• The effect of ultrasound on polycyclic aromatic hydrocarbons in aqueous media

      Wheat, Patrick E.; Tumeo, Mark; Brown, Edward; Johnson, Ronald; Reichardt, Paul; Tilsworth, Timothy (1992)
      Polycyclic aromatic hydrocarbons (PAHs) are common environmental contaminants which pose a potential threat to human health and environmental quality. An investigation to determine the ability of ultrasonic radiation to desorb PAHs adsorbed on the surface of solid substrates and to chemically alter these chemicals in aqueous solutions and suspensions has been conducted. The data indicate that enhanced transport of adsorbed PAH from a glass surface can be induced by treatment with ultrasonic radiation of varying intensities. Furthermore, chemical alteration can be induced under intense (147 watts/cm$\sp2)$ ultrasonic treatment. The extent of reaction is a function of irradation time at this ultrasonic intensity. Reaction products from ultrasonic treatment of aqueous solutions of biphenyl, analysed by gas chromatography (GC) and mass spectrometry (MS), include ortho-, meta-, and para-(1,1 biphenyl) -ol. The principal product from ultra-sonic treatment of aqueous phenanthrene appears to be a phenanthrenediol. The use of ultrasound to treat PAH contaminated aqueous solutions in tandem with other methodologies appears promising. However, the toxicity of reaction product mixtures produced by ultrasonic treatment remains to be determined.
    • Design and implementation of photodiode-based receiver systems for a 1574 nm eye-safe lidar

      Yue, Jia (2004-08)
      In this thesis we present the design, implementation and testing of a photodiode-based receiver systems for a 1574 nm eye-safe lidar. The specific goal of this thesis was to precisely and accurately convert and amplify nW optical signals into robust mV voltage signals. The receiver system incorporates both analog and digital circuitry and a software-based digital processing system. Four analog circuits were constructed and tested using both PIN diodes and APDs, and two high-speed commercial op amps. A single high-speed digital processing system was tested with each of the analog circuits. The analog circuitry was found to be the fundamental limitation on the performance of the system with the receiver bandwidth limited to -6 MHz for the PIN-based systems and -14 MHz for the APD-based systems. Inherent oscillations in the analog circuits were successfully removed using digital filtering techniques in the software-based digital processing systems. Furthermore, the APD-based systems had less rms noise than the PIN-based systems. The lidar receiver system could support measurements with a maximum resolution of 10 m and a range of up to 40 km.
    • Measurement of gas-water relative permeabilities in hydrate systems

      Jaiswal, Namit J.; Dandekar, Abhijit Y.; Chukwu, Godwin A.; Khataniar, Santanu; Patil, Shirish L. (2004-08)
      Gas hydrates are considered to be an alternative energy resource of the future, as they exist in enormous quantities in permafrost and the offshore environment. One of the primary mechanisms involved in hydrate decomposition in porous media is the gas-water two-phase flow in the formations. Despite their importance, these functions are poorly known due to the lack of fundamental understanding of gas-water flows and the difficulty of direct measurements for hydrate systems. As part of a major Alaska gas hydrate project, an experimental apparatus was designed and developed for forming gas hydrates in the laboratory and performing gas-water relative permeability experiments. In this study effective permeability and relative permeability across hydrate saturated consolidated Oklahoma 100 mesh sand and Anadarko field samples were measured. The results suggest that the relative permeability inferred from unsteady state core floods is a lumped parameter which not only includes hydrate saturation but also the effects of dissociation instabilities caused by fluid flow, fine migration and local compaction in porous media at low temperature. Furthermore, these properties are significantly altered by nature of hydrate distribution throughout the specimen, location within the pores, and concentration at specific locations.
    • Study of rheology of gas-to-liquid products, Alaska North Slope crude oil and their blends for transportation through the Trans Alaska Pipeline System

