Laser micro-processing of cardiovascular stent with fiber laser cutting system

A metallic cardiovascular stent cutting system based on fiber laser was designed in this study. In order to achieve the cutting of stent, the main modules and the key technologies were analyzed and achieved. Then with the cutting system, the kerf width size was studied for different cutting parameters including laser output power, pulse length, repeat frequency, cutting speed and assisting gas pressure. Finally, a high quality of cutting of 316L stainless steel cardiovascular stent was achieved.     

Laser cutting of polymeric materials: An experimental investigation

The CO₂ laser cutting of three polymeric materials namely polypropylene (PP), polycarbonate (PC) and polymethyl methacrylate (PMMA) is investigated with the aim of evaluating the effect of the main input laser cutting parameters (laser power, cutting speed and compressed air pressure) on laser cutting quality of the different polymers and developing model equations relating input process parameters with the output. The output quality characteristics examined were heat affected zone (HAZ), surface roughness and dimensional accuracy. Twelve sets of tests were carried out for each of the polymer based on the central composite design. Predictive models have been developed by response surface methodology (RSM). First-order response models for HAZ and surface roughness were presented and their adequacy was tested by analysis of variance (ANOVA). It was found that the response is well modeled by a linear function of the input parameters. Response surface contours of HAZ and surface roughness were generated. Mathematical model equations have been presented that estimate HAZ and surface roughness for various input laser cutting parameters. Dimensional accuracies of laser cutting on polymers were examined by dimensional deviation of the actual value from the nominal value. From the analysis, it has been observed that PMMA has less HAZ, followed by PC and PP. For surface roughness, PMMA has better cut edge surface quality than PP and PC. The response models developed can be used for practical purposes by the manufacturing industry. However, all three polymeric materials showed similar diameter errors tendency in spite of different material properties.     

Ce~(3+)-Yb~(3+)共掺YAG荧光粉量子剪裁发光的浓度及温度特性

采用高温固相法制备了不同掺杂浓度的YAG∶1%Ce~(3+),x%Yb~(3+)(x=5,10,15,20,25)系列荧光粉。在450 nm蓝光激发下,测试了样品的发射光谱,得到了中心波长在550 nm的可见宽带发射(Ce~(3+):5d→4f)和1 030 nm的近红外发射(Yb~(3+):2F_(5/2)→2F_(7/2))。可见和近红外发射强度随Yb~(3+)掺杂浓度的变化表明Ce~(3+)到Yb~(3+)存在能量传递过程,并得到Yb~(3+)的猝灭浓度为15%。在低温条件下(80~300 K)测试YAG∶1%Ce~(3+),15%Yb~(3+)样品的发射光谱和拉曼光谱,通过对其量子剪裁发光温度特性的分析,描述了基质声子在Ce~(3+)到Yb~(3+)的能量传递过程中起到的重要作用。     

Polyhedral results for the edge capacity polytope

Network loading problems occur in the design of telecommunication networks, in many different settings. For instance, bifurcated or non-bifurcated routing (also called splittable and unsplittable) can be considered. In most settings, the same polyhedral structures return. A better understanding of these structures therefore can have a major impact on the tractability of polyhedral-guided solution methods. In this paper, we investigate the polytopes of the problem restricted to one arc/edge of the network (the undirected/directed edge capacity problem) for the non-bifurcated routing case.?As an example, one of the basic variants of network loading is described, including an integer linear programming formulation. As the edge capacity problems are relaxations of this network loading problem, their polytopes are intimately related. We give conditions under which the inequalities of the edge capacity polytopes define facets of the network loading polytope. We describe classes of strong valid inequalities for the edge capacity polytopes, and we derive conditions under which these constraints define facets. For the diverse classes the complexity of lifting projected variables is stated.?The derived inequalities are tested on (i) the edge capacity problem itself and (ii) the described variant of the network loading problem. The results show that the inequalities substantially reduce the number of nodes needed in a branch-and-cut approach. Moreover, they show the importance of the edge subproblem for solving network loading problems. Received: September 2000 / Accepted: October 2001?Published online March 27, 2002     

