Compact carrier-injection photonic crystal switch for on-chip communications

Performances and metrics of an electro-optical wavelength switch in silicon?on- insulator technology using a 20 μm long photonic crystal directional coupler structure are theoretically studied using both electrical and finite difference time domain simulations. The possibility of photonic switching through carrier injection using a forward-biased PIN diode configuration is evaluated. It is shown that wavelength routing near λ=1550 nm with optical insertion loss of 1 dB and an electrical cut-off frequency of 60 MHz can be achieved with a bias voltage of 1 V and a dissipated electrical power of 700 μW. Integration of the device could be applied to active routing of light in silicon chips for the realisation of on-chip switching networks.     

Dynamic mechanical behavior of a polyimide

The dynamic mechanical properties of a polyimide (poly-4,4′-oxydiphenylene pyromellitimide) were studied from about 4 to 800°K. at audio frequencies. A prominent relaxation associated with absorbed water content occurs near 230°K. Below 270°K., the modulus undergoes a corresponding increase in value with increasing water content. Above 550°K. the onset of a major relaxation process is observed in the modulus data, and a maximum in the internal friction is observed at about 675°K. Minor relaxation peaks are also noted throughout the temperature range. Relatively minor differences are noted in the mechanical relaxation spectra for the polyimide when treated (after drying) with dimethylformamide, dimethylacetamide, and dimethylsulfoxide, whereas the treatment with water after drying has a marked effect on the relaxation behavior. A reactor radiation dose of 3000 Mrad also causes only minor alterations in the dynamic mechanical spectra.     

Impact of Stoichiometry on the Structure of van der Waals Layered GeTe/Sb2Te3 Superlattices Used in Interfacial Phase‐Change Memory (iPCM) Devices

Van der Waals layered GeTe/Sb₂Te₃ superlattices (SLs) have demonstrated outstanding performances for use in resistive memories in so‐called interfacial phase‐change memory (iPCM) devices. GeTe/Sb₂Te₃ SLs are made by periodically stacking ultrathin GeTe and Sb₂Te₃ crystalline layers. The mechanism of the resistance change in iPCM devices is still highly debated. Recent experimental studies on SLs grown by molecular beam epitaxy or pulsed laser deposition indicate that the local structure does not correspond to any of the previously proposed structural models. Here, a new insight is given into the complex structure of prototypical GeTe/Sb₂Te₃ SLs deposited by magnetron sputtering, which is the used industrial technique for SL growth in iPCM devices. X‐ray diffraction analysis shows that the structural quality of the SL depends critically on its stoichiometry. Moreover, high‐angle annular dark‐field‐scanning transmission electron microscopy analysis of the local atomic order in a perfectly stoichiometric SL reveals the absence of GeTe layers, and that Ge atoms intermix with Sb atoms in, for instance, Ge₂Sb₂Te₅ blocks. This result shows that an alternative structural model is required to explain the origin of the electrical contrast and the nature of the resistive switching mechanism observed in iPCM devices.     

3D content-based search using sketches

This paper presents a novel interactive framework for 3D content-based search and retrieval using as query model an object that is dynamically sketched by the user. In particular, two approaches are presented for generating the query model. The first approach uses 2D sketching and symbolic representation of the resulting gestures. The second utilizes non-linear least squares minimization to model the 3D point cloud that is generated by the 3D tracking of the user’s hands, using superquadrics. In the context of the proposed framework, three interfaces were integrated to the sketch-based 3D search system including (a) an unobtrusive interface that utilizes pointing gesture recognition to allow the user manipulate objects in 3D, (b) a haptic–VR interface composed by 3D data gloves and a force feedback device, and (c) a simple air–mouse. These interfaces were tested and comparative results were extracted according to usability and efficiency criteria.     

Dynamic model of a hermetic reciprocating compressor in on–off cycling operation (Abbreviation: Compressor dynamic model)

This paper presents a dynamic model of a hermetic reciprocating compressor in on–off cycling operation. The proposed model is detailed enough to account for the important phenomena influencing the suction and discharge mass flow rates and the electrical power drawn by the compressor, but simple enough to be usable for different reciprocating compressor designs with readily available data from manufacturers. The experimental validation of the model under steady-state and transient conditions in both heating and cooling modes confirms the good performance of the model.     

