Summary Strain is an essential quantity to characterize local structural behaviors and directly correlates with structural damage initiation and development that is within local regions. Strain measurement at high spatial resolution (density) locations is thus required to characterize local structural behaviors and detect potential local damage. Traditional contact‐type strain gauges are mostly discrete point‐wise sensors that can only be placed in a limited number of positions. Distributed optical fiber sensing techniques can measure strains at spatially dense measurement points, but their instrumentation is a time‐ and labor‐intensive process associated with the issue of the fragility of fibers. Noncontact optical measurement techniques, such as a family of interferometry techniques using laser beams (e.g., laser Doppler vibrometers), can provide vibration measurement at high density spatial points without the need to install sensors on the structure. However, these measurement devices are active sensing methods that are relatively expensive and vulnerable to ambient motion. Photogrammetry is an alternative noncontact optical measurement method using (passive) white‐light imaging of digital video cameras that are relatively low‐cost, agile, and provides simultaneous measurements at high spatial density locations where every pixel becomes a measurement point. Among others, digital image correlation can achieve full‐field deformation measurements and subsequently estimate the full‐field strains. However, it is computationally extensive. This study develops a new efficient approach to estimate the full‐field (as many measurement points as the pixel number of the video frame on the structure) dynamic strains at high‐spatial (pixel)‐resolution/density location points from the digital video measurement of output‐only vibrating structures. The developed approach is based on phase‐based video motion estimation and modal superposition of structural dynamic response. Furthermore, the method is augmented by a high‐fidelity finite element model, which is updated with the full‐field experimental modal parameters “blindly” identified from the video measurement of the output‐only structure. Laboratory experiments are conducted to validate the method on a bench‐scale cantilever beam structure. Results demonstrate that the full‐field dynamic strain estimated by the developed approach from the video measurement of the output‐only vibrating beam match very well those directly measured by the strain gauges (at discrete measurement points). Some factors associated with the effectiveness of the method are experimentally studied and discussed.
Automobile brake squeal noise, which is nonlinear, friction-induced vibration in the frequency range 1–16 kHz, still remains a major problem for the automotive industry. This article presents analytical and experimental investigations into the application of dither control for active suppression of automobile disc brake squeal. Dither is a concept of active control that introduces high-frequency actuation into a system to suppress a much lower frequency disturbance. In this study, a specially designed brake system is built, in which a piezoelectric stack actuator in the piston of a floating caliper brake applies the dither input. In the experiments, squeal noise generated under the drag mode and various dynamic modes are considered. The results indicate that this piezoelectric-based dither control could effectively suppress the brake squeal noise by 5–10 dB and the squeal occurrence by up to 60% under various braking conditions.
This paper presents a new sensing paradigm for structural impact detection using vibro-haptic interfaces. The goal of this study is to allow humans to 'feel' structural responses (impact, shape changes, and damage) and eventually determine health conditions of a structure. The target applications for this study are aerospace structures, in particular, airplane wings. Both hardware and software components are developed to realize the vibro-haptic-based impact detection system. First, L-shape piezoelectric sensor arrays are deployed to measure the acoustic emission data generated by impacts on a wing. Unique haptic signals are then generated by processing the measured acoustic emission data. These haptic signals are wirelessly transmitted to human arms, and with vibro-haptic interface, human pilots could identify impact location, intensity and possibility of subsequent damage initiation. With the haptic interface, the experimental results demonstrate that human could correctly identify such events, while reducing false indications on structural conditions by capitalizing on human's classification capability. Several important aspects of this study, including development of haptic interfaces, design of optimal human training strategies, and extension of the haptic capability into structural impact detection are summarized in this paper.
The number of obese people has been steadily rising over one and a half times since recent ten years in Korea. Obesity accompanied by increased body fat could lead to hyperlipidemia, hyperinsulunemia, and hypertension, contributing to metabolic syndrome. The study of metabolic syndrome‐related blood lipids predisposing to atherosclerosis have taken attention more. To know the effects of obesity program on Atherogenic Index(AI) and HOMA Index in the obese middle aged women. Obese middle aged women(age: 46.4±6, BMI: 33.1±2.9, %Fat: 33.5±3.5) had done power walking and jogging on the treadmill for aerobic exercise(50‐60 %VO2max for first 1‐6 weeks, 60‐70 %VO2max for later 7‐12 weeks), weight training for resistant exercise(50‐60 %1RM for first 1‐6 weeks, 60‐80 %1RM for later 7‐12 weeks) for a hour. AI and HOMA Index extrapolated from blood samples were analysed at the beginning of exercise, 6 weeks after beginning exercise, and 12 weeks after beginning exercise. The variables were analyzed using one‐way ANOVA. AI decreased at 12 weeks after beginning exercise(p<.05) and HOMA Index decreased at 12 weeks after beginning exercise(p<.05). Insulin decreased at 12 weeks after beginning exercise but were not statistically significant. Therefore, the maintenance of normal weight and doing exercise is beneficial to preventing the metabolic syndrome and arteriosclerosis.
