Characterization of rigid polyurethane foams containing microencapsulted phase change materials: Microcapsules type effect

Rigid polyurethane (RPU) foams were synthesized incorporating up to 18 wt % of two different kinds of thermo‐regulating microcapsules having a different shell material consisting of polystyrene or poly(methyl methacrylate), named as mSP‐(PS‐RT27) and Micronal®DS 5001X, respectively. The type of microcapsules and their content affected the final foam height, which decreased with the content and particle size. However, the foam rising curve shape was not dependent on the microcapsules type or content and was successfully predicted by means of a model of reaction curve of four tanks in series. Thermal energy storage (TES) capacity of PU foams was improved by incorporating both, mSP‐(PS‐RT27) or Micronal®DS 5001X, with the values close to those reported in the literature (16 J/g) for the highest content. Nevertheless, the highest particle size of the microcapsules from PS and the agglomeration of the microcapsules from poly(methyl methacrylate), promoted by their additive SiO₂, led to the strut rupture, damaging the final mechanical properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cross-validation of bimodal health-related stress assessment

This study explores the feasibility of objective and ubiquitous stress assessment. 25 post-traumatic stress disorder patients participated in a controlled storytelling (ST) study and an ecologically valid reliving (RL) study. The two studies were meant to represent an early and a late therapy session, and each consisted of a "happy" and a "stress triggering" part. Two instruments were chosen to assess the stress level of the patients at various point in time during therapy: (i) speech, used as an objective and ubiquitous stress indicator and (ii) the subjective unit of distress (SUD), a clinically validated Likert scale. In total, 13 statistical parameters were derived from each of five speech features: amplitude, zero-crossings, power, high-frequency power, and pitch. To model the emotional state of the patients, 28 parameters were selected from this set by means of a linear regression model and, subsequently, compressed into 11 principal components. The SUD and speech model were cross-validated, using 3 machine learning algorithms. Between 90% (2 SUD levels) and 39% (10 SUD levels) correct classification was achieved. The two sessions could be discriminated in 89% (for ST) and 77% (for RL) of the cases. This report fills a gap between laboratory and clinical studies, and its results emphasize the usefulness of Computer Aided Diagnostics (CAD) for mental health care.     

The production of advanced fine-grained alumina by carbon nanotube addition

Alumina and alumina + 1 vol.% carbon nanotube (CNT) composites were fully densified by spark plasma sintering. Post-sintering heat treatments (1300–1500 °C) were performed to completely oxidize CNTs and then densify the remaining 1 vol.% to produce fine-grained ceramics. The grain size and Vickers hardness of the heat-treated composites were compared with the monolithic alumina sintered without CNT addition. Compared to the initial powder particle size of alumina (D₅₀: 356 ± 74 nm), minimal grain growth (∼450 nm) was observed for the fully dense heat-treated composites. A 25% improvement in Vickers hardness and >10 times finer average grain size were observed for alumina produced by the heat treatment (1300 °C) of alumina + 1 vol.% CNT composite, compared to alumina sintered without CNTs.     

Poly(lactic acid)/carbon nanotube nanocomposites with integrated degradation sensing

For the first time, an in-situ degradation monitoring system for biodegradable polymers is reported in present work. The proposed concept is based on a conductive biodegradable polymer composite, where carbon nanotubes (CNTs) are incorporated in poly(lactic acid) (PLA) in order to develop an intelligent biocomposite system that can sense biodegradation. Changes in electrical resistivity of the PLA/CNT nanocomposites were successfully correlated with degradation levels of the biopolymer. PLA/CNT nanocomposites demonstrated excellent degradation sensing abilities at CNT concentrations around the percolation threshold, with resistivity changes of about four orders of magnitude with biodegradation. In contrast to many other stimuli, biodegradation resulted in a reduction in resistivity due to an increased CNT network density after partial removal of the amorphous phase of the polymer matrix.     

Jitter analysis of PLL-generated clock propagation using Jitter Mitigation techniques with laser voltage probing

A new Jitter Mitigation feature in the latest generation laser voltage probing (LVP) tool effectively removes PLL jitter from LVP waveforms [Ng Yin S, Lo W, Wilsher K. Next generation laser voltage probing. In: Proceeding, international symposium on testing and failure analysis; 2008. p. 249]. It facilitates the probing of phase-locked loop (PLL) driven circuitry inside of integrated circuits (ICs). In particular, it allows the detection of small amounts of excess jitter that would normally be masked by the much larger jitter of the PLL. To demonstrate the practical application of this Jitter Mitigation feature, we report on the jitter analysis of a PLL-generated clock signal as it propagates, through buffers and logic circuitry, to an external I/O pad of an IC. The IC was a 0.9 V, 65 nm technology graphics processing unit (GPU). The analysis was to determine where excess jitter was introduced into the clock path when the GPU was electrically stressed. Details of the jitter analysis, including Jitter Mitigation methodology, probing setup, and results of the timing measurements, will be presented in this paper.     

Comparison of manual control methods for space manipulator positioning tasks

The Russian Segment of the International Space Station will be equipped with a 10 m long anthropomorphic space manipulator with six degrees of freedom. The robot is called the European Robot Arm, or ERA. Its hand, or end-effector, contains a camera which will be used for fine positioning of the end-effector, in order to grasp an object. At the Delft University of Technology, a human-machine interface for manual control of the ERA is being developed. The control device is a Spaceball controller, which is used to control the spatial end-effector velocity. This article describes four control methods that transform the Spaceball movements into movements in the end-effector camera picture. The control methods are compared by means of human-machine experiments. The results are also useful in many other areas of spatial manipulation, like undersea robots, robots in the nuclear industry, and minimally invasive surgery.     

An experimental study to evaluate the effectiveness of different methods and intensities of law enforcement on driving speed on motorways

Two field experiments were conducted to establish the most effective method of enforcement in reducing driving speed and to establish the most efficient strategy in terms of police force personnel required. In the first experiment, the effect of three variables on driving speed on motorways was studied. The first variable, intensity of enforcement, was manipulated by creating three different objective levels of apprehension for detected speeding drivers. The second variable was method of enforcement. On-view stopping and ticketing of offenders was compared to mailing of fines on the basis of the car's licence plate number. The third variable manipulated was the time delay in the mailing of fines. Time delay between detection of the offence and feedback to the driver was shortened in one condition. In a second experiment, police enforcement effort was optimized by relating intensity level of enforcement to the proportion of speeding vehicles. In the first experiment, police enforcement was applied for four weeks; in the second experiment, enforcement activities were continued for 12 consecutive weeks. In both cases the main dependent variable was driving speed. Before, during, and after the application of enforcement, speed was registered using induction loops. In addition, driver opinion about speeding and speed enforcement was studied using postal questionnaire surveys. The results show the largest and longest lasting reduction in driving speed in the highest intensity level-condition, giving support for a relation between objective chance of apprehension and speed choice. On-view stopping of offenders was shown to be a more effective method to reduce driving speed than mailing of fines. Some of these results are discussed in the light of game theory. The questionnaire surveys indicated that most drivers did not notice the recurrence in enforcement activities due to infrequent passing of the sections of motorways studied. The preventive effect of police enforcement appeared to be far more substantial than its repressive effect. Enforcement primarily deters the current nonoffender from speeding.