Laser Shock Microforming of Thin Metal Sheets

Continuous and long-pulse lasers have been used for the forming of metal sheets in macroscopic mechanical applications. However, for the manufacturing of micro-electromechanical systems (MEMS), the applicability of such type of lasers is limited by the long-relaxation-time of the thermal fields responsible for the forming phenomena. As a consequence of such slow relaxation, the final sheet deformation state is attained only after a certain time, what makes the generated internal residual stress fields more dependent on ambient conditions and might make difficult the subsequent assembly process from the point of view of residual stresses due to adjustment. The use of ns laser pulses provides a suitable parameter matching for the laser forming of an important range of sheet components used in MEMS that, preserving the short interaction time scale required for the predominantly mechanic (shock) induction of deformation residual stresses, allows for the successful processing of components in a medium range of miniaturization, particularly important according to its frequent use in such systems. In the present paper, a discussion is presented on the physics of laser shock microforming and the influence of the different effects on the net bending angle. The experimental setup used for the experiments, sample fabrication and experimental results of influence of number of laser pulses on the net bending angle are also presented

Laser Shock Microformingof Thin Metal Sheets with ns Lasers

Continuous and long-pulse lasers have been used for the forming of metal sheets in macroscopic mechanical applications. However, for the manufacturing of micro-electromechanical systems (MEMS), the use of ns laser pulses provides a suitable parameter matching over an important range of sheet components that, preserving the short interaction time scale required for the predominantly mechanical (shock) induction of deformation residual stresses, allows for the successful processing of components in a medium range of miniaturization without appreciable thermal deformation.. In the present paper, the physics of laser shock microforming and the influence of the different experimental parameters on the net bending angle are presented

Model based optimization criteria for the generation of deep compressive residual stress fields in high elastic limit metallic alloys by ns-laser shock processing

Laser Shock Processing (LSP) is based on the application of a high intensity pulsed Laser beam (IN1 GW/cm2; τb50 ns) on a metallic target forcing a sudden vaporization of its surface into a high temperature and density plasma that immediately develops inducing a shock wave propagating into the material. The main acknowledged advantages of LSP consist on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behavior, explicitly, the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Due to these specific advantages, Laser Shock Processing is considered as a competitive alternative technology to classical treatments for improving fatigue, corrosion cracking and wear resistance of metallic materials, and is being developed as a practical process amenable to production technology. In this paper, a model based systematization of process optimization criteria and a practical assessment on the real possibilities of the technique is presented along with practical results at laboratory scale on the application of LSP to characteristic high elastic limit metallic alloys, showing the induced residual stresses fields and the corresponding results on mechanical properties improvement induced by the treatment. The homogeneity of the residual stress fields distribution following the laser treatment spatial density will be specially analyzed

Angle Dependence of the Transverse Thermal Conductivity in YBa2_2Cu3_3O7_7 single crystals: Doppler Effect vs. Andreev scattering

We have measured the transverse thermal conductivity $\kappa_{xy}$ of twinned and untwinned YBa$_2$Cu$_3$O$_7$ single crystals as a function of angle $\theta$ between the magnetic field applied parallel to the CuO$_2$ planes and the heat current direction, at different magnetic fields and temperatures. For both crystals we observed a clear twofold variation in the field-angle dependence of $\kappa_{xy}(\theta) = - \kappa^0_{xy}(T,B) \sin(2\theta)$. We have found that the oscillation amplitude $\kappa^0_{xy}$ depends on temperature and magnetic field. Our results show that $\kappa^0_{xy} = a B \ln(1/(bB))$ with the temperature- and sample-dependent parameters $a$ and $b$. We discuss our results in terms of Andreev scattering of quasiparticles by vortices and a recently proposed theory based on the Doppler shift in the quasiparticle spectrum.Comment: 5 pages, 4 figure

Multicriteria evaluation by gis to determine trail hiking suitability in a natural park

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Life cycle assessment of biowaste and green waste composting systems : A review of applications and implementation challenges

