The effects of spinal cord injuries are likely to be ameliorated with the help of functional electrical stimulation of the spinal cord, a technique that may benefit from a new style of electrode: the cylindrical multielectrode. This paper describes the specifications for, fabrication techniques for, and in vitro evaluation of cylindrical multielectrodes. Four tip shapes were tested to determine which shape required the lowest peak force and would, therefore, be expected to minimize dimpling during implantation. The impedance of the electrode interface was monitored for changes due to insertion as well as repetitive delivery of current pulses. The charge delivery capacity was determined by testing with safe (< or = 0.6 mC/cm2) and damaging levels (> or = 0.8 mC/cm2) of charge density. The results of these tests suggest that this electrode design could be used to stimulate neurons in the ventral horn of the spinal cord.

This paper investigates the effect of the variation of parameters of system elements on the overall performance of a generic model of a hydraulic actuation system. Specifically, this paper examines the effects on actuator performance of two issues: intrinsic compliance, the physical compliance within the actuator itself; and independent control of the actuator valve areas (e.g., supply and return areas for hydraulic fluid chambers) versus control of actuator valves with fixed area relationships. Increasing intrinsic compliance in the actuator degrades response to controller commands but improves the ability of the actuator to tolerate insults. Independent control of valve areas provides both better response to commands and better rejection of disturbances than control with valves that have fixed area relationships. The performance information provided by the model permits behavior-based design of hydraulic actuation systems. JNTRODUC TlON BackaroundA great deal of time has been spent on the design of robots, teleoperation systems, and prosthetics. These projects require actuation systems with specific groups of behavioral characteristics, such as grace, accuracy, strength, and speed. In order to achieve these desired characteristics, the systems need good actuators. However, defining a good actuator and describing how to design a good actuator are difficult problems because actuators are not completely understood [l].To address this problem, the Center for Engineering Design (CED) at the University of Utah decided to explore the issues involved in the behavior-based design of robot effectors [I]. Some issues brought up by that investigation were: 1) how well external disturbances can be tolerated; 2) how nonlinearities affect actuator performance; 3) how intrinsic qualities can be manipulated to produce desired'behaviors; 4) how additional control possibilities can be used to improve performance; and 5) how hydraulic systems fit into the behavior-based design strategies proposed for systems with electrical motors [I]. Of specific interest is the effect of intrinsic compliance on external disturbance rejection. It has also been suggested that independently controlling valves can improve actuator performance [2-41. Therefore, the effect of this added control flexibility on actuator performance is also sought.The purpose of this research is to develop and use a generic model of a hydraulic actuator to investigate the above issues. A generic model is needed so that the results of the investigation are valid for hydraulic actuation systems in general and not just for specific cases. Also, the model must include elements that have significant effects on actuator performance so that these effects may be analyzed. The model can then be used to quantify trade-offs resulting from these elements in order to permit the development of behavior-based design strategies for hydraulic actuators. In particular, an understanding of the effect on performance of intrinsic compliance, physical compliance within the actuator itself, is...

Progress in the development of Micro Electro Mechanical Systems (MEMS) has been limited by deficiencies in two broad areas: (1) a lack of knowledge of the physical behavior of interacting micro systems (phenomena such as micro-mbology, -fluid mechanics, -electrostatics, -elecmcal discharge, etc.), and (2) limitations in available fabrication methodologies (photolithography, sputtering, etching, etc.). This paper addresses the second problem by presenting specific Non-Planar Lithographic OJPL) techniques for use in fabricating both monolithic micromachines and microcomponents for use in larger systems. The emphasis here is on the use of numerically-controlled E-beam-based lithography, with the resist exposed over non-planar surfaces. Previously, non-planar, optical-mask-based approaches have been used to fabricate devices such as wobble motor rotors, but with less success than the NPL techniques due to depth-of-field problems.The specific focus is on etching cylindrically-shaped metal structures which are either (1) homogeneous or (2) layered by successive deposition, masking, and etching. Structures on the order of 80 to 500 microns in diameter have been constructed of either solid metals, or sputtered thin metallic layers on quartz shafts. A number of either deep or shallow patterns have been fabricated on and through the structures, with promising results. Examples include; helices, longitudinal lines, holes, notches, flexures, barbs, alphanumeric characters, and electrostatic field emitting patterns for use in wobble motors. Efforts are now proceeding toward generating complete systems, including transducers and actuators for industrial and medical applications.

Two days after the University of Utah Seismograph Stations (UUSS) staff were required to leave campus and work remotely, an Mw 5.7 earthquake struck the Salt Lake Valley near the town of Magna, Utah. This event was the largest instrumentally recorded earthquake in the Salt Lake Valley and the largest earthquake ever felt by most residents. The timing of this event—at the start of a lockdown in response to the COVID-19 pandemic—made the UUSS response to this earthquake an extra challenge. Other factors such as a toxic plume caused by the ground shaking, inclement weather, and a mountain lion also impacted the work. The response tested the continuity of operations plan that had been in place since 2007, response protocols, and communications with partners and the public. Overall, the UUSS earthquake response was successful: A valuable and arguably unprecedented dataset of strong ground motions from normal faulting was generated, magnitudes and locations of thousands of earthquakes were shared in a timely fashion, unfounded rumors and general questions were promptly responded to via traditional and social media, and initial scientific results were submitted for publication.

South‐central Utah is characterized by Quaternary volcanism, current geothermal activity, and unusually high surface heat flux across the region. Additionally, there are three operating geothermal power plants in this region, known as the Sevier thermal area. This setting is very similar to that found in the Coso geothermal area. However, the source and lateral extent of subsurface heat in Utah is poorly understood. We use temporally separated geophone arrays combined with regional broadband data to perform ambient noise seismic tomography to study the subsurface shear velocity structure in the region. We find good recovery of ocean‐seism excited Rayleigh wave signals between the periods of 5 and 10 s. For each period, we measure the Rayleigh wave phase velocity and ellipticity across the region using the beamforming methodology and horizontal to vertical (H/V) amplitude ratio. Finally, we combine spline‐based 1D shear velocity models inverted using Rayleigh wave phase velocity and H/V measurements on a 2D, beamforming discretized grid to construct a final 3D model. The final 3D model has many similarities to imaged velocity models at the Coso geothermal area. We find a strong correlation between low velocity anomalies and high surface heat flux and geothermal activity. Additionally, we find a laterally continuous low‐velocity anomaly between 5 and 15 km depth, which may represent elevated temperature of hundreds of degrees Celsius, partial melt, and/or the presence of water, and a common heat source across the region which likely originates from the mantle.