Rotary encoding for intravascular ultrasonic imaging systems

Images produced with an intravascular ultrasound system (IVUS) can be distorted because of uncertainty in the instantaneous angular position of a rotating ultrasonic transducer. A rotary encoder placed in proximity to the transducer is required to detect the problem; however, size constraints make a conventional electromechanical or optomechanical encoder difficult to implement. Measurements that test the feasibility of a software-derived encoder, based of the rate of decorrelation of ultrasonic RF lines with angle, are reported. Provided that the instantaneous angular velocity of the transducer can be measured, adjustments can be made to the pulse rate of the transducer, which would eliminate the image distortion.     

The design of a visual display for the presentation of statistical quality control information to operators on the plant floor

We applied human-centered design methodologies to enhance the presentation of product quality information to operators on a manufacturing plant floor. First, an initial visual display concept that integrated a pictorial representation of a product with standard graphical and tabular information about the product's quality was refined through iterative design and testing. A preliminary study was then conducted to determine the specific features of such a display (termed a pictorial control chart) from among eight candidate detail designs. Finally, a formal study was conducted to compare the performance of operators using this refined pictorial control chart design with their performance using a conventional control chart. Operators completed a quality control task in significantly less time using the pictorial control chart. There were no significant differences in the number of errors committed with the two charts. Subjective measures showed a significant preference for the pictorial control chart. Actual or potential applications of this research include the development of quality control tools that are useful to and usable by operators on the manufacturing plant floor.     

The Commercialization of Information Infrastructure as Technological Mediation: The Internet Access Market

The study interprets the geographic diffusion of Internet Service Providers (ISPs) and the expansion of ISPs product lines in terms of the market for technological mediation. A firm involved in technology mediation takes advantage of gaps between general technological opportunities and particular user needs in specific places at particular times. If the economic opportunities are fleeting, then so too is the business. If the economic opportunities are renewed frequently, then the business can grow and adapt to take advantage of them. The concept of technological mediation helps us understand business behavior accompanying the commercialization of internet access technology.     

A quantification of link budget differences between the cellularand PCS bands

The median propagation loss in the personal communication services (PCSs) band (near 1.9 GHz) is generally recognized to be 9-10 dB greater than that in the cellular band (near 850 MHz). It would be highly desirable to make up this deficit in order to minimize the infrastructure cost of PCS service startup. This goal is aided by three factors favorable to operation at PCS frequencies. First, the vertical pattern gain of the base-station antenna, for the same size, will be more than 3 dB higher at 1.9 GHz. Second, the gain derived from using base-station antenna diversity on the uplink will be greater at 1.9 GHz. The third factor is lower man-made noise at 1.9 GHz, especially in urban areas. We have carefully examined all these factors in order to quantify the link budget differences between the two bands for three types of environment, namely, urban, suburban, and rural. We find that link budget parity (meaning the same allowable cell sizes) can be achieved in all three environments with fairly modest remedies. These include the use of tower-top electronics and minor increases in downlink power. An alternative remedy is to use four-branch maximal ratio combining (MRC) at the base station, which would provide a natural transition toward the deployment of adaptive arrays     

A demountable interconnect system for a 50×50 ultrasonicimaging transducer array

A novel Pad Grid Array (PGA) system allows microminiature coaxial conductors to be electrically connected to a one-half wavelength, 50×50 element transducer array suitable for diagnostic ultrasound at 2.5 MHz. In order to achieve the desired one-half wavelength interconnection spacing present at the backing of the transducer module, an intermediary flexible printed circuit and other custom structures provide a transitional architecture between 42 AWG coax and inline interconnect pads at a 300 μm spacing. Due to critical alignment requirements, special processes are needed for fabrication and the successful connection of the fine-pitch circuit elements. A conductive anisotropic elastomeric material acts as the medium to effect the final interconnect between the PGA and transducer module. Because the anisotropic medium provides a separable interface, the interconnect system allows repeated connection. Acoustic performance indicates suitability for diagnostic imaging     

Optical equalization to combat the effects of laser chirp and fiberdispersion

Optical equalizers capable of combating the effects of laser chirp and fiber chromatic dispersion on high-speed long-haul fiber-optic communication links at 1.5 μm are described. They consist of both reflective and transmissive cavity structures. The equalizers are adaptive in the sense that the position of their periodic frequency responses are optimally adjusted in real time. The equalizers are evaluated by using computer simulation routines based on the rate equations for intensity-modulated lasers. It is shown that, by using equalizers of the type proposed, the receiver data eyes remain open well beyond where they would close without equalization