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关键词： Computer science  

摘要： Viscous fluids, such as honey and molten chocolate, are common materials frequently seen in our daily life. These viscous fluids exhibit characteristic behaviors. Capturing and understanding such dynamics have been required for various applications. Although recent research made advances in simulating the viscous fluid dynamics, still many challenges are left to be addressed. In this dissertation, I present novel techniques to more efficiently and accurately simulate viscous fluid dynamics and propose a parameter identification framework to facilitate the tedious parameter tuning steps for viscous materials. In fluid simulation, enforcing the incompressibility robustly and efficiently is essential. One known challenge is how to set appropriate boundary conditions for free surfaces and solid boundaries. I propose a new boundary handling approach for an incompressible particle-based solver based on the connectivity analysis for simulation particles. Another challenge is that previously proposed techniques do not scale well. To address this, I propose a new multilevel particle-based solver which constructs the hierarchy of simulation particles. These techniques improve the robustness and efficiency achieving the nearly linear scaling unlike previous approaches. To simulate characteristic behaviors of viscous fluids, such as coiling and buckling phenomena and adhesion to other materials, it is necessary to develop a specialized solver. I propose a stable and efficient particle-based solver for simulating highly viscous fluids by using implicit integration with the full form of viscosity. To simulate more accurate interactions with solid objects, I propose a new two-way fluid-solid coupling method for viscous fluids via the unified minimization. These approaches also improve the robustness and efficiency while generating rotational and sticky behaviors of viscous fluids. One important challenge for the physically-based simulation is that it is not obvious how to choose a

关键词： Computer science  

摘要： With plans for advancing into the rest of the solar system in the coming decades, an understanding of how interlinked satellite systems behave as a network will be essential. The relatively recent development of optics as a method of space communication means that inter-satellite networks are more feasible than ever. That said, there are currently no analyses which take into account a planet-wide, largely uncoordinated, optically linked satellite network. To provide a look at the properties of such a network, movement and connections of Earth's currently active satellites were simulated based on real-world data, and their networks modeled via graphs. Ultimately, it was found that many properties of such a network are periodic, fluctuating in sync with the orbital time of low-earth orbit satellites. This, among other data, suggests that the peaks of these waves are caused by a meeting of satellites near the north and south poles.

关键词： Artificial intelligence   Computer science  

摘要： Tracking multiple objects in video is critical for many applications, ranging from vision-based surveillance to autonomous driving. The popular solution to Multiple Object Tracking (MOT) is the tracking-by-detection strategy, in which, detections of each frame from an external detector are associated and connected to form target trajectories in either online or offline batch mode. Following this strategy, the challenges of robust tracking comes mainly from three aspects: discrimination of the appearance similar targets; handling of the noise from input detections; unifying the separated function modules for generalizability. Recently, deep neural network (DNN) has demonstrate its ability to automatically learn discriminative features from training samples thus achieves success in various computer vision tasks. My research works are to leverage this powerful learning ability of DNN to tackle the above challenges for robust MOT in real world application. In this dissertation, I first introduce the popular framework of MOT system, the datasets, the evaluation metric and challenges in MOT. Then I discuss a work that encodes the structure prior of curvilinear structures in the rank-1 tensor approximation tracking framework to reduce the ambiguity rising from indistinguishable curvilinear structures parts. This work uses convolutional neural network to generate more reliable candidates for tracking and consequently improves the tracking robustness. In the third chapter, I present a work that adapts the DNN based Single Object Tracking (SOT) techniques for missing detection recovery. SOT tracker in this work merges the originally separated feature extraction and similarity evaluation as an integrated affinity estimator. Learning of the integrated affinity estimator requires dedicated affinity samples to be manually fabricated from ground truth association, which usually does not guarantee the consistent data distribution between training and inference phases. In Chapter 4,

