2,767 research outputs found
DIPS: an efficient pointer swizzling strategy for incremental uncaching environments
No full textPointer swizzling improves the performance of OODBMSs by reducing the number of table lookups. However, the object replacement incurs the unswizzling overhead. In this paper, we propose a new pointer swizzling strategy, the dynamic indirect pointer swizzling (DIPS). DIPS dynamically applies pointer swizzling techniques in order to reduce the overhead of unswizzling. DIPS uses the temporal locality information which is gathered by the object buffer manager. The information is used to select the object to whose pointers the pointer swizzling techniques are applied and to dynamically bind the pointer swizzling techniques using the virtual function mechanism. We show the efficiency of the proposed strategy through experiments over various object buffer sizes and workloads. (C) 2003 Elsevier Inc. All rights reserved
EFFECTS OF THE SIDEWALL THERMAL CONDITIONS ON THE GAS-FLOWS IN A RAPIDLY ROTATING CYLINDER
No full textNumerical studies are presented of the flows of a gas in a rapidly rotating cylindrical container. The reference Ekman number is small, and the peripheral Mach number is O(1). Fluid motions are induced by small differences in the boundary temperatures. In order to assess the effects of thermal boundary conditions at the sidewall on the flow structure and temperature field, three types of conditions at the sidewall are adopted, i.e. a linearly varying, an insulated, and an isothermal temperature condition. Analyses are made of comprehensive and systematically organized numerical results, which have been acquired by solving the complete, compressible Navier-Stokes equations. Contour maps of the temperature and stream function are constructed. In the short-bowl regime, the closed circulation near the sidewall is strongly affected by the thermal conditions; the importance of the work done by compression produced in the radial motions is emphasized. However, the axial flow in the inner inviscid region is found to be mainly controlled by the Ekman suction. In the long-bowl regime, the global flow structure is considerably influenced by the sidewall thermal condition. This is due principally to the significant diffusion of momentum in the radial direction
A cost model for spatio-temporal queries using the TPR-tree
No full textA query optimizer requires cost models to calculate the costs of various access plans for a query. An effective method to estimate the number of disk (or page) accesses for spatio-temporal queries has not yet been proposed. The TPR-tree is an efficient index that supports spatio-temporal queries for moving objects. Existing cost models for the spatial index such as the R-tree do not accurately estimate the number of disk accesses for spatio-temporal queries using the TPR-tree, because they do not consider the future locations of moving objects, which change continuously as time passes. In this paper, we propose an efficient cost model for spatio-temporal queries to solve this problem. We present analytical formulas which accurately calculate the number of disk accesses for spatio-temporal queries. Extensive experimental results show that our proposed method accurately estimates the number of disk accesses over various queries to spatio-temporal data combining real-life spatial data and synthetic temporal data. To evaluate the effectiveness of our method, we compared our spatio-temporal cost model (STCM) with an existing spatial cost model (SCM). The application of the existing SCM has the average error ratio from 52% to 93%, whereas our STCM has the average error ratio from 11% to 32%. (C) 2003 Elsevier Inc. All rights reserved
Simulation of cylindrical plunge grinding based on the behaviour of cutting edge wear
No full textIn cylindrical plunge grinding, a series of workpieces are ground successively without intermediate dressing of the wheel. Through the grinding, the wheel characteristic is continuously changed by the wear, fracture and new exposure of abrasive grains, having a profound effect on the grains on wheel surfaces in the cylindrical grinding process are developed to make it possible to describe the time dependent results of grinding and to establish the grinding operation standards capable of estimating grinding wheel performance and selecting grinding conditions, in which many parameters in actual grinding operations are considered. This simulation system can display its results in graphical form including the time dependent results and the effects of various parameters as well as optimization capabilities. This simulation has the same effects as many grinding experiments, and capable of selecting the optimum grinding wheels and conditions
Effect of simultaneous application of stressful culture conditions on specific productivity and heterogeneity of erythropoietin in chinese hamster ovary cells
No full textA single stressful culture condition induced by hypoosmotic stress (210 mOsm kg(-1)), low culture temperature (32 degreesC), or NaBu addition (1 mM) resulted in a 1.8- to 2.2-fold enhancement of specific erythropoietin (EPO) productivity (q(EPO)) of recombinant Chinese hamster ovary (rCHO) cells compared to normal culture condition (37 degreesC and 310 mOsm kg(-1)). Simultaneous application of these stressful conditions further enhanced qEPO up to approximately 5-fold. However, the quality of EPO was affected by stressful culture conditions. The proportion of acidic isoforms of EPO under a single stressful condition was 2.8-13.8% lower than that under normal culture condition. Simultaneous application of the stressful conditions further decreased the portion of acidic isoforms but not significantly. Despite 5-fold enhancement of q(EPO), the portion of acidic isoforms under the simultaneous application of stressful culture conditions was 12.9-21.6% lower than that under normal culture condition. Taken together, these results suggest the potential of simultaneous application of different stressful culture conditions to the production phase of two-stage culture, where cell growth and production phases are separated, for improved EPO production
An adaptive indexing technique using spatio-temporal query workloads
No full textMany spatio-temporal access methods, such as the HR-tree, the 3DR-tree, and the MV3R-tree, have been proposed for timestamp and interval queries. However, these access methods have the following problems: the poor performance of the 3DR-tree for timestamp queries, the huge size and the poor performance of the HR-tree for interval queries, and the large size and the high update cost of the MV3R-tree. We address these problems by proposing an adaptive partitioning technique called the Adaptive Partitioned R-tree (APR-tree) using workloads with timestamp and interval queries. The APR-tree adaptively partitions the time domain using query workloads. Since the time domain of the APR-tree is automatically fitted to query workloads, the APR-tree outperforms the other access methods for various query workloads. The size of the APR-tree is on the average 1.3 times larger than that of the 3DR-tree which has the smallest size. The update cost of the APR-tree is on the average similar to that of the 3DR-tree which has the smallest update cost. (C) 2003 Elsevier B.V. All rights reserved
Efficient extraction of schemas for XML documents
No full textIn this paper, we present a technique for efficient extraction of concise and accurate schemas for XML documents. By restricting the schema form and applying some heuristic rules, we achieve the efficiency and conciseness. The result of an experiment with real-life DTDs shows that our approach attains high accuracy and is 20 to 200 times faster than existing approaches. (C) 2002 Elsevier Science B.V All rights reserved.This work was supported by the Brain Korea 21 Project
Structural Function Inlining Technique for Structurally Recursive XML Queries
No full textKowloon Shangri-La Hotel
August 20-23, 2002
Hong Kong, Chin
XPRESS: A Queriable Compression for XML Data
No full textACM SIGMOD International Conference on Management of Data(San Diego, California
June 9-12, 2003)Information Technology Research Cente
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