Feedback Phase Research Articles

Performance enhancement of piezoelectric bulk mode MEMS mode-matched gyroscopes based on a secondary phase feedback loop

This work investigates the performance enhancement of piezoelectric bulk mode mode-matched gyroscopes based on a secondary phase feedback loop. An independent phase feedback loop realized by a lock-in amplifier is applied on a 10 MHz multiple ports piezoelectric device to harness its effective stiffness and damping factor for better gyroscope performance. The multiple ports device is designed based on support transducer topology with eight transducer arms, some of which drive the central resonant tank into a secondary elliptical mode. Open-loop measurement with varied phase delay is adopted to carry out the best working condition (i.e. higher Q-factor, smaller frequency split). Therefore, the measured scale factor results in a 1.56 times improvement through boosting the Q-factor of the driving mode. The minimum frequency split compensated by the phase feedback could reach 13.4 ppm with a tuning phase of 60° and tuning voltage of 0.1 V. The bias instability of the proposed gyro through the help of phase feedback loop could be reduced by 2.13 times. The achievement in this work has shown that the phase feedback mechanism could indeed help to improve the performance of the resonant transducers.

Root exudates and rhizosphere microbiomes jointly determine temporal shifts in plant-soil feedbacks.

Plants influence numerous soil biotic factors that can alter the performance of later growing plants-defined as plant-soil feedback (PSF). Here, we investigate whether PSF effects are linked with the temporal changes in root exudate diversity and the rhizosphere microbiome of two common grassland species (Holcus lanatus and Jacobaea vulgaris). Both plant species were grown separately establishing conspecific and heterospecific soils. In the feedback phase, we determined plant biomass, measured root exudate composition, and characterised rhizosphere microbial communities weekly (eight time points). Over time, we found a strong negative conspecific PSF on J. vulgaris in its early growth phase which changed into a neutral PSF, whereas H. lanatus exhibited a more persistent negative PSF. Root exudate diversity increased considerably over time for both plant species. Rhizosphere microbial communities were distinct in conspecific and heterospecific soils and showed strong temporal patterns. Bacterial communities converged over time. Using path models, PSF effects could be linked to the temporal dynamics of root exudate diversity, whereby shifts in rhizosphere microbial diversity contributed to temporal variation in PSF to a lesser extent. Our results highlight the importance of root exudates and rhizosphere microbial communities in driving temporal changes in the strength of PSF effects.

Communication Training: Significance and Effects of a Preliminary Psychological Intervention upon an Audit Team.

Communication constitutes an essential aspect of teamwork. This is especially true for audit teams, where communication takes place not only within the work group but also with the audit recipients. For this reason, given the poor evidence in the literature, communication training was carried out on an audit team. Training was divided into 10 meetings of two hours each, with the meetings taking place over 2 months. Questionnaires were administered to identify the characteristics and styles of communication, to assess the sense of perceived self-efficacy in general and at work, and to evaluate the knowledge inherent in the communication. This battery was administered before and after the training to evaluate its effectiveness and its effects on self-efficacy, communication style, and knowledge. Furthermore, a communication audit was performed on the feedback provided by the team, to highlight satisfaction, strengths, and any critical issues that emerged during the feedback phase. The results obtained suggest that training has an effect not only on individual knowledge but also on personological aspects. Communication among colleagues and general self-efficacy appear to be improved by the process. Self-efficacy also specifically improves in the work environment, with subjects feeling more able to manage relationships and collaborations with colleagues and supervisors. Moreover, the audit team members were satisfied with the training received, perceiving an improvement in their own communication skills during the feedback phases.

