bluuebunny/crossref_metadata_2025 huggingface dataset:
“The Big WHY”: Philip Morris’s Failed Search for Corporate Social Value
Authors: McDaniel Patricia A. , Malone Ruth E.
Published: August 2012

Objectives. We examined Philip Morris USA’s exploration of corporate social responsibility practices and principles and its outcome.

Methods. We analyzed archival internal tobacco industry documents, generated in 2000 to 2002, related to discussions of corporate social responsibility among a Corporate Responsibility Taskforce and senior management at Philip Morris.

Results. In exploring corporate social responsibility, Philip Morris executives sought to identify the company’s social value—its positive contribution to society. Struggling to find an answer, they considered dramatically changing the way the company marketed its products, apologizing for past actions, and committing the company to providing benefits for future generations. These ideas were eventually abandoned. Despite an initial call to distinguish between social and economic value, Philip Morris ultimately equated social value with providing shareholder returns.

Conclusions. When even tobacco executives struggle to define their company’s social value, it signals an opening to advocate for endgame scenarios that would encourage supply-side changes appropriate to the scale of the tobacco disease epidemic and consistent with authentic social value.
Evaluation of Raising Adolescent Families Together Program: A Medical Home for Adolescent Mothers and Their Children
Authors: Cox Joanne E. , Buman Matthew P. , Woods Elizabeth R. , Famakinwa Olatokunbo , Harris Sion Kim
Published: August 2012

Objectives. This study described a medical home model for adolescent mothers and their children, and their 1- and 2-year preventive care, repeat pregnancy, and psychosocial outcomes.

Methods. In this prospective, single cohort demonstration project, adolescent mothers (14–18 years old) and their children received care in a medical home. Demographic, medical and social processes, and outcomes data were collected at enrollment through 24 months. Change over time and predictors of repeat pregnancy were analyzed.

Results. A total of 181 adolescents enrolled, with 79.6% participating for 2 years. At 2 years, 90.2% of children were completely immunized. Children and adolescent mothers met standards for health care visits, and adolescent condom use improved. Rates of cumulative repeat pregnancy were 14.7% and 24.6%, school attendance 77.6% and 68.7%, and employment 21.2% and 32.3% at 1 and 2 years, respectively.

Conclusions. A medical home model with comprehensive and integrated medical care and social services can effectively address the complex needs of adolescent parents and their children.
Association Between Availability and Quality of Health Services in Schools and Reproductive Health Outcomes Among Students: A Multilevel Observational Study
Authors: Denny Simon , Robinson Elizabeth , Lawler Catriona , Bagshaw Sue , Farrant Bridget , Bell Fionna , Dawson Dianne , Nicholson Diana , Hart Mo , Fleming Theresa , Ameratunga Shanthi , Clark Terryann , Kekus Maria , Utter Jennifer
Published: August 2012

Objectives. We determined the association between availability and quality of school health services and reproductive health outcomes among sexually active students.

Methods. We used a 2-stage random sampling cluster design to collect nationally representative data from 9107 students from 96 New Zealand high schools. Students self-reported whether they were sexually active, how often they used condoms or contraception, and their involvement in pregnancy. School administrators completed questionnaires on their school-based health services, including doctor and nursing hours per week, team-based services, and health screening. We conducted analyses using multilevel models controlling for individual variables, with schools treated as random effects.

Results. There was an inverse association between hours of nursing and doctor time and pregnancy involvement among sexually active students, with fewer pregnancies among students in schools with more than 10 hours of nursing and doctor time per 100 students. There was no association between doctor visits, team-based services, health screening, and reproductive health outcomes.

Conclusions. School health services are associated with fewer pregnancies among students, but only when the availability of doctor and nursing time exceeds 10 hours per 100 students per week.
The Adolescent Family Life Program: A Multisite Evaluation of Federally Funded Projects Serving Pregnant and Parenting Adolescents
Authors: Kan Marni L. , Ashley Olivia Silber , LeTourneau Kathryn L. , Williams Julia Cassie , Jones Sarah B. , Hampton Joel , Scott Alicia Richmond
Published: August 2012

Objectives. We evaluated the effectiveness of care demonstration projects supported by the Title XX Adolescent Family Life (AFL) program, which serves pregnant and parenting adolescents in an effort to mitigate the risks associated with adolescent childbearing.

Methods. This cross-site evaluation involved 12 projects and 1038 adolescents who received either enhanced services funded by the AFL program or usual care. We examined the effects of enhanced services on health, educational, and child care outcomes approximately 6 months to 2 years after intake and explored moderation of program effects by time since intake and project characteristics associated with outcomes.

Results. The odds of using long-acting reversible contraception (odds ratio [OR] = 1.58) and receiving regular child care (OR = 1.50) in the past month were higher in the intervention group than in the comparison group. Odds of a repeat pregnancy were lower (OR = 0.39) among intervention group adolescents than among comparison group adolescents within 12 months of intake. Several project characteristics were associated with adolescent health outcomes.

