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Caltech Authors (89,577 recursos)
Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 3,632

1. A low-power 20Gb/s transmitter in 65nm CMOS technology - Nazari, Meisam Honarvar; Emami-Neyestanak, Azita
A 20Gb/s transmitter employing an analog filtering pre-emphasis equalization technique is presented. The transmitter dissipates 10mW from a 1.2V supply and occupies 0.01mm2. This high-frequency boosting equalization technique allows for compensating channel losses up to 20dB at Nyquist-rate. The prototype was fabricated in 65nm CMOS technology and characterized using lossy cables and 5" and 10" FR4 PCB traces.

2. A 100MHz–2GHz 12.5x sub-Nyquist rate receiver in 90nm CMOS - Yoo, Juhwan; Becker, Stephen; Loh, Matthew; Monge, Manuel; Candès, Emmanuel; Emami-Neyestanak, Azita
A fully-integrated, high-speed, wideband receiver called the random modulation pre-integrator is realized in IBM 90nm digital CMOS. It achieves an effective instantaneous bandwidth of 2GHz, with >54dB dynamic range. Most notably, the aggregate digitization rate is ƒ_s =320MSPS, 12.5× below the Nyquist rate. Signal recovery can be accomplished for any signal with a concise representation. The system is validated using radar-pulses and tones as the input and recovering the time-domain waveforms.

3. An 18.6Gb/s double-sampling receiver in 65nm CMOS for ultra-low-power optical communication - Nazari, Meisam Honarvar; Emami-Neyestanak, Azita
Using optics for chip-to-chip interconnects has recently gained a lot of interest. As data rates scale to meet increasing bandwidth requirements, the shortcomings of copper channels are becoming more severe. Hybrid integration of optical devices with electronics has been demonstrated to achieve high performance, and recent advances in silicon photonics have led to fully integrated optical signaling. These approaches pave the way to massively parallel optical communications. Dense arrays of optical detectors require very low-power, sensitive, and compact optical receiver circuits. Existing designs for the input receiver, such as TIA, require large power consumption to achieve high band width and...

4. A 15Gb/s 0.5mW/Gb/s 2-Tap DFE Receiver with Far-End Crosstalk Cancellation - Nazari, Meisam Honarvar; Emami-Neyestanak, Azita
In this paper, we present a low-power receiver that supports high data rates over bandwidth-limited and coupled links. The receiver employs a half-rate 2-tap speculative DFE architecture with a far-end cross-talk (FEXT) cancellation technique. Figure 25.6.1 shows the top-level architecture of the DFE receiver. Conventionally, analog taps of the equalizer are implemented using current mode summers, thus the power consumption of the DFE increases proportion ally with the number of taps. In the proposed architecture, a switched-capacitor S/H is employed to sample the input signal and combine it with the feedback coefficients at the front-end of the receiver, as shown...

5. Energy Efficient Multipath TCP for Mobile Devices - Peng, Qiuyu; Chen, Minghua; Walid, Anwar; Low, Steven H.
Most mobile devices today come with multiple access interfaces, e.g., 4G and WiFi. Multipath TCP (MP-TCP) can greatly improve network performance by exploiting the connection diversity of multiple access interfaces, at the expense of higher energy consumption. In this paper, we design MP-TCP algorithms for mobile devices by jointly considering the performance and energy consumption. We consider two main types of mobile applications: realtime applications that have a fixed duration and file transfer applications that have a fixed data size. For each type of applications, we propose a two-timescale algorithm with theoretical guarantee on the performance. We present simulation results...

6. Further Studies of the Mechanics and Potential of Fixed Type Cavities - Knapp, Robert T.
The purpose of this discussion is to explore in more detail the mechanics of the cyclic process which occurs in fixed type cavitation, including some of the factors involved in similarity criteria. The concept of damage potential will also be examined.

