bluuebunny/crossref_metadata_2025 huggingface dataset:
Quadraturinterferometer mit automatischer Fokussierung
Authors: Gollwitzer Andreas , Fischerauer Gerhard
Published: September 2010

Oberflächenschwingungen kleiner Amplitude werden häufig interferometrisch gemessen. Um zusätzlich eine hohe örtliche Auflösung zu erreichen, muss der Laserstrahl mit einer stark vergrößernden Linse auf die Oberfläche fokussiert werden. Wegen der kleinen Schärfentiefe einer solchen Linse muss der Abstand zur Oberfläche genau eingehalten werden. Zur Unterdrückung von Störeinflüssen wie der ortsabhängigen Reflektivität der vermessenen Oberfläche und zur Extraktion der absoluten Schwingungsamplitude benutzen wir einen homodynen Aufbau mit zusätzlicher Pfadlängenmodulation. Die Messempfindlichkeit wurde dabei durch die Quadraturinterferometrie, das heißt die zeitsynchrone Erfassung der Intensitäten durch zwei Fotodioden, verbessert. Wir zeigen außerdem einen Signalverarbeitungsalgorithmus, der zur Regelung des Abstands zwischen Linse und Messoberfläche benutzt werden kann. Dies gewährleistet, dass der Laserstrahl optimal auf die Oberfläche fokussiert wird und führt zu einem insgesamt hohen Signal-zu-Rausch-Verhältnis.
Raman-Mikrospektrometer zur Untersuchung biologischer Proben
Authors: Bolwien Carsten , Sulz Gerd
Published: September 2010

Die Mikro-Ramanspektroskopie ermöglicht die schnelle und zerstörungsfreie Identifikation und Charakterisierung von biologischen Proben wie Mikroorganismen und Zellen auf der Einzelzellebene. Im Folgenden stellen wir ein flexibles Raman-Messsystem auf der Basis eines inversen Forschungsmikroskops vor, das neben einer komfortablen manuellen Bedienung die schnelle Entwicklung von skriptgesteuerten automatisierten Abläufen erlaubt.
Minimal changes in environmental temperature result in a significant increase in energy expenditure and changes in the hormonal homeostasis in healthy adults
Authors: Celi Francesco S , Brychta Robert J , Linderman Joyce D , Butler Peter W , Alberobello Anna Teresa , Smith Sheila , Courville Amber B , Lai Edwin W , Costello Rene , Skarulis Monica C , Csako Gyorgy , Remaley Alan , Pacak Karel , Chen Kong Y
Published: September 2010

Objective

Resting energy expenditure (EE) is a major contributor to the total EE and thus plays an important role in body weight regulation. Adaptive thermogenesis is a major component of EE in rodents, but little is known on the effects of exposure of humans to mild and sustainable reduction in environmental temperature.

Design

To characterize the dynamic changes in continuously measured resting EE, substrate utilization, and hormonal axes simultaneously in response to mild reduction in environmental temperature, we performed a cross-over intervention.

Methods

Twenty-five volunteers underwent two 12-h recordings of EE in whole room indirect calorimeters at 24 and 19 °C with simultaneous measurement of spontaneous movements and hormonal axes.

Results

Exposure to 19 °C resulted in an increase in plasma and urine norepinephrine levels (P<0.0001), and a 5.96% (P<0.001) increase in EE without significant changes in spontaneous physical activity. Exposure to the lower temperature resulted in a significant increase in free fatty acid levels (P<0.01), fasting insulin levels (P<0.05), and a marginal decrease in postprandial glucose levels. A small but significant (P<0.002) increase in serum free thyroxine and urinary free cortisol (P<0.05) was observed at 19 °C.

Conclusions

Our observations indicate that exposure to 19 °C, a mild and tolerable cold temperature, results in a predictable increase in EE driven by a sustained rise in catecholamine and the activation of counter-regulatory mechanisms.
Prostaglandin F2α (PGF2α) stimulates PTGS2 expression and PGF2α synthesis through NFKB activation via reactive oxygen species in the corpus luteum of pseudopregnant rats
Authors: Taniguchi Ken , Matsuoka Aki , Kizuka Fumie , Lee Lifa , Tamura Isao , Maekawa Ryo , Asada Hiromi , Taketani Toshiaki , Tamura Hiroshi , Sugino Norihiro
Published: September 2010

This study was undertaken to investigate how prostaglandin F2α(PGF2α) increases PGF2αsynthesis and PTGS2 expression in the corpus luteum of pseudopregnant rats. We further investigated the molecular mechanism by which PGF2αstimulates PTGS2 expression. PGF2α(3 mg/kg) or phosphate buffer as a control was injected s.c. on day 7 of pseudopregnancy.Ptgs2mRNA expression and PGF2αconcentrations in the corpus luteum were measured at 2, 6, and 24 h after PGF2αinjection. PGF2αsignificantly increasedPtgs2mRNA expression at 2 h and luteal PGF2αconcentrations at 24 h. PGF2αsignificantly decreased serum progesterone levels at all of the times studied. Simultaneous administration of a selective PTGS2 inhibitor (NS-398, 10 mg/kg) completely abolished the increase in luteal PGF2αconcentrations induced by PGF2α. PGF2αincreased NFKB p65 protein expression in the nucleus of luteal cells 30 min after PGF2αinjection, and electrophoretic mobility shift assay revealed that PGF2αincreased binding activities of NFKB to the NFKB consensus sequence of thePtgs2gene promoter. Simultaneous administration of both superoxide dismutase and catalase to scavenge reactive oxygen species (ROS) inhibited the increases of nuclear NFKB p65 protein expression, lipid peroxide levels, andPtgs2mRNA expression induced by PGF2α. In conclusion, PGF2αstimulatesPtgs2mRNA expression and PGF2αsynthesis through NFKB activation via ROS in the corpus luteum of pseudopregnant rats.
Epidermal growth factor receptor kinase activity is required for gap junction closure and for part of the decrease in ovarian follicle cGMP in response to LH
Authors: Norris Rachael P , Freudzon Marina , Nikolaev Viacheslav O , Jaffe Laurinda A
Published: September 2010

