Auswahl der wissenschaftlichen Literatur zum Thema „Maximal frequency selection“

AbstractWe present a general monitoring methodology to summarize news about predefined entities and topics into tractable time-varying indices. The approach embeds text mining techniques to transform news data into numerical data, which entails the querying and selection of relevant news articles and the construction of frequency- and sentiment-based indicators. Word embeddings are used to achieve maximally informative news selection and scoring. We apply the methodology from the viewpoint of a sustainable asset manager wanting to actively follow news covering environmental, social, and governance (ESG) aspects. In an empirical analysis, using a Dutch-written news corpus, we create news-based ESG signals for a large list of companies and compare these to scores from an external data provider. We find preliminary evidence of abnormal news dynamics leading up to downward score adjustments and of efficient portfolio screening.

AbstractThis chapter summarizes the overall tendering and contracting process in the pharmaceutical industry by providing an overview of the first-sealed price auction theory, auction rules, and drug pricing mechanism of different countries. Comparing procurement systems across Asia, Africa, Europe, and Latin America, the review casts light on various pharmaceutical bidding systems across the world and their impact on drug prices. Then, this review focuses on the empirical estimation of first-price auction models. In terms of model specification, we compare the two most commonly used empirical methods for bidding price estimation: structural models and reduced form approaches to test the auction theory. Maximum likelihood estimation is the most frequently used method for structural estimation in literature and selection bias correction is widely adopted using reduced form models. In addition to parametric model construction, we also provide an extensive introduction of non-parametric testing methodologies, including non-parametric estimation and quantile-based estimation to reduce the computation complexity and further illustrate how auction theory could be validated by real-world applications. Additional thoughts and adjustments on non-parametric testing are brought up based on a real-world tendering use case from a large multi-national pharmaceutical company.

Abstract This paper analyzes the performance of a generalized frequency division multiplexing scheme for multiple-input multiple-output configuration (MIMO-GFDM) in the presence of nonlinear power amplification with pilot insertion at the transmitter side to evaluate the saturation effects. For this purpose, two non-ideal transfer functions of high power amplifiers (HPA) are modeled: a Traveling Wave Tube Amplifier (TWTA) and a Solid State Power Amplifier (SSPA). In addition, for nonlinear distortion cancellation, we explore some peak-to-average power ratio (PAPR) reduction techniques, such as selective mapping (SLM), clipping, and clipping and filtering (C&F), to evaluate the best response and adaptability for the MIMO-GFDM scheme. The results show that an optimal power transmitter in the amplifier saturation region with large-scale input back-off (IBO) can mitigate out-of-band (OOB) radiation effects and consequently reduce the error floor in terms of bit error rate (BER) caused by amplifier saturation effects. In addition, we can control some trade-offs between PAPR, OOB emissions, BER performance, and power when the large-scale IBO reaches 4 dB. Finally, multicast effects in the Rayleigh channel can further saturate the amplifier when the transmit power increases, causing a proportional increase of the background noise with the channel variance. Thus, we can determine the maximum transmit power to avoid distortion and error-floor noise in poor channel conditions.

We consider the selection of two basketball teams at a neighborhood playground to illustrate the greedy method. Usually the top two players are designated captains. All other players line up while the captains alternate choosing one player at a time. Usually, the players are picked using a greedy strategy. That is, the captains choose the best unclaimed player. The system of selection of choosing the best, most obvious, or most convenient remaining candidate is called the greedy method. Greedy algorithms often lead to easily implemented efficient sequential solutions to problems. Unfortunately, it also seems to be that sequential greedy algorithms frequently lead to solutions that are inherently sequential — the solutions produced by these algorithms cannot be duplicated rapidly in parallel, unless NC equals P. In the following subsections we will examine this phenomenon. We illustrate some of the important aspects of greedy algorithms using one that constructs a maximal independent set in a graph. An independent set is a set of vertices of a graph that are pairwise nonadjacent. A maximum independent set is such a set of largest cardinality. It is well known that finding maximum independent sets is NP-hard. An independent set is maximal if no other vertex can be added while maintaining the independent set property. In contrast to the maximum case, finding maxima? independent sets is very easy. Figure 7.1.1 depicts a simple polynomial time sequential algorithm computing a maximal independent set. The algorithm is a greedy algorithm: it processes the vertices in numerical order, always attempting to add the lowest numbered vertex that has not yet been tried. The sequential algorithm in Figure 7.1.1, having processed vertices 1,... , j -1, can easily decide whether to include vertex j. However, notice that its decision about j potentially depends on its decisions about all earlier vertices — j will be included in the maximal independent set if and only if all j' less than j and adjacent to it were excluded.