      Inamdar, Abhijeet Ashok (2004-08)
      In order to bring remote natural gas to market, conversion of natural gas to a liquid form (Gas-to-liquids (GTL)) may be an alternative to utilize this gas. Alaskan North Slope might prove as one of the first sites in the USA to commercialize this technology because of the huge natural gas resources it holds. The Trans Alaska Pipeline System (TAPS) will be the means of transportation of this GTL to the market. Thus it becomes major task to evaluate the technical and economic feasibility of transporting GTL products through the TAPS. One of the modes of transporting GTL products from ANS to Valdez is commingling them with Crude oil as a single phase before pumping through TAPS. This changes the properties of GTL as well as the Crude oil. Thus it becomes important to study the physical and chemical properties of not only the GTL but also its blends with the crude oil. Four blends of GTL/crude in the ratios of 1:1, 1:2, 1:3 and 1:4 were prepared for their rheological evaluation at different temperature conditions. Results show that flow behavior of the pure and GTL blends are temperature sensitive. Viscosity and density of the blends decrease with increasing amount of GTL and increasing temperature. Optimum blend ratio is between 1:2 and 1:3 GTL/Crude oil blends.
    • Seismic performance of Alaskan structures

      Cherlopalle, Dileep; Hulsey, J. Leroy; Carlson, Robert; Shur, Yuri (2004-08)
      Alaska is the most earthquake prone area in the United States. On October 23, 2002 a 6.7 magnitude earthquake occurred in interior Alaska. This was followed by a magnitude 7.9 earthquake that occurred near Denali on November 3, 2002. The Denali earthquake was the largest inland earthquake in North America in almost 150 years. Only minimal structural damage was reported. Subsequently, structural engineers should question why minimal damage. As a part of an investigation to evaluate this unusual phenomenon, two structures were selected for seismic analysis, a building and a bridge. The building is at Alyeska Pump Station # 10 (3 miles from the epicenter) and only non-structural damage occurred. A 3 span truss bridge near Tok, Alaska was selected as the second. This structure experienced only minimal damage. Seismic analysis was performed on these two structures for horizontal excitations. A corrected seismic data from Pump Station # 10 was used as the earthquake excitation record. The maximums for displacements, member forces and member stresses were studied. The results show that no structural damage should have occurred for the building and minimal damage for the bridge. These findings compare favorably with field inspection results reported by others.
    • Stability of milling using Chebyshev collocation method

      Nindujarla, Praveen (2004-12)
      The dynamic stability of the milling process is investigated through single and two degree-of-freedom mechanical models by determining the regions where chatter (unstable) vibrations occur in the two-parameter space of spindle speed and depth of cut. Dynamic systems like milling are modeled by linear delay-differential equations (DDEs) with time-periodic coefficients. A new approximation technique for studying the stability properties of such systems is presented in this thesis. The approach is based on the properties of Chebyshev polynomials and a collocation expansion of the solution at their extremum points, the Chebyshev collocation points. The stability properties are determined by the eigenvalues of the monodromy matrix which maps collocation points from one interval to the next and which is a finite dimensional approximation to which the exact infinite dimensional Floquet transition matrix (monodromy operator). We check the results for convergence by varying the number of Chebyshev collocation points and by simulation of the transient response via the DDE23 MATLAB routine. Stability charts and chatter frequency diagrams are produced for up-milling and down-milling cases of 1, 2, 4 and 8 cutting teeth and 0 to 100 % immersion levels. The unstable regions due to both secondary Hopf and flip (period-doubling) bifurcations are found which agree with the results found by other techniques in the previous literature. An in-depth investigation in the vicinity of the critical immersion ratio for down-milling (where the average cutting force changes from negative to positive) and its implication for stability is presented.
    • Effects of electromigration on the reliability of radio frequency microelectro mechanical switches

      Karri, Naveen Kishore (2004-12)
      Radio Frequency (RF) Micro-Electro-Mechanical System (MEMS) switches have many advantages over semiconductor switches. Despite these advantages they are not implemented in reliability demanding space, defense and commercial applications because of reliability concerns. Although some failure modes have been identified so far, other failure modes are still under research. Electromigration, a well-known failure mechanism in interconnects, was recently recognized as a possible cause of failure in micro-switches. However, there have been no instances of electromigration studies in the literature. This thesis presents a preliminary study on the electromigration failure and its impact on the lifetime of MEMS switches. A simulation program that emulates the electromigration process was developed. Parametric studies were performed to study the impact of impact certain parameters on electromigration process. The combined effects of Joule heating and electromigration were analyzed. Unlike passivated interconnects, the micro-switch is cantilevered and suspended in an inert medium without encapsulation. The electromigration lifetime estimation program developed in this thesis is applicable to all such free structures. Joule heating has been demonstrated to be a key factor in the electromigration failure of micro-switches. Results showed that the electromigration process is very slow at the beginning. After a certain time, the resistance is found to increase exponentially, increasing the temperature of the strip drastically toward failure. The same trend is also observed in a gold micro-switch, but with much slower rate of electromigration degradation, indicating a longer lifetime.
    • Resource estimation and analysis for offshore placer deposit using GIS technology

