Showing papers by "Istanbul Technical University published in 1996"
TL;DR: In this article, the authors investigated the refining of the product mixture obtained by the transesterification reaction (with an alkali catalyst) of neutralized rapeseed oil (extracted from the seeds of the rape plant cultivated in the Thrace region of Turkey) with methanol.
Abstract: The ester product of the vegetable oil−alcohol transesterification reaction (biodiesel) is the best and the most popular diesel fuel alternative. The refining of the transesterification reaction products is technically difficult and brings an extra cost. Also, the purity level of the biodiesel must conform to European Union standards for alternative diesel fuels. The target of this study was to investigate the refining of the product mixture obtained by the transesterification reaction (with an alkali catalyst) of neutralized rapeseed oil (extracted from the seeds of the rape plant cultivated in the Thrace region of Turkey) with methanol. To obtain pure biodiesel conformable to the standards, methods of washing with hot distilled water, dissolving in petroleum ether and then washing with distilled water, and neutralization with H2SO4 (1:1) were tested in the refining step. Washing with hot distilled water at 50 °C was chosen as the best refining process. The purity of the biodiesel obtained was about 99%.
190 citations
TL;DR: In this article, a literature review is made to assess the information on color removal and need for systematic evaluation of the results is emphasized, and results of the study are evaluated and discussed within the context of a systematic approach.
185 citations
TL;DR: In this article, a formal derivation of the improved Boussinesq equations of Madsen and Sorens (1992) is presented to provide the correct forms of the depth-gradient related terms.
165 citations
TL;DR: In-situ alcoholysis of soybean oil with methanol, ethanol,n-propanol, andn-butanol was investigated, as well as the extraction of the oil with these solvents as discussed by the authors.
Abstract: In-situ alcoholysis of soybean oil with methanol, ethanol,n-propanol, andn-butanol was investigated, as well as the extraction of the oil with these solvents, to explain the progress ofin-situ alcoholysis and to determine the parameters that affect this reaction Because methanol is a poor solvent for soybean oil, the amount of oil dissolved in methanol and converted to methyl esters was low afterin-situ alcoholysis Ethyl, propyl, and butyl esters of soybean fatty acids could be obtained in high yields fromin-situ alcoholysis of soybean oil with these alcoholsIn-situ alcoholysis proceeded through dissolution and alcoholysis of triglycerides successively, and the overall reaction rate was determined by the extraction and alcoholysis rates The parameters, affecting yield and purity of the product esters, were mainly those that favor extraction rate
116 citations
TL;DR: In this paper, the effects of silica fume and aggregate size on the softening response and brittleness of high strength concretes were investigated by measuring the fracture energy GF, the characteristic length lch and BRittleness index B.
114 citations
111 citations
TL;DR: In this article, a performance analysis based on a power density criterion has been carried out for an irreversible Joule - Brayton (JB) heat engine and the results obtained were compared with those of a power performance criterion.
Abstract: A performance analysis based on a power density criterion has been carried out for an irreversible Joule - Brayton (JB) heat engine. The results obtained were compared with those of a power performance criterion. It is shown that design parameters at maximum power density lead to smaller and more efficient JB engines than an engine working at maximum power output conditions. Due to irreversibilities in the heat engine, the power and thermal efficiency will reduce by a certain amount, however the maximum power density conditions still give a better performance than at the maximum power output conditions. The analysis demonstrated in this paper may provide a basis for the determination of optimal operating conditions and the design parameters for real JB heat engines.
92 citations
TL;DR: The Maden unit sensu stricto as mentioned in this paper was defined as a volcanoosedimentary succession of Middle Eocene age representing a short-lived back-arc basin which reached the stage of an embryonic ocean.
Abstract: The volcanosedimentary units of Late Mesozoic-Tertiary age that outcrop in the Southeast Anatolian orogenic belt are commonly referred to as the Maden complex. There is a long-lasting controversy over its definition, age, stratigraphic and structural position, and the origin, and thus, the orogenic evolution. To solve this problem, large strips across the Southeast Anatolian orogenic belt have been studied extensively, and different rock groups which were regarded previously as the Maden unit have been differentiated. Their major characteristics and differences have been identified. The Maden unit sensu stricto is here redefined as a volcanosedimentary succession of Middle Eocene age representing a short-lived back-arc basin which reached the stage of an embryonic ocean. Presently, the Maden group occurs mainly within the lower nappe stack of the nappe zone of the Southeast Anatolian orogen. It rests stratigraphically on an amalgamated nappe package consisting of the different metamorphic tectonic units and, in turn, is overlain tectonically by the upper nappe units.
87 citations
TL;DR: In this article, the photoinitiation of the polymerization of bulk cyclohexene oxide (CHO) containing N -ethoxy-2-methyl pyridinium hexafluorophosphate (EMP + PF 6 − ) and either anthracene or thioxanthone (TX) at λ inc> 340 nm was studied.
