Silver nanocluster formation in silicate glass by single step ion-exchange

We report the formation of silver nanoclusters of average size ∼ 1.1 nm in a single step ion-exchanged silica glass. Silver clusters are formed in a glass during ion-exchange by fine-tuning the ion-exchange parameters such as salt composition, temperature and time. Such nanocluster formation during ion-exchange preserves the waveguiding properties of the ion-exchanged surface of the glass making them suitable for nonlinear waveguide device fabrication.     

The influence of Johnson–Cook material constants on finite element simulation of machining of AISI 316L steel

In literature, five different sets of work material constants used in the Johnson–Cook's (J–C) constitutive equation are implemented in a numerical model to describe the behaviour of AISI 316L steel. The aim of this research is to study the effects of five different sets of material constants of the J–C constitutive equation in finite-element modelling of orthogonal cutting of AISI 316L on the experimental and predicted cutting forces, chip morphology, temperature distributions and residual stresses. Several experimental equipments were used to estimate the experimental results, such as piezoelectric dynamometer for cutting forces measurements, thermal imaging system for temperature measurements and X-ray diffraction technique for residual stresses determination on the machined surfaces; while an elastic–viscoplastic FEM formulation was implemented to predict the local and global variables involved in this research. It has been observed that all the considered process output and, in particular the residual stresses are very sensitive to the J–C's material constants.     

Experimental investigation of adsorption of NO and SO2 on modified activated carbon sorbent from flue gases

It is indicated that modified carbon is a practical sorbent for removal of NO and SO₂ from waste gases by the adsorption method. The ideal compositions for the prepared sorbent were 4.0 wt.% and 2.5 wt.% Na₂CO₃ and KOH at the experimental conditions, respectively, shortened as ACNaK_2.5. Experimental investigation showed that the sorbent had a comparatively high breakthrough adsorption capacity of NO and SO₂, about 5.8 g (NO + SO₂)/100 g sorbent. It is indicated that a relatively high adsorption temperature would benefit the sorbent adsorption capacities on NO and SO₂ at a certain space velocity and pressure. Further study revealed that the ACNaK_2.5 sorbent had good regenerability at the experimental conditions, which implied that the ACNaK_2.5 sorbent would be a useful sorbent for simultaneous removal of NO and SO₂ from waste gases by adsorption.     

An adsorption behavior of low-density lipoprotein onto cholesterol-modified dextran studied by a quartz crystal microbalance

The use of quartz crystal microbalance (QCM) for on-line monitoring of the adsorption of low-density lipoprotein (LDL) onto cholesterol-modified dextran (CMD) was described. Kinetics studies were made and molecule interaction mechanism was discussed. Experimental results showed that kinetic curves fitted Langmuir adsorption equation quite well. When LDL concentrations (ng/μl) were 9.9, 12.38 and 14.14, respectively, the apparent rate constants (s^− 1) and adsorption capacities (ng/cm²) were estimated to be 0.0477, 0.0536, 0.0628 and 124.5, 161.6, 194.3, respectively. The maximal LDL adsorption capacity attained 329.6 ng/cm² and the adsorptive efficiency was calculated to be 72.91%. Moreover, a new method to evaluate the adsorption behavior was provided.     

A critical transition state in liquid metals

Temperature dependence of viscosities of liquid Sn, Cu, Pb_38.1Sn_61.9, Pb_44.8Bi_55.2, and Cu_0.7Sn_99.3 has been studied by a torsional oscillation viscometer. During the measurement process, a deviation from the Arrhenius behavior is found when the temperature is lowered to about 60 K higher than the melting point. The abnormal increasing of the viscosity and the activation energy indicates the changes of the elementary melt structure during cooling towards the melting point. The deviation region from Arrhenius viscosity is defined as the transition state. The differential scanning calorimeter experiments also show the existence of the critical transition state in liquid metals near the melting point. The drastic increase of the viscosity in the transition state can be regarded as continuum transition and be presented well by the amended Arrhenius equation which is based on the critical phenomenon.     

