Time-resolved Measurement of Quadrupole Wakefields in Corrugated Structures

Corrugated structures have recently been widely used for manipulating electron beam longitudinal phase space and for producing THz radiation. Here we report on time-resolved measurements of the quadrupole wakefields in planar corrugated structures. It is shown that while the time- dependent quadrupole wakefield produced by a planar corrugated structure causes significant growth in beam transverse emittance, it can be effectively canceled with a second corrugated structure with orthogonal orientation. The strengths of the time-dependent quadrupole wakefields for various corrugated structure gaps are also measured and found to be in good agreement with theories. Our work should forward the applications of corrugated structures in many accelerator based scientific facilities

Bending creep of corrugated fibreboard in cycling relative humidity : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Agricultural Engineering at Massey University

Packaging of fresh fruit for export is a major use for corrugated fibreboard manufactured in New Zealand. However the cold and humid conditions used to preserve fruit quality are particularly detrimental to the strength of corrugated packaging. The main objective of this study was to develop a method to measure the performance of corrugated fibreboard in high and cycling relative humidity environments. This method was then used to compare the performance of three corrugated fibre-boards 1 For commercial reasons these will be referred to as 'CB1', 'CB2'and 'CB3' The creep performance of corrugated fibreboard was measured by subjecting samples to four point bending stress under controlled cyclic relative humidity conditions using a computer controlled testing apparatus. A mathematical model by Urbanik (1995) and an empirical exponential model were reviewed before selecting a three term model developed by Pecht (1985) to describe the deflection of the corrugated board. Cyclic relative humidity accelerated the rate of creep compared to a static high humidity environment. The rate of creep in the machine direction was found to be considerably lower than that in the cross machine direction. It was also found that increasing the peak relative humidity from 80% to 90% RH dramatically changed the deflection response. This provides a solution to conflicting data in the literature on relative humidity cycling effects. Isochronous deflection curves were used to compare the creep performance of the corrugated fibreboard samples in an environment cycling between 50% and 90% RH. Corrugated fibreboard sample CB1 had a slightly lower creep stiffness than corrugated boards CB2 (p=0.0580, n=8) and CB3 (p=0.0398, n=8). However a greater number of tests would be required on a wider range of samples to conclusively determine if there were differences in board performance

Numerical study of an exhaust heat recovery system using corrugated tubes and twisted tape inserts

Thesis (M.S.) University of Alaska Fairbanks, 2014Diesel engine generators are the major power source for small communities in cold regions. Diesel generators waste about 1/3 of their fuel energy in the form of heat through exhaust gas. The primary goal of this work is to capture part of the heat from the exhaust and improve the efficiency of the system. A gas to liquid heat transfer performance of a concentric tube heat exchanger with corrugated tubes and twisted tape inserts is investigated by considering its effects on engine performance and economics. This type of heat exchanger is expected to be inexpensive to install and effective in heat transfer, with minimal effect on exhaust emissions of diesel engines. Most previous research has investigated liquid to liquid heat transfer in corrugated tubes at low Reynolds, not gas to liquid heat transfer. The SolidWorks Flow Simulation computer program was used to perform these studies. The program is first validated by comparing simulation results with renowned correlations and field measurements. Simulations are then conducted for a concentric tube heat exchanger with corrugated tubes and twisted tapes of different configurations to determine the optimal design. The maximum enhancement in the rate of heat transfer was found in an annularly corrugated tube heat exchanger with twisted tape inserts. This exchanger transfers about 235.3% and 67.26 % more heat compared to plain tube and annularly corrugated tube heat exchangers without twisted tapes, respectively. Based on optimal results, for a 120 kWe diesel generator, the application of an annularly corrugated tube heat exchanger with twisted tape inserts can save 2,250 gallons of fuel annually (a cost of approximately $11,330) expected payback of initial cost in one month. In addition, saving heating fuel also reduces CO₂ emissions by 23 metric tons per year

Quantitative Nanofriction Characterization of Corrugated Surfaces by Atomic Force Microscopy

Atomic Force Microscopy (AFM) is a suitable tool to perform tribological characterization of materials down to the nanometer scale. An important aspect in nanofriction measurements of corrugated samples is the local tilt of the surface, which affects the lateral force maps acquired with the AFM. This is one of the most important problems of state-of-the-art nanotribology, making difficult a reliable and quantitative characterization of real corrugated surfaces. A correction of topographic spurious contributions to lateral force maps is thus needed for corrugated samples. In this paper we present a general approach to the topographic correction of AFM lateral force maps and we apply it in the case of multi-asperity adhesive contact. We describe a complete protocol for the quantitative characterization of the frictional properties of corrugated systems in the presence of surface adhesion using the AFM.Comment: 33 pages, 9 figures, RevTex 4, submitted to Journal of Applied Physic

Design and Fabrication of cross corrugated recuperator fins for a micro gas turbine

The National Aerospace Laboratories, Bangalore is involved in the development of a 10kW micro gas turbine (MGT). A recuperator is mandatory for an MGT to boost the thermal efficiency of the unit. This paper describes in detail the fabrication process of efficient corrugated fins for deploying in the recuperator of an MGT. The use of corrugated fins in the recuperator of the MGT gives higher effectiveness compared to conventional flat fins. The paper, in detail, describes the various materials used and the heat treatment process used for manufacturing the forming and shearing die sets. All manufacturing accuracy requirements were achieved to get the required fin geometry. The formed corrugated fins were qualified through a series of tests and large number fins were formed for use in the annular recuperator of the Micro Gas Turbine

Intensity Distribution of Modes in Surface Corrugated Waveguides

Exact calculations of transmission and reflection coefficients in surface randomly corrugated optical waveguides are presented. As the length of the corrugated part of the waveguide increases, there is a strong preference to forward coupling through the lowest mode. An oscillating behavior of the enhanced backscattering as a function of the wavelength is predicted. Although the transport is strongly non isotropic, the analysis of the probability distributions of the transmitted waves confirms in this configuration distributions predicted by Random Matrix Theory for volume disorder

Lateral projection as a possible explanation of the nontrivial boundary dependence of the Casimir force

We find the lateral projection of the Casimir force for a configuration of a sphere above a corrugated plate. This force tends to change the sphere position in the direction of a nearest corrugation maximum. The probability distribution describing different positions of a sphere above a corrugated plate is suggested which is fitted well with experimental data demonstrating the nontrivial boundary dependence of the Casimir force.Comment: 5 pages, 1 figur

Spreading of a Macroscopic Lattice Gas

We present a simple mechanical model for dynamic wetting phenomena. Metallic balls spread along a periodically corrugated surface simulating molecules of liquid advancing along a solid substrate. A vertical stack of balls mimics a liquid droplet. Stochastic motion of the balls, driven by mechanical vibration of the corrugated surface, induces diffusional motion. Simple theoretical estimates are introduced and agree with the results of the analog experiments, with numerical simulation, and with experimental data for microscopic spreading dynamics.Comment: 19 pages, LaTeX, 9 Postscript figures, to be published in Phy. Rev. E (September,1966

Flexible thermal apparatus for mounting of thermoelectric cooler

A flexible heat transfer apparatus used to flexibly connect and thermally couple a thermoelectric cooler to an object to be cooled is disclosed. The flexible heat transfer apparatus consists of a pair of flexible corrugated sheets made from high thermal conductivity materials such as copper, aluminum, gold, or silver. The ridges of the corrugated sheets are oriented perpendicular to one another and bonded sandwich-fashion between three plates to define an upper section and a lower section. The upper section provides X flexure, the lower section provides Y flexure, and both sections together provide Z flexure