Outer Slots Research Articles

A study of a modified design of dumbbell-shaped flux switching tubular linear generator for regular wave energy conversion

Wave energy converters (WEC) use indirect drive hydraulic or turbine-type power take-off (PTO) mechanisms which consist of many moving parts, creating mechanical complexity and increasing the installation and maintenance costs. Linear generator-based direct drive wave energy converters could be a solution to overcome this problem, but the efficiency of the single conventional linear generator is not high enough, and it cannot work satisfactorily in the low-frequency range.In this paper, a novel dumbbell-shaped flux-switching linear generator has been proposed and studied as a power take-off unit for ocean wave energy conversion. The linear generator has a dumbbell-shaped stator, and the design is ameliorated by placing the permanent magnet rings of longitudinally alternating magnetic pole directions in the slots of its stator outer surface and is separated by thin wall steel ring shoulders. The linear generator also has a dumbbell-shaped translator. The stator is hollow where the translator slides inside axially inducing current in the coil. A long permanent magnet is inserted inside the hollow steel dumbbell core of the translator and a copper coil is wound around the outer surface of the moving translator core. The addition of permanent magnets on the outer slots of the stator is found to increase the output power significantly. To facilitate the investigation, the modified generator design has been compared to the conventional linear permanent magnet generator for their performances using the finite element method, as both machines are different in their structures. The results show that the double dumbbell-shaped flux-switching linear generator gives higher power output, magnetic flux density, branch current, and induced voltage. The double dumbbell-shaped flux-switching linear generator is then placed in a cylindrical buoy and investigated in a wave energy converter in the ocean environment. The hydrodynamic response of the cylindrical buoy has been investigated through ANSYS AQWA. The dynamic differential equations of the wave energy converter have been developed and solved for regular waves using Matlab codes. The peak output voltage, power, and the relative displacement of the linear generator translator with respect to the stator fixed with the buoy have been calculated through the Fourier Transform in the frequency domain using a Matlab code and through numerical integrations in the time domain using a Matlab Simulink code. The results in the time and frequency domains are compared and verified with each other. The relative displacement between the translator and stator buoy has been used as motion input of the ANSYS Maxwell simulation model, and the output voltage results of the ANSYS Maxwell simulation model have been compared and verified with those of the Matlab simulation models. The linear generator design in the wave energy converter under the regular wave excitation is further optimized for the maximum ratio of the peak output power to peak cogging force using the central composite design-based response surface method (RSM). The ANOVA analysis is used to validate the response surface model where its R2 coefficient of 99.93% has indicated an excellent fit. The methods and results differ from those presented in previous studies.

Macromolecular microfluidic concentrators

Microfluidic design, fabrication, and experiments have developed rapidly, leading to lab-on-chip separation or fractionation. In this work, we design a continuous concentrator for macromolecular solutions. Our design relies on the analytical solutions for orientational diffusion under laminar pressure-driven slot flow through a microchannel [W. Stasiak and C. Cohen, “Dilute solutions of macromolecules in a rectilinear Poiseuille flow,” J. Chem. Phys. 78, 553 (1983)]. Using rigid dumbbell theory, we provide analytical solutions for the design of our microfluidic macromolecular hydrodynamic chromatography. We arrive at our design through the use of well-known confinement-driven composition profiles. Using a pair of razor-sharp blades, our design separates the slot flow into a symmetric core inner slot (concentrated) between two outer slots (diluted). We discover a minimum dimensionless blade leading edge separation for complete fractionation, and that this decreases with confinement and also decreases with dimensionless shear rate.

