Omni-directional damage detection and localization with a 2-D piezoelectric ultrasonic phased array

The disadvantages of linear arrays are such that the range of damage detection is limited up to only 180°, and also that the detection accuracy is very poor at angles close to 0° and 180°. In order to solve this problem, this paper puts forward a new damage detection and localization method by coupling the image enhancement technology with two-dimensional piezoelectric ultrasonic phased arrays arranged in the shape of a cross. The basic detection principle as well as the detailed process of damage localization will be covered in this paper. Along with the implementation of the cross-shaped sensor arrays, a new image enhancement algorithm is proposed with the aim to deal with the problem of phantom image emerging in the opposite side of the original image. The results of the experiments conducted on an aluminum plate show that the above proposed method can not only effectively solve the limitation of the linear sensor array, but also accurately detect multiple damages in full angle mode

Omni-directional damage detection and localization with a cruciform piezoelectric ultrasonic phased array

A full-range (360°) damage detection is necessary for structural health monitoring of large plate-like structures. However, the linear arrays are mainly limited by the range of damage detection, which is maximum up to 180°. Moreover the detection accuracy is also very poor at angles close to 0° and 180°. In order to solve this problem, a novel damage detection and localization method is presented in this paper. The proposed method combines the image enhancement technology and the cruciform piezoelectric phased array to improve the performance of the linear array based system. In addition to the implementation of cruciform phased array, a new image enhancement algorithm is proposed with an aim to deal with the problem of phantom image emerging in the opposite side of the original image. The results of the experiments conducted on aluminum plate and epoxy composite laminate plate show that the proposed method can effectively solve the limitations of the linear sensor array, and accurately detect single or multiple damages in full angle mode

Ultrasonic phased array with dispersion compensation for monitoring multiple damages in structures

Multiple-damage-inflicted scattering signals usually overlap with each other due to Lamb wave dispersion and multi-mode characteristics. As a result, it is difficult to accurately distinguish damages that occur relatively close to each other using the conventional ultrasonic phased array method. In order to solve this problem, an improved linear mapping (ILM) dispersion compensation method is proposed and is applied to enhance the ultrasonic phased array monitoring resolution. Through a uniform linear array arrangement, the damage scattering signals are collected in a round-robin pattern of ultrasonic phased array, and then compensated based on the linear relation wavenumber curve from actual measurement. At last, the scan can be obtained by monitoring the energy scattered by the damages using delay-and-sum method. To verify the proposed method, experiments are performed on an aluminum (LY-12) plate. Two results of multiple artificial damages show that the proposed method can effectively compensate the dispersion characteristics of Lamb waves. The direction estimation error and distance estimation error are less than 4° and 2 cm, respectively

Lipid profiles in the cerebrospinal fluid of rats with 6-hydroxydopamine-induced lesions as a model of Parkinson’s disease

BackgroundParkinson’s disease (PD) is a progressive neurodegenerative disease with characteristic pathological abnormalities, including the loss of dopaminergic (DA) neurons, a dopamine-depleted striatum, and microglial activation. Lipid accumulation exhibits a close relationship with these pathologies in PD.MethodsHere, 6-hydroxydopamine (6-OHDA) was used to construct a rat model of PD, and the lipid profile in cerebrospinal fluid (CSF) obtained from model rats was analyzed using lipidomic approaches.ResultsEstablishment of this PD model was confirmed by apomorphine-induced rotation behaviors, loss of DA neurons, depletion of dopamine in the striatum, and microglial activation after 6-OHDA-induced lesion generation. Unsupervised and supervised methods were employed for lipid analysis. A total of 172 lipid species were identified in CSF and subsequently classified into 18 lipid families. Lipid families, including eicosanoids, triglyceride (TG), cholesterol ester (CE), and free fatty acid (FFA), and 11 lipid species exhibited significantly altered profiles 2 weeks after 6-OHDA administration, and significant changes in eicosanoids, TG, CE, CAR, and three lipid species were noted 5 weeks after 6-OHDA administration. During the period of 6-OHDA-induced lesion formation, the lipid families and species showed concentration fluctuations related to the recovery of behavior and nigrostriatal abnormalities. Correlation analysis showed that the levels of eicosanoids, CE, TG families, and TG (16:0_20:0_18:1) exhibited positive relationships with apomorphine-induced rotation behaviors and negative relationships with tyrosine hydroxylase (TH) expression in the midbrain.ConclusionThese results revealed that non-progressive nigrostriatal degeneration induced by 6-OHDA promotes the expression of an impairment-related lipidomic signature in CSF, and the level of eicosanoids, CE, TG families, and TG (16:0_20:0_18:1) in CSF may reveal pathological changes in the midbrain after 6-OHDA insult

