The open bin packing problem (OBPP) is a new variant of the well-known bin packing problem. In the OBPP, items are packed into bins so that the total content before the last item in each bin is strictly less than the bin capacity. The objective is to minimize the number of bins used. The applications of the OBPP can be found in the subway station systems in Hong Kong and Taipei and the scheduling in manufacturing industries. We show that the OBPP is NP-hard and propose two heuristic algorithms instead of solving the problem to optimality. We propose two offline algorithms in which the information of the items is known in advance. First, we consider the First Fit Decreasing (FFD) which is a good approximation algorithm for the bin packing problem. We prove that its asymptotic worst-case performance ratio is no more than 3/2. We observe that its performance for the OBPP is worse than that of the BPP. Consequently, we modify it by adding the algorithm that the set of largest items is the set of last items in each bin. Then, we propose the Modified First Fit Decreasing (MFFD) as an alternative and prove that its asymptotic worst-case performance ratio is no more than 91/80. We conduct empirical tests to show their average-case performance. The results show that in general, the FFD and MFFD algorithms use no more than 33% and 1% of the number of bins than that of optimal packing, respectively. In addition, the MFFD is asymptotically optimal when the sizes of items are (0,1) uniformly distributed. / Ph. D.

Salmonella has been shown to survive in soils for extended periods. Anaerobic soil disinfestation (ASD) represents a promising alternative to fumigation used to manage soilborne diseases and pests; however, little is known about ASD's impact on Salmonella. The study aimed to compare Salmonella die-off following inoculation in ASD and non-ASD processed soil and compare Salmonella die-off in amended and non-amended soils following ASD. Two independent experiments were arranged in randomized complete block designs (four replications per treatment). Sandy-loam soil was inoculated with a Salmonella cocktail (5.5±0.2 log CFU/g) and amended with field-applicable rates of rye (R), rapeseed (RS), hairy vetch (HV), or pelletized poultry litter (PPL). Non-amended, anaerobic (ANC) and non-amended, aerobic controls (AC) were performed in parallel. Soils were irrigated to saturation and covered with plastic mulch. ASD was terminated by removal of plastic (3-weeks). Triplicate soil samples were collected pre-ASD and 0, 1, 2, 3, 7, 10, 14, 21, 28, 31, 35, 38 and 42d post-ASD. Post-ASD soil was irrigated weekly. Salmonella was quantified using standard methods and a modified MPN enrichment protocol. Concentrations between treatments and time-points were analyzed for significance (P≤0.05). Separate log-linear models were used to examine effect of amendment and irrigation on Salmonella die-off during ASD and post-ASD. Salmonella concentrations decreased in all treatments during ASD with the greatest decrease being observed in ASD and non-ASD controls. Among ASD-processed, amended soil, the rye and rapeseed amendments had the greatest decrease in Salmonella concentrations. Salmonella concentrations decreased by ~1 log between pre-ASD and post-soil saturation (95% Confidence Interval (CI) =-1.31, -0.99), and by approximately 2 logs between pre-ASD and termination of ASD (CI=-2.14, -1.83). Salmonella concentrations were ~1 log higher in ASD-processed, pelletized poultry litter-amended soil, compared to the ASD control (CI=0.81, 1.26). The average daily die-off rate of Salmonella post-ASD was -0.05 log per g (CI=-0.05, -0.04). Following irrigation, Salmonella concentrations were 0.14 log greater, compared to no irrigation within 7 d (CI=0.05, 0.23). Salmonella serovar distribution differed by treatment, with >70% survival of Newport in pelletized poultry litter. ASD does not eliminate Salmonella concentrations in soil; instead some amendments may enhance Salmonella survival. / Master of Science in Life Sciences / Anaerobic soil disinfestation (ASD) is the process of removing soilborne weeds, soilborne diseases and insect by creating an anaerobic environment in the soil by incorporating easily decomposable soil amendments, covering with plastic mulch, and irrigating to saturation. The anaerobic soil environment persists for two- to six-weeks. ASD represents a promising alternative to fumigation used to manage soil-borne diseases and pests. However, little is known about ASD's impact on Salmonella, which has been shown to survive in soils for extended periods of time and can contaminate the edible part of produce. This study aimed to determine if ASD is an effective strategy to reduce or eliminate Salmonella from soils that contain typical amendments added to promote soil health, determine the distribution of Salmonella serovars in ASD treated soils, and examine the impact of irrigation. Two independent experiments were conducted in growth chambers. A common soil type in produce growing regions of the Eastern Shore of VA, sandy-loam soil was inoculated with a five-serovar Salmonella cocktail (~5.5±0.2 log CFU/g) and mixed with field-applicable rates of rye, rapeseed, hairy vetch, or pelletized poultry litter. ASD processed soils were irrigated to field saturation, covered with plastic mulch, and left for 3 weeks. Post-ASD, soils were irrigated weekly. Salmonella was quantified at least once per week for up to 6 weeks in