Conical Beam Research Articles

Microstructure and Properties of Ti-6Al-4V Articles 3D-Printed with Co-axial Electron Beam and Wire Technology

Advanced additive manufacturing technology of direct energy deposition type called x Beam 3D Metal Printing was employed for manufacturing of articles of various size and shape using titanium Ti-6Al-4V alloy wire as a feedstock material. The key distinctive feature of this process is applying of the hollow conical electron beam generated by low-voltage (< 20 kV) gas-discharge electron beam gun for heating and melting of the substrate and wire, which ensures precisely controllable liquid metal transfer from the wire end to the substrate, specific temperature gradients at the fusion area and heat flow from liquid metal pool. Such conditions of heating, melting and cooling during deposition of molten additive material provide controllable microstructure formation, including grain size and material texture. Influence of processing parameters and cooling conditions on fusion, crystallization, grain growth and intragrain structure of manufactured “chunky” Ti-6Al-4V blocks was discussed. The post-processing heat treatment was used to relieve residual stresses formed during article manufacturing. Tensile and fatigue testing has been performed for samples cut in various directions of produced articles to investigate the material uniformity. Optimization of processing parameters allowed production of 3D printed articles from Ti-6Al-4V with isotropic microstructure and mechanical characteristics which met standard requirements for Ti-6Al-4V material.

High-Gain Conical-Beam Planar Antenna for Millimeter-Wave Drone Applications

In this communication, a high-gain planar antenna with a conical beam (CB) is presented for millimeter-wave drone applications. The proposed antenna comprises a vertical monopole and a circular side reflectors. The high-gain CB is achieved by in-phase reflections from the planar annular-distributed side reflectors which is realized by a series of via walls using the printed-circuit-board (PCB) fabrication. The proposed structure was numerically and experimentally demonstrated. Full-wave analysis shows a 10 dB impedance bandwidth (BW) of 26.50–29.96 GHz, corresponding to 12.26% of the fractional BW, whereas the measured data account for 11.6% in the frequency range of 26.63–29.91 GHz. Meanwhile, a maximum peak gain of 8.51 dBi is observed at a beam-pointing angle of 22°, with a high radiation efficiency of 88.3%. Owing to these valuable features of high gain, good CB radiation performance, and simple planar structure, the proposed antenna is a promising candidate for millimeter-wave drone applications.

PENERAPAN TEKNIK DEFORMASI BENDA GEOMETRI PADA LAMPU DINDING

In general, the wall lamp has a function as lighting. Wall lamps consist of lamp shades, connectors and stands. This study aims to obtain calculation methods for designing more varied lamp shades, connectors and stands. This research method is divided into several stages. First, build some basic objects as components of wall lamps from cone deformation, ten-prism prisms, tubes and beams with Bezier curve. Second, it arranges several basic objects of wall lamp components on the modeling axis. Third, arrange a program. The results of this study obtained calculation methods for designing various forms of constituent components of wall lamps from conical base objects, triangular prisms, tubes and beams. Furthermore, assembling the components of wall light on modeling axis.

Stimulated Raman scattering signal amplification in ethanol molecules via resonant cascading

Lowering threshold and enhancing intensity of stimulated Raman scattering (SRS) have been a major focus of nonlinear optics. In our experiments, we combined SRS generation and amplification techniques to enhance the SRS signal. The amplification was achieved through a process called resonance effect, where the frequency difference between the pump laser and the Stokes light emitted from the working medium had self-matched with the vibrational energy level. The performance improvements included a higher SRS conversion efficiency, reaching up to 5.31%, approximately three times the value of a single sample cell efficiency of 1.739%, and realization of a cascaded SRS up to four orders extending from 461 to 997 nm. These Stokes and anti-Stokes coherent lights were generated coaxially to the pump beam as axial and conical ring beams, respectively, which can be explained by the four-wave mixing. This technique has the potential to contribute to the development of a multi-wavelength cascade Raman laser.

