Yes

The iron chelating molecule, ethylenediaminetetraacetic acid (EDTA) is used in food applications for the preservation of oxidation prone ingredients. Research has suggested that EDTA is also capable of enhancing the antimicrobial effectiveness of various compounds including naturally-derived antimicrobials. With consumer demand for cleaner food labels, there remains an opportunity to introduce new chelating technology to replace synthetically-derived EDTA. Through photographting and chemical conversion, hydroxamic acid ligands were covalently bound to polypropylene films resulting in polypropylene-graft-poly(hydroxamic acid) (PP-g-PHA). The resulting films demonstrated an ability to chelate 64 nmol/cm2 from an iron saturated environment or 163 nmol/cm2 of magnesium and 139 nmol/cm2 of calcium from bacterial growth media. A surface pKa of 8.97 suggested that film ligands should remain protonated under acidic and neutral pH conditions. When combined with lysozyme, PP-g-PHA films were able to reduce inhibitory concentration of lysozyme for Listeria monocytogenes by half. When tested against Bacillus cereus, Pseudomonas fluorescens, and E. coli O157:H7; PP-g-PHA films were unable to inhibit growth and showed little enhancement of lysozyme. EDTA controls revealed that similar levels of soluble chelator were more effective than immobilized chelators. EDTA results also suggested that a chelating film with a higher affinity for iron (through coordination or ligand stability) may be able to control B. cereus growth. Both EDTA and PP-g-PHA caused P. fluorescens to produce siderophores (pyoerdines), suggesting that each treatment resulted in a low-iron growth environment. These findings suggest that surface bound chelating technology can affect the growth of L. monocytogenes and enhance the effectiveness of lysozyme. With improved surface chemistry (a higher binding constant with iron), this technology has the potential to influence the growth of other pathogens and spoilage microorganisms.

For manufacturing companies, the supply chain operations can be very large. Both supplies and delivery to the end customer need to be strategically planned and executed. Inthis thesis, we have looked closer at one of the largest heavy vehicle brands in the world,Scania, and zoomed into a certain part of their supply chain. All parts that are in atruck have their origin, and from this origin, the parts are sent over and over again tothe production facilities of Scania as trucks and buses are being produced. To make surethat the flow of parts to the production units is as efficient as possible, Scania providesits own packaging to the suppliers, and that is what this thesis analyses.We investigate how Scania can make sure that their empty packaging is delivered to thesuppliers in the most cost and CO2 efficient way possible. We begin by describing thecurrent state of the packaging logistics network and what the transport flows look liketoday. From here, we describe the circumstances that are important for the supply chainoperations. Further on we describe theory related to the subject, such as various locationmodels, graphs, networks, and sustainability-related topics among other things. Withhelp from the presented theory and by data preprocessing, we are able to translate theproblem into a mixed integer linear program which tries to minimise the total transportation costs related to the distribution network of packaging. We present our findings anddiscuss the relevance of the results obtained. Finally, we give our recommendations andprovide suggestions for further studies within the area.

