Active Cancellation Research Articles

Complex frequency sink

As the time-reversed analog of the source, the sink is an abstraction of a device that can absorb incident symmetrical waves at a point. Such a device is useful for its ability to create an arbitrarily small focusing spot, surpassing the conventional diffraction limit. Sinks have been created using impedance matching and active cancellation; however, these techniques require the introduction of tailored loss or gain into the system. Here, we demonstrate a new method for creating a sink that requires no loss or gain but instead relies on complex frequency excitations, harmonic excitations that exponentially grow or decay in time. Recent work has shown how complex frequency excitations in Hermitian systems enable phenomena such as PT symmetry and perfect absorption that are typically only associated with non-Hermitian systems. We will discuss the theory of the complex frequency sink and analyze the case of a sink in a thin elastic plate. We will present experimental results where the scattering of a symmetric scatterer is minimized by complex frequency waves launched by piezoelectric patches. Laser-doppler vibrometer measurements of the plate shows the resonator’s curious behavior as a loss and gain free sink.

CMOS Channel-Selection LNA With a Feedforward N-Path Filter and Calibrated Blocker Cancellation Path for FEM-Less Cellular Transceivers

In this article, a CMOS tunable channel-selection (CH-SEL) low-noise amplifier (LNA) with a feedforward (FF) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> -path filter and a gain- and phase-calibrated interference- cancellation technique is proposed for advanced front-end module (FEM)-less cellular transceivers. The proposed LNA exhibits a high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> RF bandpass/band-rejection filter characteristic based on a four-path filter, an active blocker cancellation with an FF translational loop, and an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> tank at the input, internal node, and output, respectively. The proposed gain- and phase-calibration block and tunable high-pass filter in the FF filtering path adjust the notch frequency corresponding to the transmitter leakage signal and help realize sharp notch filtering. The proposed CH-SEL LNA with CMOS duplexers compensates for the limited filtering performance of the CMOS duplexer and improves the blocker-tolerance and linearity of the receiver, and thus, can replace surface acoustic wave duplexers in the FEM. Fabricated in the 65-nm CMOS process, the CH-SEL LNA achieves a maximum voltage gain of 19.3 dB, minimum NF of 5.1 dB, and notch rejection ratio of more than 27.8 dB. It can also cover mid-band frequencies in the range of 1.35–2.7 GHz for 5G new radio cellular applications, exhibits an average current of 20 mA from a supply voltage of 1 V, and has an active die area of 1.16 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Error cancellation.

The human cognitive system houses efficient mechanisms to monitor ongoing actions. Upon detecting an erroneous course of action, these mechanisms are commonly assumed to adjust cognitive processing to mitigate the error's consequences and to prevent future action slips. Here, we demonstrate that error detection has far earlier consequences by feeding back directly onto ongoing motor activity, thus cancelling erroneous movements immediately. We tested this prediction of immediate auto-correction by analysing how the force of correct and erroneous keypress actions evolves over time while controlling for cognitive and biomechanical constraints relating to response time and the peak force of a movement. We conclude that the force profiles are indicative of active cancellation by showing indications of shorter response durations for errors already within the first 100 ms, i.e. between the onset and the peak of the response, a timescale that has previously been related solely to error detection. This effect increased in a late phase of responding, i.e. after response force peaked until its offset, further corroborating that it indeed reflects cancellation efforts instead of consequences of planning or initiating the error.

Cardiac involvement in athletes infected by SARS COV-2 disease

ObjectivesThe aim of the present study was to conduct a review of the current literature evaluating the available evidence to date in terms of epidemiology, pathophysiology and clinical presentation of COVID-19 in relation to cardiovascular involvement, with a special focus on the myocarditis model, in the population of athletes (professional and recreational) who are preparing to return to competitions, with the ultimate aim of guaranteeing maximum safety for resuming sports activities.NewsThe COVID-19 pandemic has resulted in the inevitable cancellation of most sports activities, practiced at both a professional and amateur level, in order to minimize the risk of spreading the infection. Since the number of athletes who tested positive was rather high, the potential cardiac involvement in this peculiar population of subjects contracting the disease in a mild (asymptomatic, slightly symptomatic) or moderate form, has recently raised concerns following the observation of cases of recorded myocardial damage, myocarditis, arrhythmias and a first reported case of Sudden Cardiac Death (SCD) in a 27-year-old professional basketball player. Several studies even seem to confirm the possibility of permanent impairment of the cardiorespiratory system following the infection. Medical history, biomarkers, electrocardiographical and cardiac imaging features appear to be crucial in distinguishing cardiovascular alterations related to COVID-19 infection from typical adaptations to exercise related to athletes' heart.Prospects and ProjectsClarifications and prospective data based on long-term follow-ups on larger populations of athletes are still needed to exclude the development of myocardial damage capable of negatively affecting prognosis and increasing cardiovascular risk in athletes recovered from COVID-19 in asymptomatic (simple positivity to SARS-COV-2) or in a mild form.ConclusionFrom a clinical point of view extreme caution is necessary when planning the return to sport (Return To Play–RTP) of athletes recovered from a mild or asymptomatic form of COVID-19: a careful preliminary medical-sports evaluation should be carried out in order to assess the potential development of myocardial damage that would increase their cardiovascular risk.