Altres ajuts: acords transformatius de la UABComposting is one of the most widely applied methods for recycling organic waste. This process has been proposed as one option that facilitates the reincorporation of materials into the production cycle. However, composting also generates environmental impacts. Life Cycle Assessment (LCA) is the most common approach to evaluate the environmental impacts of a process at different system stages. Nevertheless, applying LCA in composting facilities is challenging due to the extensive information required, the lack of standardization on the initial assumptions, the definition of system boundaries, and the high diversity of existing composting technologies. This paper systematically reviews LCA studies in biowaste and/or green waste composting. The study highlights the challenges that should be met in order to improving the application of LCA to evaluate the environmental impacts of this type or waste treatment strategy. The review protocol used identified 456 papers published between 2010 and 2022. After the screening, 56 papers were selected, read, and thoroughly analyzed. The results show that: i) about 68% of the studies aimed to compare composting with other solid waste management options; ii) there was a wide diversity among the impact categories considered, which predominantly included climate change and ozone depletion; iii) there was no consensus on the functional unit or the system boundaries; iv) the main gaseous emissions studied were ammonia, methane, and nitrogen oxide, which were generally determined by emission factors; v) the avoided environmental impacts associated with the end-product quality and its application as an organic amendment or soil improver were ignored. This work demonstrates the complexity of conducting credible and valid composting LCA studies and proposes seven recommendations for improving the application of this assessment methodology to analyze this waste management alternative

Thermal Conductivity Tensor in YBa2_2Cu3_3O7−x_{7-x}: Effects of a Planar Magnetic Field

We have measured the thermal conductivity tensor of a twinned YBa$_2$Cu$_3$O$_{7-x}$ single crystal as a function of angle $\theta$ between the magnetic field applied parallel to the CuO$_2$ planes and the heat current direction, at different magnetic fields and at T=13.8 K. Clear fourfold and twofold variations in the field-angle dependence of $\kappa_{xx}$ and $\kappa_{xy}$ were respectively recorded in accordance with the d-wave pairing symmetry of the order parameter. The oscillation amplitude of the transverse thermal conductivity $\kappa^0_{xy}$ was found to be larger than the longitudinal one $\kappa^0_{xx}$ in the range of magnetic field studied here ($0 T$$\le B \le 9$$T$). From our data we obtain quantities that are free from non-electronic contributions and they allow us a comparison of the experimental results with current models for the quasiparticle transport in the mixed state.Comment: 9 Figures, Phys. Rev. B(in press

Anémonas anillo, una visión general (Cnidaria, Anthozoa, Actiniaria)

The present observations represent a new record of species of Actiniaria that are able to attach to a gorgonian branch by surrounding it with a solid piece of tissue junction and a significant reduction of the coelenteron. Ring sea anemones are provisionally placed in the Actinostolidae. They seem to be more common at depths between 85 and 1500 m., and according to our observations they are specialized to exclusively colonize on some species of gorgonians or pennatulaceans. Parasitism best describes the relationship between ring sea anemones and their hosts. We recognize five different species of ring sea anemones, one described by Hiles (1899) as Peronanthus verrucellae, and the others named by us provisionally as Peronanthus sp1, sp2, sp3 & sp4. The strategy displayed by ring sea anemones has several advantages, such as placement economy (see above), a better attachment against any current action, exploitation of food resources inaccessible to most other Actiniarians, and it allows them avoidance of habitat competition. The impossibility to colonize any other substrate but a certain group of gorgonians and a reduction of the gastric cavity are the main disadvantages detected in the ring sea anemones’ way of life. Apparently, this group of sea anemones is widespread through the Pacific Ocean.Un nuevo grupo de especies de actiniarios que desarrollan un nuevo sistema para afianzarse alrededor de los ejes de gorgonias y pennatuláceos es estudiado por nosotros en el presente trabajo. Se trata de un anillo de tejido que rodea los ejes y queda perfectamente sellado por medio de uniones del tejido produciendo una reducción del celenterón. Anémonas anillo es como las hemos denominado y provisionalmente han sido incluidas dentro de la familia Actinostolidae. Parece que son comunes en profundidades comprendidas entre los 85 y los 1500 metros, colonizando solamente determinadas especies de gorgonias y de pennatuláceos. El parasitismo es la relación que mejor describe lo que acontece entre las anémonas y los octocorales que la portan. Hay, al menos, cinco especies diferentes de anémonas anillo, la primera fue descrita por Hiles (1899) como Peronanthus verrucellae, las otras especies las denominamos provisionalmente como Peronanthus sp1, sp2, sp3 y sp4. El modo de vida de estas especies presenta ciertas ventajas como son: una reducción del espacio para asentarse, una mejor fijación frente a fenómenos de corriente, la capacidad para explotar recursos inaccesibles a la mayoría de los actiniarios y por último la falta de competencia con otras especies por el hábitat. La imposibilidad de colonizar otros sustratos y la reducción de la cavidad gástrica son las principales desventajas que presenta este modo de vida exhibido por las anémonas anillo. Aparentemente este grupo de anémonas está ampliamente distribuido en el Indo-Pacífico

