuits and other geometries. Using elliptical coordinates makes the problem separable, leading to closed-form solutions for the fundamental TEM mode and the TE/TM higher modes. It is emphasized that the presence of the thin strip is dealt with analytically by this approach. Mode patterns and TEM characteristic impedance are reported. The cutoff frequencies versus eccentricity are computed for the first eight modes.

Shielded edge-coupled coplanar waveguide structures: Modes and field configurations

In this article we present the dispersion characteristics as well as frequency-dependent field configuration and characteristic impedance for edge-coupled, shielded, coplanar waveguide structures. The structures studied include conductor-backed and suspended configurations. Phenomena such as mode conversion and dispersion of the dominant modes are explained. The characteristic impedance behavior is shown to be directly related to the phenomenon of mode conversion. The analysis uses the method of lines. © 1996 John Wiley & Sons, Inc.

吊り下げ曲面の形状解析

It is a well known fact that the suspended cable configuration under the natural gravity acceleration resists against the gravity loads only by the axial resultant stresses and it is called catenary. Similarly, the suspended membrane is also widely known to result in the curved surface in which no out-plane stress resultant acts under the gravity loads. In the present paper, the problem of the shape finding of the suspended structure in the gravity field is dealt with as a pure geometrical problem where the variational principle is utilized. The proposed method is expected to be utilized for the shape determination of shells and spacial structures.

Design parameters of asymmetric edge‐coupled microstrip open‐end discontinuities

AbstractA lumped capacitance equivalent circuit is used to characterize the asymmetric edge‐coupled microstrip discontinuity in the case in which the conducting strips are embedded in a multilayered anisotropic medium. The Galerkin method in the spectral domain is employed to determine the excess charge density on the strips of the discontinuity. Original results are provided for the general asymmetric discontinuity in conventional and suspended configurations. © 1992 John Wiley & Sons, Inc.

Analysis of broadside coupled microstrip open-end discontinuities

The capacitive equivalent circuit and the modal equivalent lengths of the symmetric broadside coupled microstrip open-end discontinuity are calculated in the case in which the conducting strips are embedded in a multilayered dielectric medium. The Galerkin method in the spectral domain is applied to solve the excess charge densities existing on the conducting strips of the discontinuity both in even and odd modes of excitation. Results are presented for broadside coupled microstrip open ends in conventional, suspended and inverted configurations.

Broadside-coupled rectangular resonators in suspended stripline with single and double dielectrics

The rigorous spectral domain method is applied to analyse the resonant frequency characteristics of rectangular resonators in three broadside-coupled suspended stripline configurations. These are (a) broadside-coupled suspended stripline with a single dielectric, (b) broadside-coupled suspended stripline with double dielectrics and (c) broadside-coupled suspended stripline with double inverted dielectrics. Computed dominant even-and odd-mode resonant frequencies of rectangular resonators in the above broadside-coupled configurations are presented as a function of various structural parameters. These characteristics are distinct from those obtained for conventional edge-coupled microstrip resonators. The computed resonant frequencies using simple basis functions are compared with the experimental values in the frequency range 5–13 GHz. The results presented in this paper should find application in the design of microwave and millimeter wave integrated circuit components.

Design and Performance of W-Band Broad-Band Integrated Circuit Mixers

Broad-band integrated circuit mixers rising a crossbar suspended stripline configuration and a finline configuration were developed with GaAs beamlead diodes. For the crossbar suspended stripline balanced mixer, less than 7.5-dB conversion loss for 15-GHz instantaneous, IF bandwidth was achieved with the LO at 75 GHz and the RF swept from 76 to 91 GHz. With the LO at 90 GHz, a conversion loss of less than 7.8 dB was achieved over a 14-GHz instantaneous bandwidth as the RF is swept from 92 to 105 GHz. For the finline balanced mixer, a conversion loss of 8 to 12 dB over a 32-GHz instantaneous IF bandwidth was achieved as the RF is swept from 76 to 108 GHz. Integrated circuit building blocks, such as filters, broadside couplers, matching circuits, and varions transitions, were also developed.

Modified suspended striplines for microwave integrated circuits

Suspended coupled striplines have very different even- and odd-mode phase velocities. A structure modified by the presence of a slot is proposed to obtain equalisation, a condition necessary to build broadband couplers. This modification has the advantage of preserving the suspended configuration.

On Computation of the Motion of Elastic Rods

A computational method is developed for the finite-amplitude three-dimensional motion of inextensible elastic rods with equal principal stiffnesses. The method also applies to the two-dimensional motion of such rods with unequal principal stiffnesses. For these two classes of problems the equations of the classical theory of rods are reduced to a non-linear vector equation of motion together with the inextensibility condition and appropriate boundary and initial conditions. Consistent finite-difference approximations are introduced and a semi-explicit method of solution is devised. The approximate limitation for numerical stability of the method is shown to be the same as for the usual explicit method in linear beam dynamics. By way of example the method is applied to the free fall of a circular pipe through water onto a rigid plane from a suspended initial configuration.

Drag reduction and turbulence modification in rigid particle suspensions

AbstractTurbulent drag reductions on the order of 50% were obtained for pipe flow of submicron, rod‐like particle suspensions at weight concentrations of less than 0.5%. Wall Reynolds numbers as high as 40,000 were obtained for the suspensions. The suspended particle configuration was rigid and non‐elastic and was not affected by local strain rate fields. Longitudinal turbulence data are presented for two suspensions and for the Newtonian solvent at an average flow velocity of about 7 fps. Distinctly modified turbulence generation and dissipation were observed. The suspension exhibited smooth transitional flow behavior and increases in both macroscale and microscale. A particle length effect, or relaxation time effect, was observed with the larger relaxation time suspension exhibiting the more extreme flow and turbulence differences.

Resistance Properties Of Sediment-Laden Streams

Experiments were made to determine relative effects on friction factor of flow of suspended sediment load and configurations which form on sand beds of streams; results showed that friction factor of stream carrying suspended sediment is less than comparable one without sediment; reduction of friction factor due to changes in bed configuration is much larger than that due to suspended sediment.