BPMN: An introduction to the standard

The Business Process Model and Notation (BPMN) is the de-facto standard for representing in a very expressive graphical way the processes occurring in virtually every kind of organization one can think of, from cuisine recipes to the Nobel Prize assignment process, incident management, e-mail voting systems, travel booking procedures, to name a few. In this work, we give an overview of BPMN and we present what are the links with other well-known machineries such as BPEL and XPDL. We give an assessment of how the OMG's BPMN standard is perceived and used by practitioners in everyday business process modeling chores.     

Performance evaluation of priority CSMA-CA mechanism on ISA100.11a wireless network

The International Society of Automation recently released ISA100.11a as an open standard for reliable wireless networks for industrial automation. ISA100.11a uses the TDMA scheme in the medium access layer to provide deterministic services. However, ISA100.11a adopts the CSMA-CA mechanism with priorities for retransmission from failure on dedicated links, sporadic data, and network configuration.This paper evaluates ISA100.11a CSMA-CA by simulation, considering the effects of backoff procedures and priority settings to probability of collision and successful use of slots. It's demonstrated that a high number of priority classes enable better network utilization resulting in less number of packets exceeding their lifetime.     

Experimental study on the package of high-g accelerometer

In this paper, the effect of the package die adhesive and package shell on the performances of silicon based MEMS high-g accelerometers was reported. Using Raman spectroscopy, the residual stress caused by different package die adhesive thickness and different package shell material was characterized. It can be concluded from the testing results that: with thicker die adhesive, the residual stress increment was much smaller; the piezoresistance variation caused by this residual stress was much smaller; and the temperature shift of the output voltage was much smaller. Comparing with the ceramic package, the stainless steel package has bigger sensitivity and bigger anti-overload ability.     

A wind-flutter energy converter for powering wireless sensors

This paper describes a low-speed wind energy harvesting system that transfers aerodynamically induced flutter energy into electrical energy. A random airflow generates mechanical vibrations due to the fluid-structure interaction between a flexible belt and the airflow. An electromagnetic resonator with copper coils and a permanent magnet is designed to efficiently harvest electrical energy from the induced mechanical vibrations. Different groups of springs are compared at various wind conditions to maximize the power output. Typically ∼7 mW of electrical energy can be obtained at ∼3 m/s wind speed with a 1 m long belt. A power conditioning circuit with a charge pump and a DC-DC converter is used to convert the generated voltage into a stable 3.3 V DC for consumption. It is demonstrated that this generator can be used to drive a commercial wireless temperature sensor.     

Influence of doping BiYO3 and Nb2O5 on PTCR characteristics of BaTiO3 thermistor ceramics

Nb₂O₅-doped (1 − x)Ba_0.96Ca_0.04TiO₃-xBiYO₃ (where x = 0.01, 0.02, 0.03 and 0.04) lead-free PTC thermistor ceramics were prepared by a conventional solid state reaction method. X-ray diffraction, scanning electron microscope, Agilent E4980A and resistivity-temperature measurement instrument, were used to characteristic the lattice distortion, microstructure, temperature dependence of permittivity and resitivity-temperature dependence. It was revealed that the tetragonality c/a of the perovskite lattice, the microstructure and the Curie temperature changed with the BiYO₃ content. In order to decrease the room temperature resistivity, the effect of Nb₂O₅ on the room temperature resistivity was also studied, and its optimal doping content was finally chosen as 0.2 mol%. The 0.97Ba_0.96Ca_0.04TiO₃-0.03BiYO₃-0.002Nb₂O₅ thermistor ceramic exhibited a low ρ_RT of 3.98 × 10³ Ω cm, a typical PTCR effect of ρ_max/ρ_min > 10³ and a T_c of 153 °C.     

