This work utilizes the commercial finite element software ABAQUS to investigate the factors influencing the mechanical behavior of tantalum carbide (TaC)-based/graphite fibrous monolithic ceramics (FMCs), such as core/shell volume ratio and fiber orientation. The good compliance between experimental and simulated results demonstrates the suitability of the finite element software ABAQUS for exploring mechanical properties in FMCs. According to the results, it was observed that the bending strength of TaC-based/graphite FMC decreased with the change in fiber orientation from 0° to 90°. The displacement amount in the core/shell volume ratio of 75/25 ( C75S25) sample with a fiber orientation of 90° was maximum (with a value of 0.0524 mm), indicating that crack propagation occurred later. Therefore, the sample exhibited better resistance to failure. Generally, C75S25 specimens started to crack later than the core/shell volume ratio of 65/35 ( C65S35) in both fiber orientations and released more energy during crack initiation. Additionally, when the 0°-fiber-oriented specimen failed, more energy was released than the [90°] sample with the same core/shell volume ratio.

We report the feasibility of TaC production via self-propagating high temperature synthesis, and the influence of the initial green compact density on the final composite particle size. Experiments are carried out from a minimum pressure of 0.3 MPa, the pressure at which the initial green body becomes self-standing, up to 3 MPa, the point at which no further combustion occurs. The green density of the pellets varies from 29.99% to 42.97%, as compared with the theoretical density. The increase in green density decreases the powder size of TaC, and the smallest particle size is observed with 1.5 MPa, at 10.36 μm. Phase analysis results confirm the presence of the TaC phase only. In the range of 0.3-0.5 MPa, traces of unreacted Ta and C residues are detected. However, results also show the presence of only C residue in the matrix within the pressure range of 0.6-3.0 MPa.

An ultra-high temperature ceramic, tantalum carbide, has received much attention for its favorable characteristics: a superior melting point and chemical compatibility with carbon and other carbides. One drawback is the high temperature erosion of carbon/carbon (C/C) composites. To address this drawback, we deposited TaC on C/C with silicon carbide as an intermediate layer. Prior to the TaC deposition, the TaCl5-C3H6-H2 system was thermodynamically analyzed with FactSage 6.2 and compared with the TaCl5-CH4-H2 system. The results confirmed that the TaCl5-C3H6-H2 system had a more realistic cost and deposition efficiency than TaCl5-CH4-H2. A dense and uniform TaC layer was successfully deposited under conditions of Ta/C = 0.5, 1200 oC and 100 torr. This study verified that the thermodynamic analysis is appropriate as a guide and prerequisite for carbide deposition.

Monte-Carlo Tree Search (MCTS) is a best-first search algorithm to evaluate states of the game tree in game playing, and has been successfully applied to various games, especially to the game of Go. Upper Confidence Bounds for Trees (UCT), which is a variant of MCTS, uses the UCB1 formula as selection policy, and balances exploitation and exploration of the states. Rapid Action-Value Estimation (RAVE), which is a All-Moves-As-First (AMAF) heuristic, treats all moves in a simulation as the first move, and therefore updates the statistics of all children of the root node. In this paper, we evaluate the performance of RAVE and UCT playing against each other in the game of Tic-Tac-Toe. The experimental results show that the first player RAVE is much inferior to the second player UCT (13.0±0.7%); on the other hand, the first player UCT is far superior to RAVE (99.9±0.1%).

This study aims to analyze effectiveness of the resource use under the total allowable catch system (TACs) of Comb pen shell, a species among TAC targeting ones through its stock assessment based on the surplus production model such as the Clark·Yoshimoto·Pooley (CYP) model. Particularly, this study is separated into five analysis periods in order to understand changes in Comb pen shell resource and its efficient use after TAC system implemented in 2001. The results of this study are as follows. First, five sustainable yield curves (SYCs) and exponential growth functions (EGFs) produced by the surplus production model based on Gompertz growth function to compare before and after implementation of the Korean TAC system show that the TAC system has generated a positive stock rebuilding effect for Comb pen shell caught by the diver fishery since 2001. Secondly, five profits based on differences between the sustainable total revenue (STR) and the total cost (TC) with respect to fishing efforts present that the TAC system has increased efficiency of resource use of Comb pen shell caught by the diver fishery after implementation of the Korean TAC system. In conclusion, the Korean TAC system has increased efficiency of resource use as well as has led a positive stock rebuilding effect for Comb pen shell.

