Load bearing capacity of an intact and a degraded pipe system under repeated simulated earthquake loading

A series of experiments were performed at the German HDR-test-facility to assess the behaviour and the reserves in load-carrying capacity of an unflawed and a degraded pipe system when subjected to repeated simulated earthquake loading.

In the case of a specially designed flexible support configuration the unflawed pipe system could be loaded up to eight times the required safe shutdown earthquake load level without any problem. The functional viability of different support configurations and support components was comprehensively tested.

The load carrying capacity margins of a pipe system containing degraded components and under operating conditions were demonstrated for earthquake type loads even when these were excessive and repeatedly applied. No noticeable crack growth occurred for a single earthquake-like loading.     

Multiaxial fatigue of quenched and tempered U2 steel: Testing and fatigue life prediction

Tension‐compression, tension‐tension, torsional, and 90° out‐of‐phase axial‐torsional fatigue tests were performed on a quenched and tempered U2 steel. All tests were conducted under force/torque control because macroscopic plastic strains were insignificant in the life range of interest (from 10⁴ to 2 × 10⁶ loading cycles). Stress‐based versions of the Fatemi‐Socie critical plane parameter and of the Smith‐Watson‐Topper parameter with a critical plane interpretation were evaluated using the experimental data. The Smith‐Watson‐Topper parameter was not able to correlate the test data. The Fatemi‐Socie method correlated most of the test data within factor‐of‐three boundaries. A modified Crossland invariant‐based parameter made of two interaction rules between the shear stress amplitude and the maximum hydrostatic stress, and of a definition of shear stress amplitude based on the maximum prismatic hull method, yielded fatigue life estimates in reasonable agreement with the experimental observations.     

Unschädlichmachung der Abwässer durch bessere Ausnutzung des Rohstoffes bei der Kartoffelstärkeerzeugung

Neutralization of Waste Waters by Better Exploitation of Raw Material During Production of Potato Starch . Neutralization of fruit juice set free during the production of potato starch can be carried out efficiently in two steps. The first step is based upon the coagulation of protein at 85 °C in acidify medium. The first step of methane fermentation, which is the acid fermentation, is made use of for this process. At this step mainly heterogeneous lactic acid fermentation takes place. Coagulated protein may be efficiently processed into feed thus making the purification of waste water more profitable. The second step is the methane fermentation as such. Considering the concentration of fruit juice from the separators a maximum load of the fermentation tank of 1.5 kg/m³ of organic matter has to be taken in account. At a higher load the period of fermentation is shortened to an extent that makes anaerobic processes impossible. During fermentation 15.25 m³ of fermentation gas per m³ raw water with a methane content of 54% are produced. This amount of gas should be sufficient for heating of the waste water up to a temperature which is necessary for caogulation. The fermentation of fruit juice has to be succeeded by a one-hour period of sedimentation of the mud. Thus, purification is made more effective. With this system the concentration of the fruit juice decreases to an extent which makes it possible to purify it further together with the processing water in a biological activation filter plant.     

Real-time reversible iterative arrays

Iterative arrays are one-dimensional arrays of interconnected interacting finite automata. The cell at the origin is equipped with a one-way read-only input tape. We investigate iterative arrays as acceptors for formal languages. In particular, we consider real-time devices which are reversible on the core of computation, i.e., from initial configuration to the configuration given by the time complexity. This property is called real-time reversibility. It is shown that real-time reversible iterative arrays can simulate restricted variants of stacks and queues. It turns out that real-time reversible iterative arrays are strictly weaker than real-time reversible cellular automata. On the other hand, a non-semilinear language is accepted. We show that real-time reversibility itself is not even semidecidable, which extends the undecidability for cellular automata and contrasts with the general case, where reversibility is decidable for one-dimensional devices. Moreover, we prove the non-semidecidability of several other properties. Several closure properties are also derived.     

The Boolean closure of linear context-free languages

Closures of linear context-free languages under Boolean operations are investigated. The intersection closure and the complementation closure are incomparable. By closing these closures under further Boolean operations we obtain several new language families. The hierarchy obtained by such closures of closures is proper up to a certain level, where it collapses to the Boolean closure which, in turn, is incomparable with several closures of the family of context-free languages. The Boolean closure of the linear context-free languages is properly contained in the Boolean closure of the context-free languages. A characterization of a class of non-unary languages that cannot be expressed as a Boolean formula over the linear context-free languages is presented.     

Reversible pushdown automata

Reversible pushdown automata are deterministic pushdown automata that are also backward deterministic. Therefore, they have the property that any configuration occurring in any computation has exactly one predecessor. In this paper, the computational capacity of reversible computations in pushdown automata is investigated and turns out to lie properly in between the regular and deterministic context-free languages. Furthermore, it is shown that a deterministic context-free language cannot be accepted reversibly if more than realtime is necessary for acceptance. Closure properties as well as decidability questions for reversible pushdown automata are studied. Finally, we show that the problem to decide whether a given nondeterministic or deterministic pushdown automaton is reversible is P-complete, whereas it is undecidable whether the language accepted by a given nondeterministic pushdown automaton is reversible.     

Cellular automata with limited inter-cell bandwidth

A d-dimensional cellular automaton is a d-dimensional grid of interconnected interacting finite automata. There are models with parallel and sequential input modes. In the latter case, the distinguished automaton at the origin, the communication cell, is connected to the outside world and fetches the input sequentially. Often in the literature this model is referred to as an iterative array. In this paper, d-dimensional iterative arrays and one-dimensional cellular automata are investigated which operate in real and linear time and whose inter-cell communication bandwidth is restricted to some constant number of different messages independent of the number of states. It is known that even one-dimensional two-message iterative arrays accept rather complicated languages such as {a^p∣p prime} or {a²ⁿ∣n∈N} (H. Umeo, N. Kamikawa, Real-time generation of primes by a 1-bit-communication cellular automaton, Fund. Inform. 58 (2003) 421-435). Here, the computational capacity of d-dimensional iterative arrays with restricted communication is investigated and an infinite two-dimensional hierarchy with respect to dimensions and messages is shown. Furthermore, the computational capacity of the one-dimensional devices in question is compared with the power of two-way and one-way cellular automata with restricted communication. It turns out that the relations between iterative arrays and cellular automata are quite different from the relations in the unrestricted case. Additionally, an infinite strict message hierarchy for real-time two-way cellular automata is obtained as well as a very dense time hierarchy for k-message two-way cellular automata. Finally, the closure properties of one-dimensional iterative arrays with restricted communication are investigated and differences to the unrestricted case are shown as well.