Influence of Aerodynamics on the Fatal Crash in Le Mans 1955

In the 1955 Le Mans race one of the worst crashes in motor racing history occurred and this accident changed the face of motor racing for decades to come. However, still fifty years after the fatal accident a number of questions remained unsolved. One open issue is the influence of aerodynamics on the scenario, since the Mercedes-Benz 300 SLR involved in the crash was equipped with an air-brake.In a recent work [1], it was shown that the air-brake in operation generates a significant drag increase, but also under certain conditions a down force on the vehicle. In the current work, CFD is utilized as a tool for the investigation of the aerodynamic aspects of the accident. More advanced parameters like the pitch angles are computed, and a simple model for the flight path is derived. It is found that the pitch angles, which were largely affected by the air brake, had a significant influence on the length of the flight path

Notice of Violation of IEEE Publication Principles: Single-Phase Common-Ground-Type Transformerless PV Grid-Connected Inverters

This paper presents a family of novel common-ground-type transformerless photovoltaic (PV) grid-connected inverters, which requires only five power switches, one capacitor, and one filter. A simple dual-closed led-loop control is used to improve control stabilization and accuracy. The main advantages of proposed inverters are: 1) the leakage current is completely eliminated (unlike traditional topologies, which can only suppress leakage current); 2) the devices used are a few and the cost is low; 3) low loss and high efficiency; 4) the ability of realizing reactive power; and 5) there is no need for high DC input voltage compared with half-bridge-type topologies. The operating principle, modulation mode, and control strategy are introduced in detail. The performance of the proposed topology is compared with that of several traditional topologies. The leakage current suppression ability and efficiency of the proposed topology are superior to those of the traditional topologies. The model predictive control (MPC) is applied in the proposed topology, which is easy to realize and can accelerate the dynamic response. Finally, the simulation and experimental results of a 1-kVA prototype are given, which proves the validity of the proposed topology in PV grid-connected system

Design of a centrifugal compressor with low specific speed for automotive fuel cell

Centrifugal compressors driven by electric motor are the promising type for fuel cell pressurization system. A low specific speed centrifugal compressor powered by an ordinary high-speed (about 25,000rpm) electric motor has been designed at Tsinghua University for automotive fuel cell engines. The experimental results indicate that the designed low specific speed centrifugal compressor has comparatively high efficiency and wide operating range. In the condition of designed speed (24,000rpm), the highest efficiency and pressure ratio of the centrifugal compressor is up to 70% and 1.6, respectively. The designed low specific speed centrifugal compressor can meet the requirement of air systems of automotive fuel cell engines preliminarily. Moreover, the low specific speed centrifugal compressor avoids difficulties of usage of ultra-high-speed electric motors (about 60,000rpm) in high specific speed compressor. Based on the preliminary results of this centrifugal compressor, a new low specific speed centrifugal compressor with higher performances is being developed

The effects and gender-related differences of guided forest therapy program on physiological and psychological health of graduating college students

Forest therapy has been proven to have a quantifiable positive impact on human physiological and psychological health. Given that graduating students at university are easy to stress due to changes in life, pressure from their studies, and independence in finance. The main purpose of this research was to explore the effects of guided forest therapy on graduating college students through a field experiment in Pacific Spirit Regional Park which held significant geographical value. This paper investigated the pressure of graduating college students and their needs for forest therapy, and explored the psychological and physiological changes after guided forest therapy. This study also analyzed gender-related psychological and physiological differences. Thirty-six healthy graduating college students were invited to participate in a 2-hour forest therapy program. Likert scales were used to assess students' pressure and the demand for forest therapy. Most of the students were facing the pressure of graduation and were willing to participate in forest therapy. Systolic and diastolic blood pressure, pulse rate, and heart rate variability (HRV) were used as physiological measurement indices. Our physiological results indicated that blood pressure significantly decreased, the high-frequency component of HRV (HF) was significantly larger, and the low-to-high-frequency component ratio (LF/HF) was smaller after the forest therapy program, and some beneficial changes in females were more significant than that in males. The participants' mean HR decreased throughout the forest therapy, but there were no significant differences. Mental status was assessed before and after forest therapy using the Profile of Mood States (POMS), employment stress scale and State-Trait Anxiety Inventory (STAI) for participants. Overall, the guided forest therapy program effectively reduced participants' employment stress and state anxiety. Our research showed that guided forest therapy had positive physiological and psychological benefits for graduating college students. In addition, females obtained more positive physiological benefits than males, and males obtained more positive psychological benefits than females throughout forest therapy

Baricitinib treatment for refractory skin changes in POEMS syndrome: a case report

Polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, and skin changes (POEMS) syndrome is a multisystem disorder that has limited treatment options. Here, we described a case of a 55-year-old female subject who was treated for multiple drugs, but the skin symptoms continued to progress; the patient responded well to baricitinib. This suggests that JAK/STAT signaling pathways play an essential role in the pathological process of POEMS syndrome