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Mechanical and Aerospace Engineering Dissertations - Archive

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Articles 181 - 210 of 266

Full-Text Articles in Mechanical Engineering

Accurate Three-Dimensional Characterization Of The Nonlinear Material Constitutive Properties For Laminated Composite Materials, Julia Elaine Cline Jan 2015

Accurate Three-Dimensional Characterization Of The Nonlinear Material Constitutive Properties For Laminated Composite Materials, Julia Elaine Cline

Mechanical and Aerospace Engineering Dissertations - Archive

Accurate and efficient full three-dimensional characterization of mechanical properties of composite materials, including stress-strain curves and strength characteristics, is essential for understanding complex deformation and failure mechanisms of composites and optimizing material qualification efforts. Non-contact full-field deformation measurement techniques such as digital image correlation (DIC) allowing for assessment of all surface strain components on the entire specimen surface, enable simpler experimental setups and material specimen designs for more efficient and accurate material characterization. This work presents a new method enabling simultaneous assessment of the shear stress-strain curves in all three principal material planes. The method uses a small rectangular plate …


Novel Neuro-Dynamic Methods For Solving Robotic Planning And Control Problems, Ghassan M. Atmeh Jan 2015

Novel Neuro-Dynamic Methods For Solving Robotic Planning And Control Problems, Ghassan M. Atmeh

Mechanical and Aerospace Engineering Dissertations - Archive

Robotic systems are growing more complex to cater to the tasks they are required to solve. Irrespective of these tasks the problem of planning and control must be solved for all robotic systems. In this dissertation a general description of that problem is given along with the issues that it faces. This problem concerns planning a trajectory in the operational space of the robot, i.e. the space in which a task is to be executed. Then solving the inverse kinematics problem to compute the joint positions that correspond to that trajectory. And lastly, controlling the robot to track those joint …


Thermo-Mechanical Design Considerations At The Server And Rack Levels To Achieve Maximum Data Center Energy Efficiency, Richard Mark Eiland Jan 2015

Thermo-Mechanical Design Considerations At The Server And Rack Levels To Achieve Maximum Data Center Energy Efficiency, Richard Mark Eiland

Mechanical and Aerospace Engineering Dissertations - Archive

Continually increasing demand for information technology (IT) applications and services has provided sustained growth and interest in data centers. The large amounts of energy consumed by data center facilities have placed a significant emphasis on the energy efficiency of their overall operation. One area of particular importance is the cooling energy required. Heat generation within a data center starts at the server level, specifically within the microelectronic devices that process digital information. Convective heat transfer is the primary driver for the removal of heat from an individual server. As such, cooling efficiency at the server level will be dictated by …


Minimizing Power Consumption At Module, Server And Rack-Levels Within A Data Center Through Design And Energy-Efficient Operation Of Dynamic Cooling Solutions, John Edwards Fernandes Jan 2015

Minimizing Power Consumption At Module, Server And Rack-Levels Within A Data Center Through Design And Energy-Efficient Operation Of Dynamic Cooling Solutions, John Edwards Fernandes

Mechanical and Aerospace Engineering Dissertations - Archive

Data center energy consumption continues to increase with the proliferation in online services such as social networking, banking, entertainment, cloud computing, etc. Recent estimates show that associated power consumption accounts for around 2% and 1.8% of electricity production in the United States and worldwide respectively. In addition to growth in the industry, power densities continue to rise in IT equipment increasing the criticality of thermal management in data center operation. Cooling systems account for around a third of overall power consumption requiring more energy-efficient solutions across all levels within the facility.Liquid cooling of high power modules using cold plates has …


Formalization Of The Engineering Science Discipline - Knowledge Engineering, Xiao Peng Jan 2015

Formalization Of The Engineering Science Discipline - Knowledge Engineering, Xiao Peng

Mechanical and Aerospace Engineering Dissertations - Archive

Knowledge is the most precious ingredient facilitating aerospace engineering research and product development activities. Currently, the most common knowledge retention methods are paper-based documents, such as reports, books and journals. However, those media have innate weaknesses. For example, four generations of flying wing aircraft (Horten, Northrop XB-35/YB-49, Boeing BWB and many others) were mostly developed in isolation. The subsequent engineers were not aware of the previous developments, because these projects were documented such which prevented the next generation of engineers to benefit from the previous lessons learned. In this manner, inefficient knowledge retention methods have become a primary obstacle for …


