选择性激光熔化制备纯钨块体材料的研究

采用选择性激光熔化技术制备了纯钨块状样品, 研究了激光参数对所制备样品的表面形貌、内部晶粒组织和密度的影响。结果表明, 随着激光能量密度的增加, 样品表面变得光滑, 样品内部孔隙减少, 密度提高。采用功率300 W、扫描速率200 mm?s-1的激光扫描参数制备出了相对密度为97%的纯钨块状样品; 当激光功率提高至350 W时, 由于裂纹增多使样品密度下降; 随着激光输入能量密度的增加, 选择性激光熔化制备的样品内部晶粒方向性变得明显, 且晶粒尺寸增大; 采用扫描策略2 (激光功率200 W, 激光扫描速度200 mm?s-1)进行制备的样品内部孔隙较多, 且孔隙大多沿样品增材制造高度方向呈一条直线分布, 样品内部部分晶粒沿样品增材制造高度方向伸长。     

国外镁合金激光表面改性技术的发展现状

综述了几种镁合金激光表面改性技术（激光表面熔凝、激光表面合金化和激光表面熔覆）的方法与特点，阐述了改性层的结构与性能，总结了国外在此研究领域的最新进展。     

Laser Welding of Ultra-Fine Grained Steel SS400

Steeliswidelyusedbecauseofitsgoodcompre hensive properties ,plentyofresourceandlowerprice .Thestrengthandtoughnessaretwoimpor tantpropertiesofsteels ,andpeoplemakeeffortstoincreasetheirvalues .Addingalloyingelementandcontrollingmicrostructurearetwobasicwaystoac complishtheaim .Therefinedmicrostructureob tainedbyprocessingtechniqueenablesthestrengthandtoughnessofsteeltobeincreasedwithoutaddingalloyingelementandtheratioofperformance costtobeincreased .Theultra finegrainedsteelshavefer ritegrains…     

浅析金属粉末选择性激光烧结快速成型技术

介绍了选择性激光烧结技术的工作原理,简述了选择性激光烧结的三种典型金属粉末成型工艺,讨论了选择性激光烧结技术成型金属零件所存在的一些问题。最后总结了选择性烧结技术的发展前景。     

Comparison of carbon dioxide and neodymium: yttrium-aluminum-garnet lasers in surgery of the inferior turbinate

At the Department of Otorhinolaryngology-Head and Neck Surgery of the University of Kiel, 533 patients with hyperplastic inferior turbinates were treated between 1987 and 1994 with various carbon dioxide (CO2) and neodymium:yttrium-aluminum-garnet (Nd:YAG) laser techniques. We report on the therapeutic results of both types of laser turbinectomy and compare their long-term results with those of submucosal diathermy. Among the different techniques, we preferred the following approaches. The CO2 laser technique involved the application of a few laser spots (laser energy density 6,100 J/cm2 per lesion) to the head of the turbinate under the operating microscope. In the Nd:YAG laser procedure, diffuse, low-power irradiation (laser energy density < 53 kJ/cm2) of the entire concha was performed under endoscopic control. The CO2 laser procedure involved little bleeding and hardly any pain. It produced a positive effect after only a few days and required no follow-up treatment. The success of Nd:YAG laser treatment, by contrast, only became evident after weeks or months, due to the slow scarring process. Compared to submucosal diathermy, both laser methods produced better long-term results. Two years postoperatively, the overall success rate, as defined by patient satisfaction, was 79.6% for the CO2 laser, 68.3% for the Nd:YAG laser, and 36% for submucosal diathermy.     

Bake Hardening of Laser Welded Dual Phase Steel

The influence of bake hardening on the mechanical properties of laser welded dual phase steel was investigated. A remarkalbe increase of the hardness in the zone influenced by laser welding was observed. The fusion zone had a low carbon lath martensite microstructure. The laser weld region had a higher interstitial carbon content than the base material. The dual phase steel exhibited a clear bake hardening effect in both the as‐received and the laser‐welded conditions. The bake hardening effect is more pronounced in the prestrained laser welded condition. A pronounced decrease of the ductility was observed for prestrained laser welded DP steel.     

