Doctor of Philosophy / Department of Biological & Agricultural Engineering / Naiqian Zhang / A three-tier wireless sensor network (WSN) was developed and deployed to remotely monitor suspended sediment concentration and stream velocity in real-time. Two years of field experiments have demonstrated the achievement of such capabilities. But several weak points emerged and required essential performance improvement and additional research on the radio propagation mechanism within the original three-tier WSN. In the original three-tier WSN, long time delay, potential data loss, and limited network throughput all restricted the network transmission performance. Upon the above issues, the transmission delay was reduced through shortening the raw data storage buffer and the data packet length; the data loss rate was decreased by adopting a mechanism using semaphores and adding feedback after data transmission; the network throughput was enlarged through the event- and time-driven scheduling method. In order to find a long-range wireless transmission method as an alternative to the commercial cellular service used in the original WSN, a central station using meteor burst communication (MBC) technology was developed and deployed. During an 8-month field test, it was capable of performing long distance communication with a low data loss rate and transmission error rate. But due to unstable availability of the meteor trails, the MBC network throughput was constrained. To reduce in-situ maintenance, over-the-air programming was implemented. Thus, programs running in the central station and the gateway station can be updated remotely. To investigate the radio propagation in densely vegetative areas, a 2.4 GHz radio propagation path loss model was derived to predict the short-range path loss from the path loss in the open area and the path loss due to dense vegetation. In addition, field experiments demonstrated that ambient air temperature, relative humidity, and heavy rainfall could also affect wireless signal strength.

Master of Science / Department of Biological & Agricultural Engineering / Wenqiao Yuan / Biomass gasification is a promising route utilizing biomass materials to produce fuels and chemicals. Gas product from the gasification process is so called synthesis gas (or syngas) which can be further treated or converted to liquid fuels or certain chemicals. Since gasification is a complex thermochemical conversion process, it is difficult to distinguish the physical conditions during the gasification stages. And, gasification with different materials can result in different product yields. The main purpose of this research was to develop a downdraft gasifier system with a fully-equipped instrumentation system and a well-functioned tar measurement system, to evaluate temperature, pressure drop, and gas flow rate, and to investigate gasification performance using different biomass feedstock. Chromel-Alumel type K thermocouples with a signal-conditioning device were chosen and installed to monitor the temperature profile inside the gasifier. Protel 99SE was applied to design the signal conditioning device comprised of several integrated chips, which included AD 595, TS 921, and LM 7812. A National Instruments (NI) USB-6008 data acquisition board was used as the data-collecting device. As for the pressure, a differential pressure transducer was applied to complete the measurement. An ISA1932 flow nozzle was installed to measure the gas flow rate. Apart from the gaseous products yield in the gasification process, a certain amount of impurities are also produced, of which tar is one of the main components. Since tar is a critical issue to be resolved for syngas downstream applications, it is important to determine tar concentration in syngas. A modified International Energy Agency (IEA) tar measurement protocol was applied to collect and analyze the tars produced in the downdraft gasifier. Solvent for tar condensation was acetone, and Soxhlet apparatus was used for tar extraction. The gasifier along with the instrumentation system and tar measurement method were tested. Woodchips, Corncobs, and Distiller’s Dried Grains with Solubles (DDGS) were employed for the experimental study. The gasifier system was capable of utilizing these three biomass feedstock to produce high percentages of combustible gases. Tar concentrations were found to be located within a typical range for that of a general downdraft gasifer. Finally, an energy efficiency analysis of this downdraft gasifer was carried out.

Master of Science / Department of Biological & Agricultural Engineering / Danny H. Rogers / Center pivot irrigation systems are used in crop production across the state of Kansas. The American Society of Agricultural and Biological Engineers (ASABE) standard on uniformity testing of a center pivot system calls for collectors to be used to measure the water depth emitted by the irrigation system. The standard was designed without specially considering the low pressure sprinklers now commonly used on center pivot systems; the recommended collectors may not accurately measure the applied depth from these sprinklers. The collector size effect on measured water depth and measured depth variability was studied for spinning plate, fixed plate, and wobbling plate sprinkler systems. Five different collector sizes (C2 (5.5 cm), C4 (10.0 cm), C6 (14.8 cm), C8 (20.0 cm), and C10 (27.4 cm)) were studied using four 5x5 Latin squares. Each collector’s water depth was measured and statistically analyzed. Two analysis of variance (ANOVA) tests of the collector size effect were reported. Past experimental results were compared to this experiment’s results. The ANOVA for the measured water depth reported no collector size effect for the spinning plate and wobbling plate systems. The ANOVA of the variability of measured depths showed significant differences between collector sizes for the spinning plate system but not for the wobbling plate system. Previous studies of spinning plate and wobbling plate systems reported acceptable variability for all collector sizes. Although some collector sizes measured significantly different mean depths, the numerical difference in mean depths was small. Any studied collector size could be used to measure the water depth of wobbling plate systems, but the C4 collector is ideal. C4 and C6 collectors are ideal for measuring spinning plate systems. Significant differences between measured depths were reported for the fixed plate system. The C10 measured significantly lower water depths than all other collectors, and the C4 collector measured lower depths than the C2 and C8 collectors. The variability of mean depths was similar and high for all collector sizes. Previous experiments also indicated that different collector sizes measured different depths and had high variability of depth measurements for the fixed plate sprinkler systems. The distinct stream pattern provides a challenge for accurately measuring the water depth with these collector sizes; other methods of measuring uniformity should be considered for fixed plate sprinklers.

