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In this paper, we explore parametric amplification of multiple resonances in multidegree-of-freedom mechanical systems, and the use of frequency sweeping with a parametric pump to amplify several adjacent resonance peaks. We develop conditions under which it is possible to sweep with direct and parametric excitation to produce a sweep response with amplified effective quality factors for all resonances over a given frequency range. We determine gain and stability conditions and include analysis for potential problematic modal interactions. This technique makes it possible to improve the measurements of resonance locations in devices, for example, sensors that rely on tracking shifts in resonance peaks. The results are demonstrated on a model for a multi-analyte micro-electromechanical systems mass sensor. [ABSTRACT FROM AUTHOR]

We investigate the use of cable tension for active vibration control in frame structures. A general formulation for this class of systems is developed using finite elements, which includes the dynamics of the structure and the effects of cable-structure interactions. It is found that the cable tension has two distinct effects on the structure. The first is a parametric effect in which the cable tension changes the stiffness of the structure, and the second is a direct effect that provides an external force on the structure. Based on this model, a general control scheme is developed that uses cable actuation to take advantage of these effects, both separately and together. The control scheme for all cases is based on modal amplitudes, and it applies and releases tension in such a manner that vibration energy is removed from the modes of the structure over a prescribed frequency range that depends on the bandwidth(s) of the actuator(s). The stability of the controlled systems is proven using nonlinear control theory. In addition, a method is developed for determining the optimal placement of cables for parametric stiffness control, which is verified via simulations. Finally, an experimental realization of the direct force control is tested on a frame structure and compared with simulations, demonstrating its effectiveness. [ABSTRACT FROM AUTHOR]

Though utilized for more than 50 years in a variety of power and communication systems, parametric amplification, the process of amplifying a harmonic signal with a parametric pump, has received very little attention in the mechanical engineering community. In fact, only within the past 15-20 years has the technique been implemented in micro-mechanical systems as a means of amplifying the output of resonant microtransducers. While the vast potential of parametric amplification has been demonstrated, to date, in a number of micro- and nanomechanical systems (as well as a number electrical systems), few, if any, macroscale mechanical amplifiers have been reported. Given that these amplifiers are easily realizable using larger-scale mechanical systems, the present work seeks to address this void by examining a simple representative example: a cantilevered beam with longitudinal and transverse base excitations. The work begins with the systematic formulation of a representative system model, which is used to derive a number of pertinent metrics. A series of experimental results, which validate the work's analytical findings, are subsequently examined, and the work concludes with a brief look at some plausible applications of parametric amplification in macroscale mechanical systems. [ABSTRACT FROM AUTHOR]

Microelectromechanical oscillators utilizing noninterdigitated combdrive actuators have the ability to be parametrically excited, which leads to distinct advantages over harmonically driven oscillators. Theory predicts that this type of actuator, when dc voltage is applied, can also be used for tuning the effective linear and nonlinear stiffnesses of an oscillator. For instance, the parametric instability region can be rotated by using a previously developed linear tuning scheme. This can be accomplished by implementing two sets of noninterdigitated combdrives, choosing the correct geometry and alignment for each, and applying ac excitation voltages to one set and proportional dc tuning voltages to the other set. Such an oscillator can also be tuned to display a desired nonlinear behavior: softening, hardening, or mixed nonlinearity. Nonlinear tuning is attained by carefully designing combdrive geometry, flexure geometry, and applying the correct dc voltages to the second set of actuators. Here, two oscillators have been designed, fabricated, and tested to prove these tuning concepts experimentally. [2006-0085] [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the dynamic response of a class of electrostatically driven microelectromechanical (MEM) oscillators. The particular systems of interest are those which feature parametric excitation that arises from forces produced by fluctuating voltages applied across comb drives. These systems are known to exhibit a wide range of behaviors, some of which have escaped explanation or prediction. In this paper we examine a general governing equation of motion for these systems and use it to provide a complete description of the dynamic response and its dependence on the system parameters. The defining feature of this equation is that both the linear and cubic terms feature parametric excitation which, in comparison to the case of purely linear parametric excitation (e.g. the Mathieu equation), significantly complicates the system''s dynamics. One consequence is that an effective nonlinearity for the overall system cannot be defined. Instead, the system features separate effective nonlinearities for each branch of its nontrivial response. As such, it can exhibit not only hardening and softening nonlinearities, but also mixed nonlinearities, wherein the response branches in the system''s frequency response bend toward or away from one another near resonance. This paper includes some brief background information on the equation of motion under consideration, an outline of the analytical techniques used to reach the aforementioned results, stability results for the responses in question, a numerical example, explored using simulation, of a MEM oscillator which features this nonlinear behavior, and preliminary experimental results, taken from an actual MEM device, which show evidence of the analytically predicted behavior. Practical issues pertaining to the design of parametrically excited MEM devices are also considered. [Copyright &y& Elsevier]