Conclusions. These projects show promise in improving effective contraceptive use, increasing routine child care, and yielding short-term decreases in repeat pregnancy.
Laser generated air contaminants released during laser cutting of fabrics and polymers
Authors: Kiefer Max , Moss C. Eugene
Published: August 2012

Environmental monitoring was conducted at an industrial facility to qualitatively identify the major contaminants generated while cutting fabrics and polymers with a 25 W CO2 continuous beam laser. Carbon monoxide, hydrogen cyanide, and particulates were also assessed, and a bulk sample of residue from the laser exhaust duct was analyzed for inorganic acids, pH, and volatile organic compounds. Samples were collected while cutting vinyl, acrylics, woven fabrics, felt, Formica®, and Plexiglass®. The laser parameters were standardized to allow for meaningful comparison of results for each target material. The volatile organic compound samples were collected in multibed sorbent tubes with subsequent analysis via thermal desorption and gas chromatography/mass spectroscopy. Depending on the material being cut, a wide variety of compounds were detected. The highest relative concentrations of volatile compounds were found during laser cutting of felt fabrics. The lowest concentrations and fewest number of compounds were from woven fabrics. The compounds detected included hydrochloric acid, aldehydes, benzene, vinyl chloride, various acrylates, acrylonitrile, acetonitrile, styrene, furans, phenol, and butyl cellosolve. Methyl methacrylate was a significant peak detected during the laser cutting of acrylic ester polymers, Plexiglass, and polyvinyl chloride with adhesive backing. Carbon monoxide was not detected above background (2 ppm) during any of the laser cutting trials. Hydrogen cyanide was detected during the laser cutting of felt (15 ppm) and Formica® (8–10 ppm). Particles ⩾ 0.3 μm in diameter (μmd) generated during the laser cutting exceeded background particle levels by a factor of ten or more. Most compounds detected in the thermal desorption air samples were also detected in the bulk sample, and the residue was acidic (pH = 3). Area samples collected outside the laser enclosure suggested the local exhaust ventilation system sufficiently contained the air contaminants.
Characteristics of CO2 laser welded high carbon steel gauge plate
Authors: Ng Eng S. , Watson Ian A.
Published: August 2012

The welding performance of CO2 lasers is strongly affected by the clamping geometry and welding speed. Moreover, the rapid cooling rate associated with laser welding results in an untempered martensitic structure and a transverse variation in the hardness profile. An untempered martensitic structure can lead to brittle welds, and particularly for samples that are subject to cyclic loading, component fatigue and failure. To avoid this problem it is useful to optimize the laser operating parameters to reduce hardness discontinuities throughout the workpiece. An experimental investigation into the weld quality was performed to quantify the effects of clamping and translation velocity by examining the hardness characteristics, weld width and weld depth. A gauge plate, 2 mm thick, was welded with a 1 kW, CW, CO2 laser for a range of translation velocities between 800 and 1500 mm per min, a He shielding was used at a pressure of 5 × 104 Pa. Two weld geometries, namely clamped and unclamped, were considered. The clamped geometry gave improved hardness characteristics and a coarse grain structure. Whereas for the same operating conditions, the unclamped geometry gave a deeper weld penetration and wider weld width.
Continuous wave Nd:YAG laser cladding modeling: A physical study of track creation during low power processing
Authors: Jouvard J-.M. , Grevey D. F. , Lemoine F. , Vannes A. B.
Published: August 2012

This paper concerns the modeling of cladding using an Nd:YAG laser operating at low powers typically less than 800 W. Experimental observation of the evolution of the mass of the clads shows two power thresholds. The theoretical study relies on a calculation of the fluence provided to the substrate and on a model of heat transfer into the substrate. We suggest that the first threshold is the power required for substrate melting. The second power is the threshold when the powder is directly melted by the beam and is therefore a liquid when contacting the substrate.
The development of a laser machining curriculum: An interdisciplinary approach (the MAST program)
Authors: Masciadrelli Gary J. , Massa Nicholas M.
Published: August 2012

The development of an industry-driven interdisciplinary curriculum in laser machining is presented. The Machine tool Advance Skills Technology (MAST) program is a US Department of Education grant to develop and demonstrate a national training model for new technologies and manufacturing processes in precision manufacturing. Springfield Technical Community College (STCC) in partnership with six other community colleges nationwide, developed, tested, and disseminated industry-specific skills standards and model curricula in laser machining and related technologies for the United States machine tool industry. STCC, with its strengths in laser and manufacturing engineering technologies, was selected to develop a true interdisciplinary program in laser machining by integrating key components from its laser electro-optics technology (LEOT) and mechanical engineering technology (MET) programs.
Laser cladding with a pulsed Nd:YAG laser and optical fibers
Authors: Brandt M. , Scott D. A. , Emms S. B. , Yellup J. M.
Published: August 2012

