Bu haftaki konumuz:Türk Mutfağı

Taha Toros Arşivi, Dosya No: 112-Lokantalar. Not: Gazetenin "Her Hafta Bir Sohbet" köşesinde yayımlanmıştır.Cooking, Turkishİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

Pneumatic-Type Non-Contact Gripper for Laparoscopic Surgery and Optimization of Test Parameters for Maximum Air Speed

During Laparoscopic surgeries, grippers are used to grasp and handle organs. Grasping joints of grippers have various toothed profiles to prevent organs from slipping. To prevent slipping, sufficient clamping force should be applied to grippers. Organ tissues may get stuck between joints and damaged. In this study, special-designed and pneumatic-type non-contact grippers for Laparoscopic surgeries relying on Bernoulliꞌs principle were produced and tested for performance in terms of the maximum air speed they can reach under specific conditions. Taguchi method was used for experimental design (with Taguchi L25 orthogonal sequence) and optimization. As parameters, 5 gripper types, 5 air pressures (3-6,5 bar), 5 flow rates (2-2,8 m3/h) were chosen. Results were evaluated with signal-to-noise ratio (S/N), analysis of variance and three-dimensional graphics. A 3rd-order polynomial regression model was used for air speed, and mathematical equation was obtained. The optimum combination was of 6 bar and 2,8 m3/h flow rate. Taguchi method results with verification tests were less than the admissible 20% error value. Reliability of optimization was tested by verification experiments performed within the specified confidence interval. The results are important in terms of developing grippers working without clamping force in laparoscopic surgeries and preventing gripper-induced tissue damage

Modeling creep and anelasticity in particle strengthened alloys with strain gradient crystal plasticity

