电信计费分析数据仓库系统的设计与实现

该文主要研究如何用数据仓库及其技术解决电信计费分析的实际问题。     

利用SHELL编程实现UNIX系统下气象资料传输与处理

本文对UNIX环境下SHELL脚本语言进行了简要介绍,并举例说明了如何利用SHELL脚本语言实现UNIX/Linux系统下气象资料传输与处理。     

Web日志挖掘与上网行为习惯分析

本文以某校校园网Web日志挖掘为例,首先阐述如何进行Web挖掘,其次运用该理论分析该校Web日志得到用户上网行为习惯,并给出合理化建议,最后引出进一步探索的方向,为以后工作奠定基础。本文采用的挖掘方法具有通用性和实用性,对于类似时序序列趋势分析都可参考本文。     

数据库推理通道的动态控制

数据库推理问题是数据库安全研究的重要组成部分,主要研究推理通道的检测方法和控制策略。该文提出一种动态控制推理通道的方法。该方法为每个推理通道建立一个标识集合,利用集合中元素和推理通道中对象的关联来控制查询的处理,使用户能灵活地访问数据但又得不到足够的信息来推理。与以前提出的方案不同,该方案保证了数据的最大可用性,同时有效地阻止推理并保持了快速的查询处理能力。     

The effects of container size, frequency and extended horizontal reach on maximum acceptable weights of lifting for female industrial workers

In the development of our present manual materials handling (MMH) guidelines (Snook, S.H., Ciriello, V.M., 1991. The design of manual tasks: revised tables of maximum acceptable weights and forces. Ergonomics 34, 1197-1213), the assumption was made that the effects of frequency on maximum acceptable weights (MAWs) of lifting with a large box (hand distance, 38 cm from chest) were similar to that of lifting with a small box (hand distance, 17 cm from chest). The first purpose of the present experiment was to investigate this assumption with female industrial workers. The second purpose was to study the effects of extended horizontal reach lifting (hand distance, 44.6 cm from chest) on MAWs as a confirmation of the results of a previous studies on this variable with males (Ciriello, V.M., Snook, S.H., Hughes, G.J., 1993. Further studies of psychophysically determined maximum acceptable weights and forces. Hum. Factors 35(1), 175-186; Ciriello, V.M., 2003. The effects of box size, frequency, and extended horizontal reach on maximum acceptable weights of lifting. Int. J. Ind. Ergon. 32, 115-120). Lastly, we studied the effects of high frequency (20 lifts/min) on MAWs of lifting. Ten female industrial workers performed 15 variations of lifting using our psychophysical methodology whereby the subjects were asked to select a workload they could sustain for 8h without "straining themselves or without becoming unusually tired weakened, overheated or out of breath". The results confirmed that MAWs of lifting with the large box was significantly effected by frequency. The frequency factor pattern in this study was similar to the frequency pattern from a previous study using the small box (Ciriello, V.M., Snook, S.H., 1983. A study of size distance height, and frequency effects on manual handling tasks. Hum. Factors 25(5), 473-483) for all fast frequencies down to one lift every 2 min with deviations of 7%, 15%, and 13% for the one lift every 5 and 30 min tasks and the one lift in 8h task, respectively. The effects of lifting with an extended horizontal reach decreased MAW 22% and 18% for the mid and center lift and the effects of the 20 lifts/min frequency resulted in a MAW that was 47% of a 1 lift/min MAW. Incorporating these results in future guidelines should improve the design of MMH tasks for female workers.     

Physiological and psychophysical responses in handling maximum acceptable weights under different footwear--floor friction conditions

A study on combined manual materials-handling tasks performed on floors under three friction levels was conducted. Eight male subjects participated in the study. The maximum acceptable weight of handling, including lifting, carrying for 3m, lowering, and walking 3m back at twice per minute was determined. The subject then performed the same tasks for 10 min. Heart rate, Vo2, energy efficiency, perceived sense of slip, and rating of perceived exertion for whole body strain were measured. The results showed that the effects of friction level on the maximum acceptable weights of handling, perceived sense of slip, Vo2, and energy efficiency were statistically significant (p相似文献   

一种通用的数据类型——十进制浮点数

为智能仪表提供一种“十进制浮点数”,其特点是值域宽、值准确,它能代替整、长整型、三字节浮点数、四字节浮点数、BCD码数。用它通信可简化和统一仪表的通信协议,为制定仪表通用通信协议标准创造条件。     

光三角式传感器测距系统

主要介绍了光三角式距离传感器测距系统的结构组成和原理 ,分析了参数之间的转换关系 ,论述了以单片机为核心构成检测电路的原理和性能 ,以及单片机的软件功能。最后给出检测系统的主要技术指标。     

Logical Representation of a Conceptual Model for Spatial Data Warehouses

The MultiDimER model is a conceptual model used for representing a multidimensional view of data for Data Warehouse (DW) and On-Line Analytical Processing (OLAP) applications. This model includes a spatial extension allowing spatiality in levels, hierarchies, fact relationships, and measures. In this way decision-making users can represent in an abstract manner their analysis needs without considering complex implementation issues and spatial OLAP tools developers can have a common vision for representing spatial data in a multidimensional model. In this paper we propose the transformation of a conceptual schema based on the MultiDimER constructs to an object-relational schema. We based our mapping on the SQL:2003 and SQL/MM standards giving examples of commercial implementation using Oracle 10g with its spatial extension. Further we use spatial integrity constraints to ensure the semantic equivalence of the conceptual and logical schemas. We also show some examples of Oracle spatial functions, including aggregation functions required for the manipulation of spatial data. The described mappings to the object-relational model along with the examples using a commercial system show the feasibility of implementing spatial DWs in current commercial DBMSs. Further, using integrated architectures, where spatial and thematic data is defined within the same DBMS, facilitates the system management simplifying data definition and manipulation.

A Generalization of a Lower Bound Technique due to Fredman and Saks

{In a seminal paper of 1989, Fredman and Saks proved lower bounds for some important data-structure problems in the cell probe model. In particular, lower bounds were established on worst-case and amortized operation cost for the union-find problem and the prefix sum problem. The goal of this paper is to turn their proof technique into a general tool that can be applied to different problems and computational models. To this end we define two quantities: Output Variability depends only on the model of computation. It indicates how much variation can be found in the results of a program with certain resource bounds. This measures in some sense the power of a model. Problem Variability characterizes in a similar sense the difficulty of the problem. } Our Main Theorem shows that by comparing a model's output variability to a problem's problem variability, lower bounds on the complexity of solving the problem on the given model may be inferred. The theorem thus shows how to separate the analysis of the model of computation from that of the problem when proving lower bounds. We show how the results of Fredman and Saks fit our framework by computing the output variability of the cell probe model and the problem variability for problems considered in their paper. This allows us to reprove their lower bound results, and slightly extend them. The main purpose of this paper though is to present the generalized technique. Received January 25, 1999; revised July 30, 1999.