Synthesis and charcterization of diblock copolymers containaing monothio-orthoester functions using raft polymerization

The acyclic and cyclic monothio-orthoester monomers were synthesized by modification of aromatic monomers containing dithioester function in the side chain. Reversible addition-fragmentation chain transfer (RAFT) polymerization was employed for the preparation of polymers containing a dithioester end as macro-chain transfer agents (macro-CTA) using 4-benzyl methyldithiobenzoate (BMDTB) as chain transfer agent (CTA) and 2,2-azobisisobutyronitrile (AIBN) as initiator. A series of diblock copolymers were prepared by RAFT copolymerization of MVDTB, MMMS and MVPOCO, using the different macro-chain transfer agents (macro-CTA) and AIBN as initiator. All polymerizations were carried out at 60 °C for 24 or 30 hours in dry THF. Homopolymers and diblock copolymers are characterized by 1H NMR, 13C NMR, IR, SEC, DSC and TGA.Keywords: Dithioesters, monothio-orthoesters, RAFT polymerization

Investigation of terahertz pulse generation in semiconductors pumped at long infrared wavelengths

We present designs of semiconductor contact grating high energy terahertz pulse sources pumped by femtosecond pulses in the 1 to 5 µm wavelength range. Nearly wavelength-independent diffraction efficiencies as high as 69% and 75% in the ±1st diffraction orders in the transverse electric field polarization state were predicted in GaAs and GaP, respectively, based on a rectangular grating. Numerical simulations—including, for the first time, to our knowledge, the effects of both a nonlinear refractive index and free carrier absorption—were performed to investigate the possible advantage of using longer pumping wavelengths to suppress the two- to seven-photon absorption. Conversion efficiency larger than 1.0% is predicted for both crystals. We also recognized that the nonlinear refractive index and the wavelength-dependent optical parametric amplifier efficiency can significantly reduce the overall terahertz generation efficiency; thus, optimum pump wavelengths exist for the highest conversion efficiency, which are 2 and 3µm for GaP and GaAs, respectively

Treatment of dredged marine sediments for their Reuse in road construction. Traitement des sédiments de dragage marins en vue de leur réutilisation en techniques routières

great quantity of marine sand and sediments are dredged each year in Europe. Dredged sediments were considered as a waste product of the dredging operations and were a serious problem for the harbour managers. Recently, sediments are seen as a natural resource that could provides opportunities for a number of beneficial uses. However, these raw material can't be used in road construction without a specific treatment process. Sediments suitablity tests has shown that most of studied sediments are not suitable to be used in road construction. In order to improve theircompacity and their mechanical performance, addition of a granular material is recommended.The use of a dredged sand, to improve the granular mixture containing sediments, allows a better management of the two types of dredge materials (sand and sediment). In this study, a new road material containing dredged marine sediments and dredged sand is formulated and treated by adding various binders. Mechanical performance investigation of different mixtures by measuring Proctor-IPI values and simple compressive strengths is realized

Miscibility and Hydrogen Bonding in Blends of Poly(4-vinylphenol)/Poly(vinyl methyl ketone)

The miscibility and phase behavior of poly(4-vinylphenol) (PVPh) with poly(vinyl methyl ketone) (PVMK) was investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). It was shown that all blends of PVPh/PVMK are totally miscible. A DSC study showed the apparition of a single glass transition (T-g) over their entire composition range. When the amount of PVPh exceeds 50% in blends, the obtained T(g)s are found to be significantly higher than those observed for each individual component of the mixture, indicating that these blends are capable of forming interpolymer complexes. FTIR analysis revealed the existence of preferential specific interactions via hydrogen bonding between the hydroxyl and carbonyl groups, which intensified when the amount of PVPh was increased in blends. Furthermore, the quantitative FTIR study carried out for PVPh/PVMK blends was also performed for the vinylphenol (VPh) and vinyl methyl ketone (VMK) functional groups. These results were also established by scanning electron microscopy study (SEM).The authors would like to acknowledge the financial support from the Basque Government (IT618-13) and Basque Country University (UFI 11/56)

Fault tolerant NPC converter control for isolated PV sytems: Application for an isolated telecommunication center

Continuity operating within isolated telecommunication sites is an important challenge. In this paper, a new fault tolerant SVM (Space Vector Modulation) strategy for 3level NPC (Neutral point Clamped) inverter used in isolated telecommunication sites is proposed. It inssures a continuous operation of the laod after a breakdown of an inverter power switch. Simulation results prove the good performances of the proposed srategyPeer ReviewedPostprint (published version

Fault tolerant NPC converter control for isolated PV sytems: Application for an isolated telecommunication center

Continuity operating within isolated telecommunication sites is an important challenge. In this paper, a new fault tolerant SVM (Space Vector Modulation) strategy for 3level NPC (Neutral point Clamped) inverter used in isolated telecommunication sites is proposed. It inssures a continuous operation of the laod after a breakdown of an inverter power switch. Simulation results prove the good performances of the proposed srategyPeer Reviewe