Self-tuning of disk input–output in operating systems

The final publication is available via http://dx.doi.org/10.1016/j.jss.2011.07.030One of the most difficult and hard to learn tasks in computer system management is tuning the kernel parameters in order to get the maximum performance. Traditionally, this tuning has been set using either fixed configurations or the subjective administrator's criteria. The main bottleneck among the subsystems managed by the operating systems is disk input/output (I/O). An evolutionary module has been developed to perform the tuning of this subsystem automatically, using an adaptive and dynamic approach. Any computer change, both at the hardware level, and due to the nature of the workload itself, will make our module adapt automatically and in a transparent way. Thus, system administrators are released from this kind of task and able to achieve some optimal performances adapted to the framework of each of their systems. The experiment made shows a productivity increase in 88.2% of cases and an average improvement of 29.63% with regard to the default configuration of the Linux operating system. A decrease of the average latency was achieved in 77.5% of cases and the mean decrease in the request processing time of I/O was 12.79%

Double-pass technique and compensation-comparison method in eyes with cataract

PURPOSE To clinically assess the objective scatter index (OSI) obtained from double-pass images and the log(s) parameter measured with the direct compensation-comparison psychophysical technique in eyes with cataract. SETTING Ophthalmology Service, Terrassa Hospital, Barcelona, Spain. DESIGN Prospective observational case series. METHODS The analysis comprised eyes diagnosed with nuclear, cortical, or posterior subcapsular cataracts and healthy eyes (control group). Patient examinations included assessment of the manifest subjective refraction, corrected distance visual acuity, contrast sensitivity, and cataract grade using the Lens Opacities Classification System III (LOCS III) score. The protocol also included the straylight (log[s]) measured by the C-Quant device, measurement of the objective optical quality (Strehl ratio and modulation transfer function cutoff frequency), and the OSI (HD Analyzer). RESULTS Significant correlations with LOCS III classification were found in terms of log(s) and OSI, although they were slightly stronger with OSI for all cataract types, which could be attributable to higher-order aberrations. The OSI and log(s) shared approximately 44% of the scattering estimation and to coincide on the visual function decline with scattering for the 3 cataract types evaluated. Limits to discriminate between healthy and cataractous eyes and sensitivity and specificity values were 1.15 (sensitivity 91%, specificity 100%) for log(s) and 1.18 (sensitivity 89%, specificity 100%) for OSI (P < .05). CONCLUSIONS Both instruments provide complementary information to diagnose cataracts and follow patients. Although backscattered light from deeper retinal layers can have an effect on OSI, the double-pass image provides information to grade different types of cataract when assessing cataractous eyes for treatment.Preprin

Characterization of high-power white leds for VLC applications

During the last years, visible light communications (VLC) have been proposed for providing connectivity while ensuring satisfactory illumination in both indoor environments and also specific outdoor scenarios without the need of deploying complex infrastructures for that purpose. Transmission for VLC is carried out through lightemitting diodes (LEDs), which correspond to semiconductors based on PN-junction materials with a direct gap. In this sense, the current flow plays a major role in the behavior and performance of these devices for VLC. Therefore, characterizing the electrical response of high-power white LED results mandatory for the successful implementation of VLC. At this point, it is worth noting that the electrical characterization is usually not available for high-power LEDs since, in fact, determining these characterization results challenging. In this sense, there exist some measurement instruments such as LCRs or impedance analyzers typically employed for characterizing materials and passive electrical components. However, these kinds of instruments are subject to a limited input impedance and a maximum value of forwarding current. In this work, the electrical characterization of the LED LXHL-BW02 of Luxeon is analyzed to show that typically commercial instrumentation for characterizing these devices is limited for high-power LEDs, which may provide polluted results when these limitations are not considered. After that, the characterization of the LXHL-BW02 based on a lock-in amplifier is proposed.This research was co-financed by Comunidad de Madrid and the FSE/FEDER Program under grant SINFOTON2-CM (S2018/NMT-4326), the Universidad Carlos III de Madrid under grant 2020/00038/001, and the Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación (PID2019-109072RB-C31), and the European Regional Development Fund (ERDF) EXP 00119337/IDI-2019029

An enhanced method for dynamic characterization of high-power LEDs for visible light communication applications

