scholarly journals Ultrawideband Antennas: Growth and Evolution

Micromachines ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 60
Author(s):  
Om Prakash Kumar ◽  
Pramod Kumar ◽  
Tanweer Ali ◽  
Pradeep Kumar ◽  
Shweta Vincent
Keyword(s):  
Medical Diagnostics ◽  
Short Pulses ◽  
Uwb Antennas ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Specific Frequency ◽  
Technical Specifications ◽  
Commercial Applications ◽  
Wireless Communications Systems ◽  
Ground Penetrating

Narrowband antennas fail to radiate short pulses of nano- or picosecond length over the broader band of frequencies. Therefore, Ultrawideband (UWB) technology has gained momentum over the past couple of years as it utilizes a wide range of frequencies, typically between 3.1–10.6 GHz. UWB antennas have been utilized for various applications such as ground-penetrating radars, disaster management through detection of unexploded mines, medical diagnostics, and commercial applications ranging from USB dongles to detection of cracks in highways and bridges. In the first section of the manuscript, UWB technology is detailed with its importance for future wireless communications systems. In the next section various types of UWB antennas and their design methodology are reviewed, and their important characteristics are highlighted. In section four the concept of a UWB notch antenna is presented. Here various methods to obtain the notch, such as slots, parasitic resonators, metamaterials, and filters are discussed in detail. In addition, various types of important notch antenna design with their technical specifications, advantages, and disadvantages are presented. Finally, the need of reconfigurable UWB notch antennas is discussed in the next section. Here various insight to the design of frequency reconfigurable notch antennas is discussed and presented. Overall, this article aims to showcase the beginnings of UWB technology, the reason for the emergence of notching in specific frequency bands, and ultimately the need for reconfiguring UWB antennas along with their usage.

scholarly journals Prospects of Upgrade of the Main Drives of CNC Machine Tools Using Mechatronic Modules

2020 ◽  
Author(s):  
V.V. Goman
Keyword(s):  
Machine Tool ◽  
Electric Motor ◽  
Machine Tools ◽  
Machine Building ◽  
Cnc Machine Tools ◽  
Final Decision ◽  
Cnc Machine ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Technical Specifications

This article observes the principles of construction and operation of the belt drives with detached electric motor and the drives with motor spindle. It also describes the characteristics of the elements used in spindles. In choosing a spindle, one proceeds from the primary and secondary requirements for the machine tool: rotation speed, power output, hardness, workspace dimensions, design complexity, application area, option of repair and replacement, and cost. The article considers the advantages and disadvantages of the spindles with additional mechanic gears and the motor spindles. As an example, we compare variants of upgrade of the «16M30F3» machine tool’s main drive. As a result, the following conclusions were made: motor spindle has more advantages than standard drive, but it is way more expensive and its repair is more difficult. Hence, this spindle type is only applicable to machine tools with high standards of quality and performance. Belt-driven spindle is special for easy repair and a wide range of technical specifications: one can choose multiple motor variants for one drive; again, it is much cheaper than motor spindle. However, final decision on spindle should concern the main requirements for the machine tool, workplace dimensions, application of the machine tool and, possibly, financial restrictions. Keywords: CNC machine tool, motor spindle, mechatronics, machine building, electric drive, electric motor, motion control, built-in motor.

The Management of Post-Tonsillectomy Morbidity in Patients With Sleep Apnoea

2019 ◽  
Vol 70 (10) ◽  
pp. 3738-3740
Keyword(s):  
Day Surgery ◽  
Sleep Apnoea ◽  
Integrative Approach ◽  
Multicenter Studies ◽  
Therapeutic Modalities ◽  
Advantages And Disadvantages ◽  
Obstructive Sleep ◽  
Wide Range ◽  
The Impact ◽  
Surgery Center

The Tonsillectomy in children or adults is an intervention commonly encountered in the ENT (Ear Nose and Throat) and Head and Neck surgeon practice. The current tendency is to perform this type of surgery in major ambulatory surgery centers. Two objectives are thus pursued: first of all, the increase of the patient quality of life through the reintegration into the family as quickly as possible and secondly, the expenses associated with continuous hospitalization are reduced. Any tertiary (multidisciplinary) sleep center must ensure the complete diagnosis and treatment (including surgery) of sleep respiratory disorders. Under these conditions the selection of patients and especially the implementation of the specific protocols in order to control the postoperative complications it becomes essential. The present paper describes our experience of tonsillectomy as treatment for selected patients with chronic rhonchopathy (snoring) and mild to moderate obstructive sleep apnoea. It was presented the impact of antibiotics protocols in reducing the main morbid outcomes following tonsillectomy, in our day surgery center. The obtained results can also be a prerequisite for the integrative approach of the patients with sleep apnoea who were recommended surgical treatment. Considering the wide range of therapeutic modalities used in sleep apnoea, each with its specific advantages and disadvantages, more extensive and multicenter studies are needed. Keywords: post-tonsillectomy morbidity, day surgery center, sleep disorders

scholarly journals Advancements in Assessments of Bio-Tissue Engineering and Viable Cell Delivery Matrices Using Bile Acid-Based Pharmacological Biotechnologies