The meiotic cell cycle in mouse oocytes is arrested in prophase, and then restarted when LH acts on the surrounding granulosa cells. The granulosa cells keep meiosis arrested by providing a source of cGMP that diffuses into the oocyte through gap junctions, and LH restarts the cell cycle by closing the junctions and by decreasing granulosa cell cGMP, thus lowering oocyte cGMP. Epidermal growth factor receptor (EGFR) activation is an essential step in triggering LH-induced meiotic resumption, but its relationship to the cGMP decrease in the follicle is incompletely understood, and its possible function in causing gap junction closure has not been investigated. Here, we use EGFR agonists (epiregulin and amphiregulin) and an EGFR kinase inhibitor (AG1478) to study the function of the EGFR in the signaling pathways leading to the release of oocytes from prophase arrest. Our results indicate that the EGFR kinase contributes to LH-induced meiotic resumption in two different ways. First, it is required for gap junction closure. Second, it is required for an essential component of the decrease in follicle cGMP. Our data show that the EGFR kinase-dependent component of the cGMP decrease is required for LH-induced meiotic resumption, but they also indicate that an as yet unidentified pathway accounts for a large part of the cGMP decrease.
Practice of treatment restriction in Hungarian intensive care units
Authors: Zubek László , Szabó Léna , Gál János , Öllős Ádám , Élő Gábor
Published: September 2010

Az életvégi döntések az intenzív osztályokon kezelt betegek többségét érintik, ezért fontos ezen döntések hazai és külföldi gyakorlatának megismerése, valamint harmonizációja az etikai irányelvekkel és a jogi szabályozással.
Célkitűzés:
A hazai intenzív terapeuták életvégi döntésekkel (kezelés meg nem kezdése, kezeléskorlátozás, haldoklási folyamat megrövidítése) kapcsolatos szokásainak felmérése és összehasonlítása nemzetközi adatokkal. Kutatásuk távlati célja, hogy az intenzív terapeuták munkájukat eredményesen, jogszerűen és a betegekkel, illetve hozzátartozóikkal egyetértésben végezhessék.
Módszer:
Magyarországon 2007–2008-ban felmérést végeztek egy kérdőív segítségével az intenzív terapeuták körében. A kérdőíveket elektronikus formában juttatták el a Magyar Aneszteziológiai és Intenzív Terápiás Társaság 743 regisztrált tagjának, és visszaérkezésük után feldolgozták őket a teljes anonimitás megőrzése mellett. A 103 választ statisztikailag elemezték, és összehasonlították más európai országok adataival.
Eredmények:
A válaszokból kiderült, hogy a hazai intenzíves orvosok gyakorlata nagyon paternalisztikus. Az intenzíves orvosok döntéseiket általában egyedül hozzák meg (3,75/5 pont), kevésbé veszik figyelembe a cselekvőképes betegek (2,57/5 pont) vagy közeli hozzátartozóik (2,14/5 pont) illetve az ápolószemélyzet véleményét (2,37/5 pont). A terápia meg nem kezdését preferálják a kezelés visszavonásával szemben. Ez a gyakorlat a tévedés jelentős veszélyét hordozza magában, és emberéletekbe kerülhet a gyors döntéshozatal során. A válaszadók becslései alapján az életvégi döntések gyakorisága 3,7–9,1%, ami kisebb, mint más európai országokban.
Következtetések:
Az első magyarországi felmérés alapján a betegjogok kiterjesztése szükséges hazánkban. Teret kell adni az önrendelkezés jobb érvényesülésének az életvégi döntésekben, valamint javítani kell az orvosi gyakorlat jogszerűségét. Orv. Hetil., 2010, 38, 1530–1536.
Sintomas psicóticos e cognitivos associados à busca de tratamento por dependentes de substâncias: um estudo qualitativo
Authors: Fontanella Bruno José Barcellos
Published: September 2010

