水雷保险器水压膜贮存寿命预测

本文以水雷保险器水压膜贮存失效数据为研究对象,建立了水压膜贮存统计模型,采用周期测量数据失效时刻划分的方法,将不完全失效数据转换为区间数据;提出了基于对数正态分布族和基于极值分布族的水压膜贮存寿命预测方法,对水雷其它零部件的寿命预测具有一定的参考价值。     

Investigation of fatigue failure prediction of Fe-Cr alloy coatings under rolling contact based on acoustic emission technique

The rolling contact fatigue (RCF) failure prediction of the coating Fe-Cr alloy coatings was investigated. The acoustic emission (AE) technique was used to monitor RCF tests of the coatings. The failure mechanism was investigated. Results showed AE signals sensitively detected the initiations and propagations of the fatigue cracks within the coatings before the obvious surface material losses. AE signals also reflected the cumulate damage procedure. So the coming RCF failures can be predicted by AE signal responses. Moreover, the micro-defects within the coatings were considered to be the fatigue crack origins.     

Twelve-Month Clinical Follow-Up Study of Voice Patients' Recovery Using the Voice Activity and Participation Profile (VAPP)

Objective

To study the effects of voice treatment including brief voice therapy for 12 months in two groups of voice patients: organic and functional.

Design and Methods

A clinical prospective follow-up study with repeated measurements in five phases: medical session, first voice therapy session, last voice therapy session, and 6 months and 12 months after voice therapy. The mean number of voice therapy sessions was 3.4. The main outcome measures were the Voice Activity and Participation Profile (VAPP) and the Symptom Questionnaire.Of consenting patients (n = 141) with chronic voice disorders, 46 dropped out during follow-up. Ninety-five patients formed the study group. Forty-one of them received only voice therapy, but the rest of them received combined treatment (medication, amplifiers, and voice massage), but also experienced life events affecting voice. Patients with any laryngeal pathology formed the organic group (n = 47), others had a functional voice disorder.

Results

Using the improvement criterion that the change of the VAPP score should exceed standard error of measurement, the percentage of individual patients achieving improvement was 47% in the mild, 59% in the moderate, and 75% in the severe disorder groups. Effect size for VAPP total score was 0.89. The positive effect continued to progress after the therapy ended. Patients with functional or organic voice disorder improved almost equally, although minor findings indicate that functional patients benefited more.

Conclusions

Voice treatment had a progressive effect for 1 year in half of our patients. No statistical difference was found between the functional and organic patient groups.     

两种组织钛合金薄板弯曲疲劳性能的研究

以具有(α+β)等轴组织和α/β粗片层组织的TC11钛合金为研究对象,研究了TC11合金薄板样品在恒总应变幅控制下的弯曲疲劳性能及其损伤行为,通过对疲劳开裂路径和断裂的观察与表征,探讨了疲劳损伤与组织结构间的关系.研究发现,恒总应变幅控制下的等轴组织TC11钛合金薄板的弯曲疲劳性能明显高于粗片层组织合金;等轴组织合金的...     

Poro-viscoelastic properties of anisotropic cylindrical composite materials

A new poro-viscoelastic mechanical model, which is able to predict strain creep, stress relaxation and instant elasticity for anisotropic cylindrical composite materials based on the characteristics of dentinal biomaterials of cylindrical microstructures, is described. The model enables evaluation of the poro-viscoelastic properties of dentinal biomaterials with no cracks and with fatigue-cracks. The predicted poro-viscoelastic properties obtained from the present anisotropic constitutive model agree well with the available experimental data for both wet and dry situations. The present model can be applied to anisotropic cylindrical composite materials other than biomaterials.     

