A 3D Framework for Characterizing Microstructure Evolution of Li-Ion Batteries

Lithium-ion batteries are commonly found in many modern consumer devices, ranging from portable computers and mobile phones to hybrid- and fully-electric vehicles. While improving efficiencies and increasing reliabilities are of critical importance for increasing market adoption of the technology, research on these topics is, to date, largely restricted to empirical observations and computational simulations. In the present study, it is proposed to use the modern technique of X-ray microscopy to characterize a sample of commercial 18650 cylindrical Li-ion batteries in both their pristine and aged states. By coupling this approach with 3D and 4D data analysis techniques, the present study aimed to create a research framework for characterizing the microstructure evolution leading to capacity fade in a commercial battery. The results indicated the unique capabilities of the microscopy technique to observe the evolution of these batteries under aging conditions, successfully developing a workflow for future research studies

Detection of Edges in Spectral Data II. Nonlinear Enhancement

We discuss a general framework for recovering edges in piecewise smooth functions with finitely many jump discontinuities, where $[f](x):=f(x+)-f(x-) \neq 0$. Our approach is based on two main aspects--localization using appropriate concentration kernels and separation of scales by nonlinear enhancement. To detect such edges, one employs concentration kernels, $K_\epsilon(\cdot)$, depending on the small scale $\epsilon$. It is shown that odd kernels, properly scaled, and admissible (in the sense of having small $W^{-1,\infty}$-moments of order ${\cal O}(\epsilon)$) satisfy $K_\epsilon*f(x) = [f](x) +{\cal O}(\epsilon)$, thus recovering both the location and amplitudes of all edges.As an example we consider general concentration kernels of the form $K^\sigma_N(t)=\sum\sigma(k/N)\sin kt$ to detect edges from the first $1/\epsilon=N$ spectral modes of piecewise smooth f's. Here we improve in generality and simplicity over our previous study in [A. Gelb and E. Tadmor, Appl. Comput. Harmon. Anal., 7 (1999), pp. 101-135]. Both periodic and nonperiodic spectral projections are considered. We identify, in particular, a new family of exponential factors, $\sigma^{exp}(\cdot)$, with superior localization properties. The other aspect of our edge detection involves a nonlinear enhancement procedure which is based on separation of scales between the edges, where $K_\epsilon*f(x)\sim [f](x) \neq 0$, and the smooth regions where $K_\epsilon*f = {\cal O}(\epsilon) \sim 0$. Numerical examples demonstrate that by coupling concentration kernels with nonlinear enhancement one arrives at effective edge detectors

Cold Dark Matter I: The Formation of Dark Halos

We use numerical simulations of critically-closed cold dark matter (CDM) models to study the effects of numerical resolution on observable quantities. We study simulations with up to $256^3$ particles using the particle-mesh (PM) method and with up to $144^3$ particles using the adaptive particle-particle --particle-mesh (P$^3$M) method. Comparisons of galaxy halo distributions are made among the various simulations. We also compare distributions with observations and we explore methods for identifying halos, including a new algorithm that finds all particles within closed contours of the smoothed density field surrounding a peak. The simulated halos show more substructure than predicted by the Press-Schechter theory. We are able to rule out all $\Omega=1$ CDM models for linear amplitude \sigma_8\gsim 0.5 because the simulations produce too many massive halos compared with the observations. The simulations also produce too many low mass halos. The distribution of halos characterized by their circular velocities for the P$^3$M simulations is in reasonable agreement with the observations for 150\kms\lsim V_{\rm circ} \lsim 350\kms.}}Comment: 41 pages, plain tex, ApJ, 236, in press; postscript figures available in ftp://arcturus.mit.edu/Preprints/CDM1_figs.tar.