Ansiedad, estrategias y recursos para el afrontamiento de trabajadores de salud en primera línea COVID-19 del primer nivel de atención, Cajamarca, 2021

The COVID 19 pandemic causes a serious disorder to the health system throughout the world, with a great effect on mental health in those who provide health services, one of the manifestations being anxiety; The magnitude of this problem in the health workers of the first level of care in Cajamarca is unknown, so a cross-sectional descriptive study is carried out with the objective of describing the anxiety, coping strategies and support resources that workers prefer.To a sample of 122 health workers (95% CI), a questionnaire is applied that collects data regarding the characteristics of health workers and health establishments; A GAD-7 test is administered to screen for anxiety and a questionnaire on coping strategies and support resources with rating scales. The prevalence of anxiety symptoms is 54.1%; corresponding to mild (32.8%), moderate and severe (10.7% respectively). 92.6% use at least one or more coping strategies, 95.9% have some level of interest in one or more proposed support resources; anxiety is more frequent in those who are interested in at least one support resource and independently in 3 of these (P <0.05). Concluding that during the COVID-19 pandemic there is a high prevalence of anxiety, one in 5 health workers requires intervention from a mental health specialist due to symptoms of moderate and severe anxiety, the majority use coping strategies and have preferences for support resources proposedLa pandemia COVID 19 ocasiona un grave trastorno al sistema de salud en todo el mundo, con gran efecto en la salud mental en los que brindan servicios de salud, siendo una de las manifestaciones la ansiedad; desconociéndose la magnitud de este problema en los trabajadores de salud del primer nivel de atención de Cajamarca, por lo que se realiza un estudio descriptivo transversal con el objetivo de describir la ansiedad, estrategias de afrontamiento y recursos de apoyo que prefieren los trabajadores. A una muestra de 122 trabajadores de salud (IC 95%), se aplica un cuestionario que recoge datos respecto a características de los trabajadores y establecimientos de salud; se administra un test de GAD-7 para cribaje de ansiedad y un cuestionario de estrategias de afrontamiento y recursos de apoyo con escalas valorativas. La prevalencia de síntomas de ansiedad es del 54,1%; correspondienedo a leve (32,8%), moderada y grave (10,7% respectivamente). El 92.6% utiliza por lo menos una o más estrategias de afrontamiento, el 95.9% tiene algún nivel de interés por uno o más recursos de apoyo propuestos; la ansiedad es mas frecuente en los que tienen interés al menos en algún recurso de apoyo e independientemente en 3 de estos (P< 0.05). Concluyéndose que durante la pandemia COVID-19 hay alta prevalencia de ansiedad, uno de cada 5 trabajadores de salud requiere intervención de especialista en salud mental por presentar síntomas de ansiedad moderada y grave, la mayoría utiliza estrategias de afrontamiento y tiene prefeencias por recursos de apoyo propuestos