Rectangular Mode Research Articles

Extreme and spectrum characteristics of wind loads on super-large cooling tower under different four-tower combinations

The wind loads distribution on the super-large cooling tower under the interference effect of tower group is very complicated. Particularly, energy distribution of fluctuation wind loads and extreme model is difficult to be predicted. However, accurate calculations of these two factors are the most direct ways for analysis of wind resistance dynamics of super-large cooling tower. The wind tunnel tests of the highest super-large cooling tower under five typical tower combinations (serial, rectangular, rhombus, L-shaped, and inclined L-shaped) with 320 working conditions were performed. On this basis, non-Gaussian and non-stationary properties of local wind pressure and overall force coefficient of super-large cooling tower were analyzed. Distribution laws of local wind pressure extremes and overall force coefficient extremes were discussed based on Hermite method and peak factor method. Key attention was paid to the mapping relationships of characteristic angles with local and overall aerodynamic force extremes. The effects of four-tower combination modes on fluctuation wind loads energy of super-large cooling tower were studied based on the power spectral density function, intrinsic mode function, and evolution power spectral density function. Besides, the estimation formulas of local wind pressure spectrum and overall pressure coefficient spectrum of super-large cooling tower under four-tower combination were proposed. It can be found that the extremes of local wind pressure and overall aerodynamic force could be predicted based on the linear relationship between characteristic angles and fluctuation wind loads. In addition, it is suggested to choose serial combination first, followed by inclined L-shaped, L-shaped, rhombus, and rectangular modes successively.

Hi-Fi Stake Piezo Single Crystal Actuator

High fidelity (Hi-Fi) piezoelectric single crystal stake actuators are presented in this work. They are made of multiple rectangular d32 mode lead-based relaxor ferroelectric (notably Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) and Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT)) single crystals bonded along their long edges with the aid of compliant polymeric edge guides into a square or polygonal pipe-like construction. Due to the highly stable engineered domain structure and high piezoelectricity of single crystal active materials, the actuators exhibit large linear displacement responses with negligible (<1%) hysteresis. Prototypes of square-pipe stake actuators were first fabricated and their phase transformation curves under different applied voltages, axial compressive loads and temperatures were established. Based on the information obtained, a range of Hi-Fi stake actuators with external square cross-sections of 5 × 5 mm2, 7.5 × 7.5 mm2 and 10 × 10 mm2, each of 4 different overall lengths of 15, 28, 41 and 54 mm, were further designed and fabricated using either PZN-PT or PIN-PMN-PT single crystals (both with TRO ≈ 110–125 °C) of 0.4 mm in crystal thickness. The stroke for the longest stake actuator fabricated (L = 54 mm) reaches −58 µm at 240 V. The working conditions, over which these Hi-Fi stake actuators remain linear with negligible hysteresis, were established for a total load of up to 10 kg and use temperature of up to 40 °C.

Interlaminar fracture toughness and electromagnetic interference shielding of hybrid-stitched carbon fiber composites

In the current study, the production of multifunctional hybrid-stitched composites with improved interlaminar fracture toughness and electromagnetic interference shielding effectiveness is reported. Unidirectional carbon fiber-epoxy composite laminates stitched with Kevlar, nylon, hybrid stitched with both Kevlar and nylon and unstitched were prepared using resin infusion process. Representative specimens from unstitched and stitched composites were tested using rectangular waveguide and Mode I double cantilever beam tests. The Mode I experimental results showed that composite stitched with Kevlar exhibited the highest crack initiation interlaminar fracture toughness (GIC-initiation), whereas composite stitched with nylon exhibited the highest maximum crack propagation interlaminar fracture toughness (GIC-maximum). The four-hybrid stitching patterns exhibited higher GIC-initiation than the unstitched and stitched with nylon composites and lower than stitched with Kevlar composite, whereas they had higher GIC-maximum than the unstitched and stitched with Kevlar composites, although lower than stitched with nylon composite. The electromagnetic shielding effectiveness experimental results showed that stitched composites exhibited improved shielding effectiveness compared to unstitched composites. For example, composite stitched with nylon had highest shielding effectiveness value of 52.17 dB compared by the composite stitched with Kevlar which had 40.6 dB. The four hybrid-stitched composites exhibited similar shielding effectiveness with an average value of 32.75 dB compared to the unstitched composite shielding effectiveness of 22.84 dB. The experimental results comply with the initial goal of this study to manufacture multifunctional hybrid stitching composites with combined properties between Kevlar and nylon-stitched composites.

