Impact Simulation and Analysis of Sandwich Structures

Impact damage on aircraft and spacecraft can be a severe problem that may cause catastrophic results. Several aerospace structures have been used to resist or absorb energy in the occasion of impact. Among these, a sandwich structure has advantages with high stiffness, strength to weight ratio, and its relatively cheap cost. However, finding the impact structural response of a sandwich structure, by performing experiments, has disadvantages. First, impact is a complex problem with a multi-parameter nature and many factors should be considered. Secondly, it is a destructive test and the test subject may be damaged during the test. On the other hand, computer simulation based on a finite element code has advantages considering both the cost factor and technical issues associated with real tests. The primary emphasis of this research is to establish the correlations between impact parameters and damage modes on sandwich structures using computer simulations. A finite element program, LS-DYNA, is used to perform impact simulations and to analyze results. A number of experiments are conducted to compare practical results with simulations

Korean Domestic Third Party Logistics Providers: Research for a Global Market

The objective of this thesis is to contribute to the globalization of Korean domestic third party logistics companies. This is accomplished through a benchmarking model for globalization based on a comparative analysis of domestic and global third party logistics provider (3PLs) companies. The research performed a SWOT analysis to identify the capabilities required by Korean domestic 3PLs to become global 3PLs. The research investigated the following areas: 1) global service, 2) infrastructure, 3) supply chain management (SCM) services, and 4) information technology (promptness, visibility). This was accomplished by an extensive literature review, case analysis of logistics companies, and telephone interviews with individuals in charge of logistics. Four areas for improvement were identified: 1) Construction of SCM for one-stop service, 2) Utilization of the advanced IT systems for e-SCM, and consolidating communication network, 3) Expansion of logistics infra-structure by analyzing each region of the world for return on investment opportunities and competition, 4) Enlargement of scale in which Korean 3PLs must enlarge their scale of operations as soon as possible by strategic methods such as mergers and acquisitions (M&A) with local companies. There is potential growth for Korean 3PLs if they strive to enhance competitiveness as noted above and have government supports. These improvement areas provide a foundation for global competitiveness

Investor Disagreement on Corporate Spin-offs News

This study analyzes temporal trading volume surge associated with a firm\u27s public announcement of its spinoff divesture. Combining Miller\u27s (1977) static difference-of-opinion (DO) model with Banerjee and Kremer\u27s (2010) dynamic DO model, this study investigates the effects of investors\u27 differential interpretations of spinoff announcements on price changes for 221 corporate spinoffs in the U.S from 1964 to 2005. We measure the ex-ante level of DO as the degree of DO about a firm\u27s value in a typical trading day prior to a spinoff announcement, and the event level of DO as the changed level of DO triggered by investors\u27 differential interpretations of its spinoff announcement. We find that spinoff announcements spark a sudden and sharp increase in the level of DO. This increase is positively correlated with abnormal returns generated by the announcements. Consistent with the notion of investors\u27 limited attention, the ex-ante level of DO is negatively related to disagreement shock. Further, defining the ex-ante level of DO as disagreement factor, we validate its statistical significance after controlling for other known determinants for these returns in the entire study period. For the first study period between 1964 and 1991, we confirm the results of prior studies on the effects of a change in industrial focus and the relative size of a spun-off on the abnormal returns. For the second study period from 1992 to 2005, all these factors are found insignificant. Only variable that consistently accounts for the cross-sectional variation in the abnormal returns is disagreement factor

A novel approach to the classification of ultrasonic NDE signals

Ultrasonic inspection methods are widely used for detecting flaws in materials. The signal analysis step plays a crucial part in the data interpretation process. A number of signal processing methods have been proposed to classify ultrasonic flaw signals. One of the more popular methods involves the extraction of an appropriate set of features followed by the use of a neural network for the classification of the signals in the feature space. This thesis describes an alternative approach which uses the least mean square (LMS) method to determine the coordinates of the ultrasonic probe followed by the use of a synthetic aperture focusing technique (SAFT). The method is employed for classifying nondestructive evaluation (NDE) signals from steam generator tubes in a nuclear power plant. The movement of the probe inside the tube is modeled using spherical and cylindrical coordinate systems. The mean square error (MSE) between the model prediction and the experimentally measured distance between the probe and the tube wall is minimized using the steepest descent algorithm to obtain estimates of the probe canting angle and its location. The information is used in conjunction with the synthetic aperture focusing technique to estimate the location of the ultrasonic reflector. An alternate approach employing a model based deconvolution has been described to facilitate comparison of results. The method uses the space alternating generalized expectation maximization (SAGE) algorithm in conjunction with the Newton-Raphson method to estimate the time of flight. Results using these schemes for the classification of ultrasonic signals from cracks and deposits within steam generator tubes are presented

Helical Dielectric Elastomer Actuator

A helical dielectric elastomer actuator (HDEA) can include a first dielectric region comprising an elastomer defining a helix. In an example, a dielectric material can be deposited, and a compliant conductive material can be deposited, such as using an additive manufacturing approach, to provide an HDEA. In an example where the HDEA has multiple mechanical degrees of freedom, at least two compliant conductive regions can be located on a first surface of the first dielectric region and at least one compliant conductive region can be located on an opposite second surface of the first dielectric region. For such an example, the at least two compliant conductive regions can be arranged to be ener­gized with respect to the at least one compliant conductive region in a manner providing at least two mechanical degrees of freedom for operation of the HDEA

Cloaking due to anomalous localized resonance in plasmonic structures of confocal ellipses

If a core of dielectric material is coated by a plasmonic structure of negative dielectric material with non-zero loss parameter, then anomalous localized resonance may occur as the loss parameter tends to zero and the source outside the structure can be cloaked. It has been proved that the cloaking due to anomalous localized resonance (CALR) takes place for structures of concentric disks and the critical radius inside which the sources are cloaked has been computed. In this paper, it is proved that CALR takes place for structures of confocal ellipses and the critical elliptic radii are computed. The method of this paper uses the spectral analysis of the Neumann-Poincar\'e type operator associated with two interfaces (the boundaries of the core and the shell)

Estimation of Flood Discharge According to Variability of Rai Nfall Distribution Using Gis-Based Method in a Basin

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Perseverance in Hebrews

Please read the abstract in the section 00front of this documentThesis (PhD)--University of Pretoria, 2009.New Testament Studiesunrestricte

Highly Stretchable, Room Temperature Self-Healing Polymer via Crosslinking and Intermolecular Network for Applications in Aerospace and Robotics

Keywords: Polymer, Self-Healing, Room temperature, Flexible, Electronics Self-healing materials have gained significant attention due to their efficient ability to intrinsically heal without the use of external human intervention. Several mechanisms for repair within self-healing materials can be found, such as catalyst containing micro beads, healing from an external energy source such as ultraviolet light or heat, and supramolecular network bonding. However, many of these techniques remain challenged due to their lack of mechanical strength, faulty energy diffusion, and poor self-healing ability within limited time. In the given project, a material with efficient self-healing ability at room temperature and high mechanical strength is exemplified. The self-healing material utilizes a soft poly(oxy-1,4-butanediyl) (PTMEG) backbone that limits monomer clumping and microphase separation. Furthermore, the dual hydrogen bonding and high crosslinking monomer allows for excessive mechanical strength, while the weak single hydrogen bonding subunit creates mechanical strain diffusion by forming a diverse supramolecular network of temporary intermolecular bonds. Varying ratios of TDI and IP are tested in conjunction with 1000MW and 2900MW PTMEG backbones to exemplify varying degrees of self-healing and mechanically strength abilities for materials with applications in dielectric applicators, biosensing, and various self-healing electronics. The characterization of the polymer was accomplished using Fourier-transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). The self-healing property was characterized by producing small slices in the material in both an aqueous and air environment at room temperature

Development of a Flexible, Room Temperature Self-Healing Polymer via Reversible Hydrogen Bond Network

Self-healing polymers are attractive materials with the ability to intrinsically or extrinsically heal without the use of external human intervention. Several mechanisms for repair within self-healing materials can be found, such as catalyst containing micro beads, healing from an external energy source such as ultraviolet light or heat, and supramolecular network bonding. However, many of these techniques remain challenged due to their lack of mechanical strength, faulty energy diffusion, and poor self-healing ability within limited time. In the given project, a material with efficient self-healing ability at room temperature and high mechanical strength is exemplified. The self-healing material utilizes a soft poly(oxy-1,4-butanediyl) (PTMEG) backbone that limits monomer clumping and microphase separation. Furthermore, the dual hydrogen bonding and high crosslinking monomer allows for excessive mechanical strength, while the weak single hydrogen bonding subunit creates mechanical strain diffusion by forming a diverse supramolecular network of temporary intermolecular bonds. Varying ratios of TDI and IP are tested in conjunction with 1000MW and 2900MW PTMEG backbones to exemplify varying degrees of self-healing and mechanically strength abilities for materials with applications in dielectric actuators, biosensing, and various self-healing electronics. The self-healing property was characterized by producing small slices in the material in both an aqueous and air environment at room temperature. The characterization of the polymer was accomplished using Fourier-transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC)