An Optimal Control Model of Technology Transition

This paper discusses the use of optimization software to solve an optimal control problem arising in the modeling of technology transition. We set up a series of increasingly complex models with such features as learning-by-doing, adjustment cost, and capital investment. The models are written in continuous time and then discretized by using different methods to transform them into large-scale nonlinear programs. We use a modeling language and numerical optimization methods to solve the optimization problem. Our results are consistent with ndings in the literature and highlight the impact the discretization choice has on the solution and accuracy.

Advanced ceramic coating development for industrial/utility gas turbine applications

The effects of ceramic coatings on the lifetimes of metal turbine components and on the performance of a utility turbine, as well as of the turbine operational cycle on the ceramic coatings were determined. When operating the turbine under conditions of constant cooling flow, the first row blades run 55K cooler, and as a result, have 10 times the creep rupture life, 10 times the low cycle fatigue life and twice the corrosion life with only slight decreases in both specific power and efficiency. When operating the turbine at constant metal temperature and reduced cooling flow, both specific power and efficiency increases, with no change in component lifetime. The most severe thermal transient of the turbine causes the coating bond stresses to approach 60% of the bond strengths. Ceramic coating failures was studied. Analytic models based on fracture mechanics theories, combined with measured properties quantitatively assessed both single and multiple thermal cycle failures which allowed the prediction of coating lifetime. Qualitative models for corrosion failures are also presented

Composite Reflective/Absorptive IR-Blocking Filters Embedded in Metamaterial Antireflection Coated Silicon

Infrared (IR) blocking filters are crucial for controlling the radiative loading on cryogenic systems and for optimizing the sensitivity of bolometric detectors in the far-IR. We present a new IR filter approach based on a combination of patterned frequency selective structures on silicon and a thin (50 $\mu \textrm{m}$ thick) absorptive composite based on powdered reststrahlen absorbing materials. For a 300 K blackbody, this combination reflects $\sim$50\% of the incoming light and blocks \textgreater 99.8\% of the total power with negligible thermal gradients and excellent low frequency transmission. This allows for a reduction in the IR thermal loading to negligible levels in a single cold filter. These composite filters are fabricated on silicon substrates which provide excellent thermal transport laterally through the filter and ensure that the entire area of the absorptive filter stays near the bath temperature. A metamaterial antireflection coating cut into these substrates reduces in-band reflections to below 1\%, and the in-band absorption of the powder mix is below 1\% for signal bands below 750 GHz. This type of filter can be directly incorporated into silicon refractive optical elements

Beta-delayed-neutron studies of 135,136^{135,136}Sb and 140^{140}I performed with trapped ions

Beta-delayed-neutron ($\beta$n) spectroscopy was performed using the Beta-decay Paul Trap and an array of radiation detectors. The $\beta$n branching ratios and energy spectra for $^{135,136}$Sb and $^{140}$I were obtained by measuring the time of flight of recoil ions emerging from the trapped ion cloud. These nuclei are located at the edge of an isotopic region identified as having $\beta$n branching ratios that impact the r-process abundance pattern around the A~130 peak. For $^{135,136}$Sb and $^{140}$I, $\beta$n branching ratios of 14.6(11)%, 17.6(28)%, and 7.6(28)% were determined, respectively. The $\beta$n energy spectra obtained for $^{135}$Sb and $^{140}$I are compared with results from direct neutron measurements, and the $\beta$n energy spectrum for $^{136}$Sb has been measured for the first time

