A new type of metallic electromagnetic structure has been developed that is characterized by having high surface impedance. Although it is made of continuous metal, and conducts dc currents, it does not conduct ac currents within a forbidden frequency band. Unlike normal conductors, this new surface does not support propagating surface waves, and its image currents are not phase reversed. The geometry is analogous to a corrugated metal surface in which the corrugations have been folded up into lumped-circuit elements, and distributed in a two-dimensional lattice. The surface can be described using solid-state band theory concepts, even though the periodicity is much less than the free-space wavelength. This unique material is applicable to a variety of electromagnetic problems, including new kinds of low-profile antennas.

/pdf/high-impedance-electromagnetic-surfaces-with-a-forbidden-3vtu72a5an.pdf

High-impedance electromagnetic surfaces with a forbidden frequency band

http://sces.phys.utk.edu/mostcited/mc1_1114.pdf

Colossal Magnetoresistant Materials: The Key Role of Phase Separation

Nanosphere lithography (NSL) is an inexpensive, simple to implement, inherently parallel, high throughput, materials general nanofabrication technique capable of producing an unexpectedly large variety of nanoparticle structures and well-ordered 2D nanoparticle arrays. This article describes our recent efforts to broaden the scope of NSL to include strategies for the fabrication of several new nanoparticle structural motifs and their characterization by atomic force microscopy. NSL has also been demonstrated to be well-suited to the synthesis of size-tunable noble metal nanoparticles in the 20−1000 nm range. This characteristic of NSL has been especially valuable for investigating the fascinating richness of behavior manifested in size-dependent nanoparticle optics. The use of localized surface plasmon resonance (LSPR) spectroscopy to probe the size-tunable optical properties of Ag nanoparticles and their sensitivity to the local, external dielectric environment (viz., the nanoenvironment) is discussed in...

Nanosphere Lithography: A Versatile Nanofabrication Tool for Studies of Size-Dependent Nanoparticle Optics

How localized electrons interact with delocalized electrons is a central question to many problems in sold-state physics1,2,3. The simplest manifestation of this situation is the Kondo effect, which occurs when an impurity atom with an unpaired electron is placed in a metal2. At low temperatures a spin singlet state is formed between the unpaired localized electron and delocalized electrons at the Fermi energy. Theories predict4,5,6,7 that a Kondo singlet should form in a single-electron transistor (SET), which contains a confined ‘droplet’ of electrons coupled by quantum-mechanical tunnelling to the delocalized electrons in the transistor's leads. If this is so, a SET could provide a means of investigating aspects of the Kondo effect under controlled circumstances that are not accessible in conventional systems: the number of electrons can be changed from odd to even, the difference in energy between the localized state and the Fermi level can be tuned, the coupling to the leads can be adjusted, voltage differences can be applied to reveal non-equilibrium Kondo phenomena7, and a single localized state can be studied rather than a statistical distribution. But for SETs fabricated previously, the binding energy of the spin singlet has been too small to observe Kondo phenomena. Ralph and Buhrman8 have observed the Kondo singlet at a single accidental impurity in a metal point contact, but with only two electrodes and without control over the structure they were not able to observe all of the features predicted. Here we report measurements on SETs smaller than those made previously, which exhibit all of the predicted aspects of the Kondo effect in such a system.

Kondo effect in a single-electron transistor

Progress in preparation, processing and applications of polyaniline

A new logging-while-drilling (LWD) technology has been developed and field-tested, which introduces directional electromagnetic (EM) measurements through the use of tilted and transverse current-loop antennas. The multispacing and multifrequency directional measurements enable monitoring distance to formation boundaries and their orientation to facilitate proactive well placement. In combination with conventional LWD resistivity, these directional EM measurements allow for accurate structure and formation resistivity interpretation around the wellbore, independent of mud type. Furthermore, specific antenna combinations provide the capability to detect and characterize resistivity anisotropy in near-vertical wells while drilling. The directional EM tool is designed with a symmetrical transmitter-receiver configuration that optimizes the sensitivity to the desired formation parameters. While canceling the influence of anisotropy and formation dip, adding the symmetrical directional measurements together maximizes the sensitivity to bed boundaries, which is optimal for geosteering. The fact that the antennas are mounted on a conductive collar significantly reduces the large borehole effects that are normally associated with transverse EM measurements in conductive mud. In addition to exploring the physics of the new directional propagation measurements, we will demonstrate their unique applications with field test examples. By detecting and tracking, in real time, formation boundaries up to 15 ft around the wellbore, the directional propagation tool allows for sufficient time to make trajectory adjustments and stay within the reservoir. The bedding orientation information also answers the question, in what direction to steer, which is often ambiguous when relying on traditional propagation measurements. Particularly interesting applications are the placement of wells in thin oil rims and in reservoirs with complex structures such as intrabedded shale silts. Field test examples will also be shown of the enhanced formation evaluation capabilities offered by directional measurements in high-angle and horizontal wells, where formation resistivities can now be determined while accurately accounting for proximate bed boundaries. The ability to measure resistivity anisotropy in near vertical wells will be demonstrated by a field test example where the anisotropy measurement was confirmed by comparing with a conventional propagation resistivity measurement run in a near-by high-angle well.