The physical supply chain relies on three components to transport products: the pallet, the package, and unit load stabilizers. The interactions between these three components can be investigated to understand the relationship between them to find potential optimization strategies. The relationship between corrugated boxes and pallets have been previously investigated and have found that the relationship can be used to reduce the quantity of material used in unit loads and can also reduce the cost per unit load if the package and pallet are designed using a systems approach. Although corrugated boxes are a common form of packaging, plastic pails are also used in packaging for liquids and powders, but they have not been previously investigated. To understand the interactions between the wooden pallet and plastic pails, physical tests were conducted and then used to create and validate a finite element model. The experiments were carried out in three phases. The first phase included physical testing of plastic pails where the deckboard gap and overhang support conditions would be isolated by using a rigid deckboard scenario. The second phase also used physical tests to investigate plastic pails but instead used flexible deckboards and used an overhang support condition and a 3.5 in. gap support condition. The third phase of experiments would develop and validate a finite element model to further understand the impact of deckboard gaps and overhang depending on the location of the gap. Previous physical experiments were used to create and validate the finite element model. Nonlinear eigen buckling analysis was used to model the plastic pail buckling failure that was seen in physical testing. The model based on the physical experiments was able to predict the behavior of the plastic pail within a range of 5-12% variation with higher variation being introduced when the flexible deckboard is introduced. The finite element model was then used to model a range of deckboard gap sizes and overhang sizes as well as different locations for deckboard gaps. The results of the experiments indicate that the percent of pail perimeter that is supported directly on the pallet impacts the compression strength of the plastic pail. Decreasing the quantity of support decreases the compression strength of the plastic pail in a linear pattern. The location of the deckboard gap also influenced the compression strength because of the quantity of pail being supported being altered. The results of the experiments can be used by industry members to provide guidelines on unit load design to prevent plastic pail failure. Industry members can also use the results as a baseline investigation and further the finite element model by incorporating their own plastic pail design. / Doctor of Philosophy / The physical movement of products relies on three main elements: pallets, packaging, and stabilizers for unit loads. Examining how these components interact helps uncover their relationships and potential strategies for optimization. Previous studies have explored the connection between corrugated boxes and pallets, revealing ways to reduce material usage and costs through a systems-based design approach. While corrugated boxes are commonly studied, plastic pails, used for liquids and powders, have not received similar attention. To understand the dynamics between wooden pallets and plastic pails, physical tests were conducted. The physical experiments illustrated the importance of investigating the relationship within unit loads but there are limitations that exist when doing physical experimentation such as time and materials. A finite element model is a mathematical model that can be used to simulate physical phenomenon to further understand physical interactions without having to conduct physical experiments. Using the results of the physical experiments that were conducted, a finite element model was developed to further investigate the system that exists between pails and pallets. The experiments occurred in three phases. The first phase focused on isolating deckboard gap and overhang support conditions using a rigid deckboard scenario in plastic pail testing. In the second phase, a pallet with flexible deckboards was used to explore overhang and a 3.5-in. gap support condition. The third phase involved creating and validating a finite element model to better grasp the impact of deckboard gaps and overhang, considering gap location. Previous physical experiments guided the model's development and validation. Nonlinear eigen buckling analysis simulated plastic pail buckling failure observed in physical tests. The model predicted plastic pail behavior within a 5-12% variation range, with greater variation when using flexible deckboards. This model explored various deckboard gap and overhang sizes, along with different gap location and found that the quantity of unsupported perimeter that the pail experiences affects the quantity of load that the pail can experience before achieving failure. These results are impactful to industry members because it quantifies the impact that pallets can have on their package. Understanding the interactions between the package and the pallet can also be used to create unit loads that are safer by quantifying the buckling load of plastic pails. Investigating plastic pails and the interactions between pallet components can lead to creating safer and better design unit loads in the industry.

