基于修正等速运动规律的自由曲面多轴加工刀轴序列优化方法

针对自由曲面多轴加工中起始位置处刀具相对工件速度、加速度不为零导致的一定程度刚性冲击现象,提出了一种基于修正等速运动规律的刀轴序列优化方法,通过控制工件坐标系中决定刀具姿态的两个约束角,使之变化遵循修正等速运动规律,获得了切削行上平稳变化的刀轴序列,避免了由于起始位置处刀具相对工件速度、加速度不为零导致刀具不能精准到达后续加工位置的现象。算例分析表明,该方法能产生平稳且光滑的刀轴序列,可一定程度改善机床运动性能,提高加工表面质量。     

The Crosstalk of Adipose-Derived Stem Cells (ADSC), Oxidative Stress,and Inflammation in Protective and Adaptive Responses

The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs is a major goal in repair medicine. Stem cells are classified by their potential to differentiate into functional cells. Compared with other sources, adipose-derived stem cells (ADSCs) have the advantage of being abundant and easy to obtain. ADSCs are considered to be tools for replacing, repairing, and regenerating dead or damaged cells. The capacity of ADSCs to maintain their properties depends on the balance of complex signals in their microenvironment. Their properties and the associated outcomes are in part regulated by reactive oxygen species, which mediate the oxidation-reduction state of cells as a secondary messenger. ADSC therapy has demonstrated beneficial effects, suggesting that secreted factors may provide protection. There is evidence that ADSCs secrete a number of cytokines, growth factors, and antioxidant factors into their microenvironment, thus regulating intracellular signaling pathways in neighboring cells. In this review, we introduce the roles of ADSCs in the protection of cells by modulating inflammation and immunity, and we develop their potential therapeutic properties.     

Cell Sheet Comprised of Mesenchymal Stromal Cells Overexpressing Stem Cell Factor Promotes Epicardium Activation and Heart Function Improvement in a Rat Model of Myocardium Infarction

Cell therapy of the post-infarcted myocardium is still far from clinical use. Poor survival of transplanted cells, insufficient regeneration, and replacement of the damaged tissue limit the potential of currently available cell-based techniques. In this study, we generated a multilayered construct from adipose-derived mesenchymal stromal cells (MSCs) modified to secrete stem cell factor, SCF. In a rat model of myocardium infarction, we show that transplantation of SCF producing cell sheet induced activation of the epicardium and promoted the accumulation of c-kit positive cells in ischemic muscle. Morphometry showed the reduction of infarct size (16%) and a left ventricle expansion index (0.12) in the treatment group compared to controls (24–28%; 0.17–0.32). The ratio of viable myocardium was more than 1.5-fold higher, reaching 49% compared to the control (28%) or unmodified cell sheet group (30%). Finally, by day 30 after myocardium infarction, SCF-producing cell sheet transplantation increased left ventricle ejection fraction from 37% in the control sham-operated group to 53%. Our results suggest that, combining the genetic modification of MSCs and their assembly into a multilayered construct, we can provide prolonged pleiotropic effects to the damaged heart, induce endogenous regenerative processes, and improve cardiac function.     

Effects of welding parameters and welding sequence on residual stress and distortion in Al6061-T6 aluminum alloy for T-shaped welded joint

The distribution of temperature and then the distribution of residual stress and distortion in the stiffened aluminum alloy Al6061-T6 plates under the metal inert gas (MIG) welding process were investigated by three dimensional thermo-mechanical coupled finite element model using Ansys software. The properties of materials were considered temperature-dependent and the filler metal was added to the workpiece by the element birth and death technique. In three modes of current, two different speeds and two various sequences, the distribution of residual stress and distortion were calculated and analyzed. The results showed that increase in welding speed decreased the vertical deflection in the plate, transverse shrinkage and angular distortion of plate and the lateral deflection of stiffener, but increased the maximum longitudinal tensile stress in the plate and stiffener. Furthermore, increase in current increased the residual stress and deformation in the plate and stiffener, and the change in the welding sequence changed the distribution of the distortion in the plate and the stiffener without significant change in the distribution of the longitudinal residual stress.     

