J. Porras - Academia.edu (original) (raw)

Papers by J. Porras

Proceedings of the 11th International Conference on Computer Systems and Technologies and Workshop for PhD Students in Computing on International Conference on Computer Systems and Technologies - CompSysTech '10, 2010

ABSTRACT The paper studies propagation models and their suitability for a harbor area. Harbor log... more ABSTRACT The paper studies propagation models and their suitability for a harbor area. Harbor logistics require mobile network services. This paper presents propagation calculations for a number of different propagation models and measurements done with 3.5 GHz Wimax wireless network. Aim of the work is to provide sufficient and cost effective data connection for the target area. Results from signal measurement experiments are compared with calculated values and the suitability of models are discussed.

Proceedings of the 15th International Conference on Computer Systems and Technologies - CompSysTech '14, 2014

In this case study we present an approach for using gamification elements to increase online stud... more In this case study we present an approach for using gamification elements to increase online student collaboration. In the study a gamified online discussion system was added to an introduction to programming course, with the aim of motivating the students to help each other. The actions in the discussion systems were analyzed and compared with user profiles and a student survey. The system had a positive impact on the course, increasing student collaboration, reduced response times and made course communications 88% more efficient by reducing email traffic.

International Journal of Technology Marketing, 2006

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2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications, 2011

The number of mobile phones has grown greatly during the last few decades. Among this trend, also... more The number of mobile phones has grown greatly during the last few decades. Among this trend, also the expectations and requirements we pose on the mobile devices is growing. As the hardware restrictions for efficient computing are slowly removed, the problem of battery life still exists. Current solutions for extending battery life take into consideration very strict energy saving methods as well as building larger batteries. This paper takes a look into saving battery life via remote execution method known as cyber foraging. In cyber foraging the mobile device can use nearby free computing resources to perform more complex tasks instead of executing them locally. A series of tests were carried out in order to evaluate the possibility of saving energy via remote execution. Not only this seems efficient for saving battery life, but also reducing computation times and improving the user experience.

Connecting Offices and Homes - Proceedings of the International Conference on Wireless LANs and Home Networks, 2001

... Porras]@ lut ... Goverment Local Police I Carl|] Car2 I 1 Entrancel l| Entrance2 ll Entrance3... more ... Porras]@ lut ... Goverment Local Police I Carl|] Car2 I 1 Entrancel l| Entrance2 ll Entrance3 Figure 1. Certiﬁcate issuer tree Instead of using plain BD_ADDR to decide whether to accept or to reject the note a certiﬁcates similar to those used at PKI (public-key infrastructure) could be ...

Computer Applications in Engineering Education, 2013

This is the peer reviewed version of the following article: Knutas, A., Hämäläinen, H., Ikonen, J... more This is the peer reviewed version of the following article: Knutas, A., Hämäläinen, H., Ikonen, J. and Porras, J. (2013), Implementation of an embedded mobile device based feedback system for real-time audience feedback. Comput. Appl. Eng. Educ., 21: E31-E40.

This paper presents a concept of an advertisement screen that is aware of the interests of the pe... more This paper presents a concept of an advertisement screen that is aware of the interests of the people in its proximity. The awareness is accomplished by fetching the preference information from the mobile devices of the people nearby the service. The information is used for deciding what kind of advertisement is shown on the screen at any given time. The structure and operation of the system is described. Description and functionality of simple prototype is shown. The performance of the system is evaluated based on simple prototype. Finally some enhancements along with future research paths are suggested.

True information society requires citizens to be able to access services easily. We propose that ... more True information society requires citizens to be able to access services easily. We propose that people should be able to access public information society services from home without the requirement of purchasing an Internet connection. In this paper modern operator neutral access networks as well as the traditional network approaches are studied and a proposal is made how they can be used to offer information society services for all users. The work includes security, service and business aspects.

Distributed simulation is generally not considered as an option when companies are deciding about... more Distributed simulation is generally not considered as an option when companies are deciding about their simulation methods. This might be due to the lack of distributed simulation software available or the complexity of implementing a distributed simulator. This paper presents aspects which should be considered when planning a distributed simulator and an experimental distributed simulator, Diworse, are presented. An example of distributed cellular system simulation illustrates that good speedups can be achieved when all aspects are properly considered.

