Position estimation delays in signal injection-based sensorless PMSM drives

The causes of position estimation delays and their effects on the sensorless control of permanent magnet synchronous motor drives are investigated. The position of a permanent magnet synchronous machine is estimated via the injection of high frequency voltage signals. The delays under investigation are due to the digital implementation of the control algorithm and to the digital filters adopted for decoupling the inspection signals from the fundamental components of the stator current measures. If not correctly modeled and compensated, such delays can reduce the performance of the control scheme. Experimental results are provided, proving the accuracy of the modeling approach and the effectiveness of the related compensation strateg

Acceptability and Feasibility of Web-based Diabetes Instruction for Latinos with Limited Education and Computer Experience

Introduction: The internet offers an important avenue for developing diabetes self-management skills, but many Latinos have limited experience with computer-based instruction. Objective: To evaluate the feasibility and acceptability of delivering a web-based diabetes education program in a computer classroom for Spanish-speaking Latinos. Methods: Spanish-speaking Latinos (n=26) attended two classroom sessions to learn computer skills while navigating a web-based diabetes education platform. Diabetes knowledge was assessed before and after the intervention; structured interviews were completed to assess program acceptability. Results: Half of participants (50%) had not previously used a computer. Post-intervention, diabetes knowledge improved significantly (p=.001). The majority of participants (86%) indicated a preference for web-based instruction as a stand-alone program or as an adjunct to traditional classroom training, particularly citing the advantage of being able to engage the material at their own pace. Conclusion: With limited support, Latinos with minimal computer experience can effectively engage in web-based diabetes education

Mechanical overtone frequency combs

Mechanical frequency combs are poised to bring the applications and utility of optical frequency combs into the mechanical domain. So far, their use has been limited by strict conditions on drive frequencies and power, small bandwidths and complicated modes of operation. We demonstrate a novel, straightforward mechanism to create a frequency comb consisting of mechanical overtones (integer multiples) of a single eigenfrequency, by monolithically integrating a suspended dielectric membrane with a counter-propagating optical trap generated via its own substrate. The periodic optical field modulates the dielectrophoretic force on the membrane at integer multiples of the membrane's frequency of motion, thus efficiently creating overtones of that frequency and forming a frequency comb. Using the same periodic optical field, we simultaneously demonstrate a strong, parametric thermal driving mechanism that requires no additional power or frequency reference. The combination of these effects results in a versatile, easy-to-use mechanical frequency comb platform that requires no precise alignment, no additional feedback or control electronics, and only uses a single, mW continuous wave laser beam. This highlights the mechanical frequency comb as a low-power, on-chip alternative to optical frequency combs for sensing, timing and metrology applications

High-Strength Amorphous Silicon Carbide for Nanomechanics

For decades, mechanical resonators with high sensitivity have been realized using thin-film materials under high tensile loads. Although there have been remarkable strides in achieving low-dissipation mechanical sensors by utilizing high tensile stress, the performance of even the best strategy is limited by the tensile fracture strength of the resonator materials. In this study, a wafer-scale amorphous thin film is uncovered, which has the highest ultimate tensile strength ever measured for a nanostructured amorphous material. This silicon carbide (SiC) material exhibits an ultimate tensile strength of over 10 GPa, reaching the regime reserved for strong crystalline materials and approaching levels experimentally shown in graphene nanoribbons. Amorphous SiC strings with high aspect ratios are fabricated, with mechanical modes exceeding quality factors 10^8 at room temperature, the highest value achieved among SiC resonators. These performances are demonstrated faithfully after characterizing the mechanical properties of the thin film using the resonance behaviors of free-standing resonators. This robust thin-film material has significant potential for applications in nanomechanical sensors, solar cells, biological applications, space exploration and other areas requiring strength and stability in dynamic environments. The findings of this study open up new possibilities for the use of amorphous thin-film materials in high-performance applications

Impact of PWM Voltage Waveforms in High-Speed Drives: A Survey on High-Frequency Motor Models and Partial Discharge Phenomenon

