A comprehensive assessment of the performance of corrosion resistant alloys in hot acidic brines for application in oil and gas production

Four stainless steels and alloys (17-4 PH, X4CrNiMo 16-5-1, F6NM and UNS N09935) were evaluated in relation to their application in the oil and gas industry. These materials were tested in solutions exhibiting a range of chloride concentrations, pH values and temperatures of interest for the oil and gas producing environments. The pitting sensitivity was investigated by means of potentiodynamic polarisation measurements, based on the ASTM G61 standard, in conjunction with a morphological study performed by scanning electron and optical microscopy. The resistance to stress corrosion cracking (SCC) was evaluated in compliance with the ASTM G123 standard. Erosion–corrosion was assessed by exposing the materials under electrochemical control to a flux of erodent glass microspheres in a rotating disc electrode device. A ranking of the materials resistance was derived, based on appropriate parameters, devised to effectively and synthetically represent the complex sets of environments of interest for the relevant application. Our results showed, as expected, that UNS N09935 displays the best performance with respect to pitting resistance and susceptibility to SCC as well as a very good resistance to erosion–corrosion. Among the other investigated materials, 17-4 PH showed higher resistance to pitting, X4CrNiMo 16-5-1 and F6NM longer time to SCC failure while 17-4 PH and X4CrNiMo 16-5-1 exhibited superior ability to withstand erosion–corrosion damaging.     

Effects of depleting ionic strength on 31P nuclear magnetic resonance spectra of micellar casein during membrane separation and diafiltration of skim milk

Membrane separation processes used in the concentration and isolation of micellar casein-based milk proteins from skim milk rely on extensive permeation of its soluble serum constituents, especially lactose and minerals. Whereas extensive literature exists on how these processes influence the gross composition of milk proteins, we have little understanding of the effects of such ionic depletion on the core structural unit of micellar casein [i.e., the casein phosphate nanocluster (CPN)]. The ³¹P nuclear magnetic resonance (NMR) is an analytical technique that is capable of identifying soluble and organic forms of phosphate in milk. Thus, our objective was to investigate changes to the ³¹P NMR spectra of skim milk during microfiltration (MF) and diafiltration (DF) by tracking movements in different species of phosphate. In particular, we examined the peak at 1.11 ppm corresponding to inorganic phosphate in the serum, as well as the low-intensity broad signal between 1.5 and 3.0 ppm attributed to casein-associated phosphate in the retentate. The MF concentration and DF using water caused a shift in the relevant ³¹P NMR peak that could be minimized if orthophosphate was added to the DF water. However, this did not resolve the simultaneous change in retentate pH and increased solubilization of micellar casein protein. The addition of calcium in combination with orthophosphate prevented micellar casein solubilization and simultaneously contributed to preservation of the CPN structure, except for overcorrection of retentate pH in the acidic direction. A more complex DF solution, involving a combination of phosphate, calcium, and citrate, succeeded in both CPN and micellar casein structure preservation while maintaining retentate pH in the region of the original milk pH. The combination of ³¹P NMR as an analytical technique and experimental probe during MF/DF processes provided useful insights into changes occurring to CPN while retaining the micellar state of casein.     

GPR data enhancement via multiple reflections' filtering

Based on a classification methodology for multiple reflections' (MR) identification recently published by the authors, this work proposes a filtering technique for GPR data to be integrated within the layer stripping (LS) approach. In LS, the reconstruction of the dielectric stack is obtained by recursively inverting the signals backscattered by each layer, from the top to the bottom. According to the state‐of‐the‐art, to simplify the solution of the problem, MR are commonly neglected. The scope of this article is therefore to first discuss the implementation of the MR filtering procedure within a LS algorithm and evaluate from the quantitative point of view which improvements this will yield to the overall performances. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Cobalt-based nanoparticles as catalysts for low temperature hydrogen production by ethanol steam reforming

Results obtained in the synthesis, characterization and application as catalyst of cobalt nanoparticles are reported. Cobalt nanoparticles were prepared via reduction method in aqueous solution. Structural characterization was carried out using X-ray diffraction (XRD), morphological studies were performed with a scanning electron microscope equipped with a field emission gun (FE-SEM). A DC-superconducting quantum interference device “SQUID” magnetometer was used to measure the room temperature (RT) magnetic hysteresis cycle in the −5 ÷ 5 Tesla (T) μ₀H magnetic field range as well as magnetization as a function of temperature. This material is constituted by very small primary particles (∼2.8 nm radius) which appear amorphous to XRD and have a superparamagnetic behaviour. However, annealing at 773 K and also utilization in the catalytic reactor at the same temperature result in XRD detectable cubic Co nanocrystals. These unsupported cobalt nanoparticles were found catalytically active in the ethanol steam reforming reaction, producing hydrogen with 90% yield at 773 K. These nanoparticles show a better catalytic behaviour compared to those of more conventional Co and Ni based catalysts, due to very low CO and methane production, and with moderate formation of carbonaceous materials.     

