Pair Of Grooves Research Articles

Wideband filtering waveguide antenna based on the stepped impedance resonator

A wideband filtering waveguide antenna is proposed. The stepped impedance waveguide resonator is used to obtain three resonance modes, widening the bandwidth from 1.9 to 5 GHz. Besides, the antenna integrates a band-stop filter, which consists of four rectangular resonant cavities, without increasing the lateral and vertical dimensions of the entire antenna. The integrated filter effectively suppresses the antenna gain near 16 GHz, which is outside the working band. Additionally, groove resonance is used to increase the gain of antenna by 4 dB, and two pair of grooves which resonant at different frequencies are employed to increase the bandwidth of realised gain. Finally, a prototype has been developed, the measured relative impedance bandwidth (|S11| < −10 dB) of the proposed antenna is 49.6% at the centre frequency of 11 GHz, and the 3 dB gain bandwidth is 5.1 GHz.

Wideband Dual-Circular-Polarization Antenna With High Isolation for Millimeter-Wave Wireless Communications

This article presents a wideband dual-circular-polarization (dual-CP) antenna with high port isolation based on a grooved-wall CP horn combined with an orthomode transducer (OMT) in the W-band. A pair of grooves on the inner wall of the horn serves as an inbuilt polarizer within the horn antenna, which is capable of generating both left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) without any septum. The continuous linearly tapered groove design also allows this multisection grooved-wall CP horn to achieve low reflection coefficients over a wide bandwidth, thereby realizing wideband dual-CP with high port isolation when it is used together with a wideband OMT. A prototype of the proposed dual-CP antenna is designed in simulation and measured in an experiment. The simulated and measured results agree very well, showing that port isolation >32.5 dB over 31.6% bandwidth from 80 to 110 GHz is achieved with axial ratio (AR) < 2.8 dB and reflection coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt; -20$ </tex-math></inline-formula> dB for both LHCP and RHCP. Rotationally symmetric radiation patterns over the entire operating bandwidth are also observed with a measured gain of 19.6 ± 2 dBic.

Thermal-hydraulic and fouling performances of enhanced double H-type finned tubes for residual heat recovery

• Both thermal-hydraulic and anti-fouling performance of double H-type finned tubes are investigated. • Grooves can create secondary saltation of fly ash particles and reduce the fouling. • LVGs can result in more particles colliding with fin surface and increase the fouling. • An advanced fin structure with three pairs of grooves and one pair of LVGs is recommended. Heat exchangers for residual heat recovery in coal-fired power plants face the issues of low heat transfer efficiency of flue gas side and the fly ash fouling. However, heat transfer enhancement structures always increase the fouling on the fin. Efficient methods are required to improve both heat transfer and anti-fouling performance of the heat exchanger. In present study, the thermal-hydraulic and anti-fouling performances of enhanced double H-type finned tubes are numerically investigated using the discrete phase model coupled with particle deposition and removal model. Five types of double H-type finned tubes with different layouts of grooves and longitudinal vortex generators (LVGs) are investigated to improve both thermal-hydraulic and anti-fouling performance of fin. The effects of particle diameter, flue gas velocity and layout of enhanced structures are discussed. It is found that the transverse vortex induced by grooves can lead to the secondary saltation of fly ash particles, which will significantly reduce particle deposition on fins. However, the longitudinal vortex generated by LVGs can result in the fly ash particles with saltation mode or suspension mode colliding with fin surface, which causes more particle deposition on fins. The recommended fin with three pairs of grooves and one pair of LVGs can enhance heat transfer by 12.92–16.63% with 21.75–30.72% flow resistance penalty and reduce the fouling rate by 2.4–23.7% for particle diameter under 20 μm. It can be considered as a promising heat transfer component for heat recovery in coal-fired power plants.

