PVC-U molding profile extruder control system based on lonworks
By studying the dual-screw profile extruder used in PVC-U molding processing, presents a temperature computer control system in which a combined-control strategy of on-off control, fuzzy-control and integral-control were adaptive elected. The control system used Lonworks constructing a net to regulate the extruder's sub-areas temperature in line. App effect shows that the temperature control precision and the method of multi-subarea control in line with Lonworks filedbus has better effect than those sub-areas self-governed control, and can prevent PVC-U decompounding in the processing effectively, so the character of PVC-U manufacture could be improved.
A Fuzzy-PID Control System of PTFE Sintering Furnace Based on Lonworks
This note introduces an industrial control system which adopts fuzzy-PID and Lonworks. According to the character of a class of time-delay and great inertia first-order system, we chose a combined-control strategy that On-off control or Fuzzy-control or PID control strategy were selected automatically, so accurate control to the four PTFE (Polytetrafluoro-ethylene) molding furnace sintering process such as sintering temperature, sintering time, cooling speed etc were achieved. App effect shows, temperature control precision is 0.5%, initial tracking error, maximum exceed error and final error are 2.5, 2.0 and 2.0 Celsius respectively. It proves that the combined-control system is better than the singularity structural such as PID or Fuzzy in fleetness and robustness and steady-state precision.
O2 constraints from Paleoproterozoic detrital pyrite and uraninite
Redox-sensitive detrital grains such as pyrite and uraninite in sedimentary successions provide one of the most conspicuous geological clues to a different composition of the Archean and early Paleoproterozoic atmosphere. Today, these minerals are rapidly chemically weathered within short transport distances. Prior to the rise of oxygen, low O2 concentrations allowed their survival in siliciclastic deposits with grain erosion tied only to physical transport processes. After the rise of oxygen, redox-sensitive detrital grains effectively vanish from the sedimentary record. To get a better understanding of the timing of this transition, we examined sandstones recorded in a scientifi c drill core from the South African 2.415 Ga Koegas Subgroup, a mixed siliciclastic and iron formation–bearing unit deposited on the western deltaic margin of the Kaapvaal craton in early Paleoproterozoic time. We observed detrital pyrite and uraninite grains throughout all investigated sandstone beds in the section, indicating the rise of oxygen is younger than 2.415 Ga. To better understand how observations of detrital pyrite and uraninite in sedimentary rocks can quantitatively constrain Earth surface redox conditions, we constructed a model of grain erosion from chemical weathering and physical abrasion to place an upper limit on ancient environmental O2 concentrations. Even conservative model calculations for deltaic depositional systems with suffi cient transport distances (approximately hundreds of kilometers) show that redox-sensitive detrital grains are remarkably sensitive to environmental O2 concentrations, and they constrain the Archean and early Paleoproterozoic atmosphere to have <3.2 × 10 –5 atm of molecular O2. These levels are lower than previously hypothesized for redox-sensitive detrital grains, but they are consistent with estimates made from other redox proxy data, including the anomalous fractionation of sulfur isotopes. The binary loss of detrital pyrite and uraninite from the sedimentary record coincident with the rise of oxygen indicates that atmospheric O2 concentrations rose substantially at this time and were never again suffi ciently low (<0.01 atm) to enable survival and preservation of these grains in short transport systems.