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This work aims to describe the physical and numerical modeling of a CFD solver for hypersonic flows in thermo-chemical non-equilibrium. This paper is the second of a two-part series that concerns the application of the solver introduced in Part I to adaptive unstructured meshes.,The governing equations are discretized with an edge-based stabilized finite element method (FEM). Chemical non-equilibrium is simulated using a laminar finite-rate kinetics, while a two-temperature model is used to account for thermodynamic non-equilibrium. The equations for total quantities, species and vibrational-electronic energy conservation are loosely coupled to provide flexibility and ease of implementation. To accurately perform simulations on unstructured meshes, the non-equilibrium flow solver is coupled with an edge-based anisotropic mesh optimizer driven by the solution Hessian to carry out mesh refinement, coarsening, edge swapping and node movement.,The paper shows, through comparisons with experimental and other numerical results, how FEM + anisotropic mesh optimization are the natural choice to accurately simulate hypersonic non-equilibrium flows on unstructured meshes. Three-dimensional test cases demonstrate how, for high-speed flows, shocks resolution, and not necessarily boundary layers resolution, is the main driver of solution accuracy at walls. Equally distributing the error among all elements in a suitably defined Riemannian space yields highly anisotropic grids that feature well-resolved shock waves. The resulting high level of accuracy in the computation of the enthalpy jump translates into accurate wall heat flux predictions. At the opposite end, in all cases examined, high-quality but isotropic unstructured meshes gave very poor solutions with severely inadequate heat flux distributions not even featuring expected symmetries. The paper unequivocally demonstrates that unstructured anisotropically adapted meshes are the best, and may be the only, way for accurate and cost-effective hypersonic flow solutions.,Although many hypersonic flow solvers are developed for unstructured meshes, few numerical simulations on unstructured meshes are presented in the literature. This work demonstrates that the proposed approach can be used successfully for hypersonic flows on unstructured meshes.

Introduction. The clinical course of Coronavirus Disease 2019 (COVID-19) is highly heterogenous, ranging from asymptomatic to fatal forms. The identification of clinical and laboratory predictors of poor prognosis may assist clinicians in monitoring strategies and therapeutic decisions. Materials and Methods. In this study, we retrospectively assessed the prognostic value of a simple tool, the complete blood count, on a cohort of 664 patients ( F 260; 39%, median age 70 (56-81) years) hospitalized for COVID-19 in Northern Italy. We collected demographic data along with complete blood cell count; moreover, the outcome of the hospital in-stay was recorded. Results. At data cut-off, 221/664 patients (33.3%) had died and 453/664 (66.7%) had been discharged. Red cell distribution width (RDW) ( χ 2 10.4; p < 0.001 ), neutrophil-to-lymphocyte (NL) ratio ( χ 2 7.6; p = 0.006 ), and platelet count ( χ 2 5.39; p = 0.02 ), along with age ( χ 2 87.6; p < 0.001 ) and gender ( χ 2 17.3; p < 0.001 ), accurately predicted in-hospital mortality. Hemoglobin levels were not associated with mortality. We also identified the best cut-off for mortality prediction: a NL ratio > 4.68 was characterized by an odds ratio for in-hospital mortality OR = 3.40 (2.40-4.82), while the OR for a RDW > 13.7 % was 4.09 (2.87-5.83); a platelet count > 166,000 /μL was, conversely, protective (OR: 0.45 (0.32-0.63)). Conclusion. Our findings arise the opportunity of stratifying COVID-19 severity according to simple lab parameters, which may drive clinical decisions about monitoring and treatment.

Objective Hypertension affects more than one billion people worldwide. There has been much discussion about clinical practice guidelines (CPGs) following the proposal of lower thresholds for starting pharmacological treatment. Some smaller groups or institutions could benefit from adapting CPGs to their local context, a process that requires high-quality CPGs with few points of conflict in their recommendations. To address this issue, we have compared high-quality hypertension CPGs and highlighted conflicting recommendations. Methods CPGs were searched in MEDLINE, Embase, the Cochrane Library, as well as specific websites. Only CPGs published between 2016 and 2019 were included. We defined CPGs as high-quality if the 'rigor of development' and 'editorial independence' AGREE II domains were scored at least 60%. We compared recommendations made by high-quality CPGs and highlighted areas of conflict (defined as disagreements between more than two CPGs). Results Nineteen CPGs were identified. The highest scoring domain was 'scope and purpose' (74.3%) and the lowest scoring was 'applicability' (40.0%). Eight CPGs were rated as high quality. Most CPG recommendations on the management of hypertension were consistent. Conflicting recommendations were regarding blood pressure (BP) levels to initiate pharmacotherapy and therapeutic goals, particularly in patients with low cardiovascular risk and older patients. Conclusion It is possible to adapt hypertension CPGs once high-quality documents have been identified with agreement between most recommendations. Guideline developers can focus on the adaption process and concentrate efforts on implementation.

