Site‐specific dual ink dip pen nanolithography™

The ability to deposit different materials with nanoscale precision at user‐specified locations is a very important attribute of dip pen nanolithography (DPN^®). However, the potential of DPN goes beyond simple deposition since DPN used in conjunction with lateral force microscopy (LFM) allows site‐specific investigations of nanoscale properties. In this work, we use two different inks, 16‐mercaptohexadecanoic acid (MHA) and 1‐octadecanethiol (ODT) to show site‐specific dual ink DPN enabled exclusively by our proprietary software. A diamond‐dot pattern was created by using a layer‐to‐layer alignment (LLA) algorithm, which enables a MHA pattern (diamond) to be written concentric with another ODT (central dot) pattern. This simple demonstration of multi‐ink DPN is not specific to alkanethiol ink systems, but is also applicable to other multi‐material patterning, interaction, and exchange studies. SCANNING 31: 122–126, 2009. © 2009 Wiley Periodicals, Inc.     

Numerical and experimental analysis of falling-film exchangers used in a LiBr–H2O interseasonal heat storage system

This paper investigates heat and mass transfer occurring in an interseasonal absorption heat storage system using LiBr/H₂O as the sorption couple. It focuses on the poor performances of the falling film exchangers with vertical tubes, which are characterized by low flow rate compared to conventional absorption machines. A numerical model was developed for the study and validated with specific experimental results. Comparison of the numerical model to experimental results from the heat storage prototype shows the presence of abnormally high thermal resistance between the falling films and the exchanger surfaces. The deterioration in performance appears to originate in the low wetting rate of the surfaces. A new design of the exchangers is proposed to solve this problem and thus attain the desired performance.     

The Squirrel-Cage Induction Motor Model and Its Parameter Identification Via Steady and Dynamic Tests

One of the most important bases for designing robust closed-loop controllers applied to induction motor with high performance is establishing its mathematical model and state observers, as well as the parameter identification with high accuracy. In this paper, a step-by-step mathematical model of the squirrel-cage induction motor is described at αβ coordinate frame where the parameters are defined in detailed form; the rotor flux linkages and load torque are estimated via an asymptotic observer; the induction motor parameter identification is performed via a data acquisition board, applying dynamic and steady-state tests. Inductances of the induction motor model are calculated using the proposed relationships between the magnetically coupled circuit and equivalent circuit model. The mathematical model, state observers, and parameter identification procedure of squirrel-cage induction motor are validated via comparison of simulation signals with their corresponding real-time signals. This validation is made experimentally by a steady-state test, where load conditions are changed via a dynamometer which is belt coupled with the squirrel-cage induction motor.     

Adhesive properties of asphalts and aggregates in tropical climates

In Central and South America, pavement deterioration due to moisture is high. The deterioration is directly related to the compatibility between the asphalt and aggregates, as well as the cohesiveness of the asphalt matrix. The affinity between these materials affects how well the bond will behave in the presence of water, and therefore the susceptibility of the asphalt mixture to moisture in the long term. It is well accepted that traditional tests for assessing moisture damage are not necessarily representative of high moisture conditions, such as those present in Colombia and Costa Rica. Therefore, it is imperative that methods to quantify the actual moisture susceptibility of hot-mix asphalt be adopted and implemented in local specifications. In order to characterise the true adhesion properties of regional materials, both physicochemical and mechanical analysis has been implemented to determine the moisture susceptibility of different binder–aggregate combinations typically used in Costa Rica and Colombia. The effect of antistrip additives on the water resistance of such combinations was also evaluated. The asphalt bond strength test was applied to mechanically determine the adhesive and cohesive strength of the binder–aggregate pairs. In addition, the measurement of physicochemical properties such as surface free energies of aggregates and binders allowed the determination of work of adhesion, cohesion and debonding of asphalt from the aggregate surface in the presence of water. A correlation between the physicochemical and the mechanical properties was found for most of the cases.     