关键词： Communication   Aerospace engineering   Computer science  

摘要： In December 2003, Congress passed the Vision 100–Century of Aviation Reauthorization Act, which mandated the overhaul of our National Airspace System. The goal of this program, called the Next Generation Air Transportation System (NextGen), is to modernize the nation’s National Airspace System (NAS) in the areas of communication, navigation, and surveillance. Included with the mandates of this program are security requirements to ensure the operation of this system in the event of malfunctions or threats. The surveillance portion of this new program, called Automatic Dependent Surveillance-Broadcast (ADS-B), relies on cooperative aircraft reporting their own Global Positioning System (GPS) position to Air Traffic Control (ATC). A perceived weakness of this system is that aircraft broadcast their position in an unencrypted message format, which allows third parties the opportunity to monitor the track of aircraft, or to copy, possibly modify, and re-transmit these messages so as to overwhelm air traffic controllers. To correct this weakness, several encryption methods have been proposed by researchers, but this requires a modification of an internationally standardized format that is already deployed in several parts of the globe. Other surveillance techniques include multilateration (MLAT), which is currently limited to remote geographic areas, and data fusion of multiple positioning sources, which has not yet been organized for a near-term solution. This paper explored the use of the NextGen data (text) communications technology, called Controller Pilot Data Link Communication (CPDLC), an alternate display mode for air traffic controllers, and additional strategies to assist pilots and controllers with a short term solution to an apparent weakness of ADS-B.

关键词： 计算机科学与技术   现代化   应用   措施  

摘要： 随着信息化的发展,在现代信息化建设中,计算机科学与技术的作用愈加突出,当前其已经很好地运用到各个领域中,推动了各个行业的发展,提高了计算机科学技术的水准.但是就当前而言,计算机科学与技术在各个行业中应用还存在一定问题,要求我们必须认真地探究其应用的必要性,并根据实际情况和需要来进行计算机科学与技术现代化应用措施的制定,希望能够推动计算机科学与技术更好地发展,将其作用真正地发挥出来.

关键词： Protocols   Optimization   Cryptography   Image color analysis   Computer science   Image quality   Image steganography   information hiding   secret text sharing   enhanced least significant bit steganography  

摘要： Text Steganography has become a dominant research field in information sharing domain and many researches are being conducted to strengthen this area. Researches around the amount of secret message that could be stored in a given cover image is always critical for any steganography technique used to share the secret text. This research paper proposes an enhanced Least Significant Bit (eLSB) embedding technique in steganography, through which the quality of cover image is improved, when compared to typical LSB algorithm used in steganography. The proposed method employs in spatial domain and it does the secret message encoding in two phases. The first phase generates the metadata and embeds the header information in first few bytes of cover image and then the following phase takes care of processing secret message and storing the secret message in cover image using an optimized way, which is possible through analyzing secret text's character sequences. Proposed work results into occupying lesser space for the given secret text in cover image and hence leads to the better stego image quality than existing LSB algorithms. As the algorithm works on optimizing secret message during embedding phase itself, this technique enables high capacity embedding rate, additional security due to secret message preprocessing and enhanced cover image quality. The results are compared with LSB algorithm and compared to Peak Signal to Noise Ratio (PSNR), Mean Square Error (MSE) and Root Mean Square Error (RMSE) values to prove the proposed algorithm performs better on secret text embedding in cover image.

