Vibration de-icing method with piezoelectric actuators

This work presents the analytic and experimental research of a vibration de-icing method for aircrafts with piezoelectric transducer as the actuator. The maximum displacement of the structure will be achieved when excited at the natural frequencies. The vibration induces shear stress at the interface of the ice and structure, which leads to the shedding off of ice. A shear model of linear Bernoulli-Euler type is derived with ice attached to a flat plate, which is capable of predicting the shear stress along the interface and gives guidance to the choice of vibration modes for de-icing. The finite element method (FEM) is used to get the relationship between the length of piezoelectric actuator and the vibration intensity of the modes to be excited. The optimal length is determined in order to maximize the shear stress. The results indicate that peak values of the shear stress at the interface appear at the edges of the ice, and the amplitudes depend upon the strains on the surface of plate underlying the edges of ice. For a specific mode the maximum excitation happens when the length of piezoelectric actuator is an odd integer multiple of the half wavelength of that mode. Actually the optimal length would be a slightly longer due to the influence of the actuator. Finally, experimental investigations on a clamped aluminum plate are carried out to verify the results of the analysis. The power consumption for vibration de-icing is about 36.5 w/m2, which is only 1.57 % of the power consumption when using the latest electro-thermal de-icing method

Special Transition and Extraordinary Phase on the Surface of a Two-Dimensional Quantum Heisenberg Antiferromagnet

Continuous phase transitions exhibit richer critical phenomena on the surface than in the bulk, because distinct surface universality classes can be realized at the same bulk critical point by tuning the surface interactions. The exploration of surface critical behavior provides a window looking into higher-dimensional boundary conformal field theories. In this work, we study the surface critical behavior of a two-dimensional (2D) quantum critical Heisenberg model by tuning the surface coupling strength, and discover a direct special transition on the surface from the ordinary phase into an extraordinary phase. The extraordinary phase has a long-range antiferromagnetic order on the surface, in sharp contrast to the logarithmically decaying spin correlations in the 3D classical O(3) model. The special transition point has a new set of critical exponents, $y_{s}=0.86(4)$ and $\eta_{\parallel}=-0.32(1)$, which are distinct from the special transition of the classical O(3) model and indicate a new surface universality class of the 3D O(3) Wilson-Fisher theory.Comment: 5 pages, 3 figures; v2: substantially revised, new fitting form in extraordinary phas

Characterization on the cardiac function of hypothermic dogs from cold water immersion

OBJECT To clarify the effects of cold water immersion on the canine cardiac function and how to prevent the immersed hypothermic ventricular fibrillation. METHODS 7 normal male dogs, which were randomly divided into two groups, the experimental (3, each with 2.5mg/kg nimodipine) and the control (4), were immersed in cold water at 6 ± 1!. The polygraph system was used to record the cardiac function and the transmission electron microscope was involved to study the ultrastructure changes of myocardium. The activity levels of Na⁺:K⁺:ATPase and Ca²⁺:ATPase were measured by means of Elisa. RESULTS As the canine core temperature going down, it was noted that the left ventricular pressure peak value (LVSP), and the isovolumetric contraction phase maximal ascending/descending velocity ( ± dP/dtmax) decreased evidently, with a prolonged Q:T duration, and that hypothermic J waves were found subsequently. The activities of Na⁺:K⁺:ATPase and Ca²⁺ATPase were both inhibited. There came rapid ventricular arrhythmia with the control dogs, while not with the experimental. CONCLUSIONS The hypothermia would result in the weakening of canine cardiac function, moreover, the appearance of J wave might be followed by the occurrence of hypothermic ventricular fibrillation. The results also suggested that nimodipine might have a potential to prevent immersed hypothermic ventricular fibrillation.Для уточнення наслідків занурення в холодну воду на функції серця собак і запобігання викликаної гіпотермією фібриляції шлуночків 7 нормальних псів, які були випадковим чином розділені на дві групи (дослідну і контрольну), були занурені в холодну воду при 6 ± 1 ° С. Тварини експериментальної групи попередньо отримали 2,5 мг/кг німодипіну. Для запису функції серця використовували систему поліграф. Для дослідження ультраструктури змін міокарда використовували просвічуючу електронну мікроскопію. Рівні активності Na⁺/K⁺АТФази і Ca²⁺:АТФази були виміряні за допомогою ELISA.При падінні температури тіла собак було відзначено, що пікове значення тиску лівого шлуночка (LVSP) та ізоволюметрічна фаза скорочення максимального зростання/убування швидкості зменшилася. Активності Na⁺/K⁺:АТФази і Ca²⁺:АТФази знижувалися. При цьому у контрольних собак спостерігалася, а у досвідчених не спостерігалася швидка шлуночкова аритмія. Показано, що гіпотермія може призвести до ослаблення функції серця собак, крім того, за появою J хвилі може послідувати виникнення викликаної гіпотермією фібриляції шлуночків. Результати дозволяють припустити, що німодипін, можливо, здатний запобігти фібриляції шлуночків, яка викликана гіпотермією.Для уточнения последствий погружения в холодную воду на функции сердца собак и предотвращения вызванной гипотермией фибрилляции желудочков 7 нормальных кобелей, которые были случайным образом разделены на две группы (опытную и контрольную), были погружены в холодную воду при 6 ± 1 °С. Животные экспериментальной группы предварительно получили 2,5 мг/кг нимодипина. Для записи функции сердца использовали систему полиграф. Для исследование ультраструктуры изменений миокарда использовали просвечивающую электронную микроскопию. Уровни активности Na⁺/K⁺:АТФазы и Ca²⁺:АТФазы определяли с помощью ELISA. При падении температуры тела собак было отмечено, что пиковое значение давления левого желудочка (LVSP) и изоволюметрическая фаза сокращения максимального возрастания/убывания скорости уменьшилась. Активности Na⁺/K⁺:АТФазы и Ca²⁺:АТФазы снижались. При этом у контрольных собак наблюдалась, а у опытных не наблюдалась быстрая желудочковая аритмия. Показано, что гипотермия может привести к ослаблению функции сердца собак, кроме того, за появлением J волны может последовать возникновение вызванной гипотермией фибрилляции желудочков. Результаты позволяют предположить, что нимодипин, возможно, способен предотвратить фибрилляции желудочков, вызванные гипотермией

