• ETRI Journal
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• v.32 no.4
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• pp.512-519
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• 2010

A cooperative model is presented to enable sharing of the spectrum with secondary users. Compared with the optimal model and competitive model, the cooperative model could reach the maximum total profit for secondary users with better fairness. The cooperative model is built based on the Nash equilibrium. Then a conceding factor is introduced so that the total spectrum required from secondary users will decrease. It also results in a decrease in cost which the primary user charges to the secondary users. The optimum solution, which is the maximum total profit for the secondary users, is called the collusion state. It is possible that secondary users may leave the collusion state to pursue the maximum of individual profit. The stability of the algorithm is discussed by introducing a vindictive factor to inhabit the motive of deviation. In practice, the number of secondary users may change. Adaptive methods have been used to deal with the changing number of secondary users. Both the total profit and fairness are considered in the spectrum allocating. The shared spectrum is 11.3893 with a total profit of 65.2378 in the competitive model. In the cooperative model, the shared spectrum is 8.5856 with the total profit of 73.4963. The numerical results reveal the effectiveness of the cooperative model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2128-2135
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• 2009

In this paper, current limiter using a magnetic switching which is based on magnetic flux change in the case of fault is proposed. This current limiter consists of iron-core and three parts of coils. One is the primary coil connected to the power system. Another is the secondary coil wound to the opposite direction of the primary coil's winding. The other is the secondary of the secondary coil which is a movable copper plate winding and located below the secondary coil. In the normal state, the magnetic flux produced in the primary and secondary coils flows to the opposite directions each other and becomes to be canceled out. Therefore the voltages induced between the coils are zero. In the case of a fault, at the moment of a fault occurrence recognition, the switch connected to a secondary coil is opened and the secondary of the secondary coil is pulled out to the outside of the iron-core. Then, magnetic flux becomes to flow through the iron-core. Accordingly, the voltage is induced between the both ends of the primary coil and makes the current reduced. Therefore it is possible to cut off the circuit breaker easily with the proposed current limiter. This paper analyzes the current limiting effects and the detailed results are given.

• Journal of Power System Engineering
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• v.17 no.4
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• pp.45-50
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• 2013

This paper presents the comparison of heat transfer and pressure drop of various secondary refrigerants (single-phase and two-phase) in the indirect refrigeration system. The main results were summarized as follows: In case of heat transfer, it is useful to use secondary refrigerants in low evaporating temperature region and the heat transfer coefficient of single-phase is larger than two-phase secondary refrigerants. In case of pressure drop, it is useful to use secondary refrigerants in high evaporating temperature region and the pressure drop of two-phase is smaller than single-phase secondary refrigerant. Also, $CO_2$ is the best useful because pressure drop of $CO_2$ among the secondary refrigerants is the smallest.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.24 no.2
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• pp.127-134
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• 2021

Purpose: In patients with acute enterocolitis, radiologic findings are sometimes accompanied by secondary inflammation of the appendix. The purpose of this study was to evaluate the clinical features of acute enterocolitis with secondary inflammation of the appendix. Methods: Medical records from patients who underwent abdominal ultrasonography or computed tomography (CT) among those admitted for acute enterocolitis were retrospectively reviewed. Clinical features were compared by distinguishing patients with inflammation of the appendix from those without, based on their symptoms and laboratory findings. Results: Of the 165 patients, 12 (7.3%) had secondary inflammation of the appendix on ultrasonography and/or CT. Patients with secondary inflammation of the appendix were significantly older than those without (11.7 vs. 6.1 years, p=0.011) and more frequently had fever (83.3% vs. 49.0%, p=0.033), and high values of C-reactive protein (CRP) (5.38 vs. 0.32 mg/dL, p<0.001). The proportion of bacterial pathogens was higher in patients with secondary inflammation of the appendix (60% vs. 15.1%, p=0.004). Conclusion: Patients with acute enterocolitis accompanied by secondary appendicitis more commonly have fever, higher CRP levels, higher bacterial pathogen detection rates, and longer hospital stays. Treatment equivalent to that of bacterial infection is required for patients with secondary appendicitis, and that their symptoms should be closely and continuously monitored and followed-up.

• Korea Trade Review
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• v.44 no.3
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• pp.253-269
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• 2019

This study examines the utilization effect of FTA on the sales and profit of the secondary auto-part suppliers in two aspects: 1) firm-level survey on the utilization of FTA and 2) statistical inference on the FTA effects on their sales and profit. We use the GLS statistical technique, panel and survey data of 130 secondary auto-part suppliers in the Daegu and Kyungpook area in 2007-2016. The evidence shows that the secondary auto-part suppliers struggle to prepare documents for the FTA certificates of origin due to their small firm size, although they utilize the FTA at the relatively high rate of 92 percent. Statistical evidence shows that an increase in the export of the first vender significantly affects the sale of the secondary auto-part vendors, but not their profit. The low profit and high managing cost of utilizing the FTA deteriorate the utilization effect of the FTA of the secondary auto-part vendors, which is a key factor in a global supply chain and for the competitiveness of the automobile industry. Government policies are required for the secondary auto-part suppliers to utilize the FTA more effectively and share the benefits of tariff reduction with first auto-part vendors under FTA transaction.