Ablation debris control by means of closed thick film filtered water immersion

The performance of laser ablation generated debris control by means of open immersion techniques have been shown to be limited by flow surface ripple effects on the beam and the action of ablation plume pressure loss by splashing of the immersion fluid. To eradicate these issues a closed technique has been developed which ensured a controlled geometry for both the optical interfaces of the flowing liquid film. This had the action of preventing splashing, ensuring repeatable machining conditions and allowed for control of liquid flow velocity. To investigate the performance benefits of this closed immersion technique bisphenol A polycarbonate samples have been machined using filtered water at a number of flow velocities. The results demonstrate the efficacy of the closed immersion technique: a 93% decrease in debris is produced when machining under closed filtered water immersion; the average debris particle size becomes larger, with an equal proportion of small and medium sized debris being produced when laser machining under closed flowing filtered water immersion; large debris is shown to be displaced further by a given flow velocity than smaller debris, showing that the action of flow turbulence in the duct has more impact on smaller debris. Low flow velocities were found to be less effective at controlling the positional trend of deposition of laser ablation generated debris than high flow velocities; but, use of excessive flow velocities resulted in turbulence motivated deposition. This work is of interest to the laser micromachining community and may aide in the manufacture of 2.5D laser etched patterns covering large area wafers and could be applied to a range of wavelengths and laser types

Using Remote Sensing and Detection of Early Season Invasives (DESI) to Analyze the Temporal Dynamics of Invasive Cheatgrass (Bromus tectorum)

The invasion of exotic annual grasses during the last century has transformed plant habitats and communities worldwide. Cheatgrass (Bromus tectorum) is a winter annual grass that has invaded over 100 million acres of the western United States (Pellant and Hall, 1994. Pellant, 1996). Cheatgrass quickly utilizes available resources especially after a disturbance to the landscape. A major impact of invasion is the increased frequency in fires (D’Antonio and Vitousek, 1992). As cheatgrass is highly successful at invading open and disturbed landscapes at a rapid pace it increases the frequency and severity of fires in arid landscapes (Brooks, 2005). Cheatgrass’ prolific seed production and flammability allows it to competitively exclude native plant species (Seabloom et al., 2003). The successful life strategy of cheatgrass gives a unique spectral image reflectance that can allow the use of remote sensing platforms to track and locate invasions

Designing for digital wellbeing: A research & practice agenda

Traditionally, many consumer-focused technologies have been designed to maximize user engagement with their products and services. More recently, many technology companies have begun to introduce digital wellbeing features, such as for managing time spent and for encouraging breaks in use. These are in the context of, and likely in response to, renewed concerns in the media about technology dependency and even addiction. The promotion of technology abstinence is also increasingly widespread, e.g., via digital detoxes. Given that digital technologies are an important and valuable feature of many people's lives, digital wellbeing features are arguably preferable to abstinence

Using Hotspot Analysis and Detection of Early Season Invasives (DESI) to analyze the temporal and spatial dynamics of invasive cheatgrass (Bromus tectorum).

The invasion of exotic annual grasses during the last century has transformed plant habitats and communities worldwide. Cheatgrass (Bromus tectorum) is a winter annual grass that has invaded over 100 million acres of the western United States (Pellant and Hall, 1994. Pellant, 1996). Cheatgrass quickly utilizes available resources especially after a disturbance to the landscape. A major impact of invasion is the increased frequency in fires (D’Antonio and Vitousek, 1992). As cheatgrass is highly successful at invading open and disturbed landscapes at a rapid pace it increases the frequency and severity of fires in arid landscapes (Brooks, 2005). Cheatgrass’ prolific seed production and flammability allows it to competitively exclude native plant species (Seabloom et al., 2003). The successful life strategy of cheatgrass gives a unique spectral image reflectance that can allow the use of remote sensing platforms to track and locate invasions

Simplified amino acid alphabets based on deviation of conditional probability from random background

The primitive data for deducing the Miyazawa-Jernigan contact energy or BLOSUM score matrix consists of pair frequency counts. Each amino acid corresponds to a conditional probability distribution. Based on the deviation of such conditional probability from random background, a scheme for reduction of amino acid alphabet is proposed. It is observed that evident discrepancy exists between reduced alphabets obtained from raw data of the Miyazawa-Jernigan's and BLOSUM's residue pair counts. Taking homologous sequence database SCOP40 as a test set, we detect homology with the obtained coarse-grained substitution matrices. It is verified that the reduced alphabets obtained well preserve information contained in the original 20-letter alphabet.Comment: 9 pages,3figure