简介:摘要:本文针对目前矿井支架硬度低、耐腐蚀性差的问题,通过在基体表面制备FeNiCrBC熔覆层的方法提高矿井支架性能。通过不同激光工艺制备熔覆层,使用EDS、XRD对熔覆层显微结构进行分析,对不同工艺参数下的熔覆层硬度、耐腐蚀性及耐磨性进行测试分析。结果表明,FeNiCrBC激光熔覆层中主要为α-Fe相,有效提高硬度及耐磨性,同时熔覆层中的Cr元素提高了其耐磨性。对不同工艺参数对比发现,激光功率2600w,扫描速度8 mm/s的熔覆层性能最优。
简介:利用粉末冶金法制备TiB2和TiC复合材料熔敷棒,并通过电火花沉积在点焊镀锌钢板用电极的表面制备TiB2和TiC复合涂层。利用SEM和XRD分析涂层的微观结构和物相,运用点焊实验测试涂层电极的使用寿命。结果表明:复合材料熔敷棒中TiB2和TiC颗粒细小均匀,电火花涂层致密无分层,涂层物相为Cu、TiB2和TiCCu从基体扩散到涂层表面,涂层表面Cu含量(原子分数)达到28%,过渡层出现Cu和Ti的梯度分布,涂层与基体间为牢固的冶金结合复合涂层存在少量裂纹,其显微硬度达到850HV,高于TiB2涂层和TiC涂层硬度点焊时电极头部的平均磨损率大大降低,电极的点焊寿命比无涂层电极提高4倍。
简介:AbstractImportance:Tics usually start around 4-6 years old and affect about 1% of school-age children. Premonitory urges (PUs) are sensory phenomena that precede tics and are often described as unpleasant feelings. Recent evidence supports a relationship between PUs and tic severity, but reports are conflicting. In addition, there is no report of PUs in the Chinese population.Objective:To investigate the correlation between PUs and tic symptoms in the Chinese population with tic disorders.Methods:We recruited 252 Chinese individuals with chronic tic disorders (age 5-16 years). The Yale Global Tic Severity Scale (YGTSS) was used to assess tic symptoms, and the Premonitory Urge for Tics Scale (PUTS) was used to assess PUs. We calculated Spearman correlations between PUTS and YGTSS scores, and constructed a linear regression model to predict the tic symptom severity by PUs.Results:There was a significant positive correlation between PU severity (PUTS scores) and motor tic severity, total tic severity, tic-caused impairment (YGTSS scores) (P < 0.05). PU severity was a significant positive predictor of tic symptom severity (standardized beta coefficient = 0.174, t = 2.786, P = 0.006).Interpretation:We provide evidence for a correlation between PUs and tic symptoms. PU severity predicts tic symptom severity. Further research on PUs is needed to clarify the shared brain mechanism with tics, and their role in tic expression. A suitable tool to assess PUs in younger children is also needed.
简介:AnewapproachtothemassiveproductionofTiCwhiskerswithhighpurityandlowcostwaspresented.Itisamodifiedcarbothermalreductionmethod(MCTR)characterizedbyargonstreamflowingverticallyandpassingthroughtheinteriorofthemixtureofrawmaterials.Itisfoundforthefirsttimethatthereisanoptimumflowoftheupwardflowingargonstream,atwhichlargequantityofhighqualityTiCcanbeobtained.Thispaperdescribedthenewmethod,analyzedthemechanismandconditionsfortheformationofhighpurityTiCwhiskersonalargescale,andcomparedMCTRwiththetraditionalcarbothermalreductionmethod(TCTR).Basedontheanalysisandcomparison,itisconcludedthatinordertoproducehighqualitytransitionmetalcarbides,nitridesandcarbonitrideswithlowcostTCTRmustbereplacedbyMCTR.
简介:AbstractTic disorders (TD) is a neurodevelopmental disorder that is often first recognized in children and adolescents and is characterized mainly by motor and phonic tics. Drug treatment of TD has been criticized because of serious side effects, and TD treatment emphasizes behavioral psychotherapy. This study reviewed the most common behavioral psychotherapy for TD: habit reversal training (HRT). We examined the contents, variation, curative effects, and premonitory urge control of HRT and other behavioral psychotherapies. The findings suggest that current understanding of HRT is insufficient and further studies are needed. First, studies of online guidance training are needed to implement technology that can help more patients. Second, the future integration of HRT and other technologies is important. Third, imaging techniques could be used to further explore the brain mechanisms underlying HRT. Research on HRT for TD in China is insufficient. We call on more Chinese researchers to study, investigate, and develop technology to promote the development of behavioral psychotherapy for TD in China.