Wall slip and melt fracture of poly(lactides)

The wall slip and melt fracture behaviour of several commercial polylactides (PLAs) as well as their rheological properties under shear and extensional have been investigated. The PLAs have had weight-average molecular weights in the range of 10⁴–10⁵ g/mol and studied in the temperature range of 160–200°C. The solution properties and linear viscoelastic behaviour of melts indicate linear microstructure behaviour. PLAs with molecular weights greater than a certain value were found to slip, with the slip velocity to increase with decrease of molecular weight. The capillary data were found to agree well with linear viscoelastic envelope once correction for slip effects was applied. The onset of melt fracture for the high molecular weight PLAs was found to occur at about 0.2 to 0.3 MPa, depending on the geometrical characteristics of the dies and independent of temperature. Addition of 0.5 wt.% of a polycaprolactone (PCL) into the PLA that exhibits melt fracture was found to be effective in eliminating and delaying the onset of melt fracture to higher shear rates. This is due to significant interfacial slip that occurs in the presence of PCL.     

Control and adaptive modified function projective synchronization of Liu chaotic dynamical system

In this work, the feedback control method is proposed to control the behaviour of Liu chaotic dynamical system. The controlled system is stable under some conditions on the parameters of the system determined by Routh-Hurwitz criterion. This paper also presents the adaptive modified function projective synchronization (AMFPS) between two identical Liu chaotic dynamical systems. Based on the Lyapunov stability theorem, adaptive control laws are designed to achieving the AMFPS. Finally, some numerical simulations are obtained to validate the proposed methods.     

Effect of the gravity on the photothermal waves in a semiconducting medium with an internal heat source and one relaxation time

The purpose of the present paper is to study the gravitational effect in a homogeneous isotropic semiconducting medium subjected to an internal heat source, based on Lord–Shulman theory. The problem is formulated in the dimensionless form and then solved analytically using the normal mode analysis method. The physical quantities are obtained and tested by a numerical study using the parameters of silicon as a target and presented graphically. The distribution of these quantities is represented graphically in the presence and absence of the internal heat source as well as gravity.     

The Interaction of a N-Type Four Level Atom with the Electromagnetic Field for a Kerr Medium Induced Intensity-Dependent Coupling

The interaction of a N-type four-level atom with a single field in the presence of an intensity-dependent coupling in a nonlinear Kerr medium is investigated. The exact analytic solution is obtained in the case that the atom and electromagnetic field are initially in a higher excited state and a coherent state, respectively. It is then demonstrated that effects such as nonclassical light generation, degree of entanglement stabilization, Kerr medium nonclassical control, and squeezed light are can be more efficiently implemented within this four-level framework than in many competing procedures. Additionally, inversion, linear entropy, Mandel Q-parameter and normal squeezing dynamics are examined.     

Intensity modulated silver coated glass optical fiber refractive index sensor

Miniature optical fiber sensors with thin films as sensitive elements could open new fields for optical fiber sensor applications. Thin films work as sensitive elements and a transducer to get response and feedback from environments, in which optical fibers act as a signal carrier. A novel Ag coated intensity modulated optical fiber sensor based on refractive index changes using IR and UV-Vis(UV-visible) light sources is proposed. The sensor with an IR light source has higher sensitivity compared to a UV-Vis source. When the refractive index is enhanced to 1.38, the normalized intensity of IR and UV-Vis light diminishes to 0.2 and 0.8, respectively.     

Electro-optical properties and(E,F) phase diagram of fluorinated chiral smectic liquid crystals

Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain. Dielectric relaxation study and electro-optical measurements are carried out with the classical SSFLC geometry. The field-induced phase transitions are studied and the(E,T) phase diagram is established.     

Some novel cholesteric liquid crystals

A novel series of cholesteric liquid crystals (CNTⁿ). made by quaternization of the new mesogenic unit cholesteryl isonicotinate (CN) with n-alkyl salts, C_nH_2n + ₁ (T) (n = 2 to 8, T = 4-MeC₆H₄SO₃) has been prepared. Differential scanning calorime-try and polarizing optical microscopy studies reveal that all of these salts exhibit an enantiotropic cholesteric phase but for the cholesteryl isonicotinate unit the cholesteric phase is monotropic. For all members of the series the cholesteric-isotropic transitions are not reversible as these salts begin to decompose before their cholesteric-isotropic transition point is reached.     

Composition and thermal-induced effects on the optical constants of Ge20Se80−xBix thin films

 The effects of composition and thermal annealing near crystallization temperature, T_c on the optical and structural properties of Ge₂₀Se_80−xBi_x (x=0, 2.5, 5 and 7.5 at%) was investigated. The influence of incorporation Bi content in Ge₂₀Se_80−xBi_x system results in a gradual decrease in the indirect optical gap from 1.89 to 1.44 eV, this behavior can be explained as increased tailing. On annealing, the optical band gap E_g decreases gradually for the crystallized films while the refractive index increases, this behavior can be attributed to transformation from amorphous to crystalline and was explained in the light of dangling bond model. The refractive index n of as-prepared and annealed films has been analyzed according to the Wwmple–DiDominico single oscillator model and the values of E_o and E_d were determined. The effect of annealing on the nature and degree of crystallization has been investigated by studying the structure using transmission electron microscope, X-ray diffraction and scanning electron microscope.     

Calix[4]arene-based, Hg2+ -induced intramolecular fluorescence resonance energy transfer chemosensor

A novel calix[4]arene-based chemosensor 1 based on Hg2+-induced fluorescence resonance energy transfer (FRET) was synthesized, and its sensing behavior toward metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of Hg2+ to a CH3CN solution of 1 gave a significantly enhanced fluorescence at approximately 575 nm via energy transfer (FRET-ON) from the pyrenyl excimer to a ring-opened rhodamine moiety. In contrast, addition of Al3+ induced a distinct increase of pyrenyl excimer emission ( approximately 475 nm), while no obvious FRET-ON phenomenon was observed. Different binding behaviors of 1 toward Hg2+ and Al3+ were also proposed for the interesting observation.