Active Feedback System Research Articles

Controlled Excitation of Supermodes in a Multicore Fiber with a 5 × 5 Square Array of Strongly Coupled Cores

Coherent propagation of supermodes in a multicore fiber is promising for power scaling of fiber laser systems, eliminating the need for the active feedback system to maintain the phases between the channels. We studied the propagation of broadband pulsed radiation at a central wavelength of 1030 nm in a multicore fiber with coupled cores arranged in a square array. We designed and fabricated a silica multicore fiber with a 5 × 5 array of cores. For controllable excitation of a desired supermode, we developed a beam-forming system based on a spatial light modulator. We experimentally measured intensity and phase distributions of the supermodes, in particular, the in-phase and out-of-phase supermodes, which matched well the numerically calculated profiles. We obtained selective excitation and coherent propagation of broadband radiation with the content of the out-of-phase supermode of up to 90% maintained without active feedback. Using three-dimensional numerical modeling with allowance for a refractive index profile similar to those of the developed fiber, we demonstrated stable propagation of the out-of-phase supermode and collapse of the in-phase supermode at a high signal power.

Extracellular Matrix Composition Is Altered Alongside Dysmorphology in the Developing Palate

Normal morphogenesis of the primary palate involves directed outgrowth of the facial primordia until they meet and fuse. Gradients of cellular proliferation induced by growth factors are the current paradigm for directed outgrowth, but active cellular migration and physical force propagated through the extracellular matrix (ECM) likely also direct growth. Previously we showed that two of the main components of the ECM, collagen IV and laminin, are thinner in regions of the frontonasal process (FNP) undergoing growth, suggesting tissue stiffness may passively constrain growth in certain directions. We have also shown that increasing Fibroblast growth factor (FGF) signaling in the FNP of chick embryos prior to palate fusion caused overgrowth and disrupted cellular organization. Since cells form and modify the ECM, and since the ECM is required for cellular organization and movement, the effects of FGF signaling on morphogenesis may be due in part to active feedback between ECM and cells. Our goal was to examine the changes to the ECM in the FNP following alteration of FGF signaling. Blocking FGF signaling with SU5402 caused hypoplasia of the FNP and increased the concentration of collagen IV and laminin in regions of expected outgrowth. Conversely, increasing FGF signaling with exogenous FGF2 caused overgrowth of the FNP and decreased concentration of the ECM components. Analysis using transmission electron microscopy of the FGF2 treated samples suggests increasing FGF signaling also decreases the thickness of the epithelium and basement membrane. These results provide preliminary evidence that ECM may play an important role in facial morphogenesis, and that FGF signaling may affect an active biomechanical feedback system between cells and ECM. In the future I will further characterize ECM composition and compliance across the FNP using Fourier transform infrared spectroscopy and atomic force microscopy to generate 3-dimensional maps of biomechanical properties in the face. I will also use confocal microscopy to map cellular organization across the face. I will overlay these maps onto representative reconstructions of the face to correlate regional variation in biomechanical properties and cellular organization with dysmorphologies that occur following exogenous modulation of FGF signaling.

External Mean Flow on Sound Radiation of Active Mechanical Metamaterials

Sound pressure level (SPL) is one of the significant parameters of the acoustic–structure coupling for the elastic wave metamaterial. This paper presents the use of the external mean flow and the active feedback control system. Based on the locally resonant mechanism, the dynamic effective mass density is also discussed and the negative density appears at a lower frequency region. From the results, it can be seen that both the SPL and the effective mass density can be controlled by the active feedback system. As the frequency region of the negative density increases obviously, it emerges two negative regions with the changing of the displacement feedback control action and leads to the changing of the SPL. Besides the Mach number of the external mean flow, other influences on the SPL are also discussed, such as the structural damping, lattice constants, excitation position, elevation angle, and azimuth angle. Finally, these interesting effects on the elastic wave metamaterial are presented and explored.

Detachment plasma achieved based on active temperature feedback system in EAST

The infrared (IR) thermography diagnostic has recently been upgraded to achieve real-time temperature measurement and feedback capability in the experimental advanced superconducting tokamak (EAST). A new control and data acquisition program for IR camera is developed with online temperature calibration and compensation. Reflective memory (RFM) is configured in the data acquisition system for real-time data transmission to the plasma control system (PCS). Based on the upgraded IR thermography diagnostic, detachment plasma has been achieved for the first time in EAST with active temperature feedback. The divertor impurity seeding system is used to inject a sequence of short neon impurity pulses with 50% D2 to increase the edge radiation of the plasma particles. The temperature of the divertor target plates decreases to the preset target value and the divertor detachment has been realized with no serious reduction of plasma stored energy and confinement observed in the temperature feedback control phase. As a new feedback control method, the IR temperature feedback control shows great application prospects for the temperature and heat flux control of the first wall components in future long pulse operation of EAST.