This research is done to know effects of financial performance toward corporate value by using the disclosure of Good Corporate Governance and Corporate Social Responsibility as a moderating variable. ROA, ROE, and Leverage as an indicator of financial performance is known as the independent variable. Company value measured by Tobin’s is known as the dependent variable. Good Corporate Governance(GCG) and Corporate Social Responsibility (CSR) is moderating variable.The companies that are in this research are manufacturing companies which are listed in the Indonesia Stock Exchange (IDX) starting from 2004 until 2007, published financial statements ending 31 December, and had complete data of Good Corporate Governance and Corporate Social Responsibility. The data is then processed by using statistical appliance that are called regression with interaction.According to the research, the financial performance (ROA and leverage) has an effect on corporate value. Disclosure of Corporate Social Responsibility(CSR) does not affect to financial performance (ROA and Leverage) toward the value of the company. Disclosure of Good Corporate Governance (GCG) affects the financial performance of relationship (ROA and Leverage) toward the value of the company.

Hypersonic flows have recently re-acquired an important role in fluids research, with many nations interested in their applications. Due to their complex multidisciplinary aspects, the limitations ...

A mesoscale model for droplet dynamics based on a quasi-molecular approach is proposed. It considers the interaction between quasi-molecules within a single liquid droplet, each quasi-molecule representing an agglomeration of a large number of actual water molecules. The goal is to improve the understanding of the dynamics of large droplet collisions over dry or wet surfaces at velocities typical of aeronautical applications. This detailed analysis will eventually be used to refine the macroscopic Eulerian description of the water impingement process by providing numerical correlations for splashing and bouncing phenomena relevant for in-flight icing applications. Based on the Equipartition Theorem, approaches for extracting macroscopic quantities such as temperature and transport coefficients from the quasi-molecular method are discussed. A proper choice of the free parameters of the model that leads to accurate values of the macroscopic properties is also addressed.