Modeling creep and anelasticity in particle strengthened alloys with strain gradient crystal plasticity For small material volumes, size effects, e.g. due to the interface constraints or heterogeneous strain ¿elds, may signi¿cantly affect the mechanical behavior of metals such that a deformation mechanism that is less important for the response in bulk form may become decisive for the performance of the material. Such second order effects were observed experimentally in the last two decades and form engineering challenges for the development and production of high-end modern technology. For example, creep and anelasticity observed in metallic thin ¿lm components of capacitive RF-MEMS switches may lead to time dependent deviations from the design speci¿cations of the device. The characterization and understanding of the mechanical behavior of the material is indispensable to overcome the reliability issues of these switches which hinder their full commercialization. In this thesis, a numerical framework is presented for modeling the time dependent mechanical behavior of thin ¿lms made of particle strengthened fcc alloys as an extension of a previously developed strain gradient crystal plasticity (SGCP) model (here referred to as Evers-Bayley type model) for pure fcc metals. A physically based ¿ow rule for crystallographic slip is developed based on the dislocation-dislocation and dislocation-particle interaction mechanisms. The extended SGCP framework is intrinsically able to capture the effect of an inhomogeneous distribution of geometrically necessary dislocation densities on the material behavior via the formulation of a back stress incorporating a material length scale. In chapter 2, the physically based Evers-Bayley type model and a thermodynamically consistent strain gradient theory of crystal plasticity by Gurtin are compared by deriving micro-stresses for the Gurtin type formulation based on the energetic back stresses of the Evers-Bayley type models, incorporating dislocation-dislocation interactions. It is shown that the defect energy function for a micro-stress that con¬tains the physical description of the interaction between dislocations of different slip systems has a more complicated form than those suggested in literature and is possibly non-convex. It is also shown that similar boundary conditions can be de¿ned for the Evers-Bayley type and Gurtin type models despite their differ¬ent additional ¿eld equations within the ¿nite element context. Thereafter, in chapter 3, the SGCP model is employed in electromechanical ¿nite element simulations of bending of polycrystalline thin beams made of a pure metal and a two phase alloy with a focus on the description of anelastic material behavior. Sim¬ulation results obtained with the SGCP model show a macroscopic strain recovery over time following the load removal. However, a detailed analysis demonstrates that the anelastic relaxation time and strength have no solid physical basis. A comparison of the results with experimental data implies that a single deformation mechanism may not be adequate for capturing the material response. Moreover, the slip law falls short in describing the behavior of a particle enhanced material. Subsequently, an extension of the SGCP model for a more realistic description of the time dependent mechanical behavior of two phase alloys, i.e. creep and anelasticity, is given in chapter 4 and its appli¬cation in multiphysical simulations of a capacitive RF-MEMS switch is presented in chapter 5. A new constitutive rule for crystallographic slip is developed by considering dislocation-dislocation interactions and three distinct dislocation-particle interactions: i) the Orowan process, ii) the Friedel process and iii) the climb of edge dislocations over particles. The new constitutive rule is obtained by the combination of separate slip laws for each type of interaction and is built based on the physically well-founded Orowan type rate equation. A ¿ow rule for the slip rate of mobile dislocations governed by dislocation-dislocation interactions is written by taking into account the jerky and continuous glide regimes of dislocations. Slip laws corresponding to the Orowan and Friedel processes are constructed by considering thermally activated dislocation motion. The climb of edge dislocations is described via a thermal detachment model. Results of ¿nite element simulations of bending of a single crystalline thin beam and a micro-clamp experiment with the extended SGCP model show that creep and anelastic behavior of a metallic thin ¿lm can be predicted with the extended SGCP framework. The amounts of the plastic deformation, anelastic recovery strength and associated relaxation times strongly rely on particle properties, the diffusional rate and the magnitude of internal stresses. The results of the simulations of the micro-clamp experiment imply that inhomoge-neous material diffusion may play an important role in the anelastic behavior of polycrystalline thin ¿lms. The results also suggest that the internal stress formulation of the extended SGCP may need to be extended by considering additional sources of internal stresses. The extended SGCP framework is applied to analyse the behavior of a capacitive RF-MEMS switch in multiphysical simulations. The electrodes of the switch are considered to be made of a metal thin ¿lm with incoherent second phases and have a polycrystalline structure with columnar grains through the thickness and passivated surfaces. The variation of the gap between the electrodes over time is analyzed. First, the in¿uences of particle size, volume fraction, surface constraints and ¿lm thickness on the performance of the switch after a loading and unloading cycle are studied. Then, the effects of cyclic loading and the duration of the unloaded state between sequential cy¬cles are investigated. The results show that the residual changes in the gap and the amount and rate of time dependent recovery after the load removal are highly sensitive to the microstructure and the ¿lm thickness. The smallest amounts of permanent deformation and anelastic recovery are obtained with an upper elec¬trode made of a relatively thin ¿lm which has a surface passivation and involves small incoherent particles with a relatively large volume fraction. Furthermore, the simulations revealed that the maximum residual change of the gap measured after completion of the unloading stage of each cycle saturates within a few cycles. A shorter duration of the unloaded state between successive loading-unloading cycles leads to a larger maximum residual gap change. Due to the decreasing gap, the pull-in voltage also decreases within a few cycles and shows a tendency to level off to a certain value. However, the release voltage does not seem to be as sensitive to the residual deformations as the pull-in voltage. Finally, in chapter 6, the conclusions and recommendations for a future work are given