A new laser cladding technique for producing wear and corrosion resistant surfaces on engineering components is reported. The technique involves the combination of the pre-placed and injected powder delivery methods for producing clad layers. The clad layers were formed with a pulsed Nd:YAG laser and optical fibers. The results using a nickel-based alloy (Hastelloy C) indicate that uniform clad layers in excess of 1 mm in thickness can be achieved in a single pass with 240 W average power incident on the workpiece. The laser beam was delivered through a step-index glass fiber of length 5 m and core diameter 600 μm. The clad layer obtained is homogeneous, without porosity or cracks, and has very low dilution (less than 2%) by the substrate, to which it is bonded. These results, combined with a relatively high powder utilization efficiency (about 60% when cladding a flat plate) and coverage rate (8 mm2 s−1), make the technique competitive with that using continuous wave lasers with powers greater than 1 kW, but at a quarter of the input power. The low heat input makes the technique particularly attractive for cladding thin substrates and engineering components that require both corrosion- or wear-resistant surfaces and high dimensional stability. In addition, the use of fiber optics to deliver the laser beam to the workpiece offers great opportunities for surfacing components remote from the laser source.
Temperature-dependent absorptivity and cutting capability of CO2, Nd:YAG and chemical oxygen–iodine lasers
Authors: Xie J. , Kar A. , Rothenflue J. A. , Latham W. P.
Published: August 2012

The most widely used high power industrial lasers are the Nd:YAG and CO2 lasers. The chemical oxygen iodine laser (COIL), whose wavelength (1.315 μm) is between that of the Nd:YAG (1.06 μm) and CO2 (10.6 μm) lasers, is another high power laser for industrial applications. The cutting capability of these lasers is investigated in this paper. The cut depth strongly depends on the absorptivity of the cut material, kerf width and cutting speed. The absorptivity is an unknown parameter for which experimental data at high temperatures are currently unavailable. Theoretical values of the absorptivities of various metals are obtained using the Hagen-Ruben relationship. It is found that the absorptivity of a metal is linearly proportional to the square root of its resistivity and also inversely proportional to the square root of the wavelength. The absorptivities of the COIL and Nd:YAG lasers are 2.84 and 3.16 times larger than that of the CO2 laser, respectively. Based on these theoretical values of the absorptivity, the cut depths for several metals are analyzed at various laser powers and cutting speeds for these lasers. For identical cutting parameters, the cut depths for stainless steel and titanium are deeper than those of most other metals. Due to the wavelength dependence of the absorptivity, the cut depths for COIL and Nd:YAG lasers are expected to be 2.84 and 3.16 times deeper than that for the CO2 laser.
Relationship between airborne acoustic and optical emissions during laser welding
Authors: Farson D. , Sang Y. , Ali A.
Published: August 2012

This paper describes experimental work directed at understanding the relationship between acoustic and optical emissions from the laser welding process. Laser welds were performed and the emissions were measured with a microphone and photodiode and recorded with a data acquisition system. A time-domain correlation analysis of the acoustic and optical signals revealed them to be highly related at a phase shift corresponding to the delay time for sound to propagate from the weld area to the microphone. A moving average model which predicted the acoustic signal from light signal measurements was fitted to experimental data using least squares regression. The acoustic signal predicted by the model was found to correspond fairly well to the experimental acoustic data. In addition, the least squares model indicated a very simple relationship between the two signals: the sound pressure predictions were proportional to the time derivative of the light signal samples. This relationship was explained by physical analysis of the mechanism for generation of sound and light signals by the plume.
Integration of real time quality control systems in a welding process
Authors: Nava-Rüdiger E. , Houlot M.
Published: August 2012

The automation of laser welding processes requires the control of the various process components as well as the control of the laser—material interaction. These systems are essential for ensuring the quality of the weld seam as they are able to react to dynamic fluctuations during the process. During the process various phenomena occur which are potential sources of diagnostic signals: these include thermal, electrical, optical, mechanical and acoustic events. This paper presents the development of an integrated real-time system based on the monitoring of several of these phenomena that provide complementary information for the detection of different defect types. A system based on the use of infrared photodiodes has been validated and successfully applied to the detection of the appearance of geometric defects such as sagging or misalignment in the weld seam. A complementary system to monitor the airborne acoustic signals of the process is under development and the experimental results for defining the acoustic pattern of welding defects are presented.
Experimental study of cutting thick aluminum and steel with a chemical oxygen–iodine laser using an N2 or O2 gas assist
Authors: Carroll David L. , Rothenflue James A.
Published: August 2012

A chemical oxygen–iodine laser (COIL) was used to cut aluminum and carbon steel. Cut depths of 20 mm in aluminum and 41 mm in carbon steel were obtained using an N2 gas assist and 5–6 kW of power on target. The same laser at the same power level produced a cut depth of 65 mm in carbon steel with an O2 gas assist; a low quality cut to a depth of nearly 100 mm in carbon steel was also demonstrated. These data are compared with existing COIL and CO2 laser cutting data. COIL cuts carbon steel and stainless steel at approximately the same rate. For a given cut depth, power and spot size, COIL cuts steel approximately three times faster than a CO2 laser using an inert gas assist. COIL cutting speeds in carbon steel are improved by approximately a factor of three when an O2 assist is used in lieu of an N2 gas assist. With an N2 gas assist, COIL cuts aluminum at approximately the same rate as CO2 cuts steel. To improve the agreement between data and an existing theoretical cutting model, an empirical correction factor was added to the model; this modification provides excellent agreement with data.
Laser through-cutting and drilling models for ablating/decomposing materials
Authors: Modest Michael F.
Published: August 2012

