ABSTRACT FLEXIBLE ASSEMBLY LINE DESIGN PROBLEM WITH FIXED NUMBER OF WORKSTATIONS Barut&ccedil / uoglu, Sirin M.S. Department of Industrial Engineering Supervisor: Prof. Dr. Meral Azizoglu July 2009, 70 pages In this thesis, we study a Flexible Assembly Line Design problem. We assume the task times and equipment costs are correlated in the sense that for all tasks the cheaper equipment gives no smaller task time. Given the cycle time and number of workstations we aim to find the assignment of tasks and equipments to the workstations that minimizes the total equipment cost. We study a special case of the problem with identical task times. For the general case, we develop a branch and bound algorithm that uses powerful lower bounds and reduction mechanisms. We test the performance of our branch and bound algorithm on randomly generated test problems. The results of our experiments have revealed that we are able to solve large-sized problem instances in reasonable times.

The main objective of this study was to investigate the removal and recovery of nutrients from anaerobic digestion residues of poultry manure through struvite (MgNH4PO4.6H2O, MAP) precipitation. To this purpose, three sets of laboratory experiments were conducted. In the first set, separate and co-digestion of poultry manure and sewage sludge were studied in laboratory-scale mesophilic anaerobic batch reactors and subsequent struvite precipitation experiments were conducted with the reactors effluents. The effects of important parameters on struvite precipitation were investigated and it is illustrated that up to 89 % of NH4-N, 84 % PO4-P and 42 % COD removals were possible. In the second set, the effluents of a full-scale co-digestion plant utilizing poultry manure and maize silage were subjected to struvite precipitation experiments. Acidic phosphorus-dissolution process was successfully applied to the solid phase effluents to obtain phosphorus-enriched solution. By the addition of external Mg and P more than 90% of NH4-N and PO4-P were recovered from phosphorus-enriched solution, whereas the addition of only Mg led to partial recovery of NH4-N. In the third set, the effluents of a full-scale poultry manure digester were subjected to struvite precipitation experiments. The findings illustrated that Ca has inhibitory effects on the struvite reaction and lead to formation of hydroxlyapatite and amorphous calcium phosphates together with struvite. Based on the results obtained in this study, it is postulated that, struvite precipitation is a viable option for the recovery of the nutrients in the anaerobically digested poultry manure. This study illustrated that, poultry manure, if managed properly, could meet one-fourth of Turkey&amp / #8217 / s domestic fertilizer demand.

We aim to classify alternatives evaluated in multiple criteria among preference ordered classes assuming an underlying additive utility function. We develop a probabilistic classification method by calculating the probability of an alternative being in each class. We assign alternatives to classes based on threshold probabilities. We require the decision maker to place an alternative to a class when no alternatives satisfy the required thresholds. We find new probabilities for unassigned alternatives in the light of new information and repeat the procedure until all alternatives are classified. We implemented our algorithm to classify MBA programs among preference ordered groups. We evaluate our algorithm based on the number of misclassified alternatives and the number of alternatives placed by the decision maker.

In this study, we propose a two-phase solution approach for approximating the efficient frontier of a bicriteria hub location problem. We develop an evolutionary algorithm to locate the hubs on the network as the first phase. In the second phase, we develop a bounding procedure based on dominance relations and using the determined bounds, we solve the allocation subproblem for each located hub set. The two-phase approach is tested on the Australian Post data set and it is observed that our approach approximates the entire efficient frontier well. In addition, we suggest an interactive procedure to find the solutions that are in the decision maker&rsquo / s preferred region of the solution space. In this procedure, we progressively incorporate the preferences of the decision maker and direct the search towards the preferred regions. Based on some computational experiments, it is observed that the interactive procedure converges to the preferred regions.

