Nanogaps formation and characterization via chemical and oxidation methods

Different materials were used to optimize the desired nano-size with smooth process and faster fabrication. Gold, polysilicon and silicon were used to apply this report (experimental). SOI and Si wafers have used as a substrate and one chrome mask to build up the nanogap devices using size reduction technique. Two chrome masks have used to fabricate the proposed pattern. Electrical characterization was applied to setup the fabricated devices with different materials. Conductivity and resistivity were measured to characterize the nanogap structure with gold, polysilicon and silicon as electrodes. However, gold nanogap has recorded an increment in the conductivity, and the silicon nanogap structures have recorded an increment in the resistivity comparing with the other used materials.     

Infiltration of Water into Soil with Cracks

This paper presents the physical basis of the FRACTURE submodel for simulating infiltration of precipitation∕irrigation water into relatively dry, cracked, fine-textured soils. The FRACTURE submodel forms part of the HYDRUS-ET variably saturated flow∕transport model. Infiltration into the soil matrix is formally divided into two components: (1) Vertical infiltration through the soil surface; and (2) lateral infiltration via soil cracks. The first component is described and solved using the 1D Richards' equation. Excess water that does not infiltrate through the soil surface is either considered to be runoff, if no soil cracks are present, or routed into soil cracks from where it may laterally infiltrate into the soil matrix. Horizontal infiltration from soil cracks into the soil matrix is calculated using the Green-Ampt approach and incorporated as a positive source∕sink term Sf in the Richards' equation describing flow in the matrix. In addition to the hydraulic properties of the soil matrix, the FRACTURE submodel requires parameters characterizing the soil cracks, notably the specific crack length per surface area lc and the relationship between crack porosity Pc and the gravimetric soil water content w. An example problem shows that infiltration from soil cracks can be an important process affecting the soil water regime of cracked soils. A comparison with the more traditional approach, involving surface infiltration only, indicates important differences in the soil water content distribution during a rainfall∕irrigation event. This extension of the classical approach to include crack infiltration significantly improves the identification and prediction of the soil water regime.     

Benchmarking flexible job-shop scheduling and control systems

Benchmarking is comparing the output of different systems for a given set of input data in order to improve the system’s performance. Faced with the lack of realistic and operational benchmarks that can be used for testing optimization methods and control systems in flexible systems, this paper proposes a benchmark system based on a real production cell. A three-step method is presented: data preparation, experimentation, and reporting. This benchmark allows the evaluation of static optimization performances using traditional operation research tools and the evaluation of control system's robustness faced with unexpected events.     

Energy storage options for wireless sensors powered by aircraft specific thermoelectric energy harvester

This paper describes an approach for efficiently storing the harvested energy from a thermoelectric module for powering autonomous wireless sensor nodes in aircraft health monitoring applications. Thermoelectric devices are the preferred option due to the widespread availability of significant levels of energy from the temperature gradients or variations at the aircraft, such as the cabin, the engine compartment, the fuel tanks or the inner and outer frame of the fuselage. Batteries and supercapacitors are popular choices of storage device, but neither represents the ideal solution, with, supercapacitors possessing low energy densities while batteries have low power density. When using a battery-only solution for storage, the runtime of a typical sensor node is typically reduced by the battery’s relatively high internal impedance and thermal loss. Supercapacitors can overcome some of these problems, but generally do not provide sufficient long-term energy to allow aircraft health monitoring applications to be operated over an extended period. A hybrid energy storage solution can provide both energy and power density to a wireless sensor node simultaneously. Techniques such as acoustic–ultrasonic, acoustic-emission, strain and crack wire sensors require storage approaches that can provide immediate energy on demand, usually in short, high intensity bursts, and that can be sustained over long periods of time, storing up to 40–50 J of energy. This application requirement is considered as a significant constraint when working with battery-only and supercapacitor-only solutions. The hybrid system described here provides an alternate viable solution.     

A Dimension‐reduced Pressure Solver for Liquid Simulations

This work presents a method for efficiently simplifying the pressure projection step in a liquid simulation. We first devise a straightforward dimension reduction technique that dramatically reduces the cost of solving the pressure projection. Next, we introduce a novel change of basis that satisfies free‐surface boundary conditions exactly, regardless of the accuracy of the pressure solve. When combined, these ideas greatly reduce the computational complexity of the pressure solve without compromising free surface boundary conditions at the highest level of detail. Our techniques are easy to parallelize, and they effectively eliminate the computational bottleneck for large liquid simulations.     

Filling of very deep, wide trenches by BenzoCycloButene polymer

A process for deep trench filling by BenzoCycloButene (BCB) polymer is explored. Deep trenches with 100-μm depth and different aspect ratios from 1.4 to 20 have been successfully filled by BCB. Besides, chemical mechanical polishing (CMP) of BCB is studied with the main goals of smoothing surface topography of substrate after BCB filling and removing excess BCB coating which may be necessary in some applications. Removal rate for BCB, V _RR, of about 0.24 μm/min has been achieved for hard cured BCB films using acid slurry. After CMP, the BCB layer showed a roughness of about 1.36 nm (Rq, measured by atomic force microscopy, AFM).     

A Skeptic's Approach to Combining HOL and Maple

We contrast theorem provers and computer algebra systems, pointing out the advantages and disadvantages of each, and suggest a simple way to achieve a synthesis of some of the best features of both. Our method is based on the systematic separation of search for a solution and checking the solution, using a physical connection between systems. We describe the separation of proof search and checking in some detail, relating it to proof planning and to the complexity class NP, and discuss different ways of exploiting a physical link between systems. Finally, the method is illustrated by some concrete examples of computer algebra results proved formally in the HOL theorem prover with the aid of Maple.     

Development of a Temporal Extension to Query Travel Behavior Time Paths Using an Object-Oriented GIS

An essential requirement to better understand activity-based travel behavior (ABTB) at the disaggregate level is the development of a spatio-temporal model able to support queries related to activities of individuals or groups of individuals. This paper describes the development and implementation of a temporal extension to a geographic information system (GIS) object-oriented model for the modeling of the time path and the retrieval of its event chaining. In this approach, time path is formulated as a totally time ordered set composed by activity events and trip events, themselves organized into time ordered sets. As sets, the time path and its components can be searched using their respective indexes. A series of methods were built that implement temporal predicates as an interface to temporally query the database. A set of positional operator methods were also designed that transform temporal topological queries into retrieval functions based on set ordering indices. Taken together, the temporal predicates and the positional operator methods define a temporal query extension that meets the retrieval needs of an ABTB database.     

A survey on the structure of approximation classes

The structure of approximability classes by the introduction of approximation preserving reductions has been one of the main research programmes in theoretical computer science during the last thirty years. This paper surveys the main results achieved in this domain.     

A physical explanation of the gas flow diode effect

Gas flow properties in channels with slightly varying cross section have a dependency on the direction of channel perfusion when the gas is in the slip and transitional flow regimes. In the past, it was observed that the flow rate in converging direction is higher compared to the case where the channel diverges alongside. This gas flow diode effect does neither exist in the continuum regime nor in the free molecular regime, and it has its maximum at the same level of gaseous rarefaction as the well-known Knudsen minimum. However, no comprehensive study on the physics of this diode effect is carried out yet. In order to overcome this knowledge gap, the current paper proceeds our previous works by an appropriate experimental study. Here we can show that the diode effect crucially depends on the proportion of inclined walls to the overall channel inner surface. Also the inclination of the wall itself determines the strength of the diode effect meaning that the diodicity increases with the opening angle. Furthermore, we found indication that the diodicity also depends on the molar mass and the internal structure of the impinging gas molecules. Finally, we propose an explanation of the diode effect that is mainly based on the tangential reflection process of gas molecules colliding with the inclined walls of a tapered channel.