Improving the performance of blocking supervisors

Son otuz yıl içerisinde bilgisayar, haberleşme ve elektronik teknolojisindeki hızlı gelişimin bir sonucu olarak yeni bir tür dinamik sistem ortaya çıkmıştır. Öyle ki bu tür dinamik sistemler incelendiğinde, büyük bir bölümünün çoğu zaman tamamının ayrık, zamandan bağımsız değişkenlerle kontrol edildiği görülmektedir. Üretim sistemleri, bilgisayar sistemleri, haberleşme sistemleri, hava trafik sistemleri gibi birçok sistem bu tür sistem sınıfına girmektedir. Bu tür sistemlerin davranışı genellikle eş zamansız olarak oluşan ayrık olaylara bağlı olarak değişir. Bu özellikleri nedeniyle bu sistemler Ayrık Olay Sistemleri olarak adlandırılmaktadır. Ayrık olay sistemi çok fazla olası kilitlenme içerdiğinde denetimsel gözetleyici olarak en az kısıtlamalı kilitlenmesiz çözümü seçmek tutucu bir çözüm oluşturabilir. O zaman toplam performansı arttırmak için kilitlenmesiz olma koşulunu esnetmek kaçınılmaz bir olgudur. Diğer bir taraftan tam başarımlı çözümü denetimsel gözetleyici olarak seçmek bazı olası kilitlenmelerden dolayı ciddi sistem arızalarına sebebiyet verebilir. O zaman bu iki sonucu bağlayan bir denetimsel gözetleyiciye ihtiyaç vardır. Bu yüzden bu çalışmada optimizasyon yaklaşımını kullanarak kilitlenme ve başarım arasındaki denge araştırılmıştır. İlk olarak kilitlenme ve başarılara karşılık gelen kelimelerin nümerik değerlerine dayanan yeni bir performans ederi ortaya çıkartılmıştır. Önerilen formülasyon klasik optimizasyon yaklaşımını barındıran temel değiş tokuş özelliğine sahiptir. Aynı zamanda istenilen işaretli dili olabildiğince üreten optimal kilitlenebilir çözümü araştıran yeni bir algoritma önerilmiştir. Anahtar Kelimeler: Ayrık olay sistemleri, kilitlenme, düzenli diller, performans değerlendirme.We can not model discrete event systems by employing ordinary differential equations, this being their most important difference from time-varying dynamic systems. Rather discrete event systems evolve in time in the form of events occurring at possibly irregular time intervals. Therefore, we often model them as regular languages represented by deterministic finite state automata. In addition, in order to examine the behavior of the system, we modify the behavior by a control action. Ramadge and Wonham's supervisory control theory is a powerful tool to build variety of modifications in the model through a supervisor. However, the supervisor can not usually mark all the desired behaviors of the system, which are built according to nonblocking and controllability constraints. Thus blocking becomes a crucial task in discrete event systems. Industrial examples give support to this observation too. We observe that supervisory control problems with blocking are generally more widespread than those without blocking, and blocking supervisors are preferred to nonblocking ones in several applications. Among these applications, database concurrency control, the protocols coupled with deadlock detection schemes are most popular since deadlock prevention and avoidance are impractical. When we examine a discrete event system within the corresponding admissible language, too many blockings may be realized. We then usually select minimally restrictive nonblocking solution as the supervisor, even though it is inadequate due to its restrictive behavior. Since it prevents all  uncontrollable  events that lead to blocking minimal restrictive nonblocking solution can provide a conservative result. As a result, the supervisor can generate only a small part of admissible marked language. As such this strategy may constrain the behavior of the system considerably. On the other hand, the completely satisfying solution generates all the admissible marked strings, but its price adds too many blockings to the supervised language. Therefore, neither of these two results can be acceptable in many discrete event system problems. Here the success of the supervisor is related to the generated admissible marked language. Then it will be of interest to relax the nonblocking requirement and consider the synthesis of blocking supervisors. What motivates us to consider blocking solutions is that by allowing a certain amount of blocking, we can increase the part of admissible marked language that can be achieved under control. At this point the following question needs to be answered. "How many blockings do arise?" This work aims to find a formal answer to this question. In the literature blocking supervisors were first studied by Chen and Lafortune. If possible, the proposed solution may improve the performance either by reducing the supervised language's blocking without affecting its achievement or by increasing the supervised language's achievement without affecting its blocking. But, the literature did not concern with improving the performance by reducing the blockings and achievements at the same time. Furthermore, the generated strings on the system have different meanings in practice. For example, some strings, which symbolize critic tasks, have high importance compared to other strings. Thus the differences between the strings have to be taken into consideration to select the best supervisor. In this work, we propose a new approach to overcome these drawbacks. Firstly, we suggest a new metric space and introduce a new performance measure including blocking. The performance of blocking supervisors hold on two concepts: blocking and failure. The defined performance measure captures the fundamental concept, as it is given over sum of blocking measure and non-satisfying measure. Afterwards we propose a new method to select an optimal blocking but also maximally permissive supervisor from the acceptable solution set. The proposed algorithm removes some strings in a sequence from the initial language in order to optimize the performance. As it is usually required to generate as many as possible admissible marked strings, the complete satisfying solution is selected as the initial language. Also it is proved that the final solution obtained will be the maximally permissive and the optimal blocking supervisor. Also, the method is explained over a database management system. Keywords: Discrete event systems, blocking, regular languages, performance evaluation

