Research on Alternating Current Field Measurement Method for Buried Defects of Titanium Alloy Aircraft Skin.

Titanium alloys are extensively used in the manufacturing of key components in aerospace engines and aircraft structures due to their excellent properties. However, aircraft skins in harsh operating environments are subjected to long-term corrosion and pressure concentrations, which can lead to the formation of cracks and other defects. In this paper, a detection probe is designed based on the principle of alternating current field measurement, which can effectively detect both surface and buried defects in thin-walled titanium alloy plates. A finite element simulation model of alternating current field measurement detection for buried defects in thin-walled TC4 titanium alloy plates is established using COMSOL 5.6 software. The influence of defect length, depth, and excitation frequency on the characteristic signals is investigated, and the detection probe is optimized. Simulation and experimental results demonstrate that the proposed detection probe exhibits high detection sensitivity to varying lengths and depths of buried defects, and can detect small cracks with a length of 3 mm and a burial depth of 2 mm, as well as deep defects with a length of 10 mm and a burial depth of 4 mm. The feasibility of this probe for detecting buried defects in titanium alloy aircraft skin is confirmed.

Internal and External Pipe Defect Characterization via High-Frequency Lamb Waves Generated by Unidirectional EMAT.

Periodic permanent magnet(PPM) electromagnetic acoustic transducers (EMATs) are commonly employed for axial defect inspection in pipelines. However, the lowest-order shear horizontal waves (SH0) guided waves have difficulties in distinctly differentiating internal and external defects. To enhance the signal-to-noise ratio and resolution, a unidirectional electromagnetic acoustic transducer (EMAT) based on Circumferential Lamb waves (CLamb waves) is developed. Through structural parameter optimization and excitation frequency adjustment, high-amplitude and low-dispersion CLamb waves are successfully generated in the high-frequency-thickness product region of the dispersion curve. Finite element simulations and experimental validation confirm the capability of this EMAT in exciting CLamb waves for the detection of crack-like defects. Experimental results demonstrate that the excitation efficiency of the CLamb EMAT exceeds that of the periodic permanent magnet electromagnetic acoustic transducer by more than tenfold. The defect reflection signal of the CLamb EMAT exhibits higher resolution and more significant amplitude compared to the PPM EMAT. The integration of this method with SH0 mode detection allows for the inspection of both internal and external defects in pipelines, offering a new avenue for EMAT applications in pipeline inspection.

Energy Transfer Efficiency Based Nonlinear Ultrasonic Testing Technique for Debonding Defects of Aluminum Alloy Foam Sandwich Panels.

In order to improve the accuracy of detection results of debonding defects of aluminum alloy thin plate, the nonlinear ultrasonic technology is used to detect the simulated defect samples, aiming at problems such as near surface blind region caused by the interaction of incident wave, reflected wave and even second harmonic wave in a short time due to the small thickness of thin plates. An integral method based on energy transfer efficiency is proposed to calculate the nonlinear ultrasonic coefficient to characterize the debonding defects of thin plates. A series of simulated debonding defects of different sizes were made using aluminum alloy plates with four thicknesses of 1 mm, 2 mm, 3 mm and 10 mm. By comparing the traditional nonlinear coefficient with the integral nonlinear coefficient proposed in this paper, it is verified that both methods can quantitatively characterize the size of debonding defects. The nonlinear ultrasonic testing technology based on energy transfer efficiency has higher testing accuracy for thin plates.

Quantitative Identification Method for Glass Panel Defects Using Microwave Detection Based on the CSAPSO-BP Neural Network.

To address the problem of the quantitative identification of glass panel surface defects, a new method combining the chaotic simulated annealing particle swarm algorithm (CSAPSO) and the BP neural network is proposed for the quantitative evaluation of microwave detection signals of glass panel defects. First, the parameters of the particle swarm optimization (PSO) algorithm are dynamically assigned using chaos theory to improve the global search capability of the PSO. Then, the CSAPSO-BP neural network model is constructed, and the return loss and phase of the microwave detection echo signal of glass panel defects are extracted as the input feature quantity of the network, from which the intrinsic connection between input and output is found through network training and testing to achieve the prediction of the depth and width of glass panel surface defects. The results show that the CSAPSO-BP network model can more accurately characterize the defect geometry of glass panels than the PSO-BP network model.

