Development of Pneumatic Servo Bearing Actuator for Nanometer Positioning

The ‘pneumatic servo bearing actuator (PSBA)’ that consists of an aerostatic bearing and a servo valve was proposed and developed for ultraprecise positioning. In the actuator, pressurized air controlled by the servo valve moves an actuated spool ultra-precisely. Even under open-loop control, the PSBA provided accurate replication and positioning resolution on a nanometer order. Applying simple positioning feedback and parallel observation that estimates the disturbance into the system increased the actuator stiffness to be almost infinite and promoted a sharp step response without drift and hysteresis, and thus the minimum positioning resolution of prototype PSBA was about 1 nm.

Apatite as an interesting seed to remove phosphorus from wastewater in constructed wetlands

Intensive use of phosphates has resulted in high P levels in surface waters and therefore eutrophication problems. Over the last decade many studies have revealed the advantage of using specific materials with efficient phosphorus retention capacities. Recent studies state that Ca materials are of particular interest for long-term retention of P, but can induce negative effects. To improve P retention and avoid negative counter-effects we tested the potential of natural apatites. Apatite sorption was evaluated using batch and open reactor experiments. Batch experiments identify sorption mechanisms and the influence of the ionic characteristics of the solution; open reactor experiments evaluate sorption capacities in relation to the ionic composition of the solution and biomass development. In parallel, observation of the material by electron microscopy was used to give more precision information about the mechanisms involved. This work reveals the strong chemical affinity between apatites and phosphorus. Compared to other calcareous materials apatite is better able to maintain low outlet P levels. After more than 550 days feeding, sorption was still present and low P outlet levels were still being obtained when sufficient contact time and calcium content in the solution were ensured. This work demonstrates the advantages of using apatites for phosphorus removal in constructed wetlands. The behaviour of apatite in phosphorus retention is explained and its suitability for use in such extensive systems defined.

RHEOLOGICAL SYNERGISTIC EFFECTS OF ELECTRIC AND MAGNETIC FIELDS IN IRON PARTICLE SUSPENSION

The effects of electric field and/or magnetic field on the rheological property of iron suspension were studied by use of parallel-plate rheometers developed for electro-magnetorheological (EMR) measurements. The EMR effect, which is defined as an increase in the shear stress under combined fields, was dependent on the strength and direction of the fields. In particular, significant synergism was found in the EMR effect when the electric and magnetic fields were applied in parallel. Observation of the suspensions solidified in parallel field and crossed field conditions revealed different structures of aggregated particles for these combined fields. The parallel field induced many chains along the field, while the crossed field induced a network structure. It is concluded that the synergistic EMR effect in parallel field is due to the increase in the number of particle chains bridging the plates.