soil samples collected in triplicate pre-ASD, post-field saturation, and post-ASD. The three-week anaerobic soil environment, created during ASD, allowed for greater Salmonella survival, compared to the aerobic soil environment. Salmonella survival in ASD processed soil was dependent on amendment. Salmonella concentrations decreased in all treatments during ASD with the greatest decrease being observed in ASD and non-ASD controls. Among ASD-processed, amended soil, the rye and rapeseed amendments had the greatest decrease in Salmonella concentrations. Pelletized poultry litter amended soil, in combination with ASD, had the highest Salmonella concentration, while rye had the lowest at each time-point post-ASD. Salmonella serovar distribution differed by treatment with greater survival of S. Poona in rye, S. Braenderup in hairy vetch and S. Newport in pelletized poultry litter. , Salmonella concentrations were 0.14 log greater, compared to no irrigation within 7 d. Overall, ASD did not eliminate Salmonella in soils. Compared to non-ASD processed soil, ASD processed soil had greater survival of Salmonella and the soil amendment used influenced the survival ability. While more research is needed on ASD and different soil amendments, the findings of this research would suggest pelletized poultry litter not be used as an amendment (i.e., carbon source in ASD) for fields used to grow produce eaten raw, especially when soils are potentially contaminated with Salmonella.

A significant number of studies address various aspects related to tire modeling; most are dedicated to the development of tire models for on-road conditions. Such models cover a wide range of resolutions and approaches, as required for specific applications. At one end of the spectrum are the very simple tire models, such as those employed in real-time vehicle dynamic simulations. At the other end of the spectrum are the very complex finite element models, such as those used in tire design. In between these extremes, various other models have been developed, at different levels of compromise between accuracy and computational efficiency. Existing tire models for off-road applications lag behind the on-road models. The main reason is the complexity added to the modeling due to the interaction with the soft soil. In such situations, one must account for the soil dynamics and its impact on the tire forces, in addition to those aspects considered for an on-road tire. The goal of this project is to develop an accurate and comprehensive, while also efficient, off-road tire model for soft soil applications. The types of applications we target are traction, handling, and vehicle durability, as needed to support current army mobility goals. Thus, the proposed approach is to develop a detailed semi-analytical tire model for soft soil that utilizes the tire construction details and parallels existing commercially available on-road tire models. The novelty of this project relies in developing a three-dimensional three-layer tire model employing discrete lumped masses and in improving the tire-soil interface model. This will be achieved by enhancing the resolution of the tire model at the contact patch and by accounting for effects and phenomena not considered in existing models. / Master of Science

NAND flash-based Solid State Devices (SSDs) provide high performance and energy efficiency and at the same time their capacity continues to grow at an unprecedented rate. As a result, SSDs are increasingly being used in high end computing systems such as supercomputing clusters. However, one of the biggest impediments to large scale deployments is the limited erase cycles in flash devices. The natural skewness in I/O workloads can results in Wear imbalance which has a significant impact on the reliability, performance as well as lifetime of the cluster. Current load balancers for storage systems are designed with a critical goal to optimize performance. Data migration techniques are used to handle wear balancing but they suffer from a huge metadata overhead and extra erasures. To overcome these problems, we propose an endurance-aware write off-loading technique (EWO) for balancing the wear across different flash-based servers with minimal extra cost. Extant wear leveling algorithms are designed for a single flash device. With the use of flash devices in enterprise server storage, the wear leveling algorithms need to take into account the variance of the wear at the cluster level. EWO exploits the out-of-place update feature of flash memory by off- loading the writes across flash servers instead of moving data across flash servers to mitigate extra-wear cost. To evenly distribute erasures to flash servers, EWO off-loads writes from the flash servers with high erase cycles to the ones with low erase cycles by first quantitatively calculating the amount of writes based on the frequency of garbage collection. To reduce metadata overhead caused by write off-loading, EWO employs a hot-slice off-loading policy to explore the trade-offs between extra-wear cost and metadata overhead. Evaluation on a 50 to 200 node SSD cluster shows that EWO outperforms data migration based wear balancing techniques, reducing up to 70% aggregate extra erase cycles while improving the write performance by up to 20% compared to data migration. / Master of Science / Exponential increase of Internet traffic mainly from emerging applications like streaming video, social networking and