• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3192-3212
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• 2016

With the advent and popularity of e-commerce, an increasing number of consumers prefer to order tourism products online. A recommender system can help these users contend with information overload; however, such a system is affected by the cold start problem. Online tourism destination searching is a more difficult task than others on account of its more restrictive factors. In this paper, we therefore propose a tourism destination recommender system that employs opinion-mining technology to refine user preferences and item opinion reputations. These elements are then fused into a hybrid collaborative filtering method by combining user- and item-based collaborative filtering approaches. Meanwhile, we embed an artificial interactive module in our recommender system to alleviate the cold start problem. Compared with several well-known cold start recommendation approaches, our method provides improved recommendation accuracy and quality. A series of experimental evaluations using a publicly available dataset demonstrate that the proposed recommender system outperforms existing recommender systems in addressing the cold start problem.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.1
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• pp.113-120
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• 2013

This study aimed to obtain quantitative data for WWTP operators in phosphorus removal process. This was done by reviewing and comparing phosphorus removal efficiency(%), coagulants dosage(Al/P and $Al_2O_3$(mg/L)), sludge production($kg/m^3$), and operation cost($won/m^3$) of start-up and normal operation data. Phosphorus removal efficiency of all tertiary treatment process was up to 70 ~ 89 % in start-up and normal operation. Average molar ratio(Al/P) was similar as 5 in both operations, but average coagulants dosage (mg/L) of start-up (8.5 mg/L) was higher than normal operation (6.2 mg/L). Average operation cost was higher for start-up ($33.6won/m^3$) than normal operation ($28.4won/m^3$), while electricity cost required for the normal operation ($9.0won/m^3$) was higher by $3.5won/m^3$.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.506-515
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• 2023

This study is to find a method to learn engine sound after the start-up of a diesel generator installed in nuclear power plant with an unsupervised deep learning algorithm (CNN autoencoder) and a new method to predict the failure of a diesel generator using it. In order to learn the sound of a diesel generator with a deep learning algorithm, sound data recorded before and after the start-up of two diesel generators was used. The sound data of 20 min and 2 h were cut into 7 s, and the split sound was converted into a spectrogram image. 1200 and 7200 spectrogram images were created from sound data of 20 min and 2 h, respectively. Using two different deep learning algorithms (CNN autoencoder and binary classification), it was investigated whether the diesel generator post-start sounds were learned as normal. It was possible to accurately determine the post-start sounds as normal and the pre-start sounds as abnormal. It was also confirmed that the deep learning algorithm could detect the virtual abnormal sounds created by mixing the unusual sounds with the post-start sounds. This study showed that the unsupervised anomaly detection algorithm has a good accuracy increased about 3% with comparing to the binary classification algorithm.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.123-132
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• 2002

A numerical study was conducted to investigate the combustion phenomena of normal start and unstart processes based on ISL's RAMAC 30 experiments with different diluent amounts and fill pressures in a ram accelerator. The initial projectile launching speed was 1.8 km/s which corresponded to the superdetonative speed of the stoichiometric $H_2/O_2$ mixture diluted with 5 $CO_2$ or 4 $CO_2$. Experiments with same condition except for projectile surface material demonstrated that ignition was successful with an aluminum projectile, but no combustion was observed in case of a steel projectile. In this study, it was found that neither shock nor viscous heating was sufficient to ignite the mixture at a low speed of 1.8 km/s, as was found in the experiments using a steel projectile. However, we could succeed in igniting the mixtures by imposing a minimal amount of additional heat to the combustor section and simulate the normal start and unstart processes found in the experiments with an aluminum projectile. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations coupled with a Baldwin-Lomax turbulence model and detailed chemistry reaction equations of $H_2/O_2/CO_2$ suitable for high-pressure gaseous combustion were considered. The governing equations were discretized by a high order accurate upwind scheme and solved in a fully coupled manner with a fully implicit, time accurate integration method. The numerical results matched almost exactly to the experimental results. As a result, it was found that the normal start and unstart processes depended on the strength of gas mixture, development of shock-induced combustion wave stabilized by the first separation bubble, and its size and location.