W‐band grooved‐wall circularly polarised horn antenna

This study presents a novel design of circularly polarised horn antenna in W-band with wide impedance bandwidth and 3 dB axial ratio (AR) bandwidth. By introducing a pair of grooves on the wall of a horn antenna, this simple and compact structure is capable of generating a circular polarisation (CP) wave without any extra polariser and is expecting a better power-handling capability. The full-wave simulation results show that 36.9% bandwidth from 75.4 to 109.5 GHz can be achieved with S 11<−21 dB and AR<3 dB, while the directivity is 16.56 ± 1.37 dBic. It is anticipated that the proposed antenna is suitable for wideband mmWave applications.

Enhanced optical transmission by exciting hybrid states of Tamm and surface plasmon polaritons in single slit with multi-pair groove nanostructure

In recent years, a metallic single slit nanostructure or slit array structure, due to simple structure and easy-to integration, has been used to construct a light source in the nanostructures based on the surface plasmon polaritons (SPPs). However, the problem of low transmission through an isolated subwavelength single slit nanostructure is still existent. The main reason is that the excitation efficiency of SPPs in the single slit nanostructure is not too high. Therefore, how to effectively enhance the optical transmission has become a research focus. In order to further improve the transmittance of the metallic single slit nanostructure, in this paper, we improve the single slit nanostructure imbedded in the metal silver thin film on a distributed Bragg reflector (DBR) proposed in previous literature. As a result, a novel method of designing a single slit on a DBR is proposed to effectively enhance the optical transmission in a single slit by improving the excitation efficiency of SPPs. Our proposed novel structure is made up of a subwavelength single nano-slit surrounded symmetrically by a pair of grooves on both sides of metal silver film on a distributed Bragg reflector. When the TM polarized light is illuminated from the DBR side of our proposed structure to the DBR-silver slit-grooves nanostructure, the Tamm plasmon polaritons (TPPs) at the interface between the silver film and the DBR and the SPPs in the slit on the entrance side of the silver film are excited at the DBR-silver film interface, and the SPPs in the slit and grooves pair on the exit side of the silver film are excited simultaneously. In our proposed structure, coupling between the TPPs and the SPPs leads to the hybrid state of Tamm and surface plasmon polaritons in the slit and grooves. Finally, taking advantage of constructive interference between SPPs excited by the grooves and exciting hybrid states of TPPs-SPPs in the slit, due to the local field enhancement effect of the TPPs mode and the coupling effect of constructive interference between the pair grooves and the nano-slit, the excitation efficiency of the SPPs can be increased significantly. Furthermore, the quasi Fabry-Pérot resonance effect in the nano-slit is taken into consideration, and the transmittance of our proposed structure is enhanced greatly. In the present paper, the finite element method is used to study the transmission properties of the single nano-slit embedded with paired grooves on the DBR-sliver nanostructure. After a series of parameters are optimized, the maximum transmittance through the single slit in DBR-silver slit-groove nanostructure can increase to 0.22, and this transmittance is expected to be about 22 times the transmittance (0.01) of the light through a single slit in a silver film on the TiO2 substrate (without DBR and grooves), which is higher than the maximum light transsmission 0.166 given in Ref.[23]. The research results of this study have a certain application value in the fields of nano-light source design, photonic integrated circuits and optical signal transmission and so on.

Compact Ultrabroadband Plasmonic Antenna: Potential Applications in Logic Binary Encoding

A compact ultrabroadband coupling and binary encoding structure based on an array of aperiodic nanoslits cascaded by two different pairs of grooves in a metallic-dielectric-air waveguide is proposed and theoretically analyzed. The nanoslits array function as a broadband antenna to couple the incident lights into surface plasmon polaritons (SPPs) over an ultrawide wavelength range (spectral full-width-half-maximum >430 nm). The two ports composed of different grooves exhibit different transmission for the coupled multiwavelength SPPs. After traveling through different ports, the incident lights dropping in different wavelength ranges are differentiated and endowed with different logic state encodings. The operation principle is clarified and a coupled-mode model is developed for facilitating design.

