Planar sensors for local conductivity measurements in biological objects—Design, modelling, sensitivity maps

The paper focuses on the realisation of the idea of local electrical conductivity measurement in biological objects. In particular, it presents a set of planar electrode sensors that can be used in such measurements. Properties and parameters essential for local conductivity measurements have been analysed and compared for proposed electrode arrangements. The analyses were performed using the Finite Elements Method. The correctness of the results obtained using this method was verified by comparison with the results obtained experimentally and calculated analytically. The influence of the sample volume and its environment conductivity on the measurement result has been analysed for the presented electrode configurations. These parameters determine which of the proposed sensors are preferable in local conductivity measurements and can help to increase credibility and repeatability of the result. The outcome of these analyses also determines requirements that have to be met to perform correct conductivity measurement. Alternatively, if these requirements cannot be met, at least the error of the measurement result can be estimated. Biological objects are usually heterogeneous so the knowledge of sensitivity maps of the sensor can be very useful. Therefore, the modelling procedure for sensitivity map calculations of any four-electrode planar conductivity sensor was proposed and described in this paper. This procedure has been used to calculate and present sensitivity maps of the sensors. The results of these calculations allow the sensitivity of the sensor for the selected area of the sample to be estimated and indicate which part of the measured object has the greatest influence on the measurement result.     

A sensitivity analysis for the design of small-scale hydropower plant: Kayabogazi case study

In this study, the feasibility of hydroelectric power generation from the Kayabogazi dam, which was built by The State Hydraulic Works of Turkey (DSI) in 1987 in the town of Tavsanli, Kutahya, for irrigation and flood control purposes is investigated. Since a certain amount of water is supplied from the dam to the town of Tavsanli as drinking water, that amount is deducted from the total and is not allowed to be used in the process of electric power generation. By evaluating the amount of incoming water to the Kayabogazi dam in the period of 1995 and 2003 years, the most agreeable turbine type and size is decided for a small hydropower plant (SHP). In this purpose, seven different cases have been taken into consideration. As a conclusion, the case used three turbines which one of them is installed to utilize from the higher flow rates has been determined as the best configuration. In this study, a power generation ranging between 0.313 and 4.997 MW has been achieved in the viewpoint of installed capacity for Kayabogazi dam. Hence, it has been estimated an electricity generation up to 10,579 MWh per annum.     

Charge,mass and heat transfer interactions in solid oxide fuel cells operated with different fuel gases—A sensitivity analysis

The interaction between charge, heat and mass transfer occurring in SOFCs is investigated applying a finite-volume-based SOFC model. The strong interactions are the consequence of the high degree of integration of different processes (chemical/electrochemical reactions, diffusion, heat and mass transfer) within SOFCs. The understanding of these interactions is a key for the future development and application of SOFCs. The investigation was conducted by means of a sensitivity analysis for two different fuel gases, where one gas features a considerable amount of methane inducing steam reforming reactions as additional disturbance factor in the energy and mass balance system of SOFCs. In order to isolate the impact of the varied model parameters and the according changes in the interactions of charge, mass and heat transfer from side effects, the sensitivity analysis was conducted at constant fuel utilization. It was found that the impact of different fuel gases on the operational conditions of SOFCs dominates geometrical and material-induced phenomena. The power output was most affected by the fuel, followed by the values for the activation polarization activation energy that reflects the employed electrode catalysts activity.     

Metrological Aspects of Auto-normalized Front Photopyroelectric Method to Measure Thermal Effusivity in Liquids

The metrological aspects related to the sensitivity and signal-to-noise ratio of the auto-normalized front pyroelectric technique for the measurement of thermal effusivity in liquids are investigated. The effect of the thermally thick approximation in the theoretical expressions for the photopyroelectric signal and its effect on the sensitivity of the technique are discussed. It is shown that the sensitivity of the technique decreases with frequency. In contrast, the signal-to-noise ratio increases for higher frequencies.     

Sensitivity analysis of the influence of slurry characteristics and pipe size on Wasp model's accuracy

Sensitivity analysis of Wasp model for pressure gradient in solid-liquid slurries was conducted. The experimental work was carried out in 22-mm ID and 45-mm ID pipelines utilizing slurries composed of spherical glass beads having particle size distribution (PSD) following the Rosin-Rammler distribution and mean size of 50 μm. The spreads of the distribution were 1.7 and 7, corresponding to wide and narrow distributions, respectively. The slurries examined in this study had concentrations ranging from 5% to 25% by volume. Statistical tests for equivalence of means and variances provided some evidence that Wasp model is more accurate in predicting pressure gradients for the slurries of narrower PSD and at higher solid concentrations. Although the model was designed specifically for relatively large pipes, it was found more accurate in predicting pressure gradients in the 22-mm ID pipeline than in the 45-mm pipeline. Experimental results obtained in the same flow loop diameter indicated that the slurry of the narrower distribution produced higher-pressure gradients than those for the slurry of wider distribution. Pressure gradient increased markedly with increasing slurry concentration regardless of the pipe diameter and slurry PSD. However, the pipe diameter was found to have more significant influence on the pressure gradient than the slurry concentration does.     

