• Korean Journal of Materials Research
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• v.27 no.3
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• pp.132-136
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• 2017

We synthesized potassium hexatitanate, ($K_2Ti_6O_{13}$, PT6), with a non-fibrous shape, by acid leaching and subsequent thermal treatment of potassium tetratitanate ($K_2Ti_4O_9$, PT4), with layered crystal structure. By controlling nucleation and growth of PT4 crystals, we obtained splinter-type crystals of PT6 with increased width and reduced thickness. The optimal holding temperature for the layered PT4 was found to be ${\sim}920^{\circ}C$. The length and width of the PT4 crystals were increased when the nucleation and growth time were increased. After a proton exchange reaction using aqueous 0.3 M HCl solution, and subsequent heat treatment at $850^{\circ}C$, the PT4 crystal transformed into splinter-type PT6 crystals. The frictional characteristics of the friction materials show that as the particle size of PT6 increases, the coefficient of friction (COF) and wear amounts of both the friction materials and counter disc increase.

• Journal of Communications and Networks
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• v.11 no.5
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• pp.518-528
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• 2009

IEEE 802.11 wireless local area network (WLAN) has become the prevailing solution for wireless Internet access while transport control protocol (TCP) is the dominant transport-layer protocol in the Internet. It is known that, in an infrastructure-based WLAN with multiple stations carrying long-lived TCP flows, the number of TCP stations that are actively contending to access the wireless channel remains very small. Hence, the aggregate TCP throughput is basically independent of the total number of TCP stations. This phenomenon is due to the closed-loop nature of TCP flow control and the bottleneck downlink (i.e., access point-to-station) transmissions in infrastructure-based WLANs. In this paper, we develop a comprehensive analytical model to study TCP dynamics in infrastructure-based 802.11 WLANs. We calculate the average number of active TCP stations and the aggregate TCP throughput using our model for given total number of TCP stations and the maximum TCP receive window size. We find out that the default minimum contention window sizes specified in the standards (i.e., 31 and 15 for 802.11b and 802.11a, respectively) are not optimal in terms of TCP throughput maximization. Via ns-2 simulation, we verify the correctness of our analytical model and study the effects of some of the simplifying assumptions employed in the model. Simulation results show that our model is reasonably accurate, particularly when the wireline delay is small and/or the packet loss rate is low.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1845-1851
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• 2016

In this paper, a design method for a wideband square loop antenna for Digital TV applications is studied. The proposed loop antenna is a square loop antenna combined with circular sectors to connect with central feed points. The square loop is used instead of the circular loop in order to miniaturize the antenna size. The input reflection coefficient and gain characteristics of the proposed antenna are analyzed to match with the 75 ohm port impedance for DTV applications. The effects of the gap between the circular sectors and the length of the square loop on the input reflection coefficient and gain characteristics are examined to obtain the optimal design parameters. The optimized antenna is fabricated on an FR4 substrate, and the experiment results show that it operates in the frequency band of 470-1,300 MHz for a VSWR < 2, which assures the operation in the DTV band.

• Journal of the East Asian Society of Dietary Life
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• v.26 no.1
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• pp.55-62
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• 2016

As interest in health has recently increased, many researchers have investigated the utilization of functional foods by confectioneries and bakeries. However, research on loaf bread containing beets has not been conducted. To investigate the optimal ratio of beet in loaf bread containing beet powder, characteristics of loaf bread according to 2%(B2), 4%(B4), and 6%(B6) beet powder per wheat flour were examined. The experimental results were as follows. Fermentation rate was reduced as content of beet powder increased compared with the control, whereas pH levels of dough and loaf bread significantly increased as content of beet powder increased. As content of beet powder increased, volume of loaf bread decreased, whereas specific volume increased. There was no significant difference in volume of loaf bread between the samples. As far as color changes are concerned, as content of beet powder increased, L value decreased, whereas a and b values increased with significant differences between the samples. Characteristics were examined by sensory evaluation of loaf bread containing beet powder. Color of inner texture and peel color of loaf bread significantly increased as content of beet powder increased. Size of air pores was largest in B4, and there was no significant difference in the uniformity of loaf bread between the control and experiment groups. As content of beet powder increased, rigidity of bread was reduced. Control showed the highest elasticity, whereas moisture level was highest in B2 with no significant differences between the samples. The flavor of beet was stronger as content of beet powder increased. In the preference test, B4 showed the highest preference scores for texture, flavor, taste, and overall likeness but not appearance. The experimental results showed that B4 among all control and experimental groups had the most suitable baking characteristics and an optimum content of beet powder. Therefore, B4 can be considered as the most appropriate for making loaf bread containing 4% beet powder in terms of physical and sensory characteristics. This is a new product that satisfies overall sensory preferences and has improved functionality.