Foamy viruses (FVs), like other retroviruses, have gained interest due to their applications as viral vectors in gene therapy and various other fields. Despite their potential applications, FV stands out as a unique retrovirus, with distinct features in its replicative cycle that make it a compelling subject of study. However, it remains one of the least studied retroviruses. A crucial aspect of the retroviral replicative cycle, especially for its use as in gene transfer, is the selective packaging of its viral genomic RNA (vgRNA) out of the vast pool of RNAs found in virus producing host cells. This process, known as vgRNA enrichment, involves efficiently packaging vgRNA among the cellular and processed viral genetic material. Unlike other retroviruses, the selective packaging process of vgRNA in FV has not been explored, making it largely unknown. Previous studies on other retroviruses have indicated that vgRNA packaging selectivity is achieved through specific features within the vgRNA itself, such as specific sequences elements called packaging signals as well as dimerization of vgRNA resulting in the presence of two copies vgRNA in each retrovirus particle. Additionally, viral structural proteins, particularly Gag, play a significant role by interacting with vgRNA through specific protein regions. To shed light on the selective packaging process of FV vgRNA, the roles of structural proteins Env, Pol, and Gag were investigated, along with the vgRNA's dimerization capacity. To quantify the vgRNA selective packaging, an enrichment assay (E-assay) and a competitive assay (C-assay) were established. The E-assay allows to compare FV vgRNA packaging efficiency relative to non-viral RNAs, whereas the C-assay enables the determination of the preferential packaging of one vgRNA over another when both are present within a cell. The results obtained regarding the role of the structural proteins on the vgRNA selective packaging emphasized the delicate balance required between viral protein expression and vgRNA levels. Overexpression of Env and Gag severely disrupted selective packaging. Particularly the excess of Env protein amount led to an increased production of subviral particles that lack the capability to selectively package vgRNA. An interesting observation was the impact of the RNA template used for translating Gag on vgRNA enrichment. Expressing Gag from vgRNA (cis) enhanced vgRNA packaging selectivity, while expression from an RNA containing only expression-optimized gag ORF sequences (trans) reduced vgRNA enrichment. Nevertheless, the results from the C-assays suggest that non-Gag-translating vgRNA can still be selectively packaged over non-selectively packable dimerization deficient vgRNA. This indicates that while Gag might have a cis-acting mechanism in FV vgRNA selective packaging, this role appears to be non-essential. As mentioned earlier, vgRNA dimerization appears to be a crucial factor in the selective packaging process of most retroviruses. In the case of FV, the dimerization process was previously reported to be facilitated by three specific regions on the vgRNA known as dimerization sites one to three (DS-I to -III). Among these sites, DS-II stands out as being indispensable for vgRNA dimerization due to its 10 nt palindromic sequence, a determinant reported to be essential for the interaction between the two strands of vgRNA for most retroviruses. To investigate the significance of FV vgRNA dimerization in its selective packaging, we conducted E- and C-assays to assess the vgRNA packaging efficiency and specificity in FV DS-II mutants, previously identified as non-dimerizing (DS-II-M6 and -M7) or exhibiting a low dimerization rate (DS-II-M2). Intriguingly, FV vgRNA packaging was significantly negatively affected in the non-dimerizing FV mutants (DS-II-M6 and -M7), and to a lesser extent in the DS-II-M2 mutant, where dimerization was reported of occur at lower rates. This reveals a direct correlation between vgRNA packaging efficiency and the reported vgRNA dimerization potential of these DS-II mutants. These results suggest that, similar to other retroviruses, vgRNA dimerization plays a pivotal role in FV's selective packaging. Furthermore, it is well-documented that secondary structures within vgRNA in some retroviruses facilitate dimerization, thereby enhancing the selective packaging process. In-silico analyses of the FV vgRNA predicted the