      Li, Hui (2004-12)
      In this thesis, an advanced GIS system is developed to manage, analyze and distribute Alaskan near-shore marine mineral deposition data. The developed GIS system is applied in a case study of the marine gold deposits in the offshore area of Nome, Alaska. The data collected during the previous phases of the research project are compiled using several computer application softwares such as ArcGIS8.3, Microsoft Access 2000 and others. Two improved relational geodatabases are created, in which various maps integrated with digital data sets are stored. The first database is known as the 'Integrated Geodatabase', which stores all the relative data collected in the Nome area, such as borehole data, bedrock geology, surficial geology, and geochemical data. database, a 'Regularized 2.5D Geodatabase', is generated based on the Geodatabase to store the layered orebody parameter for each regularized cell. The other Integrated With these GIS geodatabases, many important applications of data management and analysis, such as information query, data visualization, geostatistical analysis, gold distribution analysis, sediment distribution analysis, and resources estimation, are carried out readily for better understanding of Nome offshore mineral resources. Based on the enhanced GIS structure, a GIS-based website is developed using ArcIMS. Users can integrate local data sources with Internet data sources for display, query, and analysis in an easy-to-use web browser.
    • Predictive semi-empirical analysis for tire/snow interaction

      Sankapalli, Naveen Kumar; Lin, Chuen-Sen; Liu, Qing; Zhang, Tinggang; Lee, Jonah (2004-12)
      A semi-analytical method is presented to predict the shear stress and motion resistance at the tire/snow interaction. The shear stress model is a function of normal pressure and slip. The main goal was to develop a simplified model by reducing the number of parameters in the model, so that the computational time could be reduced towards real time simulations. Motion resistance is calculated by integrating the horizontal component of normal pressure along the tire/terrain contact surface. The motion resistance obtained is slip dependent because the sinkage is a function of slip. The calculations of motion resistance and sinkage were done using the presented model and an existing model. Also the calculated results were compared with the FEA (Finite Element Analysis) data, which matched reasonably well. In the second part of the thesis shear force is expressed as a function of normal load, slip and slip angle. Shear force parameters tire stiffness, friction coefficients, and contact pressure constants were assumed as the functions of normal load and the coefficients of parameters were found through curve fitting using FEA data. These functions were used to calculate tire stiffness, friction coefficient and contact pressure constant. The calculated results matched well with FEA simulation results for the same tire and snow conditions. Pure shear force and the combined shear force were compared, and the pure shear force is always greater than the combined shear force for the same slip and slip angle.
    • An experimental investigation of natural freezing and biopolymers for permeability modification to reduce the volume of dense non-aqueous phase liquids in groundwater

      D'Cunha, Neil John (2004-12)
      Dense Non-Aqueous Phase Liquid (DNAPL) contamination is one of the major environmental concerns today. DNAPL can remain in significant quantities as residual contaminants in the low permeability zones even after the bulk phase has been removed. As the drive fluid sweeps through the aquifer it follows the path of least resistance, which is the high permeability zone. Thus the contaminants trapped in the low permeability zones remain as residuals and serve as a source for prolonged contamination. Conventional remediation techniques are ill-equipped to deal with the heterogeneities of the aquifers. Various techniques to enhance the efficiency of the conventional methods are tried without significant success. Reducing the temperature of soil formations can modify aquifer flow paths. The natural freezing of soils in winter may be used effectively to modify the flow paths. In summer, permeability modification can be accomplished by emplacement of microbial polymer gels. In this thesis, we have investigated using a laboratory scale one dimensional column experiment, a novel technique to reduce the volume of residual DNAPL using a combination of natural freezing in winter and biopolymer in summer.
    • Analysis of a generic flip chip under shock and vibration

