Near infrared high efficiency InAs/GaAsSb QDLEDs: band alignment and carrier recombination mechanisms

The development of high efficiency laser diodes (LD) and light emitting diodes (LED) covering the 1.0 to 1.55 μm region of the spectra using GaAs heteroepitaxy has been long pursued. Due to the lack of materials that can be grown lattice-macthed to GaAs with bandgaps in the 1.0 to 1.55 μm region, quantum wells (QW) or quantum dots (QD) need be used. The most successful approach with QWs has been to use InGaAs, but one needs to add another element, such as N, to be able to reach 1.3/1.5μm. Even though LDs have been successfully demonstrated with the QW approach, using N leads to problems with compositional homogeneity across the wafer, and limited efficiency due to strong non-radiative recombination. The alternative approach of using InAs QDs is an attractive option, but once again, to reach the longest wavelengths one needs very large QDs and control over the size distribution and band alignment. In this work we demonstrate InAs/GaAsSb QDLEDs with high efficiencies, emitting from 1.1 to 1.52 μm, and we analyze the band alignment and carrier loss mechanisms that result from the presence of Sb in the capping layer.

Evidence of charge carrier number fluctuations in InN thin films?

Due to its small band-gap and its high mobility, InN is a promising material for a large number of key applications like band-gap engineering for high efficiency solar cells, light emitting diodes, and high speed devices. Unfortunately, it has been reported that this material exhibits strong surface charge accumulation which may depend on the type of surface. Current investigations are conducted in order to explain the mechanisms which govern such a behavior and to look for ways of avoiding it and/or finding applications that may use such an effect. In this framework, low frequency noise measurements have been performed at different temperatures on patterned MBE grown InN layers. The evolution of the 1/f noise level with temperature in the 77 K-300 K range is consistent with carrier number fluctuations thus indicating surface mechanisms: the surface charge accumulation is confirmed by the noise measurements.

Estabilidad de un buque ultra heavy lift carrier

Se plantea la posible demanda en un futuro del transporte de grandes plataformas petrolíferas semisumergibles de más de 70.000 t de peso, para perforaciones a más de 10.000 pies de profundidad. Estudia la estabilidad de buques Heavy Lift Carrier con mangas atípicas, capaces de transportar estas cargas, y en algunos casos sobresaliendo por sus amuras. Para esto se: 1. Estudia y genera posibles carenas, su compartimentación y lastre para la inmersión o emersión de la cubierta de intemperie, a más de 10 m de profundidad para tomar o dejar la carga, optimizando el proceso. 2. Analiza la estabilidad del buque tanto en inmersión/emersión y navegación, con máximas cargas y con altos centros de gravedad, y establece ábacos de estabilidad límite en función de los parámetros del buque. 3. Plantea la corrección de estabilidad excesiva del buque en condiciones de navegación para evitar las excesivas aceleraciones. Los resultados obtenidos aportan ábacos que permiten, en función de los parámetros carga a transportar (Zg max) - Peso Carga), elegir el buque más adecuado, capaz de efectuar la inmersión, emersión, y navegación, y plantea acciones futuras de investigación. ABSTRACT This work raises the potential demand in the future, to transport large semisubmersible oil rigs over 70,000 tonnes of weight for drilling to 10,000 feet deep. Study vessel stability Heavy Lift Carrier with atypical breadths capable of carrying these burdens, and in some cases standing out for their bows. 1. Examines possible hulls, their partitioning and ballast for immersion or emersion of the weather deck, more than 10 m deep to take –loading (lifting) - or leave (off- loading). 2. Analyzes the stability of the vessel both immersion / emersion and navigation, with maximum loads with high centers of gravity and stability limit states abacus according to the parameters of the ship. 3. Correction raises the stability of the ship over navigation to prevent excessive accelerations. The results allow, in terms of cargo transport parameters (Zg max) - Weight Load), choosing the most suitable vessel capable of carrying out the immersion, emersion, and navigation, and suggests future research activities.

