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排序方式: 共有1359条查询结果,搜索用时 937 毫秒
81.
Z. T. Zhang T. Matsushita S. Seetharaman W. C. Li 《Metallurgical and Materials Transactions B》2006,37(3):421-429
The wetting characteristics of liquid iron on dense MgAION-based composite ceramics were investigated using X-ray sessile
drop technique. The contact angles were measured on substrates of different composites as functions of temperature and varying
partial pressures of oxygen. The results with pure argon gas showed that contact angles kept almost constant in the temperature
range 1823 to 1873 K. The contact angle was found to show a slight increase with increasing boron nitride (BN) content in
MgAION-BN composites. These are attributed to the higher contact angle between BN substrate and liquid iron drop compared
with that obtained for MgAION substrate. When the CO-CO2-Ar gas mixtures were introduced into the system, the contact angle showed an initial quick decrease followed by a slow decrease
and then a period of nearly constant contact angle at a given temperature corresponding to the steady-state condition. Even
in this case, BN seemed to cause an increase in the equilibrium contact angle. The equilibrium contact angle was found to
decrease with increasing temperature. XRD results indicated that the substrate was oxidized and the oxidation products combined
with FeO formed by the oxidation of the iron drop to from FeAl2O4 and Mg1−xFex) These were likely to form a ternary FeO-Al2O3-MgO slag or a quaternary slag by combining with B2O3. An interesting observation is that the iron drop moved away from the original site, probably due to the Marangoni effect. 相似文献
82.
This paper provides several stability tests for piecewise linear systems and proposes a method of stabilization for bimodal systems. In particular, we derive an explicit and exact stability test for planar systems, which is given in terms of coefficients of transfer functions of subsystems. Restricting attention to the bimodal and planar case, we show simple stability tests. In addition, we drive a necessary stability condition and a sufficient stability condition for higher-order and bimodal systems. They are given in terms of the eigenvalue loci and the observability of subsystems. All the stability tests provided in this paper are computationally tractable, and our results are applied to the stabilizability problem. We confirm the exactness and effectiveness of our approach by illustrative examples. 相似文献
83.
Recent research in mobile robot navigation make it feasible to utilize autonomous robots in service fields. But, such applications require more than just navigation. To operate in a peopled environment, robots should recognize and act according to human social behavior. In this paper, we present the design and implementation of one such social behavior: a robot that stands in line much as people do. The system employs stereo vision to recognize lines of people, and uses the concept of personal space for modeling the social behavior. Personal space is used both to detect the end of a line and to determine how much space to leave between the robot and the person in front of it. Our model of personal space is based on measurements from people forming lines. We demonstrate our ideas with a mobile robot navigation system that can purchase a cup of coffee, even if people are waiting in line for service. 相似文献
84.
Yasushi Sakurai Masatoshi Yoshikawa Shunsuke Uemura Haruhiko Kojima 《The VLDB Journal The International Journal on Very Large Data Bases》2002,11(2):93-108
We propose a novel index structure, the A-tree (approximation tree), for similarity searches in high-dimensional data. The
basic idea of the A-tree is the introduction of virtual bounding rectangles (VBRs) which contain and approximate MBRs or data
objects. VBRs can be represented quite compactly and thus affect the tree configuration both quantitatively and qualitatively.
First, since tree nodes can contain a large number of VBR entries, fanout becomes large, which increases search speed. More
importantly, we have a free hand in arranging MBRs and VBRs in the tree nodes. Each A-tree node contains an MBR and its children
VBRs. Therefore, by fetching an A-tree node, we can obtain information on the exact position of a parent MBR and the approximate
position of its children. We have performed experiments using both synthetic and real data sets. For the real data sets, the
A-tree outperforms the SR-tree and the VA-file in all dimensionalities up to 64 dimensions, which is the highest dimension
in our experiments. Additionally, we propose a cost model for the A-tree. We verify the validity of the cost model for synthetic
and real data sets.
Edited by T. Sellis. Received: December 8, 2000 / Accepted: March 20, 2002 Published online: September 25, 2002 相似文献
85.
86.
To evaluate the mechanical strength of fiber reinforced composites it is necessary to consider singular stresses at the end of fibers because they cause crack initiation, propagation, and final failure. The singular stress is expressed by generalized stress intensity factors defined at the corner of fibers. As a 2D model an interaction between rectangular inclusions under longitudinal tension is treated in this paper. The body force method is used to formulate the problem as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where the unknown functions are the densities of body forces distributed in infinite plates having the same elastic constants as those of the matrix and inclusions. In order to analyze the problem accurately, the unknown functions are expressed as piecewize smooth functions using two types of fundamental densities and power series, where the fundamental densities are chosen to represent the symmetric stress singularity of 1/r
1–
1 and the skew-symmetric stress singularity of 1/r
1–
2. Then, generalized stress intensity factors at the end of inclusions are systematically calculated for various locations, spacings and elastic modulus of two rectangular inclusions in a plate subjected to longitudinal tension. 相似文献
87.