Association between Left Ventricular Longitudinal Strain (GLS) and Prognosis of the Patients Undergoing Heart Valve Surgery with Preserved Left Ventricular Ejection Fraction.

PURPOSE: Global longitudinal strain (GLS) seems accurate for detecting subclinical myocardial dysfunction. This study aimed to determine the association between GLS and postoperative intensity of inotropic support in the patients undergoing heart valve surgery with preserved left ventricular ejection fraction. METHODS: 74 patients with preserved left ventricular ejection fraction who underwent valve surgery during the period between March 2021 and June 2022 were included in this prospective observational study. Transthoracic echocardiography including strain analysis with speckle tracking was performed before surgery. Patients were stratified according to the left ventricle (LV) GLS: LV-GLS ≥-16% (Impaired GLS group) and LV-GLS <-16% (Normal GLS group). The primary endpoint was postoperative vasoactive inotropic score. A high vasoactive inotropic score (VIS) was defined as a maximum VIS of ≥15 within 24 hours postoperatively. Postoperative adverse events, baseline clinical and echocardiographic data were also recorded. We invested the ability of preoperative GLS in predicting adverse postoperative outcomes, such as prolonged mechanical ventilation and the need for pharmacologic hemodynamic support after cardiac surgery. RESULTS: Seventy-four patients were included and analyzed in this study, including thirty-three in impaired GLS group and forty-one in normal GLS group. In-hospital mortality was 1.27% (1/74). Patients in impaired GLS group were more likely to have prolonged mechanical ventilation (p = 0.041). Multivariable logistic regression analysis revealed that the apical four-chamber view of the left ventricle (A4C)-GLS was significantly associated with high VIS (OR 1.373, p = 0.007). A4C-GLS had a sensitivity of 62.5% and a specificity of 89.66% for predicting high VIS (area under the curve, 0.78). The relationships between GLS and other secondary outcome measures were not statistically significant. The optimal cutoff of A4C-GLS for postoperative high vasoactive inotropic score was -10.85%. CONCLUSION: Preoperative LV dysfunction is an independent risk factor for postoperative high VIS. A4C-GLS may be a reliable tool in predicting high VIS after cardiac surgery. Those patients with impaired contractility were at high risk for elevated inotropic support and prolonged mechanical ventilation after cardiac surgery. These findings suggest an important role for echocardiographic GLS in perioperative assessment of cardiac function in the patients undergoing cardiac surgery.

Risk factors and long-term prognosis for postoperative hypoxemia in patients with acute type A aortic dissection: A retrospective observational study.

Hypoxemia is 1 of the most common complications in the patients with acute Type A aortic dissection (ATAAD). This study aimed to summarize the risk factors, management strategies and long-term prognosis for postoperative hypoxemia in ATAAD patients. Baseline characteristics and clinical data of all the patients were collected. Patients were divided into 2 groups according to the PaO2/FiO2 after surgery: Hypoxemia group (n = 142) and Non-hypoxemia group (n = 68). The differences in gender, age, body mass index, operation time, cardiopulmonary bypass (CPB) time, aortic cross-clamping time, deep hypothermic circulatory arrest time, preoperative PaO2/FiO2, postoperative PaO2/FiO2, PaO2/FiO2 before extubating, time of mechanical ventilation, length of intensive care unit stay, length of hospital stay, in-hospital mortality, and overall mortality were compared between the 2 groups. The incidence of postoperative hypoxemia in this study was 67.6% (142/210). body mass index (26.4 ±â€…3.8 vs 24.4 ±â€…3.3kg/m2, P < .001) in the hypoxemia group were markedly higher and CPB time (196.3 ±â€…41.0 vs 181.0 ±â€…37.3 minutes, P = .010) in the hypoxemia group were significantly longer than those in the non-hypoxemia group. While preoperative PaO2/FiO2 (229.7 ±â€…91.4 vs 299.7 ±â€…101.2mmHg, P < .001) was significantly lower than those in the non-hypoxemia group. In the hypoxemia group, PaO2/FiO2 before extubating was significantly higher than that after operation, and the difference was significant. Logistic regression analysis showed that overweight (odds ratio [OR]: 1.113, P = .030), CPB time (OR: 1.009, P = .043) and preoperative PaO2/FiO2 (OR: 0.994, P = .001) were independent risk factors for postoperative hypoxemia. Further follow-up results showed no significant difference in long-term mortality between the 2 groups. Logistic regression analysis revealed that PaO2/FiO2 before extubating (OR: 0.985, P < .001), paraplegia (OR: 10.994, P = .019), acute renal failure (OR: 12.590, P < .001), re-operation (OR: 4.721, P = .014) and re-admission to intensive care unit (OR: 13.727, P = .001) were independent risk factors for long-term mortality. Our results showed that overweight and prolonged CPB time were risk factors for postoperative hypoxemia in ATAAD patients. While PaO2/FiO2 before extubating were independent risk factors for long-term mortality, indicating that active correction of hypoxemia and maintain a higher PaO2/FiO2 before extubating may help to improve the prognosis of the ATAAD patients.