Wideband, Millimeter Wave Domain SI Canceling (&gt;50dB) In-Band Full-Duplex Circulator Receiver

This paper describes a 26-GHz fully integrated In-band Full-duplex Circulator (IBFD) Receiver (RX), which employs passive and active Self-interference Cancellation (SIC) techniques in the mm-wave domain. Coverage of wireless networks at mm-wave frequencies can be enhanced by deploying a large number of base stations economically based on Integrated Access and Backhaul (IAB) relays and repeaters. However, to retain the channel capacity, IAB needs to be implemented using full-duplex schemes that suffer from a strong Transmitter (TX) to RX SI. This SI leakage can significantly impact the receiver sensitivity and increase the baseband/ADC dynamic range requirements. Canceling SI at mm-wave applications is particularly challenging given the high frequency of operation, wide bandwidth, and antenna (ANT) impedance sensitivity to the surroundings. Proposed mm-wave RX with a shared ANT interface based on a circulator with active SI cancelers provide ~53 dB SIC over 400 MHz and ~40 dB SIC over 400 MHz in mm-wave domain to meet the link budget requirements. Proposed architecture achieves SIC by (i) introducing a shared ANT interface based on a hybrid-coupler and a non-reciprocal delay line that provides wideband SIC and additionally creates a SI replica (ii) subsequent active cancellation using SI replica processed with variable gain amplifiers and phase shifters. This system also accommodates SI channel variations due to surroundings. Proposed 26-GHz circulator RX has >100x better SIC at high TX power (>10dBm) levels in comparison to the state-of-the-art and it consumes ~111 mW power. The system is implemented in 45nm SOI CMOS and has an active area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.54\, mm^{2}$ </tex-math></inline-formula> . Stand-alone RX NF is ~5.8 dB and TX to ANT insertion loss (IL) is ~3.1 dB. Over-the-air measurements with modulated TX (128 QAM 2.1 Gb/s) and RX (128 QAM 4.2 Gb/s) signals show an EVM of 3.3%.

Covid-19 pandemic and school sporting activities in Ghana: The perceived impacts on students well-being

The Coronavirus pandemic has extremely affected various activities worldwide including school sports. Despite this, little has been done on the consequences of the cancellation of school sporting activities due to the pandemic on the well-being of students. The present study ascertained how cancellation of school sports due to the Covid-19 pandemic influenced the general well-being of students and suggested appropriate interventions to bring back school sports. The purposive sampling technique was used to collect data from Nineteen (19) Senior High School Student` athletes through semi-structured interviews. The data collection tool was created on seven themes: sports programmes, sedentary activities, impacts of the pandemic on sports, sports opportunities, impacts of sports on students` well-being, consequences, and measures to bring back school sports. Content analysis procedures were the main analytical technique. The findings revealed that students are faced with physical, psychological, emotional, economic, mental, and social health challenges. Consequently, students have gained weight, lost scholarship opportunities and friends, and go through fear and anxiety. Therefore, appropriate measures and directives such as; reduction in the number of spectators at stadiums, fumigation of stadiums, vaccination of students, and testing and quarantine are recommended to be followed to help bring back the school sports.