Car Carrier 5.800 TPM

Tipo de Buque: Car Carrier. Capacidad de carga: carga 1: 3000 coches sin trailers. Carga 2: Carga combinada para 1500 ml de trailers y coches en el resto de las cubiertas del buque no ocupadas por los trailers. Peso muerto 5800 TPM. Capacidad de conductores: 100 personas en camarotes dobles. Sociedad de clasificación: Det Norske Veritas. Reglamentos: Solas, Marpol, Convenio de líneas de carga. Velocidad: 19 nudos al 85% MCR en pruebas. Autonomía: 4500 millas al 80% MCR y 15% al margen de mar. Tripulación 25 personas.

Sonar bat for visually impaired people

Visually impaired people have many difficulties when traveling because it is impossible for them to detect obstacles that stand in their way. Bats instead of using the sight to detect these obstacles use a method based on ultrasounds, as their sense of hearing is much more developed than that of sight. The aim of the project is to design and build a device based on the method used by the bats to detect obstacles and transmit this information to people with vision problems to improve their skills. The method involves sending ultrasonic waves and analyzing the echoes produced when these waves collide with an obstacle. The sent signals are pulses and the information needed is the time elapsed from we send a pulse to receive the echo produced. The speed of sound is fixed within the same environment, so measuring the time it takes the wave to make the return trip, we can easily know the distance where the object is located. To build the device we have to design the necessary circuits, fabricate printed circuit boards and mount the components. We also have to design a program that would work within the digital part, which will be responsible for performing distance calculations and generate the signals with the information for the user. The circuits are the emitter and the receiver. The transmitter circuit is responsible for generating the signals that we will use. We use an ultrasonic transmitter which operates at 40 kHz so the sent pulses have to be modulated with this frequency. For this we generate a 40 kHz wave with an astable multivibrator formed by NAND gates and a train of pulses with a timer. The signal is the product of these two signals. The circuit of the receiver is a signal conditioner which transforms the signals received by the ultrasonic receiver in square pulses. The received signals have a 40 kHz carrier, low voltage and very different shapes. In the signal conditioner we will amplify the voltage to appropriate levels, eliminate the component of 40 kHz and make the shape of the pulses square to use them digitally. To simplify the design and manufacturing process in the digital part of the device we will use the Arduino platform. The pulses sent and received echoes enter through input pins with suitable voltage levels. In the Arduino, our program will poll these two signals storing the time when a pulse occurs. These time values are analyzed and used to generate an audible signal with the user information. This information is stored in the frequency of the signal, so that the generated signal frequency varies depending on the distance at which the objects are. RESUMEN Las personas con discapacidad visual tienen muchas dificultades a la hora de desplazarse ya que les es imposible poder detectar los obstáculos que se interpongan en su camino. Los murciélagos en vez de usar la vista para detectar estos obstáculos utilizan un método basado en ultrasonidos, ya que su sentido del oído está mucho más desarrollado que el de la vista. El objetivo del proyecto es diseñar y construir un dispositivo basado en el método usado por los murciélagos para detectar obstáculos y que pueda ser usado por las personas con problemas en la vista para mejorar sus capacidades. El método utilizado consiste en enviar ondas de ultrasonidos y analizar el eco producido cuando estas ondas chocan con algún obstáculo. Las señales enviadas tendrán forma de pulsos y la información necesaria es el tiempo transcurrido entre que enviamos un pulso y recibimos el eco producido. La velocidad del sonido es fija dentro de un mismo entorno, por lo que midiendo el tiempo que tarda la onda en hacer el viaje de ida y vuelta podemos fácilmente conocer la distancia a la que se encuentra el objeto. Para construir el dispositivo tendremos que diseñar los circuitos necesarios, fabricar las placas de circuito impreso y montar los componentes. También deberemos diseñar el programa que funcionara dentro de la parte digital, que será el encargado de realizar los cálculos de la distancia y de generar las señales con la información para el usuario. Los circuitos diseñados corresponden uno al emisor y otro al receptor. El circuito emisor es el encargado de generar las señales que vamos a emitir. Vamos a usar un emisor de ultrasonidos que funciona a 40 kHz por lo que los pulsos que enviemos van a tener que estar modulados con esta frecuencia. Para ello generamos una onda de 40 kHz mediante un multivibrador aestable formado por puertas NAND y un tren de pulsos con un timer. La señal enviada es el producto de estas dos señales. El circuito de la parte del receptor es un acondicionador de señal que transforma las señales recibidas por el receptor de ultrasonidos en pulsos cuadrados. Las señales recibidas tienen una portadora de 40 kHz para poder usarlas con el receptor de ultrasonidos, bajo voltaje y formas muy diversas. En el acondicionador de señal amplificaremos el voltaje a niveles adecuados además de eliminar la componente de 40 kHz y conseguir pulsos cuadrados que podamos usar de forma digital. Para simplificar el proceso de diseño y fabricación en la parte digital del dispositivo usaremos la plataforma Arduino. Las señales correspondientes el envío de los pulsos y a la recepción de los ecos entraran por pines de entrada después de haber adaptado los niveles de voltaje. En el Arduino, nuestro programa sondeara estas dos señales almacenando el tiempo en el que se produce un pulso. Estos valores de tiempo se analizan y se usan para generar una señal audible con la información para el usuario. Esta información ira almacenada en la frecuencia de la señal, por lo que la señal generada variará su frecuencia en función de la distancia a la que se encuentren los objetos.

