A mechanistic approach to evaluate the potential of the debonding distress in asphalt pavements

The debonding distress in asphalt pavement structures is a critical problem that affects the performance of asphalt concrete pavements. It occurs at the layer interface due to the poor bond quality between adjacent asphalt concrete layers and/or when stresses at the layer interface exceed the strengths of the material at the interface. The debonding of the adjacent layers, especially the top surface layer of an asphalt pavement, is a contributing factor to the premature cracking of pavements. Hence, the debonding distress can lead to a reduction in the life of the pavement. This paper presents an analytical and experimental framework to evaluate the potential for debonding at the layer interface of asphalt concrete pavements. Computational analysis was performed to determine the critical stress and strain states in layered asphalt pavements under moving vehicle loads using the Layered ViscoElastic pavement analysis for Critical Distresses (LVECD) computer program developed at North Carolina State University. This computational analysis enables a greater understanding of the critical stress that is involved in debonding and the ways that such stress is affected by pavement design parameters and environmental conditions. In addition, a prediction model was developed that can determine the shear bond strength at the interface of asphalt concrete layers with different tack coat materials at various temperatures, loading rates and normal confining stresses. The systematic and mechanistic framework developed in this study employs the maximum shear ratio concept as a shear failure criterion and provides a tool to evaluate the effects of various loading, environmental and pavement factors on the debonding potential of asphalt pavements. The overall advantages of the mechanistic framework and approach using the LVECD analysis tool will help lead to better understanding of the debonding mechanism, proper selection of the tack coats, and economic benefit in highway pavement maintenance and rehabilitation costs.     

Surface‐treatment effects of a sapphire substrate by He+‐, Ar+‐, and Xe+‐ion implantations for GaN epitaxial layers

Abstract— The structural, electrical, and optical properties of GaN epilayers grown on various ion‐implanted sapphire(0001) substrates by MOCVD were investigated. GaN or AlN buffer layers and pre‐treatment were indispensably introduced before GaN‐epilayer growth. The ion‐implanted substrate's surface had decreased internal free energies during the growth of the ion‐implanted sapphire(0001) substrates. The crystal and optical properties of the GaN epilayers grown in ion‐implanted sapphire(0001) substrates were improved. Also, an excessively roughened and modified surface caused by ions degraded the GaN epilayers. Not only the ionic radius but also the chemical species of implanted sapphire(0001) substrates improved the properties of the GaN epilayers grown by MOCVD. It is obvious that the ion‐implanted pre‐treatment of sapphire(0001) substrates can be an alternative pre‐treatment procedure for GaN deposition and has the potential to improve the properties of the GaN epilayers on sapphire(0001) substrates.     

Whole Exome Sequencing for a Patient with Rubinstein-Taybi Syndrome Reveals de Novo Variants besides an Overt CREBBP Mutation

Rubinstein-Taybi syndrome (RSTS) is a rare condition with a prevalence of 1 in 125,000–720,000 births and characterized by clinical features that include facial, dental, and limb dysmorphology and growth retardation. Most cases of RSTS occur sporadically and are caused by de novo mutations. Cytogenetic or molecular abnormalities are detected in only 55% of RSTS cases. Previous genetic studies have yielded inconsistent results due to the variety of methods used for genetic analysis. The purpose of this study was to use whole exome sequencing (WES) to evaluate the genetic causes of RSTS in a young girl presenting with an Autism phenotype. We used the Autism diagnostic observation schedule (ADOS) and Autism diagnostic interview revised (ADI-R) to confirm her diagnosis of Autism. In addition, various questionnaires were used to evaluate other psychiatric features. We used WES to analyze the DNA sequences of the patient and her parents and to search for de novo variants. The patient showed all the typical features of Autism, WES revealed a de novo frameshift mutation in CREBBP and de novo sequence variants in TNC and IGFALS genes. Mutations in the CREBBP gene have been extensively reported in RSTS patients, while potential missense mutations in TNC and IGFALS genes have not previously been associated with RSTS. The TNC and IGFALS genes are involved in central nervous system development and growth. It is possible for patients with RSTS to have additional de novo variants that could account for previously unexplained phenotypes.     

Material characterization of glass/polypropylene composite bone plates according to the forming condition and performance evaluation under a simulated human body environment

The mechanical performance of a composite bone plate made of a glass/polypropylene (Twintex) for the biologic fixation of diaphyseal long bone fractures was investigated in this paper. To find out the most appropriate forming condition of the composite bone plate, tensile and bending tests and microscopic observations of the specimens fabricated by various forming conditions were carried out. The measured mechanical properties, the morphology of the material cross-section, the fibre volume fractions, etc., were mutually correlated, and the results were used for determining the most appropriate forming condition. An environmental test of composite bone plates under a simulated human body also was carried out using the fabricated composite bone plate. The material degradation according to the water-exposure time was quantitatively investigated by a four-point bending test. Finally, the serviceability of the proposed composite bone plate was verified by fatigue tests.     

