Annular Impinging Jet Controlled by Radial Synthetic Jets

This experimental study focuses on generation and control of annular impinging jets. The annular nozzle used in the investigations was designed with an active flow control system using 12 synthetic jets issuing radially from the central nozzle body. Measurements of the control effects were made on the impingement wall. The data acquisition involved wall pressure and wall mass transfer (by the naphthalene sublimation technique) using air as the working fluid. Also measured was time-mean flow velocity (by a Pitot probe) in the jet flow field. Moreover, flow visualization was carried out. Two main flow-field patterns (A and B) were identified. The patterns differ in the size of the separated-flow recirculation regions that develop attached to the nozzle central body: While pattern A is characterized by a quite small recirculation region (bubble) extending not far from the nozzle exit, pattern B exhibits a large recirculation region, reaching up to the impingement wall, on which it forms a stagnation circle. The control action modifies the flow field, resulting in changes of the corresponding heat/mass transfer distributions. The convective transfer rate on the stagnation circle can be demonstrably enhanced by 20% at a moderate nozzle-to-wall distance, equal to 0.6 of the nozzle outer diameter.     

Formation and evolution of phosphorus-containing species during high-temperature oxidation of TiAl dipped in a low-concentrated phosphoric acid solution

TiAl samples were dipped in a low-concentrated phosphoric acid solution, air dried, then heated to 800 °C under argon gas before oxidation under reconstituted air at this temperature. At the end of the heating ramp, sample surfaces were covered by a titanium pyrophosphate (TiP₂O₇) layer, well adhered to the substrate. This pyrophosphate was shown to be detectable from 400 °C. Chemical reactions have been proposed for the formation of this compound. TiP₂O₇ coating strongly increased the oxidation resistance of TiAl at 800 °C for 100 h. After 100 h, a transition period occurred leading to the change of TiP₂O₇ into TiO₂, which was achieved after 230 h, total mass gain always remaining below that of raw substrate. This evolution was demonstrated not resulting from a thermal decomposition of pyrophosphate compound.     

VUV photo-ionization parameters and effective mean free path of epithermal photoelectrons in pure non-polar dielectric liquids

VUV photo-ionization spectra of cyclohexane, 2,2 dimethylbutane, tetramethylsilane and polydimethylsiloxane oils were experimentally obtained, using a new experimental set-up. Power laws for photocurrent were observed and photoionization thresholds, confirming our previous data, were deduced. Using a 3-parameter adjustment method and Onsager theory, parameters specific of photoionization process were extracted from curves giving the photocurrent as a function of an applied electric field, at photon excess energies between 0.5 eV and 2 eV above the corresponding ionization thresholds. Assuming the range distribution function of thermalized photoelectrons to be a modified exponential function, called PE3, an effective mean free path along the thermalization path in each liquid was deduced from B/sub 3/, the experimental range parameter associated with the range distribution function. These mean free path values, at the epithermal stage, were compared to those of the thermal mean free path of conduction electrons.     

Ethyl propionate: Synergistic kairomone for african palm weevil,Rhynchophorus phoenicis L. (Coleoptera: Curculionidae)

Small trunk pieces of a freshly felled 10-year-old oil palm,Elaeis quineensis (Jacq.), were placed in a modified Nalgene desiccator, and volatiles captured for six days on Porapak Q. Gas chromatographic (GC) analysis of Porapak-Q-trapped volatiles with both flame ionization (FID) and electroantennographic detection (EAD) using male or femaleR. phoenicis antennae revealed several EAD-active compounds. They were identified as: ethyl acetate, ethyl propionate, isobutyl propionate, ethyl butyrate, and ethyl isobutyrate. In field experiments in the La Me Research Station, Côte d'Ivoire, ethyl propionate (50 mg/24 hr) but not all esters combined (50 mg/24 hr each) significantly increased capture ofR. phoenicis in pheromone-baited (3 mg/24 hr) traps. One kilogram of 1- to 3-day-old palm tissue was significantly more effective than ethyl propionate in enhancing pheromone attraction. Superior attraction of palm tissue may be attributed to additional as yet unknown semiochemicals. Alternatively, release rates and/or ratios of synthetic volatiles differed from those of palm tissue at peak attraction.     

Enhancement of the neural network modeling accuracy using a submodeling decomposition-based technique, application in gas sensor

This paper presents an algorithm based on the use of artificial neural networks (ANNs) in order to reduce the processing time and to improve the accuracy in ANN modeling, which can be accomplished with a division of the model to submodels by input subintervals. We apply this method with a gas sensor aiming to accurately control the small gas leaks, thus decreasing the risk of false alarms and missed detections. The sensor model accurately, especially in small concentrations, expresses the nonlinear character of the response and the dependence on temperature and relative humidity in addition to the gas nature dependency. The corrector linearizes and compensates the sensor’s responses. The results obtained show the effectiveness of the proposed technique.     