Go is an extremely complex strategic board game despite its simple rules and is the great challenging classic game for AI due to its enormous search space. The computer program AlphaGo finally defeated Fan Hui, the European Go champion, without handicaps on a full-sized 19 ×19 board in October 2015. Monte-Carlo Tree Search (MCTS) is a widely-used algorithm for game-tree search in game playing. MCTS based on statistical sampling is a best-first tree search technique to evaluate states; UCT which is a variant of MCTS uses the UCB1 formula as selection policy. In this paper, we evaluate the performance of MCTS and UCT playing against each other in the game of Tic-Tac-Toe. The experimental results show that the first player UCT is slightly superior to the second player MCTS (54.3±1.0%), the first player is always advantageous to the second player regardless of the MCTS and UCT players, and the result of each game should be a tie if both players do their best in Tic-Tac-Toe.

Go is an extremely complex strategic board game despite its simple rules. Recently computer Go based on MCTS plays at human-master level and also has defeated top professional players with handicap games in 19×19 Go. Before implementing computer Go, in this paper we show weakness of pure MC algorithm for playing robust Tic-Tac-Toe game and present alternative method to make up the weakness. Furthermore we show how UCB algorithm works for balancing exploration and exploitation in game tree and discuss the need of a hybrid algorithm combined with UCB and strategy based MCTS, for implementing an enhanced computer Go.

Evolutionary computation is a powerful tool for developing computer games. Back-propagation neural network(BPNN) was proved to be a universal approximator and genetic algorithm(GA) a global searcher. The game of Tic-Tac-Toe, also known as Naughts and Crosses, is often used as a test bed for testing new AI algorithms. We tried to recognize the strategic fitness of a finished Tic-Tac-Toe game when the parameters, such as a sequence of moves, its game depth and result, are provided. To implement this, we've constructed an evolutionary model using GA with back-propagation NNs(GANN). The experimental results revealed that GANN, in the very long training time, converges very slowly; however, performance of recognizing the strategic fitness does not meet we expected and, further, increase of the population size does not significantly contribute to the performance of GANN.

This study aimed to evaluate the TAC policy and to examine the effective annual TAC quota in the sandfish stock rebuilding plan using a bioeconomic modelling method. In the analysis, first, a sandfish bioeconomic model was developed by combining a sandfish stock population model and economic models by fishery and second, achieving stock rebuilding targets and changes of fishing revenues by the level of annual TAC quota were examined. Model results indicated that the TAC 1,500ton policy would have the greatest impact on the increase of sandfish stock biomass comparing to the status quo and other TAC policies. In addition, it was evaluated that the total fishing revenues of coastal gillnet and danish seine fisheries could be increased the most in the TAC 2,500ton policy. In both cases of TAC 3,500ton and 4,000ton, the fishing revenues of both fisheries were inversely reduced due to the decrease of catch by coastal gillnet and the decline of market prices by danish seine’s excessive catch. Furthermore, they would have a negative impact on sandfish stock biomass.

Thermal shock resistance property has recently been considered to be one of the most important basic properties, in the same way that the transverse-rupture property is important for sintered hard materials such as ceramics, cemented carbides, and cermets. Attempts were made to evaluate the thermal shock resistance property of 10 vol% TaC added Ti(C,N)-Ni cermets using the infrared radiation heating method. The method uses a thin circular disk that is heated by infrared rays in the central area with a constant heat flux. The technique makes it possible to evaluate the thermal shock strength (Tss) and thermal shock fracture toughness (Tsf) directly from the electric powder charge and the time of fracture, despite the fact that Tss and Tsf consist of the thermal properties of the material tested. Tsf can be measured for a specimen with an edge notch, while Tss cannot be measured for specimens without such a notch. It was thought, however, that Tsf might depend on the radius of curvature of the edge notch. Using the Tsf data, Tss was calculated using a consideration of the stress concentration. The thermal shock resistance property of 10 vol% TaC added Ti(C,N)-Ni cermet increased with increases in the content of nitrogen and Ni. As a result, it was considered that Tss could be applied to an evaluation of the thermal shock resistance of cermets.

