Itemset trees for targeted association querying

Association mining techniques search for groups of frequently co-occurring items in a market-basket type of data and turn these groups into business-oriented rules. Previous research has focused predominantly on how to obtain exhaustive lists of such associations. However, users often prefer a quick response to targeted queries. For instance, they may want to learn about the buying habits of customers that frequently purchase cereals and fruits. To expedite the processing of such queries, we propose an approach that converts the market-basket database into an itemset tree. Experiments indicate that the targeted queries are answered in a time that is roughly linear in the number of market baskets, N. Also, the construction of the itemset tree has O(N) space and time requirements. Some useful theoretical properties are proven.     

Wake capturing in potential flow calculations

Summary In this paper, we present a formulation for irrotational, isentropic flows in terms of velocity components which is equivalent to the classical potential equation, except the wake is not fixed and it is captured as part of the solution with no special treatment. Preliminary numerical results are presented to validate this new approach.     

Comparison studies between cement and cement-kaolinite properties for incorporation of low-level radioactive wastes

Comparison between the properties of cement and cement mixed with 7.5% kaolinite was performed to choose the most suitable matrix to incorporate radio-active wastes. The cement-kaolinite mixtures were prepared as uncured, cured, and heated specimens. The physical properties of the cement-kaolinite mixture, namely density, porosity, and water absorption percent, were determined. Compressive strength, infrared spectra, thermal analysis, and the effect of gamma rays on the samples were studied. The studies were extended to the cement-kaolinite mixture in the presence of some chemical additives at different concentrations. Leachability of radioactive isotopes from the cement-kaolinite mixture was measured as a function of time. The physical and mechanical properties of cement were decreased in the presence of 7.5% kaolinite, whereas ¹³⁷Cs and ⁶⁰Co were less leached from the cement-kaolinite mixture.     

Pulpal response to a resin-modified glass-ionomer material on nonexposed and exposed monkey pulps

OBJECTIVE: This study evaluated the biocompatibility of a resin-modified glass-ionomer material on monkey pulps. METHOD AND MATERIALS: Standardized Class V cavities were prepared in 112 teeth distributed in six healthy adult monkeys. The resin-modified glass-ionomer cement was placed in 24 nonexposed and 36 exposed pulps according to manufacturer's instructions. ZOE was used as a control in nonexposed pulps, while calcium hydroxide was used as a control for exposed pulps. Tissues were collected at 6 to 7, 21 to 27, and 90 to 97 days. After demineralization, the teeth were serially sectioned, stained, and observed by light microscopy. RESULTS: Except for one resin-modified glass-ionomer pulp at 6 days, there were no differences between the responses of nonexposed pulps to resin-modified glass-ionomer specimens and ZOE controls. In exposed pulps, eight of 36 resin-modified glass-ionomer pulps showed various grades of inflammatory response, all associated with stained bacteria. Pulpal healing was similar in both resin-modified glass-ionomer and calcium hydroxide direct-capped exposures. Twenty-two of 26 exposed pulps restored with the resin-modified glass-ionomer cement showed dentin bridge formation at 21 and 97 days. CONCLUSION: The resin-modified glass-ionomer material exhibited acceptable biologic compatibility in exposed and nonexposed cavities.     

Vertical scaling of 0.25-/spl mu/m emitter InP/InGaAs single heterojunction bipolar transistors with f/sub T/ of 452 GHz

Vertical scaling of the epitaxial structure has allowed submicron InP/InGaAs-based single heterojunction bipolar transistors (SHBTs) to achieve record high-frequency performance. The 0.25/spl times/16 /spl mu/m/sup 2/ transistors, featuring a 25-nm base and a 100-nm collector, display current gain cut-off frequencies f/sub T/ of 452 GHz. The devices operate at current densities above 1000 kA/cm/sup 2/ and have BV/sub CEO/ breakdowns of 2.1 V. A detailed analysis of device radio frequency (RF) parameters, and delay components with respect to scaling of the collector thickness is presented.     

Resource smoothening in repetitive projects

To manage construction projects properly, it is necessary to establish a project plan for resources utilization. This management function, usually, is carried out in two steps: resource allocation and resource usage smoothening. In this paper, a linear programming model for a single resource allocation and smoothening in repetitive construction project has been achieved. The linear programming model is based on one of the following objectives:

1. 1. The resource requirements nearly follow a desirable resource histogram, Model M1.

2. 2. Minimizing the number of changes in resource requirements, Model M2.

     

Improved transmit steering for MIMO-OFDM downlinks with distributed base station antenna arrays

Space-division multiple-access (SDMA) is a communication technique that enables a base station to communicate with several mobile users simultaneously. The ability of the base station to spatially separate several users depends on the pairwise cross correlations between the channel matrices of the users (the inter-user correlation). In this paper, we propose an improved steering downlink multiple-input-multiple-output-orthogonal frequency-division multiplexing (OFDM) system that reduces both the inter-user correlation and the near-far problem resulting in a significant enhancement in system performance. In this system, several base station multiantenna arrays are distributed in a given area. Each array communicates with the base station via optical fiber links, and all transmitter signal processing is performed at the base station. Multiantenna users are spatially separated such that only a subset of the users is served by each tone of the OFDM symbol. The served users are selected based on an algorithm that reduces the inter-user correlations. Distributing the arrays around the users also balances the channel matrix leading to significant reduction in the effect of the near-far problem. The channel matrix of each user is assumed correlated and Ricean distributed. Several data symbols can be spatially multiplexed to each user over each OFDM tone with high reliability and with good total system capacity.     

Fluoride and dental age

The dental ages of 1286 (674 males and 612 females) Egyptian children born and grown up in a community with naturally occurring overfluoride ions in the drinking water (more than the optimal level) in Matrouh Governorate, were compared with the Egyptian standards of the fluoride deficient area of the same socioeconomic level. The age ranged from 8 years to 14 years and 6 months. The results of the present study revealed that the communal water supply with a fluoride ions concentration more than optimal level has no long term effect on the dental age, as judged from the tooth emergence of the growing children.     

A Time-Slot Assignment Strategy for ATM Broadband Indoor Wireless Networks

The rapid development of wireless in-building communication systems, has widened the scope of supported applications. Remote terminals may be capable of producing broadband real-time traffic such as variable bit-rate (VBR) video or bursty data transfers. Consequently one of the important issues in indoor broadband wireless networks (IBWN) is employment of an efficient bandwidth management protocol. In such a protocol, both the effects of radio channel behavior and the traffic heterogeneity have to be considered. In this paper we present a bandwidth allocation scheme based on the interplay of the radio channel characteristics and the traffic parameters and requirements. In the proposed scheme the base station visits the terminals in a non-uniform cyclic fashion. The inter-visit interval and the amount of service which is provided to each user during a visit, is determined using the channel and traffic parameters based on an analytical approach. This system is evaluated by simulations and is found to provide improved performance in fulfilling the requirements of multimedia services in IBWN.