Useful Rule Of Thumb Research Articles

Low–high SNR transition in multiuser MIMO

Multiuser multiple-input–multiple-out (MU-MIMO) plays a key role in the widely adopted 3GPP LTE standard for wireless cellular networks. Although exact and asymptotic sum-rate results are well known, the problem of obtaining intuitive analytical results for medium signal-to-noise ratios (SNRs) is still not solved. As a result of the present reported work, the bend point is proposed, which quantifies the transition between low and high SNR, i.e. the beginning of the high SNR region. The bend point is derived for MU-MIMO with zero-forcing precoding and is obtained, that it is intimately related to the intercept of the high SNR asymptote with the zero sum-rate line. Using this result, a new approximation of the sum-rate at the bend point it is shown providing a useful rule of thumb for the effect of increasing the number of antennas at medium SNR.

On the electromagnetic response of a resistive cylinder buried in a conductive host

The frequency-domain electromagnetic response of a confined conductor buried in a resistive host has received much attention, particularly in the context of mineral exploration. In contrast, the problem of the electromagnetic response of a confined resistor buried in a conductive host has been less thoroughly studied. However, resistive targets are important in geotechnical and hydrologic studies, archaeological prospecting, and, more recently, offshore hydrocarbon exploration. I analytically address the problem of the electromagnetic response of a completely resistive cylindrical cavity buried in a conductive host in the presence of a simplified 2D electric dipole source. In contrast to the confined conductor, which channels and induces current systems, the confined resistor deflects current and produces additional eddy current systems in the conductive host. I apply this theory to model the response of a grounded electric dipole-dipole system operating over a range of frequencies from 0 Hz to 10 kHz, in the presence of a horizontal 5-m radius insulating cylinder located 1-m beneath the surface of a uniform earth. This represents a common hazard encountered during mining and civil engineering operations. Results show that such an insulating cavity increases the recorded electric field amplitude and phase delay at all transmitted frequencies. These observations suggest that a broadband electromagnetic prospecting system may provide additional information about the location and extent of a void, over and above a standard dipole-dipole resistivity survey. When the host skin depth is much larger than all other length scales, the response can be approximated by an equivalent single dipole unless the cylinder’s radius is much larger than its distance from the transmitter. This result provids a useful rule of thumb to determine the acceptable range over which a resistive target can be modeled by a distribution of dipoles.

Optimal booking and scheduling in outpatient procedure centers

Patient appointment booking, sequencing, and scheduling decisions are challenging for outpatient procedure centers due to uncertainty in procedure times and patient attendance. We extend a previously developed appointment scheduling model to formulate a model based on a two-stage stochastic mixed integer program for optimizing booking and appointment times in the presence of uncertainty. The objective is to maximize expected profit. Analytical insights are reported for special cases and experimental results show that they provide useful rules of thumb for more general problems. Three solution methods are described which take advantage of the underlying structure of the stochastic program, and a series of experiments are performed to determine the best method. A case study based on an endoscopy suite at a large medical center is used to draw a number of useful managerial insights for procedure center managers.

Even Birds Follow Pareto's 80–20 Rule

Abstract Vilfredo Pareto noted in 1906 that 80% of the land in Italy was owned by 20% of the population – and that the ratio seemed to apply to many countries, many time periods, and many economies. But is it more than a useful rule of thumb? Pareto also observed that 20% of the pea pods in his garden contained 80% of the peas. His ratio seems to pop up everywhere. Fred J. Rispoli, Suhua Zeng, Tim Green and Jennifer Higbie try telling it to the birds.

Profiling e-Science infrastructures with kernel and application benchmarks

Resources benchmarking is a promising though challenging opportunity for research communities to better exploit e-Science infrastructures. The paper investigates the suitability of an integrated two-level benchmarking approach in supporting resources ranking on a performance basis. The coupling of different benchmarking techniques i.e. kernel and application benchmarks is intended to grasp the behaviour of computational environments also with respect to real workloads so as to address a more suitable and efficient assignment of resources to the applications submitted by users. To confirm the appropriateness of our approach, an experimentation on a test bed was carried out which highlighted significant differences amongst the performance figures of the two levels of benchmarks. Some useful rules of thumb emerged from our experimentation that could be taken into account to fruitfully adopt this double-space approach to similar scenarios of use.

UNEXPECTED PROPERTIES OF BANDWIDTH CHOICE WHEN SMOOTHING DISCRETE DATA FOR CONSTRUCTING A FUNCTIONAL DATA CLASSIFIER.