Comparison of a commercial and home-assembled fixed-wing UAV for terrain mapping of a post-mining site under leaf-off conditions

Unmanned aerial vehicle (UAV) platforms are rapidly becoming popular in many research and industry sectors. Due to their relatively low purchase price and the fact they can be used to monitor areas that are difficult or even unsafe to access, they have been increasingly used in land surveying and mapping of smaller areas. Numerous UAV platforms equipped with various cameras are increasingly available on the market, differing in their suitability for environmental mapping. Surveyors therefore face a question whether to buy or assemble their own UAV. The objective of this study is to assess the performance of two fixed-wing UAV systems for land survey and mapping applications. In particular, we: (1) compared a commercial eBee platform equipped with a Sony Cybershot DSC-WX220 camera with zoom lens and a home assembled EasyStar II equipped with Nikon Coolpix A with a lens of fixed focal length to find out if a home-assembled solution can compete with specialized commercial platform; (2) investigated the utilization of UAV images acquired under leaf-off conditions for digital terrain model (DTM) generation with respect to vegetation cover (steppes and forests); (3) assessed whether an increase in the image quantity can compensate for a lower quality of images; and (4) compared the DTM derived from UAV imagery with the official Czech Republic airborne laser scanning (ALS)-derived DTM. One flight with Easystar II and two perpendicular flights with eBee were performed. From these three flights, four point clouds were derived (one from each flight, and one resulting from a combination of two eBee flights), supplemented with four ground filtered point clouds. The accuracy of point clouds and DTM was assessed through a comparison with a conventional GNSS survey. We successfully identified the bare ground during the leaf-off period in the deciduous forest using images from both platforms. Point densities of point clouds acquired with Easystar II exceeded the densities of those acquired with eBee even after combining images from two eBee flights. Root mean square error of all derived point clouds ranged between 0.11 and 0.19 m, exceeding the accuracy of a nationwide ALS-derived DTM in both forest and open steppe areas. The most accurate point cloud was acquired using Easystar II. This is likely due to a combined effect of the quality of onboard cameras, camera settings and environmental conditions during the flight. For users who prefer to have greater control over their options rather than being dependent on the commercially available kit solution, home-assembled kits utilizing drones capable of carrying any camera available on the market may be an advantage.     

ANN modeling of a smart MEMS-based capacitive humidity sensor

This paper presents a design of a smart humidity sensor. First we begin by the modeling of a Capacitive MEMS-based humidity sensor. Using neuronal networks and Matlab environment to accurately express the non-linearity, the hysteresis effect and the cross sensitivity of the output humidity sensor used. We have done the training to create an analytical model CHS “Capacitive Humidity Sensor”. Because our sensor is a capacitive type, the obtained model on PSPICE reflects the humidity variation by a capacity variation, which is a passive magnitude; it requires a conversion to an active magnitude, why we realize a conversion capacity/voltage using a switched capacitor circuit SCC. In a second step a linearization, by Matlab program, is applied to CHS response whose goal is to create a database for an element of correction “CORRECTOR”. After that we use the bias matrix and the weights matrix obtained by training to establish the CHS model and the CORRECTOR model on PSPICE simulator, where the output of the first is identical to the output of the CHS and the last correct its nonlinear response, and eliminate its hysteresis effect and cross sensitivity. The three blocks; CHS model, CORRECTOR model and the capacity/voltage converter, represent the smart sensor.     

自然之美

<正>来自美国的家具设计师Robert Brou有着15年丰富的设计经验。他的设计作品别具一格,犹如雕塑,并且散发出一种随意而自然的美感。早年的他曾经在新奥尔良工作,受过长达6年的专业训练。起初,他并不是从事家具的设计,而是为一家有名的艺术品店铺工作。工作内容主要是古     

Synthetic and Continuous Jets Impinging on a Circular Cylinder

Synthetic and continuous water jets impinging onto an electrically heated circular cylinder were experimentally investigated. The slot nozzle width was 0.36 mm, the cylinder diameter was 1.2 mm, and the cylinder-to-nozzle spacing related to the slot width was 5–21. Two optical methods were used: qualitative laser-induced fluorescence (LIF) visualization and laser Doppler vibrometry (LDV) measurements. Simultaneously with the optical experiments, the overall convective heat transfer from the circular cylinder was evaluated. The LDV quantified the velocity of the oscillating piezo-driven diaphragm at frequencies from 30 to 68 Hz. A majority of the study was performed at the near-resonant frequencies from 46 to 49 Hz. For all investigated jets, the Reynolds numbers based on the nozzle width ranged from 36 to 171. The LIF visualization revealed a dominant flow separation occurring on the windward cylinder side. This result is attributed to the effect of the miniscales, a relatively small ratio of the nozzle width to the cylinder diameter, and low Reynolds numbers. An increase in the Reynolds number changes the flow pattern from a steady jet-flow separation to a vortex shedding wake-flow regime. The heat transfer experiments were validated in a natural convection regime. An enhancement of the average Nusselt numbers by 4.2–6.2 times by means of the synthetic jets was quantified by comparison with the natural convection regime. A correlation for the average Nusselt number was proposed for both the continuous and synthetic jets.     

Fenspiride inhibits histamine-induced responses in a lung epithelial cell line

Using the human lung epithelial WI26VA4 cell line, we investigated the capacity of fenspiride, an anti-inflammatory drug with anti-bronchoconstrictor properties, to interfere with histamine-induced intracellular Ca2+ increase and eicosanoid formation. Histamine and a histamine H1 receptor agonist elicited a rapid and transient intracellular Ca2+ increase (0-60 s) in fluo 3-loaded WI26VA4 cells. This response was antagonized by the histamine H1 receptor antagonist, diphenhydramine, the histamine H2 receptor antagonist, cimetidine, having no effect. Fenspiride (10(-7)-10(-5) M) inhibited the histamine H1 receptor-induced Ca2+ increase. In addition, histamine induced a biphasic increase in arachidonic acid release. The initial rise (0-30 s), a rapid and transient arachidonic acid release, was responsible for the histamine-induced intracellular Ca2+ increase. In the second phase release (15-60 min), a sustained arachidonic acid release appeared to be associated with the formation of cyclooxygenase and lipoxygenase metabolites. Fenspiride (10(-5) M) abolished both phases of histamine-induced arachidonic acid release. These results suggest that anti-inflammatory and antibronchoconstrictor properties of fenspiride may result from the inhibition of these effects of histamine.