Whiplash injuries as a result of rear impact are among the most common injuries in traffic accidents. This is why whiplash injuries have reached a high priority in the research area. In this study, the effects of head restraint position and impact pulse to the whiplash injury have been analyzed by performing whiplash tests using the sled test facility of METU-BILTIR Center Vehicle Safety Unit. Although there are many whiplash test protocols, the test sample has been prepared according to the most recent one, Euro NCAP Whiplash Test Protocol. Three different head restraint positions and three different impact pulses with different severities, totally nine tests have been performed. The tests are performed with a three point generic seat belt and an instrumented Hybrid III 50th percentile male adult crash test dummy is used as the occupant in driver seat of a light commercial vehicle. High speed cameras, sensors on the crash test dummy and a data acquisition system are used to take the test data. This test data has been analyzed and presented according to the defined whiplash assessment criteria and the performance scores of the particular seat for each test have been determined using the whiplash assessment criteria values according to the Euro NCAP Test Protocols.

Modeling of the ionosphere has been a highly interesting subject within the scientific community due to its effects on the propagation of electromagnetic waves. The development of the Global Positioning System (GPS) and creation of extensive ground-based GPS networks started a new period in observation of the ionosphere, which resulted in several studies on GPS-based modeling of the ionosphere. However, software studies on the subject that are open to the scientific community have not progressed in a similar manner and the options for the research community to reach ionospheric modeling results are still limited. Being aware of this need, a new MATLAB&reg / based ionosphere modeling software, i.e. TECmapper is developed within the study. The software uses three different algorithms for the modeling of the Vertical Total Electron Content (VTEC) of the ionosphere, namely, 2D B-spline, 3D B-spline and spherical harmonic models. The study includes modifications for the original forms of the B-spline and the spherical harmonic approaches. In order to decrease the effect of outliers in the data a robust regression algorithm is utilized as an alternative to the least squares estimation. Besides, two regularization methods are employed to stabilize the ill-conditioned problems in parameter estimation stage. The software and models are tested on a real data set from ground-based GPS receivers over Turkey. Results indicate that the B-spline models are more successful for the local or regional modeling of the VTEC. However, spherical harmonics should be preferred for global applications since the B-spline approach is based on Euclidean theory.

Mainly used food packaging materials are petro-chemical based polymers which present environmental problems since they are not biodegradable and ecologically sustainable. In this study, biodegradable biofilms are produced from xylan, extracted from cotton stalk which is an agricultural biowaste without nutritional value. Antimicrobial property was given to the biofilms with either titanium dioxide sol-gel coatings or titanium dioxide powder addition into the biofilm forming solutions. The antimicrobial activities of biofilms were tested against Escherichia coli. Among two different sol-gels coated and at different temperatures dried biofilms, BWX and CSX-50 biofilms treated at 120&deg / C and coated with SiO2/TiO2 showed 88&plusmn / 1% and 75&plusmn / 2% antimicrobial activities, respectively. Same samples treated at the same conditions but coated with non-SiO2 added TiO2 sol-gel yielded 63&plusmn / 3% and 63&plusmn / 2% antimicrobial activities, respectively after 2 h black light illumination. So, it was determined that the highest photocatalytic antimicrobial property was achieved with SiO2/TiO2 coated biofilms. Moreover different concentrations of TiO2 powder were integrated into xylan based biofilms and 100% photocatalytic inactivation was gathered at 5% (w/w) TiO2 addition achieved at both biofilms at the end of 90 min black light illumination. Biodegradability properties of the biofilms were investigated in soil burial test during 180 days and 10% (w/w) TiO2 powder added CSX-50 biofilms were recorded to be 91% biodegradable where non-powder added blank biofilms was found to be 95% biodegradable.