The characteristics of percolation olive oils produced with a new processing enzyme aid

Theee olive varieties ( Leccino , Coratina and Dritta ) were processed using the percolation–centrifugation system with a new olive enzyme processing aid, 'Cytolase 0'. The enzyme adjuvant led to oils characterized (with respect to reference oils) mostly by: (i) higher contents of total phenols, o -diphenols, tyrosol- and hydroxytyrosol-aglycones, tocopherols, trans -2-hexenal and other pleasant aromatic volatile compounds, and triterpene alcohols; (ii) higher values of oxidative stability and carotenoid colour index; (iii) higher ratios of 1,2-diglycerides/1,3-diglycerides, campesterol/stigmasterol, trans -2-hexenal/hexanal, and trans -2-hexenal/total aroma; (iv) lower values of turbidity; (v) similar values of acidity, peroxide index, carbonyl index, UV (ultraviolet) spectrophotometric indices and alcoholic index; (vi) similar contents of saturated fatty acids, unsaturated fatty acids, triglycerides, diglycerides, sterols, and green lipochromes; and (vii) similar sensory score. Stigmastadienes, trans -oleic, trans -linoleic, and trans -linolenic acid isomers were not detected. Hence, the enzyme adjuvant produced better qualitative characteristics and higher extraction outputs.     

Clock and data recovery IC for 40-Gb/s fiber-optic receiver

The integrated clock and data recovery (CDR) circuit is a key element for broad-band optical communication systems at 40 Gb/s. We report a 40-Gb/s CDR fabricated in indium-phosphide heterojunction bipolar transistor (InP HBT) technology using a robust architecture of a phase-locked loop (PLL) with a digital early-late phase detector. The faster InP HBT technology allows the digital phase detector to operate at the full data rate of 40 Gb/s. This, in turn, reduces the circuit complexity (transistor count) and the voltage-controlled oscillator (VCO) requirements. The IC includes an on-chip LC VCO, on-chip clock dividers to drive an external demultiplexer, and low-frequency PLL control loop and on-chip limiting amplifier buffers for the data and clock I/O. To our knowledge, this is the first demonstration of a mixed-signal IC operating at the clock rate of 40 GHz. We also describe the chip architecture and measurement results.     

A New Label-Free Impedimetric Affinity Sensor Based on Cholinesterases for Detection of Organophosphorous and Carbamic Pesticides in Food Samples: Impedimetric Versus Amperometric Detection

Due to their increasing use in agriculture, the presence of pesticide residues in food and water currently represents one of the major issues for the food safety. Among the pesticides, organophosphate and carbamate species are the most used, and their toxicity is mainly due to their inhibitory effect on acetylcholinesterase (AChE). For this reason, a monoenzymatic acetylcholinesterase impedimetric biosensor was developed in order to sensitively detect carbamate and organophosphate compounds with a very fast response. The working principle of the AChE biosensor exploits the capability of carbamate and organophosphate pesticides to form a stable complex with the enzyme, which causes an impedimetric change. The impedimetric biosensor showed a linearity between 5 and 170 ppb for carbamates and 2.5–170 ppb for organophosphate compounds, with a reproducibility (RSD%) interelectrode equal to 4.8 and 3.1% for organophosphates and carbamates, respectively. Moreover, the common amperometric evaluation of AChE inhibition degree was correlated to the impedimetric changes of the electrode surface, showing a good correlation (R ² = 0.99 for carbamates and R ² = 0.98 for organophosphates) between the two methods. In contrast to amperometric evaluation that needs a response time of 20 min, impedimetric detection requires only 4 min. Finally, the impedimetric biosensor was used to measure carbaryl and dichlorvos spiked in different concentrations in tap water and lettuce samples, showing a recovery near to 100% for all concentrations and for both pesticides.     

A portable class of 3‐transistor current references with low‐power sub‐0.5 V operation

This work proposes a new class of current references based on only 3 transistors that allows sub‐0.5 V operation. The circuit consists of a 2‐transistor block that generates a proportional‐to‐absolute‐temperature or a complementary‐to‐absolute‐temperature voltage and a load transistor. The idea of a 3T current reference is validated by circuit simulations for different complementary metal‐oxide‐semiconductor technologies and by experimental measurements on a large set of test chips fabricated with a commercial 0.18 μm complementary metal‐oxide‐semiconductor process. As compared to the state‐of‐art competitors, the 3T current reference exhibits competitive performance in terms of temperature coefficient (578 ppm/°C), line sensitivity (3.9%/V), and power consumption (213 nW) and presents a reduction by a factor of 2 to 3 in terms of minimum operating voltage (0.45 V) and an improvement of 1 to 2 orders of magnitude in terms of area occupation (750 μm²). In spite of the extremely reduced silicon area, the fabricated chips exhibit low‐process sensitivity (2.7%). A digital trimming solution to significantly reduce the process sensitivity is also presented and validated by simulations.     

Analysis of energy demand in residential buildings for different climates by means of dynamic simulation

The aim of the present paper is to propose an analysis of energy consumption of a standard building in different climates. The analysis is developed by simulating the dynamic behaviour of the building subjected to different climatic conditions according to the considered location. Simulations are performed by means of an in-house developed code, validated by comparison with the outcomes from leading software, particularly TRNSYS and EnergyPlus. The use of a self-developed code guarantees a high flexibility and allows the implementation of new capabilities if necessary. The impact on the energy consumption of various parameters, namely internal and external wall insulation, window surface areas, thermal capacity and orientation, is investigated. Results show that the insulation of external walls has a fundamental role in reducing energy consumption, because it allows to exploit the thermal capacity of the walls. This is particularly useful for buildings which necessitate to keep the internal temperature constant.