Nanofocusing via Efficient Excitation Surface Plasmon Polaritons in a Hollow Aluminum Wedge

Efficient nanofocusing down to a few nanometers in a hollow aluminum wedge is numerically investigated. The waveguide propagation modes are efficiently converted to internal surface plasmon polaritons via a pair of grooves fabricated at the inner surface of the wedge and a remarkable field enhancement is realized at the aperture. The excitation efficiency can be further improved by optimizing spatial wavefront modulation of the incident light field via a binary optical element, and the output intensity through a 5-nm aperture is enhanced by 786 times compared with a conventional 100-nm aperture hollow metallic wedge.

The female genitalic morphology of “micronetine” spiders (Araneae, Linyphiidae)

Current knowledge of "micronetine" female genitalia is almost exclusively based on transmitted light microscopy data. As such, our understanding of the epigynal anatomy is incomplete and somewhat misleading, to the extent that it hinders comparative studies of linyphiid diversity. We used scanning electronic microscopy (SEM) to study the complex epigynal morphology of "micronetine" spiders. Enzymatic digestion of soft tissues allowed us to examine the internal chitinized structures in detail using SEM. A taxonomic sample of nine species was selected to represent the morphological genitalic diversity of female "micronetines" (including one member of the Erigoninae clade). Results reveal that the epigynum consists of a pair of grooves formed by integument folds (copulatory and fertilization grooves). The protruding epigynal region is divided into a ventral and a dorsal plate by the grooves; both plates can be modified to form an epigynal cavity and/or a scape. Our observations confirm the widespread occurrence of epigynal grooves, rather than ducts, in "micronetines". Epigynal grooves seem to be common in linyphioids and other spider groups.

Morphogenetic significance of the conchal furrow in nautiloids: evidence from early embryonic shell development of Jurassic Nautilida

As reported by many workers over the past two centuries, the inner part of the shell of various straight and coiled Palaeozoic to tertiary nautiloid taxa bears a continuous mid-ventral furrow that extends into the phragmocone and the body chamber nearly to the aperture. Study of the early embryonic shell development of Jurassic Nautilida shows that the most apical part of this so-called conchal furrow originates from the inner part of the initial, calcified shell apex, in line with the inner ventral termination of the central linear depression of the cicatrix, the initial site of shell deposition. The conchal furrow corresponds to a morphological feature arising as a developmental by-product. Rare specimens of scattered ammonoid species (and possibly of bactritoids) display a similar feature, whereas their protoconch lacks a cicatrix. However, the protoconch of recent cuttlefish, Sepia officinalis, often displays a longitudinal fold of the primary shell epithelium. A longitudinal groove or a pair of grooves appears connected with this cicatrix-like structure. Although the mid-ventral ridge in ammonoids must probably be viewed as an incidental ‘fabricational noise’, whether or not it originates from a so far undocumented optional ridge on the protoconch or from some other structure related to shell development remains an open question.

1627 円弧型溝付き円柱周りの流動特性

This paper describes the flow characteristics around circular cylinder with arc grooves. In this study, cylinders with arc grooves of different depths are used. There are 32 grooves in the direction of the axis. Three pressure holes inside the grooves and one between a pair of grooves are prepared in order to measure the surface pressure around the cylinder. Drag and lift coefficient are calculated from the pressure distribution measured in the range of Reynolds number Re=0.35×(10)^5&acd;1.8×(10)^5. And the velocity distributions on the surface of the cylinders are measured by means of the hot wire. From these experimental results, the change of drag and lift coefficient to the depth of grooves and Reynolds number of the cylinder with arc grooves and effect of the grooves in decrease of drag are developed.

