Global ETD Search

11	Estimating Thermal Conductivity and Volumetric Specific Heat of a Functionally Graded Material using Photothermal Radiometry Koppanooru, Sampat Kumar Reddy 12 1900 (has links) Functionally graded materials (FGMs) are inhomogeneous materials in which the material properties vary with respect to space. Research has been done by scientific community in developing techniques like photothermal radiometry (PTR) to measure the thermal conductivity and volumetric heat capacity of FGMs. One of the problems involved in the technique is to solve the inverse problem, i.e., estimating the thermal properties after the frequency scan has been obtained. The present work involves finding the unknown thermal conductivity and volumetric heat capacity of the FGMs by using finite volume method. By taking the flux entering the sample as periodic and solving the discretized 1-D thermal wave field equation at a frequency domain, one can obtain the complex temperatures at the surface of the sample for each frequency. These complex temperatures when solved for a range of frequencies gives the phase vs frequency scan which can then be compared to original frequency scan obtained from the PTR experiment by using a residual function. Brute force and gradient descent optimization methods have been implemented to estimate the unknown thermal conductivity and volumetric specific heat of the FGMs through minimization of the residual function. In general, the spatial composition profile of the FGMs can be approximated by using a smooth curve. Three functional forms namely Arctangent curve, Hermite curve, and Bezier curve are used in approximating the thermal conductivity and volumetric heat capacity distributions in the FGMs. The use of Hermite and Bezier curves gives the flexibility to control the slope of the curve i.e. the thermal property distribution along the thickness of the sample. Two-layered samples with constant thermal properties and three layered samples in which one of the layer has varying thermal properties with respect to thickness are considered. The program is written in Fortran and several test runs are performed. Results obtained are close to the original thermal property values with some deviation based on the stopping criteria used in the gradient descent algorithm. Calculating the gradients at each iteration takes considerable amount of time and if these gradient values are already available, the problem can be solved at a faster rate. One of the methods is extending automatic differentiation to complex numbers and calculating the gradient values ahead; this is left for future work. Volumetric specific heat Volumetric heat capacity Functionally Graded Materials Brute force Gradient descent optimization Heat -- Transmission. Radiation -- Measurement.
12	Serving IoT applications in the Computing Continuum Gallage, Malaka, De Silva, Dasith January 2024 (has links) This thesis tackles the topic of serving IoT applications in the computing continuum. It proposes an approach to place applications in the tiers of the continuum, considering latency and energy as predefined metrics. It presents a system model to represent the computing continuum environment, and then, defines an optimization function that is tailored to meet the specific requirements of the IoT applications. The optimization function addresses the relationship between latency and energy consumption in the framework of IoT service provision, and it is implemented in two different directions: (1) the first direction uses a modified Genetic algorithm, and (2) the second direction utilizes the Machine learning concept. To evaluate the performance of the proposed approach, we incorporate different testbed setups and network configurations. All the setups and configurations are designed to represent the diverse demands of IoT applications. Then, different algorithms (such as Non-dominated Sorting Genetic Algorithm (NSGA), Brute Force, and Machine Learning) are implemented to provide different application placement scenarios. The results highlight the efficiency of the proposed approach in comparison with the Brute Force optimal solution while meeting the application requirements. This thesis proposes an optimized solution for serving IoT applications in the computing continuum environment. It considers two essential metrics (latency and energy consumption) in the applications placement processes while meeting the diverse functional and non-functional requirements of these applications. The study provides insights and ideas for future research to refine strategies that will minimize latency and energy consumption. It also urges researchers to consider more metrics while developing and implementing IoT applications. The requirements related to computing resources and performance levels make the development and implementation of these applications complex and challenging. This study serves as a foundational stepping stone towards addressing those challenges. Computing Continuum Cloud Computing Fog Computing Edge Computing IoT Applications Latency Energy Consumption Genetic Algorithm NSGA Brute Force Machine Learning. Computer and Information Sciences Data- och informationsvetenskap
13	A shoulder-surfing resistant graphical password system Alesand, Elias, Sterneling, Hanna January 2017 (has links) The focus of this report is to discuss graphical password systems and how they can contribute to handle security problems that threaten authentication processes. One such threat is shoulder-surfing attacks, which are also reviewed in this report. Three already existing systems that are claimed to be shoulder-surfing resilient are described and a new proposed system is presented and evaluated through a user study. Moreover, the system is compared to the mentioned existing systems to further evaluate the usability, memorability and the time it takes to authenticate. The user study shows that test subjects are able to remember their chosen password one week after having registered and signed in once. It is also shown that the average time to sign in to the system after five minutes of practice is within a range of 3.30 to 5.70 seconds. The participants in the experiments gave the system an average score above 68 on the System Usability Scale, which is the score of an average system. shoulder-surfing resistant graphical password system guessing attacks graphical passwords recognition-based recall-based pure recall-based password security password space pictorial superiority effect brute-force attack dictionary attack hot-spots memorability graphical components authentication Computer Sciences Datavetenskap (datalogi)
14	Užití techniky lámání hesel u komprimačních formátů RAR, ZIP a 7z a extrakce hesel z samorozbalovacích archivů / Analysis of the Possibility of Password Break through for RAR, ZIP and 7z Formats Prustoměrský, Milan January 2013 (has links) This Thesis deals with analysis of the possiblity of password breakthrough for common compression formats and password extraction from self-extraction archives used for malicious software. Structure of compression programs, ciphers and connection between cipher and archives is described. Common and specialized attacks on archives and ciphers are described. Structure of self-extracting archives and password location is used to create extractor of passwords in self-extracting archives.