A previously-developed three-dimensional conduction model for scribing of a thick solid has been extended to predict the transient temperature distribution inside a finite thickness slab that is irradiated by a moving laser source, and the cutting rate and profile carved by evaporation of material. The laser may operate in CW or in pulsed mode (with arbitrary temporal intensity distribution) and may have an arbitrary spatial intensity profile. The governing equations are solved using a finite-difference method on a boundary-fitted co-ordinate system. Results for cutting rates and profiles are presented for materials that ablate or decompose upon laser irradiation (without significant formation of liquid), for different material thicknesses, traverse speeds, and pulsing conditions. For drilling (zero traverse speed), a numerically much more efficient two-dimensional axisymmetric version of the model has also been implemented, and similar results for drilling behavior are also presented.
Diode laser scribing of non-oriented 3 wt% Si-steel for core loss reduction
Authors: Gurusamy Ravisankar , Molian P. A.
Published: August 2012

The electrical power industries are experiencing a considerable energy loss in transformers and motors because of inefficiencies caused by core loss. The objective of our research is to investigate any effect of laser scribing on the reduction of the core loss in the low cost, non-oriented steels used in numerous utility applications. A 15 W diode laser transmitted through fiber optics was used to scribe 0.35 mm thick, non-oriented 3 wt% Si steel. The magnetic properties including the core loss and permeability were evaluated both before and after laser scribing. A maximum core loss reduction of 0.08 W kg−1 at a magnetic induction of 1 T and a 21% increase in relative permeability were obtained at the optimum laser parameters. These results are comparable to those of laser scribed, expensive grain-oriented steels. The core losses were further reduced using a treatment procedure consisting of laser scribing, chemical etching, and stress relief annealing performed in sequence. The laser scribing method is simpler, energy efficient, and can be implemented in the production line.
In-process monitoring of laser welding by the analysis of ripples in the plasma emission
Authors: Mori Kiyokazu , Miyamoto Isamu
Published: August 2012

A novel in-process monitoring system employing two detectors set above the workpiece at different aiming angles of 5° and 75° has been developed to detect whether or not CO2 laser welding fully penetrates through to the back surface of steel sheets. The acquired signal contained a.c. components of the emission of the laser-induced plasma in the plume and in the keyhole with frequencies up to approximately 10 kHz. The mean square value of the a.c. signal obtained by using the 75° sensor during full penetration welding was much larger than that of the partial penetration welding, showing that full penetration welding can be monitored with a high accuracy by using the 75° sensor.
A power distribution model of industrial CO2 lasers for system diagnosis
Authors: Katter James G. , Tu Jay F. , Gartner Mark
Published: August 2012

Industrial lasers are high power pieces of equipment that occasionally function under undesirable operating conditions. For example, the performance of a transverse-flow d.c.-excited gas laser can be adversely affected by many factors such as electrode arcing, poor lens and mirror cleanliness, focusing problems, improper gas mixture composition, poor gas quality, poor beam stability, poor beam path cleanliness, operator error, poor maintenance, poor chiller water temperature and flow rate stability, and improper laser beam ramp-in/ramp-out rates. Many of these factors which occur in the production environment are unpredictable and therefore difficult to simulate in the laboratory or the laser manufacturer's facilities. In this paper, a power distribution model of a transverse flow d.c.-excited CO2 laser is developed and validated to link the input discharge power to the output laser beam power, as well as the heat losses. This model establishes a foundation for monitoring the laser performance by measuring signals critical to the laser performance such as temperature, pressure, voltage, current, and gas mixture flow rate and quality. The results show that quantitative thresholds can be defined based on the proposed model to detect some impending system faults for preventative maintenance purposes.
Effective laser ablation of enamel and dentine without thermal side effects
Authors: Kohns Peter , Zhou Ping , Störmann Reinhard
Published: August 2012

We present a feasibility study into laser treating dental materials by using femtosecond pulses generated by a titanium:sapphire laser system which consisted of an oscillator and a regenerative amplifier. The pulse duration was varied between 200 fs and 2 ps. The observed energy thresholds for the ablation process of dentine and enamel were clearly smaller than those observed when longer pulse durations were used. The consequence of this observation is a lower thermal load within the vicinity of the radiated area. Thus no thermal damage or mechanical damage, such as cracks, were produced during the laser treatment. Commercially available femtosecond laser systems can produce ablation rates in healthy and in-vitro demineralized dental material of 2 mm3 per min and 6–16 mm3 per min, respectively. These values are an order of magnitude larger than those produced by picosecond laser systems at the same pulse energy and pulse repetition rate. The brightness of the plasma spark generated by the laser treatment depended on the extent of the demineralization of the teeth. This may allow online control of the laser treatment.
In the beginning there was ANSI Z136.1
Authors: Charschan Sidney S.
Published: August 2012