cloud computing has created the need for more powerful data centers. Datacenters are composed of three main components- compute, network and storage. While there have been rapid advancements in the field of compute and networking, storage technologies have not advanced as much in comparison. Traditionally, storage consists of magnetic disks with magnetic parts which are slow and consume more power. However, Solid State Disks (SSDs) offer both better performance and lower energy. With the price of these SSDs being comparable to magnetic disks, they are increasingly being used in storage clusters. However, one of the biggest drawback of SSDs is the limited program erase (P/E) cycles. There is a need to ensure the uniform wearing of blocks in a SSD. While solutions for this do exist for a single SSD device, usage of these devices in a cluster poses new problems. This work introduces EWO which is a wear balancing algorithm that balances wear in a flash storage cluster. It carried out load balancing in a flash storage cluster while incorporating the wear characteristics as a cost function. EWO carries out lazy data migration also referred to as write offloading. To alleviate the metadata overhead, the migration is performed at the slice level. To evaluate EWO, a distributed key value store emulator was built to simulate the behavior of an actual flash storage cluster.

The nation's Section 404 permitting program, of the Clean Water Act (CWA), represents one of the longest regulatory histories of designing and implementing credit trading programs to satisfy regulatory requirements. The role and the function of in-lieu fee (ILF) programs in supporting this regulatory structure have undergone a substantial change. For the first time in the history of the Sec. 404 program, 33 CFR Part 332 and 40 CFR Part 230, Subpart J (the "2008 mitigation rule" or "rule"), prioritizes the use of off-site mitigation over on-site-mitigation. Additionally, the rule prioritizes advanced, third-party mitigation; especially as achieved through mitigation banks; over any off-site compensatory mitigation provided by ILF programs (33 CFR 332.3(b)(1)). This new regulatory environment favors the use of commercial mitigation bank credits while acknowledging that the limited permittee demand of off-site mitigation credits, in particular areas, justifies the continuing need for ILF programs (Corps and EPA 2008, p.19606,19611). This research examines how regulatory officials use ILF programs under the 2008 mitigation rule, and, it determines the extent to which ILF programs are capable of fulfilling the role envisioned for them under the 2008 mitigation rule. Simulation results indicate that commercial mitigation banks cannot meet risk adjusted returns under limited credit demand conditions. ILF programs offer some additional financial capacity to fill the void in commercial bank coverage; but, this potential is limited in low demand conditions. Furthermore, empirical case studies of a Virginia and Georgia provide evidence that regulatory officials rely on ILF programs to provide off-site compensatory mitigation almost exclusively in the absence of private credit supply, as intended in the 2008 rule. Evidence in Georgia and Virginia also indicate that, in some situations, ILF programs face difficulties in providing mitigation under the constraints of limited demand and more stringent regulatory requirements. / Master of Science / National permitting programs require people that impact wetlands or streams to offset unavoidable, adverse impacts by improving wetlands or streams elsewhere, a process called compensatory mitigation. A new regulatory rule, approved in 2008 (33 CFR Part 332 and 40 CFR Part 230, Subpart J), prioritizes that mitigation is provided at larger projects off-site of the impact. Key policy questions of “who should provide the mitigation?” and “when the mitigation should be provided” were an important part of the debate during the rule’s development. Wetland and stream mitigation may be provided by commercial (for profit) businesses, called mitigation banks. Commercial banks make wetland/stream improvement projects before permitted (adverse) impacts occur in anticipation of selling wetland/stream “credits” (quantified levels of improvement). Off-site mitigation may also be provided by in-lieu fee (ILF) programs operated by the government or nonprofit organizations. ILF programs first accept funds from permittees and then construct mitigation projects once sufficient funds have been collected, thus creating a lag between adverse impact and compensatory mitigation. The 2008 regulatory rule favors the use of commercial mitigation bank credits over ILF credits, but allows regulatory officials, under certain circumstances, to use ILF credits when commercial bank credits of the appropriate type are unavailable. This research examines how regulatory officials use ILF programs, and it investigates the extent to which ILF programs are financially capable of providing off-site mitigation in situations where the appropriate commercial credits are unavailable. A financial simulation model is developed to examine the feasibility of mitigation projects under different costs and credit demand conditions. Results indicate that commercial mitigation banks cannot meet financial objectives under limited credit demand conditions. ILF programs offer some additional financial capacity to fill the void in commercial bank coverage, but ILF programs also face financial limitations under conditions with low demand for credits. Empirical case studies of Virginia and Georgia provide evidence that regulatory officials rely on ILF programs to provide off-site compensatory mitigation almost exclusively in the absence of a private credit supply, as intended in the 2008 rule. However, evidence in Virginia and Georgia also affirm that ILF programs face difficulties in providing mitigation in some situations of limited demand and stringent regulatory requirements.

