高速铁路钢轨RCF伤损特征及NDT研究进展

随着我国高速列车的大量开行,滚动接触疲劳(RCF)伤损成为了高速铁路钢轨的主要伤损,严重威胁行车安全。本文介绍了我国提速段高速铁路钢轨的滚动接触疲劳伤损的类型、特征和发展模式。相关机构的调研和分析结果表明,轨头裂纹和隐伤是我国提速段钢轨最主要的RCF伤损,且伤损类型与钢轨的强度级别有关。同时介绍了钢轨RCF伤损的无损检测方法研究情况,重点阐述了低频超声表面波检测方法的研究进展。

Feature extraction and damage alarming using time series analysis

Aiming at the problem of on-line damage diagnosis in structural health monitoring （SHM）, an algorithm of feature extraction and damage alarming based on auto-regressive moving-average （ARMA） time series analysis is presented. The monitoring data were first modeled as ARMA models, while a principalcomponent matrix derived from the AR coefficients of these models was utilized to establish the Mahalanobisdistance criterion functions. Then, a new damage-sensitive feature index DDSF is proposed. A hypothesis test involving the t-test method is further applied to obtain a decision of damage alarming as the mean value of DDSF had significantly changed after damage. The numerical results of a three-span-girder model shows that the defined index is sensitive to subtle structural damage, and the proposed algorithm can be applied to the on-line damage alarming in SHM.

DAMAGE CLASSIFICATION BY PROBABILISTIC NEURAL NETWORKS BASED ON LATENT COMPONENTS FOR TIME-VARYING SYSTEM

A new approach to damage classification for health monitoring of a time-varylng system is presented. The functional-series time-dependent auto regressive moving average （FS-TARMA） time series model is applied to the vibration signal observed in the time-varying system for estimating the TAR/TMA parameters and the innovation variance. These parameters are the functions of the time, represented by a group of projection coefficients on the certain functional subspace with specific basis functions. The estimated TAR/TMA parameters and the innovation variance are further used to calculate the latent components （LCs） as the more informative data for health monitoring evaluation, based on an eigenvalue decomposition technique. LCs are then combined and reduced to numerical values （NVs） as feature sets, which are input to a probabilistic neural network （PNN） for the damage classification. For the evaluation of the proposed method, numerical simulations of the damage classification for a tlme-varylng system are used, in which different classes of damage are modeled by the mass or stiffness reductions. It is demonstrated that the method can identify the damages in the course of operation and the change of parameters on the time-varying background of the system.

Signaling mechanisms in alcoholic liver injury: Role of transcription factors, kinases and heat shock proteins

Alcoholic liver injury comprises of interactions of various intracellular signaling events in the liver. Innate immune responses in the resident Kupffer cells of the liver, oxidative stress-induced activation of hepatocytes, fibrotic events in liver stellate cells and activation of liver sinusoidal endothelial cells all contribute to alcoholic liver injury. The signaling mechanisms associated with alcoholic liver injury vary based on the cell type involved and the extent of alcohol consumption. In this review we will elucidate the oxidative stress and signaling pathways affected by alcohol in hepatocytes and Kupffer cells in the liver by alcohol. The toll-like receptors and their down-stream signaling events that play an important role in alcohol-induced inflammation will be discussed. Alcohol-induced alterations of various intracellular transcription factors such as NFKB, PPARs and AP-1, as well as MAPK kinases in hepatocytes and macrophages leading to induction of target genes that contribute to liver injury will be reviewed. Finally, we will discuss the significance of heat shock proteins as chaperones and their functional regulation in the liver that could provide new mechanistic insights into the contributions of stress-induced signaling mechanisms in alcoholic liver injury.

Implication of altered proteasome function in alcoholic liverinjury

The proteasome is a major protein-degrading enzyme, which catalyzes degradation of oxidized and aged proteins, signal transduction factors and cleaves peptides for antigen presentation. Proteasome exists in the equilibrium of 26S and 20S particles. Proteasome function is altered by ethanol metabolism, depending on oxidative stress levels： low oxidative stress induces proteasome activity, while high oxidative stress reduces it. The proposed mechanisms for modulation of proteasome activity are related to oxidative modification of proteasomal proteins with primary and secondary products derived from ethanol oxidation. Decreased proteolysis by the proteasome results in the accumulation of insoluble protein aggregates, which cannot be degraded by proteasome and which further inhibit proteasome function. Mallory bodies, a common signature of alcoholic liver diseases, are formed by liver cells, when proteasome is unable to remove cytokeratins. Proteasome inhibition by ethanol also promotes the accumulation of pro-apoptotic factors in mitochondria of ethanol-metabolizing liver cells that are normally degraded by proteasome. In addition, decreased proteasome function also induces accumulation of the negative regulators of cytokine signaling （I-~B and SOCS）, thereby blocking cytokine signal transduction. Finally, ethanol-elicited blockade of interferon type 2 and 2 signaling and decreased proteasome function impairs generation of peptides for MHC class Ⅰ-restricted antigen presentation.

