Simultaneous measurement of void fraction and fundamental bubble parameters in subcooled flow boiling

Visualization was performed for the vapor bubbles in water subcooled flow boiling in a vertical heated tube to measure simultaneously the void fraction and the four fundamental bubble parameters: nucleation site density, bubble release frequency, bubble lifetime and bubble size. Using the mass flowrate and liquid subcooling as the experimental parameters, the changes of void fraction and bubble parameters with the wall heat flux were measured. The results of image analysis showed that the vapor void fraction could be approximated by the function of nucleation site density and bubble lift-off diameter; the bubble lift-off diameter was more influential than the nucleation site density. It was hence concluded that the bubble lift-off diameter could be regarded as the key parameter to determine the vapor void fraction under the present experimental conditions. The strong relation of bubble lift-off diameter to superheated liquid layer thickness was indicated for the future model development studies of bubble lift-off diameter.     

Analytic Flow Design Method for an Automated Distribution Center with Multiple Shipping Areas

An analytic flow design algorithm for an automated distribution center with multiple shipping areas is presented. The main elements of the analytic flow design are the number of devices and the volumes of product flow between the devices. In the design of an automated distribution center, it is necessary to satisfy the demand throughput while minimizing construction costs. In the conventional design process, system engineers utilize experimental and intuitional approaches. However, conventional approaches are time-consuming and the design outcome is dependent on the skill of the designer. Therefore, a theoretical design algorithm is needed. We propose an analytic flow design algorithm using a dynamic network flow model and considering time-variable flow volumes according to shipment and storage schedules. To verify the feasibility of the proposed method, we perform analytic flow design using real data and confirm that the proposed method can yield a feasible analytic flow design in several minutes.     

Basin-scale extrapolation of shipboard pCO2 data by using satellite SST and Chla

A new method for the estimation of basin-scale distribution of pressure of carbon dioxide on the sea surface (pCO₂) by satellite-derived sea surface temperature (SST) and chlorophyll-a concentration (Chla) is presented. 28?557 shipboard pCO₂ data were regressed by second-order multiple regression equations of SST and Chla with a regression error of ±14?µatm and ±17?µatm in the subtropical and subarctic domain, respectively. The monthly-average SST and monthly-maximum Chla (Chlmax) field determined from the Advanced Earth Observing Satellite/Ocean Color Temperature Scanner (ADEOS/OCTS) level 3 Daily Binned Map data were substituted into the multi-regression equation to generate the ‘monthly-typical’ basin-scale pCO₂ field in the North Pacific, and the results agreed well with the climatological field of shipboard pCO₂ observations with an error bar of ±21?µatm except in the case of springtime subarctic North Pacific. The satellite-pCO₂ field also satisfactorily reproduced the principle distribution of pCO₂ in the springtime subarctic North Pacific such as the location of each low-pCO₂ patch observed by the shipboard measurements. The extent of pCO₂ depletion in each pCO₂ patch, however, was not well approximated by the satellite-pCO₂ field. This was caused by the underestimation of Chlmax in these low-pCO₂ patches due to the low frequency of satellite-Chla observations in the springtime subarctic North Pacific due to the cloudiness.     

Design of sampled-data critical control systems based on the fast-discretization technique

The fast-discretization is known as an approximate but efficient technique for design and analysis of sampled-data systems. In this paper, we propose a fast-discretization-based design for sampled-data critical control systems. Supposing a tracking problem or a slow-changing disturbance rejection problem, we assume that an exogenous input is a persistent and/or transient input with bound on the rate of change. It is shown that the critical constraint for such exogenous inputs can be given in the form of the inequality constraint on the unit step response. The design parameters are determined by a numerical search method subject to this constraint. However, instead of evaluating it strictly, we check the corresponding constraint which is obtained from the fast-discretized system. Although this approach is approximate, it provides an efficient numerical procedure for a computer-aided design. To show the validity of the proposed method, an example of a multi-objective critical control system design is presented.     

Transformation of Lower Alkanes into Aromatic Hydrocarbons over ZSM-5 Zeolites

Much attention has been paid to the transformation of lower alkanes such as propane and butanes into aromatic hydrocarbons from both industrial and academic points of view. The aromatic hydrocarbons can be utilized as a booster for high octane number gasoline and are fundamental raw chemicals in petroleum chemistry. The activation of lower alkanes is an intriguing subject. In early work, Csicsery [1–5] described dehydrocyclodimerization of lower alkanes over bifunctional catalysts such as platinum on alumina and Cr₂O₃ on alumina.     

Ultrafine particles of the ZrO2-SiO2 system prepared by the spray-ICP technique

Ultrafine powders of the ZrO₂-SiO₂ system prepared by spraying aqueous mixed solutions of ZrO(NO₃)₂·2H₂O and silicone oil into an ultrahigh temperature inductively coupled plasma (the spray-ICP technique) have been investigated in connection with particle growth and phase change caused by heat treatment. The prepared powders were composed of roundish ultrafine particles 10 to 20 nm in size, and their components were tetragonal ZrO₂ (t-ZrO₂) and amorphous SiO₂ (a-SiO₂).a-SiO₂ alone did not crystallize below 1400° C, though the particles grew above 900° C.t-ZrO₂ converted to monoclinic ZrO₂ (m-ZrO₂) above 400° C, also followed by particle growth. On the other hand composite powders oft-ZrO₂ anda-SiO₂ exhibited no particle growth below 1200° C. Above 1200° Ct-ZrO₂ converted tom-ZrO₂, and its amount decreased with an increase in SiO₂ content. At 1400° C particle growth occurred, and the round particles of ZrO₂ were dispersed in ana-SiO₂ glass medium. These results indicate that ZrO₂ and SiO₂ mutually block particle growth, and that SiO₂ contributes to the quenching oft-ZrO₂ by keeping the particles of ZrO₂ within the critical particle size oft-ZrO₂.     

Preparation of SrBi 2 Ta 2 O 9 Thin Films by Liquid-Delivery MOCVD Without Additional Solvents

SrBi 2 Ta 2 O 9 thin films were prepared by ECR plasma enhanced metalorganic chemical vapor deposition (ECR-MOCVD) with a liquid-delivery system using one cocktail source without an additional solvent. The strontium-tantalum double alkoxide, Sr{Ta[OC 2 H 4 H(CH 3 ) 2 ](OC 2 H 5 ) 5 } 2 , was dissolved in stabilized trimethyl bismuth, Bi(CH 3 ) 3 / dioxane. This source system has been used in a conventional bubbling system. Deposition rate and the composition of the films were strictly controlled by the concentration and the composition of the cocktail source. Therefore, high reproducibility was realized by using this system. The constituent phase of the stoichiometric SBT film as-deposited at 500 C on a (111)Pt/TiO 2 /SiO 2 /Si substrate was a fluorite phase and transformed to the single phase of SBT by the post annealing at 800 C. It showed almost the same ferroelectricity as the stoichiometric composition film.     

A camera calibration technique using three sets of parallel lines

This paper presents a new method for three-dimensional camera calibration in which the rotation parameters are decoupled from the translation parameters. First, the rotation parameters are obtained by projecting three sets of parallel lines independently of the translation parameters and the imaging distance from the lens to the image plane. The virtual line passing through the image center, which is calculated by perspective projection of a set of parallel lines, depends only on the rotation parameters. Next, the translation parameters and the imaging distance are analytically obtained. Experimental results are used to show how the camera model can be accurately reconstructed in an easily prepared environment.