Index selection is an important part of physical database design. Its goal is to select an appropriate set of indexes to minimize the cost for a given workload under storage constraint. However, selecting a suitable configuration of indexes is a difficult problem to solve. The problem becomes more complex for indexes defined on multiple tables such as bitmap join indexes, since it requires the exploration of a much more search space. Studies dealing with the bitmap join indexes selection problem mainly focused on proposing pruning solutions of the search space by the means of data mining techniques or heuristic approaches. So far, the data mining based approaches have used closed frequent itemsets to reduce the search space for the selection process. These approaches have two notable shortcomings. Firstly, they generate a huge number of indexes with a lot of redundancy that it is very difficult to manage according to the system limitation (number of Indexes per table, storage space constraint). Secondly, when they construct the extraction context for mining frequent sets of attributes, they have used indexable attributes only once for each query in the workload which does not reflect the importance of a given query in the workload. Indeed, the queries in a workload are unlikely to have the same probability of being requested. To overcome these imitations, we propose to combine maximal frequent itemsets and query frequencies to improve the quality of generated indexes. This paper describes an approach that refines the index selection process, incorporating query frequencies in the extraction context for mining frequent set of attributes. We experimentally prove that our approach reduces the storage space and improves the quality of the recommended indexes.

Abstract Besides the induction coil and workpiece, the induction generator (source of ac power) is probably the most important component of an overall induction heating system. Such equipment is typically rated in terms of its frequency and maximum output power (in kilowatts). This chapter addresses the selection of power supplies in terms of these two factors as well as the operational features of different types of sources. The six different types of power supplies for induction heating applications covered in this chapter are line-frequency supplies, frequency multipliers, motor-generators, solid-state (static) inverters, spark-gap converters, and radio-frequency power supplies. The chapter discusses the design and characteristics of each of the various types of power supplies.

At-site flood frequency analysis (FFA) of extreme hydrological events under Bayesian paradigm has been carried out and compared with frequentist paradigm of maximum likelihood estimation (MLE). The main objective of this chapter is to identify the best approach between Bayesian and frequentist one for at-site FFA. As a case study, the data of only two stations were used, Kotri and Rasul, and Bayesian and MLE approaches were implemented. Most commonly used tests were applied for checking initial assumptions. Goodness of fit (GOF) tests were used to identify the best model, which indicated that the generalized extreme value (GEV) distribution appeared to be best fitted for both stations. Under Bayesian paradigm, quantile estimates are constructed using Markov Chain Monte Carlo (MCMC) simulation method for their respective returned periods and non-exceedance probabilities. For MCMC simulations, as compared to other sampler, the M-H sampling technique was used to generate a large number of parameters. The analysis indicated that the standard errors of the parameters' estimates and ultimately the quantiles' estimates using Bayesian methods remained less as compared to maximum likelihood estimation (MLE), which shows the superiority of Bayesian methods over conventional ones in this study. Further, the safety amendments under two techniques were also calculated, which also show the robustness of Bayesian method over MLE. The outcomes of these analyses can be used in the selection of better design criteria for water resources management, particularly in flood mitigation.

This chapter introduces visual evoked responses. Transient VEPs are maximal across the posterior scalp and consist of three main deflections—N75, P100, and N135. Magnetic VEFs also show a prominent occipital response peaking at around 100 ms. Visual stimulation can include light flashes, pattern onset/offsets, pattern reversals and natural images. The extent and eccentricity of the visual stimulus can selectively encompass foveal or extrafoveal regions, or include quadrants, hemifield or the entire visual field. Stimulus attributes such as visual angle, spatial frequency, luminance and contrast greatly affect VEF and VEP amplitudes and latencies. Selective responses in the dorsal and ventral visual streams can be elicited with carefully chosen stimuli. Steady-state responses to periodically varying visual stimuli can be used to frequency-tag different aspects of the visual stimulus.

Abstract Fatigue testing castings in aggressive, corrosive media presents particular problems with regard to specimen size, thermal history, quality and configuration. This paper presents factors to be considered when selecting test methods and specimen configurations based on experience in programs with bronze and stainless steel castings. Issues considered include frequency effects, crack propagation, extrapolation of data and the influence of mean stresses. It is concluded that if the key variables are properly studied and understood useful guidance in materials selection can be obtained. Equally important to the user, however, are decisions made in design and fabrication. Cost effective test programs depend on identifying the optimum frequency to be used in running tests to the maximum practical number of cycles.

