Modelling of the activated sludge process for microprocessor-based state estimation and control

A simple dynamic model of the activated sludge process including the volatile suspended solids (VSS) concentration in the aeration basin, the VSS or suspended solids (SS) concentration in the recycle flow and the SS concentration in the effluent was obtained by simplifying a comprehensive model using empirically verified assumptions. The model can be used for on-line estimation of the influent BOD-load and the effluent BOD, in combination with a recursive algorithm for oxygen uptake rate (OUR) and k_La estimation requiring only dissolved oxygen and air flow rate measurements. The estimation procedure has been implemented and tested at a real plant using a microprocessor. Control of the activated sludge process is discussed and concluded to be a hierarchical two-level problem. The upper level control actions are aimed at bringing the process to an optimal state of operation. For this purpose verbally formulated control laws are used. On the lower level the control task is to maintain the process in the optimal state.     

Quantitative trait loci affecting health traits in Swedish dairy cattle

The purpose of this study was to map quantitative trait loci (QTL) affecting health traits in Swedish dairy cattle. A genome scan covering 17 chromosomes was performed. Ten grandsire families were used in a granddaughter design. Nine of the families belonged to the Swedish Red and White breed, which is related to other Nordic Ayrshire breeds, and one family was of the Swedish Holstein breed. A total of 417 bulls were genotyped for 116 microsatellite markers distributed over 17 chromosomes. Daughter yield deviations for clinical mastitis, somatic cell count (SCC), and other diseases (OD) were included in the analysis. Least squares interval mapping using putative QTL as cofactors was applied both within and across grandsire families. Significance thresholds were set by permutation tests. In the across-family analysis, we detected 8 suggestive QTL and 3 QTL significant at the genome level. The QTL affecting clinical mastitis were found on 3 chromosomes (9, 11, and 25), 4 QTL for SCC were found (on chromosomes 5, 9, 11, and 23), and we detected 4 QTL for OD (on chromosomes 9, 11, 15, and 25). In addition, we found several QTL that segregated within single families but where the QTL effect was not significant in the across-family analysis. In conclusion, we were able to locate QTL for all 3 analyzed traits, and overlapping QTL for several traits were observed.     

非木材制浆技术的未来

目前,非木浆厂已能采用现代木浆厂的最先进技术。泵送、筛选、洗涤、漂白等可在更高浆浓下运行,减少了新鲜水用量和废水量。最新安装的世界上最大的麦草浆和蔗渣浆生产线都采用了基于木材制浆的技术,包括TwinRollTM压榨、氧脱木素和无元素氯（ECF）漂白。但近2年的调查发现非木浆生产停滞,其中一个主要原因就是大量非木浆厂没有蒸煮废液回收系统,或极少量有蒸煮废液回收的小型工厂已被关闭。同时,非木材制浆的最大问题仍有待解决,即溶解在蒸煮液中的高浓硅化合物会给蒸发和新鲜蒸煮液再制备带来一系列问题。一个新的工艺概念FreeFiberTM是通过限制硅在蒸煮液中的溶解解决硅干扰问题。FreeFiberTM蒸煮中以气相乙醇作为加热介质;以碳酸钠作为碱源,无需苛化;纸浆可以漂到非常高的白度,而且纸浆强度性能可以与传统碱法纸浆相媲美。     

Tribological Performance of Coated Surfaces

The fundamentals of coating tribology is presented in a generalised holistic approach to friction and wear mechanisms of coated surfaces in dry sliding contacts. It is based on a classification of the tribological contact process into macromechanical, micromechanical, tribochemical contact mechanisms and material transfer. The tribological contact process is dominated by the macromechanical mechanisms, which have been systematically analysed by using four main parameters: the coating-to-substrate hardness relationship, the film thickness, the surface roughness and the debris in the contact. In this paper special attention is given to the microlevel mechanisms, and in particular new techniques for modelling the elastic, plastic and brittle behaviour of the surface by finite element (FEM) computer simulations. The contact condition with a sphere sliding over a plate coated with a very thin hard coating is analysed. A three dimensional FEM model has been developed for calculating the first principal stress distribution in the scratch tester contact of a diamond spherical tip moving with increased load on a 2μm thick titanium nitride (TIN) coated steel surface. The model is comprehensive in that sense that it considers elastic, plastic and fracture behaviour of the contact surfaces. By identifying from a scratch experiment the location of the first crack and using this as input data can the fracture toughness of the coating be determined.     

Flow induced fiber orientation in compression molded glass mat thermoplastics

This study examines how the mechanical properties in GMT are affected by axisymmetric flow during compression molding. Two types of GMT with different architecture are used, swirled mat and short fiber GMT. Tree different grades are tested for each fiber architecture 20, 30, and 40% fiber content by weight. These are in principle the grades of GMT commercially available today. It is found that the flow reduced the tensile strength by 30 to 50% and the tensile modulus up to 30% in the flow direction. The reduction in mechanical properties, which is mainly caused by flow‐induced fiber orientation, is larger at high fiber contents. The study also showed that there is no major difference in behavior between swirled mat and short fiber GMT regarding flow induced fiber orientation.