Historic Building Stones and Flooding: Changes of Physical Properties due to Water Saturation

Natural stone is a common material in historic constructions. Flood events may directly affect surfaces of historic stone buildings. Since ashlars and stone sculptures often carry valuable cultural information, a more detailed knowledge about changes in physical properties due to water saturation is crucial for the assessment of their surface stability in case of flooding. Water saturation of stones leads to loss of mechanical strength and to expansion of volume (hydric dilatation). On the basis of data from literature, a rough scheme of vulnerability is suggested for different kinds of building stones. The majority of igneous and metamorphic rock types with dense crystalline structure are not vulnerable to flooding, whereas some types of pyroclastic rocks (tuffs) as well as clay-bearing sandstones are highly vulnerable. Detailed laboratory investigations on Elbe sandstone demonstrate the influence of petrographic features on material behavior due to water saturation. Results of laboratory tests are in good accordance to on-site observations made after the great summer flood in Dresden, Germany in 2002.     

Distributed Hydrological Modeling and Sensitivity Analysis in Torysa Watershed, Slovakia

The spatially distributed hydrologic model WetSpa is applied to the Torysa river basin (1,297 km²) located in Slovakia. Daily hydrometeorological data from 1991 to 2000 are used as input to the model. The spatial characteristic of the basin are described by three base maps, i.e. DEM, landuse and soil type, in GIS form using 100 m cell size. Results of the simulations show a good agreement between calculated and measured hydrographs at the outlet of the basin. The model predicts the daily discharge values with a good accuracy, i.e. about 73% according to the Nash–Sutcliff criterion. Sensitivity analysis of the model parameters is performed using a model-independent parameter estimator, PEST. It is found that the correction factor for calculating the actual evapotranspiration from potential evaporation has the highest relative sensitivity. Parameter K _gm which controls the amount of evapotranspiration from the groundwater has the least relative sensitivity.     

Application of fuzzy numerical techniques for product performance analysis in the conceptual and preliminary design stage

Uncertainty and variability modelling tools greatly enhance the value of virtual prototypes at the different design stages of a CAE process. The fuzzy analysis technique is suited to deal with models containing subjective non-deterministic parameters. This technique is finding its way to different disciplines of mechanical engineering. The objective of this paper is to increase the value of this technique in early stages of mechanical design procedures. For this purpose, new numerical procedures are proposed. First, the degree of influence is introduced. This new concept measures the relative effect of highly uncertain design properties on the performance of a design. Next, this paper proposes a new reduced optimisation scheme in order to improve the computational efficiency of the interval analysis, which is at the core of the implementation of the fuzzy technique. The practical applicability of the newly developed procedures is demonstrated on two numerical applications from the automotive industry. The analysed models represent the design at the conceptual stage, and contain parameters with a high and subjective level of uncertainty. The parametrised models are used to demonstrate the value and efficiency of the developed numerical procedures: significant parameters are identified using the degree of influence analysis, the optimal configuration is identified through an interval analysis based on the reduced optimisation scheme, and finally the fuzzy technique is applied as design space exploration tool.     

苏德尔特油田兴安岭群储层物性及渗流特征分析

通过对苏德尔特油田兴安岭储层的岩心样品进行储层物性分析和统计,利用X-衍射法测量粘土矿物、压汞法测定孔隙结构、储层敏感性测定、启动压力梯度测定和油水相对渗透率曲线检测等室内实验手段,综合评价和分析了该地区兴安岭储层的基本物性和渗流特征。结果表明,兴安岭储层属于强水敏、强酸敏和中等速敏的低渗透储层,粘土含量较高,有较高的启动压力梯度,水相相对渗透率较低,两相共渗区较小,含水率上升速度快,注水开发较为困难。     

On Generalized Reduced Gradient method with multi-start and self-optimizing control structure for gas lift allocation optimization

In most of the gas lifted oil fields, multiple oil wells share lift gas from a common gas distribution source. The lift gas should be distributed optimally among the wells to maximize total oil production. In this paper, a nonlinear dynamic model of the oil field is developed from first principles modeling. One of the objectives of this paper is to solve the optimal lift gas distribution problem using the Generalized Reduced Gradient (GRG) method. In addition, multi-start search routine is developed to ensure that the local optimal solution is closer to the global solution. Sensitivity of the optimal solution to changes in oil field parameters like reservoir pressure, Productivity Indices (PI), total lift gas supply (input disturbance) and separator pressure is studied. It is shown that the available lift gas is distributed among the wells according to the PI values of the wells and the optimal values are highly sensitive to the changes in PI values. A self-optimizing control structure using simple controllers is designed which is capable of keeping the oil field in optimal operating conditions without having to re-optimize the whole process when the input disturbance occur in the system. The simulation results show that the outcome of optimization is increased total oil production which leads to increased profit.