The high costs and high risks of transporting fuel to combat zones make fuel conservation a dire need for the US military. A towable hybrid electric system can help relieve these issues by replacing less fuel efficient standalone diesel generators to deliver power to company encampments. Currently, standalone generators are sized to meet peak demand, even though peak demand only occurs during short intervals each day. The average daily demand is much less, meaning generators will be running inefficiently most of the day. In this thesis, a simulation is created to help determine an optimal system design given a load profile, size and weight constraints, and relocation schedule. This simulation is validated using test data from an existing system. After validation, many hybrid energy components are considered for use in the simulation. The combination of components that yields the lowest fuel consumption is used for the optimal design of the system. After determining the optimal design, a few design parameters are varied to analyze their effect on fuel consumption. The model presented in this thesis agrees with the test data to 7% of the measured fuel consumption. Sixteen system configurations are run through the simulation and their results are compared. The most fuel efficient system is the system that uses a 3.8kW diesel engine generator with a 307.2V, maximum capacity LiFeMgPO? battery pack. This system is estimated to consume 21% less fuel than a stand-alone generator, and up to 28% less when solar power is available. / Master of Science

Nature reserves affect the local environment and communities. I use household data from the Chinese Household Income Project (CHIP) to estimate the impacts of nature reserves on several aspects of rural households: migration, local off-farm work, and off-farm income. This thesis also examines the heterogeneous impacts of nature reserves across administrative levels, lengths of existence time, and types. To reduce selection bias, propensity scores matching (PSM) is carried out to match counties with nature reserves to counties that have a similar possibility of establishing nature reserves, but that do not yet have any. Considering that counties with nature reserves might affect their neighboring counties without nature reserves, I construct two additional samples: one that excludes adjacent counties, and the other that generates new indicators for adjacent counties to check spillover effects directly. I use models with year fixed effects and county fixed effects to estimate the impacts across samples. The estimation results show that national nature reserves (NNRs) generally decrease the possibility of migration, while the impact depends on how long the NNRs have been in place. In the short run, NNRs increase migration. Forest NNRs significantly decrease migration but increase participation in local off-farm work and off-farm income. Nonforest NNRs have positive influences on migration and off-farm income. Although both forest and nonforest NNRs increase off-farm income, the sources might be different. The off-farm income increase in counties with forest NNRs might come from local off-farm work because forest NNRs encourage local off-farm work. The off-farm income increase in counties with nonforest NNRs might come from migration work because nonforest NNRs increase migration. Provincial nature reserves (PNRs) increase the likelihood of migration and the estimates also imply that PNRs only have short-run impacts on the local communities. Forest PNRs increase migration while nonforest ones decrease migration. PNRs generally decrease participation in local off-farm work and off-farm income, except for nonforest PNRs increase both of them. The results indicate that nature reserves of different administrative levels and lengths of existence time negatively affect local off-farm participation and off-farm income. These results imply that nature reserves in China during 2002-2013 had overall negative impacts on the local livelihood. / M.S. / Nature reserves are a crucial ecological policy in China for protecting endangered species and the environment. There is no doubt that nature reserves are beneficial to the environment. However, the multi-faceted social impacts of the establishment of nature reserves on the local households are unclear. This thesis studies the impacts of nature reserves on migration, participating in local off-farm work, and household off-farm income. I obtained household data from the Chinese Household Income Project (CHIP). The selection of nature reserves' locations is nonrandom: counties with nature reserves and those without are different in geographic characteristics, such as the distances to the nearest provincial capital and prefecture, average slope, and average elevation, which could be correlated with local economic development. Without eliminating those differences, the results will be misleading when comparing counties