Next Generation M2M Cellular Networks: Challenges and Practical Considerations

In this article, we present the major challenges of future machine-to-machine (M2M) cellular networks such as spectrum scarcity problem, support for low-power, low-cost, and numerous number of devices. As being an integral part of the future Internet-of-Things (IoT), the true vision of M2M communications cannot be reached with conventional solutions that are typically cost inefficient. Cognitive radio concept has emerged to significantly tackle the spectrum under-utilization or scarcity problem. Heterogeneous network model is another alternative to relax the number of covered users. To this extent, we present a complete fundamental understanding and engineering knowledge of cognitive radios, heterogeneous network model, and power and cost challenges in the context of future M2M cellular networks

On the Performance of MIMO FSO Communications over Double Generalized Gamma Fading Channels

A major performance degrading factor in free space optical communication (FSO) systems is atmospheric turbulence. Spatial diversity techniques provide a promising approach to mitigate turbulence-induced fading. In this paper, we study the error rate performance of FSO links with spatial diversity over atmospheric turbulence channels described by the Double Generalized Gamma distribution which is a new generic statistical model covering all turbulence conditions. We assume intensity modulation/direct detection with on-off keying and present the BER performance of single-input multiple-output (SIMO), multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) FSO systems over this new channel model.Comment: 6 Pages, 4 figure, IEEE ICC conference 201

Interviews With College Students: Evaluating Computer Programming Environments For Introductory Courses

Different methods, strategies, or tools have been proposed for teaching Object Oriented Programming (OOP). However, it is still difficult to introduce OOP to novice learners. The problem may be not only adopting a method or language, but also use of an appropriate integrated development environment (IDE). Therefore, the focus should be on the needs of learners when selecting an IDE and the evaluations for instructional purposes may allow making objective decisions for an introductory course design. There are different methods or frameworks for evaluating IDEs and the majority focuses on the experts’ needs. Unfortunately, studies done on instructional appropriateness of IDEs are insufficient. In this study, an evaluation framework is initially proposed, then the candidate IDEs are evaluated, and finally, the perceptions of college students are explored by conducting semi-structured interviews. The data are analyzed by the Verbal Analysis technique, and the results are discussed in view of the evaluation criteria. The results imply that the learners view one of the criteria relatively more supportive for learning

Stakeholders’ views on improving the organic certification system: Results from an EU level workshop

The FP7 CERTCOST project has the overall objective to give recommendations to the public authorities and private actors in the whole organic certification chain on how to improve the organic food certification systems in terms of efficiency, transparency and cost effectiveness. According to the project description (the Description of Work, or DoW) this will be done based on a scientific economic in depth analysis of the certification systems from the farmer to the consumer in 5 EU countries (the Czech Republic, Denmark, Germany, Italy and the United Kingdom), plus Switzerland and the candidate country, Turkey. To safeguard that the CERTCOST objectives, work plan and methodology is in line with the expectations of key stakeholders from all levels of the certification chain the DoW foresaw a Stakeholder workshop to be organised in the beginning of the project. The current report documents the main points of the discussions and recommendation given by the stakeholders at this CERTCOST Stakeholder workshop, which took place on November, 13-15, 2008 in Izmir, Turkey, 2.5 months after the project had started. A total of 20 stakeholders were invited, of whom 16 could participate in the workshop. The participant profile included both users and providers of the certification system at different levels such as representatives of farmers’ organizations certification/control bodies, government authorities, EU Commission, processors/ traders, private experts/consultants. Together with the representatives of the partner institutions in the CERTCOST project, the total number of workshop participants was 35 representing 12 European countries. Given the diverse backgrounds of the workshop participants, a working group approach (World Café approach) was applied in order to give the participants the opportunity to reflect their experiences and ideas on the implementation of the project in a synergetic, comfortable and free environment. After a brief presentation of the project, outlining the tasks of the work packages and describing the proposed links between the project and the stakeholders by the project coordinator, the stakeholders were divided into four groups according to their level in the organic certification chain, as farmers, processors/traders, certification bodies and consumers. Two working group sessions were carried out around the questions provided to the stakeholders before the workshop through electronic mails. The questions had been compiled based on input from the managers of the four work packages which were relevant to the workshop discussion. After the first working group session, a plenary discussion session for clustering of the output given by the working groups, their validation and assessment was carried out. In the second session of the working groups, it was rather aimed to harmonize the understanding between the diversified opinions mentioned in Session 1. The working group approach concluded in a final plenary discussion. On the second day, the CERTCOST work package managers presented how the discussions, comments and inputs of the working group sessions could impact on their working plans. In the final session the stakeholders were addressed directly for providing further ideas both on the project and on future collaboration options. The workshop was strongly focused on the identification of key characteristics of cost factors along the supply chain in relation to their impact on the quality of the given service. However a broad range of related subjects were discussed. The Stakeholder workshop put forward that, the ‘cost’ was among the most important topics relating to the certification system performance. The focus of the project aiming at cost effectiveness and not cost minimization was confirmed by the stakeholders. All of the stakeholders present in the workshop demonstrated elevated levels of interest on several outputs of the project. The workshop revealed very positive expectations among the stakeholders towards the risk based approach to be followed in the CERTCOST project. The detailed picture of the organic certification sector obtained through the workshop will constitute an important input to the CERTCOST project and the workshop is considered to be a successful first step in the project-stakeholder interaction. The Stakeholder workshop provided important insight into the many discussion subjects of the organic certification systems in the EU and worldwide, among others the following should be mentioned. Farmers expect to have, clear rules, fair implementation, and high skilled guidance in the inspection and certification process, and underline the need for training of farmers and certifiers and for better communication between all parties in the certification chain. Processors point out the need for a good relationship with the inspectors and certifiers as well as the fact that there existed different schemes in different countries regarding the inspection process and the related cost structure. They also highlighted the difficulty of managing the relations with increasing number of different standards and different certification bodies. It is agreed that consumers expect something they can trust and they can easily recognize, a label, a logo, a certifier, a brand, a farmer or the word ‘organic’; at local, regional, national, or EU-level. It is also concluded that whether, why and how much some consumers might be willing to pay more for particular logos was unknown and was needed to be investigated. Authorities/certification bodies stress that the issue of knowledge and education is extremely important and that there are complex legislations, no common standards, and differences within and between countries. They underline that there are different catalogues in different countries to deal with irregularities which should be harmonized. They emphasize that a clear definition of certification should be made covering its objectives, principles and tools. While on some of the issues there has been a highlighted consensus among the groups, on some others contrasting ideas became evident. Among those subjects of absolute agreement were the importance of and the need for a more clear understanding of the certification system, its components and rules by all the parties involved. Education and elevated levels of necessary skills from farmer to inspector and to consumer; increased transparency and information exchange, well defined relationships between parties were considered to be an indispensable basis for a well functioning and more efficient certification system. The inspection concept came into prominence, with a discussion on policing vs. development approaches. While an efficient and comparable control system was judged to be crucial, promising private governmental formulations were agreed to be based on country conditions. Complexity of the legislation and lack of transparency were the remarkable barriers to a more efficient control system. The EU logo and the new EU Regulation for organic certification were also discussed among stakeholders. It was suggested that the EU logo might have the potential to boost demand in the ‘less developed’ organic markets, but more promotion then currently planned would be needed. It was agreed that most consumers do not look for logos of particular standards but for the word ‘organic’ and/or an organic logo they are familiar with. This might be different for ‘committed’ organic consumers in more mature markets. Overall, it was agreed that ‘trust’ is the most crucial aspect of organic certification regarding the consumer side. The issue of multiple certification and standards appeared to be a factor deserving more attention in the certification world. Harmonization in certification of the same characteristic of a product was deemed necessary. On the other hand, exchange of experiences and cooperation with markets like ‘Fair Trade’ was agreed to be potentially beneficial

