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1

A note on the complexity of scheduling of communication-aware directed acyclic graph

Musial J., Guzek M., Bouvry P., Blazewicz J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2018

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Vol. 66, nr 2

187--191

EN

The most recent incarnation of distributed paradigm is cloud computing. It can be seen as the first widely accepted business model of mass consumption of the distributed computing resources. Despite the differences in business models and technical details regarding cloud platforms, the distributed computing underlies cloud. Communications in cloud systems include transmissions of the results of cloud applications, users interactions, and exchange of data between different services that compose applications. The latter becomes more critical as applications become richer as well as more complex, and may consist of services operated by various providers. The effective communication between components of cloud systems is thus critical to the end user satisfaction and to the success of cloud services. We will discuss different cloud computing models (communication aware and unaware). Main focus will be placed on communication-aware directed acyclic graph (CA-DAG), which extends the classical DAG model by explicitly modeling communication tasks. Moreover, we will analyze and consult computational complexity of this innovative distributed computation model inspired by the characteristics of cloud computing. Providing a proof of strong NP-hardness of the problem allows for a future implementation and evolution of the communication-aware DAG models.

2

Trustworthy online shopping with price impact

Musial J., Lopez-Loces M. C.

Foundations of Computing and Decision Sciences

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2017

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Vol. 42, No. 2

121--136

EN

Internet shopping is one of the main pillars of electronic commerce. According to the literature, the Internet Shopping Optimization Problem (ISOP) has been defined in order to optimize the global cost of online purchase, taking into account both the cost of products and shipping. In this study, it was decided to propose and analyze a very interesting, and really substantial, extension of the ISOP. Namely, trust factors were subjected to careful analysis from the customer point of view. The analysis is based on a specially prepared questionnaire, supplemented by the information from the literature and our own observations. Thus, it was possible to propose a definition of a new mathematical model of the problem, and to prove its affiliation to the class of strongly NP-hard problems. In addition, the heuristic algorithm is proposed, which can be used to solve the problem.

3

Exact and heuristic approaches to solve the Internet shopping optimization problem with delivery costs

Lopez-Loces M. C., Musial J., Pecero J. E., Fraire-Huacuja H. J., Blazewicz J., Bouvry P.

International Journal of Applied Mathematics and Computer Science

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2016

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Vol. 26, no. 2

391--406

EN

Internet shopping has been one of the most common online activities, carried out by millions of users every day. As the number of available offers grows, the difficulty in getting the best one among all the shops increases as well. In this paper we propose an integer linear programming (ILP) model and two heuristic solutions, the MinMin algorithm and the cellular processing algorithm, to tackle the Internet shopping optimization problem with delivery costs. The obtained results improve those achieved by the state-of-the-art heuristics, and for small real case scenarios ILP delivers exact solutions in a reasonable amount of time.

4

Derivation and validation of the high resolution satellite soil moisture products: a case study of the Biebrza Sentinel-1 validation sites

Musial J., Dabrowska-Zielinska K., Kiryla W., Oleszczuk R., Gnatowski T., Jaszczynski J.

Geoinformation Issues

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2016

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Vol. 8, no. 1(8)

37--53

EN

Soil moisture content is a key variable for numerous disciplines hence the need for its constant monitoring at a global scale. Satellite imagery is the only mean to fulfil this objective. New generations of satellite sensors such as the Sentinel-1 SAR (Synthetic Aperture Radar) system provide measurements at fine spatial and temporal scales. In order to validate such estimates dense in-situ networks measuring soil moisture are required. The scarcity of such networks was the main motivation to establish two validation sites over the Biebrza wetlands within the project funded by the ESA (European Space Agency). The sites are covered by grassland and marshland and are internally homogeneous as far as the soil type and vegetation cover are concerned. Each site is equipped with 9 soil moisture monitoring stations installed every 130 m which allows the derivation of reliable mean soil moisture estimates across the site featuring small standard deviation (0.035 m3/m3 for the grassland site and 0.074 m3/m3 for the marshland site). The main objective of the presented study is to review the soil moisture derivation and validation methodologies suitable for the Sentinel-1 SAR satellite data and to describe physiographical settings of the Biebrza validation sites together with the installed instrumentation. Furthermore, the relationship between the time series of soil moisture measurements and Sentinel-1 sigma nought backscatter coefficient (σ0) is examined. Ultimately, the validation results of the low resolution SM-DAS-2 soil moisture product are presented due to the unavailability of the high resolution product.

