A Piezoelectric on Substrate Phononic Band Gap High-Q Micromechanical Resonator

2009 ◽  
Author(s):  
Saeed Mohammadi ◽  
Ali Asghar Eftekhar ◽  
Ali Adibi
Keyword(s):  
High Frequency ◽  
High Efficiency ◽  
Mechanical Energy ◽  
Phononic Crystal ◽  
Building Blocks ◽  
Piezoelectric Medium ◽  
Resonant Structure ◽  
High Quality ◽  
High Q ◽  
Sensing Applications

Micromechanically-fabricated phononic crystal (PnC) structures with phononic band gaps (PnBGs) are gaining a growing attention due to their high efficiency in controlling and confining mechanical energy in micro and nano-scale structures. Preliminary PnC devices such as waveguides and resonators based on the complete PnBG of the micro-machined PnC structures have shown a great potential to improve the characteristics of the conventional micro-mechanical (MM) devices [1–5]. Especially high-frequency, high-quality factor (Q) MM resonators are of great interest as they are main building blocks for realizing compact and complex devices such as filters, multiplexers and de-multiplexers for wireless communications and sensing applications. Therefore, development of high-Q, high-frequency PnC-based MM resonators is an important step towards realizing functional PnC-based devices with potentially better performance compared to their conventional counterparts. In this paper, we report, for the first time, a PnC slab piezoelectric-on-substrate MM resonator operating at VHF frequencies which supports high Q modes. The excitation of the resonant modes in these structures is done directly on the resonant structure (in contrast to the resonant tunneling excitation method reported earlier [5]) and therefore, no coupling from outside of the resonant structure is required. In such a structure, enough number of PnC periods can be placed around the resonant region to provide enough isolation from the surroundings; consequently the loss of the mechanical energy will be limited to material and friction losses only. We report a Fabry-Perot-type PnC slab resonator with an electrode and a piezoelectric medium directly fabricated on top of a resonant structure and show that high quality factors can be obtained in such a compact resonator. As a result, a flexural and a longitudinal mode are excited. Q’s of more than 3600 and 10,000 are obtained for the two modes with motional resistances of 1200 Ω and 5000 Ω. Such piezoelectrically excited high-Q resonators operating at such high frequencies evidence the possibility of suppressing support loss (an important source of loss) in MM resonators through the use of the especial structure of a PnC. Such PnC resonators can have a great impact on the current state-of-the-art MM devices used in wireless communication and sensing systems.

GHz Heterogeneous Phononic Crystal Slab Resonators

2015 ◽  
Author(s):  
Razi Dehghannasiri ◽  
Reza Pourabolghasem ◽  
Ali Asghar Eftekhar ◽  
Ali Adibi
Keyword(s):  
Wireless Communications ◽  
High Frequency ◽  
Phononic Crystal ◽  
Smooth Transition ◽  
Frequency Range ◽  
High Q ◽  
Guided Modes

In this paper, we present a new design for waveguide-based phononic crystal (PnC) resonators in pillar-based piezoelectric membranes at the GHz frequency range based on mode-gap waveguide termination. The mode confinement in these resonators is achieved by a smooth transition from a phononic waveguide to another phononic waveguide that does not support (and therefore reflects) the guided modes of the first waveguide over a certain frequency range. These resonators can be utilized for applications including wireless communications and sensing [1, 2] where high-Q and high-frequency resonators are highly desirable.

scholarly journals Ultra-high frequency, high Q/volume micromechanical resonators in a planar AlN phononic crystal

2016 ◽  
Vol 120 (3) ◽  
pp. 034502 ◽  
Author(s):  
M. Ghasemi Baboly ◽  
S. Alaie ◽  
C. M. Reinke ◽  
I. El-Kady ◽  
Z. C. Leseman
Keyword(s):  
High Frequency ◽  
Phononic Crystal ◽  
Micromechanical Resonators ◽  
Ultra High Frequency ◽  
High Q

scholarly journals Anchor Loss Reduction of Lamb Wave Resonator by Pillar-Based Phononic Crystal

Micromachines ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 62
Author(s):  
Yinjie Tong ◽  
Tao Han
Keyword(s):  
Lamb Wave ◽  
High Frequency ◽  
Transmission Loss ◽  
Mechanical Energy ◽  
Phononic Crystal ◽  
Center Frequency ◽  
Electromechanical Coupling Coefficient ◽  
Wave Resonator ◽  
Energy Leakage ◽  
Anchor Loss

