Assessment of a practical technique for active control of sound using microphone and speaker

AbstractIn this analytical study, it has been desired to develop a practical and simple control mechanism to control, at a given point and its neighborhood, the sound arriving from a distant source, assuming that a primary pure-tone sound pressure is propagated from a relatively far distance. The control model consists of a microphone as a sensor for measuring the sound pressure and a loud speaker for applying the control force. Corresponding equations have been developed to determine an optimum control force, and afterwards a parametric study on the factors affecting the control results has been performed. The results show that the control system can significantly reduce low frequency sound pressure in the region near the target point. The results also demonstrate less effectiveness in controlling high frequency sound pressures. Moreover, the larger the distance of the loudspeaker to the given controlled point is, the wider the controlled area will be. Also, it was found that though the distance between the sensor and the actuator does not have any effect on the size of the area which can be controlled, such distance is of greatest importance in that the available time to control increases directly by increasing the distance

Effect of hydroalcoholic extract of Matricaria chamomilla on passive avoidance memory and pain induced by global cerebral ischemia in Wistar rat

زمینه و هدف : ایسکمی مغزی و خونرسانی مجدد علت اصلی ناتوانی جدی و طولانی مدت در جهان است. هدف از مطالعه حاضر بررسی اثر عصاره هیدروالکلی بابونه بر اختلالات حافظه و درد ناشی از ایسکمی بود. روش بررسی: گل‌های خشک بابونه (Matricaria chamomilla) از عطاری تهیه شده و توسط الکل 70 درصد عصاره گیری شد. حیوانات به صورت تصادفی به 6 گروه 7 تایی تقسیم شدند. گروه کنترل فقط نرمال سالین دریافت کردند، گروه ایسکمی تحت ایسکمی قرار گرفته و نرمال سالین دریافت کردند، گروه شاهد(sham): تحت جراحی قرار گرفتند بدون اینکه شریان‌های کاروتید آن‌ها بسته شود. گروه‌های درمانی با عصاره تحت ایسکمی قرار گرفته و عصاره بابونه را به صورت داخل صفاقی در دوز 50، 100 و 200 میلی‌گرم بر کیلوگرم وزن بدن دریافت کردند. تست رفتاری توسط شاتل باکس و تست ضد درد توسط تست تیل فیلیک انجام شد. یافته ها : عصاره بابونه در غلظت‌های 50، 100 و 200 میلی‌گرم بر کیلوگرم حافظه احترازی غیرفعال موش‌های صحرایی تحت ایسکمی را به طور معنی‌دار افزایش داد. علاوه بر این عصاره بابونه زمان تأخیر ظهور رفلکس دردناک دم را در تست تیل فلیک به طور معنی‌داری افزایش داد و غلظت 50 میلی‌گرم بر کیلوگرم عصاره اثر بیشتری نسبت به غلظت‌های بالاتر آن نشان داد. بحث و نتیجه گیری: نتایج مطالعه حاضر حاکی از اثرات حفاظتی عصاره بابونه در برابر اختلال حافظه احترازی و درد ایجاد شده در اثر ایسکمی بود که احتمالا به دلیل اثرات آنتی‌اکسیدانی و ضدالتهابی عصاره گیاه می‌باش

Robust prescribed trajectory tracking control of a robot manipulator using adaptive finite-time sliding mode and extreme learning machine method

This study aims to provide a robust trajectory tracking controller which guarantees the prescribed performance of a robot manipulator, both in transient and steady-state modes, experiencing parametric uncertainties. The main core of the controller is designed based on the adaptive finite-time sliding mode control (SMC) and extreme learning machine (ELM) methods to collectively estimate the parametric model uncertainties and enhance the quality of tracking performance. Accordingly, the global estimation with a fast convergence rate is achieved while the tracking error and the impact of chattering on the control input are mitigated significantly. Following the control design, the stability of the overall control system along with the finite-time convergence rate is proved, and the effectiveness of the proposed method is investigated via extensive simulation studies. The results of simulations confirm that the prescribed transient and steady-state performances are obtained with enough accuracy, fast convergence rate, robustness, and smooth control input which are all required for practical implementation and applications

Experimental and numerical study of elasto-inertial focusing in straight channels.

Elasto-inertial microfluidics has drawn significant attention in recent years due to its enhanced capabilities compared to pure inertial systems in control of small microparticles. Previous investigations have focused mainly on the applications of elasto-inertial sorting, rather than studying its fundamentals. This is because of the complexity of simulation and analysis, due to the presence of viscoelastic force. There have been some investigative efforts on the mechanisms of elasto-inertial focusing in straight channels; however, these studies were limited to simple rectangular channels and neglected the effects of geometry and flow rates on focusing positions. Herein, for the first time, we experimentally and numerically explore the effects of elasticity accompanying channel cross-sectional geometry and sample flow rates on the focusing phenomenon in elasto-inertial systems. The results reveal that increasing the aspect ratio weakens the elastic force more than inertial force, causing a transition from one focusing position to two. In addition, they show that increasing the angle of a channel corner causes the elastic force to push the particles more efficiently toward the center over a larger area of the channel cross section. Following on from this, we proposed a new complex straight channel which demonstrates a tighter focusing band compared to other channel geometries. Finally, we focused Saccharomyces cerevisiae cells (3-5 μm) in the complex channel to showcase its capability in focusing small-size particles. We believe that this research work improves the understanding of focusing mechanisms in viscoelastic solutions and provides useful insights into the design of elasto-inertial microfluidic devices

Development of a Biomimetic Semicircular Canal with MEMS Sensors to Restore Balance

