Guideline for Measurement of Ozone Concentration in the Process Gas From an Ozone Generator

A joint meeting of members of the Quality Assurance Committees of the International Ozone Association Pan American Group (PAG), European-African Group (EAG), and Nippon Islands Group (NIG) was held in Oxford, Ohio on November 8 and 9, 1995. The purpose of the meeting was to establish a single, shared guideline for ozone concentration measurement in the gas phase and, in particular, from commercial ozone generators.     

Design and verification of a model secondary clarifier for activated sludge

A model clarifier was designed using conventional methods for the surface calculation and an alternative pathway for the determination of the height and constructed accordingly. In addition, a new approach was used to evaluate the necessary scraper speed in comparison to full-scale clarifiers. Scaling effects were taken into account. The model clarifier was first tested by tracer experiments. Conductivity measurements were used for the clarification zone, whereas the thickening zone was tested using pyrene as an organic tracer compound. Finally, the behaviour of the model clarifier was compared with a full-scale settler. The results indicated that operation of the model clarifier was representative of full-scale behaviour, except for severe overloads. Hence, the small-scale clarifier qualified as a model for small-scale studies and could be installed on large-scale plants to monitor more transparently plant performance and sludge behaviour     

"大昆明区"空间规划面临的机遇和挑战

本文针对昆明的发展特征及面临的挑战,引入了一种全覆盖的综合规划方法来从整体上协调空间的各种职能及保护自然潜力.对大昆明区采用基于GIS的区域模型模拟了这些政策和方法的潜在影响力.结果显示,污染减少、土地利用成本和基础设施的建设成本降低,同时城市的竞争力提高.     

利用可持续指标监测与调控大昆明区区域城镇发展

本文针对昆明的发展特征及面临的挑战,引入了一种全覆盖的综合规划方法来从整体上协调空间的各种职能及保护自然潜力.对大昆明区采用基于GIS的区域模型模拟了这些政策和方法的潜在影响力.结果显示,污染减少、土地利用成本和基础设施的建设成本降低,同时城市的竞争力提高.     

Bacterial carbonate precipitation improves the durability of cementitious materials

Shortcomings of conventional surface treatments have drawn the attention to alternative techniques for the improvement of the durability of concrete. This paper reports the effects of bacterial carbonate precipitation (biodeposition) on the durability of mortar specimens with different porosity. Durability was assessed from the permeation properties and resistance towards degradation processes. The surface deposition of calcium carbonate crystals decreased the water absorption with 65 to 90% depending on the porosity of the specimens. As a consequence, the carbonation rate and chloride migration decreased by about 25-30% and 10-40% respectively. An increased resistance towards freezing and thawing was also noticed. The results obtained with the biodeposition treatment were similar as those obtained with conventional surface treatments.     

Benefits of amplification in an inertial stepping motor

Inertial stepping motors (ISMs) are widely used in high precision applications, such as scanning tunnelling microscopy and/or micro manipulation. The resolution they are able to reach makes them especially suitable when long stroke and high resolution are needed simultaneously. However, the limited speed of this technology is its main drawback. To overcome this drawback, the present paper proposes to use an amplified actuator in an ISM instead of a classical direct actuator. The impact of this choice is studied here, from speed and electrical current points of view.This study determined in an analytical way the influence of the actuator stroke on the step size of an ISM via an optimised control signal. The results are then confronted to a lumped model to identify potential limitations. Finally, a test bench is built using three different piezoelectric actuators to obtain experimental feedback about the benefits of actuator amplification in ISMs.     

Practical approach to tuning MPC

This paper presents the results of a heuristic approach for developing model predictive control (MPC) tuning rules. The tuning has been applied and tested in easy-to-use MPC. Process modeling in this MPC uses normalized input/ output range. As a result there is no need for tuning outputs, a procedure known as adjusting equal concern error. Penalties on moves are set as a function of process dead time as the primary factor, with some correction from process gain. The default calculation delivers robust control, which tolerates up to triple increase in process static gain. If control is too aggressive, further on-line adjustment can be done by set point reference trajectory. Test results show that this tuning is robust for process gain change, however, it is much less efficient in compensating for process dead-time changes. It was found that dead-time mismatch is much better compensated with the model correction filter. Combining the three handles, i.e., penalties on moves, reference trajectory, and model filter, easy and intuitively understandable MPC tuning was achieved. The findings are illustrated by numerous MPC simulated tests.     

Phosphate removal in agro-industry: Pilot- and full-scale operational considerations of struvite crystallization

Pilot-scale struvite crystallization tests using anaerobic effluent from potato processing industries were performed at three different plants. Two plants (P1 & P2) showed high phosphate removal efficiencies, 89 ± 3% and 75 ± 8%, resulting in final effluent levels of 12 ± 3 mg PO₄³⁻-P L⁻¹ and 11 ± 3 mg PO₄³⁻-P L⁻¹, respectively. In contrast, poor phosphate removal (19 ± 8%) was obtained at the third location (P3). Further investigations at P3 showed the negative effect of high Ca²⁺/PO₄³⁻-P molar ratio (ca. 1.25 ± 0.11) on struvite formation. A full-scale struvite plant treating anaerobic effluent from a dairy industry showed the same Ca²⁺ interference. A shift in the influent Ca²⁺/PO₄³⁻-P molar ratio from 2.69 to 1.36 resulted in average total phosphorus removal of 78 ± 7%, corresponding with effluent levels of 14 ± 4 mg P_total L⁻¹ (9 ± 3 mg PO₄³⁻-P L⁻¹). Under these conditions high quality spherical struvite crystals of 2-6 mm were produced.