Integer codes correcting burst and random asymmetric errors within a byte

In most communication networks, error probabilities 1?→?0 and 0?→?1 are equally likely to occur. However, in some optical networks, such as local and access networks, this is not the case. In these networks, the number of received photons never exceeds the number of transmitted ones. Hence, if the receiver operates correctly, only 1?→?0 errors can occur. Motivated by this fact, in this paper, we present a class of integer codes capable of correcting burst and random asymmetric (1?→?0) errors within a b-bit byte. Unlike classical codes, the proposed codes are defined over the ring of integers modulo 2^b ?1. As a result, they have the potential to be implemented in software without any hardware assist.     

Unique-order interpolative coding for fast querying and space-efficient indexing in information retrieval systems

This paper presents a size reduction method for the inverted file, the most suitable indexing structure for an information retrieval system (IRS). We notice that in an inverted file the document identifiers for a given word are usually clustered. While this clustering property can be used in reducing the size of the inverted file, good compression as well as fast decompression must both be available. In this paper, we present a method that can facilitate coding and decoding processes for interpolative coding using recursion elimination and loop unwinding. We call this method the unique-order interpolative coding. It can calculate the lower and upper bounds of every document identifier for a binary code without using a recursive process, hence the decompression time can be greatly reduced. Moreover, it also can exploit document identifier clustering to compress the inverted file efficiently. Compared with the other well-known compression methods, our method provides fast decoding speed and excellent compression. This method can also be used to support a self-indexing strategy. Therefore our research work in this paper provides a feasible way to build a fast and space-economical IRS.     

Selection of prefix and postfix word fragments for data compression

In this paper a simple algorithm is used for selection of a set of codeable substrings that occur at the front or rear of the words in a textual data base. Since the words are assumed to be non-repeating, the technique is useful for data compression of dictionaries. The time complexity of the algorithm is governed by the associated sorting algorithm and hence is 0 (n log n). It has been applied to three sample data bases, consisting of words selected from street names, authors names, or general written English text. The results show that the substrings at the rear of the words, yield better compression than those at the front. By application of results of an earlier study in compression coding, efficient encoding and decoding procedures are presented for use in on-line transmission of data.     

DACs: Bringing direct access to variable-length codes

We present a new variable-length encoding scheme for sequences of integers, Directly Addressable Codes (DACs), which enables direct access to any element of the encoded sequence without the need of any sampling method. Our proposal is a kind of implicit data structure that introduces synchronism in the encoded sequence without using asymptotically any extra space. We show some experiments demonstrating that the technique is not only simple, but also competitive in time and space with existing solutions in several applications, such as the representation of LCP arrays or high-order entropy-compressed sequences.     

Inferring user knowledge level from eye movement patterns

The acquisition of information and the search interaction process is influenced strongly by a person’s use of their knowledge of the domain and the task. In this paper we show that a user’s level of domain knowledge can be inferred from their interactive search behaviors without considering the content of queries or documents. A technique is presented to model a user’s information acquisition process during search using only measurements of eye movement patterns. In a user study (n = 40) of search in the domain of genomics, a representation of the participant’s domain knowledge was constructed using self-ratings of knowledge of genomics-related terms (n = 409). Cognitive effort features associated with reading eye movement patterns were calculated for each reading instance during the search tasks. The results show correlations between the cognitive effort due to reading and an individual’s level of domain knowledge. We construct exploratory regression models that suggest it is possible to build models that can make predictions of the user’s level of knowledge based on real-time measurements of eye movement patterns during a task session.     

Characteristics of character usage in Chinese Web searching

The use of non-English Web search engines has been prevalent. Given the popularity of Chinese Web searching and the unique characteristics of Chinese language, it is imperative to conduct studies with focuses on the analysis of Chinese Web search queries. In this paper, we report our research on the character usage of Chinese search logs from a Web search engine in Hong Kong. By examining the distribution of search query terms, we found that users tended to use more diversified terms and that the usage of characters in search queries was quite different from the character usage of general online information in Chinese. After studying the Zipf distribution of n-grams with different values of n, we found that the curve of unigram is the most curved one of all while the bigram curve follows the Zipf distribution best, and that the curves of n-grams with larger n (n = 3–6) had similar structures with β-values in the range of 0.66–0.86. The distribution of combined n-grams was also studied. All the analyses are performed on the data both before and after the removal of function terms and incomplete terms and similar findings are revealed. We believe the findings from this study have provided some insights into further research in non-English Web searching and will assist in the design of more effective Chinese Web search engines.     