77 citations
TL;DR: A parametric shape grammar which can generate the plans of traditional Turkish houses is presented and the shape rule schemata are used for characterizing formal compositional aspects of this historical style.
Abstract: In this paper, a parametric shape grammar which can generate the plans of traditional Turkish houses is presented. The grammar is based on a corpus of traditional Turkish houses that have been built in Anatolia and Rumelia for the past five centuries. The shape rule schemata are used for characterizing formal compositional aspects of this historical style.
75 citations
TL;DR: In this article, the crystallization behavior of basalt glass at elevated temperatures was studied using glass samples prepared by melting the natural basalt rock from the Thrace region of Turkiye.
02 Sep 1996
TL;DR: In this article, a model improved as a part of the NATO TU Excavation project, that relates the cutting performance of mechanical excavators to rock mass cuttability index, is discussed with the recent data collected.
Abstract: In this paper the recent sewerage and metro tunnel projects in Istanbul are summarized. A model improved as a part of NATO TU Excavation project, that relates the cutting performance of mechanical excavators to rock mass cuttability index, is discussed with the recent data collected. The model may serve as a useful guide to contractors and machine manufacturers prior starting a tunnel project. RESUME: Dans cet expose on a resume les derniers travaux dans les tunnels d’Istanbul. On a realise ce model soutenu par le projet “ NATO-TU Excavation” et on a defini l’index de rupture des roches en tenant compte la performance mecanique des tunneliers a l’etat de creusement. On a critique aussi ce model en prenant base les donnees obtenues durant les travaux dans les tunnels. Nous pouvons dire que ce modele sera guide aux autres participants aux creusement des tunnels. ZUSAMMENFASSUNG: Mit dieser Arbeit werden die jungsten Tunnelprojekte in Istanbul vorgestellt. Im Rahmen NATO-Excavation Project wurde ein Modell, das die Leistungen der mechanischen Vortriebsmaschinen mit Hilfe eines definierten Schneidindex fur Gesteine feststellt, entwickelt. Das Modell wird mit den hier gesammelten Daten getestet. Es wird noch erklart, das das hier vorgestellte Modell schon in der Planungpshase des Tunnels fur den Zuliefererund Tunnelbaufirmen ein Wegweiser sein wird.
TL;DR: In this article, the effects of temperature on the efficiency of capillary imbibition mechanism were investigated, and the validity of scaling law when the temperature effect is involved was investigated.
TL;DR: In this article, the authors provided the conceptual proof that the yield coefficient is significantly lower for the anoxic growth on the basis of the energetics of the related metabolic processes, which is used for the interpretation of the very high values for the correction factor experimentally determined for a number of industrial wastewaters.
TL;DR: In this article, the fundamental equations of a thermopiezoelectric medium are expressed as the Euler-Lagrange equations of certain variational principles, deduced from a general principle of continuum physics by modifying it through an involutory (Legendre's or Friedrichs's) transformation.
TL;DR: In this paper, an analysis using maximum power density criteria has been carried out for an endoreversible Carnot heat engine, and the results have been compared with known results on maximum power analysis.
TL;DR: In this paper, the amplitude decay rate of the S-wave coda in seven frequency bands from 1.5 to 24 Hz was calculated from the analysis of each seismogram using four coda lengths.
TL;DR: In this article, the phase transition during free-radical crosslinking copolymerization of methyl methacrylate and ethylene glycol dimethACrylate was studied using the steady-state fluorescence method.
TL;DR: In this paper, a steady-state fluorescence technique was used to examine the annealing of films formed from high-T latex particles above the glass transition temperature, and the films were prepared by sintering pyrene-labeled poly(methyl methacrylate) latex particles.
Abstract: A steady-state fluorescence technique was used to examine the annealing of films formed from high- T latex particles above the glass transition temperature. The films were prepared by sintering pyrene-labeled poly(methyl methacrylate) latex particles. During the annealing processes, the transparency of the film changed considerably. Direct fluorescence emission from excited pyrene was monitored as a function of annealing temperature to detect these changes. Scanning electron microscopy in conjunction with Monte Carlo simulations of photon diffusion in latex film were used to interpret the fluorescence results. Healing temperature and time were measured at the point where the fluorescence emission intensity becomes maximum. This was associated with the longest optical path of a photon in latex film during healing of particle-particle boundaries. Healing activation energy was measured and found to be 10 kcal/mol.
TL;DR: In this paper, the thermal analysis of a hot box solar cooker which is manufactured in Istanbul Technical University, named as I.T.U.-2, has been done by using the fourth-order Runge-Kutta method.
TL;DR: In this article, the Winkler hypothesis is considered for the foundation and the effects of shear deformation and torsional effect of the foundation are included, and a special case finite element formulation is given for straight bars on elastic foundations.