Effect of receptors on the resonant and transient harmonic vibrations of Coronavirus

The paper is concerned with the vibration characteristics of the Coronavirus family. There are some 25–100 receptors, commonly called spikes protruding from the envelope shell of the virus. Spikes, resembling the shape of a hot air balloon, may have a total mass similar to the mass of the lipid bi-layer shell. The lipid proteins of the virus are treated as homogeneous elastic material and the problem is formulated as the interaction of thin elastic shell with discrete masses, modeled as short conical cross-sectional beams. The system is subjected to ultrasonic excitation. Using the methods of structural acoustics, it is shown that the scattered pressure is very small and the pressure on the viral shell is simply the incident pressure. The modal analysis is performed for a bare shell, a single spike, and the spike-decorated shell. The predicted vibration frequencies and modes are shown to compare well with the newly derived closed-form solutions for a single spike and existing analytical solutions for thin shells. The fully nonlinear dynamic simulation of the transient response revealed the true character of the complex interaction between local vibration of spikes and global vibration of the multi-degree-of-freedom system. It was shown that harmonic vibration at or below the lowest resonant modes can excite large amplitude vibration of spikes. The associated maximum principal strain in a spike can reach large values in a fraction of a millisecond. Implications for possible tearing off spikes from the shell are discussed. Another important result is that after a finite number of cycles, the shell buckles and collapses, developing internal contacts and folds with large curvatures and strains exceeding 10%. For the geometry and elastic properties of the SARS-CoV-2 virus, these effects are present in the range of frequencies close to the ones used for medical ultrasound diagnostics.

On The Vibrations of Pyramidal Beams With Rectangular Cross-Section and Application to Unswept Wings

Summary The bending frequencies of an unswept wing are calculated based on the model of a beam clamped at the root and free at the tip. For a tapered wing with straight leading- and trailing-edges, the chord is a linear function of the span; the same linear function of the span applies to thickness, in the case of constant thickness-to-chord ratio. The latter is usually small, so that the beam differs from the more frequent cases of a conical beam with a circular cross-section or a prismatic beam with a square cross-section. Thus, the bending modes of a non-uniform beam are considered, with mass and area moment of inertia which are respectively quadratic and quartic functions of the span. There is no exact solution expressible in finite terms using elementary functions, and thus power series expansions are used. The bending frequencies are calculated for a delta wing and compared with a rectangular wing, with the same span, mean chord and thickness, mass density and Young’s modulus. It is shown that the fundamental frequency is higher by a factor 4.96 for the delta wing; it is also shown that the general case of the tapered wing is intermediate between the delta and the rectangular wing. Lastly, the analytical results obtained for the bending modes are compared with numerical modal analyses of general tapered wing beams using high-fidelity finite-element model software.

Optimizing laboratory X-ray diffraction contrast tomography for grain structure characterization of pure iron.

Laboratory diffraction contrast tomography (LabDCT) is a recently developed technique for 3D nondestructive grain mapping using a conical polychromatic beam from a laboratory-based X-ray source. The effects of experimental parameters, including accelerating voltage, exposure time and number of projections used for reconstruction, on the characterization of the 3D grain structure in an iron sample are quantified. The experiments were conducted using a commercial X-ray tomography system, ZEISS Xradia 520 Versa, equipped with a LabDCT module; and the data analysis was performed using the software package GrainMapper3D, which produces a 3D reconstruction from binarized 2D diffraction patterns. It is found that the exposure time directly affects the background noise level and thus the ability to distinguish weak spots of small grains from the background. With the assistance of forward simulations, it is found that spots from the first three strongest {hkl} families of a large grain can be seen with as few as 30-40 projections, which is sufficient for indexing the crystallographic orientation and resolving the grain shape with a reasonably high accuracy. It is also shown that the electron current is a more important factor than the accelerating voltage to be considered for optimizing the photon numbers with energies in the range of 20-60 keV. This energy range is the most important one for diffraction of common metals, e.g. iron and aluminium. Several suggestions for optimizing LabDCT experiments and 3D volume reconstruction are finally provided.