Use of widgets as information management tools in online shared spaces

Online shared spaces are destinations where people of common interests interact to achieve common goals or borrow each other's expertise for personal pursuits. Due to a multitude of users, such spaces generate large amounts of content, thus creating a potential for information overload. To deal with it, users of online shared spaces develop information management strategies that frequently involve the use of information technology. In this paper we present a case study of the use of widgets as information management tools in uCern, an online shared workspace where healthcare industry stakeholders get involved in various types of interactions. To understand how widgets served the purpose of information management and whether they were considered useful, we administered an online questionnaire (n = 183) followed by qualitative interviews (n = 5). Data analysis revealed that study participants used widgets as tools that promoted their situation and activity awareness of events and activities going on in uCern and helped them with organizing and accessing the content in a quick and efficient manner. We also describe issues associated with the use of widgets and their usefulness as reported by participants and propose implications for design and development of online shared spaces in relation to information management tools.     

The relationship between race and library anxiety among graduate students: A replication study

Despite the large volume of literature on racial differences in academic performance between African Americans and Caucasian Americans at various educational levels, there has been a dearth of research examining whether the academic library experience is an important variable that helps explain the racial differences observed in educational outcomes. To date, only one empirical study has examined the racial differences in library anxiety among college students. Specifically, Jiao et al. [Jiao, Q. G., Onwuegbuzie, A. J., & Bostick, S. L. (2004). Racial differences in library anxiety among graduate students. Library Review, 53(4), 228–235] found that African-American graduate students reported statistically significantly lower levels of library anxiety associated with three library anxiety dimensions than did their Caucasian-American counterparts. However, because the two racial groups selected for the study differed in the types of institution they attended, the researchers were unable to conclude whether the differences found in the library anxiety levels were the result of race or the groups’ educational experience/aptitude. Therefore, the present study replicated Jiao et al.’s earlier research while addressing this concern. Findings revealed that the African-American graduate students (n = 25) reported consistently lower levels across all five dimensions of library anxiety than did the Caucasian-American graduate students (n = 155). These two studies suggest that racial differences in library anxiety exist in the college student population.     

The MacWilliams identity for m-spotty Rosenbloom–Tsfasman weight enumerator

The communication systems and disk or tape memory can sometimes cause clusters of errors, namely burst errors. There have been many designs in order to detect and even correct such errors. Recently, a new class of codes called m-spotty byte error correcting codes has found applications in high speed memory systems that employ random access memory chips wide Input/Output data, especially at 8, 16, or 32 bits. The MacWilliams identity provides the relationship between the weight distribution of a code and that of its dual code. Also, an interesting new metric called Rosenbloom–Tsfasman metric has been studied as an alternative metric for linear codes recently. In this paper, we combine these two interesting topics and introduce the m-spotty Rosenbloom–Tsfasman weights and the m-spotty Rosenbloom–Tsfasman weight enumerator of a binary code. Moreover, we prove a MacWilliams identity for the m-spotty Rosenbloom–Tsfasman weight enumerators.     

Growth dynamics of citations of cumulative papers of individual authors according to progressive nucleation mechanism: Concept of citation acceleration

Using data generated by progressive nucleation mechanism on the cumulative fraction of citations of individual papers published successively by a hypothetical author, an expression for the time dependence of the cumulative number L_sum(t) of citations of progressively published papers is proposed. It was found that, for all nonzero values of constant publication rate ΔN, the cumulative citations L_sum(t) of the cumulative N papers published by an author in his/her entire publication career spanning over T years may be represented in distinct regions: (1) in the region 0 < t < Θ₀ (where Θ₀ ≈ T/3), L_sum(t) slowly increases proportionally to the square of the citation time t, and (2) in the region t > Θ₀, L_sum(t) approaches a constant L_sum(max) at T. In the former region, the time dependence of L_sum(t) of an author is associated with three parameters, viz. the citability parameter λ₀, the publication rate ΔN and his/her publication career t. Based on the predicted dependence of L_sum(t) on t, a useful scientometric age-independent measure, defined as citation acceleration a = L_sum(t)/t², is suggested to analyze and compare the scientific activities of different authors. Confrontation of the time dependence of cumulative number L_sum(t) of citations of papers with the theoretical equation reveals one or more citation periods during the publication careers of different authors.     