Relative susceptibilities of XPA knockout mice and their heterozygous and wild-type littermates to UVB-induced skin cancer

Sensitometric techniques for performing processor quality control in laser imaging systems are analyzed in this study. The sensitivity of conventional x-ray films using simulated screen-light sensitometry is compared with helium-neon (HeNe) laser film exposed with a simulated red-light sensitometer, a standalone (reference) laser sensitometer, an experimental (unstable) laser sensitometer, and laser printers. Infrared (IR) laser film exposed with an IR laser diode and a simulated IR sensitometer are also evaluated. It is demonstrated that laser-generated step tablets provide an easy and reliable method of performing laser film processor quality control.     

Improving care of eczema in general practice

BACKGROUND AND OBJECTIVE: This study was designed to evaluate the relative cost effectiveness of the Holmium:YAG laser and the pulsed dye laser for the treatment of ureteral calculi. Cost containment is a priority for every health care facility. As a result, the staff of the Lutheran Medical Center (Wheat Ridge, CO) looked at alternative ways to provide quality laser treatment of ureteral stones. As part of our study, the laser committee offered the Holmium:YAG laser to urologists for ureteral lithotripsy. Previously, the pulsed dye laser was rented for ureteral calculi on a per case basis at $1,500. A hospital processing fee was added to this cost, resulting in a total charge of $1,638 to the patient. Our organization owns a Holmium:YAG laser and uses it primarily in orthopedics. STUDY DESIGN/MATERIALS AND METHODS: Two ureteral lithotripsy cases were performed and compared. One case used the Holmium:YAG for ureteral lithotripsy; the other procedure used the pulsed dye laser. A cost analysis was performed after the procedures. RESULTS: The data indicated a significant difference in cost between the two lasers. Approximately $1,000 was eliminated when using the Holmium:YAG laser. CONCLUSION: A cost savings of $15,000 per year would be realized if 15 cases were performed. The Holmium:YAG laser also can be used on cystine calculi, a procedure for which the pulsed dye laser is ineffective. The potential for ureteral injury exists. When using the Holmium:YAG laser, appropriate training is required. Due to this risk, not all urologists will use the Holmium:YAG laser. We also found a positive correlation between the proficiency of the urologists' laser skills and overall cost effectiveness.     

Transmyocardial laser revascularization in allograft coronary artery disease

We used transmyocardial laser revascularization to treat accelerated cardiac allograft atherosclerosis in 2 patients. One patient received transmyocardial laser revascularization as sole therapy, the other as an adjunct to coronary artery bypass grafting. The systolic function improved in both patients, although the patient who had adjunctive transmyocardial laser revascularization died of systemic infection and renal failure on postoperative day 55. The second patient is alive and well 1 1/2 years after the laser procedure. We discuss 4 other patients who received transmyocardial laser revascularization treatment elsewhere in the United States. Transmyocardial laser revascularization has the potential to become important in the treatment of transplant atherosclerosis. Randomized clinical trials are warranted to assess the efficacy of transmyocardial laser revascularization in this setting.     

铝合金化铣保护胶激光刻型形貌仿真研究

为了揭示铝合金化铣保护胶激光刻型工艺规律,针对铝合金化铣保护胶脉冲激光刻型展开计算仿真研究,借助于有限元仿真软件传热学分析直观地展示了化铣保护胶在激光辐照作用下的温度场分布及变化过程,通过设置模型动网格动态地显示整个刻型过程中化铣保护胶的形貌演变规律。分析了激光光斑重叠率不足以及保护胶厚度不均对刻型质量的影响,得到了刻型形貌及尺寸随激光功率、重复频率、入射角度以及扫描速度的演变规律。为实现铝合金化铣保护胶脉冲激光刻型的大面积、高效、精准加工提供基础理论支持。     

The evaluation of argon laser photocoagulation in a series of animal models of upper gastrointestinal bleeding