Households’ potential to decrease their environmental impacts

Purpose The purpose of this paper is to quantify the potential levels of greenhouse gas (GHG) and cost savings from a set of households’ energy saving measures, considered as “everyday choices”. Design/methodology/approach Four areas of living were selected for the study: household electricity, space heating, transport and food consumption. The study used a quantitative research approach in which the impact of selected scenarios of an average Finnish household was assessed. Findings Findings suggest that GHG savings from behavioural change regarding household electricity remain marginal in comparison to savings gained from transportation related measures. Transportation also provides the most cost-efficient ways to decrease GHGs but not in all cases. Based on the results, the authors suggest that smart technologies, such as on-line, active feedback systems could have a major role in guiding household energy use. Also, given the high GHG savings from transport, the authors highlight the importance of providing infrastructure and services for clean mobility, and in designing well-functioning and compact cities enabling shorter travels. Originality/value The aim of our study was twofold – by analysing the case household’s choices, we obtained information on environmental and economic impacts, but in addition to this, the aim was to open discussion on the role of households in tackling climate change and how to support households in making sustainable choices. Although research regarding household energy behaviour is vast, so far very few studies have focused on both economic and environmental impacts of households’ everyday actions.

Unmanned aerial vehicle trajectory data fusion based on an active and passive feedback system

The surveillance data obtained from an unmanned aerial vehicle during real-time operation are very important for unmanned aerial vehicle supervision. In this study, in order to obtain more reliable and accurate unmanned aerial vehicle flight paths, we have proposed a trajectory fusion method of unmanned aerial vehicle data based on an active and passive feedback system. The active surveillance data are obtained from automatic dependent surveillance – broadcast and the passive surveillance data are derived from the unmanned aerial vehicle ground control station. The convex combination fusion algorithm is employed to fuse the two sets of data to obtain the accurate flight state and a continuous stable running track for the unmanned aerial vehicle. The simulation results showed that the fusion trajectory obtained using the convex combination fusion algorithm was smoother than the local trajectory obtained by the interacting multiple model algorithm.

Microcontainer-based waterborne epoxy coatings for AA2024-T3: Effect of nature and number of polyelectrolyte multilayers on active protection performance

New insights on the effect of nature and number of polyelectrolyte (PE) shells on active anticorrosion potential of microcontainers (MCs) applied as pH-sensitive reservoirs in coatings for the protection of AA2024-T3 is reported. Mesoporous silica particles (MSP) were loaded with benzotriazole (BTA) and shelled with different polyelectrolyte multilayers (PEM), demonstrating pH sensitivity. Weak-weak polyelectrolyte (W-W PE) shells allow immediate release of inhibitor, but weak-strong polyelectrolyte (W-S PE) shells encourage slower, more controlled and prolonged release, as revealed by release profiles of BTA from microcontainers. Active anticorrosion protection characterizations of the coatings doped with microcontainers were carried out by electrochemical techniques (EIS, SVET) and salt spray tests. Results reveal dependence of active properties of coatings on the nature and number of polyelectrolyte multilayers of microcontainers. We anticipate that proper choice of PEMs on smart containers can aid controlled functionalization of active feedback systems.

Mode-locked pulse oscillation of a self-resonating enhancement optical cavity

A power enhancement optical cavity is a compelling means of realizing a pulsed laser with a high peak power and high repetition frequency, which is not feasible using a simple amplifier scheme. However, a precise feedback system is necessary for maintaining the narrow resonance condition of the optical cavity; this has become a major technical issue in developing such cavities. We have developed a new approach that does not require any active feedback system, by placing the cavity in the outer loop of a laser amplifier. We report on the first demonstration of a mode-locked pulse oscillation using the new system.

