scholarly journals An Accurate DDS Method Using Compound Frequency Tuning Word and Its FPGA Implementation

Electronics ◽  
2018 ◽  
Vol 7 (11) ◽  
pp. 330 ◽  
Author(s):  
Yuqing Hou ◽  
Changlong Li ◽  
Sheng Tang
Keyword(s):  
Frequency Synthesizer ◽  
Frequency Tuning ◽  
Low Cost ◽  
Atomic Clock ◽  
Frequency Error ◽  
Frequency Synthesis ◽  
Direct Digital Synthesizer ◽  
Low Power Dissipation ◽  
Conversion Time ◽  
The Stability

Because of its high resolution, low cost, small volume, low power dissipation and less conversion time consumption, the direct digital synthesizer (DDS) method has been applied more and more in the fields of frequency synthesis and signal generation. However, only a limited number of precise frequency signals can be synthesized by the traditional DDS, for the reason that its accumulator modulus is fixed, and its frequency tuning word must be integer. In this paper, a precise DDS method using compound frequency tuning word is proposed, which improves the accuracy of synthesized signals at any frequency points on the premise of guaranteeing the stability of synthesized signals. In order to verify the effectiveness of the new method, a DDS frequency synthesizer based on FPGA is designed and implemented. Taking the rubidium atomic clock PRS10 as standard frequency source, the experiments shows that the frequency stability of the synthesized signal is better than 8.0 × 10−12/s, the relative frequency error is less than 4.8 × 10−12, and that the frequency accuracy is improved by three orders of magnitude compared with the traditional DDS method.

Design and Simulation of Signal Generator Based on FPGA

2014 ◽  
Vol 608-609 ◽  
pp. 949-953
Author(s):  
Qiang Chen
Keyword(s):  
Frequency Synthesizer ◽  
Low Cost ◽  
Basic Structure ◽  
Frequency Synthesis ◽  
Function Generator ◽  
Current Function ◽  
Digital Frequency ◽  
Development Cycle ◽  
Short Development Cycle ◽  
Direct Digital Frequency Synthesizer

The article introduced the basic structure and the realization principle of direct digital frequency synthesizer (DDS), and analyzed main properties of DDS system, compared the different ways to achieve frequency synthesis to determine the design scheme in this paper. In addition to the realization of general waveform, the output of the system can realize any hand-painted waveform, improve the shortcomings of the current function generator, and also has the advantages of low cost, low power consumption, short development cycle, flexible design, has the very good practical value and broad application prospect.

scholarly journals Exploring the Structural Competition between the Black and the Yellow Phase of CsPbI3

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1282
Author(s):  
Ioannis Deretzis ◽  
Corrado Bongiorno ◽  
Giovanni Mannino ◽  
Emanuele Smecca ◽  
Salvatore Sanzaro ◽  
...  
Keyword(s):  
Perovskite Phase ◽  
Low Cost ◽  
Δ Phase ◽  
Nanocrystalline Structures ◽  
Halide Perovskites ◽  
The Stability ◽  
Structural Competition ◽  
Lead Halide ◽  
Main Candidate ◽  
Spontaneous Phase

The realization of stable inorganic perovskites is crucial to enable low-cost solution-processed photovoltaics. However, the main candidate material, CsPbI3, suffers from a spontaneous phase transition at room temperature towards a photo-inactive orthorhombic δ-phase (yellow phase). Here we used theoretical and experimental methods to study the structural and electronic features that determine the stability of the CsPbI3 perovskite. We argued that the two physical characteristics that favor the black perovskite phase at low temperatures are the strong spatial confinement in nanocrystalline structures and the level of electron doping in the material. Within this context, we discussed practical procedures for the realization of long-lasting inorganic lead halide perovskites.

scholarly journals Longevity of Raw and Lyophilized Crude Urease Extracts

2021 ◽  
Vol 2 (2) ◽  
pp. 325-334
Author(s):  
Neda Javadi ◽  
Hamed Khodadadi Tirkolaei ◽  
Nasser Hamdan ◽  
Edward Kavazanjian
Keyword(s):  
Crude Extract ◽  
Room Temperature ◽  
Low Cost ◽  
Extraction Process ◽  
Crude Extracts ◽  
Simple Extraction ◽  
Commercial Applications ◽  
Stable Source ◽  
The Stability ◽  
The Cost