Design and Performance Research of a New Dual-Excitation Uniform Eddy Current Probe.

A dual-excitation uniform eddy current probe, composed of two excitation coils placed tangentially and one detection coil placed horizontally, is developed to solve the difficulties of detection rate and direction recognition of crack defect. Firstly, a probe simulation model is established using COMSOL Multiphysics, and the differences of eddy current distribution between the dual-excitation probe and the traditional probe are investigated. Then, the influence of the distance between excitation coils on sensitivity and the test capability for crack defects with different depths and directions are investigated. Besides, the sensitivity of the dual-excitation probe is compared to that of the traditional probe made of the same coils. Finally, a physical probe and an experimental system are developed, and the performance of the dual-excitation probe is tested. The experimental results show that the probe developed in this paper exhibits a slightly higher sensitivity than the traditional probe for crack defects with different depths in the range of 0.5 mm-4.0 mm; the measurement accuracy of crack length is about 3.0 mm and can avoid missing detection of crack defects with different directions. In testing, the detection signal can be compensated to achieve precision measurement by identifying the angle of crack defects. This dual-excitation uniform eddy current probe can be used for precise quantification and direction identification of crack defect in eddy current testing.

Prediction of low cardiac output syndrome in patients following cardiac surgery using machine learning.

Background: This study aimed to develop machine learning models to predict Low Cardiac Output Syndrome (LCOS) in patients following cardiac surgery using machine learning algorithms. Methods: The clinical data of cardiac surgery patients in Nanjing First Hospital between June 2019 and November 2020 were retrospectively extracted from the electronic medical records. Six conventional machine learning algorithms, including logistic regression, support vector machine, decision tree, random forest, extreme gradient boosting and light gradient boosting machine, were employed to construct the LCOS predictive models with all predictive features (full models) and selected predictive features (reduced models). The discrimination of these models was evaluated by the area under the receiver operating characteristic curve (AUC) and the calibration of the models was assessed by the calibration curve. Shapley Additive explanation (SHAP) and Local Interpretable Model-Agnostic Explanations (LIME) were used to interpret the predictive models. Results: Data from 1,585 patients [982 (62.0%) were male, aged 18 to 88, 212 (13.4%) with LCOS] were employed to train and validate the LCOS models. Among the full models, the RF model (AUC: 0.909, 95% CI: 0.875-0.943; Sensitivity: 0.849, 95% CI: 0.724-0.933; Specificity: 0.835, 95% CI: 0.796-0.869) and the XGB model (AUC: 0.897, 95% CI: 0.859-0.935; Sensitivity: 0.830, 95% CI: 0.702-0.919; Specificity: 0.809, 95% CI: 0.768-0.845) exhibited well predictive power for LCOS. Eleven predictive features including left ventricular ejection fraction (LVEF), first post-operative blood lactate (Lac), left ventricular diastolic diameter (LVDd), cumulative time of mean artery blood pressure (MABP) lower than 65 mmHg (MABP < 65 time), hypertension history, platelets level (PLT), age, blood creatinine (Cr), total area under curve above threshold central venous pressure (CVP) 12 mmHg and 16 mmHg, and blood loss during operation were used to build the reduced models. Among the reduced models, RF model (AUC: 0.895, 95% CI: 0.857-0.933; Sensitivity: 0.830, 95% CI: 0.702-0.919; Specificity: 0.806, 95% CI: 0.765-0.843) revealed the best performance. SHAP and LIME plot showed that LVEF, Lac, LVDd and MABP < 65 time significantly contributed to the prediction model. Conclusion: In this study, we successfully developed several machine learning models to predict LCOS after surgery, which may avail to risk stratification, early detection and management of LCOS after cardiac surgery.