A IRCRAFT flying through clouds of supercooled liquid droplets (SLD) can be subjected to in-flight ice accretion. Surface tension prevents the expansion of the droplets that would occur with phase change, forcing them to remain in liquid form even though their temperature is below the freezing point. When the droplets hit an aircraft’s surfaces, the surface tension decreases at the contact point, and theymay freeze completely on impact if the temperature is very low or freeze partially at higher temperatures, whereas the remaining liquid portion runs back on the surface, transported by the pressure gradient and the shear stress of the airflow. If no ice protection is provided, the aerodynamic characteristics of the aircraft and its handling can be severely degraded when ice accretes. The increased drag generated by the roughness of the ice can lead to flow separation, reduction of the stall margins, control reversals, and engine blockages [1]. Airworthiness of transport airplanes in icing conditions is demonstrated by compliance with certification standards (Appendix C of the FAA Federal Aviation Regulations, part 25) set by agencies, such as the Federal Aviation Administration, European Air Safety Association, Transport Canada, etc. These standards, frozen for 50 years, will soon undergo significant revisions with the adoption of Appendix O to address the icing threat posed by SLD conditions. Unlike smaller droplets, SLD can distort, break into smaller droplets, splash, bounce off surfaces, get carried downstream by the flow, and reimpinge, increasing the potential for ice contamination on unprotected surfaces [2–4]. Nowadays, wind tunnel tests, icing tunnel tests, and computer simulations play major complementary roles in the process of certifying a new aircraft [5,6]. Advances in modeling capabilities have created the conditions to accurately simulate the ice accretion process in a realistic three-dimensional (3-D) context [7,8]. Unfortunately, the computational cost associated with performing a multitude of 3-D simulations of various aeroicing conditions somewhat limits the widespread use of computational fluid dynamics (CFD), even if advanced computational resources are available [9,10]. To overcome this difficulty, mostly low-cost and, consequently, low-fidelity tools are usually employed. These may be based on empirical correlations, two-dimensional (2-D) approximations, inviscid or incompressible flow assumptions, and/or other simplifications that result in limited accuracy and realism. A viable alternative is the reduced-order modeling (ROM) approach [11,12], which dramatically reduces the cost of highfidelity simulations while providing solutions of superior accuracy to low-fidelity methods because it preserves the detailed physical modeling of the problem under consideration [13–16]. Although the use of this approach in the aeroicing environment is in its pioneering phase, recent results support the effectiveness of this methodology as a valuable tool in the context of a multicondition, multiparameter certification process [17–20]. In a framework of ice accretion simulation as the succession of airflow, water concentration, and heat transfer calculations, the most time-consuming part is obtaining the water impact patterns. The common practice is to assume a distribution of discrete droplet diameters, compute the impingement distribution of each diameter class, andweight-average thesemonodispersed solutions. In the case of the droplet sizes of Appendix C, seven distinct monodispersed sizes (Langmuir-D distribution) are used to compute the overall impingement distribution. In the SLD regime, however, due to the complex phenomena of droplet breakup, splashing, and bouncing, distributions containing up to 27 diameters of monodispersed droplets are needed to obtain realistic impingement predictions [5–7]. The computational cost of an SLD simulation is hence four times that of a Langmuir-D distribution. In the presentwork, it will be shown that the ROM approach can dramatically reduce cost with only a very modest degradation of the overall accuracy of the simulation. The essentials of the ROM approach used to extract the solution eigenfunctions (or modes) and compute solutions at unknown states are introduced in sections II and III of this paper, whereas section IV illustrates the interpolation technique used to compute the surrogate solutions. Finally, 2and 3-D results and comparison with experiments and other methods are presented to validate the present methodology. Received 29 July 2011; revision received 14 September 2011; accepted for publication 15 September 2011. Copyright © 2011 by Wagdi Habashi. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0021-8669/12 and $10.00 in correspondence with the CCC. Postdoctoral Research Associate, Mechanical Engineering, Computational Fluid Dynamics Laboratory, 688 Sherbrooke Street West; mfossati@cfdlab.mcgill.ca. Member AIAA (Corresponding Author). Professor and Director, NSERC-J. Armand Bombardier-Bell HelicopterCAE Industrial Research Chair of Multidisciplinary Computational Fluid Dynamics Laboratory, Department of Mechanical Engineering, 688 Sherbrooke Street West, Fellow AIAA. Research &Development Director, 688 Sherbrooke StreetWest, Member AIAA. JOURNAL OF AIRCRAFT Vol. 49, No. 2, March–April 2012

In-flight ice accretion, even though driven by a steady flow airstream, is an inherently unsteady phenomenon. It is, however, completely ignored in icing simulation codes (one-shot) or, at best approximated via quasi-steady modeling (multishot). The final ice shapes thus depend on the length of the total accretion time (one-shot), or of the arbitrarily prescribed time intervals (multishot), during which the impact of ice growth on both airflow and water impingement is ignored. Such a longstanding heuristic approximation is removed in this paper by coupling in time the dilute two-phase flow (air and water droplets flow) with ice accretion, and is implemented in a new code, FENSAP-ICE-Unsteady. The two-phase flow is solved using the coupled Navier–Stokes and water concentration equations, and the water film characteristics and ice shapes are obtained from laws of conservation of mass and energy within the thin film layer. To continually update the geometry of the iced surface in time, arbitrary Lagrangian–Eulerian terms are added to all governing equations to account for mesh movement in the case of stationary components. In the case of rotating/stationary interacting components, a dynamically stitched grid is used. The numerical results clearly show that unsteady modeling improves the accuracy of both rime and glaze ice shape prediction, compared with the traditional quasi-steady approach with frozen solutions. The unsteady model is shown to open the door for a unified approach to icing on fixed wings, on helicopters with blades/rotors/fuselage systems. Problems of current concern in the icing community such as the ingestion of ice crystals at high altitude become tractable with the new formulation.

