Characterization of wall dispersive and attenuative effects on UWB radar signals

This paper addresses the potentials of ultra-wideband (UWB) through-wall imaging radars compared with conventional narrowband systems. The challenges that limit the utilization of high precision UWB systems are examined with the aim of mitigating them. These challenges include multi-path, pulse dispersion, and antenna effects on the pulse shape due to angles of transmission and arrival. The propagation of UWB signals through walls is a crucial factor in determining the success of UWB radar technology. UWB signals, when propagating through walls, not only suffer attenuation but also distortion due to dispersive properties of the walls. This paper examines time- and frequency-domain techniques for measuring the electromagnetic properties of construction materials in the UWB frequency range. The measured parameters provide valuable insights in appreciating the capabilities and limitations of the UWB technology. Special attention is paid to time gating as a mean to extract the direct-path signal from the multi-path components. Both single-pass and multi-pass models are discussed. Multi-pass models account for the multiple reflections within the wall while the single-pass model assumes the possibility of gating out a single transmission. The partition-dependent narrowband propagation model is modified to account for the ultra-wide bandwidth of the signal. The paper illustrates the application of the modified model in indoor environments. The modified model is helpful in estimating the link power budget. It is also useful in studying the performance of UWB systems for indoor communication and positioning applications.     

A new method for performance evaluation of bit decoding algorithms using statistics of the log likelihood ratio

This paper presents a new method for the performance evaluation of bit decoding algorithms. The method is based on estimating the probability density function (pdf) of the bit log likelihood ratio (LLR) by using an exponential model. It is widely known that the pdf of the bit LLR is close to the normal density. The proposed approach takes advantage of this property to present an efficient algorithm for the pdf estimation. The moment matching method is combined with the maximum entropy principle to estimate the underlying parameters. We present a simple method for computing the probabilities of the point estimates for the estimated parameters, as well as for the bit error rate. The corresponding results are used to compute the number of samples that are required for a given precision of the estimated values. It is demonstrated that this method requires significantly fewer samples as compared to the conventional Monte-Carlo simulation.     

Isolation and purification of rat islet cells by flow cytometry

Flow cytometry has been employed as a method to study homogeneity of isolated islet subpopulations. After collagenase digestion of rat pancreas and elutriation of tissue fragments, islets were isolated and dissociated, and cells were analyzed and sorted according to their low forward angle light scattering properties by using automated flow cytometry. A standardized procedure was developed for the preparation of rat islet cell grafts for purification of islet cells. In this process, after collagenase digestion of pancreas, islets were isolated, dissociated, identification by dithizone method and then with enzymatic procedure by DNase and trypsin, the islet cells changed into single cells and beta cells were identified by immunofluorescence method and then assayed by flow cytometry. Methods have been developed for the preparation of suspension of viable rat pancreatic islet cells and their analysis and sorting in the fluorescence activated cell sorter (FACC IV, Becton Dickinson, Sunnyvale, Ca). Flow cytometry of these cells indicated that there were 91% of beta cells in cell suspension. Most of the exocrine particles were lost during digestion. Purified endocrine islet cell grafts were prepared by pure beta-cells, without endocrine non-beta cells. The purified aggregates were devoid of endocrine non-beta cells and damaged cells.     

孔子与哲拉鲁丁·鲁米对新世纪的启迪——基于家庭自然观、道德观和生态观的比较

比较和对照两位伟大的思想家——孔子与鲁米在家庭自然观、道德观、生态观等方面内在的相似性与不同点,可以丰富和拓宽我们对自然和自身的认知,建立针对生态破坏和过度消费自然的道德意识的基础.更重要的是,他们的智慧为我们构造了不同文化和文明之间理解和沟通的桥梁.     

Determining Optimal Skillsets for Business Managers Based on Local and Global Job Markets: A Text Analytics Approach

We are experiencing a significant shift in management practices—moving from intuition, experience, and gut‐feeling driven decision‐making to one that is driven by data, evidence, and computational sciences. This shift, which is often called the analytics revolution, is not only changing the business landscape from a practical perspective but also redefining the white‐collar job market. The goal of this study is to employ a data‐ and analytics‐driven approach to analyze a large and feature‐rich dataset (which is composed of the recent job postings and the extant published literature) to characterize the state of the current business job market, especially to magnify the analytics related features and expectations including the geographic (i.e., local vs. global) differentiators. Using several graphical and tabular representations, in this paper we report on our thought‐provoking findings that collectively illustrate the changing face of knowledge, skills, and abilities required by the current local and global business job markets.