No description available.

No description available.

No description available.

No description available.

No description available.

Current trends in electronics are toward the use of reduced voltages. In the past, 5 V and higher voltages have been the standard, however, currently, 3.3V and 2.5V circuits are becoming increasingly common. While the operating voltage is decreasing, electronic systems are becoming more complex. The net result is that in many, cases, the current required by the next generation of electronics will be far greater than in the past. These increased currents and low voltages pose dramatic problems for designers not the least of which is the effect of electronic packaging and circuit implementation on the overall power supply performance. In addition, for many applications, space and weight are at a premium and converters are needed to power low voltage circuit assemblies that are highly efficient, low in weight, and small in total height and foot print. This dissertation addresses these trends and needs through the design, fabrication and evaluation of a 3.3V DC/DC converter. Designs of 3.3V, 2.5V, and 1.5V are presented and evaluated while a 3.3V, 100 watt converter with a power density of 157 watts/in³ has been fabricated and evaluated in a miniature form. This converter utilizes a implementation strategy developed by the author which was selected due to its ability to handle the current levels required and its compact size. Specific contributions of this work include: • Analysis of the effects of packaging on low voltage high current converters in order to provide a guideline for converter implementation. This analysis has been performed for 3.3 V, 2.5 V, and 1.5 V designs, respectively. • Development of high efficiency 2.5 V, 100 watt and 1.5 V, 75 watt designs based on previously reported half bridge topologies. • Development of a packaging strategy which allows the fabrication of low voltage compact converters with high efficiency. A 3.3 V converter has been fabricated and with the simulated data validated these experimental results. For very low (less than 50 watts and / or less than 10 amps) and high power levels (hundreds of amps or kilowatts), the implementation strategy is normally clear; PCB/IMS, and DBC respectively. However, for applications in the middle range of power or current level, the optimum implementation is often unclear. The question that this work seeks to answer is under what conditions are different implementation schemes most suitable. / Ph. D.

Corrugated paper boxes are the predominant packaging and shipping material and account for the majority of packaging refuse by weight. Wooden pallets are equally predominant in shipping, transportation and warehousing logistics. The interaction between these two components is complex and unexplored leaving industry to compensate with outdated component specific safety factors. Providing a focused exploration of the box and pallet interaction will open the door for holistic design practices that will reduce cost, weight, damage, and safety incidents. This study was separated into four chapters exploring different aspects of the corrugated box to pallet interaction. The first chapter evaluates the support surface provided by a pallet consists of deckboards spaced perpendicular to the length of the pallet. The resulting gaps between deckboards reduce the support to the box. Gaps were limited to 55% of box sidewall length for practical reasons. The effect of gaps was significant and produced a nonlinear reduction in box strength. Small boxes were more susceptible to gaps than larger boxes. Moving the gap closer to the corner increased its effect while increasing the number of gaps did not increase the effect. A modification to the McKee equation was produced that was capable of predicting the loss in strength due to gaps. The equation is novel in that is modifies a widely used equation and is the first such equation capable of handling multiple box sizes. This study also has practical implications for packaging designers who must contend with pallet gap. Chapter 2 explores the relationship between deckboard deflection and box compression strength. Testing found that reducing the stiffness of the deckboard decreases the compression strength of the box by 26.4%. The location of the box relative to the stringer also had varying effects on the box strength. A combination of deckboard stiffness and gaps produced mixed with results with gaps reducing the effect of stiffness. It was observed that lower stiffness deckboards not only deflect but also twist during compression. The torsion is suspected to have a significant influence on compression but further exploration is needed. The third chapter tests the effect of box flap length on box compression strength under various support conditions. Variables included four flap lengths, gaps between deckboards, low stiffness deckboards, column stacking and misaligned stacking. The results show that the box flaps can be reduced by 25% with no significant effect of box strength under any support condition tested. Furthermore, the box flap can be reduced by 50% with less than 10% loss in compression strength under all scenarios. These results have significant sustainability implication as 25% and 50% reduction in box flap reduce material usage by approximately 12% and 24%, respectively. In the fourth and final chapter, the theory of beam-on-elastic foundation is applied to deckboard bending and corrugated boxes. In this model the corrugated box acts and the foundation and the deckboard is the beam. Rotational stiffness, load bridging, and foundation stiffness changes required the development of novel testing solution and model development. The model was capable of predicting the distribution of force along the length sidewall but was not capable of predicting the ultimate strength of the box. The model developed in the study will be applicable in determining potential weakness in the unit load in addition to optimizing those that are over designed. These four chapters represent a considerable contribution of applicable research to a field that relied on outdated safety factors over thirty years. These safety factors often lead to costly over design in an industry where corrugated box and pallets volumes make event the smallest improvements highly beneficial. Furthermore, this research has opened the door for significant additional research that will undoubtedly provided even greater economic and sustainability benefits. / Ph. D.