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1861
Author(s):  
Armin Mooranian ◽  
Melissa Jones ◽  
Corina Mihaela Ionescu ◽  
Daniel Walker ◽  
Susbin Raj Wagle ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Viable Cell ◽  
Cell Delivery ◽  
Artificial Organ ◽  
Bioartificial Pancreas ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Bioartificial Organs ◽  
Significant Interest ◽  
Modern Technologies

The utilisation of bioartificial organs is of significant interest to many due to their versatility in treating a wide range of disorders. Microencapsulation has a potentially significant role in such organs. In order to utilise microcapsules, accurate characterisation and analysis is required to assess their properties and suitability. Bioartificial organs or transplantable microdevices must also account for immunogenic considerations, which will be discussed in detail. One of the most characterized cases is the investigation into a bioartificial pancreas, including using microencapsulation of islets or other cells, and will be the focus subject of this review. Overall, this review will discuss the traditional and modern technologies which are necessary for the characterisation of properties for transplantable microdevices or organs, summarizing analysis of the microcapsule itself, cells and finally a working organ. Furthermore, immunogenic considerations of such organs are another important aspect which is addressed within this review. The various techniques, methodologies, advantages, and disadvantages will all be discussed. Hence, the purpose of this review is providing an updated examination of all processes for the analysis of a working, biocompatible artificial organ.

scholarly journals Formation of Carbon Quantum Dots via Hydrothermal Carbonization: Investigate the Effect of Precursors

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 986
Author(s):  
Md Rifat Hasan ◽  
Nepu Saha ◽  
Thomas Quaid ◽  
M. Toufiq Reza
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Microcrystalline Cellulose ◽  
Uv Light ◽  
Synthesis Method ◽  
Hydrothermal Carbonization ◽  
Carbon Quantum Dots ◽  
Medical Diagnostics ◽  
Particle Size Range ◽  
Wide Range

Carbon quantum dots (CQDs) are nanomaterials with a particle size range of 2 to 10 nm. CQDs have a wide range of applications such as medical diagnostics, bio-imaging, biosensors, coatings, solar cells, and photocatalysis. Although the effect of various experimental parameters, such as the synthesis method, reaction time, etc., have been investigated, the effect of different feedstocks on CQDs has not been studied yet. In this study, CQDs were synthesized from hydroxymethylfurfural, furfural, and microcrystalline cellulose via hydrothermal carbonization at 220 °C for 30 min of residence time. The produced CQDs showed green luminescence behavior under the short-wavelength UV light. Furthermore, the optical properties of CQDs were investigated using ultraviolet-visible spectroscopy and emission spectrophotometer, while the morphology and chemical bonds of CQDs were investigated using transmission electron microscopy and Fourier-transform infrared spectroscopy, respectively. Results showed that all CQDs produced from various precursors have absorption and emission properties but these optical properties are highly dependent on the type of precursor. For instance, the mean particle sizes were 6.36 ± 0.54, 5.35 ± 0.56, and 3.94 ± 0.60 nm for the synthesized CQDs from microcrystalline cellulose, hydroxymethylfurfural, and furfural, respectively, which appeared to have similar trends in emission intensities. In addition, the synthesized CQDs experienced different functionality (e.g., C=O, O-H, C-O) resulting in different absorption behavior.

scholarly journals Ureido Functionalization through Amine-Urea Transamidation under Mild Reaction Conditions

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1583
Author(s):  
Natalia Guerrero-Alburquerque ◽  
Shanyu Zhao ◽  
Daniel Rentsch ◽  
Matthias M. Koebel ◽  
Marco Lattuada ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Reaction Times ◽  
Reaction Rates ◽  
Secondary Amines ◽  
Isocyanic Acid ◽  
Advantages And Disadvantages ◽  
Major Disadvantage ◽  
Wide Range ◽  
Potential Alternative ◽  
Full Conversion

