Active Control of Fabricating Nanofibrous Wavy/Helical Arrays Using Near-Field Electrospinning

2018 ◽  
Author(s):  
Xiangyu You ◽  
Ping Guo
Keyword(s):  
Active Control ◽  
Process Parameters ◽  
Electric Field Distribution ◽  
Structural Parameters ◽  
Near Field ◽  
Stretchable Electronics ◽  
Time Varying ◽  
Photovoltaic Devices ◽  
Feature Size ◽  
Experimental Process

A novel and simple near-field electrospinning (NFES) method has been developed to fabricate wavy or helical nanofibrous arrays. By alternating the electrostatic signals applied on auxiliary-electrodes (AE), the structural parameters of deposited patterns can be actively controlled. Compared with the traditional electrospinning methods based on the bending and buckling effects or collector movement, the proposed method shows advantages in the controllability, accuracy, and minimal feature size. Forces operating on the electrospinning jet and the time-varying electric field distribution were analyzed to explain the kinematics of the jet. Nanoscale wavy and helical patterns with various structural parameters were fabricated. The effects of experimental process parameters on structural parameters of deposited patterns were analyzed to demonstrate the controllability of our method in fabricating wavy or helical nanofibrous structures. It is envisioned that this method will benefit the applications in the field of photovoltaic devices, sensors, transducers, resonators, and stretchable electronics.

Real-Time Tuning of Delayed Resonator-Based Absorbers for Spectral and Spatial Variations

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Ryan Jenkins ◽  
Nejat Olgac
Keyword(s):  
Real Time ◽  
Active Control ◽  
Design Guidelines ◽  
Spatial Variations ◽  
Time Varying ◽  
Vibration Absorption ◽  
Spatial Tuning ◽  
System Components ◽  
Hybrid Concept ◽  
Time Variations

This paper offers two interlinked contributions in the field of vibration absorption. The first involves an active tuning of an absorber for spectral and spatial variations. The second contribution is a set of generalized design guidelines for such absorber operations. “Spectral” tuning handles time-varying excitation frequencies, while “spatial” tuning treats the real-time variations in the desired location of suppression. Both objectives, however, must be achieved using active control and without physically altering the system components to ensure practicality. Spatial tuning is inspired by the concept of “noncollocated vibration absorption,” for which the absorber location is different from the point of suppression. This concept is relatively under-developed in the literature, mainly because it requires the use of part of the primary structure (PS) as the extended absorber—a delicate operation. Within this investigation, we employ the delayed resonator (DR)-based absorber, a hybrid concept with passive and active elements, to satisfy both tuning objectives. The presence of active control in the absorber necessitates an intriguing stability investigation of a time-delayed dynamics. For this subtask, we follow the well-established methods of frequency sweeping and D-subdivision. Example cases are also presented to corroborate our findings.

A shuffled frog-leaping algorithm based mixed-sensitivity H∞ control of a seismically excited structural building using MR dampers

2017 ◽  
Vol 24 (13) ◽  
pp. 2832-2852 ◽  
Author(s):  
Xiufang Lin ◽  
Shumei Chen ◽  
Guorong Huang
Keyword(s):  
Active Control ◽  
Passive Control ◽  
Structural Parameters ◽  
Mr Damper ◽  
Inverse Model ◽  
Shuffled Frog Leaping Algorithm ◽  
Weighting Functions ◽  
Inference System ◽  
Mr Dampers ◽  
Shuffled Frog Leaping