Abstract With the popularization and application of production enhancement measures such as nitrogen gas injection gas lift and nitrogen drainage in oil and gas wells in western China, corrosion failures of wellhead devices, downhole tubing strings and tools occur frequently. Oxygen ingress has become one of the main causative factors inducing the failure of metallic materials. In this work, the corrosion behavior of a variety of materials in O2-CO2 coexistence environment was investigated. Based on the experimental results of general corrosion, maximum pitting rate, morphology and composition of corrosion products, the corrosion characteristics and possible mechanisms were discussed. The results showed that the presence of oxygen significantly enhanced the corrosion of low alloy steels (P110 and 3Cr) and stainless steels (13Cr and 316), especially promoted the localized corrosion of 13Cr stainless steel. The critical oxygen content and the suitability of several materials for use in oxygen-containing environments were discussed. Based on a comprehensive consideration of material upgrading, oxygen content control and the use of corrosion inhibitors, it was concluded that the combined use of low alloy steel and corrosion inhibitors may be a relatively more practical and economical solution.

Abstract Coiled tubing (CT) has been used extensively for underbalanced drilling in non-sour applications with great success; however, attempts to utilize it for sour service produced frequent failures due to tubing environmental cracking. Specific operational conditions of CT, involving a combination of cyclic plastic strain of CT material (associated with travel on/off a reel) and periodic exposure to sour environments, typically result in a significantly poorer CT performance in comparison with non-sour applications, or with sour service at stresses below yield. An experimental program was implemented using Slow Strain Rate Test (SSRT) to evaluate suitability of CT candidates for sour underbalanced drilling. Out of a variety of standard tests for stress corrosion cracking (SCC) resistance, this test was chosen because it assesses dynamic cracking in the plastic region, accounting for synergy effects between plastic strain and exposure to sour environment. Effects of variable strain rate and loading path on maximum strain and CT life were examined for several CT material candidates. To facilitate assessment of actual CT products, full-body specimens were tested, offering a large test area with as-manufactured surface finish, inclusion of welds, and an option to apply a multi-axial stress state. Various modes of environmentally assisted cracking such as sulfide stress cracking (SSC), hydrogen induced cracking (HIC) and blistering, commonly observed in the field, were successfully simulated in the laboratory. This paper presents a brief description of the test setup, and provides examples of test results obtained for several CT specimens of different material grades and pre-fatigued with a varying number of strain cycles. The study demonstrates applicability of the selected test methodology for initial selection of CT products for sour service.

Microwave and radio frequency heating has great promise in many engineering and biomedical applications because of its non-contact, volumetric selective heating. However, the heating patterns and temperature distributions are non-uniform due to non-uniform electromagnetic power absorptions. In this study, we present a closed-form analytic expression of electromagnetic field distribution and power absorption in a spherical shaped object. A simplified Maxwell’s equation that represents plane wave is solved in spherical coordinates using vector potentials and separation of variables. The electromagnetic power absorption is obtained from the electromagnetic field distribution within the object using Poynting theorem. The analytical expressions of the electric field and power generation are evaluated for meat balls of 1.0, 2.0, 3.0 and 5.0 cm radii and two different electromagnetic frequencies. Results show that the strength of the absorbed electromagnetic wave and power absorption is highly dependent on the radius of the dielectric sphere. The presence of local maxima of electric and magnetic field strength due to the constructive interference of the reflection and transmission of electromagnetic wave in the target object are found in all sizes. However numbers of peaks or valleys are more in larger meat balls. The spatial distribution of microwave power absorption follows the trend of electromagnetic field distribution. The positions of local maxima and minima of power absorption and electromagnetic field distributions vary with the radius of the sphere and applied frequencies. It indicates that the uniform and effective electromagnetic power absorption can be facilitated by the proper design of the object of interest and selection of an appropriate frequency.