Há algumas décadas, busca-se compreender melhor o processo subjacente ao comportamento de procura de tratamento por usuários que fazem uso nocivo ou são dependentes de substâncias psicoativas. Os modelos atualmente propostos baseiam-se principalmente na análise epidemiológica de certas características individuais quanto ao poder que têm de influenciar esse comportamento de disposição para tratamento. OBJETIVOS: Interpretar e compreender possíveis significados pessoais associados a alterações psicopatológicas, sobre como podem se relacionar à procura de tratamento, na visão dos próprios pacientes. MÉTODO: Pesquisa qualitativa com entrevistas semidirigidas com amostra intencional de 13 dependentes de substâncias que procuraram tratamento. RESULTADOS: Houve relatos espontâneos de alterações de forma, curso e conteúdo de pensamento e juízo de realidade, alterações de sensopercepção, de atenção, memória e linguagem. Os membros da amostra pareceram relacioná-las à motivação para tratamento. Os dados foram interpretados considerando o contexto psicocultural dos entrevistados e seus quadros clínicos de síndrome de dependência, de abstinência e de comorbidade. CONCLUSÕES: Pesquisas qualitativas contribuem para aprimorar os modelos explicativos sobre procura de tratamento por dependentes de substâncias. Investigar clinicamente alterações psicopatológicas parece poder contribuir para motivar pacientes para tratamentos específicos do uso disfuncional de substâncias.
Simultaneous Premaxillary Repositioning and Cheiloplasty in Adult Patients with Unrepaired Bilateral Cleft Lip and Palate
Authors: Lee Ui-Lyong , Cho Jun-Bum , Choung Pill-Hoon
Published: September 2010

Primary cheiloplasty in adult patients with unrepaired complete bilateral cleft lip and palate is quite challenging due to severe premaxillary anterior projection. To get the best repair results, the author carried out repositioning of the premaxilla and repair of the lip deformity in a single stage. Positive results for the primary lip repair and appropriate repositioning of the premaxilla were achieved. No avascular necrosis of the premaxilla was observed. Repositioning of the premaxilla and repair of the lip deformity in a single operation appears to be a reliable method for treating adult patients with previously unrepaired or poorly repaired bilateral cleft lip and palate.
A Case Report of a Patient with Cleft Palate Carrying the Risk of Tetraplegia
Authors: Isik Daghan , Guner Savas , Avcu Serhat , Goktas Ugur , Atik Bekir
Published: September 2010

Spondyloepiphyseal dysplasia congenita (SEDC) is an inherited disorder of bone growth that results in short-trunk dwarfism, skeletal abnormalities, disorders in vision and hearing, atlanto-axial instability, and cleft palate. This important anomaly of the cervical vertebrae carries the risk of tetraplegia during cleft palate operations. In this case report, we discuss a case of spondyloepiphyseal dysplasia congenita, the perioperative and postoperative measures, and the risk of tetraplegia.
Phenol biodegradation and simultaneous nitrogen removal using a carbon fiber felt biofilm reactor
Authors: Chen Yingwen , Liu Mingqing , Xu Fuyuan , Zhu Shemin , Shen Shubao
Published: September 2010

Phenol biodegradation and its effect on the biological nitrogen removal were studied in a biofilm reactor (15 L) packed with carbon fiber felt carriers. Meanwhile, the effects of the effluent internal recirculation ratios (0, 100% and 200%) and the air flow rates (0.42, 0.83, 1.46, 2.08 and 3.33 L/min) on the performance of system were tested. The system exhibited an excellent capacity for simultaneous phenol biodegradation and biological nitrogen removal without effluent internal recirculation when the influent phenol concentration was as high as 1,000 mg/L (organic loading rate of 9.54 kg COD/(m3 d)) and the ammonia loading rates of 0.20, 0.32 and 0.40 kg NH4+-N/(m3 d) respectively). Nitrification process was inhibited at the influent phenol concentration of 1,200–1,300 mg/L with average ammonia removal efficiency of 26.9%. The nitrifiers activity could be recovered in the perfect performance of system for phenol biodegradation. However, denitrification was not affected by the process of phenol biodegradation. In the air flow rates of 1.46–2.08 L/min, the system manifested stable operation for phenol elimination and nitrogen removal. Dissolved oxygen (DO) distributions in carbon fiber felt biofilm descended gradually from the external to the center of the carrier in all air flow rates.
Behind International Rankings of Infant Mortality: How the United States Compares with Europe
Authors: MacDorman Marian F. , Mathews T. J.
Published: September 2010

In 2005, the United States ranked 30th in the world in infant mortality. Infant mortality rates for preterm (<37 weeks of gestation) infants are lower in the United States than in most European countries; however, infant mortality rates for infants born at 37 or more weeks of gestation are higher in the United States than in most European countries. One in 8 births in the United States were preterm in 2005, compared with 1 in 18 births in Ireland and Finland, and 1 in 16 in France and Sweden. If the United States had Sweden's distribution of births by gestational age, nearly 8,000 infant deaths in the United States would be averted each year, and the U.S. infant mortality rate would be one-third lower. The main cause of the United States' high infant mortality rate when compared with Europe is the very high percentage of preterm births in the United States, the period when infant mortality is greatest.
A Framework for Financial Reporting Standards: Issues and a Suggested Model
Authors:   American Accounting Association’s Financial Accounting Standards Committee (AAA FASC), Ohlson James A. , Penman Stephen , Bloomfield Robert , Christensen Theodore E. , Colson Robert , Jamal Karim , Moehrle Stephen , Previts Gary , Stober Thomas , Sunder Shyam , Watts Ross L.
Published: September 2010

