Reducibility: A ubiquitous method in lambda calculus with intersection types

A general reducibility method is developed for proving reduction properties of lambda terms typeable in intersection type systems with and without the universal type Ω. Sufficient conditions for its application are derived. This method leads to uniform proofs of confluence, standardization, and weak head normalization of terms typeable in the system with the type Ω. The method extends Tait's reducibility method for the proof of strong normalization of the simply typed lambda calculus, Krivine's extension of the same method for the strong normalization of intersection type system without Ω, and Statman-Mitchell's logical relation method for the proof of confluence of βη-reduction on the simply typed lambda terms. As a consequence, the confluence and the standardization of all (untyped) lambda terms is obtained.     

几种满足汇合性质的Petri网子类

证明活的标识S-图、活的标识T-图、有界的冲突无关的Petri网、有界的标识T．图具有汇合性质,讨论共享合成与同步合成操作对Petri网汇合性质的保持性,得出由上述简单的Petri网子类通过共享合成及同步合成得到的复杂的网系统也具有汇合性质。通过一个具有汇合性质的复杂网系统实例验证该结论。     

明渠干支河流直角交汇区整流方法探讨

由于便利的水运条件,有相当一部分重要的城市和乡镇位于河流交汇处,但由于交汇水流结构的复杂性,在交汇区常形成冲击河岸和泥沙淤积等一系列问题,因而对交汇区水流进行有效地整治是非常必要的。本文利用数值模拟试验,对入汇角为90°的河流交汇处产生的分离区水流特征进行了研究,并在此基础上提出了一种可以减小或消除分离区的优化堤线的整流方案,即优化后的堤线满足椭圆方程,椭圆长半轴长度为分离区长度,短半轴为分离区宽度,以改善交汇区的泥沙淤堵及水位抬高等灾害问题。通过对不同干支流动量比堤线整流效果对比分析,结果表明：当动量比M*=0.40时得出的椭圆型堤线为最佳整流方案。     

嘉陵江与长江交汇水流顶托效应特性研究

干支河流交汇是河流水系发育与演化的重要形式,在河流交汇区常发生水流顶托现象。水流顶托显著影响着干支流交汇区水位、水面比降及床面切应力特性,从而制约着交汇区水沙运动特性及河床演变过程。本文以嘉陵江与长江交汇区为例,基于实测资料与不同组合干支来流的数值模拟结果,突出分析了不同干支来流条件下典型区域水位、水面比降及床面切应力变化特性,结果表明嘉陵江对长江的顶托作用随汇流比的增大而增大,长江上游水面比降随汇流比增大而减小,床面切应力随汇流比增大而减小。     

城市排水工程中排水制度的分析

对城市排水分流制和合流制实际运行中存在的不正常现象进行了思考，分析了可能影响排水制度正常运行的各种因素，找出潜在的原因，提出了解决的方法和建议。     

Impact of the Budha Nallah brook on the river Satluj waters. i—some physico‐chemical parameters

The impact of grossly polluted waters of the Budha Nallah on the water quality in the realm of physico‐chemical characteristics of the river Satluj after its confluence with the river was studied. The analysis of water at downstream spot (3 km after the point of confluence of Budha Nallah) revealed a significant increase in the levels of free‐CO₂, alkalinity, chlorides, total hardness, sulphates, water soluble phosphates, nitrates, ammonia, suspended solids, biochemical oxygen demand (BOD) and the chemical oxygen demand (COD), whereas levels of dissolved oxygen and pH declined when compared with the water quality at the upstream spot (3 km before the point of confluence of Budha Nallah).     

Shallow confluence of conditional term rewriting systems

Recursion can be conveniently modeled with left-linear positive/negative-conditional term rewriting systems, provided that non-termination, non-trivial critical overlaps, non-right-stability, non-normality, and extra variables are admitted. For such systems we present novel sufficient criteria for shallow confluence and arrive at the first decidable confluence criterion admitting non-trivial critical overlaps. To this end, we restrict the introduction of extra variables of right-hand sides to binding equations and require the critical pairs to have somehow complementary literals in their conditions. Shallow confluence implies [level] confluence, has applications in functional logic programming, and guarantees the object-level consistency of the underlying data types in the inductive theorem prover QuodLibet.     

Inductive expansion: A calculus for verifying and synthesizing functional and logic programs

Guarded Horn clauses over a many-sorted polymorphic signature provide a powerful syntax for design specifications. Expressed as a set of positive Gentzen clauses with a common guard, requirements to such a specification can be proved top-down by inductive expansion: conclusions and generators of the clauses are transformed via resolution and paramodulation upon axioms, lemmas and induction hypotheses into the guard. Case distinctions are generated when axioms or lemmas are applied in parallel. They split the proof into subexpansions, which are later rejoined by applying disjunctive lemmas. Induction orderings need not be selected before redices for induction hypotheses have been created.The controlled expansion of requirements to a function (or predicate) may produce axioms representing a program for that function. This generalizes traditional approaches to program synthesis such as fold& unfold, divide&conquer or deductive tableaus. Ground confluent and strongly terminating design specifications yield decidable criteria for constructors and unsolvable goals and thus reduce the search space of inductive expansion.     

降雪对乌鲁木齐市海绵城市LID设施的影响

为研究冬季降雪对海绵城市LID(low impact development)设施的影响,以乌鲁木齐市某城市主干道为例,借助SWMM模拟软件建立海绵化改造模型,讨论模型各重要参数的取值方式,进行降雪及融雪模拟,分析降雪在不同模拟环境下对道路海绵化改造的影响。结果显示:在冬季降雪期,蒸发速率对模型的影响较大,在没有当地准确的蒸发速率资料时,推荐使用基于Hargreaves方程的公式法进行模拟分析。利用SWMM模拟冬季融雪期径流过程,各汇水区域的积雪处理方式对模拟结果影响很大,应合理分析并结合当地实际情况进行设定。模拟结果表明:若乌鲁木齐市冬季降雪全部堆积在道路两旁生物滞留设施上,可利用融雪量达10.6万m~3,能够减轻乌市的水资源压力。研究成果对积雪量较大而水资源短缺地区海绵城市的建设具有工程上的参考价值。     

宁夏黄河干流和干支流交汇处河床冲淤演变分析

分别采用沙量平衡法和断面法计算宁夏黄河干流和干支流交汇处的冲淤量,以刘家峡、青铜峡水库运行前(1951-1968年)、刘家峡、青铜峡水库运行后(1969-1985年)、龙刘联合运用(1986-2005年)和近期(2006-2011年)四个阶段对干流的冲淤变化进行了研究,对干支流交汇处1993-2015年历次实测大断面资料进行套绘,分析了1993-2015年干支流交汇处的断面特征变化以及干、支流不同水沙组合对干流和干支流交汇处冲淤的影响。分析结果表明:宁夏黄河干流年均来沙系数越大,干流河床淤积越严重,但支流来沙量的增大对干流河床冲淤的影响不大;干支流交汇处年均全断面冲淤量与干流年均来沙系数无明显相关关系;支流年均来沙系数越大,干支流交汇处断面反而冲刷越严重。