The data functions that are studied in the course of functional data analysis are assembled from discrete data, and the level of smoothing that is used is generally that which is appropriate for accurate approximation of the conceptually smooth functions that were not actually observed. Existing literature shows that this approach is effective, and even optimal, when using functional data methods for prediction or hypothesis testing. However, in the present paper we show that this approach is not effective in classification problems. There a useful rule of thumb is that undersmoothing is often desirable, but there are several surprising qualifications to that approach. First, the effect of smoothing the training data can be more significant than that of smoothing the new data set to be classified; second, undersmoothing is not always the right approach, and in fact in some cases using a relatively large bandwidth can be more effective; and third, these perverse results are the consequence of very unusual properties of error rates, expressed as functions of smoothing parameters. For example, the orders of magnitude of optimal smoothing parameter choices depend on the signs and sizes of terms in an expansion of error rate, and those signs and sizes can vary dramatically from one setting to another, even for the same classifier.

Adapting restoration and management to climate change

Adapting restoration and management to climate change

The Impact of the Maquiladora Industry on U.S. Border Cities

AbstractFor decades, the maquiladora industry has been a major economic engine along the U.S.–Mexico border. Since the 1970s, researchers have analyzed how the maquiladora industry affects cities along both sides of the border. Hanson produced the first comprehensive study on the impact of the maquiladoras on U.S. border cities, considering the effects of in‐bond plants on both employment and wages. His estimates became useful rules of thumb for the entire U.S.–Mexico border; however, they have become dated. Using Hanson's framework, we estimate the maquiladora industry impact on U.S. border cities from 1990 to 2006. We find that a 10 percent increase in maquiladora production leads to a 0.5 to 0.9 percent increase in employment. We also find large differences among individual border cities. Furthermore, we estimate the cross‐border maquiladora impacts before and after 2001 when border security begins to rise, and the global low‐wage competition intensified after China joined the World Trade Organization. Empirical results indicate that U.S. border cities are less responsive to growth in maquiladora production from 2001 to 2006 than in the earlier period; however, when looking into specific sectors, we find that U.S. border city employment in service sectors is more responsive post‐2001.

Semi-Supervised Learning and Domain Adaptation in Natural Language Processing

This book introduces basic supervised learning algorithms applicable to natural language processing (NLP) and shows how the performance of these algorithms can often be improved by exploiting the marginal distribution of large amounts of unlabeled data. One reason for that is data sparsity, i.e., the limited amounts of data we have available in NLP. However, in most real-world NLP applications our labeled data is also heavily biased. This book introduces extensions of supervised learning algorithms to cope with data sparsity and different kinds of sampling bias. This book is intended to be both readable by first-year students and interesting to the expert audience. My intention was to introduce what is necessary to appreciate the major challenges we face in contemporary NLP related to data sparsity and sampling bias, without wasting too much time on details about supervised learning algorithms or particular NLP applications. I use text classification, part-of-speech tagging, and dependency parsing as running examples, and limit myself to a small set of cardinal learning algorithms. I have worried less about theoretical guarantees (this algorithm never does too badly) than about useful rules of thumb (in this case this algorithm may perform really well). In NLP, data is so noisy, biased, and non-stationary that few theoretical guarantees can be established and we are typically left with our gut feelings and a catalogue of crazy ideas. I hope this book will provide its readers with both. Throughout the book we include snippets of Python code and empirical evaluations, when relevant. Table of Contents: Introduction / Supervised and Unsupervised Prediction / Semi-Supervised Learning / Learning under Bias / Learning under Unknown Bias / Evaluating under Bias

Maintenance best practice and recent research

This paper sets out to capture the recent discussions on maintenance ‘best practice’ for artificial turf surfaces and some related research. The information presented comes partly from a seminar in 2009, providing a mix of quantitative and qualitative information and opinions from a range of contributors both academic and industrial organized by the research network SportSURF (based at Loughborough University), and is supplemented with a case study of practices at Loughborough University on three different outdoor synthetic surfaces. The best practice information is further enhanced with recent research findings from a study investigating damage to artificial carpet fibres caused by power brushing. The outcomes of the maintenance seminar showed a good consensus for aspects of the most relevant type and frequency of maintenance tasks, with a useful rule of thumb for pitch managers of one hour of maintenance for every 10 hours of use of the surface system. Maintenance costs for artificial turf has traditionally been marketed as being ‘low’, but the data show costs per annum should be expected to be similar to natural turf but when expressed as a cost ‘per hour of use’ then the relative cost to be much lower for artificial turf than natural turf. Damage caused by power brushing, from a short laboratory study, was found to be minimal in terms of fibre splits or breaks for three (standard) brush systems of varying stiffness and for three different carpet systems (both sand and rubber infill systems). This paper collectively provides an advance in the knowledge and debate for the specialist practice of artificial surface maintenance, currently under-researched and poorly disseminated.

