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  • Articles  (769)
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  • Springer  (769)
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  • 1
    Electronic Resource
    Electronic Resource
    A formal approach to automating conceptual structural design, part II: Application to floor framing generation (1991)
    Springer
    Engineering with computers 7 (1991), S. 91-107 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The function of the structural system in a building is to transfer gravity as well as lateral loads from their points of origin to the ground. Floor framing generation involves providing a path to transfer the gravity loads to the ground through various structural elements in an architectural plan while meeting the requirements imposed by other entities, such as the architect, the mechanical engineer, and the contractor, involved in the design/construct process. In this paper a formal approach for generating floor framing plans for steel office buildings is presented. We describe the knowledge and the reasoning behind a computer system, FFG (floor framing generator), which generates floor framing schemes for steel office buildings that are rectangular in plan and have a single service core. Constraints arising from structural as well as exogenous considerations are enumerated and their effect on framing schemes is identified. We also elaborate on the evaluation mechanism for ranking alternative schemes, in addition to providing details of the computer implementation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01195563
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  • 2
    Electronic Resource
    Electronic Resource
    Announcement (1991)
    Springer
    Engineering with computers 7 (1991), S. 129-129 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01195566
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  • 3
    Electronic Resource
    Electronic Resource
    Design of an optimal damper to minimize the vibration of machine tool structures subject to random excitation (1991)
    Springer
    Engineering with computers 7 (1991), S. 199-208 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The vibration of machine tools during machining adversely affects machining accuracy and tool life, and therefore must be minimized. The cutting forces for stable turning are generally known to be random, and hence excite all the resonance modes. Of all these modes, those that generate relative motions between a cutting tool and a workpiece are of concern. This paper presents a new approach for designing an optimal damper to minimize the relative vibration between the cutting tool and workpiece during stable machining. An approximate normal mode method is employed to calculate the response of a machine tool system with nonproportional damping subject to random excitation. The major advantage of this method is that it reduces the amount of computation greatly for higher-order systems when responses have to be calculated repeatedly in the process of optimization. An optimal design procedure is presented based on a representative lumped parameter model that can be constructed by using existing experimental or analytical techniques. The two-step optimization procedure based on the modified pattern search and univariate search effectively leads the numerical solution to the global minimun irrespectively of initial values even under the existence of many local minima.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206362
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  • 4
    Electronic Resource
    Electronic Resource
    Toward the integration of knowledge for engineering modeling and computation (1991)
    Springer
    Engineering with computers 7 (1991), S. 209-224 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Recent developments in computer science, especially in the area of artificial intelligence (AI), have made possible the representation of knowledge in symbolic terms. This, in turn, has made it possible to represent and integrate a broader range of engineering knowledge so as to provide new kinds of computer support for both analysis and design. This paper presents a typology of engineering knowledge to provide a conceptual basis for its computational integration. A review of the roles of numerical, geometric, and symbolic representations is also given within the context of the knowledge typology. Illustrations are provided from the domain of structural engineering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206363
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  • 5
    Electronic Resource
    Electronic Resource
    Localization of rational B-spline surfaces (1991)
    Springer
    Engineering with computers 7 (1991), S. 237-252 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Localization of curved surfaces is an important problem in the manufacturing and inspection of mechanical elements and in the simulation of manufacturing processes. The objective of this paper is to provide an efficient method for accurate localization of a single free-form surface of the rational B-spline form. Our approach is based on the following components—first, representation of position tolerances in terms of a ball offset tolerance region around the ideal rational spline surface; to facilitate interrogation and data exchange, this is followed by approximation of the bounding surfaces of the tolerance region with rational B-splines; next, optimal positioning of the target surface with respect to the ideal surface by minimizing a distance-based norm; finally, verification of compliance with position tolerance constraints. Examples illustrate our technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206365
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  • 6
    Electronic Resource
    Electronic Resource
    In vitro effects of CO2 laser irradiation on platelets: Influence of aspirin (1991)
    Springer
    Lasers in medical science 6 (1991), S. 15-21 
    Details
    ISSN: 1435-604X
    Keywords: Laser ; Platelets ; Aspirin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Laser angioplasty involves intravascular laser irradiation which may affect platelets and aggregation. In this study we examined the in vitro effects of different energy doses and modes of CO2 laser irradiation on the platelet number, function and ultrastructure. Since aspirin is used in many patients suffering from coronary artery disease, the consequences of laser irradiation on aspirin-treated platelets were studied as well. We found that CO2 laser irradiation causes a dose-response reduction of the platelet number that is most pronounced with high energy-short duration irradiation, and a dose-response reduction in platelet aggregation which is independent of the mode of irradiation. Pretreatment with aspirin does not change the effects of laser irradiation on platelet number, while aggregation is reduced only at relatively high energy doses. Electron microscopy revealed significant intracellular injury following low energy irradiation, while progressive damage to membranes occurred in a dose-response mode, both in untreated and aspirin-treated platelets. The clinical application of our findings should be done cautiously since important in vivo factors, such as the effect of laser irradiation on the vessel wall and coagulation system, were not studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042641
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  • 7
    Electronic Resource
    Electronic Resource
    Book review (1991)
    Springer
    Lasers in medical science 6 (1991), S. 53-53 
    Details
    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042647
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  • 8
    Electronic Resource
    Electronic Resource
    Percutaneous peripheral laser angioplasty with a pulsed Nd-YAG laser and sapphire tips (1991)
    Springer
    Lasers in medical science 6 (1991), S. 43-48 
    Details
    ISSN: 1435-604X
    Keywords: Atherosclerosis ; Peripheral arteries ; Laser angioplasty ; Pulsed Nd-YAG laser ; Sapphire tips
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Percutaneous transluminal laser angioplasty with a pulsed Nd-YAG laser (1064 nm wavelength, 100μs pulse duration, up to 0.4 J per pulse, 10 Hz repetition rate) coupled to optical fibres with sapphire tips of 1.8 and 2.2 mm diameter was performed under experimental conditions and then in 30 chronic occlusions of femoral and popliteal arteries in 22 patients. The experimental study in 11 human cadaverous arteries revealed that this laser system was effective in the recanalization of seven femoropopliteal occlusions, but the relative rigidity of the sapphire-tipped contact probe prevented its access to two infrapopliteal vessels. Two perforations occurred after the recanalization of 18 and 15 cm, respectively. Clinically the procedure was successful in 17 out of 25 sessions (68%). The probe formed a primary channel of at least 2.0 mm width which was further dilated by conventional balloon catheter. Ankle/brachial systolic pressure index (ABPI) increased from 0.43±0.13 to 0.79±0.21 after the procedure. In eight cases complications occurred. Two reocclusions were treated by Streptokinase infusion, two procedures were repeated 2 months later, one patient was referred to elective bypass surgery, and three patients were treated conservatively. Six patients were followed-up for more than 6 months. In one patient claudication of 400 m reappeared. ABPI showed a moderate decrease from 0.84±0.20 to 0.69±0.19. These first results are encouraging and it is likely that this method could become an important adjunct to balloon angioplasty.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042645
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  • 9
    Electronic Resource
    Electronic Resource
    Improved criteria for the recognition of atherosclerotic plaque using fluorescence spectroscopy (1991)
    Springer
    Lasers in medical science 6 (1991), S. 141-146 
    Details
    ISSN: 1435-604X
    Keywords: Laser angioplasty ; Coronary artery disease ; Nitrogen laser ; Tissue fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract To determine the fluorescence pattern for distinguishing normal (N) from calcified and fibrous plaque (P), fluorescence spectra of cadaveric aorta were measured with a spectrofluorometer. Emission (Em) and excitation (Ex) spectra corrected for instrumental response were obtained from 200 to 1000 nm. Specimens from 50 patients were measured less than 24 h after autopsy and then examined histologically. Spectra from 25 specimens demonstrated that the ratio of fluorescence intensity 460 nm/385 nm with Ex=337 nm provided separation of N from P (1.53±29 vs 0.82±0.25,p〈0.01) and that a ratio of 1.25 correctly identified all N and P. A prospective test of this ratio on an additional 25 specimens yielded a significant difference between N and P (1.70±0.37 vs 0.87±0.23,p〈0.0001) with a value of 1.25 correctly identifying all (10/10) N and 93% (14/15) P. Prospective analysis of previously proposed fluorescence ratios (600 nm/580 nm at Ex=480 nm; 530 nm/550 nm at Ex=459 nm; 448 nm/514 nm and 538 nm/514 nm at Ex=337 nm) all resulted in poor separation of N from P. The ratio of 460 nm/385 nm with Ex=337 nm is superior to previously reported criteria for distinguishing N from P and may be useful for guiding laser angioplasty systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02032541
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  • 10
    Electronic Resource
    Electronic Resource
    Cutaneous phototoxicity in photodynamic therapy: Clinical experience with and without histamine antagonists (1991)
    Springer
    Lasers in medical science 6 (1991), S. 179-182 
    Details
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Skin photosensitivity ; Antihistamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract We have investigated the incidence of cutaneous phototoxicity in 47 patients who received photodynamic therapy between April 1988 and March 1990. Of these, 15 patients received antihistamines as part of a pilot study to evluate their photoprotective role. Patients were followed-up for a minimum of 8 weeks. One out of the fifteen who received antihistamines and 15 out of the 32 patients who did not (p〈0.005), developed cutaneous phototoxicity. On the basis of these results we have initiated a randomized double-blind trial to evaluate the role of antihistamines in haematoporphyrin derivative-induced cutaneous phototoxicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02032545
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  • 11
    Electronic Resource
    Electronic Resource
    In vitro Alexandrite laser angioplasty: A study on fibre conduction and tissue effects (1991)
    Springer
    Lasers in medical science 6 (1991), S. 183-188 
    Details
    ISSN: 1435-604X
    Keywords: Atherosclerosis ; Alexandrite ; Angioplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Pulsed ultra-violet excimer laser radiation is capable of tissue ablation with only minimal thermal injury of adjacent tissue structures. Since difficult fibre optic coupling of energy was observed, alternative Q-switched laser sources capable of ablation of atherosclerotic plaque are under current investigation. To evaluate tissue effects of Alexandrite laser radiation, 160 arterial segments with macroscopic evidence of atherosclerotic disease were treated. The laser light was transmitted via silica based quartz fibres with different diameters. Using the Q-switched Alexandrite laser at the fundamental wavelength (748 nm) with a pulse duration of 300 ns the energy density threshold for tissue ablation was found to be in the range of 63 to 126 J cm−2 using a 300μm fibre. On macroscopic examination only limited thermal and acoustic injury was found in crater adjacent tissue structures. Crater edges were even and did not reveal signs of crater charring or debris in the crater lumen. However, the histological cross-sections revealed thermal injury extending from 100 up to 200μm lateral into adjacent tissue. The crater margins revealed fissuring as a result of shock wave injury. Thermal damage was most evident if irradiation of atherosclerotic tissue was performed in blood.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02032546
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  • 12
    Electronic Resource
    Electronic Resource
    Book review (1991)
    Springer
    Lasers in medical science 6 (1991), S. 215-215 
    Details
    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02032553
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  • 13
    Electronic Resource
    Electronic Resource
    Laser angioplasty versus balloon angioplasty: The need for imaging (1991)
    Springer
    Lasers in medical science 6 (1991), S. 223-233 
    Details
    ISSN: 1435-604X