In the early 1960s concerns about eye safety were concentrated in a handful of research laboratories and the military. Memoranda and guidelines were circulated internally with their own set of priorities and recommended practices. Then, in 1968, the First International Laser Safety Conference (the brainchild of Dr Leon Goldman), was held in Cincinnati with one of its avowed purposes, the development of a consensus among the most prominent investigators as to what exposure criteria should be adopted. They saw the (laser) light. By 1969 it had become clear that, because of widespread differences in the many laser safety practices, a national consensus standard was needed. The American National Standards Institute (ANSI) was requested by the US Department of Labor to initiate that project, and the Z136 committee began its work under Chairman George Wilkening. And, I was his secretary. The secretariat was the Telephone Group. It gives me great pleasure to point out that three of the original subcommittee chairs, R. James Rockwell Jr, David H. Sliney, and Myron I. Wolbarsht, are still actively committed to the Z136 Committee and the International Laser Safety Conference '97. One last final note: George M. Wilkening died June 30, 1995. The Laser Institute of America, Secretariat to the Z136 Committee, has established a ‘Wilkening’ Award for Laser Safety which was awarded March 17, 1997, at the meeting of the ILSC'97 in Orlando FL, to Dr W. T. Ham. Wilkening's dedication to laser safety lives on in Z136, and indeed throughout the world. He will be remembered as a tall man (6′6″) whose legs over-hung the beds on his travels, whose airplane seats were never big enough, whose technical knowledge of industrial health and safety was surpassed by none, and who always took the time to educate and explain. A great leader, a mediator, and a friend! We were told by ANSI that the ANSI Z136.1 standard ‘for the Safe Use of Lasers’ was completed in record time — only three years to final draft and publication in 1973. Since those early hectic days, the ASC Z136 Committee has revised and updated Z136.1 in 1976, 1980, 1986, and 1993. These we will touch upon. Meanwhile, the ASC Z136 Committee has issued, updated and is working on five other ANSI Z136.X standards. These standards have served as models for state, federal and international laser safety documents throughout the world.
Dual wavelength laser beam alloying of aluminum alloy for enhanced corrosion resistance
Authors: Liu Z. , Watkins K. G. , Steen W. M. , Vilar R. , Ferreira M. G.
Published: August 2012

Aluminum alloys are known for their poor resistance to localized attack and, in particular, for pitting in chloride-containing electrolytes. In this paper, improvement of the pitting corrosion resistance of 2014-T6 aluminum alloy has been investigated by means of laser surface alloying of Cr into the substrate. Since aluminum is a highly reflective and thermally conductive material, it is often difficult to process with laser beams. Oxide films on the surface can prevent surface alloying as with the case of Cr alloying into aluminum by in-situ powder feeding. This work describes a new technique using mixed excimer laser and CO2 laser beam processing to generate a Cr alloyed layer on a 2014 aluminum alloy substrate. It is shown that improvement of alloying homogeneity following in-situ powder feeding can be achieved with mixed beam processing. Conditions under which this can be achieved have been studied and the effect of laser processing parameters on the surface roughness, oxidation and absorption is discussed. Microstructural and surface morphological analysis using optical microscopy, scanning electron microscopy and energy dispersive spectroscopy are also discussed. The electrochemical behavior of the treated samples in de-aerated 1 m NaCl solution has also been studied and has indicated that an improvement of pitting resistance by laser surface treatment can be achieved.
Investigation into first and second law efficiencies of solid state laser head: A case study
Authors: Yilbas B. S. , Kar A. , Sunar M.
Published: August 2012

The efficiency of a solid state pulsed laser is very low which is generally ascribed to the poor optical and electrical efficiencies of the components used in the laser head. The temperature of the laser rod rises during the optical pumping process which causes thermally induced distortions in the laser output beam and hence a low quality laser beam is obtained. In the present study, the temperature rise in the laser rod during the pulsed optical pumping process is investigated, and the first and second law efficiencies relevant to the laser head are calculated. The radial temperature profiles are predicted for different optical pumping repetition rates. The energy dissipation chart during the lasing process in the laser head is developed. The first and second law efficiencies of the laser head and the laser rod are computed for different repetition rates of the optical pumping process.
Threshold laser beam irradiances for melting and welding
Authors: Leong K. H. , Geyer H. K. , Sabo K. R. , Sanders P. G.
Published: August 2012

