Shape from focus based on 3D structure tensor using optical microscopy

Shape from focus (SFF) is a widely used passive optical method for 3D shape reconstruction. In SFF, a focus measure, which is used to estimate the relative focus level, plays a critical role in depth estimation. In this article, we present a new focus measure for accurate 3D shape estimation in optical microscopy based on the analysis of 3D structure tensor. First, the 3D tensors are computed from the input image sequence for each pixel. Then, each tensor is decomposed into point, curve, and surface tensors by decomposing tensors into eigenvalues and eigenvectors. Finally, the surfaceness is used to measure the quality of sharpness. The proposed focus measure provides accurate focus values and better resistance against noise. The proposed measure is evaluated by conducting experiments using image sequences of simulated and microscopic real objects. The comparative analysis demonstrates the effectiveness of the proposed focus measure in recovering 3D shape.     

平面桁架构建的定日镜面形支撑结构优化及实验

针对反射面成型的复杂影响因素，提出平面桁架构建的定日镜面形支撑结构优化技术路线. 利用模拟仿真、数值计算和优化算法等方法，解析20 m²定日镜面形定义技术路线的4个组成环节：面形规格及宽高比、上弦杆的截面矩、平面桁架组间距的最优值、机加工中工艺控制要点的量化. 试制小型定日镜进行实验，分析光斑形状和能流密度分布特性，并与理想球面形光斑比较，两者的拟合优度大于0.98. 实验结果表明，当反射镜宽高比取1.2，上弦杆截面矩取40 000 mm⁴，桁架组间距取950 mm，上弦杆和斜杆的开孔公差小于0.9 mm时，反射面形的质量提升. 研究从原理和实践上证明了该优化技术路线的可行性.     

Resistive switching characteristics of ZnO–graphene quantum dots and their use as an active component of an organic memory cell with one diode-one resistor architecture

We investigated the resistive switching characteristics of a polystyrene:ZnO–graphene quantum dots system and its potential application in a one diode-one resistor architecture of an organic memory cell. The log–log I–V plot and the temperature-variable I–V measurements revealed that the switching mechanism in a low-current state is closely related to thermally activated transport. The turn-on process was induced by a space-charge-limited current mechanism resulted from the ZnO–graphene quantum dots acting as charge trap sites, and charge transfer through filamentary path. The memory device with a diode presented a ∼10³ I_ON/I_OFF ratio, stable endurance cycles (10² cycles) and retention times (10⁴ s), and uniform cell-to-cell switching. The one diode-one resistor architecture can effectively reduce cross-talk issue and realize a cross bar array as large as ∼3 kbit in the readout margin estimation. Furthermore, a specific word was encoded using the standard ASCII character code.     

Non-proportional multiaxial whole-life transformation ratchetting and fatigue failure of super-elastic NiTi shape memory alloy micro-tubes

Experimental observations are performed to investigate the non-proportional multiaxial whole-life transformation ratchetting and fatigue failure of superelastic NiTi SMA micro-tubes in stress-controlled loadings at human-body temperature (310 K). The effects of axial mean stress and stress hold on the whole-life transformation ratchetting and fatigue life are investigated with uniaxial, torsional and five different multiaxial loading paths. The results show that the stress holds on the upper or lower transformation plateaus will both promote forward and reverse transformation, and lead to shorter fatigue life. The multiaxial fatigue lives of NiTi shape memory alloy depend significantly on loading paths and applied stress levels.     

Engineering a Bacterial Tape Recorder

A method has been developed to produce and integrate single‐stranded DNA into genomic locations in bacteria in response to exogenous signals. The system functions similarly to a cellular tape recorder by writing information into DNA and reading it at a later time. Much like other cellular memory platforms, its operation is based on DNA recombinase function. However, the scalability and recording capacity have been improved over previous designs. In addition, memory storage was reversible and could be recorded in response to analogue inputs, such as light exposure. This modular memory writing system is an important addition to the genomic editing toolbox available for synthetic biology.     

Experimental and numerical study of the compact heat exchanger with different microchannel shapes

Experimental and numerical analysis of heat transfer and fluid flow in the compact heat exchanger has been done in this paper. In an open circuit wind tunnel, developed on purpose for this investigation, the measurement of working media temperatures and mass flow rates for heat exchanger with microchannel coil has been accomplished. In accordance with the heat exchangers used for experiments, numerical 3D simulation of adequate geometry shapes has been done. With utilization of air/water side numerical simulation, more detailed results have been achieved in relation to the simulation that assumes constant temperature or constant heat flux on the pipe wall. Good agreement between experimentally measured and numerically calculated results has been accomplished. The influence of different microchannel shapes on heat transfer effectiveness and pressure drop has been studied numerically. Comparison of results has been made accompanied by the discussion and final conclusions.     

Thermodynamics cycle analysis and numerical modeling of thermoelastic cooling systems

To avoid global warming potential gases emission from vapor compression air-conditioners and water chillers, alternative cooling technologies have recently garnered more and more attentions. Thermoelastic cooling is among one of the alternative candidates, and have demonstrated promising performance improvement potential on the material level. However, a thermoelastic cooling system integrated with heat transfer fluid loops have not been studied yet. This paper intends to bridge such a gap by introducing the single-stage cycle design options at the beginning. An analytical coefficient of performance (COP) equation was then derived for one of the options using reverse Brayton cycle design. The equation provides physical insights on how the system performance behaves under different conditions. The performance of the same thermoelastic cooling cycle using NiTi alloy was then evaluated based on a dynamic model developed in this study. It was found that the system COP was 1.7 for a baseline case considering both driving motor and parasitic pump power consumptions, while COP ranged from 5.2 to 7.7 when estimated with future improvements.     

Cognitive abilities,digital games and arithmetic performance enhancement: A study comparing the effects of a math game and paper exercises

Besides entertainment, games have shown to have the potential to impact a broader variety of cognitive abilities. Research has consistently shown that several aspects in cognition such as visual short-memory, multitasking and spatial skills can be enhanced by game play. In a previous study, it was found that playing Monkey Tales, a game aimed at training arithmetic skills, helped second grade pupils to increase their accuracy in mental calculation as compared to paper exercises. In this follow up study we explore whether traditional methods and game training differ in terms of the cognitive processes that both are able to impact. We incorporated standardized measures of working memory and visuo-motor skills. Additionally, the mathematics game was modified and its contents extracted to allow precise comparison between the gaming and paper exercises condition. Thus each single math exercise, type of question (e.g., multiple choice), quantity and order was perfectly matched in the game training and the traditional training conditions. Gains in arithmetical performance, and self-reported measures of enjoyment were also investigated. We found some evidence suggesting that arithmetic performance enhancement induced by game play and paper exercises differ not only in terms of enjoyment but also of working memory capacity improvements.