    Keywords: Angioplasty ; Recanalization ; Laser ; Balloon ; Intravascular ultrasound ; Restenosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The current state of clinical laser angioplasty is reviewed. Compared to balloon dilation at the beginning of the past decade, both peripheral and coronary laser angioplasty devices produce better results. Compared to current balloon angioplasty techniques, however, laser angioplasty does not seem to offer improved initial or long term results. Intravascular ultrasound imaging may help to improve laser ablation of atherosclerotic plaque. It remains to be established, however, whether precise debulking of the obstruction will result in a reduced restenosis rate compared to balloon angioplasty.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030875
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  • 14
    Electronic Resource
    Electronic Resource
    Biophysics of the photoablation process (1991)
    Springer
    Lasers in medical science 6 (1991), S. 241-254 
    Details
    ISSN: 1435-604X
    Keywords: Laser angioplasty ; Photoablation ; Photohydraulic effect ; Fast thermal explosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Besides the coagulation, where the body digests the necrotic tissue and direct evaporation of tissue, the photoablation effect turns out to be very important in tissue removal. In the case of high tissue absorption the process channels in photoablation can either be photochemical (bond breaking) or fast thermal. In the case of transparent media, a plasma formation due to high irradiances and an optical breakdown is necessary for ablation or photodisruption. All the process channels lead to a fast microscale explosion and to Shockwaves. For soft tissue the main process channel is the fast thermal explosion. Assuming that tissue will be disintegrated, if the energy deposited within a single laser pulse is larger than a material specific threshold, the thresholds for the radiant exposure and ablation rates respectively can be calculated. There is a large difference, whether the laser radiation is applied to the tissue surface in noncontact or through a fibre in contact. In contact the ‘fast thermal explosion’ happens in a closed chamber and hence the photohydraulic effect will support the photoablation. The thermally damaged zone in the surrounding tissue depends on the optical penetration depth mainly in cases that the pulse duration is shorter than a critical time given by the heat conductivity. Pulsed lasers can be used ‘non-thermally’ only if the average power is less than a tenth of a watt. With a higher amount of average power a pulsed laser will act comparable to a cw laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030877
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  • 15
    Electronic Resource
    Electronic Resource
    Laser-assisted fluorescence detection of plaque (1991)
    Springer
    Lasers in medical science 6 (1991), S. 289-296 
    Details
    ISSN: 1435-604X
    Keywords: Atherosclerosis ; Dihaematoporphyrin ether/ester, DHE ; Haematoporphyrin derivative, HPD ; Laser angioplasty ; Laser-induced fluorescence ; Plaque
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Selective fluorescence-marking of plaque offers new possibilities in cardiovascular diagnosis and therapy. Angioscopic investigations and spectrometry-assisted laser angioplasty will be simplified and more effective as compared with methods of today. It might help to make laser angioplasty a further promising interventional method to overcome, at least partially, the problems caused by atheromatous or atherosclerotic changes in the cardiovascular system. Fluorescence detection and imaging of markers is usually limited by the intrinsic fluorescence of tissue. Optical differential methods in combination with two-wavelength laser excitation and computer-assisted image processing, however, allow for discrimination of background-related signals and enable plaque detection and imaging at a high contrast. Plaque consists of either fibrotic, lipoid, or calcified depositions and is rather bradytrophic. For that reason in vitro experiments on human specimens post mortem seem to be justified and of clinical evidence. Due to intrinsically different fluorometric properties of plaque and normal vascular tissue imaging of marker-free plaque areas is possible. Additionally the specimens have been incubated with a haematoporphyrin-containing fluorescence marker at concentrations of 10–40μg ml−1 and incubation times of 60 min in order to obtain a corresponding increase in contrast. Lipoid depositions show the highest contrast because of lipophilic properties of the marker, while fibrotic and calcified plaque is slightly less effectively marked. The results, however, so far obtained indicate that fluorescence detection of plaque promises further progress in diagnosis and therapy of cardiovascular diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030882
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  • 16
    Electronic Resource
    Electronic Resource
    Improved results of coronary excimer laser angioplasty by the use of advanced transmission devices (1991)
    Springer
    Lasers in medical science 6 (1991), S. 317-321 
    Details
    ISSN: 1435-604X
    Keywords: Laser angioplasty ; Coronary artery disease ; PTCA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Excimer laser angioplasty is an alternative method for the treatment of obstructive coronary lesions. Initial clinical results demonstrated the safety and feasibility of the procedure. However, efficacy was limited by low catheter flexibility and unreliable energy transmission. Advanced transmission devices were used in 80 interventions in 79 patients. The catheter diameter is 1.3, 1.5 or 1.8 mm, the catheters consist of 20, 30 or 35 quartz fibres (100 μm) respectively. The mean energy density was 55 ±18 mJ mm−2, mean loss of energy transmission was 20%. The pulse width was 60 ns and 115 ns in 40 interventions each. The target vessel was the LAD in 53, the LCX in 6 and the RCA in 21 interventions. Failure of laser angioplasty occurred in 10 patients due to failed guidewire placement (N=6), failed catheter placement (N=3) or impossibility to cross the lesion with the catheter (N=1). Stand-alone laser angioplasty was performed in 43/70 procedures. Additional balloon angioplasty was necessary due to an unsatisfactory result (N=10) or due to complications (N=17) in 27 patients. Vessel occlusion occurred in 18 patients (25%) and could be successfully resolved by balloon dilatation (N=16) or additional laser angioplasty (N=1) in 17 patients. Two early occlusions were found at the 24-h control angiography. The incidence of myocardial infarction and in-hospital death (N=1) was 1.4%. Conclusion: The use of an advanced energy delivery system with trusted energy transmission and higher energy density increased the primary success rate of stand-alone excimer laser angioplasty. However, further improvement of catheter flexibility and reduction of dead space at the catheter tip is necessary to optimize ablation efficacy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030887
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  • 17
    Electronic Resource
    Electronic Resource
    Excimer laser coronary angioplasty: Initial experience at St. Thomas' Hospital (1991)
    Springer
    Lasers in medical science 6 (1991), S. 339-347 
    Details
    ISSN: 1435-604X
    Keywords: Xenon chloride ; Excimer laser ; Coronary angioplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photochemical ablation of coronary artery atheroma using pulsed xenon-chloride excimer laser has, over the past 18 months produced promising results. Worldwide experience amounts to some 2000 cases. In the first 6 months following installation of the Dymer 200+ laser (Advanced Interventional Systems, Irvine, California, USA) at St. Thomas' Hospital, 53 procedures have been performed in 49 patients. Of these, 52.8% were ‘high risk’ (triple vessel disease, unstable angina, LV ejection fraction 〈35%, need to treat sole remaining coronary conduit). Complications were two in hospital deaths (18 and 48 h post-procedure-3.8%); one ELCA related myocardial infarct (1.9%); two haemorrhage requiring transfusion (3.8%); no emergency bypass graft surgery (0%). Current indications for the use of laser include: (1) long-segment diffuse disease; (2) proximal or ostial stenoses in coronary artery or graft; (3) restenosis after balloon angioplasty; (4) total occlusions crossed by a guidewire; (5) severe stenoses crossed by guidewire but not balloon; and (6) bifurcation lesions or stenoses compromising an important side-branch. Potential complications include: arterial perforation; aneurysm formation; peripheral embolization by plaque material; abrupt thrombotic closure; dissection; late sudden occlusion; spasm; and restenosis. Minor problems at the start of the programme involved: modifications to the machine to meet local laser safety requirements; special gases required for the machine; supply and design of fibre optic catheters; guiding catheters; heparin dose; dissection of the coronary artery (major and minor); and selection of patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030891
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  • 18
    Electronic Resource
    Electronic Resource
    Has the argon laser ever been used optimally for the treatment of port wine stain birthmarks? (1991)
    Springer
    Lasers in medical science 6 (1991), S. 371-371 
    Details
    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042458
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  • 19
    Electronic Resource
    Electronic Resource
    A study of gelatin ablation induced by a novel design TEA CO2 laser (1991)
    Springer
    Lasers in medical science 6 (1991), S. 429-435 
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    ISSN: 1435-604X
    Keywords: TEA CO2 laser ; Ablation ; Thermal modelling ; Pulse width ; Gelatin ; Absorption coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Ablation of gelatin samples was performed by using a semiconductively preionized TEA CO2 laser, emitting pulses of the lower TEM mode, 100 ns duration, at a repetition rate of 2.4Hz. Ablation rate experiments were performed at a range of fluences from 2J cm−2 to 10J cm−2. Assuming that the absorption coefficient is much larger than the scattering coefficient, experimental data were explained by simple models of ablation. The ablation depth per pulse and the specific absorption depth were calculated from the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042466
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  • 20
    Electronic Resource
    Electronic Resource
    Activity of haematoporphyrin derivative photoproduct in photodynamic therapy in vivo (1991)
    Springer
    Lasers in medical science 6 (1991), S. 425-428 
    Details
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Tumour ; Haematopor-phyrin derivative ; Photoproduct ; Laser illumination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Illumination of haematoporphyrin derivative in phosphate-buffered solutions causes the formation of a stable photoproduct with new absorption and fluorescence bands. We report data showing photodynamic activity of the photoproduct. Praestomic tumour OJ-5, carcinosarcoma W-256 (mice) and adenocarcinoma Akatol of colon (rats) have been used. Dynamics of tumour growth, life span of animals and morphological changes of tumour tissues have been the main criteria used to show the photoproduct activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042465
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  • 21
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    The propagation of optical radiation in tissue. II: Optical properties of tissues and resulting fluence distributions (1991)
    Springer
    Lasers in medical science 6 (1991), S. 379-390 
    Details
    ISSN: 1435-604X
    Keywords: Tissue optics ; Absorption ; Scattering ; Fluence distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract This paper is the second of two reviewing the propagation of electromagnetic radiation of wavelength 0.25–10μm in tissue. This part begins with a discussion of how the fundamental optical interaction coefficients of tissue may be measured. Both direct methods, in which the coefficients are measured for optically thin samples, and indirect methods, in which the coefficients are inferred from measurements on bulk samples are described. The difficulties inherent in both types of measurement are outlined. Next the wavelength dependence of the scattering and absorption coefficient is discussed, both from a heuristic point of view and by illustration from current literature. We illustrate how the optical spectrum can be divided into regions where the propagation of light is dominated by absorption or scattering effects. Finally we show how the distribution of light fluence in these spectral regions is dramatically different and illustrate the important features of these distributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042460
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  • 22
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    Preliminary experience with the 1.32 μm neodymium-YAG laser in the treatment of tracheobronchial malignancy (1991)
    Springer
    Lasers in medical science 6 (1991), S. 407-413 
    Details
    ISSN: 1435-604X
    Keywords: Laser bronchoscopy ; 1.32μm Nd-YAG laser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Endoscopic laser treatment for tracheobronchial malignancy is usually given with the neodymium-YAG laser using the 1.064μm output beam. However, recent experimental work suggests that the 1.32μm output beam of this laser has more desirable tissue effects. We have now treated 55 patients with the 1.32μm Nd-YAG laser (MBB-Medizintechnic) under general anaesthesia, using power settings of 10–20 W and pulse durations of up to 1 s. The indications for treatment were localized airway obstruction in each case. Airway calibre was improved in 46 (84%) patients and this was associated with an improvement in symptoms of cough and breathlessness. Patients with tracheal and carinal obstruction exhibited the most striking clinical improvements with up to four-fold increases in peak expiratory flow. In patients with more peripheral endobronchial obstruction, treatment improved airway calibre less frequently and resulted in a smaller clinical improvement. Of 11 patients with obstruction of a main bronchus and lung collapse, treatment led to partial or complete re-expansion in 10 cases (91%). The 1.32μm wavelength allows treatment to be conducted efficiently and safely but at a considerably lower power than is required for the 1.064μmwavelength. The ability to use low powers has the apparent advantage of generating only negligible quantities of smoke. Our experience with this new laser system demonstrates its considerable potential in the management of tracheobronchial malignancy.