Co-flow jet diffusion flames in a multi-slot burner: Flow field and emissions

Motivated by the application of internally air-assisted flares and recent anomalous data that black carbon (BC) emissions changes are not monotonic with the amount of air added inside the fuel stream, a burner was designed to study the flow, emissions, and stability aspects of the existence of both normal and inverse jet diffusion flames in close proximity. Since the radius of curvature of a burner affects all aspects of combustion, such as dynamics, stability, flame structure, and emissions, a slot burner configuration, inspired by the Wolfhard-Parker burner, was adopted. This multi-slot burner consists of five parallel rectangular slots (i.e., the central slot for the inner air, sandwiched between two fuel slots, and surrounded by two outer air slots). When operated with laminar fuel and air flows, this burner produced flame sheets at each fuel-air mixing layer with open optical access to all the flows. Flow fields were characterized using two-dimensional two-component particle image velocimetry, while simultaneous single-lens reflex photography was used to establish the overall height and the location of the flames. Emission measurements specifically targeted BC, a precursor of soot, and oxides of nitrogen (NOx). The experimental test conditions involved constant flows of outer air and propane, and variable inner air flow. At one extreme, i.e., zero inner air flow, two flame bases were produced at the interfaces between the fuel and outer air streams. These flames merged to produce a normal diffusion flame. With the addition of inner air, two more flame bases appeared (referred to as the inner flame) and formed an inverse diffusion flame. With increasing inner air flow, the inner flame transitioned from a closed-tip flame, to an open-tip flame, and eventually to a lifted flame. With increasing inner air flow, the NOx emissions remained constant while the BC emissions, which were 3 g/kg-fuel with no inner air, rose by an order of magnitude as it became an open-tip flame. Only when the inner flame finally lifted off due to the inner air flow, did the BC emissions collapse to near zero. Phenomenological models associated with the importance of partial premixing were proposed to explain this collapse, thereby generalizing this finding to other combustion systems when attempting to reduce BC emissions through secondary internal air addition.

Betrayal through obedience: on the history of the unusual inflectional chain in Siyuewu Khroskyabs

AbstractThis paper focuses on the verbal inflection chain of Siyuewu Khroskyabs, a Gyalrongic language (Trans-Himalayan). Siyuewu Khroskyabs goes against two general typological tendencies: first, as an SOV language, it shows an overwhelming preference for prefixes, which is rarely reported typologically; second, the inflectional prefixes in the outer slots are older than those in the inner slots, which is the reverse case of most languages. In this paper, I will first identify distinct historical layers within the inflectional prefixes, and then focus on two of the prefixes,də-‘even’ andɕə-‘q’ whose evolutionary pathways are relatively clear. The essential part of the hypotheses is that the prefixes originate from enclitics which could be attached to the end of a preverbal chain, originally loosely attached to the verb stem. The preverbal chain later became tightly attached to the verbal stem and eventually became a part of it as a chain of prefixes. As a result, the original enclitics are reanalysed as prefixes. The integration of preverbal morphemes is responsible for the prefixing preference in Modern Siyuewu Khroskyabs. However, despite this superficial prefixing preference, Siyuewu Khroskyabs underlyingly favours postposed morphemes. By following the general suffixing tendency, this language finally managed to create a typologically rare, overwhelmingly prefixing verbal template.

A Novel High-Performance Consequent Pole Dual Rotor Permanent Magnet Vernier Machine

This article proposes a novel structure of consequent pole dual rotor permanent magnet vernier machine (CPDRVM). This structure consists of dual-sided stator in which windings are placed on the stator slots and magnets placed on the inner and outer rotor slots. Operation principles of the proposed VM carried out using flux modulation theory. The Finite Element analysis is utilized in order to evaluate the effect of magnet geometry on the produced torque and power factor. The motor characteristics and performance assessment are performed numerically. Furthermore, the parametric and sensitivity analysis are used to optimize the motor geometry. The proposed VM compared with PM machine and two conventional VMs. In this regard, performance indices such as flux, cogging torque, power factor, magnet volume, torque per magnet volume, Back-EMF, losses and efficiency profiles are calculated and compared. Results evidence better performance of the proposed structure. In fact, CPDRVM could produce higher torque density than conventional VMs. In addition, high power factor is reached for suggested topology.