The roles of inactivated vaccines in older patients with infection of Delta variant in Nanjing, China.

BACKGROUND: The coronavirus disease 2019 (COVID-19) is spreading around the world. The COVID-19 vaccines may improve concerns about the pandemic. However, the roles of inactivated vaccines in older patients (aged ≥60 years) with infection of Delta variant were less studied. METHODS: We classified the older patients with infection of Delta variant into three groups based on the vaccination status: no vaccination (group A, n = 113), one dose of vaccination (group B, n = 46), and two doses of vaccination (group C, n = 22). Two inactivated COVID-19 vaccines (BBIBP-CorV or CoronaVac) were evaluated in this study. The demographic data, laboratory parameters, and clinical severity were recorded. RESULTS: A total of 181 older patients with infection of Delta variant were enrolled. 111 (61.3%) patients had one or more co-morbidities. The days of "turn negative" and hospital stay in Group C were lower than those in the other groups (P < 0.05). The incidences of multiple organ dysfunction syndrome (MODS), septic shock, acute respiratory distress syndrome (ARDS), acute kidney injury, and cardiac injury in Group A were higher than those in the other groups (P < 0.05). The MV-free days and ICU-free days during 28 days in Group A were also lower than those in the other groups (P < 0.05). In patients with co-morbidities, vaccinated cases had lower incidences of MODS (P = 0.015), septic shock (P = 0.015), and ARDS (P = 0.008). CONCLUSIONS: The inactivated COVID-19 vaccines were effective in improving the clinical severity of older patients with infection of Delta variant.

The association between lymphocyte-monocyte ratio and postoperative acute kidney injury in patients with acute type A aortic dissection.

BACKGROUND: The aim of this study was to investigate the relationship between baseline lymphocyte-monocyte ratio (LMR) and postoperative acute kidney injury (AKI) in patients with acute type A aortic dissection (ATAAD). METHODS: ATAAD patients undergoing surgery in Nanjing First Hospital were enrolled from January 2019 to April 2021. Lymphocyte and monocyte were measured on admission. Multivariable logistic regression analyses were performed to explore the relationship between LMR and postoperative AKI. We also used receiver operating characteristic (ROC), net reclassification index (NRI) and integrated discrimination improvement (IDI) analyses to assess the predictive ability of LMR. RESULTS: Among the 159 recruited patients, 47 (29.6%) were diagnosed with AKI. Univariate logistic regression analysis indicated that ATAAD patients with higher levels of LMR were prone to have lower risk to develop AKI (odds ratio [OR], 0.493; 95% confidence interval [CI] 0.284-0.650, P = 0.001). After adjustment for the potential confounders, LMR remained an independent related factor with postoperative AKI (OR 0.527; 95% CI 0.327-0.815, P = 0.006). The cutoff value for LMR to predict AKI was determined to be 2.67 in the ROC curve analysis (area under curve: 0.719). NRI and IDI further confirmed the predictive capability of LMR in postoperative AKI. CONCLUSION: Elevated baseline LMR levels were independently associated with lower risk of postoperative AKI in ATAAD patients.

Mechanism of Magnetic Permeability Perturbation in Magnetizing-Based Eddy Current Nondestructive Testing.

DC magnetization is generally considered to suppress the usual local magnetic permeability variation and increase the penetration depth for magnetizing-based eddy current testing (MB-ECT) of ferromagnetic materials. In fact, such simple explanations lead to rough nondestructive evaluation and cause new neglected non-uniform magnetic characteristics. Hence, the "perturbation" of the internal magnetic field variation is analyzed using a magnetic dipole model and the mechanism of magnetic permeability perturbation in MB-ECT is revealed. The theoretical analysis and simulations show that a significant permeability perturbation always appears around a defect and presents opposite features with strong and weak magnetization. Furthermore, experimental results indicate that the hidden signal component arising from the local permeability perturbation is critical for both far-side surface and near-side surface defects in the MB-ECT method.