The importance of axial effects for borehole design of geothermal heat-pump systems

This paper studies the effects of axial heat conduction in boreholes used in geothermal heat pump systems. The axial effects are examined by comparing the results obtained using the finite and infinite line source methods. Using various practical design problems, it is shown that axial effects are relatively important. Unsurprisingly, short boreholes and unbalanced yearly ground loads lead to stronger axial effects. In one example considered, it is shown that the borehole length is 15% shorter when axial conduction effects are considered. In another example dealing with underground water freezing, the amount of energy that has to be removed to freeze the ground is three times higher when axial effects are considered.     

Attachment State of Mind, Learning Dispositions, and Academic Performance During the College Transition.

The purpose of this study was to examine the relation among attachment state of mind, students' learning dispositions, and academic performance during the college transition. Sixty-two students were involved in a short-term longitudinal study and were interviewed with the Adult Attachment Interview. Students' learning dispositions were assessed at the end of high school (Time 1) and halfway through their 1st semester in college (Time 2). Academic records were collected at Time 1 as well as at the end of the 1st, 2nd, and 3rd college semesters. Autonomous students showed better learning dispositions throughout the transition and were less likely than dismissing and preoccupied students to experience a decrease in these dispositions between Time 1 and Time 2. In addition, dismissing students obtained the lowest average of grades in college, and this association was mediated by changes in quality of attention during the transition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

比利时高放废物处置库设计及与基岩和工程屏障体系的热-水-力性状的相关研究

在比利时，泥岩中地质处置是高放废物最终处置的首选，处置库在高放废物与生物圈之间的多重屏障基础上设计的，而Boom泥岩作为基岩的研究已有20多年历史，1980年比利时做出重大决定，建立名为HADES的地下研究机构，以研究Boom泥岩在地下223m处的力学性质，并调查和论证处置的可行性，为处置库屏障（天然和人工）提供可靠数据，在HADES的众多现场试验中很多试验用来对基岩和工程屏障体系（包括封口和回填的可行性）热-水-力性状进行研究，包括CACTUS，ATLAS，BACCHUS和RESEAL等项目。自1995年以来，研究开发计划向大型和示范性试验方向发展。最主要成果是运用工业技术建立地下研究设施（竖井和井巷）可行性得到了验证，且这种工业技术给研究提供一个较好机会，便于进一步认识基岩泥岩（CLIPEX方案）的水-力性状及了解隧道开挖工程（SELFRAC课题）对挖掘破坏区的影响，另一个重大成果是成功地实现对一种称为“OPHELE”的预掉膨润土（人工屏障材料）加热和水化地面大型试验。下一步工作内容包括实现大尺寸现场加热器试验（PRACLAY试验），此试验预计于2006年开始，并可持续10a之久，据此，首先简要描述比利时高效废物处置库设计，然后回顾Boom泥岩和工程屏障体系的热-水-力性状相关试验，最后介绍下一步大规模PRACLAY试验。     

Bcl-2 protein as a marker of neuronal immaturity in postnatal primate brain

The distribution of neurons expressing immunoreactivity for the protein Bcl-2 was studied in the brain of squirrel monkeys (Saimiri sciureus) of various ages. Several subsets of small and intensely immunoreactive neurons displaying an immature appearance were disclosed in the amygdala and piriform cortex. The piriform cortex exhibited clusters of various forms in which Bcl-2+ neurons appeared linked to one another by their own neurites. The subventricular zone, which is known to harbor the largest population of rapidly and constitutively proliferating cells in the adult rat brain, was intensely stained, particularly at the basis of the lateral ventricle. A long and dorsoventrally oriented Bcl-2+ fiber fascicle was seen to emerge from the subventricular zone, together with numerous Bcl-2+ cells that formed a densely packed column directed at the olfactory tubercle. In adult and aged monkeys, the small and intensely labeled neurons were progressively replaced by larger and more weakly stained neurons in the amygdala and piriform cortex. In contrast, Bcl-2 immunostaining did not change with age in the subventricular zone and olfactory tubercle, the islands of Calleja of which were markedly enriched with Bcl-2. The dentate gyrus contained only a few layers of intensely labeled granule cells in juvenile monkeys, but the number of these layers increased markedly in adult and aged monkeys. These findings suggest that Bcl-2 can serve as a marker of both proliferating and differentiating neurons and indicate that such immature neurons may be much more widespread than previously thought in postnatal primate brain.