Thin Lift Research Articles

Conformal Mapping Model of Vortex Interaction Forces on Foils of Realistic Shape

An analytical modeling approach is developed to compute the unsteady force on a foil, with any specified chordwise thickness profile, due to a passing point vortex. The model uses a generalized Joukowsky mapping technique to map the flow about a circular cylinder to a foil of any specified shape. An expression based on the unsteady Blasius force equation is developed to compute the force response of the foil due to individual, frozen vortices that drift by the foil along mean flow streamlines. Calculations of lift force spectra for NACA 0007-61 foil shapes show 6 and 10 decibels of reduction at reduced frequencies, based on half-chord and freestream speed, of 30 and 50, respectively, relative to a NACA 0007-65 foil shape, thus highlighting the importance of foil leading-edge shape in high-frequency lift response to incident vortices. The lift response for reduced frequencies above 10 is then approximated by the vortex inertia force, and normalization of this high-frequency force term by the thin foil response shows a frequency-dependent exponential relationship that can be merged with thin foil lift response theory to compute the lift spectrum over the broad reduced frequency range between 0.1 and 50.

Feasibility of 9.5-mm Stone Matrix Asphalt for Thin Lift Overlays in Washington State

Due to budget constraints, highway agencies tend to use thin lifts as a primary rehabilitation strategy. The construction of a thin lift requires a small nominal maximum aggregate size (NMAS), e.g., 9.5 mm or smaller. However, hot-mix asphalt (HMA) with a small NMAS is prone to rutting and/or studded tire wear. Stone matrix asphalt (SMA) is a gap-graded asphalt mixture with interlocking aggregate that enhances the mixture’s mechanical properties compared with HMA, especially with regard to resistance to both rutting and studded tire wear. Therefore, SMA mixes with a small NMAS may provide a viable solution to these distress types. Few studies have evaluated the performance of small NMAS SMA for thin overlays, especially for high levels of studded tire traffic. To address this gap in the literature, this study assessed the laboratory performance of 9.5-mm NMAS SMA compared with that of commonly used 12.5-mm NMAS SMA and 9.5-mm NMAS HMA mixtures to determine the feasibility of using 9.5-mm NMAS SMA in thin lift overlays subjected to heavy traffic in the State of Washington, where the use of studded tires is widespread in winter. Three types of mixtures were tested for their resistance to bottom-up fatigue cracking, top-down fatigue cracking, thermal cracking, rutting and moisture susceptibility, and studded tire wear. The resistance to top-down fatigue cracking of the 9.5-mm SMA was comparable to that of the 9.5-mm HMA and the 12.5-mm SMA. The 9.5-mm HMA and 9.5-mm SMA had comparable resistance to bottom-up fatigue cracking and performed better than the 12.5-mm SMA. Both the 9.5-mm HMA and the 9.5-mm SMA had better thermal cracking resistance than the 12.5-mm SMA. The 12.5-mm SMA had better rutting and moisture susceptibility resistance than the 9.5-mm SMA and 9.5-mm HMA. Both the 9.5-mm SMA and 12.5-mm SMA had comparable resistance to studded tire wear and performed better than the 9.5-mm HMA. Overall, the results showed that 9.5-mm NMAS SMA is a viable material for thin-lift overlays, outperforming 9.5-mm NMAS HMA in terms of resistance to rutting, moisture, and studded tire wear. Further studies are needed to assess the field performance, constructability, and life-cycle costs of 9.5-mm SMA.