SYNOPSIS: This paper addresses the issues that confront the FASB and IASB in developing a new conceptual framework document. First, we suggest characteristics that a conceptual framework ought to exhibit. Most of these suggestions are based on our critique of the existing framework and the FASB-IASB work in progress. Second, we present a model framework that exhibits these characteristics. We emphasize up front that this framework is quite explicit. It goes to the heart of what a framework document should do: it places specific restrictions on what constitutes admissible accounting standards. The purpose of our effort is to stimulate broad discussion of alternative approaches to foundational documents and to offer a specific example of such an alternative approach.
The Contribution of Philip W. Bell to Accounting Thought
Authors: Peasnell Kenneth , Whittington Geoffrey
Published: September 2010

SYNOPSIS: This paper reviews the contribution of the late Philip Bell to accounting thought. He is best known for his joint work with Edgar O. Edwards, The Theory and Measurement of Business Income. This seminal work is put in context by exploring Bell’s earlier work as an economist and his later work, in which he developed applications and extensions of the Edwards and Bell model. Many of his concerns are relevant to the policy and research issues of today.
Welding of ship structural steel A36 using a Nd:YAG laser and gas–metal arc welding
Authors: Jokinen Tommi , Vihervä Teppo , Riikonen Hannu , Kujanpää Veli
Published: September 2010

Laser welding has the potential of offering both technical and economical advantages in many applications in the shipbuilding industry. A limiting factor is currently the power level available with commercial lasers, since steel plates of more than 5 mm in thickness are used in almost every shipbuilding application. In addition, the high hardness of the welds produced using laser welding is a disadvantage compared with the requirements of existing classification society standards. It has been reported that by using a hybrid welding method in which a laser beam and a gas–metal arc weld (GMAW) arc are combined it is possible to weld thicker sections, because the penetration is increased. Hardness values are correspondingly lower than those using the laser process because of the increased energy input. Results of a study of hybrid high power Nd:YAG laser and GMA welding are reported. All plates were welded in a butt joint configuration. When laser and GMAW were combined into a single process, I grooves were used. The air gaps between the welded plates varied. Some tests were made using a partially grooved V joint. In these cases, the root faces were welded by a Nd:YAG laser, and the upper part of the joint was welded by GMAW. It was seen that it is possible to produce defect-free welds using these processes. Macrosections of the welds, hardness values and parameters are presented and discussed.
Compact laser system for microprocessing applications
Authors: Hafez Moustapha , Benjamin Simon , Sidler Thomas , Salathé René-Paul
Published: September 2010

We propose a compact laser system for micromachining and microfabrication applications. The system is mainly composed of a laser source, a beam handling system for two-dimensional scanning, and can be combined with an auto focus allowing a third degree of freedom. The laser source is a high power direct diode side-pumped pulsed solid state laser, which produces a high quality and high intensity laser beam. The crystal is a Nd:yttrium–aluminum–garnet emitting at 1.06 μm for industrial micromaterial processing, at 1.35 μm, and also at 1.44 μm for tissue treatments in biomedical applications. The beam handling system consists of a compact tip/tilt laser scanner. Electromagnetic actuators drive the mirror and its suspension is based on a cone-ball bearing. The scanner achieves a scan range of ±3° around X and Y axis with an accuracy better than 0.1%. Such a system finds diverse applications in the field of industrial cutting, drilling, and welding. Furthermore, its small volume allows an easy integration in fabrication processes.
High-speed simultaneous observation of plasma and keyhole behavior during high power CO2 laser welding: Effect of shielding gas on porosity formation
Authors: Seto Naoki , Katayama Seiji , Matsunawa Akira
Published: September 2010

Laser welding can produce a deeply penetrated bead at high speed. However, in high power cw CO2 laser welding, the characteristic porosity is easily formed in the weld metal, but its formation mechanism has not been well understood. Therefore, the authors have conducted systematic studies of the elucidation of porosity formation mechanism and the development of preventive remedies. They have revealed that many bubbles are formed, mainly from the bottom tip of the keyhole by intense evaporation of the metal. It has also been revealed that the keyhole fluctuates frequently and changes its size and shape, corresponding to the intermittent bubble formation. The majority of bubbles are trapped at the solidifying front in the rear part of the molten pool. However, there are few reports that deal with the simultaneous observation of keyhole and plasma dynamic behavior as well as the formation of bubbles and porosity. In this study, therefore, the interrelationship between keyhole and plasma behavior was examined by using two synchronized high-speed cameras and an x-ray transmission observation system. Especially, the effect of shielding gas on porosity formation was investigated in terms of plasma and keyhole behavior. In the case of He shielding gas, metallic plasma emanated from a keyhole, and the keyhole was open continuously. On the other hand, in the case of N2 shielding gas, a big gas plasma was formed above the weld bead periodically, and metallic plasma and keyhole disappeared just like in the pulsed laser welding. Such periodical interval and duty were different depending on the materials used and exerted an effect on porosity formation tendency.
The effects of Ni and Au/Ni platings on laser welding of thin sheets
Authors: Biro E. , Zhou Y. , Weckman D. C. , Ely K. J.
Published: September 2010