Ureido-functionalized compounds play an indispensable role in important biochemical processes, as well as chemical synthesis and production. Isocyanates, and KOCN in particular, are the preferred reagents for the ureido functionalization of amine-bearing compounds. In this study, we evaluate the potential of urea as a reagent to graft ureido groups onto amines at relatively low temperatures (<100 °C) in aqueous media. Urea is an inexpensive, non-toxic and biocompatible potential alternative to KOCN for ureido functionalization. From as early as 1864, urea was the go-to reagent for polyurea polycondensation, before falling into disuse after the advent of isocyanate chemistry. We systematically re-investigate the advantages and disadvantages of urea for amine transamidation. High ureido-functionalization conversion was obtained for a wide range of substrates, including primary and secondary amines and amino acids. Reaction times are nearly independent of substrate and pH, but excess urea is required for practically feasible reaction rates. Near full conversion of amines into ureido can be achieved within 10 h at 90 °C and within 24 h at 80 °C, and much slower reaction rates were determined at lower temperatures. The importance of the urea/amine ratio and the temperature dependence of the reaction rates indicate that urea decomposition into an isocyanic acid or a carbamate intermediate is the rate-limiting step. The presence of water leads to a modest increase in reaction rates, but the full conversion of amino groups into ureido groups is also possible in the absence of water in neat alcohol, consistent with a reaction mechanism mediated by an isocyanic acid intermediate (where the water assists in the proton transfer). Hence, the reaction with urea avoids the use of toxic isocyanate reagents by in situ generation of the reactive isocyanate intermediate, but the requirement to separate the excess urea from the reaction product remains a major disadvantage.

Effect of antennas on velocity estimates obtained from crosshole GPR data

Geophysics ◽  
2005 ◽  
Vol 70 (5) ◽  
pp. K39-K42 ◽  
Author(s):  
James D. Irving ◽  
Rosemary J. Knight
Keyword(s):  
Numerical Modeling ◽  
Ground Penetrating Radar ◽  
Significant Fraction ◽  
High Angle ◽  
Standard Assumption ◽  
Tomographic Images ◽  
Wide Range ◽  
Antenna Length ◽  
Ground Penetrating

To obtain tomographic images with the highest possible resolution from crosshole ground-penetrating radar (GPR) data, raypaths covering a wide range of angles between the boreholes are required. In practice, however, the inclusion of high-angle ray data in crosshole GPR inversions often leads to tomograms so dominated by inversion artifacts that they contain little reliable subsurface information. Here, we investigate the problems that arise from the standard assumption that all first-arriving energy travels directly between the centers of the antennas. Through numerical modeling, we show that this assumption is often incorrect at high transmitter-receiver angles and can lead to significant errors in tomographic velocity estimates when the antenna length is a significant fraction of the borehole spacing.

Application of neural networks in membrane separation

2020 ◽  
Vol 36 (2) ◽  
pp. 265-310 ◽  
Author(s):  
Morteza Asghari ◽  
Amir Dashti ◽  
Mashallah Rezakazemi ◽  
Ebrahim Jokar ◽  
Hadi Halakoei
Keyword(s):  
Neural Networks ◽  
Chemical Engineering ◽  
Membrane Separation ◽  
Mechanistic Model ◽  
Computing Time ◽  
Permeate Flux ◽  
Practical Applications ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Physical And Chemical

AbstractArtificial neural networks (ANNs) as a powerful technique for solving complicated problems in membrane separation processes have been employed in a wide range of chemical engineering applications. ANNs can be used in the modeling of different processes more easily than other modeling methods. Besides that, the computing time in the design of a membrane separation plant is shorter compared to many mass transfer models. The membrane separation field requires an alternative model that can work alone or in parallel with theoretical or numerical types, which can be quicker and, many a time, much more reliable. They are helpful in cases when scientists do not thoroughly know the physical and chemical rules that govern systems. In ANN modeling, there is no requirement for a deep knowledge of the processes and mathematical equations that govern them. Neural networks are commonly used for the estimation of membrane performance characteristics such as the permeate flux and rejection over the entire range of the process variables, such as pressure, solute concentration, temperature, superficial flow velocity, etc. This review investigates the important aspects of ANNs such as methods of development and training, and modeling strategies in correlation with different types of applications [microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), electrodialysis (ED), etc.]. It also deals with particular types of ANNs that have been confirmed to be effective in practical applications and points out the advantages and disadvantages of using them. The combination of ANN with accurate model predictions and a mechanistic model with less accurate predictions that render physical and chemical laws can provide a thorough understanding of a process.

scholarly journals Free or paid: the uses of Roses Citadel (Catalonia)

2019 ◽  
Vol 9 (1) ◽  
pp. 111-120
Author(s):  
Josep Burch ◽  
Modest Fluvià ◽  
Ricard Rigall ◽  
Albert Saló ◽  
Gabriel Alcalde
Keyword(s):  
Public Space ◽  
Local Community ◽  
Free Access ◽  
Content Type ◽  
Advantages And Disadvantages ◽  
The Social ◽  
Wide Range ◽  
Economic Analyses ◽  
Social Use ◽  
The Town

