Presupposition failure — A comedy of errors

Presuppositions of utterances are the pieces of information you convey with an utterance no matter whether your utterance is true or not. We first study presupposition in a very simple framework of updating propositional information, with examples of how presuppositions of complex propositional updates can be calculated. Next we move on to presuppositions and quantification, in the context of a dynamic version of predicate logic, suitably modified to allow for presupposition failure. In both the propositional and the quantificational case, presupposition failure can be viewed as error abortion of procedures. Thus, a dynamic assertion logic which describes the preconditions for error abortion is the suitable tool for analysing presupposition.     

A novel cyclic process using CaSO<Subscript>4</Subscript>/CaS pellets for converting sulfur dioxide to elemental sulfur without generating secondary pollutants: Part I. Feasibility and kinetics of the reduction of sulfur dioxide with calcium-sulfide pellets

Certain new sulfide-smelting processes and coal-gasification processes generate high-strength sulfur dioxide streams, for which a new process for converting sulfur dioxide to elemental sulfur needs to be developed because no process exists that is generally and economically applicable to the treatment of such streams. A thermodynamic and experimental investigation to develop a new process for converting sulfur dioxide to elemental sulfur by a cyclic process involving calcium sulfide and calcium sulfate without generating secondary pollutants was carried out. In this process, the starting raw material, calcium sulfate, is reduced by a suitable reducing agent, such as hydrogen, to produce calcium sulfide, which is used to reduce sulfur dioxide to elemental sulfur vapor and calcium sulfate. The latter is, in turn, reduced to regenerate calcium sulfide. In this Part I, detailed experimental results are presented on the kinetics of the reaction between sulfur dioxide and calcium-sulfide pellets, which produces elemental sulfur and calcium sulfate. The experiments were carried out at temperatures between 1023 and 1088 K and sulfur-dioxide partial pressures between 9 and 60 kPa by the use of a thermogravimetric analysis (TGA) technique. The rate of this reaction was demonstrated by the conversion of 40 pct calcium-sulfide pellets obtained from the hydrogen reduction of fresh calcium sulfate in 10 minutes at 1073 K under a sulfur-dioxide partial pressure of 43 kPa. The reactivity decreased somewhat during the first three cycles but remained largely unchanged thereafter up to the tenth cycle. This characteristic of the pellets is important because the solids must be reusable for repeated cycles to avoid generating secondary pollutants. A pore-blocking model was found to fit the reaction rate. The reaction is first order with respect to sulfur-dioxide partial pressure and has an activation energy of 101 to 134 kJ/mol (24 to 32 kcal/mol) for calcium-sulfide pellets reacted and regenerated several different times. Sulfur dioxide-containing streams from certain sources, such as the regenerator off-gas from an integrated-gasification, combined-cycle, desulfurization unit and new sulfide-smelting plants, contain much higher partial pressures of SO₂. In these cases, the rate of the first reaction is expected to be proportionally higher than in the test conditions reported in this article. The reduction kinetics of calcium-sulfate pellets with hydrogen gas is reported in the accompanying Part II.     

NGO-Ⅲ催化剂的异构化性能评价

直馏汽油非临氢高效异构化使用最新一代NGO－Ⅲ型催化剂，生产的产品汽油辛烷值、产品收率及催化剂稳定性等全面超过现用的工业催化剂，达到目前国内同类产品的领先水平。     

Microbiological denitrification of red beet juice

The purpose of study was the determination of optimal conditions for red beet juice denitrification by Paracoccus denitrificans bacteria as well as the evaluation of the usefulness of microbiologically treated juice for the production of a natural colouring preparation for foods. Total reduction of nitrates was found during bacterial culturing at 25 and 30 °C, at an initial pH of 7.0-8.0 and juice osmotic pressure of 900-1100 mOsm/kg. Microbiological denitrification procedure affected colour, taste and aroma of the juice. However, the use of juice as food colouring and component was made feasible by acidification and partial evaporation of water together with volatile substances.     

再谈石材幕墙干挂中存在的安全隐患

随着社会经济的发展，在建筑物装饰中，石材幕墙已占有相当大的比例，华丽的石材幕墙确实为装点城市增添了光彩。庞大的幕墙所用石材每块重达几十斤，并且是由一个个小小的、很不起眼的干挂件与结构体相连接，可见质量是何等的重要。　　但是，令人担忧的是，目前市场上的干挂件质量不容乐观。近几年，外交部大楼、首都机场候机楼等均发生过石板从天而降砸坏汽车和其他物品的事件。导致事件的原因是因挂件质量低劣、焊接头缝不饱满，且经过高温退火产生氧化而断裂所造成。去年中央电视台《焦点访谈》节目对江苏兴化生产的不锈钢产品质量…     

Suspension force and mechanism of debris flows

The paper discusses the postulated suspension force, by which it is possible to explain some enigmatic phenomena observed in different types of mass movements. This force is generated in thick suspensions as a result of friction between sinking solid particles and static water. The suspension force is related to the seepage force but they have opposite directions. Both forces form flow networks. Having explained the suspension force, the paper describes how this influences the movement of material, particularly in debris flows. Enigmatic features and the mechanism of debris flows and lahars are explained by virtue of the suspension force. Electronic Publication     

Scheduling railway traffic at a construction site

We consider the problem of rescheduling trains in the case where one track of a railway section consisting of two tracks in opposing directions is closed due to construction activities. After presenting an appropriate model for this situation we derive a polynomial algorithm for the subproblem of finding an optimal schedule with minimal latenesss if the subsequences of trains for both directions outside the construction site are fixed. Based on this algorithm we propose a local search procedure for the general problem of finding good schedules and report test results for some real world instances. Received: December 8, 1999 / Accepted: May 2, 2001     

CuO/ZnO甲醇合成催化剂的正电子湮没谱学研究

发展了用正电子湮没寿命参数测定用共沉淀方法制备的金属氧化物系固溶度的新方法。测量了一系列用共沉淀方法制备的不同CuO at％含量的CuO/ZnO甲醇合成催化剂粉末(压制成片)还原前后的正电子寿命谱。分析该种催化剂的固溶特性及其与正电子寿命参数的关系,得出还原后样品的固溶度为12CuOat％.支持了CuO/ZnO甲醇合成催化剂以Cu~+离子为活性中心的观点。