Right-Angled Coplanar Waveguide Using Short-Circuited Slotline

In this article, a right-angled coplanar waveguide using the short-circuited slotline is proposed to eliminate the coplanar waveguide mode to coupled slotline mode conversion suffered by the conventional right-angled coplanar waveguide. As compared with the simulation and measurement results of the conventional right-angled coplanar waveguide, the reflection coefficient is greatly reduced from -2.44 to -9.52 dB, whereas the transmission coefficient is greatly increased from -16.07 to -4.49 dB. Besides, the peak-to-peak noise of the time-domain reflection is reduced from 0.033 to 0.027 V, whereas the peak-to-peak noise of the time-domain transmission is reduced from 0.040 to 0.029 V. Furthermore, the electric fields of the inner and outer slots of the coplanar waveguide are now made equal phase throughout the right-angled bend. As a result, the power loss is reduced from 60% to 55% and the signal integrity is improved.

Ionized gas Thermoelectric Generator

The behavior of charged particles mixed with neutral particles laid in Circular Ratchet Potential (CRP) inside circular tube container was studied, showing a net Counter-clockwise flow of charged particles and other net flow of neutral particles equal in magnitude and opposite in direction (Clockwise), the neutral flow of particles will not cancel the positive particles flow; by Causality Principle. These two opposite flow of particles will reach terminal intensity at some stage inside the circular path; the charged particles are confined to move in a semi-circular (Nut Shape) trajectory according to the CRP, while the neutral particles can escape out of the container in tangential trajectory, hence producing perpetual disequilibrium in the thermodynamic properties of the system.Allowing the neutral particles to escape through outer tangential slots, and allow new neutral particles to enter the container through inner slots to compensate neutral particles. This gives the basic idea for a new concept of Brownian Motor (Plyukhin, 2013) [1] or Thermoelectric Generator (TEG) (Bqoor, 2013) [2], then the excess in charged particles flow will reduce the neutral particle flow and produce micro-turbulences. This mechanism will allow extracting power from the ambient thermal energy.Several considerations including efficiency, manufacturing and improvement aspects were evaluated and discussed in this paper. However, this Ionized Gas TEG can be assumed as a Perpetual Motion Machine (Rao, 2004) [3] of the second type, hence questioning the validity of the “empirical” Second Law of Thermodynamics, were several phenomena showing the necessity for new formula amending the Second Law of Thermodynamics (Crosignani and Di Porto, 2001; Wang et al., 2002) [4,5].

Dual-Band Annular Slot Antenna Loaded by Reactive Components for Dual-Sense Circular Polarization With Flexible Frequency Ratio

This paper proposes a new design of dual-band reactively loaded annular slot antenna for dual-sense circular polarization radiation. Two concentric annular slots excited by a common microstrip feedline are employed to realize dual-band operation. Each slot can radiate a circularly polarized (CP) wave with a specified sense at its one or one-and-a-half wavelength resonance, given that an appropriately valued reactive component, i.e., capacitor or inductor, is introduced at a pre-determined location. A small frequency ratio (FR) can be achieved between the two oppositely sensed CP bands when a capacitor and an inductor are loaded, respectively, onto the inner and outer annular slots. Contrarily, two oppositely sensed CP bands that possess a large FR can be yielded when an inductor and a capacitor are loaded onto the inner and outer annular slots, respectively. For experimental verification, two antenna prototypes with FRs of 1.63 and 2.41 have been designed, fabricated, and measured. The measurement results exhibit a good agreement with the simulated ones. Details of design concerns and experimental results are presented and discussed.

Broad-range microstrip patch refflectarray element loaded with multiple L-shaped slots

A single-layer microstrip patch unit element, which is loaded with eight concentric L-shaped slots, is proposed for reflectarray design. In this case, the lengths of the inner and outer slots are varied concurrently to function as the phase-shifting geometrical parameters. The reflection characteristics of the element are analyzed using the waveguide method, and the simulation results have been verified with experiments. A broad reflection phase range of 631.83° with slow gradient has been successfully achieved with the use of the slotted patch with constant size. Parametric analysis has been performed and it is found that the S-curve can be easily fine-tuned by changing some of the design parameters.