formation of a stem loop created by the palindromic sequence (SL-Pal). To gain insight into the role of these secondary structures within the DS-II region of FV vgRNA in its selective packaging, we designed a series of new dimerization mutants. These mutants were meticulously engineered to disrupt, modify, or restore the SL-Pal structure by introducing mutations inside or in proximity to the palindromic sequence based on computational secondary structure prediction. Notably, we observed that the palindrome's sequence could be mutated, as long as the SL-Pal structure and G-C proportion along all the stem-loop were preserved in a manner identical to the original structure. This preservation was crucial to ensuring the selective packaging of vgRNA and maintaining viral infectivity. Lastly, the evaluation encompassing protein analysis, vgDNA quantification, and infectivity assessment conducted on DS-I and DS-II mutants revealed a significant decrease not only on vgRNA selective packaging but also on viral infectivity, Pol packaging, cleaving, and the RTr process in non-dimerizing mutants. This underscores the intricate interrelation of these processes, emphasizing their collective importance for successful viral production. In summary, the findings presented in this project represent a significant advancement in understanding FV vgRNA selective packaging and dimerization. They offer valuable and novel insights that contribute to the expansion of our knowledge about FV molecular biology and its potential applications as a viral transfer vector.:I. ACKNOWLEDGEMENTS I II. TABLE OF CONTENT III III. INDEX OF FIGURES VI IV. INDEX OF TABLES VIII 1 INTRODUCTION 1 1.1 Retroviruses 1 1.1.1 Taxonomy of retroviruses 2 1.1.2 General features of retroviruses 3 1.2 Foamy viruses 6 1.2.1 PFV virion structure and genome organization 8 1.2.2 Viral proteins 11 1.2.2.1 Gag 11 1.2.2.2 Pol 13 1.2.2.3 Env 15 1.2.3 Replication cycle 17 1.2.3.1 Early phase 18 1.2.3.2 Late phase 19 1.3 Selective packaging of retroviral vgRNA 20 1.3.1 selective vgRNA packaging in orthoretroviruses 20 1.3.1.1 Role of the capsid protein Gag on the selective vgRNA packaging 20 1.3.1.2 vgRNA packaging signals 22 1.3.1.3 vgRNA dimerization and selective packaging 23 1.3.1.4 Factors that determine the vgRNA fate 24 1.3.2 Selective packaging in Hepadnaviruses 26 1.3.3 Selective packaging in PFV 26 2 THESIS AIM 29 3 MATERIALS AND METHODS 30 3.1 Buffers and solutions 30 3.2 Enzymes 34 3.3 Commercial kits 34 3.4 Nucleic acids 35 3.4.1 Oligonucleotides 35 3.4.1.1 Oligonucleotides for cloning 35 3.4.1.2 Oligonucleotides for qPCR analysis 37 3.4.2 Plasmids 39 3.4.2.1 Plasmid constructs used in this project: 39 3.4.2.2 New plasmid constructs 42 3.5 Bacteria strains 52 3.6 Cell lines 52 3.7 Antibodies 53 3.8 Software and Devices 54 3.9 Consumables 56 3.10 Molecular Biology methods 56 3.10.1 Bacteria culture 56 3.10.2 Transformation of competent bacteria 57 3.10.3 Plasmid extraction 57 3.10.4 Molecular cloning 58 3.10.4.1 Polymerase Chain Reaction (PCR) 58 3.10.4.2 Plasmid digest 59 3.10.4.3 Fragment purification 59 3.10.4.4 Ligation 60 3.10.4.5 Transformation of ligated plasmid constructs 60 3.10.4.6 Plasmid preparation small-scale 61 3.10.4.7 Plasmid Sequencing 61 3.10.4.8 Plasmid quantification 61 3.10.4.8.1 Photometric quantification 61 3.10.4.8.2 Fluorometric quantification 62 3.1 Biochemistry methods 62 3.1.1 SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) 62 3.1.2 Semi-Dry Western Blot 63 3.1.3 Immunodetection 63 3.1.4 Quantification of viral proteins by Western Blot 63 3.2 Cell Culture and Virological Methods 64 3.2.1 Cell lines 64 3.2.2 Cell passaging 64 3.2.3 Calcium phosphate transfection 65 3.2.4 Harvest of viral particles 65 3.2.5 Cell harvesting 66 3.2.6 Viral infectivity determination 66 3.3 Molecular virology methods 67 3.3.1 Viral RNA extraction 67 3.3.2 Cellular RNA extraction 67 3.3.3 DNase treatment 68 3.3.4 RNA quantification by RT-qPCR 68 3.3.5 DNA quantification by qPCR 69 3.3.6 Enrichment assay (E-assay) 70 3.3.7 Competitive assay 72 3.3.8 Secondary RNA structure prediction 74 4 RESULTS 75 4.1 Establishment of methodologies for quantification of selective vgRNA packaging efficiency 75 4.1.1 Establishment of the Enrichment (E)-assay 75 4.1.1.1 Reference mRNA 75 4.1.1.2 Background subtraction 77 4.1.2 Establishment of the Competition (C)-assay 80 4.1.2.1 Silent mutants characterization 81 4.1.2.2 Primer