This study aimed to empirically investigate the applicability of ecosystem-based TAC (Total Allowable Catch) fisheries management targeting the large purse seine fishery where multi-species are regulated by TAC. Using a linear programming, the optimal fishing effort and the catch amount by species which maximize fishing profits were analyzed under the constraint condition of catch limits by species. Analytical results showed that an application of TAC on only chub mackerel would have negative impacts on fish stocks such as hairtail and jack mackerel by increasing the level of fishing effort to achieve its allocated catch limit. However, under the constraint condition of catch limits of all species, it was shown that optimal catches of all species were achieved within their catch limits. It implies the importance of ecosystem-based management considering biological and technical interactions of species those were excluded in the traditional single species fisheries management.

The game of Go is an oriental strategic board game originated from China at least more than 2,500 years ago. The Monte-Carlo Tree Search (MCTS) algorithm in Go is a method that uses a large number of simulations to approximately estimate the winning rate of candidate moves by sampling the game. The two computer Go programs called Crazy Stone and Mogo defeated human Go professionals on the 9⨯9 board in 2006. Prior to our implementing MCTS into computer Go, we tried to find out the best move sequence in playing Tic-Tac-Toe game as a test bed. The experimental results revealed that the first player should play the center to ensure the highest winning rate, and the game result becomes a draw if two players do their best.

Using artificial neural network (ANN) technique, auction prices for common mackerel were forecasted with the daily total sale and auction price data at the Busan Cooperative Fish Market before introducing Total Allowable Catch (TAC) system, when catch data had no limit in Korea. Virtual input data produced from actual data were used to improve the accuracy of prediction and the suitable neural network was induced for the prediction. We tested 35 networks to be retained 10, and found good performance network with regression ratio of 0.904 and determination coefficient of 0.695. There were significant variations between training and verification errors in this network. Ideally, it should require more training cases to avoid over-learning, which leads to improve performance and makes the results more reliable. And the precision of prediction was improved when environmental factors including physical and biological variables were added. This network for prediction of price and catch was considered to be applicable for other fishes.

The present study investigates the behavior of the sintering and hardness of stainless steel samples reinforced with NbC and TaC. Matrixes of pure stainless steel were compacted with addition of up to 3% wt NbC or TaC in a cylindrical die of steel at 700 MPa and sintered in an electrical resistance furnace under argon atmosphere. The sintered samples were characterized by density and hardness measurement, optical microscopy and scanning electron microscopy (SEM). The preliminary results show that the size and distribution of carbides influence in the sintering and hardness of the sintered samples.

WC-TiC-TaC binderless cemented carbide was oxidized under low partial pressure of oxygen (50ppm) at 873K for 1 to 20 h. Surface roughness was measured using atomic force microscope, and effect of TiC amount on oxidation behavior of the carbide was investigated. WC phase was oxidized more easily than WC-TiC-TaC solid solution phase. With an increase in TiC amount, WC-TiC-TaC phase increased and the oxidation resistance of the carbide increased.

The effect of TiC content on oxidation behavior of the sintered WC-TiC-TaC alloys with 2 mass% TaC and different TiC amounts of 3-45 mass% was investigated through oxidation tests in air at 973K. As a result of the tests, it was revealed that with increasing TiC content in the alloys, mass changes caused by oxidation and thickness of the scale decreased. Thus, it is considered that the main component of the scales changed gradually from to with increasing TiC content in the alloys, and oxygen diffusion through the scale to the alloys was inhibited gradually.