Safe harbor and privacy protection: a looming issue for IT professionals

The 25 European Union (EU) Member States require that their residents' personal information not be transferred to countries that do not protect that information adequately. In 2000, the EU ruled that the United States (US), through its voluntary Safe Harbor program, met that requirement. Since that time, however, the EU has charged that many US companies that claim to be in compliance with Safe Harbor policies are not. In this article, I report on a study of the privacy-policy statements of 20 randomly selected US companies that claim to be in compliance. Of the 20, 19 are not in compliance. This study argues that as EU Member States begin to examine Safe Harbor carefully, they are likely to force US companies to adhere to more stringent privacy policies. The burden of this adherence will be borne by US IT professionals.     

Passive Multiterminal Networks Without Transformers

It is known that any scalar function f(p) of the complex frequency variable that is the admittance function of a passive finite network is in fact the admittance function of a network that can be realized without transformers. This paper shows that an m times m matrix-valued function Y(p), m ges 2, given that it is an admittance matrix, is the admittance of a network that contains no transformers if and only if it enjoys two further properties: 1) for each real p > 0 Y(p) is the admittance of a passive resistive network specific to p; and 2) a property defined as the null space property. It is shown that property 1) severely limits the class of m-terminal networks, m > 1, that can be realized without transformers. The author concludes that, for passive systems, transformers are here to stay.     

Arithmetic coding with dual symbol sets and its performanceanalysis

We propose a novel adaptive arithmetic coding method that uses dual symbol sets: a primary symbol set that contains all the symbols that are likely to occur in the near future and a secondary symbol set that contains all other symbols. The simplest implementation of our method assumes that symbols that have appeared in the previously are highly likely to appear in the near future. It therefore fills the primary set with symbols that have occurred in the previously. Symbols move dynamically between the two symbol sets to adapt to the local statistics of the symbol source. The proposed method works well for sources, such as images, that are characterized by large alphabets and alphabet distributions that are skewed and highly nonstationary. We analyze the performance of the proposed method and compare it to other arithmetic coding methods, both theoretically and experimentally. We show experimentally that in certain contexts, e.g., with a wavelet-based image coding scheme that has appeared in the literature, the compression performance of the proposed method is better than that of the conventional arithmetic coding method and the zero-frequency escape arithmetic coding method.     

Why software projects escalate: the importance of project management constructs

Previous research has documented that software projects are frequently prone to escalation. While the escalation literature acknowledges that project-related (as well as psychological, social, and organizational) factors can promote escalation behavior, there has been no investigation regarding the role that project management factors may have in discriminating between projects that escalate and those that do not. The objective of this study was to explore whether project management constructs could be used to distinguish between projects that escalated and those that did not. Based on a survey administered to IS audit and control professionals, data were gathered on projects that did not escalate as well as those that did escalate. We then applied logistic regression to model the relationship between various project management constructs and project escalation. The model was then evaluated for its ability to correctly classify the projects. The results of our research suggest that a logistic regression model based on project management constructs is capable of discriminating between projects that escalate and those that do not. Moreover, the model compares favorably to a previously published logistic regression model based on constructs derived from escalation theory. The implications of these findings are discussed.     

Woman as mediatrix: women as writers on science and technology inthe eighteenth and nineteenth centuries

It is argued that although the writing on science and technology produced by women in the eighteenth and nineteenth centuries has usually been considered peripheral to scientific and technological advancement, the history of the mediatrix, or woman mediator, reveals that women writers carried out essential tasks. History suggests that women assumed the role of mediatrix much more frequently than they assumed other roles, largely because that role allowed women to contribute to science and technology without seriously violating gender norms. The careers and writing of four women mediators are described, showing that mediation is an unrecognized but crucially important aspect of the intellectual activity of science and that mediative writing often clarifies, rather than debases, scientific knowledge. The history of women mediators also suggests that intermediaries are essential for the functioning of the interlocking and overlapping groups and institutions that constitute science and technology and that it might be beneficial to restructure organizations so that the role of mediator is clearly defined and valued     

Jointly optimal receivers for the optical pulse-position modulationchannel

Jointly optimal receivers that make decisions in the absence of symbol synchronization are derived and analyzed for a pulse-position modulation, optical direct-detection channel. Both receivers that observe the complete sample-path (count record data) and receivers that observe histogram data are studied, and approximations to them are derived. It is seen that jointly optimal receivers are superior to conventional receivers that have separately designed synchronization and decision subsystems. However, their performance advantage is significant only at very low signal levels. Perhaps more significant is that an approximation to the jointly optimal receivers that is much easier to implement than an optimal, separately synchronized receiver achieves nearly the same performance as the latter. Simulation results indicate that the much less complicated receivers that observe histogram data perform as well as receivers that observe the complete sample path at a rather small number of bins per slot     