Sample Size Calculation for Two Independent Groups: A Useful Rule of Thumb

InTRodUCTIon There is a great little book by Gerald van Belle written “for practitioners of statistical science” called Statistical Rules of thumb1. It is a collection of widely applicable simple rules that capture the essence of key statistical concepts. One of the topics addressed is sample size calculation — in particular, the basic problem of calculating a sample size when the aim is to compare means from 2 independent samples.

Second thoughts about the NHS reforms

![Formula][1] Having discovered the breadth of opposition to its proposed reforms of the NHS, the coalition government is apparently having second thoughts about some aspects of its plans to hand over financial control of the system to GP consortia.1 Given the dubious records and political commitments of some of the individuals and organisations now opposing the government's plans, I find myself — as someone who regarded the reforms as irrational, ill-considered, and illegitimate from the outset — obliged to reconsider my own position. I have generally found it a useful rule of thumb in medical politics to assume that, if the British Medical Association opposes something (like the … [1]: /embed/graphic-1.gif

Management Insights

Management Insights

Measuring individual differences in reaction norms in field and experimental studies: a power analysis of random regression models

Summary 1. Interest in measuring individual variation in reaction norms using mixed‐effects and, more specifically, random regression models have grown apace in the last few years within evolution and ecology. However, these are data hungry methods, and little effort to date has been put into understanding how much and what kind of data we need to collect in order to apply these models usefully and reliably. 2. We conducted simulations to address three central questions. First, what is the best sampling strategy to collect sufficient data to test for individual variation using random regression models? Second, on occasions when precision is difficult to assess, can we be confident that a failure to detect significant variance in plasticity using random regression represents a biological reality rather than a lack of statistical power? Finally, does the common practice of censoring individuals with one or few repeated measures improve or reduce power to estimate individual variation in random regressions? 3. We have also developed a series of easy‐to‐use functions in the ‘pamm’ statistical package for R, which is freely available, that will allow researchers to conduct similar power analyses tailored more specifically to their own data. 4. Our results reveal potentially useful rules of thumb: large data sets (N > 200) are needed to evaluate the variance of individual‐specific slopes; a number of individuals/number of observations per individual ratio of approximately 0·5 consistently yielded the highest power to detect random effects; individuals with one or few observations should not generally be censored as this reduces power to detect variance in plasticity. 5. We discuss the wider implications of these simulations and remaining challenges and suggest a new way to standardize results that would better facilitate the comparison of findings across empirical studies.

A note on the surface volume change of shallow earthquakes

This note presents an exact analytical formula for determining the magnitude of coseismic surface volume change (δV) of earthquake faults in a half-space. For a Poisson solid, the formula is remarkably simple; δV=Mzz|8µ, where Mzz is one of the moment tensor elements of the source. Maximum δV values derive from dip slip on faults plunging 45°. For these events, surface volume changes of 0.0001 and 4.3 km3 can be expected for magnitude 5 and 8 earthquakes respectively. All of the coseismic surface volume change is recovered in the interseismic period through relaxation of the Earth and rebound of the surface. A useful rule of thumb for estimating the magnitude of vertical rebound in 45° dip slip events is δhp=Δs/24, where Δs is the coseismic slip on the fault.

Slowdowns in Diversification Rates from Real Phylogenies May Not be Real

Studies of diversification patterns often find a slowing in lineage accumulation toward the present. This seemingly pervasive pattern of rate downturns has been taken as evidence for adaptive radiations, density-dependent regulation, and metacommunity species interactions. The significance of rate downturns is evaluated with statistical tests (the gamma statistic and Monte Carlo constant rates (MCCR) test; birth-death likelihood models and Akaike Information Criterion [AIC] scores) that rely on null distributions, which assume that the included species are a random sample of the entire clade. Sampling in real phylogenies, however, often is nonrandom because systematists try to include early-diverging species or representatives of previous intrataxon classifications. We studied the effects of biased sampling, structured sampling, and random sampling by experimentally pruning simulated trees (60 and 150 species) as well as a completely sampled empirical tree (58 species) and then applying the gamma statistic/MCCR test and birth-death likelihood models/AIC scores to assess rate changes. For trees with random species sampling, the true model (i.e., the one fitting the complete phylogenies) could be inferred in most cases. Oversampling deep nodes, however, strongly biases inferences toward downturns, with simulations of structured and biased sampling suggesting that this occurs when sampling percentages drop below 80%. The magnitude of the effect and the sensitivity of diversification rate models is such that a useful rule of thumb may be not to infer rate downturns from real trees unless they have >80% species sampling.