Ultrasonic cutting tool

The ultrasonic surgical tool has an elongate waveguide (1) operatively connected or connectable at a proximal end to a source of ultrasonic vibrations. At a distal end, an operative element comprises a radially-extending ridge (2) defined between a substantially parallel pair of grooves (4) extending longitudinally of the waveguide (1). The operative element is curved in a plane transverse to that of the ridge (2). This arrangement is ergonomically superior and allows a surgeon to work for longer and with improved control. It also allows a clear visualisation of the operative elements of the tool and the target tissue.

Reassessing the Function of Grooves in Mycenaean Tombs

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning /> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas /> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL /> <w:BalanceSingleByteDoubleByteWidth /> <w:DoNotLeaveBackslashAlone /> <w:ULTrailSpace /> <w:DoNotExpandShiftReturn /> <w:AdjustLineHeightInTable /> <w:BreakWrappedTables /> <w:SnapToGridInCell /> <w:WrapTextWithPunct /> <w:UseAsianBreakRules /> <w:DontGrowAutofit /> <w:UseFELayout /> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--> <!-- /* Font Definitions */ @font-face {font-family:PMingLiU; panose-1:2 1 6 1 0 1 1 1 1 1; mso-font-alt:"Arial Unicode MS"; mso-font-charset:136; mso-generic-font-family:auto; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:1 134742016 16 0 1048576 0;} @font-face {font-family:TimesNewRoman; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:auto; mso-font-format:other; mso-font-pitch:auto; mso-font-signature:3 0 0 0 1 0;} @font-face {font-family:"\@PMingLiU"; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:136; mso-generic-font-family:auto; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:1 134742016 16 0 1048576 0;} @font-face {font-family:TimesNewRomanPS-ItalicMT; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:auto; mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:PMingLiU; mso-ansi-language:EN-GB; mso-fareast-language:EN-US;} /* Page Definitions */ @page {mso-page-border-surround-header:no; mso-page-border-surround-footer:no;} @page Section1 {size:612.0pt 792.0pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> <!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> <p class="MsoNormal"><span style="font-size: 8pt; font-family: TimesNewRoman;" lang="EN-US">Among the Chamber and Tholos Tombs that were built in Greece during the Late Helladic period are some that show a particular feature: a pair of grooves that are carved on the floor of the </span><em><span style="font-size: 8pt; font-family: TimesNewRomanPS-ItalicMT;" lang="EN-US">stomion </span></em><span style="font-size: 8pt; font-family: TimesNewRoman;" lang="EN-US">(a short corridor that leads inside the tomb), leading from the </span><em><span style="font-size: 8pt; font-family: TimesNewRomanPS-ItalicMT;" lang="EN-US">dromos </span></em><span style="font-size: 8pt; font-family: TimesNewRoman;" lang="EN-US">(a long road that leads towards the tomb itself) into the chamber. Archaeologists have suggested a number of explanations regarding their function; however, none of these seems entirely plausible. In this article, we offer a different kind of hypothesis mostly based on architectural evidence. We will suggest that, rather than being related to ritual practices, the grooves were mainly used to facilitate the construction of the graves.</span>

Characteristics of molecular-beam epitaxially grown pair-groove-substrate GaAs/AlGaAs multiquantum-well lasers

Growth and device characteristics of an index-guided GaAs/AlGaAs multiquantum-well (MQW) laser, called a pair-groove-substrate (PGS) MQW laser, are described in detail. The laser structure is fabricated by using single-step molecular-beam epitaxy on a (001) GaAs substrate with a pair of etched grooves along the 〈11̄0〉 direction. A mesa between a pair of grooves, where the lasing action occurs, becomes narrow during growth, and the narrow mesa offers lateral waveguiding that stabilizes a fundamental transverse mode. The superior crystalline quality of the mesa top, which is examined by a microprobe photoluminescence technique, serves to lower the lasing threshold currents. The lasers with mesa widths below 2 μm show stable transverse mode operation with a low threshold current of 20 mA, as well as a high external differential quantum efficiency of 68%. The low threshold and high characteristic temperature accomplish a high-temperature continuous-wave operation at 153 °C for the lasers mounted on silicon heat sinks.

Direct Measurement of Piezoelectric Strain Using a Diffraction Grating

Piezoelectric strain under a large de electric field, D33 is directly measured by using an electrically controllable diffraction (ECD) grating. The ECD grating consists of a lead lanthanum zirconate titanate piezoelectric ceramic with 65 pairs of grooves having 40‐μm width and 80‐μm period on its surface. The operational principle for the diffraction grating and the procedure for obtaining D33 are described. D33 is measured experimentally with a He‐Ne 3.39‐μm laser, yielding a value of 5.9 × 10−9 m/V under a dc electric field of 1 kV/mm. This value is discussed along with the piezoelectric constant d33 calculated from a conventional electrical resonant method.

Pair-groove-substrate GaAs/AlGaAs multiquantum well lasers by molecular beam epitaxy

We investigated molecular beam epitaxial growth characteristics on (001) GaAs substrates with a pair of etched grooves along the 〈11̄0〉 direction. It is found that, as the growth proceeds, the mesa width between the pair of grooves gradually decreases and that the grown mesa surface becomes slightly concave. These results offer great advantages for precisely defining the lateral width of index guided lasers during growth. A pair-groove-substrate GaAs/AlGaAs multiquantum well laser has been newly developed, which shows stable fundamental transverse mode oscillation and a high external differential quantum efficiency of 68% as well as a low threshold current of 23 mA.

Low-threshold MBE GaAs/AlGaAs quantum well lasers with dry-etched mirrors

An index-guided GaAs/AlGaAs multiquantum well laser with etched mirrors has been fabricated by molecular beam epitaxy and a dry etching process. The transverse mode is stabilised by a built-in optical waveguide, which is formed on the substrates with a pair of grooves. The etched mirrors are fabricated by reactive ion beam etching. The lasers with 200 μm-long cavities exhibit threshold currents as low as 30 mA and external differential quantum efficiencies as high as 41%.

Mandibular molar tooth configurations in different racial groups.

The basic human molar configuration-five cusps, a longitudinal groove, and a Y shaped transverse groove-has changed during evolution. The most deviant type (+4) possesses four main cusps separated by a cruciform groove system; the hypoconulid is eliminated. A further deviant is the X pattern. Although the four main cusps meet at a point, the pairs of grooves surrounding the protoconid and entoconid form an acute angle. Other modifications are the Y4 and +5. Studies have tended to ba confined to single population samples. Categorization of occlusal configurations tends to be subjective. Thus it is difficult to compare data from different investigators. This study was undertaken to compare occlusal configurations of permanent mandibular molars of four major racial groups. One hundred thirty sets of permanent first, second, and third molars from the left side of the mandible were examined. Three hundred eighty-one teeth were from caucasians, 319 from mongoloids, 286 from negroids, and 44 from australoids. The australoid teeth were examined from dried skulls only, whereas the negroid and mongoloid samples were based on dried skulls and hydrocolloid casts. Thus, this study was confined to casts or skulls with a full complement of mandibular molars, which were all assessed to bear a definitely recognizable groove and cusp configuration. Each molar was scored according to groove configuration and cusp number. The resulting categories were Y and + groove configurations and 4 and 5 cusps. The category of + groove configuration included the X category, since preliminary trials revealed various gradations between the X and + configurations, which made discrimination difficult and arbitary. The frequencies of occurrence of these categories were compared between the various racial groups by means of the chi-square test. The frequencies of both groove configurations and cusp numbers showed significant differences between the various racial groups (P < 0.001). No significant differences were detected, however, within either the caucasoid or negroid racial groups. There was a significant difference for the groove configuration within the negroid sample (P < 0.001), but no such variation was apparent for the cusp frequency. The data showed considerable molar occlusal variation both between and within the major racial groups, so it is difficult to distinguish with certainty the racial grouping of single, isolated permanent mandibular molars. CO