design 83 4.2 Selective packaging in foamy virus 88 4.2.1 Role of the viral structural proteins on the selective vgRNA packaging 92 4.2.1.1 Role of Env on the selective vgRNA packaging 92 4.2.1.2 Role of Pol on the selective vgRNA packaging 97 4.2.1.3 Role of Gag on the selective vgRNA packaging 100 4.2.1.3.1 Gag cis-acting mechanism on the selective vgRNA packaging 103 4.2.2 Role of dimerization on the selective packaging 109 4.2.2.1 Characterization of the dimerization mutants 111 4.2.2.2 Selective vgRNA packaging and dimerization 114 4.2.2.3 PFV vgRNA secondary structure (prediction) and dimerization potential 118 4.2.2.4 Dimerization and RTr 124 5 DISCUSSION 129 5.1 Establishment of methodologies for vgRNA selective packaging determination 129 5.1.1 E-assay 129 5.1.2 C-assay 130 5.2 Viral factors involved in the FV vgRNA selective packaging 132 5.2.1 Selective packaging in PFV 132 5.2.2 Role of the structural viral proteins on the vgRNA selective packaging 133 5.2.2.1 Env 133 5.2.2.2 Pol 136 5.2.2.3 Gag 136 5.2.3 Role of vgRNA dimerization on its selective packaging 139 5.2.3.1 vgRNA DS-II secondary structure and dimerization 141 5.2.3.2 vgRNA dimerization and RTr 142 6 CONCLUSION 145 7 REFERENCES 146 8 APPENDICES 162 8.1 Abbreviations list 162 8.2 Anlage 1 165 8.3 Anlage 2 166

This research is focused on the processing of an innovative three-dimensional packaging architecture for power electronics building blocks with soldered device interconnections and subsequent characterization of the module's critical interfaces. A low-cost approach termed metal posts interconnected parallel plate structure (MPIPPS) was developed for packaging high-performance modules of power electronics building blocks (PEBB). The new concept implemented direct bonding of copper posts, not wire bonding of fine aluminum wires, to interconnect power devices as well as joining the different circuit planes together. We have demonstrated the feasibility of this packaging approach by constructing PEBB modules (consisting of Insulated Gate Bipolar Transistors (IGBTs), diodes, and a few gate driver elements and passive components). In the 1st phase of module fabrication with IGBTs with Si₃N₄ passivation, we had successfully fabricated packaged devices and modules using the MPIPPS technique. These modules were tested electrically and thermally, and they operated at pulse-switch and high power stages up to 6kW. However, in the 2nd phase of module fabrication with polyimide passivated devices, we experienced significant yield problems due to metallization difficulties of these devices. The under-bump metallurgy scheme for the development of a solderable interface involved sputtering of Ti-Ni-Cu and Cr-Cu, and an electroless deposition of Zn-Ni-Au metallization. The metallization process produced excellent yield in the case of Si₃N₄ passivated devices. However, under the same metallization schemes, devices with a polyimide passivation exhibited inconsistent electrical contact resistance. We found that organic contaminants such as hydrocarbons remain in the form of thin monolayers on the surface, even in the case of as-received devices from the manufacturer. Moreover, in the case of polyimide passivated devices, plasma cleaning introduced a few carbon constituents on the surface, which was not observed in the case of Si₃N₄ passivated devices. X-Ray Photoelectron Spectroscopy (XPS) Spectra showed evidence of possible carbon contaminants, such as carbide (~282.9eV) and graphite (~284.3eV) on the surface at binding energies below the binding energy of the hydrocarbon peak (C 1s at 285eV). Whereas above the hydrocarbon peak energy level, carbon-nitrogen compounds, single bond carbon compounds (~285.9eV) and double bond carbon compounds (~288.5eV) were evident. The majority of the carbon composition on the pad surface was associated with hydrocarbons, which were hydrophobic in nature, thus making the device contact pad less wettable. XPS data showed that, after the plasma cleaning process, absorbed monolayers on the Si₃N₄ passivated and polyimide passivated surfaces consisted of different chemical compositions and accordingly, the attraction forces of these absorbed layers are also different, which affects the bonding properties of the subsequent metallization, resulting in different contact resistances. On the other hand, with an electroless Zn-Ni-Au deposition, it was found that the polyimide passivation