The Effects of Objects-First and Objects-Late Methods on Achievements of OOP Learners

Our research explored the effects of objects-first and objects-late methods on achievements of object-oriented programming (OOP) learners during a graduate course. The course’s scope was virtually identical for two groups, but the structure of the contents differed in sequence. The objects-first method emphasized the design and discussion of the object-oriented concepts from the very beginning while the objects-late deferred these concepts to the late lectures. The objects-first learners used all visual functionalities of BlueJ IDE. However, the objects-late learners started with only the text-based interfaces of BlueJ and they benefited its visual support in the last lectures. At the end of the study, we found that there was a statistically significant difference between OOP learner groups

Prijenos topline u mjehurastim stupcima

Bubble columns are gas-liquid contactors often used in industry. Although they are used primarily for mass transfer purpose, since gas and liquid phases are fed to the column at different temperatures, direct contact heat transfer becomes important as well. This research is about the heat transfer characteristics of bubble columns. Experiments were carried out using a plexiglass column with dimensions 160x160x1180 mm. Water was first put into the column to the height of 1 m and heated to the desired temperature, and then experiments were performed by introducing ambient air to the column and recording the variation in temperature of water and inlet and outlet air temperatures and humidities. Models developed for the convective heat transfer from the liquid interface to the gas in the bubble were used together with the experimental data to determine the heat and mass transfer coefficients. The volumetric heat transfer coefficient (hGa) was found to vary over the range 0,3-16 kW/(m3·K) with gas flow rate and the volumetric mass transfer coefficient (kGa) in the range 0,35-7,49 kmol/ m3·s·atm.Mjehurasti stupci su dodiri između plina i kapljevine koji se često koriste u industriji.. Iako ih se primarno koristi s ciljem prijenosa mase, budući da se plinska i kapljevita faza razdvajaju u stupce pri različitim temperaturama. tada njihov izravni dodir postaje važan za prijenos topline.. Ovo se istraživanje bavi karakteristikama prijenosa topline mjehurastih stupaca. Eksperimenti su napravljeni koriste cilindar od plexiglasa dimenzija 160x160x1180 mm. U cilindar je prvo ulivena voda do visine od 1 m i koja je zagrijavana do željene temperature, nakon čega se u tu vodu uvodio zrak okolišnje temperature, pri čemu se mjerila promjena temperature vode, kai i ulazna i izlazna vlažnost zraka. Modeli razvijeni za konvektivni prijenos topline sa slobodne površine kapljevine na mjehur su korišteni zajedno sa eksperimentalnim podacima za određivanje koeficijenata prijenosa topline i mase.. Iznađeno je da je volumetrički koeficijent prijenosa topline varirao u području 0.3-16 kW/(m3·K) s protokom zraka i volumetričkim koeficijentom prijenosa mase u području 0.35 – 7,39 kmol/(m3·s·atm

On the Optimization of Underwater Quantum Key Distribution Systems with Time-Gated SPADs

In this paper, we study the effect of various transmitter and receiver parameters on the quantum bit error rate (QBER) performance of underwater quantum key distribution. We utilize a Monte Carlo approach to simulate the trajectories of emitted photons transmitting in the water from the transmitter towards receiver. Based on propagation delay results, we first determine a proper value for bit period to avoid the intersymbol interference as a result of possible multiple scattering events. Then, based on the angle of arrival of the received photons, we determine a proper field-of-view to limit the average number of received background noise. Finally, we determine the optimal value for the single photon avalanche diode (SPAD) gate time in the sense of minimizing the QBER for the selected system parameters and given propagation environment