Laboratory and Economic Evaluations of Thin Lift Asphalt Overlay for Pavement Preservation

Abstract The overall objective of this study was to assess the use of locally available materials in Nevada for the development of two durable fine-graded thin lift hot-mix asphalt overlay mixtures for pavement preservation. The investigation considered establishing two mix designs using typical local materials for the northern and southern part of the state. An optimal asphalt binder content was selected for each mixture based on the volumetric properties and following the Nevada Department of Transportation volumetric requirements. For each mixture, the optimal asphalt binder content was varied within the allowable tolerances to simulate the potential variation in asphalt binder content during plant production. The performance of the designed mixtures were evaluated at the various asphalt binder contents in terms of their resistance to moisture damage using indirect tensile strength, resistance to surface raveling and abrasion, dynamic modulus |E*| property, resistance to rutting using the flow number test, resistance to reflective cracking using the IPC overlay jig, workability, and the developed interlayer bond strength using the Louisiana interlayer shear strength tester (LISST). Overall, both designed fine-graded mixtures showed a very good performance and are expected to perform well when used as a thin lift hot-mix asphalt overlay. In particular, good stability, very good resistance to surface raveling and abrasion, and excellent resistance to reflective cracking were observed for both thin lift hot-mix asphalt overlay mixtures at all evaluated asphalt binder contents. A preliminary life cycle cost analysis was also conducted between the thin lift asphalt overlay and a typically used pavement surface treatment for Nevada: the chip seal. Based on the findings from this study, conclusions and recommendations were provided for implementing thin lift hot-mix asphalt overlay as a pavement preservation technique for the state of Nevada.

Comparison of Density Tests for Thin Hot-Mix Asphalt Overlays

The thin overlay mix (TOM) and ultrathin overlay mix (UTOM) specifications in Texas test falling head water flow as a surrogate measure of density. Current flow time criterion has never been correlated to density; furthermore, there is no maximum flow time to prevent overcompaction. A rolling density meter (radar) and a circular track meter may also be used to measure thin lift density. These tests and traditional core testing were used on three projects, and the correlations between tests were analyzed. Correlations were strong on a project-by-project basis but generally poor when data sets were combined. Flow time and mean profile depth, flow time and core voids, and surface dielectric and core voids were the strongest correlations overall; measured voids were unusually high. The reliability of taking core measurements on such thin samples is questionable and may be overly influenced by the surface texture. The flow test should continue to be used as a surrogate measure of density. No minimum flow time was recommended because of unusually high void measurements. To avoid overcompaction in TOMs, flow time should be less than 6 min on higher-speed or critical sections and less than 10 min on lower-speed, noncritical sections. From the standpoint of macrotexture in the UTOM, no upper limit is recommended for flow time. The rolling density meter should be employed on project-specific issues when full-coverage density measurements are desired. Further testing should be conducted on the reliability of measuring voids on very thin cores.

Direct Growth of Horizontally Aligned Carbon Nanotubes between Electrodes and Its Application to Field-Effect Transistors

This paper presents direct growth of horizontally-aligned carbon nanotubes (CNTs) between two predefined various inter-spacing up to tens of microns of electrodes (pads) and its use as CNT field-effect transistors (CNT-FETs). Using the conventional photolithography technique followed by thin film evaporation and lift off, the catalytic electrodes (pads) were prepared, consisting of Pt, Al and Fe triple layers on SiO2/Si substrate. The grown CNTs were horizontally-aligned across the catalytic electrodes on the modified gold image furnace hot stage (thermal CVD) at 800 degrees C by using an alcohol vapor as the carbon source. Scanning and transmission electron microcopies (SEM/TEM) were used to observe the structure, growth direction and density of CNTs, while Raman spectrum analysis was used to indicate the degree of amorphous impurity and diameter of CNTs. Both single- and multi-wall CNTs with diameters of 1.1-2.2 nm were obtained and the CNT density was controlled by thickness of Fe catalytic layer. Following horizontally-aligned growth of CNTs, the electrical properties of back-gate CNT-FETs were measured and showd p-type conduction behaviors of FET.