The effects of Ni and Au/Ni plating on laser seam welding of 200 μm thick aluminum, nickel, Kovar, and cold-rolled steel sheet in the lap-joint configuration has been studied. Seam welds were made using a pulsed Nd:YAG laser and a range of weld process conditions. The strength of the welds was characterized using tensile shear tests and all welds were examined metallographically. All material combinations were found to be weldable. The platings were not found to affect the range of process conditions that produced acceptable welds in the nickel, Kovar, and steel specimens. However, the Ni and Au/Ni platings reduced the power density required to form a joint in the aluminum specimens due to the higher absorptivity of Ni. In all cases, the power density which resulted in blowthrough was unaffected by the platings. The strength of the majority of the joints was equivalent to that of the annealed base material. The aluminum weld metal hardness was increased fourfold by alloying from the Ni plating and Au/Ni plating, but this did not affect the tensile shear strength of the joint because failure of the Ni and Au/Ni-plated Al specimens always occurred in the unalloyed softer heat affected zone. Not all of the higher melting point Ni and Au/Ni plating was melted during welding of the Al specimens and significant gas porosity was observed at the interface between the Al weld pool and the unmelted Ni and Au/Ni plating layers. However, this did not affect the tensile shear strengths of the Al welds. A Au/Ni braze joint was observed at the sheet interface adjacent to the fusion boundary of the Au/Ni-plated Ni, Kovar, and cold-rolled steel specimens. This did not affect the strength of the Kovar and cold-rolled steel specimens; however, the Au/Ni braze increased the strength of the Au/Ni-plated Ni specimens to that of the base material.
Visible lesion threshold dependence on retinal spot size for femtosecond laser pulses
Authors: Cain Clarence P. , Toth Cynthia A. , Noojin Gary D. , Stolarski David J. , Thomas Robert J. , Cora Steven , Rockwell Benjamin A.
Published: September 2010

National laser safety standards have only recently been specified for laser pulse widths below 1 ns, with the publication of the ANSI Z136.1-2000 American National Standard for Safe Use of Lasers. A number of in vivo retinal injury studies using ultrashort laser pulses have been documented for pulse widths from nanoseconds to femtoseconds and having wavelengths from 1064 to 530 nm. These studies report data corresponding to the smallest retinal image diameters that can be achieved experimentally. The resulting data have been used to establish the exposure limits for small-source laser emitters. Data have shown that the thresholds decrease with pulse width and with wavelength for minimal retinal spot sizes. In this article we present measurements of the retinal lesion threshold as a function of retinal image size for 150 fs ultrashort laser pulses at 1060 nm. Retinal image size was varied from approximately 48 to 800 μm in diameter using external optics. Thresholds were determined using probit analysis of the data. The retinal spot sizes were calculated using the Gaussian beam propagation and multiple-lens formulas. The thresholds as a function of retinal image size were then compared to previously reported spot size studies. Results of our measurements show that as the retinal image diameter is increased from 48 to 800 μm, the threshold at 24 h postexposure increases from 1 to 54.1 μJ, corresponding to the fluence at the retina decreasing by a factor of five (from 56 to 11 mJ cm−2). Our results also show that as the retinal spot size increases, the radiant exposure necessary to cause a minimal visible lesion decreases, but not in proportion to the retinal image area. This decreasing radiant exposure for increasing retinal spot sizes at 150 fs follows the trends shown for previous studies with pulse duration from 30 ps to 10 s. Thus, extended sources for 150 fs and 1060 nm show no deviation from the trend of decreasing radiant exposure for increasing retinal image sizes. We conclude from our data that the current correction factors used in the laser safety standards also apply to femtosecond laser exposures between 400 and 1400 nm.
Spatter removal characteristics and spatter prevention during laser percussion drilling of aerospace alloys
Authors: Low David K. Y. , Li Lin , Byrd Pamela J.
Published: September 2010

The aerospace industry has been employing laser drilling to produce high quantity closely spaced holes in turbine engine components for effusion cooling. However, laser drilled holes are inherently associated with the deposition of spatter as the ejected material resolidifies and adheres around the periphery of the holes. This article presents an investigation on the effectiveness of an antispatter composite coating (ASCC) for the drilling of closely spaced array (2 mm hole pitch) holes in three aerospace materials (IN 100, Nimonic PK 33, and 263 alloys) with an optical fiber delivered 400 W Nd:YAG laser. The ASCC, comprised of a mixture of ceramic filler particles embedded in a silicone elastomer matrix, was applied on the surfaces of the alloy substrates before laser percussion drilling. The work shows that the ASCC effectively prevents the spatter deposition such that laser drilled through holes are produced while maintaining the as-received surface characteristic when using either O2 or Ar assist gas. The spatter prevention mechanism and the characteristic of the ASCC have been investigated. Contact angle analysis revealed that the contact angles for the ASCC and one of alloys (Nimonic 263) were 118° and 46°, respectively. Such a difference was identified to be primarily due to the low surface tension of the silicone elastomer matrix. The thermal resistance of the ASCC was increased due to the embedding of the ceramic particles, which absorb a significant proportion of the heat generated by the ejected molten material and prevented the coating from being burned away.
Comparative study of the cutting of car interior trim panels reinforced by natural fibers
Authors: Pou J. , Boutinguiza M. , Quintero F. , Lusquiños F. , Soto R. , Pérez-Amor M.
Published: September 2010