On-line parameter estimation and optimal control strategy of a double-skin system

To reduce the potential problems of window systems such as undesired heat gain (loss), glare, and thermal discomfort due to asymmetric radiation, double-skin systems have been introduced. The current problem with double-skin systems is that their operation requires an adequate simulation model to realize optimal control of the system. The estimation of the parameters in the lumped model developed in a previous study [1] was based on ‘laborious’ off-line calibration procedure. This effort has to be repeated for every different size, different type, or differently oriented façade system. Different façade components are characterized by different thermal and optical properties of glazing and blind slats, system configurations [height, width, depth], other simulation variables, etc. For each type the parameter set in the lumped model has to be established through a calibration procedure. In view of micro climate variations even same type systems within one façade but on different heights may have to be calibrated separately. In order to avoid the laborious off-line calibration of every single façade component, an on-line self-calibrating procedure is developed in this paper. The true advantage of the technique is that every component can be pre-wired and ready to be hooked to the calibration set-up when it is brought to the site. The paper will explain the simulation model, selection of calibration parameters, and the process of on-line self-calibration, model validation and application of optimal control. It is shown that the on-line self-calibrating simulation model far outperforms the off-line calibrated model. Consequently, the plug and play self-calibration technique will render the current in-situ ‘laborious’ off-line calibration process obsolete.     

Optimal design of a variable-twist proprotor incorporating shape memory alloy hybrid composites

The tiltrotor blades, or proprotor, act as a rotor in the helicopter mode and a propeller in the airplane mode. The helicopter mode generally requires relatively a low built-in twist angle, whereas in the airplane mode, a high built-in twist is desired. Meeting these rather conflicting requirements make the tiltrotor design a challenging task. This paper explores an optimal design of a variable-twist proprotor that changes the built-in twist in an adaptive manner by using the shape memory alloy hybrid composite (SMAHC). The optimum design problem attempts to find the cross-section internal layout that maximizes the twist actuation of the variable-twist proprotor while satisfying a series of design constraints. An optimum design framework is constructed in the current work by combining various analysis and design tools, such as an active composite cross-sectional analysis, a nonlinear flexible multibody dynamics analysis, a 3-D strain analysis, and a gradient-based optimizer. The MATLAB is used to integrate and synthesize the individual tools. A static tip twist is chosen as an objective function that should be maximized for the best performance. The optimum results exhibit that the twist actuation of the variable-twist proprotor can be maximized while satisfying all the prescribed design constraints.     

Full wafer scale nanoimprint lithography for GaN-based light-emitting diodes

A UV-imprinting process for a full wafer was developed to enhance the light extraction of GaN-based green light-emitting diodes (LEDs). A polyvinyl chloride flexible stamp was used in the imprinting process to compensate for the poor flatness of the LED wafer. Two-dimensional photonic crystal patterns with pitches ranging from 600 to 900 nm were formed on the p-GaN top cladding layer of a 2 inch diameter wafer using nanoimprint and reactive ion etching processes. As a result, the optical output power of the patterned LED device was increased by up to 44% at a driving current of 20 mA by suppressing the total internal reflection and enhancing the irregular scattering of photons at the patterned p-GaN surface.     

Physicochemical and antioxidative properties of selected barnyard millet (Echinochloa utilis) species in Korea

Food Science and Biotechnology - The purpose of this study was to analyze and report the nutritional and physicochemical properties of 13 barnyard millet varieties (Echinochloa spp.) in Korea....     

Adaptive VM Management with Two Phase Power Consumption Cost Models in Cloud Datacenter

As cloud computing models have evolved from clusters to large-scale data centers, reducing the energy consumption, which is a large part of the overall operating expense of data centers, has received much attention lately. From a cluster-level viewpoint, the most popular method for an energy efficient cloud is Dynamic Right Sizing (DRS), which turns off idle servers that do not have any virtual resources running. To maximize the energy efficiency with DRS, one of the primary adaptive resource management strategies is a Virtual Machine (VM) migration which consolidates VM instances into as few servers as possible. In this paper, we propose a Two Phase based Adaptive Resource Management (TP-ARM) scheme that migrates VM instances from under-utilized servers that are supposed to be turned off to sustainable ones based on their monitored resource utilizations in real time. In addition, we designed a Self-Adjusting Workload Prediction (SAWP) method to improve the forecasting accuracy of resource utilization even under irregular demand patterns. From the experimental results using real cloud servers, we show that our proposed schemes provide the superior performance of energy consumption, resource utilization and job completion time over existing resource allocation schemes.