Aspects Of Intuitive Control Framework: Stabilize, Optimize, And Identify, Pavan Kumar Nuthi Jan 2015

Aspects Of Intuitive Control Framework: Stabilize, Optimize, And Identify, Pavan Kumar Nuthi

Mechanical and Aerospace Engineering Dissertations - Archive

The duality of estimation and control problems is a well known fact in control theory literature. Parameter convergence and closed loop stability are usually competing interests for a given control scheme. This motivates identification routines to be performed only in offline experiments. On the other hand stable controllers do not guarantee parameter convergence to true parameters. Thus there is a need for a higher level abstraction for a control scheme which acts in stages and prioritizes various aspects at different stages. The stage abstraction for controller is inspired by human intuition towards dealing with control and identification simultaneously and hence …


A Numerical Study Of Microfluidic Droplet Motions In Parallel-Plate Electrowetting-On-Dielectric (Ewod) Devices, Yin Guan Jan 2015

A Numerical Study Of Microfluidic Droplet Motions In Parallel-Plate Electrowetting-On-Dielectric (Ewod) Devices, Yin Guan

Mechanical and Aerospace Engineering Dissertations - Archive

Microscale water droplet motions in parallel-plate electrowetting-on-dielectric (EWOD) devices including transport, splitting, merging and dispensing have been numerically studied. The transient governing equations for the microfluidic flow are solved by a finite volume scheme with a two-step projection method on a fixed computational domain. The interface between liquid and gas is tracked by a coupled level set and volume-of-fluid (CLSVOF) method. A continuum surface force (CSF) model is employed to model the surface tension at the interface. Contact angle hysteresis which is an essential component in EWOD modeling is implemented together with a simplified model for the viscous stresses exerted …


Improving Fracture Toughness Of Silicon Carbide Based Ceramics By Microstructure Tailoring, Sheikh Fahad Ferdous Jan 2015

Improving Fracture Toughness Of Silicon Carbide Based Ceramics By Microstructure Tailoring, Sheikh Fahad Ferdous

Mechanical and Aerospace Engineering Dissertations - Archive

Ceramic materials are one of the most promising materials for wide variety of technical applications such as automotive, aerospace, medical, and other applications. They have very high strengths and high melting points relative to metals. However, low fracture toughness is one of the main barriers of ceramics prohibiting their wide-spread applications. This is because ceramics are mainly bonded with directional bonds which don’t allow dislocations based deformation. Several attempts have been made to increase the toughness of ceramic materials without sacrificing significantly the other mechanical properties. Here three different types of SiC based ceramics have been computationally (atomistic and up-scaled …


Novel Device And Methods For Composite Material Characterization, Michael M. Tadros Jan 2015

Novel Device And Methods For Composite Material Characterization, Michael M. Tadros

Mechanical and Aerospace Engineering Dissertations - Archive

Composite materials have several advantages over metallic materials, with their high specific strength and ability to be elastically tailored to create advantageous structural responses. However, the widespread implementation of composite materials in primary structures is limited by our knowledge of how damage mechanisms interact and spread inside composite parts. To date, characterization has been conducted using one of two methods, surface measurements and subsurface measurements. Surface measurements cannot in general capture the failure of multidirectional composite laminates. Subsurface measurements allow for observations of the internal material structure and damage mechanisms inside the composite which might facilitate greater understanding of the …


Cacti- And Shorebirds-Inspired Transports Of Liquid Drops And Two Related Fog Collectors, Xin Heng Jan 2015

Cacti- And Shorebirds-Inspired Transports Of Liquid Drops And Two Related Fog Collectors, Xin Heng

Mechanical and Aerospace Engineering Dissertations - Archive

Motivated by what has been used in cacti and shorebirds to directionally manipulate water drops, we have explored two approaches to guide the movement of liquid drops. Based on these approaches, in addition to separating oil from its mixture with water, we have further developed two fog collectors. The first fog collector has a configuration similar to its counterpart in a cactus. This collector includes a large ZnO wire and an array of small ZnO wires that are branched on the large wire. All these wires have conical shapes, whose diameters gradually increase from the tip to the root of …