The use of natural fibers, such as flax, sisal, or kenaf to reinforce plastic body panels for automotive applications is being introduced for car interior trim parts such as door panels, hat shelves, roofing, etc. The benefits derived from using natural fibers instead of glass fibers are mainly ecological and economical. As a renewable product, natural fibers have a greater environmental interest than oil based plastics. Natural fibers can be recycled and reused in a better way than glass fibers. On the other hand, panels made of natural fibers have good mechanical properties but are lighter than glass fiber reinforced panels, which means lower fuel consumption and therefore cost savings. The aim of this work is to explore the capabilities of lasers to effectively cut these new types of natural fiber reinforced panels. A comparison between the abrasive water jet cutting and the use of a CO2 and Nd:YAG lasers is carried out. The experiments show that the laser can be used satisfactorily to cut the car interior panels reinforced by natural fibers.
Temperature distribution in laser marking
Authors: Conde J. C. , Lusquiños F. , González P. , León B. , Pérez-Amor M.
Published: September 2010

A theoretical model describing the temperature distribution on plastic material during the laser marking process has been developed. The heat conduction differential equation was solved analytically by the Green function method, and numerically, based on the finite element method using ANSYS®(5.5). The experimental irradiation of a methacrylate piece by a CO2 laser was carried out in order to check the validity range of the model.
Minimization of elastic thermal stresses during laser machining of ceramics using a dual-beam arrangement
Authors: Modest Michael F.
Published: September 2010

Lasers are emerging as a valuable tool for shaping and cutting hard and brittle ceramics. Unfortunately, the large, concentrated heat flux rates that allow the laser to efficiently cut and shape the ceramic also result in large localized thermal stresses in a small heat-affected zone. These notable thermal stresses can lead to microcracks, a decrease in strength and fatigue life, and possibly catastrophic failure. In order to assess where, when, and what stresses occur during laser scribing, an elastic stress model has been incorporated into a two-dimensional drilling as well as a three-dimensional scribing and cutting code. The results of the analysis for a single Gaussian laser source show that substantial tensile stresses develop over a thick layer below and parallel to the surface, which may be the cause of experimentally observed subsurface cracks. In this work the effect of splitting the beam into two parts is discussed: a highly focused beam that does the actual drilling or scribing, and a partially defocused beam, used to heat the material ahead of, around, or behind the laser beam. Different secondary beam scenarios are investigated, and their effect on reducing the damaging tensile stresses is evaluated.
Surface cleaning of silicon wafer by laser sparking
Authors: Lee J. M. , Watkins K. G. , Steen W. M.
Published: September 2010

The removal of small particles (∼1 μm diameter) on a silicon wafer surface has been carried out by laser sparking, i.e., an intense laser pulse is focused in air generating a gas breakdown. It has been found that the airborne plasma shock waves induced by laser sparking initiated above the surface can successfully remove the particles such as tungsten, copper, and gold from the silicon surface. This new cleaning technique provides superior characteristics as an efficient, fast, damage-free process compared with conventional laser cleaning employing direct interactions between laser pulse and particles. The basic idea behind this technique and how to apply it for cleaning of the surface are described in detail. The cleaning mechanism is also discussed by comparing the adhesion force of a particle on a surface with the pressure of the shock wave generated by laser sparking in air.
Wavelet analysis of acoustic emission signals and quality control in laser welding
Authors: Zeng Hao , Zhou Zude , Chen Youping , Luo Hong , Hu Lunji
Published: September 2010

AE (acoustic emission) signals generated in laser welding were studied using wavelet time-frequency signal analysis methods. The AE signals were decomposed into a series of discrete sequences distributed over different frequency bands through wavelet transform. Further data processing was then carried out after selecting several decomposition sequences consistent with specific research goals. More detailed information of the welding process can be revealed through analyzing the time-frequency properties of the AE signals than can be obtained through statistical analysis or simple magnitude measurements. There is a significant difference between the AE signal from the desired deep-penetration weld and that which is acquired when there are problems with misalignment and excessive joint gap. The intensity of low-frequency (<781 Hz) components of the AE signals is dramatically reduced when welding defects occur. The same phenomena are found in the oscillation amplitude of frequency components between 781 and 1562 Hz. Based on the detailed information obtained from AE signals via wavelet analysis, a signal intensity moving average (IMA) curve is defined in this article. The curve is an effective tool for recognizing transitions of welding states and identifying defects quickly and reliably. The potential application of the IMA curve is also described in this article.
A thermoelastic analysis of the laser scabbling of concrete
Authors: Dowden John , Lazizi Antar , Johnston Emma , Nicolas Sebastien
Published: September 2010

The process of scabbling is used in the decommissioning of nuclear power stations and consists of the removal of the radioactive surface layer of the shielding concrete. It is proposed that the process can be analyzed in terms of a thermoelastic model. Point solutions can be used in the study of such problems. We describe the method and present the relevant solutions for semi-infinite homogeneous media with a plane boundary. The method is applied with particular reference to the problem of laser scabbling of concrete but can be applied much more generally, for example to the stresses induced during surface heat treatment of metals or, at a certain level of approximation, in welding. In the case of the scabbling of concrete there is only a very thin thermal layer at the surface, resulting in a simplification of the analysis. Three special solutions are obtained in the two-dimensional approximation and they show that the strength of the tendency to fragmentation depends on the maximum rate of decrease of incident intensity at the rear of the scanning beam and that the depth of penetration depends on the overall front-to-backwidth of the beam. A broad beam is preferable in order not to reduce the penetration possible with the chosen overall depth of beam. These general characteristics are consistent with the results of experiments.
Marangoni effect in laser deep penetration welding of steel
Authors: Fuhrich T. , Berger P. , Hügel H.
Published: September 2010