PL

Stały monitoring wilgotności gleby jest kluczowy dla różnorodnych zastosowań i może być realizowany na globalną skalę jedynie za pomocą teledetekcji satelitarnej. Nowe generacje satelitów środowiskowych np. Sentinel-1 posiadają sensory umożliwiające wysokorozdzielcze pomiary o dużej częstości czasowej. Uzyskane z nich produkty dotyczące wilgotności gleby wymagają gęstej sieci pomiarów naziemnych do celów walidacyjnych. Fakt ten stanowił główną motywację dla założenia dwóch poligonów walidacyjnych wilgotności gleby zlokalizowanych w dolinie Biebrzy w ramach projektu finansowanego przez Europejską Agencję Kosmiczną (ESA). Obiekty te pokrywają łąkę i zbiorowisko turzycowe i są homogenicznie pod względem roślinności i typu gleby. Każdy poligon wyposażony jest w 9 stacji do pomiaru wilgotności gleby oddalonych od siebie o 130 metrów. Pozwala to na rzetelne oszacowanie średniej wilgotności dla całego obiektu odznaczającej się niskim odchyleniem standardowym (0.035 m3/m3 dla poligonu łąkowego i 0.074 m3/m3 dla poligonu turzycowego). Głównym celem tego opracowania jest opis metodyki wyznaczania i walidacji wilgotności gleby z wysokorozdzielczych radarowych danych satelitarnych oraz charakterystyka obu poligonów badawczych wraz z instrumentami pomiarowymi umożliwiającymi zaawansowany monitoring środowisk bagiennych. Ponadto przeanalizowana została zależność pomiędzy wilgotnością gleby a współczynnikiem rozproszenia wstecznego (σ0) sygnału radarowego satelity Sentinel-1. Ostatecznie wykorzystano dane z opisywanej sieci pomiarowej do walidacji niskorozdzielczego produktu SM-DAS-2 opisującego wilgotność gleby.

5

Algorithms solving the Internet shopping optimization problem with price discounts

Musial J., Pecero J. E., Lopez-Loces M. C., Fraire-Huacuja H. J., Bouvry P., Blazewicz J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2016

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Vol. 64, nr 3

505--516

EN

The Internet shopping optimization problem arises when a customer aims to purchase a list of goods from a set of web-stores with a minimum total cost. This problem is NP-hard in the strong sense. We are interested in solving the Internet shopping optimization problem with additional delivery costs associated to the web-stores where the goods are bought. It is of interest to extend the model including price discounts of goods. The aim of this paper is to present a set of optimization algorithms to solve the problem. Our purpose is to find a compromise solution between computational time and results close to the optimum value. The performance of the set of algorithms is evaluated through simulations using real world data collected from 32 web-stores. The quality of the results provided by the set of algorithms is compared to the optimal solutions for small-size instances of the problem. The optimization algorithms are also evaluated regarding scalability when the size of the instances increases. The set of results revealed that the algorithms are able to compute good quality solutions close to the optimum in a reasonable time with very good scalability demonstrating their practicability.

6

Database Scheme Optimization For Online Applications

Marszałkowski J., Marszałkowski Jędrzej, Musial J.

Foundations of Computing and Decision Sciences

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2011

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Vol. 36, No. 2

121-129

EN

With a rapid growth of Internet usage, e-commerce projects, such as content management systems, on-line shops, social networking pages, and online web- based gaming, meet new performance challenges. In this note we enclose information on database systems using MySQL working in the background of web-based applications. Effect of table name length in simple queries is measured in experimental environment. Conclusions over execution time and amounts of data sent are made. Moreover, comparison performance tests for long and short table names are made on a model and two real web-based applications. Finally, simple yet effective database scheme optimization is proposed.

7

A customer assistance system: optimizing basket cost

Wojciechowski A., Musial J.

Foundations of Computing and Decision Sciences

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2009

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Vol. 34, No. 1

59-69

EN

A strong advantage of buying products in on-line shops is a wide choice of alternatives. From customers' point of view it is good to know where to go in order to buy all required products - the entire shopping list - at the best possible price. Making such decisions requires three elements: information where the required products are available, access to price lists in considered shops, and finally, specialized analytical tool that could find the minimal subset of shops where all the products from the customers' shopping list could be bought at the lowest price. In the paper we propose the mini-mini algorithm and describe a web-based customer assistance system dedicated to pharmacy shopping that helps customers find shops in a geographically defined range where the entire shopping list could be realized at the best price total. The same algorithms might be applied to other applications optimizing Internet shopping where the cost of basket delivery is negligible when compared to product prices.

8

Diagnozowanie stanu struktury geometrycznej powierzchni o rozwiniętej rzeźbie

Liubimov V., Musial J., Styp-Rekowski M.

Diagnostyka

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2005

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Vol. 33

129--134

PL

W niniejszym opracowaniu przedstawiono pewien sposób oceny powierzchni, w którym wykorzystano metodę pomiaru geometrycznych cech wgłębień występujących w strukturze geometrycznej powierzchni roboczych łożysk tocznych. Wykorzystując specjalistyczną aparaturę pomiarową Talyscan, dla wgłębień i pików określono: powierzchnię objętość, maksymalną oraz średnią wartość głębokości lub wysokości. Wyniki przeprowadzonych badań doświadczalnych świadczą o tym, że możliwe jest opisanie za pomocą proponowanej metody zmian, jakie zaszły w strukturze geometrycznej badanych powierzchni podczas procesu zużywania.

EN

In this paper some method of surface estimation was shown. To this aim measures geometric features of holes and pikes exist in geometric structure of tested surfaces of rolling bearings were used. Appilicating specialistic measuring Talyscan apparatus, for the holes and the pikes following quantities were obtained: area, volume, maximum and average values of depth or height, respectively. The results of worked out experimental investigations confirm ability of description by mentioned method of the changes in geometric structure of tested surfaces which occur during wear processes. Thus, there are possibilities applications of these results in diagnostic processes.