Observations of transient high temperature vortical microstructures in solids during adiabatic shear banding

By using a unique infrared high-speed camera especially constructed for recording highly transient temperature fields at the microscale, we are able to reveal the spatial and temporal microstructure within dynamically growing shear bands in metals. It is found that this structure is highly nonuniform and possesses a transient, short range periodicity in the direction of shear band growth in the form of an array of intense "hot spots" reminiscent of the well-known, shear-induced hydrodynamic instabilities in fluids. This is contrary to the prevailing classical view that describes the deformations and the temperatures within shear bands as being essentially one-dimensional fields. These observations are also reminiscent of the nonuniform structure of localized shear regions believed to exist, at an entirely different length scale, in the earth's lower crust and upper mantle

Million frames per second infrared imaging system

An infrared imaging system has been developed for measuring the temperature increase during the dynamic deformation of materials. The system consists of an 8×8 HgCdTe focal plane array, each with its own preamplifier. Outputs from the 64 detector/preamplifiers are digitized using a row-parallel scheme. In this approach, all 64 signals are simultaneously acquired and held using a bank of track and hold amplifiers. An array of eight 8:1 multiplexers then routes the signals to eight 10 MHz digitizers, acquiring data from each row of detectors in parallel. The maximum rate is one million frames per second. A fully reflective lens system was developed, consisting of two Schwarszchild objectives operating at infinite conjugation ratio. The ratio of the focal lengths of the objectives determines the lens magnification. The system has been used to image the distribution of temperature rise near the tip of a notch in a high strength steel sample (C-300) subjected to impact loading by a drop weight testing machine. The results show temperature rises at the crack tip up to around 70 K. Localization of temperature, and hence, of deformation into "U" shaped zones emanating from the notch tip is clearly seen, as is the onset of crack propagation

Volatility Shifts of Indian Stocks Surronding Global Depositary Receipt Issues: Working Paper Series--00-03

Most Indian firms that issue equity-backed SEC Rule 144A and Regulation S Global Depositary Receipts (GDRs) in the US and Europe experience post-issue reductions in stock price volatility. The Indian index experiences similar declines. Neither the European nor the US index experiences systematic decreases in volatility, nor does volatility spill over from Europe and the US to India after GDRs are issued. Thus, the decline in volatility for Indian stocks in Bombay is not caused by changes in volatility in foreign markets where the GDRs trade. These findings support Bekaert and Harvey (1997 and 2000) and Aggarwal, Inclan, and Leal (1999) who report that changes in volatility in emerging markets come from local vis-a-vis global factors. Local influences that contribute to the volatility decline are both systematic and firm-specific influences

Technical Report on Argo Data Processing

In this document, details of Argo program, data acquisition system and data processing are documented to serve as a reference for Argo data. Several plots are included to serve as quick reference. The data will be useful to describe major thermo-haline features in the Indian Ocean. In conjunction with other sources of data from various platforms, the data can be used for studying meso-scale structure and dynamics of upper ocean process. At smaller scales, the float temperature and salinity data will be useful to document the seasonal to intra seasonal variability of temperature, salinity and various other derived parameters. This temperature and salinity data can be useful for updating the climatology and for assimilation into ocean model for better forecasts

Keamanan Energi dan Hubungan Kerja Sama Cina-Jepang

This article explores the Chinese and Japanese energy relationship by describing changes in the Chinese energy situation as a starting point. The article breaks down that the strength of the Chinese domestic energy since the 1970s and the decade of the 1980s make the country's independent in energy and become the largest oil exporter country, especially to the energy poor neighbor, Japan. However, entering the decade of the 1990s or the end of the post-Cold War era, the situation changed drastically when China faces the energy crisis. The change status bring a wide range of implications for Japan and influence the bilateral energy relations of the two countries, which tend to be ambivalent or ambiguous, between energy cooperation and the potential of conflict. As main purpose of this paper is to identify which energy issues are a direct influence on the behavior of the interaction between China and Japan and as knowledge contribution in understanding the issues of energy itself and the Sino-Japanese relations as a whole. The main assumption of this article is that the energy security factor is a very important issue and significant in shaping the nature and pattern of Sino-Japanese relations, because it raises consideration of national interests and national security of both countries, particularly in the present and the future

Understanding droplet collisions through a model flow: Insights from a Burgers vortex

We investigate the role of intense vortical structures, similar to those in a turbulent flow, in enhancing collisions (and coalescences) which lead to the formation of large aggregates in particle-laden flows. By using a Burgers vortex model, we show, in particular, that vortex stretching significantly enhances sharp inhomogeneities in spatial particle densities, related to the rapid ejection of particles from intense vortices. Furthermore our work shows how such spatial clustering leads to an enhancement of collision rates and extreme statistics of collisional velocities. We also study the role of poly-disperse suspensions in this enhancement. Our work uncovers an important principle which, {if valid for realistic turbulent flows, may be a factor in} how small nuclei water droplets in warm clouds can aggregate to sizes large enough to trigger rain.Comment: 9 pages, 7 figure

Experimental investigation of the shearing resistance of SODA-Lime glass at pressures of 9 GPa and strain rates of 10^6 s^(-1)

Pressure-Shear Plate Impact (PSPI) experiments were conducted to measure the high-rate shearing resistance of soda-lime glass at pressures of 9 GPa and at shearing rates of approximately 10^6 s^(−1). Samples of soda lime glass, 5 µm thick, were sandwiched between pure tungsten carbide (WC) plates and impacted by pure WC flyers. Impacting plates were inclined to the direction of approach by an angle of 18°. Normal stress and shearing resistance of the sample were calculated from measured free surface velocities using 1D elastic wave theory. The experimental results show that, at a pressure of 9GPa, the shear stress increases almost linearly up to 1 GPa and then falls quickly to approximately 0.3 GPa — after which it decreases slowly to approximately 0.17 GPa. Comparisons with results of previous experiments on nominally identical samples, impacted to generate lower peak pressures, showed the peak shearing resistance to be much higher at higher pressures; however, the sharp fall in shearing resistance occurs at comparable shear strains (1.5-2)