Synthesis of new extended surfactants containing a carboxylate or sulfate polar group

New extended anionic surfactants with a carboxylate or sulfate polar head were synthesized from polypropoxylated alcohols, and their structures were confirmed by ¹H and ¹³C nuclear magnetic resonance analysis. The extended surfactant critical micelle concentration was found to decrease with the length of the polypropylene glycol spacer. Surfactants containing a diethylene glycol link to the head group exhibited a higher critical micelle concentration than did their nondiethoxylated homologs.     

Design methodology for fully dynamic-controlled polynomial profiles and reduced tracking error in CNC machines

High speed and high precision on computer numerically controlled (CNC) machines are major issues for most industrial automation processes. Among the most important factors for precise motion control are the control law, the controller implementation, and the profile reference. The effects of the control law and controller implementation on the tracking error in CNC machines have been widely studied, while the issue of profile reference has not received the required attention. To improve the dynamics provided by the conventional profile reference, several techniques have been proposed, focusing on peak jerk limitation. The novelty of this work is to develop a generalized methodology designed for producing dynamically constrained higher degree piecewise polynomial profiles, without limits in maximum polynomial degrees. They lead to define in an arbitrary way the dynamics shape, while the peak dynamics values constrained are maintained in order to improve the tracking error on CNC systems and giving the possibility to design fully dynamic-controlled trajectories. For experimentation purposes, a two-axis proportional–integral–derivative controller and profile reference generator are implemented in a low-cost field programmable gate array. The experimentation demonstrates the efficiency of the proposed methodology, showing the peak jerk and tracking error reduction, compared against recent reports from literature.     

Electromagnetic Modeling of Quasi‐Square Open Metallic Ring Frequency Selective Surface Using Wave Concept Iterative Procedure

The wave concept iterative procedure (WCIP) is used to analyze a quasi‐square open metallic ring frequency selective surface (FSS). The quasi‐square open metallic ring FSS is dual‐polarized. When the incident plane wave is polarized in a direction parallel to the FSS’ coupled parallel strips, it shows two rejecting bands. Moreover, another rejecting band can be obtained if the source plane wave is perpendicularly polarized with respect to the FSS’ coupled parallel strips. The three resonant frequencies are inversely proportional to the length of the FSS’ coupled strips to provide an easy fine tuning of the FSS structure. The simulated results obtained using WCIP are compared to the measured results, and a good agreement is reported.     

在超高精度电压基准中利用滤波器降低I/f噪声

本文在分析了电压基准中 I／f噪声特点的基础上,提出了滤除此噪声的滤波器设计方案,此方案可满足超高精度的应用要求。     

Seasonal changes and temperature-dependent accumulation of polycyclic aromatic hydrocarbons in high-altitude soils

Polycyclic Aromatic Hydrocarbons (PAHs) are a major group of pollutants whose occurrence in the environment is mainly of anthropogenic origin. In this paper, we examine the effect of topographical slope exposure on PAH contamination and seasonal change in PAH concentrations in soils. We collected soil samples on three dates in 2007 (early May, end of July and beginning of November) from south- and north-facing aspects at 1900 m a.s.l. in the central Italian Alps. We found greater PAH contamination in soils from a north-facing slope than in those from a south-facing slope at all seasons. We calculated North-South Enrichment Factors as the ratio between the concentrations measured in soils from northern and southern aspects. These ratios ranged from 1.4 to 1.9 for lighter PAHs (from 2 to 4 rings). These values are consistent with theoretical calculations based on temperature-specific octanol-air partition coefficients (predicted North-South Enrichment Factors range from 1.6 to 2.0). For heavier PAHs (from 5 to 6 rings), smaller differences were observed between soils from northern and southern aspects, due to the gas/particle distribution of these compounds. We also found consistent differences in normalised PAH concentrations across the three sampling periods. The majority of compounds showed a significant decreasing trend from the beginning of May to the end of July, due to the annual cycles of physical processes (deposition vs. volatilisation) and biological processes (uptake and/or biotransformation). Only a few compounds showed different trends, presumably due to season-specific local emission sources.     