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    Clinical recording of laser-induced fluorescence spectra for evaluation of tumour demarcation feasibility in selected clinical specialities (1991)
    Springer
    Lasers in medical science 6 (1991), S. 415-424 
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    ISSN: 1435-604X
    Keywords: Autofluorescence ; Fluorescence ; Laser spectroscopy ; Tumour detection ; Tumour diagnosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Laser-induced autofluorescence spectra from humans were recorded in vivo at three different clinics in a study aimed at investigating the capability of this method to discriminate between malignant tumours and normal surrounding tissues. For the recordings a mobile trolley with the necessary equipment was constructed for use in an examination room or in an operating theatre environment. Laser light was guided through a 600μm optical fibre to the target tissue. The fluorescence from the excited tissue was collected with the same fibre and was fed to an optical multichannel analyser. Two excitation wavelengths were used (337 and 405 nm) in order to optimize the fluorescence signals in two interesting wavelength regions (380–500 and 550–700 nm). Oral and oropharyngeal tumours excited with 405 nm light contained detectable endogenous porphyrins and were in this way discriminated from the normal mucosa. Astrocytoma grade III–IV fluorescence different from that of normal brain tissue, while tumours in the bronchial tree were not detectable using the spectral shape of the pure tissue autofluorescence.
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    The value of laser in the treatment of malignant disease of the larynx (1991)
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    Lasers in medical science 6 (1991), S. 451-455 
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    ISSN: 1435-604X
    Keywords: Larynx ; Endoscopic microlaryngeal surgery ; CO2 laser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The value of functional and reconstructive surgery to the larynx in the treatment of malignant tumours to preserve residual function as far as possible has been clearly demonstrated. A further step in the development of ‘functional surgery’ is classical microsurgery of the larynx which facilitates diagnosis and endoscopic microsurgical treatment of benign tumours. However, recently following the introduction of the carbon dioxide (CO2) laser it has been shown that it is possible to treat also malignant tumours of the larynx by endoscopic microsurgery. An incision made by the photo-thermal CO2 laser scalpel is characterized by the relative absence of bleeding, lack of post-operative oedema, rapid epithelialization without associated infection or cicatrization and this results in optimal post-operative laryngeal function. This paper presents the results of treatment of selected cases of T1 and T2 carcinoma of the glottis treated by CO2 laser excision under microlaryngoscopic control. In this series healing was rapid with minimal hospitalization and without a tracheostomy. Excellent functional results were achieved and the patient was able to return rapidly to his original occupation. It is our opinion that at present this treatment modality represents the optimal treatment for T1 and T2 carcinoma of the glottis.
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    Announcements (1991)
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    Research in engineering design 2 (1991), S. 116-116 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    URL: http://dx.doi.org/10.1007/BF01579256
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    Grammatical approaches to engineering design, part I: An introduction and commentary (1991)
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    Research in engineering design 2 (1991), S. 121-135 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A grammar is a definition of a language written in a transformational form. To the extent that design requirements and designed artifacts can be represented by some language, and to the extent that design is a transformation from function to form, grammars might facilitate the development of theories and methods for design. The syntax, lexicon, and semantics of a formal language are analogous to the configuration, components, and behavior of an engineering design. Furthermore, the computational complexity of various grammatical formalisms might provide a foundation upon which to base complexity measures in design. We discuss grammatical formalisms and give examples of how grammars might facilitate design automation.
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    Editorial: Improving Engineering Design (1991)
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    Research in engineering design 2 (1991), S. 183-183 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    URL: http://dx.doi.org/10.1007/BF01579216
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    Design synthetic reasoning: A methodology for mechanical design (1991)
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    Research in engineering design 2 (1991), S. 221-238 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Design synthetic reasoning is a methodology to support the process of design synthesis and includes within its scope support for associated processes of design verification, behavior derivation, and function justification. The design synthesis of machines is viewed as the development of a specification of required behavior, and transformation of the specification into the description of a structure (or assembly) of machine components. In this paper, the process of design synthesis is modeled as a sequence of applications of transformation rules. These rules either respecify, elaborate, reduce, or reformulate the expression of required behavior, and ultimately allow matching and selection of structurally compatible machine components and relationships from a design library. The specification of required behavior for a simple rotary actuator is developed and progressively transformed to synthesize the structures of two different patented rotary actuating devices. The ability of both devices to produce the required behavior is verified, and the property of self-locking for both the devices is derived from the structure descriptions. The functions (purposes) of components and relationships in each device are extracted from the trace of transformation rules applied during the verification and derivation process for each device.
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    Announcements (1991)
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    Research in engineering design 3 (1991), S. 57-59 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    URL: http://dx.doi.org/10.1007/BF01580068
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    Dimensional Variable Expansion—A formal approach to innovative design (1991)
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    Research in engineering design 3 (1991), S. 75-85 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A methodology called Dimensional Variable Expansion (DVE) is presented to formalize the process of design space expansion and design innovation. Unlike parametric design, where the structure of the design is specified and only the parameters are allowed to vary, DVE creates new structures, including new variables, constraints, and a reformulation of the objective function. Via DVE, a body is expanded into multiple regions by dividing along a dimensional variable, and then each region is permitted independent properties. Optimality conditions are used to determine which variables to expand and which regions should be subject to property modifications. With DVE the degrees-of-freedom of a design can be expanded and designs with unique features can be derived.
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    Evolutionary design theory using dynamic variation and thermodynamic selection (1991)
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    Research in engineering design 3 (1991), S. 39-55 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A general evolutionary design theory is presented which incorporates variation processes and selection processes to design fluid/thermal/chemical devices. A biologically consistent view of evolution splits the process into variation and selection. The variation process is quantitatively modeled using dynamic equations that govern structural changes. Steady-state and stability of design variation is related to growth and decay factors and environmental control parameters. The selection process is quantitatively modeled using nonequilibrium thermodynamics to indicate performance. Both structure and environment contribute to entropy production. This requires computational modeling of fluid dynamics, heat transfer, chemical diffusion, and reactions. Special cases of engineering design evolution are shown theoretically and with a numerical example. The theory could rectify the impact of engineered structures on the natural environment and provide a basis for designing machines with coupled physics.
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    Paconius and the pedestal for Apollo: A case study of error in conceptual design (1991)
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    Research in engineering design 3 (1991), S. 123-128 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A classic case history of an engineering failure related by Vitruvius is presented as a paradigm of human error in the design process. It is argued that a familiarity among designers with such case studies could be instrumental in reducing conceptual errors in the design process generally.
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    Effects of Nd-YAG laser on platelet function in vitro: A comparative study using the spectraprobe, ‘hot tip’ and bare fibres (1991)
    Springer
    Lasers in medical science 6 (1991), S. 1-6 
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    ISSN: 1435-604X
    Keywords: Laser angioplasty ; Arterial thrombosis ; Reocclusion ; Platelet aggregates ; Platelet function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The effects of Nd-YAG laser irradiation on platelet function in vitro were studied using platelet rich plasma obtained from the blood of healthy volunteers. Laser delivery was effected via the ‘bare’ optical fibre, thermal ‘hot tip’ fibre and spectraprobe and the effects of these probes on platelet function were compared. Fall in platelet count and mean platelet volume (MPV) were proportional to increasing energy delivery with all three probes, the effect being maximal with the spectraprobe, moderate with the ‘hot tip’ and least with the ‘bare’ optical fibre. A significant decrease in percentage aggregation of platelets in response to added ADP, collagen and ristocetin with increasing energy delivery was also observed with all three probes. The formation of preformed aggregates, however, showed an increase proportional to energy delivery with all three probes. The differential effects of the various probes used in this study on platelet function may enhance our understanding of the complex role played by platelets in the pathogenesis of complications such as arterial thrombosis and re-occlusion after laser angioplasty.
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    Acute effects of a copper vapour laser on atheroma (1991)
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    Lasers in medical science 6 (1991), S. 23-27 
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    Keywords: Copper vapour laser ; Laser angioplasty ; Atherosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The acute histological effects of a commercially available copper vapour laser (CVL) on normal and atherosclerotic arterial wall were studied. The multi-cyclic CVL produces a quasi continuous wave output at 511 nm (green) and 578 nm (yellow) [green/yellow ratio 2∶1]. Tissue craters were produced in segments of normal and atherosclerotic human femoral artery using a maximum of 8 J of laser energy delivered with a bare 1 mm quartz fibre in contact and perpendicular to the tissue. Crater dimensions and ablation volumes were determined histologically using an optical graticule. Ablation of atheroma was almost three times more efficient than ablation of normal arterial wall (p〈0.001). A narrow zone of vacuolization and coagulative thermal damage lined the crater margins suggesting a predominantly photothermal ablative mechanism. In conclusion, selective ablation of atheroma using low power copper vapour laser light is possible. The CVL is an attractive alternative to the argon ion laser because of its low running costs and applicability to other medical disciplines. Therefore, its potential application in laser angioplasty merits further study, preferably using a modified optical fibretip delivery system.
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    New laser literature (1991)
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    Lasers in medical science 6 (1991), S. 55-58 
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    Topics: Medicine , Physics , Technology
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    URL: http://dx.doi.org/10.1007/BF02042648
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    Skin surface temperatures during argon and tunable dye laser therapy of port wine stains (1991)
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    Lasers in medical science 6 (1991), S. 29-34 
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    Keywords: Port wine stains ; Skin surface temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The thermographic camera has been used to measure the surface temperature of the skin in subjects undergoing laser therapy for treatment of their port wine stains. Skin temperatures during therapy with the tunable dye laser reached a maximum of 46 °C at 6–7 J output. A normal subject showed a skin temperature of 38 °C at 5 J output and 46 °C at 10 J output. Skin temperatures during argon laser therapy in continuous mode reached estimated maxima of approximately 75 °C at an output of 1.2 W. A normal subject showed temperatures of 45–50 °C with a 0.2 s pulse at 1 W output and 50 °C with a 0.5 s pulse at 1 W output. At 5 W, the normal subject showed temperatures in excess of 70 °C with either 0.2 or 0.5 s pulses. The conclusion must be reached that there is little chance of heat damage to the skin with the tunable dye laser, but that heat damage to the skin in general is a significant risk with the argon laser.
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    The propagation of optical radiation in tissue I. Models of radiation transport and their application (1991)
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    Lasers in medical science 6 (1991), S. 155-168 
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    ISSN: 1435-604X
    Keywords: Light propagation ; Radiation transport ; Tissue optics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract This paper is the first of two reviewing the propagation of electromagnetic radiation of wavelength 0.25–10μm in tissue. After a brief discussion of light/tissue interactions, a mathematical description of light propagation in terms of radiative transfer is developed. Formal solutions of the resulting equation are outlined, but the emphasis is on approximate method of solution—namely the discrete ordinates method, the technique of functional expansion and Monte Carlo simulation. The application of the simplest of these approximate methods, namely the 2-flux and diffusion models, to tissue optics is discussed in some detail. The second paper deals with the optical properties of tissue and the salient characteristics of light fluence distributions in these tissues.
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    The effect of a combined HeNe and i.r. laser treatment on the regeneration of the lymphatic system during the process of wound healing (1991)
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    Lasers in medical science 6 (1991), S. 193-199 
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    ISSN: 1435-604X
    Keywords: HeNe laser ; I.r. laser ; Wound healing ; Lymphatic regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract To study the effect of a combined HeNe and i.r. laser treatment on the regeneration of the lymphatic system during the process of wound healing, we compared the evolution of a surgical induced incision wound in two groups of mice. In the control group (N=500) as well as in the test group (N=100) we studied the evolution of four parameters (adhesion, local oedema, regeneration of the vein and regeneration of the lymph vessel) by means of microscopic observations using a cold light source to illuminate the everted skin of the mice. The wounds in the test group were irradiated twice a day with a combined HeNe and i.r. laser. The adhesion of the scar with the underlying tissues disappeared after 10 days in the control group and after 4 days in the test group. The local oedema disappeared in the test group after 8 days while in the control group it lasted until 10 days. A considerable acceleration of the regeneration of both vein and lymph vessel was seen in the test group.
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    On the scientific reporting of laser surgery (1991)
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    Lasers in medical science 6 (1991), S. 213-214 
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    Topics: Medicine , Physics , Technology
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    Preface (1991)
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    Lasers in medical science 6 (1991), S. I 
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    URL: http://dx.doi.org/10.1007/BF02030874
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    Laser systems for cardiovascular applications (1991)
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    Lasers in medical science 6 (1991), S. 255-259 
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    Keywords: Laser ; Angioplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Different laser systems have been proposed for angioplasty. A brief overview is given in order to describe the basic concepts which characterize each case. The results of a comparison are presented.
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    Laser angioplasty (1991)
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    Lasers in medical science 6 (1991), S. 303-305 
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    Keywords: Percutaneous transluminal angioplasty ; Laser thermal angioplasty
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Percutaneous transluminal angioplasty is an useful non-invasive technique. Recently laser thermal angioplasty has been suggested as an alternative technique. Until the end of 1989, laser angioplasty was carried out on 156 cases. The authors present their experience. The immediate results were excellent in 89% cases, with a distal ratio of Doppler ankle/arm ±0.22. A difference is shown between the angiographic results and the clinical results.
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    Excimer laser coronary angioplasty: Initial experience in Amsterdam (1991)
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    Lasers in medical science 6 (1991), S. 281-288 
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    Keywords: Coronary angioplasty ; Excimer laser ; Light fluence rate distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract This paper reports on the initial clinical experience with 308 nm XeCl-excimer laser coronary angioplasty (ELCA) in the Academic Medical Center in Amsterdam and on calculations of light fluence rate distributions resulting from laser beams incident on tissue. Monte Carlo numerical computations were used to compute the light fluence rate distributions of a finite 308 nm excimer laser beam with various diameters incident on a liquid-tissue interface. It was found that light scattering is an important component in the resulting light distribution in aortic tissue. The calculations predict that there will be hardly any broadening of the beam outside the laser beam area. Therefore, the distributions from different fibres in multifibre catheters will not overlap unless the fibres are closely packed together. As a consequence of scattering the fluence rate at the surface of the tissue was larger than the incident power density and showed a considerable decrease from the centre to the edge of the beam. However, the physics of tissue ablation by fibres in contact with tissue are different and at present not well understood. The clinical results of the first 18 patients treated with the Dymer 200+ excimer laser (Advanced Interventional Systems, Irvine, CA, USA) are given. Six patients had abrupt closure solved by balloon angioplasty, but complicated by a small myocardial infarction. One patient had emergency by-pass surgery for abrupt closure after laser followed by balloon angioplasty (probably a dissection and thrombus). In one patient we perforated in a bend of a RCA with a 2.0 catheter following a second pass. We had two in hospital deaths (4 and 14 days after treatment). At 6 months follow-up, eight patients had restenosis or occlusion at the lased segment. However, the results of the first 1000 patients enrolled in the American ELCA-Registry are more promising. In the light of these results it can be concluded that a randomized trial balloon angioplasty versus excimer laser angioplasty appears to be indicated.
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    Nd-YAG laser ablation of arteriosclerotic obstructions: Clinical long-term results in femoropopliteal artery occlusions (1991)
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    Lasers in medical science 6 (1991), S. 311-315 
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    Keywords: Arteriosclerotic obstructions ; Laser recanalization ; Nd-YAG laser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Laser recanalization of peripheral artery occlusions was performed in 338 patients. A continuous wave Nd-YAG laser was used in combination with ‘sapphire-probe’ laser catheters. The initial recanalization rate was 85%. Complications such as dissections, perforations, emboli and spasm were observed in 14%. The cumulative patency rate after 3 years was 48%.
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    Percutaneous mid infra-red laser coronary angioplasty (1991)
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    Lasers in medical science 6 (1991), S. 331-334 
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    Keywords: Mid infra-red laser ; Coronary laser angioplasty ; Multifibre catheter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Thirty patients with stenosis or total occlusion of the coronary artery were treated with mid infra-red pulsed laser angioplasty. The device consisted of a holmium-YAG laser operating at 2.1μm, 500 mJ pulse−1, 3.5 Hz, 250μs pulse−1. The laser was coupled into a multifibre catheter consisting of 37 optical fibres of 150μm each concentrically arranged around a central lumen for the passage of a guidewire. This ‘over-the-wire’ system allowed for safe and effective recanalization without perforation, death, arrythmia, distal embolus. Chest sensation but not pain occurred during laser emission. There was spasm in six patients which could be relieved by nitrates. In previously failed balloon angioplasty laser angioplasty allowed for successful repeat dilatation with low inflation pressure. Technical improvement should be made in reducing the dead space left in between the fibres at the distal catheter tip, in distal tip flexibility and in increasing the channel diameter for more laser ‘stand-alone’ therapy.
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    Histomorphological aspects of vascular anastomosis established by laser (1991)
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    Lasers in medical science 6 (1991), S. 363-366 
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    Keywords: Laser vascular welding ; Tissue fusion ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The central problem in microsurgery is the reconstruction of small vessels. The long operating time, foreign body granuloma formation around the suture material as well as aneurysmal alterations of the vessel wall after conventional suture technique make the search for alternatives indispensable. Some of these disadvantages can be avoided as demonstrated by our animal experiments and histological examinations in laser-assisted anastomosing. The aim of this study is to show these aspects in connection with laser application and compare them with conventional suture techniques.
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    A thermal appraisal of the ablation process in canine aorta in vivo using a 100 μm pulsed Nd-YAG laser (1991)
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    Lasers in medical science 6 (1991), S. 373-378 
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    ISSN: 1435-604X
    Keywords: Heat necrosis ; Modelling ; Nd-YAG laser ; Dog aorta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A model has been developed to calculate distal tissue necrosis in vascular tissue after application of a 100μ laser pulse from a Nd-YAG laser (5 kW peak pulse power on a 0.13 mm2 spot size). The model assumes that the temperature profile in the tissue is proportional to the laser light fluence rate and that the distal tissue necrosis depth is that depth in the tissue where there is a temperature increase of 42 °C minus the etch rate (ablation depth per laser pulse). The fluence rate has been calculated using the diffusion approximation to the radiative transport equation. The tissue optical parameters (absorption and reduced scattering coefficients) have been derived from published data. The etch rate used (10μm per pulse) is derived from in vivo experimental results. The model predicts a damage depth varying between 0 and 2.33 mm (mean 1.10 mm) and this is compared with an experimental result (0.77 mm) in dog aorta.
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    New laser literature (1991)
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    Lasers in medical science 6 (1991), S. 457-459 
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    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
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    URL: http://dx.doi.org/10.1007/BF02042470
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    Experimental photodynamic therapy with tetrapropyl-porphycene: Ultrastructural studies on the mechanism of tumour photodamage (1991)
    Springer
    Lasers in medical science 6 (1991), S. 437-442 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Tetrapropylporphycene ; Liposomes, Electron microscopy ; Tumour necrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Red light irradiation of a transplanted MS-2 fibrosarcoma in mice at 24 h after injection of liposome-zbound tetra-n-propyl-porphycene (TPP, 2mg kg−1 b.w.) caused an efficient tumour necrosis. Electron microscopy analysis of tumour specimens taken at different times after the phototherapeutic treatment showed the development of direct damage of malignant cells between 3 and 6 h; the earliest detectable alterations occurred at the level of mitochondria. The endocellular damage gradually progressed with extensive vacuolization of the cytoplasm and, at later stages, formation of pyknotic nuclei. On the other hand, the vascular system of the tumour appeared to be well preserved up to about 9 h, when several endothelial alterations were detected. The damage of the tumour tissue was essentially complete 24 h after the phototreatment. The pattern of tumour modification is consistent with a preferential transport and tumour release of the liposome-bound TPP by low-density lipoproteins.
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    Basic mechanisms in laser lithotripsy. 1: Optoacoustic-mechanical analysis (1991)
    Springer
    Lasers in medical science 6 (1991), S. 443-450 
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    ISSN: 1435-604X
    Keywords: Laser lithotripsy ; Flashlamp pumped dye laser ; Urinary calculi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Extensive studies on laser lithotripsy of urinary and gall calculi using a microsecond pulsed dye laser have yielded information on the mechanism of plasma initiation, expansion and shock wave fragmentation relevant to the determination of optimum fragmentation conditions. The key to plasma formation lies in the initial absorption of laser energy by the calculus surface to produce a sufficient density of localized vapour to absorb strongly laser energy. The subsequent ionization of the vapour by the further absorption of laser energy leads to plasma formation. The absorbance of several calculi pigmentations have been measured giving an indication of the individual susceptibility to laser induced breakdown. The plasma threshold is measured to be fluence dependence, which is caused by the vaporization and the further heating of the vapour. The transient expansion of the plasma imparts an impulse on stone and induces a sharp shock wave with peak pressure as high as 10 kilobar leading to the fragmentation of calculi.
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    Trade-off strategies in engineering design (1991)
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    Research in engineering design 3 (1991), S. 87-103 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A formal method to allow designers to explicitly make trade-off decisions is presented. The methodology can be used when an engineer wishes to rate the design by the weakest aspect, or by cooperatively considering the overall performance, or a combination of thesestrategies. The design problem is formulated with preference rankings, similar to a utility theory or fuzzy sets approach. This approach separates the designtrade-off strategy from the performance expressions. The details of the mathematical formulation are presented and discussed, along with two design examples: one from the preliminary design domain, and one from the parameter design domain.
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    Effective Łojasiewicz inequalities in semialgebraic geometry (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 1-14 
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    ISSN: 1432-0622
    Keywords: Łojasiewicz inequalities ; Real algebraic geometry ; Computer algebra ; Complexity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract The main result of this paper can be stated as follows: letV ⊂ ℝ n be a compact semialgebraic set given by a boolean combination of inequalities involving only polynomials whose number and degrees are bounded by someD 〉 1. LetF, G∈∝[X1,⋯, Xn] be polynomials with degF, degG ≦ D inducing onV continuous semialgebraic functionsf, g:V→R. Assume that the zeros off are contained in the zeros ofg. Then the following effective Łojasiewicz inequality is true: there exists an universal constantc 1∈ℕ and a positive constantc 2∈∝ (depending onV, f,g) such that $$|g(x)|^{D^{c_1 .n} } \leqq c_2 \cdot |f(x)|$$ for allx∈V. This result is generalized to arbitrary given compact semialgebraic setsV and arbitrary continuous functionsf,g:V → ∝. An effective global Łojasiewicz inequality on the minimal distance of solutions of polynomial inequalities systems and an effective Finiteness Theorem (with admissible complexity bounds) for open and closed semialgebraic sets are derived.
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    An optimal algorithm for multiplication in F256/F4 (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 15-20 
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    ISSN: 1432-0622
    Keywords: Elliptic curves ; Bilinear complexity ; Interpolation algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract Applying an interpolation algorithm invented by D. V. Chudnovsky and G. V. Chudnovsky to the Fermat-curvex 3 + y3 = 1 overF 4, we present a bilinear algorithm for the multiplication in theF 4-algebraF 256 which requires 8 essential multiplications.
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    Primitive elements in finite fields and costas arrays (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 45-53 
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    ISSN: 1432-0622
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract In [7] Golomb made four conjectures concerning the existence of pairs of primitive elements in finite fields. In this note we resolve each of the conjectures in the affirmative. As a consequence several conjectured classes of Costas arrays do indeed exist.
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    On the computation of hilbert—Poincaré series (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 21-33 
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    ISSN: 1432-0622
    Keywords: Hilbert functions ; Poincaré series ; Borel-normed ideals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract We prove a theorem, which provides a formula for the computation of the Poincaré series of a monomial ideal ink[X1,⋯, Xn], via the computation of the Poincaré series of some monomial ideals ink[X 1,⋯, Xi,⋯, Xn]. The complexity of our algorithm is optimal for Borel-normed ideals and an implementation in CoCoA strongly confirms its efficiency. An easy extension computes the Poincaré series of graded modules over standard algebras.
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    Improved upper complexity bounds for the discrete fourier transform (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 35-43 
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    ISSN: 1432-0622
    Keywords: Fast Fourier transform ; Group algebra ; Linear complexity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract The linear complexityL 2 (G) of a finite groupG is the minimal number of additions, subtractions and multiplications by complex constants of absolute value ≦2 sufficient to evaluate a suitable Fourier transform of ℂG. Combining and modifying several classical FFT-algorithms, we show thatL 2(G)≦8|G|log2|G| for any finite metabelian groupG.
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    Computational problems in the theory of finite fields (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 81-89 
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    ISSN: 1432-0622
    Keywords: Finite fields ; Polynomials ; Computational complexity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract We give a survey of selected topics in the theory of finite fields with emphasis on computational aspects including recent advances and open problems.
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    On the number of term orders (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 55-79 
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    ISSN: 1432-0622
    Keywords: Term order ; Separating hyperplane ; Gröbner basis ; Universal Gröbner basis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract By an admissible order on a finite subsetQ of ℚ n we mean the restriction toQ of a linear order on ℚ n compatible with the group structure of ℚ n and such that ℕ n is contained in the positive cone of the order. We first derive upper and lower bounds on the number of admissible orders on a given setQ in terms of the dimensionn and the cardinality ofQ. Better estimates are possible if the setQ enjoys symmetry properties and in the case whereQ is a discrete hyperbox of the form $$\mathop \Pi \limits_{k = 1}^n [1,d_k ].$$ In the latter case, we also give asymptotic results as $$\mathop {\min }\limits_{1 \leqq k \leqq n} d_k \to \infty $$ d k → ∞ for fixedn. We finally present algorithms which compute the set of admissible orders that extend a given binary relation onQ and their number. The algorithms are useful in connection with the construction of universal Gröbner bases.
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    Procedures to investigate injectivity of polynomial maps and to compute the inverse (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 91-103 
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    ISSN: 1432-0622
    Keywords: System identifiability ; Polynomial maps ; Gröbner bases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract In this paper a polynomial map from C n to C m is studied in order to investigate if it is injective out of a set of measure zero. We propose a procedure, based on truncated Gröbner basis computations, which when successful, allows to reduce the problem to an easier map, and so gives a speed-up of the general algorithms using Gröbner basis techniques. Moreover, for the special case of a polynomial map from C n to C n where the polynomials are at most quadratic, we propose two criteria for non-injectivity based on the structure of the Jacobian matrix and requiring only basic symbolic computations.
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    An isomorphism theorem between the 7-adic integers and a ring associated with a hexagonal lattice (1991)
    Springer
    Applicable algebra in engineering, communication and computing 2 (1991), S. 105-118 
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    ISSN: 1432-0622
    Keywords: p-adic integers ; Hexagonal tilings ; Isomorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract The primary goal of this paper is to prove that a ring defined by L. Gibson and D. Lucas is isomorphic to the ring of 7-adic integers. The ring, denoted byR 2, arises naturally as an algebraic structure associated with a hexagonal lattice. The elements ofR 2 consist of all infinite sequences in ℤ/(7). The addition and multiplication operations are given in terms of remainder and carries tables. The Generalized Balanced Ternary, denoted byG, is the subring ofR 2 consisting of all the finite sequences ofR 2. IfI k ′ is the ideal ofG consisting of all those sequences whose firstk digits are zero, then the second goal of the paper is to show that the inverse limit ofG/I k ′ is also isomorphic to the 7-adic integers.
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    Polynomial description of binary linear codes and related properties (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 119-138 
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    ISSN: 1432-0622
    Keywords: Coding theory ; Finite fields ; Polynomials over finite fields
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    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract We introduce a description of everyk-dimensional binary linear code (without repetitions) by means of a polynomial overF 2 k and the trace function ofF 2 k overF 2. Several properties of parameters, weights, automorphism group and related cyclic codes are deduced. Special cases and a connection with algebraic curves over finite fields are also investigated.
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    Determining concepts by group membership (1991)
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    Applicable algebra in engineering, communication and computing 2 (1991), S. 139-146 
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    ISSN: 1432-0622
    Keywords: Abelian group ; Genetic algorithm ; Quotient group ; Relation ; Schema ; Subgroup
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract One contribution of this paper is an efficient algorithm for deciding membership in a subgroupH of an Abelian groupG whenG andH are in a special form. Our approach is particularly fast because calculations are postponed until needed, and because some decisions can be made based on the existence of certain objects without actually calculating them. This mathematical problem arises naturally in machine learning, and is particularly relevant to concept modeling. We use genetic algorithms as a nontrivial example of how concept formation may correspond to subgroup formation and to illustrate that analysis may reveal abstract concepts determined by group membership which are not initially apparent. This example forms another contribution of this paper; genetic search has not previously been framed within an algebraic context.
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    Experimental and numerical studies of weak blast waves in air (1991)
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    Shock waves 1 (1991), S. 111-119 
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    ISSN: 1432-2153
    Keywords: Blast wave ; N-wave ; Dispersed wave ; Random choice method ; Vibrational relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Effects of viscosity and vibrational nonequilibrium on the profile of a weak, spherical N-wave in air are experimentally and numerically studied. Weak blast waves were generated, in a quiescent air dome, by spark discharges and exploding wires and observed by high frequency response microphones over 40 meters. Some similarity relationships were obtained from the blast wave experiments. For observed N-waves having less than 100 Pa peak overpressure, the peak overpressure Δp f and the duration of the positive phaset d+ are found to vary with the radial distance from the sourcer as Δp f ∝r −1.38 andt d + ∝r 0.19, whilst the rise time of the blast wave Δt f linearly increases with distance. Similar trends were also found for the negative phase of the blast wave. Numerical simulations were carried out to compare with the blast wave data. The Navier-Stokes equations for spherical symmetric flows were solved by coupling with a relaxation equation for vibrational excitation of oxygen using the random choice method (RCM) adapted to supercomputing with an operator splitting technique. The resultant N-wave profiles are in good agreement with the experimental results. The numerical results clearly indicate that the wave-easing process due to the dispersive effect of vibrational relaxation plays a dominant role in determining the rise time of the N-wave.
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    Optimization of a pyrotechnic igniter with the release of reactive particles (1991)
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    Shock waves 1 (1991), S. 121-133 
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    ISSN: 1432-2153
    Keywords: Center-core igniter ; Reactive particles ; Internal ballistics ; flash tube
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract This paper deals with the effects of reactive particles on the performance of a pyrotechnic igniter. These particles are placed on the inner surface of a “flash tube”, released into the main flow of the gas and ignited by the passage of one of the two discontinuities (the shock wave or the contact surface). Two particle sizes have been studied (3μm and 10μm). It is shown that the best performance is achieved with small particles released into the flow by the shock wave. Another focal point of this study is the combining of two fundamentally different methods to calculate the two phase flow.
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    Boundary layer flows behind constant speed shock waves moving into a dusty gas (1991)
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    Shock waves 1 (1991), S. 135-144 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Laminar boundary layer flows behind constant speed shock waves moving into a dusty gas are analyzed numerically. The basic equations of two-phase flows are derived in shock fixed coordinates and solved by an implicit finite-difference method for the side wall boundary layer in a dusty gas shock tube. The development of the boundary layer and resulting velocity and temperature profiles, respectively, for the gas and particles are given from the shock front to far downstream. The effects of diaphragm pressure ratio, mass loading ratio of particles and particle size upon the flow properties are discussed in detail.
