Laser machined macro and micro structures on glass for enhanced light trapping in solar cells

In order to increase the efficiency of solar cell modules it is necessary to make the optimum use of light incident upon them. Much research has been done on improving light absorption through front surface texturisation and light trapping schemes. Laser light is commonly used in industry for various applications including marking and texturisation. By controlling laser parameters, it is possible to tailor macro and micro structures in most materials. The CO2 laser used in this investigation emits radiation at 10.6 μm with the ability to pulse in the micro-second range. The laser was used to ablate grooved textures in the fused quartz material, used in this study as the light trapping medium, following which an analysis of the effects of the laser parameters on the texture geometry and surface morphology was performed through a combination of cross sectioning and scanning electron microscopy. Transmission through the textured glass was improved for most samples after acid etching. The light trapping effects of the best performing textures were analysed by investigating the effects on a silicon solar cell’s performance at varying angles of incidence. Results indicated a significant increase in light trapping when light was incident at acute angles. For an angle of incidence of 10◦ a relative increase in efficiency of up to 51 % was observed

Evolutionary multi-stage financial scenario tree generation

Multi-stage financial decision optimization under uncertainty depends on a careful numerical approximation of the underlying stochastic process, which describes the future returns of the selected assets or asset categories. Various approaches towards an optimal generation of discrete-time, discrete-state approximations (represented as scenario trees) have been suggested in the literature. In this paper, a new evolutionary algorithm to create scenario trees for multi-stage financial optimization models will be presented. Numerical results and implementation details conclude the paper

Surface modification of HVOF thermal sprayed WC–CoCr coatings by laser treatment

In this work the affects of laser characteristics on microstructure and microhardness of high velocity oxygen fuel sprayed (HVOF) WC–CoCr coatings were investigated. The coating was deposited with a Sulzer Metco WokaJet™-400 kerosene fuel and the laser surface treatments were applied using CO2 laser with 10.6 μm wavelength. Large variations in surface properties were produced from variation in the laser processing parameters. In total, four levels of peak power (100, 200, 300 and 350 W), four levels of spot diameter (0.2, 0.4, 0.6 and 1 mm) and three levels of pulse repetition frequency (PRF) were investigated. An initial set of tests were followed by a more detailed 33 factorial design of experiments. Pulse repetition frequency and duty cycle were set in order to maintain the same overlap in the x and y directions for the raster scanned sample spot impact dimensions. Overlaps of 30% were used in the initial tests and 10% in the more detailed trials. The results have shown that care must be taken to keep the irradiance at a relatively low level compared to uncoated surfaces. High irradiance can in this case result in rough and porous surfaces. Lower levels of irradiance are shown to provide more uniform microstructures, reduced porosity and increased microhardness

Advances in three-dimensional rapid prototyping of microfluidic devices for biological applications

The capability of 3D printing technologies for direct production of complex 3D structures in a single step has recently attracted an ever increasing interest within the field of microfluidics. Recently, ultrafast lasers have also allowed developing new methods for production of internal microfluidic channels within the bulk of glass and polymer materials by direct internal 3D laser writing. This review critically summarizes the latest advances in the production of microfluidic 3D structures by using 3D printing technologies and direct internal 3D laser writing fabrication methods. Current applications of these rapid prototyped microfluidic platforms in biology will be also discussed. These include imaging of cells and living organisms, electrochemical detection of viruses and neurotransmitters, and studies in drug transport and induced-release of adenosine triphosphate from erythrocytes

Habitat suitability assessment of constructed wetlands for the smooth newt (Lissotriton vulgaris [Linnaeus, 1758]): A comparison with natural wetlands

Given the current decline of natural wetlands worldwide and the consequent negative impacts on amphibians, wetlands constructed for the treatment of wastewaters have the potential to play a role in the protection of these animals. However, there is a paucity of information regarding the value of constructed wetlands (CWs) to amphibians, particularly relating to the terrestrial phase of their life-cycle. This study compares the terrestrial habitats of natural wetlands (NWs) and CWs as refuges for the smooth newt (Lissotriton vulgaris, [L., 1758]) with the aim of developing recommendations for CWs (both new and existing) to enhance their usefulness as newt-friendly habitats. Terrestrial habitats surrounding NWs and CWs were mapped using ArcGIS. Potential barriers to newt movement in addition to the presence of features such as wood or stone which could act as potential newt refuges were also mapped. Natural wetlands had significantly more terrestrial habitat types than CWs and while woodlands at both wetland types were most likely to contain features of benefit to newts, terrestrial habitats of NWs contained more features compared to those of CWs. The application of a Habitat Suitability Index, which assesses the likelihood of the presence of newts, resulted in seven of eight NWs compared to only two of eight CWs receiving “good” scores, the lower scores for CWs being due primarily to the presence of a barrier to newt movement. Recommendations for enhancing the design and management of CWs for smooth newts include less intensive ground maintenance, reduction of barriers to newt movement, judicious planting of suitable trees or shrubs and the provision of additional refuges such as wood or stone

Collaborative approaches in initial teacher education: lessons from approaches to developing student teachers’ use of the Internet in science teaching

In many countries, governments are keen to persuade teachers at all levels to seek to enhance the learning of their students by incorporating information and communication technologies within their classrooms. This paper reports on the development of collaborative approaches to supporting use of the Internet by Post Graduate Certificate of Education (PGCE) science students on initial teacher education (ITE) courses in England, drawing on data from five higher education institution (HEI)–school partnerships across four years. A mixed-method approach was used, involving questionnaires, structured interviews, lesson observations and case studies. The outcomes of the first three years identified barriers to practice and suggested the need to develop more collaborative approaches to development. The focus of this paper is on examining ways in which university faculty tutors and mentors or cooperating teachers can work together with students on PGCE courses in developing practice. The lessons from this focus on the Internet, no longer a new technology, have enabled us to identify implications for HEI partnerships in ITE and suggest a need for further collaborative structures in order to support and develop practices, including those involving the innovative use of new technologies in the post-industrial society

In-situ sensing, process monitoring and machine control in Laser Powder Bed Fusion: a review

Process monitoring and sensing is widely used across many industries for quality assurance, and for increasing machine uptime and reliability. Though still in the emergent stages, process monitoring is beginning to see strong adoption in the additive manufacturing community through the use of process sensors recording a wide range of optical, acoustic and thermal signals. The ability to acquire these signals in a holistic manner, coupled with intelligence-based machine control has the potential to make additive manufacturing a robust and competitive alternative to conventional fabrication techniques. This paper presents an overview of the state-of the art of in-situ process monitoring in laser powder bed fusion processes and highlights some current limitations and areas for advancement. Also presented is an overview of real-time process control requirements, which when combined with the emergent process monitoring tools, will eventually allow for in-depth process control of the powder bed fusion process, which is essential for wide-scale industrial credibility and adoption of this technology