认知无线电多信道下的感知时间优化

主要研究了认知无线电中多信道连续感知结构下,多个感知时隙和单个传输时隙的感知时间优化问题。首先在信道的空闲概率已知的条件下,当信道的信噪比保持不变时,经证明最佳感知时间是存在的;其次在信道的空闲概率未知的条件下,提出了一种单时隙感知时间的次优方法,逐步的计算出来各个时隙中下一个时隙的最优化感知时间。仿真实验证明,提出的方法优于固定感知时间的感知方法,同时降低了算法的复杂度,且在不同的条件下,此方法吞吐量性能接近于理论上的最佳感知时间吞吐量性能,并优于固定感知时间方法的吞吐量。     

Designing Negative Differential Resistance Devices Based on Self‐Heating

There are a number of important emerging applications that would benefit from simple circuit elements that exhibit tunable current‐controlled negative differential resistance (NDR). The advent of such devices would enable, for example, key components for threshold logic and neuromorphic computing such as threshold switches, periodic and chaotic oscillators, and small signal amplifiers. Circuit elements that provide NDR with modifiable electrical characteristics would also be useful for creating optimized “selectors” that enable addressing of individual memory cells in large resistance‐based memory arrays. Currently, there are no simple, bipolar, two‐terminal commercial devices that exhibit current‐controlled NDR. This paper demonstrates that current‐controlled NDR can, in principal, arise from any electrical conduction mechanism that depends superlinearly on temperature, and that in practice a broad spectrum of materials can be utilized to yield NDR. A model is presented that accurately predicts conditions under which NDR can be observed and guidelines are provided for choosing materials that result in desired electrical characteristics. This model accurately predicts the behavior of some existing structures and can be used to tailor future circuit elements for emerging applications. It may also explain the onset of a number of “soft breakdown” phenomena.     

Computers and epidemiology

Analogies with biological disease with topological considerations added, which show that the spread of computer viruses can be contained, and the resulting epidemiological model are examined. The findings of computer virus epidemiology show that computer viruses are far less rife than many have claimed, that many fail to thrive, that even successful viruses spread at nowhere near the exponential rate that some have claimed, and that centralized reporting and response within an organization is an extremely effective defense. A case study is presented, and some steps for companies to take are suggested     

Comment on `Sallen and Key filter networks with amplifier gain larger than or equal to unity'

Refers to an article by G. S. Moschytz (see abstr. B6114 of 1968) that gives consideration to the realization of a second-order transfer function of specified form through utilization of RC elements plus a noninverting operational amplifier. Moschytz claims in the abstract that he has presented a suitable realization, a modified Sallen and Key network, that contains a noninverting amplifier having a gain that can always be made greater than or equal to unity. Such a gain then permits one to incorporate a noninverting operational amplifier into the design. This correspondence shows that there exists a subclass of second-order transfer functions that, when realized by Moschytz's realization procedure, results in a gain constant that is less than unity for all values of the available parameters. It is then not possible to incorporate a noninverting operational amplifier without altering the network structure. A simple modification of Moschytz's work is presented that assures the existence of a realization that includes a noninverting operational amplifier.     

Variable length coding over an unknown channel

Burnashev in 1976 gave an exact expression for the reliability function of a discrete memoryless channel (DMC) with noiseless feedback. A coding scheme that achieves this exponent needs, in general, to know the statistics of the channel. Suppose now that the coding scheme is designed knowing only that the channel belongs to a family Q of DMCs. Is there a coding scheme with noiseless feedback that achieves Burnashev's exponent uniformly over Q at a nontrivial rate? We answer the question in the affirmative for two families of channels (binary symmetric, and Z). For these families we show that, for any given fraction, there is a feedback coding strategy such that for any member of the family: i) guarantees this fraction of its capacity as rate, and ii) guarantees the corresponding Burnashev's exponent. Therefore, for these families, in terms of delay and error probability, the knowledge of the channel becomes asymptotically irrelevant in feedback code design: there are blind schemes that perform as well as the best coding scheme designed with the foreknowledge of the channel under use. However, a converse result shows that, in general, even for families that consist of only two channels, such blind schemes do not exist.     