Analysis Of Thin-Walled Cylindrical Composite Shell Structures Subject To Axial And Bending Loads: Concept Development, Analytical Modeling And Experimental Verification, Sthanu Mahadev Jan 2015

Analysis Of Thin-Walled Cylindrical Composite Shell Structures Subject To Axial And Bending Loads: Concept Development, Analytical Modeling And Experimental Verification, Sthanu Mahadev

Mechanical and Aerospace Engineering Dissertations - Archive

Several studies have focused on the modeling and response characterization of composite structural members, with particular emphasis on thin-walled cylindrical composite shells. This class of shell configurations is explored to determine their mechanical response in primary aerospace structural members. The present work is focused on formulating a modified composite shell theory prognosis methodology for investigating the structural response of thin-walled cylindrical shell type composite configurations under axial and bending loads, respectively. The prime motivation to develop this theory arises from its capability to generate simple yet accurate closed-form analytical results that can efficiently charecterize cylindrical composite shell constructions. This work …


Characterization Of Flapping Wing Aerodynamics And Flight Dynamics Analysis Using Computational Methods, Alok Ashok Rege Jan 2015

Characterization Of Flapping Wing Aerodynamics And Flight Dynamics Analysis Using Computational Methods, Alok Ashok Rege

Mechanical and Aerospace Engineering Dissertations - Archive

Insect flight comes with a lot of intricacies that cannot be explained by conventional aerodynamics. Even with their small-size, insects have the ability to generate the required aerodynamic forces using high frequency flapping motion of their wings to perform different maneuvers. The maneuverability obtained by these flyers using flapping motion belies the classical aerodynamics theory and calls for a new approach to study this highly unsteady aerodynamics. Research is on to find new ways to realize the flight capabilities of these insects and engineer a micro-flyer which would have various applications, ranging from autonomous pollination of crop fields and oil …


Numerical And Experimental Investigation Of Variable Transportation Cooling For Reusable Thermal Protection Systems, Stefano Gulli Dec 2014

Numerical And Experimental Investigation Of Variable Transportation Cooling For Reusable Thermal Protection Systems, Stefano Gulli

Mechanical and Aerospace Engineering Dissertations - Archive

This research work is focused on the numerical and experimental investigation of the transpiration cooling technique for reusable thermal protection systems. The transpiration cooling has been considered because of its higher cooling effectiveness, with respect to other active cooling techniques, in terms of minimum amount of coolant to be used and minimum interference to the external flow. An innovative approach based on the coupling of the hypersonic boundary layer with the thermal response of porous materials is used to numerically study the thermal management potential of the transpiration cooling technique. The new concept of the variable transpiration is introduced by …


Thermal Conduction And Heat Generation Phenomena In Li-Ion Cells, Stephen Drake Jan 2014

Thermal Conduction And Heat Generation Phenomena In Li-Ion Cells, Stephen Drake

Mechanical and Aerospace Engineering Dissertations - Archive

Cylindrical lithium ion (Li-ion) cells have demonstrated high power density and energy capacity among other energy storage devices. Despite their already widespread use, the thermal transport properties of cylindrical Li-ion batteries are not well documented and understood, while a sizable amount of work has been carried out for electrical, electrochemical, and materials optimization of Li-ion cells. These thermal phenomena are particularly important for high discharge rate batteries. With this uncertainty, if thermophysical properties are not accounted for in thermal models, the result may be a significant under-prediction or over-prediction of the temperature field in a Li-ion cell.Experimental techniques are described …


Unsteady Thrust Measurement Techniques For Pulse Detonation Engines, Dibesh Dhoj Joshi Jan 2014

Unsteady Thrust Measurement Techniques For Pulse Detonation Engines, Dibesh Dhoj Joshi

Mechanical and Aerospace Engineering Dissertations - Archive

Thrust is a critical performance parameter and its correct determination is necessary to characterize an engine. Many conventional thrust measurement techniques prevail. However, further developments are required for correct measurement of thrust in the case of a pulse detonation engine (PDE), since the entire thrust generation process is intermittent. The significant effect of system dynamics in the form of inertial forces, stress wave propagation and reflections initiated in the structure due to detonations and pulse-to-pulse interaction in a fast operating PDE further complicate the thrust measurement process. These complications call for a further, detailed study of the unsteady thrust characteristics. …


