Types Of Extreme Conditions Research Articles

Microstructural control of alloy 718 fabricated by electron beam melting with expanded processing window by adaptive offset method

This paper presents microstructures of Inconel 718 fabricated by electron beam melting (EBM), a powder bed fusion (PBF), additive manufacturing (AM) process, under various conditions with an extended range of electron beam power (P) and scanning speed (V). An adaptive offset method (AOM) was used to optimize the beam scanning line offset adaptively to fabricate blocks without macroscopic defects. In the AOM, the line offset is changed depending on the geometry of melt-pools of adjacent scanning lines. The AOM is valid as long as melt pool depth is larger than layer thickness, and it greatly broadens the process window for building dense and even parts. The broadened process window extends the range of the solidification condition and the variation of the resultant microstructures. Fully columnar grains and mixtures of columnar and equiaxed grains were formed. Mixtures of columnar grains and equiaxed grains were formed under two different types of extreme conditions. The first type is with low line energy/small line offset, which causes equiaxed grains associated with a small number of defects. The second type is with high line energy/large line offset, which causes equiaxed grains via the columnar-to-equiaxed transition (CET). The fully columnar grains are preferably oriented to <001> direction in the build direction. The blocks with the different microstructure exhibited similar strengths but different elongations. A processing map was established by plotting the points indicating the build condition and resultant microstructure in the P–V space as a guide for controlling microstructure.

Nucleotide Second Messenger-Based Signaling in Extreme Acidophiles of the Acidithiobacillus Species Complex: Partition Between the Core and Variable Gene Complements.

Cyclic and linear nucleotides are key elements of the signal transduction networks linking perception of the environment to specific cellular behavior of prokaryotes. These molecular mechanisms are particularly important in bacteria exposed to different, and frequently simultaneous, types of extreme conditions. This is the case in acidithiobacilli, a group of extremophilic bacteria thriving in highly acidic biotopes, that must also cope with significant variations in temperature, osmotic potentials and concentrations of various transition metals and metalloids. Environmental cues sensed by bacteria are transduced into differential levels of nucleotides acting as intracellular second messengers, promoting the activation or inhibition of target components and eliciting different output phenotypes. Cyclic (c) di-GMP, one of the most common bacterial second messengers, plays a key role in lifestyle changes in many bacteria, including acidithiobacilli. The presence of functional c-di-GMP-dependent signal transduction pathways in representative strains of the best-known linages of this species complex has been reported. However, a comprehensive panorama of the c-di-GMP modulated networks, the cognate input signals and output responses, are still missing for this group of extremophiles. Moreover, little fundamental understanding has been gathered for other nucleotides acting as second messengers. Taking advantage of the increasing number of sequenced genomes of the taxon, here we address the challenge of disentangling the nucleotide-driven signal transduction pathways in this group of polyextremophiles using comparative genomic tools and strategies. Results indicate that the acidithiobacilli possess all the genetic elements required to establish functional transduction pathways based in three different nucleotide-second messengers: (p)ppGpp, cyclic AMP (cAMP), and c-di-GMP. The elements related with the metabolism and transduction of (p)ppGpp and cAMP appear highly conserved, integrating signals related with nutrient starvation and polyphosphate metabolism, respectively. In contrast, c-di-GMP networks appear diverse and complex, differing both at the species and strain levels. Molecular elements of c-di-GMP metabolism and transduction were mostly found scattered along the flexible genome of the acidithiobacilli, allowing the identification of probable control modules that could be critical for substrate colonization, biofilm development and intercellular interactions. These may ultimately convey increased endurance to environmental stress and increased potential for gene sharing and adaptation to changing conditions.

Hard rock TBM tunneling in challenging ground: Developments and lessons learned from the field

TBM tunneling is an ever-increasing challenge for underground construction, and with each new tunnel bored there are unknown elements when boring through the earth. The most extensive Geotechnical Baseline Reports can miss fault lines, water inflows, squeezing ground, rock bursting, and other types of extreme conditions. This paper will draw on the considerable experience within Robbins to analyze successful methods of dealing with the most challenging conditions encountered, with a particular focus on fractured and faulted ground, mixed face tunneling, and tunneling in karst or water-bearing conditions. It will discuss new methods, including Dual Mode or “Crossover” type machines, which can increase the efficiency of excavation in such conditions.

The Rule of Law Under Extreme Conditions and International Law: A Law and Economics Perspective

The ‘rule of law’ has attracted a lot of scholarly writings as well as political and public rhetoric in recent years. On the one hand, scholars found that adherence to the rule of law can be regarded as the most significant explanatory factor for various measures of a country’s success, both in social - quality of life - realm and in the pure economic realm. On the other hand, various governments’ responses to terror threats since 9/11, including responses of established liberal democracies, brought about a surge in positive and normative writings, as well as public debates, about the rule of law under extreme conditions or the deviations from the rule of law, even by the most liberal democracies. However, the international law aspects regarding the rule of law under extreme conditions is a field that had received almost no attention so far. Discussing the rule of law under extreme conditions in the international arena from a Law and Economics perspective raises several challenges. First, although the concept of the rule of law as an ingredient of the ‘good’ state, is established (although its precise definition is not agreed upon), the basic definition of the rule of law in the international arena is a much more virgin field. Second, Extreme conditions may challenge the normative and positive analysis of the rule of law. The theory of the state from which we derive the common understanding of the principle of the rule of law deals with the regular operation of collective life, institutions and decision-making. Under extreme conditions most countries establish a different form of the rule of law (an emergency constitution, as phrased by some), compromising some of its essentials during regular times. It can be argued on the normative level that this is justifiable; but to what extent and in which format? There is no coherent paradigm yet for the analysis of the desirable as well as the de-facto rule of law “balance” (e.g. state security versus human rights) under extreme conditions. The third major challenge relates to the definition of those extreme conditions that merit a special look vis-a-vis the rule of law. Three types of extreme conditions have been discussed by the literature: (1) belligerency, war, terror and alike; (2) natural and man-made disasters; and (3) political or economic meltdowns. Are extreme conditions in the international arena identical to extreme conditions in the context of the state? Is the familiar distinction between the three types of extreme conditions referred to in the context of the state applicable to the international sphere?I will try to contribute a few preliminary thoughts about each of these challenges, highlighting the perspective of Law and Economics. Section 1 will explore the concept of the rule of law in the international arena and in international law; Section 2 will elaborate on the economic philosophical foundations of the theory of the state and will examine their applicability to the international sphere and to extreme conditions; Section 3 will focus on the characterization of extreme conditions vis-a-vis the rule of law, including a short overview of the models put forward in the literature and also some methodological remarks for those who engage with a Law and Economics approach towards this topic.

Optimal Sensor Placement Method for Gantry Crane SHM System

The choice of the number and location of sensors in the structure is the foundation of cranes structural health monitoring, which has major influence on the monitoring results. This paper taking a gantry crane as a SHM research object, uses optimal sensor placement based on Finite Element Method, the stress concentration points could be drawn by the FEM calculation results. This method carry out dynamic load stress analysis for the structure with virtual prototype, which make up for the lack of static analysis; compared with the type test methods, not only reduce the test cost, but also more flexible, and break through the restrictions of all types of extreme conditions. This method makes the sensor data obtained more realistically reflects the crane structure condition; provides reliable data support for crane safety monitoring and safety evaluation. The promotion of this method will provide important technical support for the development of the crane SHM.