Volatile Metal Oxide Evaporation during Aerosol Decomposition

The role of particle evaporation during synthesis of volatile metal oxide powders (Bi₂O₃, MoO₃, PbO, and V₂O₅) by aerosol decomposition (spray pyrolysis) in a heated flow reactor was investigated. Solid particles (0.1–0.6 (Am) of predominantly β-Bi₂O₃ were formed with smooth spherical shape at all reactor temperatures (673–1173 K) employed. Solid MoO₃ particles (0.1–1.2 μm) produced at low temperatures (673–773 K) had a roughly spherical or faceted morphology and at high temperatures (873 K) had a platelike or layered structure. Solid V₂O₅ particles produced at low temperatures (573–673 K) were spherical and at high temperatures (973–1073 K) were platelike. The PbO particles were solid and spherical for all temperatures studied (773°–1073°C). Evaporative losses of up to 100% to the reactor walls were observed for all the metal oxides, due to their substantial vapor pressures. The evaporative losses were modeled by considering simultaneous particle evaporation and mass transfer of the metal oxide vapor to the reactor walls. The calculations indicated that, for most of these volatile metal oxides, evaporative losses were limited by diffusional transport of the vapor to the reactor walls and that evaporative losses occur when the vapor pressure of the oxides in the reactor is above 10^-5-10^-3 mm Hg.     

Dopants in Vapor-Phase Synthesis of Titania Powders

Gas-phase synthesis of titania by TiCl₄ oxidation in the presence of dopants (SiCl₄, POCl₃, and BCl₃) was investigated in an aerosol reactor as a function of temperature (1300–1700 K) and dopant concentration (0–25 mol% of TiCl₄). The addition of dopants, most notably silicon and phosphorus, drastically altered the morphology of titania particles from polyhedral to spheroidal, increased the extent of aggregation, increased the specific surface area, reduced the primary particle size, and decreased the rutile content. The observed morphology/crystallinity changes were explained in terms of ionic radii and valence of the dopant element.     

Combining bagging,boosting, rotation forest and random subspace methods

Bagging, boosting, rotation forest and random subspace methods are well known re-sampling ensemble methods that generate and combine a diversity of learners using the same learning algorithm for the base-classifiers. Boosting and rotation forest algorithms are considered stronger than bagging and random subspace methods on noise-free data. However, there are strong empirical indications that bagging and random subspace methods are much more robust than boosting and rotation forest in noisy settings. For this reason, in this work we built an ensemble of bagging, boosting, rotation forest and random subspace methods ensembles with 6 sub-classifiers in each one and then a voting methodology is used for the final prediction. We performed a comparison with simple bagging, boosting, rotation forest and random subspace methods ensembles with 25 sub-classifiers, as well as other well known combining methods, on standard benchmark datasets and the proposed technique had better accuracy in most cases.     

Adaptive Energy Management for Incremental Deployment of Heterogeneous Wireless Sensors

We introduce a new modelling assumption for wireless sensor networks, that of node redeployment (addition of sensor devices during protocol evolution) and we extend the modelling assumption of heterogeneity (having sensor devices of various types). These two features further increase the highly dynamic nature of such networks and adaptation becomes a powerful technique for protocol design. Under these modelling assumptions, we design, implement and evaluate a new power conservation scheme for efficient data propagation. Our scheme is adaptive: it locally monitors the network conditions (density, energy) and accordingly adjusts the sleep-awake schedules of the nodes towards improved operation choices. The scheme is simple, distributed and does not require exchange of control messages between nodes. Implementing our protocol in software we combine it with two well-known data propagation protocols and evaluate the achieved performance through a detailed simulation study using our extended version of the network simulator ns-2. We focus on highly dynamic scenarios with respect to network density, traffic conditions and sensor node resources. We propose a new general and parameterized metric capturing the trade-offs between delivery rate, energy efficiency and latency. The simulation findings demonstrate significant gains (such as more than doubling the success rate of the well-known propagation protocol) and good trade-offs achieved. Furthermore, the redeployment of additional sensors during network evolution and/or the heterogeneous deployment of sensors, drastically improve (when compared to “equal total power” simultaneous deployment of identical sensors at the start) the protocol performance (i.e. the success rate increases up to four times while reducing energy dissipation and, interestingly, keeping latency low). This work has been partially supported by the IST Programme of the European Union under contract number IST-2005-15964 ( ), the Programme under the European Social Fund (ESF) and Operational Program for Educational and Vocational Training II (EPEAEK II) and the Programme of GSRT under contract number 03ED568. A preliminary version of this work has appeared in [13].     