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    Anti-miss-shot control device for selective stone disintegration in extracorporeal shock wave lithotripsy (1991)
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    Shock waves 1 (1991), S. 145-148 
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    ISSN: 1432-2153
    Keywords: ESWL ; Shock wave ; Anti-miss-shot device ; Tissue injury
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    Topics: Physics , Technology
    Notes: Abstract A new device to prevent erroneously focused shock waves to the renal parenchyma during extracorporeal shock wave lithotripsy (ESWL) has been developed; an anti-miss-shot control device (AMCD) and experiments have been conducted to evaluate its effectiveness. For shock wave generation and stone localization, piezoceramic elements (PSE) and ultrasound localization, respectively were used. After stone localization, probing ultrasounds (PU) were emmitted from the PSE towards the focal region and the reflected sound levels (RSL) were monitored by the PSE which also functioned as a microphone. A direct hit by the PU to the stone or a miss was judged from the RSL, i.e. a high RSL indicates a direct hit and a low RSL indicates a miss. Shock waves were generated only when the RSL exceeded the level which indicated a direct hit. The experimental results showed that the injury to the renal parenchyma was decreased by using the AMCD. Clinical application of the AMCD is expected to increase the safety of ESWL.
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    Editorial (1991)
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    Shock waves 1 (1991), S. 1-1 
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    Experimental investigation of ram accelerator propulsion modes (1991)
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    Shock waves 1 (1991), S. 17-25 
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    ISSN: 1432-2153
    Keywords: Ram accelerator ; Ramjet-in-tube ; Detonation speed ; Transdetonative ; Superdetonative
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Experimental investigations on the propulsive modes of the ram accelerator are reviewed in this paper. The ram accelerator is a ramjet-in-tube projectile accelerator whose principle of operation is similar to that of a supersonic air-breathing ramjet. The projectile resembles the centerbody of a ramjet and travels through a stationary tube filled with a premixed gaseous fuel and oxidizer mixture. The combustion process travels with the projectile, generating a pressure distribution which produces forward thrust on the projectile. Several modes of ram accelerator operation are possible which are distinguished by their operating velocity range and the manner in which the combustion process is initiated and stabilized. Propulsive cycles utilizing subsonic, thermally choked combustion theoretically allow projectiles to be accelerated to the Chapman-Jouguet(C-J) detonation speed of a gaseous propellant mixture. In the superdetonative velocity range, the projectile is accelerated while always traveling faster than the C-J speed, and in the transdetonative regime (85–115 % of C-J speed) the projectile makes a smooth transition from a subdetonative to a superdetonative propulsive mode. This paper examines operation in these three regimes of flow using methane and ethylene based propellant mixtures in a 16 m long, 38 mm bore ram accelerator using 45–90 g projectiles at velocities up to 2500 m/s.
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    Numerical simulation for nonstationary Mach reflection of a shock wave: A kinetic-model approach (1991)
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    Shock waves 1 (1991), S. 43-49 
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    ISSN: 1432-2153
    Keywords: Shock wave ; Mach reflection ; Rarefied gas dynamics ; Kinetic-model ; Finite difference method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract A numerical simulation was performed for the process of formation of single Mach reflection on a wedge by solving a BGK type kinetic equation for the reduced distribution function with a finite difference scheme. The calculations were carried out for a shock Mach number 2.75 and wedge angle 25° in a monatomic gas, which corresponds to the conditions of single Mach reflection in the classical von Neumann theory. The calculations were performed for both diffuse and specular reflection of molecules at the wall surface. It is concluded that the diffuse reflection of molecules at the wall surface or the existence of the viscous or thermal layer is an essential factor for a nonstationary process at the initial stage of Mach reflection. Furthermore, the numerical results for diffuse reflection are found to simulate the experimental results very well, such as a transient process from regular reflection to Mach reflection along with shock propagation.
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    On flows behind shock waves reflected from a solid wall (1991)
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    Shock waves 1 (1991), S. 293-299 
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    ISSN: 1432-2153
    Keywords: Kinetic theory ; CFD ; Reflected shock wave
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The flow fields associated with the interaction of a normal shock wave with a plane wall kept at a constant temperature were studied based on kinetic theory which can describe appropriately the shock structure and its reflection process. With the use of a difference scheme, the time developments of the distributions of the fluid dynamic quantities (velocity, temperature, pressure and number density of the gas) were obtained numerically from the BGK model of the Boltzmann equation subject to the condition of diffusive-reflection at the wall for several cases of incident Mach number:M 1=1.2, 1.5, 2.0, 3.0, 4.0, 5.0 and 6.0. The reflection process of the shocks is shown explicitly together with the resulting formation of the flow fields as time goes on. The nonzero uniform velocity toward the wall occurring between the viscous boundary layer and the reflected shock wave is found to be fairly large, the magnitude of which is of the order of several percent of the velocity induced behind the incident shock, decreasing as the incident Mach number increases. It is also seen that a region of positive velocity (away from the wall) within the viscous boundary layer manifests itself in the immediate vicinity of the wall, which is distinct for larger incident Mach numbers. Some of the calculated density profiles are compared with available experimental data and also with numerical results based on the Navier-Stokes equations. The agreement between the three results is fairly good except in the region close to the wall, where the difference in the conditions of these studies and the inappropriateness of the Navier-Stokes equations manifest themselves greatly in the gas behavior.
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    Experimental study on spherically imploding detonation waves (1991)
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    Shock waves 1 (1991), S. 27-34 
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    ISSN: 1432-2153
    Keywords: Imploding detonation ; Spherical detonation ; Similarity laws
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Spherically imploding detonation waves propagating in a stoichiometric propane-oxygen mixture in a convergent hemispherical space having an innerdiameter of 800 mm were experimentally investigated with an intention to clarify the reason for the anomalous increase of the pressure and temperature behind the imploding detonation waves observed in a smaller vessel having an inner-diameter of 360 mm. The relations between the radial distance of the detonation front, the peak pressure, spectroscopic temperature at the imploding detonation front and those behind the shock waves reflected from the implosion focus show almost the same tendencies as in the smaller convergent space. The pressure as well as the temperature at the imploding detonation front increases, with the propagation of the implosion, more rapidly than theoretically estimated. The reason for it is attributed to the double imploding detonation waves.
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    Evidence for shock wave effect of meteoritic impact (1991)
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    Shock waves 1 (1991), S. 35-41 
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    ISSN: 1432-2153
    Keywords: Shock waves ; Meteoritic impact ; Hypervelocity impact ; K/T boundary
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract There is material evidence for the existence of shock waves generated by meteoritic impact. This is demonstrated by the pressure and temperature dependent formation processes that exist in the memory of constituent minerals. Stishovite of high-pressure type silica mineral can be observed to be a relict of the compression stage of shock impact. Almost all of the silica minerals evolved from shock impact phenomena are α-quartz crystals of a low-temperature type silica polymorph. By using precise measurements of cell parameters and the corresponding calculated density of the quartz crystal grains collected by an ultrasonic cutter method, shocked quartz grains can be interpreted as the principle relict of meteoritic impact from natural impact craters, artificial impact craters and Cretaceous-Tertiary (K/T) boundary samples.
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    Color schlieren methods in shock wave research (1991)
    Springer
    Shock waves 1 (1991), S. 51-63 
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    ISSN: 1432-2153
    Keywords: Flow visualization ; Color schlieren ; Shock wave interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Schlieren methods are widely known and well established to visualize refractive index variations in transparent media. The use of color allows one to obtain more data and previously inaccessible information from a picture taken with this technique. In general, a hue can be related to a certain strength or a certain direction of a refractive index gradient. While the first case essentially corresponds to the usual black- and-white system the latter correlation cannot be made adequately evident without the use of color. Two color schlieren techniques are presented here, which reach or even exceed the quality and sensitivity range of conventional black- and-white methods. Using a powerful short duration light source these methods are applied to visualize transient flow phenomena in a shock tube.
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    Announcements (1991)
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    Shock waves 1 (1991), S. 87-87 
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    Source: Springer Online Journal Archives 1860-2000
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    URL: http://dx.doi.org/10.1007/BF01414871
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    Computation of shock wave diffraction at a ninety degrees convex edge (1991)
    Springer
    Shock waves 1 (1991), S. 89-98 
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    ISSN: 1432-2153
    Keywords: Shock diffraction ; Finite difference scheme ; Compressible vortex
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract This paper presents a numerical study of shock wave diffraction at a sharp ninety degrees edge, using an explicit second-order Godunov-type Euler scheme based upon the solution of a generalized Riemann problem (GRP). The Euler computations produce flow separation very close to the diffraction edge, leading to a realistic development of the separated shear layer and subsequent vortex roll-up. The diffracted shock wave, and the secondary shock wave, are both reproduced well. In addition a pair of vortex shocks are shown to form, extending well into the vortex core.
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    A new method for manufacture of thin film heat flux gauges (1991)
    Springer
    Shock waves 1 (1991), S. 161-164 
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    ISSN: 1432-2153
    Keywords: Thin film flux gauge ; Heat flux measurement ; Shock tunnel instrumentation
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The manufacture of thin film gauges for measuring transient temperatures and heat fluxes is described. A new method of using ceramic substrates (ZrO2) with two sintered platinum wires is described. Examples of static and dynamic calibrations are given. Sample measurements in a shock tunnel are presented. The gauges show good mechanical strength and sensitivity.
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    Pressure and temperature history in diamond silicon mixtures during dynamic compaction (1991)
    Springer
    Shock waves 1 (1991), S. 165-167 
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    ISSN: 1432-2153
    Keywords: Dynamic compaction ; Diamond ; Shock in condensed matter ; Numerical simulation
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Diamond powders with silicon additives were shock compressed by using a flyer impact technique. Pressure and temperature histories in the powder mixtures were numerically simulated in order to determine the optimum experimental condition which resulted in the highest Vicker's hardness. This was found to be: an initial diamond particle size of 2–4μm at 7.2 % silicon by volume. The results of the simulations were consistent with the distribution of the microstructure and the microhardness in the compact.
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    Measurement of recombination rate parameters in nonequilibrium supersonic expansions of ionized argon and neon (1991)
    Springer
    Shock waves 1 (1991), S. 177-185 
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    ISSN: 1432-2153
    Keywords: Supersonic expansion ; Recombination rate Ionized flow
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Two wavelength interferometry techniques and a two dimensional Fourier transform analysis are used to produce contour maps of the heavy particle densities and ionization fractions for supersonic corner expansions of ionized argon and neon. A new phase unwrapping algorithm is employed to minimize noise problems previously encountered because of phase discontinuities associated with shock waves and flow luminosity. Determination of recombination rate coefficients is achieved through the measurement of gradients in the ionization fraction.
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    Numerical and analytical study of transverse supersonic flow over a flat cone (1991)
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    Shock waves 1 (1991), S. 197-203 
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    ISSN: 1432-2153
    Keywords: Cone ; Euler equation ; Mach reflection ; CFD ; Supersonic flow
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Quasisteady supersonic flow over a flat cone on a plane surface is studied. A formula is derived for the angle through which the flow lines turn at the cone. The results are used to justify the use of two-dimensional simulations of the flow. Peak pressures and total impulses are obtained numerically for various cone angles.
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    Technique for aerodynamic force measurement within milliseconds in shock tunnel (1991)
    Springer
    Shock waves 1 (1991), S. 223-232 
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    ISSN: 1432-2153
    Keywords: Force measurement ; Acceleration measurement ; Short-duration flow ; Shock tunnel
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract For aerodynamic force measurement in shock tunnels and similar short duration aerodynamic testing facilities we have developed a novel measurement technique. Its key feature is a mounting support, which releases the test model and grips it again after a free flight duration of about 10 milliseconds. The model is equipped with small accelerometers and may contain additional installations. The short free flight allows the use of thin wires because the model travels only a few millimeters during this time. Validation experiments with a cone-cylinder of known drag coefficient show good accuracy with a response time of about half a millisecond. Pitot pressure measurement and suitable data processing allow for direct evaluation of aerodynamic coefficients in slowly changing flow.
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    Analysis of the wave configuration resulting from the termination of an inverse Mach reflection (1991)
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    Shock waves 1 (1991), S. 237-241 
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    ISSN: 1432-2153
    Keywords: Shock wave reflections ; Inverse Mach reflection
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract An analytical model for solving the wave configuration which is formed when an inverse Mach reflection terminates after its triple point collides with the reflecting surface has been developed. The predictions of the model were compared with available experimental results and good agreement was obtained.
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    Experiments on the interaction of a pair of cylindrical weak blast waves in air (1991)
    Springer
    Shock waves 1 (1991), S. 275-284 
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    ISSN: 1432-2153
    Keywords: Blast waves ; Exploding wire ; Mach reflection ; CFD ; Similarity rule
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract This paper reports the results of experiments and computations on the interaction of a pair of cylindrical blast waves in air. The waves were generated by exploding wires, and both symmetrical and unsymmetrical interactions were observed. The experimental data includes schlieren photographs of the wave interactions, their radii, shock Mach number and pressure versus time, as well as various cross plots and data on the shock regular/irregular interaction transition condition. The flow fields were computed with the help of the “Total Variation Diminishing” (TVD) method, and appear to represent the experimental results reasonably well. Some attention is also given to the blast scaling laws of the type discussed by Sakurai (1965) and Oshima (1960).
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    A generalisation of the theory of geometrical shock dynamics (1991)
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    Shock waves 1 (1991), S. 251-273 
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    ISSN: 1432-2153
    Keywords: Geometrical shock dynamics ; A-M relation ; Shock diffraction ; Underwater blast
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The study of the propagation of a shock down a tube of slowly varying cross sectional area has proved to be most valuable in understanding the dynamics of shocks. A particular culmination of this work has been the theory of geometrical shock dynamics due to Whitham (1957, 1959). In this theory the motion of a shock may be approximately computed independently of a determination of the flow field behind the shock. In this paper the propagation of a shock down such a tube is reconsidered. It is found that the motion of the shock is described by an infinite sequence of ordinary differential equations. Each equation is coupled to all of its predecessors but only to its immediate successor, a feature which allows the system to be closed by truncation. Of particular relevance is the demonstration that truncation at the first equation in the sequence yields the A-M relation that is the basis for Whitham's highly successful theory. Truncation at the second equation yields the next level of approximation. The equations so obtained are investigated with analytic solutions being found in the strong shock limit for the propagation of cylindrical and spherical shock waves. Implementation of the theory in the numerical scheme of geometrical shock dynamics allows the computation of shock motion in more general geometries. In particular, investigation of shock diffraction by convex corners of large angular deviation successfully yields the observed inflection point in the shock shape near the wall. The theory developed allows account to be taken of non-uniform flow conditions behind the shock. This feature is of particular interest in consideration of underwater blast waves in which case the flow behind the shock decays approximately exponentially. Application of the ideas developed here provides an excellent description of this phenomenon.
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    Shock wave diffraction over a 90 degree sharp corner — Posters presented at 18th ISSW (1991)
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    Shock waves 1 (1991), S. 301-312 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract A special poster session was run during the 18th International Symposium on Shock Waves, held on July 21 – 26, 1991, in Sendai, Japan. The purpose of this session was to compare various CFD schemes which are useful for simulating shock wave phenomena. A 2-D planar shock wave diffraction over a 90 degree sharp corner was selected as a bench mark problem. The problem specification and the output format are described below. Experimental outputs for the close flow conditions to the computational ones were also called for. Twenty six poster presentations were made at this session and the majority of the posters reflected a standard of excellence that warrants publication in the Shock Waves journal. Therefore these results are reproduced here. However, since there is a limit on the available page numbers, it was not possible to publish all the posters that were presented at the special poster session. We express our sincere thanks to all the participants in this session.
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    The use of Hugoniot analysis for the propagation of vapor explosion waves (1991)
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    Shock waves 1 (1991), S. 99-110 
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    ISSN: 1432-2153
    Keywords: Vapor explosions ; Hugoniot analysis ; Thermal detonations
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Experimental studies have shown that a mixture of molten metal and water can support the propagation of a quasi-steady vapor explosion wave. Analysis of steadily propagating vapor explosion waves has been carried out by applying the one-dimensional conservation laws of mass, momentum and energy and appropriate equations of state to a homogeneous mixture of molten tin, water and steam. The effects of void fraction, melt/water volume fraction and melt temperature on the Hugoniot curves have been considered. For low temperature melts, the Hugoniot curve lies partially inside the saturation dome and a Chapman-Jouguet (CJ) detonation point occurs only for low void fractions. For high melt temperatures, the downstream states lie entirely outside the saturation region. Increasing the volatility of the coolant or the addition of chemical reactions increases the predicted CJ detonation pressure and velocity. CJ deflagration solutions were obtained in all cases. The existence of a CJ detonation or CJ deflagration for a multiphase fuel-coolant mixture has yet to be substantiated experimentally and nonequilibrium effects may play a role in the divergence between theory and experiments.
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    Shock and shear initiation of explosive (1991)
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    Shock waves 1 (1991), S. 285-292 
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    ISSN: 1432-2153
    Keywords: Explosive ; Initiation ; Shock ; Shear ; Impact ; Detonation
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Three reaction-rate models, Forest Fire, Arrhenius and a combined Forest Fire and Arrhenius, are incorporated in the hydrocode DEFEL. Simulations with this code for PBX-9404 explosive for bare and covered explosives by fragment impact are made. Results confirm the well-known shock-initiation theory for bare explosives. For explosives with a thick cover plate, code results show macroscopic shear initiation, as proposed by Howe (1985) and Frey (1981).
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    The discovery of the Mach reflection effect and its demonstration in an auditorium (1991)
    Springer
    Shock waves 1 (1991), S. 3-15 
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    ISSN: 1432-2153
    Keywords: Ernst Mach ; History of shock wave research ; Mach reflection ; Hydraulic analogy
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract This paper examines the historical background leading to the discovery of the Mach reflection effect and applies original documents from Mach's residue which are kept in the archives of the Ernst-Mach-Institut in Freiburg. Two experimental setups for the generation and demonstration of the Mach reflection effect, incorporating an overhead projector, are described: (a) Mach's historic mechanical shock wave reflection and interaction experiments with soot covered glass plates, performed in 1875. The Mach triple points sharply erase the soot which results in a residual picture of funnel-shaped V-formations. The head-on collision of two shock waves is marked as a narrow line of piled-up soot. (b) CalTech's hydraulic jump reflection experiments in a shallow ripple tank, performed during World War II. Regular reflection and its transition into a Mach reflection wave. Using a slightly inclined tank and providing a “shoreline” in the middle of the tank, Mach stem propagation slows down to zero when hitting the shore line and, therefore, can be observed “live” without the use of a slow motion technique.
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    Reflection of shock wave from a compression corner in a particle-laden gas region (1991)
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    Shock waves 1 (1991), S. 65-73 
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    Keywords: Two phase compressible flow ; Compression corner ; Shock wave diffraction ; TVD scheme ; Particle parameters
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract We investigated in this paper the progression of a shock-wave reflected from a compression corner in a particle-laden gas medium using a TVD class numerical technique and a MacCormack scheme. For a gas-only flow, the numerical results agreed well with the existing experimental data, suggesting that the gas phase is correctively solved. The effect of particle size and mass fraction ratio is investigated for a dilute gas-particle flow. It has been shown that the shock-wave diffraction and the flow configuration after the shock can become remarkably different from the gas-only flow depending on the particle parameters. Relaxation phenomenon due to the momentum drag and the heat exchange between the gas and the particle phases is explained.
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    Over forty years of continuous research at UTIAS on nonstationary flows and shock waves (1991)
    Springer
    Shock waves 1 (1991), S. 75-86 
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    ISSN: 1432-2153
    Keywords: Shock wave ; Nonstationary flow
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Analytical and experimental research on non-stationary shock waves, rarefaction waves and contact surfaces has been conducted continuously at UTIAS since its inception in 1948. Some unique facilities were used to study the properties of planar, cylindrical and spherical shock waves and their interactions. Investigations were also performed on shock-wave structure and boundary layers in ionizing argon, water-vapour condensation in rarefaction waves, magnetogasdynamic flows, and the regions of regular and various types of Mach reflections of oblique shock waves. Explosively-driven implosions have been employed as drivers for projectile launchers and shock tubes, and as a means of producing industrial-type diamonds from graphite, and fusion plasmas in deuterium. The effects of sonic-boom on humans, animals and structures have also formed an important part of the investigations. More recently, interest has focussed on shock waves in dusty gases, the viscous and vibrational structure of weak spherical blast waves in air, and oblique shock-wave reflections. In all of these studies instrumentation and computational methods have played a very important role. A brief survey of this work is given herein and in more detail in the relevant references.
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    Stability of converging cylindrical shock waves (1991)
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    Shock waves 1 (1991), S. 149-160 
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    ISSN: 1432-2153
    Keywords: Converging cylindrical shock wave ; Stability ; Holographic interferometry ; TVD finite difference scheme
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract An experimental and numerical study was made of converging cylindrical shock waves. The goal of the present study was to clarify the movement and instability of the converging cylindrical shock waves. Experiments were conducted in an annular shock tube of 230 mm o.d. and 210 mm i.d. connected to a cylindrical test section of 210 mm diameter. Double exposure holographic interferometry was used to visualize the converging cylindrical shock waves. Incident shock Mach numbers ranged between 1.1 and 2.0 in air. A numerical simulation was conducted using the TVD finite difference scheme. It was found in the experiments that although the initial shock wave configuration looked cylindrical, it was gradually deformed with propagation towards the center and finally showed mode-four instability. This is attributable to the existence of initial disturbances which were introduced by the struts which supported the inner tube of the annular shock tube. This trend was significant for stronger shock waves indicating that at the last stage of shock wave convergence the initial perturbations of the converging cylindrical shock wave were amplified to form the triple point of Mach reflection. The numerical results correctly predicted the experimental trend.