on the devices degraded due to due alkaline exposure in the plating baths, thus lowering the device breakdown voltage significantly. Furthermore, interfacial thermal resistances of solder preform, solder paste and silver epoxy (between the power module and the heat spreader) were characterized for process optimization. Void content at the resulting interface was found to be dependent on the flux content and flux activity. Solder preform with no-clean flux, reflowed in nitrogen results in the least resistant and minimized void-content interface. It is most likely that the flux added to the preform had a higher fluxing action than the flux contained in the solder paste. On the other hand, the outgassing of the entrapped flux profoundly affects the void formation and a lower void content indicates a lesser amount of trapped flux. In the case of a solder paste, the flux is in direct contact with the surface oxide of the powders and the surface to be soldered. Consequently, during reflow, any residual oxide can be expected to have some flux adhered to it. In the case of solder preform with added flux, the higher activity flux eliminated the oxide more rapidly and more thoroughly, thus leaving fewer spots for the flux to adhere to. Void contents in all cases of nitrogen reflow are consistently lower than the air-reflowed samples. Silver epoxy with a higher thermal conductivity (60W/mK) than Pb-Sn eutectic solder did not produce low-resistance interfaces. We found that thermal conductivity of the interface material is not the most crucial factor in reducing thermal resistance, rather it is the contact thermal resistance of the interfaces, which constitutes the largest part of the total interfacial thermal resistance. Process optimization with applied pressure and nitrogen reflow resulted in a significant lowering of contact resistance (from 0.55°C/W to 0.25°C/W) for the solder preform interfaces. We concluded that contact resistance needs to be duly accounted for in thermal modeling for an accurate representation of an interface; at the same time, the module attachment process must be tailored to reduce contact resistance for improved thermal management. / Ph. D.

Synthetic antioxidants have traditionally been added directly to food products in a single initial dose to protect against oxidation of lipids and generation of free radicals. Natural antioxidants have been shown to undergo loss of activity and become prooxidants at high concentrations; therefore, a need exists to develop active packaging which can gradually deliver antioxidants in a controlled manner. The objectives of this research were to (1) form and characterize cyclodextrin inclusion complexes with the natural antioxidants, alpha-tocopherol and quercetin, (2) incorporate cyclodextrin inclusion complexes of natural antioxidants into linear low density polyethylene (LLDPE), and (3) measure the release kinetics of inclusion complexes of natural antioxidants from LLDPE into a model food system. Cyclodextrin inclusion complexes of alpha-tocopherol and quercetin were formed by the coprecipitation method and characterized in the solid state by NMR, IR spectroscopy, and thermal analyses. Solid inclusion complex products of alpha-tocopherol:beta-cyclodextrin and quercetin:gamma-cyclodextrin had molar ratios of 1.7:1 as determined by UV spectrophotometry, which were equivalent to 18.1% (w/w) alpha-tocopherol and 13.0% (w/w) quercetin. Free and cyclodextrin complexed antioxidant additives were compounded with a twin-screw mixer into two LLDPE resin types followed by compression molding into films. Release of alpha-tocopherol and quercetin from LLDPE films into coconut oil at 30 °C was quantified by HPLC during 4 weeks of storage. The total release of alpha-tocopherol after 4 weeks was 70% from the free form and 8% from the complexed form averaged across both LLDPE resins. The mechanism by which alpha-tocopherol was released was modified due to its encapsulation inside the beta-cyclodextrin cavity within the LLDPE matrix as indicated by its diffusion coefficient decreasing by two orders of magnitude. Molecular encapsulation of natural antioxidants using cyclodextrins may be used as a controlled release mechanism within polymer food packaging to gradually deliver an effective antioxidant concentration to a food product, thereby, limiting oxidation, maintaining nutritional quality, and extending shelf life. / Ph. D.