Energy leakage via anchors in substrate plates impairs the quality factor (Q) in microelectromechanical system (MEMS) resonators. Most phononic crystals (PnCs) require complicated fabrication conditions and have difficulty generating a narrow bandgap at high frequency. This paper demonstrates a pillar-based PnC slab with broad bandgaps in the ultra high frequency (UHF) range. Due to Bragg interference and local resonances, the proposed PnC structure creates notably wide bandgaps and shows great advantages in the high frequency, large electromechanical coupling coefficient (k2) thin film aluminum nitride (AlN) lamb wave resonator (LWR). The dispersion relations and the transmission loss of the PnC structure are presented. To optimize the bandgap, the influence of the material mechanical properties, lattice type, pillar height and pillar radius are explored. These parameters are also available to adjust the center frequency of the bandgap to meet the desirable operating frequency. Resonators with uniform beam anchors and PnC slab anchors are characterized. The results illustrate that the Q of the resonator improves from 1551 to 2384, and the mechanical energy leakage via the anchors is significantly decreased using the proposed PnC slab anchors. Moreover, employment of the PNC slab anchors has little influence on resonant frequency and induces no spurious modes. Pillar-based PnCs are promising in suppressing the anchor loss and further improving the Q of the resonators.

Transistors based on solution-processed 2D materials for chemical and biological sensing

2021 ◽  
Author(s):  
Wanzhen Xu ◽  
Wei Han ◽  
Junliang Shen ◽  
Wenjie Zhu ◽  
Wenming Yang ◽  
...  
Keyword(s):  
High Performance ◽  
High Efficiency ◽  
2D Materials ◽  
High Sensitivity ◽  
Research Field ◽  
High Quality ◽  
Solution Processed ◽  
Environmental Friendliness ◽  
Sensing Applications ◽  
Solution Methods

Abstract Two-dimensional (2D) materials have attracted much attention due to their unique chemical and physical characteristics. The specific structures and large surface area of 2D materials lead to great potentials in sensing applications with the advantages of high sensitivity, high efficiency and environmental friendliness. As a result, a great variety of devices have been developed based on 2D materials and utilized as electronic, chemical, biological, and even multifunctional sensors. Importantly, the high performance of these sensors is largely attributed to the synthetic strategies of high-quality 2D materials, where the exfoliation in the liquid phase is one of the most efficient methods. In this review, we firstly summarize the recent progress on the solution methods for the synthesis of high-quality graphene as well as non-carbon 2D materials. Then the main focus of this review article is shifted to the transistor-type sensors, especially the biosensors and chemical sensors, on the basis of these solution-processed 2D materials. In addition, the remaining challenges in this research field are discussed, and possible future directions of development are also proposed from the aspects of materials, processing and devices.

Method of high frequency therapy at cows' mastitis during machine milking

2020 ◽  
pp. 9-12
Author(s):  
Viktor E. Lyubimov ◽  
Keyword(s):  
Dairy Cows ◽  
Electromagnetic Fields ◽  
High Frequency ◽  
High Efficiency ◽  
Environmentally Friendly ◽  
Ultrahigh Frequency ◽  
Machine Milking ◽  
High Frequency Electromagnetic Field ◽  
Milking Machine ◽  
Methods Of Treatment

Health of dairy cows ensures human health, so it is important that dairy products do not contain antibiotics that are used to treat any inflammation, including mastitis. In Russia at present, the problem of mastitis in cows exists with both attached and loose housing of cows. Mastitis of dairy cows are the great problem in milking husbandry. Losses from mastitis in milk yield can reach 15-20%. The main reasons for the occurrence of nonspecific mastitis of cows are the shortcomings of the working components of the milking machine: the degree of deterioration of the nipple rubber and the violation of machine milking technology (the reduction in pre-milking time and vacuum fluctuations account for 70% of all causes). Treatment of mastitis with antibiotics is effective, but not environmentally friendly and unacceptable. For the treatment of inflammation of the udder, it is necessary to use more environmentally friendly methods of treatment, one of which is the exposure to ultra-high frequency electromagnetic field tested by medicine. Use of three types of medical-mobile milking machines with the same method of exposure to ultrahigh-frequency electromagnetic fields on cow's nipples through electrodes in milking cups: LPDA-1-UHF, LPDA-2-UHF and LPDA-UHF-30 M, is described in the article. Author proved that cows with subclinical forms of mastitis recovered faster during milking with exposure to the ultrahigh frequency than when treated by antibiotics, and milking with the ultrahigh frequency device helps to recover 82% of the affected quarters with clinical forms and 100% of cows with subclinical forms of mastitis or with udder irritation. The high efficiency of the method of exposure to electromagnetic fields of the ultrahigh frequency during machine milking by means of medical-mobile milking machines LPDA-UHF for the prevention and treatment of mastitis of cows was shown.

