Bootstrapping the Local Periodogram of Locally Stationary Processes

Abstract. Locally stationary processes are non‐stationary stochastic processes the second‐order structure of which varies smoothly over time. In this paper, we develop a method to bootstrap the local periodogram of a locally stationary process. Our method generates pseudo local periodogram ordinates by combining a parametric time and non‐parametric frequency domain bootstrap approach. We first fit locally a time varying autoregressive model so as to capture the essential characteristics of the underlying process. A locally calculated non‐parametric correction in the frequency domain is then used so as to improve upon the locally parametric autoregressive fit. As an application, we investigate theoretically the asymptotic properties of the bootstrap method proposed applied to the class of local spectral means, local ratio statistics and local spectral density estimators. Some simulations demonstrate the ability of our method to give accurate estimates of the quantities of interest in finite sample situations and an application to a real‐life data‐set is presented.     

Identification of peptides in traditional and probiotic sheep milk yoghurt with angiotensin I-converting enzyme (ACE)-inhibitory activity

Two sets of traditional Greek sheep milk yoghurt were produced: the first one (YC) using normal yoghurt culture (Lactobacillus delbrueckii subsp. bulgaricus ?10.13 and Streptococcus thermophilus ?10.7) and the second (PR) with the same normal culture mixed with Lactobacillus paracasei subsp. paracasei DC412. YC and PR had similar physicochemical properties and proteolysis patterns throughout storage. Both products showed similar peptide profiles by RP-HPLC but quantitative differences were observed in respect to storage time. Single-strain cultures of the microorganisms used showed similar peptide profiles for both lactobacilli, yet L. delbrueckii subsp. bulgaricus was the most proteolytic of all three microorganisms. The peptide content and the ACE-inhibitory activity of the water-soluble extracts of yoghurts, YC and PR, increased throughout storage. Major peptides were identified from yoghurt PR and from the separate cultures of L. delbrueckii subsp. bulgaricus and L. paracasei subsp. paracasei. Most of these peptides were derived from β-casein. A peptide, β-CN f114-121, with well-established ACE-inhibitory and opiate-like activity was identified in yoghurt PR. Further identified peptides were regarded as potential ACE-inhibitors according to their sequence.     

Cellular Network Performance Analysis: Handoff Algorithms Based on Mobile Location and Area Information

Mobile world's rapid growth has spurred development of new protocols and new algorithms to meet changing operation requirements such as mobile networking, and quality-of-service support. A key requirement in the bearer capabilities is the handover. The freedom to be able to make and receive calls anywhere, at any time, creating a totally new dimension in human communications has frequently been advertised as the main advantage of new wireless systems. Handovers are a key concept in providing this mobility. It makes it possible for a user to travel from one cell to another while having a seamless connection. Network operators give emphasis to optimize handover, since it is strongly related to dropped calls, network overload and subsequently users' criticism. The ability of a cellular network to perform efficient handovers is crucial to offer attractive services as real-time applications or streaming media as planned in third generation networks. Since signal propagation and pathloss are complex in nature, we can expect unnecessary and wrong handoff executions. Both UMTS and those of the second generation (GSM) systems will require redefined handoff algorithms of active connections as the smooth mobility support and continuous connection are essential issues for obtaining high performance and increasing user satisfaction. In this paper we present a set of intelligent algorithms using the mobile terminal (MT) location information and area awareness to assist safe handoff decisions. The implemented algorithms are validated by means of cellular network simulators that clearly show the impact of these techniques to major system performance metrics.     

Performance bounds of a multiple-step paging strategy in future universal mobile telecommunication systems

In future mobile telecommunications, due to the huge number of users and the specific functions that support mobility, a significant amount of signaling load will have to be carried by the finite capacity of the radio link. Hence, methods aiming at radio link signaling load reduction are welcome. In this paper we propose and analyze a method that saves paging signaling load by exploiting information related to the terminal location during the most recent interaction between the terminal and the network. The penalty paid is extra processing power and extra paging delays. An analytical model is developed so as to describe the performance versus traffic intensity and mobility conditions. The performance of the proposed paging scheme is investigated, and it is shown that the method operates well even in the worst case, which is the high user mobility conditions. Possible extensions of the method, which exploit information related to the mobility degree of each individual user or information characterizing the mobility conditions in a certain location area, are also proposed.This paper has been partially funded by CEC through the RACE 2066 Mobile Network (MONET) project. The paper does not present the views of the project as a whole, but those of the authors.     

