Five degree-of-freedom control of an ultra-precision magnetically-suspended linear bearing

The authors constructed a high precision linear bearing. A 10.7 kg platen measuring 125 mm by 125 mm by 350 mm is suspended and controlled in five degrees of freedom by seven electromagnets. The position of the platen is measured by five capacitive probes which have nanometer resolution. The suspension acts as a linear bearing, allowing linear travel of 50 mm in the sixth degree of freedom. In the laboratory, this bearing system has demonstrated position stability of 5 nm peak-to-peak. This is believed to be the highest position stability yet demonstrated in a magnetic suspension system. Performance at this level confirms that magnetic suspensions can address motion control requirements at the nanometer level. The experimental effort associated with this linear bearing system is described. Major topics are the development of models for the suspension, implementation of control algorithms, and measurement of the actual bearing performance. Suggestions for the future improvement of the bearing system are given

Printing of Contact Holes for the 45nm Generation using Immersion Interference Lithography

Interference lithography is a valuable tool for evaluating photoresist performance at the resolutions unattainable with conventional exposure tools. interference lithography is most commonly used to generate one dimensional patterns such as lines and spaces. however two dimensional patterns are of much greater interest to both the resist developers and the device manufacturers in microlithography. This paper presents a technique to produce two dimensional images of contact holes at the resolution of 45nm half pitch. To our knowledge this is the highest resolution contacts printed to date using 193nm radiation. Photoresist patterns with a half-pitch of 45 nm were formed with an effective NA of 1.05 utilizing the JUT Immersion Interference system [4]. The wafer was subsequently rotated and the same pattern was printed at an angle relative to the original pattern. This double exposure technique allowed the formation of the two dimensional features. The images formed were processed, and the scanning electron micrograph (SEM) images and analysis of the data will be presented

Development and Characterization of a GaAs nipi Superlattice Solar Cell

The development of photovoltaics as an energy source has been propelled by numerous technological advancements over the past 60 years to now enable the conversion of sunlight into power at an efficiency of 46%. This enables power production that is cleaner, and more transferrable to locations off the grid than ever before, however new technologies are required to further increase efficiency while driving down costs. Currently a large effort is being made to achieve intermediate band solar cells (IBSC) that more efficiently convert energy from the entire solar spectrum. This is enabled through multiple techniques, including quantum dots (QDs), and potentially through doping superlattice solar cells. Doping superlattices have been explored theoretically and some historic work has used these superlattices to form nipi solar cells with alternating n-type, intrinsic, p-type, intrinsic layers. Multiple purposes exist for evaluating nipi solar cells, which include radiation hardness, an electronically adjustable absorption edge, use with nanostructures, and the possibility of an IBSC. The primary motivation for this work is to develop the nipi solar cell for evaluation as an IBSC, while also evaluating the radiation tolerance of the design for potential use in space applications. This has been completed through a theoretical and experimental analysis of nipi superlattice layers, and an extensive evaluation of the fabrication and growth processes required to achieve a high efficiency solar cell. Additionally an improved model for nipi diodes and solar cells has been developed. Also a novel process for fabricating nipi solar cells through epitaxial regrowth and diffused junctions has been developed, where record efficiencies for nipi solar cells have been measured for devices fabricated via epitaxial regrowth at 12.5%. An understanding of the effect of adding QD into a nipi superlattice has been obtained. Finally a greater understanding of the intrinsic radiation hardness of the nipi design has been achieved and possible methods to improve it have been evaluated. The techniques and processes developed here have the possibility to be used to further the understanding of nipi devices, and lead to the potential development of an IBSC with a QD-nipi design

Jumpstart your Week with a Monday Mile

Research shows that people view Monday as a day for a fresh start and are more likely to start diet and exercise programs, quit smoking, and schedule doctor’s appointments on Monday than any other day. This issue brief discusses the benefits of kick starting your week with a Monday Mile and profile a local community that created several Monday Mile routes where local residents can interact and be active

Use Explicit Instruction

Highly effective instruction for struggling learners requires both excellent instructional materials and excellent interactive teaching that delivers instruction clearly and responds to students’ unique needs and strengths. Explicit Instruction is an evidence-based approach to both designing materials and delivering instruction that is effective for a wide range of learners. It has been shown to be effective for teaching many types of academic content (e.g., reading, writing, mathematics, science) and with students ranging from kindergarten to high school. It is comprised of 16 inter-related elements (see Table 1) that contribute to the effectiveness of the overall system (Archer et al., 2011). Explicit Instruction is designed to systematically prepare students to learn complex skills, present information clearly and unambiguously, support students to engage in new skills while receiving feedback, reduce support as students gain skills, and provide sufficient practice so that students are able to independently apply their new skills in a wide variety of situations