Fluorescent light exposure has well documented negative effects on fluid milk through oxidation reactions. A shift to light-emitting diode (LED) lights in retail dairy cases has occurred due to increased energy efficiency, but the effects of LED light on fluid milk are not known. The objective was to study the interaction of light protective additives (LPA) with a high oxygen barrier package under fluorescent and LED lighting conditions simulating a retail refrigerated dairy case. The extent of oxidation in 2% milk packaged in polyethylene terephthalate (PET) packages with different light interference properties (UV barrier, 2.1% titanium dioxide (TiO2) LPA, 4.0% TiO2 LPA, 6.6% TiO2 LPA) under light exposure up to 72h was compared to control packages (light-exposed, light-protected). Chemical measures of oxidation included dissolved oxygen content, formation of secondary lipid oxidation products, riboflavin degradation, and volatile analysis by electronic nose. Changes in dissolved oxygen content were associated closely with oxidation changes in milk over 72h. PET with 6.6% TiO2 was the most successful package, based on triangle test methodology, protecting milk sensory quality similar to light-protected milk through 8h LED light exposure. Based on a 9-point hedonic scale, (1=dislike extremely, 9=like extremely), consumers liked milk stored under LED light more (α=0.05; 6.59 ± 1.60) than milk stored under fluorescent light (5.87 ± 1.93). LED light is less detrimental to milk quality than fluorescent light and PET with high levels of TiO2 can protect milk quality for short periods of time under typical retail storage conditions. / Master of Science in Life Sciences

The objective of this study was to use MAP technology to produce safe, shelf-stable, high quality, hard grated cheeses not requiring preservatives or refrigeration during distribution and sale. Initially, a challenge study with Staphylococcus aureus (S. aureus) was conducted to determine the water activity (Aw) level of high-moisture cheeses necessary to prevent the growth of a food pathogen when packaged under a modified atmosphere (25% CO, and 75% N,). Other microbial analysis included mold and yeast enumerations. Secondly, product quality and shelf stability were determined biweekly by sensory, microbial, and instrumental analysis to evaluate product safety and changes in the natural aromas and flavors of hard grated cheeses. Instrument color analysis CIE L* a* b* values were determined to measure color changes. Parmesan cheese with high Aw levels (Aw= 0.90 and 0.88) supported the growth and survival of S. aureus. The microorganism was incapable of surviving at Aw levels of 0.86 and below. S. aureus was not able to survive on Romano cheese. Mold and yeast proliferated on higher Aw Parmesan cheeses. Visible mold was detected on the Parmesan sample of Aw= 0.90 after 8 weeks of storage. No mold growth was observed on Romano cheese. However, yeast were capable of growing on Romano cheese. The sensory evaluation study of hard grated cheeses was unable to detect a difference between the fresh cheese sample and the cheeses packaged under MAP. / Master of Science

Milk is often packaged in translucent containers providing little protection against flavor degradation from light. The effectiveness of TiO2 modifications of high density polyethylene (HDPE) packaging in affecting light-induced oxidation of extended shelf-life milk (2% total fat) and omega-3 fatty acid enriched milk (2% total fat) was studied. Packaging effectiveness was determined by assessing product quality, including changes in flavor, measuring changes in volatile compounds, thiobarbituric reactive substances and riboflavin concentrations.  Products were evaluated over a 35-day shelf-life when stored under fluorescent light (2200 lux) at 4"C. HDPE packaging included clear (no TiO2) serving as control (light exposed: no light barrier, light protected (foil overwrap) and three different TiO2 levels (low, medium, high) for the experimental treatments (total of five packaging treatments). TBARS was a good predictor of the perception of changes in sensory characteristics in 2% milk.. Under the experimental conditions used, a TBARS value of 1.3 mg/L could be considered the limiting sensory threshold for oxidized milk. Riboflavin concentration decreased by 10.5% in the light-protected control over 36 days and 28.5% in the high TiO2 packaged 2% milk, but losses were greater than 40% for all other packages. In omega-3 enriched milk, the high TiO2-HDPE package provided greater protection of sensory quality and riboflavin than clear, low and medium TiO2 packaging. However riboflavin decreased by 28% even in the light protected control which is a higher loss than observed in 2% fluid milk without omega-3 lipids. TBARS was greater than 4 mg/L in all products, including the light-protected control within three days, suggesting that oxidative stability was low. Omega-3 milk packaged in clear HDPE package exceeded MDA of 3 mg/L by day 7, suggesting the milk would have changes in sensory quality related to oxidation. The high TiO2 package protected riboflavin concentration from degradation and controlled MDA concentration the best of the TiO2 treatments through the test period in both fish oil enriched and non-enriched products. / Master of Science in Life Sciences