Industrial scale microwave applicator for high temperature alkaline hydrolysis of PET

AbstractA microwave design for an industrial scale applicator of a continuous microwave assisted depolymerization of polyethylene terephthalate (PET) has been developed. The cavity is designed for use in combination with an Archimedean screw pump to transport the reaction material, surrounded by a cylindrical pipe with a diameter of 250 mm and a length of 250 mm at the 2.45 GHz ISM band. The proposed design is modular and can be easily expanded for the heating of longer reactor tubes. Simulation results show that a homogeneous heating of the process material along the screw axis can be achieved by using a novel cavity design which is based on the TE1,0,x– rectangular waveguide cavity mode. The achieved design provides high energy efficiency with a reflected power of less than 10%. It is robust against changes in the permittivity of the reactants. The electromagnetic design is based on the dielectric properties of the solvolytic reaction mixture measured in the relevant temperature range. It is verified over the full range of the expected permittivities.

Numerical study of 3D gaseous detonations in a square channel

The multidimensional structure of mildly unstable detonations are examined by numerical computations. These phenomenon have grown in interest since the development of propulsion devices such as pulsed and rotating detonation engines. Rectangular, diagonal and spinning modes are observed in a near-limit propagation detonation. High-order numerical integration of the reactive Euler equations have been performed to analyze the averaged structure, the shock dynamics of a single-cell detonation propagating in a square channel. Computations show a good agreement with the experimental cellular structure, showing the relevance of the slapping waves in the rectangular modes. The hydrodynamic thickness as well as the pdf shock dynamics are similar in the 2D and 3D cases, but the mean quantities vary on a quantitative basis. Moreover, the presence of strong forward jets is attested, which comes from simultaneous triple point line collisions with the walls.

Dynamic rheological behavior of poly(ether ketone ketone) from solid state to melt state

ABSTRACTHigh performance thermoplastic poly(ether ketone ketone) (PEKK) polymers with various meta phenyl links ratio were investigated by dynamical mechanical analysis. Analyses were carried out in a wide range of temperature from solid state (torsion rectangular mode) to the melt state (torsion parallel plates mode) as function of thermal history and environmental conditions. In the solid state, this study was focused on the secondary relaxations in the vitreous state. A complementary investigation conducted with different poly(aryl ether ketones) allowed us to propose a molecular interpretation of PEKK sub‐vitreous relaxations. In the molten state, storage modulus (G′), loss modulus (G″), storage viscosity (η′), and loss viscosity (η″) were studied to determine zero shear‐rate viscosity (η0) and thermal activation energy Ea. Master curves were built and the shift factor aT was determined. Thermal activation energies were extracted from an Arrhenius model on the shift factor temperature's dependency. Finally, Ea and η0 were determined thanks to the dynamic viscosity fit with Cross model and Cole–Cole representation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46456.

A transmitting and receiving structure for high power applications

A high-power-capacity transmitting and receiving structure (TRS) is proposed. It has the ability of transmitting the GW-level high power microwave from the microwave sources with the horizontal polarized TE11 mode and receiving the microwave signal from the target with the orthogonal polarized TE11 mode. It is realized by the cooperation of a polarization-isolation-structure (PIS) and a two-way circular TE11 mode to rectangular TE10 mode power divider. Simulation shows that from 9.65 to 9.71 GHz, its power capacity is more than 3 GW at the transmitting format. The transmitting and receiving channel have an isolation of 60 dB which can prevent the receivers connecting to the receiving channel suffering from breakdown. The insertion losses for the transmitting and receiving format are both less than 0.03 dB.

3D printed dielectric rectangular waveguides, splitters and couplers for 120 GHz.

We use a 3D printer to fabricate rectangular dielectric single mode waveguides for 120 GHz. The rectangular waveguides consisting of polystyrene showed an attenuation of 6.3 dB/m, which is low enough for short devices. We also characterize 3D printed Y-splitters and a 1x3-splitter based on multimode interference. Further, we construct and measure a variable planar waveguide coupler which can be used as a 3-dB coupler, a cross-coupler and no coupler at all.