15	Students’ Perception of Cyber Threat Severity : Investigating Alignment with Actual Risk Levels Erfani Torbaghani, Ramtin January 2023 (has links) This study aims to investigate the alignment between students’ perception of cyber threats and their actual risk levels. A mixed-method approach was used, where data was collected from Swedish university students through questionnaires, capturing their perception, familiarity, experience, and protective behaviors. Information regarding the actual risk levels of cyber attacks was obtained from interviews with cyber security professionals and other expert sources, such as cyber security reports. The results showed that students perceive malware, ransomware, phishing, and insecure passwords as the most dangerous threats to society, while denial of service (DoS) attacks and packet sniffing were considered less severe. These findings align somewhat with the suggested threat levels. However, notable proportions of students perceived these threats as moderately dangerous or less severe, suggesting room for improvement in their understanding. The results also showed that protective behaviors among students are generally low, particularly in regards to IoT security. Future work should therefore explore the public’s perception, protective behavior and knowledge of IoT security, but also attacks that are common against such devices. / Denna studie jämför universitetsstudenters uppfattning om hur farliga olika cyberhot är med de faktiska risknivåerna för dessa hot. Data på studenternas uppfattning, bekantskap, erfarenhet och beteenden samlades in genom frågeformulär, medans information om cyberhotens faktiska risknivåer inhämtades från intervjuer med cybersäkerhetsproffs och andra experskällor som cybersäkerhetsrapporter och artiklar. Resultaten visade att studenterna uppfattar malware, ransomware, phishing och osäkra lösenord som de farligaste hoten mot samhället, medan denial of service (DoS)-attacker och packet sniffing ansågs vara mindre allvarliga. Dessa fynd överensstämde något med de föreslagna risknivåerna. Dock ansåg en anmärkningsvärd andel av studenterna dessa hot som måttligt farliga eller mindre allvarliga, vilket tyder på utrymme för förbättringar i deras förståelse. Resultaten visade också att skyddande beteenden bland studenter generellt är låga, särskilt när det gäller IoT-säkerhet. Framtida studier bör därför utforska allmänhetens uppfattning, skyddsbeteende och kunskap om IoT-säkerhet, men även attacker som är vanliga mot sådana enheter. Cyber Security Cyber Threat Perception Cyber Attack Ransomware Malware Phishing Packet Sniffing Denial of Service Insecure Passwords IoT Vulnerability Scanning Brute Force Attacks Awareness Behaviour Familiarity University Students Computer and Information Sciences Data- och informationsvetenskap
16	Data Encryption on a Network Luque González, Jorge, Arenchaga Fernandez, Ignacio January 2010 (has links) In this project you can find a study about different encryption algorithms, which are use to safeguard the information on messages over the network. We have developed a client-server application which will send information through the network which has to be secured. There are two kinds of encryption algorithms, the symmetric and the asymmetric key algorithms. Both were used to establish the communication, the asymmetric algorithm (RSA) is used to set up a symmetric key and then, all the communication process is done only with the symmetric algorithm (Blowfish). / En este proyecto encontraras un estudio sobre diferentes algoritmos de encriptación, que son usados para salvaguardar la información en mensajes por la red. Además hemos desarrollado una aplicación cliente-servidor que enviara información a través de la red de forma segura. Hay dos tipos de algoritmos de encriptación, los simétricos y los asimétricos. Ambos tipos de algoritmos son utilizados para establecer la comunicación, el asimétrico (RSA) es utilizado para establecer la clave del simétrico y a partir de entonces se utilizara exclusivamente el algoritmo simétrico (Blowfish). encryption decryption DES Triple-DES security serpent blowfish Diffie-Hellman RSA AES private key public key security attack brute force man-in-the-middle. encriptacion decriptacion DES Triple-DES seguridad serpent blowfish Diffie-Hellman RSA AES clave privada clave pública ataque fuerza bruta man-in-the-middle Computer Sciences Datavetenskap (datalogi) Telecommunications Telekommunikation Computer Sciences Datavetenskap (datalogi)
17	Kryptoanalýza symetrických šifrovacích algoritmů s využitím symbolické regrese a genetického programování / Cryptanalysis of Symmetric Encryption Algorithms Using Genetic Programming Smetka, Tomáš January 2015 (has links) This diploma thesis deals with the cryptanalysis of symmetric encryption algorithms. The aim of this thesis is to show different point of view on this issues. The dissimilar way, compared to the recent methods, lies in the use of the power of evolutionary principles which are in the cryptanalytic system applied with help of genetic programming. In the theoretical part the cryptography, cryptanalysis of symmetric encryption algorithms and genetic programming are described. On the ground of the obtained information a project of cryptanalytic system which uses evolutionary principles is represented. Practical part deals with implementation of symmetric encrypting algorithm, linear cryptanalysis and simulation instrument of genetic programming. The end of the thesis represents experiments together with projected cryptanalytic system which uses genetic programming and evaluates reached results.

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