High-speed active feedback systems mimicking functions of outer hair cells for artificial sensory epithelium

High-speed active feedback systems mimicking functions of outer hair cells for artificial sensory epithelium

Suppression of transverse beam instabilities by stripline kickers at TPS

Collective beam instabilities could limit the accelerator performance if proper countermeasures are not in place. Active beam feedback systems are commonly used to suppress beam instabilities. The resistive wall impedance including phase-II insertion devices at TPS are calculated with analytic formulas. The growth rate of transverse coupled bunch instabilities due to wall impedance is estimated by theory. The RF properties of existing stripline kickers in TPS are analysed with a 3-D electromagnetic simulation code GdfidL. Based on the above analysis, the requirements for a beam feedback system are calculated and the results are reported.

Development of compact stand-off hazardous chemical detector based on Michelson interferometer

A compact stand-off chemical detector using a Michelson interferometer has been developed and is presented. Its size is only 104 × 183 × 108 mm3 and its weight is 2.5 kg, which makes it suitable for hand-held operation. This compact detector is a minimized version of the conventional Michelson interferometer. The housing for the interferometer was designed to be divided into two parts for minimization and convenient assembly. All the optics composing the interferometer were directly fastened to the housing. The moving mirror module in the Michelson interferometer was specially designed for the small size detector. Using a symmetrically positioned linear elastic plate, the tip and tilt angle of reflected light from the moving mirror were smaller than 8 arc sec during linear back-and-fourth motion without any active alignment feedback system, which results in low noise in the interference signal. The spectra of SF6 and NH3 were measured with changing concentration and the detection limit was determined to be 46.7 and 65.2 mg / m2, respectively. Additionally, outdoor measurement was demonstrated with a distance of about 1 km.

Development of active feedback system for mimicking function of outer hair cells

Development of active feedback system for mimicking function of outer hair cells

A cost-effective measurement-device-independent quantum key distribution system for quantum networks

We experimentally realize a measurement-device-independent quantum key distribution (MDI-QKD) system. It is based on cost-effective and commercially available hardware such as distributed feedback lasers and field-programmable gate arrays that enable time-bin qubit preparation and time-tagging, and active feedback systems that allow for compensation of time-varying properties of photons after transmission through deployed fiber. We examine the performance of our system, and conclude that its design does not compromise performance. Our demonstration paves the way for MDI-QKD-based quantum networks in star-type topology that extend over more than 100 km distance.

Effects of active feedback gait retraining to produce a medial weight transfer at the foot in subjects with symptomatic medial knee osteoarthritis.

This study aimed to determine if active feedback gait retraining to produce a medial weight transfer at the foot significantly reduces the knee adduction moment in subjects with medial compartment knee osteoarthritis. Secondarily, changes in peak knee flexion moment, frontal plane knee and ankle kinematics, and center of pressure were investigated. Ten individuals with medial compartment knee osteoarthritis (9 males; age: 65.3 ± 9.8 years; BMI: 27.8 ± 3.0 kg/m2 ) were tested at self-selected normal and fast speeds in two conditions: Intervention, with an active feedback device attached to the shoe of their more affected leg, and control, with the device de-activated. Kinematics and kinetics were assessed using a motion capture system and force plate. The first peak, second peak, and impulse of the knee adduction moment were significantly reduced by 6.0%, 13.9%, and 9.2%, respectively, at normal speed, with reductions of 10.7% and 8.6% in first peak and impulse at fast speed, respectively, with the active feedback system, with no significant effect on the peak knee flexion moment. Significant reductions in peak varus knee angle and medialized center of pressure in the first half of stance were observed, with reductions in peak varus knee angle associated with reductions in the knee adduction moment. This study demonstrated that active feedback to produce a medial weight-bearing shift at the foot reduces the peaks and impulse of the knee adduction moment in patients with medial compartment knee osteoarthritis. Future research should determine the long-term effect of the active feedback intervention on joint loading, pain, and function. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2251-2259, 2017.

Causes of resident lapses in professional conduct during the training: A qualitative study on the perspectives of residents

Background: The residency is a critical period for doctors to establish their professional identity and ethical standards, and yet during this time, residents are susceptible to engage in a diverse range of unprofessional behaviors. To prevent the misconduct of residents, it is critical to have a thorough understanding of the contributing factors or circumstances.Methods: We conducted a qualitative study on 20 residents at one Korean university-affiliated tertiary hospital. During in-depth interviews, residents were asked to reveal their experiences or observations of misconduct, and describe their perceptions on the attributes of professional lapses.Results: Diverse unethical and unprofessional behaviors were extracted from the transcripts and reported in a previous paper. In the current paper, the attributes that residents regarded as the causes of their unprofessional behaviors were identified within four categories: (1) inadequate systems within training hospitals; (2) lack of professionalism education; (3) strong hierarchical structure; and (4) poor character of individuals. The residents tended to perceive their misconduct as situation-sensitive, and emphasized the importance of systematic and cultural changes.Conclusions: To enhance medical professionalism among residents, the results of this study suggest the need of systematic and structured training programs, adequate professionalism education with clear codes of conduct, and active monitoring and feedback systems.