Exploring time series retrieved from cardiac implantable devices for optimizing patient follow-up

Current cardiac implantable devices (IDs) are equipped with a set of sensors that can provide useful information to improve patient follow-up and prevent health deterioration in the postoperative period. In this paper, data obtained from an ID with two such sensors (a transthoracic impedance sensor and an accelerometer) are analyzed in order to evaluate their potential application for the follow-up of patients treated with a cardiac resynchronization therapy (CRT). A methodology combining spatiotemporal fuzzy coding and multiple correspondence analysis (MCA) is applied in order to: 1) reduce the dimensionality of the data and provide new synthetic indexes based on the "factorial axes" obtained from MCA; 2) interpret these factorial axes in physiological terms; and 3) analyze the evolution of the patient's status by projecting the acquired data into the plane formed by the first two factorial axes named "factorial plane." In order to classify the different evolution patterns, a new similarity measure is proposed and validated on the simulated datasets, and then, used to cluster observed data from 41 CRT patients. The obtained clusters are compared with the annotations on each patient's medical record. Two areas on the factorial plane are identified, one being correlated with a health degradation of patients and the other with a stable clinical state.     

On the reduction of thermal and flicker noise in ENG signal recording amplifiers

Because of the extremely low amplitude of the input signal, the design of electro-neuro-graph (ENG) amplifiers involves a special care for flicker and thermal noise reduction. The task becomes really challenging in the case of implantable electronics, because power consumption is restricted to few hundreds μW. In this work, two different circuit techniques aimed to reduce flicker and thermal noise, in ultra-low noise amplifiers for implantable medical devices, are demonstrated. The circuit design, and measurement results are presented, in both cases showing an excellent performance, and noise to power consumption trade-off. In the first circuit, a very simple low-pass G_m–C chopper amplifier is used for flicker noise cancellation. It consumes only 28 mW, with a measured input referred noise and offset of 2  $ {{{\text{nV}}} \mathord{\left/ {\vphantom {{{\text{nV}}} {\sqrt {{\text{Hz}}} }}} \right. \kern-0em} {\sqrt {{\text{Hz}}} }} $ , and 2.5 μV, respectively. In the second circuit, a ultra-low noise amplifier, a energy-efficient DC–DC down-converter, and low voltage design techniques are combined, for the reduction of thermal noise with a minimum power consumption. Measured input referred noise in this case was 5.5  $ {{{\text{nV}}} \mathord{\left/ {\vphantom {{{\text{nV}}} {\sqrt {{\text{Hz}}} }}} \right. \kern-0em} {\sqrt {{\text{Hz}}} }} $ at only 380 μW power consumption. Both circuits were fabricated in a 1.5 μm technology.     

为快速ADC提供电压箝位与DC偏置模拟电路

许多快速ADC都推荐0.6V-2.6V输入电压范围,如美国国家半导体公司的ADC1175（参考文献1）。但在某些应用中,必须要转换一个对称的模拟输入信号。本设计实例中的电路将一个-0．2V－＋0．2V范围的对称输入电压转换到推荐的0．6V－2．6V范围（图1）。该电路亦能防止输出电压低于-0.3V,以防止损坏ADC。     

Surface roughness evaluation in medium density fibreboard rip sawing

Wood/panel specific gravity is a factor that has to be evaluated in the machining process because it affects the cutting forces behavior, plays an important role in the tool wear mechanisms and it is closely related to the surface roughness of the manufactured product. In the case of medium density fibreboard (MDF), which compared to solid wood is a homogeneous wood product, it is recognized that the specific gravity varies regularly across its profile, and these variations generate an uneven surface quality at the edge of the panel when machined. Among the operational parameters affecting the quality of the new surface, the cutting process kinematics is one of the most important parameters, namely the cutting speed and the chip thickness. In MDF industrial rip sawing operations, climb cutting and conventional cutting are additional parameters that affect the cutting quality. The objective of this study was to assess the surface roughness across the MDF panel profile produced by the rip sawing operation and to study the effect of cutting speed, mean chip thickness and cutting direction. The findings lead to the conclusion that low levels of surface roughness are reached when the cutting speed is increased at even higher feed speeds, particularly at the edge of the board. High correlation coefficients were found between mean chip thickness and surface roughness for both cutting directions. Finally, the specific gravity variation within the profile of the panel explains very well the resulting surface roughness found.