Master of Science / Department of Biological and Agricultural Engineering / Wenqiao Yuan / Many of the current industrial fermentation processes cannot use pentose as the carbon source. However, complete substrate utilization of sugars in lignocellulose is one of the prerequisites to render economic development of biofuels or bioproducts from biomass. In this study we proposed a new process for DHA production from renewable carbon sources by first using anaerobic bacteria, Clostridium tyrobutyricum to convert pentose into organic acids with butyric acid as the main product, and then using the organic acids to feed microalgae, Crypthecodinium cohnii to produce DHA. The effect of glucose and xylose on the yield of butyric acid produced by C. tyrobutyricum was investigated, separately. Cell growth of C. tyrobutyricum increased with increasing initial glucose or xylose concentration, but was not affected significantly when the concentration was above 55g/l for glucose or 35g/l for xylose. Butyric acid yield increased as the initial sugar concentration increased in both xylose and glucose, but the conversion rate from xylose or glucose to butyric acid decreased as the sugar concentration increased. The xylose to glucose ratio in their mixture did not significantly affect cell growth or butyric acid yield. The effect of arabinose on the yield of butyric acid produced by C. tyrobutyricum was also studied. As for butyric acid production, compared with glucose or xylose, the arabinose was in a low efficiency, with butyric acid output of 2.25g/l in 10g/l arabinose and a long lag period of about 3-4 d. However, a low concentration of arabinose could be used as a nutritional supplement to improve the fermentability of a mixture of xylose and glucose. The conversion rate of sugar to butyric acid increased as the supplement arabinose increased. In order to obtain low cost xylose, corncobs were hydrolyzed and this xylose-rich product was used to culture C. tyrobutyricum. The results showed that at end of the 9 d fermentation, the concentration of butyric acid from corncob hydrolysate reached 10.56 g/l, and the mimic medium reached 11.3 g/l. This suggests that corncob hydrolysate can be used as a carbon source for butyric acid production by C. tyrobutyricum, although some inhibitory effects were found on cell growth with corncob hydrolysate. The effect of butyric acid, lactic acid and acetic acid on the yield of DHA produced by C. cohnii was also investigated, separately. The DHA yield was highly related to both biomass and DHA content in the cell, whereas lower growth rate could bring higher DHA content. The best concentration for DHA yield seemed to be 1.2g/l in three single organic acid media. In two organic acids mixture media, acetic acid tended to be beneficial for biomass accumulation, regardless whether butyric acid or lactic acid was mixed with acetic acid, the OD could reach 1.3 or above. When butyric acid was mixed with lactic acid, the highest DHA yield was achieved, due to increased DHA content from mutual influence between butyric acid and lactic acid.

No description available.

A number of alternatives were considered to keep pecan processing economically competitive and sustainable. The industry needed a low risk evaluation technique for testing new high capital plant configurations. A simulation model was developed using the AweSimTM simulation system to form the model structure and framework. The Visual SLAMTM and Visual BASIC programming languages were used to build a network model that provided a mathematical-logical representation of the system. The model mathematically expresses all sub-processes including moisture conditioning, pasteurizing, cracking, shelling, sizing, manual and electronic sorting, resizing, resorting, and packaging. The pecan process simulation model consists of 24 RESOURCES, 353 ACTIVITIES, 48 AWAIT/QUEUE and FREE nodes, 83 BATCH and UNBATCH nodes, 79 ASSIGN nodes, 20 COLCT nodes, 39 GOON nodes, 10 other miscellaneous nodes and a graphic user interface (GUI). The model provides information on equipment utilization, delays, queues and bottlenecks for each process in the system. It also predicts total pecan cracked and total pecan packed, including details of production for each size class i.e. halves; large; medium; small; midget; fine; granule; and oil stock. The model was validated quantitatively by comparing output with actual production figures and qualitatively by plant management. Five options of process alternatives were simulated using the pecan simulation model. The first alternative (including 3 options) was a management proposed configuration for dual electronic sorting of pecan halves to reduce the shell pieces and ensure a lighter color product. Two options were found not viable as they required major capital investments and plant reconfiguration. The third option for dual sorting was found to be a viable process alternative with minor labor additions.