Electrochemical potentials (Quasi-Fermi Levels) and the operation of hot-carrier, impact-ionization, and intermediate-band solar cells

In the framework of the so-called third generation solar cells, three main concepts have been proposed in order to exceed the limiting efficiency of single-gap solar cells: the hot-carrier solar cell, the impact-ionization or multiple-exciton-generation solar cell, and the intermediate-band solar cell. At first sight, the three concepts are different, but in this paper, we illustrate how all these concepts, including the single-gap solar cell, share a common trunk that we call "core photovoltaic material." We demonstrate that each one of these next-generation concepts differentiates in fact from this trunk depending on the hypotheses that are made about the physical principles governing the electron electrochemical potentials. In the process, we also clarify the differences between electron, phonon, and photon chemical potentials (the three fundamental particles involved in the operation of the solar cell). The in-depth discussion of the physics involved about the operation of these cells also provides new insights about the operation of these cells.

Controlled exercise as a tool for preventing obesity and metabolic diseases in Arg64 carrier women.

Genética y ejercicio.

Analysis of wave attenuation and shore protection of a bulk carrier ship performing as a detached floating breakwater

Análisis de la atenuación del oleaje por un carguero funcionando como dique flotante y aplicación a dos casos de protección portuaria y costera. The effectiveness of a bulk carrier working as a detached floating breakwater to protect a stretch of coast and form salients or tombolos is assessed in this paper. Experiments were conducted in the Madrid CEDEX facilities in a 30 m long, 3 m wide, 1/150 scale flume. The bulk carrier ship is 205 m long, 29 m wide and 18 m in height with a draught of 13 m, and has been subjected to irregular waves with significant heights from 2 m to 4 m and peak periods from 6 s to 12 s at a depth of 15 m, all prototype dimensions. Three probes were placed between the wave paddle and the ship to record incident and reflected waves and four probes were placed between the ship and the coastline to measure the transmitted waves. Transmission, reflection and dissipation coefficients (Ct, Cr, Cd) were calculated to determine wave attenuation. Results show good shelter in the lee of the ship with values of Ct under 0.5 for peak periods from 6 s to 11 s. In addition, forces on the mooring chains were measured showing maximum values of about 2000 tons at a 10 speak period. Finally, two analytical models were used to determine the shoreline’s response to the ship’s protection and to assess the possible forming of salients or tombolos. According to the results, salients - but not tombolos - are formed in all tests.

On the Absence of Carrier Drift in Two-Terminal Devices and the Origin of Their Lowest Resistance per Carrier RK= h/q^2

After a criticism on today’s model for electrical noise in resistors, we pass to use a Quantum-compliant model based on the discreteness of electrical charge in a complex Admittance. From this new model we show that carrier drift viewed as charged particle motion in response to an electric field is unlike to occur in bulk regions of Solid-State devices where carriers react as dipoles against this field. The absence of the shot noise that charges drifting in resistors should produce and the evolution of the Phase Noise with the active power existing in the resonators of L-C oscillators, are two effects added in proof for this conduction model without carrier drift where the resistance of any two-terminal device becomes discrete and has a minimum value per carrier that is the Quantum resistance RK/(2pi)