• Journal of Nutrition and Health
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• v.31 no.4
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• pp.747-755
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• 1998

In order to study the relationship between body core temperature and adiposity , the core temperatures of normal weight female college students were measured during an instant-noodle lunch eaten in a laboratory at the ambient temperature of 22-24.8$^{\circ}C$. Ambient temperature was positively correlated with meal-start core temperature and meal duration. The difference between the peak postprandial and the meal-start core temperature was negatively correlated with body weight and BMI. This means that the thermogenic response induced by meal consumption was negatively associated with adiposity. Meal duration also showed a negative correlation with body weight, BMI, and hip girth. Thus, the obese eating style characterized by a rapid rate of food intake was also associated with adiposity in normal weight women. It was possibly a contributing factor in the development of obesity. In conclusion, adiposity is negatively associated with the difference between the peak postprandial and the meal-start core temperature and meal duration during a meal.

• Journal of Technology Innovation
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• v.29 no.2
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• pp.59-85
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• 2021

This study aims to examine whether the characteristics such as a start-up company, possessing a research organization, and benefiting from government R&D programs significantly contributed to the conversion of marginal companies to normal companies, from the viewpoint of technological innovation. The result shows supporting government R&D programs to start-up companies that have become a marginal company positively contributes to the transition to a normal company, centering on the high-tech industry. In addition, it was confirmed that the research organization of marginal companies positively contributed to the transition to a normal company. These results imply that a paradigm shift from the existing industrial policy focusing on restructuring of marginal companies to a selective support policy for marginal companies with a high possibility of transition to normal companies is strongly needed. It is also necessary to strengthen the strategic use of government R&D programs to support the transition of a marginal company to a normal company.

• Korean Management Science Review
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• v.21 no.1
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• pp.77-86
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• 2004

In this paper, we present a methodology for solving the multicommodity network flow problems using interior point methods. In our method, the minimum cost network flow problem extracted from the given multicommodity network flow problem is solved by primal-dual barrier method in which normal equations are solved partially using preconditioned conjugate gradient method. Based on the solution of the minimum cost network flow problem, a warm-start point is obtained from which Castro's specialized interior point method for multicommodity network flow problem starts. In the computational experiments, the effectiveness of our methodology is shown.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1007-1012
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• 2016

Induction motors are used widely in driving load of a fluid, such as a pump or a fan in the industry. Induction motor has been generated the voltage drop by the occurrence of a high current during startup. In addition, high start-up current can act as a mechanical stress on the shaft of the motor. So there is need a way to reduce the starting current. Soft start method is one of the many ways to reduce the starting current. This method uses silicon-controlled rectifiers(SCRs) for varying value of the voltage applied to the motor. There is a case for fixing or changing the thyristor firing angle to adjust the magnitude of the voltage. Starting power factor of induction motor is very low compared to the normal operation. Soft starting with the firing angle fixed needs to be considered a low power factor at startup. In this study, we compared the direct start characteristics and soft start characteristics considering the low power factor at the time of start-up. It was possible to confirm that the starting current and the voltage drop is present differently according to the firing angle.

• Journal of Information Processing Systems
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• v.17 no.5
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• pp.879-891
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• 2021

With improvements in living conditions, an increasing number of people are choosing to spend their time traveling. Comfortable tour routes are affected by the season, time, and other local factors. In this paper, the influencing factors and principles of scenic spots are analyzed, a model used to find the available routes is built, and a multi-route choice model based on a game theory utilizing a path recommendation weight is developed. A Monte Carlo analysis of a tourist route subjected to fixed access point conditions is applied to account for uncertainties such as the season, start time, end time, stay time, number of scenic spots, destination, and start point. We use the Dijkstra method to obtain multiple path plans and calculate the path evaluation score using the Monte Carlo method. Finally, according to the user preference in the input path, game theory generates path ordering for user choice. The proposed approach achieves a state-of-the-art performance at the pseudo-imperial palace. Compared with other methods, the proposed method can avoid congestion and reduce the time cost.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.2
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• pp.153-159
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• 2010

This work focuses on finding a method to reduce the noise of a hermetic reciprocating compressor during start-up using an acoustical analysis. The noise of compressor during start-up, which is a higher level than that of a normal operating condition, has transient and non-stationary characteristics. The acoustical analysis of compressor cavity is performed to find an effective method to reduce the noise level. In the acoustical analysis, the shape variations of frequency response function in the neighborhood of resonances are tested for three parameters: the height of remained oil, the suction position of refrigerant and the position of driving part. As a conclusion of this result, to reduce the emission noise of compressor during start-up, the height of remained oil should be kept at 16 mm, the refrigerant should be sucked at the cross point of nodal lines of X and Y directional cavity modes, and the driving part should be positioned in the center of cavity.