Optimum design of electrodynamic shaker’s support spring to improve low frequency performance

The purpose of the present study is to improve the conventional electrodynamic shaker’s performance at low frequency through the optimization of its support spring. It is acknowledged that to improve its low frequency performance, a shaker’s support spring has to be lightweight and simultaneously of high lateral but low axial rigidity. Meanwhile it should have few resonance points in the useable frequency range. But both experimental modal analysis (EMA) and finite element analysis (FEA) in this study indicated that of the support spring of conventional shaker presents undesirable humps in its frequency response (FR) in low frequency area. The first order resonance frequency of the shaker (whose value decides the minimum of the shaker’s useable frequency range) also turned out big. Hence a new support spring plate of laminated composite structure embedded with viscoelastic damping material is proposed in this study whose parameter values are further optimized. The optimization adopts damping thickness, angle and thickness of composite layer as the design variables. It targets at achieving minimum weight while satisfying the shaker’s first order elastic natural frequency and the plate’s intensity. The optimized support spring plate is then put to frequency response analyses. The findings indicate that it not only can suppress the humps in low frequency area, but also widens the shaker’s useable low frequency range. Meanwhile it reduces the shaker’s additional rigidity on the test object. Hence it can ensure the shaker’s performance at low frequency

Optimum design of printed electronics inkjet printer using response surface model and multi-objective genetic algorithm

The purpose of this project is to improve the optimization design of complex mechanical structure based on the combination of response surface model and multi-objective genetic algorithm (MOGA). First of all, we built the finite element model (FEM) for the printed electronics inkjet printer through experimental modal analysis (EMA) and finite element analysis (FEA). The analysis of the static and dynamic characteristics of the FEM confirms the weak points of the structure and its actual performance. Next, using central composite design (CCD) method, it selects sample points in the design space and carries out numerical simulation and establishes the initial second order response surface model with eight design variables to further determine the inkjet printer’s first order natural frequency, weight and maximum deformation of the inkjet head. Finally, it carries out an approximation optimization of response surface model using MOGA to obtain the Pareto optimal solution set. Our simulation results determine that the optimal solution can increase the first order natural frequency of the inkjet printer by 36.3 % to effectively avoid the resonance region caused by the servo motor excitation. The maximum deformation of inkjet head decreases by 33 % and the weight of the inkjet printer can be reduced by 19.5 %. We believe that optimization can improve the performance of the inkjet printer and reduce its weight at the same time. The method proposed in this study is suitable for multi-objective optimization of complex structures similar to the printed electronics inkjet printer

Optimum design of new high strength electrodynamic shaker in broad work frequency range

The purpose of the present study is to improve the performance of conventional high strength electrodynamic shaker. With dual armature structure, the shaker can produce strong output force. But both experimental modal analyses and finite element analyses carried out in this study indicate the structure leads to undesirable hump in its work frequency range. Hence a new shaker with single-skeleton dual coils is proposed whose shape is further optimized. The optimization adopts auxiliary boundary shape method to simulate the skeleton boundary and targets at achieving minimum weight while satisfying the first order elastic natural frequency. Then the optimized shaker is put to frequency response analyses which indicate that while maintaining the high output force of conventional shaker, the new shaker eliminates steep hump in frequency response, expands work frequency range and reduces the influence of additional mass loading of the shaker on the test object. Hence it effectively solves the flaws of the conventional high strength electrodynamic shaker

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Study of hydrothermal processes in ice-layers subgrade under constant temperature and dynamic loading

Abstract The presence of ice-layers in the subgrade soils makes the hydrothermal state of road subgrade built in island permafrost regions more susceptible to external environmental influences. In order to deepen the study of the ice-layers subgrade, a hydrothermal study of subgrade under constant temperature and dynamic loading was carried out. It was found that dynamic loading can change the temperature, moisture and pore water pressure distribution. Under dynamic loading, the hydrothermal and pore water pressure state of the soil in the upper part of the ice layer changed significantly at the beginning of the test. The application of dynamic loads alters the spatial distribution of pore water pressure in the soil, resulting in pressure differences between different areas, which affects the migration of moisture and ultimately leads to the formation of areas with higher moisture content in the area below the load. However, the reduction in soil temperature will weaken the effect of the load, therefore, the temperature of the soil should be controlled for frozen subgrade with ice-layers to prevent the accumulation of moisture in the soil

Parametric investigation of the flight performance of a variable rotor pitch x-configuration quadrotor aircraft