Inter- and intraspecific plant-soil feedbacks of grass species

Plants continuously interact with soil microbiota. These plant-soil feedbacks (PSFs) are considered a driving force in plant community dynamics. However, most PSF information comes from inter-family studies, with limited information on possible causes. We studied the variation of PSFs between and within grass species and identified the soil microbes that are associated with the observed PSFs effects. We grew monocultures of ten cultivars of three grass species (Lolium perenne, Poa pratensis, Schedonorus arundinaceus) using a two-phase PSF experiment. We measured plant total biomass to determine PSFs between and within species and correlated it with sequenced rhizosphere bacteria and fungi. In the soil conditioning phase, grass species developed microbial legacies that affected the performance of other grass species in the feedback phase. We detected overall negative interspecific PSFs. While we show that L. perenne and P. pratensis increased their performance respectively in conspecific and heterospecific soils, S. arundinaceus was not strongly affected by the legacies of the previous plant species. Contrary to our expectation, we found no evidence for intraspecific variation in PSFs. Bacterial taxa associated with PSFs included members of Proteobacteria, Firmicutes, Verrucomicrobia and Planctomycetes whereas fungal taxa included members of Ascomycota. Our results suggest differences in PSF effects between grass species, but not between cultivars within species. Thus, in the studied grass species, there might be limited potential for breeding on plant traits mediated by PSFs. Furthermore, we point out potential microbial candidates that might be driving the observed PSF effects that could be further explored.

Time-Delay Signature Concealment in a Security-Enhanced Optical System With Dual-Loop Electro-Optic Self- Feedback Phase Encryption

In this paper, a novel phase encryption scheme based on a dual-loop electro-optic self-feedback structure is proposed for time-delay signature (TDS) concealment. As for a conventional single-loop feedback structure, the TDS is extremely vulnerable to exposure in the common link, resulting in a fatal weakness in the entire security system, whereas, the introduction of an additional feedback branch, brings about the mutual dynamics between the phase feedbacks, and effectively solves the problem. The modulation depth and dispersion values, which are two crucial variables affecting TDS concealment, are investigated in detail. In principle, the scheme is verified to have better robustness, more security, and can supply large key space. Error-free transmission of high-speed signals is possible. Thanks to the aforementioned benefits, the dual-loop electro-optic structure proposed could inspire fresh ideas for secure optical communication systems in the future.

Contract Learning as Individualized Instructional Strategies in Improving Students’ Performance in Academic Writing Courses

The use of contract learning is essential to involve students actively in the classroom activities and to facilitate teachers’ control and flexibility in the teaching and learning process, while letting students to work on activities independently. Therefore, this research is aimed at 1) revealing out whether or not contract learning instruction has a significant difference in the students’ academic writing performance; 2) describing to what extent the contract learning promotes students’ learning and autonomy; and 3) elaborating how the students perceive the diagnostic and feedback phases of individualized strategy as embedded in the contract learning. This study is mixed method interventional research design because the data are obtained from quantitative and qualitative. The participants of the study was the year 3 students of English Department at Mandalika University of Education consisting of 21 students. The instruments used in collecting the data are diagnostic test of academic writing performance, contract form, and questionnaires. The quantitative data are analyzed through the inferential paired t-test. Meanwhile, the qualitative data of each individual’s response to each item on the questionnaire are broken down according to the responses to each question, and the responses are compared, contrasted, and explored to find patterns and themes. The results revealed that 1) contract learning has affected positively students’ learning and performance in academic writing, 2) contract learning brings positive improvement on academic writing performance and 3) positive perception towards the application of contract learning was shown by the students as it provided self-study materials and multiple types of feedback from the the lecturer. This implies that students may benefit from multiple types of feedback and that instructors’ expertise in effective feedback delivery is of paramount importance.

Research on generation of stable mid-infrared lasers with narrow linewidths based on optical feedback locking

Mid-infrared precision spectroscopy has important applications in the fields of trace gas detection and the determination of fundamental physical constants. However, due to the limited commercialization of related technologies, there is a lack of narrow linewidth laser sources or linewidth narrowing approaches in the mid-infrared region, as well as stable mid-infrared frequency standards. The most commercialized and widely used mid-infrared laser source is the quantum cascade laser (QCL). But its free-running linewidth is more than MHz scale due to the influence of laser drive current noise and temperature fluctuation. This impedes the development of precision spectroscopy in this region. In this work, we introduce a technique for generating a narrow linewidth, stable mid-infrared laser by using optical feedback frequency locking, with a high-finesse mid-infrared ultrastable Fabry-Pérot cavity as the frequency reference. The optical cavity consists of two high reflectivity mirrors separated by ultra-low expansion (ULE) material with a low temperature expansion coefficient, and its temperature is precisely controlled. And the cavity is also surrounded in a vaccum cavity made of stainless steel. All these measures ensure the cavity length and its longitudinal mode stability. By using optical feecback, a QCL is locked to the cavity, which stabilizes the laser frequency and narrows the laser linewidth. In order to improve the long-term stability of the optical feedback, an active servo is leveraged to control the feedback phase. The error signal for the servo is obtained by using the method similar to the Pound-Derver-Hall locking. In this work, we first theoretically analyze the feasibility of laser to F-P cavity frequency locking by optical feedback. We propose the laser frequency response model with a linear F-P cavity under optical feedback, and analyze the influence of the direct cavity reflection on the laser frequency. Then the experimental demonstration is conducted. Firstly, we measure the reflectivity of the cavity mirror by using cavity ring-down spectroscopy, resulting in a cavity finesse of 30200 and a cavity mode linewidth of 49.7 kHz. After that, we successfully achieve optical feedback frequency locking, and consecutive cavity transmission is observed. The error signal for the control of the optical feedback phase is used to evaluate the locking performance by converting it into the laser frequency noise. By analyzing the noise spectral density, the QCL linewidth is narrowed to 0.3 Hz on a short timescale (< 10 ms). And the long-term stability is suspected to be dedicated by the temperature variation of the optical cavity, resulting in a laser frequency drift 20 kHz/12 h. The narrow linewidth stabilized mid-infrared laser source obtained with this technique is expected to serve as an effective frequency reference source for mid-infrared precision spectroscopic measurements.

Comparison of gluteus medius and hamstring activation during seven plyometric exercises on three training surfaces

IntroductionPlyometric exercise is known as one of the key components of neuromuscular training programs. It is also possible to obtain higher muscular activity by exercising on tatami and mats. The purpose of the study was to evaluate the activity of hamstring and gluteus medius in 7 typical plyometric exercises on 3 different surfaces and identify the best exercises and surfaces that would further increase hamstring and gluteus medius activity.MethodsThe study involved 20 male athletes. The participants performed 7 plyometric exercises on 3 surfaces: ground, tatami, and mat. The electromyographic activity of muscles was recorded with a ME6000 device in 2 phases: feedforward and feedback. To analyse the data, 2-way ANOVA with repeated measures and a Bonferroni post-hoc test were used.ResultsGluteus medius was most active in the feedforward phase in single-leg frontal plane hop (SLFPH), and in the feedback phase in SLFPH and single-leg sagittal plane hop (SLSPH) (<i>p</i> = 0.001). The medial hamstring and lateral hamstring showed the highest values of activity in the feedforward phase in SLSPH, SLFPH, and double-leg sagittal plane hop (DLSPH) (<i>p</i> = 0.001). There was no significant difference between the surfaces (<i>p</i> > 0.05).ConclusionsSLSPH, DLSPH, and SLFPH improve the recruitment and the strength of gluteus medius and hamstrings and should be given considerable attention in training programs. Exercise on the ground, tatami, and mattress is allowed and in terms of the purpose of the research, there is no difference between them.

Efeito de um pacote de ensino sobre o desempenho de cuidadoras no treino de ocupações para crianças com TEA

Abstract Introduction The functional limitations observed in people with Autistic Spectrum Disorder (ASD) may prevent independent participation in community settings. Learning everyday activities can increase the inclusive participation and quality of life of these people. Teaching strategies via professionals are described in the literature, while teaching via caregivers for these skills needs to be explored and becomes essential when considering that the increase in children with ASD is not accompanied by a proportional increase in qualified professionals, in addition to the fact that the parents deal directly with teaching these activities. Objective To elaborate and evaluate the application of a training package for caregivers of children with ASD, for teaching sandwich preparation and toothbrushing. Method Four caregivers participated. The teaching package included Instructional Video Modeling, Self-Monitoring, Delayed and Immediate Feedback. A performance accuracy criterion equal to or greater than 90% was adopted for two consecutive sessions. Results All caregivers showed an increase in performance accuracy after exposure to the training package components. One caregiver reached the accuracy criterion by going through just one component or a combination of them. Three caregivers necessarily needed to go through the combination of components and the feedback phases to reach the criterion. Conclusion Corroborating other studies, there was no significant difference in the performance of caregivers when comparing the components. As with previous studies, it is shown that the feedback phases played an important role in achieving the criterion. It is attested that the training package was satisfactory in teaching the caregivers.

A two server tandem queueing model with Markovian arrival process, phase type service, working vacation, feedback, re-service, unreliable server, interrupted closedown and customers intolerance.

A two server tandem queueing model with Markovian arrival process, phase type service, working vacation, feedback, re-service, unreliable server, interrupted closedown and customers intolerance.

Plant-soil feedbacks in Hydrocotyle vulgaris: Genotypic differences and relations to functional traits

Plant-soil feedbacks (PSFs) may vary among genotypes within the same species and may also be predicted by plant functional traits. So far, however, it is still unclear whether PSFs can be correlated with plant functional traits across genotypes of the same species. We conducted a two-phase PSF experiment with a clonal plant Hydrocotyle vulgaris. In the conditioning phase, we planted 12 genotypes of H. vulgaris separately in the soil. In the feedback phase, all these genotypes of H. vulgaris were grown again separately in each of the conditioned soil that was trained either by the same genotype (home soil) or by the other 11 genotypes (non-home soil). Most of the genotypes showed negative PSFs, as indicated by significant lower biomass and number of ramets in the home soil than in the non-home soil. However, there were also genotypes showing neutral PSFs as neither biomass nor number of ramets differed significantly between the home and the non-home soil or positive PSFs as biomass and number of ramets were higher in the home than in the non-home soil. In addition, we found a significant positive relationship between the PSF strength with lamina area, specific lamina area, petiole length, specific petiole length and internode length, but a negative relationship between the PSF strength and specific internode length. We conclude that the PSFs can vary among genotypes within the same species and negative PSFs are more common compared to positive PSFs. The results also highlight the role of plant functional traits in predicting PSFs across genotypes.

Supervised Learning in Neural Networks: Feedback-Network-Free Implementation and Biological Plausibility.

The well-known backpropagation learning algorithm is probably the most popular learning algorithm in artificial neural networks. It has been widely used in various applications of deep learning. The backpropagation algorithm requires a separate feedback network to back propagate errors. This feedback network must have the same topology and connection strengths (weights) as the feed-forward network. In this article, we propose a new learning algorithm that is mathematically equivalent to the backpropagation algorithm but does not require a feedback network. The elimination of the feedback network makes the implementation of the new algorithm much simpler. The elimination of the feedback network also significantly increases biological plausibility for biological neural networks to learn using the new algorithm by means of some retrograde regulatory mechanisms that may exist in neurons. This new algorithm also eliminates the need for two-phase adaptation (feed-forward phase and feedback phase). Hence, neurons can adapt asynchronously and concurrently in a way analogous to that of biological neurons.

A deep learning solution to the marginal stability problems of acoustic feedback systems for hearing aids

For hearing aids, it is critical to reduce the acoustic coupling between the receiver and microphone to ensure that prescribed gains are below the maximum stable gain, thus preventing acoustic feedback. Methods for doing this include fixed and adaptive feedback cancellation, phase modulation, and gain reduction. However, the behavior of hearing aids in situations where the prescribed gain is only just below the maximum stable gain, called here "marginally stable gain," is not well understood. This paper analyzed marginally stable systems and identified three problems, including increased gain at frequencies with the smallest gain margin, short whistles caused by the limited rate of decay of the output when the input drops, and coloration effects. A deep learning framework, called deep marginal feedback cancellation (DeepMFC), was developed to suppress short whistles, and reduce coloration effects, as well as to limit excess amplification at certain frequencies. To implement DeepMFC, many receiver signals in closed-loop systems and corresponding open-loop systems were simulated, and the receiver signals of the closed-loop and open-loop systems were paired together to obtain parallel signals for training. DeepMFC achieved much better performance than existing feedback control methods using objective and subjective measures.

Sensorless Brushless Motor Phase Compensation Speed Control

This paper proposes angular velocity vector feedback speed control system, the amplitude and phase signals of diagonal velocity are extracted, and signals are converted into current and voltage vector signals to achieve high efficiency and speed precision. Brushless motor rotational stability on speed and torque are classified, comparative characteristics analysis of dynamic speed and torque between conventional method and proposed method are simulated, results consisting of speed accuracy, the waveform of stator current and back electromotive force of each phase are all compared and analyzed, verifying fitness and validation of the proposed method.

Arbuscular mycorrhizal fungi communities shaped by host‐plant affect the outcome of plant–soil feedback in dryland restoration

Abstract Plant inoculation with arbuscular mycorrhizal fungi (AMF) can be a useful tool to overcome challenges in dry forest restoration. However, advances are still needed to guide choices regarding soil origin and inoculum production methods, since outcomes can vary due to plant–soil feedbacks (PSF). We evaluate how soil origin and host plant used for inoculum production affect AMF community and therefore the plant biomass accumulation and functional traits. In the conditioning phase, we investigated whether soils originating from a recovered area (Quarry) and a vegetation fragment (Caatinga) would have their AMF communities modified due to the growth of Sorghum bicolor (used for inoculum production) and Senna uniflora (used in Brazilian semiarid restoration). In the feedback phase, we compared the performance of four plants species growing on a degraded soil and inoculated or not by a mixture of AMF isolates in comparison to soil inoculum prepared from the conditioning phase. The inoculum from Caatinga presented seven times more AMF species compared to that from the Quarry, which presented ruderal and stress tolerant species. The soil inoculum conditioned by S. uniflora, regardless of origin, presented greater evenness compared to the soil inoculum produced with S. bicolor and promoted 33% more plant biomass compared to the control without inoculation. Root colonization by AMF increased PSF and decreased plant investment in functional traits such as specific root length (SRL) and specific leaf area (SLA). Our results demonstrate the importance of adopting strategies that preserve local adaptation of inoculants produced. The use of native plant for propagation of native AMF in the conditioning phase provided more positive responses for Mesosphaerum suaveolens and Rhaphiodon echinus than inoculated with introduced AMF isolates. This is probably due to the interaction of inoculated plants with responsive AMF present in the soil. Synthesis and applications. Our study shows that conditioning field‐collected soil with Senna uniflora and using it for inoculation can be a simple technique to promote biomass accumulation for other native herbaceous species. This preserves the compatibility between the soil inoculum produced with native AMF and native plants, representing an important tool for restoration programs.

Self-regulating soliton switching waves in microresonators

Dissipative soliton Kerr frequency combs in microresonators have recently been demonstrated with the self-injection locking process. They have the advantage of turnkey deterministic comb generation and simplifying dark soliton generation in the normal dispersion regime. Here, the formation process of dark pulses triggered by self-injection locking is studied by regarding them as a pair of domain walls that connect domains having different intracavity powers. The self-injection locking mechanism allows the domain walls to self-regulate their position so that a wide range of dark comb states can be accessed, and the duty cycle is controlled by the feedback phase. Direct imaging of the dark pulse shape using the electro-optic sampling technique is used to verify the theory. The results provide new physical insights as well as a new operational modality for this important class of nonlinear waves.