Die attachment is one of the most important processes in the packaging of power semiconductor devices. The current die-attach materials/techniques, including conductive adhesives and reflowed solders, can not meet the advance of power conversation application. Silver paste sintering has been widely used in microelectronics and been demonstrated the superior properties. The high processing temperature, however, prevents its application of interconnecting power semiconductor devices. This research focuses processing and characterization of micron-scale and nanoscale silver paste for power semiconductor devices attachment. Lowering the processing temperature is the essential to implement sintering silver paste for power semiconductor devices attachment. Two low-temperature sintering techniques - pressure-assisted sintering micro-scale silver paste and sintering nanoscale silver paste without external pressure - were developed. With the large external pressure, the sintering temperature of micro-scale silver paste can be significantly lowered. The experimental results show that by using external pressure (>40MPa), the commercial micro-scale silver paste can be sintered to have eighty percent relative density at 240oC, which is compatible with the temperature of solder reflowing. The measured properties including electrical conductivity, thermal conductivity, interfacial thermal resistance, and the shear strength of sintered silver joints, are significantly better than those of the reflowed solder layer. Given only twenty percent of small pores in the submicron range, the reliability of the silver joints is also better than that of the solder joints under the thermal cycled environment. The large external pressure, however, makes this technique difficult to automatically implement and also has a potential to damage the brittle power semiconductor devices. Reducing silver particles in the paste from micro-size to nanoscale can increases the sintering driving force and thus lowers the sintering temperature. Several approaches were developed to address sintering challenges of nanoscale silver particles, such as particles aggregation and/or agglomeration, and non-densification diffusion at low temperature. These approaches are : nanoscale silver slurry, instead of dry silver powder, is used to keep silver particles stable and prevent their aggregation. Ultrasonic vibration, instead of conventional ball milling, is applied to disperse nanoscale silver particles in the paste from to avoid from agglomerating. Selected organics in the paste are applied to delay the onset of mass-diffusion and prevent non-densification diffusion at low temperature. The measured results show that with heat-treatment at 300oC within one hour, the sintered nanoscale silver has significantly improved electrical and thermal properties than reflowed solders. The shear strength of sintered silver interconnection is compatible with that of solder. The low-temperature sinterable nanoscale silver paste was applied to attach the bare Silicon carbide (SiC) schottky barrier diode (SBD) for high temperature application. Limited burn-out path for organics in the silver layer challenges the sintering die-attach. This difficulty was lessened by reducing organics ratio in the silver paste. The effects of die-size and heating rate on sintering die-attach were also investigated. The single chip packaging of SiC SBD was fabricated by sintering die-attach and wire-bonding. The tested results demonstrate that the sintering nanoscale silver paste can be applied as a viable die-attach solution for high-temperature application. / Ph. D.

The global supply chain has been built on the material handling capabilities provided by the use of pallets and corrugated boxes. Current pallet design methodologies frequently underestimate the load carrying capacity of pallets by assuming they will only carry uniformly distributed, flexible payloads. But, by considering the effect of various payload characteristics and their interactions during the pallet design process, the structure of pallets can be optimized. This, in turn, will reduce the material consumption required to support the pallet industry. In order to understand the mechanical interactions between stacked boxes and pallet decks, and how these interactions affect the bending moment of pallets, a finite element model was developed and validated. The model developed was two-dimensional, nonlinear and implicitly dynamic. It allowed for evaluations of the effects of different payload configurations on the pallet bending response. The model accurately predicted the deflection of the pallet segment and the movement of the packages for each scenario simulated. The second phase of the study characterized the effects, significant factors, and interactions influencing load bridging on unit loads. It provided a clear understanding of the load bridging effect and how it can be successfully included during the unit load design process. It was concluded that pallet yield strength could be increased by over 60% when accounting for the load bridging effect. To provide a more efficient and cost-effective solution, a surrogate model was developed using a Gaussian Process regression. A detailed analysis of the payloads' effects on pallet deflection was conducted. Four factors were identified as generating significant influence: the number of columns in the unit load, the height of the payload, the friction coefficient of the payload's contact with the pallet deck, and the contact friction between the packages. Additionally, it was identified that complex interactions exist between these significant factors, so they must always