Martinus Bos

Energy-efficient adaptive wireless network design

Energy efficiency is an important issue for mobile computers since they must rely on their batteries. We present an energy-efficient highly adaptive architecture of a network interface and novel data link layer protocol for wireless networks that provides quality of service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations are necessary to achieve energy efficiency and an acceptable quality of service. The paper provides a review of ideas and techniques relevant to the design of an energy efficient adaptive wireless network.

Energy-efficient wireless ATM design

Energy efficiency is an important issue for mobile computers since they must rely on their batteries. We present an architecture for wireless ATM and a novel MAC protocol that achieves a good energy efficiency of the wireless interface of the mobile and provides QoS support for diverse traffic types. The scheduler of the base station is responsible for providing the required QoS to connections on the wireless link and to minimize the amount of energy spent by the mobile. The main principles used are to avoid unsuccessful actions, to minimize the number of transitions, and to synchronize the mobile and the base station. In the protocol the actions of the mobile are minimized. The base station with plenty of energy performs actions in courtesy of the mobile. We have paid much attention in reducing the cost for a mobile of just being connected. The protocol is able to provide near-optimal energy efficiency (i.e., energy is spent for the actual transfer only) for a mobile within the constraints of the QoS of all connections in a cell, and only requires a small overhead.

Energy management for dynamically reconfigurable heterogeneous mobile systems

Dynamically reconfigurable systems offer the potential for realising efficient systems as well asproviding adaptability to changing system requirements. Such systems are suitable for futuremobile multimedia systems that have limited battery resources, must handle diverse data types, and must operate in dynamic application and communication environments. We propose an approach in which reconfiguration is applied dynamically at various levels of a mobile system, whereas traditionally, reconfigurable systems mainly focus at the gate level only. The research performed in the CHAMELEON project 1aims at designing such a heterogeneous reconfigurable mobile system. The two main motivations for the system are 1) to have an energy-efficient system, while 2) achieving an adequate Quality of Service for applications.

Voltammetric investigation of the complexation equilibria in the presence of a low level of supporting electrolyte part 1: Steady-state current-potential curves for inert complexes

The use of microelectrodes for voltammetric investigations of the complexation equilibria at very low concentrations of supporting electrolyte allows the risk of competitive complexation or contamination to be avoided, makes the activities of the species involved closer to their concentrations (which facilitates comparisons with the spectroscopic results) and finally, allows the concentrations of the species to be varied over a broader range. This paper presents the calculations of the steady-state currents for a wide range of complexes that are inert on the experimental time scale, and reports the influence of the concentration of the electroinactive ionic species on the limiting currents. Also, for a number of cases the variation of halfwave potential with the ligand concentration, resulting from changes in the ohmic drop, is given. It is assumed that only one species (the complex or the uncomplexed form) is electroactive; if this is the complex, it may or may not change the number of ligands. The theoretical results were obtained either employing the Myland-Oldham theory extended in this paper or by digital simulation. The results of calculations show that the magnitude of the changes in the steady-state limiting current on complexation depends on the type of complexation equilibrium, the type of the change in the reactant charge number in the electrode process, and the complex formation constant. In a number of situations migrational effects are negligibly small and no special treatment is necessary, despite the lack of supporting electrolyte. In other cases, where migration is significant, the relations between the measured steady-state limiting current and the complex formation constant s are given in the form of fitted equations that can be used to obtain s from appropriate experimental data.

Chemically modified ion-sensitive field-effect transistors: elimination of the liquid juction potential in a double sensor flow-injection analysis cell

A flow-through cell was designed that can be used for flow-injection analysis with two chemically modified ion-sensitive field-effect transistors (CHEMFETs) in close proximity. This offers the possibility of a differential measurement without influence of the liquid junction potential. The differential signal of a potassium- and a sodium-selective CHEMFET responded in a Nernstian manner and selectively towards potassium in an excess (fixed) concentration of sodium. A highly lead-selective CHEMFET was used in the same flow cell in combination with a potassium-selective CHEMFET.

Liquid-liquid phase transfer of uronium salts via complexation by (di)benzo crown ethers. X-Ray structure of the benzo-27-crown-9 uronium perchlorate (1:1) complex

The complexation of uronium perchlorate with crown ethers of different ringsizes (18–33 ring atoms) has been studied by using two-phase extraction experiments. Crown ethers with 27 or more ring atoms are the best hosts to transfer uronium salts from an aqueous phase to an organic phase. The amount of uronium perchlorate transferred was measured by coulometric titration of the stoichiometric amount of ammonia produced by enzymatic degradation of urea. The crystal and molecular structure of the 1:1 complex of uronium perchlorate with benzo-27-crown-9 has been determined by X-ray crystallography. The uronium cation is encapsulated in the crown ether cavity with all its hydrogen atoms bonded to the macrocyclic host. A 1:1 complex of uronium picrate with benzo-21-crown-7 was isolated and is assumed to be a perching complex.