Yazar "Kokten, Erkan Sami" seçeneğine göre listele

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    A cutting stock problem in the wood products industry: a two-stage solution approach
    (Wiley, 2022) Kokten, Erkan Sami; Sel, Cagri
    In this study, a cutting stock problem is addressed to determine the width/length of the wooden boards and select lumber in standard lengths for cutting a cable spool. A nonlinear mathematical model is introduced using Pythagoras' theorem. The aim is to minimize the total length of lumber used and equivalently the total amount of wood wasted. To reduce the computational burden, the mathematical model is decomposed into two submodels for sizing and cutting decisions, and a two-stage decomposition algorithm is proposed for solving the submodels subsequently. A simulated annealing metaheuristic combining the first-fit decreasing and increasing techniques (SA-FFD/I) is proposed to show the computational efficiency of the decomposition approach. The savings on the total length of lumber used and the total amount of wood wasted in production are achieved by the decomposition algorithm, which is 8% and 86.4% on average compared to the SA-FFD/I heuristic. Accordingly, a numerical analysis is conducted on a real case to assess how capacity load and demand pattern scenarios impact the solution. The ratio between the total amount of wood waste and the total length of lumber does not exceed 2.54% for a weekly planning horizon.
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    Effects of Catalysts on Modulus of Rupture and Chemical Structure of Heat-Treated Wood
    (Zagreb Univ, Fac Forestry, 2018) Ozcifci, Ayhan; Kokten, Erkan Sami; Ayrilmis, Nadir; Ozbay, Gunay; Altun, Suat
    Heat treatment process, which is widely used in the wood industry, has shown some negative effects on the mechanical strength of wood. The objective of this study was to investigate the effects of catalysts on the modulus of rupture (MOR), mass loss and chemical structure of heat-treated Scotch pine (Pinus sylvestris L.) samples. For this purpose, some catalysts (50 % NaOH and 47 % KOH solutions, solid KOH) were added to the heat treatment process. Heat treatment experiments were performed under the nitrogen atmosphere at the temperature of 212 degrees C for 2 h. The MOR and chemical changes monitored by FT-IR spectra were then examined for the test groups. According to the results of this study, the use of commercial solid potassium hydroxide (KOH) in heat treatment decreased the degree of strength loss and mass loss of heat-treated wood. The strength (MOR) loss of samples heat-treated in the presence of potassium hydroxide was found to be only 5.4 %, while the strength loss in non-catalytic treatment was found to be 12.5 %.
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    Modeling of Bio-Oil Production by Pyrolysis of Woody Biomass: Artificial Neural Network Approach
    (Gazi Univ, 2020) Ozbay, Gunay; Kokten, Erkan Sami
    This study is dedicated to developing a reliable artificial neural network (ANN) model to model the pyrolysis liquid product (bio-oil). Some related parameters with the bio-oil yield such as the pyrolysis temperature, duration, catalyst type, catalyst ratio, particle size, proximate, and ultimate analysis of the biomass were tested. Due to the different characteristics of different biomass types and pyrolysis methods, only slow and intermediate pyrolysis data from woody biomass were used in modeling. The correlation coefficients (R) were 0.992, 0.933, and 0.951 for training, validation, and testing, respectively. In order to evaluate the predictability of the ANN model, the predicted results were compared with the experimental results that were not introduced before. The simulated data were in good agreement with the experimental results indicating the reliability of the developed model. The relative impact results revealed that the most important parameter that affects the bio-oil yield was catalyst type (11.4%).
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    The pyrolysis characteristics of wood waste containing different types of varnishes
    (Tubitak Scientific & Technological Research Council Turkey, 2016) Ozbay, Gunay; Ozcifci, Ayhan; Kokten, Erkan Sami
    The wood industry produces large amounts of wood waste. This waste usually contains a number of nonwood materials, such as paints or varnishes. In this study, the pyrolysis characteristics of wood waste containing synthetic, polyurethane, and polyester varnishes were investigated for conversion into renewable liquid fuels. The elemental analysis and higher heating values of the bio-oils were determined. The chemical compounds present in the bio-oils obtained at an optimum temperature were identified by gas chromatography/mass spectroscopy analysis. The product yields and compositions were affected by the types of varnishes. The maximum bio-oil yield of 46.7% was obtained from pyrolysis of waste wood containing polyester varnish at a final pyrolysis temperature of 500 degrees C. The bio-oil produced from wood waste containing varnishes was composed mainly of phenols, aldehydes, acids, ketones, alcohols, benzenes, and N-containing compounds. The phenols accounted for the largest amount of compounds in the bio-oils. Therefore, the bio-oil produced from varnished wood waste could be a potential substitute for biofuels and green chemicals.