A polyhedral approach to a production planning problem

Production planning in manufacturing industries is concerned with the determination of the production quantities (lot sizes) of some items over a time horizon, in order to satisfy the demand with minimum cost, subject to some production constraints. In general, production planning problems become harder when different types of constraints are present, such as capacity constraints, minimum lot sizes, changeover times, among others. Models incorporating some of these constraints yield, in general, NP-hard problems. We consider a single-machine, multi-item lot-sizing problem, with those difficult characteristics. There is a natural mixed integer programming formulation for this problem. However, the bounds given by linear relaxation are in general weak, so solving this problem by LP based branch and bound is inefficient. In order to improve the LP bounds, we strengthen the formulation by adding cutting planes. Several families of valid inequalities for the set of feasible solutions are derived, and the corresponding separation problems are addressed. The result is a branch and cut algorithm, which is able to solve some real life instances with 5 items and up to 36 periods. This revised version was published online in June 2006 with corrections to the Cover Date.     

Quantum cutting in Gd<Subscript>2</Subscript>SiO<Subscript>5</Subscript>: Eu<Superscript>3+</Superscript> by VUV excitation

The emission and excitation spectra of Gd₂SiO₅∶Eu³⁺ were investigated using the VUV beam line of the Beijing Synchrotron Radiation Facility (BSRF). The experimental results were discussed in the frame of visible quantum cutting process involved in Gd³⁺−Eu³⁺ system. Upon direct excitation into the⁶G _J states of Gd³⁺, two visible photon emissions from Eu³⁺ were observed. Cursory evaluation proved that Gd₂SiO₅∶Eu³⁺ is an efficient visible quantum cutter.     

CO2 laser cutting of slate

Slate is a natural stone which has the characteristic that shows a well-developed defoliation plane, allowing to easily split it in plates parallel to that plane which are particularly used as tiles for roof building. At present, the manufacturing of slate is mostly manual, being noisy, powdery and unsafe for the worker. Thus, there is a need to introduce new processing methods in order to improve both the working conditions and the quality of the products made of slate.Following the previous work focused on the drilling and cutting of slate tiles using a Nd : YAG laser, we present in this paper the results of the work carried out to explore the possibilities to cut slate plates by using a CO₂ laser. A 1.5 kW CO₂ laser was used to perform different experiments in which, the influence of some processing parameters (average power, assist gas pressure) on the geometry and quality of the cut was studied. The results obtained show that the CO₂ laser is a feasible tool for a successful cutting of slate.     

微织构刀具正交切削Ti6Al4V的试验研究

仿生摩擦学的出现,为刀具减摩技术提出了新的研究方向,通过钛合金的正交切削试验研究了表面微织构刀具在微量润滑和无润滑剂条件下的减摩性能.结果表明：表面微沟槽在润滑剂条件下可以有效地改善刀屑之间的摩擦,降低切削力与切削温度,同时表面微沟槽还可以改善钛合金的粘结现象;在无润滑剂条件下,微沟槽依然具有一定的＂润滑＂作用.     

Er0.3Gd0.7VO4晶体红外量子剪裁效应及其在太阳能电池应用上的研究

研究了高浓度的Er_0.3Gd_0.7VO₄晶体材料的红外量子剪裁现象,结果发现光激发²H_11/2能级和⁴G_11/2能级的⁴I_13/2→⁴I_15/2荧光跃迁的近似的量子剪裁效率η’已达约178.55%和177.61% 关键词： 红外的量子剪裁 太阳能电池 0.3Gd_0.7VO₄晶体材料')" href="#">Er_0.3Gd_0.7VO₄晶体材料     

直读光谱法测定析出锌中铅、铜、铁、镉、锡、铝的含量

研究了湿法冶炼产出的析出锌,经过冲床冲压脱模、马弗炉高温熔化、模具浇铸成型、车床切削等过程,于直读光谱仪上测定析出锌中铅、铜、铁、镉、锡、铝含量的方法.通过实验确认了仪器的工作条件、熔样器皿、熔样温度、析出锌取样位置,并对熔样铸锭后铅、铜、铁、镉、锡、铝的偏析情况进行了分析,铅最大偏差达到30％,经玻璃棒搅动后保温,铅...