An intelligent robust controller, which combines a shuffled frog-leaping algorithm (SFLA) and an H∞ control strategy, is designed for a semi-active control system with magnetorheological (MR) dampers to reduce seismic responses of structures. Generally, the performance of mixed-sensitivity H∞ (MSH) control highly depends on expert experience in selecting the parameters of the weighting functions. In this study, as a recently-developed heuristic approach, a multi-objective SFLA with constraints is adopted to search for the optimal weighting functions. In the proposed semi-active control, firstly, based on the Bouc–Wen model, the forward dynamic characteristics of the MR damper are investigated through a series of tensile and compression experiments. Secondly, the MR damper inverse model is developed with an adaptive-network-based fuzzy inference system (ANFIS) technique. Finally, the SFLA-optimized MSH control approach integrated with the ANFIS inverse model is used to suppress the structural vibration. The simulation results for a three-story building model equipped with an MR damper verify that the proposed semi-active control method outperforms fuzzy control and two passive control methods. Besides, with the proposed strategy, the changes in structural parameters and earthquake excitations can be satisfactorily dealt with.

scholarly journals Wavelet multi-resolution approximation of time-varying frame structure

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879559 ◽  
Author(s):  
Min Xiang ◽  
Feng Xiong ◽  
Yuanfeng Shi ◽  
Kaoshan Dai ◽  
Zhibin Ding
Keyword(s):  
Parameter Estimation ◽  
Degrees Of Freedom ◽  
Structural Parameters ◽  
Identification Problem ◽  
Frame Structure ◽  
Structural Parameter ◽  
Time Varying ◽  
Engineering Structures ◽  
Time Frequency ◽  
Non Parametric

Engineering structures usually exhibit time-varying behavior when subjected to strong excitation or due to material deterioration. This behavior is one of the key properties affecting the structural performance. Hence, reasonable description and timely tracking of time-varying characteristics of engineering structures are necessary for their safety assessment and life-cycle management. Due to its powerful ability of approximating functions in the time–frequency domain, wavelet multi-resolution approximation has been widely applied in the field of parameter estimation. Considering that the damage levels of beams and columns are usually different, identification of time-varying structural parameters of frame structure under seismic excitation using wavelet multi-resolution approximation is studied in this article. A time-varying dynamical model including both the translational and rotational degrees of freedom is established so as to estimate the stiffness coefficients of beams and columns separately. By decomposing each time-varying structural parameter using one wavelet multi-resolution approximation, the time-varying parametric identification problem is transformed into a time-invariant non-parametric one. In solving the high number of regressors in the non-parametric regression program, the modified orthogonal forward regression algorithm is proposed for significant term selection and parameter estimation. This work is demonstrated through numerical examples which consider both gradual variation and abrupt changes in the structural parameters.

Numerical Simulation of Viscous Jet for Near-Field Electrospinning

2009 ◽  
Vol 60-61 ◽  
pp. 465-469 ◽  
Author(s):  
Yuan Yuan Zhong ◽  
Gao Feng Zheng ◽  
Dao Heng Sun
Keyword(s):  
Numerical Simulation ◽  
Field Strength ◽  
Process Parameters ◽  
Near Field ◽  
Solution Concentration ◽  
Electrospinning Process ◽  
Substrate Distance ◽  
Viscous Jet ◽  
Set Up ◽  
The Impact

Near-Field Electrospinning (NFES) is a newly developed method to fabricate continuous and ordered solid nanofibers, with smaller spinneret-to-collector-distance the behavior of viscous jet would play a more prominent effect on the deposition and morphology of nanofiber. In this paper, a 2-dimentional physical model based on electrohydrodynamics and rheology was set up to discuss the morphology of viscous jet for NFES. The profile of the jet along z direction can be predicted by this model, and the impact of process parameters on the jet radius is analyzed. Radius of jet decreases with spinneret-to-substrate-distance decreasing; jet radius decreases with applied voltage and electric field strength increasing; jet electrospun from PEO solution is thinner than that from PVA solution with the same solution concentration; solution concentration has insignificant influence on the radius of jet from solution of the same polymer (PVA or PEO). This numerical simulation would improve the control of electrospinning process in NFES.

scholarly journals High precision epidermal radio frequency antenna via nanofiber network for wireless stretchable multifunction electronics

