J. van Deventer

Integration of Wireless Sensor and Actuator Nodes With IT Infrastructure Using Service-Oriented Architecture

A large number of potential applications for Wireless Sensor and Actuator Networks (WSAN) have yet to be embraced by industry despite high interest amongst academic researchers. This is due to various factors such as unpredictable costs related to development, deployment and maintenance of WSAN, especially when integration with existing IT infrastructure and legacy systems is needed. Service-Oriented Architecture (SOA) is seen as a promising technique to bridge the gap between sensor nodes and enterprise applications such as factory monitoring, control, and tracking systems where sensor data is used. To date, research efforts have focused on middleware software systems located in gateway devices that implement standard service technology, such as Devices Profile for Web Services (DPWS), for interacting with the sensor network. This paper takes a different approach-deploying interoperable Simple Object Access Protocol (SOAP)-based web services directly on the nodes and not using gateways. This strategy provides for easy integration with legacy IT systems and supports heterogeneity at the lowest level. Twofold analysis of the related overhead, which is the main challenge of this solution, is performed; Quantification of resource consumption as well as techniques to mitigate it are presented, along with latency measurements showing the impact of different parts of the system on system performance. A proof-of-concept application using Mulle-a resource-constrained sensor platform-is also presented.

PSpice simulation of ultrasonic systems

The usage of electrical analogies for the simulation of wave generation and propagation in ultrasound transducers is well established. In this paper a PSpice approach that includes the temperature and frequency dependency of the transducer performance is proposed. The analogy between acoustic wave propagation and wave propagation in an electric transmission line is given. Further ways to deduce temperature and frequency dependencies are discussed. The simulation approach is applied to a pulse-echo setup for the determination of speed of sound and attenuation in liquids and solids. Experiments and simulations are made for three temperatures and in the frequency range 1-12 MHz using water, glycerine, and polymers (PMMA and PEEK) as test samples. Comparison shows a good agreement between simulation and experiments. Results for glycerine indicates that the available attenuation models for high viscosity liquids is inappropriate.

Frequency and temperature dependence of acoustic properties of polymers used in pulse-echo systems

In ultrasonic pulse-echo systems, polymers like PMMA (polymethylmethacrylate) and PEEK (polyetheretherketone) are often used as buffer-rods, placed between the ultrasound transducer and the unknown material (liquid, gas, or solid material). Provided the acoustic properties of the buffer-rods are known, it is possible to calculate these also for the unknown material, based on reflections between the buffer-rod and the unknown medium. However, temperature changes also affect these properties. In this paper we present a method for measuring acoustic attenuation, speed of sound and density, for buffer-rod materials. We also give experimental values for PMMA and PEEK, for temperatures between 5/spl deg/C and 37/spl deg/C, and for 5 MHz and 10 MHz ultrasound frequency.

Thermostatic and dynamic performance of an ultrasonic density probe

The thermally static and dynamic performance of an ultrasonic density probe for liquids is investigated in the density range of 750 to 1300 kg/m/sup 3/ at temperature ranging from 0 to 40/spl deg/C. The single transducer probe uses a pulse echo technique to obtain the characteristic acoustic impedance of the liquid and, subsequently, the speed of sound through the liquid to obtain the density of the liquid. Variations in the initial sound amplitude are addressed by the design of a layered two material probe. It is shown that it is possible to obtain an accuracy of 0.4% in the experiments carried out. For changing temperature, the probe exhibits large errors because of problems in estimating the temperatures in certain regions of the probe.

Thermodynamic Simulation of a Detached House with District Heating Subcentral

A physical thermodynamic model of a detached house connected to a low-tempered district heating network is presented. The model is created in Mathworks Simulink@ with a pedagogic approach in mind, e.g. masked subsystems divided in to physical components. The house model is easily modified to any detached house. Provision is also made to make it scalable to multi-family houses. The district heating substation modeled is a parallel coupled plate heat exchanger, which is the most common substation in smaller buildings such as villas. The purpose of creating the model was to provide a platform for test and evaluation of new control methods for district heating system based on wireless sensor networks. Initial validation of the model is presented.

Evaluating demand response programs by means of key performance indicators

Demand response (DR) has received significant attention in recent years and several DR programs are being deployed and evaluated worldwide. DR systems provide a wide range of economic and operational benefits to different stakeholders of the electrical power system including consumers, generators and distributors. DR can be achieved through a number of different mechanisms such as direct-load-control, incentives, pricing signals, or a combination of these schemes. Due to the remarkable variation in demand response systems, it becomes a challenge to evaluate and compare the effectiveness of different DR programs holistically. In this work, we define a number of different performance metrics that could be used to evaluate DR programs based on peak reduction, demand variation and reshaping, and economic benefits.

Introduction of a 2 transducer ultrasonic mass flow meter

This article presents a new ultrasonic mass flow meter that has only two transducers. The mass flow is inferred from volumetric flow and density. Each of the transducers is an ultrasonic densitometer based on a design by Lynnworth. The flow is estimated by the transit time difference of the sound pulse between the up and downstream acoustic propagation. Beyond presenting the meter, this article does looks at its signal at zero flow to address the issue of reciprocity in transit time flow meters which is in contradiction with the theory of transit time flow meters