Fabrication of ZnO nanorod-based hydrogen gas nanosensor

We report a first work on nanofabrication of hydrogen nanosensor from single ZnO branched nanorods (tripod) using in-situ lift-out technique and performed in the chamber of focused ion beam (FIB) system. Self-assembled ZnO branched nanorod has been grown by a cost-effective and fast synthesis route using an aqueous solution method and rapid thermal processing. Their properties were analyzed by X-ray diffraction, scanning electron microscopy, energy dispersion X-ray spectroscopy, transmission electron microscopy, and micro-Raman spectroscopy. These analyses indicate high quality ZnO nanorods. Furthermore, our synthesis technique permits branched nanorods to be easily transferred to other substrates. This flexibility of substrate choice opens the possibility of using FIB system for handling.

The main advantage of the proposed in-situ approach is a controllable lift-out procedure which permitted us to obtain a 90% success rate for building nanodevices. The fabricated nanosensor uses only single self-assembled ZnO branched nanorod (tripod) to gauge the 150 ppm H₂ in the air at room temperature. The hydrogen sensitivity is in the range of 0.6–2% depending on which two branches to use. The nanosensor has selectivity against other gases such as O₂, CH₄, CO and LPG, which shows sensitivity of <0.02%. The single ZnO branched nanorod sensor can operate at low power of <5 μW.     

High Sensitivity,Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing

A pressure sensor based on irregular microhump patterns has been proposed and developed. The devices show high sensitivity and broad operating pressure regime while comparing with regular micropattern devices. Finite element analysis (FEA) is utilized to confirm the sensing mechanism and predict the performance of the pressure sensor based on the microhump structures. Silicon carbide sandpaper is employed as the mold to develop polydimethylsiloxane (PDMS) microhump patterns with various sizes. The active layer of the piezoresistive pressure sensor is developed by spin coating PEDOT:PSS on top of the patterned PDMS. The devices show an averaged sensitivity as high as 851 kPa^?1, broad operating pressure range (20 kPa), low operating power (100 nW), and fast response speed (6.7 kHz). Owing to their flexible properties, the devices are applied to human body motion sensing and radial artery pulse. These flexible high sensitivity devices show great potential in the next generation of smart sensors for robotics, real‐time health monitoring, and biomedical applications.     

A novel feature selection method and its application

In this paper, a novel feature selection method based on rough sets and mutual information is proposed. The dependency of each feature guides the selection, and mutual information is employed to reduce the features which do not favor addition of dependency significantly. So the dependency of the subset found by our method reaches maximum with small number of features. Since our method evaluates both definitive relevance and uncertain relevance by a combined selection criterion of dependency and class-based distance metric, the feature subset is more relevant than other rough sets based methods. As a result, the subset is near optimal solution. In order to verify the contribution, eight different classification applications are employed. Our method is also employed on a real Alzheimer’s disease dataset, and finds a feature subset where classification accuracy arrives at 81.3 %. Those present results verify the contribution of our method.     

An argumentation-oriented multi-agent system for automating the freight planning process

This paper advocates the use of multi-agent systems in the freight forwarding industry. We propose an intelligent mobile agent system to cope with a dynamic freight forwarding environment where up-to-date information is crucial but time-consuming to obtain. A key component of our system is an agent argumentation mechanism that allows decision support agents to discuss, argue, and come to a compromise in order to derive well-explained freight planning solutions. A number of artificial intelligence mechanisms are implemented, namely: (1) a mobile-agent-based automated information gathering mechanism, where designated mobile agents access various websites automatically to gather information (e.g., weather conditions on a candidate route) critical for cargo consolidation and route planning, (2) a fuzzy logics engine for risk evaluation, and (3) a simulated annealing engine for optimizing cargo consolidation. A system prototype is developed and the feasibility of our approach is demonstrated in a case study. A series of experiments are also conducted to evaluate the system’s performance.     

