scholarly journals Feasibility analysis for active near/far field acoustic pattern synthesis in free space and shallow water environments

Acta Acustica ◽  
2021 ◽  
Vol 5 ◽  
pp. 39
Author(s):  
Chaoxian Qi ◽  
Neil Jerome A. Egarguin ◽  
Daniel Onofrei ◽  
Jiefu Chen
Keyword(s):  
Control Region ◽  
Free Space ◽  
Feasibility Analysis ◽  
Mutual Distance ◽  
Power Budget ◽  
Pattern Synthesis ◽  
Process Error ◽  
Control Scheme ◽  
Field Control ◽  
Acoustic Pattern

In this paper, a detailed sensitivity and feasibility analysis of the active manipulation scheme for scalar Helmholtz fields proposed in our previous works, in both free space and constant-depth homogeneous ocean environments, is presented. We apply the method of moments (MoM) together with Tikhonov regularization with the Morozov discrepancy principle to investigate the effects of varying the problem parameters to the accuracy and feasibility of the proposed active field control strategy. We discuss the feasibility of the active scheme (with respect to power budget, control accuracy and process error) as a function of the frequency, the distance between the control region and the source, the mutual distance between the control regions, and the size of the control region. Process error is considered as well to investigate the possibility of an accurate active control in the presence of manufacturing or feeding noise. The numerical simulations show the accuracy of the active field control scheme and indicate some challenges and limitations for its physical implementation.

Hybrid WDM free space optical system using CSRZ and Rayleigh backscattering noise mitigation

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Rupinder Kaur ◽  
Charanjit Singh ◽  
Rajbir Kaur
Keyword(s):  
Wavelength Division Multiplexing ◽  
Free Space ◽  
Free Space Optical ◽  
Power Budget ◽  
Noise Mitigation ◽  
Wavelength Division ◽  
Rayleigh Backscattering ◽  
Beat Noise ◽  
Optical Line ◽  
Insertion Losses

Abstract Hybrid wavelength-division-multiplexing (WDM) and free space optical (FSO) access networks are getting great attention due to numerous advantages. In this work, hybrid WDM-FSO system is demonstrated for 55 km at capacity of 5 × 10 Gbit/s using compressed spectrum return to zero (CSRZ) WDM-FSO in downstream and nonreturn to zero (NRZ) in upstream for demonstrating transmitter diversity which inturn decrease the interchannel interference. For the suppression of Rayleigh backscattering (RB) interferometric beat noise, bidirectional cyclic multiplexer is employed. Cyclic multiplexer provide λ 1 to λ 5 wavelengths for optical line terminal (OLT) to ONU transmission and λ 2 to λ 6 for ONU to OLT transmission. Insertion losses of each component are considered and in the end, power budget is also calculated. Results revealed that FSO length of 780–1050 m are obtained using various WDM-FSO downstream signals and their power budget, redundant budget, maximum distance, and insertion losses also calculated.

Feasibility analysis of an active local field control at the poloidal gap of RFX

1997 ◽  
pp. 771-774 ◽  
Author(s):  
F. Bellina ◽  
G. Chitarin ◽  
P. Fiorentin ◽  
E. Gaio ◽  
G. Marchiori ◽  
...  
Keyword(s):  
Local Field ◽  
Feasibility Analysis ◽  
Field Control

A Hierarchical Approach to Manipulator Velocity Field Control Considering Dynamic Friction Compensation

2005 ◽  
Vol 128 (3) ◽  
pp. 670-674 ◽  
Author(s):  
Javier Moreno-Valenzuela ◽  
Rafael Kelly
Keyword(s):  
Velocity Field ◽  
Degrees Of Freedom ◽  
Friction Compensation ◽  
Velocity Control ◽  
Hierarchical Approach ◽  
Direct Drive ◽  
Kinematic Control ◽  
Control Scheme ◽  
Field Control ◽  
Joint Velocity

The velocity field control of robot manipulators is addressed in this paper. The proposed algorithm has a hierarchical structure based on a velocity field kinematic control scheme for joint velocity resolution and an inner loop of joint velocity control that uses an observer for friction compensation. Experiments on a two degrees-of-freedom direct-drive arm illustrate the performance of the proposed controller.

scholarly journals Feasibility Analysis Of Free Space Earth To Satellite Optical Link In Tropical Region

2012 ◽  
Vol 12 (5) ◽  
Author(s):  
Norhanis Aida M. Nor ◽  
Md. Rafiqul Islam ◽  
Wajdi Al-Khateeb
Keyword(s):  
Electromagnetic Interference ◽  
Free Space ◽  
Elevation Angle ◽  
Rain Attenuation ◽  
Low Earth Orbit ◽  
Feasibility Analysis ◽  
Free Space Optics ◽  
Tropical Region ◽  
Earth Orbit ◽  
Space Optics

