Gridlock in 2030?

A few years ago, former Secretary of Energy Bill Richardson characterized the U.S. electric grid, the system of physical and human systems linking generators to loads, as “third-world.” 1 More recently, others have claimed that smart grid technologies promise to “spur the kind of transformation the Internet has already brought to the way we live, work, play and learn.” [superscript 2

Audio denoising using wavelet filter banks aimed at real-time application

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (p. 84-85).by Peter W. Kassakian.S.M

Overeating Among Black American Women: The Role of Racism, Racial Socialization, and Stress

Thesis advisor: Maureen E. KennyRecent research suggests that eating disorders exist across genders, races and ethnicities (e.g., Smolak & Striegel-Moore, 2001; Striegel-Moore & Smolak, 2000; Talleyrand, 2002, 2006; Taylor, Caldwell, Baser, Faison, & Jackson, 2007; Thompson, 1994, 1996), but most findings and frameworks within the eating disorders literature are based on research with White women who engage in restrictive eating patterns. Given the rapid rise in rates of obesity and related illnesses in the United States — particularly among Black American women (e.g., Hedley et al., 2004), an understanding of overeating that accounts for race-related factors is needed. By exploring the relationship between perceived racism, racial socialization, perceived stress, and overeating patterns among Black American women, the current study sought to develop a model of disordered eating that accounts for the unique contextual, emotional, and behavioral factors in the lives of Black American women. Using a sample of Black American women (N = 201), the results of the data analysis revealed that perceived racism was related to overeating by way of perceived stress. This finding supports theories that race–related factors underlie the development of eating disorder symptoms (e.g., Harris & Kuba, 1997) and that perceived racism may be a significant etiological factor in the development of eating disturbances among Black American women (Mastria, 2002; Root, 1990; Smolak & Striegel-Moore, 2001; Thompson, 1994, 1996; Talleyrand, 2006). This finding also adds to the larger body of literature, which links perceived racism to a range of negative psychological, behavioral, and physical outcomes (e.g., Mays et al., 2007). Racial socialization was not found to have a significant moderating effect in the relationship between perceived racism and overeating, but was unexpectedly found to be related to disinhibition around food. Although the explanation for this finding is unclear, it is consistent with some evidence that that identification with Black American culture may promote greater levels of comfort regarding food (Talleyrand, 2006; Villarosa, 1994).Thesis (PhD) — Boston College, 2011.Submitted to: Boston College. Lynch School of Education.Discipline: Counseling, Developmental, and Educational Psychology

Nonlinear System Modeling, Optimal Cam Design, and Advanced System Control for an Electromechanical Engine Valve Drive

A cam-based shear force-actuated electromechanical valve drive system offering variable valve timing in internal combustion engines was previously proposed and demonstrated. To transform this concept into a competitive commercial product, several major challenges need to addressed, including the reduction of power consumption, transition time, and size. As shown in this paper, by using nonlinear system modeling, optimizing cam design, and exploring different control strategies, the power consumption has been reduced from 140 to 49 W (65%), the transition time has been decreased from 3.3 to 2.7 ms (18%), and the actuator torque requirement has been cut from 1.33 to 0.30 N·m (77%).Sheila and Emanuel Landsman Foundatio

Realistic litz wire characterization using fast numerical simulations

The losses of realistic litz wires are characterized while explicitly accounting for their construction, using a procedure that computes the current-driven and magnetic-field-driven copper losses using fast numerical simulations. We present a case study that examines loss variation in one- and two-level litz wires as a function of twisting pitch, over a wide range of values and in small increments. Experimental confirmation is presented for predictions made by numerical simulations. Results confirm the capability and efficiency of numerical methods to provide valuable insights into the realistic construction of litz wire.MIT Energy InitiativeSingapore-MIT Allianc

Sacred landscape and cultural astronomy on the Marcahuasi Plateau, Peru

The Marcahuasi plateau, in the highlands of Huarochirí Province, Peru, is touristed today for its landscape of evocative stone formations and archaeological remains. We present ethnohistorical documentation of the cultural salience of stone features and celestial alignments to the inhabitants of the region and propose that such notions extend to the prehispanic era at Marcahuasi. Although most formations likely are wholly natural features, a preliminary analysis involving Monte Carlo simulation with analysis of statistical significance of astronomical alignments suggest the plateau combines elements of a “natural” landscape and at least partially modified “cultural” monuments that were part of an animated Andean cosmology.Published versio

Analysis and Control of a Cellular Converter System with Stochastic Ripple Cancellation and Minimal Magnetics

Abstract-A parallel converter architecture based on the resonant pole inverter (RPI) topology is presented. It is shown that this architecture minimizes the output magnetics required for current sharing. A new current control scheme is introduced which reduces peak currents, losses, and output voltage ripple for many operating conditions. This new control method is applicable to both the single RPI and the parallel architecture. Additionally, the paper analytically quantifies the degree of passive ripple cancellation between cells of a parallel architecture. It is shown that the rms ripple current of an N -cell paralleled converter system is a factor of 1= p N lower than for an equivalent single converter. These results are verified using a piecewise-linear model. We conclude that the parallel architecture overcomes some of the major disadvantages of the conventional RPI

Phase synchronization of autonomous AC grid system with passivity-based control

This paper discusses a ring‐coupled buck‐type inverter system to harness energy from direct current (DC) sources of electricity. The DC‐DC buck converter circuit is modified with an H‐bridge to convert the DC input voltage to a usable alternating current (AC) output voltage. Passivity‐based control (PBC) with port‐controlled Hamiltonian modelling (PCHM) is a method where the system is controlled by considering not only the energy properties of the system but also the inherent physical structure. PBC is applied to achieve stabilization of the AC output voltage to a desired amplitude and frequency. Unsynchronized output voltages in terms of phase angle or frequency can cause detrimental effects on the system. Phase‐locked loop (PLL) is employed in the ring structure to maintain synchronization of the AC output voltage of all inverter units in the ring‐coupled system