Disturbance-Estimated Adaptive Backstepping Sliding Mode Control of a Pneumatic Muscles-Driven Ankle Rehabilitation Robot.

A rehabilitation robot plays an important role in relieving the therapists' burden and helping patients with ankle injuries to perform more accurate and effective rehabilitation training. However, a majority of current ankle rehabilitation robots are rigid and have drawbacks in terms of complex structure, poor flexibility and lack of safety. Taking advantages of pneumatic muscles' good flexibility and light weight, we developed a novel two degrees of freedom (2-DOF) parallel compliant ankle rehabilitation robot actuated by pneumatic muscles (PMs). To solve the PM's nonlinear characteristics during operation and to tackle the human-robot uncertainties in rehabilitation, an adaptive backstepping sliding mode control (ABS-SMC) method is proposed in this paper. The human-robot external disturbance can be estimated by an observer, who is then used to adjust the robot output to accommodate external changes. The system stability is guaranteed by the Lyapunov stability theorem. Experimental results on the compliant ankle rehabilitation robot show that the proposed ABS-SMC is able to estimate the external disturbance online and adjust the control output in real time during operation, resulting in a higher trajectory tracking accuracy and better response performance especially in dynamic conditions

SegPrompt: Boosting Open-world Segmentation via Category-level Prompt Learning

Current closed-set instance segmentation models rely on pre-defined class labels for each mask during training and evaluation, largely limiting their ability to detect novel objects. Open-world instance segmentation (OWIS) models address this challenge by detecting unknown objects in a class-agnostic manner. However, previous OWIS approaches completely erase category information during training to keep the model's ability to generalize to unknown objects. In this work, we propose a novel training mechanism termed SegPrompt that uses category information to improve the model's class-agnostic segmentation ability for both known and unknown categories. In addition, the previous OWIS training setting exposes the unknown classes to the training set and brings information leakage, which is unreasonable in the real world. Therefore, we provide a new open-world benchmark closer to a real-world scenario by dividing the dataset classes into known-seen-unseen parts. For the first time, we focus on the model's ability to discover objects that never appear in the training set images. Experiments show that SegPrompt can improve the overall and unseen detection performance by 5.6% and 6.1% in AR on our new benchmark without affecting the inference efficiency. We further demonstrate the effectiveness of our method on existing cross-dataset transfer and strongly supervised settings, leading to 5.5% and 12.3% relative improvement.Comment: Accepted to Proc. Int. Conf. Computer Vision (ICCV) 2023. Code is at: https://github.com/aim-uofa/SegPromp

Metal Oxide Gas Sensors: Sensitivity and Influencing Factors

Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above

Modeling and Quantifying the Impact of Personified Communication on Purchase Behavior in Social Commerce

The advancement of mobile internet technology has enabled companies to leverage social media for e-commerce, where some use personified images and language to communicate with consumers. This paper investigates how personified communication affects consumer behavior in social commerce and whether consumers are willing to accept this new form of communication. Specifically, the study explores consumers’ willingness to accept personified communication in social commerce, considering the role of cognitive needs in regulating the internal mechanism. The paper proposes suggestions for enterprises to improve their social media communication and presents an improved model based on the Technology Acceptance Model (TAM). The model introduces perceived interaction as a new independent variable and adds cognitive needs as a regulatory variable, which is more suitable for social commerce. The study conducts a questionnaire survey online and analyzes the data using AMOS and SPSS. The results demonstrate that perceived usefulness and perceived interaction positively impact consumers’ attitudes, which subsequently influences their willingness to purchase. Furthermore, cognitive needs as a regulatory variable significantly affect the path from perceived usefulness to attitude and purchase intention