Presents a nonlinear state feedback controller designed using a Lyapunov-based approach in order to stabilize a nonlinear 3-DOF ship model in beam seas. Design of the stabilizing controller; Ship dynamic state model and its general structure.

The copy number variation (CNV) of 15q11.2, an emerging and common condition observed during prenatal counseling, is encompassed by four highly conserved and non-imprinted genes—TUBGCP5, CYFIP1, NIPA1, and NIPA2—which are reportedly related to developmental delays or general behavioral problems. We retrospectively analyzed 1337 samples from genetic amniocentesis for fetal CNV using microarray-based comparative genomic hybridization analysis between January 2014 and December 2019. 15q11.2 CNV showed a prevalence of 1.5% (21/1337). Separately, 0.7% was noted for 15q11.2 BP1–BP2 microdeletion and 0.8% for 15q11.2 microduplication. Compared to the normal array group, the 15q11.2 BP1–BP2 microdeletion group had more cases of neonatal intensive care unit transfer, an Apgar score of <7 at 1 min, and neonatal death. Additionally, the group was symptomatic with developmental delays and had more infantile deaths related to congenital heart disease (CHD). Our study makes a novel contribution to the literature by exploring the differences in the adverse perinatal outcomes and early life conditions between the 15q11.2 CNV and normal array groups. Parent-origin gender-based differences may help in the prognosis of the fetal phenotype; development levels should be followed up in the long term and echocardiography should be offered prenatally and postnatally for the prevention of a delayed diagnosis of CHD. [ABSTRACT FROM AUTHOR]