The effect of zirconium addition on the microstructure and properties of chopped carbon fiber/carbon composites

Carbon/carbon composites containing zirconium were prepared using chopped carbon fiber, mesophase pitch and Zr powder by the traditional process including molding, carbonization, densification and graphitization. The influence of Zr on the microstructure and properties of the composites were investigated. Results show that Zr can improve the interface bonding, promote more perfect and larger crystallites and enhance the conductive/mechanical properties of the composites. The high in-plane thermal conductivity of 464 W/(m K) and excellent bending strength of 83.6 MPa was obtained for a Zr content of 13.9 wt% at heat treatment temperature(HTT) of 2500 °C. However the conductive/mechanical properties of the composites decrease dramatically for an higher HTT of 3000 °C. SEM micrograph of the fracture surface for the composites shows that lower disorder crystallite arrangement of fiber and carbon matrix come into being in the composites during HTT of 3000 °C, which should be responsible for the low properties. Correlation between the content of Zr and the microstructure and properties are discussed.     

Priority mix planning for semiconductor fabrication by fuzzy AHP ranking

With today’s keen competition, semiconductor market has changed from producer-oriented to customer-oriented. To be successful, companies need to consider both customer satisfaction in demand and the ultimate profit goal of companies. Semiconductor fabricators today must face an environment with multi-product types and multi-priority orders. Since semiconductor fabrication has a very complicated production process, the production planning of different products types and priority levels is an even more difficult task to experts. The objective of this study is to construct an analytical approach under a fuzzy subjective judgment environment, in which fuzzy analytic hierarchy process (AHP) method with entropy weight is utilized to deal with uncertainty, to generate performance ranking of different priority mixes. The results provide guidance to experts in a fab regarding strategies for accepting orders with the consideration of manufacturing efficiency in the aspects of product, equipment efficiency and finance.     

Use of the time constant to detect corrosion speed in reinforced concrete structures

The relatively simple to measure ‘time constant’ is presented as an index for characterizing the level of corrosion experienced by steel in concrete. This communication, largely in the form of a technical note, explicitly illustrates that the time constant determined from electrochemical testing has significant merit for monitoring corrosion of steel in concrete, and appears to be insensitive to the area of electrode being probed. In this work, the time constant, κ, is determined following a galvanostatic excitation signal, revealing a good correlation between the value of κ and corrosion status across specimens of widely varying geometry. Although this notion has been suggested in the past, this work presents both a survey and consolidated review to indicate the utility of the parameter as an index to corrosion rate on-site.     

Electrochemical detection of catechol at integrated carbon nanotubes electrodes

The mechanical stability of the electrode plays a very important role in the long-term stability of electrochemical behavior. In this paper, multi-wall carbon nanotubes (MWCNTs) electrodes were prepared in the holes of glass directly by microwave plasma chemical vapor deposition and the electrochemical behavior of catechol at the integrated MWCNT electrodes was investigated. The oxygen plasma treated CNTs had excellent electrochemical behavior for the analysis of catechol. The catechol was detected in the linear concentration range of 1.0 × 10^− 6 mol L^− 1–1.0 × 10^− 3 mol L^− 1. And because CNTs were integrated directly on the substrate, the stable response to catechol solution showed that the carbon nanotubes electrodes had long-term stability.     

Detection of acylated homoserine lactones in gram-negative proteolytic psychrotrophic bacteria isolated from cooled raw milk

Through a mechanism called quorum sensing, bacteria are able to express specific genes in response to population density. Cell-to-cell communication in bacteria is mediated by signal molecules such as acylated homoserine lactones (AHLs). This work aimed to detect AHL production in Gram-negative psychrotrophic bacteria isolated from raw milk. A total of 84.9% of the bacteria were identified as AHL producers eliciting a diversity of responses in the AHL-monitor systems. These results demonstrate that AHL-production is common among psychrotrophic bacteria isolated from milk, and indicate that quorum sensing may play an important role in the spoilage of this product.