Availability-based simulation and optimization modeling framework for open-pit mine truck allocation under dynamic constraints

We present a novel system productivity simulation and optimization modeling framework in which equipment availability is a variable in the expected productivity function of the system. The framework is used for allocating trucks by route according to their operating performances in a truck–shovel system of an open-pit mine, so as to maximize the overall productivity of the fleet. We implement the framework in an originally designed and specifically developed simulator–optimizer software tool. We make an application on a real open-pit mine case study taking into account the stochasticity of the equipment behavior and environment. The total system production values obtained with and without considering the equipment reliability, availability and maintainability (RAM) characteristics are compared. We show that by taking into account the truck and shovel RAM aspects, we can maximize the total production of the system and obtain specific information on the production availability and productivity of its components.     

Low power impedance measurement integrated circuit for sensor applications

In this paper an integrated circuit for the measurement of the real and imaginary part of an impedance is presented. The circuit is intended for its use in a wireless integrated system. A mixed analog/digital approach has been adopted in order to minimize power and area requirements, as requested by the application. The four electrode configuration is used for impedance measurement using two excitation current sources and a buffer instead of an instrumentation amplifier, therefore reducing the circuit complexity. The digital block controls the working frequency and can compensate the phase error introduced by the analog filters, thereby reducing the total error in the measurement. The integrated circuit has been designed in a CMOS process and it works with 3.3 V with a power consumption of . Experimental results to verify its functionality are presented.     

维修工程系统——维修功能的演化机遇

世界上的各知名公司始终面临着不断提高竞争力以确保其在全球市场上占有一席之地这样的问题。在这种挑战中,维修功能尽管只是服务于产品,却扮演着一个基础性的角色,因为它通过对生产力(全球成本下降)、系统灵活性(面向顾客的适应性)和人性因素(环境和人的考虑)的影响而对竞争力产生直接的影响。为了满足这些新的需求,产品的维修必须产生质的跨跃,这种跨跃是由以干预为中心向以预防为中心的职能演化来带动。     

Continuous transesterification of biodiesel in a helicoidal reactor using recycled oil

The main problem with biodiesel is the high cost of oils made from oleaginous crops. For this reason, various raw materials have been analysed with a view to reducing production costs and obtaining a product that can compete with the price of petrodiesel. Recycled oil is one of the most promising alternatives in the production of biodiesel because not only is the cheapest raw material but it also avoids the expense of treating the oil as a residue.Another way to reduce costs is to make the process more economical. Conventional technology uses sodium hydroxide as the basic catalyst and large-scale batch reactors, whose mechanical agitation requires high energy consumption due to residence times of at least 60 min and temperatures of 60 °C.In this paper we use a recycled pretreated oil to compare conventional transesterification with continuous transesterification in a tubular reactor. In this reactor the reactants (oil, methanol and sodium hydroxide) flow through a helicoidal tube submerged in a heating bath at 60 °C. The reactor has five outlets distributed non-uniformly to enable samples to be taken at different reaction times. This is to reduce the reaction time and avoid the need for mechanical agitation. With the aim of improving the quality of the biodiesel obtained, we varied the helicoidal system by incorporating a static micromixer and supplying energy in the form of ultrasound from the heating bath. This reactor produced biodiesel and glycerine at compositions roughly equal to those obtained in the batch process (89% FAME content at 75 min) but did so continuously (2.5 mL/min) and just 13 min after the reactants were integrated in a single line using a T device. Both the oil and the biodiesel were characterized and analysed in accordance with European standard UNE EN14214 for biodiesel.     

维修工程系统——维修功能的演化机遇（续）

下图(图4)是维修工程过程的示意图。整个过程基本上可以分为以下几个步骤:第1步:系统逻辑配置。对生产设备的功能、辑和影响进行分析。第2步:数据。有两种获取数据的方法。第一是通过对设备功能的历史数据分析,第二是通过标准或者制造商的说明来获得数据。第3步:寿命周期费用决