• Journal of the Society of Naval Architects of Korea
• /
• v.44 no.2 s.152
• /
• pp.93-100
• /
• 2007

Post swirl stator is an energy saving device to recover rotational energy of the propeller. To optimize the performance of post swirl stator in container vessels, computational fluid dynamics using body force method was introduced. A commercial code Fluent was used in conjunction with body force distributed on the surface of actuator disk which is located in the propeller plane to optimize pitch angle of the post swirl stator blade. This study showed that CFD is an important tool to simulate flow behind ship with propeller, rudder and post swirl stator.

• Nuclear Engineering and Technology
• /
• v.47 no.4
• /
• pp.407-415
• /
• 2015

A developing post-dryout region is characterized by significant heat transfer enhancements compared with the fully developed post-dryout region. The heat transfer enhancements are mainly due to upstream disturbance and entrained droplets in the region immediately downstream of the critical heat flux location. In this paper, an improved heat transfer correlation is developed for the developing post-dryout regions in vertical tubes over a wide range of flow conditions. The correlation represents a correction factor for the fully developed film-boiling look-up table to be applied to the developing post-dryout region. The new correlation significantly improves the heat transfer prediction in the developing post-dryout regions and provides very good agreement with the experimental data.

• The Journal of the Acoustical Society of Korea
• /
• v.4 no.3
• /
• pp.33-41
• /
• 1985

이 논문에서는 frequency-weighted MSE를 최소화하는 적응 pre-filter와 post-filter를 음성파형 부호화기에 적용했을 때의 성능을 분석한다. 먼저 여러 다양한 pre-filter와 post-filter에 의한 noise shaping 효과를 이론적으로 보여준다. 그리고 frequency-weighted SNR 척도를 사용하여 적응 pre-filter 와 post filter에 의한 성능면에서의 이득을 이론적으로 유도한다. 적응 pre-filter와 post-filter를 ADM과 ADPCM 부호화기에 적용해본 결과에 의하면 음성파형 부호화기의 성능을 FWSNR\sub SEG\ 척도로 약 3dB 정도 개선할 수 있음을 알 수있다. 또한 pre-filter와 post-filter를 사용하면 청각적으로 중요한 영향을 미치는 1kHz에서 3kHz 사이의 양자화 잡음을 효과적으로 줄일 수 있다.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.165-168
• /
• 2006

Carbon fiber reinforced polymer(CFRP) have superior mechanical and chemical properties in comparison with conventional materials. And post-tensioning method has been used for structural reinforcement of RC structures due to easy installation and good effect of resisting capacity of structures. But the higher cost of CFRP and the loss of prestressing force with time are considered the major problems to use it. In this study, CFRP Strips and external post tensioning for rehabilitation of old concrete structures were adapted and optimal combination of these methods is considered. A total of 17 concrete members were made and tested. The types and numbers of CFRP strips and post-tensioning types were selected as major test variables. From test results, it is shown that the concrete members that post tensioned and bonded CFRP strips has a pronounced effect on the strength and deformational behavior. This present study indicates that external temporally post tensioning can reduce the amount of CFRP strips required and the combination of temporally post tensioning and CFRP strips may meet the strength and ductility requirements of old structures.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.22 no.4
• /
• pp.809-817
• /
• 2012

One of the OSI 7 Layer DDoS Attack, HTTP POST DDoS can deny legitimate service by web server resource depletion. This Attack can be executed with less network traffic and legitimate TCP connections. Therefore, It is difficult to distinguish DDoS traffic from legitimate users. In this paper, I propose an anomaly HTTP POST traffic detection algorithm and http each page Content-Length field size limit with defense method for HTTP POST DDoS attack. Proposed method showed the result of detection and countermeasure without false negative and positive to use the r-u-dead-yet of HTTP POST DDoS attack tool and the self-developed attack tool.

• Journal of the Korea Society of Computer and Information
• /
• v.14 no.3
• /
• pp.217-226
• /
• 2009

In this paper, we analyze process of implementing and successful enabler of Postal Logistics Integrated Information Systems(PostNet) through a case study on Korea Post. PostNet was integrated by considering contingently organizational integration (organizational structure redesign), strategical integration (business process reengineering), and technical integration(data integration, application integration, and integrated platform implementation). And also integration was implemented for supporting three aspects. PostNet has implication for advanced integration with business mission and operational efficiency by comparing integration with physical level and hardware level. Korea Post has the biggest logistics network, organization, and service in logistics industry area. The results of this paper will suggest theoretical framework for the future information system integration, and will be utilized as a practical guideline for the information system integration.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.415-426
• /
• 2010