Exergy analysis is applied in the thesis research to evaluate the energy usage of a pilot scale milk processing system. Using water as made-up fluid milk, the performance of separate components of the system was examined during steady state operation using both exergy and energy principles. The irreversibility distribution among these components was obtained to show the impact of energy degradation in each component on the overall system thermal performance. The difference between energy and exergy methods is discussed through comparisons of First and Second Law efficiencies to demonstrate the importance of exergy analysis. A mathematical programming model was constructed in terms of the exergy concept and solved numerically in an attempt to find a set of optimal operating state variables (temperatures and flow rates) under which irreversibility of the entire system is theoretically minimized. Finally, suggestions for operational management of the system and its components are presented which could increase the efficiency of energy usage in the system, thus reducing energy costs.

Two field investigations were undertaken to study the role of water table management in reducing herbicide pollution of ground water. One of the three-year studies (1992-1995) was conducted in a sandy field near Joliette (Laurin farm), (Quebec) to monitor the herbicide metribuzin where potatoes were grown. Two water table management systems were evaluated, namely subsurface drainage and subirrigation. Soil and ground water samples were taken at two week intervals, once before and six times after the herbicide application. / The amount of rainfall received in the first few weeks following herbicide application is crucial in assessing the extent of ground water contamination. In 1992, fewer rainfall events occurred after the application as compared to 1993, so metribuzin leached slowly. In 1992, it appears that subirrigation reduced ground water contamination by a factor of 10 through enhanced degradation and the greater effect of dilution. However, the role of subirrigation in reducing the metribuzin contamination of ground water was negligible in 1993 due to considerable leaching soon after the application. / The second project was conducted in an organic soil in St-Patrice-de-Sherrington (Van Winden farm) where the herbicide prometryn was studied. Surface irrigation with a controlled water table was also used as a water table management system. One experimental unit was used for each of the three treatments (subirrigation, surface irrigation and subsurface drainage). / The herbicide application rate was greater at the Van Winden farm than in the Laurin farm (5.5 kg/ha versus 1.0 kg/ha). However, a higher adsorption coefficient of the organic soil minimized the leaching process. Ground water contamination was less extensive in the organic deposit. The effect of subirrigation in reducing ground water contamination was significant when the water table was shallow. Prometryn degradation was relatively slow during the summer. Moreover, significant amounts of prometryn carried-over into the soil after the winter season, so it appears to be a quite persistent herbicide in our climate.

Within the scope of a project funded by the Quebec Ministry of the Environment and Fauna (MEF), alternative wastewater phosphorus removal methods to alum or ferric chloride coagulation were assessed. The most promising technologies were found to be enhanced biological phosphorus removal, treatment plant process optimization and on-line process control. The use of alum sludges from potable water treatment plants appeared promising although it has not yet been widely practised or studied. The MEF therefore decided to retain the process as one requiring further study. / Through batch sorption tests with synthetic solutions, it was found that aluminum hydroxide has a significant sorptive capacity for orthophosphate, condensed phosphate and organic phosphate. The removal of these phosphates was independent of pH between pH 3 and pH 6. The solubility of the aluminum hydroxide was highly pH-dependent. In all the tests, except that with organic phosphate at pH 3.6, the measured soluble aluminum was consistent with solutions saturated with solid-phase Al(OH)$ sb3$. With organic phosphate at pH 3.6, an aluminum-organic phosphate appears to have formed. A theoretical analysis of Al(OH)$ sb3$ and Al(PO$ sb4)$ precipitation showed that phosphate removal is not achieved through Al(PO$ sb4)$ precipitation when dosing with conventional alum, but rather that a mixed aluminum hydroxide phosphate precipitate is formed. / Jar tests performed with full-scale alum sludge and wastewater showed that phosphate is removed by the particulate fraction of the sludge. The removal of reactive phosphate (orthophosphate) decreased with an increase in the storage time of the alum sludge. This decrease was not seen with the non-reactive phosphate. It was therefore suggested that reactive phosphate removal is carried out by adsorption and that non-reactive phosphate removal is performed by a sweep-floc mechanism. (Abstract shortened by UMI.)

Thesis (Ph.D.)--Auburn University, 2005. / (UnM)AAI3201458. Source: Dissertation Abstracts International, Volume: 66-12, Section: B, page: 6759. Director: Vitaly J. Vodyanoy.