High Acceleration Environments Research Articles

The effect of bending strength via doping (Pr25Nd75)90Ni10 alloy in sintered Nd-Fe-B magnets

The brittleness of magnetic materials limits their application in high-frequency and high-acceleration environments. This study investigates the effect of (Pr25Nd75)90Ni10 doping on the magnetic and mechanical properties of sintered Nd-Fe-B magnets. The results show that the magnet with a doping content of 1.2% (Pr25Nd75)90Ni10 exhibits the best bending strength of 343.40 MPa, with almost no impact on the magnetic properties. Microstructural analysis reveals that the addition of Ni enriches the grain boundaries, promoting the formation of a new phase Nd2Ni7 and enhancing the coherence between the grain boundary phase(GBP) and the main phase(MP), thereby improving the strength of the GBP. This study provides a theoretical basis for the preparation of sintered Nd-Fe-B magnets with superior mechanical properties.

Mechanical model analysis and reliability design approach of Quartz Flexible Accelerometer under fractured state

AbstractCurrently, the Quartz Flexible Accelerometer (QFA) mounted for the applications working in high acceleration environment are suffering from the fracture of the flexible beams under external acceleration shock. This paper presents the mechanical model and reliability design approach of QFA to maintain the measuring ability under a fractured state. The structural parameters changed significantly in the mechanical model under a fractured state compared to those in the original model. A modified structure to maintain the measuring ability of QFA under a fractured state is designed with the reference of the sensitive module in Electrostatic Suspended Accelerometer (ESA). The corresponding close‐loop system is corrected and discretised to ensure the stability requirements of the mechanical model. A static experiment is conducted to prove the effectiveness of the proposed model by a prototype QFA with completely fractured flexible beams. The result shows helpful on the preliminary research for QFA with the similar sensitive structure to ESA.

Simplification of calibration of low-cost MARG sensors without high-precision laboratory equipment

AbstractIn mechatronic-related applications, estimating orientation from a magnetic, angular rate, and gravity (MARG) sensor array is a significant topic. Representing attitude orientation is a well-known topic in the aerospace industry, where it plays a critical role in airplanes and unmanned aerial vehicles (UAVs), but it has also gained relevance in other sectors. However, most of the sensors utilized are quite expensive, heavy, and large, making them unsuitable for modest applications. This paper examines the performance of several sensors in low-cost hardware and high-acceleration environments. A theorical method was adopted to estimate Euler angles by using accelerometer, gyroscope and magnetometer, and a robust and easy to implement method calibration was proposed to calibrate the MARG sensor without any external equipment. An experimental verification of the proposed calibration method was completed. The experimental results are then interpreted to provide an insight to advantages and disadvantages for using each sensor separately.

Super-twisting sliding mode controller for maximum power transfer efficiency tracking in hybrid energy storage based wireless in-wheel motor

Conventionally, the in-wheel motor is powered by cables from the battery attached to electric vehicle (EV) body which has a risk of disconnection in case of high acceleration or harsh environment. To solve this issue, using wireless power transfer (WPT) technology, a wireless in-wheel motor (WIWM) based on LCC-S Compensation topology is proposed. To cater for varying power requirements of WIWM, and generate optimal power from WPT system, an ultracapacitor (UC) is connected in parallel with WIWM. The UC and onboard battery make a hybrid energy storage system for the in-wheel motor system. A super-twisting sliding mode controller-based control system has been designed to drive the WIWM at desired speed and track UC current to required reference. The stability of proposed control system is verified by Lyapunov stability criteria. The performance of the proposed controller has been compared against conventionally used PID and Lyapunov controller by driving EV according to European Extra Urban Driving Cycle (EUDC). Finally, the real-time performance of proposed control scheme has been validated by controller hardware-in-loop (C-HIL) experiments.

Effect of High Positive Acceleration (+Gz) Environment on Dental Implant Osseointegration: A Preliminary Animal Study

ObjectiveTo observe the effect of high positive acceleration (+Gz) environment on dental implant osseointegration in a rabbit model and to investigate its mechanism. MethodsForty-eight New Zealand white rabbits were randomly divided into 6 groups. The rabbit's mandibular incisors were extracted and 1 implant was placed in each socket immediately. After 1 week of rest, the rabbits were exposed to a high +Gz environment, 3 times a week. The rabbits were sacrificed at 3 weeks (2 weeks +Gz exposure), 5 weeks (4 weeks +Gz exposure), and 12 weeks (4 weeks +Gz exposure and 7 weeks normal environment) after surgery, respectively. Specimens were harvested for micro-CT scanning, histological analysis, and real-time polymerase chain reaction examination. ResultsCompared with those in the control group, the mRNA expression levels of bone morphogenetic protein-2 (BMP-2), osteopontin (OPN), and transforming growth factor-β1 (TGF-β1) were significantly lower (P < 0.05), while the mRNA expression level of receptor activator of nuclear factor kB ligand (RANKL) and the RANKL/osteoprotegerin (OPG) ratio were significantly higher (P < 0.05) at 3 weeks; values of bone volume fraction, trabecular number, bone-implant contact (BIC), and TGF-β1 and OPG mRNA expression levels were significantly lower (P < 0.05), and the value of trabecular separation, RANKL mRNA expression level and RANKL/OPG ratio were significantly higher (P < 0.05) at 5 weeks; and the value of BIC was still significantly lower (P < 0.05) at 12 weeks in the experimental group. ConclusionEarly exposure to the high +Gz environment after implant surgery might have an adverse effect on osseointegration, and its mechanism could be related to the inhibition of osteoblast activity and promotion of osteoclast activity.