Experiment K-6-09. Morphological and biochemical investigation of microgravity-induced nerve and muscle breakdown. Part 1: Investigation of nerve and muscle breakdown during spaceflight; Part 2: Biochemical analysis of EDL and PLT muscles

The present findings on rat hindlimb muscles suggest that skeletal muscle weakness induced by prolonged spaceflight can result from a combination of muscle fiber atrophy, muscle fiber segmental necrosis, degeneration of motor nerve terminals and destruction of microcirculatory vessels. Damage was confined to the red adductor longus (AL) and soleus muscles. The midbelly region of the AL muscle had more segmental necrosis and edema than the ends. Macrophages and neutrophils were the major mononucleated cells infiltrating and phagocytosing the cellular debris. Toluidine blue-positive mast cells were significantly decreased in Flight AL muscles compared to controls; this indicated that degranulation of mast cells contributed to tissue edema. Increased ubiquitination of disrupted myofibrils may have promoted myofilament degradation. Overall, mitochondria content and SDH activity were normal, except for a decrease in the subsarcolemmal region. The myofibrillar ATPase activity shifted toward the fast type in the Flight AL muscles. Some of the pathological changes may have occurred or been exacerbated during the 2 day postflight period of readaptation to terrestrial gravity. While simple atrophy should be reversible by exercise, restoration of pathological changes depends upon complex processes of regeneration by stem cells. Initial signs of muscle and nerve fiber regeneration were detected. Even though regeneration proceeds on Earth, the space environment may inhibit repair and cause progressive irreversible deterioration during long term missions. Muscles obtained from Flight rats sacrificed immediately (within a few hours) after landing are needed to distinguish inflight changes from postflight readaptation

A dynamics-driven approach to precision machines design for micro-manufacturing and its implementation perspectives

Precision machines are essential elements in fabricating high quality micro products or micro features and directly affect the machining accuracy, repeatability and efficiency. There are a number of literatures on the design of industrial machine elements and a couple of precision machines commercially available. However, few researchers have systematically addressed the design of precision machines from the dynamics point of view. In this paper, the design issues of precision machines are presented with particular emphasis on the dynamics aspects as the major factors affecting the performance of the precision machines and machining processes. This paper begins with a brief review of the design principles of precision machines with emphasis on machining dynamics. Then design processes of precision machines are discussed, and followed by a practical modelling and simulation approaches. Two case studies are provided including the design and analysis of a fast tool servo system and a 5-axis bench-top micro-milling machine respectively. The design and analysis used in the two case studies are formulated based on the design methodology and guidelines

Observations of Anomalous Cosmic Rays at 1 AU

Anomalous cosmic rays (ACRs) provide a sensitive probe of the access of energetic particles to the inner heliosphere, varying in intensity by more than two orders of magnitude during the course of the solar cycle. New data which are becoming available from the Advanced Composition Explorer (ACE) can provide a detailed record of ACR intensity and spectral changes on short (~ 1 day) time scales during the approach to solar maximum, which will help address issues of ACR modulation and transport. The elemental and isotopic composition of ACRs provides important information on the source or sources of these particles, while their ionic charge state composition and its energy dependence serves as a diagnostic of their acceleration time scale. We review measurements of the ACR elemental, isotopic, and charge state composition and spectra as determined at 1 AU by SAMPEX, ACE, Wind, and other spacecraft. These results are important input to models of the acceleration, modulation, and transport of ACRs

The Solar Energetic Particle Event of 6 May 1998

The abundances of elements from helium to iron have been measured in more than a dozen moderate to large solar energetic particle (SEP) events using the Solar Isotope Spectrometer (SIS) on-board the Advanced Composition Explorer (ACE). Time variations within some of these events and from event to event have been reported previously. This paper presents an analysis of the event of 6 May 1998, for which relatively time-independent abundance ratios are found. This event has been considered to be an example of an impulsive event, a gradual event, and as a hybrid of the two. Difficulties with classifying this event are discussed