The stability (longevity of activity) of three crude urease extracts was evaluated in a laboratory study as part of an effort to reduce the cost of urease for applications that do not require high purity enzyme. A low-cost, stable source of urease will greatly facilitate engineering applications of urease such as biocementation of soil. Inexpensive crude extracts of urease have been shown to be effective at hydrolyzing urea for carbonate precipitation. However, some studies have suggested that the activity of a crude extract may decrease with time, limiting the potential for its mass production for commercial applications. The stability of crude urease extracts shown to be effective for biocementation was studied. The crude extracts were obtained from jack beans via a simple extraction process, stored at room temperature and at 4 ℃, and periodically tested to evaluate their stability. To facilitate storage and transportation of the extracted enzyme, the longevity of the enzyme following freeze drying (lyophilization) to reduce the crude extract to a powder and subsequent re-hydration into an aqueous solution was evaluated. In an attempt to improve the shelf life of the lyophilized extract, dextran and sucrose were added during lyophilization. The stability of purified commercial urease following rehydration was also investigated. Results of the laboratory tests showed that the lyophilized crude extract maintained its activity during storage more effectively than either the crude extract solution or the rehydrated commercial urease. While incorporating 2% dextran (w/v) prior to lyophilization of the crude extract increased the overall enzymatic activity, it did not enhance the stability of the urease during storage.

scholarly journals A Real-Time Method for Improving Stability of Monolithic Quartz Crystal Microbalance Operating under Harsh Environmental Conditions

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4166
Author(s):  
Román Fernández ◽  
María Calero ◽  
Yolanda Jiménez ◽  
Antonio Arnau
Keyword(s):  
Real Time ◽  
Quartz Crystal Microbalance ◽  
Quartz Crystal ◽  
Limit Of Detection ◽  
Quartz Substrate ◽  
Low Cost ◽  
Discrete Wavelet ◽  
Reagent Consumption ◽  
Measurement Cell ◽  
The Stability

Monolithic quartz crystal microbalance (MQCM) has recently emerged as a very promising technology suitable for biosensing applications. These devices consist of an array of miniaturized QCM sensors integrated within the same quartz substrate capable of detecting multiple target analytes simultaneously. Their relevant benefits include high throughput, low cost per sensor unit, low sample/reagent consumption and fast sensing response. Despite the great potential of MQCM, unwanted environmental factors (e.g., temperature, humidity, vibrations, or pressure) and perturbations intrinsic to the sensor setup (e.g., mechanical stress exerted by the measurement cell or electronic noise of the characterization system) can affect sensor stability, masking the signal of interest and degrading the limit of detection (LoD). Here, we present a method based on the discrete wavelet transform (DWT) to improve the stability of the resonance frequency and dissipation signals in real time. The method takes advantage of the similarity among the noise patterns of the resonators integrated in an MQCM device to mitigate disturbing factors that impact on sensor response. Performance of the method is validated by studying the adsorption of proteins (neutravidin and biotinylated albumin) under external controlled factors (temperature and pressure/flow rate) that simulate unwanted disturbances.

Modal Analyses of Deployable Truss Structures Based on Shape Memory Polymer Composites

2016 ◽  
Vol 08 (07) ◽  
pp. 1640009 ◽  
Author(s):  
Fengfeng Li ◽  
Liwu Liu ◽  
Xin Lan ◽  
Tong Wang ◽  
Xiangyu Li ◽  
...  
Keyword(s):  
Finite Element ◽  
Shape Memory ◽  
Polymer Composites ◽  
Dynamic Properties ◽  
Low Cost ◽  
Shape Memory Polymer ◽  
Truss Structures ◽  
Modal Test ◽  
The Stability ◽  
Mechanical Devices

With large spatial deployable antennas used more widely, the stability of deployable antennas is attracting more attention. The form of the support structure is an important factor of the antenna’s natural frequency, which is essential to study to prevent the resonance. The deployable truss structures based on shape memory polymer composites (SMPCs) have made themselves feasible for their unique properties such as highly reliable, low-cost, light weight, and self-deployment without complex mechanical devices compared with conventional deployable masts. This study offers deliverables as follows: an establishment of three-longeron beam and three-longeron truss finite element models by using ABAQUS; calculation of natural frequencies and vibration modes; parameter studies for influence on their dynamic properties; manufacture of a three-longeron truss based on SMPC, and modal test of the three-longeron truss. The results show that modal test and finite element simulation fit well.

Thinking about Jointly Preventing the “Color Revolution” by China and Russia

2021 ◽  
pp. 100
Author(s):  
chensheng wang
Keyword(s):  
International System ◽  
Low Cost ◽  
The United States ◽  
Regional Security ◽  
Healthy Development ◽  
Regional Coordination ◽  
Color Revolution ◽  
Return Method ◽  
The Stability ◽  
Surrounding Areas