BACKGROUND: This trial aimed to assess the efficacy, acceptability, and safety of a first-trimester screen-and-prevent strategy for preterm preeclampsia in Asia. METHODS: Between August 1, 2019, and February 28, 2022, this multicenter stepped wedge cluster randomized trial included maternity/diagnostic units from 10 regions in Asia. The trial started with a period where all recruiting centers provided routine antenatal care without study-related intervention. At regular 6-week intervals, one cluster was randomized to transit from nonintervention phase to intervention phase. In the intervention phase, women underwent first-trimester screening for preterm preeclampsia using a Bayes theorem-based triple-test. High-risk women, with adjusted risk for preterm preeclampsia =1 in 100, received low-dose aspirin from <16 weeks until 36 weeks. RESULTS: Overall, 88.04% (42 897 of 48 725) of women agreed to undergo first-trimester screening for preterm preeclampsia. Among those identified as high-risk in the intervention phase, 82.39% (2919 of 3543) received aspirin prophylaxis. There was no significant difference in the incidence of preterm preeclampsia between the intervention and non-intervention phases (adjusted odds ratio [aOR], 1.59 [95% CI, 0.91-2.77]). However, among high-risk women in the intervention phase, aspirin prophylaxis was significantly associated with a 41% reduction in the incidence of preterm preeclampsia (aOR, 0.59 [95% CI, 0.37-0.92]). In addition, it correlated with 54%, 55%, and 64% reduction in the incidence of preeclampsia with delivery at <34 weeks (aOR, 0.46 [95% CI, 0.23-0.93]), spontaneous preterm birth <34 weeks (aOR, 0.45 [95% CI, 0.22-0.92]), and perinatal death (aOR, 0.34 [95% CI, 0.12-0.91]), respectively. There was no significant between-group difference in the incidence of aspirin-related severe adverse events. CONCLUSIONS: The implementation of the screen-and-prevent strategy for preterm preeclampsia is not associated with a significant reduction in the incidence of preterm preeclampsia. However, low-dose aspirin effectively reduces the incidence of preterm preeclampsia by 41% among high-risk women. The screen-and-prevent strategy for preterm preeclampsia is highly accepted by a diverse group of women from various ethnic backgrounds beyond the original population where the strategy was developed. These findings underpin the importance of the widespread implementation of the screen-andprevent strategy for preterm preeclampsia on a global scale. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the performance of an artificial intelligence (AI) and machine learning (ML) model for first‐trimester screening for pre‐eclampsia in a large Asian population. Methods: This was a secondary analysis of a multicenter prospective cohort study in 10 935 participants with singleton pregnancies attending for routine pregnancy care at 11–13+6 weeks of gestation in seven regions in Asia between December 2016 and June 2018. We applied the AI+ML model for the first‐trimester prediction of preterm pre‐eclampsia (<37 weeks), term pre‐eclampsia (≥37 weeks), and any pre‐eclampsia, which was derived and tested in a cohort of pregnant participants in the UK (Model 1). This model comprises maternal factors with measurements of mean arterial pressure, uterine artery pulsatility index, and serum placental growth factor (PlGF). The model was further retrained with adjustments for analyzers used for biochemical testing (Model 2). Discrimination was assessed by area under the receiver operating characteristic curve (AUC). The Delong test was used to compare the AUC of Model 1, Model 2, and the Fetal Medicine Foundation (FMF) competing risk model. Results: The predictive performance of Model 1 was significantly lower than that of the FMF competing risk model in the prediction of preterm pre‐eclampsia (0.82, 95% confidence interval [CI] 0.77–0.87 vs. 0.86, 95% CI 0.811–0.91, P = 0.019), term pre‐eclampsia (0.75, 95% CI 0.71–0.80 vs. 0.79, 95% CI 0.75–0.83, P = 0.006), and any pre‐eclampsia (0.78, 95% CI 0.74–0.81 vs. 0.82, 95% CI 0.79–0.84, P < 0.001). Following the retraining of the data with adjustments for the PlGF analyzers, the performance of Model 2 for predicting preterm pre‐eclampsia, term pre‐eclampsia, and any pre‐eclampsia was improved with the AUC values increased to 0.84 (95% CI 0.80–0.89), 0.77 (95% CI 0.73–0.81), and 0.80 (95% CI 0.76–0.83), respectively. There were no differences in AUCs between Model 2 and the FMF competing risk model in the prediction of preterm pre‐eclampsia (P = 0.135) and term pre‐eclampsia (P = 0.084). However, Model 2 was inferior to the FMF competing risk model in predicting any pre‐eclampsia (P = 0.024). Conclusion: This study has demonstrated that following adjustment for the biochemical marker analyzers, the predictive performance of the AI+ML prediction model for pre‐eclampsia in the first trimester was comparable to that of the FMF competing risk model in an Asian population. Synopsis: Machine learning model achieved comparable predictive performance to that of the FMF competing risk model in predicting preterm and term pre‐eclampsia in an Asian population. [ABSTRACT FROM AUTHOR]

Focuses on a study which outlined an approach that can be used to define and construct normal modes of motion for a wide class of nonlinear vibratory systems. Background on normal modes of nonlinear systems; Information on reduced-order modeling; Cases of harmonic excitation.

We has identified a founder homozygous E3_E4 del: 2870 bp deletion + 9 bp insertion in AGT gene encoding angiotensinogen responsible for autosomal recessive renal tubular dysgenesis (ARRTD) with nearly-fatal outcome. High-dose hydrocortisone therapy successfully rescued one patient with an increased serum Angiotensinogen (AGT), Ang I, and Ang II levels. The pathogenesis of ARRTD caused by this AGT mutation and the potential therapeutic effect of hydrocortisone were examined by in vitro functional studies. The expression of this truncated AGT protein was relatively low with a dose-dependent manner. This truncated mutation diminished the interaction between mutant AGT and renin. The truncated AGT also altered the glucocorticoid receptor (GR)-dependent transactivation, indicating that AGT may affect the development of proximal convoluted tubule by alteration of glucocorticoid-dependent transactivation. In hepatocytes, hydrocortisone increased the AGT level by accentuating the stability of mutant AGT and increasing its binding with renin. Therefore, hydrocortisone may exert the therapeutic effect through the enhanced stability and interaction with renin of truncated AGT in patients carrying this AGT mutation. [ABSTRACT FROM AUTHOR]

