X-ray induced alterations in the differentiation and mineralization potential of murine preosteoblastic cells

To evaluate the effects of ionizing radiation (IR) on murine preosteoblastic cell differentiation, we directed OCT-1 cells to the osteoblastic lineage by treatment with a combination of β-glycerophosphate (β-GP), ascorbic acid (AA), and dexamethasone (Dex). In vitro mineralization was evaluated based on histochemical staining and quantification of the hydroxyapatite content of the extracellular bone matrix. Expression of mRNA encoding Runx2, transforming growth factor β1 (TGF-β1), osteocalcin (OCN), and p21^CDKN1A was analyzed. Exposure to IR reduced the growth rate and diminished cell survival of OCT-1 cells under standard conditions. Notably, calcium content analysis revealed that deposition of mineralized matrix increased significantly under osteogenic conditions after X-ray exposure in a time-dependent manner. In this study, higher radiation doses exert significant overall effects on TGF-β1, OCN, and p21^CDKN1A gene expression, suggesting that gene expression following X-ray treatment is affected in a dose-dependent manner. Additionally, we verified that Runx2 was suppressed within 24 h after irradiation at 2 and 4 Gy. Although further studies are required to verify the molecular mechanism, our observations strongly suggest that treatment with IR markedly alters the differentiation and mineralization process of preosteoblastic cells.     

缝隙间隙密封在阀设计中的运用

在某型飞机使用的阀中采用了缝隙间隙密封,依据计算、设计和试验阐述了泄漏量与压力、间隙尺寸、粘度及材质的关系。当间隙尺寸确定时,粘度越大,压力越小,材质越硬,则泄漏量越小,即阀在采用缝隙间隙密封时,泄漏量与工作介质的种类有关,每种工作介质粘度不同,泄漏量也不同,阀体材质越密,抗泄漏越好。因此,应尽量选择粘度系数大的介质和材质较密的材料。     

基于空间相关函数的二维紊流场数值生成法

大气紊流是复杂的扰动形式，影响飞行品质、飞行安全。对于复杂的飞行任务，有必要生成二维紊流场模型，从而更准确地反映扰动情况。传统方法是以时间频谱为基础，利用谱分解定理得到所需的成形滤波器结构，进而生成紊流递归模型。这种方法需要经过对模型进行简化，以便利用谱分解定理，使仿真模型的统计特性受到影响；另外，从理论上讲，传统方法只能生成一维大气紊流递归模型。本文直接从空间相关函数入手，提出建立离散自递归模型的新方法，给出了二维紊流场的递归模型     

Single track and single layer formation in selective laser melting of niobium solid solution alloy

Selective laser melting (SLM) was employed to fabricate Nb-37Ti-13Cr-2Al-1Si (at%) alloy, using pre-alloyed powders prepared by plasma rotating electrode processing (PREP). A series of single tracks and single layers under different processing parameters was manufactured to evaluate the processing feasibility by SLM, including laser power, scanning speed, and hatch distance. Results showed that continuous single tracks could be fabricated using proper laser powers and scanning velocities. Both the width of a single track and its penetration depth into a substrate increased with an increase of the linear laser beam energy density (LED), i.e., an increase of the laser power and a decrease of the scanning speed. Nb, Ti, Si, Cr, and Al elements distributed heterogeneously over the melt pool in the form of swirl-like patterns. An excess of the hatch distance was not able to interconnect neighboring tracks. Under improper processing parameters, a balling phenomenon occurred, but could be eliminated with an increased LED. This work testified the SLM-processing feasibility of Nb-based alloy and promoted the application of SLM to the manufacture of niobium-based alloys.     

Training effectiveness evaluation of helicopter emergency relief based on virtual simulation

Helicopters are playing an increasingly important part in emergency relief, such as earthquake rescue, firefighting and medical transport. With the development of virtual simulation technology, virtual simulation-based training is widely used in the training of the helicopter crew especially for the dangerous and costly missions mentioned above. A complete training effectiveness evaluation method is proposed to evaluate the trainees’ training effect based on virtual simulation in this paper. A key to this method is regarding the complicated process as a discrete event-activity flow system and establishing the evaluation indicator system. Then expert group and Analytical Network Process (ANP) are applied to determine the weight of indicators. When the training data are processed, there is a novel attempt to apply Fuzzy Comprehensive Evaluation (FCE) model to calculate the two categories of indicators. Eventually, an experiment and the analysis were carried out to validate the evaluation method.     

审核的有效性与体系的有效性

论述了质量体系认证审核的有效性与体系有效性的关系。国内外在质量体系认证中通常只注重符合性审核，而忽视有效性审核，故此使得体系审核的有效性大打折扣。英国《质量世界》杂志于１９９７年１０月号在“问答”专栏中反映了这种情况，并以举例形式说明了如何确定质量体系的有效性。     

Evaluation of multiple radar target trackers in stressfulenvironments

This paper evaluates the performance of multiple target tracking (MTT) algorithms in real-life stressful radar tracking environments. Real closely spaced maneuver radar data, generated by six F-18 fighters and other targets, were collected jointly by the defence departments of Canada and United States to support this practical MTT algorithm evaluation study. A set of performance metrics was defined here to compare the suboptimal nearest neighbor (SNN), global nearest neighbor (GNN), and various variants of the joint probabilistic data association (JPDA) MTT trackers. Results reveal an interesting result that all these MTT algorithms exhibited very close performance. In addition, the weighted sum approach of the PDA/JPDA trackers which are theoretically effective were observed to perform poorly in tracking closely spaced targets. Overall speaking, the GNN filter based on the Munkres algorithm had the best performance in terms of both tracking performance and robustness     

内埋电阻丝阵列检测复合材料表面裂伤初探

探讨了用层间埋置Ｎｉ－Ｃｒ合金丝构成局部网络实现对复合材料表面损伤位置和损伤程度检测。对表面裂纹尖端附近的应力场分布进行了分析，并将试验结果与预测结果进行了比较。实验结果表明：Ｎｉ－Ｃｒ合金丝阵列可以在玻纤／环氧树脂复合材料中用作传感元件，合金丝阵列所反映的裂端附近应力场分布是合理的。     

多机场地面等待问题模型研究

近几年世界民用航空事业的飞速发展 ,机场容量的限制引起了交通拥挤并造成了巨额损失 ,使得流量管理问题变得越来越迫切。文中针对多机场的地面等待问题 ,建立了一种行之有效的地面等待管理系统模型 ,并提出了忽略航路交叉点容量、空中延误为 0及起飞容量无限的简化模型。     

AutoCAD环境下图形参数化实现方法研究

在ＡｕｔｏＣＡＤ图形环境下，基于对图形理解的策略，通过数据库中图形实体数据的分析和图形之间约束关系的推理，判断其中图形实体和尺寸实体的关系，并参照机械制图的隐含约束关系，建立图形和尺寸之间的联系，最后基于约束联系，生成ＡｕｔｏＬＩＳＰ参数化绘图程序，避免了人工编程，由此实现了图形的参数化，提高了绘图效率和ＣＡＤ技术的应用水平。