A model based on the conservation of energy for a moving heat source incident on a flat plate is used to predict the threshold laser beam irradiance required to initiate melting on a metal surface. With the use of a non-dimensional variable and its solution, the threshold irradiance can be predicted with the use of a simple equation. This equation is a function of the absorptivity of the surface, thermal conductivity of the metal, temperature increase for melting, diameter of the laser beam at the surface and the non-dimensional variable value for the ratio of the thermal diffusivity of the metal to the product of the beam diameter and velocity used. Laser beam irradiances exceeding these predicted values are required for welding. The model predictions are validated with experimental results of beam irradiances required for welding different metals.
Experimental development of a machining database for the CO2 laser cutting of ceramic tile
Authors: Livingstone S. A. J. , Chua K. L. , Black I.
Published: August 2012

This paper covers the cutting of commercially-available ceramic tiles using a CO2 laser cutting machine, with the object of producing a laser beam machining database which contains the essential parameter information for their successful processing. Various laser cutting parameters were investigated that would generate a cut in ceramic tile which required minimal posttreatment. The effects of various shield gases, multipass cutting and underwater cutting were also examined.
Characteristics of Nd:YAG laser welded high carbon steels
Authors: Ng Eng S. , Watson Ian A.
Published: August 2012

A quantitative study of the relationship between the laser process parameters and the mechanical properties of welded high carbon steels was performed utilizing a Lumonics Nd:YAG pulsed laser, operating at 1.06μm, and a robotically manipulated fiber optic beam delivery system. A gage plate (0.88 mm thick) was butt welded with a constant power of 200 W and a He shielding gas was used at a pressure of 5 × 104 Pa. The welding performance of the Nd:YAG laser was strongly affected by the translation velocity, pulse length and pulse repetition frequency (PRF). The effects of varying these process parameters were quantified by measuring the sample's hardness profile, weld width, weld penetration, and tensile strength. Furthermore, micrographic examinations were conducted at the welded joints. It was shown that by increasing the pulse length and pulse repetition frequency a deeper weld penetration and a wider bead width were achieved; moreover, the weld region became tougher. Hardness profiles transverse across the weldment and as a function of weld depth were greatly reduced with increasing PRF. The quality of the laser weld was dominated by the rapid quenching rate which resulted in the weld structure being completely modified near the heat affected zone.
Laser safety analysis of a retinal scanning display system
Authors: Viirre Erik , Johnston Richard , Pryor Homer , Nagata Satoru , Furness Thomas A.
Published: August 2012

The Virtual Retinal Display (VRD) is a visual display that scans modulated laser light on to the retina of the viewer's eye to create an image. Maximum permissible exposures (MPE) have been calculated for the VRD in both normal viewing and possible failure modes. The MPE power levels are compared to the measured power that enters the eye while viewing images with the VRD. The power levels indicate that the VRD is safe in both normal operating mode and in failure modes.
Laser-Induced Damage in Optical Materials at the October 7–9, 1996 Symposium on Optical Materials for High-Power Lasers (the Boulder Damage Symposium) Boulder, Colorado
Authors: Guenther Arthur H.
Published: August 2012

The 28th annual symposium on optical materials for high-power lasers (Boulder damage symposium) was held at the National Institute of Standards and Technology in Boulder, CO, 7–9 October 1996. The symposium was held under the joint sponsorship of Bennett Optical Research, the Center for Research and Education in Optics and Lasers (CREOL) at the Center for Research and Education in Optics and Lasers (CREOL) at the University of Central Florida, Los Alamos National Laboratory, Lawrence Livermore National Laboratory, Sandia National Laboratories, and SPIE—The International Society for Optical Engineering. Over 130 scientists attended the symposium, including representatives from France, Germany, Japan, Russia, South Africa, Hungary, Armenia, Israel, the UK, and the US. The symposium was divided into sessions concerning materials and measurements, surfaces and mirrors, thin films, fundamental mechanisms, and a mini-symposium on ‘Laser-Induced Damage in Optical Fibers,’ organized by R. E. Setchell and Sandia National Laboratories. As in previous years, the emphasis of the papers presented at the symposium was directed toward new frontiers and new developments. Particular emphasis was given to materials for high-power laser systems. The wavelength range of prime interest was from 10.6 μm in the infrared to the UV region. Highlights included surface characterization, thin film/substrate boundaries, and advances in fundamental laser-matter interactions and mechansims. Harold E. Bennett of Bennett Optical Research, Inc., Arthur H. Guenther of Sandia National Laboratories, Mark R. Kozlowski of the Lawrence Livermore National Laboratory, Brian E. Newnam of the Los Alamos National Laboratory, and M. J. Soileau of the University of Central Florida were co-chairs of the symposium. The 29th annual symposium is scheduled for 6–8 October 1997 at the National Institute of Standards and Technology, Boulder, CO. An added feature will be a wholly self-contained mini-symposium on ‘Damage in Laser Diodes’ organized by David Welch of Spectra Diode Laboratories.
Scaling laws for thick-section cutting with a chemical oxygen–iodine laser
Authors: Kar A. , Rothenflue J. A. , Latham W. P.
Published: August 2012

