Octave-tunable miniature RF resonators

The development and testing of a miniaturized, high-Q, broadly tunable resonator is described. An exemplary device, with a center frequency that is continuously tunable from 1.2 to 2.6 GHz, was tested in detail. Experimental results demonstrated a resonator Q of up to 380, and typical insertion loss of -1.9 dB for a 25 MHz 3-dB bandwidth. These resonators have been used to stabilize a broadly-tunable oscillator with phase noise of -132 dBc/Hz at 100-kHz offset, with a center frequency tunable from 1.2-2.6 GHz, and a tuning speed of 1 GHz/ms

Design of a dynamic calibration phantom to be used to calculate the temporal resolution of a tomographic imaging device

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 36).What follows is an account of the design and development of a calibration device for determining the temporal resolution of a tomographic imaging device. Current practice for characterizing the dynamic response of a tomographic imaging device, such as a Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) machine, uses image acquisition time as a surrogate for temporal resolution. At present, no standard method for characterizing the temporal resolution of a tomographic imaging device exists. Analogous to the spatial modulation transfer function used for characterizing spatial resolution, the concept of temporal Modulation Transfer Function (t-MTF) can be used to enable characterization of temporal resolution. A scanner's t-MTF represents the percent amplitude modulation in the image as a function of the input frequency. The calibration device uses slotted disks mounted to planetary gear sets' rotating ring gears. The sun gears are driven by a common shaft, thus allowing for about two decades of input frequencies to be obtained using a single motor and driveshaft. Preliminary results show a monotonic decline in the temporal modulation transfer as the input signal frequency is increased. As was hypothesized, there is more modulation at lower frequency and less modulation at higher frequency. Analogous to the definition of spatial resolution, one can define the frequency for which there is 10% temporal modulation transfer as the temporal resolution of a scanner.by Alexander Henry Slocum, Jr.S.B

Kinematic couplings: A review of design principles and applications

From the humble three-legged milking stool to a SEMI standard wafer pod location to numerous sub-micron fixturing applications in instruments and machines, exactly constrained mechanisms provide precision, robustness, and certainty of location and design. Kinematic couplings exactly constrain six degrees of freedom between two parts and hence closed-form equations can be written to describe the structural performance of the coupling. Hertz contact theory can also be used to design the contact interface so very high stiffness and load capacity can also be achieved. Potential applications such as mechanical/electrical couplings for batteries could enable electric vehicles to rapidly exchange battery packs

An ROV operated undersea hydraulic hose repair coupling

A hydraulic hose repair system is presented that was developed for use at the Deepwater Horizon accident site. The system can be deployed with a single ROV with two controllable arms. One arm holds the device and the other arm pushes a severed hose into the device. Hydraulic pressure is applied from the ROV to the device and a hydraulic coupling within the device is crimped into one end of the hose. The second hose end to be spliced to the first is pushed into the other side of the device and the second half of the coupling is crimped onto the second hose end. The device itself is left in place as part of the splice. The design, on-shore testing, and fabrication of multiple devices ready to deploy at the accident site took on the order of a week to complete. They stand ready to be deployed in the case of another deep-water accident. Keywords: Deepwater Horizon; Hydraulic; Hose; Repair; Couplin

A New Phenomenon: Sub-Tg, Solid-State, Plasticity-Induced Bonding in Polymers

Polymer self-adhesion due to the interdiffusion of macromolecules has been an active area of research for several decades [70, 43, 62, 42, 72, 73, 41]. Here, we report a new phenomenon of sub-Tg, solid-state, plasticity-induced bonding; where amorphous polymeric films were bonded together in a period of time on the order of a second in the solid-state at ambient temperatures nearly 60 K below their glass transition temperature (Tg) by subjecting them to active plastic deformation. Despite the glassy regime, the bulk plastic deformation triggered the requisite molecular mobility of the polymer chains, causing interpenetration across the interfaces held in contact. Quantitative levels of adhesion and the morphologies of the fractured interfaces validated the sub-Tg, plasticity-induced, molecular mobilization causing bonding. No-bonding outcomes (i) during the compression of films in a near hydrostatic setting (which inhibited plastic flow) and (ii) between an 'elastic' and a 'plastic' film further established the explicit role of plastic deformation in this newly reported sub-Tg solid-state bonding

A Two-Pressure Humidity Generator

A device for precisely humidifying a process gas is presented, with particular application to document preservation. The machine is designed to minimize the risk of damage from overpressure by incorporating multiple safety mechanisms and a simple user interface. The design theory is presented, discussed, and verified. This device is capable of generating humidified gases with relative humidities between 7 and 96 to high accuracy. At conditions suitable for document preservation, the machine is accurate to within 3.5 %, generating a relative humidity of (40 1.4)

Direct Absorption Volumetric Molten Salt Receiver With Integral Storage

A new design is presented for a concentrating solar power central receiver system with integrated thermal storage. Concentrated sunlight penetrates and is absorbed within a passive molten salt pool, also acting as a single-tank assisted thermocline storage system. The receiver has a relatively small aperture, open to the environment without requiring a transparent window to isolate the system, exhibiting low losses while achieving high temperatures needed for efficient power generation. The use of an insulated divider plate provides a physical and thermal barrier to separate the hot and cold salt layers within the receiver. The position of the divider plate is controlled throughout the day to enhance the natural thermocline which forms within the salt. As a result, continuous, high temperature heat extraction is possible even as the average temperature of the salt is declining. Experimental results are presented for an optically heated 5 L capacity sodium-potassium nitrate salt volumetric receiver equipped with a movable divider plate. Topics: Absorption, StorageBill & Melinda Gates Foundation (Graduate Student Fellowship)Chesonis Family Foundation (Graduate Student Fellowship

Sensor system design to determine position and orientation of articulated structures

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.Includes bibliographical references.by Alexander H. Slocum.Ph.D

Precision Robot Calibration Using Kinematically Placed Inclinometers

In the field of industrial robotics, many different calibration methods exist to reduce error in the robot system. Locating the manipulator home position is a common calibration technique, which can be divided into three main categories relative, optimal and leveling based methods. The home position of an industrial manipulator is a position where all joint angles have a pre-defined value (e.g. zero or 90 degrees), which can be transformed into Cartesian space via the robot kinematics. Large industrial manipulators, with a working range in the order of several meters, require an accurately defined home position that can be restored with repeatability in the order of 0.2mm in Cartesian space or 0.01 degrees in Joint space

Enhancing the Performance of the T-Peel Test for Thin and Flexible Adhered Laminates

Symmetrically bonded thin and flexible T-peel specimens, when tested on vertical travel machines, can be subject to significant gravitational loading; with the associated asymmetry and mixed-mode failure during peeling. This can cause erroneously high experimental peel forces to be recorded which leads to uncertainty in estimating interfacial fracture toughness and failure mode. To overcome these issues, a mechanical test fixture has been designed for use with vertical test machines, that supports the unpeeled portion of the test specimen and suppresses parasitic loads due to gravity from affecting the peel test. The mechanism, driven by the test machine cross-head, moves at one-half of the velocity of the cross-head such that the unpeeled portion always lies in the plane of the instantaneous center of motion. Several specimens such as bonded polymeric films, laminates, and commercial tapes were tested with and without the fixture, and the importance of the proposed T-peel procedure has been demonstrated