      Kasturi, Uday Bhaskar; Chen, Cheng-fu; Butcher, Eric; Lin, Chuen-Sen (2004-12)
      A flip chip package, underfilled or non-underfilled, was analyzed under mechanical shock and/or vibration at the device and board levels, respectively. For the tests at the device level, the maximum stress developed at the corner-most solder joint. The horizontal drop orientation, with the chip facing up, produced the worst scenario for solder joint lifetime prediction. The underfilled package is better than non-underfilled under the excitation of mechanical shock and vibration. Parametric studies of the underfill material strength suggested that the higher the elastic modulus, the better it carried the mechanical shock. However, practically the upper bound of the elastic modulus is limited to avoid die cracking due to thermal mismatch of material expansion. The combined loading of thermal residual stress and mechanical shock was also conducted to study their influence on the solder lifetime prediction. It was found that the thermal pre-stressed condition plays a key role for the von Mises stress excursion, but has almost no influence on the shock-induced normal stress. The phenomenon appears similarly in the board level testing, but with worse reliability in solders due to the higher stresses induced.
    • Axisymmetric numerical heat transfer analysis of natural gas hydrates reservoir

      Subbaihaannadurai, Vijayagandeeban; Das, Debendra K.; Patil, Shirish L.; Goering, Douglas J. (2004-12)
      Gas hydrates are crystalline substances, occurring in nature under high pressure and low temperature. Numerical studies were conducted on dissociation of gas hydrate to recover natural gas. The model is a cylindrical geometry with a wellbore at the center through which hot water is injected. Through this thermal stimulation technique frozen hydrate reservoir is melted and natural gas is released. The computational fluid dynamics software FLUENT was adopted to generate the model. The initial model was solely comprised of a hydrate layer. This model was refined by adding the overburden and the underburden to the hydrate and exploring the thermal regime of the entire composite medium. Unsteady state results showing the dissociation front propagation with respect to time were calculated. In the first part, the hydrate medium is dissociated by the conduction phenomenon only. In the second part, due to the porous nature of the hydrate medium, both conduction and convection phenomena are considered. This thesis presents the following results obtained from simulations using Fluent. They are: temperature rise within the reservoir with time, temperature profiles in the radial direction, and steady and transient state solutions of the dissociation of gas hydrate with the liquid fraction in the reservoir. Comparison of our results with a finite difference model and a finite element model is also included. Volumes of gas released with respect to time and thermal efficiency ratios are also determined.
    • Economic evaluation of gas to liquids (GTL), crude oil commingled product transportation through the Trans Alaska Pipeline System (TAPS)

      Ibironke, Adejoke Motunrayo; Patil, Shirish L.; Chukwu, Godwin A.; Khataniar, Santanu A.; Reynolds, Douglas B.; Dandekar, Abhijit (2004-12)
      The Alaska North Slope is a potential candidate for the Gas to Liquid (GTL) technology. With over 38 TCF of natural gas reserves stranded on the Alaska North Slope, the GTL technology is considered as a possible method of harnessing the abundant resources. GTL fuels are environmentally friendly (sulfur free) with better ignition and burning properties than conventional petroleum products from crude oil. Economic evaluation using Rate of Return analysis and the Net Present Value (NPV) to identify the most favorable commingled mode for the transportation of the GTL products was performed. The Crystal Ball software was also used to run sensitivity analysis by using the probabilistic approach to give a clear view of the various scenarios on the project economics. Evaluating the options of transporting GTL products as a blend (Commingled) with the Alaska North Slope Crude Oil through the existing Trans-Alaska Pipeline System (TAPS) is the main focus of this study.
    • How chemical differences in dissolved organic matter relate to vegetation

      Seelen, Sarah Jean (2004-12)
      The purpose of this study was to better understand the link between dissolved organic matter (DOM) in soil leachate and different vegetation attributes. Soil cores were collected from the Caribou Poker Creeks Research Watershed (CPCRW) and subjected to a laboratory leaching procedure. The leachates were then subjected to a number of analytical tests, including pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). Py-GC/MS is a 'molecular fingerprinting' technique that was used to help determine similarities and differences in organic matter leached from soils with different vegetation attributes. Numerous statistical tests were performed including Student-t, analysis of variance, principal components analysis, and partial least squares regression (PLS). Results from Student-t tests indicated that local vegetation plays an important role in the character of the DOM in soil leachate. Additionally, a principal components test revealed relationships between soil leachates and vegetation attributes. A prediction model was created using PLS to predict components of leachate DOM based on vegetation attributes. This model, while in its early development, was able to predict 70% of the total molecular fingerprint of leachate DOM based on cover vegetation.
    • Biosorption of heavy metals by citrus fruit waste materials