A silicon-glass-based microfabricated wide range thermal distribution gas flow meter

Recently, there has been high demand on miniaturizations of bio-instruments and wide range gas flux measurement in the field of chemistry and mechanics. This paper presents the design, fabrication, and characterization of a silicon-glass-based thermal distribution gas flow meter (20 mm × 10 mm × 1.6 mm) with a wide detection range. To facilitate the fabrication and maintain the stability of the sensor, a platinum (Pt) thin film was adopted as the heater and thermometers. Both the thermal property and temperature sensitivity of Pt thin film were characterized. SiO₂ passivation layers were deposited on top of the Pt film to prevent thermal and electrical shift of sensitive elements. Three pairs of thermometers were constructed beside the heater. Sensitivity and gas flux range of the gas flow meter can be increased by alternate use of these three sensor pairs. We also introduced a specific hardware control circuit system for real-time gas flux monitoring through the connection with a computer interface. The proposed gas flow sensor device was capable of measuring gas flux within the range of 0.8-2800 ml/min, thus demonstrating the potential for a wide range of applications.     

Sensitivity optimization of surface plasmon sensors for detection of intermediate layers

A sensitivity optimization method for the detection of an intermediate layer using a surface plasmon sensor is presented. The dependence of detection sensitivity on distance from the metal surface and the average refractive index over the sensing region are considered. Based on the calculated results, the sensitivity for detecting an intermediate layer in a multilayered sample is determined by varying the refractive index and thickness of each layer. It is shown that, in particular cases, controlling the refractive index and thickness increases the detection sensitivity. The proposed method is useful for designing multilayered samples.     

Study of the influence of nickel ions substitutes in barium stannates used as humidity resistive sensors

In the present work, we report the results of the influence of the Ni ions which partly substitute the Ba ions in the barium stannate (Ba_1−xNi_xSnO₃, where x = 0; 0.1; 0.2; 0.5), on the structural and electronic properties, as well as on the sensitivity to humidity. With the view to obtain a porous and finer structure, thus providing a high specific surface, these materials were obtained through the precursor method of self-combustion (co-precipitation in a colloidal environment and self-combustion), followed by heat treatments. The phase composition and morphology were studied by XRD and SEM. The pure sample, as well as that with the substitution x = 0.1, are single phased after 40 min sintering at 1000 °C. For substitutions with x > 0.1 secondary phases appear, which favorably influence the humidity sensitivity. All the samples show a significant sensitivity to humidity within 22% RH and 75% RH for the substitution with x = 0 and 0.1, and 22% RH - 98% RH for the substitution with x = 0.5. For this interval, the material resistivity logarithmically decreases by over four orders. The sample with the substitution x = 0.5 is characterized by a very fine structure (∼250 nm) and a high effective porosity (47%). This sample presents a shorter absorption response time than the other samples. Its high sensitivity, its sensitivity range, linearity of the sensitivity characteristic and the quick response time recommend the material with the composition Ba_0.5Ni_0.5SnO₃ for the realization of a very good resistive humidity sensor.     

Contactless hybrid sensor for simultaneous detection of light reflectance and eddy currents

We demonstrate a contactless hybrid sensor for the simultaneous detection of light reflectance and eddy currents. The sensor is based on combining an optical system with an RLC self-resonator, wherein the reflected light intensity and resonance frequency are measured. We demonstrate that the hybrid sensor can be used for monitoring metals coated with non-metallic films. Whereas the self-resonator can efficiently distinguish between metals and non-metals, the optical subsystem is sensitive to changes in the reflectance of light. A systematic investigation of the detector response as a function of distance to the material under test is undertaken to characterize its behavior.     

A supervisory loop approach to fulfill workspace constraints in redundant robots

An approach based on geometric invariance and sliding mode ideas is proposed for redundancy resolution in robotic systems to fulfill configuration and workspace constraints caused by robot mechanical limits, collision avoidance, industrial security, etc. Some interesting features of the proposal are that: (1) it can be interpreted as a limit case of the classical potential field-based approach for collision avoidance which requires using variable structure control concepts, (2) it allows reaching the limit surface of the constraints smoothly, depending on a free design parameter, and (3) it can be easily added as a supervisory block to pre-existing redundancy resolution schemes. The algorithm is evaluated in simulation on a 6R planar robot and on the freely accessible 6R robot model PUMA-560, for which the main features of the method are illustrated.