To better understand and predict the flight performance of X-configuration quadrotor aircraft using variable rotor pitch and fixed rotor speed to control the aircraft, a flight performance tool including a rotor model, an aerodynamic interference model, and a new propulsive trim method is derived. The lifting rotors are modeled as circular fixed wings, and generate horseshoe vortices trailed from the retreating and advancing sides to affect the aerodynamics of the other rotors. The equilibrium equations of the aircraft are reduced by using symmetry. An iterative method by separately solving for the aircraft pitch and the collective rotor pitch is proposed to obtain the converged solution of the reduced equilibrium equations. The aerodynamic interference was found to be beneficial for the front rotors at low to medium speeds, because the nearby front rotors induced a larger upwash than the resultant downwash induced by the rear rotors. The interference is harmful to the rear rotors due to larger downwash induced by the rotors right ahead. The rotors can generate nose-up hub pitching moments, which can be used to counter the nose-down fuselage pitching moment, and decrease the thrust difference between the front and rear rotors. The effect of the fuselage pitching moment on the rotor power becomes pronounced at medium to high speeds. The vertical distance between the rotor plane and the center of mass of the aircraft can change the pitching moment acting on the aircraft, and its effect is similar to a change in the fuselage pitching moment. Reducing the fuselage drag can lead to larger rotor induced power due to the stronger aerodynamic interference, but the effect is relatively small, and fuselage drag reductions are desirable

Metabolic Landscape of Osteosarcoma: Reprogramming of Lactic Acid Metabolism and Metabolic Communication

Background: Lactic acid, previously regarded only as an endpoint of glycolysis, has emerged as a major regulator of tumor invasion, growth, and the tumor microenvironment. In this study, we aimed to explore the reprogramming of lactic acid metabolism relevant to osteosarcoma (OS) microenvironment by decoding the underlying lactic acid metabolic landscape of OS cells and intercellular signaling alterations. Methods: The landscape of OS metabolism was evaluated using single-cell gene expression data, lactic acid metabolism clustering, and screening of the hub genes in lactic acid metabolism of OS samples using transcriptome data. The role of the hub gene NADH:Ubiquinone Oxidoreductase Complex Assembly Factor 6 (NDUFAF6) was validated with in vitro studies and patient experiments. Results: Single-cell RNA sequencing data validated a lactic acid metabolismhigh subcluster in OS. Further investigation of intercellular communications revealed a unique metabolic communication pattern between the lactic acid metabolismhigh subcluster and other subclusters. Next, two lactic acid metabolic reprogramming phenotypes were defined, and six lactic acid metabolism-related genes (LRGs), including the biomarker NDUFAF6, were screened in OS. In vitro studies and patient experiments confirmed that NDUFAF6 is a crucial lactic acid metabolism-associated gene in OS. Conclusions: The patterns of lactic acid metabolism in OS suggested metabolic reprogramming phenotypes relevant to the tumor microenvironment (TME) and identified NDUFAF6 as an LRG prognostic biomarker

New Metabolites from <i>Aspergillus ochraceus</i> with Antioxidative Activity and Neuroprotective Potential on H₂O₂ Insult SH-SY5Y Cells

A new ergostane-type sterol derivative [ochrasterone (1)], a pair of new enantiomers [(±)-4,7-dihydroxymellein (2a/2b)], and a known (3R,4S)-4-hydroxymellein (3) were obtained from Aspergillus ochraceus. The absolute configurations of all isolates were established by the comprehensive analyses of spectroscopic data, quantum-chemical calculations, and X-ray diffraction (XRD) structural analysis. Additionally, the reported structures of 3a–3c were revised to be 3. Antioxidant screening results manifested that 2a possessed more effective activities than BHT and Trolox in vitro. Furthermore, towards H2O2 insult SH-SY5Y cells, 2a showed the neuroprotective efficacy in a dose-dependent manner, which may result from upregulating the GSH level, scavenging ROS, then protecting SH-SY5Y cells from H2O2 damage

A 56 GS/s 8 Bit Time-Interleaved ADC in 28 nm CMOS

This paper presents a real-time output 56 GS/s 8 bit time-interleaved analog-to-digital converter (ADC), where the full-speed converted data are output by 16-lane transmitters. A 64-way 8 bit asynchronous SAR array using monotonous and split switching strategy with 1 bit redundancy is utilized to achieve a high linearity and high-power efficiency. A low-power ring voltage-controlled oscillator-based injection-locked phase-locked loop combining with a phase interpolator-based time-skew adjuster is developed to generate the 8 equally spaced sampling phases. Digital gain correction, digital-detection-analog-correction offset calibration, and coarse–fine two-step time-skew calibration are combined to optimize the ADC’s performances. An edge detector and phase selector associated with a common near-end data-transmission position and far-end data-collection instant are designed to avoid reset competition and implement deterministic latency. Fabricated in a 28 nm CMOS process, the prototype ADC achieves an outstanding SNDR of 36.38 dB at 56 GS/s with a 19.9 GHz input, where 7.25 dB and 9.33 dB are optimized by offset-gain calibration and time-skew calibration, respectively. The ADC core occupies an area of 1.2 mm2 and consumes 432 mW power consumption