A secured message transmission protocol for vehicular ad hoc networks

Vehicular Ad hoc Networks (VANETs) become a very crucial addition in the Intelligent Transportation System (ITS). It is challenging for a VANET system to provide security services and parallelly maintain high throughput by utilizing limited resources. To overcome these challenges, we propose a blockchain-based Secured Cluster-based MAC (SCB-MAC) protocol. The nearby vehicles heading towards the same direction will form a cluster and each of the clusters has its blockchain to store and distribute the safety messages. The message which contains emergency information and requires Strict Delay Requirement (SDR) for transmission are called safety messages (SM). Cluster Members (CMs) sign SMs with their private keys while sending them to the blockchain to confirm authentication, integrity, and confidentiality of the message. A Certificate Authority (CA) is responsible for physical verification, key generation, and privacy preservation of the vehicles. We implemented a test scenario as proof of concept and tested the safety message transmission (SMT) protocol in a real-world platform. Computational and storage overhead analysis shows that the proposed protocol for SMT implements security, authentication, integrity, robustness, non-repudiation, etc. while maintaining the SDR. Messages that are less important compared to the SMs are called non-safety messages (NSM) and vehicles use RTS/CTS mechanism for NSM transmission. Numerical studies show that the proposed NSM transmission method maintains 6 times more throughput, 2 times less delay and 125% less Packet Dropping Rate (PDR) than traditional MAC protocols. These results prove that the proposed protocol outperforms the traditionalMAC protocols

ExploreASL: an image processing pipeline for multi-center ASL perfusion MRI studies

Arterial spin labeling (ASL) has undergone significant development since its inception, with a focus on improving standardization and reproducibility of its acquisition and quantification. In a community-wide effort towards robust and reproducible clinical ASL image processing, we developed the software package ExploreASL, allowing standardized analyses across centers and scanners. The procedures used in ExploreASL capitalize on published image processing advancements and address the challenges of multi-center datasets with scanner-specific processing and artifact reduction to limit patient exclusion. ExploreASL is self-contained, written in MATLAB and based on Statistical Parameter Mapping (SPM) and runs on multiple operating systems. To facilitate collaboration and data-exchange, the toolbox follows several standards and recommendations for data structure, provenance, and best analysis practice. ExploreASL was iteratively refined and tested in the analysis of >10,000 ASL scans using different pulse-sequences in a variety of clinical populations, resulting in four processing modules: Import, Structural, ASL, and Population that perform tasks, respectively, for data curation, structural and ASL image processing and quality control, and finally preparing the results for statistical analyses on both single-subject and group level. We illustrate ExploreASL processing results from three cohorts: perinatally HIV-infected children, healthy adults, and elderly at risk for neurodegenerative disease. We show the reproducibility for each cohort when processed at different centers with different operating systems and MATLAB versions, and its effects on the quantification of gray matter cerebral blood flow. ExploreASL facilitates the standardization of image processing and quality control, allowing the pooling of cohorts which may increase statistical power and discover between-group perfusion differences. Ultimately, this workflow may advance ASL for wider adoption in clinical studies, trials, and practice

Türkiye ekonomisinde parasal aktarımın ampirik bir analizi

The purpose of this two-essay thesis is to empirically investigate the characteristics of the monetary transmission mechanism in the Turkish economy. The first essay is an attempt to test the presence of a bank lending channel of monetary transmission by exploiting a dynamic panel data modelling approach. The empirical investigations are focused on the bank lending behaviour of 58 deposit money banks covering the period of 1988-1999. The results of the model estimations provide no evidence of a potential for a bank lending channel to exist in the Turkish economy. Such an outcome is reflected by the lack of a significant relationship between monetary policy indicators and the growth rate of the loan msupply in the estimated models. However, the findings imply that bank lending behaviour is influenced significantly by bank specific factors such as the balance sheet strength and the quality of the asset portfolio, and by government debt sales to the banking system. The second essay of the thesis is an attempt to trace the adjustment dynamics of the monetary transmission process by using the cointegration analysis of time series. The quarterly macroeconomic data exploited in the empirical investigations cover the period of 1985:1-2001:4. The findings imply that the monetary transmission process in the Turkish economy can be characterised by the monetary accommodation of high inflation and budget deficits, the outcome of which is an endogenous credit money expansion.Bu iki makaleli tezin amacı, Türkiye ekonomisinde, parasal aktarım mekanizmasının özelliklerini ampirik olarak incelemektir. Bu bağlamda, birinci makale, parasal aktaranda banka kredisi kanalının işlerliğinin olup olmadığım, dinamik panel veri modelleme yaklaşımmdan yararlanarak sınamak için bir girişimdir. Çalışmadaki ampirik incelemeler, 1988-1999 dönemi kapsamında 58 mevduat bankasının kredi verme davranışı üzerinde odaklanmaktadır. Model tahminlerinin sonuçlan, Türkiye ekonomisinde bir banka kredisi kanalının olma potansiyeli konusunda hiç bir kanıt sağlamamaktadır. Böyle bir sonuç, tahmin edilen modellerde, para politikası göstergeleri ile kredi arzı büyüme oram arasındaanlamlı bir ilişkinin yokluğu ile ortaya konmaktadır. Bununla beraber, bulgular, kredi verme davranışının, bilanço gücü ve aktif portföyü kalitesi gibi bankaya özgü etkenlerden ve kamu borçlarının bankacılık sistemi kanalıyla finansmamndan önemli derecede etkilendiği sonucunu ortaya koymaktadır. Tezin ikinci makalesi ise, zaman serilerinde eşbütünleşme analizi kullanmak yoluyla, parasal aktarım sürecinin uyum dmamiklerini ortaya çıkarmak için bir girişimdir. Ampirik incelemelerde kullanılan üçer aylık makroekonomik veriler 1985:1-2001:4 dönemini kapsamaktadır. Bulgulara göre; Türkiye ekonomisinde parasal aktaran süreci, yüksek enflasyona ve bütçe açıklarına olan parasal eşlik edicilikle tanımlanabilir ki, bunun sonucu içsel bir kredi-para genişlemesidir.Ph.D. - Doctoral Progra

