Analisis Dinamik Model Seirs Penyebaran Virus Worm Pada Komputer

Pada skripsi ini dibahas konstruksi dan analisis model SEIRS penyebaran virus worm pada komputer. Pada model diasumsikan terdapat sistem keamanan komputer yang hanya memberikan kekebalan sementara sehingga komputer dapat kembali menjadi rentan terkena virus worm. Analisis dinamik yang dilakukan pada model meliputi penentuan titik kesetimbangan, angka reproduksi dasar R0, analisis kestabilan lokal dan global titik kesetimbangan bebas virus worm, analisis kestabilan lokal titik kesetimbangan endemik, dan analisis sensitivitas. Berdasarkan hasil analisis diperoleh dua titik kesetimbangan model, yaitu titik kesetimbangan bebas virus worm dan titik kesetimbangan endemik. Titik kesetimbangan bebas virus worm selalu eksis, sedangkan eksistensi titik kesetimbangan endemik bergantung pada angka reproduksi dasar (R0). Kestabilan titik kesetimbangan bebas virus worm bergantung pada angka reproduksi dasar (R0) dan kestabilan titik kesetimbangan endemik stabil asimtotik lokal tanpa syarat. Hasil analisis sensitivitas menunjukkan bahwa laju kontak antara populasi komputer rentan dengan komputer terinfeksi merupakan parameter yang paling sensitif. Simulasi numerik yang dilakukan menunjukkan hasil yang sesuai dengan hasil analisis

Multiple-Point and Multiple-Time Correlations Functions in a Hard-Sphere Fluid

A recent mode coupling theory of higher-order correlation functions is tested on a simple hard-sphere fluid system at intermediate densities. Multi-point and multi-time correlation functions of the densities of conserved variables are calculated in the hydrodynamic limit and compared to results obtained from event-based molecular dynamics simulations. It is demonstrated that the mode coupling theory results are in excellent agreement with the simulation results provided that dissipative couplings are included in the vertices appearing in the theory. In contrast, simplified mode coupling theories in which the densities obey Gaussian statistics neglect important contributions to both the multi-point and multi-time correlation functions on all time scales.Comment: Second one in a sequence of two (in the first, the formalism was developed). 12 pages REVTeX. 5 figures (eps). Submitted to Phys.Rev.

Multistep Parametric Processes in Nonlinear Optics

We present a comprehensive overview of different types of parametric interactions in nonlinear optics which are associated with simultaneous phase-matching of several optical processes in quadratic nonlinear media, the so-called multistep parametric interactions. We discuss a number of possibilities of double and multiple phase-matching in engineered structures with the sign-varying second-order nonlinear susceptibility, including (i) uniform and non-uniform quasi-phase-matched (QPM) periodic optical superlattices, (ii) phase-reversed and periodically chirped QPM structures, and (iii) uniform QPM structures in non-collinear geometry, including recently fabricated two-dimensional nonlinear quadratic photonic crystals. We also summarize the most important experimental results on the multi-frequency generation due to multistep parametric processes, and overview the physics and basic properties of multi-color optical parametric solitons generated by these parametric interactions.Comment: To be published in Progress in Optic