Quasi-zero stiffness (QZS) vibration isolators have broad application prospects in effectively suppressing low-frequency vibrations; most current quasi-zero stiffness vibration isolator response ...studies are based on the ideal case of design parameters. Considering the structural complexity of quasi-zero stiffness vibration isolators, the existence of parameter errors is difficult to ignore. Due to the strong nonlinearity of the QZS system, small changes in the system parameters may lead to a sharp deterioration of the vibration isolation performance in an undesired direction. In this paper, the classical QZS system response under the influence of parameter uncertainties is investigated by using the arbitrary polynomial chaos expansions method (aPCE), and the effects of the individual and coupling effects of the uncertainties of the main parameters on the steady-state displacement response of the system are analyzed. On this basis, the distribution law of the steady-state response under non-normal parameter distributions is further investigated, and Sobol global sensitivity indices in different frequency bands under the coupling effect are studied.
The negative Poisson's ratio (NPR) structures exhibit some unusual but highly useful mechanical properties. In comparison to two-dimensional (2D) NPR structures, less attention has been paid to the ...studies on three-dimensional structures due to the complex manufacturing process. In this paper, based on the two-dimensional nonconvex hexagonal cell, a novel three-dimensional (3D) NPR energy-absorbing structure is proposed. According to the beam theory, the equivalent Young's modulus and Poisson's ratio are deduced. Subsequently, numerous finite element (FE) simulations and compression tests were performed and a good agreement was observed among the theoretical results, the numerical simulations, and the experimental results. Moreover, a typical fuselage section of aircraft during a crash landing was considered and the fuselage section with the 3D NPR structure presented in this work showed better energy absorption capacity than the one without the 3D NPR structure.
Quasi-zero-stiffness (QZS) vibration isolation can increase the isolation frequency and improve the isolation performance by using a negative stiffness mechanism. However, most of the QZS isolation ...are sensitive to the loads applied for achieving effective isolation. This paper focuses on the dynamic phenomenon of the pneumatic QZS isolator with mistuned mass. A pneumatic QZS vibration isolator is proposed. The dynamic equation of the QZS vibration isolator under mass mistuning is derived. Amplitude–frequency relationship and force transmissibility are analyzed and simulated. It is observed that the system exhibits the possible response period and chaos phenomenon in the case of a large mass mistuning. It is very interesting that mass detuning will lead to a more complex nonlinear response of the QZS isolator, and the dynamic response will also be more sensitive to changes in parameters, such as external excitation frequency and amplitude, and damping ratio. The presented works will be helpful to improve the structure of the pneumatic QZS vibration isolator and determine the applicable working frequency of the isolator.
Piezoelectric shunting vibration absorber (PSVA) has attracted considerable attention in recent years. Nonlinearity widely exists in practice although a linear host system is the original design ...intention. What would happen when the predesigned PSVA under the linear host system assumption is applied to those nonlinear vibration systems? To address this issue, a nonlinear host system with a PSVA is constructed. The nonlinear responses of the electromechanical-coupled system are obtained by using the incremental harmonic balance method. Semi-analytical solutions demonstrate that the predesigned shunting circuit under linear host system assumption does not only work effectively but also makes the stability of the host system worse. To suppress the resonant peak of the host system efficiently, the particle swarm algorithm is applied to determine the proper shunting circuit of the PSVA. The performances of the proper PSVA, such as the suppression effects on the resonant peak, and its influence on the stability of the host system are investigated by numerical examples. Together with the parametric analysis, the tuning rule of the shunting circuit is given which can be the guide in the practical application.
Purpose: This study evaluated the tibial torsional angle changes of 72 knees before and after open-wedge high tibial osteotomy (OWHTO) and compared the results according to the osteotomy level.
...Materials and methods: Seventy patients (72 knees) with Kellgren-Lawrence grade 3 underwent OWHTO. Demographic data, operation procedures, and measurement of mechanical tibiofemoral angle (mTFA), anatomical tibiofemoral angle (aTFA), tibial torsional angle (TTA), and pre- and postoperative Lysholm and International Knee Documentation Committee (IKDC) scores were obtained. The authors analyzed TTA changes between 30 knees with high-level osteotomy (group A) and 42 knees with low-level osteotomy (group B).
Results: The changes of TTAs in the subjects of 72 knees went from 29.26 ± 5.6° preoperative mean to 25.36 ± 6.4° postoperative mean (p = 0.032). The postoperative TTAs of group A (mean 27.4 ± 4.8°) and B (mean 25.7 ± 4.9°) were statistically significant (p < 0.01). Preoperative Lysholm and IKDC scores of 72 knees had means of 49.1 ± 3.5 and 49.0 ± 15.2, respectively, and postoperative means of 85.7 ± 8.56 and 78.0 ± 17.6, respectively, which were statistically significant (p < 0.01).
Conclusions: Changes of TTA with internal rotation of distal tibia were observed following OWHTO. High-level osteotomy on the proximal tibia’s lateral cortex had less internal rotation of the distal tibia than low-level osteotomy.
