This paper presents an accurate procedure to design, characterize and test a radome for millimeter-wave applications. In this procedure, an accurate analytical model is presented to design a radome ...structure that takes into consideration the bandwidth, losses, reflections and depolarization factor as a function of frequency and incident angle. To guarantee a good operational electrical performance, the proposed procedure includes a material characterization and accurate test procedure based on the free-space Gaussian beam method and time gating filtering technique. Four radomes (two-monolithic and two A-sandwich) at 82 GHz and 94 GHz are designed, characterized and tested to validate the proposed technique. Results obtained with this procedure are compared with numerical simulations and experimental results. This method is shown to be accurate and versatile for radomes in mm-Wave applications.
A design of an X-band dual-polarization slotted waveguide antenna (SWGA) array for high polarization performance over 200 MHz bandwidth and wide scan in the azimuth plane, ideal for high-power ...dual-polarized radar system, is presented. The proposed design uses a compact array unit cell where the overall dimensions are reduced to 50% in comparison with that of the dual-polarization slotted waveguide array antenna using the conventional rectangular waveguides. The new design overcomes the fundamental limitation of zero electronically scanning, due to the large element spacing (<inline-formula> <tex-math notation="LaTeX">1.2\lambda _{\circ } </tex-math></inline-formula>), when conventional waveguides are used. Reducing the element spacing to <inline-formula> <tex-math notation="LaTeX">0.6\lambda _{\circ } </tex-math></inline-formula> (in the azimuth plane), based on a partial H-plane waveguide, enables a 1D e-scanning range up to 84°(±42°) in the azimuth plane perpendicular to the waveguide axis. An active sub-array panel of <inline-formula> <tex-math notation="LaTeX">8\times 8 </tex-math></inline-formula> elements, excited with 8 high-power transmit and receive modules, is proposed. This active sub-array can be scaled to obtain a large array without any constraints in size and power. The proposed design uses longitudinal shunt slots on the partial H-plane waveguide for V-polarization antenna and non-inclined edge wall slots on the conventional waveguide for H-polarization antenna. The proposed design offers stable impedance, gain, cross-polarization isolation and excellent co-polar pattern mismatch over the whole frequency band of interest. Having a cross-polarization isolation better than −60 dB and co-polar pattern mismatch around ± 0.12 dB across the scanning range, make this array unit cell (<inline-formula> <tex-math notation="LaTeX">8\times 8 </tex-math></inline-formula> elements) a perfect candidate for high power e-scanned dual-polarized phased array radar for weather observations.
This paper presents a new design technique to develop a multi-layer radome for ultra-wide-band, dual-polarized radar and communication systems. In the proposed technique, a multi-layer radome is ...designed using a combination of A-sandwich structures, which are not used in conventional multi-layer radomes. In contrast with conventional radomes, this technique enables a substantial increase of bandwidth with a negligible change in the overall radome thickness. In addition, it provides excellent RF performance, thermal isolation, and mechanical strength. Three different multi-layer radomes for different bandwidths are designed. Parameters such as co-polarization mismatch and depolarization ratio are used to evaluate the proposed dual-polarized radome as a function of incident angle and frequency. To validate this new technique, a 5A-sandwich radome is designed to operate from 1 GHz to 14 GHz and its RF performance is evaluated by measuring S-parameters. The proposed radome is further investigated by measuring the radiation patterns of horn antennas at different bands (S-, C-, X- and Ku-bands) with and without the radomes. The measured losses recorded are below 0.5 dB with an absolute error less than 0.05 dB between the calculations and measurements. An S-band electronically scanned active phased array antenna is also used to evaluate the radome as a function of incident angles. In this case, the maximum recorded losses are below 0.4 dB and the absolute errors between the calculations and measurements are below 0.1 dB. The proposed technique and radome can be used in different applications such as surveillance systems, earth exploration satellite, aeronautical radio-navigation, and especially in dual-polarized weather radars that require a high polarization performance.
•The top 50 cited articles published in Photodiagnosis and Photodynamic Therapy during 2004–2019 were analyzed.•The citation count of an article plays a vital role to indicate its’ impact on the ...particular specialty.•The citation count for top 50 cited articles ranged between 1073−42.
The aim of the article was to identify the top 50 cited articles in the journal of Photodiagnosis and Photodynamic Therapy during 2004–2019.