An acute exercise concomitant with transient plasma shifts caused by the modified colloid osmotic pressure gradient contributes to the plasma volume correction(PVC) demands. However, relations between physiological effects of an exercise and the physical characteristics of permeating molecules or endothelial barriers raise doubts about quantitative benefits of PVC. The present study was conducted to determine the limitation of widely applied PVC on measuring concentration of serum protein in an acute exercise. Nine college men(age: 25.4±0.5, BMI: 22.6±1.9) were assigned to non‐exercise group(NG) on the first day and to exercise group(EG)(45 min., 65‐75 %HRmax, running) on the next day. Blood samples were drawn for the serum protein electrophoresis analysis(t‐test, pearson correlation) twice(pre‐event, post‐event). Albumin(p<.05), α1(p<.01), α2(p<.01), β(p<.05), and λ(p<.05) fraction concentration increased after the exercise. Negative correlations between the percentage of change in albumin and that of other fractions concentration in NG(α1(r=‐.755, p<.05), α2(r=‐.947, p<.01), β(r=‐.954, p<.01), λ(r=‐.928, p<.01)) decreased by wide gaps in EG(α1(r=.377), α2(r=‐.210), β(r=‐.349), γ(r=‐.289)). These correlations moved from the positive direction to the negative according to the increasing size of serum proteins in both groups except for γfraction. The results suggest that not only relatively small‐sized albumin but large‐sized serum proteins permeate endothelial barriers with conformational strain in proportion to the size. Therefore, the application of current PVC on a study measuring serum protein concentration in an acute exercise may underestimate the accurate concentration in situ.
Modern infrastructure systems, such as bridges, dams, power generation stations, and buildings increasingly have an intrinsic cyber-physical nature to them. Infrastructure now commonly, includes actuators, network connections, sensors, control systems, and computational resources. It is of increasing concern that modern infrastructure is vulnerable to cyber-attacks that can damage both the cyber and physical nature of the infrastructure. To date, the physical and cyber health of infrastructure has been considered separately. However, the increasing concerns associated with the cyber-physical security of infrastructure coupled with the emergence of 5G networks made using components that are not universally considered trustworthy, and the emergence of techniques for creating deepfakes and adversarial examples suggests the time has come to begin considering cyber health and structural health with a more holistic approach. In this work, a protocol is developed for ensuring the imagery data captured by a structural health monitoring system can be unambiguously attributed to legitimate sensors associated with the structural health monitoring system. A computer vision approach based on the idea of mutual information is then presented to detect damage in an image. This work presents the protocol for authenticating the provenance of imager data and demonstrates that this protocol does not have overly adverse effects when used with the mutual information-based technique for detecting damage in the resulting imagery data.
The present study was conducted to know the effects of combined exercise on inflammatory markers and hormones relevant to obesity. Obese middle aged women(age: 46.4±6, BMI: 33.1±2.9, %Fat: 33.5±3.5) had done yoga for stretching, running for aerobic exercise(55‐65 %VO2max for first 1‐6 weeks and 66‐75 %VO2max for later 7‐12 weeks), and dumbbell exercise for resistant exercise(55‐65 %1RM for first 1‐6 weeks and 66‐75 %1RM for later 7‐12 weeks) for a hour per exercise, differently progressed by the day in every week. Blood plasma was extracted at the beginning of exercise, 6 weeks after beginning exercise, and 12 weeks after beginning exercise to analyse inflammatory markers(CRP, TNF‐α), obesity‐related hormones(leptin, adiponectin). One‐way ANOVA was used for data analysis. CRP, TNF‐α decreased at 12 weeks after beginning exercise, comparing to that at the beginning of exercise, but were not statistically significant. Leptin decreased and Adiponectin increased statistically significantly at 12 weeks after beginning exercise, comparing to those at the beginning of exercise(p<.05). Therefore, the combined exercise may be the preventive action against vascular diseases.
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