• Journal of Information Technology Applications and Management
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• v.28 no.1
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• pp.33-41
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• 2021

In this study, we estimated the number of secondary COVID-19 infections caused by students with potential transmission potential home. When the existing Monte Carlo method was applied to Korean data, the average number of household members of the second COVID-19 infected was predicted. The summary of this study is as follows. First, in general, the number of secondary infections by students returning home from school is greatly influenced by the virus infection rate of each student group they contact while returning home from school. Korea-based empirical research on this is needed. Second, the number of secondary infections by Korean students was relatively lower than that of previous studies. This can be interpreted as being due to the domestic furniture structure. Third, unlike previous studies that assumed the distribution of secondary infected individuals as normal distribution, assuming a negative binomial distribution, the number of secondary infected individuals was sensitively changed according to the estimated parameters. Interpretation of this result shows that the number of secondary infections may vary depending on the time of decision making, the target region, and the target student group. Finally, according to the results of this analysis, a proposal was made to support education policy decisions.

• Journal of Astronomy and Space Sciences
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• v.40 no.4
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• pp.131-148
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• 2023

Lunar permanently shadowed regions (PSRs) never see direct sunlight and are illuminated only by secondary illumination - light reflected from nearby topography. The ShadowCam imaging experiment onboard the Korea Pathfinder Lunar Orbiter is acquiring images of these PSRs. We characterize and discuss the nature of secondary illumination for the Shackleton PSR from ShadowCam radiance-calibrated images. We also use modeling to understand the magnitude and direction of the secondary illumination. Results from our analysis highlight the non-homogeneous, dynamic, and complex nature of PSR secondary lighting. Knowledge of the direction of the secondary illumination is crucial for reli-able interpretation of contrasts observed in ShadowCam images. This preliminary analysis of the floor of Shackleton crater from images acquired over multiple secondary illumination conditions does not reveal indications of exposed surface ice, even though temperatures are constantly below 110K.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.641-646
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• 2011

In this paper, we investigate a power control problem which is very critical in underlay-based spectrum sharing systems. Although an underlay-based spectrum sharing system is more efficient compared to an overlay-based spectrum sharing system in terms of spectral utilization, some practical problems obstruct its commercialization. One of them is a real-time-based power adaptation of secondary transmitters. In the underlay-based spectrum sharing system, it is essential to adapt secondary user's transmit power to interference channel states to secure primary users' communication. Thus, we propose a practical power control scheme for secondary transmitters. The feedback overhead of our proposed scheme is insignificant because it requires one-bit signaling, while the optimal power control scheme requires the perfect information of channel states. In addition, the proposed scheme is robust to feedback delay. We compare the performance of the optimal and proposed schemes in terms of primary user's outage probability and secondary user's throughput. Our simulation results show that the proposed scheme is almost optimal in terms of both primary user's outage probability and secondary user's throughput when the secondary user's transmit power is low. As the secondary user's transmit power increases, the primary user's outage probability of the proposed scheme is degraded compared with the optimal scheme while the secondary user's throughput still approaches that of the optimal scheme. If the feedback delay is considered, however, the proposed scheme approaches the optimal scheme in terms of both the primary user's outage probability and secondary user's throughput regardless of the secondary user's transmit power.

• Archives of Plastic Surgery
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• v.32 no.3
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• pp.287-292
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• 2005

The definitive correction of secondary lip nasal deformities is a great challenge for plastic surgeons. To rectify the secondary lip nasal deformities, various procedures and its modifications have been reported in many centers. However, no universal agreement exist to correct the various components of secondary nasal deformities. The secondary nasal deformity of the unilateral cleft lip has its own characteristic abnormalities including the retroplaced dome of the ipsilateral nasal tip, hooding of the alar rim, a secondary alar-columellar web, short columella, depressed alar base and so forth. Among these components of secondary nasal deformity, maxillary hypoplasia, especially in the area of piriform aperture, and alveolar bone defect can make the alar base depressed, which in turn, leads to wide and flat nasal profile, obtuse nasolabial angle coupled with subnormal nasal tip projection in aspect of aesthetic consideration. Moreover, the maxillary hypoplasia contributes to reduced size of the nasal airway in combination with other component of external nasal deformity and therefore the nasal obstruction may be developed functionally. Therefore, the current authors have performed corrective rhinoplasty with the augmentation of alar base with various methods which include rearrangement of soft tissue, vertical scar tissue flap and use of allogenic or autologous materials in 42 patients between 1998 and 2003. The symmetric alar base could be achieved, which provides the more accurate evaluation and more appropriate management of the various component of any coexisting secondary nasal deformity. In conclusion, the augmentation of alar base, as a single procedure, is a basic and essential to correct the secondary lip nasal deformities.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2769-2774
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• 2007

In vacuum ejector-diffuser systems where a finite volume secondary chamber is used, the secondary jet exhibits transient characteristics during start-up. A steady state is achieved after some time in which mass entrainment prevails indefinitely inside the ejector, though there is no flow from the secondary chamber. An attempt is made in this work to study the infinite entrainment of secondary jet into the primary jet from a finite secondary chamber, with the help of a computational fluid dynamics method. The present study is also intended to identify the operating range of vacuum ejector-diffuser systems where the steady flow assumption can be applied without uncertainty. The results obtained show that the only condition in which an infinite mass entrainment is possible is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium at this point. Steady flow assumption is valid only after this point.