Methane and sulfide fluxes in permanent anoxia: in situ studies at the Dvurechenskii mud volcano (Sorokin Trough, Black Sea)

The Dvurechenskii mud volcano (DMV), located in permanently anoxic waters at 2060 m depth (Sorokin Trough, Black Sea), was visited during the M72/2 cruise with the RV Meteor to investigate the methane and sulfide release from mud volcanoes into the Black Sea hydrosphere. We studied benthic fluxes of methane and sulfide, and the factors controlling transport, consumption and production of both compounds within the sediment. The pie shaped mud volcano showed temperature anomalies as well as solute and gas fluxes indicating high fluid flow at a small elevation north of the geographical center. The anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) was excluded from this zone due to fluid-flow induced sulfate limitation and a fresh mud flow and consequently methane escaped into the water column with a rate of 0.46 mol/m**2/d. In the outer center of the mud volcano fluid flow and total methane flux were decreased, correlating with an increase in sulfate penetration into the sediment, and with higher SR and AOM rates. Here between 50-70% of the methane flux (0.07-0.1 mol/m**2/d) was consumed within the upper 10 cm of the sediment. Also at the edge of the mud volcano fluid flow and rates of methane and sulfate turnover were substantial. The overall amount of dissolved methane released from the mud volcano into the water column was significant with a discharge of 1.4x10**7 mol/yr. The DMV maintains also high areal rates of methane-fueled sulfide production of on average 0.05 mol/m**2/d. However, we concluded that sulfide and methane emission into the hydrosphere from deep water mud volcanoes does not significantly contribute to the sulfide and methane inventory of the Black Sea.

The informal labour market in India : transitory or permanent employment for migrants?

The informal economy is a very important sector of the Indian economy. The National Council of Applied Economic Research estimates that the informal sector - "unorganised sector" - generates about 62% of GDP and provides for about 55% of total employment (ILO 2002, p. 14). This paper studies the characteristics of the workers in the informal economy and whether internal migrants treat this sector as a temporary location before moving on to the organised or formal sector to improve their lifetime income and living conditions. We limit our study to the Indian urban (non-agricultural) sector and study the characteristics of the household heads that belong to the informal sector (self-employed and informal wage workers) and the formal sector. We find that household heads that are less educated, come from poorer households, and/or are in lower social groups (castes and religions) are more likely to be in the informal sector. In addition, our results show strong evidence that the longer a rural migrant household head has been working in the urban sector, ceteris paribus, the more likely that individual has moved out of the informal wage sector. These results support the hypothesis that, for internal migrants, the informal wage labour market is a stepping stone to a better and more certain life in the formal sector.

Torque control of switched reluctance motors

This paper presents the performance of an instantaneous torque control method. The simulation and experimental results illustrate the capability of Switched Reluctance Motors (SRM) being used in the motor drive industry. Based on experimental data, the advantages of this control method and its disadvantages in practical implementation were studied. The model used in the simulation is the linear magnetic model which has the 12/8 structure, the same structure as the experimental switched reluctance motor.

Modelling and Control of Stepper Motors for High Accuracy Positioning Systems Used in Radioactive Environments

Hybrid Stepper Motors are widely used in open-loop position applications. They are the choice of actuation for the collimators in the Large Hadron Collider, the largest particle accelerator at CERN. In this case the positioning requirements and the highly radioactive operating environment are unique. The latter forces both the use of long cables to connect the motors to the drives which act as transmission lines and also prevents the use of standard position sensors. However, reliable and precise operation of the collimators is critical for the machine, requiring the prevention of step loss in the motors and maintenance to be foreseen in case of mechanical degradation. In order to make the above possible, an approach is proposed for the application of an Extended Kalman Filter to a sensorless stepper motor drive, when the motor is separated from its drive by long cables. When the long cables and high frequency pulse width modulated control voltage signals are used together, the electrical signals difer greatly between the motor and drive-side of the cable. Since in the considered case only drive-side data is available, it is therefore necessary to estimate the motor-side signals. Modelling the entire cable and motor system in an Extended Kalman Filter is too computationally intensive for standard embedded real-time platforms. It is, in consequence, proposed to divide the problem into an Extended Kalman Filter, based only on the motor model, and separated motor-side signal estimators, the combination of which is less demanding computationally. The efectiveness of this approach is shown in simulation. Then its validity is experimentally demonstrated via implementation in a DSP based drive. A testbench to test its performance when driving an axis of a Large Hadron Collider collimator is presented along with the results achieved. It is shown that the proposed method is capable of achieving position and load torque estimates which allow step loss to be detected and mechanical degradation to be evaluated without the need for physical sensors. These estimation algorithms often require a precise model of the motor, but the standard electrical model used for hybrid stepper motors is limited when currents, which are high enough to produce saturation of the magnetic circuit, are present. New model extensions are proposed in order to have a more precise model of the motor independently of the current level, whilst maintaining a low computational cost. It is shown that a significant improvement in the model It is achieved with these extensions, and their computational performance is compared to study the cost of model improvement versus computation cost. The applicability of the proposed model extensions is demonstrated via their use in an Extended Kalman Filter running in real-time for closed-loop current control and mechanical state estimation. An additional problem arises from the use of stepper motors. The mechanics of the collimators can wear due to the abrupt motion and torque profiles that are applied by them when used in the standard way, i.e. stepping in open-loop. Closed-loop position control, more specifically Field Oriented Control, would allow smoother profiles, more respectful to the mechanics, to be applied but requires position feedback. As mentioned already, the use of sensors in radioactive environments is very limited for reliability reasons. Sensorless control is a known option but when the speed is very low or zero, as is the case most of the time for the motors used in the LHC collimator, the loss of observability prevents its use. In order to allow the use of position sensors without reducing the long term reliability of the whole system, the possibility to switch from closed to open loop is proposed and validated, allowing the use of closed-loop control when the position sensors function correctly and open-loop when there is a sensor failure. A different approach to deal with the switched drive working with long cables is also presented. Switched mode stepper motor drives tend to have poor performance or even fail completely when the motor is fed through a long cable due to the high oscillations in the drive-side current. The design of a stepper motor output fillter which solves this problem is thus proposed. A two stage filter, one devoted to dealing with the diferential mode and the other with the common mode, is designed and validated experimentally. With this ?lter the drive performance is greatly improved, achieving a positioning repeatability even better than with the drive working without a long cable, the radiated emissions are reduced and the overvoltages at the motor terminals are eliminated.