数字视频精细可扩展性编码的研究

随着Internet和无线通信的发展,大量视频数据需要通过网络传输,使得视频压缩编码的目标从传统的面向存储转变为面向传输。然而面对网络带宽变化和传输中的包错误等两个主要问题,压缩编码需要有自适应能力。提供完全可伸缩的增强层码流,它可以在任意地点截断,具有很强的网络带宽适应能力。本文主要对精细可伸缩编码(fine granular scalable coding,FGS)进行了分析、对比、研究,实验表明FGS具有编码效率较高,图像质量好,自适应能力强的优点。     

Effective factors on accuracy of principal diagnosis coding based on International Classification of Diseases,the 10th revision (ICD-10)

Quality of diagnostic data depends on accurate coding. The purpose of this study was to assess the accuracy of principal diagnosis coding and its effective factors. To achieve this aim, three hundred and seventy medical records were randomly selected and recoded blindly (as gold standard). The effects of possible factors on accuracy of coding which was gathered through observation method were analyzed by Chi-square (χ²), Fisher exact test, odds ratio (OR), and confidence interval 95% for OR.     

On recursive averaging processes and Hilbert space extensions of the contraction mapping principle

If T maps a convex domain D_T into itself, and if {ω_n} is a real sequence with range in (0, 1] then the recursive averaging process,

$\text{X}{}_{\mathrm{n+1}}\text{=(1?omega;}{}_{\mathrm{n}}\text{)}\text{X}{}_{\mathrm{n}}\text{+ω}{}_{\mathrm{n}}\text{+ω}{}_{\mathrm{n}}\text{T}\text{x}{}_{\mathrm{n}}\text{,}\text{x}{}_0\text{=ξ?D}{}_{\mathrm{T}}$

generates a sequence {x?_n}; with range in D_T. Under suitable conditions on D_T, T and {ω_n} the sequence {x?_n} will converge in some sense to a fixed point of T. We prove that if D_T is a closed convex subset of a complex Hilbert space H, if Tω = (1 ? ω) I + ωT is a strict contraction for some ω ? (0, 1], and if {ω_n} satisfies the conditions,

$\text{ω}{}_{\mathrm{n}}\text{→ 0}$

and

$\text{∑}\text{n=0}\text{∞}\text{ω}{}_{\mathrm{n}}\text{=∞}$

then, for arbitrary ξ ? D_T, {x?_n} converges strongly to (the unique) fixed point of T. We also prove that if D_T and {ω_n} satisfy the foregoing conditions, if T has at least one fixed point, and if Tω is non-expansive for some ω ? (0, 1], then for all ξ ? D_T, {x?_n} converges at least weakly to some fixed point of T. Finally, we apply these results to linear equations involving bounded normal operators and obtain an extension of the classical Neumann operator series.     

Inverted file compression through document identifier reassignment

The inverted file is the most popular indexing mechanism for document search in an information retrieval system. Compressing an inverted file can greatly improve document search rate. Traditionally, the d-gap technique is used in the inverted file compression by replacing document identifiers with usually much smaller gap values. However, fluctuating gap values cannot be efficiently compressed by some well-known prefix-free codes. To smoothen and reduce the gap values, we propose a document-identifier reassignment algorithm. This reassignment is based on a similarity factor between documents. We generate a reassignment order for all documents according to the similarity to reassign closer identifiers to the documents having closer relationships. Simulation results show that the average gap values of sample inverted files can be reduced by 30%, and the compression rate of d-gapped inverted file with prefix-free codes can be improved by 15%.     