Dual-band capacitively loaded annular-ring slot antenna for dual-sense circular polarization

This paper investigates a simplified and new capacitively loaded annular-ring slot antenna (ARSA) for dual-band and dual-sense circular polarization. The antenna is comprised of two concentric annular-ring slots coupled to a microstrip feed line to achieve dual-band operation. With introducing proper distributed capacitances fulfilled by two closely spaced T-shaped arc strips across the outer and inner annular-ring slots at opposite positions with respect to the microstrip feed line, the dual-sense circular polarization can hence be obtained. The antenna features that the impedance and circular polarization characteristic for the upper band can be independently adjusted. Numerical analysis and experimental validation have been carried out. The measured 10-dB return loss impedance bandwidths for both bands are greater than 22.0%. The measured 3-dB axial ratio (AR) bandwidths are 3.6 and 5.6%, respectively, for the lower and upper bands.

Ground‐embedded dual‐slot perturbation for switchable circularly polarized microstrip antenna

ABSTRACTThis article reports a new ground‐embedded dual‐slot perturbation for a reconfigurable circularly polarized microstrip antenna. The perturbation consists of the small inner and the large outer slots with two PIN diodes in one diagonal corner for generating and alternating right‐/left‐handed circular polarization, respectively. The measured results of the implemented antenna which used the ground‐embedded dual slot show an agreement with the simulation and successfully demonstrate circularly‐polarized radiations with good controllability. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2537–2539, 2014

Thermal Optimization of a High-Speed Permanent Magnet Motor

This paper investigates the losses of a high-speed permanent magnet motor. The iron losses are calculated by a model that can consider the skin effect and rotational loss. The rotor eddy current losses are estimated by a fast hybrid method that can consider the end effect. Pulse-width modulation (PWM) harmonics brought by the voltage source inverter (VSI) are considered in the loss calculations. Then the temperature distribution of the motor is evaluated by using the calculated loss results and computational fluid dynamic (CFD) modeling. Finally, based on the CFD results, the motor structure is optimized to achieve better rotor cooling. The outer slots are closed to force the cooling air flow through the rotor surface. Calculated temperature distributions and optimization results are verified by measurements.

Dual‐Band Ring Slot Antenna with Circular Polarization

ABSTRACTA design for dual‐band circularly polarized (CP) antennas is presented. The antenna is composed of two concentric shorted annular slots, and each slot can generate CP radiation at its one wavelength resonant mode or one‐and‐a‐half wavelength resonant mode by varying the position of the shorted section. When the one wavelength mode of the outer slot and the one‐and‐a‐half wavelength mode of the inner slot are simultaneously excited with a microstrip line, the antenna has two CP operating frequencies with a large frequency ratio (FR). A small FR can also be achieved when the outer and inner annular slots are operated at the one‐and‐a‐half wavelength mode and one wavelength mode, respectively. For the proposed design, two examples with the FRs of 1.05 and 1.9 are designed and implemented. Details of the experimental results are shown. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2077–2080, 2013

The role of matrices in preserving non-genetic data

The article deals with the subject of the ways of preserving non-genetic data in cultural communication. It is emphasized that there exist matrices that are responsible for transferring data through generations. The imitation matrix is a key concept of iconic origin that gives sense to the mimicking of an object. The referential matrices are embedded in the deictic structures of the utterances. The hierarchical senses embody symbol concepts. Behind non-genetic data stands the force of semiosis, that is, of autopoetic nature. The summary of the message is that humans possess stable “outer slots” to be filled with predictable content.