Association Between Hypernatremia and Delirium After Cardiac Surgery: A Nested Case-Control Study.

Background: The association between hypernatremia and delirium after cardiac surgery has rarely been investigated. This study aimed to determine whether hypernatremia increases the risk of delirium after exposure. Materials and Methods: From April 2016 to June 2021, 7,831 consecutive patients receiving cardiac surgery were screened for potential enrollment. The primary outcome was postoperative delirium (POD). For the respective case of delirium, 10 controls were matched according to the index date within the nested case-control design. Hypernatremia exposure was defined as serum sodium > 145 mmol/L within 7 days before the index date. A generalized estimation equation was performed to assess excess risks for POD associated with hypernatremia, adjusted for demographics and clinical variables. Results: About 7,277 patients were included in the final analyses. About 669 (9.2%) patients with POD were assigned to the case group, and 6,690 controls were identified from the whole population. About 66.5% of the cases and 36.3% of the controls had hypernatremia exposure. After being adjusted to certain well-recognized confounding factors, hypernatremia showed a significant correlation with increased risk of delirium after cardiac surgery (adjusted OR, 1.73; 95% CI, 1.41~2.12). An e-value analysis suggested the robustness to unmeasured confounding. Conclusions: Hypernatremia was associated with an increased risk of delirium after cardiac surgery. This finding could have implications for risk stratification, early detection, and management of delirium in patients receiving cardiac surgery.

Decreased triiodothyronine (T3) as a predictor for prolonged mechanical ventilation in critically ill patients with cardiac surgery.

BACKGROUND: This study aimed to examine the correlation between thyroid hormone and prolonged mechanical ventilation (MV) in adult critically ill patients having undergone cardiac surgery. METHODS: The present study refers to a retrospective, cohort study conducted at Nanjing First Hospital from March 2019 to December 2020. Patients receiving cardiac surgery and admitting to the Cardiovascular Intensive Care Unit (CVICU) in the study period were screened for potential inclusion. Demographic information, thyroid hormone and other laboratory measurements and outcome variables were recorded for analysis. Prolonged MV was defined as the duration of MV after cardiac surgery longer than 5 days. Thyroid hormones were assessed for the prognostic significance for prolonged MV. RESULTS: One thousand eight hundred ninety-six patients who underwent cardiac surgery were screened for potential enrollment. Overall, 118 patients were included and analyzed in this study. Patients fell to the control (n = 64) and the prolonged MV group (n = 54) by complying with the duration of MV after cardiac surgery. The median value of total triiodothyronine (TT3) and free triiodothyronine (FT3) were 1.03 nmol/L and 3.52 pmol/L in the prolonged MV group before cardiac surgery, significantly lower than 1.23 nmol/L (P = 0.005) and 3.87 pmol/L, respectively in control (P = 0.038). Multivariate logistic regression analysis indicated that TT3 before surgery (pre-op TT3) had an excellent prognostic significance for prolonged MV (OR: 0.049, P = 0.012). CONCLUSIONS: This study concluded that decreased triiodothyronine (T3) could be common in cardiac patients with prolonged MV, and it would be further reduced after patients undergo cardiac surgery. Besides, decreased T3 before surgery could act as an effective predictor for prolonged MV after cardiac surgery.

A New Design of the Dual-Mode and Pure Longitudinal EMAT by Using a Radial-Flux-Focusing Magnet.

An electromagnetic acoustic transducer (EMAT) is suitable for measuring the propagation time more accurately without causing abrasion to the transducer during testing due to the principle of its excitation. This work designs a flux-concentrating EMAT with a radial-flux-focusing permanent magnet to significantly enhance static magnetic field strength. Through theoretical analysis and finite element simulation, two kinds of coils are designed according to the concentration areas of the horizontal and vertical components of the magnetic field. One is used to generate pure longitudinal waves, and the other is used to generate both longitudinal waves and shear waves. The experimental comparison shows that the amplitudes of the pure longitudinal wave and the dual-mode wave excited by the two kinds of coils with the radial-flux-focusing magnet are more than two times higher than those with the ordinary magnet. Therefore, the flux-concentrating EMAT with the appropriate coil provides an insight into realizing more accurate detection where longitudinal wave detection is required.