Theoretical solution for the lift force of “ecranoplan” moving near rigid surface

This paper develops a theoretical solution for the problem of determining thin wing's lift force while moving near flat surface (a screen). The solution is determined under the assumption of fluid being ideal and incompressible. The Chaplygin–Zhukovsky hypothesis of rear-edge-limited solution is taken into consideration. The solution of a problem is reduced to the Fredholm equation that is solved numerically. The generalization of the Zhukovski solution was obtained, which provides the lift force dependence on the altitude of the flight. The behavior of the lift force is very peculiar: it increases on decreasing altitude above the rigid surface. The screen effect becomes essential on moving wing altitude being smaller than the wing's length. The effect was detected experimentally before and gave birth to construction of a special flying vehicle named “ecranoplan”. It is shown in the paper that the lift force could increase several orders of magnitude. This effect could be used in developing flying vehicles of high loading capacity, which could be used in the territories of smooth surface: savannas, steppes, deserts, lakes, swamps, etc. The effect could be used for developing vehicles for operation on other planets having not very dense atmosphere and relatively smooth surface (like Mars). Flights in such an atmosphere are energy consuming, while using the effect of lift force increase near the surface could be very effective.

Lateral growth of single-walled carbon nanotubes across electrodes and the electrical property characterization

To realize the commercialization of single-walled carbon nanotube (SWNT)-based nanoelectronic and optoelectronic devices, the development of a fabrication process of catalytic chemical vapour deposition (CCVD) growth of SWNTs across electrodes is required. In this work, we report on the process of the lateral growth of SWNTs across catalytic pads. Using the conventional photolithography technique followed by thin film evaporation and lift off, the catalytic pads were prepared, consisting of nickel (Ni) and silicon dioxide (SiO 2) double layers, on the thermal silicon oxide substrate. The SWNTs were laterally grown across the catalytic pads in a thermal pyrolysis CVD system at 800–900 °C fed with a mixed gas flow of methane (CH 4) and hydrogen (H 2). The SiO 2, as the upper layer on Ni pads, not only plays a role as a barrier to prevent vertical growth but also serves as a porous medium that helps in forming smaller nano-sized Ni particles, so that the use of ultrathin Ni film would not be necessary for growth of SWNTs. Lateral growth across pads of various inter-spacing up to tens of microns was conducted for devices of different applications. The characterization by micro-Raman spectroscopy, atomic force microscopy and electron microscopy revealed the structure and diameters of the SWNTs and most importantly the SWNT density controlled by changing growth temperature. Following SWNTs growth, post-definition of metallic electrodes was conducted and the electrical properties were also measured.

Investigation of Permeability on Indiana SR-38

In 1999, a 9.5 mm nominal maximum size hot-mix asphalt mixture, designed according to the Superpave mixture design method, was placed as an overlay on Indiana State Road 38. Within one year of construction, the pavement showed signs of significant distress, including aggregate pop-outs and degradation, the presence of free water (weeping) on the driving surface, and longitudinal and fatigue cracking. At the request of the District, an investigation was undertaken to determine the cause of the pavement distress. As part of the investigation, core samples were taken from the roadway surface and tested for compliance with material properties and volumetrics, and to determine the mixture permeability. The mixture met all applicable materials and volumetric specifications, but had a low in-place density and was permeable. The results indicate that the mixture was too coarsely graded to achieve compaction in the relatively thin lift specified by the Department of Transportation. The resulting recommendations were that the mixture be removed and replaced, and that the mixture specifications be revised to more closely control gradation and increase mixture lift thickness.

Fabrication of ultra-short T gates by a two-step electron beam lithography process

This paper proposes a two-step electron beam lithography process, i.e., exposing feet and heads in two separate steps for ultra-short T gates, using a PMMA/UNIII resist stack separated by a thin lift off resist (LOR) layer. Results from both experiments and Monte Carlo simulations show that the two-step lithography process has advantages over the traditional one-step process of being able to pattern shorter feet with a much thicker top layer. The optimum thickness of the LOR for patterning T shape profiles in the PMMA/UVIII resist stack has been found to be about 20 nm.