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    Statistical process control applications in plywood manufacturing
    (Pamukkale Univ, 2024) Yilmaz, Merve; Kokten, Erkan Sami
    Wood is a widely used material in industry due to its sufficient loadcarrying capacity, obtaining from sustainable sources and easiness in its processing, etc. Plywood is a wood panel manufactured from layers of wood veneer and combined under pressure with an adhesive. Plywood panels are widely used in the furniture and construction industry. In this study, the nonconformities during the plywood production process are analyzed using statistical process control methods. First, check sheet are created. p -quality control chart is created using this data. p -control chart is evaluated to investigate whether the process provides the desired quality level. In addition, the tree diagram and the cause -effect diagram are created after the information obtained by brainstorming technique. Also, in order to control the improvements in the process, an additional data including 15 days of data were collected in the 2nd Stage and a p -control chart was created. In this research, the nonconformities of plywood production process and their possible causes are analyzed.
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    SYNTHESIS AND CHARACTERIZATION OF RESOL TYPE PHENOL-FORMALDEHYDE RESIN IMPROVED BY SIO2-NP
    (Slovak Forest Products Research Inst, 2021) Ozbay, Gunay; Kokten, Erkan Sami; Ozcifci, Ayhan
    In this work, resol type phenol-formaldehyde (RPF) resin was modified with silicon dioxide nanoparticles (SiO2-Np). SiO2-Np was added at varying ratios from 1 to 4 wt.% to improve the bonding performance of the RPF resins. The physical characteristics of the nano-modified RPF (nano-RPF) resins were examined. The effects of modification were studied by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The results of FT-IR revealed that the nano-RPF resins were successfully produced by phenol, formaldehyde, and SiO2-Np. The nano-RPF resins demonstrated high thermal stability at temperatures above 500 degrees C. The adhesive performance of the nano-RPF resins was investigated under dry and wet conditions. The nano-RPF resins indicated better adhesive performance than unmodified RPF resin. The RPF resin could be improved by SiO2-Np.
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    Synthesis of Bio-Oil-phenol-Formaldehyde Resins under Alkali Conditions: Physical, Chemical and Thermal Properties of Resins and Bonding Performance
    (Zagreb Univ, Fac Forestry, 2020) Ozbay, Gunay; Cekic, Caglar; Ahmad, Muhammad Syarhabil; Kokten, Erkan Sami
    In the present study, bio-oil produced from vacuum pyrolysis of woody biomass has been investigated as a source of chemical feedstock. Bio-based resins were produced using the bio-oil with phenol substitutions ranging from 10 to 30 wt%. The conventional GC/MS analysis was carried out for the evaluation of the chemical composition of bio-oil. TGA, DSC and FT-IR analyses were used in order to characterize the bio-oil-phenol-formaldehyde (BPF) resins. The bonding quality of wood samples bonded with the BPF resins was investigated under different pre-treatment conditions. The highest shear strength was observed for the control samples bonded with the laboratory PF resin. As the amount of bio-oil was increased up to 30 wt%, the shear strength of the samples decreased from 12.08 to 11.76 N/mm(2). The bonding performance was not negatively affected by the combination of bio-oil under dry conditions. According to TS EN 12765 standard, the relevant performance requirements for bonded samples under dry conditions must be at least 10 N/mm(2). Relating to the standard, all samples bonded with BPF resins obtained the requirements for durability class C1. Under wet conditions, the bonding performance was negatively affected by the addition of bio-oil. However, the BPF resins fulfilled the durability requirements for C1, C2, and C3 specified in EN 12765 (2002).