Local defects in rotating machinery give rise to periodic impulses in vibrations. In order to acquire the information of these faults, various diagnostic methods have been proposed in the past decades. Most methods used the squared envelope spectrum (i.e., the spectrum of the squared envelope) as the final diagnostic tool, but different preprocessing steps were used before obtaining the envelope signal. The key problem is to obtain the center frequency and bandwidth of the fault signal, then analyze the envelope (squared envelope spectrum) of the band-pass filtered signal. The framework of accuracy rate method was proposed by means of cross validation of the nearest neighbor classifier in this paper: a) obtain the piecewise signal through original signal segmentation; b) calculate the feature of each piecewise signal; c) then an accuracy rate is calculated based on cross validation of the nearest neighbor classifier; and d) repeat the above steps in different frequency band, then find a frequency band with the maximum accuracy rate. Through this algorithm, we can obtain a fault frequency band, and then we can find out the type of the fault by the spectrum of the squared envelope. At the end of this paper, the proposed method is validated by two examples and compared with the other two diagnostic methods: conventional envelope analysis and Fast kurtogram. Through the comparison of results, the validity and superiority of this method has been proved.

Channel Islands National Park includes the five northern islands off the coast of southern California (San Miguel, Santa Rosa, Santa Cruz, Anacapa, and Santa Barbara Islands) and the surrounding waters out one nautical mile. There are approximately 176 miles of coastline around the islands, about 80% of which is composed of rock. The diversity and undisturbed nature of the tidepools of this rocky coastline were recognized as special features of the islands in the enabling legislation. To conserve these communities unimpaired for future generations, the National Park Service has been monitoring the rocky intertidal communities at the islands since 1982. Sites were established between 1982 and 1998. Site selection considered visitation, accessibility, presence of representative organisms, wildlife disturbance, and safety. This report summarizes the 2018–2019 sampling year efforts (from November 2018 to April 2019) and findings of the Channel Islands National Park Rocky Intertidal Community Monitoring Program. Specific monitoring objectives are 1) to determine the long-term trends in percent cover of key sessile organisms in the rocky intertidal ecosystem, and 2) to determine population dynamics of black abalone (Haliotis cracherodii), owl limpets (Lottia gigantea), and ochre sea stars (Pisaster ochraceus). Objectives were met by monitoring percent cover of core species in target intertidal zones using photoplots and transects, and by measuring size frequency and abundance of black abalone, owl limpets, and sea stars using fixed plots or timed searches. Twelve key species or assemblages, as well as the substrate, tar, have been monitored twice per year at 21 sites on the five park islands as part of the rocky intertidal community monitoring program. Fixed photoplots were used to monitor the percent cover of thatched and acorn barnacles (Tetraclita rubescens, Balanus glandula/Chthamalus spp., respectively), mussels (Mytilus californianus), rockweeds (Silvetia compressa, and Pelvetiopsis californica (formerly Hesperophycus californicus), turfweed (Endocladia muricata), goose barnacles (Pollicipes polymerus) and tar. Point-intercept transects were used to determine the percent cover of surfgrass (Phyllospadix spp.). Information about size distribution (i.e., “size frequency” data) was collected for owl limpets in circular plots. Size distribution and relative abundance of black abalone and ochre sea stars were determined using timed searches. The maximum number of shorebirds and pinnipeds seen at one time were counted at each site. The number of concession boat visitors to the Anacapa tidepools was collected and reported. All sites were monitored in 2018–2019. This was the third year that we officially reduced our sampling interval from twice per year (spring and fall) to once in order to streamline the program and allow for the implementation of additional protocols. Weather conditions during the site visits were satisfactory, but high wind coupled with strong swell and surge limited or prevented the completion of some of the abalone and sea star searches. The percent cover for most key species or assemblages targeted in the photoplots was highly variable among sites. Mussel (Mytilus californianus) cover remained below average at Anacapa and Santa Barbara Islands. Record or near record low abundances for Mytilus were measured at Middle West Anacapa (Anacapa Island), Harris Point (San Miguel Island), Prisoner’s Harbor (Santa Cruz Island), and Sea Lion Rookery (Santa Barbara Island) sites. The only site that appeared to have above average Mytilus cover was Scorpion Rock on Santa Cruz Island. All other sites had mussel cover near or below the long-term mean. Qualitatively, Mytilus recruitment appeared low at most sites. Both rockweed species, Silvetia compressa and Pelvetiopsis californica (formerly Hesperophycus