Purpose The Roses Citadel is a bastioned fortification that has archaeological remains from the Greek, Roman and medieval periods in its interior. Currently, the area inside the Citadel is used for a wide range of activities; some directly related with the heritage item, others associated with its use as a public space for the town. The purpose of this paper is to analyse the economic interest of charging an entrance fee vs the alternative of free access and offers a framework to address this issue. Design/methodology/approach The proposal is to consider the marginal cost of increasing the number of users and to carry out a travel cost analysis. It is vital to take into account the results of specifically economic analyses, but the evaluations of social policies should also be considered, and should have a considerable weight in decision making. Findings It is proposed that free entry would bring about an increase in the number of visitors and users of Roses Citadel. In turn, this increase would lead to a greater social use of this heritage asset, and a chance for the least privileged sectors of society to use the site more. Financial resources for the maintenance of the asset would not be raised through entry fees, but through contributions relating to the increase in the social consideration of the site. Originality/value In the context of a discussion on the advantages and disadvantages of paying an entry fee for heritage assets, the example of Roses Citadel provides several factors for consideration. It shows that payment of an entry fee affects use of the site by society, and particularly by the local community, whereas free access leads to a wide range of opportunities for use.

scholarly journals Update Regarding Imaging of Neuroendocrine Neoplasms

2019 ◽  
Vol 192 (02) ◽  
pp. 171-182
Author(s):  
Jens Holger Figiel ◽  
Simon G. Viniol ◽  
Jannis Görlach ◽  
Anja Rinke ◽  
Damiano Librizzi ◽  
...  
Keyword(s):  
Neuroendocrine Neoplasm ◽  
Neuroendocrine Neoplasms ◽  
Primary Tumors ◽  
Advantages And Disadvantages ◽  
Key Points ◽  
Wide Range ◽  
Small Primary ◽  
Noninvasive Therapy ◽  
Spectrum Of Indications

Background Neuroendocrine neoplasms (NEN) are a heterogeneous group of tumors characterized by the expression of typical proteins. A wide range of morphological and functional imaging methods is required in order to adequately assess the course of the disease and to optimally treat the patient. The spectrum of indications ranges from the detection of small primary tumors to the documentation of the metastasis pattern and the assessment of the suitability for certain invasive or noninvasive therapy methods. The exact recording and quantification of findings is indispensable. Methods This article is based on a comprehensive literature search on the different aspects of neuroendocrine neoplasm imaging. Results This article is intended to provide an overview of the available imaging procedures with their respective advantages and disadvantages for diagnostics and their value for the follow-up of neuroendocrine neoplasms. Recommendations for examination protocols, typical image findings, and an outlook regarding future developments are presented. Key Points:  Citation Format

scholarly journals LDA method in psychological assessment of text comprehension

2021 ◽  
Author(s):  
С.А. Свердлов
Keyword(s):  
Psychological Assessment ◽  
Text Comprehension ◽  
Advantages And Disadvantages ◽  
Text Understanding ◽  
Modern Psychology ◽  
Wide Range ◽  
Psychology Pedagogy ◽  
The Moment ◽  
Comparison Of The Results ◽  
Different Content

Проблема понимания текстов и способов его оценки является одной из фундаментальных для современной психологии, педагогики, лингвистики. На настоящий момент имеется большое количество попыток выработки метода оценки понимания текстов, который бы отражал объективную картину интериоризации материала текста читателем, и вместе с тем подходил бы для стандартизации и применения на широком диапазоне текстов различного содержания и структуры, по возможности с минимальными затратами ресурсов оценщика и самого читателя. В настоящей статье раскрываются современные подходы к оценке понимания текстов, их преимущества и недостатки, и формулируется новый перспективный метод оценки понимания текстов, использующий в своём основании модель Латентного размещения Дирихле. Данный метод затем проходит исследование валидности через сравнение результатов его применения и наиболее часто используемых современных методов оценки понимания текстов, делается вывод о его применимости в реальных условиях и перспективах использования в спектре прикладных задач. The problem of understanding texts and methods of assessing it is one of the fundamental for modern psychology, pedagogy, linguistics. At the moment, there are a large number of attempts to develop a method for assessing the understanding of texts, which would reflect an objective picture of the internalization of the material of the text by the reader, and at the same time would be suitable for standardization and application on a wide range of texts of different content and structure, if possible with minimal expenditure of resources of the evaluator and the reader himself. This article reveals modern approaches to assessing text understanding, their advantages and disadvantages, and formulates a new promising method for assessing text understanding, based on the Dirichlet Latent Placement model. This method then goes through a validity study through a comparison of the results of its application and the most commonly used modern methods for assessing text understanding, a conclusion is made about its applicability in real conditions and the prospects for use in a range of applied problems.

Sign in / Sign up

Export Citation Format

Share Document