Molecular and Cellular Mechanisms of Sperm-Oocyte Interactions Opinions Relative to in Vitro Fertilization (IVF)

One of the biggest prerequisites for pregnancy is the fertilization step, where a human haploid spermatozoon interacts and penetrates one haploid oocyte in order to produce the diploid zygote. Although fertilization is defined by the presence of two pronuclei and the extraction of the second polar body the process itself requires preparation of both gametes for fertilization to take place at a specific time. These preparations include a number of consecutive biochemical and molecular events with the help of specific molecules and with the consequential interaction between the two gametes. These events take place at three different levels and in a precise order, where the moving spermatozoon penetrates (a) the outer vestments of the oocyte, known as the cumulus cell layer; (b) the zona pellucida (ZP); where exocytosis of the acrosome contents take place and (c) direct interaction of the spermatozoon with the plasma membrane of the oocyte, which involves a firm adhesion of the head of the spermatozoon with the oocyte plasma membrane that culminates with the fusion of both sperm and oocyte membranes (Part I). After the above interactions, a cascade of molecular signal transductions is initiated which results in oocyte activation. Soon after the entry of the first spermatozoon into the oocyte and oocyte activation, the oocyte’s coat (the ZP) and the oocyte’s plasma membrane seem to change quickly in order to initiate a fast block to a second spermatozoon (Part II). Sometimes, two spermatozoa fuse with one oocyte, an incidence of 1%–2%, resulting in polyploid fetuses that account for up to 10%–20% of spontaneously aborted human conceptuses. The present review aims to focus on the first part of the human sperm and oocyte interactions, emphasizing the latest molecular and cellular mechanisms controlling this process.     

纤维缠绕复合材料环形容器设计优化(英文)

纤维缠绕环形容器可充分利用空间,节省结构质量和消除系统质心漂移,目前在很多工业领域中发挥着日益重要的作用。本文基于复合材料层合理论和测地线缠绕原理,提出了纤维缠绕环形压力容器的线型优化设计方法。应用微分几何,导出了圆环面上测地缠绕轨迹和纤维不架空判据。以初始缠绕角和缠绕层厚度为变量,对结构重量进行最小化设计,得到了对应于不同管径比的优化缠绕线型。对优化线型进行了计算机缠绕仿真,并给出了缠绕铺层的各向正轴应力分布。结果表明,优化设计的缠绕线型模式精确可靠,满足纤维缠绕的基本要求。纤维缠绕角度大小更趋于合理,从而能充分发挥缠绕结构的力学性能,减经系统重量,使优化得到的环形容器结构性能比传统测地线缠绕环形容器有很大提高。本文的设计计算方法可直接用于复合材料环形气瓶的初步设计。     

A new CNC turning canned cycle for revolved parts with free-form profile

Laser micromilling technique is a thermal machining process which is used to remove material on the target geometry and has been widely employed in mold and die making industry. In this technique, the control factors of process such as scan speed, scan direction, frequency, and fill spacing play major affect on the surface quality. The selected quality characteristics are the mean surface roughness and milling depth. The main objective of this study is to determine the optimal milling conditions based on machining direction for minimizing the surface roughness and maximizing the milling depth. Therefore, L18 orthogonal array is constituted and subsequently signal/noise ratio and analysis of variance were employed to investigate the optimal levels of process parameters. The analysis results show that the scan speed has the highest effect on the surface roughness of which percentage contribution is 39.68% and also the beam scan direction and fill spacing have significant effects which contribute 19.67% and 16.09%, respectively. The experimental result for optimal condition is 2.23?μm. The results for milling depth show that only scan speed and fill spacing have significant effects which contribute 69.08% and 19.21%, respectively. Moreover, the scan direction has the least effect on the milling depth which can be neglected. The frequency has no effect on both surface roughness and milling depth. The result obtained from experiment at the optimal condition is 121.4?μm.