Torque Ripple Minimization Control Strategy in Synchronous Reluctance Machines

Torque smoothness is an essential requirement for high-performance motor drive applications. Synchronous reluctance machines (SyRM) have high torque ripple due to non-linear magnetic circuit and saturation. Typically, in Permanent magnet machines the active torque ripple compensation is achieved by injecting a compensating ripple current in the <i>q-axis</i>. For SyRM, the current injection method for active torque ripple cancellation can be used in both the <i>d-axis</i> and <i>q-axis</i>. However, the saturation of the motor parameters with the changing current can result in varied performance between the two methods. This paper evaluates the effectiveness of both of these methods for torque ripple cancellation. For evaluation, the impact of parameter saturation with ripple current injection on the <i>d-axis</i> and the <i>q-axis</i> is studied. The mathematical conclusions obtained are evaluated by both the simulation and the experimental results performed on a 4 pole 1200W Synchronous reluctance machine.

Impact of Self-Energy Recycling and Cooperative Jamming on SWIPT-Based FD Relay Networks With Secrecy Constraints

This paper investigates the secrecy performance of a power splitting-based simultaneous wireless information and power transfer cooperative relay network in the presence of an eavesdropper. The relay is considered to operate in full-duplex (FD) mode to perform both energy harvesting and information decoding simultaneously. To accomplish that, the relay is assumed to employ two rechargeable batteries, which switch between power supplying mode and charging mode at each transmission block. We also assume that the self-interference inherent of the FD mode is not completely suppressed. Therefore, it is assumed that, after some stages of passive and active self-interference cancellation, there is still a residual self-interference (RSI). A portion of this RSI (remaining after passive cancellation) is recycled for energy harvesting. In order to improve the system secrecy performance, it is considered that the relay can split its transmit power to send the information signal and to emit a jamming signal to degrade the eavesdropper&#x2019;s channel. The secrecy performance is evaluated in terms of the secrecy outage probability and the optimal secrecy throughput. Tight-approximate and asymptotic expressions are obtained for the secrecy outage probability, and the particle swarm optimization method is employed for addressing the secrecy throughput optimization problem. From numerical results, we show that the secrecy performance can be increased depending on the self-energy recycling channel condition. Finally, our derived expressions are validated via Monte Carlo simulations.

The Effects of Hearing-Aid Amplification and Noise on Conversational Dynamics Between Normal-Hearing and Hearing-Impaired Talkers.

There is a long-standing tradition to assess hearing-aid benefits using lab-based speech intelligibility tests. Towards a more everyday-like scenario, the current study investigated the effects of hearing-aid amplification and noise on face-to-face communication between two conversational partners. Eleven pairs, consisting of a younger normal-hearing (NH) and an older hearing-impaired (HI) participant, solved spot-the-difference tasks while their conversations were recorded. In a two-block randomized design, the tasks were solved in quiet or noise, both with and without the HI participant receiving hearing-aid amplification with active occlusion cancellation. In the presence of 70 dB SPL babble noise, participants had fewer, slower, and less well-timed turn-starts, while speaking louder with longer inter-pausal units (IPUs, stretches of continuous speech surrounded by silence) and reducing their articulation rates. All these changes are indicative of increased communication effort. The timing of turn-starts by the HI participants exhibited more variability than that of their NH conversational partners. In the presence of background noise, the timing of turn-starts by the HI participants became even more variable, and their NH partners spoke louder. When the HI participants were provided with hearing-aid amplification, their timing of turn-starts became faster, they increased their articulation rate, and they produced shorter IPUs, all indicating reduced communication effort. In conclusion, measures of the conversational dynamics showed that background noise increased the communication effort, especially for the HI participants, and that providing hearing-aid amplification caused the HI participant to behave more like their NH conversational partner, especially in quiet situations.

COVID-19 Impacts on Mental Health Care in Veterans Health Administration Community Living Centers

COVID-19 forced VHA Community Living Centers (CLC) to adjust how mental health (MH) care is provided. Beginning March 2020, admissions and staff entering CLC space were restricted in response to the pandemic. Some care shifted from in-person to virtual. Veterans were more isolated due to visitor restrictions and cancellation of communal activities. Pre-COVID, CLC teams cared for an already complex population – 80% of residents had a MH diagnosis (24% with serious mental illness). Changing resident composition and increased isolation may intensify challenges in providing MH care. Using VHA administrative data, we assess the impact of the changing CLC environment during the pandemic by comparing monthly average rates of MH diagnoses and provision of MH care and as-needed psychotropics to CLC residents pre-COVID (Oct 2019 – Feb 2020) to the COVID period (Mar 2020 – Feb 2021). CLCs experienced a 26% decline in the monthly resident census. However, the monthly percentage of residents with a serious mental illness increased 13%. Pre-COVID, virtual MH encounters were received by 2% of residents; 35% received an in-person MH encounter. During COVID, 8% received a virtual MH encounter and 33% received in-person. As-needed antipsychotics remained unchanged, while as-needed benzodiazepine prescriptions decreased 15%. Despite increased MH concerns, CLC teams did not appear to respond with increased pharmacological interventions. Rather, teams seem to have maintained clinical service connection for those with MH concerns. Documenting successful approaches for addressing MH needs during this challenging time will be instructive for future care during times of crisis.