Receiver and transmitter monolithic microwave integrated circuit (MMIC) multifunction chips (MFCs) for active phased-array antennas for Ka-band satellite communication (SATCOM) terminals have been ...designed and fabricated using a 0.15-㎛ GaAs pseudomorphic high-electron mobility transistor (pHEMT) process. The MFCs consist of four-channel radio frequency (RF) paths and a 4:1 combiner. Each channel provides several functions such as signal amplification, 6-bit phase shifting, and 5-bit attenuation with a 44-bit serial-to-parallel converter (SPC). RF pads are implemented on the bottom side of the chip to remove the parasitic inductance induced by wire bonding. The area of the fabricated chips is 5.2 mm × 4.2 mm. The receiver chip exhibits a gain of 18 dB and a noise figure of 2.0 dB over a frequency range from 17 GHz to 21 GHz with a low direct current (DC) power of 0.36 W. The transmitter chip provides a gain of 20 dB and a 1-dB gain compression point (P1dB) of 18.4 dBm over a frequency range from 28 GHz to 31 GHz with a low DC power of 0.85 W. The P1dB can be increased to 20.6 dBm at a higher bias of +4.5 V.
Objective: Spent ginger is a byproduct of juice extraction from the rhizome of ginger (Zingiber officinale). Despite its nutritional value, it is difficult to preserve or further process and thus is ...often wasted. This study uses spent ginger as a substrate for fermentation and cultivates spent ginger yeast cultures (SGYCs) that are then added to the feed of laying hens. The effects of SGYCs on production performance, egg quality, serum composition, and intestinal microbiota of laying hens were investigated. Methods: Eighty 60-week-old Hy-Line Brown hens were separated into 5 experimental groups with 4 replicates per group (4 hens per cage, 4 cages per replicate). The control group was fed a basal diet while experimental groups were also given SGYCs at the levels of 5, 10, 20, and 40 g/kg for 6 weeks. Results: The addition of SGYCs significantly increased the laying rate and nutrient digestibility, decreased feed conversion ratio, and enhanced the color of egg yolks (p<0.05). No changes were observed in activity levels of alanine aminotransferase and aspartate aminotransferase in the serum (p>0.05), but the activities of superoxide dismutase, glutathione peroxidase, and peroxidase all significantly increased, and contents of malondialdehyde were significantly reduced (p<0.05). In addition, changes in the relative abundance of Firmicutes and Bacteroidetes might be the main factor contributing to the significant increase in the apparent digestibility of crude protein and crude fat in laying hens (p<0.05). Conclusion: The current evidence shows that dietary supplementation of SGYCs to the feed of laying hens can improve laying rates, enhance antioxidative defenses, and influence dominant intestinal bacteria.
To investigate the effect of aerobic exercise on AKT/GSK3β pathway-mediated hepatocyte apoptosis in non-alcoholic fatty liver diseases(NAFLD).
A total of 30 6-week-old male C57BL/6J mice, and mice ...were fed adaptively for one week. The control group was fed with ordinary diet, and the model group and model exercise group were fed with high-fat diet until 18 weeks. At the 10th week of the experiment, the model exercise group received aerobic exercise intervention for 8 consecutive weeks until the end of the experiment at the 18th week. Automatic biochemical analyzer to detect serum total cholesterol(TC), triglycerides(TG), alanine aminotransferase(ALT), aspartate aminotransferase(AST), low-density lipoprotein(LDL-C) and high-density lipoprotein(HDL-C) levels. Liver pathological morphology was observed by staining with oil red O and HE. The expression changes of AKT, P-AKT~( Ser473), GSK3β, P-GSK3β~(Ser9) and Caspase-3 proteins were detected by western blot, and the apoptosis of hepatocytes was detected by in si
Social media has been widely used for health-related purposes, especially during the COVID-19 pandemic. Previous reviews have summarized social media uses for a specific health purpose such as health ...interventions, health campaigns, medical education, and disease outbreak surveillance. The most recent comprehensive review of social media uses for health purposes, however, was conducted in 2013. A systematic review that covers various health purposes is needed to reveal the new usages and research gaps that emerge in recent years.
This study aimed to provide a systematic review of social media uses for health purposes that have been identified in previous studies.
The researchers searched for peer-reviewed journal articles published between 2006 and 2020 in 12 databases covering medicine, public health, and social science. After coding the articles in terms of publication year, journal area, country, method, social media platform, and social media use for health purposes, the researchers provided a review of social media use for health purposes identified in these articles.
This study summarized 10 social media uses for various health purposes by health institutions, health researchers and practitioners, and the public.
Social media can be used for various health purposes. Several new usages have emerged since 2013 including advancing health research and practice, social mobilization, and facilitating offline health-related services and events. Research gaps exist regarding advancing strategic use of social media based on audience segmentation, evaluating the impact of social media in health interventions, understanding the impact of health identity development, and addressing privacy concerns.
Abstract
Breast cancer is often called the pink killer. The most recent statistics from the 2018 International Agency for Research on Cancer (IARC) survey show that the incidence rate of breast ...cancer is 24.2%, placing it first among women’s cancers globally, with 52.9% of cases occurring in developing nations. When cells in the breast start to grow abnormally, it can lead to the formation of tumours. These tumours can be detected through X-ray imaging or felt as lumps in the breast area, so early detection and treatment are the key to reducing the mortality rate of breast cancer. In this paper, machine learning techniques are employed to construct a breast cancer prediction model using the breast cancer dataset. Different algorithms were utilized in this paper, e.g., 3 machine learning algorithms - Support Vector Machines (SVM), Random Forest (RF), and Principal Component Analysis (PCA) - were utilized to build models for this task. The resulting models achieved impressive performance metrics, with accuracy rates of 94%, 97%, and 96% respectively. The author also finds that some features in the data are insignificant for prediction, and discarding them can lead to faster training time. However, more data is needed to achieve better performance in actual scenarios. These models can help doctors diagnose breast cancer more quickly and accurately.
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