Experimental Investigation Of Nucleate Boiling And Thin-Film Evaporation On Enhanced Silicon Surfaces, Shailesh Malla Jan 2014

Experimental Investigation Of Nucleate Boiling And Thin-Film Evaporation On Enhanced Silicon Surfaces, Shailesh Malla

Mechanical and Aerospace Engineering Dissertations - Archive

The present work consists of two major studies. The first study investigates the effects of surface energy or wettability on nucleate pool boiling and the second study investigates the thin-film evaporative cooling for near junction thermal management. For the first study, effects of surface energy or wettability on critical heat flux (CHF) and boiling heat transfer (BHT) of smooth heated surfaces was studied in saturated pool boiling of water at 1 atm. For this purpose hydrophilic and hydrophobic surfaces were created on one side of 1cm x 1cm double-side polished silicon substrates. A resistive heating layer was applied on the …


Degradation Mechanics Of Bone And Bone Like Materials Via Multiscale Analysis, Md Farzad Sarker Jan 2014

Degradation Mechanics Of Bone And Bone Like Materials Via Multiscale Analysis, Md Farzad Sarker

Mechanical and Aerospace Engineering Dissertations - Archive

Bone fracture is a common health risk for older people suffering from bone disease like osteoporosis. The more severe the osteoporosis is the more structural degradation in bones occurs, which eventually makes bones more fracture prone. The mechanical behavior of bone depends on the structural response of bone constituents over a broad range of length scales spanning from the nanoscale collagen fibril level to the macroscale trabeculae level. As such, in order to understand bone fracture, it is important to know the structure-property relations of bone material over the entire length of scale. Surprisingly, a quantitative understanding of bone fracture …


Wind Field Estimation And Its Utilization In Trajectory And Input Prediction, Jane-Wit Kampoon Jan 2014

Wind Field Estimation And Its Utilization In Trajectory And Input Prediction, Jane-Wit Kampoon

Mechanical and Aerospace Engineering Dissertations - Archive

This dissertation work develops a method for onboard estimation of wind field with spatial and temporal variation based on local wind vector estimation and/or measurements from multiple aircraft flying in the same airspace. Aircraft flying in the same airspace of operation are considered airborne wind sensors scattered over the airspace because of the fact that aircraft carry along with them wind information inherent in their dynamics and kinematics. The onboard wind field estimation is formulated in the framework of parameter estimation based on various wind field models, which are different function of position and time. The online wind field estimation …


Electrowetting On Dielectric Digital Microfluidics For 3-Dimensional Cell Culture And Chemical Screening, Subin Mac George Jan 2014

Electrowetting On Dielectric Digital Microfluidics For 3-Dimensional Cell Culture And Chemical Screening, Subin Mac George

Mechanical and Aerospace Engineering Dissertations - Archive

Microfluidic devices have allowed improved cell culture studies to be carried out by allowing greater spatiotemporal control over the cell environment while at the same time providing greater throughput, increased automation capabilities and reagent savings. To improve the relevancy of such studies, 3-dimensional (3D) cell culture has been attempted in microfluidic devices. 3D cell culture is known to better mimic and recreate the environment that cells in the body experience as compared to conventional 2-dimensional cell culture. However, incorporating 3D cell culture into conventional channel based microfluidic devices have proven to be challenging. Hydrogels which provide the 3D environment in …


Modeling, Estimation, And Analysis Of Unresolved Space Object Tracking And Identification, Laura Suarez Henderson Jan 2014

Modeling, Estimation, And Analysis Of Unresolved Space Object Tracking And Identification, Laura Suarez Henderson

Mechanical and Aerospace Engineering Dissertations - Archive

The problem of orbit determination along with shape determination is significant. The orbit determination problem has been tackled for centuries by some of the greatest mathematicians and physicists. The issue of shape determination of space objects, although more recent, has also been addressed quite extensively. Nevertheless, these problems remain of great interest in the scientific and engineering community, and are addressed in this work. The greatest motivation for the tracking and identification of Earth orbiting objects is the ever-increasing population of space assets and man-made debris. It is of interest to implement new and better techniques to track and identify …


Investigation Of Wetting States On Microstructures After Liquid Drops Contact Groove Base, Mingming Xiang Jan 2014

Investigation Of Wetting States On Microstructures After Liquid Drops Contact Groove Base, Mingming Xiang

