Asphalt colloidal types differentiated by Korcak distribution

Asphalt in a colloidal context can be considered as a sol, sol-gel or gel type where in all three cases the asphaltene particle plays an important role. Usually the three colloidal types can be differentiated by refinery processes or by rheological properties. The aggregation or clustering of the asphaltene particles (or micelles) from sol to sol-gel and finally to the gel state with a fixed lattice can follow the stochastic process of fractal Brownian motion which can fit a hyperbolic (or Korcak) distribution. A test was carried out using the same mass of various asphalts of different colloidal types for floc formation with a series of n-alkanes (dispersion media) of increasing characteristic lengths. Results from floc formation studies indicate that the value of the size distribution for the gel type is small, is higher for the sol-gel type, and is highest for the sol type. On the other hand, the surface irregularities for all three types of asphalt do not have any correlation. These observed facts are consistent with principles based on the fractal approach.     

Fatty acid synthesis in the oil palm (Elaeis guineensis): Incorporation of acetate by tissue slices of the developing fruit

Oil palm (E. guineensis) fruits at three stages of development were studied. At week 12–13 after anthesis, the endosperm had started accumulating oil and tissue slices incorporated [1-¹⁴C] acetate into fatty acids which resembled those found in the mature endosperm. The mesocarp contained very little oil and incorporated acetate into polar lipids. At week 16–17, the mesocarp started to accumulate oil; this was reflected in the [¹⁴C] lipid products from acetate incubation. At or just prior to this stage, an increase in the endogenous linoleic and linolenic acid content and the increase in fruit size indicated cellular growth in the mesocarp tissue. At week 20–21 the fruit was ripe, and both endosperm and mesocarp tissues were filled with storage oil. [¹⁴C] Fatty acids synthesized from acetate by mesocarp slices at this stage were the same as the endogenous storage fatty acids in bothE. guineensis andE. oleifera. A very weak fatty acid synthesizing activity was seen in the mature endosperm, but the products had no relationship to the storage lipid.     

A grating-based OCDMA coding-decoding system incorporating anonlinear optical loop mirror for improved code recognition and noisereduction

We demonstrate an elementary grating-based optical code division multiple access (OCDMA) code generation and recognition system incorporating a nonlinear optical loop mirror (NOLM) within the receiver. We show that the NOLM can act as a nonlinear processing element capable of reducing both the pedestal associated with conventional matched filtering and the width of the associated code-recognition pulse. The pedestal rejection allows for an improved code recognition signal-to-noise ratio (SNR) relative to simple matched filtering alone, and reduced intra- and interchannel interference noise due to code overlap. The system benefits of using the NOLM are experimentally demonstrated under both single- and multiuser operation within a variety of seven- and 63-chip 160-Gchip/s code generation, recognition, and transmission experiments based on the use of bipolar superstructure fiber Bragg grating (SSFBG) coding-decoding pairs. Incorporation of the NOLM is shown to allow error-free penalty-free operation at data rates as high as 2.5 Gb/s under single-user operation, and to provide error-free performance with reduced power penalty in two-user experiments. The narrowed pulse recognition signature offers major advantages in terms of the further all-optical processing of decoded signals, such as code regeneration and recoding     

Mechanical properties of copper‐clad laminate using composite naphthalene–phenyl‐based epoxy as prepreg

A composite was prepared that contained diglycidyl ether of tetrabromobisphenol A (DGETBA) and 1,5‐di(2,3‐epoxypropoxy)naphthalene (A), 4,4′‐bis(2,3‐epoxypropoxy)benzylideneaniline (B), or 4,4′‐bis(2,3‐epoxypropoxy)biphenyl (C), and then was cured using different ratios of dicyandiamide (DICY). The results of DSC, TGA, coefficient of thermal expansion, dielectric constant, and dissipation factor testing of the composite epoxy resins were analyzed, and investigation of the copper‐clad laminate using the composite epoxy resins as prepreg was also performed. Additionally, moisture absorption, peel strength, arc resistance, comparative tracking index, and flammability of the copper‐clad laminate were examined. Clearly, some of the physical or mechanical properties of the composite and the copper‐clad laminate can be improved by optimal addition of naphthalene–phenyl‐based epoxy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1485–1492, 2005     

MODELING OF COMPETITIVE ADSORPTION OF NITROGEN SPECIES IN HYDRODESULFURIZATION

Previously, we developed a simple, one-parameter model reproducing the observed inhibiting effect of nitrogen species in the hydrodesulfurization (HDS) of hindered sulfur heterocycles. The model owes its simplicity to some nontrivial assumptions. Here we develop a full model by relaxing these assumptions, which gives a more quantitative picture of how sulfur, nitrogen, and catalyst surface interact on many widely disparate time scales. Computational results build a strong case for the accuracy of the previous one-parameter theory. As such, the theory should be applicable to reaction systems in which catalyst poisoning is driven by nonequilibrium adsorption. Some of the complexities and subtleties in modeling the competitive adsorption effects in distillate HDS are discussed, giving special attention to the design of robust catalyst-deactivation-compensation operating strategies.     

Partial-band jamming rejection of FFH/BFSK with product combiningreceiver over a Rayleigh-fading channel

An exact closed-form expression of the characteristic function is derived for a fast frequency-hopping (FFH) binary orthogonal frequency-shift-keying (FSK) spread-spectrum (SS) communication system. The FFH system employs a product combining receiver over a Rayleigh-fading channel with partial-band jamming and additive white Gaussian noise (AWGN). The derived characteristic function is then used to obtain a compact bit error rate (BER) expression for different diversity levels. Our study shows that there exists an optimum diversity level under certain channel conditions