The present study examined whether bladder detrusor dysfunction due to partial bladder outlet obstruction (pBOO) could be improved after the treatment of human amniotic fluid stem cells (hAFSCs). 72 female rats were grouped into sham operation, pBOO, and pBOO with hAFSCs treatment (pBOO + hAFSCs) for in vitro and in vivo studies. Bladder weight, bladder wall thickness, the ratio of collagen to smooth muscle and the levels of positive CD11b/c and HIS48 cells was significantly increased after pBOO but improved after hAFSCs treatment. Cystometries showed impaired bladder function after pBOO. Protein and mRNA levels of hypoxia inducible factor-1α, CCL2, interleukin-1β, transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), α-smooth muscle actin, collagen I and collagen III were increased at 2 and/or 6 weeks, but proteins and mRNA expressions of protein gene product 9.5 were decreased at 2 and 6 weeks after pBOO. These abnormalities were improved after hAFSCs treatment. The expressions of TGF-β1 and CTGF in cultured detrusor cells of pBOO rats were increased but were improved after hAFSCs treatment. The present results showed hAFSCs treatment could improve bladder detrusor dysfunction in pBOO rats, which may be related to the reduction of inflammatory and pro-fibrotic markers in detrusor muscle cells. [ABSTRACT FROM AUTHOR]

In contrast to the well-known phenomenon of frequency stabilization in a synchronized noisy nonlinear oscillator, little is known about its amplitude stability. In this paper, we investigate experimentally and theoretically the amplitude evolution and stability of a nonlinear nanomechanical self-sustained oscillator that is synchronized with an external harmonic drive. We show that the phase difference between the tones plays a critical role on the amplitude level, and we demonstrate that in the strongly nonlinear regime, its amplitude fluctuations are reduced considerably. These findings bring to light a new facet of the synchronization phenomenon, extending its range of applications beyond the field of clock-references and suggesting a new means to enhance oscillator amplitude stability. Synchronization, a ubiquitous phenomenon in nature, has been extensively studied from the frequency point of view for micro- and nano-electromechanical systems, but less so when amplitude stability is concerned. The authors investigate, theoretically and experimentally, the amplitude stabilization in an externally harmonic drive synchronized noisy nonlinear oscillator, showcasing the effect of the amplitude noise reduction in these devices. [ABSTRACT FROM AUTHOR]

