Search

Most of the existing studies of the welfare state have dealt with OECD countries. Moreover, these studies have focused on government partisanship (left versus right), or institutional features under democracy, as primary causal variables. By providing four primary causal mechanisms (the power of popularly based parties, labor strength, democracy, and political instability) that are different from those of OECD countries, I answer the question of whether and why the efficiency or compensation hypothesis holds for developing countries. I show that either the efficiency or compensation thesis can hold for developing countries depending on the type of globalization with which popularly based governments interact.

Simulation has become an indispensable tool in the design and evaluation of mobile systems. By using mobility models that describe constituent movement, one can explore large systems, producing repeatable results for comparison between alternatives. In this paper, we show that a large class of mobility models - including all those in which nodal speed and distance or destination are chosen independently - have a transient period in which the average node speed decreases until converging to some long-term average. This speed decay provides an unsound basis for simulation studies that collect results averaged over time, complicating the experimental process. In this paper, we derive a general framework for describing this decay and apply it to a number of cases. Furthermore, this framework allows us to transform a given mobility model into a stationary one by initializing the simulation using the steady-state speed distribution and using the original speed distribution subsequently. This transformation completely eliminates the transient period and the decay in average node speed and, thus, provides sound models for the simulation of mobile systems.

The purpose of this paper is to present a numerical model predicting the shock response of a rotating-shaft spindle motor with nonlinear fluid-dynamic bearings (FDBs). The paper consists of three parts. The first part is to modify an existing linear spindle vibration model to include arbitrary FDB nonlinearity. The model consists of a rotating part, a stationary part, and nonlinear FDB. Equations of motion are derived and numerically integrated to predict nonlinear shock response of the spindle. The second part summarizes requirements on global coordinates and operating points in formulating nonlinear FDB-load characteristics to be used in the nonlinear spindle model. If bearing stiffness and damping appear as nonlinear functions of bearing eccentricity in local coordinates, the global-bearing stiffness and damping matrices can be obtained through coordinate transformation. The third part of this paper is to apply the mathematical model to various hard disk drive designs. When FDB nonlinearity appears as stiffening springs and dampers, the nonlinear spindle model predicts a slight increase in resonance frequencies and a slight decrease of resonance amplitude for the half-speed whirls. Also, peak amplitude of shock response from the nonlinear analysis is much less than that obtained from the linear analysis.

In this paper, we propose a simple yet effective method of identifying traffic conditions on surface streets given location traces collected from on-road vehicles---this requires only GPS location data, plus infrequent low-bandwidth cellular updates. Unlike other systems, which simply display vehicle speeds on the road, our system characterizes unique traffic patterns on each road segment and identifies unusual traffic states on a segment-by-segment basis. We developed and evaluated the system by applying it to two sets of location traces. Evaluation results show that higher than 90% accuracy in characterization can be achieved after ten or more traversals are collected on a given road segment. We also show that traffic patterns on a road are very consistent over time, provided that the underlying road conditions do not change. This allows us to use a longer history in identifying traffic conditions with higher accuracy.

Simulation has become an indispensable tool in the construction and evaluation of mobile systems. By using mobility models that describe constituent movement, one can explore large systems, producing repeatable results for comparison between alternatives. Unfortunately, the vast majority of mobility models---including all those in which nodal speed and distance or destination are chosen independently---suffer from decay; average speed decreases until converging to some long-term average. Such decay provides an unsound basis for simulation studies that collect results averaged over time, complicating the experimental process.This paper shows via analysis that such decay is inevitable in a wide variety of mobility models, including the most common in use today. We derive a general framework for describing this decay, and apply it to a number of practical cases. Furthermore, this framework allows us to transform any given mobility model into a stationary one: choose initial speeds from the steady-state distribution, and subsequent speeds from the original. This transformation provides sound models for simulation, eliminating variations in average nodal speed.