      Patil, Santosh Bramhadev (2004-12)
      Conventionally used processes for removing heavy metals from wastewater are usually either expensive, such as ion exchange, or inefficient, such as precipitation. An innovative technique that is both efficient and economical is biosorption, in which living and dead biomass can act as biosorbents through physical-chemical processes like ion exchange and micro-precipitation. Pectin, a structural polysaccharide present in plant cell walls, is similar to alginate, a molecule that is often responsible for the high metal uptake by algae. Based on the structural similarity between alginate and pectin, it was expected that pectin rich bio-wastes may be as good a biosorbent material as brown algae. A comparison between different pectin-rich materials showed high stability and metal binding capacity of citrus peels. Sorption isotherms for citrus peels showed higher metal uptake capacity at pH 5 compared to pH 3. Kinetic studies revealed the time required to reach equilibrium for lemon fruit waste (0.177 mm) was 20 min while for larger particles the time increased to 30 min-60 min. For lemon fruit waste, the content and pKa values of acidic groups were determined by using a pKa spectrum technique. Isotherm modeling was carried out by using Langmuir isotherms and pH sensitive modeling.
    • Measurement of electron density in the earth's magnetosphere using discrete whistler mode echoes observed on the image satellite

      Li, Jingbo (2004-12)
      In this thesis, a new whistler mode sounding method has been developed to measure magnetospheric electron density using the RPI instrument on the IMAGE satellite. During the 2000-2002 period, RPI frequently recorded discrete whistler mode (WM) echoes in the ~10-400 kHz frequency range when IMAGE was at low altitudes (<7000 km) in the inner plasmasphere or near its perigee in the southern hemisphere. Most discrete cases were observed in the wintertime in the southern hemisphere during the local morning or nighttime. Ray tracing simulations indicate that the discrete echoes may result from reflections of RPI signals from the earth-ionosphere boundary. By comparing the measured and calculated time dispersion of discrete WM echoes, it is possible to determine the plasma density along the ray path as well as the nonducted or ducted modes of propagation. The ray tracing simulations were carried out for 8 cases observed in the year 2002 when discrete echoes were accompanied by Z mode echoes. The 8 cases were chosen to cover the maximum and minimum local electron densities, which varied from ~300 - 4000 el/cc at the satellite location as measured from Z mode echoes. The simulations showed that the electron densities at the F2 layer peak (~250 km altitude) varied from 1 x 10⁵ to 7 X 10⁵ el/ cc for all the cases. The extrapolated electron density of the calculations at ~4000 km altitude varied from ~200 - 2000 el/cc (L <4) and ~60 - 1000 el/cc (L> 4). The extrapolated electron density at ~8000 km altitude ranged from ~100 -1000 el/cc (L <4) and from 20 - 60 el/cc (L> 4). These results are in general consistent with previous observations of plasma density in the low altitude magnetosphere. The ray tracing simulation results also indicate that in each of the 8 cases studied whistler mode waves incident on the Earth-ionosphere boundary have incident angles that fall within the transmission cone angle and hence can be observed at the Earth's surface.
    • Performance analysis for remote power systems in rural Alaska

      Chubb, Tyler (2004-12)
      Due to the logistical difficulties involved in maintaining a rural Alaskan power generation facility, it is extremely important that the system function as efficiently as possible. Presently, many rural generation systems are not equipped with automated monitoring that enables knowledgeable personnel to view the performance of the system from a distant location. Consequently, system deficiencies resulting in increased fuel consumption and operating expense often go unnoticed as do potential system improvements. This thesis describes the design and implementation of a sophisticated monitoring system that consists of measurement sensors connected to an internet enabled data recorder. The monitoring system was used to continuously record the various forms of energy entering and leaving a diesel generator operating on the UAF campus. While in operation, the monitoring system was instrumental in identifying several measures that could be taken to improve the operating efficiency of the generator and also provided sufficient means to examine the economic feasibility of their implementation. The measures that were examined included heat recovery, conditioning of output power, and improvement of operating techniques.
    • The Physical Dynamics Of Patterned Ground In The Northern Foothills Of The Brooks Range, Alaska

