Flexible Choice-of-Law Rules: Panacea or Oxymoron?
Flexibility is not an acknowledged legal concept, however, and there is no common understanding what fl exibility really means. In fact, the term “fl exibility” is hardly ever defi ned, it is not used uniformly and it may consequently carry rather different meanings depending on the context.2 Furthermore, the doctrinal viability of fl exibility normally remains unexplained. I have previously discussed related general aspects in an article which was published in 2011.3 Based on feedback which I have received in the meantime and further research, this article refi nes my conclusions and – more importantly – explores the signifi cance of fl exibility in the choice-of-law context. To set the scene the fi rst section provides a brief introduction to the potential meanings of “fl exibility” and how this term is used in the legal discourse.4
The Operation of the Escape Clauses in the Rome Convention, Rome I Regulation and Rome II Regulation
An escape clause is a provision inserted in a legal instrument to supplement or cure the defect in the main rule, especially where the main rule has little or no connection with the issue to be resolved before the court. Escape clauses honour the claim that no legal instrument is perfect and strive to improve the instrument by giving the court the discretion to locate the law of a country that is more or most closely connected with the subject-matter. This feature in an escape clause makes it deserving of special attention.
Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet
In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.