TL;DR: In this article, the cationic polymerization of cyclic ethers such as cyclohexane oxide (CHO) and vinyl monomers such as butyl vinyl ether (BVE) and N-vinyl carbazole (NVC) is initiated upon irradiation at λ 380 nm in CH 2 CI 2 solution containing an allylic sulfonium salt.
Abstract: The cationic polymerization of cyclic ethers such as cyclohexane oxide (CHO) and vinyl monomers such as butyl vinyl ether (BVE) and N-vinylcarbazole (NVC) is initiated upon irradiation at λ 380 nm in CH 2 CI 2 solution containing an allylic sulfonium salt, namely, 2-ethoxycarbonyl-2-propenylthiophenium hexafluoroantimonate (1) (EMT + SbF 6 - ), and one of the following compounds : benzophenone, anthracene, thioxanthone, perylene or phenothiazine. Electron transfer and hydrogen abstraction mechanisms were proposed for the initiation step. Stable cation radicals of phenothiazine were also prepared, and the cationic polymerization of butyl vinyl ether was initiated by these cation radicals.
TL;DR: In this paper, the authors provide a critical appraisal of the relevant conceptual basis and propose a new approach for the experimental determination of the maximum specific growth rate in nitrification, which is successfully tested on domestic sewage.
TL;DR: In this article, the structured singular value method is applied to continuous-time SISO repetitive control systems in order to determine their stability and performance robustness in the presence of structured parametric modeling error in the plant.
Abstract: The structured singular value method is applied to continuous-time SISO repetitive control systems in order to determine their stability and performance robustness in the presence of structured parametric modeling error in the plant. Performance measures for repetitive control systems are introduced and the robust performance analysis using structured singular values is modified, taking the alternating magnitude behaviour of the sensitivity function of a repetitive control system into account. The analysis procedure is simplified considerably in the case of large time delay by noting that the upper and lower envelopes of the structured singular value plots are obtained from corresponding finite dimensional systems without any time delay. The analysis procedures developed are applied to an example on repetitive control of an electrohydraulic material testing machine, available in the literature, to demonstrate their usefulness.
TL;DR: In this article, the Direct Fluorescence method was used to study the healing process during latex film formation above the glass transition temperature, which was found to depend linearly on (time) 1/2, which was proposed by Prager and Tirrell.
Abstract: The Direct Fluorescence method was used to study the healing process during latex film formation above the glass transition temperature. The latex film was prepared from pyrene (P)-labeled poly(methyl methacrylate) (PMMA) particles. Heptane was used as a mixing agent. The steady-state fluorescence technique was employed to measure the density of polymer chains crossing the particle particle interface. Various latex films with different latex content were used to study the transparency below and above the healing temperature. Crossing density was found to depend linearly on (time) 1/2 , which was proposed by Prager and Tirrell.
TL;DR: In this paper, the regeneration of MnO/γ-Al 2 O 3 used as a sorbent to remove H 2 S from fuel gases was studied with a packed bed reactor.
01 Jan 1996
TL;DR: Gelation during solution free radical crosslinking copolymerization (FCC) of methyl methacrylate (MMA) and EDM was studied by using the steady state fluorescence technqiue as discussed by the authors.
Abstract: Gelation during solution free radical crosslinking copolymerization (FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) was studied by using the steady state fluorescence technqiue. FCC was performed in the presence of toluence at 75°C. Sol-gel transitions were monitored by observing the direct intensity of an excited pyrene (Py) during in situ fluorescence experiments for various toluence content. Gel points were determined and critical β exponents were found to be around 0.38. In situ swelling and drying experiments were performed at 50°C by monitoring Py intensity in disk-shaped gels produced by solution FCC. Li-Tanaka equation was employed to produce the cooperative diffusion coefficient, D c for swelling process. D c values were found to the around 10−6 cm2/s at 50°C. It was also observed that loosly formed gels swell much faster than densely formed gels.
TL;DR: In this article, the organic matter in 9 recent (not more than 250 years old) and ‘organic-rich’ sediments from the southern Black Sea shelf and upper slope have been characterized semi-quantitatively by Pyrolysis/Gas Chromatography/Mass Spectrometry (PY/GC/MS) and 13C Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CPMAS-NMR) spectrometry.
TL;DR: In this paper, the free vibrations of a stiffened conical thin shell within the context of the Donnell-Mushtari theory were studied, where a truncated cone with simply supported ends is reinforced by relatively closely spaced elastic stringers and/or rings.
TL;DR: In this paper, combined SO2 and total suspended particulate (TSP) concentrations from different locations in Istanbul province were used to investigate intense air pollution episodes from 1985 through 1991, which were associated mainly with high-pressure systems, inversions and low wind speeds.