Bionanocomposites based on 3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and cellulose nanowhiskers (CNWs)

Over the past decade, bio-based polymers, especially in packaging, have gained a bigger role due to the over consuming of petrol derivates and the gradually growing concerns relating environment and sustainability issues. The urgent need to have high-performance renewable and natural-base polymers is increasing world-wide. At the same time, the price of those polymers is rising in direct proportion of its studies. Therefore, many researchers have focused in combining those polymers with other natural materials such as cellulose fibers to reduce its cost while maintaining or enhancing their properties. Here, we reproduce a system to obtain the functional reinforcement cellulose nanowhiskers (CNWs) for enhancing mechanical behavior and understanding the interaction between the CNWs PHBV. We divide the main objective in two parts: manufacturing the CNWs and the composite with PHBV of it in the lab, and an evaluation of the mechanical and thermal properties of the composite. The result shows that the CNWs can be obtained by acid hydrolysis in lab and can enhance part of the physical properties of PHBV.En la darrera década, el biopolímers, sobretot en el negoci de l'empaquetatge, han adquirit una major importancia, degut al consum massiu de derivats del petroli i la creixent preocupació per temes com el medi ambient i la sostenibilitat. La urgent neccessitat de tenir polímers d'alta eficiencia, renovables i de base natural, s'està expandint mundialment. Al mateix temps, el preu d'aquests polímers augmenta proporcionalment al nombre d'estudis que hi ha sobre aquests. Per aquesta raó, molt investigadors s'han centrar en la combinació de polímers amb materials naturals com fibras de celulosa, per així reduir el seu cost, mantenint i fins i tot millorar les seves propietats. En aquest projecte, reproduïm un sistema d'obtenció de CNWs per a millorar el comportament mecànic i la comprensió de les interaccions entre CNWs i PHBV. Dividim el treball en dos sub-objectius: la manufacturació de CNWs i el composit amb PHBV, i la avaluació de les propietats mecàniques i tèrmiques del composit.En la última década, bio-polímeros, sobretodo en embalajes, han adquirido mayor importancia, debido al sobre consumo de los derivados del petróleo y la creciente preocupación por temas como el medio ambiente y la sostenibilidad. La urgente necesidad de tener polímeros de alta eficiencia, renovables y de base natural, está expandiéndose mundialmente. Al mismo tiempo, el precio de esos polímeros aumenta proporcionalmente al número de estudios sobre estos. Por esa razón, muchos investigadores se han centrado en la combinación de polímeros con materiales naturales como fibras de celulosa, para así reducir su coste, manteniendo o incluso mejorando sus propiedades. En este proyecto, reproducimos un sistema de obtención de CNWs para mejora de comportamiento mecánico y la comprensión de las interacciones entre CNWs y PHBV. Dividimos el trabajo en dos sub-objetivos: la manufacturación de CNWs i el composit con PHBV, y la evaluación de las propiedades mecánicas y términcas del composit

Verification of Solutions for Almost Linear Complementarity Problems

We present a computational enclosure method for the solution of a class of nonlinear complementarity problems. The procedure also delivers a proof for the uniqueness of the solution

Beamforming and Power Splitting Designs for AN-aided Secure Multi-user MIMO SWIPT Systems

In this paper, an energy harvesting scheme for a multi-user multiple-input-multiple-output (MIMO) secrecy channel with artificial noise (AN) transmission is investigated. Joint optimization of the transmit beamforming matrix, the AN covariance matrix, and the power splitting ratio is conducted to minimize the transmit power under the target secrecy rate, the total transmit power, and the harvested energy constraints. The original problem is shown to be non-convex, which is tackled by a two-layer decomposition approach. The inner layer problem is solved through semi-definite relaxation, and the outer problem, on the other hand, is shown to be a single- variable optimization that can be solved by one-dimensional (1- D) line search. To reduce computational complexity, a sequential parametric convex approximation (SPCA) method is proposed to find a near-optimal solution. The work is then extended to the imperfect channel state information case with norm-bounded channel errors. Furthermore, tightness of the relaxation for the proposed schemes are validated by showing that the optimal solution of the relaxed problem is rank-one. Simulation results demonstrate that the proposed SPCA method achieves the same performance as the scheme based on 1-D but with much lower complexity.Comment: 12 pages, 6 figures, submitted for possible publicatio

Parallel Graph Connectivity in Log Diameter Rounds

We study graph connectivity problem in MPC model. On an undirected graph with $n$ nodes and $m$ edges, $O(\log n)$ round connectivity algorithms have been known for over 35 years. However, no algorithms with better complexity bounds were known. In this work, we give fully scalable, faster algorithms for the connectivity problem, by parameterizing the time complexity as a function of the diameter of the graph. Our main result is a $O(\log D \log\log_{m/n} n)$ time connectivity algorithm for diameter-$D$ graphs, using $\Theta(m)$ total memory. If our algorithm can use more memory, it can terminate in fewer rounds, and there is no lower bound on the memory per processor. We extend our results to related graph problems such as spanning forest, finding a DFS sequence, exact/approximate minimum spanning forest, and bottleneck spanning forest. We also show that achieving similar bounds for reachability in directed graphs would imply faster boolean matrix multiplication algorithms. We introduce several new algorithmic ideas. We describe a general technique called double exponential speed problem size reduction which roughly means that if we can use total memory $N$ to reduce a problem from size $n$ to $n/k$, for $k=(N/n)^{\Theta(1)}$ in one phase, then we can solve the problem in $O(\log\log_{N/n} n)$ phases. In order to achieve this fast reduction for graph connectivity, we use a multistep algorithm. One key step is a carefully constructed truncated broadcasting scheme where each node broadcasts neighbor sets to its neighbors in a way that limits the size of the resulting neighbor sets. Another key step is random leader contraction, where we choose a smaller set of leaders than many previous works do