A morphological study on the venom apparatus of spider Larinioides cornustus (Araneae, Araneidae)

The morphological structure of the venom apparatus of Larinioides cornutus was studied using a scanning electron microscope(SEM). The Venom glands are situated in the anterior cephalic part of the prosoma, and each gland consists of a long cylindrical part and an adjoining duct, which terminates at the tip of the cheliceral fang. Each chelicera consists of 2 parts: a stout basal part covered by hair, and a movable fang. There are parallel grooves on the dorsal surface of the fang. The ventral surface has hollows like saw teeth. A venom pore is situated on the subterminal part of the fang. Below the fang, there is a cheliceral groove between the teeth. Each side of the groove is armed with cuticular teeth. Venom glands are small and similar to an aurbergine in shape. Each gland is surrounded by completely striated muscular fibers. The venom produced in the venom glands is ejected into the fang through the duct by contraction of these muscular fibers. © TÜBİTAK

Calibration of 2D ultrasound in 3D space for robotic biopsies

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Freehand Ultrasound technique is widely used in intraoperative biopsy procedures for detecting the volumes of interest. Freehand ultrasound probe is faster and flexible with 6 degrees of freedom. Thats why the imaging system must be calibrated in 3D space before integrating it with Robotics Biopsy System. In this paper we present a 3D space calibration method using a multipoint cross-wire phantom. The Ultrasound probe is attached to a robotic manipulator arm which moves it over the phantom in precise steps of distances and angles. The position and orientation of the probe is tracked by an optical tracking system. Optical markers are placed on the probe, phantom tank and the validation needle. The optical tracking system returns the position and orientation of the reference frames attached to these optical markers. The location of threads with reference to the frame of Ultrasound probe is found using this information. These values and the values returned by a mathematical model of the calibration box are used to construct the calibration matrix. The whole system is automated so it can process high number of frames which makes it rapid and more accurate. This process is used to calibrate the space for an automated needle insertion biopsy robot. The accuracy of the system was checked by a validation needle in 3D space. RMS error of the experiment groups on average was 1.67mm.TÜBİTA

Calibration of 2D ultrasound in 3D space for robotic biopsies

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Freehand Ultrasound technique is widely used in intraoperative biopsy procedures for detecting the volumes of interest. Freehand ultrasound probe is faster and flexible with 6 degrees of freedom. Thats why the imaging system must be calibrated in 3D space before integrating it with Robotics Biopsy System. In this paper we present a 3D space calibration method using a multipoint cross-wire phantom. The Ultrasound probe is attached to a robotic manipulator arm which moves it over the phantom in precise steps of distances and angles. The position and orientation of the probe is tracked by an optical tracking system. Optical markers are placed on the probe, phantom tank and the validation needle. The optical tracking system returns the position and orientation of the reference frames attached to these optical markers. The location of threads with reference to the frame of Ultrasound probe is found using this information. These values and the values returned by a mathematical model of the calibration box are used to construct the calibration matrix. The whole system is automated so it can process high number of frames which makes it rapid and more accurate. This process is used to calibrate the space for an automated needle insertion biopsy robot. The accuracy of the system was checked by a validation needle in 3D space. RMS error of the experiment groups on average was 1.67mm.TÜBİTA