Investigation of an air-coupled transducer with a closed-cell material matching strategy and an optimization design considering the electrical input impedance.

A high sensitivity air-coupled transducer with a hollow polymer microsphere filled epoxy resin matching layer is investigated. A new closed-cell porous material is introduced and a new acoustic impedance matching solution is discussed. An electrical impedance matching and parameter optimization method based on artificial bee colony algorithm is investigated which can significantly improve the sensitivity on the basis of acoustic impedance matching approach. The diameter of the piezoelectric plate and the thickness of the acoustic matching layer play an important role in this method. Experimental results are given, illustrating a 20.9 dB sensitivity enhancement by applying our acoustic impedance matching method, and an 8.4 dB additional sensitivity enhancement by applying our electrical impedance matching and parameter optimization method.

Effect of Del Nido cardioplegia on ventricular arrhythmias after cardiovascular surgery.

BACKGROUND: Del Nido cardioplegia (DNC) has been proven safe and effective in pediatric patients. However, the use of DNC in adult undergoing cardiovascular surgery lacks support with substantial evidence. This study aimed to evaluate the efficacy of DNC as a cardioplegia of prophylaxis to ventricular arrhythmias associated to cardiovascular surgery in adult patients. METHODS: This study recruited nine hundred fifty-four patients who underwent cardiopulmonary bypass surgeries in Nanjing Hospital affiliated to Nanjing Medical University between January 2019 and December 2019. Among 954 patients, 324 patients were treated with DNC (DNC group), and 630 patients were treated with St. Thomas cardioplegia (STH group). The incidence of postoperative arrhythmia as well as other cardiovascular events relavant to the surgery were investigated in both groups. RESULTS: In DNC group, the incidence of postoperative ventricular arrhythmias was lower (12.4% vs. 17.4%, P = 0.040), and the length of ICU stay was shorter (1.97 ± 1.49 vs. 2.26 ± 1.46, P = 0.004). Multivariate logistic regression demonstrated that the use of DNC helped to reduce the incidence of postoperative ventricular arrhythmias (adjusted odds ratio 0.475, 95% CI 0.266-0.825, P = 0.010). The propensity score-based analysis and subgroup analysis indicated that DNC has the same protecting effects towards myocardial in all kinds of cardiopulmonary bypass surgeries. CONCLUSIONS: Del Nido cardioplegia may potentially reduce the incidence of postoperative ventricular arrhythmias, shorten the length of ICU stay and improve the overall outcome of the patients undergoing cardiovascular surgery.

A retrospective study of ulinastatin for the treatment of severe sepsis.

This retrospective study aimed to investigate the efficacy and safety of existing approach of ulinastatin for the treatment of severe sepsis (SS).A total of 130 eligible patients with SS were included in this study. We divided them into an intervention group (n = 65) and a control group (n = 65). Patients in both groups received conventional therapy. In addition, patients in the intervention group received ulinastatin for 7 days. Outcomes were measured by Acute Physiology and Chronic Health Evaluation II (APACHE II), Multiple Organ Failure (MOF), Glasgow Coma Scale (GCS), CD3, CD4, CD8, CD4/CD8, and adverse events. We assessed all outcomes before and after treatment.After treatment, patients in the intervention group showed better improvement in APACHE II (P < .01), MOF (P < .01), GCS (P < .01), CD3 (P = .03), CD4 (P = .03), and CD4/CD8 (P < .01), than those of patients in the control group. There are similar safety profiles between both groups.This study suggests that ulinastatin may be beneficial for SS. Future studies are still needed to warrant the results of this study.

Therapeutic Effect of Perioperative Mild Hypothermia on Postoperative Neurological Outcomes in Patients with Acute Stanford Type A Aortic Dissection.