The color revolution, which is a “low-cost and high-return” method in regime change, has become the main mean and priority option for America to subvert dissident regimes. In recent years, with the raising strength of containing and suppressing between China with Russia by the United States, America has tried its best to plan “color revolution” not only around China and Russia, but also within the borders of the two countries. China and Russia have become the key target of America in implementing the “color revolution”, however, the situation of the two countries to prevent the “color revolution” is particularly urgent. The “color revolution” not only disrupts the balance of the international system and regional security, but also seriously affects the stability of the country's political power and the healthy development of the economy. In view of this, it is now necessary for China and Russia to work together to prevent “color revolution”. Regarding the new changes, methods changed from non-violent to violent me, more advanced organizational methods, the younger generation of the participants, and changes in manifestations by the “color revolution”, as well as the underlying causes of the “color revolution”, China and Russia should have uindividualized strategies. China and Russia can strengthen cooperation in different areas, such as politics, economy, culture, ideological education, and regional coordination. China and Russia should take advantages of their respective experiences in dealing with “color revolution”, strengthen sharing and communicating experience with other countries in the region, and jointly build a barrier to prevent “color revolution” and protect the security and stability in China and Russia and the surrounding areas.

scholarly journals Design of area-efficient GHz range current mode frequency synthesizer using standard CMOS technology

2019 ◽  
Vol 70 (4) ◽  
pp. 323-328
Author(s):  
Dan-Dan Zheng ◽  
Yu-Bin Li ◽  
Chang-Qi Wang ◽  
Kai Huang ◽  
Xiao-Peng Yu
Keyword(s):  
Frequency Synthesizer ◽  
Frequency Tuning ◽  
Supply Voltage ◽  
Current Mode ◽  
Cmos Technology ◽  
Mode Frequency ◽  
Loop Filter ◽  
Silicon Area ◽  
Power Efficient ◽  
A Current

Abstract In this paper, an area and power efficient current mode frequency synthesizer for system-on-chip (SoC) is proposed. A current-mode transformer loop filter suitable for low supply voltage is implemented to remove the need of a large capacitor in the loop filter, and a current controlled oscillator with additional voltage based frequency tuning mechanism is designed with an active inductor. The proposed design is further integrated with a fully programmable frequency divider to maintain a good balance among output frequency operating range, power consumption as well as silicon area. A test chip is implemented in a standard 0.13 µm CMOS technology, measurement result demonstrates that the proposed design has a working range from 916 MHz to 1.1 l GHz and occupies a silicon area of 0.25 mm2 while consuming 8.4 mW from a 1.2 V supply.

scholarly journals Low cost and stable quinoxaline-based hole-transporting materials with a D–A–D molecular configuration for efficient perovskite solar cells

2018 ◽  
Vol 9 (27) ◽  
pp. 5919-5928 ◽  
Author(s):  
Hao Zhang ◽  
Yongzhen Wu ◽  
Weiwei Zhang ◽  
Erpeng Li ◽  
Chao Shen ◽  
...  
Keyword(s):  
Solar Cells ◽  
Electron Acceptor ◽  
Low Cost ◽  
Photovoltaic Performance ◽  
Perovskite Solar Cells ◽  
Molecular Configuration ◽  
Hole Transporting ◽  
The Stability ◽  
Hole Transporting Materials ◽  
Weak Electron

Molecular hole-transporting materials containing a weak electron acceptor core can simultaneously improve the stability and photovoltaic performance of perovskite solar cells.

Solution-processed whispering-gallery-mode microsphere lasers based on colloidal CsPbBr3 perovskite nanocrystals

2021 ◽  
Author(s):  
Minghong Xie ◽  
Wenxiao Gong ◽  
Lei Kong ◽  
Yang Liu ◽  
Yang Mi ◽  
...  
Keyword(s):  
High Performance ◽  
Low Cost ◽  
Single Mode ◽  
Whispering Gallery Mode ◽  
Solution Processed ◽  
Time Resolved ◽  
Perovskite Nanocrystals ◽  
Whispering Gallery ◽  
Low Threshold ◽  
The Stability

Abstract Perovskite nanocrystals (NCs) have emerged as attractive gain materials for solution-processed microlasers. Despite the recent surge of reports in this feld, it is still challenging to develop low-cost perovskite NCbased microlasers with high performance. Herein, we demonstrate low-threshold, spectrally tunable lasing from ensembles of CsPbBr3 NCs deposited on silica microspheres. Multiple whispering-gallery-mode lasing is achieved from individual NC/microspheres with a low threshold of ∼3.1 µJ cm−2 and cavity quality factor of ∼1193. Through time-resolved photoluminescence measurements, electron-hole plasma recombination is elucidated as the lasing mechanism. By tuning the microsphere diameter, the desirable single-mode lasing is successfully achieved. Remarkably, the CsPbBr3 NCs display durable room-temperature lasing under ∼107 shots of pulsed laser excitation, substantially exceeding the stability of conventional colloidal NCs. These CsPbBr3 NC-based microlasers can be potentially useful in photonic applications.

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