Expanded subalphabets in the theories of languages and semigroups†

A new type of code, called an expanded subalphabet, is introduced. It is shown that the following four conditions on a subset L of the free monoid A ^? over a finite or infinite alphabet A are equivalent: (1) L is the submonoid generated by an expanded subalphabet; (2) L is a retract; (3) L is the fixed language of an endomorphism; (4) L is the stationary language of an endomorphism. Expanded subalphabets are used as a tool for the investigation of fixed languages (=retracts). Special results for the case of a finite alphabet are given and the relationship with the theory of L-systems is indicated.     

具有稳定子集的奇异压缩变换半群

半群理论广泛地应用于数学、计算机语言、编码理论等领域。Clay定理表明任何半群都同构于某个变换半群,具有各种性质的奇异变换半群的子半群是半群理论研究的热点问题之一。Sn（4）是定义在瓦上的具有稳定子集的奇异压缩变换半群,研究该半群的Green-关系、生成集、半群的基数等代数和组合性质。     

具有时滞的人口动力系统的近似能控性

针对人口动力系统能控性问题,该文运用算子半群方法,在解半群意义下利用无时滞人口动力系统的精确能控性结果讨论了具有时滞的人口动力系统的近似能控性,并给出了近似能控性,证明。     

AG: A set of Maple Packages for Manipulating Automata and Semigroups

AG is a set of packages for manipulating finite state automata and finite semigroups. This software includes on the one hand the AUTOMAP package which affords the usual operations on automata (union, concatenation, Kleene closure,.) as well as the usual transformations (trimming, minimization,.) and on the other hand the GREEN package which yields the (regular or not) D-class structure of a finite monoid. The AG software has been implemented using the Maple symbolic computation system. ©1997 by John Wiley & Sons, Ltd.     

Air–steam gasification of biomass in a fluidised bed: Process optimisation by enriched air

The effect of oxygen concentration in the gasification agent was studied by enriched–air–steam biomass gasification tests in a bubbling fluidised-bed gasification (FBG) plant. The oxygen content in the enriched air was varied from 21% (v/v, i.e. air) to 40% (v/v), aiming at simulating FBG where enriched air is produced by membranes. The stoichiometric ratio (ratio of actual to stoichiometric oxygen flow rates) and steam-to-biomass ratio (ratio of steam to biomass, dry and ash-free, flow rates) were varied from 0.24 to 0.38 and from 0 to 0.63, respectively. The tests were conducted under simulated adiabatic and autothermal conditions, to reproduce the behaviour of larger industrial FBG. The temperature of the inlet gasification mixture was fixed consistently at 400 °C for all tests, a value that can be achieved by energy recovery from the off-gas in large FBG without tar condensation. It was shown that the enrichment of air from 21 to 40% v/v made it possible to increase the gasification efficiency from 54% to 68% and the lower heating value of the gas from 5 to 9.3 MJ/Nm³, while reaching a maximum carbon conversion of 97%. The best conditions were found at intermediate values of steam-to-biomass ratio, specifically within the range 0.25–0.35. The enriched-air–steam gasification concept explored in this work seems to be an interesting option for the improvement of standalone direct air–blown FBG because it considerably improves the process efficiency while maintaining the costs relatively low as compared to oxygen-steam gasification.     

全球治水模式思辨与发展展望

近百年来全球治水取得了巨大成就,为保障可持续发展提供了关键支撑;然而,全球水问题愈演愈烈,亟待进一步创新治水模式。结合水问题发展历程,剖析了水问题的根本症结;从治水目标、总体路径和治理措施等方面解析了全球治水模式的不足,认为当前的全球治水模式未能充分融合水循环及多要素过程的自然属性,存在末端治理和过程分离等突出问题。对下一步治水模式提出了发展建议:从耦合流域水循环多过程互馈机制的角度,提升自然属性和自然力的作用,协调多要素多过程的功能,建设富自然-功能协调流域,系统治理复杂水问题。     

rIL—1和rIL—2对浓缩铀UO2F2的防护作用

本文介绍用3H-TdR 掺入示踪技术,探讨了外源性白细胞介素-1(rIL-1)和外源性白细胞介素-2(rIL-2)对浓缩铀 UO_2F_2损伤小鼠脾脏 B 淋巴细胞的防护作用。经 BALB/c 小白鼠尾静脉注入20mg/kg 体重的浓缩铀 UO_2F_2 48 h 后,无菌取脾,制成单细胞悬液加入细菌脂多糖(LPS)、rIL-1或 rIL-2常规培养,以淋巴细胞 DNA 中~3H-TdR 掺入量的变化来衡量 B 淋巴细胞的增殖能力。结果表明,浓缩铀 UO_2F_2能明显抑制小鼠脾脏 B 淋巴细胞 DNA 的合成,使 B 淋巴细胞增殖受到明显抑制;rIL-1和 rIL-2可使受浓缩铀 UO_2F_2损伤的小鼠脾脏 B 淋巴细胞的增殖抑制部分逆转,最大增殖率分别为67%和51%;二者合并使用时可使增殖率增至83%。     

Semigroups of matrices with dense orbits

We give examples of n?×?n matrices A and B over the field 𝕂?=?? or ? such that for almost every column vector x?∈?𝕂 ⁿ , the orbit of x under the action of the semigroup generated by A and B is dense in 𝕂 ⁿ .     

金针菇富硒薜荔汁复合饮料的研制

用金针菇Fr19菌丝体液体培养富硒，硒浓度为10μg／ml时富集率最高，用试验确定了复合饮料最佳配方，金针菇菌丝提取液、薜荔汁液、白砂糖、柠檬酸为20％、15％、2％、0．2％。该饮料具有人体吸收率高的生物硒，对人体安全无害，同时具有金针菇菌体蛋白、多糖体、薜荔汁等丰富的营养成份，为研制功能型复合保健饮料提供了实验模型。