A comparison of classical, robust, and decentralized controldesigns for multiple power system stabilizers

Several control design techniques, namely, the classical phase compensation approach, the μ-synthesis, and a linear matrix inequality technique, are used to coordinate two power system stabilizers to stabilize a 5-machine equivalent of the South/Southeast Brazilian system. The open-loop system has an unstable intearea mode and cannot be stabilized using only one conventional power system stabilizer. Both centralized and decentralized controllers are considered. The different designs are compared and several interesting observations are provided     

Recast layer removal after electrical discharge machining via Taguchi analysis: A feasibility study

This study explores the feasibility of removing the recast layer (RCL) using etching and mechanical grinding for Ni-based superalloy materials by means of electrical discharge machining (EDM). The EDM process is widely used for machining hard metals and performing specific tasks that cannot be achieved using conventional techniques. The sparks produced during the EDM process melt the metal's surface, which then undergo ultra rapid quenching. A layer forms on the workpiece surface defined as a recast layer after solidification. Molds and dies desire to remove the RCL even though it is hard and has good matrix adherence.This experiment is divided into three stages. The first stage acquires a thick recast layer by using EDM with a larger discharging energy. A thick recast layer is essential for verification of the EDM technique for observing the recast process. Thus, this work applies the Taguchi L₁₈ analytical method to acquire the thick recast layer. The second stage optimizes the recast layer removal technique. Therefore, the thick recast layer is intentionally made in the first stage. This work determines the second stage setting using Taguchi's recommendation. Thus, the L₉ orthogonal array sets up the etching and mechanical grinding parameters and observes the recast layer removal quantity analysis. Finally, an experiment studies the surface characteristics of Ni-based superalloys, such as composition and micro-hardness after removing the recast layer.     

Longitudinal ventilation for smoke control in a tilted tunnel by scale modeling

Longitudinal ventilation systems are commonly installed in new tunnels in large cities of the Far East including Mainland China, Hong Kong and Taiwan. Many tunnels are found in big cities and some of them are inclined at an angle to the horizontal. However, smoke movement in tilted tunnels is not fully understood. In some of the tunnels, the ventilation system was designed based on presumed smoke movement pattern without experimental demonstration. Smoke movement pattern in a tilted tunnel model was studied by using a scaled model. A 1/50 tunnel model of length 2 m with adjustable angle to the horizontal was constructed by transparent acrylic plastics. A small 0.097 kW propanol pool fire was used as the heat source combined with burning pellets generating smoke. A fan placed at the upstream end was used to create longitudinal ventilation. Different ventilation rates were set using a transformer to control or adjust the fan speed. Experiments were performed with the tunnel angle varying up to 30° to the horizontal. Effect of smoke screens was also studied. The observed smoke movement patterns indicated that the shape of the buoyant plume inside the tunnel depends on the tilted angle. Smoke would flow along the tunnel floor due to gravity. The bending angle of the plume depends on the tunnel angle. Tunnel inclined at greater angles to the horizontal would give larger amount of smoke flow. Smoke movement pattern for a tilted tunnel with smoke screens was observed to be very different from some design projects. All results will be reported in this paper.     

A fast computational method for near field capacitive couplings

The near-field capacitive couplings are analyzed by using a hybrid method incorporating the finite difference method and the method of moment. A dielectric post is used as the model for analysis. Results from the formerly developed technique of synthetic asymptote are used for comparison. The speed of computation of the developed method is extremely fast.     

The current distribution and AC resistance of a microstripstructure

The AC resistance of the strip in a microstrip structure is compared with that of an isolated strip for better understanding of the conductor loss mechanism. An analysis is presented of the AC resistance in a microstrip structure for any metallization thickness by deriving the current distribution over the strip cross section. The analysis uses the separation of variables technique and the Green's function method. It shows that the skin current of the strip is concentrated toward the ground plane in a microstrip structure. In the extreme case, the AC resistance of the strip can be twice as high as the AC resistance of the same isolated strip. The imperfect ground plane also adds to the total conductor loss of a microstrip line. For a wide strip over a lossy ground plane at high frequency, the ground plane surface current distribution is concentrated directly under the strip, and the ground plane AC resistance can be as large as the strip AC resistance. Therefore, the total AC resistance at the microstrip line can be four times as high as that of an isolated strip conductor