New Directional Electromagnetic Tool For Proactive Geosteering And Accurate Formation Evaluation While Drilling

A novel on-the-fly data processing technique is useful for extracting signals from the azimuthal variation of the directional measurements acquired by a logging tool within a borehole. The relevant boundary, anisotropy and fracture signals are extracted from the formation response through fitting of the azimuthal variation of the measured voltages to some sinusoidal functions. The orientation of the bedding is also obtained as a result. The extracted directional signals are useful for obtaining boundary distances and making geosteering decisions. Two techniques involving inversion and cross-plotting may be employed, depending on the nature of the boundary. A Graphical User Interface (GUI) is part of a system to facilitate flexible definition of inversion objectives, for improving the inversion results, and for visualization of the formation model as well as inversion measurements.

Directional electromagnetic wave resistivity apparatus and method

The disclosure has application for use in conjunction with an operation of drilling an earth borehole using: a drilling rig, a drill string having its generally upper end mechanically coupleable with and suspendable from the drilling rig, and a bottom hole assembly adjacent the lower end the drill string, the bottom hole assembly including a drill bit at its lower end. A method is set forth for obtaining information about at least one parameter sensed at the bottom hole assembly, including the following steps: providing at least one measuring device in the bottom hole assembly, the at least one measuring device producing measurement data representative of a measured condition at the bottom hole assembly; providing an uphole processor system at the earth's surface; providing a drill string telemetry system coupled with the at least one measuring device and coupled with the uphole processor system; and transmitting the data from the measuring device to the uphole processor system via the drill string telemetry system.

Bidirectional drill string telemetry for measuring and drilling control

We present here a granular-rod model for the metallic state of the conducting polymer, polyaniline. In this model the metallic islands correspond to single strands of the polymer. The macroscopic conductivity results from anisotropic three-dimensional variable-range hopping in the network of metallic rods. We incorporate the experimentally observed temperature dependence of the charge carrier density and show that this model is capable of explaining (1) the temperature dependence of the conductivity \ensuremath{\sigma}=${\mathrm{\ensuremath{\sigma}}}_{0}$exp[-(${\mathit{T}}_{0}$/T${)}^{1/2}$], (2) the doping dependence of ${\mathit{T}}_{0}$, (3) the anomalous 1/T dependence of the thermoelectric power, as well as (4) the linear increase of the Pauli susceptibility with dopant concentration. We show that the quantitative agreement between our predictions for the doping dependence of ${\mathit{T}}_{0}$, the temperature dependence of the thermoelectric power, and the experimental data is excellent. We also illustrate that the temperature range where variable-range hopping is valid is decreased below the experimentally observed temperature range over which \ensuremath{\sigma}=${\mathrm{\ensuremath{\sigma}}}_{0}$exp[-(${\mathit{T}}_{0}$/T${)}^{1/2}$] if the metallic islands correspond to three-dimensional bundles of the polymer strands. It would appear then that a single strand model of the metallic state of polyaniline is more consistent with a variable-range hopping picture.

Granular-rod model for electronic conduction in polyaniline.

A system for bidirectional communication between the downhole equipment and a processor subsystem at the earth's surface, including: a section of wired drill pipes (180) comprising at least the upper portion of a string of drill pipes (12), and forming at least a portion of a bidirectional communication link between downhole equipment and the top of the string of drill pipes; a drive string portion of the drill string, mechanically coupleable with the topmost wired drill pipe; a drive mechanism mechanically coupleable with said drive string portion, for rotating the drill string; a first wireless transceiver subsystem (185) mounted on the drive string portion of the drill string, for rotation in conjunction with the drill string; a cable, electrically coupled between the top joint of the topmost wired drill pipe and the first transceiver subsystem; and a second wireless transceiver subsystem (110) coupled with the uphole processor subsystem, the second wireless transceiver subsystem communicating bidirectionally with the first wireless transceiver subsystem.

Qiming Li

Papers

New Directional Electromagnetic Tool For Proactive Geosteering And Accurate Formation Evaluation While Drilling

Directional electromagnetic wave resistivity apparatus and method

Bidirectional drill string telemetry for measuring and drilling control

Granular-rod model for electronic conduction in polyaniline.

Surface communication apparatus and method for use with drill string telemetry