BACKGROUND: Postoperative patients of acute Stanford type A aortic dissection (AAAD) often experience complications consisting of nervous system injury. Mild hypothermia therapy has been proven to provide the therapeutic effect of cerebral protection. We aimed to investigate the therapeutic effects of perioperative mild hypothermia on postoperative neurological outcomes in patients with AAAD. METHODS: A prospective randomized controlled study was conducted on adult patients undergoing aortic dissection surgery between February 2017 and December 2017. Patients in the treatment group underwent mild hypothermia (34° to 35°C) immediately after surgery, and in the conventional therapy group, patients were rewarmed to normal body temperature (36° to 37°C). Postoperative time to regain consciousness, postoperative serum neuron-specific enolase (NSE) and S-100ß levels, cerebral tissue oxygen saturation, presence of delirium or permanent neurological dysfunction, intensive care unit (ICU) and hospital stay duration, and 28-day mortality were compared. RESULTS: We enrolled 55 patients who underwent AAAD surgery and were randomly allocated into to 2 groups, 27 patients in the treatment group and 28 patients in the conventional therapy group. Compared with the conventional therapy group, postoperative time to regain consciousness was much shorter for patients in the mild hypothermia group (12.65 hours, interquartile range [IQR] 8.28 to 23.82, versus 25.80 hours, IQR 14.00 to 59.80; P = .02), and the rate of regaining consciousness in 24 hours after surgery was much higher (74.07% versus 46.42%; P = .037). At the same time, the ICU stay of patients in the mild hypothermia therapy group was significantly shorter than that in the conventional therapy group (5.53 ± 3.13 versus 9.35 ± 8.76 days; P = .038). Cerebral tissue oxygen saturation, incidence of delirium or permanent neurological dysfunction, duration of hospital stay, and 28-day mortality showed no statistical difference. Postoperative serum NSE and S-100ß levels increased compared with preoperative baseline values in both groups (P < .05), and the serum NSE levels of patients in the mild hypothermia therapy was significantly lower than the conventional therapy group 1 hour (P = .049) and 6 hours (P = .04) after surgery. There was no difference in the chest drainage volume or shivering between the 2 groups 24 hours after surgery. CONCLUSIONS: Perioperative mild hypothermia therapy is able to significantly reduce brain cell injury and shorten the postoperative time to regain consciousness, thus improving the neurological prognosis of patients with AAAD.

Research on Detection Mechanism of Weld Defects of Carbon Steel Plate Based on Orthogonal Axial Eddy Current Probe.

The uneven surface of the weld seam makes eddy current testing more susceptible to the lift-off effect of the probe. Therefore, the defect of carbon steel plate welds has always been a difficult problem in eddy current testing. This study aimed to design a new type of eddy current orthogonal axial probe and establish the finite element simulation model of the probe. The effect of the probe structure, coil turns, and coil size on the detection sensitivity was simulated. Further, a designed orthogonal axial probe was used to conduct a systematic experiment on the weld of carbon steel specimens, and the 0.2 mm width and 1 mm depth of weld defects of carbon steel plates were effectively detected. The experimental results showed that the new orthogonal axial eddy current probe effectively suppressed the unevenness effect of the weld surface on the lift-off effect during the detection process.

Pure SH1 Guided-Wave Generation Method with Dual Periodic-Permanent-Magnet Electromagnetic Acoustic Transducers for Plates Inspection.

High frequency guided-waves offer a trade-off between the high sensitivity of local bulk ultrasonic thickness measurements and the large area scanning of lower frequency guided-waves, so it has been a growing interest for corrosion inspection with the dispersive SH1 mode. However, according to the dispersive curve, it is hard to generate the pure SH1 mode since the non-dispersive SH0 mode will be excited simultaneously. Thus, this paper investigates a transducer design method to generate a pure SH1 guided-wave, where the dual periodic-permanent-magnet electromagnetic acoustic transducers (PPM EMATs) are placed on exactly opposite positions either side of the plate symmetrically. The suppression effect for SH0 and the enhancement effect for SH1 of the dual PPM EMATs are mainly discussed by theoretical analysis and simulation analysis, and the influence of positioning errors of PPM EMATs placed on opposite sides of the plate on its performances are analyzed. Employing the proposed dual PPM EMATs, some experiments are performed to verify the reliability of finite element simulation. The results indicate that the dual PPM EMATs can suppress the SH0 mode and generate the pure SH1 mode effectively. Moreover, the longitudinal and lateral positioning errors can affect the dual PPM EMATs performances significantly.