Background: The administration of aspirin <16 weeks gestation to women who are at high risk for preeclampsia has been shown to reduce the rate of preterm preeclampsia by 65%. The traditional approach to identify such women who are at risk is based on risk factors from maternal characteristics, obstetrics, and medical history as recommended by the American College of Obstetricians and Gynecologists and the National Institute for Health and Care Excellence. An alternative approach to screening for preeclampsia has been developed by the Fetal Medicine Foundation. This approach allows the estimation of patient-specific risks of preeclampsia that requires delivery before a specified gestational age with the use of Bayes theorem-based model.Objective: The purpose of this study was to examine the diagnostic accuracy of the Fetal Medicine Foundation Bayes theorem-based model, the American College of Obstetricians and Gynecologists, and the National Institute for Health and Care Excellence recommendations for the prediction of preterm preeclampsia at 11-13+6 weeks gestation in a large Asian population STUDY DESIGN: This was a prospective, nonintervention, multicenter study in 10,935 singleton pregnancies at 11-13+6 weeks gestation in 11 recruiting centers across 7 regions in Asia between December 2016 and June 2018. Maternal characteristics and medical, obstetric, and drug history were recorded. Mean arterial pressure and uterine artery pulsatility indices were measured according to standardized protocols. Maternal serum placental growth factor concentrations were measured by automated analyzers. The measured values of mean arterial pressure, uterine artery pulsatility index, and placental growth factor were converted into multiples of the median. The Fetal Medicine Foundation Bayes theorem-based model was used for the calculation of patient-specific risk of preeclampsia at <37 weeks gestation (preterm preeclampsia) and at any gestation (all preeclampsia) in each participant. The performance of screening for preterm preeclampsia and all preeclampsia by a combination of maternal factors, mean arterial pressure, uterine artery pulsatility index, and placental growth factor (triple test) was evaluated with the adjustment of aspirin use. We examined the predictive performance of the model by the use of receiver operating characteristic curve and calibration by measurements of calibration slope and calibration in the large. The detection rate of screening by the Fetal Medicine Foundation Bayes theorem-based model was compared with the model that was derived from the application of American College of Obstetricians and Gynecologists and National Institute for Health and Care Excellence recommendations.Results: There were 224 women (2.05%) who experienced preeclampsia, which included 73 cases (0.67%) of preterm preeclampsia. In pregnancies with preterm preeclampsia, the mean multiples of the median values of mean arterial pressure and uterine artery pulsatility index were significantly higher (mean arterial pressure, 1.099 vs 1.008 [P<.001]; uterine artery pulsatility index, 1.188 vs 1.063[P=.006]), and the mean placental growth factor multiples of the median was significantly lower (0.760 vs 1.100 [P<.001]) than in women without preeclampsia. The Fetal Medicine Foundation triple test achieved detection rates of 48.2%, 64.0%, 71.8%, and 75.8% at 5%, 10%, 15%, and 20% fixed false-positive rates, respectively, for the prediction of preterm preeclampsia. These were comparable with those of previously published data from the Fetal Medicine Foundation study. Screening that used the American College of Obstetricians and Gynecologists recommendations achieved detection rate of 54.6% at 20.4% false-positive rate. The detection rate with the use of National Institute for Health and Care Excellence guideline was 26.3% at 5.5% false-positive rate.Conclusion: Based on a large number of women, this study has demonstrated that the Fetal Medicine Foundation Bayes theorem-based model is effective in the prediction of preterm preeclampsia in an Asian population and that this method of screening is superior to the approach recommended by American College of Obstetricians and Gynecologists and the National Institute for Health and Care Excellence. We have also shown that the Fetal Medicine Foundation prediction model can be implemented as part of routine prenatal care through the use of the existing infrastructure of routine prenatal care. [ABSTRACT FROM AUTHOR]

Aims/Introduction: The association between gestational diabetes mellitus (GDM) and adverse maternal and perinatal outcomes in twin pregnancies remains unclear. This study was undertaken to highlight risk factors for GDM in women with dichorionic (DC) twins, and to determine the association between GDM DC twins and adverse maternal and perinatal outcomes in a large homogeneous Taiwanese population. Materials and Methods: A retrospective cross‐sectional study was carried out on 645 women with DC twins, excluding pregnancies complicated by one or both fetuses with demise (n = 22) or congenital anomalies (n = 9), who gave birth after 28 complete gestational weeks between 1 January 2001 and 31 December 2018. Univariable and multiple logistic regression analyses were carried out. Results: Maternal age >34 years (adjusted odds ratio 2.52; 95% confidence interval 1.25–5.07) and pre‐pregnancy body mass index >24.9 kg/m2 (adjusted odds ratio 2.83, 95% confidence interval 1.47–5.46) were independent risk factors for GDM in women with DC twins. Newborns from women with GDM DC twins were more likely to be admitted to the neonatal intensive care unit (adjusted odds ratio 1.70, 95% confidence interval 1.06–2.72) than newborns from women with non‐GDM DC twins. Other pregnancy and neonatal outcomes were similar between the two groups. Conclusions: Advanced maternal age and pre‐pregnancy overweight or obesity are risk factors for GDM in women with DC twins. Except for a nearly twofold increased risk of neonatal intensive care unit admission of newborns, the pregnancy and neonatal outcomes for women with GDM DC twins are similar to those for women with non‐GDM DC twins. [ABSTRACT FROM AUTHOR]

