科创中国

Many researches on drilling force and temperature have been done with the aim to reduce the labour intensiveness of surgery, avoid unnecessary damage and improve drilling quality. However, there has not been a systematic study of mid- and high-speed drilling under dry and physiological conditions(injection of saline). Furthermore, there is no consensus on optimal drilling parameters. To study these parameters under dry and physiological drilling conditions, pig humerus bones are drilled with medical twist drills operated using a wide range of drilling speeds and feed rates. Drilling force and temperature are measured using a YDZ-II01 W dynamometer and a NEC TVS-500 EX thermal infrared imager, respectively, to evaluate internal bone damage. To evaluate drilling quality, bone debris and hole morphology are observed by SEM(scanning electron microscopy). Changes in drilling force and temperature give similar results during drilling such that the value of each parameter peaks just before the drill penetrates through the osteon of the compact bone into the trabeculae of the spongy bone. Drilling temperatures under physiological conditions are much lower than those observed under dry conditions, while a larger drilling force occurs under physiological conditions than dry conditions. Drilling speed and feed rate have a significant influence on drilling force, temperature, bone debris and hole morphology. The investigation of the effect of drilling force and temperature on internal bone damage reveals that a drilling speed of 4500 r/min and a feed rate of 50 mm/min are recommended for bone drilling under physiological conditions. Drilling quality peaks under these optimal parameter conditions. This paper proposes the optimal drilling parameters under mid- and high-speed surgical drilling, considering internal bone damage and drilling quality, which can be looked as a reference for surgeons performing orthopedic operations.

There is less research on vertical sculptured grinding technology.Especially in high vertical surface grinding process with the cup abrasive wheel,the thermal damage is prone to happen and undermine the grinding surface integrity.This problem limits to improve the grinding efficiency and the grinding ratio greatly.Through the analysis of vertical surface grinding process and features in depth,this paper revealed the inherent mechanism of higher grinding temperature in the process of vertical sculptured grinding using the cup wheel.Based on the previous research achievements,the grinding experiments on TC4(Ti-6Al-4V)and GH4169 are carried out utilizing the self-inhaling internal cooling wheel.The experimental results show that the self-inhaling internal cooling wheel can efficiently reduce the grinding surface temperature.Moreover,the inherent mechanism of reducing the grinding temperature using the internal cooling method is revealed.Meanwhile,under the same grinding conditions,the grinding ratio during the experiments on GH4169 using self-inhaling internal cooling method is about 3 times as high as using conventional external cooling method.And the grinding forces can be reduced by about 20%.This research revealed the inherent mechanism of higher grinding temperature in the process of vertical sculptured grinding using the cup wheel,which provides theoretical basis for the design and application of self-inhaling internal cooling wheel.At the same time,an efficient and non-invasive surface grinding method of TC4 and GH4169 is presented.

Lightweight design requires an accurate life prediction for structures and components under service loading histories. However, predicted life with the existing methods seems too conservative in some cases, leading to a heavy structure. Because these methods are established on the basis that load cycles would only cause fatigue damage, ignore the strengthening effect of loads. Based on Palmgren-Miner Rule(PMR), this paper introduces a new method for fatigue life prediction under service loadings by taking into account the strengthening effect of loads below the fatigue limit. In this method, the service loadings are classified into three categories: damaging load, strengthening load and none-effect load, and the process for fatigue life prediction is divided into two stages: stage I and stage II, according to the best strengthening number of cycles. During stage I, fatigue damage is calculated considering both the strengthening and damaging effect of load cycles. While during stage II, only the damaging effect is considered. To validate this method, fatigue lives of automobile half shaft and torsion beam rear axle are calculated based on the new method and traditional methods, such as PMR and Modified Miner Rule(MMR), and fatigue tests of the two components are conducted under service loading histories. The tests results show that the percentage errors of the predicted life with the new method to mean life of tests for the two components are –3.78% and –1.76% separately, much lesser than that with PMR and MMR. By considering the strengthening effect of loads below the fatigue limit, the new method can significantly improve the accuracy for fatigue life prediction. Thus lightweight design can be fully realized in the design stage.