with nature reserves with those without nature reserves. This thesis considers the heterogeneous impacts of nature reserves across administrative levels, lengths of existence time, and types. Considering that counties with nature reserves might also affect their adjacent counties without nature reserves, I construct two additional samples: one that excludes adjacent counties and the other that generates new indicators for adjacent counties to measure the spillover effects directly. The results show that different designations of nature reserves have various impacts on migration. National nature reserves (NNRs) decrease migration, while provincial nature reserves (PNRs) generally increase migration. In the short run, NNRs increase migration and PNRs also increase migration. In general, nature reserves across different administrative levels and lengths of existence time all decrease local off-farm participation and off-farm income. This result implies that nature reserves in China during 2002-2013 had overall negative impacts on the local livelihood in the aspects of participation in local off-farm work and off-farm income.

Understanding the effects of various wheel parameters on tractive performance is not completely understood. In order to properly quantify the individual effects of wheel parameters on the mobility of rigid and flexible wheels in soft soil, tests were performed, in cooperation with NASA Glenn Research Center (NASA-GRC), using the terramechanics rig at the Virginia Tech Advanced Vehicle Dynamics Lab (AVDL). To conduct such a study, four different wheels were evaluated under similar normal loads, slip ratios, and soil density. The first wheel represents the baseline, against which all the others were benchmarked. The remaining three wheels included the following parameter changes: 1) same diameter as the baseline but wider, 2) same width as the baseline but smaller in diameter, and 3) same width and diameter as the baseline but with a longer contact length. For each test the normal load, drawbar pull, and driving torque were measured and recorded for further analysis. To measure the effect of the changes in the wheels' parameters on the contact patch under different loads, a pressure pad was embedded below the surface of the Lunar simulant to measure the contact patch shape, size, and pressure distribution. Analysis of the experimental results showed that the drawbar pull was more significantly affected by the wheel diameter than by the contact width, and that same trend followed suit for the driving torque. Overall, the greater contact patch area resulted in a higher drawbar pull and torque. / Master of Science

Ideas for ways to use textiles and other materials as body coverings, or as a form of apparel decoration, as well as protection, continued to evolve throughout history. More complex ideas and outcomes developed with the advent of weaving, and rectangular shapes were draped in folds, tied, or wrapped around the body. An accepted practice in the apparel industry is seeking inspiration for ideas from a variety of people, places, and things. This practice of seeking inspiration from the environment leads to the question of whether copying is inherent within the apparel industry. History of costume research and study indicate that it is generally accepted that people wear differing apparel for each season of the year, with some repeat, or copying, in the same season in subsequent years. The terms counterfeiting, knocking-off, and copying are often used interchangeably, but further exploration of the terms show they are not the same. Counterfeiting has become, and remains a hot topic in the apparel industry, particularly in product development. Some designers have begun to challenge and demand their work be protected in some manner such as copyrights, trademarks, or patents. Questions and concerns abound among product developers. This study was exploratory in nature, seeking a definition, and identifying a specific point in the product development process, when a certain activity (i.e., copying) is more likely to be performed. Therefore, qualitative methods were used to achieve the objectives of the research. This research took a cross-sectional approach within a qualitative design study when selecting the participants. The cross-sections for the participants of this study were those participants in positions of direct influence on apparel product development. Analyzing the perceptions of the participants from the cross-sections in detail, inferences were made about the industry definition and method of copying, time of occurrence, and those most likely involved in decision making. The instrument for the study was an online survey with open-ended questions and fixed-response questions. Of the 20 participants, 11 accessed the survey with 10 choosing to participate. While some degree of similarity was observed in several of the definitions of copying, such as taking existing products to create new products, there was distinction when participants used phrases such as copying 'without changing anything' to 'copying the idea and concept.' Participants' definition of knocking-off can be summarized as a copy with variation in price point. Participants noted that the process of counterfeiting was an unauthorized or illegal copy of a product and often included copying labels or logos. Key reasons for copying products were reported as following trends and speed to market. / Ph. D.