Imaging of subsurface lineaments in the southwestern part of the Thrace Basin from gravity data

Linear anomalies, as an indicator of the structural features of some geological bodies, are very important for the interpretation of gravity and magnetic data. In this study, an image processing technique known as the Hough transform (HT) algorithm is described for determining invisible boundaries and extensions in gravity anomaly maps. The Hough function implements the Hough transform used to extract straight lines or circles within two-dimensional potential field images. It is defined as image and Hough space. In the Hough domain, this function transforms each nonzero point in the parameter domain to a sinusoid. In the image space, each point in the Hough space is transformed to a straight line or circle. Lineaments are depicted from these straight lines which are transformed in the image domain. An application of the Hough transform to the Bouguer anomaly map of the southwestern part of the Thrace Basin, NW Turkey, shows the effectiveness of the proposed approach. Based on geological data and gravity data, the structural features in the southwestern part of the Thrace Basin are investigated by applying the proposed approach and the Blakely and Simpson method. Lineaments identified by these approaches are generally in good accordance with previously-mapped surface faults

Highlands of Giresun City in Prehistoric Era in the Light of Current Archaeological Findings

Archaeological researches in Giresun, started in 2009 with archaeological surveys and excavations. These works were mostly carried out at the shore of Giresun and on Giresun island. The works at the highlands of the region was started in 1944 and no significant findings were discovered in Alucra and Şebinkarahisar, which are located in this region. The works, which are carried out in the inner part of the Giresun city and in Alucra district and its vicinity, show a dense settlement pattern in Late Chalcolithic Age and in Early Bronze Age

Tectono-stratigraphical evolution of the Çankırı Basin (Central Anatolia, Turkey)

The Izmir-Ankara-Erzincan Suture Zone (IAESZ) demarcates the former position of the northern Neotethys ocean. Along the IAESZ, the Rhodope-Pontide fragments and Taurides collided and amalgamated in the Early Tertiary, leaving behind a number of basins with a thick in-fill that was accumulated during the subduction and collision processes. The Çankırı Basin is one of the largest of such Tertiary basins in Turkey and is located within the IAESZ. It is a unique area to study the subduction and collisionary processes and post-collisional history of central Anatolia, owing to a nearly complete sedimentary record from Late Cretaceous to Recent. This thesis presents an integrated stUdy concerning the Late Cretaceous to Recent tectono-stratigraphical evolution of the Çankırı Basin using stratigraphical studies, structural geology, kinematic analysis, paleomagnetic studies, 3D modeling, seismic interpretation and gravimetric analysis