Effect of laser power on conductivity and morphology of silver nanoparticle thin films prepared by a laser assisted electrospray deposition method

Silver nanoparticle-based electrodes were studied extensively in recent years as an electrode material for wearable and flexible electronics due to their stability and conductivity. A wet chemical deposition technique is considered as a low-cost scalable technique. The current wet chemical-based nanoparticle deposition techniques include electrospray deposition, drop casting, spin coating, and the inkjet printing process. These techniques generally require a separate postdeposition annealing step. This can be a problem for substrates with a low melting point. In addition, some of the above-mentioned methods require physical contact, which increases the probability of cross-contamination. In this research, we present a technique that combines electrospray and laser radiation to deposit and sinter nanoparticles simultaneously on a rigid or flexible substrate. In this process, the microdroplets of aqueous silver nanoparticle suspension ejected in what is known as the microdripping mode from a metallic capillary nozzle, which can be controlled by an electric potential. A conical hollow laser beam is used to vaporize the liquid and sinter the nanoparticles at desired locations on a substrate. This is a promising technique compared to the traditional methods to fabricate conductive micropatterns due to its simplified one step deposition, suppressed cross-contamination, and applicability to various surfaces. Thin-film micropatterns of silver nanoparticles were fabricated using a Nd:YAG laser with powers from 5 to 13 W. The correlation between the grain size distribution, composition, and electrical resistivity was studied using a scanning electron microscope, energy-dispersive x ray, and four-point probe analysis. The results are comparable to the conventional thermal sintering method.

Theoretical Modeling and Analysis of Circularly Polarized Annular Leaky-Wave Antenna Based on Travelling-Wave Structure

In this paper, a theoretical model based on the electric field integration method is proposed to analyse radiation properties of the slotted annular Leaky-Wave Antenna (LWA), which can generate a Circularly Polarized (CP) conical beam or broadside beam. The annular LWA contains radiating elements arranged along a circular travelling-wave structure with equal intervals. By combining the proposed model and LWA theory, the design procedure for the annular SIW LWA is presented. To verify the model, three examples of LWAs with different beam angles have been designed and fabricated. Calculation results from the proposed model are consistent with the simulation and measurement results. The model can significantly reduce the design period and is an instructive tool for antenna design.

A Low‐Profile Circularly Polarized Conical‐Beam Antenna with Wide Overlap Bandwidth

In this paper, a low‐profile circularly polarized (CP) conical‐beam antenna with a wide overlap bandwidth is presented. Such an antenna is constructed on the two sides of a square substrate. The antenna consists of a wideband monopolar patch antenna fed by a probe in the center and two sets of arc‐hook‐shaped branches. The monopolar patch antenna is loaded by a set of conductive shorting vias to achieve a wideband vertically polarized electric field. Two sets of arc‐hook‐shaped parasitic branches connected to the patch and ground plane can generate a horizontally polarized electric field. To further increase the bandwidth of the horizontally polarized electric field, two types of arc‐hook‐shaped branches with different sizes are used, which can generate another resonant frequency. When the parameters of the arc‐hook‐shaped branches are reasonably adjusted, a 90° phase difference can be generated between the vertically polarized electric field and the horizontally polarized electric field, so that the antenna can produce a wideband CP radiation pattern with a conical beam. The proposed antenna has a wide impedance bandwidth (∣S11 | &lt;−10 dB) of 35.6% (4.97‐7.14 GHz) and a 3 dB axial ratio (AR) bandwidth at phi = 0° and theta = 35° of about 30.1% (4.97‐6.73 GHz). Compared with the earlier reported conical‐beam CP antennas, an important feature of the proposed antenna is that the AR bandwidth is completely included in the impedance bandwidth, that is, the overlap bandwidth of ∣S11 | &lt;−10 dB and AR &lt; 3 dB is 30.1%. Moreover, the stable omnidirectional conical‐beam radiation patterns can be maintained within the whole operational bandwidth.

To tailor the conical beam by using planar superstrate

Here, the planar superstrate is used to tailor the conical beam. In the applications of conical beam antenna, making a good balance between the wider coverage and the higher gain is always a challenge, while the planar superstrate provides the freedom of design. Through adjusting the parameters of the planar superstrate, it is possible to change the coverage range and to make the beam more flat. To verify the proposed method, some simulated results are presented and two prototypes with homogeneous dielectric slab superstrate and with patterned dielectric slab superstrate are fabricated and measured. The simulated results and the measured ones are in good agreement.

The effects of periapical lesion healing on bone density

Operative dental procedures may promote pulpal infections, such as tooth cavity, trauma and teeth abrasion, anaerobic microorganism colonization causing total pulp necrosis, and periapical lesions that result in bone destruction in the periapical region. Periapical radiographs are important tools for identifying periapical pathologies. However, given that the imaging system shows three-dimensional formations in two dimensions, the knowledge about the actual size of the lesion and the real relationship with the anatomic structures is limited. These limitations force clinicians to choose the high resolution and current imaging methods that show all the details of the oral structures, such as conic beam computed tomography (CBCT). CBCT is a highly effective diagnostic device for early period bone lesion detection in which the gray value for bone density is measured in Hounsfield unit (HU). Other than using CBCT, bone mineral density measurement can be done to assess the healing of existing lesions. When the periapical lesion is healing, a series of formation and destruction processes follow each other. On the one hand, mediators and tissues that must be removed from the region are destroyed by host defense cells; on the other hand, cells included in the repair process provide new tissue generation and remodelling to provide the pre-disease anatomic properties in the lesion region. This review discusses recent studies using current three-dimensional imaging methods, compared with traditional methods for bone damage due to periapical lesion formation and healing after suitable treatment. This study aims to investigate the advantages and shortcomings of existing treatment and diagnosis approaches in endodontic periradicular lesion diagnosis and treatment. The findings highlight promising diagnosis and treatment tools and suggest the expansion of minimally invasive approaches to eliminate the problems in periapical lesions.&#x0D; &#x0D; How to cite this article:&#x0D; How to cite this article: Akın Tartuk G, Tekin Bulut E. The effects of periapical lesion healing on bone density. Int Dent Res 2020;10(3):90-9. https://doi.org/10.5577/intdentres.2020.vol10.no3.5&#x0D; &#x0D; Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Inhibition and enhancement of linear and nonlinear optical effects by conical phase front shaping for femtosecond laser material processing

The emergence of high-powered femtosecond lasers presents the opportunity for large volume processing inside of transparent materials, wherein a myriad of nonlinear optical and aberration effects typically convolves to distort the focused beam shape. In this paper, convex and concave conical phase fronts were imposed on femtosecond laser beams and focussed into wide-bandgap glass to generate a vortex beam with tuneable Gaussian-Bessel features offset from the focal plane. The influence of Kerr lensing, plasma defocussing, and surface aberration on the conical phase front shaping were examined over low to high pulse energy delivery and for shallow to deep processing tested to 2.5 mm focussing depth. By isolating the underlying processes, the results demonstrate how conical beams can systematically manipulate the degree of nonlinear interaction and surface aberration to facilitate a controllable inhibition or enhancement of Kerr lensing, plasma defocussing, and surface aberration effects. In this way, long and uniform filament tracks have been generated over shallow to deep focussing by harnessing surface aberration and conical beam shaping without the destabilizing Kerr lensing and plasma defocussing effects. A facile means for compressing and stretching of the focal interaction volume is presented for controlling the three-dimensional micro- and nano-structuring of transparent materials.

Accuracy assessment of different CBCT acquisition protocols used in rapid prototyping models

This study compared the acquisition protocols of the Conical Beam Computed Tomography (CBCT) system, to assess the influence on image accuracy by different voxel sizes and the presence of soft tissue. Tomographic acquisition was performed in a fresh (F) and dry (D) pork jaw with voxel sizes of 0.4, 0.3 and 0.25 mm. The gold standard was obtained by scanning dry jaws covered with barium sulfate with a voxel size of 0.25 mm. The images were treated in the MIMICS® program, and noise areas were removed manually, using a fixed threshold for the purpose of generating 3D printing windows. Each window was virtually overlaid with the gold standard using the MeshLab software, obtaining absolute error values ​​between the meshes, generating a map of discrepancies. Significant differences were found between windows D 0.30 vs. F 0.30, D 0.30 vs. F 0.25, D 0.30 vs. D 0.25, D 0.30 vs. F 0.40, F 0.30 vs. D 0.25, F 0.25 vs. D 0.25, F 0.25 vs. D 0.40, D 0.25 vs. F 0.40, D 0.25 vs. D 0.40 and F 0.40 vs. D 0.40, (p &lt;0.05). It was observed that the dry jaw windows showed a lower mean and standard deviation when compared to the fresh jaw windows. The 0.25 mm voxel protocol showed the most accurate result and the presence of soft tissues influenced the accuracy of the image when some protocols were compared statistically.

Close relationship between Bessel-Gaussian and conical refraction beams.

We demonstrate that the conical refraction of the input elegant Laguerre-Gaussian beams can be effectively described through generalized Bessel-Gaussian light beams. We performed numerical simulations and show good agreement between the exact solution and our proposed Bessel-Gaussian approximation model. Physical clarity of the proposed model has allowed us to explain the transition of the classical double-ring pattern of conical refraction in the Lloyd plane into a multi-ring one and predict new phenomenon such as the Raman spot shift and dependence of the conical refraction ring radius on the value of the orbital angular momentum.

Picosecond stimulated Raman scattering at 3000 and 3430 cm-1 OH vibrations without optical breakdown.

For the first time, to the best of our knowledge, stimulated Raman scattering (SRS) of picosecond laser pulses without optical breakdown has been detected simultaneously (as the first Stokes and anti-Stokes paired components) at ∼3430 and ∼3000cm-1 vibrations of water OH band. These components were generated coaxially to the pump beam in the forward direction as axial and conical ring beams, respectively, when the pump beam was focused at the water-air interface. We suggest an explanation of these new SRS phenomena by non-collinear four-wave parametric interaction.

Low‐profile ring slot SIW antenna based on higher‐order cylindrical cavity modes

A novel ring slot substrate-integrated waveguides (SIW) antenna is presented based on higher-order cylindrical cavity mode. First, TM02 is used to realise a conical beam antenna. Electric field distribution on slot aperture generates four pairs of magnetic monopoles, each rotated 90° with respect to the centre of the cavity, resulting in a conical beam. By applying an offset to the feed point, the loading effect of slots generates a hybrid mode, which is a combination of TM31 and TM12. The hybrid mode aligns the magnetic monopoles; thus, a high-gain antenna with broadside radiation can be realised. The measured results show a 10.5% impedance bandwidth, 11.5 dBi gain, and 90% radiation efficiency. The proposed antenna is low-profile and compact with a planar structure that could be integrated with other planar circuits; therefore, it could have many practical applications in communication systems.