During the past five years we have evaluated argon laser photocoagulation in various canine models of upper gastrointestinal hemorrhage. In gastric erosions, the eight-watt argon laser was uniformly effective in stopping bleeding. In our standard acute ulcer model the seven-watt argon laser was effective in stopping bleeding from most ulcers and only occasionally produced deep injury. With the addition of a jet of CO2 exiting the laser catheter coaxial to the laser beam, the argon laser was 100% effective and no deep injury resulted. The application of the argon laser in a more physiologic canine bleeding model using a single bleeding vessel in an ulcer base is currently under study. The development of improved animal models of gastrointestinal bleeding should contribute to the identification of effective and safe endoscopic hemostatic methods.     

Apoptosis in rat prostatic adenocarcinoma is associated with rapid infiltration of cytotoxic T-cells and activated macrophages

The laser has played a valuable primary and adjunctive role in the management of nasal and sinus disorders. When using the laser there must be appropriate knowledge about safety, instrumentation, and types of pathologic conditions in which the laser is effective. The laser is effective for turbinate dysfunction of various causes. Its coagulating, cutting, and vaporization ability make it useful in managing intranasal vascular disorders such as hereditary hemorrhagic telangiectasia and hemangioma. There is some promise in using the laser for nasal polyposis with eosinophilia.     

Combined iodine-125 plaque irradiation and indirect ophthalmoscope laser therapy of choroidal malignant melanomas: comparison with iodine-125 and cobalt-60 plaque radiotherapy alone

The authors studied the short-term impact of combined episcleral iodine-125 plaque radiotherapy and argon laser treatment in a series of 24 patients with choroidal malignant melanoma. All patients underwent plaque therapy prior to their initial laser session. All laser treatments were performed with an indirect ophthalmoscope argon green laser, using low-power, long-duration exposures. The endpoint of laser therapy was a well-defined atrophic circumbasal chorioretinal laser scar and complete or nearly complete nonfluorescence of the lesion on fluorescein angiography. In a case-by-case matched comparison study, the authors evaluated the relative local regression of tumors treated by combined plaque-laser therapy, iodine-125 plaque therapy alone, and cobalt-60 plaque therapy alone. The tumors treated with supplemental laser regressed substantially faster and more completely than did those treated by either type of plaque therapy alone. However, the short-term visual loss was greater in eyes treated by the combined therapy.     

Investigation on the effect of laser pulse shape during Nd:YAG laser microwelding of thin Al sheet by numerical simulation

In the welding of thin A3003 Al sheet by a Nd:YAG laser beam, the laser pulse shape plays an important role in enhancing the welding penetration stability. In order to evaluate the effect of laser pulse shape during Nd:YAG laser welding of a thin Al sheet and to predict the welding performance by numerical simulation, a three-dimensional finite differential method (FDM) analysis is presented for heating with different laser pulse shapes and related welding parameters. The simulated results give good agreement with experimental results, where a sound weld shape and crack-free weld pool are obtained. The simulation results show that the welding stability is greatly affected by the modulation of laser pulse shape for the same laser energy and welding parameters. As a rectangular laser pulse is modulated to have three stages with high, medium, and low power levels for the first, second, and third stages, respectively, more energy is absorbed in the melt pool, and the cooling rate is reduced. While a high power level at the first stage increases the laser beam absorption, the thermal energy of the third stage prevents fast cooling of the melt pool. Also, evaporation is prevented by proper modulation of the laser pulse. If the laser pulse is modulated properly, the optimum melt-pool size and cooling rate can be obtained; also, the desired weld depth and welding stability are achieved for the conduction welding mode. The numerical simulation method can be used to determine the proper conditions for good welding performance.     