      Overduin, Pier Paul; Kane, Douglas L. (2005)
      Periglacial landforms, called patterned ground, change the vegetation, microtopography and organic content of the surface soil horizons. Because they are uniquely products of the periglacial environment, changes in that environment affect their distribution and activity. As surface features, they mitigate heat and mass transfer processes between the land and atmosphere. For environmental change detection, the state of the soil and active layer must be monitored across temporal and spatial scales that include these features. It is suggested here that changes in the state of the active layer due to the abrupt spatial changes in surface soil character lead to changes in the distribution of soil components, soil bulk thermal properties and the thermal and hydrological fluxes result. The determination of soil volumetric moisture content using the relative dielectric permittivity of the soil is extended to include live and dead low-density feathermoss. High temporal resolution monitoring of the thermal conductivity of mineral and organic soil horizons over multiple annual cycles is introduced, along with a new method for analyzing the results of transient heat pulse sensor measurements. These results are applied to studies of frost boils and soil stripes in the northern foothills of the Brooks Range in Alaska. Active layer ice dynamics determine the thermal properties of the frozen soil in the frost boil pedon. Annual heaving and subsiding of the ground surface reflects these changes in ice content and can be used to estimate active layer ice content as a function of depth. These estimates correlate with bulk soil thermal diffusivity, inferred as a function of depth from temperature data. Differences in soil thermal diffusivity determine thaw depth differences between frost boil and tundra, and between wet and dry soil stripes. For the latter, deeper subsurface flow through the high organic content wet stripes is delayed until mid-summer; when it does occur, it has a large component normal to the hillslope as a consequence of differential heave. Dynamics in these periglacial landforms can be identified from surface features, highlighting the potential for scaling up their net effect using remote sensing techniques.
    • Improved Membrane Filtration For Water And Wastewater Using Air Sparging And Backflushing

      Psoch, Christian (2005)
      The goal of this research was to investigate methods and techniques that enhance mass transfer through the membranes. Two general types of fluids were investigated: synthetic wastewater treated in a membrane bioreactor (MBR) and natural and simulated river water. For both fluids, a wide range of solid concentrations (up to 18 g/L) were tested. The membranes investigated were all tubular modules at pilot scale between 0.75 and 1.20 m length, with tubular diameters of 5.5--6.3 mm, 0.2 mum pore size, and membrane surface areas of 0.036--0.1 m2. For flux enhancement, two techniques were applied: air sparging (AS), and backflushing (BF). Both techniques were compared with the sponge ball cleaning method. The experimental temperature ranged between 10 and 30�C, cross-flow velocities (CFV) ranged between 0.5 and 5.2 m/s, and transmembrane pressure (TMP) ranged between 30 and 350 kPa. Research results showed, that AS was able to enhance the conventional flux over weeks to months up to factor of 4.5 for river water and a factor of 3 for wastewater. At modest CFV of 1.5--2 m/s, AS was as successful as BF. If higher CFV (up to 5.2 m/s) were supplied for BF, this technique could enhance the wastewater flux by factor 4.5. The supply of AS and BF combined was superior to the single application even at moderate CFV. The major finding of this research was that cake thickness on the membrane surface was decreased by AS, contrary to research by other authors. AS can be used as substitute aeration in MBRs, without impairing the degradation performance. The combination of AS and BF generated the least filter cake, but the lowest fouling was observed for AS. An empirical equation was proposed to calculate the viscosity in a sidestream MBR depending on reactor temperature and mixed liquor suspended solids (MLSS).
    • Nanotribological Characterization Of Dynamic Surfaces

      Ingole, Sudeep Prabhakar; Liang, Hong (2005)
      This dissertation research includes three fundamental areas: utilizing an atomic force microscope (AFM) to study the nanomechanical and tribological properties, to understand friction and wear at nanometer length, and to study wear mechanisms of boride coatings for biological applications. This was the first time that an AFM was used to study the nanomechanical and tribological properties and the performance of the materials. The AFM enables detailed investigation of the wear modes at multi-length scales as well as the surface mechanical properties. Surface analysis using an AFM included the surface texture, profile of indents, wear tracks, and wear scars. The friction force microscope (FFM) revealed the relationship between surface texture and frictional properties, thus contributing to the fundamental understanding of nanotribology. A new wear model was proposed. Also, hardening was discovered under the indents. The multi-scale wear study was focused on fundamental wear mechanisms. New wear modes, different than the traditional ones, were proposed. In this research, nanocracks and other damage (hardening and plastic flow) were found at different scales. Boride coatings on refractory metals were investigated for biological applications. Tribological performance of these coatings was studied in dry and wet (biofluid) conditions. It was found that boron plays an important role in forming amorphous and crystalline wear debris.