Enhancement of synchronization bandwidth in an arch beam

Synchronization in microstructures has been widely investigated because of its rich dynamics and promising applications. Most investigations are devoted to revealing the basic features or enhancing the application performance in oscillator with hardening nonlinearity. However, few theoretical and experimental studies have been conducted on synchronization with softening nonlinearity, which easily occurs in imperfect manufacturing. In this paper, we built up a phase feedback loop with an arch beam that exhibits softening effect subjected to a synchronization perturbation. Theoretical analysis and experimental verification are applied to explore the effects of the feedback phase delay and nonlinearity on the synchronization bandwidth. The optimal phase delay for best synchronization bandwidth is determined and the significant enhancement of nonlinearity on the synchronization bandwidth is observed. An practical approach of manipulating the nonlinearity strength is proposed by tuning the ratio of the applied ac voltage VAC to DC voltage VDC. The presented foundings provide novel strategies to enhance the synchronization bandwidth in nonlinear oscillator with softening effects.

Phase Stability Control of Optical Fiber Partial Discharge Ultrasonic Sensing System

Optic fiber interferometers are highly sensitive ultrasonic sensors for partial discharge detection. However, low-frequency vibration and environmental noise will disturb the sensors in the field, and cause a phase fading suppression effect that reduces sensitivity. This paper analyzed the problems existing in the phase feedback control system based on PZT, and an improved scheme incorporating a high-frequency carrier phase demodulation is proposed. Based on an acousto-optic modulator, the proposed phase feedback control system overcomes the phase fading suppression effect. A test is carried out on an ultrasonic calibration platform and a transformer oil discharge platform. The test results show that the stability of the improved phase demodulation system has been significantly improved, and meets the requirements of field applications. Compared with the signal-to-noise ratio at the time of phase fading of the system before the improvement, the signal-to-noise ratio of the improved system is improved by 69 dB.

Enlarging the frequency dynamic range of DMZI sensors based on the switching control feedback system.

The feedback loop in dual Mach-Zehnder interferometer (DMZI) sensors stabilizes the system operating at the quadratic point for the highest sensitivity but requires the minimum measurable vibration frequency out of the feedback bandwidth, resulting in a limited dynamic range. In this paper, we point out that the feedback operation is unnecessary while vibration is occurring and propose a strategy to adaptively enable/disable the feedback phase compensation depending on the vibration state, lowering the minimum measurable vibration frequency tenfold. Moreover, the state variable employed enables direct extraction of vibration-related data, with no need of complicated postprocessing algorithms.

Study on the multitime scale rolling optimization operation of a near-zero energy building energy supply system

The combined cooling, heating and power system of near-zero energy buildings can provide cold energy, heat energy and electricity to users at the same time, realizing combined cold, heat and power generation. However, the randomness of renewable energy output and the volatility of user loads lead to an imbalance between energy supply and demand. Therefore, a three-stage multitime scale optimization operation method is proposed. This method establishes a three-stage optimization model of ‘day-ahead, day-in rolling, real-time feedback’ to optimize the output of the unit step by step. In the day-ahead phase, the optimization goal is to take the lowest daily operating cost while considering the environmental cost. In the day-in rolling stage, the optimization goal is to control the minimum cost of energy purchase in the time domain and the minimum penalty cost of unit output change. The real-time feedback phase optimizes with the minimum total device power adjustment. The results show that the cost saving rates of multitime scale optimization strategies on typical winter days, typical transition season days and typical summer days are 0.90%, 2.32% and 2.12%, respectively. Compared with the ideal cost of different typical days, the cost deviation rates are 0.21%, 0.51% and 1.97%, respectively. Compared with the optimization of the previous day, the total power of the grid connection line on different typical days is −8.0%, −10.65% and −6.23%, respectively. Therefore, this novel optimization method has good economy, stability and accuracy and has a guiding effect on the formulation of each equipment operation plan.