The insulation system’s dielectric of the electric motor is very often subjected to severe electrical stress generated by the high dv/dt seen at the machine’s terminals. The electrical stress and high reflected wave transient overvoltage are even more evident in case of high-speed machines fed by high-frequency (HF) converters featuring very fast wide-bandgap devices. They are promoting the occurrence of partial discharges and consequently accelerate ageing. As this is serious issue and the main cause of the drive failure, it is important to analyse and characterise the surges at the motor terminals. Several HF models of motors have been proposed in the literature for this purpose. This article presents a survey on HF motor models, which is crucial in understanding and studying the most critical parameter identification and overvoltage mitigation techniques. Moreover, it offers a comparison of the models’ main features as well as a comparison with the experimental voltage waveform at motor terminals. A general overview of the partial discharge (PD) phenomenon is also provided, as it is favoured by HF operation and together with HF motor modelling provides key insights to the insulation ageing issue. In particular, an analysis of the effects of PWM waveform affecting insulation is given, as well as useful methods for developing strategies for the inspection and maintenance of winding insulation

Metodologia de avaliacao de germoplasma de Lycopersicon visando resistencia ao virus de vira-cabeca do tomateiro.

Verificou-se, previamente, que a inoculacao mecanica do virus de vira-cabeca nas folhas primarias de feijao 'Manteiga', nao completamente expandidas, resultou em maior numero de lesoes locais em condicoes de estufa (18-40oC) do que em camara de crescimento (18-25oC). Com base na concentracao do virus, avaliada pelo numero de lesoes em feijao 'Manteiga', constatou-se que as melhores hospedeiras para multiplicacao do virus foram N. rustica e fumo 'TNN', seguidas de tomate 'Santa Cruz'. Outrossim, a concentracao do virus, nessas hospedeiras, foi mais alta em camara de crescimento do que em estufa. Em ambas condicoes, o pico de concentracao do virus ocorreu entre 10 e 15 dias. A melhor diluicao do inoculo foi a de 1:5. Mudas de tomate 'Angela I-5.100', inoculadas nos estadios de (a) 1-2 folhas (14 dias apos o semeio - DAS), (b) 3-4 folhas (19 DAS) ou (c) 5-6 folhas (24 DAS) apresentaram maior percentagem de infeccao, maior reducao de tamanho e maior severidade dos sintomas em (a) e (b) do que em (c)

Adherence to clinical follow-up recommendations for liver function tests: A cross-sectional study of patients with HCV and their associated risk behaviors

This study examined whether patients with Hepatitis C virus (HCV) infection adhered to their physicians\u27 recommendation and HCV clinical guidelines for obtaining a regular liver function test (LFT), and whether high-risk behaviors are associated with behavioral adherence. A cross-sectional survey was administered to 101 eligible patients with HCV who were recruited from health centers in New Jersey and Washington, DC. Adherence outcomes were defined as the patients\u27 self-report of two consecutive receipts of LFTs in accordance with their physicians\u27 recommended interval or the clinical guidelines for a LFT within 3-6 months. 67.4% of patients (66/98) reported a receipt of their physicians\u27 recommendation for a LFT. The rate of adherence to physician recommendation was about 70% (46/66), however over 50% (52/101) of patients with HCV did not obtain regular LFTs. 15.8% (16/101) of patients continued to use injection drugs. Patients who used injection drugs had 0.87 (adjusted odds ratio (aOR) = 0.13, 95% confidence interval 0.03-0.59) times lower odds adhering to their physician recommendation, relative to non-users. Patients with HIV co-infection had increased odds of adhering to the clinical guidelines (odds ratio 3.41, 95% confidence interval 1.34-8.70) vs. patients who did not report HIV co-infection. Additionally, patients who had received a physician\u27s recommendation had 7.21 times (95% confidence interval of 2.36-22.2) greater odds adhering to the clinical guidelines than those who had not. Overall, promoting HCV patient-provider communication regarding regular LFTs and reduction of risk behaviors is essential for preventing patients from HCV-related liver disease progression

Aerosol-assisted CVD of cadmium diselenoimidodiphosphinate and formation of a new iPr2N2P3+ ion supported by combined DFT and mass spectrometric studies

Aerosol-assisted chemical vapour deposition (AACVD) of Cd[(SePiPr2)2N]2 is shown to deposit cadmium selenide and/or cadmium phosphide on glass substrates, depending upon the growth conditions. The phase, structure, morphology and composition of the films were characterised by X-ray powder diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The XRD indicated a hexagonal phase for cadmium selenide, whilst cadmium phosphide was monoclinic. Pyrolysis gas chromatography-mass spectrometry and density functional theory were used to deduce a breakdown mechanism for the deposition that favoured the formation of a new aromatic iPr2N2P3+ ion