... IEEE Software, Jan./Feb. 2010, vol. 27 (1), pp. 78-85. [7] Loth, R., D. Battistelli, F. Chaum... more ... IEEE Software, Jan./Feb. 2010, vol. 27 (1), pp. 78-85. [7] Loth, R., D. Battistelli, F. Chaumartin, HD Mazancourt, J. Minel, A. Vinckx. ... http://www.ek.fi/tietoalojen_liitto/suomi/ tietoa_toimialasta/ IT-alan_tehtavanimikkeisto.php. [11] Todd, PA, JD McKeen and RB Gallupe (1995). ...

On this paper, an online virtual environment to increase student participation in a classroom tea... more On this paper, an online virtual environment to increase student participation in a classroom teaching situation is presented. The presented teaching environment allows students to give anonymous real-time feedback for the teacher. Teacher sees the feedback immediately and has a possibility to react depending on the given comments. This environment is based on the use of modern wireless communication technologies.

Physical Review Letters, 2015

We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered pho... more We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa2Cu3O6+x over a wide range of doping levels (0.1 ≤ x ≤ 1). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from incoherent particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002(2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.

2009 13th IEEE/ACM International Symposium on Distributed Simulation and Real Time Applications, 2009

ABSTRACT This article describes problems of distributing a real-time, human-in-the-loop simulator... more ABSTRACT This article describes problems of distributing a real-time, human-in-the-loop simulator. The simulator itself is a dynamics simulator solving the dynamics of Multi-Body Systems in real-time. Techniques used to distribute computation are presented and their suitability for general purpose interactive simulation are discussed.

Lappeenranta Model is a framework for building open operator neutral access networks with local s... more Lappeenranta Model is a framework for building open operator neutral access networks with local services. The focus is in locality: to provide an easy local network connection available to everyone and to encourage people on developing their knowledge and abilities on networking. This publication describes the operating principle, structure and different implementation options and analyzes the performance of Lappeenranta Model.

27th Annual IEEE Conference on Local Computer Networks, 2002. Proceedings. LCN 2002., 2002

As IEEE introduced the 802.11 WLAN standard in 1997 the wireless scene began to grow rapidly. Int... more As IEEE introduced the 802.11 WLAN standard in 1997 the wireless scene began to grow rapidly. Internet service providers (ISP) opened the game by building wireless access networks for their customers. Access to the ISP networks is usually limited only to ISP customers: On the other hand, the ISP networks are easy to administer. The next trend in wireless is public community networks built by individuals. The community networks are open for everyone, but the main problem is the lack of centralized management. However, an open and centrally managed wireless network can be built by using a specialized solution taking care of the network management. The main purpose of this paper is to introduce the &amp;quot;Lappeenranta model&amp;quot; allowing next generation centrally managed wireless multi-ISP networks, which are open to the public. As the solution offers new opportunities to all the participants connected to the network, the paper also evaluates the influences to each of them.

Physical Review B

We discuss the mechanism of coherent phonon generation by Stimulated Ionic Raman Scattering, a pr... more We discuss the mechanism of coherent phonon generation by Stimulated Ionic Raman Scattering, a process different from conventional excitation with near visible optical pulses. Ionic Raman scattering is driven by anharmonic coupling between a directly excited infrared-active phonon mode and other Raman modes. We experimentally study the response of YBa2Cu3O6+x to the resonant excitation of apical oxygen motions at 20 THz by mid-infrared pulses, which has been shown in the past to enhance the interlayer superconducting coupling. We find coherent oscillations of four totally symmetric (Ag) Raman modes and make a critical assessment of the role of these oscillatory motions in the enhancement of superconductivity.

2008 International Wireless Communications and Mobile Computing Conference, 2008

In this paper, an approach to service profiling and thus enabling effective service use is presen... more In this paper, an approach to service profiling and thus enabling effective service use is presented. This approach is built on the characteristics of mobile peer-to-peer environment. The proof-ofconcept of our approach is demonstrated by PeerHood implementation, in which lightweight service, profile manager enables the efficient service profiling.

Lecture Notes in Computer Science, 2013

ABSTRACT Understanding human behavior on the Internet is a complex problem. One important part of... more ABSTRACT Understanding human behavior on the Internet is a complex problem. One important part of the problem is measuring cultural attributes and their effect on human behavior. A clear understanding and comprehensive description of the link between human behavior and cultural attributes is essential for quantifying behavioral change. The objective of this paper is to introduce the result of a survey in which (n = 152) university participants participated in quantifying cultural attributes. The study results suggest that human behavior on the Internet can be linked to various cultural attributes. Notably the qualitative feedback and quantitative statistical results found following the cultural attributes to be important: safety, privacy, self, intuition and networking.