Analysis and Design of Quasi-Circulating Quadrature Hybrid for Full-Duplex Wireless

This article presents a new electronic device – the four-port quasi-circulating quadrature hybrid (QCQH), which combines desirable features of electronic circulators and quadrature hybrids. The QCQH comprises three quarter-wavelength transmission lines and a 90° non-reciprocal phase shifter (NRPS) and is suitable for inband full duplex applications. We derive the four-port S-parameter matrix of the QCQH and the transfer functions under termination scenarios of interest. The resulting closed-form expressions are compared with the prior art electronic circulator. A 90° transmission line and lumped transformer alternatives are considered for designing a QCQH based on a two-port N-path circuit. TX isolation and transmission expressions are derived and verified against simulations, and a new wideband leakage cancellation approach is proposed. A TSMC 65 nm CMOS N-path chip is integrated on-board with a discrete, lumped, LCL transformer implementation. TX-to-antenna insertion loss of 1.4 dB and an RX NF of 4.7 dB at the frequency of 1 GHz were measured with a primary passive TX-RX isolation of 21 dB. Total isolation of more than 50 dB for an 80 MHz OFDM WiFi TX signal employing digitally equalized active leakage cancellation was achieved along with better than −40 dB TX EVM with SIC ON.

Expanding Indications of Primary Arthrodesis in Selected Individuals for Managing Complex Hindfoot Trauma During COVID-19 Pandemic.

BackgroundDuring the COVID-19 pandemic, public health measures to encourage social distancing have been implemented, including cancellation of outdoor activities, organized sports, and schools/colleges. Neglected hindfoot fractures have emerged as a consequence with increased frequency. Similarly, complex ankle and pilon fractures that require staged management, prolonged hospital stay, and soft-tissue care have emerged as a potential concern as prolonged exposure to healthcare setting adds to risk of acquiring as well as transmitting COVID-19 infection. The authors present their experience with expanding these indications for hindfoot arthrodesis as they encounter a greater number of neglected ankle and hindfoot trauma.MethodsThis was a retrospective observational study of collected data from the trauma unit of our hospital. Inclusion criteria included all trauma classified by the AO/OTA as occurring at locations 43, and who underwent subtalar and ankle arthrodesis. This included distal tibia, malleolar, talus, and calcaneus fractures. These patients were followed up to at least 6 months till complete fracture union.ResultsA total of 18 patients underwent arthrodesis of either the ankle or subtalar joint between March and October 2020. Mean age of patients undergoing arthrodesis of the hindfoot was 69.2 years (43–84 years). Indications for the procedure included Displaced and comminuted intra-articular distal tibia fractures in elderly (6 patients), Malunited ankle fractures (2 patients), Neglected Ankle fractures managed conservatively (3 patients), Calcaneus fractures (5 patients), and neglected Talus body fracture (2 patients). All patients were followed up to at least 6 months and everyone went onto successful painless union between 3 and 6 months of the arthrodesis procedure without any significant complications.ConclusionIn summary, COVID-19 pandemic has led to a change in paradigm of trauma management and foot and ankle management is no different than other musculoskeletal trauma systems. The authors propose an expansion of indications for hindfoot arthrodesis in managing complex hindfoot trauma in pandemic situation.

On the performance of active analog self-interference cancellation techniques for beyond 5G systems

The in-band full-duplex (IBFD) mechanism is of interest in beyond 5G systems due to its potential to enhance spectral efficiency and reduce delay. To achieve the maximum gain of IBFD systems, the significant self-interference (SI) must be efficiently suppressed. The challenges of wideband self-interference cancellation (SIC) lie in the radio frequency (RF) domain, where the performance will be limited by the hardware. This paper reviews current RF cancellation mechanisms and investigates an efficient mechanism for future wideband systems with minimum complexity. The working principle and implementation details of multi-tap cancellers are first introduced, then an optical domain-based RF canceller is reviewed, and a novel low-cost design is proposed. To minimize the cost and complexity of the canceller, the minimum required number of taps are analyzed. Simulation results show that with the commonly used 12-bits analog-to-digital converter (ADC) at the receiver, the novel optical domain-based canceller can enable efficient SIC in the 3GPP LTE specifications compatible system within 400 MHz bandwidth.