Chornobai CA Damasceno JC Visentainer JV de Souza NE Matsushita M 《Archivos latinoamericanos de nutrición》1999,49(3):283-286
The analyzed milk samples were collected from cross Saanen goats of different ages and different cross breeding types, throughout the lactation period, from September 1996 to December 1997. For the physical-chemical characteristics measured in this experiment, the following average values were obtained, followed by their respective standard deviations: pH (6.69 +/- 0.20); acidity (12.96 +/- 3.64 degrees D); density (1.030 +/- 0.009 mg.cm-3); fat (3.83 +/- 1.04%); crude protein (3.34 +/- 0.73%) and total solids (12.25 +/- 1.94 g.100 g-1). The lactation period influenced the values of acidity, fat, crude protein and total solids; these values decreased during the initial months and increased at the end of the lactation. The correlations were analyzed among the studied characteristics during the lactation, resulting in positive (p < 0.05) acidity/density correlation (r = 0.2115), stand out also the positive correlations (p < 0.01) among fat/total solids (r = 0.7715) and crude protein/total solids (r = 0.6228). 相似文献
88.
H Bai R Morishita I Kida T Yamakawa W Zhang M Aoki H Matsushita A Noda R Nagai Y Kaneda J Higaki T Ogihara Y Sawa H Matsuda 《Canadian Metallurgical Quarterly》1998,5(6):761-769
OBJECTIVE: To define the distribution and determinants of cardiovascular disease events among participants undergoing long-term antihypertensive therapy, and to stratify them into risk groups on the basis of pretreatment clinical profiles. DESIGN: A prospective cohort study of participants in a worksite-based antihypertensive treatment program in New York city (1973-1994). PATIENTS: We studied 8690 systematically treated patients who had at least 6 months of follow-up (average of 5.7 years) and, at entry, had had a systolic blood pressure of > or = 160 mmHg or a diastolic blood pressure of > or = 95 mmHg (after 1992 > or = 140/90 mmHg), or had been being administered antihypertensive medication. MAIN OUTCOME MEASURES: Blood pressure and incidence of morbid and mortal cardiovascular events. RESULTS: Blood pressure control (to 140 +/- 3/87 +/- 7 mmHg) was achieved by the first year and maintained through 18 years of therapy. In nearly 50,000 person-years of follow-up, there were 468 cardiovascular disease events [myocardial infarction including revascularization (282), strokes (93), congestive heart failure (30) and other cardiovascular deaths (63)]. Deaths from cardiovascular disease events accounted for 68% of all deaths. Myocardial infarction was most common throughout, but congestive heart failure incidence surpassed stroke incidence after 10 years. A scheme for risk stratification was constructed after analysis of the independent association of baseline factors and incident cardiovascular events. Upon the basis of ease of ascertainment and their demonstrated associations with occurrence of cardiovascular disease during treatment, we selected five pretreatment factors (history of heart attack, stroke, diabetes, age > or = 55 years and pulse pressure > or = 60 mmHg) to stratify patients into four groups. Those with no risk factor had a low risk (n=2999), those with one had a moderate risk (3042), those with two had a high risk (2237), and those with three or more had a very high risk (412). Overall, the unadjusted rates of incidence of cardiovascular disease events per 1000 person-years for patients in very high and low risk groups differed by factors of six and 14 for men and women, respectively. CONCLUSION: These results demonstrate that long-term control of blood pressure can be achieved in a general population. Nevertheless, cardiovascular disease events still accounted for most morbidity and mortality among these 'recovered' hypertensive patients. At entry, on the basis of readily identifiable characteristics, it was possible to stratify patients according to likelihood of subsequent events occurring despite control of blood pressure. This scheme could provide the basis for targeting more aggressive therapy where the potential for further cardioprotection is greatest. 相似文献
89.
Y Matsushita K Yoshiie Y Imamura H Ogawa H Imamura S Takao S Yonezawa T Aikou I Maruyama E Sato 《Canadian Metallurgical Quarterly》1998,127(1-2):195-201
Inside-out vesicles of plasma membranes prepared from a plant source were used as models to investigate effects of centrifugal forces on separations of early and late endosome populations by aqueous two-phase partition. Endosome subpopulations were resolved readily by preparative free-flow electrophoresis where acidification of the interiors of late endosomes occurred upon addition of ATP to activate a proton translocating ATPase. The resultant increased diffusion potential provided for a surface difference between late and early endosomes to permit electrophoretic separation. With the plant membranes, unincubated inside-out plasma membrane vesicles modeled early endosomes, whereas inside-out vesicles incubated with 1 mM ATP modeled late endosomes. A latent, 2,4-dichlorophenoxyacetic acid (2,4-D)-(auxin)-stimulated NADH:protein disulfide reductase measured spectrophotometrically was used as an enzymatic marker for both populations of inside-out vesicles. Phase partition behavior of each population was quantitated using total protein as the parameter. 相似文献
90.
Yasushi Wada 《Journal of Low Temperature Physics》1976,24(5-6):709-732
The magnetization of a type II superconductor in the mixed state is a sum of two contributions, one from an array of flux lines and the other from shielding currents flowing along the surface. The former can be evaluated with the help of results of neutron diffraction experiments, using an extrapolation procedure. The observed magnetization curve thus enables us to estimate the surface contribution. This process is applied to the data on niobium obtained by Schelten, Ullmaier, and Lippmann. It is found that at low temperatures (T/T
c
=0.161 and 0.457), the surface contribution may not be reduced atH
c2
as much as theories predict. At higher temperatures (T/T
c
=0.717 and 0.891), it is likely to be paramagnetic in a region rather close toH
c1
. Attractive interaction between flux lines is suggested to be a mechanism of this anomaly. However, more experimental and theoretical work is needed to establish these findings to help us understand the surface magnetism of type II superconductors. 相似文献