In welding, the resulting weld-seam geometry may vary significantly although using constant process parameters and steels with the same material number. One likely reason for this are small variations in the concentration of sulfur, phosphorus, oxygen, and other chemical elements that are well within the tolerance of the standard of a specific alloy. These substances act as surfactants and even marginal changes strongly effect the temperature-dependent coefficient of surface tension. In simulations of conventional electric arc welding and laser heat conduction welding, the effect of the temperature-dependent coefficient of surface tension (Marangoni effect) has been identified as one of the primary driving forces of the liquid melt. In laser deep penetration welding simulations this effect has been widely neglected, so far. In this contribution, simulations of flow fields in the weld pool resulting from different temperature dependencies of the coefficient of surface tension are presented. The simulations show the same effect in laser deep penetration welding that is already known in gas tungsten arc welding. Consequently, it becomes clear that the chemical specifications for many steel alloys are too crude for reliable predictions of the seam geometry in laser deep penetration welding.
Process instability in laser welding of aluminum alloys at the boundary of complete penetration
Authors: Forsman T. , Powell J. , Magnusson C.
Published: September 2010

Intrinsic instabilities in the depth of penetration achieved when laser welding aluminum alloys were investigated in this article. Four types of weld pool configuration, resulting in different welds, were identified, only two of which are associated with full penetration. A simple phenomenological explanation of the unstable welding process at the boundary of complete penetration was proposed. The nature and cause of the instabilities were discussed and suggestions were offered for process control.
Use of “assist” gas in the laser drilling of titanium
Authors: Rodden W. S. O. , Kudesia S. S. , Hand D. P. , Jones J. D. C.
Published: September 2010

A series of experiments is reported which investigate the effect of an “assist” gas on the single-pulse Nd:YAG laser drilling of titanium. Hole breakthrough percentages are determined for arrays of holes drilled without an assist gas and with assist gasses of different pressures and compositions. Breakthrough percentages are given as functions of laser pulse energy for various thicknesses of material under different assist gas conditions. Regimes are identified in which the use of a gas assists drilling and others in which it hinders drilling—mechanisms for these effects are proposed. The effect of the reactivity of the assist gas on hole dimensions is also reported.
Free space optical communication a new industry and a new challenge in defining laser safety in the public sector
Authors: Britz D. M.
Published: September 2010

This article discusses the application and implications of a new class of optical wireless broadband communications technology utilizing line-of-sight optical links commonly referred to as free space optical communications (FSOC). As the emergence of this technology is likely to spawn an industry with rapid growth in the broadband access telecommunications market, the article will also briefly examine some of the technologies unique operational considerations and focus on the public safety issues associated with large-scale public deployment, and will conclude with a brief review of future directions and recent and very preliminary committee drafts on the operational and safety standards being proposed by members of ANSI Z136.6 and IEC TC76 working group 5-part 12. Comprehensive standards for FSOC applications are not expected before 2003.
High-power laser cladding Stellite 6+WC with various volume rates
Authors: Zhong Minlin , Yao Kefu , Liu Wenjin , Goussain Jean-Claude , Mayer Cécile , Becker Ahim
Published: September 2010

Laser cladding of Stellite+WC with WC volume percentages of 0%, 9%, 18%, 27%, 36%, 45%, 54%, 72%, and 100% was investigated by dual powder feeding. The results demonstrated that no cracking happened until the WC volume percentage was over 18%. The average hardness and cracking rate increased while the height/width rate decreased with increased WC volume percentage. The microstructure evolution can be divided into two domains. The first domain is from 0% to 36% WC, in which the added WC was completely melted and dissolved into the melt pool and the resolidified structure dominated by Co-rich dendrites and interdendrite eutectic containing 9.7 and 21 wt % W, respectively. The second domain is for the WC volume percentage from 45% to 100%, in which most of the WC was melted, and the microstructure was dominated by the matrix and the various faceted dendrites. The dissolution of W into the matrix was limited to a maximum of about 26 wt % and reached 64.6 wt % in the faceted dendrites.
Three-dimensional modeling of the gas field distribution of a high-pressure gas jet used in laser fusion cutting
Authors: Duan J. , Man H. C. , Yue T. M.
Published: September 2010

A three-dimensional mathematical model for investigating theoretically the gas flow field distribution of the free exit gas jet from both subsonic and supersonic nozzles under the regime of high-pressure gas-assisted laser fusion cutting is presented in this article. The influence of the flow nonuniformity in the subsonic nozzle exit upon the field distribution in the free gas jet is considered in this model. The calculated results are in good agreement with those observed by shadowgraphy. The relationships between the inlet stagnation pressure and the flow field distribution, incident shock, and normal shock of a gas jet in free space are established. The processing characteristics of the free space gas jet in the high-pressure gas-assisted laser cutting process for both subsonic and supersonic nozzles are analyzed in detail. Compared with that from the subsonic nozzle, such as the commonly used conical or conical–cylindrical nozzle, the gas jet from the supersonic nozzle (Laval nozzle) possesses good features such as uniform distribution, maximum even momentum thrust, and a parallel jet boundary under the condition of the designed “working pressure.”
Single-stage sealing of ceramic tiles by means of high-power diode laser radiation
Authors: Lawrence J. , Li L. , Edwards R. E. , Gale A. W.
Published: September 2010