OPENING PANDEMIC’S BOX: SUPPORTING DEVELOPING ADOLESCENTS

Developmental tasks of adolescence involve identity formation, building relationships, and achieving independence. This session will highlight some important aspects of adolescent development: sports/athletics, racial identity and racism, school and learning, and digital media. Special focus will be given to challenges with COVID-19, including activity cancellation, school changes/virtual schooling, increased awareness of racial and social disparities, and the role of media in social connections. Effects on mental health and well-being and the role of child and adolescent psychiatrists will also be discussed. Presentations will review the relevant literature and data with didactics, videos, case examples, polling, and interactive discussion. Raymond Pan, MD, child and adolescent psychiatrist, will discuss the role of athletics in adolescence, stressors involved with athletics, and issues related to concussions. Brandon Newsome, MD, psychiatry resident, will approach racial identity and racism in adolescence and how COVID-19 has influenced social determinants of mental health. Desiree Shapiro, MD, early-career child and adolescent psychiatrist, will discuss school- and learning-related mental health and explore disparities and injustices. Meredith Gansner, MD, early-career child and adolescent psychiatrist, will discuss media use and screen time in adolescence, effects of the pandemic, and potential risks of excessive digital media while maintaining interpersonal connectedness. Discussants Eugene Beresin, MD, and Liwei Hua, MD, PhD, both of whom are child and adolescent psychiatrists, will synthesize the material presented and facilitate discussion. Participants will: 1) recognize the role of sports, racial identity and racism, school and learning, and digital media in the context of normal adolescent development as they relate to identity and relationship formation, as well as independence; 2) learn about risks to these areas of development in the context of the pandemic; and 3) identify the role of child and adolescent psychiatrists in addressing the effects on mental health associated with the pandemic’s disruption of expected adolescent developmental milestones. The session focuses on topics relevant to adolescent life (sports/athletics, racial identity and racism, school and learning, and digital media) from a developmental perspective and seeks to educate clinicians on issues related to the topics.

Full-Duplex Quadrature Spatial Modulation for Multi-Antenna Systems

Devices with full-duplex (FD) radios are able to transmit and receive at the same time without requiring orthogonal resources, thereby creating strong self-interference (SI) that results from their own transmissions. Spatial modulation (SM), on the other hand, is a multi-antenna scheme that activates only one transmit antenna to send a data symbol, where the index of the activated antenna depends on the input bits. In this manner, additional data can be conveyed implicitly via the selection of the active transmit antenna. Quadrature spatial modulation (QSM) is a variant of SM, in which the quadrature components of the constellation symbol are separately modulated on the indices of the transmit antenna, leading to an increase in the data rate by implicitly encoding on the spatial domain. This article provides an overview of the research activity on FD-SM and proposes a novel FD-QSM scheme that exploits multiple antennas to achieve antenna cancellation at the receiving side to mitigate the SI signal. Assuming active cancellation mechanisms are also in place, the performance of FD-QSM is studied in the presence of residual SI (RSI). The results reveal that FD-QSM can provide more than 40 percent capacity gain over its half-duplex (HD) counterpart in the presence of strong RSI and roughly the same gain over HD spatial multiplexing (SMX)-based multiple-input-multiple-output (MIMO) systems with moderate RSI. When applied to the downlink of a cellular network, FD-QSM provides 2dB gain over FD-SM and 5dB gain over FD-MIMO, operating at the same spectral efficiency, while huge gains are observed when FD-QSM is applied to non-orthogonal multiple access (NOMA)-aided FD relay network.

44 Trends in Pediatric Emergency Department Acuity and Trauma During the COVID-19 Pandemic

SARS-CoV-2 was declared a pandemic March 11, 2020 by the WHO. Adult health care systems faced tremendous challenges in volume and acuity; however, morbidity and mortality among children is low and pediatric emergency departments (EDs) have been spared the same challenges. Treatment of SARS-CoV-2 patients and efforts to curb disease transmission affected health care delivery in the United States causing negative effects on the delivery of routine primary care, the closures of schools, the implementation of shelter-in-place orders, and the cancellation of typical activities for children.