A precision cryostat design for manual and semi-automated cryo-plunge instruments.

Here we describe a bench-top cryostat system to control the temperature of liquid ethane in a cryo-plunge apparatus designed for biological specimen preparation for electron cryomi-croscopy. It comprises a foam insulated Dewar containing a copper cryostat cup, whose temperature is controlled via an active feedback system to within 0.1 K. The device can easily be incorporated into existing manual and semi-automatic cryo-plunge instruments that are not equipped with cryogenic temperature control. Over the course of normal use, we find that using a cryostat is convenient, fast, and does not require special mixtures of cryogens like ethane/propane. This simple cryostat improves the reliability and reproducibility of biological specimen preparation for electron cryomicroscopy.

Direct measurement of optical-trap-induced decoherence

Thermal decoherence is a major obstacle to the realization of quantum coherence for massive mechanical oscillators. Although optical trapping has been used to reduce the thermal decoherence rate for such oscillators, it also increases the rate by subjecting the oscillator to stochastic forces resulting from the frequency fluctuations of the optical field, thereby setting a fundamental limit on the reduction. This is analogous to the noise penalty in an active feedback system. Here, we directly measure the rethermalizaton process for an initially cooled and optically trapped suspended mirror, and identify the current limiting decoherence rate as due to the optical trap. Our experimental study of the trap-induced decoherence rate will enable future advances in the probing of fundamental quantum mechanics in the bad cavity regime, such as testing of deformed commutators.

A mutated hybrid firefly approach to mitigate dynamic oscillations of second order PLL based PV-battery system for microgrid applications

This paper proposes a new mutated hybrid firefly (MHF) algorithm to improve overall system stability by optimizing the gain parameters for active and reactive power control of Distributed Energy Resources (DERs) in a microgrid system. A comprehensive optimization of entire DERs conditioning gain parameters are studied in terms of error function minimization. Photovoltaic (PV) system with battery energy storage (BESS) is proposed as one of the DERs to the microgrid. BESS system is used as an auxiliary power supply to improve the DC link stability of the voltage source converter (VSC). A second order PLL based VSC is considered for grid synchronization for this DER. Diesel engine (DG) with Padè approximation based governor control is incorporated in the proposed microgrid. A low voltage weak AC microgrid is considered for confirmation of increased stability limits through computer simulations using MATLAB editor. The stability limits are studied in terms of DERs dynamic performance. Both active and reactive power dynamic relations and 2nd order PLL feedback system of the PV-VSC system are further studied for validation of stability. Various case observations are presented including both microgrid operational and solar irradiation deviations for performance evaluation of the DERs.

Feedback-free optical cavity with self-resonating mechanism

We demonstrated the operation of a high finesse optical cavity without utilizing an active feedback system to stabilize the resonance. The effective finesse, which is a finesse including the overall system performance, of the cavity was measured to be 394 000 ± 10 000, and the laser power stored in the cavity was 2.52 ± 0.13 kW, which is approximately 187 000 times greater than the incident power to the cavity. The stored power was stabilized with a fluctuation of 1.7%, and we confirmed continuous cavity operation for more than two hours. This result has the potential to trigger an innovative evolution for applications that use optical resonant cavities such as compact photon sources with laser-Compton scattering or cavity enhanced absorption spectroscopy.

Characterization of the room temperature payload prototype for the cryogenic interferometric gravitational wave detector KAGRA.

KAGRA is a cryogenic interferometric gravitational wave detector currently under construction in the Kamioka mine in Japan. Besides the cryogenic test masses, KAGRA will also rely on room temperature optics which will hang at the bottom of vibration isolation chains. The payload of each chain comprises an optic, a system to align it, and an active feedback system to damp the resonant motion of the suspension itself. This article describes the performance of a payload prototype that was assembled and tested in vacuum at the TAMA300 site at the NAOJ in Mitaka, Tokyo. We describe the mechanical components of the payload prototype and their functionality. A description of the active components of the feedback system and their capabilities is also given. The performance of the active system is illustrated by measuring the quality factors of some of the resonances of the suspension. Finally, the alignment capabilities offered by the payload are reported.