Non-linear response of point-reactors to stochastic inputs

Statistical properties of the non-linear response of a point reactor to a white Gaussian reactivity insertion and an external source are investigated through the general Fokker-Planck theory for linear systems with random coefficients. The autocorrelation function and power spectral density of the reactor power are obtained, and the effect of non-linearities on the corner frequencies is discussed. The response to a Gaussian (not necessarily white) reactivity insertion and an arbitrary neutron source is also considered in the absence of delayed neutrons.     

Production of a dry sausage from African catfish (Clarias gariepinus, Burchell, 1822): microbial, chemical and sensory evaluations

Production of a dry sausage from African catfish and determination of its microbial, chemical and sensory properties during a 70‐day storage at both 4 and 22 °C were prompted. pH of the samples at 4 and 22 °C did not significantly change during the storage (P > 0.05). Moisture content of the samples was 74%, and reduced to 45% at 4 °C and to 22% at 22 °C. Protein content of the samples was 20.71%, and increased to 42.5% at 4 °C and to 57.99% at 22 °C. Total lipid content was 4.5%, and increased to 10.98% at 4 °C and to 15.68% at 22 °C (P < 0.05). Microbial analyses showed that there was a significant reduction in total aerobic mesophilic and psychrotrophilic bacteria, total mould and yeast, total lactic acid bacteria, total Enterobacteriaceae and Staphylococcus aureus counts at both 4 and 22 °C (P < 0.05). Samples stored at 4 °C had significantly higher sensory ratings than that of the samples stored at 22 °C (P < 0.05).     

Synthesis and characterization of novel polyfuran/poly(2‐iodoaniline) conducting composite

The electrically conducting polyfuran/poly(2‐iodoaniline) (PFu/P2IAn) and P2IAn/PFu composites were prepared by chemical oxidative polymerization using polyfuran and poly(2‐iodoaniline) in HCl and CHCl₃ media. The conductivities of composites were determined as a function of the amount of guest polymer. It was found out that the conductivities of P2IAn/PFu composites increased 100‐fold, whereas the conductivities of PFu/P2IAn composites did not show a specific increase. The composite compositions were altered by varying guest polymer feed ratios during preparation. Generally, the electrical conductivities of P2IAn/PFu composites increased with increasing the amount of PFu. Homopolymers and composites were further characterized thermally, employing thermogravimetry (TGA) and morphologically employing scanning electron microscopy (SEM). Further evidences concerning the polymer structures were obtained by FTIR and UV‐vis spectroscopies and magnetic susceptibility measurements. TGA results revealed that PFu/P2IAn among the homopolymers (PFu and P2IAn) and P2IAn/PFu composite have the highest thermal stability. The composites synthesized varying the host and the guest polymer order have different conductivities, morphological structures, and thermal properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2823–2830, 2003     

Poly(vinyl alcohol)-colloidal silica composite membranes for fuel cells

The aim of this study is to develop an environmentally and friendly poly(vinyl alcohol) based low cost membrane with improved ionic conductivity, thermal and mechanical stability. In this work, the effect of colloidal silica content on membrane properties was investigated. Sulfosuccinic acid (SSA) was used as the sulfonating agent. In order to enhance the mechanical and ionic conduction properties, colloidal silica was used. The range of silica content in the membrane solution investigated was 5–20%. For the characterizations, the synthesized membranes were subjected to FT-IR, TGA, tensile strength analysis, water uptake, ion exchange capacity (IEC) and impedance measurements for proton conductivity. Synthesized membranes demonstrated high water uptake (up to 80%) without swelling, high ion exchange capacities was found to increase with increasing SSA content. The proton conductivity of CS doped membranes increased with increase in temperature and the temperature dependence showed significant change in the CS doped membranes. An increase in the values of the proton conductivity was driven by the mobility of free charges (free ions) as the temperature was increased. Addition of SSA and CS to the polymer matrix improved the thermal stability of the membranes. It was also discovered that membranes were in a composite structure and colloidal silica particles did not contribute to the structure of the polymer matrix at the molecular level. Mechanical durability of the membranes having SSA content above 15% decreased and these membranes showed a more fragile structure.     

Theoretical investigation of the proton effect on electropolymerization of aniline

The effect of the protonation on electropolymerization of aniline was elucidated theoretically. It was shown that the proton effects stabilities of p-aminodiphenylamine which is the primary species formed following electrooxidation in acidic media. The position of protonation is elucidated. Geometrical optimizations and calculated energies (strain and total energy and heat of formation) and proton affinity values predict that the p-aminodiphenylamine is preferably protonated on the amine nitrogen between the phenyl rings. It is concluded that the polymer backbone is relaxed and the strained structure is removed upon stepwise protonation during the growth of the polymer.     

Determination of impedance parameters for mild steel/HCl interface using integration method

Impedance measurements for the interface between mild steel/hydrochloric acid as a function of cysteine (Cys) concentration were carried out for a wide enough frequency range. The validity of the impedance data was checked using the Kramers–Kronig (K–K) transforms. Despite the deviations at low frequencies for both transforms, imaginary-to-real and real-to-imaginary, a successful fit for the high frequencies was reached. The impedance parameters were determined from imaginary component of experimental impedance vs. logf diagrams using integration method and from complex plane plots fitting experimental results to an appropriate equivalent circuit. A compromise of parameters from two different plot methods was seen.     

铜添加对近共晶Al-Si-xCu合金的微观组织和硬度的影响

研究铜含量对Al-Si-xCu（x=2%,3%,4%and5%）合金的微观组织和硬度的影响。不同铜含量的铝合金经熔炼后于690°C铸造成湿砂模并固化,于500°C保温7h进行固溶处理后对样品进行水冷。随后于190°C进行时效处理,分别保温5,10和15h,研究时效时间对基体硬度的影响。采用差热分析法,在冷却速度30K/min下确定平衡相的转变温度,并研究铜含量对四元共晶合金的形成和α（Al）＋Si熔点的影响。结果表明,随着铜含量的增加,发生析出硬化从而导致基体硬度增加,α（Al）＋Si的熔点降低,共晶相的含量增加。当铜含量超过2%时,生成熔点为507°C的四元共晶相。     

Oxalate Ion Decomposition under UV Light from Low Pressure Mercury Vapor Lamps

Kinetics of oxalate ion decomposition under UV light from low pressure mercury vapor lamps (LPMVL) was studied in a batch reactor. The effects of UV light intensity (1.38×10^?6 to 5.27×10^?6 EL^?1s^?1, where E: Einstein or 1 mole of photons), temperature (15?35°C), initial oxalate concentration ((2.05?21.1)?×?10^?5 M), initial pH (5.45?8.94) and alkalinity (0–50 mg L^?1 as CaCO₃) on the photodecomposition kinetics of oxalate in de-ionized water were investigated. Oxalate decay followed split-rate pseudo-first-order kinetics. The decay rate constants decreased with increasing initial oxalate concentration, initial pH, alkalinity and temperature, but increased with UV light intensity. Solution pH increased during oxalate decomposition and reached a plateau as oxalate reached the analytical detection limit in de-ionized water. Addition of carbonate alkalinity virtually eliminated the pH profile. Time-dependent profiles for non-purgeable organic carbon (NPOC) and total carbon (TC) showed that the carbon not accounted for in NPOC is likely to have been converted to CO₂. The pH profile of oxalate decay was estimated using closed system carbonate equilibrium analysis. The dissolved oxygen (DO) utilization during oxalate decay ranged between 0.3–0.8 mol O₂ / mol oxalate. The effect of DO and the decay of natural dissolved organic carbon (DOC) were also explored. Natural DOC retarded oxalate photodecomposition. The decay rate constants were slightly lower in the absence of DO.     

Influence of Ti addition on the microstructure and hardness properties of near-eutectic Al–Si alloys

In this study, the influence of Ti addition on the microstructure and hardness of near-eutectic Al–Si has been investigated. Near-eutectic Al–Si alloys (13.1 wt.% Si) with 0.1, 1, 2, 3, 5, and 10% Ti have been utilized for this purpose. The melting operation was carried out in an electrical furnace, where the charge materials were placed in a graphite crucible. After melting, alloys have been cast in the metal mold at 1100 °C and solidified.     

ORACM: Online region-based active contour model

A new online region-based active contour model (ORACM) is proposed in this paper. The classical geodesic active contour (GAC) model has only local segmentation property, although the Chan–Vese (C–V) model possesses global. An up-to-date active contour model (ACM with SBGFRLS) proposed in Zhang, Zhang, Song, and Zhou (2010) both has the properties of global/local segmentation and incorporates the GAC and the C–V models to raise active contours’ performance on image segmentation. However it has two major disadvantages. First, it deforms the active contour model just using the gradient of current level set iteratively and so works too slowly. Second, it needs a parameter α which plays major impact on the results and to be tuned according to input images. The proposed model ORACM eliminates these two disadvantages by using a new binary level set formula and a new regularization operation such as morphological opening and closing. Without changing segmentation accuracy, ORACM requires no parameter and less time over the traditional ACMs. Experiments on synthetic and real images demonstrate that the computational cost of ORACM with the morphological operations is 3.75 times less than the traditional ACMs on average.