Almost all laser-assisted materials processing involves melting, vaporization and plasma formation which affect the utilization of laser energy for materials processing. To account for the effect of these phases, an effective absorptivity is defined, and a simple mathematical model is developed for the cutting of thick-section stainless steel using a high power chemical oxygen—iodine laser (COIL). The model is based on an overall energy balance, and it relates the cutting depth with various process parameters that can be used to predictively scale the laser materials processing performance to very thick sections. The effects of various process parameters such as laser power, spot size, cutting speed and cutting gas velocity on the cutting depth are discussed. The results of the mathematical model are compared with experimental data. Such a comparison provides a means of determining the effective absorptivity during laser materials processing.
Improved hole drilling using a high peak power Nd:YAG laser at the second harmonic wavelength
Authors: Chen Xiangli , Ortiz Angel L. , Staver P. Randall , Lotshaw William T. , Rockstroh Todd J. , McLaughlin Michael H.
Published: August 2012

We have previously described the drilling of advanced materials such as intermetallics, superalloys, and composites using an Nd:YAG laser operating at the fundamental wavelength of 1.064 μm [1]. We have now extended these studies to the second harmonic wavelength of 532 nm of a high peak power Nd:YAG laser. The results show that drilling using the shorter wavelength further reduces undesired thermal effects such as recast layers and heat affected zones. A comparison of these results with those obtained at the fundamental wavelength is reported.
Intrapulpar temperature during continuous CO2 laser irradiation in human molars: An in vitro study
Authors: Niccoli-Filho Walter , Furlani José Camilo , Schwab Carlos , Raldi Fernando Vagner , de Paula Eduardo Carlos
Published: August 2012

To establish safety parameters, we in vitro studied the increase in intrapulpal temperature caused by the use of a cw CO2 laser. A thermistor was implanted in the inner part of the pulpal chamber of 25 human lower third molars to measure the intrapulpal temperature produced by laser powers between 2–10 W and exposure times of 0.5–25.0 s. The Pearson linear correlation factor applied to the measured values showed there is a direct relationship between the independent variable and the applied power. A variance analysis produced the linear regression equation: T = 1.10 + (0.127)E where T is the temperature and E the energy. The results showed that, with a power of 4 W and maximum exposure time of 2.5 s (10 J) and a power density of 12738.85 W cm−2, there will be no damaging reactions affecting the pulpal tissues.
Evolving issues in laser safety
Authors: Sliney David H.
Published: August 2012

The approach to laser safety has come a long way since the 1960s when the first guidelines were issued by defense research organizations in the US and the UK, and then by the American Conference of Governmental Industrial Hygienists. Although the search for ‘eye-safe’ numbers continues in a few laboratories, this work is almost exclusively centered on deriving retinal thresholds for ultra-short (sub-nanosecond) lasers. Setting limits in this temporal region has been difficult, since there are conflicting data sets and there is a limited amount of data to extrapolate to other spectral regions. In the standards arena, the concentrated efforts have been in terms of product classification and attempts to resolve the eternal question of ‘how safe is safe?’. Recent efforts to revise safety standards have not always taken into account the historical rationale for the maximum permissable exposures and forget that safety factors were already factored into the limits, and further safety factors are quite unnecessary. Finally, the study of accidents raises the question of whether our approach to eye protection and enclosures are adequate and whether separate standards and guidance is needed for different applications.
Amendments to the Center for Devices and Radiological Health Federal Performance Standard for laser products
Authors: Dennis Jerome E.
Published: August 2012

Federal law requires that all laser products that are imported into or introduced into commerce in the United States comply with the performance standard published in the Code of Federal Regulations (CRF), Title 21, Parts 1040.10 and 1040.11, administered by the Center for Devices and Radiological Health (CDRH), US Food and Drug Administration. Although it contains somewhat different requirements for hazard classification, engineering controls and labeling, the ANSI Z136.1 standard defers to the CDRH standard. The CDRH standard became effective in August, 1976 and was amended, in 1978 and also in 1985. In the early 1990s, US experts met to formulate an approach to bring the requirements of the CDRH standard and those of the International Electrotechnical Commission (IEC) standard, IEC 825, into closer agreement in order to lower barriers to international trade and to remove any excessive compliance burdens on manufacturers. In 1993, the CDRH published, formally in the Federal Register and informally, a Notice of Intent to amend the CDRH standard. Responses to those notices have now been analyzed and informal draft amendments were distributed in 1996. This draft is now being prepared for formal issuance as a Notice of Proposed Rulemaking. Meanwhile, the IEC standard was amended in 1993 and republished as IEC 825-1; these amendments created considerable controversy since they resulted in over classification of the hazard of many products, especially light emitting diodes (LEDs) that have a large divergence and increased source dimensions. Additional amendments are now being developed to correct this problem. The CDRH has carefully monitored developments in the IEC and actively participated in its proceedings as a guide in developing its own proposal. This paper describes the major changes that are being proposed for the CDRH standard and presents some rationale for the major changes. The more significant changes include expansion of applicability to include LEDs, reduced emission durations for classification, revised measurement procedures for hazard classification, reduced performance requirements for lower power visible radiation products, and revised requirements for medical products.
Chatting in Paragraphs: Towards Academic Discourse in Foreign Language Chat
Authors: Mendelson Adam
Published: August 2012