Perception of the sport events held in a permanent facility: the case of the Madrid Sports Palace

The aims of this study were to analyse perceptions regarding the sporting events held in the Madrid Sports Palace and to analyse whether those perceptions vary by age or gender. One hundred and ninetyfive residents answered the Ntloko and Swart (2008) questionnaire. The dimensions most highly rated were economic benefits (3.9±0.8), the event as a regional showcase (3.6±0.7), and the event as entertainment (3.4±0.6). However, the respondents did not agree with the negative environmental impact (2.0±0.8). Men rated the use of public money (z=2.4; pmenor que.05) and the regional showcase (z=2.0 pmenor que.05) more positively than women. Finally, women rated the increase in prices (z=2.0; pmenor que.05) more highly than men. The age groups differed significantly only regarding the promotion of community pride. Seniors and middle-aged adults rated it more positively than young adults (?2(2)=9.9; pmenor que.01). The fact that in an urban sports facility regular sporting events take place on a regular basis means that there are diverse perceptions, though mainly positive, and those perceptions differ from the perceptions about mega events that take place once in a life time at temporary sports facilities.

Permanent deformation estimates of dynamic equipment foundations: Application to a gas turbine in granular soils

Permanent displacements of a gas turbine founded on a fine, poorly graded, and medium density sand are studied. The amplitudes and modes of vibration are computed using Barkan´s formulation, and the “High-Cycle Accumulation” (HCA) model is employed to account for accumulated deformations due to the high number of cycles. The methodology is simple: it can be easily incorporated into standard mathematical software, and HCA model parameters can be estimated based on granulometry and index properties. Special attention is devoted to ‘transient’ situations at equipment´s start-up, during which a range of frequencies – including frequencies that could be similar to the natural frequencies of the ground – is traversed. Results show that such transient situations could be more restrictive than stationary situations corresponding to normal operation. Therefore, checking the stationary situation only might not be enough, and studying the influence of transient situations on computed permanent displacements is needed to produce a proper foundation design

Effects of gamma-Ray radiation on magnetic properties of NdFeB and SmCo permanent magnets for space applications

Several samples of NdFeB and SmCo permanent magnets have been irradiated with gamma rays up to different total irradiation doses until 1Mrad(Si). Magnetic properties of the samples have been measured at different temperatures before and after irradiation. The modifications of the magnetic parameters are presented. From these results it is highlighted which permanent magnets show more resistance to radiation and are more suitable to be included in devices for space applications or high radiation environments.

Comparativa de diferentes tipos de efemérides GNSS en cálculo de grandes líneas base con Magnet Office.

El objetivo de este Trabajo de Fin de Grado es hallar la influencia de cada tipo de efeméride en la precisión a posteriori de las coordenadas de un punto de la línea base. Para ello, se plantea una comparativa entre líneas base en función de la longitud, la duración de la sesión, la constelación y el tipo de efemérides. Todo ello, eligiendo puntos de control en la Península Ibérica y contrastando las soluciones sobre el marco de referencia ETRS89. No se pretende buscar la máxima precisión en cada línea base, sino tratar de emular las características de un uso común del GNSS en topografía y geodesia. En la comparativa se plantean situaciones al límite con sesiones de observación de poca duración y con distancias muy largas. Los tiempos de observación son inferiores a los recomendados en libros y manuales, para así evitar que la redundancia enmascare la verdadera precisión de las efemérides y llevar al límite de lo posible este test.