Three-dimensional detonation cellular structures in rectangular ducts using an improved CESE scheme**Project supported by the National Natural Science Foundation of China (Grant Nos. 10732010 and 10972010).

The three-dimensional premixed H2-O2 detonation propagation in rectangular ducts is simulated using an in-house parallel detonation code based on the second-order space–time conservation element and solution element (CE/SE) scheme. The simulation reproduces three typical cellular structures by setting appropriate cross-sectional size and initial perturbation in square tubes. As the cross-sectional size decreases, critical cellular structures transforming the rectangular or diagonal mode into the spinning mode are obtained and discussed in the perspective of phase variation as well as decreasing of triple point lines. Furthermore, multiple cellular structures are observed through examples with typical aspect ratios. Utilizing the visualization of detailed three-dimensional structures, their formation mechanism is further analyzed.

A Millimeter Wave High-Order TE13 Mode Converter

In this paper a methodology to excite a circular high-order TE13-mode via a rectangular TE50 mode was proposed and verified by the millimeter wave measurement. This topology can also be applied to launch other high-order modes (HOMs) such as TE $_{1n}$ , TE $_{2n^\prime }$ and TE $_{0n^\prime }$ (n or $n^\prime =1$ , 2, 3) modes via different transition rectangular TE $_{m0}$ ( $m = 2n-1$ or $m = 2n^\prime $ ) modes, which can be achieved by adjusting the number of coupling apertures and optimizing dimensions of tapered waveguides. A W-band TE13 mode converter was designed and analyzed. Two identical converters connected back to back as a proof-of-principle operating at $Q$ -band were fabricated and measured. Good performance was observed, which was in good agreement with the simulation results. This HOM converter has many potential applications in areas such as gyro-devices, high-power transmission lines, RF multimode systems of accelerators, microwave/plasma, and antenna systems.

Investigations of the CLOCK and BMAL1 Proteins Binding to DNA: A Molecular Dynamics Simulation Study.

The circadian locomotor output cycles kaput (CLOCK), and brain and muscle ARNT-like 1 (BMAL1) proteins are important transcriptional factors of the endogenous circadian clock. The CLOCK and BMAL1 proteins can regulate the transcription-translation activities of the clock-related genes through the DNA binding. The hetero-/homo-dimerization and DNA combination of the CLOCK and BMAL1 proteins play a key role in the positive and negative transcriptional feedback processes. In the present work, we constructed a series of binary and ternary models for the bHLH/bHLH-PAS domains of the CLOCK and BMAL1 proteins, and the DNA molecule, and carried out molecular dynamics simulations, free energy calculations and conformational analysis to explore the interaction properties of the CLOCK and BMAL1 proteins with DNA. The results show that the bHLH domains of CLOCK and BMAL1 can favorably form the heterodimer of the bHLH domains of CLOCK and BMAL1 and the homodimer of the bHLH domains of BMAL1. And both dimers could respectively bind to DNA at its H1-H1 interface. The DNA bindings of the H1 helices in the hetero- and homo-bHLH dimers present the rectangular and diagonal binding modes, respectively. Due to the function of the α-helical forceps in these dimers, the tight gripping of the H1 helices to the major groove of DNA would cause the decrease of interactions at the H1-H2 interfaces in the CLOCK and BMAL1 proteins. The additional PAS domains in the CLOCK and BMAL1 proteins affect insignificantly the interactions of the CLOCK and BMAL1 proteins with the DNA molecule due to the flexible and long loop linkers located at the middle of the PAS and bHLH domains. The present work theoretically explains the interaction mechanisms of the bHLH domains of the CLOCK and BMAL1 proteins with DNA.

