Browsing by Author "Peng, Peng"
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Item Biosynthesis of PHB-‐b-‐PHV block-‐copolymer from CO2, O2, H2 by using Ralstonia eutropha(2013-04-20) Peng, PengItem Modeling of Concentrated High Intensity Electric Field (CHIEF) and Its Comparison with Other Non-thermal Liquid Food Pasteurization Technologies(2015-12) Peng, PengNon-thermal preservations of food have received rising attention due to the increase concern of environmental sustainability and the demand of safer food with improved nutritional functionalities. High pressure and electric field treatment are two non-thermal food treatment strategies that have been widely studied. Some representatives of non-thermal technologies that utilize high-pressure and electric field to pasteurize food products include High hydrostatic pressure (HHP), high-pressure homogenization (HPH), and pulsed electric field (PEF). These non-thermal technologies, together with concentrated high intensity electric field (CHIEF) are studied and compared in this thesis research. This study used finite element (FEM) and computational fluid dynamics (CFD) methods to model and simulate the fluid flow, electric field distribution and temperature rise in CHIEF reactor. The simulation was confirmed to be valid by comparing it with experimental results. The model built in this study showed that the performance of CHIEF system was influenced by a set of intrinsic and extrinsic parameters. This model could be used to control and set variables in further optimization of the CHIEF system. Each of the non-thermal technologies discussed in this study has its advantages and unique field of use. HHP, dynamic high-pressure treatment and PEF are relatively mature technologies, while CHIEF system is an innovative and promising non-thermal method that can potentially be used as alternative to PEF.Item Novel MEMS tactile sensors for In-Vivo tissue characterization measurements.(2011-12) Peng, PengThis dissertation focuses on developing a tactile sensor system for the measurement of contact force and elasticity. By using the developed sensors, the elasticity of various objects (e.g. tissue) can be measured by simply touching the targeted object with the sensor. In its most basic form, each developed sensor consists of a pair of contact elements that have different values of stiffness. The relative deformations of the two sensing components during contact can be used to calculate the elasticity parameters of Young's modulus or shear modulus. Analytical formulations that validate the proposed sensing technique are presented followed by sensor fabrication and experimental evaluation. Several prototypes of tactile sensors are fabricated through various MEMS processes. The first generation of prototype sensor is built with a surface micromachining process. Silicon nitride is selected as the structural material. With this fabrication process, the sensor can be fabricated down to a size of 1mm x 1mm x 500µm. A second generation of prototypes is developed through a polymer MEMS process. This type of sensor has a favorable flexible structure, which enables the sensor to be integrated on end-effectors for robotic or biomedical applications. Further, the sensing principle can be extended to measure shear force and shear elasticity. This extended ability with the polymer sensor is obtained by a design that includes a quad-electrode structure in each sensing cell. Finally, an easily fabricated tactile sensor of larger size is developed and attached on a touch probe. This prototype of sensor can provide reliable elasticity measurement in a handheld operating mode. Along with the advancement of tactile sensors, an estimation algorithm for the hand-held device, which employs a recursive least square method with adaptive forgetting factors, has also been developed. Experimental results show that this sensor can differentiate between a variety of rubber specimens. Further, the sensors have been characterized by fresh porcine tissue specimens and show the potential to provide reliable in-vivo measurement of tissue elasticity. The dissertation starts with introducing the background and motivation for this effort. This is followed by the conceptual design and mathematical models of the sensing principle. Different generations of prototype sensors are then discussed in the following chapters. Characterization results with tissue specimens obtained with these sensors will then be presented. Finally, the dissertation concludes with a discussion and summary of the work.Item Sustainable atmospheric ammonia synthesis and nitrogen fixation using non-thermal plasma (NTP)(2018-10) Peng, PengAmmonia has recently been intensively studied as a clean, sustainable fuel source and an efficient energy storage medium due to its effectiveness as a hydrogen carrier molecule. However, the current method of ammonia synthesis, known as the Haber-Bosch process, requires a large fossil fuel input, high temperatures and pressures, as well as a significant capital investment. These volatile conditions and high operating costs prevent decentralized and small-scale ammonia production at the level of small farms and local communities. Non-thermal plasma technology represents a promising alternative method of clean ammonia synthesis, as it circumvents the volatile operating conditions, fossil fuel use, and high capital costs of the Haber-Bosch process. In this thesis research, this emerging technology was realized at the bench scale and was optimized by various efforts, including catalyst improvement, system development, and absorption enhancement. For the catalyst improvement, a multi-functional catalyst was introduced and deposited onto various supporting materials. For absorption enhancement, MgCl2 was implemented for the absorption enhancement, taking advantage of its capability of forming Mg3N2 and Mg(NH3)6Cl2 during the process. Meanwhile, the pulse density modulation (PDM) was introduced to improve the performance of system. The series of efforts improved the energy efficiency of the system by approximately one fold compared with previous studies, and achieved the highest value of 20 g/kwh. Furthermore, an innovative plasma gas-liquid ammonia synthesis approach was explored. It was found that this approach could produce other nitrogen compounds (nitrate and nitrite acids) while generating ammonium, which could potentially add value to the products of the plasma-assisted ammonia synthesis process. Based on the results, the challenges and future opportunities of the plasma-assisted ammonia synthesis approach were discussed. Lastly, recommendations were made on how this technology could be beneficial to the ammonia industry, through its potential to promote localized and environmentally friendly energy production and storage.