Sökresultat

Filtyp

Din sökning på "*" gav 529951 sökträffar

Simple modeling techniques for base-stock inventory systems with state dependent demand rates

In this paper new modeling techniques of (S- 1 , S) inventory systems (continuous review base-stock inventory systems) with state dependent demand rates are proposed. Examples of single-location (S- 1 , S) inventory systems where the demand, experienced by the system, varies due to the state of the system are, e.g., inventory models with partial backorders, inventory models with lost sales, invent

Large-scale and distributed optimization : An introduction

The recent explosion in size and complexity of datasets and the increased availability of computational resources has led us to what is sometimes called the big data era. In many big data fields, mathematical optimization has over the last decade emerged as a vital tool in extracting information from the data sets and creating predictors for unseen data. The large dimension of these data sets and

Biomarkers of Exposure to Pyrimethanil After Controlled Human Experiments

Pyrimethanil (PYM) is a fungicide used pre- and post-harvest on many crops. It has a low acute toxicity but is of toxicological concern because of its antiandrogenic properties. The aim of the current work was to investigate some metabolism and estimate elimination kinetics of PYM in humans after experimental oral and dermal exposure. A liquid chromatography triple quadrupole mass spectrometry (LC

Timing of maternal exposure to toxic cyanobacteria and offspring fitness in Daphnia magna : Implications for the evolution of anticipatory maternal effects

Organisms that regularly encounter stressful environments are expected to use cues to develop an appropriate phenotype. Water fleas (Daphnia spp.) are exposed to toxic cyanobacteria during seasonal algal blooms, which reduce growth and reproductive investment. Because generation time is typically shorter than the exposure to cyanobacteria, maternal effects provide information about the local condi

Effects of an MPL on water and thermal management in a PEMFC

In this study, the effects of adding a microporous layer (MPL) as well as the impact of its physical properties on polymer electrolyte fuel cell (PEMFC) performance with serpentine flow channels were investigated. In addition, numerical simulations were performed to reveal the effect of relative humidity and operating temperature. It is indicated that adding an extra between the gas diffusion laye

Impact of Harvest Date and Cutting Length of Grass Ley and Whole-Crop Cereals on Methane Yield and Economic Viability as Feedstock for Biogas Vehicle Fuel Production

Grass ley and whole-crop cereals used for biogas production are often finely chopped for subsequent ensiling and anaerobic digestion. Chopping can impact not only ensiling stability, digestibility and risk of process hick-ups in the digester but also harvesting capacity and fuel consumption. Based on field experiment data, the aim of this study was to investigate how three different nominal cuttin

Linking bacterial community composition to soil salinity along environmental gradients

Salinization is recognized as a threat to soil fertility worldwide. A challenge in understanding the effects of salinity on soil microbial communities is the fact that it can be difficult to disentangle the effects of salinity from those of other variables that may co-vary with salinity. Here we use a trait-based approach to identify direct effects of salinity on soil bacterial communities across

On the Performance of Cell-Free Massive MIMO in Ricean Fading

We consider an uplink time–division duplex cell–free massive multiple–input multiple–output (MIMO) system in which many user equipments (UEs) are simultaneously served by many access points (APs) via simple matched filtering processing. The propagation channel is modeled via the Ricean distribution, which includes a dominant line–of–sight component on top of diffuse scattering. The Ricean K–factor

Spatial Correlation Variability in Multiuser Systems

Spatial correlation across an antenna array is known to be detrimental to the terminal signal-to- interference-plus-noise-ratio (SINR) and system spectral efficiency. For a downlink multiuser multiple-input multiple-output system (MU-MIMO), we show that the widely used, yet overly simplified, correlation models which generate fixed correlation patterns for all terminals tend to underestimate the s

Differentiation between glioblastomas and brain metastases and regarding their primary site of malignancy using dynamic susceptibility contrast MRI at 3T

Background: Differentiation between glioblastoma and brain metastasis may be challenging in conventional contrast-enhanced MRI. Purpose: To investigate if perfusion-weighted MRI is able to differentiate glioblastoma from metastasis and, as a second aim was to see if it was possible in the latter group, to predict the primary site of neoplasm. Material and methods: Hundred and fourteen patients wit

Impact of Line-of-Sight and Unequal Spatial Correlation on Uplink MU-MIMO Systems

Closed-form approximations of the expected per-terminal signal-to-interference-plus-noise-ratio (SINR) and ergodic sum spectral efficiency of a multiuser multiple-input multiple-output system are presented. Our analysis assumes spatially correlated Ricean fading channels with maximum-ratio combining on the uplink. Unlike previous studies, our model accounts for the presence of unequal correlation

Thermoregulatory disorders in Huntington disease

Huntington disease (HD) is a paradigmatic autosomal-dominant adult-onset neurodegenerative disease. Since the identification of an abnormal expansion of a trinucleotide repeat tract in the huntingtin gene as the underlying genetic defect, a broad range of transgenic animal models of the disease has become available and these have helped to unravel the relevant molecular pathways in unprecedented d

Enantioselective Binding of Propranolol and Analogues Thereof to Cellobiohydrolase Cel7A

At the catalytic site for the hydrolysis of cellulose the enzyme cellobiohydrolase Cel7A binds the enantiomers of the adrenergic beta-blocker propranolol with different selectivity. Methyl-to-hydroxymethyl group modifications of propranolol, which result in higher affinity and improved selectivity, were herein studied by 1H,1H and 1H,13C scalar spin–spin coupling constants as well as utilizing the

On the General Analysis of Coordinated Regularized Zero-Forcing Precoding: An Application to Two-Tier Small-Cell Networks

General analysis of expected per-terminal signalto-interference-plus-noise-ratio (SINR) and ergodic per-cell sum spectral efficiency for a multi-cellular system with coordinated regularized zero-forcing (RZF) precoding is presented.An application to two-tier small-cell networks is considered, assuming independent and identically distributed (i.i.d.) and semi-correlated Rayleigh fading channels, wi

Thermoregulation in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the major adult-onset motor neuron disease, and is clinically, pathologically, and genetically associated with frontotemporal dementia, the second cause of dementia in the elderly. Here, we review the evidence linking thermoregulation and ALS. Indeed, while ALS is not classically associated with defective thermoregulatory function, its progression severely af

Uplink Analysis of Large MU-MIMO Systems with Space-Constrained Arrays in Ricean Fading

Closed-form approximations to the expected perterminal signal-to-interference-plus-noise-ratio (SINR) and ergodic sum spectral efficiency of a large multiuser multiple-input multiple-output system are presented. Our analysis assumes correlated Ricean fading with maximum ratio combining on the uplink, where the base station (BS) is equipped with a uniform linear array (ULA) with physical size restr

Emerging attosecond technologies

The quest for fundamental scientific knowledge triggers technological advancement. This has been particularly true for attosecond science in recent years: we assisted in the development of many new approaches - both experimentally and theoretically - that will have a high impact, not only on atomic and molecular physics, but also on optical technology. This special issue collects several of these

Zero-Forcing Precoding Performance in Multiuser MIMO Systems With Heterogeneous Ricean Fading

An accurate approximation is developed for the distribution of the instantaneous per-terminal signal-to-noise-ratio (SNR) of a downlink multiuser multiple-input multiple-output system with zero-forcing (ZF) precoding. Our analysis assumes a Ricean fading environment, where we show that the SNR at a given terminal is well approximated by the gamma distribution and we derive its parameters. The anal

Analysis of Multiuser Cellular Systems Over Heterogeneous Channels

This thesis considers the analysis of current and future cellular communication systems. The main focus is on multiuser multiple-input multiple-output (MU-MIMO) antenna systems. The goal of this work is to characterize the achievable spectral efficiency of MU-MIMO systems, as well as to analyze the performance of practical, linear MU-MIMO transceiver structures in heterogeneous propagation environ