The impact of multicast layering on network fairness

Many definitions of fairness for multicast networks assume that sessions are single rate, requiring that each multicast session transmits data to all of its receivers at the same rate. These definitions do not account for multirate approaches, such as layering, that permit receiving rates within a session to be chosen independently. We identify four desirable fairness properties for multicast networks, derived from properties that hold within the max-min fair allocations of unicast networks. We extend the definition of multicast max-min fairness to networks that contain multirate sessions, and show that all four fairness properties hold in a multirate max-min fair allocation, but need not hold in a single-rate max-min fair allocation. We then show that multirate max-min fair rate allocations can be achieved via intra-session coordinated joins and leaves of multicast groups. However, in the absence of coordination, the resulting max-min fair rate allocation uses link bandwidth inefficiently, and does not exhibit some of the desirable fairness properties. We evaluate this inefficiency for several layered multirate congestion control schemes, and find that, in a protocol where the sender coordinates joins, this inefficiency has minimal impact on desirable fairness properties. Our results indicate that sender-coordinated layered protocols show promise for achieving desirable fairness properties for allocations in large-scale multicast networks     

Design and implementation of a lightweight online certificate validation service

A PKI (public key infrastructure) provides for a digital certificate that can identify an individual or an organization. However, the existence of a certificate is a necessary but not sufficient evidence for its validity. The PKI needs to provide applications that use certificates with the ability to validate, at the time of usage, that a certificate is still valid (not revoked). One of the two standard protocols to check the revocation status of certificates is the Online Certificate Status Protocol (OCSP). In this article, we propose an OCSP-based implementation that enhances the performance of standard OCSP. In particular, we put special emphasis on those issues that affect security and performance when the validation service is deployed in a real scenario. Finally, we provide experimental results that show that our implementation outperforms standard OCSP.     

Comparing Selected Mapping and Partial Transmit Sequence for PAR Reduction

Selected mapping (SLM) and partial transmit sequence (PTS) are two existing distortionless peak-to-average power ratio (PAR) reduction schemes that have been proposed for orthogonal frequency division multiplexing (OFDM). Previously, it was argued that SLM and PTS have comparable PAR reduction performance but that the latter has lower computational complexity because it uses fewer IFFTs. In this paper, we show that the overall computational complexity of PTS is only lower than that of SLM in certain cases, and that SLM always has better PAR reduction performance. We compare the two schemes using three different performance metrics by assuming a given amount of computational complexity that can be afforded. Using the metrics, we show that SLM outperforms PTS for a given amount of complexity.     

Tussle in cyberspace: defining tomorrow's Internet

The architecture of the Internet is based on a number of principles, including the self-describing datagram packet, the end-to-end arguments, diversity in technology and global addressing. As the Internet has moved from a research curiosity to a recognized component of mainstream society, new requirements have emerged that suggest new design principles, and perhaps suggest that we revisit some old ones. This paper explores one important reality that surrounds the Internet today: different stakeholders that are part of the Internet milieu have interests that may be adverse to each other, and these parties each vie to favor their particular interests. We call this process "the tussle". Our position is that accommodating this tussle is crucial to the evolution of the network's technical architecture. We discuss some examples of tussle, and offer some technical design principles that take it into account.     

On the accuracy of the UTD for the scattering by a cylinder

The UTD formulation for the scattering by a cylinder is valid for antennas that are removed from the cylinder surface. The usual guideline is that reliable results can be obtained for antennas that are about λ/4 or more away from the surface. By exploring a few cases, we show that λ/4 is unnecessarily large for the lit region and sometimes too small for the shadow region. In addition, we find that with a simple heuristic modification to the UTD, heights as small as λ/20 can be accommodated, with an accuracy that is sufficient for most engineering applications     

Exploring How We Enjoy Antihero Narratives

Affective disposition theory (ADT), which nicely explains enjoyment of traditional hero narratives, appears somewhat limited in its ability to explain antihero narratives, primarily because of the moral complexity of the protagonists. Recent work proposes that viewers over time develop story schema that permit antihero enjoyment, despite character immorality. This article reports results from three studies that support this claim. Specifically, the findings indicate that moral judgment may be less important to antihero enjoyment than ADT would predict, that previous exposure to an antihero narrative alters responses to similar narratives, and that moral disengagement cues impact the enjoyment process. Ultimately, the studies offer empirical evidence of how antihero narratives are enjoyed differently than their traditional hero counterparts.     

城域网骨干网络业务流量的性能分析

近期研究分析表明很多信息源会产生在多时间尺度下具有自相似特性的信息流，本文分析了西安宽带多媒体城域网骨干网的数据流量分布特性，以及自相似特性，实验表明真实骨干网的流量分布接近正态分布．并且具有共同特性，即左尾比正态分布短，右尾比正态分布长，即正态右偏性。     

一种人机结合的真随机模拟方法

利用计算机间隔时间存储的功能，结合键盘敲击随机点过程，通过时间间隔分布的小数分布及其极限性质，给出了一种人机组合的真随机模拟方法，并指出了其计算机实现方法和在经济学以及遗传进化算法等中的应用。     

虚拟设备在嵌入式LINUX系统中的使用

在Linux系统中，系统是把设备映射为一个特殊的设备文件，用户程序可以象对其它文件一样对此设备文件进行操作。我们可以根据这一点，构造一个不连接任何硬件的设备文件，即虚拟设备。利用这个设备，我们可以把一系列的底层操作转化为应用层操作，以减低上层工作量。