Electrochemical Oxidative Esterification of Thiophenols: Efficient Access to Sulfinic Esters

2020 ◽  
Vol 17 (7) ◽  
pp. 540-547
Author(s):  
Chun-Hui Yang ◽  
Cheng Wu ◽  
Jun-Ming Zhang ◽  
Xiang-Zhang Tao ◽  
Jun Xu ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Efficient Method ◽  
High Efficiency ◽  
Building Blocks ◽  
Constant Current ◽  
Good Efficiency ◽  
Oxidative Esterification ◽  
Efficient Access ◽  
New Applications ◽  
Sulfinic Esters

Background: The sulfinic esters are important and useful building blocks in organic synthesis. Objective: The aim of this study was to develop a simple and efficient method for the synthesis of sulfinic esters. Materials and Methods: Constant current electrolysis from thiols and alcohols was selected as the method for the synthesis of sulfinic esters. Results and Discussion: A novel electrochemical method for the synthesis of sulfinic esters from thiophenols and alcohols has been developed. Up to 27 examples of sulfinic esters have been synthesized using the current methods. This protocol shows good functional group tolerance as well as high efficiency. In addition, this protocol can be easily scaled up with good efficiency. Notably, heterocycle-containing substrates, including pyridine, thiophene, and benzothiazole, gave the desired products in good yields. A plausible reaction mechanism is proposed. Conclusion: This research not only provides a green and efficient method for the synthesis of sulfinic esters but also shows new applications of electrochemistry in organic synthesis. It is considered that this green and efficient synthetic protocol used to prepare sulfinic esters will have good applications in the future.

scholarly journals 2D-3D integration of hexagonal boron nitride and a high-κ dielectric for ultrafast graphene-based electro-absorption modulators

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hitesh Agarwal ◽  
Bernat Terrés ◽  
Lorenzo Orsini ◽  
Alberto Montanaro ◽  
Vito Sorianello ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hafnium Oxide ◽  
High Speed ◽  
Hexagonal Boron Nitride ◽  
Temperature Stability ◽  
Cost Effective ◽  
Fold Increase ◽  
Building Blocks ◽  
High Quality ◽  
New Device

AbstractElectro-absorption (EA) waveguide-coupled modulators are essential building blocks for on-chip optical communications. Compared to state-of-the-art silicon (Si) devices, graphene-based EA modulators promise smaller footprints, larger temperature stability, cost-effective integration and high speeds. However, combining high speed and large modulation efficiencies in a single graphene-based device has remained elusive so far. In this work, we overcome this fundamental trade-off by demonstrating the 2D-3D dielectric integration in a high-quality encapsulated graphene device. We integrated hafnium oxide (HfO2) and two-dimensional hexagonal boron nitride (hBN) within the insulating section of a double-layer (DL) graphene EA modulator. This combination of materials allows for a high-quality modulator device with high performances: a ~39 GHz bandwidth (BW) with a three-fold increase in modulation efficiency compared to previously reported high-speed modulators. This 2D-3D dielectric integration paves the way to a plethora of electronic and opto-electronic devices with enhanced performance and stability, while expanding the freedom for new device designs.

scholarly journals An Underwater Image Enhancement Algorithm Based on Generative Adversarial Network and Natural Image Quality Evaluation Index

2021 ◽  
Vol 9 (7) ◽  
pp. 691
Author(s):  
Kai Hu ◽  
Yanwen Zhang ◽  
Chenghang Weng ◽  
Pengsheng Wang ◽  
Zhiliang Deng ◽  
...  
Keyword(s):  
Image Quality ◽  
Image Enhancement ◽  
Quality Evaluation ◽  
High Efficiency ◽  
Natural Image ◽  
High Quality ◽  
Generative Adversarial Network ◽  
Image Quality Evaluation ◽  
Adversarial Network ◽  
Underwater Image

When underwater vehicles work, underwater images are often absorbed by light and scattered and diffused by floating objects, which leads to the degradation of underwater images. The generative adversarial network (GAN) is widely used in underwater image enhancement tasks because it can complete image-style conversions with high efficiency and high quality. Although the GAN converts low-quality underwater images into high-quality underwater images (truth images), the dataset of truth images also affects high-quality underwater images. However, an underwater truth image lacks underwater image enhancement, which leads to a poor effect of the generated image. Thus, this paper proposes to add the natural image quality evaluation (NIQE) index to the GAN to provide generated images with higher contrast and make them more in line with the perception of the human eye, and at the same time, grant generated images a better effect than the truth images set by the existing dataset. In this paper, several groups of experiments are compared, and through the subjective evaluation and objective evaluation indicators, it is verified that the enhanced image of this algorithm is better than the truth image set by the existing dataset.

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