Recently, the dual-permanent-magnet-excited (DPME) machine has attracted growing attention due to its high torque density. Due to the bidirectional field modulated effect (BFME), airgap flux density ...harmonics (AFDHs) are more complex and abundant than traditional permanent magnet synchronous machines (PMSMs). Moreover, the back-electromotive force (EMF) generated by AFDHs is also complex. Unfortunately, only a few papers qualitatively analyze back-EMF. The qualitative analysis for back-EMF can reveal some important conclusions; for example, only AFDHs meeting specific pole pair numbers (PPNs) can generate back-EMF. However, it may also ignore some details and valuable findings. In this paper, a purely analytical magnetomotive force (MMF) permeance model (PAMPM) for a DPME machine is built to quantitatively analyze the back-EMF. The PAMPM does not require a numerical method, such as conformal transformation. With the PAMPM, AFDHs that contribute to the generation of back-EMF can be recognized and quantified. Interestingly, AFDHs with <inline-formula> <tex-math notation="LaTeX">m_{2}p_{2}=np_{3} </tex-math></inline-formula> cause PM flux-linkage to have a dc bias, and not all AFDHs play a positive role in the generation of back-EMF. The main recognition results are as follows: 1) the S-II and R-II types of AFDHs in a 12/10 DPME machine overall make a negative contribution to the generation of back-EMF; and 2) AFDHs with PPN=22 in the two types mainly cause a negative contribution. To further verify the above results, 2D finite element simulation and experimental tests of a prototype machine are also conducted.
Stretchable temperature sensors are necessary to enable tactile interaction and thermoregulation in the human body and soft robots. These sensors should be conformably adhered to a deformable surface ...and maintain temperature perception accuracy when stretched. However, current mainstream stretchable temperature sensors based on thermistors suffer from inherently unstable sensing during stretching due to the mutual interference of resistance changes caused by temperature and mechanical deformations. Herein, we propose an ultra-stretchable hydrogel thermocouple that provides unaltered temperature sensing upon stretching. The ultrastretchability of this thermocouple is achieved by constructing thermogalvanic hydrogels with dynamic crosslinked double networks. By connecting P-type and N-type thermogalvanic hydrogels, the thermocouple exhibits a high equivalent See-beck coefficient of 1.93 mV K
−1
and a stable sensitivity even under a 100% tensile strain. The advantage of this ultra-stretchable thermocouple is demonstrated in a smart glove prototype, which enables haptic feedback. Our work provides a new strategy for stretchable temperature sensors and may promote the development of intelligent wearables.
Osteosarcoma (OS) is the most common primary malignant bone tumor in adolescents. Lung metastasis (LM) occurs in more than half of patients at different stages of the disease course, which is one of ...the important factors affecting the long-term survival of OS. To develop and validate machine learning radiomics model based on radiographic and clinical features that could predict LM in OS within 3 years.
486 patients (LM = 200, non-LM = 286) with histologically proven OS were retrospectively analyzed and divided into a training set (n = 389) and a validation set (n = 97). Radiographic features and risk factors (sex, age, tumor location, etc.) associated with LM of patients were evaluated. We built eight clinical-radiomics models (k-nearest neighbor KNN, logistic regression LR, support vector machine SVM, random forest RF, Decision Tree DT, Gradient Boosting Decision Tree GBDT, AdaBoost, and extreme gradient boosting XGBoost) and compared their performance. The area under the receiver operating characteristic curve (AUC) and accuracy (ACC) were used to evaluate different models.
The radscore, ALP, and tumor size had significant differences between the LM and non-LM groups (t
= -5.829, χ
= 97.137, t
= -3.437, P < 0.01). Multivariable LR analyses showed that ALP was an important indicator for predicting LM of OS (odds ratio OR = 7.272, P < 0.001). Among the eight models, the SVM-based clinical-radiomics model had the best performance in the validation set (AUC = 0.807, ACC = 0.784).
The clinical-radiomics model had good performance in predicting LM in OS, which would be helpful in clinical decision-making.
An electret material with high charge storage ability is the key factor for fabricating high performance electret generator for wearable electronics and self‐powered sensor systems. This work ...presents a new sandwiched composite fluorocarbon (SCF) film, which stores more residual charges compared to traditional electret materials such as dense fluorinated ethylene propylene or fibrous polytetrafluoroethylene films with the same thickness. Electret generator based on the SCF film shows a largest peak power density of ≈31.4 μW cm−2 with load resistance of 40 MΩ. Moreover, the application of the electret generator for a self‐powered human breathing sensor is also demonstrated. This work offers a new strategy to enhance the output of the electret generators.
Flexible FEP/f‐PTFE/FEP sandwiched composite fluorocarbon (SCF) film is fabricated via hot pressing, showing larger surface charge density compared to dense FEP and f‐PTFE with the same thickness. The electret generator based on this SCF film reaches a largest peak power density of ≈31.4 μW cm−2 and is applied as a self‐powered human breathing sensor. This study provides a new strategy to fabricate high performance electret materials and will promote the development of wearable energy harvester and electronics.