Free Space Optics (FSO) becomes a great attention because of the chances in transmitting data up to 2.5Gbps. There are a lot of advantages offered by FSO such as easily deployment with saving time and cost and no electromagnetic interference. In spite of the advantages, FSO has an uncontrolled drawback which is highly sensitive to atmospheric phenomena because uses air as tranmission medium. Current studies and researches are only focusing on FSO terrestrial link with short path length and based on data from temperate region. Therefore, this paper is aiming to provide feasibility analysis of FSO link from earth to satellite especially Low Earth Orbit (LEO) based on atmospheric data in tropical region. The analysis will include the losses from geometrical attenuation, absorption, scintillation, haze attenuation, and rain attenuation. ABSTRAK: Ruang Bebas Optik (Free Space Optics (FSO)) mendapat perhatian kerana kebolehannya memancarkan data pada kelajuan tinggi. Di sebalik kelebihannya, FSO amat sensitif terhadap fenomena atmosfera kerana ia menggunakan udara sebagai perantara transmisi. Penyelidikan dan kajian terkini hanya memfokus kepada jalinan darat FSO dengan kepanjangan jarak pendek dan bergantung kepada kawasan tenang.  Oleh itu, kertas ini menyasarkan untuk memberikan analisis kebolehlaksanaan  jalinan FSO dari bumi ke satelit terutamanya Orbit Rendah Bumi (Low Earth Orbit (LEO)) bergantung kepada data atmosfera di kawasan tropika. Analisa termasuklah kehilangannya akibat pengecilan geometri, penyerapan, kelipan, pelemahan jerebu dan pelemahan hujan.KEYWORDS:  feasibility; Free Space Optics; availability; atmospheric attenuation; beam divergence angle; elevation angle

scholarly journals Dispersion Limited versus Power Limited Terahertz Transmission Links Using Solid Core Subwavelength Dielectric Fibers

2020 ◽  
Author(s):  
Kathirvel Nallappan ◽  
Yang Cao ◽  
Hichem Guerboukha ◽  
Chahé Nerguizian ◽  
Maksim Skorobogatiy
Keyword(s):  
Free Space ◽  
Communication Systems ◽  
High Speed ◽  
Short Range ◽  
Numerical Study ◽  
Propagation Loss ◽  
Superior Performance ◽  
Solid Core ◽  
Power Budget ◽  
Link Length

Terahertz (THz) band (0.1 THz-10 THz) is the next frontier for the ultra-high-speed communication systems. Currently, most of communications research in this spectral range is focused on wireless systems, while waveguide/fiber-based links have been less explored. Although free space communications have several advantages such as convenience in mobility for the end user, as well as easier multi-device interconnectivity in simple environments, the fiber-based communications provide superior performance in certain short-range communication applications such as multi-device connectivity in complex geometrical environments (ex. intra-vehicle connectivity), secure communications with low probability of eavesdropping, as well as secure signal delivery to hard-to-reach or highly protected environments. In this work, we present an in-depth experimental and numerical study of the short-range THz communications links that use subwavelength dielectric fibers for information transmission and define main challenges and tradeoffs in the link implementation. Particularly, we use air or foam-cladded polypropylene-core subwavelength dielectric THz fibers of various diameters (0.57-1.75 mm) to study link performance as a function of the link length of up to ~10 m, and data bitrates of up to 6 Gbps at the carrier frequency of 128 GHz (2.34 mm wavelength). We find that depending on the fiber diameter, the quality of the transmitted signal is mostly limited either by the modal propagation loss or by the fiber velocity dispersion (GVD). An error-free transmission over 10 meters is achieved for the bit rate of 4 Gbps using the fiber of smaller 0.57 mm diameter. Furthermore, since the fields of subwavelength fibers are weakly confined and extend deep into the air cladding, we study the modal field extent outside of the fiber core, as well as fiber bending loss. Finally, the power budget of the rod-in-air subwavelength THz fiber-based links is compared to that of free space communication links and we demonstrate that fiber links offer an excellent solution for various short-range applications.

scholarly journals A Multiposture Locomotor Training Device with Force-Field Control

2014 ◽  
Vol 6 ◽  
pp. 173518 ◽  
Author(s):  
Jianfeng Sui ◽  
Yali Liu ◽  
Runze Yang ◽  
Linhong Ji
Keyword(s):  
Lower Limb ◽  
Closed Loop ◽  
Closed Loop Control ◽  
Locomotor Training ◽  
Training Device ◽  
Loop Control ◽  
Lower Limb Exoskeleton ◽  
Weight Support ◽  
Control Scheme ◽  
Field Control

This paper introduces a multiposture locomotor training device (MPLTD) with a closed-loop control scheme based on joint angle feedback, which is able to overcome various difficulties resulting from mechanical vibration and the weight of trainer to achieve higher accuracy trajectory. By introducing the force-field control scheme used in the closed-loop control, the device can obtain the active-constrained mode including the passive one. The MPLTD is mainly composed of three systems: posture adjusting and weight support system, lower limb exoskeleton system, and control system, of which the lower limb exoskeleton system mainly includes the indifferent equilibrium mechanism with two degrees of freedom (DOF) and the driving torque is calculated by the Lagrangian function. In addition, a series of experiments, the weight support and the trajectory accuracy experiment, demonstrate a good performance of mechanical structure and the closed-loop control.

scholarly journals Stratospheric QKD: feasibility analysis and free-space optics system concept

2019 ◽  
Author(s):  
Florian Moll ◽  
Thierry Botter ◽  
Christoph Marquardt ◽  
David Pusey ◽  
Amita Shrestha ◽  
...  
Keyword(s):  
Free Space ◽  
Feasibility Analysis ◽  
Free Space Optics ◽  
Space Optics ◽  
System Concept
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