be considered. / Doctor of Philosophy / Pallets are a key element of an efficient global supply chain. Most products that are transported are commonly packaged in corrugated boxes and handled by stacking these boxes on pallets. Currently, pallet design methods do not take into consideration the product that is being carried, instead using generic flexible loads for the determination of the pallet's load carrying capacity. In practice, most pallets carry discrete loads, such as corrugated boxes. It has been proven that a pallet, when carrying certain types of packages, can have increased performance compared to the design's estimated load carrying capacity. This is caused by the load redistribution across the pallet deck through an effect known as load bridging. Being able to incorporate the load bridging effect on pallet performance during the design process can allow for the optimization of pallets for specific uses and the reduction in costs and in material consumption. Historically, this effect has been evaluated through physical testing, but that is a slow and cumbersome process that does not allow control of all of the variables for the development of a general model. This research study developed a computer simulation model of a simplified unit load to demonstrate and replicate the load bridging effect. Additionally, a surrogate model was developed in order to conduct a detailed analysis of the main factors and their interactions. These models provide pallet designers an efficient method to use to identify opportunities to modify the unit load's characteristics and improve pallet performance for specific conditions of use.

In the supply chain there are three components: transportation method, the pallet, and the packaging. Traditionally, there has been a poor understanding of the way that pallet design can impact the supply chain. There are historical studies that illustrate the importance of investigating how box stacking pattern, unit load type, unit load size, and containment can impact the pallet's performance. However, there have been no studies that have investigated the impact of drums and plastic pails on pallet performance. The goal of the current research study was to investigate how plastic pails and drums affect pallet bending and the distribution of the pressure on the top surface of the pallet. The investigation was conducted using four different support conditions commonly found in warehouses: racking across the width and length, single stacking, and double stacking. The results of the investigation indicated that for most support conditions, loading the pallet with plastic pails or drums results in a significant reduction in deflection when compared to a uniformly distributed load. The maximum observed reduction in pallet deflection was 85% when testing with drums in the double stack condition and 89% when testing with plastic pails in the single stack condition. The large reductions in deflection could indicate that the pallets were over-designed for the unit load that they were supporting. Pressure mat distribution images collected during the experiment display a load bridging effect where the stress of the drums and pails are redistributed to the supported sides of the pallet. The data also show that drums made of different materials distribute the pressure onto the pallet in a significantly different manner. / Master of Science / Wood pallets are crucial to the supply chain that delivers the goods and objects that sustain our economy. Every product order or product that is seen in stores was sent through the supply chain. The supply chain is made up of three major interacting components, the material handling system, the packaging, and the pallet. By further understanding the interaction between these components, pallet and packaging designers can better utilize materials and maximize the efficiency of the supply chain. There is a need to understand how different types of packages interact with the pallet to effectively design pallets and to potentially reduce costs and material usage. Historical studies focused on investigating how corrugated boxes affect pallet performance. They mainly focused on the effect of corrugated box size, flute type, stretch wrapping and containment, and the influences that pallet design have on pallet performance. Past studies identified that packages on the top of the pallet could create a bridging between the packages that can reduce the stresses on the pallet and consequently increase its load capacity. By using this load bridging effect for their advantage, pallet designers can design pallets that are safer, cheaper, and be more environmentally friendly since current wood pallets are designed under the assumption of a uniformly distributed, rather than bridged, load. The goal of the current study was to investigate how the load bridging effect created by pails and drum affects the deflection of the pallet in the floor stacked loading condition. The investigation was conducted using four different support conditions commonly found in warehouses such as racking across the length, racking across the width, single stacking, and double stacking. The results of the investigation indicated that for most investigated support conditions, the interaction between pails and drums causes an increase in load bridging which significantly reduces the bending of the pallet. The reductions reached a maximum of 85% when testing with drums in the double stack condition and 89% when testing with plastic pails in the single stack condition. The large reductions in deflection could indicate that the pallets were over-designed for the unit load that they were supporting.