The recent development of wearable devices is revolutionizing the way of human–machine interaction (HMI). Nowadays, an interactive interface that carries more embedded information is desired to ...fulfill the increasing demand in era of Internet of Things. However, present approach normally relies on sensor arrays for memory expansion, which inevitably brings the concern of wiring complexity, signal differentiation, power consumption, and miniaturization. Herein, a one‐channel based self‐powered HMI interface, which uses the eigenfrequency of magnetized micropillar (MMP) as identification mechanism, is reported. When manually vibrated, the inherent recovery of the MMP causes a damped oscillation that generates current signals because of Faraday's Law of induction. The time‐to‐frequency conversion explores the MMP‐related eigenfrequency, which provides a specific solution to allocate diverse commands in an interference‐free behavior even with one electric channel. A cylindrical cantilever model is built to regulate the MMP eigenfrequencies via precisely designing the dimensional parameters and material properties. It is shown that using one device and two electrodes, high‐capacity HMI interface can be realized when the magnetic micropillars (MMPs) with different eigenfrequencies have been integrated. This study provides the reference value to design the future HMI system especially for situations that require a more intuitive and intelligent communication experience with high‐memory demand.
A single channel based human–machine interactive interface is reported. The interface is composed of magnetized micropillars (MMPs) and a flexible coil. By precisely regulating eigenfrequency of various MMPs, different signals or commands can be transmitted with only 1 channel in form of induced current, which will significantly enlarge the capacity and improve the wearability of devices.
Although organic semiconductors with high mobility and thermal stability are particularly desirable for practical applications, facile methods for their development still remains a big challenge. In ...this work, a charge-transfer cocrystal based on fullerene (C
70
)/cobalt porphyrin supramolecular architecture was prepared by a solution-processable co-assembly strategy. This supramolecular architecture showed hole mobility as high as 4.21 cm2·V−1·s−1, and a relatively high mobility of 0.02 cm2·V−1·s−1 even after thermal treatment at 1,000 °C. Further studies confirmed the occurrence of charge-transfer from 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrinato cobalt(II) (CoTMPP) to C
70
and the paramagnetic character within the supramolecular system. These factors were found to be responsible for the aforementioned superior performances. Thus, a novel organic semiconductor has been reported in this work, which can be potentially used for next generation electronic devices. Furthermore, it has been demonstrated that charge-transfer co-crystallization is a powerful strategy for the rational design and construction of a broad class of new multifunctional organic co-crystalline materials.
An electret-based mechanical antenna (EBMA), which can transmit extremely low frequency (ELF) electromagnetic signals, has the advantages of miniaturization and high transmitting efficiency, with ...great potential applications in air, underwater, and underground communications. To improve the charge density of the electret, which is a key factor in determining the radiation performance of an EBMA, this work proposes a fluorinated ethylene propylene/terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (FEP/THV) unipolar electret exhibiting negative polarity, reaching a total charge density up to -0.46 mC/m
for each layer of electret. Long transmission distances can be achieved in sea water, soil, and air using a 3-layer-FEP/THV-based EBMA with a compact volume of 5 × 10
m
. As an application demonstration, binary ASCII-coded ELF information of "BUAA" is successfully transmitted with a power consumption < 5 W.
Due to the unique electromechanical energy conversion capability of ferroelectric materials, they have been at the forefront of materials science for a variety of applications such as sensors, ...actuators and energy harvesting. Researchers have focused on exploring approaches to achieve improved ferroelectric performance, and to ensure that the available material systems are more environmentally friendly. This comprehensive review summarizes recent research progress on porous ceramics and highlights the variety of factors that are often ignored, namely the influence of porosity on the Curie temperature, and applications of porous ferroelectric materials with adjustable Curie temperature. Finally, the development trends and challenges of porous ferroelectric materials are discussed, aiming to provide new insights for the design and construction of ferroelectric materials.
Harvesting energy from human body motions is an appropriate option as an assistant or even subversive way for powering the booming wearable electronics, in which smart textiles are important ...components. Here, we fabricate a robust power textile with working mechanism of triboelectrification effect and electrostatic induction effect by simply integrating the normal textiles and polydimethylsiloxane (PDMS)/conductive yarns electrodes. Maximum peak loading voltage and current reaching 230 V and 11.6 μA are obtained by rubbing our power textile, and this alternating and irregular electricity can be accumulated in a capacitor or directly light up 20 blue LEDs. The recovered energy generation ability of the power textile after washing successfully demonstrate its robustness, showing the potential application in powering the electronics in smart textiles.
Abstract
Flexible loudspeakers that can be easily distributed in the surrounding environment are essential for creating immersive experiences in human-machine interactions, as these devices can ...transmit acoustic information conveniently. In this paper, we present a flexible electret loudspeaker that offers numerous benefits, such as eco-friendly, easy fabrication, flexible customization, strong durability, and excellent outputs. The output sound pressure level (SPL) and frequency response characteristic are optimized according to the simulation and experiment results. At a distance of 50 meters, a large-size loudspeaker (50 × 40 cm
2
) can produce an average SPL of 60 dB (normal SPL range of human voices is between 40 to 70 dB). The frequency response of our loudspeaker is high and relatively consistent up to 15 kHz, which covers the normal frequency range of human voices (<8 kHz). As demonstrated in this work, our loudspeakers can be used for scalable applications, such as being integrated with curtains or hung up like posters, offering a promising and practical solution for creating better human-machine interaction experiences.
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