On the motivating impact of price and online recommendations at the point of online purchase

Do online recommendations have the same motivating impact as price at the point of online purchase? The results (n = 268) of an conjoint study show that: (1) when the price is low or high relatively to market price, it has the strongest impact (positive and negative) on the likelihood of an online purchase of an mp3 player, (2) when the price is average to market price, online recommendation and price are equal in their impact at the point of online purchase, and, (3) the relative impact from price increases when online shopping frequencies increases. The implications these results give are that online retailers should be aware that online recommendations are not as influential as a good offer when consumers purchase electronics online. However, other customer recommendations have a stronger impact on novice online shoppers than towards those consumers that shop more frequently online.     

Delay-dependent stability criteria for systems with asymmetric bounds on delay derivative

This paper discretizes the states, a method introduced in [18] for constant delayed systems, not only in constructing the Lyapunov-Krasovskii (L-K) functional but also in designing the integral inequality technique [17] and [19] for time-varying delayed systems, which increase the order of uncorrelated augmentation [5], [21] and [22]. Based on the discretized state, [10] and [27]'s piecewise analysis method is applied to confirm the system stability in whole delay bound. Asymmetric variation of the delay derivative is assumed so that direct extension to all constraints of the delay derivative can be achieved. Examples show the resulting criteria improve the allowable delay bounds over all existing ones in the literature.     

Characterization of two-dimensional cellular automata over ternary fields

The set of papers [3], [4], [6] and [7] (Chattopadhyay et al., 1999; Dihidar and Choudhury, 2004; Khan et al., 1997, 1999) deals with the behavior of the uniform two-dimensional cellular automata over binary fields (Z₂). Some structural properties and precise mathematical models using matrix algebra over the field Z₂ are reported for characterizing the behavior of two-dimensional nearest neighborhood linear cellular automata with null and periodic boundary conditions [3], [4], [6] and [7] (Chattopadhyay et al., 1999; Dihidar and Choudhury, 2004; Khan et al., 1997, 1999). In this paper, we characterize two-dimensional linear cellular automata transformations by using matrix algebra built on Z₃. We analyze some results for two-dimensional CA with rule numbers 2460N and 2460P. Finally, we investigate the dimension of the kernel of two-dimensional cellular automata defined by the rule number 2460N.     

Bidirectional delta files

A bidirectional delta file is a novel concept, introduced in this paper, for a two way delta file. Previous work focuses on single way differential compression called forwards and backwards delta files. Here we suggest to efficiently combine them into a single file so that the combined file is smaller than the combination of the two individual ones. Given the bidirectional delta file of two files S and T and the original file S, one can decode it in order to produce T. The same bidirectional delta file is used together with the file T in order to reconstruct S. This paper presents two main strategies for producing an efficient bidirectional delta file in terms of the memory storage it requires; a quadratic time, optimal, dynamic programming algorithm, and a linear time, greedy algorithm. Although the dynamic programming algorithm often produces better results than the greedy algorithm, it is impractical for large files, and it is only used for theoretical comparisons. Experiments between the implemented algorithms and the traditional way of using both forwards and backwards delta files are presented, comparing their processing time and their compression performance. These experiments show memory storage savings of about 25% using this bidirectional delta approach as compared to the compressed delta file constructed using the traditional way, while preserving approximately the same processing time for decoding.     

Cluster-K: Network topology for searching replicated data in p2p systems

This paper proposes a new scheme for ensuring data consistency in unstructured p2p networks where peers can subscribe to multiple content types (identified by labels) and are rapidly informed of content updates. The idea is based on using a static tree structure, the Cluster-K⁺ tree, that maintains most of the structural information about peers and labels. A label denotes a set of replicated or co-related data in the network. The Cluster-K⁺ tree provides efficient retrieval, addition, deletion and consistent updates of labels. Our proposed structure guarantees a short response search time of O(H + K), where H denotes the height of the tree and K the degree of an internal tree node. We present theoretical analytic bounds for the worst-case performance. To verify the bounds, we also present experimental results obtained from a network simulation. The results demonstrate that the actual performance of our system is significantly better than the theoretical bounds.