关键词： Computer science  

摘要： The purpose of the article is the theoretical rationale of the communicative training as a means of forming the communicative competence of a preschool child’s parent, the specification of the training contents and technology in the context of its application in the process of solving the enrichment problems of all the parent's competence components in matters of communication and interaction with the child. Turning to the question of the parent's communicative competence formation is due to its importance for the forehanded socialization and upbringing of a preschool child, inadequate attention of teachers and specialists in preschool organizations to solving the problems of forming such competence, and the limited use of interactive technologies in the process of parents education. The methodological basis for the authors’ position is the provisions of a multisubject approach to communication as a condition, a mechanism for a child socialization and education at the preschool stage, a competence building approach about the essence, structure, contents and ways of parents communicative competence formation, an activ approach to communication as a communicative activity, and a personal approach about the need to take into account the characteristics of parents as communicators in the interpersonal interactions, about partnership and dialogue as conditions of personal development and self-education of adults and children. The results of the theoretical and practical aspects analysis within the framework of the problem under consideration are the concretization of the concept of "the pedagogical parents competence", "the communicative parents competence", the characteristic of training as a means of forming the communicative parents competence, correlation of the components and contents of the parent’s communicative competence forming process with the structural components of the training. The novelty of the article is to detect and justify the potential of the traini

关键词： Data analysis   Clustering algorithms   Anomaly detection   Trajectory   Task analysis   Data models   Computer science   Cluster analysis   spatial-temporal cluster relationships   spatial-temporal data   spatial-temporal data analysis  

摘要： In spatial-temporal data analysis, location data and its evolution through time are investigated with the goal of uncovering important information to provide novel insights. These insights, for example, may involve congestion identification in transportation, mobility patterns in urban computing, and storm prediction in weather forecasting. Clustering, one data analysis technique, groups spatial-temporal data based on location. Current spatial-temporal data analysis techniques fail to investigate relationships between spatial-temporal clusters, such as splitting from a cluster and merging with another one because of a change of properties over time. These relationships could hold valuable information about the existence of a cluster and its interactions with other clusters and trajectories. In this paper, we introduce a framework to identify, process, and analyze relationships between clusters of spatial-temporal data (e.g. enter, merge, or split). We describe its architecture and components, as well as a proposed clustering technique, the different approaches for distance calculation, and how we calculate cluster similarity of temporally separated clusters. The result of these operations are used in the identification of cluster relationships over space and time. The analysis of these relationships helps uncover hidden values that could support novel approaches to more effective decision-making. We evaluate our framework with two case studies, based on truck and human trajectories.

关键词： Computer science  

摘要： Partitioned Global Address Space (PGAS) languages are becoming more important aswe move into the Exascale era. The complexities brought on by the architectures of thesemachines make traditional message passing approaches challenging. Currently, we lack aportable and flexible runtime for PGAS languages. The suggestion is that this is possiblewith an OpenSHMEM-based runtime. OpenSHMEM is a PGAS library for the C language aiming to provide a standardApplication Programming Interface (API) for Symmetric Hierarchical MEMory (SHMEM).OpenSHMEM is a portable, flexible, and performant API for PGAS runtimes throughits use of thread safety semantics and grouping of processes through teams. This allowsOpenSHMEM to make performance-oriented decisions on behalf of the language or librarybeing implemented. This thesis demonstrates a mapping and implementation of a Unified Parallel C (UPC)runtime based on OpenSHMEM, and an evaluation our runtime’s performance in comparisonto the popular Berkeley UPC implementation. Berkeley UPC uses a runtime based onGlobal-Address Space Networking (GASNet), a language independent middleware forPGAS programming languages.

关键词： Journalism   Communication   Computer science  

摘要： Journalists are considered as “watchdogs” of our society. However, their “watchdog” roles are limited by digital surveillance and malware attacks. In various parts of the globe, journalists now are targeted by governments and malicious actors. This thesis focuses on threats to journalists’ digital safety and protection strategies. By reviewing the extant literature, this work explores journalists’ vulnerabilities to digital surveillance and malware attacks. It also investigates the far-reaching consequences of these digital threats, and analyzes factors contributing to journalists’ vulnerabilities. The thesis conducts a data analysis to answer the research questions. Key findings show the alarming situation of journalists’ digital safety. Over 65% of journalists never or rarely used digital protection, including journalists in vulnerable groups, such as female journalists, politics or crime reporters. In light of these key findings, the thesis will also provide recommendations for journalists and other stakeholders to shield journalists from digital threats, as well as directions for future studies.