Browsing by Author "Yang, Guang"
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Item Fabrication, Analysis, Simulation, and Application of the Nanohole Array Sensor(2020-12) Yang, Guang; Bao, Jiming; Ruchhoeft, Paul; Wu, Tianfu; Shan, Xiaonan; Willson, Richard C.Nanohole arrays in metal films have many amazing optical properties based on the surface plasmon resonance, which makes it popular in the sensing field. Usually, the change of the refractive index on the metal surface of nanohole arrays, caused by the binding of an analyte, can be reflected on the peak shift or intensity change of the transmission or reflection spectra. As sensing components, nanohole arrays provide many important advantages, including high reproducibility, miniaturization, the ability to integrate with other techniques, the capability of high-throughput analysis, and so on. Nanohole array sensing is quite compatible with the lab-on-chip technology and meets the tendency of point-of-care diagnostics that have been dramatically developed in recent years. Point-of-care diagnostics require low cost and portable devices with reliable and robust sensitivity for special analytes such as viruses. With the help of the nanohole arrays, the individual molecule of nanoscale size can be directly and precisely located. In this work, we have fabricated nanohole arrays with 150 nm diameter and 2 μm period, which have a larger period than those reported by other papers. Silica-shelled gold nanospheres with 70 nm core diameter and 20 nm shell thickness are used to block the nanoholes; and darkfield imaging system is used to obtain the images by the CCD and spectra by the spectrometer. The images and spectra of the nanoholes blocked by the individual nanospheres are analyzed and compared with those of the nanoholes before blocking. Results show a significant reduction of the light intensity in the blue and green light regions but an unusual enhancement in the red light region. FDTD simulations are also conducted to not only confirm the experimental results but also provide the information about the position and the size of the nanospheres inside the nanoholes, and the wavelength of the exciting light. Furthermore, we demonstrate that our nanohole array samples can be integrated into a home-made inexpensive darkfield microscope and analyzed by a smartphone with an application developed by ourselves, which make it viable for future POC diagnostics.Item Material Laws of Frp Strengthened Reinforced Concrete under Uniaxial Tension and Biaxial Tension-Compression Stress Fields(2015-08) Yang, Guang; Belarbi, Abdeldjelil; Ayoub, Ashraf S.; Mo, Yi-Lung; Gencturk, Bora E.; Gao, LuWell established analytical models and design guidelines are already available for analyzing and designing FRP strengthened structures under flexural and axial-confinement actions. However, the understanding of the behavior of such members under in-plane stress field remains a subject of on-going discussion among several researchers and practitioners. Several analytical models have been proposed to predict the gain and upgrade of shear capacity due to FRP strengthening, among which, most models resulted in large discrepancies and produced large scatter when compared to experimental database. This is due to the lack of accurate constitutive models for strengthened reinforced concrete (RC) with FRP (FRP-RC) members. An efficient method to study the overall response of an RC member is to identify the characteristic behavior and the contribution of each material constituting the structure, the behavior of that specific element can be predicted by taking into account the inherent characteristics and material laws of the constituents that leads to understanding the global shear response of the structure. As a first step of developing a shear model of FRP-RC elements, constitutive laws of each material component, namely concrete, steel reinforcement, and FRP sheets were studied in this research project through experimental and analytical investigations. Thirteen full-scale prismatic specimens and six full-scale panels were tested using the Universal Panel Tester (UPT) to study the stress-strain relationships of concrete, steel and FRP in tension as well as concrete in compression and the Poisson effect resulting from the biaxial loading. The results indicate that compared to the un-strengthened RC element, the presence of the externally bonded FRP material typically alters the main characteristics of the stress-strain relationships for each components in FRP-RC element. These newly developed material laws will be used to further develop a model to predict the behavior of FRP strengthened RC elements subjected to shear and torsion. The results from both experimental and analytical study in this research project will provide a promising contribution to the prediction of the behavior of FRP-RC members under shear that will ultimately improve the accuracy of the available design guidelines.