A binary-flashing geothermal power plant

A novel type of binary geothermal installation is analyzed. It would increase the work obtained by more than 20%. This installation utilizes partial evaporation of the secondary fluid and flashing of the remaining liquid. Freon, ammonia and isobutane are examined as secondary fluids for the new installation. They all yield superior thermodynamic performance with respect to a conventional binary unit because the binary-flashing installation optimizes two parameters rather than one only. It also appears that the new installation is economically advantageous over existing installations.     

A comparison of artificial neural networks and partial least squares modelling for the rapid detection of the microbial spoilage of beef fillets based on Fourier transform infrared spectral fingerprints

A series of partial least squares (PLS) models were employed to correlate spectral data from FTIR analysis with beef fillet spoilage during aerobic storage at different temperatures (0, 5, 10, 15, and 20 °C) using the dataset presented by Argyri et al. (2010). The performance of the PLS models was compared with a three-layer feed-forward artificial neural network (ANN) developed using the same dataset. FTIR spectra were collected from the surface of meat samples in parallel with microbiological analyses to enumerate total viable counts. Sensory evaluation was based on a three-point hedonic scale classifying meat samples as fresh, semi-fresh, and spoiled. The purpose of the modelling approach employed in this work was to classify beef samples in the respective quality class as well as to predict their total viable counts directly from FTIR spectra. The results obtained demonstrated that both approaches showed good performance in discriminating meat samples in one of the three predefined sensory classes. The PLS classification models showed performances ranging from 72.0 to 98.2% using the training dataset, and from 63.1 to 94.7% using independent testing dataset. The ANN classification model performed equally well in discriminating meat samples, with correct classification rates from 98.2 to 100% and 63.1 to 73.7% in the train and test sessions, respectively. PLS and ANN approaches were also applied to create models for the prediction of microbial counts. The performance of these was based on graphical plots and statistical indices (bias factor, accuracy factor, root mean square error). Furthermore, results demonstrated reasonably good correlation of total viable counts on meat surface with FTIR spectral data with PLS models presenting better performance indices compared to ANN.     

Changes in volatile compounds and related biochemical profile during controlled fermentation of cv. Conservolea green olives

The effect of controlled fermentation processes on the profile of volatile and other biochemical compounds of cv. Conservolea green olives processed by the Spanish method was studied. The different treatments included: (a) inoculation with a commercial starter culture of Lactobacillus pentosus, (b) inoculation with a wild strain of Lactobacillus plantarum isolated from a previous fermentation, (c) uninoculated spontaneous process (control). Microbial growth, pH, titratable acidity, reducing sugars, organic acids and volatile compounds were monitored. Starter cultures were effective in establishing an accelerated fermentation process. Both were able to reduce the survival period of Enterobacteria by 7 days, minimizing thus the likelihood of spoilage. Higher acidification of the brines and faster pH drop was observed in inoculated processes, with L. pentosus presenting better performance than the wild strain of L. plantarum. Lactic and acetic were the major organic acids detected by HPLC, the concentration of which increased in the course of fermentation. Citric and malic acids were also present in the brines but they were degraded completely within the first 2 weeks of fermentation. Ethanol, methanol, acetaldehyde, ethyl acetate, isobutyric acid were the major volatile compounds identified by GC. Their concentration varied greatly among the fermentation processes, reflecting varying degrees of microbial activity in the brines.     

Analysis and Future Prospects for Cross-border Congestion Management Methods for the European Electricity Market

This paper presents an analysis of current and potential cross-border congestion management methods for the EU electricity market. Many currently used techniques are reported and the main aspects of possible future are presented. The main steps of the newly established coordinated auction technique will be reported and an example of a real case for the South European Region will be implemented. Moreover, in order to eliminate loop flows, avoid congestions at the day ahead stage and increase the total transfer capacity of the south UCTE region (countries Greece, Albania and FYROM), it will be shown that Flexible Ac Transmission Systems technology can help market players to get access to more transfer capacity for their transactions, while security margins are being maintained.     

Paraphrase plagiarism identification with character-level features

Pattern Analysis and Applications - Several methods have been proposed for determining plagiarism between pairs of sentences, passages or even full documents. However, the majority of these methods...