激光加工技术在造船工业上的应用

介绍以激光切割、激光焊接以及激光成形技术为代表的船用钢板激光加工技术的主要特点、发展现状和发展趋势，并介绍船用钢板激光加工技术在欧美和日本主要船厂中的工业应用情况。     

Anti-B4-blocked ricin: a phase II trial of 7 day continuous infusion in patients with multiple myeloma

Skin ultrastructure was examined in patients undergoing CO2 laser resurfacing for facial rejuvenation. The lasers used in this study were the Coherent Ultrapulse CO2 laser with computerized pattern generator, the Sharplan Feathertouch laser, and the Laserscope Paragon-70 pulsed CO2 laser with computerized pattern generator. Results showed that the epidermis was totally removed with one pass of the CO2 laser. After one laser pass, there was little compaction of collagen in the dermis, but after two and three passes, there were sequential graded increases in collagen compaction with loss of the intervening extracellular gel matrix. There was no "collagen shrinkage," and the collagen itself was marginally affected, except for occasional losses in striations at the surface of the specimens. Elastin was very much affected by the laser such that with only one pass, the elastin was abnormal, presenting with a mottled heterogeneous structure. This elastin aberrancy was present in both the papillary and reticular dermis. After one laser pass, fibroblast necrosis was present in the papillary dermis and the reticular dermis (depending on which laser was used), and the extent and depth of necrosis increased with multiple laser passes.     

Delayed healing of rhytidectomy flap resurfaced with CO2 laser

Combining facial rhytidectomy with laser resurfacing, theoretically, provides the best opportunity for achieving an optimal facial rejuvenation result. Previous studies have demonstrated the pernicious effect of a deep peel on a skin flap, but the safety of treating the rhytidectomy flap with laser has not been investigated. This study was conducted to investigate the safety of using these techniques concomitantly. Sixty sites were selected on three Yucatan minipigs, a species of swine chosen because of its hairless nature and opportunity to raise a true skin flap (without the panniculus carnosus). The healing time of 20 laser-treated sites without flap elevation was compared with that of 20 areas treated with laser following flap elevation, shortening (to emulate a more realistic rhytidectomy process), and repair. Twenty flaps were elevated and shortened without laser treatment to serve as a control. The CO2 laser parameters were set at 500 mJ, 50 watts, and a density of 5. Two passes were made to penetrate the upper dermis. The mean healing time for areas treated with laser alone was 12.05 days, ranging from 11 to 14 days. In comparison, the healing time for the laser-treated areas subsequent to flap elevation averaged 17.95 days, with a range of 14 to 24 days (p < 0.05). Two flaps treated with laser (10 percent) failed to heal completely in 24 days. At the time that all 20 of the areas treated solely with laser had re-epithelialized completely, only one of the flaps treated with laser had re-epithelialized completely (p < 0.001). A delay in healing, as well as return of pigment, was demonstrated in the distal portions of all flaps receiving laser treatment. The control flaps all healed normally except for a 5-percent superficial loss on a single flap. It was concluded from this study, and from clinical observation of delayed healing on six of seven patients who underwent concomitant rhytidectomy and laser resurfacing at a conservative laser setting, that laser resurfacing of the rhytidectomy flap is unsafe and results in delayed re-epithelialization. This combination should be avoided altogether or performed with extreme prudence on patients undergoing a deeper plane facial rhytidectomy or by using very low laser settings.     

浅谈激光腔研磨技术

为了使激光腔反射的激光能量损失最小,必须使激光腔的表面粗糙度达到很高的水平。采用的方法是:用铜合金作激光腔的本体,然后在其内腔镀金。为达到此要求,其镀覆表面必须进行研磨,使基体表面粗糙度达到一定的要求后,方能使镀覆后的表面有较高的表面粗糙度。     

激光陶瓷合金化

通过陶瓷合金化涂料的研制,在激光淬火的工艺条件下获得激光陶瓷合金化层.经过陶瓷合金化的钢铁材料,其耐磨性能比激光淬火高约一倍.陶瓷合金化涂料具有与目前广泛使用的激光淬火吸光涂料同样的粘结性能,吸光性能和施涂工艺性能.激光陶瓷合金化是纳米技术、氮化硅应用技术、稀土应用技术、不同质材料之间的偶联技术,激光加工技术和涂料粘结...