Türk Çini Sanatında Saz Yolu Ekolü

Kanûnî Sultan Süleyman dönemi Osmanlı Saray nakkaşhânesi sernakkaşı olan Şah Kulu, “Saz Yolu” adıyla bilinen bezeme üslûbunun ilk temsilcisidir. XVI. yüzyıl ilk yarısından XVII. yüzyıl başlarına kadar üretilmiş resimlerde, sivri uçlu kıvrık hançerî yapraklar, hatâyî üslûbu çiçekler, efsanevî hayvanlar (ejderha, zümrüd-ü ankā, ch’i-lin), orman hayvanları ve periler görülmektedir. Kanûnî Sultan Süleyman devrinde en parlak dönemi yaşayan Osmanlı sanatında ortaya çıkmış olan bu üslûp padişah tarafından büyük beğeni kazanmış yüzyıllar içinde tezhip, halkâr, cilt, çini ve seramik sanatlarında, kalem işlerinde, kumaş, halı ve maden gibi sanatlarda en güzel örneklerini vermiştir. XVI. yüzyılın ikinci yarısında Mimar Sinan’ın bazı yapılarında çiniyi bir tezyîni eleman olarak kullanması, bu yeni üslûbun çinide de en güzel örneklerinin ortaya çıkmasını sağlamıştır. Saray nakkaşhânesinin hazırlamış olduğu bezemeler İznik atölyelerinde çiniye sıraltı tekniği ile uygulanmıştır. Bu dönemde çinide teknik açıdan ulaşılan kalite, motif ve desenlerle birleşmiş ve mükemmel eserler ortaya çıkmıştır. Şah Kulu tarafından Osmanlı süsleme sanatına katılmış olan saz üslûbunun çini sanatında da örnekleri görülmektedir. “Türk Çini Sanatında Saz Yolu Ekolü” adlı tezimizde, bu üslûpta kullanılmış karakteristik motiflerin çini sanatında daha önce değerlendirilmemiş olması, çalışmanın önemini arttırmaktadır. Tez üç bölümden oluşmaktadır: Birinci bölümde Şah Kulu’nun hayatı, saz üslûbu ve bu üslûbun kullanıldığı diğer sanat dalları incelenmiştir. İkinci bölümde Topkapı Sarayı Sünnet Odası dış cephesindeki yekpâre saz üslubu pano’nun motif özellikleriyle beraber tanıtılmasına çalışılmış, üçüncü bölümde ise, İstanbul’daki bazı çinili yapılarda, Saz Yolu Ekolü’nün üslûp özelliklerini gösteren örneklerden yola çıkılarak, resimleri ile ayrıntılı olarak ele alınmıştır. Değerlendirme ve Sonuç bölümde, saz üslûbu özellikleri taşıyan İstanbul’daki çinili yapılara ait örneklerin birbirleriyle benzerliklerini ve farklılıklarını ortaya koyan karşılaştırmalar, motif çizimleriyle bir arada verilmiştir. Türk Çini sanatında saz üslûbu motiflerinin yeri ve öneminin çizimlerle ele alındığı bu tezin, bundan sonraki çalışmalara yardımcı olacağı düşüncesindeyiz.Şah Kulu who was the chief muralist of The Ottoman Palace Design-House (Nakkaşhâne) during the period of Suleiman The Magnificent is the first representative of Saz üslûbu (Leafy Way) decoration style. We can see the sharp-pointed, curved dagger-shaped leaves, (hatâyî) style flowers, mythical animals (dragon, phoenix, ch’i-lin), forest animals and fairies on the paintings made during from the first half of XVI. to the early XVII. centuries. This style had its brightest era during the period of Suleiman The Magnificent who has shown a strong appreciation to its outcomes. And this style had produced its best samples in the arts of ornamentation, (halkâr), gold, book-binding, hand-drawn painting (kalem işi), clothes, carpet arts, mine working, tiling and ceramics for the centuries to come. In the second half of XVI. century; by use of tiles on many of the structures, Royal Achitect (Mimar) Sinan had provided the best samples of this new style in tile art. Tiles designed by artists of Nakkaşhane were produced at Iznik (Nikeae) workhouses by applying the underglaze (sıraltı) technique. In this period; with a combintion of designs, figures and the technique, many tiles and kitchenware (evani) were produced with excellent quality. Moreover, in the same period, many good examples of saz-yolu style ornamentation by Şah Kulu were created. In the present thesis, as its name “Saz-Yolu Ecole In Turkish Tile Art” (Türk Çini Sanatında Saz Yolu Ekolü) implies, an evaluation of the characteristic motifs used in this style attaching a special importance to it in the develoment of Turkih tile art. Present volume is composed of the following chapters: Şah Kulu’s life, the “saz-style” and many branches of art that uses this style are summarized in the first chapter. In the second chapter; the motif characteristic and description of the massive “Saz-Yolu” Pane on the external wall of the “Sünnet Odası” (The Circumcision Room) in Topkapı Palace has taken place. In the third chapter; the samples that show the style characteristics of Saz üslûbuEcole on some tiled structures in İstanbul have been specified together with further information about these structures. Characteristics of specified motifs have also been represented in detail with their pictures. In the assessment and conclusion chapter; the comparisons that represent the similarities and differences of the samples we have determined in Istanbul on the tiled structures showing the characteristics of saz style have been given with the motif drawings. We have the opinion that our present perspective and approach with the detailed drawings, on the The Saz Style motifs in Turkish Tile Art will help the further studies in the area