Deformation-induced martensite and nanotwins by cryogenic laser shock peening of AISI 304 stainless steel and the effects on mechanical properties

Laser shock peening (LSP) of stainless steel 304 was carried out at room and cryogenic temperature (liquid nitrogen temperature). It was found that the deformation-induced martensite was generated by LSP only when the laser-generated plasma pressure is sufficiently high. Compared to room temperature laser shock peening (RT-LSP), cryogenic laser shock peening (CLSP) generates a higher volume fraction of martensite at the same laser intensity. This is due to the increase in the density of potential embryos (deformation bands) for martensite nucleation by deformation at cryogenic temperature. In addition, CLSP generates a high density of deformation twins and stacking faults. After CLSP, an innovative microstructure, characterised by networks of deformation twins, stacking faults and composite structure (martensite and austenite phases), contributes to material strength and microstructure stability improvement. The combined effect of higher surface hardness and a more stabilised microstructure results in greater fatigue performance improvement of the CLSP samples compared to that of the RT-LSP samples.     

An extensive 3D dislocation dynamics investigation of stage-I fatigue crack propagation

Stage-I fatigue crack propagation is investigated using 3D discrete dislocation dynamics (DD) simulations. Slip-based propagation mechanisms and the role of the pre-existing slip band on the crack path are emphasized. Stage-I crack growth is found to be compatible with successive decohesion of the persistent slip band/matrix interface rather than a mere effect of plastic irreversibility. Corresponding crack tip slip displacement magnitude and the associated crack growth rate are evaluated quantitatively at various tip distances from the grain boundary. This shows that grain boundaries systematically amplify slip dispersion ahead of the crack tip and consequently, slow down the stage-I crack growth rate. The results help in developing an original crack propagation model, accounting for the boundary effects relevant to polycrystals. The crack growth trend is then evaluated from calculations of the energy changes due to crack length increments. It is shown that the crack necessarily propagates by increments smaller than 10 nm.     

High pressure inactivation of relevant target microorganisms in poultry meat products and the evaluation of pressure-induced protein denaturation of marinated poultry under different high pressure treatments

In this study, the possibility of extending shelf life of marinated poultry meat products by high pressure processing was evaluated. Relevant spoilage and pathogenic strains were selected and used as target microorganisms (MOs) for challenge experiments. Meat and brine were inoculated with MOs and treated at 450 MPa, 4 °C for 3 min. The results of inactivation show a decreasing pressure tolerance in the series Lactobacillus > Arcobacter > Carnobacterium > Bacillus cereus > Brochothrix thermosphacta > Listeria monocytogenes. Leuconostoc gelidum exhibited the highest pressure tolerance in meat. A protective effect of poultry meat was found for L. sakei and L. gelidum. In parallel, the influence of different marinade formulations (pH, carbonates, citrates) on protein structure changes during a pressure treatment was investigated. Addition of sodium carbonate shows a protection against denaturation of myofibrillar proteins and provides a maximum water-holding capacity. Caustic marinades allowed a higher retention of product characteristics than low-pH marinades.     

首发脑梗死患者认知功能与1H- MRS的相关性研究

目的探讨首发脑梗死患者认知功能与左前额叶白质氢质子磁共振波谱（1H- MRS）、日常生活能力量表（ADL）的关系。方法对38例首发脑梗死患者在发病1周内、3个月末、6个月末检测左前额叶白质1H- MRS中的氮-乙酰门冬氨酸（NAA）、胆碱（Cho）、肌酐（Cr）,同时进行中文版蒙特利尔认知评估量表（MoCA）、ADL评分。按MoCA结果分为脑梗死后血管性认知功能损害（VCI）组、正常组、变化组,分析3组间各时间点1H- MRS（Cho、Cho/Cr、NAA、NAA/Cr）、ADL的差异。结果3个月末VCI组与变化组各1H- MRS差异均有统计学意义（均P＜0.05）,VCI组与正常组各1H- MRS差异均有统计学意义（P＜0.01或0.05）;6个月末VCI组与正常组、变化组各1H- MRS差异均有统计学意义（P＜0.01或0.05）。1周内、3个月末VCI组与正常组的ADL评分差异均有统计学意义（P＜0.01或0.05）;3个月末VCI组与变化组的ADL评分差异有统计学意义（P＜0.05）;6个月末VCI组与变化组、正常组ADL评分差异均有统计学意义（均P＜0.01）。结论首发脑梗死后VCI患者左前额叶白质1H- MRS出现变化,3个月末的1H- MRS对VCI的转变有预测价值。