7. Experiments on the Mechanics of Sediment Suspension - Rouse, Hunter
Fluid Turbulence as a Medium of Lateral Transport: For many decades the problem of sediment transportation has claimed the attention of the hydraulic engineer, particularly in connection with river regulation, irrigation, and the protection of arable land. Laboratory and field investigations of this problem have dealt primarily with the movement of rock debris along the bed of a stream, and only in recent years has the study of suspended matter come into prominence. Yet while research on bed load has remained essentially empirical, the close relationship between fluid turbulence and sediment suspension has permitted the analysis of the suspended load...

8. New Results on Electron Neutrino Appearance in MINOS - Orchanian, Mhair
Neutrino oscillation is now an established phenomenon, thanks to a variety of experiments [1, 2, 3, 4, 5, 6, 7] which have probed various apparent anomalies in expected neutrino spectra from the sun, atmosphere, nuclear reactors, and accelerator-based beams. The three weak eigenstates - v_e, v_μ, v_r - are related to the three mass eigenstates - v_1, v-2, v_3 - via the PMNS (for Pontecorvo, Maki, Nakagawa, and Sakata) matrix, a unitary mixing matrix U parametrized by three mixing angles - θ_(12), θ_(13), θ_(23) - and three CP-violating phases - δ, ɑ_1, ɑ_2 [8]. No hints exist yet as to the...

9. The Water Tunnel as a Tool in Hydraulic Research - Daily, James W.
The expanding scope of application of the water tunnel is largely the result of war research needs. Since the first known elementary water tunnel was used by Parsons in England in 1898 to investigate propellers, its application has remained primarily in the field of ship propeller testing. Meanwhile, investigations of other submerged bodies and of most fundamental phenomena in fluid dynamics have been performed in the many wind tunnels throughout the world. Even the broad development in hydraulic laboratory techniques that accompanied the revival of interest in scientific hydraulic research during the last twenty-five years did not emphasize the water tunnel as a...

10. Estimating Characteristics of the Heliosphere Using Anomalous Cosmic Ray Observations at Solar Maximum - Stone, E. C.; Cummings, A. C.
Observations of the energy spectra of anomalous cosmic ray (ACR) oxygen were acquired in the outer heliosphere during the last solar maximum period in 1990 when the particle distributions are expected to be more nearly spherically symmetric than at solar minimum. Hence, we use a simple one-dimensional model of ACR acceleration and transport to fit the observed energy spectra at Voyagers 1 and 2 and Pioneer 10. The inferred interplanetary radial diffusion coefficient is remarkably consistent with recent theoretical estimates. The next solar maximum is expected to occur in the outer heliosphere in early 2001 when Voyager 1 will be...

11. Local Analysis for 3D Reconstruction of Specular Surfaces - Part II - Savarese, Silvio; Perona, Pietro
We analyze the problem of recovering the shape of a mirror surface. We generalize the results of [1], where the special case of planar and spherical mirror surfaces was considered, extending that analysis to any smooth surface. A calibrated scene composed of lines passing through a point is assumed. The lines are reflected by the mirror surface onto the image plane of a calibrated camera, where the intersection and orientation of such reflections are measured. The relationship between the local geometry of the surface around the point of reflection and the measurements is analyzed. We give necessary and sufficient conditions,...

12. Unsupervised learning of human motion models - Song, Yang; Goncalves, Luis; Perona, Pietro
This paper presents an unsupervised learning algorithm that can derive the probabilistic dependence structure of parts of an object (a moving human body in our examples) automatically from unlabeled data. The distinguished part of this work is that it is based on unlabeled data, i.e., the training features include both useful foreground parts and background clutter and the correspondence between the parts and detected features are unknown. We use decomposable triangulated graphs to depict the probabilistic independence of parts, but the unsupervised technique is not limited to this type of graph. In the new approach, labeling of the data (part...

13. Grouping and dimensionality reduction by locally linear embedding - Polito, Marzia; Perona, Pietro
Locally Linear Embedding (LLE) is an elegant nonlinear dimensionality-reduction technique recently introduced by Roweis and Saul 2]. It fails when the data is divided into separate groups. We study a variant of LLE that can simultaneously group the data and calculate local embedding of each group. An estimate for the upper bound on the intrinsic dimension of the data set is obtained automatically.

14. A visual category filter for Google images - Fergus, Robert; Perona, Pietro; Zisserman, Andrew
We extend the constellation model to include heterogeneous parts which may represent either the appearance or the geometry of a region of the object. The pans and their spatial configuration are learnt simultaneously and automatically, without supervision, from cluttered images. We describe how this model can be employed for ranking the output of an image search engine when searching for object categories. It is shown that visual consistencies in the output images can be identified, and then used to rank the images according to their closeness to the visual object category. Although the proportion of good images may be small,...

15. Recognition by probabilistic hypothesis construction - Moreels, Pierre; Maire, Michael; Perona, Pietro
We present a probabilistic framework for recognizing objects in images of cluttered scenes. Hundreds of objects may be considered and searched in parallel. Each object is learned from a single training image and modeled by the visual appearance of a set of features, and their position with respect to a common reference frame. The recognition process computes identity and position of objects in the scene by finding the best interpretation of the scene in terms of learned objects. Features detected in an input image are either paired with database features, or marked as clutters. Each hypothesis is scored using a...

16. An improved scheme for detection and labelling in Johansson displays - Fanti, Claudio; Polito, Marzia; Perona, Pietro
Consider a number of moving points, where each point is attached to a joint of the human body and projected onto an image plane. Johannson showed that humans can effortlessly detect and recognize the presence of other humans from such displays. This is true even when some of the body points are missing (e.g. because of occlusion) and unrelated clutter points are added to the display. We are interested in replicating this ability in a machine. To this end, we present a labelling and detection scheme in a probabilistic framework. Our method is based on representing the joint probability density...

17. The emergence of visual categories - A computational perspective - Perona, Pietro
When we are born we do not know about sailing boats, frogs, cell-phones and wheelbarrows. By the time we reach school age we can easily recognize these categories of objects and many more using our visual system; by some estimates, we learn around 10 new categories per day with minimal supervision during the first few years of our lives. How can this happen? I will outline a computational approach to the problem of representing the visual properties of object categories, and of learning such models without supervision from cluttered images. Both static images of objects and dynamic displays such as...

18. Recovering local shape of a mirror surface from reflection of a regular grid - Savarese, Silvio; Chen, Min; Perona, Pietro
We present a new technique to recover the shape of an unknown smooth specular surface from a single image. A calibrated camera faces a specular surface reflecting a calibrated scene (for instance a checkerboard or grid pattern). The mapping from the scene pattern to its reflected distorted image in the camera changes the local geometrical structure of the scene pattern. We show that if measurements of both local orientation and scale of the distorted scene in the image plane are available, this mapping can be inverted. Specifically, we prove that surface position and shape up to third order can be...

19. Geochemical modeling of a steeply dipping boundary between continental and oceanic-arc lithosphere, west-central Idaho - Manduca, Cathryn A.; Silver, Leon T.; Taylor, Hugh P.
The western margin of the Cretaceous Idaho Batholith intruded the boundary between accreted oceanic and terranes and the continental margin. The geochemistry of the plutonic rocks indicates that it is an abrupt, steeply dipping boundary which extends through the lithosphere.

20. Early Mesozoic paleotectonic-paleogeographic reconstruction of the southern Sierra Nevada region - Saleeby, J. B.; Goodin, S. E.; Sharp, W. D.; Busby, C. J.
Metamorphic country rocks of the southern Sierra Nevada occur as isolated roof pendants and as the western wall of the batholith. Metasedimentary rocks are primarily Triassic to early Jurassic in age as shown by fossil dates in conjunction with field and petrographic data. The lower Mesozoic strata were deposited across a complex paleo-basement consisting of two contrasting terranes. The western terrane is exposed along the foothills and consists of the Kings-Kaweah ophiolite belt, a latest Paleozoic to possibly earliest Mesozoic remnant of disrupted oceanic lithosphere. This belt appears to represent an oceanic fracture zone complex that was transported northward into the region by large-scale wrench faulting. The eastern terrane which can only be inferred...

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