Three-dimensional detonation simulations with the mapped WENO-Z finite difference scheme

Abstract We perform a very long time numerical simulation to capture the three-dimensional detonation structures in a rectangular duct by solving the reactive Euler equations using the high order/resolution WENO-Z conservative finite difference scheme (Gao et al. J. Sci. Comput. 55 : 351–371, 2013). In the algorithm, the perfectly matched layer (PML) absorbing boundary condition (ABC) for the reactive Euler equations is used to reduce the spurious wave reflection from the open left boundary which allows one to use a significant smaller truncated physical domain. Moreover, a tangent grid mapping is used to enhance the grid resolution within the half reaction zone that greatly reduces the memory usage and computational time compared with solving the problem with a uniform grid. The initial Zeldovich-von Neumann-Doring (ZND) profile of two classical stable and slightly unstable detonation waves is perturbed to generate the rectangular in-phase, diagonal in-phase and spinning detonation structures. Depending on the initial perturbation, the stable case shows the presence of a rectangular mode and a diagonal mode of the detonation front, which are suggested to be geometrically similar. The slightly unstable case, as expected, generates the spinning detonations instead in a narrow duct. The results show that a short time simulation is insufficient to capture the cellular detonation structures. The width-to-length ratio of the cellular patterns depends on the gas properties only, but independent of the perturbation of the initial conditions.

Self-consistent simulation of an electron beam for a new autoresonant x-ray generator based on TE102 rectangular mode

The space cyclotron autoresonance interaction of an electron beam with microwaves of TE102 rectangular mode is simulated. It is shown that in these conditions the beam electrons can achieve energies which are sufficient to generate hard x-rays. The physical model consists of a rectangular cavity fed by a magnetron oscillator through a waveguide with a ferrite isolator, an iris window and a system of dc current coils which generates an axially symmetric magnetic field. The 3D magnetic field profile is that which maintains the electron beam in the space autoresonance regime. To simulate the beam dynamics, a full self-consistent electromagnetic particle-in-cell code is developed. It is shown that the injected 12keV electron beam of 0.5A current is accelerated to energy of 225keV at a distance of an order of 17cm by 2.45GHz standing microwave field with amplitude of 14kV/cm.

Design Study of a 372-GHz Higher Order Mode Input Coupler

The design of a higher order mode (HOM) input coupler for a low-terahertz gyrotron travelling wave amplifier is presented. A two-branch waveguide coupler based on the even distribution of incident power is designed to couple the rectangular TE10 mode to the circular TE61 mode. The optimised tapered waveguide input coupler achieved an operating frequency range of 359–385 GHz, equating to a bandwidth of 7%. A prototype waveguide coupler scaled to $W$ -band (75–110 GHz) was manufactured. The vector network analyser measured return loss of the HOM coupler is shown to be <10 dB at 90–96 GHz. A transmission and phase measurement is presented to analyse TE61 mode conversion in the coupler.

A TE&lt;sub&gt;13&lt;/sub&gt; Mode Converter for High-Order Mode Gyrotron-Traveling-Wave Tubes

A methodology to generate a circular TE13 mode for the operation of high-order mode (HOM) gyrotron-traveling-wave tubes is presented in this paper. A rectangular TE10 mode is efficiently converted into a circular TE13 mode using Y-type power dividers. Symmetric curved lossy dielectrics and dielectric rings are, respectively, positioned to suppress the potential coupling TE32 and TE71 modes according to their electric and magnetic field distribution properties. An HOM converter without dielectrics loaded was designed, constructed, and cold tested. Back-to-back transmission measurements exhibit good agreement with the results of computer simulations.

0.43 THz emission from high-Tc superconducting emitters optimized at 77 K

A liquid helium-free, compact and continuous sub-terahertz radiation system operating at 77 K has been developed using a rectangular mesa device made from a high -superconducting Bi2Sr2CaCu2O single crystal, based on a different design of a stand-alone mesa sandwich structure to reduce the dc-current Joule heating effects. The mesa was thermally connected to sapphire plates through thin thermal grease embedded with diamond nano-crystals. When immersed in liquid N2, the device emits intense radiation at 0.437 THz, the highest frequency ever achieved at 77 K, due to excitation of the TM(1, 0) rectangular cavity mode. By varying the dc current–voltage bias and the bath temperature in a He-flow cryostat, the device’s emission frequency is broadly tunable from 0.31 THz at 79 K to 1.31 THz at 30 K.

Poly(aryl ether) Dendrons with Monopyrrolotetrathiafulvalene Unit-Based Organogels exhibiting Gel-Induced Enhanced Emission (GIEE).