Mineral treatment processes generally produce wastewaters containing ultrafine and colloidal particles that cause pollution upon their discharge into environment. It is essential that they should be removed from the wastewater before discharge. This study was undertaken by using synthetic turbid systems containing kaolinite and quartz particles in water with the amount of 0.20 g/L and 0.32 g/L, respectively. Removal of the turbidity was tried in two ways / electrocoagulation with aluminum anode and conventional coagulation with aluminum sulfate. Several key parameters affecting the efficiency of electrocoagulation and coagulation were investigated with laboratory scale experiments in search of optimal parameter values. Optimal values of the parameters were determined on the basis of the efficiency of turbidity removal from ultrafine suspensions. The parameters investigated in the study were suspension pH, electrical potential, current density, electrocoagulation time, and aluminum dosage. This study was also performed to compare electrocoagulation and conventional coagulation regarding the pH ranges under investigation and coagulant dosages applied. A comparison between electrocoagulation and coagulation was made on the basis of total dissolved aluminum, revealing that electrocoagulation and coagulation were equally effective at the same aluminum dosage for the removal of ultrafine particles from suspensions. Coagulation was more effective in a wider pH range (pH 5-8) than electrocoagulation, which yielded optimum effectiveness in a relatively narrower pH range around 9. In both methods, these pH values corresponded to near-zero zeta potentials of coagulated kaolinite and quartz particles. The mechanism for both coagulation methods was aggregation through charge neutralization and/or enmeshment in aluminum hydroxide precipitates. Furthermore, the experimental results confirmed that electrocoagulation could display some pH buffering capacity. The kinetics of electrocoagulation was very fast (&lt / 10 min) in approaching a residual turbidity, which could be modeled with a second-order rate equation.

Non-ductile reinforced concrete frame buildings constitute an important part of the vulnerable buildings in seismic regions of the world. Collapse of non-ductile multi story concrete buildings during strong earthquakes in the past resulted in severe casualties and economic losses. Their rehabilitation through retrofitting is a critical issue in reducing seismic risks worldwide. A displacement-based retrofitting approach is presented in this study for seismic retrofitting of medium height non-ductile concrete frames. A minimum amount of shear walls are added for maintaining the deformation levels below the critical level dictated by the existing columns in the critical story, which is usually at the ground story. Detailing of shear walls are based on conforming to the reduced deformation demands of the retrofitted frame/wall system. Member-end rotations are employed as the response parameters for performance evaluation. Initial results obtained from the proposed displacement based approach have revealed that jacketing of columns and confining the end regions of added shear walls are usually unnecessary compared to the conventional force-based approach, where excessive force and deformation capacities are provided regardless of the actual deformation demands.

In munitions technologies, hazard investigations for explosive (or more generally energetic material) including systems is a very important issue to achieve insensitivity. Determining the response of energetic materials to different types of mechanical or thermal threats has vital importance to achieve an effective and safe munitions design and since 1970&rsquo / s, lots of studies have been performed in this research field to simulate the dynamic response of energetic materials under some circumstances. The testing for hazard investigations is a very expensive and dangerous topic in munitions design studies. Therefore, especially in conceptual design phase, the numerical simulation tools for hazard investigations has been used by ballistic researchers since 1970s. The main modeling approach in such simulation tools is the numerical simulation of deflagration-todetonation transition (DDT) phenomenon. By this motivation, in this thesis study, the numerical simulation of DDT phenomenon in solid energetic materials which occurs under some mechanical effects is performed. One dimensional and two dimensional solvers are developed by using some well-known models defined in open literature for HMX (C4 H8 N8 O8) with 73 % particle load which is a typical granular, energetic, solid, explosive ingredient. These models include the two-phase conservation equations coupled with the combustion, interphase drag interaction, interphase heat transfer interaction and compaction source terms. In the developed solvers, the governing partial differential equation (PDE) system is solved by employing high-order central differences for time and spatial integration. The two-dimensional solver is developed by extending the complete two-phase model of the one-dimensional solver without any reductions in momentum and energy conservation equations. In one dimensional calculations, compaction, ignition, deflagration and transition to detonation characteristics are investigated and, a good agreement is achieved with the open literature. In two dimensional calculations, effect of blunt and sharp-nosed projectile impact situations on compaction and ignition characteristics of a typical explosive bed is investigated. A minimum impact velocity under which ignition in the domain fails is sought. Then the developed solver is tested with a special wave-shaper problem and the results are in a good agreement with those of a commercial software.