Daniel Merezeanu

Simulation Platform for Virtual Manufacturing Systems

The paper presents the design of a cloud simulation platform and the associated services and the computing resources for hybrid simulation of Virtual Manufacturing Systems. At the core of the research is the design of a framework defined as Virtual Development Environment (VDE). Associated to VDE is a set of block functions and algorithms defined as software assets, stored in a large repository implemented within an on-line cloud supported library. The platform offers flexibility concerning the continuous testing and updates regarding the algorithms in order to improve the existing ones.

Large Scale Wireless Sensor Networks Based on Fixed Nodes and Mobile Robots in Precision Agriculture

The paper presents an innovative design for wireless sensor networks (WSNs) which can increase their performances in the precision agriculture (PA). The authors argue on the reasons why presently WSNs are not integrated in PA on a larger scale. To this end, the paper describes the state of art in WSNs used in PA, and develops the proposed solution on the basis of the identified conjectures. The conceived solution proves how nodes can have small dimensions without mitigating the communication range or energy autonomy. Small dimensions bring benefits also to costs and operations. Such results can be achieved by overcoming the misalignment between advances in unmanned agricultural vehicles (AVs) and advances in WSN. The fixed nodes and mobile nodes (AVs), cooperate to fulfil sensor and communication coverage. Endowing the WSN nodes only with necessary sensors together with an energy awareness communication algorithm adopted in resonance with PA requirements proves to be a new competitive approach. Some simulations to validate these concepts are also provided.

Process simulation platform for virtual manufacturing systems evaluation

Abstract The paper presents the design of a cloud simulation platform and the associated services that will provide the computing resources and services for hybrid simulation of Virtual Manufacturing Systems. At the core of the research is the design of a framework defined as Virtual Development Environment (VDE). Associated to VDE is a set of block functions and algorithms defined as software assets, stored in a large repository implemented within an on-line cloud supported library. The platform offers flexibility concerning the continuous testing and updates regarding the algorithms in order to improve the existing ones.

Fractal Organization in Healthcare Information Systems

The paper presents a new solution for a Healthcare Information System (HIS) architecture that take account of the multi-layer hierarchy and the complexity of interactions between entities distributed at different levels, considered as being components of a multi-agent system. The proposed architectural model follows the requirements for interoperability derived from standards that support the concept of software-oriented architecture. In addition, the HIS topology is associated with a novel construct named Fractal Social Organizations (FSO), a class of socio-technical complex systems based on the recursive application of a same building block, the Service-oriented Community (SoC). Finally, a virtual case study describing a FSO for healthcare services is discussed in order to validate the proposed solutions.

Emergence in Hierarchical Complex Systems Structured as Social Networks

The paper aims to identify the elements that make possible the appearance of emergent properties in organizations structured as social networks, considered as adaptive multi-agent complex systems. The dynamics of these communities (referring primarily to the increasing number of members who interact) was analyzed by the specific rules of scale-free networks growth and the specific principles of multi-agent systems self-organization. Finally, a framework that allow to study the development of such networks according to the preferential attachment rule is introduced.

Secure Communication Method Based on Encryption and Steganography

Encryption is a traditional method of scrambling data beyond recognition. For years, encryption has been widely used in various areas and domains where secrecy and confidentiality were required. However, there are certain encryption techniques that are not allowed in some countries. In these cases, steganography may come as a solution for hiding data using an apparently inoffensive and innocent carrier. The purpose of steganography is to deliver secret information from a sender to a receiver by scrambling the communication channel not the information itself. This way, it is very unlikely for someone to identify and extract the secret message without knowing exactly how it was embedded into the carrier. Moreover, this task is more difficult since most steganographic methods rely on file or packet header redundancy, lossy multimedia algorithms or insignificant content alteration. All of these are very hard to detect. In this paper, a combination of encryption with image based steganography is presented in order to offer similar robustness as offered by advanced encryption algorithms such as RSA, AES or DES but with lower resource needs. The most original contribution of this paper consists in how a secret message is embedded into a image carrier generating 3 different but very similar images. These images are sent to the destination using different channels and then used to recover the original (secret) message.

Communication issues in e-Health context

The paper proposes a modern solution to sustain data communication in an e-Health framework and also the design principles for an e-Health Interoperability Platform for Health Information Systems support. Additionally, the paper presents a mediating service mechanism used to map and convert the context-specific data exchanged between the different parties that are communicating and a dedicated interface mechanism which enables the access of the platform in a cloud computing applications.

Advanced solutions for medical information storing: Clinical data warehouse

The paper presents a number of research challenges for medical data storing into Health Information Systems (HIS), such as complex-data modeling features, advanced classification structures, integration of very complex data, and demonstrates how this area may benefit from the functionality offered by data warehousing. In addition it is presented a case study that configures a data warehouse developed using multi-agent technology that integrates information from heterogeneous sources of a healthcare unit.

Tandem Queueing Systems Maximum Throughput Problem.

In this paper we consider the problem of maximum throughput for tandem queueing system. We modeled this system as a Quasi-Birth-Death process. In order to do this we named level the number of customers waiting in the first buffer (including the customer in service) and we called phase the state of the remining servers. Using this model we studied the problem of maximum throughput of the system: the maximum arrival rate that a given system could support before becoming saturated, or unstable. We considered different particular cases of such systems, which were obtained by modifying the capacity of the intermediary buffers, the arrival rate and the service rates. The results of the simulations are presented in our paper and can be summed up in the following conclusions: 1. The analytic formula for the maximum throughput of the system tends to become rather complicated when the number of servers increase 2. The maximum throughput of the system converges as the number of servers increases 3. The homogeneous case reveals an interesting characteristic: if we reverse the order of the servers, maximum thruoughput of the system remains unchanged The QBD process used for the case of Poisson arrivals can be extended to model more general arrival processes.

Applications of QBD Process in the Study of Tandem Queueing Systems

Abstract This paper is considering the possibility of using the Quasi-Birth-and-Death process in studying a tandem queueing system, particularly on the problem of systems maximum throughput. The structure of this tandem queueing system consists of a serial link of buffers and servers. Naming phase the number of customers waiting in the first buffer and phase the state of the remaining servers, on obtain the equivalent QBD process. This model is then generalized for the MMPP case. The proposed model is used to study the problem of maximum throughput of the system. There are considered different particular systems, which were obtained by modifying the capacity of the intermediary buffers, the arrival rate and the service rates. The paper presents the results of the simulations and the obtained conclusions.