Cryptographic algorithms have been used not only to create robust ciphertexts but also to generate cryptograms that, contrary to the classic goal of cryptography, are meant to be broken. These ...cryptograms, generally called puzzles, require the use of a certain amount of resources to be solved, hence introducing a cost that is often regarded as a time delay—though it could involve other metrics as well, such as bandwidth. These powerful features have made puzzles the core of many security protocols, acquiring increasing importance in the IT security landscape. The concept of a puzzle has subsequently been extended to other types of schemes that do not use cryptographic functions, such as CAPTCHAs, which are used to discriminate humans from machines. Overall, puzzles have experienced a renewed interest with the advent of Bitcoin, which uses a CPU-intensive puzzle as proof of work. In this article, we provide a comprehensive study of the most important puzzle construction schemes available in the literature, categorizing them according to several attributes, such as resource type, verification type, and applications. We have redefined the term puzzle by collecting and integrating the scattered notions used in different works, to cover all the existing applications. Moreover, we provide an overview of the possible applications, identifying key requirements and different design approaches. Finally, we highlight the features and limitations of each approach, providing a useful guide for the future development of new puzzle schemes.
Data for OECD countries document: 1. imports and exports are about three times as volatile as GDP; 2. imports and exports are pro-cyclical, and positively correlated with each other; 3. net exports ...are counter-cyclical. Standard models fail to replicate the behavior of imports and exports, though they can match net exports relatively well. Inspired by the fact that a large fraction of international trade is in durable goods, we propose a two-country two-sector model in which durable goods are traded across countries. Our model can match the business cycle statistics on the volatility and comovement of the imports and exports relatively well. The model is able to match many dimensions of the data, which suggests that trade in durable goods may be an important element in open-economy macro models.
International risk cycles Gourio, François; Siemer, Michael; Verdelhan, Adrien
Journal of international economics,
03/2013, Letnik:
89, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Recent work in international finance suggests that exchange rate puzzles can be accounted for if (1) aggregate uncertainty is time-varying, and (2) countries have heterogeneous exposures to a world ...aggregate shock. We embed these features in a standard two-country real business cycle framework, and calibrate the model to equity risk premia in low and high interest rates countries. Unlike traditional real business cycle models, our model generates volatile exchange rates, a large currency forward premium, “excess comovement” of asset prices relative to quantities, and an imperfect correlation between relative consumption growth and exchange rates. Our model implies, however, that high interest rate countries have smoother quantities, equity returns and interest rates than low interest rate countries, contrary to the data.
•Our proposal in the context of Puzzle-based Learning is centered on puzzle dynamics.•Puzzle dynamics is viewed as having two components: a mechanism (the Puzzle Trigger) and a process (the ...Puzzle-solving).•The relevance of introducing the Puzzle trigger to engage students in learning contexts and develop their critical thinking and creativity skills is considered.
The Puzzle-based Learning approach has been applied to several fields of knowledge. In education research papers, the instructional usage of puzzles is considered to improve learners' motivation and engagement and help them to develop critical skills but difficulties concerning learners' interaction with puzzles have also been pointed out. Our paper investigates the dynamics of the concept of a puzzle and its interface to provide a better understanding of its form and functions, and help learners interact with puzzles. We consider Puzzle-based Learning tenets as well as their educational impacts on both critical thinking and learner engagement and provide an original proposal concerning the understanding of puzzles. Our proposal centered on the dynamics of puzzles bears conceptual and educational facets. Conceptually, puzzle dynamics is viewed as composed of two elements: a mechanism, the Puzzle Trigger, and a process, the Puzzle-Solving. From an educational point of view, the rationale for integrating Puzzle Triggers in Puzzle-based Learning is meant to help learners interact with puzzles and consequently become motivated and engaged in the Puzzle-Solving process. This way, learners' critical thinking skills are reinforced and focused on finding solutions to challenges. We illustrate the implementation of Puzzle Triggers and Puzzle-Solving by considering two instructional activities in a Software Development undergraduate course of an online learning Informatics Engineering Program.
Hospitalisasi dapat menjadi faktor stress yang menimbulkan kecemasan pada anak karena menganggap dirinya kehilangan lingkungan yang aman dan hal tersebut dapat menghambat proses penyembuhan anak. ...Maka dari itu anak perlu mengalihkan rasa takut dan cemas sebagai koping dalam menghadapi cemas, salah satu terapi bermain yang sesuai dengan anak usia prasekolah adalah bermain Puzzle. Studi kasus ini bertujuan untuk mengetahui efektifitas terapi bermain dalam menurunkan kecemasan anak akibat hospitalisasi. Studi ini menggunakan metode deskriptif dengan pendekatan asuhan keperawatan. Responden dalam studi kasus ini sejumlah 2 anak yang mengalami kecemasan ketika sedang hospitalisasi, dilakukan selama 3 hari durasi waktu 10-15 menit dengan langkah pretest – terapi bermain – posttest disetiap pertemuan. Menggunakan alat ukur Facial Image Scale (FIS). Berdasarkan studi kasus didapatkan bahwa terapi bermain puzzle menunjukkan penurunan kecemasan pada responden 1 dari tingkat kecemasan sedang ke tingkat kecemasan tidak cemas dan pada responden 2 dari tingkat kecemasan berat mengalami penurunan ke tingkat kecemasan ringan. Berdasarkan hasil studi kasus ini menunjukkan bahwa penerapan terapi bermain puzzle efektif dalam mengurangi kecemasan anak akibat hospitalisasi. Diharapkan dapat menjadi referensi terapi non-farmakologi yang diterapkan pada anak yang mengalami kecemasan akibat hospitalisasi.
The 15 puzzle is a classic reconfiguration puzzle with fifteen uniquely labeled unit squares within a 4×4 board in which the goal is to slide the squares (without ever overlapping) into a target ...configuration. By generalizing the puzzle to an n×n board with n2−1 squares, we can study the computational complexity of problems related to the puzzle; in particular, we consider the problem of determining whether a given end configuration can be reached from a given start configuration via at most a given number of moves. This problem was shown NP-complete in 1. We provide an alternative simpler proof of this fact by reduction from the rectilinear Steiner tree problem.
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