The effects of meclizine on motion sickness revisited.

AimsAntihistamines make up the first line of treatments against motion‐sickness. Still, their efficacy and specific mechanism have come into question. The aim of this study was to investigate the effect of meclizine on motion‐sensitivity.MethodsThis study was carried out as a triple‐blinded randomized trial involving 12 healthy subjects who were exposed to (i) vestibular (VES), (ii) visual (VIS) and (iii) visual–vestibular (VIS+VES) stimulations in the roll plane. Subjects were divided into 2 groups by stratified randomization, receiving either meclizine or a placebo. Stimulations were carried out before, and after, drug administration, presented at 2 intensity levels of 14 and 28°/s2. Eye movements were tracked, and torsional slow‐phase velocities, amplitudes and nystagmus beats were retrieved. Subjects initially graded for their motion‐sickness susceptibility.ResultsSusceptibility had no effect on intervention outcome. Despite large variations, repeated ANOVAS showed that meclizine led to a relative increase in torsional velocity compared to placebo during vestibular stimulation for both intensities: 2.36 (7.65) from −0.01 (4.17) during low intensities, and 2.61 (6.67) from −3.49 (4.76) during high. The visual–vestibular stimuli yielded a decrease during low acceleration, −0.40 (3.87) from 3.75 (5.62), but increased during high, 3.88 (6.51) from −3.88 (8.55).ConclusionsMeclizine had an inhibitory effect on eye movement reflexes for low accelerations during VIS+VES trials. This indicates that meclizine may not primarily work through sensory‐specific mechanisms, but rather on a more central level. Practically, meclizine shows promise in targeting motion‐sickness evoked by everyday activities, but its use may be counterproductive in high‐acceleration environments.

Model and experiment of scale factor acceleration sensitivity of MEMS gyroscope in high acceleration environment

With the development of MEMS gyroscope, acceleration sensitivity is becoming an important factor in application. The acceleration sensitivity would produce an obvious output error, and researchers mainly focus on bias acceleration sensitivity. Yet, in environment of high acceleration and angular rate, it is the scale factor acceleration sensitivity that influences the output most, and there is little research on it. In this paper, scale factor acceleration sensitivity of MEMS gyroscope in high acceleration environment is investigated with our established theoretical model and experimental measurement. Based on our proposed method of measuring the acceleration sensitivity in environment of high acceleration and angular rate, the MEMS tuning fork gyroscope is used for the measurement. The results show that the output error caused by acceleration can be up to − 30.1°/s and the scale factor acceleration sensitivity contributes the most. The coefficient of scale factor acceleration sensitivity is 35 ppm/g under 50g acceleration, and this coefficient increases linearly with acceleration that coincides with theoretical model. Lastly, some suggestions of decreasing scale factor acceleration sensitivity are given. This work is useful for the researchers to improve the performance of acceleration sensitivity of MEMS gyroscope.

Flexible and Robust Multilayer Micro-Vibrational Harvesters for High Acceleration Environments

This paper presents the fabrication and characterization of multilayer PVDF resonant micro-vibrational energy harvesters designed to withstand environments in which high levels of acceleration are present. The multilayer cantilevers are fabricated by combining two folded PVDF stacks into a multilayered, bimorph structure. This acts to increase the overall capacitance of the harvester, a problem that plaques PVDF cantilevers as a result of its low dielectric constant. Moderate powers (7 μW) are produced from the cantilevers even at high acceleration levels (20 g) due to the limited piezoelectric coefficient of PVDF; however, as a result of the high tensile strength and low elastic modulus of PVDF, the cantilevers are able to survive extremely high accelerations (> 4000 g) without breakage – a critical problem for harvesters based on brittle piezoelectric materials and substrates.

