Endüstri Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/279

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Citation - WoS: 204
Citation - Scopus: 231
Ammonia Removal From Anaerobically Digested Dairy Manure by Struvite Precipitation
(Elsevier Sci Ltd, 2005) Uludag-Demirer, S; Demirer, GN; Chen, S
Ammonia is one of the most important contaminants impairing the quality of water resources. When this is considered along with the fact that the global demand for nitrogenous fertilizers is in constant rise, the need for recovery as well as removal of nitrogen is well justified. Crystallization of N and P in the form of struvite (MgNH4PO4 center dot 6H(2)O), which is a slow releasing and valuable fertilizer, is one possible technique for this purpose. This study investigated the removal of NR4+ through struvite precipitation from the effluents of one- (R1) and two-phase (R2) anaerobic reactors digesting dairy manure. To force the formation of struvite in the anaerobic reactor effluents, Ma(2+) ion was added by using both Mg(OH)(2) and MgCl2 center dot 6H(2)O. To prevent the effect of different total phosphorus (TP) concentration in the effluents of RI and R2, as well as to not limit the formation of struvite, an excess amount Of PO43- (0.14 M) was added in the form of NaHPO4. Different stoichiometric Mg2+:NH4+:PO43- ratios were tested to determine the required Mg2+ concentrations for maximum NH4+ removal by keeping NH4+:PO43- ratio constant for the effluents of reactors RI and R2. The results revealed that very high NH4+ removal efficiencies (above 95%) were possible by adding Mg 21 ions higher than 0.06 M concentration in the effluents from reactors RI and R2. It was also observed that the initial pH adjustment to 8.50 using NaOH did not result in any significant increase in the removal of NH4+ and the removal of NH4+ in the reactors treated with MgCl2 center dot 6H(2)O was higher than those treated with Mg(OH)(2) for the same Mg2+ concentration. (c) 2005 Published by Elsevier Ltd.
An approach to discrete convexity and its use in an optimal fleet mix problem
(Springer-Verlag Berlin, 2006) Cambini, Riccardo; Riccardi, Rossana; Yüceer, Ümit
A notion of convexity for discrete functions is first introduced, with the aim to guarantee both the increasing monotonicity of marginal increments and the convexity of the sum of convex functions. Global optimality of local minima is then studied both for single variable functions and for multi variables ones. Finally, a concrete optimal fleet mix problem is studied, pointing out its discrete convexity properties.
Citation - WoS: 98
Citation - Scopus: 117
Anaerobic Digestion of Dairy Manure With Enhanced Ammonia Removal
(Academic Press Ltd- Elsevier Science Ltd, 2008) Uludag-Demirer, S.; Demirer, G. N.; Frear, C.; Chen, S.
Poor ammonia-nitrogen removal in methanogenic anaerobic reactors digesting animal manure has been reported as an important disadvantage of anaerobic digestion (AD) in several studies. Development of anaerobic processes that are capable of producing reduced ammonia-nitrogen levels in their effluent is one of the areas where further research must be pursued if AD technology is to be made more effective and economically advantageous. One approach to removing ammonia from anaerobically digested effluents is the forced precipitation of magnesium ammonium phosphate hexahydrate (MgNH4PO4-6H(2)O), commonly called struvite. Struvite is a valuable plant nutrient source for nitrogen and phosphorus since it releases them slowly and has non-burning features because of its low solubility in water. This study investigated coupling AD and controlled struvite precipitation in the same reactor to minimize the nitrogen removal costs and possibly increase the performance of the AD by reducing the ammonia concentration which has an adverse effect oil anaerobic bacteria. The results indicated that Lip to 19% extra COD and almost 11% extra NH3 removals were achieved relative to a control by adding 1750 mg/L of MgCl2-6H(2)O to the anaerobic reactor. (C) 2007 Elsevier Ltd. All rights reserved.
Citation - WoS: 12
Analysis of Dengue Transmission Dynamic Model by Stability and Hopf Bifurcation With Two-Time Delays
(Imr Press, 2023) Ambalarajan, Venkatesh; Sivakumar, Vinoth; Dhandapani, Prasantha Bharathi; Baleanu, Dumitru; Murugadoss, Prakash Raj
Background: Mathematical models reflecting the epidemiological dynamics of dengue infection have been discovered dating back to 1970. The four serotypes (DENV-1 to DENV-4) that cause dengue fever are antigenically related but different viruses that are transmitted by mosquitoes. It is a significant global public health issue since 2.5 billion individuals are at risk of contracting the virus. Methods: The purpose of this study is to carefully examine the transmission of dengue with a time delay. A dengue transmission dynamic model with two delays, the standard incidence, loss of immunity, recovery from infectiousness, and partial protection of the human population was developed. Results: Both endemic equilibrium and illness-free equilibrium were examined in terms of the stability theory of delay differential equations. As long as the basic reproduction number (R0) is less than unity, the illness-free equilibrium is locally asymptotically stable; however, when R0 exceeds unity, the equilibrium becomes unstable. The existence of Hopf bifurcation with delay as a bifurcation parameter and the conditions for endemic equilibrium stability were examined. To validate the theoretical results, numerical simulations were done. Conclusions: The length of the time delay in the dengue transmission epidemic model has no effect on the stability of the illness-free equilibrium. Regardless, Hopf bifurcation may occur depending on how much the delay impacts the stability of the underlying equilibrium. This mathematical modelling is effective for providing qualitative evaluations for the recovery of a huge population of afflicted community members with a time delay.
Citation - WoS: 22
Citation - Scopus: 23
Bi-Objective Dynamic Weapon-Target Assignment Problem With Stability Measure
(Springer, 2022) Karasakal, Esra; Karasakal, Orhan; Silav, Ahmet
In this paper, we develop a new bi-objective model for dynamic weapon-target assignment problem. We consider that the initial weapon assignment plan of defense is disrupted during engagement because of a destroyed air target, breakdown of a weapon system or a new incoming air target. The objective functions are defined as the maximization of probability of no-leaker and the maximization of stability in engagement order of weapon systems. Stability is defined as assigning same air target in sequence in engagement order of a weapon system so that reacquisition and re-tracking of air target are not required by sensors. We propose a new solution procedure to generate updated assignment plans by maximizing efficiency of defense while maximizing stability through swapping weapon engagement orders. The proposed solution procedure generates non-dominated solutions from which defense can quickly choose the most-favored course of action. We solve a set of representative problems with different sizes and present computational results to evaluate effectiveness of the proposed approach.
Citation - WoS: 6
Citation - Scopus: 10
Bi-Objective Missile Rescheduling for a Naval Task Group With Dynamic Disruptions
(Wiley, 2019) Karasakal, Orhan; Karasakal, Esra; Silav, Ahmet
This paper considers the rescheduling of surface-to-air missiles (SAMs) for a naval task group (TG), where a set of SAMs have already been scheduled to intercept a set of anti-ship missiles (ASMs). In missile defense, the initial engagement schedule is developed according to the initial state of the defensive and attacking units. However, unforeseen events may arise during the engagement, creating a dynamic environment to be handled, and making the initial schedule infeasible or inefficient. In this study, the initial engagement schedule of a TG is assumed to be disrupted by the occurrence of a destroyed ASM, the breakdown of a SAM system, or an incoming new target ASM. To produce an updated schedule, a new biobjective mathematical model is formulated that maximizes the no-leaker probability value for the TG and minimizes the total deviation from the initial schedule. With the problem shown to be NP-hard, some special cases are presented that can be solved in polynomial time. We solve small size problems by the augmented epsilon-constraint method and propose heuristic procedures to generate a set of nondominated solutions for larger problems. The results are presented for different size problems and the total effectiveness of the model is evaluated.