Wire-Bond Free Technique for Right-Angle Coplanar Waveguide Bend Structures

This paper presents a new wire-bond free technique for suppressing slot-line mode excitation in coplanar waveguides (CPWs) bends. The suppression of slot-line mode is obtained by applying a slow wave structure to the shorter slot of the right-angle bend. The structure is modified into a circular-shaped bend where the slow wave compensation is then used to equalize the electrical length of the inner and outer slots. The insertion loss of the modified CPW bend with slow wave structure is evaluated on a silicon substrate and is similar to straight CPW lines with return loss ( S 11) values below -20 dB over a 50-GHz bandwidth.

Structure and mixing of a transient flow of helium injected into an established flow of nitrogen: two dimensional measurement and simulation

The transient injection and mixing between nitrogen and helium in a confined chamber at atmospheric pressure is studied experimentally. The 2D injector and mixing chamber contained a middle injection slot for nitrogen flanked by a pair of outer slots for helium. Experiments were conducted by introducing the helium streams into a previously established quasi-steady flow of nitrogen. The nitrogen stream was seeded with nitric oxide (NO) that served as a source for quantitative, planar laser-induced fluorescence (PLIF) imaging of the transient mixing process. PLIF images were acquired by triggering an Nd:YAG laser system at selected times following helium valve actuation. The observed flow structures and extent of mixing between the two streams proved to be highly unsteady and irregular with the helium/nitrogen jets frequently deviating from the centerline toward the confining walls. Representative unsteady CFD solutions also show this same absence of symmetry and the same general flow structures as the measurements, however, they predict somewhat higher helium concentration in recirculation regions than were observed in the measurements.

The evolution of incipient soot particles in an inverse diffusion flame of ethene

Motivated by the application of internally air-assisted flares and recent anomalous data that black carbon (BC) emissions changes are not monotonic with the amount of air added inside the fuel stream, a burner was designed to study the flow, emissions, and stability aspects of the existence of both normal and inverse jet diffusion flames in close proximity. Since the radius of curvature of a burner affects all aspects of combustion, such as dynamics, stability, flame structure, and emissions, a slot burner configuration, inspired by the Wolfhard-Parker burner, was adopted. This multi-slot burner consists of five parallel rectangular slots (i.e., the central slot for the inner air, sandwiched between two fuel slots, and surrounded by two outer air slots). When operated with laminar fuel and air flows, this burner produced flame sheets at each fuel-air mixing layer with open optical access to all the flows. Flow fields were characterized using two-dimensional two-component particle image velocimetry, while simultaneous single-lens reflex photography was used to establish the overall height and the location of the flames. Emission measurements specifically targeted BC, a precursor of soot, and oxides of nitrogen (NOx). The experimental test conditions involved constant flows of outer air and propane, and variable inner air flow. At one extreme, i.e., zero inner air flow, two flame bases were produced at the interfaces between the fuel and outer air streams. These flames merged to produce a normal diffusion flame. With the addition of inner air, two more flame bases appeared (referred to as the inner flame) and formed an inverse diffusion flame. With increasing inner air flow, the inner flame transitioned from a closed-tip flame, to an open-tip flame, and eventually to a lifted flame. With increasing inner air flow, the NOx emissions remained constant while the BC emissions, which were 3 g/kg-fuel with no inner air, rose by an order of magnitude as it became an open-tip flame. Only when the inner flame finally lifted off due to the inner air flow, did the BC emissions collapse to near zero. Phenomenological models associated with the importance of partial premixing were proposed to explain this collapse, thereby generalizing this finding to other combustion systems when attempting to reduce BC emissions through secondary internal air addition.

Particle control and SOL plasma flow in the W-shaped divertor of JT-60U tokamak

Effect of divertor pumping on the scrape-off layer (SOL) plasma and impurities has been studied in many divertor tokamaks. Recent experimental studies of particle exhaust and SOL flow in JT-60U are reviewed. Pumping flux at the inner and outer pumping slots of the W-shaped divertor was investigated under the attached and detached divertor conditions. The SOL flow pattern was determined, for the first time, at three locations, i.e. at the low-field-side SOL (the outer midplane and divertor X-point) and at the high-field-side SOL (above the inner baffle), using three reciprocating Mach probes. The measured profiles were compared with modelling results from two-dimensional plasma simulations, UEDGE-code, with the ion drift effects included.