Mongolia - Privatization and system transformation in an isolated economy

The authors examine the process of economic transformation in Mongolia, a huge, isolated, sparsely populated country. After identifying factors that led to formulation of a radical adjustment program in such an isolated country, they focus on Mongolia's innovative voucher privatization scheme, and the interplay between the speed of contraction in resource availability and that of the movement to a market economy. They show that the reform process was not smooth: that after the rapid formulation and implementation of major reforms, there was a marked slowdown, when reform timetables were revised and a more gradualist approach adopted. Later, reforms driven by the privatization program picked up momentum again. But one important lesson learned in Mongolia is that voters are likely to shy away from radical reformers when faced with growing shortages and a collapsing economy. In June 1922, the Mongolian People's Revolutionary Party (the former communist party) was returned to power in general elections, capturing 72 of 76 parliamentary seats. The authors identify factors related to speed versus caution: organization and institutional limitations; political considerations; whether a model of transformation exists; and a contracting resource envelope. Using a simple computable general equilibrium model, they analyze the impact of the cutoff of Soviet aid, which amounted to 30 percent of GDP, and of the disruption of trade. They conclude that preventing a decline in welfare of more than 20 percent - which is close to the decline in 1991 - would require aid flows of about 15 percent of GDP. Their model suggests that the rural sector is reasonably well insulated from external shocks, in sharp contrast with the urban sector. One response scenario explored by the model is that of massive reverse migration to rural areas. They point out that the more the resource envelope tightens and squeezes away the margin above subsistence, the harder it will be to sustain an orderly pattern of reform. In the extreme, this pattern may force the country to adopt a rationed wartime economy, despite intentions to shift to a market system.Economic Theory&Research,Banks&Banking Reform,Environmental Economics&Policies,Municipal Financial Management,Access to Markets

Improving the dynamics of aid : towards more predictable budget support

This paper considers approaches towards improving the predictability of aid to low income countries, with a special focus on budget support. In order to accelerate progress towards the Millennium Development Goals, the donor community is increasing aid flows while pushing for more coordination and tighter performance-based selectivity. However, these factors may increase the unpredictability of aid from current levels, which are already high enough to impose significant costs. Predictability is a particular challenge in the area of budget support, which will continue to increase in importance as aid is sought to underpin longer-term recurrent spending commitments. Budget support reduces transactions costs and drains on capacity, but it tends to be more vulnerable to fluctuations than multi-year project support. Poor predictability raises the threat of a low-level equilibrium: countries, budgeting prudently within a medium-term fiscal framework, will discount commitments; donors will see few funding gaps, so pledges will fall. With some countries discounting aid commitments in formulating budgets, some already see signs of this happening. To improve predictability, donors must extend their funding horizons. However, even if this can be done, several major issues will remainat country level. First, how can countries deal with residual short-run volatility of disbursements relative to commitments? Second, can donors lengthen commitment horizons to individual developing countries without excessive risk of misallocating aid? Third, within a country's overall aid envelope, how should donors set the shares of project aid and budget support? Finally, the paper considers the other main approach to budget support, the output or outcome-driven approach of the European Union. The paper concludes that many of these issues can be addressed. Simple spending and savings rules built around a buffer reserve fund of 2-4 months of imports can help smooth public spending. Aid can be pre-committed several years ahead with only small efficiency losses, using a strategy of"flexible pre-commitment."Guidelines can be set to limit the volatility of budget support while keeping it performance-based, and past experience can be used more systematically to develop"outcome"norms to better guide aid allocation.Development Economics&Aid Effectiveness,School Health,Economic Theory&Research,Markets and Market Access,Country Strategy&Performance

Trade in banking services : issues for multilateral negotiations

When the General Agreement on Tariffs and Trade was instituted in 1948, its mandate excluded such industries as banking, insurance and telecommunciaitons. These services sectors were highly regulated and protected in most countries, partly because of their sensitivity to national security and cultural identity. Under U.S. pressure, the Uruguay Round talks have included financial services, particularly banking. The response of developing countries to the U.S. proposal to liberalize trade in financial services ranges from cautious to hostile. Partly this reflects concern about the perceived comparative advantage of industrial countries and the desire of strong vested interests to continue to use the financial system as an instrument of public policy. It also reflects the weak situation of the banking industry in many developing countries. In some there is no real banking industry; in many the banking sector is technically insolvent and needs costly restructuring and reform. Opening the borders to foreign competition is essential to liberalization. But this process must proceed at the pace appropriate to the wide-ranging domestic reforms essential in most developing countries.Banks&Banking Reform,Financial Intermediation,Financial Crisis Management&Restructuring,Knowledge Economy,Education for the Knowledge Economy