© 2001-2012 IEEE. A third of adults over the age of 50 suffer from chronic impairment of balance, posture, and/or gaze stability due to partial or complete impairment of the sensory cells in the inner ear responsible for these functions. The consequences of impaired balance organ can be dizziness, social withdrawal, and acceleration of the further functional decline. Despite the significant progress in biomedical sensing technologies, current artificial vestibular systems fail to function in practical situations and in very low frequencies. Herein, we introduced a novel biomechanical device that closely mimics the human vestibular system. A microelectromechanical systems (MEMS) flow sensor was first developed to mimic the vestibular haircell sensors. The sensor was then embedded into a three-dimensional (3D) printed semicircular canal and tested at various angular accelerations in the frequency range from 0.5Hz to 1.5Hz. The miniaturized device embedded into a 3D printed model will respond to mechanical deflections and essentially restore the sense of balance in patients with vestibular dysfunctions. The experimental and simulation studies of semicircular canal presented in this work will pave the way for the development of balance sensory system, which could lead to the design of a low-cost and commercially viable medical device with significant health benefits and economic potential

Fabrication of unconventional inertial microfluidic channels using wax 3D printing.

Inertial microfluidics has emerged over the past decade as a powerful tool to accurately control cells and microparticles for diverse biological and medical applications. Many approaches have been proposed to date in order to increase the efficiency and accuracy of inertial microfluidic systems. However, the effects of channel cross-section and solution properties (Newtonian or non-Newtonian) have not been fully explored, primarily due to limitations in current microfabrication methods. In this study, we overcome many of these limitations using wax 3D printing technology and soft lithography through a novel workflow, which eliminates the need for the use of silicon lithography and polydimethylsiloxane (PDMS) bonding. We have shown that by adding dummy structures to reinforce the main channels, optimizing the gap between the dummy and main structures, and dissolving the support wax on a PDMS slab to minimize the additional handling steps, one can make various non-conventional microchannels. These substantially improve upon previous wax printed microfluidic devices where the working area falls into the realm of macrofluidics rather than microfluidics. Results revealed a surface roughness of 1.75 μm for the printed channels, which does not affect the performance of inertial microfluidic devices used in this study. Channels with complex cross-sections were fabricated and then analyzed to investigate the effects of viscoelasticity and superposition on the lateral migration of the particles. Finally, as a proof of concept, microcarriers were separated from human mesenchymal stem cells using an optimized channel with maximum cell-holding capacity, demonstrating the suitability of these microchannels in the bioprocessing industry

The attentive focus on T cell-mediated autoimmune pathogenesis of psoriasis, lichen planus and vitiligo

T cell-mediated autoimmune skin diseases develop as a result of the aberrant immune response to the skin cells with T cells playing a central role. These chronic inflammatory skin diseases encompass various types including psoriasis, lichen planus and vitiligo. These diseases show similarities in their immune-pathophysiology. In the last decade, immunomodulating agents have been very successful in the management of these diseases thanks to a better understanding of the pathophysiology. In this review, we will discuss the immunopathogenic mechanisms and highlight the role of T lymphocytes in psoriasis, lichen planus and vitiligo. This study could provide new insights into a better understanding of targeted therapeutic pathways and biological therapies. © 2020 The Scandinavian Foundation for Immunolog

C17 Prevents Inflammatory Arthritis and Associated Joint Destruction in Mice

C17 was first described about ten years ago as a gene expressed in CD34+ cells. A more recent study has suggested a role for C17 in chondrogenesis and development of cartilage. However, based on sequence analysis, we believe that C17 has homology to IL-2 and hence we present the hypothesis that C17 is a cytokine possessing immune-regulatory properties. We provide evidence that C17 is a secreted protein preferentially expressed in chondrocytes, hence in cartilage-rich tissues. Systemic expression of C17 in vivo reduces disease in a collagen antibody-induced arthritis model in mice (CAIA). Joint protection is evident by delayed disease onset, minimal edema, bone protection and absence of diverse histological features of disease. Expression of genes typically associated with acute joint inflammation and erosion of cartilage or bone is blunted in the presence of C17. Consistent with the observed reduction in bone erosion, we demonstrate reduced levels of RANKL in the paws and sera of mice over-expressing C17. Administration of C17 at the peak of disease, however, had no effect on disease progression, indicating that C17's immune-regulatory activity must be most prominent prior to or at the onset of severe joint inflammation. Based on this data we propose C17 as a cytokine that s contributes to immune homeostasis systemically or in a tissue-specific manner in the joint

Coupling of CFD and semiempirical methods for designing three-phase condensate separator: case study and experimental validation

This study presents an approach to determine the dimensions of three-phase separators. First, we designed different vessel configurations based on the fluid properties of an Iranian gas condensate field. We then used a comprehensive computational fluid dynamic (CFD) method for analyzing the three-phase separation phenomena. For simulation purposes, the combined volume of fluid–discrete particle method (DPM) approach was used. The discrete random walk (DRW) model was used to include the effect of arbitrary particle movement due to variations caused by turbulence. In addition, the comparison of experimental and simulated results was generated using different turbulence models, i.e., standard k–ε, standard k–ω, and Reynolds stress model. The results of numerical calculations in terms of fluid profiles, separation performance and DPM particle behavior were used to choose the optimum vessel configuration. No difference between the dimensions of the optimum vessel and the existing separator was found. Also, simulation data were compared with experimental data pertaining to a similar existing separator. A reasonable agreement between the results of numerical calculation and experimental data was observed. These results showed that the used CFD model is well capable of investigating the performance of a three-phase separator