Flame stretch effects on partially premixed flames

Flame stretch is an important characteristic of flame behavior that arises due to flow motion and nonuniformity, and flame curvature. Various investigators have obtained different expressions for flame stretch by employing dissimilar analytical approaches for diverse flame configurations. In this investigation, we consider two such formulations, one which is “exact” and the other that assumes a simplified unidirectional flow, and apply both relations to characterize the behavior of the rich premixed reaction zone in partially premixed flames (PPFs). Steady two-dimensional partially premixed methane–air slot burner flames are established by introducing a rich fuel–air mixture from the inner slot and air from the two outer slots. The flames contain two distinct spatially separated reaction zones. In order to characterize the flame stretch, the corresponding flame deformation must be first measured. The experimental diagnostics include the use of C ∗ 2-chemiluminescence images, holographic interferometry, and particle image velocimetry. The flame structure depends upon the heat release, temperature, and fluid velocity (therefore, momentum) associated with a particular burner or flame configuration. We focus attention on stretch effects on the inner premixed reaction zone of the PPFs, which exhibits a highly curved portion near its tip and planar portions along its sides. By applying the two formulations, we have inferred unstretched flame speeds and found these to be in good agreement with previously measured results. The methodology also allows us to infer “effective flame speeds” for rich methane–air mixtures with compositions that lie beyond the rich flammability limits for which no data is available in the literature. In general, both formulations provide satisfactory results, although the exact relation is a more accurate representation, as is to be expected. Unidirectional flow can be assumed for relatively larger flames in which the flow behind the flamefront is relatively unperturbed by the preheat zone. As we follow the flame curvature, both the sign and magnitude of the corresponding values of the stretch rate change in a systematic manner. This suggests that the dominating effect in these flames occurs more due to flame curvature and less due to flow nonuniformity effects. In the curved region, the deduced “unstretched” flame speed S uc o is greater than S u o . The measured values of Ma are of O(10 −1).

The structure of triple flames stabilized on a slot burner

A triple flame is a partially premixed flame that contains two premixed reaction zones (one fuel-lean and the other rich) that form exterior wings and a nonpremixed reaction zone that is established in between these wings. The three reaction zones merge at a “triple point.” Triple flames may play an important role in the stabilization and liftoff of laminar nonpremixed flames. They are also of fundamental importance in the reignition of turbulent mixtures. Despite their importance, many aspects of triple flames have not been adequately investigated and are, consequently, not clearly understood. Herein, laminar triple flames stabilized on a Wolfhard-Parker slot burner are investigated. The flow consists of a rich mixture of methane and air emerging from the inner slot and a lean mixture from two symmetric outer slots. In this configuration the three reaction zones that characterize a triple flame can be clearly distinguished. The loci of the “triple points” form a “triple line” in this planar configuration. The velocity field is characterized using laser Doppler velocimetry, and the temperature distribution using laser interferometric holography. In addition, C∗2-chemiluminescence images of the three reaction zones are obtained. A detailed numerical model is employed to completely characterize the flame. It is based on a 24-species and 81-reaction mechanism. The numerical results are validated through comparisons with the experimental measurements. Our results focus on the detailed structure, the interaction between the three reaction zones, the dependence of the flame structure on the initial velocities and mixture equivalence ratios, and the dominant chemical pathways. The lean premixed reaction zone (external wing) exhibits different features from the rich premixed reaction zone. In particular, it is characterized by strong HO2 formation and consumption reactions, and by relatively weak methane consumption reactions. Radical activity is higher in the nonpremixed reaction zone than in the other reaction zones. Overall, radicals from the nonpremixed reaction zone are transported to both the rich and lean premixed reaction zones where they attack the reactants. Simplifying the chemical mechanism by removing the C2-containing species produces significant differences in the predicted results only for the inner rich premixed reaction zone.