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    Monte Carlo analysis of dissociation and recombination behind strong shock waves in nitrogen (1991)
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    Shock waves 1 (1991), S. 169-176 
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    ISSN: 1432-2153
    Keywords: Shock Waves ; Dissociation ; Recombination ; Monte Carlo simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Computations are presented for the relaxation zone behind strong, one-dimensional shock waves in nitrogen. The analysis is performed with the direct simulation Monte Carlo method (DSMC). The DSMC code is vectorized for efficient use on a supercomputer. The code simulates translational, rotational and vibrational energy exchange and dissociative and recombinative chemical reactions. A new model is proposed for the treatment of three body recombination collisions in the DSMC technique which usually simulates binary collision events. The new model represents improvement over previous models in that it can be employed with a large range of chemical rate data, does not introduce into the flow field troublesome pairs of atoms which may recombine upon further collision (pseudo-particles) and is compatible with the vectorized code. The computational results are compared with existing experimental data. It is shown that the derivation of chemical rate coefficients must account for the degree of vibrational nonequilibrium in the flow. A nonequilibrium chemistry model is employed together with equilibrium rate data to compute successfully the flow in several different nitrogen shock waves.
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    A universal cubic interpolation solver for compressible and incompressible fluids (1991)
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    Shock waves 1 (1991), S. 187-195 
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    ISSN: 1432-2153
    Keywords: Computational method ; Compressible fluid ; Incompressible fluid ; Navier-Stokes equation
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract A universal numerical solver commonly usable for compressible and incompressible fluids is proposed. The method approaches the MAC algorithm at very high sound speed and continuously approaches the algorithm for compressible fluid with decreasing sound speed. The advection term is treated by the CIP algorithm which was previously proposed. A single program is applied to one- and two-dimensional shock-tube problems, and two-dimensional liquid flow inside a cavity at high Reynolds number.
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    Shock-wave equation-of-state studies at Los Alamos (1991)
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    Shock waves 1 (1991), S. 213-222 
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    ISSN: 1432-2153
    Keywords: Equation of State ; Hugoniot ; Shock waves in condensed matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract A history of the shock-wave equation-of-state (EOS) studies at Los Alamos is given. Particular emphasis is placed on the pioneering research in the 1950s where many of the experimental techniques and methods of analysis were developed, which we now take for granted. A brief review of shock-wave physics is given, which illustrates important hydrodynamic and thermodynamic concepts. Recent studies on the EOS of Ti are presented with emphasis on theα-to-ω phase transition. VISAR wave profiles for polycrystalline Ni and singlecrystal Ni are presented to determine the strengths of these materials under pressure. Low-density polystyrene foam Hugoniot experiments are described and results analyzed.
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    The reflected pressure field in the interaction of weak shock waves with a compressible foam (1991)
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    Shock waves 1 (1991), S. 205-211 
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    ISSN: 1432-2153
    Keywords: Shock wave reflection ; Foam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract This paper deals with the waves that are reflected from slabs of porous compressible foam attached to a rigid wall when impacted by a weak shock wave. The interest is in establishing possible attenuation of the pressure field after a shock or blast wave has struck the surface. Foam densities from 14 to 38 kg/m3 were tested over a range of shock wave Mach numbers less than 1.4. It is shown that the initial reflected shock wave strength is accurately predicted by the pseudo-gas model of Gelfand et al. (1983), with a pressure ratio of approximately 80% of the value for reflection off a rigid wall. Evidence is presented of gas entering the foam during the early stages of the process. A second wave emerges from the foam at a later stage and is separated from the first by a region of constant velocity and pressure. This second wave is not a shock wave but a compression front of significant thickness, which emerges from the foam earlier than predicted by the pseudo-gas model. Analysis of the origin of this wave points to much more complex flows within the foam than previously assumed, particularly in an apparent decrease in average wave front speed as the foam is compressed. It is shown that the pressure ratio across both these waves taken together is slightly higher than that for reflection off a rigid wall. In some cases this compression wave train is followed by a weak expansion wave.
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    A free-flight experiment of projectiles ranging from high subsonic to high supersonic Mach numbers (1991)
    Springer
    Shock waves 1 (1991), S. 233-236 
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    ISSN: 1432-2153
    Keywords: Free-flight range ; High speed aerodynamics
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract This paper reports a preliminary experiment with a free-flight range which was designed to be able to be driven by means of a sort of fast-acting valve. The notable characteristics pertinent to this type of range is the pliancy of operation and also the wide coverage of flight speed from the high subsonic to the high supersonic range. For both spherical and vehicle models, flight tests were conducted with shadowgraph observations and flight speed measurements in order to examine the capability of this type of facility.
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    Least energy as a criterion for transition between regular and Mach reflection (1991)
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    Shock waves 1 (1991), S. 243-249 
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    ISSN: 1432-2153
    Keywords: Shock waves ; Regular reflection ; Mach reflection ; Transition criterion ; Least energy
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract A new criterion is suggested to define the point of transition between regular and Mach reflection. The suggested criterion is based on the natural tendency of a physical system to minimize its energy. The increases of the specific energy behind the reflected shock of a regular reflection and behind the Mach stem of a Mach reflection are calculated. It is hypothesized that the type of reflection that will occur is that which produces the smaller change of specific energy. The transition angles predicted using this criterion show better agreement with experimental results than those predicted using the detachment criterion for incident shock waves with Mach numbers between 1.1 and 2.0.
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    Effect of bias and temperature on the bulk and surface properties of gold-containing plasma-polymerized fluorocarbons (1991)
    Springer
    Plasma chemistry and plasma processing 11 (1991), S. 1-13 
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    ISSN: 1572-8986
    Keywords: Composite films ; plasma polymerization ; RF sputtering ; fluorocarbons ; gold clusters ; chemical structure ; optical properties ; aging ; contact angle hysterisis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Gold-containing plasma-polymerized fluorocarbon thin films have been deposited in an RF glow discharge fed with hexafluoroethane, while a gold target was simultaneously sputtered. Tile temperatureT s and RF-induced biasU s of a third electrode, used as a substrate holder, were separately varied. The influence ofT s andU s on the plasma and file lihn characteristics were individually studied using actinometric optical emission spectroscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, and measurements of optical transmission and surface contact angles. IncreasingU s (up to −200 V) andT s (up to 90°C) resulted in similar effects, namely a higher degree of cross-linking, higher gold concentration, better film stability with time, and increased wettability. A key role of the energy flux of particles impinging on the growing surface has been shown to account far the experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01447031
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  • 98
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    Formation of aluminum nitrides in thermal plasmas (1991)
    Springer
    Plasma chemistry and plasma processing 11 (1991), S. 41-56 
    Details
    ISSN: 1572-8986
    Keywords: Thermal plasma synthesis ; aluminum nitride ; aluminum anode ; experimental
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Aluminum nitride has been synthesized by evaporation of the aluminum anode of a free-burning atmospheric-pressure nitrogen arc. About 40% of the product was collected in the form of highly oriented polycrystalline aluminum nitride (from the gaseous phase) with a high deposition rate (≈ 1 μm/s) and very low oxygen content (0.34%). The rest was deposited on the reactor walls as an ultrafine powder with an average particle diameter of 300 Å. Destructive and nondestructive tests on the powder and crystals were carried out to determine the morphology and purity of the materials. The impact of other gases on the AlN formation has been studied. The probable mechanism in the AlN crystal growth is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01447033
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  • 99
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    Optical emission spectroscopy of electron-cyclotron-resonance-heated helium mirror plasmas (1991)
    Springer
    Plasma chemistry and plasma processing 11 (1991), S. 15-39 
    Details
    ISSN: 1572-8986
    Keywords: Emission spectroscopy ; helium ; ECR mirror plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In this experiment emission spectroscopy in the 3000–5000 Å range has been utilized to determine the electron temperature (15–60 eV) and ion density (2–5 x 1011 cm−3) of helium plasmas produced by the Michigan mirror machine(1) (MIMI). The plasma is generated and heated by whistler-mode electron-cyclotron resonance (ECR) waves at 7.43 GHz with 400–900 W power in 80-ms-long pulses. Gas fueling is provided at the midplane region by a leak valve with a range in pressure of 3 x 10 to 2 x 104 Torr. Emission line intensities are interpreted using a model of the important collisional and radiative processes occurring in the plasma. The model examines secondary processes such as radiation trapping, excitation transfer between levels of the carne principle quantum number, and excitation front metastable states for plasmas in the parameter range of MIMI (n c = 1−6 x 1011 cm−3). Front the analysis of line intensity ratios for neutral helium, the electron temperature is measured and its dependence upon the gas pressure and microwave power is determined. These temperatures agree with those obtained by Langmuir probe measurements. Art analysis of the line intensity ratio between singly ionized helium and neutral helium yields a measurement of the ion density which is in good agreement with electron density measurements made by a microwave interferometer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01447032
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  • 100
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    Electronic Resource
    Heat transfer from a transferred-arc plasma to a cylindrical enclosure (1991)
    Springer
    Plasma chemistry and plasma processing 11 (1991), S. 57-79 
    Details
    ISSN: 1572-8986
    Keywords: Thermal plasmas ; transferred arc ; plasma reactor ; radiated power ; heat transfer to enclosure ; voltage gradient ; electric field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Hear-transfer rates from an axially enclosed transferred arc to a surrounding water-cooled cylindrical sleeve, 15 cm high, were measured. The arc (argon or nitrogen) was struck between a movable cathode within the sleeve and a bath of molten copper below the sleeve, serving as anode. The distance from the bottom of the sleeve to the surface of the molten copper (L o) was constant. Variables studied were the diameterD of the sleeve (5, 7.5. and 10 cm), the length of the arc within the sleeveL (5, 10, and 15 cm), the currentI (200, 250, and 300 A) and a tangential flow of gas or vortex within the sleeve (0, ?0, and 50 liters/min). The total power transferred to the sleeve,P s was measured caloronetrically and was the sure ofP r the effective power radiated by the arc of lengthL within the sleeve.P a, the power radiated into the sleeve from the arc of length Lo below the sleeve, andP o , the power radiated from the melt surface (a constant of small value), minusP a , the power lost by convection from the sleeve (negligible, except for a strong vortex). BothP r andP o were found to be equal to the product of the Joule heat released within their respective arc lengths, IVgL and IVg0L0 (where Vg and Vg0 are the voltage gradients), and dimenonless efliciency factors, ηr and η0. which are functions ofL/D andL 0 /D, respectively, for each gas, regardless of the geometry of the sleeve, the current, and the strength of the vortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01447034
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