Broiler House Performance Analysis and Chick Entrance Planning for a Broiler Chicken Integration
(2012) Satır, Benhür; Yıldırım, Gonca; Kırca, Ömer
Increasing rates of chicken meat production has a substantial impact on the Turkish economy. Per capita production in Turkey is close to the average production of the top 20 countries in the world. The production is done by integrated organizations, incorporating an integrator chicken company affiliated with all aspects of the production in an organization. There are many complicated processes, stages and parties involved in a typical integration, bringing with them many interesting problems. In this paper, we focus on tactical and operational decisions required during the broiler growing stage, motivated by the requirements of a moderate-sized integrator in the Marmara Region of Turkey. We use analysis of variance to compare the performances of available broiler houses, and to find the factors effecting the performance measures. Then, we present a mixed-integer linear program which uses the results of our performance analysis to find the least costly set of broiler houses with which the integrator should work, and the chick entrance times into these houses over a planning period.
Citation - WoS: 3
Citation - Scopus: 4
Comparison of Classroom Furniture To Anthropometric Measures of Turkish Middle School Students
(Ios Press, 2021) Erdogan, Filiz Celikci; Satir, Benhur
BACKGROUND: The match between classroom furniture and students' anthropometry is an important factor in students' academic performance. OBJECTIVE: Our aim was to investigate the ergonomic suitability of the classroom furniture to the students, and to propose design suggestions for both desks and chairs. METHODS: We analyzed the ergonomics of classroom furniture that students aged 10-14 years old in Turkey currently use. To this end, we selected Maltepe Primary Education School, one of the largest schools in the cankaya district of Turkey's capital city, Ankara, in which to conduct the study. A sample of 119 students was selected, and seven anthropometric measurements were taken for each of these students. We then calculated five relationships between the dimensions of the furniture and the students' anthropometric measures. RESULTS: We observed high levels of mismatch rates, with an average of 66.6% and high values of over 95% for the relations of two furniture measures, seat depth (related with buttock-popliteal length) and seat-to-desk height (related with elbow height, sitting). Each anthropometric measure was applied a fit probability distribution, and based on those distributions; we suggested the most appropriate classroom furniture dimensions in order to maximize suitability of the furniture to the anthropometric measures in terms of fixed-size (i.e., non-adjustable) classroom furniture. CONCLUSIONS: High mismatch rates can be reduced by 52.0% on average based on the classroom furniture dimensions suggested in this study.
Control of trichloroethylene emissions from sparging systems by horizontal bio- and chemo- barriers
(2005) Tezel, U.; Demirer, G.N.; Uludag, Demirer S.
The scope of this study was to develop a continuous system to clean-up a trichloroethylene (TCE) contaminated gas stream, where biotic and abiotic removal mechanisms are undertaken sequentially simulating the horizontal bio- and chemo-barriers proposed for the in-situ remediation of the contaminated sites. The bio- and chemo-barriers were simulated by using glass columns packed with granular anaerobic mixed culture and Fe(0) filings, respectively. The effect of gas residence time, which is adjusted by the gas flowrate, on the TCE removal efficiency of the reactor system was investigated. TCE removal efficiency of over 90% was achieved at gas residence times above 1hr. Furthermore, the effluent of reactor system contained only ethane and ethylene, which are non-toxic by-products of TCE reduction reactions, along with trace amounts of TCE.
Citation - WoS: 16
Citation - Scopus: 24
A Decision Support System for Locating Weapon and Radar Positions in Stationary Point Air Defence
(Springer, 2012) Maras, Hakan; Gencer, Cevriye; Aygunes, Haluk; Tanerguclu, Turker
In this study, a decision support system (DSS) based on the interactive use of location models and geographical information systems (GIS) was developed to determine the optimal positions for air defence weapons and radars. In the location model, the fire units are considered as the facilities to be located and the possible approach routes of air vehicles are treated as demand points. Considering the probability that fire by the units will miss the targets, the objective of the problem is to determine the positions that provide coverage of the approach routes of the maximum number of weapons while considering the military principles regarding the tactical use and deployment of units. In comparison with the conventional method, the proposed methodology presents a more reliable, faster, and more efficient solution. On the other hand, owing to the DSS, a battery commander who is responsible for air defence becomes capable of determining the optimal weapon and radar positions, among the alternative ones he has identified, that cover the possible approach routes maximally. Additionally, he attains the capability of making such decisions in a very short time without going to the field over which he will perform the defence and hence without being subject to enemy threats. In the decision support system, the digital elevation model is analysed using Map Objects 2.0, the mathematical model is solved using LINGO 4.0 optimization software, and the user interface and data transfer are supported by Visual Basic 6.0.