Field-Effect and Single-Electron Transistors Based on Single-Walled Carbon Nanotubes Catalyzed by Al/Ni Thin Films

Growth of single-walled carbon nanotubes (SWNTs) via a chemical vapor deposition technique catalyzed by a thin Al/Ni stack is presented. Catalyst islands are defined by lithography, thin film evaporation and lift off technique. The process is fully compatible with conventional micro- and nanolithography techniques. Micrometer size semiconducting SWNT devices have been used to explore field-effect properties of the nanotubes at room temperature while smaller length semiconducting SWNT islands are used to study single-electron charging effects at low temperatures.

Development of Mix Design Criteria for 4.75-mm Superpave® Mixes

The Superpave® mix design system includes design criteria for a range of mixes with nominal maximum aggregate sizes (NMASs) between 9.5 and 37.5 mm. Many agencies in the United States have expressed an interest in using a 4.75-mm NMAS mix. Such a mix could provide benefits; that is, it should provide a very smooth riding surface, could be used for thin lift applications, could correct surface defects (leveling), could decrease construction time, could provide a use for manufactured screening stockpiles, and could provide a very economical surface mix for facilities with low traffic volumes. A study was done to establish the standard mix design criteria needed for 4.75-mm mixes. On the basis of the findings of the study, the recommended Superpave mix design criteria include a specified gradation control of 30% to 54% passing on the 1.18-mm (No. 16) sieve and 6% to 12% passing the 0.075-mm (No. 200) sieve. During design, the following were recommended: a design air void content of 4%, minimum voids in mineral aggregate (VMA) of 16% for all traffic levels, maximum VMA of 18% for mix designs with more than 75 gyrations, voids filled with asphalt (VFA) of 75% to 78% for mix designs with 75 gyrations and above, and VFA of 75% to 80% for mix designs with 50 gyrations. The results of the study showed that 4.75-mm NMAS mixes can be successfully designed. These types of mixes should provide economical mixes for low-volume roadways.

K. U. Short Leg Brace for Knee Extensor Weakness

We usually prescribe a long leg brace for the knee extensor weakness. The SKA Orthosis (New-York University, 1968) and Saltiel Brace (Israel, 1969) were invented in order to substitute a short leg brace for a long leg brace.Our plastic K. U. Short Leg Brace for flaccid knee extensor weakness has two special features.1) The brace's degree of plantar flexion can be changed in order to accommodate to the difference in the heel height of the shoe. For instance, it is enough to attach thin heel lift plates with Velcro to the outer heel base of the brace in case the brace needs more dorsi-flexion to prevent instability that occurs, for example, in walking without shoes.2) There are three types of pre-tibial shell and one can select proper type of pre-tibial shell according to the instability of the knee joint.In the Japanese way of life, there are frequent opportunities to walk without shoes. In such a case, reasonable knee stability can be obtained with the K. U. Short Leg Brace.The Advantages of the K. U. Short Leg Brace are as follow:1) light weight, 2) excellent cosmesis, 3) fit to any shoes, 4) it allows sitting in maximally flexed position of the knee, 5) easy wearing and easy to take off, 6) noiselessness, 7) easy to clean the brace, 8) reasonable purchase price, 9) it decreases energy consumption due to movable knee joint.

Short Leg Brace for Knee Extensors Weakness (K. U. Short Leg Brace)

We usually prescribed a long leg brace for the knee extensors weakness as seen in poliomyelitis.The SKA orthosis (New York University) and Saltiel brace (Israel) were invented in order to substitute a short leg brace for a long leg brace. We made a plastic short leg brace (K. U. Short Leg Brace) which has fixed ankle joint, the STP shaped pre-tibial shell, and thin heel lift plates. The proper heel lift plates may be attached to the outer heel base in case the brace needs more dorsi-flexion as walk without shoes.In the Japanese way of life, there are frequent opportunities to walk without shoes. In such case, you can get reasonable knee tability with this Short Leg Brace because of the brace can accomodate to the heel height variations.The features of K. U. Short Leg Brace are as follow:1. light weight2. excellent cosmesis3. fit any shoes4. can sit in knee maximal flexed position5. easy donning and easy to take off6. easy to clean the brace7. noiseless8. cheap9. decrease energy consumption due to movable knee joint