A Low-Noise and Fast-Settling UHF RFID Receiver With Digitally Controlled Leakage Cancellation

UHF RFID reader suffers from a strong transmitter (Tx) leakage signal coupled to a receiver (Rx), especially for an area-compact single-antenna implementation. Then, several Tx leakage cancellation schemes have been developed not to saturate the Rx and to minimize the performance degradation. This brief proposes a UHF RFID reader Rx with a low noise performance and a fast settling time by employing a digitally controlled leakage cancellation method in both passive and active realizations. A digitally-controlled passive vector reflector enhances the Tx to Rx isolation ratio by providing the optimum load impedance. An active anti-leakage feedback loop adaptively tracks the time-varying leakage and generate the phase-inverted leakage replica to suppress the leakage. The prototype chip is fabricated in a CMOS 55 nm process and the area of the chip is 2.1 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.8$ </tex-math></inline-formula> mm. The passive leakage cancellation (PLC) with a vector reflector endures the 1 dBm leakage with a low Rx noise figure of 12.5 dB and 35.7 mW power consumption. The active leakage cancellation (ALC) with an anti-leakage feedback loop covers 6 dBm leakage with a fast settling time of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.6~\mu \text{s}$ </tex-math></inline-formula> and 58 mW power consumption.

Is malaria elimination a distant dream? Reconsidering malaria elimination strategies in Zimbabwe

Malaria remains a public health problem decimating vulnerable populace especially in resource-constrained areas in Zimbabwe. Significant progress towards malaria elimination has beenik made in the previous decades through intensified and improved malaria control measures such as indoor residual spraying (IRS), distribution of long-lasting insecticidal nets (LLIN), artemisinin-based combination therapy and administration of intermittent preventive treatment in pregnancy. However, the outbreak of pandemics like coronavirus disease (COVID-19), cyclones and tropical storms, lack of funding, porous political environment, dearth of resources for vector control, changes in vector behaviour, vector resistance to insecticides, community behavioural change and lack of feasible and sustainable digital technologies for managing malaria control interventions retards progress made towards malaria elimination. Also, arbitrary political environment and unstable economic situation often interfere with health programmes which subsequently lead to malaria outbreaks. Most recently, the country recorded a sharp increase in malaria incidences in malaria-endemic areas especially during the pandemic due to some factors such as movement restrictions, temporary cancellation of IRS activities, delayed delivery of IRS chemicals and recursive lockdown. Therefore, we propose ways to mitigate future malaria outbreaks and advocate for reconsidering malaria elimination strategies to addresses emerging challenges in eradicating malaria in Zimbabwe.

Investigation of Controllable Modes in Active Vibration Cancellation Induced by Piezoelectric Patches

Piezoelectric (PZT) patches are widely preferred for actuators and sensors for achieving active vibration cancellation (AVC). When PZT actuators and sensors are placed at the region of maximum strain energy for structural modes, there are still uncontrollable and controllable modes in the actual application. When an uncontrollable mode is excited, the structural vibration problem may not be solved by AVC, and may even be aggravated. However, a few studies have specifically targeted this problem. In this study, the controllable modes of a plate with free boundaries are investigated to ensure the AVC effect. To specify the controllable modes in advance, a criterion for controllable modes is proposed. The proposed criterion is firstly obtained by defining the ratio of the open-loop and closed-loop energies of AVC, and then simplified by considering the dominating modes. Corresponding simulations and experiments are conducted on a smart plate consisting of PZT patches to verify the correctness of the theoretical analysis. Results show that the proposed criterion is reliable to specify the controllable modes. The vibration response of the plate is significantly attenuated at the selected controllable mode, and conversely enlarged at a specified uncontrollable mode. It is verified that controllable modes can be effectively predicted by the proposed criterion, which promotes the application of AVC.

MANAGEMENT OF STUDENT MOBILITY IN THE CASE OF UNIVERSITY MANAGEMENT DURING THE SPREAD OF THE COVID-19 PANDEMIC

The COVID-19 pandemic outbreak already in the first months of 2020 has dramatically affected the situation in higher education in various aspects, including the transition from face-to-face teaching to online technologies, the cancellation of activities and the development of activities aimed at «next normal» in a university management. The revision of management decisions in the sphere of academic mobility means an opportunity for various university management stakeholders to rethink and even modernize project activities according to effective plans of risk management in order to make international cooperation more sustainable and effective in the future. The purpose of this work is to examine the international landscape of the transformation of international student mobility, which has changed significantly during the 2020-2021 academic year shift as a result of the spread of the coronavirus infection.