Visible light communications (VLC) have been proposed for several applications beyond the traditional indoor scenarios, from vehicular to underwater communications. The common element in all these applications is the use of light-emitting diodes (LEDs) in which the forward current that flows through each LED plays a major role. Therefore, knowing the electrical equivalent of the LEDs is a useful tool for the proper design of the VLC systems. Currently, some measurement instruments exist, such as the LCR (inductance, capacitance, and resistance) meters or impedance analyzers to characterize the main parameters of the LEDs. However, these instruments and measurement procedures are subject to satisfying some requirements, such as a minimum value of the input impedance or the maximum forward current. In this work, the LED LXHL-BW02 is used to obtain its equivalent circuit, using different measurement methods and traditional methods of measurement with our proposed method. The equivalent model is implemented on the simulation tool LTSPICE. Our alternative method can be used for determining the electrical equivalent circuit of LEDs subject to high current variations at very high frequencies, in the MHz range, i.e., in an operating range for VLC applications.This research was co-financed by Comunidad de Madrid and the FSE/FEDER Program under grant SINFOTON2-CM (S2018/NMT-4326), the Madrid Government (Comunidad de Madrid) under the Multiannual Agreement with UC3M in the line of “Fostering Young Doctors Research” (GEOVEOLUZ-CM-UC3M), and in the context of the V PRICIT (Regional Programme of Research and Technological Innovation, and the Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación (PID2019-109072RB-C31) and under the CDTI (Centre for the Development of Industrial Technology, Ministerio de Ciencia e Innovación) throughthe European Regional Development Fund (ERDF) EXP 00119337/IDI-2019029

Microwave foaming of sodium silicate-ortodibasic calcium phosphate mixtures

[ES] La acción de la energía de las microondas, genera porosidad interna en un material cerámico húmedo. En el presente trabajo, se analiza el efecto del tiempo de aplicación de las microondas sobre el comportamiento térmico, cambio de volumen, tamaño y distribución de poros, reacciones químicas y disolución de probetas cerámicas de silicato de sodio / ortofosfato cálcico dibásico (FCD). Para caracterizar las espumas cerámicas, se utilizó, análisis de imágenes, microscopía electrónica de barrido, difracción de rayos X y picnometría de helio. Se obtuvieron espumas cerámicas con una porosidad de 71 a 79 % y un rango de tamaño de poro de 10 a 200 μm. Después de 90 segundos, las probetas alcanzaron una temperatura de aproximadamente 130°C y una pérdida de peso de 23% con respecto al peso total de la muestra. Se observaron cambios de volumen y de los compuestos químicos en las muestras espumadas cuando se varió la proporción del FCD en la mezcla. Para contenidos de 10, 20 y 30% en peso de FCD, el incremento de volumen se redujo a 350, 300 y 250% respectivamente. En muestras con 30% de FCD calentadas por microondas durante 90 segundos la cantidad de un nuevo compuesto en la espuma, constituido por β-NaCaPO4, fue del orden de 42.9%. En esa misma muestra, el 57.1 % restante fue FCD. Considerando pruebas de disolución de un gramo de muestra en 100 ml de agua destilada, la disolución obtenida en muestras espumadas por microondas después de 20 días fue de 900 ppm/gr para el Na y de 2.7 ppm/gr para el Ca en muestras con 10% de FCD. En muestras con 30% de FCD la disolución de Na fue de 470 ppm/gr y del Ca de 5 ppm/gr.[EN] The effect of microwave application on the thermal behaviour, volume change, size and pore size distribution as well as chemical reactions and dissolution of sodium silicate/dibasic calcium phosphate ceramic (DCF) samples have been analysed. Ceramics foams with porosities between 71 and 79 wt% and pore sizes ranging from 10 to 200 microns have been obtained. After 90 seconds the temperature of samples reach about 130 °C with a weight loss of 23 wt%. Differences in the proportion of DCF in the initial mixture originate changes in volume and different chemical compounds in the final obtained foams. Additions of 10, 20 and 30 wt% of DCF originates volume increases of 350, 300 and 250 % respectively. In foam samples with 30 wt% of DCF, heated by microwave during 90 sec., the amount of the new compound β-NaCaPO4 was about 42.9 wt%. The other component of this sample, 57.1 wt%, was DCF. Dissolution tests were made, using one gram of sample, in 100 ml of distilled water. The dissolution of 10 wt% DCF foamed samples, after 20 days into water, were 900 ppm/gr of Na and 2.7 ppm/gr of Ca. In samples with 30 wt% of DCF the dissolution were 470 ppm/gr and 5 ppm/gr for Na and Ca respectively.Peer reviewe