The online search was conducted on Scopus database to retrieve all the articles published during 2004–2019 in the journal of Photodiagnosis and Photodynamic Therapy. The papers were identified and ranked as per the citation counts >42. Additionally the authors; institute and country of origin; type of study and availability of funding in these highly cited articles was identified. VOS viewer software was used to analyze the occurrence of most commonly used keywords by the authors.
Majority of the highly cited studies published during last 15 years were literature reviews (n = 34) followed by the qualitative/quantitative studies (n = 15). The largest number of articles published were single nations without any collaborations (n = 45). The institutes publishing highest number of top cited articles included Massachusetts General Hospital, East Carolina University, 21 st Century Oncology, The Norwegian Radium Hospital and Trinity College Dublin. The country with largest number of top cited articles was USA. The keyword most commonly associated with the 50 top cited articles was ‘Photodynamic therapy’.
Extensively, various specialties of medicine and dentistry have been explored in the last 15 years in the journal of Photodiagnosis and Photodynamic Therapy. Based on citatations, we have highlighted those that can be considered as classic research.
•Er, Cr: YSGG laser showed a reversal effect of bleached enamel compared to ascorbic acid.•Bleached enamel reversal using methylene blue photosensitizer needs further investigation.•Pre dominant ...failure type amongst experimental groups was adhesive.
The purpose of the present study was bleached enamel reversal using conventional ascorbic acid (AA) and contemporary methods including Photodynamic therapy (PDT), Er, Cr: YSGG (ECL) on bond integrity to composite resin.
Forty sound permanent mandibular premolars were collected from a dental clinical setting and disinfected. All forty samples were mounted vertically in a rubber mold exposing only the clinical crown. All samples were bleached using Opalescence Boost Professional Teeth Whitening. After the bleaching procedure, each sample was randomly allocated into four groups according to surface treatment. Samples in group 1 were treated with methylene blue photosensitizer (MBP). Samples in group 2 were exposed to 10% sodium ascorbate. Samples in group 3 were treated with Er, Cr: YSGG laser (ECL). Samples in group 4 were not treated (control). All Samples were treated with 37% phosphoric acid and a bonding agent was applied. A bulk-fill composite was cured to all specimens and all samples were treated in a thermocycler. Specimens were placed in a universal testing machine for shear bond strength (SBS) testing. Descriptive statistics were associated by analysis of variance (ANOVA) and Tukey's post hoc test maintaining level of significance (p<0.05)
The lowest SBS scores were achieved in the bleached enamel (BE) group (15.25±1.745 MPa). Whereas, the highest bond integrity was attained by AA group (32.23±1.854 MPa). Samples treated with ECL (31.87±1.659 MPa) and AA (32.23±1.854) were comparable (p>0.05). Samples treated with PDT exhibited significantly different SBS (22.41±1.258) compared to other experimental groups
ECL showed a reversal effect of BE compared to AA and has the potential to be used in clinical settings. BE reversal using MBP needs further investigation.
This paper presents the design and synthesis of a low-loss substrate with low effective permittivity (<inline-formula> <tex-math notation="LaTeX">\varepsilon _{eff} </tex-math></inline-formula>) for ...microwave and mm-Wave applications. The proposed design is based on the two-phase Maxwell Garnet mixing theory, where the <inline-formula> <tex-math notation="LaTeX">\varepsilon _{eff} </tex-math></inline-formula> of the RF substrate can be synthesized depending on the geometry and the permittivity of mixing particles and the permittivity of the host material. A comprehensive review and error analysis of the most common mixing techniques are conducted to guarantee an accurate design for high-performance RF substrates. Several analyses based on the geometries of various particles are carried out to identify the most accurate mixing model used in the design of the proposed substrate. The effects of the direction of excitation as well as the polarization of the incident field on the <inline-formula> <tex-math notation="LaTeX">\varepsilon _{eff} </tex-math></inline-formula> of the anisotropic particle are analyzed and discussed. The proposed method enables the use of existing high-performance materials that do not necessarily provide a low dielectric constant and low loss tangent. For mm-Wave antenna applications, materials with a dielectric constant of 2-4, and loss tangent of less than 0.002 are desirable to maximize gain and radiation efficiency. Commercial RF substrates can satisfy those requirements, however limited thermal expansion coefficient and lamination difficulties increase the cost significantly. The proposed method enables the use of inexpensive materials that provide excellent thermal properties and great compatibility with a multi-layer fabrication process with desirable <inline-formula> <tex-math notation="LaTeX">\varepsilon _{eff} </tex-math></inline-formula> and loss tangent. For validation of the analysis, samples are fabricated and tested in the microwave frequency (S-band) at 3.5 GHz as well as in the mm-Wave frequency (W-band) at 77 GHz. Measured results show a reduction of 45% in the <inline-formula> <tex-math notation="LaTeX">\varepsilon _{eff} </tex-math></inline-formula> and 38% in the loss tangent values in the S-band, and 32% and 72% reduction in <inline-formula> <tex-math notation="LaTeX">\varepsilon _{eff} </tex-math></inline-formula> and tan<inline-formula> <tex-math notation="LaTeX">\delta </tex-math></inline-formula>, respectively, in the mm-Wave frequency band. The measured results are in excellent agreement with the simulation and calculated results.
Resorbable collagen has been utilized to treat wounds, close graft, and tooth extraction sites, and enhance recovery. Collagen-based membranes are also used as barriers in periodontal and implant ...therapy to limit epithelial migration and allow cells with the regenerative capacity to fill the problem area. This systematic review was carried out to analyze the studies focusing on collagen structure, synthesis, and its applications. A detailed and extensive search was performed with the help of the keywords "collagen structure", "collagen synthesis" and "collagen applications". There was extensive literature search in reliable and authentic databases like PubMed, Scopus, Web of Sciences, Ovidsp, and Cochrane library to obtain papers focusing on collagen structure, synthesis, and applications. During the systematic review, data were obtained concerning the following parameters. Type of study, nature of aim of the study, size of the sample in the study, gender and age of the subjects included in the study, prevalence of skin diseases where collagen was used for treatment, dose of collagen used, form in which collagen was used, the origin of collagen used, analysis of different variables, structure, and synthesis of collagen. Twenty-two studies were included in this systematic review. The studies discussed the structure, synthesis, and applications of collagen in treatment. In studies focusing on the application of collagen supplements, most of the study subjects were females (68.3%). The study subjects included both healthy and unhealthy subjects. The study subjects were divided into two categories. One category was the intervention group, while another group was the placebo group. Collagen was administered in hydrolysate form (90%) in some studies, bovine form (2.3%), and porcine form (3.4%) in other studies. Collagen supplementation was found to provide better results in both healthy and unhealthy effects in improving the health of skin, cornea, bone, periodontium, face, etc. It can be concluded that collagen is an integral part of the body. The application of collagen supplements can be pretty effective in maintaining the proper health of several important structures of the body like skin, face, cornea, nails, periodontium, etc. Thus, a detailed study of the molecular structure of collagen and genes associated with each type of collagen is essential for further research and treatment of collagen-associated disorders.
This paper presents the modeling and design of a frequency agile antenna using an anisotropic artificial dielectric layer (AADL) for multi-band phased array radar applications. The proposed AADL ...material is placed underneath the patch radiator and is designed using periodically arranged metallic cylinders in which varying height, diameter, and the distance used between them allows the control of the effective permittivity of the patch antenna. Closed form design expressions are formulated to synthesize the dielectric properties of the AADL as a function of the cylindrical unit cell dimensions. Design trade-offs based on the proposed formulation and numerical simulations show the overall performance of the AADL on microstrip patch (MS) antennas. To validate the proposed concept, five individual AADL MS patch antennas in C-band were designed, fabricated, and tested. Simulated and measured results (s-parameters and radiation patterns) are in good agreement with the results obtained from the theoretical model. The proposed AADL concept has the potential to be used in the development of future reconfigurable tunable multiband antennas that use liquid metal to dynamically change the heights of the cylinders.
This paper presents a new set of analytical equations to calculate the impedance bandwidth of electrically thin and thick proximity-coupled square microstrip patch antenna (PC-MSPA). The proposed ...mathematical model uses the relationship among different antenna parameters, material, and antenna dimensions to estimate the percentage impedance bandwidth with high accuracy. The proposed model was validated with rigorous full-wave solutions, and experimental antenna prototypes implemented for different thicknesses, patch dimensions, frequencies, and different substrates. The theoretical bandwidth results of S-, C- and X-band PC-MSPA antennas obtained using the new model are in very good agreement with simulations and the experimental results. Errors between the proposed analytical model and both simulation and measurement are less than 3.1%. These equations are mostly valid for permittivities between 2.2 and 6.15, and with feed substrate thickness less than 0.1λr. The PC-MSPA is a candidate element for integration with MIMIC devices and wireless communication applications.
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