Citation - WoS: 2
Citation - Scopus: 3
Effects of Privatization: a Case Study From Cayirhan Coal District, Turkey
(Elsevier Sci Ltd, 2006) Eyyuboglu, E. Mustafa
Privatization of lignite coal-fired power plants in Turkey began in the middle of 1990 and is still an ongoing process. Among the 10 power plants offered to bidders in 1996, only Cayirhan power plant bundled with the coal mine was privatized. Considerable improvements have been obtained following the privatization of both the power plant and the coal mine. In view of its success, it is considered that Cayirhan experience could serve as a model for further privatization in energy sector, planned to be completed by the end of 2006 according to the agenda issued by government. This paper deals with the overall improvements following the privatization of both the power plant and the coal mine. In particular, mechanized roadway drivage performances before and after privatization are compared in order to highlight the specific effects of privatization in this area. It is found that competition, organizational and operational changes are the main causes of improvements attained in the post-privatization period. (c) 2005 Elsevier Ltd. All rights reserved.
Citation - WoS: 8
Citation - Scopus: 12
Estimating Parameters of a Multiple Autoregressive Model by the Modified Maximum Likelihood Method
(Elsevier, 2010) Bayrak, Oezlem Tuerker; Akkaya, Aysen D.
We consider a multiple autoregressive model with non-normal error distributions, the latter being more prevalent in practice than the usually assumed normal distribution. Since the maximum likelihood equations have convergence problems (Puthenpura and Sinha, 1986) [11], we work Out modified maximum likelihood equations by expressing the maximum likelihood equations in terms of ordered residuals and linearizing intractable nonlinear functions (Tiku and Suresh, 1992) [8]. The solutions, called modified maximum estimators, are explicit functions of sample observations and therefore easy to compute. They are under some very general regularity conditions asymptotically unbiased and efficient (Vaughan and Tiku, 2000) [4]. We show that for small sample sizes, they have negligible bias and are considerably more efficient than the traditional least Squares estimators. We show that Our estimators are robust to plausible deviations from an assumed distribution and are therefore enormously advantageous as compared to the least squares estimation. We give a real life example. (C) 2009 Elsevier B.V. All rights reserved.
Forecasting Day of Week Volume Fluctuations in the Intermodal Freight Transportation
(Institute of Industrial Engineers, 2011) Ertem, M.A.; Ertem, Mustafa Alp; Endüstri Mühendisliği
Average daily volume fluctuates intensely based on the day of week in the intermodal freight transportation. Shippers tend to peak around Thursdays and receivers tend to peak around Mondays. These fluctuations bring challenges to the industry in terms of capacity management and getting reliable service from the railroad companies. The purpose of this study is to forecast J. B. Hunt Transport Services, Inc.'s load volume on railroads. Load is meant to be the number of containers that will arrive at a rail ramp during a 24hrs time window. The end in mind is to have better service from the railroad companies and to manage the company owned equipment better. The forecasting model applied to tackle this problem is a multiple linear regression model and is based on the historical in-gate numbers. It uses the previous two year's data and day of week information as independent variables, and current year's data as the response variable. The results indicate better accuracy levels for the model when compared to the two week moving average.
