Subcooled flow boiling in water is thought to be advantageous in removing high heat load of more than 10 MW/m2. Characteristics of the critical heat flux (CHF), which determines the upper limit of heat removal, are ve...
详细信息
ISBN:
(纸本)0819412465
Subcooled flow boiling in water is thought to be advantageous in removing high heat load of more than 10 MW/m2. Characteristics of the critical heat flux (CHF), which determines the upper limit of heat removal, are very important for the design of cooling systems. In this paper, studies on subcooled flow boiling CHF, which have been conducted by the authors, are reported. Experiments were conducted using direct current heating of stainless steel tube. For uniform heating conditions, CHF increment in small diameter tubes (1 - 3 mm inside diameter) and the CHF characteristics in tubes with internal twisted tapes were investigated, and also the existing CHF correlations for ordinary tubes (more than 3 mm inside diameter) were evaluated. For peripherally non-uniform heating conditions using the tube, whose wall thickness was partly reduced, the CHF for swirl flow was higher than the CHF under uniform heating conditions with an increase of the non-uniformity factor.
A cellular multilayer phase grating with hexagonal closest packing proves to be the ideal focal plane architecture for the human eye, and is thus also the best model for designing stimulus- adaptive robot eyes which a...
详细信息
ISBN:
(纸本)0819410268
A cellular multilayer phase grating with hexagonal closest packing proves to be the ideal focal plane architecture for the human eye, and is thus also the best model for designing stimulus- adaptive robot eyes which achieve the spatial and chromatic performance of the human eye. Crystal-optical calculation of the retinal cellular multilayer chip and the resulting correlations between the physical stimulus parameters and the adaptive shifts in human vision at the retinal level give rise to a time-frequency diagram of the eye and its stimulus-adaptive latitudes, which will become relevant in the design of future chips for robot eyes with performance comparable to that of human vision. The current presentation shows that 3-D grating optical parameters ensure the frequency-related chromatic adaptive shifts (transition from photopic to scotopic vision in the Purkinje shift, Stiles-Crawford effects I/ii, Bezold-Bruecke phenomenon, chromatic adaptation to artificial light sources of different spectral composition, etc.) and also indicates what 3-D grating optical parameters are relevant to spatial transfer and adaptation, i.e., the time-related aspects in the time-frequency diagram (adaptation of the spatial modulation transfer function to the image parameters;log term for spatial adaptation to the intensity level;coding of spatial phase relationships between a fundamental spatial frequency and higher frequencies up to the third harmonic, etc.).
This paper deals with the problem of robust fast recognition of partially occluded or incomplete views of `flat' objects. Robustness is accomplished through hypothesis confirmation using complementary or supportin...
详细信息
ISBN:
(纸本)0819411914
This paper deals with the problem of robust fast recognition of partially occluded or incomplete views of `flat' objects. Robustness is accomplished through hypothesis confirmation using complementary or supporting information available for the current hypothesis and by model-based hypothesis verification. Classification speed is obtained by pruning the hypothesis hierarchy using simple pruning procedures based on structural properties derived from current object representation. In addition, classification speed is also improved through the use of simple model-based decision making procedures instead of computationally expensive transformations. Normalized Interval Vertex Descriptors (NIVD) are used to represent objects. NIVDs are representations derived from the physical characteristics of an object (vertices and sides) that are easy to obtain, especially for polygon like shapes. They provide not only a compact representation, but they also allow the definition of features that can be used to speed up the classification process. Experimental results of this process are also included.
The hydroxyl radical (OH) is important for many processes involved in tropospheric chemistry. For instance, it initiates the photochemical degradation of gases that cause global climate change, such as methane and the...
详细信息
ISBN:
(纸本)0819408808
The hydroxyl radical (OH) is important for many processes involved in tropospheric chemistry. For instance, it initiates the photochemical degradation of gases that cause global climate change, such as methane and the chlorofluorocarbon substitutes (HCFCs). Because of its reactivity, its abundances are less than 0.1 pptv. Thus, OH has been very difficult to measure accurately, despite its importance. Techniques have evolved, however, so that good measurements of tropospheric OH abundances are now possible. One of these techniques that is adaptable to aircraft measurements is the laser induced fluorescence detection of the OH radical in a detection chamber at low pressures, a technique first developed by R. J. O'Brien and T. M. Hard. Because OH is both excited and detected in the A2Σ+(υ′ = 0) &rarr X2ii(υ″ = 0) transition near 308 nm (approximately 10 milliwatts at 10 kHz repetition rate), significant laser generation of OH and interference signals from other trace gases are avoided. The current ground-based instrument, which can be readily adapted to aircraft, can detect OH abundances of 1.4 × 105 OH molecules cm-3 with S/N = 2 in 30 seconds, and 5 × 104 cm-3 in five minutes.
The nature of the dry develop process demands controllable ion energies for good etch selectivity, a large highly directional ion flux for good anisotropy, and a clean etch. As a part of the plasma characterization, t...
详细信息
Companies must constantly improve their technologies to survive the competitive battle in the nineteen nineties and beyond. This now holds more than ever for producers of engineering thermoplastics, who traditionally ...
Companies must constantly improve their technologies to survive the competitive battle in the nineteen nineties and beyond. This now holds more than ever for producers of engineering thermoplastics, who traditionally have enjoyed significantly higher margins than the commodity plastic producers. In today's competitive environment it is vital to be the high quality, low cost producer. At the same time products and processes need to become ''greener''. The drivers call for specific R&D approaches focused at cost and ecological improvements of processes and products. Examples are: (i) novel catalysis with fewer process steps, higher yields and selectivity for the production of monomers and polymers. (ii) solvent-free polymerisation processes, resulting in lower investment cost, lower operating cost and the lack of solvent traces in the final product (iii) design of polymer modifications, e.g. higher flow and/or higher heat copolymers such that products can be produced in existing equipment resulting in acceptable Return-on-Investment (ROI). Higher flow products are specifically needed for thin-wall designs to allow optimum use of the high mechanical properties of engineering thermoplastics, making shorter processing cycles possible during moulding and bringing less material in the environment. This paper reviews various routes to high flow technology, such as improving processing window, molecular engineering and blends. The pull for these technology developments come from optical data storage, thin wall bumper and super thin note bloc computer applications. The need for greener products is addressed through improved flame and fire retardant product design.
暂无评论