Much is known about the nonlinear resonant response of mechanical systems, but methods for the systematic design of structures that optimize aspects of these responses have received little attention. Progress in this area is particularly important in the area of micro-systems, where nonlinear resonant behaviour is being used for a variety of applications in sensing and signal conditioning. In this work, we describe a computational method that provides a systematic means for manipulating and optimizing features of nonlinear resonant responses of mechanical structures that are described by a single vibrating mode, or by a pair of internally resonant modes. The approach combines techniques from nonlinear dynamics, computational mechanics and optimization, and it allows one to relate the geometric and material properties of structural elements to terms in the normal form for a given resonance condition, thereby providing a means for tailoring its nonlinear response. The method is applied to the fundamental nonlinear resonance of a clamped-clamped beam and to the coupled mode response of a frame structure, and the results show that one can modify essential normal form coefficients by an order of magnitude by relatively simple changes in the shape of these elements. We expect the proposed approach, and its extensions, to be useful for the design of systems used for fundamental studies of nonlinear behaviour as well as for the development of commercial devices that exploit nonlinear behaviour. [ABSTRACT FROM AUTHOR]

This review provides a summary of work on the resonant nonlinear dynamics of micro- and nanoelectromechanical systems. This research area, which has been active for approximately a decade, involves the study of nonlinear behaviors arising in small scale, vibratory, mechanical devices that are typically integrated with electronics for use in signal processing, actuation, and sensing applications. The inherent nature of these devices, which includes low damping, desired resonant operation, and the presence of nonlinear potential fields, sets an ideal stage for the appearance of nonlinear behavior. While nonlinearities are typically avoided in device design, they have the potential to allow designers to beneficially leverage nonlinear behavior in certain applications. This paper provides an overview of the fundamental research on nonlinear behaviors arising in micro-/nanoresonators, including direct and parametric resonances in individual resonators and coupled resonator arrays, and also describes the active exploitation of nonlinear dynamics in the development of resonant mass sensors, inertial sensors, and electromechanical signal processing systems. This paper closes with some brief remarks about important ongoing developments in the field. [ABSTRACT FROM AUTHOR]

Objective: To assess risk factors for anxiety and depression among pregnant women during the COVID‐19 pandemic using Mind‐COVID, a prospective cross‐sectional study that compares outcomes in middle‐income economies and high‐income economies. Methods: A total of 7102 pregnant women from 12 high‐income economies and nine middle‐income economies were included. The web‐based survey used two standardized instruments, General Anxiety Disorder‐7 (GAD‐7) and Patient Health Questionnaire–9 (PHQ‐9). Result: Pregnant women in high‐income economies reported higher PHQ‐9 (0.18 standard deviation [SD], P < 0.001) and GAD‐7 (0.08 SD, P = 0.005) scores than those living in middle‐income economies. Multivariate regression analysis showed that increasing PHQ‐9 and GAD‐7 scales were associated with mental health problems during pregnancy and the need for psychiatric treatment before pregnancy. PHQ‐9 was associated with a feeling of burden related to restrictions in social distancing, and access to leisure activities. GAD‐7 scores were associated with a pregnancy‐related complication, fear of adverse outcomes in children related to COVID‐19, and feeling of burden related to finances. Conclusions: According to this study, the imposed public health measures and hospital restrictions have left pregnant women more vulnerable during these difficult times. Adequate partner and family support during pregnancy and childbirth can be one of the most important protective factors against anxiety and depression, regardless of national economic status. Synopsis: Imposed public health measures and hospital‐level restrictions have made pregnant women more vulnerable to anxiety and depression during the COVID‐19 pandemic. [ABSTRACT FROM AUTHOR]