Improving Evaluation System of Program Educational Objectives and Outcomes based on MÜDEK Criteria Using Fuzzy Approach
(2015) Başkır, Mükerrem Bahar; Yıldırım, Gonca; Yıldırım, Fetih
Citation - WoS: 8
Citation - Scopus: 8
Intermodal Humanitarian Logistics Using Unit Load Devices
(Springer Heidelberg, 2022) Kavlak, Hasan; Ertem, Mustafa Alp; Satir, Benhur
Intermodal freight transportation facilitates today's global trade. The benefits of intermodal freight transportation have been studied and are more observable in commercial logistics; however, the potential benefits of humanitarian logistics have not been thoroughly investigated. This research aims to present a resilient transportation framework by modeling intermodal transportation utilizing interoperable loading devices during disaster responses. We developed an integer programming model based on a time-space network by considering route and vehicle availabilities that are allowed to change with time. We consider vehicles with varying capacities in three transportation modes (i.e., ground, maritime, and air). The contribution of this study is threefold: (1) Two compatible unit load devices are proposed for humanitarian logistics; (2) a mathematical model that includes integer variable representation for vehicle fleets in different transportation modes is developed; and (3) intermodal transportation is compared with single-mode transportation using a real-life dataset. Our main results are as follows: In terms of cost, intermodal transportation is effective when demand occurs in consecutive periods and response time is short. Inventory is held more in intermodal transportation when it is cost-effective to use transportation modes with large capacities. Thus, the benefits of the responsiveness of intermodal transportation outweigh the costs of mode interchange and inventory holding for sudden-onset disasters where quick responses are needed within a short time.
Citation - WoS: 3
Citation - Scopus: 6
Lot Streaming in a Two-Machine Mixed Shop
(Springer London Ltd, 2010) Duman, Mehmet; Cetinkaya, Ferda C.
Most classical scheduling models overlook the fact that products are often produced in job lots and assume that job lots are indivisible single entities, although an entire job lot consists of many identical items. However, splitting an entire lot (process batch) into sublots (transfer batches) to be moved to downstream machines allows the overlapping of different operations on the same product while work needs to be completed on the upstream machine. This approach is known as lot streaming in scheduling theory. In this study, the lot streaming problem of multiple jobs in a two-machine mixed shop where there are two different job types as flow shop and open shop is addressed so as to minimize the makespan. The optimal solution method is developed for the mixed shop scheduling problem in which lot streaming can improve the makespan.
Mathematical Modelling Approach to Increase Cell Efficiency in a Furniture Firm
(2018) Yozgat, Simge; Atmaca, H.E.
Minisum and maximin aerial surveillance over disjoint rectangles
(2016) Karasakal, Orhan
The aerial surveillance problem (ASP) is finding the shortest path for an aerial surveillance platform that has to visit each rectangular area once and conduct a search in strips to cover the area at an acceptable level of efficiency and turn back to the base from which it starts. In this study, we propose a new formulation for ASP with salient features. The proposed formulation that is based on the travelling salesman problem enables more efficient use of search platforms and solutions to realistic problems in reasonable time. We also present a max–min version of ASP that maximizes the minimum probability of target detection given the maximum flight distance of an aerial platform. We provide computational results that demonstrate features of the proposed models.
Citation - Scopus: 1
Multi-Manned Assembly Line Balancing Problems With Sequence-Dependent Setup Times
(Curran Associates Inc., 2017) Güner, F.; Güner, Funda; Kellegöz, T.; Toklu, B.; Çankaya Meslek Yüksekokulu
In the production of large-size products (such as automobiles, buses, trucks etc.), designing assembly lines with multi-manned workstations may provide decreasing number of total workstations, requirement of large plant area and product flow time. Depending on the characteristics of the tasks about to be started and the one just completed on the same worker, setup times may be significant. Therefore, in some real life situations, it is possible to see setup times between tasks processed successively. In this study, assembly line balancing problems with multi-manned workstations and sequence dependent setup times are addressed. The formal definition of the problem is firstly presented. Then, its mixed integer programming formulation and is developed. In the computational study, by using these formulations, a set of test instances is solved, and results are provided.
Multiple Criteria Target Classification Using Heterogeneous Sensor Data
(2019) Karasakal, Orhan; Atıcı, Bengü; Karasakal, Esra

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