Laser ablation modelling of aluminium, silver and crystalline silicon for applications in photovoltaic technologies

Laser material processing is being extensively used in photovoltaic applications for both the fabrication of thin film modules and the enhancement of the crystalline silicon solar cells. The two temperature model for thermal diffusion was numerically solved in this paper. Laser pulses of 1064, 532 or 248 nm with duration of 35, 26 or 10 ns were considered as the thermal source leading to the material ablation. Considering high irradiance levels (108–109 W cm−2), a total absorption of the energy during the ablation process was assumed in the model. The materials analysed in the simulation were aluminium (Al) and silver (Ag), which are commonly used as metallic electrodes in photovoltaic devices. Moreover, thermal diffusion was also simulated for crystalline silicon (c-Si). A similar trend of temperature as a function of depth and time was found for both metals and c-Si regardless of the employed wavelength. For each material, the ablation depth dependence on laser pulse parameters was determined by means of an ablation criterion. Thus, after the laser pulse, the maximum depth for which the total energy stored in the material is equal to the vaporisation enthalpy was considered as the ablation depth. For all cases, the ablation depth increased with the laser pulse fluence and did not exhibit a clear correlation with the radiation wavelength. Finally, the experimental validation of the simulation results was carried out and the ability of the model with the initial hypothesis of total energy absorption to closely fit experimental results was confirmed

Componente de indexación de huellas dactilares basado en características globales

The fingerprint orientation field is a widely used feature for developing indexing strategies. Such feature brings stability and decreases the response times during the identification process. The use of attribute relational graphs and dynamic masks can exploit the features provided by the partitioning scheme. The penetration index and the error rate for each of the proposed strategies were determined. To verify the results obtained were used the databases provided by the Fingerprint Verification Competition. Both search schemes reveal the facilities offered by the orientation field for guiding the searching process; reducing the number of comparisons in 53.24%; proving its stability against different fingerprint image qualities. Based on the results, it was proven that the adoption of such indexing strategies will reduce the response time in the identification module proposed by the Identification and Digital Security Center at the University of Informatics Sciences.El campo de orientación de la huella dactilar como característica global es fundamental para el desarrollo de una estrategia de indexación, aportando estabilidad y disminuyendo los tiempos de respuesta durante el proceso de búsqueda de un sistema de identificación basado en huellas dactilares. El empleo de grafos relacionales de atributos y máscaras dinámicas permite explotar las características brindadas por el esquema de particionado para la búsqueda. De cada una de las estrategias propuestas se determinó el índice de penetración de la base de datos, así como el error en que incurren los algoritmos de indexación implementados. Para corroborar los resultados obtenidos fueron empleados los bancos de datos aportados por la Competencia de verificación de huellas dactilares. La implementación computacional de las estrategias de búsquedas propuestas demuestra las virtudes que ofrece el campo de orientación para dirigir el proceso de búsqueda, logrando reducir el número de comparaciones en un 53.24% como promedio, comportándose de manera estable ante imágenes de huellas dactilares de diferente calidad. Basado en los resultados del estudio se concluyó que la adopción de dichas estrategias de indexación permitirá reducir el tiempo de respuesta en el módulo de identificación de individuos basado en patrones de la huella dactilar propuesto por el Centro de Identificación y Seguridad Digital de la Universidad de las Ciencias Informáticas

Dependency, White Privilege, and Transnational Hegemonic Reconfiguration: Investigating Systems of Power and Identity Privilege in The Bahamas

White cultural hegemony has been used as a determinant of identity privilege in The Bahamas since the beginning of British colonialism. This ideal justifies and confers the dominance of whiteness while also including a moral responsibility to enforce the racial hierarchy as a part of a "global cognitive dysfunction" (Mills 18) that sees non-white actors as intrinsically lesser; an understanding Charles Mills argues is needed to uphold a racialized social contract. This “grammar of racial difference” inculcates the need for whiteness to act as savior through the subjugation and cultural integration of the “other” (Mahmud). However, beyond its role as a dysfunction, this conception of a moral obligation—or colloquially, a ‘white savior complex’—guides understandings of why colonial leaders forged hegemonic relationships with the U.S. despite the country’s apparent intent to achieve independence. These relationships were a strategic part of a colonial-savior complex and adherence to a global system that values 'whiteness.'  This paper suggests that despite independence, The Bahamas remains subjected to the dependency role under a system of white privilege, resulting from colonial agreements made with the United States, and multi-national agencies, and regulatory bodies that enforce a hegemonic reconstruction of influence. Ergo, the cultural hegemony of the United States as an industrialized giant merely filled the void that the British rule left behind

Green Gold Is No More

With the collapse of the Banana industry, Gabriel was thrust into a new reality that highlights the challenges of life under the externalities of neocolonialism. Almost 10 years later, Allahdua is one of many who have endured Canada’s migrant worker programmes and is currently an advocate for change