A numerical simulation of a complex wind turbine icing event is performed using the FENSAP-ICE simulation system. First, 2D and 3D simulations of a characteristic atmospheric icing event on a small wind turbine are compared to experimental data. Comparable results are obtained with both methods, supporting the use of the 2D blade section approach for more computationally intensive simulations, which would be prohibitively expensive in 3D. A complex, historical weather event is then simulated on an industrial-scale wind turbine. The selected weather event is 17 hours long and based on data collected at a wind farm in the Gaspe Peninsula, Quebec, Canada. Since the actual turbine geometry was not available, the WindPACT 1.5 MW wind turbine rotor was selected for use in the simulations as it is of comparable size and rating to the wind turbines located on the Gaspe site. The performance simulation of the contaminated turbine compares well to the characteristics of the actual contaminated turbines at the Gaspe wind farm.

A fine-scale model of Supercooled Large Droplets dynamics is proposed based on a quasi-molecular approach, a meso-scale method that mimics the interaction between quasimolecules within a single liquid droplet. Each quasi-molecule is a combination of a large number of real molecules which are considered to be an ensemble. The goal is to simulate the deformation and the splashing processes of a droplet to obtain a better understanding of the dynamics of large droplets collisions with aircraft at realistic flight conditions in order to refine the macroscopic Eulerian description of the process.

Background: Acquired flat foot is generated by the fall of the medial arch of the foot. Spring Ligament (SL) lesions and posterior tibial insufficiency have been associated with fall of medial arch. In addition, some variations of sustentaculum tali have been associated with subtalar joint osteoarthritic changes and a high risk of acquired flat foot. Anatomical variations of spring ligament have been reported. Thus, some authors observed two fascicles that composed the ligament and some observed three fascicles. The purpose of this research is to study the anatomical variations of SL and its relations with the sustentaculum tali anatomical variations to establish which fascicles of spring ligament might coincide with a sustentaculum tali-risk factor for acquired flat foot. Materials and Methods: Fifteen feet in 10% formalin solution were reviewed. Anatomical dissections of subtalar joint were done, and the spring ligament fascicles and sustentaculum tali variations were studied. Results: A correlation was found between the type of sustentaculum tali and the numbers of fascicles that composed the ligament. Sustentaculum tali with two articular facets were related to spring ligaments with three fascicles, and sustentaculum tali with one articular surface were related to spring ligaments with two fascicles. The third fascicle of spring ligament was observed along with sustentaculum tali described as more stable and with less osteoarthritic changes. This observation might implicate a special role of the third fascicle in the stability of subtalar joint and the pathogenesis of acquired flat foot.

Standard preconditioners such as incomplete LU decomposition perform well when used with conjugate gradient-like iterative solvers such as GMRES for the solution of elliptic problems. However, efficient computation of convection-dominated problems requires, in general, the use of preconditioners tuned to the particular class of fluid-flow problems at hand. This paper presents three such preconditioners. The first is applied to the finite element computation of inviscid (Euler equations) transonic and supersonic flows with shocks and uses incomplete LU decomposition applied to a matrix with extra artificial dissipation. The second preconditioner is applied to the finite difference computation of unsteady incompressible viscous flow; it uses incomplete LU decomposition applied to a matrix to which a pseudo-compressible term has been added. The third method and application are similar to the second, only the LU decomposition is replaced by Beam-warming approximate factorization. In all cases, the results are in very good agreement with other published results and the new algorithms are found to be competitive with others; it is anticipated that the efficiency and robustness of conjugate-gradient-like methods will render them the method of choice as the difficulty of the problems that they are applied to is increased.

Ice accretion in aircraft engine components has raised safety and performance concerns. When flying in hazardous weather conditions, engines can ingest a mix of iced and liquid particles that can potentially result in a dangerous build-up on the forward components of the engines. The ice can then shed from the fan, spinner or IGV, and may cause mechanical damage and performance losses to downstream components. In order to cost-effectively replicate such an environment, a three-dimensional quasi-steady numerical approach is developed to model both rotating and static components, and their interaction. An inter- component mixing-plane approach, along with stagnation and radial equilibrium boundary conditions, has been implemented within FENSAP-ICE allowing the treatment of multi- stage unequal-pitch blade rows via a finite element interpolation method and proper circumferential averaging. The approach is first validated for the well-documented Aachen turbine and then used on a compressor stage to obtain impingement locations of supercooled droplets and ice shapes.

