Victor Asavei

A visual comparison between voltage and power wave reflection coefficients of microwave circuits

This paper analyzes and compares voltage and power wave reflection coefficients using a visual representation which fully exploits that both coefficients are directly related to the geometry of direct inversive transformations in the extended impedance plane. In order to compare the two concepts for complex impedance ports, the 3D Smith chart tool is used in premiere. The paper gives a geometrical and more intuitive insight of these two parameters and proposes a novel tool for handling both types of reflection coefficients.

From HTML to 3DMMO – A Roadmap Full of Challenges

WWW is everywhere, embraced by humankind to share information and collaborate. The basic schema of hyperlinked web pages has evolved with revolutionary technologies, altogether with the devices used to access the web, but still carries on strong limitations. Virtual reality and 3D MMO, with their sheer power of representation and interaction, is seen by many as the future of human computer based interaction and collaboration and would, naturally, mix with the WWW model sooner or later. The complexity of the technology, from technical point of view but also with many interdisciplinary issues (medical, ethical, economical, socio-political etc.) would make this transition challenging and exciting. This paper classifies, identifies and proposes basic conceptual solution for these issues - of moving from interconnected web pages to interconnected 3D virtual spaces with massive number of interacting users.

Extended Capabilities of the 3-D Smith Chart With Group Delay and Resonator Quality Factor

This paper extends the capabilities of the 3-D Smith chart for representing positive and negative differential-phase group delay and the associated loaded resonator quality factor, displayed simultaneously with scattering (S)-parameters. Here, mathematical concepts, inspired from elementary differential geometry and topology, are used to implement 3-D projections. It is shown that a condition for a circuit to exploit negative differential-phase group delay is that its S-parameter winding number should be ≥ 0 (relative to its origin). Finally, exemplar network responses that exhibit both positive and negative differential-phase group delay and loaded resonator quality factor are shown with the 3-D Smith chart. The convenience of being able to simultaneously display a wider range of parameters on one visualization platform, with the 3-D Smith chart, may help to speed-up the design and analysis of microwave circuits by the user.

Lossy coupling matrix filter synthesis based on hyperbolic reflections

The paper introduces the concept of hyperbolic reflections in order to complement the hyperbolic rotation matrices used in the lossy coupling matrix filter synthesis. A complex transversal coupling matrix representing a lossy filter is chosen and it is seen how by applying a succession of similarity transformations based also on hyperbolic reflections one obtains different results than by using hyperbolic rotations which are nowadays used in the coupling matrix reconfiguration. Finally a lossy symmetrical filter is designed and simulated based on a folded coupling matrix by shifting the losses into the first and last resonators of the filter.

Practical GPU and Voxel-Based Indirect Illumination for Real Time Computer Games

Indirect illumination techniques greatly improve the realism of computer generated 3D scenes. However, most of these techniques are used offline and rely on pre-baked solutions which do not support dynamic updates. There are some real time solutions but usually the degree of realism that they achieve is not convincing enough. We present a real time solution based on a voxel representation of the scene generated from the mesh representation paired with an approximate voxel cone tracing technique which achieves good visual results and interactive frame rates. We also present an integration of this solution into a custom game engine to demonstrate the usage viability of the method in real world scenarios.

On the sum of the reflection and transmission coefficient on the Smith chart and 3D Smith chart

The paper presents in premiere a simple mapping property of the sum of the reflection and transmission parameters of reciprocal two port networks. It is proved that although the reflection and transmission parameter may have very complicated paths on the Smith chart, their sum will be always moving on the unit circle if the circuit is symmetric and lossless. Further once symmetrical losses at the ports occur their sum path will switch on a family of circles through one point. Using inversive geometry we construct a new function which maps this family of circles in lines on the extended Smith chart. The proposed method for checking the symmetry uses just two parameters and avoids testing the phase of the corresponding input and output parameters. By means of the 3D Smith chart we propose in the end an alternative approach to visualize the parameters.

QUESTOR -- Automatic Searching for Reports

Vast arrays of reporting are nowadays in use, allowing ever increasing flexibility and control over the displayed results. However, as IT developed and became available to all business domains, the number of reports used by companies started to challenge the possibility of good management. The European funded project Questor aims to create a revolutionary product that will eliminate the complexities inherent in the report management workflow. The motivation of this project is to substitute the time consuming manual search for information in reports with an automatic one. The final purpose is to make querying the report database as simple as addressing a question in natural language. This paper gives an overview over the concept of the Questor project, its software architecture and its preliminary results.

Multi GPGPU Optimizations for 3D MMO Virtual Spaces

The constantly growing demand for 3D Massively Multiuser Online (MMO) virtual spaces has led to an increase of the load that current 3D MMO server architectures need to cope with in order to accommodate a large user base that interacts inside the virtual space at a given moment of time. The traditional methods that are employed to solve this computational challenge by the current 3D MMO server architectures have inherent drawbacks regarding scalability, reliability, redundancy, cost and the realism of the virtual world. In the last few years, the graphics hardware has evolved in a spectacular manner in terms of computing power and architectural design, switching from a “single-core” to current “many-core” architecture. In this paper we propose an innovative approach to tackle the heavy computational operations that are executed by the simulations of 3D MMO Virtual Spaces using Multi GPGPU (General Purpose programming on Graphical Processing Units).

A Review and Mathematical Treatment of Infinity on the Smith Chart, 3D Smith Chart and Hyperbolic Smith Chart

This work describes the geometry behind the Smith chart, recent 3D Smith chart tool and previously reported conceptual Hyperbolic Smith chart. We present the geometrical properties of the transformations used in creating them by means of inversive geometry and basic non-Euclidean geometry. The beauty and simplicity of this perspective are complementary to the classical way in which the Smith chart is taught in the electrical engineering community by providing a visual insight that can lead to new developments. Further we extend our previous work where we have just drawn the conceptual hyperbolic Smith chart by providing the equations for its generation and introducing additional properties.

Comparison between Incompressible SPH Solvers

In this paper, we present two high performing and efficient Smoothed Particle Hydrodynamics (SPH) methods used to physically simulate incompressible fluids: Implicit Incompressible SPH (IISPH) and Divergence-Free SPH (DFSPH). At the moment, the most stable SPH methods employ density correctors that reduce the density error of the fluid particles to achieve very low levels of compressibility. We analyze the performance of the correctors used for the methods previously mentioned. We also compare IISPH against DFSPH to study several characteristics such as the stability of the particles, the compressibility levels of the fluid achieved during the simulations, the execution speed of each corrector, the maximum possible increase of the time steps, etc.