Learning to be prepared

Behavioral economics provides several motivations for the common observation that agents appear somewhat unwilling to deviate from recent choices. More recent choices can be more salient than other choices, or more readily available in the agent’s mind. Alternatively, agents may have formed habits, or use rules of thumb. This paper provides discrete-time adjustment processes for strategic games in which players display such a bias towards recent choices. In addition, players choose best replies to beliefs supported by observed play in the recent past. We characterize the limit behavior of these processes by showing that they eventually settle down in minimal prep sets (Voorneveld in Games Econ Behav 48:403–414, 2004).

Editor's Foreword: Pioneering Multidisciplinary Research on Latin America

Editor's Foreword: Pioneering Multidisciplinary Research on Latin America Philip Oxhorn For more than forty-five years, the Latin American Research Review has been recognized as a leading venue for publishing multidisciplinary research. As a result, it is one of the oldest journals of its kind in the Americas, regularly publishing articles from a wide range of disciplines in the humanities and the social sciences. But apart from trying to meet LARR 's demanding standards, what does this actually imply for researchers who might want to submit their work to LARR for possible publication? When should they consider submitting their manuscripts to LARR rather than to more traditional disciplinary journals? As a multidisciplinary journal, what do we look for when considering a manuscript's potential for publication? And after four decades of publishing, what would we like to see submitted to LARR that we do not necessarily receive now? When to Submit to A Journal Like LARR Researchers have a variety of alternatives when it comes to publishing their work. One key to their success is being able to match a particular manuscript with the most appropriate venue for its eventual publication. This involves many factors, not the least of which is knowing when a more traditional disciplinary journal might be best. Although there is no simple answer, especially given the fact that many articles could be published in either a disciplinary journal or a multidisciplinary journal, there are a few useful rules of thumb to follow. First, does the manuscript itself use more than one traditional methodology, or does it make use of a hybrid methodology that does not neatly fit into any single discipline? In either case, a multidisciplinary journal such as LARR would be an appropriate choice. Yet the vast majority of manuscripts that are published in the humanities and social sciences do not fit either category. So what other factors might be considered? Researchers generally want to achieve the largest readership for their work, but this is not necessarily the same as the widest readership or even the most appropriate readership. Multidisciplinary journals offer an exceptionally wide audience in terms of disciplinary breadth. At the same time, area studies journals offer a targeted readership in terms of geographical interest. LARR epitomizes these strengths, as more than five thousand members of the Latin American Studies Association receive it, as well as hundreds of institutional subscribers and the countless others who have access to LARR through institutional subscriptions. So why should an author opt for multidisciplinary breadth over interdisciplinary depth? The most obvious reason is to attempt to reach a wide [End Page 3] audience because the research likely appeals to a variety of disciplines. Multidisciplinary journals like LARR are an ideal vehicle for this because people who would otherwise tend to concentrate on their own discipline's flagship publications regularly consult them. Disciplinary boundaries are often notorious for the artificial barriers they create, but sometimes the convenience of having various disciplines represented in the same volume can begin to break down those barriers. At the same time, cutting-edge research in Latin American studies may not necessarily be considered cutting edge in more traditional disciplinary journals; the issues, both theoretical and empirical, just may not be the same. A disciplinary journal may be less likely to publish a manuscript that LARR might endorse enthusiastically simply because other issues appear to be more prominent in the field. And if the journal does publish the article, those same issues dominating a particular discipline may drown out the article such that it becomes lost. By targeting an audience with similar shared regional interests, an author's impact on the profession may therefore be higher through publishing in a journal like LARR. What We Look for in A Manuscript Because LARR is a multidisciplinary journal, we also look for certain qualities in prospective manuscripts that may be less relevant to more traditional disciplinary journals. Aside from the requisite focus on Latin American research, it is important that articles published in LARR address larger issues that are of interest to its disparate readership. For some, there is a myth that LARR is not interested in more theoretical work because we publish actual...

Commercial Space Tourism and Space Weather

Commercial Space Tourism and Space Weather

On Tracking Properties of Real-Valued Generalized Adaptive Notch Filters

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Generalized adaptive notch filters (GANFs) are used for identification/tracking of quasi-periodically varying dynamic systems and can be considered an extension, to the system case, of classical adaptive notch filters. The paper presents results of local performance analysis of a real-valued GANF algorithm, i.e., algorithm designed to track parameters of a real-valued system. This is an extension of the previous work which focused on complex-valued systems. Tracking properties of the algorithm are studied analytically using an approximating linear filter technique and an averaging approach. Even though restricted to a single frequency case, the presented analysis provides interesting insights into the tracking mechanisms of GANF and allows one to formulate some useful rules of thumb for choosing design parameters. </para>