Gas Sensing Has Become a Very Important and Attractive Technique Because of Its Various Applications, Such as in the Increasingly Concerning Case of Environmental Issues, Automobile Emission Detection, Natural Gas Leakage Detection, Etc. It Also Has Significant Applications in Industries, Such as Safety and Health Monitoring in Underground Mines. Among Those Sensing Areas, Fiber-optic Sensors Have Drawn Considerable Attention Because of Its Small Size, Light Weight, High Sensitivity, and Remote Sensing Capability. However, Current Fiber-optic Gas Sensing Techniques Have Several Limitations on Their Potential for Multiplexed or Distributed Sensing Due to Difficulties Such as High Complexity or Large Loss. To Accomplish the Goal for Multiplexed Gas Sensing, an Off-centered Core Fiber Design Is Investigated. The Eccentric Core Can Reduce Attenuation, Keep Mechanical Strength, and Lower Fabrication Cost. To Verify the Feasibility of the Design, Fiber Field Distribution Is First Studied in Simulation, Which Will Be Discussed in Detail in Chapter 2. Then Two Fiber Samples with a Length of 10 Cm and 40 Cm Are Prepared and Placed in a Custom Methane Sensing System for Gas Absorption Testing, Which Is Detailed in Chapter 3. From Etching Analysis, Localized Surface Defects Are Found as the Main Reason for Power Loss. Performance Such as Detection Resolution and Sensitivity Are Investigated. In Chapter 4, Theoretical Evaluations Have Been Conducted for Multiplexed Sensors Performances Using the Off-centered Core Fiber to Study the Impact Fiber Parameters on Sensing System Design. The Conclusion and Summary Are Presented in Chapter 5. / Master of Science / Gas Sensing Has Become a Very Important and Attractive Technique Because of Its Various Applications, Such as in the Increasingly Concerning Case of Environmental Issues, Automobile Emission Detection, Natural Gas Leakage Detection, Etc. It Also Has Significant Applications in Industries, Such as Safety and Health Monitoring in Underground Mines. Among Those Sensing Areas, Fiber-optic Sensors Have Drawn Considerable Attention Because of Its Small Size, Light Weight, High Sensitivity, and Remote Sensing Capability. However, Current Fiber-optic Gas Sensing Techniques Have Several Limitations on Their Potential for Long Distance Distributed Sensing Due to Difficulties Such as High Fabrication Complexity. In This Work, a Fiber-optic Gas Sensor with Special Structure Was Designed. The Sensor Can Reduce Attenuation, Keep Mechanical Strength, and Lower Fabrication Cost. To Verify the Feasibility of the Design, Theory Analysis and Simulation Were Conducted, Which Will Be Discussed in Detail in Chapter 2. Then Two Samples with a Length of 10 Cm and 40 Cm Were Prepared and Placed in a Custom Methane Sensing System for Testing. And Their Performance Such as Sensitivity Is Investigated. In Chapter 4, Theoretical Evaluations Have Been Conducted for Multiplexed Sensors Performances Evaluation to Study the Impact Fiber Parameters on Sensing System Design. The Conclusion and Summary Are Presented in Chapter 5.