The FENSAP-ICE system was first conceived for fixed-wing aircraft and air induction system icing, but major developments are underway to augment its capabilities for icing simulation of rotorcraft and tiltrotor aircraft. A project is underway, under the auspices of the RITA (Rotorcraft Industry Technology Association) to reduce icing certification flight tests through use of second-generation three-dimensional (3D) Computational Fluid Dynamics (CFD) based technologies. The plan is to supplement traditional icing tunnel and flight-testing with modern 3D inflight icing simulation tools that facilitate the development and certification of all-weather operations rotorcraft and tilt-rotor aircraft. A viscous fully 3D ice accretion and runback modeling capability is being developed and initial correlation studies to both 2D and 3D icing test cases have produced very good results. An actuator disk model has also been developed to account for the effects of the main and tail rotors on the flow field and the subsequent changes to ice accretion patterns. The present paper will describe droplet impingement and ice accretion results in terms of increasing geometrical complexity from 2D trimmed airfoil sections, to full 3D tiltrotor aircraft in forward flight, with propellers modeled.

To assess muscle remodeling and functional adaptation to exercise and diet interventions, 26 men and women aged 72–98 yr underwent a vastus lateralis biopsy before and after placebo control condition, and progressive resistance training, multinutrient supplementation, or both. Type II atrophy, Z band, and myofibril damage were present at baseline. Combined weight lifting and nutritional supplementation increased strength by 257 ± 62% ( P = 0.0001) and type II fiber area by 10.1 ± 9.0% ( P = 0.033), with a similar trend for type I fiber area (+12.8 ± 22.2%). Exercise was associated with a 2.5-fold increase in neonatal myosin staining ( P = 0.0009) and an increase of 491 ± 137% ( P < 0.0001) in IGF-I staining. Ultrastructural damage increased by 141 ± 59% after exercise training ( P = 0.034). Strength increases were largest in those with the greatest increases in myosin, IGF-I, damage, and caloric intake during the trial. Age-related sarcopenia appears largely confined to type II muscle fibers. Frail elders respond robustly to resistance training with musculoskeletal remodeling, and significant increases in muscle area are possible with resistance training in combination with adequate energy intakes.

Carbon dioxide medical lasers are being used for various clinical applications with considerable success. Despite the bulk of the generating equipment, the use of light, articulated arms to deliver the power beam to either hand-held or microscope-mounted aiming heads allows accurate power placement. In addition, the beam can be focussed to a small spot size, minimizing damage to adjacent tissue provided that the output power and the precise duration of application are known, and the shielding of deeper tissue has been adequate. In an attempt to assess the reliability of the laser beam as a significant surgical tool (particularly suitable for fine cutting functions in microsurgical procedures), we tested the power output of some of the CO2 surgical lasers now available in Australia. An alarming discrepancy was found between the actual power delivered and the higher power value displayed as being delivered. As these medical lasers were tested and passed as fully functioning by their local agents, it is suggested that purchasers of CO2 lasers should be aware of these possible power inadequacies and subject their equipment to frequent power checks. Otherwise much longer applications of the laser beam will be needed to accomplish the cutting action required, with the consequent infliction of more damage to the surrounding tissues.

Determination of heart rate variation (RR interval variation) is a non-invasive technique which may be used for assessment of diabetic autonomic dysfunction. Interpretation has been complicated by age changes in the normal population and by uncertainty as to the optimum conditions for the performance of the test. This study was designed to establish a normal age-related range for RR interval variation performed under the simplest conditions (resting, seated) applicable to an outpatient diabetic clinic and to compare these measurements with augmented RR variation due to deep breathing (ARRIV) and with the Valsalva ratio (VR). Using an ECG recorder and a computer analysis program, resting RR interval variation (RRIV) was assessed in 100 non-diabetics (N) aged 12–80 years and 60 randomly selected diabetics (D) aged 14–74 years. RRIV, the standard deviation of RR intervals, declined progressively after age 40 in normal subjects. The diabetics had significantly (p < 0.001) reduced RRlV compared with normals; 65% having RRIV values more than 1 SD and 25% more than 2 SD below the age related mean for normals. RRlV was compared with ARRIV in 54 subjects (N40, 014) and with VR in 84 subjects (N54, D27). There was a significant correlation of RRlV with both indices but RRlV resulted in greater discrimination between N and D than ARRIV or VR. There was no significant correlation between RRlV and duration of diabetes but mean RRlV was significantly reduced in diabetics with peripheral neuropathy compared to those without. In seven diabetics studied both before and after substantial improvement in metabolic control RRlV improved by a mean of 51% (p < 0.005). Measurement of RRlV is a simple non-invasive technique for assessment of diabetic autonomic dysfunction. Interpretation, however, depends on knowledge of an age-related reference range.