Mechanical and Aerospace Engineering Dissertations - Archive

Wetting properties of roughness surfaces have attracted a considerable attention because of both the scientific insight and the practical applications. One of the most intriguing topics of wetting is the so-called Cassie-Baxter and Wenzel transition. Recently, theoretical and experimental works have been done to explore this transition on microstructure-formed surfaces. One of the criteria that most commonly used to judge such transition is whether a liquid drop contacts the base of a roughness groove. It is expected that, after the contact, liquid immediately fills the roughness groove, and subsequently the wetting state is changed from Cassie-Baxter state to that of …


Finite Element Based Methodology For Prediction Of Matrix-Dominated Failure In Composites, Guillaume Seon Jan 2014

Finite Element Based Methodology For Prediction Of Matrix-Dominated Failure In Composites, Guillaume Seon

Mechanical and Aerospace Engineering Dissertations - Archive

The objective of this work is to develop a computational failure prognosis methodology applicable to virtual testing of composites. The major motivation for the establishment of virtual testing is the ability to reduce actual testing of composite structures, which is oftentimes expensive and time consuming, by numerical simulations. A successful virtual test methodology should be applicable to monotonic and fatigue loading, account for strong anisotropy of composite materials and capture the effects of manufacturing irregularities. This work proposes to use three-dimensional finite element modelling for predicting the onset and progression of matrix-dominated failures modes, such as matrix cracks and delaminations, …


Analytical And Experimental Investigation Of Thermal Transport In Three-Dimensional Integrated Circuits (3d Ics), Leila Choobineh Jan 2014

Analytical And Experimental Investigation Of Thermal Transport In Three-Dimensional Integrated Circuits (3d Ics), Leila Choobineh

Mechanical and Aerospace Engineering Dissertations - Archive

Thermal management of three-dimensional integrated circuits (3D ICs) is recognized to be one of the foremost technological and research challenges currently blocking the widespread adoption of this promising technology. The computation of steady-state temperature fields in a 3D IC is critical for determining the thermal characteristics of a 3D IC and for evaluating any candidate thermal management technology. An analytical solution for the three-dimensional temperature field in a 3D IC based on solution of the governing energy equations using Fourier series expansion for steady-state temperature fields is studied. Comparison of the predicted temperature fields with finite-element simulation shows excellent agreement. …


A New Multiscale Approach For Dynamic Modeling And Simulation Of Micro-Nano Biomolecular Systems Characterized By A Low Reynolds Number, Mahdi Haghshenas-Jaryani Jan 2014

A New Multiscale Approach For Dynamic Modeling And Simulation Of Micro-Nano Biomolecular Systems Characterized By A Low Reynolds Number, Mahdi Haghshenas-Jaryani

Mechanical and Aerospace Engineering Dissertations - Archive

In this dissertation, a new multiscale computational framework was developed in order to model and simulate motility of micro-nano-sized objects in fluid environments, characterized with a low Reynolds number. Especially, it has been used for studying the dynamic behavior of biomolecular systems such as motor proteins inside cells.Long simulation run time is one of the most important issues in modeling of cellular and biomolecular systems at the nanoscale due to the multiple time and length scales involved in the dynamics of these systems. These multiscale features are caused by either structure-structure (e.g. flexibility in biological structure or contact) or structure-fluid …


Dynamic Simulation Of Multibody Systems In Simultaneous, Indeterminate Contact And Impact With Friction, Adrian Rodriguez Jan 2014

Dynamic Simulation Of Multibody Systems In Simultaneous, Indeterminate Contact And Impact With Friction, Adrian Rodriguez

Mechanical and Aerospace Engineering Dissertations - Archive

This research is focused on improving the solutions obtained using theory in contact and impact modeling. A theoretical framework is developed which can simulate the performance of dynamic systems within a real world environment. This environment involves conditions, such as contact, impact and friction. Numerical simulation provides an easy way to perform numerous iterations with varying conditions, which is more cost effective than building equivalent experimental setups. The developed framework will serve as a tool for engineers and scientists to gain some insight on predicting how a system may behave. The current field of research in multibody system dynamics lacks …


Design And Fabrication Of Microfluidic Photoelectrochemical Reactors For Efficient Conversion Of Carbon Dioxide To Liquid Fuel, Homayon Homayoni Jan 2014