We aim to establish a prediction model for pregnancy outcomes through a combinatorial analysis of circulating biomarkers and maternal characteristics to effectively identify pregnant women with higher risks of preeclampsia in the first and third trimesters within the Asian population. A total of two hundred and twelve pregnant women were screened for preeclampsia through a multicenter study conducted in four recruiting centers in Taiwan from 2017 to 2020. In addition, serum levels of sFlt-1/PlGF ratio, miR-181a, miR-210 and miR-223 were measured and transformed into multiples of the median. We thus further developed statistically validated algorithmic models by designing combinations of different maternal characteristics and biomarker levels. Through the performance of the training cohort (0.848 AUC, 0.73–0.96 95% CI, 80% sensitivity, 85% specificity, p < 0.001) and the validation cohort (0.852 AUC, 0.74–0.98 95% CI, 75% sensitivity, 87% specificity, p < 0.001) from one hundred and fifty-two women with a combination of miR-210, miR-181a and BMI, we established a preeclampsia prediction model for the first trimester. We successfully identified pregnant women with higher risks of preeclampsia in the first and third trimesters in the Asian population using the established prediction models that utilized combinatorial analysis of circulating biomarkers and maternal characteristics. [ABSTRACT FROM AUTHOR]

In this work, a design methodology for robust and effective centrifugal pendulum absorbers is presented with a relative center of mass translation along a given path and angular body rotation. This type of absorber is used in rotatory machines with rotor angle synchronous excitation, allowing for a reduction of angular rotor fluctuations over the entire speed range. The main areas of application are aircraft drives and automotive drive trains with internal combustion engines. Since the requirements placed on absorbers are increasingly demanding in terms of reducing their mass without sacrificing effectiveness, new design approaches must be pursued. The linear theory used in the past has been replaced by the nonlinear tautochronic design philosophy that provides an increased working range of the pendula. This approach has been extended in recent years with regard to nonlinear detuning in order to obtain effective and robust absorbers. It is known that, in addition to the translation of the pendula, the rotation of the pendulum bodies, contributes to absorber performance, and the nonlinear design tools are extended to this case. The proposed unified design approach allows one to apply existing tuning methodologies of centrifugal pendulum absorbers with their relative rotational movement, referred to as "rocking" absorbers. Maintaining generality, the equations of motion are derived for a system with multiple absorbers and prepared for the application of simulations and continuation algorithms for parameter studies. Additionally, a state transformation is presented, which allows the application of perturbation methods and averaging under the assumption of small parameters. The increased effectiveness of these rocking absorber class when compared to non-rocking absorbers is quantified and demonstrated by numerical case studies. • Nonlinear dynamics of rocking centrifugal vibration absorbers. • Framework for tautochronic and nonlinear detuned absorbers. • Analytical solutions of special rocking absorbers. • Complete and consistent incorporation of roller dynamics, including their kinematic cutout contours. [ABSTRACT FROM AUTHOR]

Clamping loss in micromechanical resonators can strongly depend on the boundary conditions far away from the actual vibrating structure because the acoustic wavelength greatly exceeds the device dimensions. We demonstrate a scheme for post-fabrication tuning of the clamping loss in flexural-mode and bulk-mode resonators by modifying the boundary conditions of the chip with the frame. The measured quality factor increases by more than an order-of-magnitude for the microcantilevers and more than a factor of three for the bulk-mode resonators when frame contact is minimized via suspension of the chip by wirebonds. We propose a two-degree-of-freedom fluctuation-dissipation model to describe the thermomechanical noise and forced response in the presence of this tunable anchor damping. By studying the thermomechanical displacement spectrum with tunable clamping loss, we show that variable clamping loss tunes the mechanical quality factor, modifying both the resonator transfer function and thermomechanical noise force. We delineate the dependence of the tunable clamping loss mechanism on microcantilever beam length and ambient temperature from 300 K down to 40 K, and observe potential temperature dependence to clamping loss with reducing temperature. [2021-0141] [ABSTRACT FROM AUTHOR]

Abstract: Electromagnetic micro-transducers have been utilized in a number of distinct applications in recent years due, in large part, to their scalability, low power consumption, self-sensing capabilities and ease of integration with external hardware. In the present work, the highly non-linear dynamic behavior of a new class of parametrically excited, electromagnetically actuated microcantilevers is explored. The system is modeled using classical energy methods and its frequency response behavior is subsequently characterized using perturbation methods and bifurcation analysis. The recovered results provide a clear understanding of the effects of fifth-order non-linearities in a parametrically excited microresonator, and are currently guiding experimental work on electromagnetically actuated oscillators and microresonator arrays. [Copyright &y& Elsevier]