On TiN-particle fuel based helium-cooled transmutation systems

We have designed a sub-critical helium-cooled core with TiN-coated particle fuel, dedicated to the transmutation of minor actinides. The excellent neutronic properties of helium allows for a low plutonium fraction in the fuel, which yields a low reactivity swing, Δk = 2600 pcm, for a burnup of 31.2%. Further the neutron spectrum is hard, limiting the buildup of Cm and Cf. The high burnup combined with a minor actinide burning rate of 355 kg/GWth year makes the present design an attractive transmutation system.     

Organic memory using [6,6]-phenyl-C(61) butyric acid methyl ester: morphology, thickness and concentration dependence studies

We report a simple memory device in which the fullerene-derivative [6,6]-phenyl-C(61) butyric acid methyl ester (PCBM) mixed with inert polystyrene (PS) matrix is sandwiched between two aluminum (Al) electrodes. Transmission electron microscopy (TEM) images of PCBM:PS films showed well controlled morphology without forming any aggregates at low weight percentages (<10?wt%) of PCBM in PS. Energy dispersive x-ray spectroscopy (EDX) analysis of the device cross-sections indicated that the thermal evaporation of the Al electrodes did not lead to the inclusion of Al metal nanoparticles into the active PCBM:PS film. Above a threshold voltage of <3?V, independent of thickness, a consistent negative differential resistance (NDR) is observed in devices in the thickness range from 200 to 350?nm made from solutions with 4-10?wt% of PCBM in PS. We found that the threshold voltage (V(th)) for switching from the high-impedance state to the low-impedance state, the voltage at maximum current density (V(max)) and the voltage at minimum current density (V(min)) in the NDR regime are constant within this thickness range. The current density ratio at V(max) and V(min) is more than or equal to 10, increasing with thickness. Furthermore, the current density is exponentially dependent on the longest tunneling jump between two PCBM molecules, suggesting a tunneling mechanism between individual PCBM molecules. This is further supported with temperature independent NDR down to 240?K.     

楼宇电梯配置和目标选层系统

楼宇内的电梯配置取决于上行高峰和运输能力的计算结果，以满足楼宇内运输流量的需求。基于上行，下行呼梯按钮的集选控制系统，考虑到电梯运输能力时上行高峰是最需要满足的交通工况。如果电梯可以满足上行高峰状况，电梯就具有足够的运输能力满足其他运行状况。使用安装在大厅的目标选层系统（DCS），在上行高峰的状况下，电梯的运输能力可以达到与下行高峰相近的水平。用于常规集选控制下的计算上行高峰往返行程时间的方程式是无效的。在本篇文章中，介绍了一种使用DCS控制系统来选配电梯的方法．使得电梯在任何运输状况下都提供良好的服务。     

Supplemental safety? Exploring experienced safety in relation to other qualities of successful public spaces

ABSTRACT

Combining insights from the urban design and criminological literature, this paper explores the degree to which conviviality, feeling welcome, and feeling at home are related to peoples’ experiences of safety. A questionnaire was distributed on four squares in the city of Utrecht, the Netherlands. While participants valued the positive qualities of the squares differently, feeling safe was connected to a wider, positive evaluation of the quality of space and especially to feeling at home. By investing primarily in public spaces that are ‘homely’ or ‘domesticated’, a ‘supplemental safety’ might therefore be nurtured. This poses important insights for safety management.     

An improved synthesis method of ceria-carbonate based composite electrolytes for low-temperature SOFC fuel cells

SDC-carbonate composite electrolytes for low-temperature Solid Oxide Fuel Cells (LTSOFC) have been synthesized by an improved freeze drying method based on the formation of lanthanide citrate complex solution/gel. This method can not only maintain small particle sizes in composite, but also control the carbonate composition precisely. To optimize the electrochemical performance of the composite electrolytes, SDC-carbonate samples with different carbonate contents were prepared and investigated. SEM, EDS, MPD and XRD analyses were applied to characterize the morphology and carbonate content and EIS was used to determine the ionic conductivity of the electrolyte. The highest conductivity achieved was 400 mS/cm at 600 °C.     

Effect of apartment building energy renovation on hourly power demand

ABSTRACT

Optimal energy renovations of apartment buildings in Finland have a great impact on annual energy demand. However, reduction of energy demand does not necessarily translate into similar changes in peak power demand. Four different types of apartment buildings, representing the Finnish apartment building stock, were examined after optimal energy retrofits to see the influence of retrofitting on hourly power demand. Switching from district heating to ground-source heat pumps reduced emissions significantly under current energy mix. However, the use of ground-source heat pumps increased hourly peak electricity demand by 46–153%, compared to district heated apartment buildings. The corresponding increase in electrical energy demand was 30–108% in the peak month of January. This could increase the use of high emission peak power plants and negate some of the emission benefits. Solar thermal collectors and heat recovery systems could reduce purchased heating energy to zero in summer. Solar electricity could reduce median power demand in summer, but had only a little effect on peak power demand. The reduction in peak power demand after energy retrofits was less than the reduction in energy demand.     

Diffractive elements designed to suppress unwanted zeroth order due to surface depth error

Abstract

We consider a design approach to reduce unwanted zero-order intensity due to profile depth error in diffractive elements. Our method is based on addition of local bias phase to a binary element phase, leading to the introduction of a third phase level. We show theoretically and experimentally that gratings obtained with such modifications are more tolerant to profile depth error than conventionally designed binary or multilevel elements, thus reducing the appearance of unwanted zero order.     

Spatial filtering for robust myoelectric control

Pattern recognition techniques have been applied to extract information from electromyographic (EMG) signals that can be used to control electrical powered hand prostheses. In this paper, optimized spatial filters that enhance separation properties of EMG signals are investigated. In particular, different multiclass extensions of the common spatial patterns algorithm are applied to high-density surface EMG signals acquired from the forearms of ten healthy subjects. Visualization of the obtained filter coefficients provides insight into the physiology of the muscles related to the performed contractions. The CSP methods are compared with a commonly used pattern recognition approach in a six-class classification task. Cross-validation results show a significant improvement in performance and a higher robustness against noise than commonly used pattern recognition methods.     

Determining electrical efficiency of permanent magnet synchronous machines with different control methods

An algorithm to calculate the electrical efficiency of permanent magnet synchronous machines with four different control methods is presented. The direct- and quadrature-axis stator current components are optimized to find the control method producing the maximum electrical efficiency. The developed computation algorithm was tested with three different permanent magnet synchronous machine applications, i.e., a low-speed high-torque direct-driven wind power generator with rotor surface magnets, a hybrid drive for an energy recovery system and a geared wind power generator with rotor buried magnets. The performance of the developed computation algorithm was verified by comparing the calculated electrical efficiencies with the measurements in the case of the hybrid drive machine.