Design And Fabrication Of Microfluidic Photoelectrochemical Reactors For Efficient Conversion Of Carbon Dioxide To Liquid Fuel, Homayon Homayoni

Mechanical and Aerospace Engineering Dissertations - Archive

The world's energy demand is expected to increase dramatically over the next few decades. At the same time the availability of cheap fossil fuels is expected to decrease. In addition to the increase in energy cost, the use of fossil fuels results in the release of greenhouse gases into the atmosphere. A lot research effort has been invested in the development of renewable energy resources that are cost competitive, sustainable, and emission free. Although these renewable technologies are available, many are not implemented widely due low efficiency and high capital cost. Therefore, fossil fuels are expected to remain a major …


Enhancement Of Pool Boiling And Evaporative Heat Transfer Using High Temperature Thermally Conductive Microporous Coatings, Ajay Gurung Jan 2014

Enhancement Of Pool Boiling And Evaporative Heat Transfer Using High Temperature Thermally Conductive Microporous Coatings, Ajay Gurung

Mechanical and Aerospace Engineering Dissertations - Archive

The present research is an experimental study of the enhancement of pool boiling and evaporative heat transfer using high temperature thermally conductive microporous coatings. Two major types of coatings were investigated: one that is based on copper powders on copper substrate and the other on aluminum powders on aluminum substrate. Both coatings were easy to fabricate with low costs compared to conventional sintering and plasma spraying techniques, yet have high bonding strength and some of them can operate at temperatures up to 670 oC. Multiple coating options were fabricated and tested in pool boiling of water in order to optimize …


Experimental Study Of Separated Ramp-Induced Shock/Boundary-Layer Interaction With Upstream Micro-Vortex Generator At Mach 2.5, Yusi Shih Jan 2014

Experimental Study Of Separated Ramp-Induced Shock/Boundary-Layer Interaction With Upstream Micro-Vortex Generator At Mach 2.5, Yusi Shih

Mechanical and Aerospace Engineering Dissertations - Archive

Shock wave/boundary layer interactions (SBLIs) are important issues for high-speed vehicles. SBLIs reduce the performance of aerodynamic surfaces and engine inlets, amongst a number of adverse effects. Micro-vortex generators (MVGs) are a flow control method with strong potential to mitigate the effects of SBLI by energizing the boundary layer through momentum transfers from the freestream. They have been implemented in actual configurations at low speeds. The present research includes a combined experimental and theoretical analysis of the evolution of the perturbation downstream the MVG, the formation of vortices, and their interaction with the shock front. Experiments were performed with a …


Analytical Solutions Of Steady-State Heat Conduction In Multi-Layer Stack Packaging, Saeed Ghalambor Jan 2014

Analytical Solutions Of Steady-State Heat Conduction In Multi-Layer Stack Packaging, Saeed Ghalambor

Mechanical and Aerospace Engineering Dissertations - Archive

Analytical models that can be utilized in modeling the steady-state temperature solutions of planar and 3D packaged integrated circuits are discussed. This mathematically-driven model will include solutions for uniform and non-uniform footprint die stack systems as well as planar flip chip packages. These analytically obtained temperature solutions will include the contribution of thermal resistance for both cases as well as perfect contact scenarios. The acquired solution will accommodate any kind of boundary conditions (first, second and third kind) on the top and bottom surfaces of the stack system with the sides being adiabatic. Furthermore, the algorithm developed will consider volumetric …


Phoresis Of A Solid Particle In Real Fluid, Yuan Ting Wu Jan 2014

Phoresis Of A Solid Particle In Real Fluid, Yuan Ting Wu

Mechanical and Aerospace Engineering Dissertations - Archive

For micro- and nano-scale particles driven by interfacial non-contact forces in fluid, known as phoresis, this dissertation provides a general formulation and a systematic investigation. It starts with an analytical continuum-mechanics formulation that covers various important aspects of an interfacial structure, including viscosity and mass density variations as well as a body force field, in real fluid. It then reduces to specific solutions due to characteristic mechanisms. A closed-form analytical solution to the case of viscosity variation (which manifests itself as Navier's slip boundary condition) is derived. Furthermore, a novel mechanism for thermophoretic mobility driven by near-surface phase transition is …