目的 观察伤椎置钉并椎体内植骨内固定术在胸腰椎骨折治疗中的应用效果.方法 至少一侧椎弓根完整的胸腰椎骨折26例,予伤椎撬拨复位置钉、椎体内植骨、椎弓根内固定,据胸腰段正侧位片比较术前、术后即刻、术后6个月的椎体高度及Cobb's角,并评估脊髓神经功能和融合情况.结果 术后随访7~28个月.患者术后即刻伤椎椎体前缘高度占正常高度百分比及Cobb's角优于术前(P均<0.05);伤椎外形恢复满意;按ASIA脊髓神经功能分级,伴神经损伤者15例中,A级1例无恢复,余均改善1~3级(P均<0.05),内固定无失效,植骨皆融合.结论 伤椎置钉并椎体内植骨内固定术治疗胸腰椎骨折可重建椎体结构,增强脊柱稳定,近期疗效较好.

目的 探讨精液处理前后精子DNA损伤程度的改变及与过氧化氢(H2O2)、过氧化氢酶(CTA)之间的关系.方法 接受体外受精-胚胎移植(IVF-ET)助孕且进行常规IVF受精的夫妇75例,男性患者作为研究对象.在IVF当日精液采集后0.5h留取精液标本1ml,剩余精液以Pure Sperm梯度离心法进行精液处理,于处理后将精子浓度调整为10*106/ml,留取标本1ml.采用精子吖啶橙染色方法测定精子DNA损伤,H2O2及CTA含量测定采用分光光度比色测定法.结果 精液处理后的精子DNA损伤程度与处理前相比明显降低(P<0.05),H2O2浓度亦显著降低(P<0.05),CTA浓度变化不显著.精子DNA损伤率在精液处理前及处理后均与H2O2浓度呈正相关(r值在处理前后分别为0.684和0.753,P<0.05),精子DNA损伤率在精液处理前与CTA浓度呈负相关(r=-0.476,P<0.05),而处理后两者无相关性(r=-0.087,P>0.05).结论 高过氧化物水平可导致精子DNA损伤,精液优化处理可以使精子脱离高活性氧的环境,并且减少DNA损伤的精子.

美国公共行政理论中的管理主义范式经历了萌芽、形成、拓展和成熟四个发展阶段.实证主义是管理主义的哲学基础,因为实证主义为管理主义提供了方法论基础,而管理主义是实证主义在管理领域的具体应用.美国公共行政理论中的管理主义是在与宪政主义的争论中得以发展和完善的,其理论体系由单一化、片面化逐渐走向多元化、系统化;理论研究由注重经济、效率价值转向既注重经济、效率价值,又兼顾人本价值,这是美国公共行政理论中管理主义发展的内在逻辑.

Eddy current pulsed thermography(ECPT) is an emerging Non-destructive testing and evaluation(NDT & E) technique, which uses hybrid eddy current and thermography NDT & E techniques that enhances the detectability from their compensation. Currently, this technique is limited by the manual selection of proper contrast frames and the issue of improving the efficiency of defect detection of complex structure samples remains a challenge. In order to select a specific frame from transient thermal image sequences to maximize the contrast of thermal variation and defect pattern from complex structure samples, an energy driven approach to compute the coefficient energy of wavelet transform is proposed which has the potential of automatically selecting both optimal transient frame and spatial scale for defect detection using ECPT. According to analysis of the variation of different frequency component and the comparison study of the detection performance of different scale and wavelets, the frame at the end of heating phase is automatically selected as an optimal transient frame for defect detection. In addition, the detection capabilities of the complex structure samples can be enhanced through proper spatial scale and wavelet selection. The proposed method has successfully been applied to low speed impact damage detection of carbon fibre reinforced polymer(CFRP) composite as well as providing the guidance to improve the detectability of ECPT technique.

肝着liver fixity:a diseased condition arisingwhen qi and blood of the liver meridian becomedepressed and stagnant The so-called肝着,used first in Synopsis ofGolden Chamber (《金匮要略》),describes a path-ological condition caused by stagnation of qi andblood in the liver and characterized by thoracic