Tungsten Nitride,Well‐Dispersed on Porous Carbon: Remarkable Catalyst,Produced without Addition of Ammonia,for the Oxidative Desulfurization of Liquid Fuel

Polyanilines (pANIs), loaded with phosphotungstic acid (PTA), are pyrolyzed to get WO₃ or W₂N (≈6 and ≈7 nm, respectively), which is well‐dispersed on pANI‐derived porous carbons (pDCs). Depending on the pyrolysis temperature, WO₃/pDC, W₂N/pDC, or W₂N‐W/pDCs could be obtained selectively. pANI acts as both the precursor of pDC and the nitrogen source for the nitridation of WO₃ into W₂N during the pyrolysis. Importantly, W₂N could be obtained from the pyrolysis without ammonia feeding. The obtained W₂N/pDC is applied as a heterogeneous catalyst for the oxidative desulfurization (ODS) of liquid fuel for the first time, and the results are compared with WO₃/pDC and WO₃/ZrO₂. The W₂N/pDC is very efficient in ODS with remarkable performance compared with WO₃/pDC or WO₃/ZrO₂, which is applied as a representative ODS catalyst. For example, W₂N/pDC shows around 3.4 and 2.7 times of kinetic constant and turnover frequency (based on 5 min of reaction), respectively, compared to that of WO₃/ZrO₂. Moreover, the catalysts could be regenerated in a facile way. Therefore, W₂N/pDC could be produced facilely from pyrolysis (without ammonia feeding) of PTA/pANI, and W₂N, well‐dispersed on pDC, can be suggested as a very efficient oxidation catalyst for the desulfurization of liquid fuel.     

采用轮廓特征匹配的红外-可见光视频自动配准

为了精确地配准近平面场景下的红外-可见光视频序列,本文提出了一种基于轮廓特征匹配的自动配准方法,通过迭代匹配目标轮廓特征来解决异源图像中配准特征的提取和匹配难题。首先,采用运动目标检测技术获取目标轮廓,并由曲率尺度空间(CSS)角点检测算法提取轮廓特征点。此后,建立全局形状上下文描述子和局部边缘方向直方图描述子描述特征,从而实现可靠的特征匹配。来自不同时刻的匹配点对被保存在一个基于高斯距离准则的特征匹配库中。最后,为了克服近平面场景中目标深度变化的影响,本文结合前景样本随机抽样策略计算配准矩阵的损失函数,完成对全局配准矩阵的更新。在LITIV数据库上对方法进行实验验证,结果表明本文方法的配准精度优于当前先进的对比方法,在9个测试视频上的平均重叠率误差仅为0.194,与对比方法相比下降了18.5%。基本满足了近平面场景下红外-可见光视频序列配准的精度要求,且具有较高的鲁棒性。     

港里矿软破围岩采矿的分析与研究

港里矿围岩软弱破碎，随开采深度延伸，地压显现越来越剧烈，严重影响港里矿正常回采。为研究港里矿软破围岩采矿，分析了影响采矿正常进行的因素和机理，调整采矿的顺序，使港里矿软破围岩采矿的困难得到根本扭转，保证了采矿生产的正常进行，选择围岩稳固及充分卸压部位布置斜坡道和联巷、优先回采围岩破碎的高应力区是地压管理的关键问题。     

Compilation of Modern Technologies To Map Genome-Wide Cytosine Modifications in DNA

Over the past few decades, various DNA modification detection methods have been developed; many of the high-resolution methods are based on bisulfite treatment, which leads to DNA degradation, to a degree. Thus, novel bisulfite-free approaches have been developed in recent years and shown to be useful for epigenome analysis in otherwise difficult-to-handle, but important, DNA samples, such as hmC-seal and hmC-CATCH. Herein, an overview of advances in the development of epigenome sequencing methods for these important DNA modifications is provided.     

高大软岩边坡下开采程序研究

结合胜利煤田发生大型滑坡的露天矿地质赋存条件，以高大软岩边坡条件下松散物料压覆的煤炭资源安全高效回收为目标，提出采用“横采内排-尾随压脚”的开采程序方案将工作线从直线型变为“Π”字型。从地表水与地下水防治、边坡安全监测等方面提出了保证工程顺利实施的安全保障措施。计算分析了采用“横采内排-尾随压脚”开采程序方案的可观资源回收量及减少运距和提升高度带来的经济效益，同时对矿山实现可持续发展和安全开采的价值进行了预测。     

Synthesis and characterization of Ce/SiOC nanocomposites through the polymer derived ceramic method and evaluation of their catalytic activity

Cerium oxide and silicon oxycarbide (Ce/SiOC) porous nanocomposites have been synthesized through the polymer derived ceramic route. In the synthesis of the preceramic precursors, the addition of urea facilitates the deposition of Cerium atoms on the surface of SiO₂ nanoparticles since it prevents the SiO₂ from agglomeration. Both Ce and urea affects the structural and textural parameters of the obtained ceramics. Less crosslinked structures are formed when the urea concentration increases and it also provokes a reduction of the carbon crystallite size. Cerium, on the other hand, induces an increase of the carbon size as well as the number of SiOC units. Pore anisotropy and smoothness of the surface are also dependent on the composition of the material. As expected, the better thermocatalytic behavior against CO₂ decomposition is found at the largest Ce amounts but also, smooth surfaces and low pore anisotropies favor the accessibility of the gases to the thermocatalytic centers.