Using an extended Roofline Model to understand data and thread affinities on NUMA systems

Today’s microprocessors include multicores that feature a diverse set of compute cores and onboard memory subsystems connected by complex communication networks and protocols. The analysis of factors that affect performance in such complex systems is far from being an easy task. Anyway, it is clear that increasing data locality and affinity is one of the main challenges to reduce the access latency to data. As the number of cores increases, the influence of this issue on the performance of parallel codes is more and more important. Therefore, models to characterize the performance in such systems are broadly demanded. This paper shows the use of an extension of the well known Roofline Model adapted to the main features of the memory hierarchy present in most of the current multicore systems. Also the Roofline Model was extended to show the dynamic evolution of the execution of a given code. In order to reduce the overheads to get the information needed to obtain this dynamic Roofline Model, hardware counters present in most of the current microprocessors are used. To illustrate its use, two simple parallel vector operations, SAXPY and SDOT, were considered. Different access strides and initial location of vectors in memory modules were used to show the influence of different scenarios in terms of locality and affinity. The effect of thread migration were also considered. We conclude that the proposed Roofline Model is an useful tool to understand and characterise the behaviour of the execution of parallel codes in multicore systemsThis work has been partially supported by the Ministry of Education and Science of Spain, FEDER funds under contract TIN 2010-17541, and Xunta de Galicia, EM2013/041. It has been developed in the framework of the European network HiPEAC and the Spanish network CAPAP-HS

Design and experimental implementation of a multi-cloak paraxial optical system

Electromagnetic cloaking has being continuously pursued using a large variety of approaches. In recent years, this effect has been observed using either complex devices based on the so-called Transformation Optics or simple systems based on conventional optics with proper characteristics. In the latter case, a simple arrangement of lenses working in the paraxial regime can provide broadband visible cloaking in a wide area. In this work, we analyzed and generalized this method by proposing a five-lens system producing at least three potential invisible regions with a large cloaked area (>90% of the visual field). In particular, we developed the mathematical formalism and show, both numerically and experimentally, the successful operation of the cloaking system with the naked eye.AF-H wants also to express her grattitude to the Ministerio de Universidades for her predoctoral grant (FPU19/04133)

Induced Magnetic Anisotropy in Liquid Crystals Doped with Resonant Semiconductor Nanoparticles

Currently, there are many efforts to improve the electrooptical properties of liquid crystals by means of doping them with different types of nanoparticles. In addition, liquid crystals may be used as active media to dynamically control other interesting phenomena, such as light scattering resonances. In this sense, mixtures of resonant nanoparticles hosted in a liquid crystal could be a potential metamaterial with interesting properties. In this work, the artificial magnetism induced in a mixture of semiconductor nanoparticles surrounded by a liquid crystal is analyzed. Effective magnetic permeability of mixtures has been obtained using the Maxwell-Garnett effective medium theory. Furthermore, permeability variations with nanoparticles size and their concentration in the liquid crystal, as well as the magnetic anisotropy, have been studied

Aplicación de las normas internacionales de información financiera en pequeñas y medianas entidades en la Argentina

El presente trabajo tiene por finalidad brindar mayor conocimiento y explicación sobre las normas internacionales de información financiera para pequeñas y medianas entidades (NIIF para PyMEs) y sus diferencias con las normas contables argentinas. Actualmente la coyuntura internacional de los negocios indica que el contar con un lenguaje contable común representa una gran ventaja. En nuestro país favorecerá la homogenización de la información contable, permitiendo así su transparencia y comparabilidad respecto de entidades de otros países, como así también aumentando su confiabilidad. Por tal motivo se ha decidido profundizar en este tema y tratar de analizar y comprender, a través de una comparación simple, las diferencias y similitudes con las normas contables profesionales argentinas. Ello a través de un material claro y de fácil comprensión de los aspectos teóricos y prácticos que hacen a la casuística de dicho tema.Fil: Moreno, Gabriel Eduardo. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas.Fil: Mugneco, Carlos Fernando. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas.Fil: Pena, Laura Patricia. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas.Fil: Petito, Juan Jesús. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas.Fil: Ruiz Díaz, Maximiliano. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas