Effects of equivalence and fuel ratios on combustion characteristics of an RCCI engine fueled with methane/n-heptane blend

Rising fuel costs and efforts for reducing greenhouse gases have led researchers to propose optimized models of combustion which have high efficiency and low emissions. Reactivity controlled compression ignition (RCCI) engines are attractive due to their high efficiency and low NO_x and soot emissions over a wide range of operating conditions. In this study, methane and n-heptane are used as low and high reactive fuels, respectively, to create suitable fuel stratification within the cylinder. Modeling is carried out by AVL FIRE coupled with a chemical kinetics solver to investigate the effects of fuel ratio, initial temperature and equivalence ratio on the combustion performance and emission characteristics. Methane/n-heptane ratios are varied according to the energy ratio of each fuel while total input energy and total equivalence ratios are fixed. By increasing methane energy ratio from 65% to 85% in the constant intake temperature and pressure, the mixture Octane number increases, which would lead to an increase in ignition delay up to 5 crank angles. As a result, IMEP would be enhanced and also NO_x emission decreases because of lower combustion temperature. By increasing intake temperature, the maximum in-cylinder pressure, heat release rate and NO_x emission would increase significantly while soot emission decreases, and also ringing intensity increases up to 10%. On the other hand, increasing intake temperature reduces volumetric efficiency; as a result, IMEP is reduced by 11%. Also by increasing equivalence ratio from 0.35 to 0.55 in a constant energy ratio, noticeable growth in the maximum amount of pressure and temperature could be achieved; consequently, NO_x emission would increase significantly, IMEP increases by 43%, and ISFC decreases by 30%. The results indicate that these parameters have significant effects on the heavy-duty RCCI engine performance and emissions.

     

Mass Activated Droplet Sorting (MADS) Enables High-Throughput Screening of Enzymatic Reactions at Nanoliter Scale

Microfluidic droplet sorting enables the high-throughput screening and selection of water-in-oil microreactors at speeds and volumes unparalleled by traditional well-plate approaches. Most such systems sort using fluorescent reporters on modified substrates or reactions that are rarely industrially relevant. We describe a microfluidic system for high-throughput sorting of nanoliter droplets based on direct detection using electrospray ionization mass spectrometry (ESI-MS). Droplets are split, one portion is analyzed by ESI-MS, and the second portion is sorted based on the MS result. Throughput of 0.7 samples s⁻¹ is achieved with 98 % accuracy using a self-correcting and adaptive sorting algorithm. We use the system to screen ≈15 000 samples in 6 h and demonstrate its utility by sorting 25 nL droplets containing transaminase expressed in vitro. Label-free ESI-MS droplet screening expands the toolbox for droplet detection and recovery, improving the applicability of droplet sorting to protein engineering, drug discovery, and diagnostic workflows.     

Synthesis and characterization of a novel hydroxy terminated polydimethylsiloxane and its application in the waterborne polysiloxane–urethane dispersion for potential marine coatings

α‐Butyl ω‐N, N‐dihydroxyethyl aminopropylpolymethylhydrosiloxane (PDMS), a monotelechelic polydimethylsiloxane with a diol‐end group, which is used to prepare siloxane–urethane dispersion, was successfully synthesized. Then, novel silicone‐based polyurethane (PU)‐dispersion was prepared by the addition polymerization of hexamethylene diisocyanate, to PDMS, polyethylene glycol (PEG) and dimethylol propionic acid. The goal of this study was to explore the potential use of polysiloxane–urethane in marine coatings in order to boost the flexibility, adhesion, erosion and foul‐release property with respect to PDMS/PEG ratio (PDMS wt%). The PDMS was characterized by Fourier‐transform infrared (FT‐IR), proton nuclear magnetic resonance and carbon‐13 nuclear magnetic resonance spectroscopic techniques. The results showed that each step was successfully carried out and the targeted products were synthesized in all cases. The structural elucidation of the synthesized waterborne PU and waterborne polysiloxane–urethane (WBPSU) was carried out by FT‐IR spectroscopic technique. Thermal properties of the resins were studied by using thermogravimetric analysis and differential scanning calorimetry. The antifouling property of the coatings was investigated by the immersion test under a marine environment for 90 days. The fouled area was calculated for all the samples, and the fouled area (%) decreased with increasing PDMS content. After 90 days, the lowest fouled area (6%) was observed in the sample using WBPSU2 (PDMS 4.48 wt%) among all of the samples. Copyright © 2012 John Wiley & Sons, Ltd.     

Electrochemical preparation of effective and low cost catalyst for electrooxidation of ethanol

A nanocatalyst coating was prepared at surface of a glassy carbon electrode by electropolymerization of pyrrole by cycling the electrode potential between ?0.8 and 0.8 V (vs. Ag/AgCl). Then, polypyrrole film was potentiostatically coated with platinum nanoparticles at constant potential of ?0.2 V (vs. Ag/AgCl). The resulting electrode was denoted as GCE/PPy/Pt. This modified electrode was characterized by IR, SEM, TEM and EDX. The electrocatalytic oxidation of ethanol at the GCE/PPy/Pt has been investigated using cyclic voltammetric and chronoamperometric methods. The effects of various parameters on electrocatalytic oxidation of the ethanol, such as the thickness of PPy film, the amount of platinum nanoparticles, ethanol concentration, potential scan rate and working potential limit in anodic direction, were investigated. The kinetic of the ethanol oxidation is discussed on the GCE/PPy/Pt. The stability and reproducibility of this modified electrode were also studied.     

Spectral features of Co–Ge–Te amorphous thin film

Optical spectral features of Co_xGe_yTe_100?x?y amorphous thin films where 10≤x≤35 and 41≤y≤47 were studied for the first time. The transmittance and reflectance at normal incidence have been measured at room temperature in the spectral range 190–2500 nm. Refractive index and extinction coefficient have been evaluated in the above spectral range. Band tail width and energy gap were strongly affected by cobalt concentration in the “as prepared” amorphous thin film. Absorption band spectrum on the basis of the imaginary parts of the dielectric constant, ε₂, ε_1, refractive index, and extinction coefficient are also affected by cobalt content. On the other hand, the band edge parameter β remains almost constant.     

On the stability of adaptation process in active noise control systems

The stability analysis of the adaptation process, performed by the filtered-x least mean square algorithm on weights of active noise controllers, has not been fully investigated. The main contribution of this paper is conducting a theoretical stability analysis for this process without utilizing commonly used simplifying assumptions regarding the secondary electro-acoustic channel. The core of this analysis is based on the root locus theory. The general rules for constructing the root locus plot of the adaptation process are derived by obtaining root locus parameters, including start points, end points, asymptote lines, and breakaway points. The conducted analysis leads to the derivation of a general upper-bound for the adaptation step-size beyond which the mean weight vector of the active noise controller becomes unstable. Also, this analysis yields the optimum step-size for which the adaptive active noise controller has its fastest dynamic performance. The proposed upper-bound and optimum values apply to general secondary electro-acoustic channels, unlike the commonly used ones which apply to only pure delay channels. The results are found to agree very well with those obtained from numerical analyses and computer simulation experiments.     

Effect of the conversion degree and multiple healing on the healing efficiency of a thermally reversible self‐healing polymer

In this paper, the effect of the cross‐links' conversion degree on the healing efficiency of a thermally remendable polymer based on the Diels‐Alder (DA) reaction was studied quantitatively. By using the differential scanning calorimetry (DSC) results along with the Kissinger method, the conversion degree of the thermally reversible cross‐links was predicted as a function of time and temperature. For investigating the healing efficiencies at different conversion degrees, three‐point bending specimens were fabricated under certain curing conditions, which guaranteed the formation of both reversible and irreversible bonds. Afterward, specimens failed under three‐point bending test and healed up to certain conversion degrees. The results revealed on average 15%, 38%, and 83% recovery of flexural strength and 89%, 91%, and 93% recovery of flexural modulus at conversion degrees of 0.6, 0.8, and 1, respectively. Moreover, by repeating the damaging and healing procedure, it was shown that the synthesized polymer has the capability to be healed several times.     

Microfluidic characteristics of a multi-holed baffle plate micro-reactor

As part of a larger project aiming at development of a miniaturized hydrogen generator for small mobile/onboard fuel cell applications, a series of experiments was conducted on a novel micro-reactor to examine the effectiveness of its design in promoting the mixing of reactant agents. The reactor is essentially a tubular vessel fitted with a multi-holed baffle plate mounted on a central tube. The mixing phenomenon within the micro-reactor was studied using the micro-PIV (micro-particle image velocimetry) flow visualization technique. Experiments were conducted on a 1:1 scale replica of the reactor. Results indicate that the application of the multi-holed baffle plate considerably improves the mixing performance of the reactor when compared with a simpler co-axial jet tubular reactor. However, the geometrical characteristics of the baffle plate and central tube are found to have dramatic impacts upon the flow structure and mixing patterns within the reactor. Hence, the optimization of the reactor geometry is required to achieve the desirable mixing performance. For the range of Reynolds numbers studied here, the optimum reactor geometry is achieved when the central tube and baffle holes are of similar diameters and baffle holes are located half way between the stream-wise axis and the reactor wall.     

Construction of an Amperometric Glucose Biosensor by Immobilization of Glucose Oxidase on Nanocomposite at the Surface of FTO Electrode

Fluorine? tin oxide (FTO) nanostructure was developed on the surface of a glass plate using spray payroliziz method. A new electrochemical biosensor was fabricated based on a layer by layer process. In this process chitosan? Fe₃O₄ (CH? Fe₃O₄) nanocomposite film was prepared at the surface of FTO electrode by dip? coating method. In the next step, the glucose oxidase (GOx) was immobilized on the CH? Fe₃O₄/FTO nanocomposite electrode. The GOx/CH? Fe₃O₄/FTO bioelectrode has a linear range of 10–270 µM and a detection limit of 5 µM. The highest sensitivity was obtained at 1.2 µA mM^?1 cm^?2.     

Sensitivity Enhancement in Nickel Hydroxide/3D‐Graphene as Enzymeless Glucose Detection

A nickel hydroxide (Ni(OH)₂)/3D‐graphene composite is used as monolithic free‐standing electrode for enzymeless electrochemical detection of glucose. Ni(OH)₂ nanoflakes are synthesized by using a simple solution growth procedure on 3D‐graphene foam which was grown by chemical vapor deposition (CVD). The pore structure of 3D‐graphene allows easy access to glucose with high surface area, which leads to glucose detection with an ultrahigh sensitivity of 3.49 mA mM^?1 cm^?2 and a significant lower detection limit up to 24 nM. Cyclic voltammetry (CV) and potentionstatic mode is used for non‐enzymatic glucose sensing. The impedance and effective surface area have been studied well. The high sensitivity, low detection limit and simple configuration of Ni(OH)₂/three dimensional (3D)‐graphene composite electrodes can evoke its industrial application in glucose sensing devices.