Fracture evolution and localization effect of damage in rock based on wave velocity imaging technology

By utilizing wave velocity imaging technology,the uniaxial multi-stage loading test was conducted on siltstone to attain wave velocity imagings during rock fracture.Based on the time series parameters of acoustic emissions(AE),joint response characteristics of the velocity field and AE during rock fracture were analyzed.Moreover,the localization effect of damage during rock fracture was explored by applying wave velocity imagings.The experimental result showed that the wave velocity imagings enable three-dimensional(3-D)visualization of the extent and spatial position of damage to the rock.A damaged zone has a low wave velocity and a zone where the low wave velocity is concentrated tends to correspond to a severely damaged zone.AE parameters and wave velocity imagings depict the changes in activity of cracks during rock fracture from temporal and spatial perspectives,respectively:the activity of cracks is strengthened,and the rate of AE events increases during rock fracture;correspondingly,the low-velocity zones are gradually aggregated and their area gradually increases.From the wave velocity imagings,the damaged zones in rock were divided into an initially damaged zone,a progressively damaged zone,and a fractured zone.During rock fracture,the progressively damaged zone and the fractured zone both develop around the initially damaged zone,showing a typical localization effect of the damage.By capturing the spatial development trends of the progressively damaged zone and fractured zone in wave velocity imagings,the development of microfractures can be predicted,exerting practical significance for determining the position of the main fracture.

Protective effects of ursodeoxycholic acid on chenodeoxycholic acid-induced liver injury in hamsters

AIM： TO investigate the effects of ursodeoxycholic acid （UDCA） on chenodeoxycholic acid （CDCA）-induced liver injury in hamsters, and to elucidate a correlation between liver injury and bile acid profiles in the liver.METHODS： Liver injury was induced in hamsters by administration of 0.5% （w/w） CDCA in their feed for 7 d. UDCA （50 mg/kg and 150 mg/kg） was administered for the last 3 d of the experiment.RESULTS： At the end of the experiment, serum alanine aminotransferase （ALl） increased more than 10 times and the presence of liver injury was confirmed histologically. Marked increase in bile acids was observed in the liver. The amount of total bile acids increased approximately three-fold and was accompanied by the increase in hydrophobic bile acids, CDCA and lithocholic acid （LCA）. UDCA （50 mg/kg and 150 mg/kg） improved liver histology, with a significant decrease （679.3 ±77.5 U/L vs 333.6 ± 50.4 U/L and 254.3 ±35.5 U/ L, respectively, P 〈 0.01） in serum ALT level. UDCA decreased the concentrations of the hydrophobic bile acids, and as a result, a decrease in the total bile acid level in the liver was achieved.CONCLUSION： The results show that UDCA improves oral CDCA-induced liver damage in hamsters. The protective effects of UDCA appear to result from a decrease in the concentration of hydrophobic bile acids, CDCA and LCA, which accumulate and show the cytotoxicity in the liver.

Leprosy without typical skin involvement but with concurrent tuberculosis: a case report

Leprosy is characterized by skin lesions and peripheral nerve damage. It may take a long time before the diagnosis can be confirmed if the patients have no typical skin involvements. Here we report an unusual case. A 40-year-old male with lepromatous leprosy showed a gradual onset of bilateral symmetrical neuropathies without characteristic skin manifestations seven years after onset and with pulmonary tuberculosis simultaneously. He was misdiagnosed as having Guillani-Barr6 syndrome and systemic necrotizing vasculitis for 10 years until the skin biopsy was performed. This case indicates that the risk of leprosy exists, though new cases being detected have significantly declined over the last 50 years; neurologists need to pay more attention to leprosy with various manifestations .

Multi-dimensional and Multi-threshold Airframe Damage Region Division Method Based on Correlation Optimization

In order to obtain the image of airframe damage region and provide the input data for aircraft intelligent maintenance,a multi-dimensional and multi-threshold airframe damage region division method based on correlation optimization is proposed.On the basis of airframe damage feature analysis,the multi-dimensional feature entropy is defined to realize the full fusion of multiple feature information of the image,and the division method is extended to multi-threshold to refine the damage division and reduce the impact of the damage adjacent region’s morphological changes on the division.Through the correlation parameter optimization algorithm,the problem of low efficiency of multi-dimensional multi-threshold division method is solved.Finally,the proposed method is compared and verified by instances of airframe damage image.The results show that compared with the traditional threshold division method,the damage region divided by the proposed method is complete and accurate,and the boundary is clear and coherent,which can effectively reduce the interference of many factors such as uneven luminance,chromaticity deviation,dirt attachment,image compression,and so on.The correlation optimization algorithm has high efficiency and stable convergence,and can meet the requirements of aircraft intelligent maintenance.

Temporal bone fracture and its complications

Objective:: To explore the characteristics and treatment of temporal bone fractures and injuries in the medial-inner ear. Methods: The clinical data of 48 cases of temporal bone fractures admitted to our hospital from January 1989 to November 1999 were retrospectively analyzed. Results: Forty-eight patients with temporal bone fractures accounted for 17.00 % of the homochronous craniofacial fractures. Of the 48 cases, temporal bone fractures induced by traffic accidents accounted for 66.67 %, capillary fractures for 93.75 %, medial-inner ear injuries or craniocerebral injuries for 77.08 % and hearing loss or tinnitus for 48.00 %. The cerebrospinal fluid (CSF) otorrhea and facioplegia accounted for 36.70 % and 3.00 %, respectively, in the longitudinal fractures, while they were 25.00 % and 37.50 %, respectively, in the transversal fractures. Primary emergent operations were performed on 46 cases and neurosurgery accounted for 46.00 %. Secondary procedures accounted for 16.70 %. As a result, 43 cases survived ( 89.58 %) and 5 died ( 10.41 %). Conclusions: Traffic injury is the first high-dangerous factor for temporal bone fractures, which are often complicated with medial-inner ear or craniocerebral injury. The CSF otorrhea is common in the longitudinal fractures and facioplegia is common in the transversal fractures. The key step is to rescue the life, keep the airway unobstructed and maintain the circulation in the primary emergency treatment.

Treatment of limb arterial injuries caused by traffic accidents

Objective: To analyze the features, diagnosis and treatment of limb arterial injuries caused by traffic accidents. Methods: A total of 43 patients with limb arterial injury admitted in our department over the past 30 years (about 50% of them happened during the last 10 years) were analyzed retrospectively in this article. The popliteal, femoral and brachial arteries were mainly involved, accounting for 43.2 %, 20.5 % and 20.5 % respectively of all the involvements. There were 35 cases of open injury and 9 of close injury. The involved vessels were transected in 43.2 % of the cases and contused in 40.9 %. All the patients had various complications, such as fractures, dislocations and severe soft tissue injuries. The injured vessels were repaired by means of end to end anastomosis in 10 cases, autogenous vein graft in 23 cases and intraluminal hydraulic dilatation in 4 cases. Results: Successful limb salvage was achieved in 34 cases initially, whereas 10 amputations were carried out due to injuries to popliteal arteries in 7, femoral arteries in 2 and humeral artery in 1 and severe soft tissue damages in 9 cases. Twenty nine patients were followed up for 1 156 months, with the average of 48.8 months. There was good circulation in 22 cases and certain ischemia in 5 cases. Two amputations were carried out in the late stage because of popliteal artery thrombosis after repair in 2 cases. There was no death in this series. Conclusions: The limb arterial injuries caused by traffic accidents are severe and complicated. It is proposed that particular attentions should be paid to the features in diagnosis and treatment for this type of injury and special efforts should be made for both life saving and limb salvage.

Real-time damage analysis of 2D C/SiC composite based on spectral characters of acoustic emission signals using pattern recognition

In this study,unsupervised and supervised pattern recognition were implemented in combination to achieve real-time health monitoring.Unsupervised recognition(k-means++)was used to label the spectral characteristics of acoustic emission(AE)signals after completing the tensile tests at ambient temperature.Using in-plane tensile at 800 and 1000°C as implementing examples,supervised recognition(K-nearest neighbor(KNN))was used to identify damage mode in real time.According to the damage identification results,four main tensile damage modes of 2D C/SiC composites were identified:matrix cracking(122.6–201 kHz),interfacial debonding(201–294.4 kHz),interfacial sliding(20.6–122.6 kHz)and fiber breaking(294.4–1000 kHz).Additionally,the damage evolution mechanisms for the 2D C/SiC composites were analyzed based on the characteristics of AE energy accumulation curve during the in-plane tensile loading at ambient and elevated temperature with oxidation.Meanwhile,the energy of various damage modes was accurately calculated by harmonic wavelet packet and the damage degree of modes could be analyzed.The identification results show that compared with previous studies,using the AE analysis method,the method has higher sensitivity and accuracy.

Diagnosis and treatment of penetrating craniocerebral injury

Objective: To evaluate the clinical characteristics and present the experience in the treatment of patients with penetrating craniocerebral injury (PCCI). Methods: The data of 7 cases with PCCI by foreign body were retrospectively studied and compared with associated literatures. The strategies of diagnosis and treatment of PCCI were analyzed. In this series, 3 cases underwent emergency debridements and 4 cases underwent craniotomies. All patients received surgical intervention within 3 hours after admission. Results: Outcomes were good in 3 cases, moderate disability was in 2 cases, severe disability in 1 case and persistent vegetative state in 1 case. One case developed wound and intracranial infection, but made good recovery after treatment. During the follow-up period, one patient died one month after discharge and other six patients (range from 8 months to 3 years) recovered well and no epilepsy, leakage of cerebrospinal fluid (CSF), or traumatic vascular disease occurred. Conclusions: Early diagnosis and prompt debridement are the fundamental factors affecting the outcome of PCCI. CT scans are the mainstay in evaluating PCCI and three dimensional (3D) images reconstructed from spiral CT scans provide more information. Efficient debridement should be performed as early as possible. Minimizing the degree of surgical management of PCCI is preferred when there is no indication for aggressive operation. It is important to stress the rapid and effective management of CSF leakage in early stage of PCCI. Use of prophylactic broad-spectrum antibiotics is recommended for patients with PCCI. Traumatic vascular injury should be paid attention to after PCCI.

Hip and pelvic fractures and sciatic nerve injury

To investigate the influence of hip a nd pelvic fracture, especially acetabular fracture complicated by sciatic nerve injury on clinical features and prognosis of sciatic nerve injury. Methods: From January 1987 to January 2000, 17 patients (14 mal e and 3 female) who had hip and pelvic fractures complicated by sciatic nerve in jury were treated with operative reduction and internal fixation and followed up from 10 months to 5 years. The average age was 38 years (ranging 23 56 years). The left extremities were involved in 11 patients and the right in 6. Twelve pa tients underwent primary exploration and neurolysis and 5 patients underwent sec ondary operation. Results: Preoperatively, 8 patients were treated with large dos es of oral narcotics to control their severe sciatic pain. Three of the 8 patien ts underwent patient controlled analgesia and epidural analgesia. After operati on, excellent and good rates of reduction and functional recovery of sciatic ner ve were 94.1 % and 88% respectively. Four patients still had sciatic pain and 2 patients failed to recover. Sciatic nerve function improved within 3 6 month s after surgery in 11 patients. Conclusions: Hip and pelvic fractures can result in sciatic ner ve injury, especially common peroneal nerve injury and prognosis is poor. Open r eduction and internal fixation combined with nerve exploration and neurolysis sh ould be used as early as possible for severe sciatic pain.

Forensic medical study on morphology and formative mechanism of blunt head injury

Objective： To study the patterns and morphologic characteristics of blunt head injury and analyse its formative mechanism in attempt to provide references for medicolegal expertise. Methods： The statistical analysis was done in terms of gender, age, as well as the nature, pattern, location, and feature of the injuries. Results： Among the 202 cases of head injury-induced death, 124 were male and 78 female with the age ranging from 1-81 years. Death caused by homicide was dominant （106, 52.5%）, followed by suicide （49, 24.3%） and accident （44, 21.8%）. The majority of suicide-induced death were byfalling from height, and traffic crash was responsible for majority of unexpected death cases. The morphology and pathogenesis of the injuries varied according to differences on the mode, magnitude, and orientation of the outside force giving rise to blunt injury as well as the character of vulnerants. Conclusion： Studies on the morphology and its forma- tive rationale of blunt head injury will offer easy access to medicolegal expertise on the mode and character of the injury.