The serum insulin elevation after subcutaneous (s.c.) infusion of 10 U of neutral regular insulin given over 5 or 30 min has been examined in normal subjects to find a delivery profile that would simulate the normal serum insulin response to a meal. Endogenous insulin release, assessed by measurement of C-peptide, was suppressed by an i.v. infusion of 1 U/h neutral regular insulin, beginning 60 min before the s.c. administration and continuing throughout the study. The increment in serum insulin levels after the 5-min s.c. infusion reached a peak of 62 ± 9.5 mU/L at 45 min, and the rate of elevation of insulin levels closely approximated the normal insulin response to a 50-g, 500 kcal mixed meal. The increment in serum insulin levels with the 30-min s.c. infusion reached a peak of 41 ± 1.4 mU/L at 75 min. The incremental insulin response up to 180 min (area under the curve) after the 5-min s.c. infusion was 30% greater than the response to the 30-min infusion. On the basis of these studies, we conclude that insulin delivery for meals during s.c. insulin infusion need not be initiated before the meal, but should be given over a period of approximately 5 min or less. Further study is required to delineate the effects of concentration, local degradation, and rate of delivery on entry of s.c. insulin to the vascular system.

Modern active hand prostheses include myoelectric controlled electronics and actuators to restore the lost biomechanics functionalities. It is here investigated the feasibility of a wireless transcutaneous telemetry link based on the UHF Radiofrequency Identification aimed at collecting the electromyographic signal just at the level of the muscular tissues. The link should interconnect one or more implanted battery-less antennas with an external miniaturized and conformal reader's antenna integrated with the prosthetic socket. Numerical models and preliminary laboratory experimentations demonstrated the possibility to successfully establish an RFID data link with a multiplicity of implanted tags even by using a low-power (0.25 W) embedded reader with a displacement-tolerance among interrogating and sensor antennas of 1-2 cm.

Background and aim: Searching for alternative therapies that are effective, safe and less expensive of those currently used for ulcerative colitis, we investigated the efficacy of a polyphenol extract from apple in rat colitis. Methods: Rats with trinitrobenzensulphonic acid-induced colitis were treated daily with rectal administration of apple polyphenols 10(-4) M for 14 days. COX-2, TNF-alpha, tissue transglutaminase and calpain in colon mucosa samples were assessed by reverse transcription-polymerase chain reaction and western blot analyses. To ascertain the role of tissue transglutaminase in mucosal healing, wounded rat fibroblasts were incubated with cystamine (a tissue transglutaminase activity inhibitor). Results: Colitis was associated with increased COX-2, TNF-alpha, calpain, and tissue transglutaminase mRNA. The protein expression of COX-2, TNF-alpha and calpain was increased whilst tissue transglutaminase was decreased. Apple extract treatment reduced the severity of colitis (p < 0.05) and restored all the considered biomarkers at the baseline level. Apple polyphenols reduced the degradation of tissue transglutaminase protein occurring through calpain action. Apple polyphenols-treated wounded fibroblast recovered within 24 h showing intense immunoreactivity for tissue transglutaminase. Conclusion: The efficacy of apple extract is mediated by its effects on COX-2 and TNF-alpha. The unbalance between calpain and tissue transglutaminase may play a role in colonic damage and future therapeutic interventions in ulcerative colitis can target this mechanisms. (C) 2012 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Energy harvesting at low frequency is a challenge for microelectromechanical systems. In this work we present a piezoelectric vibration energy harvester based on freestanding molybdenum (Mo) and aluminum nitride (AlN) ring-microelectromechanical-system (RMEMS) resonators. The freestanding ring layout has high energy efficiency due to the additional torsional modes which are absent in planar cantilevers systems. The realized RMEMS prototypes show very low resonance frequencies without adding proof masses, providing the record high power density of 30.20 μW mm−3 at 64 Hz with an acceleration of 2g. The power density refers to the volume of the vibrating RMEMS layout.