Abstract:

This paper presents a case study of an individual student’s increasing approximation of academic discourse during a third-semester Spanish class that included chat-based instruction. During both chat-based activities and oral discussions in class, the student’s language use became increasingly characterized by longer turns and the use of subordination to express opinions. At the same time, her engagement in online play decreased over the course of the semester. This case suggests that, depending on the overall instructional context in which text-based chat is integrated, this medium, which is generally assumed to be social and informal, may actually be flexible enough to also support the development of academic discourse. Furthermore, the detailed description of language use and development across online and off-line environments invites consideration of the relationship between chatting and speaking.
Telecollaboration for Professional Purposes: Towards Developing a Formal Register in the Foreign Language Classroom
Authors: Cunningham D. Joseph , Vyatkina Nina
Published: August 2012

Abstract:

This study reports on the development of a professional spoken register among learners of German as they participate in four synchronous Web conferences with German-speaking professionals. The researchers investigated the effect of interaction with expert German speakers combined with an instructional intervention focusing on pragmatic competence on the development of learners’ ability to communicate in a second language (L2) professional register. The data reveal a positive effect on the strategic use of modal verbs for expressing polite requests as well as a moderate effect on learners’ use of the subjunctive mood to establish social distance. These results add further support for the use of intercultural online exchanges mediated by data-driven instruction in the foreign language classroom and highlight the utility of a microgenetic approach to analyzing spoken data.
New Dietetic Practitioners’ Perspectives: On Their Education and Training
Authors: Brady Jennifer , Lordly Daphne , MacLellan Debbie , Gingras Jacqui
Published: August 2012

Purpose: To elucidate the complex phenomenon of dietitian professional socialization, we examined factors that influence people’s decisions to pursue a career in dietetics and how education and training processes influence the professional socialization of dietitians.

Methods: Participants (n=12) had less than three years of work experience and included alumni from three Canadian universities representing different models of entry to practice. Three one-on-one interviews were conducted with each participant.

Results: The key influencing factor in participants’ decision to pursue dietetics was the perceived congruence between dietetics and other aspects of their lives, including early interests and experiences (sports, food and cooking, an eating disorder), career aspirations (science, health care), and social networks (the desire to be a professional). A pivotal experience during high school or while enrolled in or after graduation from another program prompted participants’ awareness of and subsequent decision to pursue a career in dietetics. Supportive relationships were vital to participants’ professional socialization.

Conclusions: Recruitment materials and education opportunities should help aspiring dietitians develop a clear idea of what being a dietitian means. Dietetic educators must attend to the informational and relational aspects involved in shaping future practitioners’ dietitian identities.
The Role of Diet in Predicting: Iron Deficiency Anemia in HIV-Positive Women
Authors: Renouf Ladan Shahvarani , Sheps Samuel , Hubley Anita , Pick Neora , Johansen Diana , Tyndall Mark W.
Published: August 2012

Purpose: The association between medical, social, and nutritional factors and iron deficiency anemia was examined in adult women who had tested positive for human immunodeficiency virus (HIV) and were living in the Greater Vancouver Area.

Methods: This was a cross-sectional observational study of 102 HIV-positive women, aged 19 or older, who were patients of one of three chosen community health clinics in Vancouver, British Columbia. Information on usual dietary intake and other nutrition-related factors was collected with a short diet survey, while medical information and laboratory data were obtained from each participant’s medical chart.

Results: Of the predictors studied, a CD4 cell count below 200 cells/µL, a regular menstrual pattern, and African ethnicity were associated with an increased risk of iron deficiency anemia. Dietary intake was not independently associated with iron status.

Conclusions: Iron deficiency anemia in HIV-positive women has multifactorial and complicated causation, but is strongly associated with poorer immune status and greater menstrual losses. Health disparities in Aboriginal and African women may lead to a higher risk for iron deficiency anemia. Routine screening and ongoing nutrition education are necessary for the prevention and management of iron deficiency anemia. Further research into factors associated with iron deficiency anemia is essential to improve prevention and management efforts.
Stepping Out: Dare to Step Forward: Step Back, or Just Stand Still and Breathe
Authors: Waisman Mary Sue
Published: August 2012

It is important to step out and make a difference. We have one of the most unique and diverse professions that allows for diversity in thought and practice, permitting each of us to grow in our unique niches and make significant contributions. I was frightened to ‘step out’ to go to culinary school at the age of 46, but it changed forever the way I look at my profession and I have since experienced the most enjoyable and innovative career. There are also times when it is important to ‘step back’ to relish the roots of our profession; to help bring food back into nutrition; to translate all of our wonderful science into a language of food that Canadians understand. We all need to take time to ‘just stand still and breathe’: to celebrate our accomplishments, reflect on our actions, ensure we are heading toward our vision, keep the profession vibrant and relevant, and cherish one another.