Pulse Design of Constant Strain Rate Loading in SHPB Based on Pulse Shaping Technique.

The Split Hopkinson pressure bar (SHPB) is widely used for characterizing the mechanical behavior of materials at high strain rates. One of the most challenging factors is achieving constant strain rate (CSR) loading of the specimen at a certain strain rate. Obtaining the effective incident pulse based on the experimental material for achieving CSR loading remains unresolved. This research focuses on obtaining the proper incident pulse for achieving constant strain rate loading using the pulse-shaping technique. A parameterized objective incident model in terms of the strain rate and quasi-static (or dynamic stress-strain) behavior of the material is established utilizing the three-wave method. Experimental pulses that closely resemble the desired objective pulses can be generated by adjusting parameters such as the geometry of the shaper, the shaper material, striker velocities, and the length of the striker according to the pulse-shaping model. The model is applied to the design of the incident pulse for B4CP/2024Al composite material, and the dynamic stress-strain curves at different strain rates are obtained under CSRs. This model provides effective guidance for selecting an appropriate shaper and achieving CSR loading in SHPB tests.

Diagnostic value of combined serological markers in the detection of acute cerebral infarction.

ABSTRACT: To evaluate the value of the combination schemes of 10 serological markers in the clinical diagnosis of acute cerebral infarction.The level of total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, high-sensitivity C-reactive protein, homocysteine (HCY), lipoprotein-related phospholipase A2, ischemia-modified albumin, complement C1q, and lipoprotein a were analyzed in 154 patients with acute ischemic cerebral infarction. The optimized diagnostic combination for acute cerebral infarction was explored by calculating the maximum area under the receiver operating characteristic curves (AUC).The levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, high-sensitivity C-reactive protein, HCY, lipoprotein-related phospholipase A2, ischemia-modified albumin, complement C1q, and lipoprotein a were significantly higher in the patient vs the control group. Moreover, the positive rate of HCY reached 89.9%. The analysis of the receiver operating characteristic curve of each index and their combinations showed that the minimum AUC of HDL-C alone was 0.543, while the maximum AUC of HCY was 0.853. A multiple logistic regression analysis indicated that HDL-C was a slightly significant variate in the diagnosis of acute cerebral infarction.The value of individual serological markers in the diagnosis of acute cerebral infarction was slightly significant, while the combination of the markers significantly improved the efficiency of its diagnosis.

A Spray-on, Nanocomposite-Based Sensor Network for in-Situ Active Structural Health Monitoring.

A new breed of nanocomposite-based spray-on sensor is developed for in-situ active structural health monitoring (SHM). The novel nanocomposite sensor is rigorously designed with graphene as the nanofiller and polyvinylpyrrolidone (PVP) as the matrix, fabricated using a simple spray deposition process. Electrical analysis, as well as morphological characterization of the spray-on sensor, was conducted to investigate percolation characteristic, in which the optimal threshold (~0.91%) of the graphene/PVP sensor was determined. Owing to the uniform and stable conductive network formed by well-dispersed graphene nanosheets in the PVP matrix, the tailor-made spray-on sensor exhibited excellent piezoresistive performance. By virtue of the tunneling effect of the conductive network, the sensor was proven to be capable of perceiving signals of guided ultrasonic waves (GUWs) with ultrahigh frequency up to 500 kHz. Lightweight and flexible, the spray-on nanocomposite sensor demonstrated superior sensitivity, high fidelity, and high signal-to-noise ratio under dynamic strain with ultralow magnitude (of the order of micro-strain) that is comparable with commercial lead zirconate titanate (PZT) wafers. The sensors were further networked to perform damage characterization, and the results indicate significant application potential of the spray-on nanocomposite-based sensor for in-situ active GUW-based SHM.

The Value of Serum Complement C1q in the Diagnosis of Acute Ischemic Stroke.

BACKGROUND: To investigate the relationship between the levels of serum complement C1q and the risk and severity of acute ischemic stroke, a total of 154 patients with acute ischemic stroke and 42 healthy volunteers as normal controls were enrolled in the present study. METHODS: According to the onset time of stroke, patients were divided into three groups. Using an immune transmission turbidity method, the levels of serum complement C1q were detected to investigate the relationship between the level of serum complement C1q and the incidence and severity of acute ischemic stroke. The risk factors of these groups were calculated using a conditional logistic regression model. The assessment of neurological function impairment was carried out according to the National Institute of Health Stroke Scale. Then correlation anal- ysis was carried out between the level of serum complement C1q among patients with acute ischemic stroke and the degree of neurological function impairment. RESULTS: The results showed that the level of serum complement C1q was higher in the ischemic stroke group than in the control group. Using a conditional logistic regression model it was discovered that serum complement C1q was the independent pathogenic factor of cerebral infarction. There also was a decreasing trend in the level of serum complement C1q with the extension of the onset time and an increasing trend in the level of serum complement C1q with the increase in the maximum diameter of infarction volume. CONCLUSIONS: Serum complement C1q is an independent risk factor for acute outbreak of ischemic stroke, whose level is closely related to the outbreak and infarct size and neurological function impairment.