A Tri-Polarized Antenna With Diverse Radiation Characteristics for 5G and V2X Communications

A tri-polarized antenna with diverse radiation characteristics is proposed in this paper. This design mainly consists of two pairs of loop radiating dipoles and an omnidirectional monopole antenna element, which are used for the fifth generation (5G) and vehicle to everything (V2X) communications, respectively. By adding eight pairs of inverted L-shaped patches with unequal sizes around the proposed dipoles, wide beamwidths in both E- and H-planes can be obtained across the desired lower and upper frequency bands. Furthermore, by employing eight fork-shaped microstrip stubs to combine the circular monopole antenna element and the L-shaped patches, the flare angle of the conical beam can be increased to 180°, which results in gain enhancement in the azimuth plane. Finally, the proposed loop radiating dipoles are excited by a pair of symmetrical differentially-fed feeding lines. Consequently, high port isolation for the proposed loop radiating dipoles as well as low gain variations for the monopole antenna element can be achieved. Measured results show that the impedance bandwidths of 32.84% (2.8-3.9 GHz) and 18.18% (4.5-5.4 GHz) can be achieved for the 5G communications. Wide half power beamwidths (HPBW) of larger than 103° in E-plane and 91° in H-plane can be achieved across the operating bands. In addition, a bandwidth of 5.5% (5.82-6.15 GHz) with gain of 2.47 ± 0.69 dBi in the azimuth plane can also be obtained for V2X communications.

CONSERVATIVE TREATMENT OF ODONTOGENIC KERATOCYST: OBSERVATION FOR 4 YEARS

A 61-year-old male patient was asymptomatic. In 2016, he sought a dental service for oral rehabilitation. Extraoral physical examination is not worth noting. Intraoral examination found dental absences bilaterally in the posterior region of the mandible. Panoramic radiograph and conical beam tomography showed a radiolucent, unilocular, well-delimited image, affecting the region of teeth 45/46 without causing root resorption of adjacent teeth. Aspiration punch was performed, and yellow-colored liquid was noted. Incisional biopsy was performed, and the histopathologic diagnosis was compatible with odontogenic keratocyst. A marsupialization was performed for 1 month, and the iodopovidone-soaked gasses were changed daily. After 3 and 6 months, the imaging examinations showed a significant reduction of the lesion accompanied by circumferential bone neoformation. Thus enucleation/curettage of the lesion followed by guided bone regeneration was performed. The patient has been under follow-up for 4 years, and the imaging tests show bone neoformation without signs of relapse.

Approach to the Design and Manufacturing of Prosthetic Dental Restorations According to the Rules of Industry 4.0

Abstract The paper contains an extensive, richly illustrated literature study, theoretical studies, and practical work on current development trends of technical support for dental prosthetics. Dentistry 4.0 is the concept closely inspired by the highest stage Industry 4.0 of the industrial revolution. An augmented holistic Industry 4.0 model, which takes into account all other aspects, i.e., materials, processes, and technological machines and their development and informatics service, was developed and presented. The basis for consideration is the analysis of the disease in the human stomatognathic system and the possibility of prosthetic treatment in the event of a partial or total loss of natural dentition. In several centers, independent work on the popularization of individual implants manufactured using information obtained using conical beam computed tomography (CBCT) is carried out. The developed procedure requires one to make a three-dimensional bone base model based on the CBCT tomogram and its connection with the three-dimensional model of the dentition and soft tissues in the oral cavity, prepared on the basis of impression material, and most preferably a three-dimensional scan directly from the mouth. The presented and fully digitized approach is a radical turnaround in both clinical procedures and the method of technical implant preparation using Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) methods and additive manufacturing technologies (AMT), including mainly Selective Laser Sintering (SLS) and stereolithography (SLA). The concept of hybrid multilayer biological-engineering composites is much more technologically advanced. The application of the principles of the augmented holistic Industry 4.0 model in modern dental engineering, according to the analysis, indicates a change in the traditional relationship between a dentist and dental engineer. The practical application of the Dentistry 4.0 approach is illustrated by projects regarding the manufacturing of a few dental restorations. The general conclusion indicates that the implementation of the ideas of Dentistry 4.0 following the assumptions of the augmented holistic model Industry 4.0 is inevitable and extremely beneficial.