A series of poly(aryl ether) dendrons with a monopyrrolo-tetrathiafulvalene unit linked through an acyl hydrazone linkage were designed and synthesized as low molecular mass organogelators (LMOGs). Two of the dendrons could gelate the aromatic solvents and some solvent mixtures, but the others could not gel all solvents tested except for n-pentanol. A subtle change on the molecular structure produces a great influence on the gelation behavior. Note that the dendrons could form the stable gel in the DMSO/water mixture without thermal treatment and could also form the binary gel with fullerene (C60 ) in toluene. The formed gels undergo a reversible gel-sol phase transition upon exposure to external stimuli, such as temperature and chemical oxidation/reduction. A number of experiments (SEM, FTIR spectroscopy, (1) H NMR spectroscopy, and UV/Vis absorption spectroscopy, and XRD) revealed that these dendritic molecules self-assembled into elastically interpenetrating one-dimensional fibrillar aggregates and maintain rectangular molecular-packing mode in organogels. The hydrogen bonding, π-π, and donor-acceptor interactions were found to be the main driving forces for formation of the gels. Moreover, the gel system exhibited gel-induced enhanced emission (GIEE) property in the visible region in spite of the absence of a conventional fluorophore unit and the fluorescence was effectively quenched by introduction of C60 .

DIRECT DIGITAL SYNTHESIS BASED CORDIC ALGORITHM: A NOVEL APPROACH TOWARDS DIGITAL MODULATIONS

Modulation is the technique in which carrier signal varies according to amplitude of modulating signal. A brilliant solution for realizing digital modulators is CORDIC (CO-ordinate Rotation Digital Computer) algorithm. Rotation mode and vector mode are two modes in which this algorithm is used. Here rotation mode is used to convert the coordinates from polar mode to rectangular mode. This paper presents the implementation of different communication subsystems like ASK, FSK, PSK, BPSK, QPSK, 4 QAM, 16 QAM that can be found in software defined radio by using CORDIC algorithm. The focus of this paper is to analysis and simulation of modulation scheme using Direct Digital Synthesizer having CORDIC algorithm.

An Overmoded W-Band Coupled-Cavity TWT

A 94-GHz overmoded traveling-wave tube (TWT) has been designed, fabricated, and successfully tested. The TWT operates in the rectangular TM31 mode of the cavity, while lower order modes are suppressed using selectively placed strips of lossy dielectric. The 87-cavity TWT circuit was directly machined from Glidcop, a dispersion-hardened copper. The TWT was tested in a 0.25 T solenoidal magnetic field in 3- $\mu \text{s}$ pulses. Operating at a voltage of 30.6 kV with 250 mA of collector current, the TWT was zero-drive stable and achieved 21 ± 2 dB linear device gain with 27-W peak output power. Taking into account 3 dB of loss in both the input and output coupling circuits, the gain of the TWT circuit itself is 27 ± 2 dB with 55 W of saturated circuit output power. Using the 3-D particle-in-cell code CST Particle Studio, the linear circuit gain was estimated to be 28 dB and the saturated output power 100 W, in good agreement with the experimental results. The measured bandwidth of 30 MHz was significantly smaller than the predicted value of 250 MHz. The overmoded TWT is a promising approach to high-power TWT operation at W-band and to the extension of the TWT to terahertz frequencies.

IJARCCE - Computer and Communication Engineering

The modern communication systems and software radio based applications demands smart transceivers, consisting of only an antenna and a fully programmable circuit with digital modulators and demodulators. A basic communication system's transmitter modulates the amplitude, phase or frequency proportional to the signal being transmitted. An efficient solution (that doesn't require large tables/memory) for realizing universal modulator is CORDIC (CO-ordinate Rotation Digital Computer) algorithm. The CORDIC algorithm is used in the rotation mode, to convert the coordinates from polar mode to rectangular mode. CORDIC is a versatile algorithm widely used for VLSI implementation of digital signal processing applications. This paper presents how to use CORDIC to implement different communication subsystems that can be found in software defined radio. Specifically, it shows how to use CORDIC to implement direct digital synthesizers and ASK, PSK, FSK Modulators. The focus of this paper is to analysis and simulation of ASK, FSK, PSK modulation scheme using Direct Digital Synthesizer having CORDIC algorithm at the place of ROM Look up Table. CORDIC Algorithm provides many significant advantages over Conventional ROM Look up Table.