Post-grouting for the drilled shaft is known to increase the end bearing capacity of pile 2~3 times higher by consolidating and reinforcing the disturbed ground containing slime around the pile end. However, the general design guideline for post-grouting has not been established yet in Korea. Especially in the domestic application, the post-grouting is employed just for repairing the pile with the unacceptable resistance rather than for increasing the design resistance of pile. Therefore, little is reported about the effect of post-grouting on the pile resistance itself. In this study, the effect of post-grouting on the resistance of drilled shafts installed in the weathered rock in Korea was estimated by performing the bi-directional load tests on the piles with and without the post-grouting. The test results presented that the initial slope of end bearing-base displacement curve in the pile with post-grouting was 4 times higher than that without post-grouting. At the acceptable settlement (1% of pile diameter), the end bearing capacities of piles with and without the post-grouting were estimated to be 12.0 MPa and 7.0 MPa, respectively, indicating that the post-grouting could increase the end bearing resistance of pile in weathered rock more than 70%.

• Journal of the Korea Convergence Society
• /
• v.12 no.3
• /
• pp.247-259
• /
• 2021

This study aimed to look for educational ways to prepare for the future society for education and people of talent who will lead the post-COVID-19 era. To this end, the factors necessary for the type of future talent in the post-COVID-19 era were identified by analyzing Big data. Based on the deducted factors composing the type of talent in the post-COVID-19 era, policy direction according to the emergence of the post-COVID-19 era were deducted through the interviews with the group of experts and delphi survey, and on the basis of this, this study sought for"a plan for the educational change in line with cultivation of people of talent in the post-COVID-19 era. The results of this study are as follows. First, through the big data analytics and analysis of the interviews, convergence, ICT utilization ability, creativity, self-regulated competency and leadership were found to be the factors necessary for the type of talent in the post-COVID-19 era. Second, it considered the innovation of digital education system and the support for vulnerable classes as the issue for cultivation of people of talent in the post-COVID-19 era. Third, the most important policy with regard to the educational direction for cultivation of people of talent in the post-COVID-19 era was cultivation of convergence talents. Convergence is a very important variable in the post-COVID-19 era since it creates new values by connecting things that are separated from each other. Hopefully, this study will build a basis for competency development, education and training in preparation for the post-COVID-19 era.

• Korean Journal of Ichthyology
• /
• v.10 no.2
• /
• pp.200-206
• /
• 1998

Several specimens belonging to the family Bothidae were collected by trawls in Kwangyang Bay and off Kadeok Island in March 1996 and June 1998. These specimens were confirmed to be the post-larvae and juveniles of Laeops kitaharae (Smith and Pope, 1906) that have not been reported in Korea. According to the Amaoka's criterion (1972), four specimens belong to the middle metamorphic post-larval stage, one specimen to the late metamorphic post-larval stage, and two specimens to the juvenile stage. The middle metamorphic post-larval stage can be distinguished from the late metamorphic post-larval stage by the characters such as a notch between foreside of the dorsal fin and dorsal region of the right eye, and greatly elongated second spine of the dorsal fin. In the juvenile stage, the intestine was not externally exposed. However, the early metamorphic post-larval stage was not occurred in this study.

• The Journal of Advanced Prosthodontics
• /
• v.13 no.2
• /
• pp.89-99
• /
• 2021

PURPOSE. This study aimed to compare the accuracy (trueness and precision) of interim crowns fabricated using DLP (digital light processing) according to post-curing time. MATERIALS AND METHODS. A virtual stone study die of the upper right first molar was created using a dental laboratory scanner. After designing interim crowns on the virtual study die and saving them as Standard Triangulated Language files, 30 interim crowns were fabricated using a DLP-type 3D printer. Additively manufactured interim crowns were post-cured using three different time conditions-10-minute post-curing interim crown (10-MPCI), 20-minute post-curing interim crown (20-MPCI), and 30-minute post-curing interim crown (30-MPCI) (n = 10 per group). The scan data of the external and intaglio surfaces were overlapped with reference crown data, and trueness was measured using the best-fit alignment method. In the external and intaglio surface groups (n = 45 per group), precision was measured using a combination formula exclusive to scan data (10C2). Significant differences in accuracy (trueness and precision) data were analyzed using the Kruskal-Wallis H test, and post hoc analysis was performed using the Mann-Whitney U test with Bonferroni correction (α=.05). RESULTS. In the 10-MPCI, 20-MPCI, and 30-MPCI groups, there was a statistically significant difference in the accuracy of the external and intaglio surfaces (P<.05). On the external and intaglio surfaces, the root mean square (RMS) values of trueness and precision were the lowest in the 10-MPCI group. CONCLUSION. Interim crowns with 10-minute post-curing showed high accuracy.