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

Understanding Coalition Dynamics: A Role Play Class Activity

The purpose of this activity is to illustrate the role and challenges of coalitions in group conflict and decision making. In this activity, students take on the roles of organizational members tasked to arrive at consensus, but having different goals, interests, and information that could impact the decision. In discussing this activity experience, instructors can illustrate the six principles of coalitions presented in Wilmot and Hocker’s Interpersonal Conflict text. This activity is applicable to any course that addresses conflict and group interaction, including interpersonal and group communication, organizational and professional communication, family communication, and workplace skills seminars

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

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

A cloud-based parallel system for locating customers in indoor malls

Advances in techniques of locating mobile users have promoted the development of marketing campaigns based on customers’ location. WiFi-based location methods have proven their usefulness in tracking and locating customers within a indoor mall. Nevertheless, in some cases the performance of these methods prevents them from being used in real scenarios. In this paper, we have faced the problem of improving the execution time and reducing the cost of one of these WiFi-based location methods. Parallel programming techniques, service-oriented technologies and the cloud computing paradigm have been combined to solve efficiently these problems. The resulting system has been deployed in the Amazon EC2 environment, evaluating different configuration and deployment options