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排序方式: 共有116条查询结果,搜索用时 46 毫秒
1.
Seong-Hwan Cho Afshin Karshenas Akhtarhusein A. Tayebali Murthy N. Guddati 《International Journal of Pavement Engineering》2017,18(12):1098-1110
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. 相似文献
2.
Jihoon Yeo Jejun Ryu Bong-Kee Lee Euihyeon Byeon Tai Hun Kwon Dong Sung Kim 《Microsystem Technologies》2010,16(8-9):1425-1430
Various types of polymer surfaces with a nanolens array, which has an entrant shape with a low aspect ratio, were fabricated and the wettability of the fabricated surfaces was evaluated in both theoretical and experimental ways. The nanolens array was replicated on three different polymer surfaces of polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), and polymethylmethacrylate (PMMA) by means of replica molding and hot embossing with a nanodimpled aluminum mold that was manufactured by a chemical oxidation process. From the theoretical and experimental evaluations of the wettability it was found that the measured contact angles were very similar with the theoretically estimated ones and also the hydrophilicity and hydrophobicity of the hydrophilic PMMA and hydrophobic PDMS, respectively, surfaces were reinforced by the nanolens array within the Wenzel wetting state. 相似文献
3.
Computational Analysis of Oxide Ion Conduction in Orthorhombic Perovskite Structured La0.9A0.1InO2.95 (A = Ca,Sr and Ba)
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Mi‐Young Yoon Kuk‐Jin Hwang Dae‐Seop Byeon Joosun Kim Hae‐Jin Hwang Seong‐Min Jeong 《Journal of the American Ceramic Society》2015,98(2):515-519
Oxide ion conduction in orthorhombic perovskite structured oxides, La0.9A0.1InO2.95 (A = Ca, Sr and Ba) is analyzed using molecular dynamics simulation. Factors influencing oxide ion conductivity of the compositions considered are analyzed using radial distribution function, bond energies between dopant and oxide ions, and the diffusion path. It is known that perovskite oxides with smaller ion size mismatch between host and dopant ions have higher electrical conductivities. However, exceptions exist, such as a La0.9A0.1InO2.95 (A = Ca, Sr and Ba) system, where high electrical conductivities occur with large ion size mismatches. Based on this study, a dopant with smaller ion than host ion results in the formation of strong ionic bonds with oxide ions, suggesting that the A‐site dopant should be larger than the host ion for forming weaker O–A bonds. Consequently, the trade‐off between ion size mismatch and O–A bond needs to be considered for enhancing oxide ion conductivity of perovskite oxides. 相似文献
4.
K. Park Y. Kim J. Byeon K. Sung C. Yeom S. Rhee 《Journal of Mechanical Science and Technology》2007,21(10):1720-1725
A control rod device (CRD) nozzle attaches to the hemispherical surface of a reactor head with J-groove welding. Primary water
stress corrosion cracking (PWSCC) causes degradation in these welds, which requires that these defect areas be repaired. To
perform this repair welding automatically on a complicated weld groove shape, an auto-welding system was developed incorporating
a laser vision sensor that measures the 3-dimensional (3D) shape of the groove and a weld-path creation program that calculates
the weld-path parameters. Welding trials with a J-groove workpiece were performed to establish a basis for developing this
auto-welding system. Because the reactor head is placed on a lay down support, the outer-most region of the CRD nozzle has
restricted access. Due to this tight space, several parameters of the design, such as size, weight and movement of the auto-welding
system, had to be carefully considered. The cross section of the J-groove weld is basically an oval shape where the included
angle of the J-groove ranges from 0 to 57 degrees. To measure the complex shape, we used double lasers coupled to a single
charge coupled device (CCD) camera. We then developed a program to generate the weld-path parameters using the measured 3D
shape as a basis. The program has the ability to determine the first and final welding positions and to calculate all weld-path
parameters. An optimized image-processing algorithm was applied to resolve noise interference and diffused reflection of the
joint surfaces. The auto-welding system is composed of a 4-axis manipulator, gas tungsten arc welding (GTAW) power supply,
an optimized designed and manufactured GTAW torch and a 3D laser vision sensor. Through welding trials with 0 and 38-degree
included-angle workpieces with both J-groove and U-groove weld, the performance of this auto-welding system was qualified
for field application. 相似文献
5.
Hee Jeong Yoo Kyung Kim In Hyang Kim Seong-Hwan Rho Jong-Eun Park Ki Young Lee Soon Ae Kim Byung Yoon Choi Namshin Kim 《International journal of molecular sciences》2015,16(3):5697-5713
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. 相似文献
6.
Jae Hong Park Ki Young Yoon Kwang Chul Noh Jeong Hoon Byeon Jungho Hwang 《Journal of aerosol science》2010,41(10):935-943
This study evaluated the charging characteristics of a carbon fiber ionizer for PM2.5 and carried out particle capture laboratory tests after an ionizer was installed upstream of the media of an electret cabin air filter. When the ion concentration per particle (Ni) of the carbon fiber charger was 106 ions/cm3, the average charge numbers for each particle were 1.54, 0.88, and 0.49 at 0.6, 1.2, and 1.8 m/s of face velocity, respectively (the particle charging times, τ, were 167, 83, and 56 ms, respectively). For these face velocities, the PM2.5 removal efficiencies of the filter media were 69.3%, 65.2% and 62.2%, respectively, but increased to 80.4%, 71.2% and 65.5%, respectively, when the ionizer was turned on. The carbon fiber ionizer was then installed in front of an electret cabin filter in the air conditioning system of an automobile, after which field tests were performed at a roadside area. For the same Niτ used in the lab-scale tests, the effects of the carbon fiber ionizer on increasing PM2.5 %Reduction were mild as 9.4%, 4.0%, and 2.8% when the flow rates were at the second, fourth, and sixth levels, respectively (the face velocities were 0.6, 1.2, and 1.8 m/s, respectively). The PM2.5 %Reduction can be substantially increased by 20–21%, for a higher value of Niτ (=1.0×108 ions s/cm3), which is realized by increasing the power consumption of the carbon fiber ionizer. 相似文献
7.
8.
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. 相似文献
9.
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. 相似文献
10.