californicus), continued to decrease markedly in abundance this year at the majority of sites compared to combined averages for previous years. Fossil Reef and Northwest-Talcott on Santa Rosa Island, Sea Lion Rookery on Santa Barbara Island, and South Frenchy’s Cove on Anacapa Island were the only sites that supported Silvetia cover that was near the long-term mean. No sites exhibited above average cover of rockweed. Extremely high levels of recruitment for Silvetia and Pelvetiopsis were documented at many sites. Most sites exhibited marked declines in S. compressa abundances beginning in the early 2000s, with little recovery observed for the rockweed through this year. Barnacle (Chthamalus/Balanus spp.) cover fell below the long-term means at all islands except Anacapa, where barnacle cover was slightly above average. Endocladia muricata abundances remained comparable to the grand mean calculated for previous years at Santa Barbara, Santa Cruz, and Santa Rosa Islands, while cover of the alga decreased slightly below the long-term means at Anacapa and San Miguel Islands. Black abalone (Haliotis cracherodii) abundances at the islands remain less than one percent of 1985 population levels. Zero abalone were found throughout the entire site at Landing Cove on Santa Barbara Island and South Frenchy’s Cove on Anacapa Island. Above average abundances relative to the long-term mean generated from post-1995 data were observed at all but five sites. Juvenile black abalone were seen at all islands except Santa Barbara. Ochre sea star (Pisaster ochraceus) populations crashed in 2014 at all monitoring sites due to Sea Star Wasting Syndrome, an illness characterized by a suite of symptoms that generally result in death. The mortality event was widely considered to be the largest mortality event for marine diseases ever seen. Beginning in June 2013, the disease swiftly and significantly impacted P. ochraceus (among other species of sea stars) populations along the North American Pacific coast from Alaska to Baja California, Mexico. By the beginning of 2014, P. ochraceus abundances had declined by >95% at nearly all Channel Islands long-term intertidal monitoring sites, in addition to numerous other locations along the West Coast. At various times during the past decade, extremely high abundances (~ 500 P. ochraceus) have been observed at multiple sites, and most locations have supported >100 sea stars counted during 30-minute site-wide searches. This year, abundances ranged 0–13 individuals per site with all but one site having fewer than 10 P. ochraceus seen during routine searches. Insufficient numbers of sea stars were seen to accurately estimate the size structure of P. ochraceus populations. Only two juveniles (i.e., <50 mm) were observed at all sites combined. Giant owl limpet densities in 2018–2019 were comparable or slightly above the long-term mean at seven sites. Exceptionally high densities were measured at Northwest-Talcott on Santa Rosa Island, Otter Harbor on San Miguel Island, and Willows Anchorage on Santa Cruz Island. The sizes of L. gigantea this year varied among sites and islands. The smallest L. gigantea were observed at Otter Harbor followed closely by Willows Anchorage and Anacapa Middle West, and the largest were seen at Northwest-Talcott. Temporally, the mean sizes of L. gigantea in 2018–2019 decreased below the long-term mean at each island except Anacapa. Surfgrasses (Phyllospadix spp.) are typically monitored biannually at two sites each on Santa Cruz and Santa Rosa Islands. Beginning in 2015, all transects at each of the monitoring sites were only sampled once per year. At East Point on Santa Rosa Island, the conditions were not conducive to sampling the surfgrass transects, but qualitatively, percent cover of surfgrass appeared to be near 100% on all three transects. Relative to past years, cover of surfgrass increased above the long-term mean at Fraser Cove on Santa Cruz Island, fell slightly below the mean at Trailer on Santa Cruz Island, and remained approximately equivalent to the mean at the two Santa Rosa Island sites. Overall, the abundance and diversity of shorebirds in 2018–2019 at all sites appeared similar to observations made in recent years, with the exception of elevated numbers of brown pelicans (Pelecanus occidentalis) observed at East Point on Santa Rosa Island. Black oystercatchers (Haematopus bachmani) were the most ubiquitous shorebird seen at all sites. Black turnstones (Arenaria melanocephala) were not common relative to past years. Pinniped abundances remained comparable in 2018–2019 to historical counts for all three species that are commonly seen at the islands. Harbor seals (Phoca vitulina) were seen in the vicinity of eight sites this year. As in past years, harbor seals were most abundant at Otter Harbor and Harris Point on San Miguel Island. Elephant seals (Mirounga angustirostris) were seen at six sites during the year, where abundances ranged 1–5 individuals per location. California sea lions (Zalophus californianus) were common at Santa Barbara Island; 117 individuals were observed at Sea Lion Rookery. Sea lion abundances were higher than usual at Harris Point (N = 160) and Otter Harbor (N = 82) on San Miguel Island. Relative to past years, abundances this year were considered average at other locations.