An investigation has been carried out using a 60 W high-power diode laser (HPDL) to determine the feasibility of sealing the void between adjoining ceramic tiles with a specially developed grout material. A single-stage process has subsequently been devised using a new grout material which consists of two distinct components: a crushed ceramic tile mix substrate and a glazed enamel surface; the crushed ceramic tile mix provides a tough, inexpensive bulk substrate, while the enamel provides an impervious surface glaze. HPDL processing has resulted in crack- and porosity-free seals produced in normal atmospheric conditions. The single-stage grout is simple to formulate and easy to apply. Tiles were successfully sealed with power densities as low as 750 W/cm2 and at rates of up to 420 mm/min. Bonding of the enamel to the crushed ceramic tile mix was identified as being primarily due to van der Waals forces and, on a very small scale, some of the crushed ceramic tile mix material dissolving into the glaze.
Ultrashort pulsed laser ablation of diamond
Authors: Shirk M. D. , Molian P. A. , Malshe A. P.
Published: September 2010

Laser processing of diamond and chemical-vapor-deposited diamond thin films are important in the microelectronics and cutting tool industries because the manufacture of diamond films with low surface roughness and complex shapes has proven to be difficult. In this paper we present a review of current laser polishing and ablation processes followed by a discussion of ultrashort pulsed processing of diamond. Compared with the use of longer pulsed lasers, the use of 248-nm, 500-fs duration pulses at extreme intensity offered multiple advantages, including a lack of lateral thermal damage and significant improvements in the structural purity of the ablated surface. Experimental data, including Raman spectra and scanning electron micrographs, were presented to demonstrate the superior capabilities of this new class of lasers for diamond processing.
The Taguchi method for determining CO2 laser cut quality
Authors: Yilbas B. S. , Hyder S. J. , Sunar M.
Published: September 2010

The rapid growth in the application of lasers as a cutting tool has generated considerable interest in the quality of the cut edges produced. Consequently, the present study is conducted to assess cut edge quality, by defining the measurable variables, using international standards for thermal cutting. The measurable variables defining the cut edges may include waviness and flatness. Cutting speed, oxygen pressure, and workpiece thickness are considered as cutting parameters, therefore the Taguchi method is used to classify the relevant parameters. The study is extended to include the detection of light emission from the surface plasma. This makes it possible to monitor temporal behavior of the surface plasma, which in turn gives information about the formation of striations. Scanning electron microscope microphotography is conducted to examine the resulting cut surfaces. It is found that the cut quality is mainly affected by the oxygen gas pressure and cutting speed. However, flatness depends significantly on the thickness. Microcracks appear on the cut edge surfaces due to rapid solidification of the molten oxide layer formed on the surface.
Interaction of superconducting Y1Ba2Cu3O7−x targets with 1.064 μm Q-switched Nd:yttrium–aluminum–garnet laser
Authors: Mishra Anurag , Bansal S. K. , Mehra R. M.
Published: September 2010

Bulk superconducting targets of Y1Ba2Cu3O7−x were prepared and characterized for resistance, structure, morphology, and composition. The targets were irradiated by a Q-switched 1.064 μm wavelength Nd:yttrium–aluminum–garnet (YAG) laser having 20 ns pulse duration at 2.0 J/cm2 (shot) energy density. A cumulative laser exposure of the target surface results in the formation of microscopic conical columnar structures aligned parallel to the incident laser beam. Evolution of these structures in the present case is attributed to the longer penetration depth of optical radiation and localized material removal by microexplosions beneath the surface. Energy dispersive analysis by an x ray of the individual column shows microscopic phase segregation and erosion accompanied by shadowing as the primary cause of the cone formation process.
Calculation of process parameters for laser alloying and cladding
Authors: Bamberger M. , Kaplan W. D. , Medres B. , Shepeleva L.
Published: September 2010

This article presents a simplified theoretical model for estimating the operating parameters of laser surface alloying and cladding by the direct injection of powder into the molten bath. It is shown that use of the Mie theory takes into account the influence of the injected particles on laser beam energy transfer to the treated surface. Due to the reasonably good agreement between the calculated and the experimental data, this analytical model is applicable to the development of laser surface alloying and cladding by direct powder injection.
EU643 Safety in the Industrial Application of Lasers: Results of the UK program
Authors: Green J. Michael
Published: September 2010

The EUREKA 643 project “Safety in the Industrial Application of Lasers” was one of the biggest European collaborative projects in the field of lasers, involving approximately 100 companies across Europe. The UK program, which ran from April 1992 to April 1996, was the largest and most diverse of the national programs. Topics addressed in the program covered safety and performance standards; risk assessment; training and education; machine control; radiation measurement and calculation; free space and fiber optic delivery; safety enclosures; fume extraction, treatment, sampling, and analysis. An appraisal of the program is given, together with a summary of technical achievements and other highlights of the program. The likely long term impact of this major European effort is assessed, in particular its success in addressing the concerns of industrial users considering exploiting laser technology for materials processing.