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Yufei Zhang ◽  
Zhihao Huo ◽  
Xiandi Wang ◽  
Xun Han ◽  
Wenqiang Wu ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Near Field ◽  
Transmission Efficiency ◽  
Stretchable Electronics ◽  
Information Communication ◽  
Long Distance ◽  
Human Machine Interaction ◽  
Natural Systems ◽  
Content Recognition ◽  
Healthcare Monitoring

Abstract Recently, stretchable electronics combined with wireless technology have been crucial for realizing efficient human-machine interaction. Here, we demonstrate highly stretchable transparent wireless electronics composed of Ag nanofibers coils and functional electronic components for power transfer and information communication. Inspired by natural systems, various patterned Ag nanofibers electrodes with a net structure are fabricated via using lithography and wet etching. The device design is optimized by analyzing the quality factor and radio frequency properties of the coil, considering the effects of strain. Particularly, the wireless transmission efficiency of a five-turn coil drops by approximately only 50% at 10 MHz with the strain of 100%. Moreover, various complex functional wireless electronics are developed using near-field communication and frequency modulation technology for applications in content recognition and long-distance transmission (>1 m), respectively. In summary, the proposed device has considerable potential for applications in artificial electronic skins, human healthcare monitoring and soft robotics.

scholarly journals Generation of Flat Top Surface Plasmon Polariton Beams by Near Field Holography

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1377
Author(s):  
Peizhen Qiu ◽  
Chunyan Bai ◽  
Taiguo Lv ◽  
Dawei Zhang
Keyword(s):  
Surface Plasmon ◽  
Surface Plasmon Polariton ◽  
Structural Parameters ◽  
Near Field ◽  
Practical Application ◽  
Plasmonic Device ◽  
Transverse Profile ◽  
Plasmon Polariton ◽  
The Relationship

Controlling the shape and trajectory of the surface plasmon polariton (SPP) beams is the key to all SPP-based applications. In this paper, a novel plasmonic device that can generate in-plane flat top SPP beams is designed by near field holography. The relationship between the transverse profile intensity of the generated flat top SPP beams and the structural parameters of the designed device is analyzed. The results of this paper can provide the possibility for further practical application utilizing flat top SPP beams.

scholarly journals Measurement of the Near Field Distribution of a Microwave Horn Using a Resonant Atomic Probe

2019 ◽  
Vol 9 (22) ◽  
pp. 4895 ◽  
Author(s):  
Jingxu Bai ◽  
Jiabei Fan ◽  
Liping Hao ◽  
Nicholas L. R. Spong ◽  
Yuechun Jiao ◽  
...  
Keyword(s):  
Field Distribution ◽  
Electric Fields ◽  
Microwave Field ◽  
Electric Field Distribution ◽  
Near Field ◽  
Field Measurements ◽  
Amplitude Distribution ◽  
Field Coupling ◽  
All Optical ◽  
Atomic Probe

We measure the near field distribution of a microwave horn with a resonant atomic probe. The microwave field emitted by a standard microwave horn is investigated utilizing Rydberg electromagnetically inducted transparency (EIT), an all-optical Rydberg detection, in a room temperature caesium vapor cell. The ground 6 S 1 / 2 , excited 6 P 3 / 2 , and Rydberg 56 D 5 / 2 states constitute a three-level system, used as an atomic probe to detect microwave electric fields by analyzing microwave dressed Autler–Townes (AT) splitting. We present a measurement of the electric field distribution of the microwave horn operating at 3.99 GHz in the near field, coupling the transition 56 D 5 / 2 → 57 P 3 / 2 . The microwave dressed AT spectrum reveals information on both the strength and polarization of the field emitted from the microwave horn simultaneously. The measurements are compared with field measurements obtained using a dipole metal probe, and with simulations of the electromagnetic simulated software (EMSS). The atomic probe measurement is in better agreement with the simulations than the metal probe. The deviation from the simulation of measurements taken with the atomic probe is smaller than the metal probe, improving by 1.6 dB. The symmetry of the amplitude distribution of the measured field is studied by comparing the measurements taken on either side of the field maxima.

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