The Effect of Training Type on Oxidative DNA Damage and Antioxidant Capacity during Three-Dimensional Space Exercise

Objective: Orbotron training is a popular training method for fighter pilots because it replicates a high-acceleration environment with excessive G-force. The purpose of this study was to investigate the effects of 9 weeks of orbotron training on oxidative DNA damage and antioxidant capacity in humans during 3-dimensional space exercise. Subjects and Methods: The subjects comprised 15 senior cadets from the Korea Air Force Academy who had no record of medical disorders and who participated in a regular exercise program (3 times per week). They were randomly divided into three groups consisting of 5 subjects each: a weight training group (21.97 ± 1.12 years), a running training group (21.53 ± 0.18 years) and an orbotron training group (21.48 ± 0.29 years). Three-dimensional exercise tests were performed before and after training, and blood samples were taken to measure the concentration of plasma lactate, malondialdehyde (MDA), erythrocyte superoxide dismutase (SOD) activity, and leukocyte DNA damage. Results: Plasma lactate concentrations decreased in all three groups when measured after training and after 30 min of recovery compared to before training (p < 0.05). The concentration of plasma MDA also decreased after training in all blood samples compared to the values obtained before training although there was no significant difference in the weight training and orbotron training groups. In contrast, the activity of erythrocyte SOD increased for all three groups compared to before training (p < 0.05). In the comet assay results, the greatest lymphocyte DNA damage was demonstrated at the end of exercise compared to the other three samples under all conditions, and these aspects were commonly observed in all three parameters of lymphocyte DNA damage (tail DNA, tail length and tail moment) (p < 0.05). Conclusion: It can be concluded that the three types of exercise training reduced plasma lactate concentration, improved antioxidant enzyme activity, and further protected the body against oxidative stress (lipid peroxidation and DNA damage). Although we have identified an effect of exercise training on the levels of antioxidants and oxidants, our cohort was small, so further studies are needed to evaluate the different types of exercise training.

Numerical advances in gross-motion simulations of head/neck dynamics.

An efficient method for gross-motion simulation of head/neck dynamics in accidents and high acceleration environments is presented. The method uses finite-segment modelling to develop a 3-body model of the head/neck system. The model is shown to compare favorably with an analogous 9-body model and with experimental data. The model is expected to be useful for: efficient analysis of gross-motion head/neck dynamics during accidents; for developing increased intuitive understanding of head/neck behavior; and for use with gross-motion, whole-body, crash-victim simulators.

Absolute stability of symmetric highly maneuverable missiles

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Use of microspheres in measurement of regional blood flows during +GZ stress

The use of the radiolabeled microsphere technique for the study of the effects of +GZ acceleration on regional blood flow is examined. A theoretical analysis of the limits of this technique in a high acceleration environment is presented. Chronically implanted, electromagnetic, aortic flow probes were used to determine the relationship between aortic blood flow velocity and +GZ acceleration in conscious adult miniature swine. It was found that conscious straining adult miniature swine, with the assistance of an inflated anti-G suit, are able to compensate quite well to acceleration levels less than or equal to +7 GZ. Exposure to +9 GZ often resulted in unstable cardiovascular states involving relative bradycardia, often progressing to asystole, declining aortic blood pressure, and markedly diminished cardiac outputs approaching zero. It was found that, if aortic pressure and heart rate attain a relatively steady state during acceleration, and if heart level mean aortic pressure is greater than or equal to 100 Torr, the application of the microsphere technique during +GZ acceleration is theoretically valid. This hypothesis was tested using the microsphere technique (9.0 +/- 0.8 microns diam) in conscious miniature swine during exposure to +GZ acceleration. It is concluded that within the defined limits the radiolabeled microsphere technique is as accurate for use during acceleration studies as it is for use in routine laboratory studies.

Nonmetallized Solid Propellant Combustion in Standard and High Acceleration Environments

Abstract Nonmetallized double-base propellant and ammonium perchlorate (AP)/binder sandwich combustion were studied in standard and high acceleration environments in order to determine the acceleration sensitive combustion mechanisms. Experimental techniques used were high speed motion pictures, two-color schlieren, and centrifuge mounted combustion bombs. It was found for double-base propellant that the temperature increased continuously from the surface into the visible flame. Acceleration induced burning rate augmentation occurred and resulted in elimination of the visible flame. A modified surface or subsurface zone is proposed as the acceleration sensitive combustion mechanism. AP/binder sandwich combustion was also found to be acceleration sensitive with binder flow-AP interactions proposed as the mechanism.

An Experimental Study of Ammonium Perchlorate-Binder Sandwich Combustion in Standard and High Acceleration Environments

Abstract An experimental investigation of ammonium perchlorate (AP)-binder (PBAA) sandwich combustion was made in standard and high acceleration environments. An optically equipped combustion bomb mounted on a centrifuge and a standard combustion bomb were used in the investigation. High speed color motion pictures and schlieren were taken during the combustion process. Principal results were: binder thickness as little effect upon regression rate; sandwich combustion is acceleration sensitive and results in part from binder melt/AP deflagration interaction; below the low pressure deflagration limit (P dt ) of ammonium perchlorate the sandwich combustion process is laminar with combustion continuing for large distances above the binder/AP interface; above the P dt of AP the sandwich combustion process appears to be turbulent and consists of two distinct flame regions.