• Journal of Digital Convergence
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• v.15 no.2
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• pp.81-88
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• 2017

I conducted a study on the capacity evaluation and management of the main homepage screen to improve the availability of government institutions. As a result of three times evaluating the size of the homepage main page of the major institutions, the capacity of the homepage of the institution was very enormous, and when there were many concurrent users, the server was easily loaded. Governmental management guidelines are needed to fundamentally solve these problems, with the periodic and ongoing homepage management of each institution. In the future, the web site management detailed checkpoints should be additionally established in the government web site installation and management guidelines, and the recommended checking items; homepage performance evaluation, lightening homepage capacity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2351-2358
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• 2014

In this paper, a design method for a compact CPW-fed slot antenna using SRRs is studied. The structure of the proposed slot antenna is a rectangular slot antenna loaded with SRR conductors inside the slot to reduce the antenna size. Optimal design parameters are obtained by analyzing the effects of the gap between the SRR conductors and slot, and the width of the SRR conductors on the input VSWR characteristic. The optimized compact slot antenna operating at 2.45 GHz band is fabricated on an FR4 substrate with a dimension of 36 mm by 30 mm. The length of the proposed compact slot antenna is reduced to 14.3% compared to that of a conventional rectangular slot antenna. Experiment results show that the antenna has a desired impedance characteristic with a frequency band of 2.4-2.49 GHz for a VSWR < 2, and measured gain of 2.3 dBi at 2.45 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.3
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• pp.377-383
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• 2021

Recently, in accordance with the 4th industrial revolution, The use of autonomous mobile robots for flexible logistics transfer is increasing in factories, the warehouses and the service areas, etc. In large factories, many manual work is required to use Simultaneous Localization and Mapping(SLAM), so the need for the improved mobile robot autonomous driving is emerging. Accordingly, in this paper, an algorithm for mapless navigation that travels in an optimal path avoiding fixed or moving obstacles is proposed. For mapless navigation, the robot is trained to avoid fixed or moving obstacles through Deep Q Network (DQN) and accuracy 90% and 93% are obtained for two types of obstacle avoidance, respectively. In addition, DQN requires a lot of learning time to meet the required performance before use. To shorten this, the target size change algorithm is proposed and confirmed the reduced learning time and performance of obstacle avoidance through simulation.

• Archives of Plastic Surgery
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• v.49 no.5
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• pp.617-632
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• 2022

Tracheoesophageal puncture (TEP) and voice prosthesis insertion following laryngectomy may fail to form an adequate seal. When spontaneous closure of the fistula tract does not occur after conservative measures, surgical closure is required. The purpose of this study was to summarize the available evidence on surgical methods for TEP site closure. A comprehensive search across PubMed, Web of Science, SCOPUS, and Cochrane was performed to identify studies describing surgical techniques, outcomes, and complications for TEP closure. We evaluated the rate of unsuccessful TEP closure after surgical management. A meta-analysis with a random-effect method was performed. Thirty-four studies reporting on 144 patients satisfied inclusion criteria. The overall incidence of an unsuccessful TEP surgical closure was 6% (95% confidence interval [CI] 1-13%). Subgroup analysis showed an unsuccessful TEP closure rate for silicone button of 8% (95% CI < 1-43%), 7% (95% CI < 1-34%) for dermal graft interposition, < 1% (95% CI < 1-37%) for radial forearm free flap, < 1% (95% CI < 1-52%) for ligation of the fistula, 17% (95% CI < 1-64%) for interposition of a deltopectoral flap, 9% (95% CI < 1-28%) for primary closure, and 2% (95% CI < 1-20%) for interposition of a sternocleidomastoid muscle flap. Critical assessment of the reconstructive modality should take into consideration previous history of surgery or radiotherapy. Nonirradiated fields and small defects may benefit from fistula excision and tracheal and esophageal multilayer closure. In cases of previous radiotherapy, local flaps or free tissue transfer yield high successful TEP closure rates. Depending on the defect size, sternocleidomastoid muscle flap or fasciocutaneous free flaps are optimal alternatives.

• IEMEK Journal of Embedded Systems and Applications
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• v.19 no.1
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• pp.19-25
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• 2024

This paper proposes an artificial intelligence-based personal information area object detection optimization method in an embedded system to de-identify personal information in video data. As an object detection optimization method, first, in order to increase the detection rate for personal information areas when detecting objects, a gyro sensor is used to collect the shooting angle of the image data when acquiring the image, and the image data is converted into a horizontal image through the collected shooting angle. Based on this, each learning model was created according to changes in the size of the image resolution of the learning data and changes in the learning method of the learning engine, and the effectiveness of the optimal learning model was selected and evaluated through an experimental method. As a de-identification method, a shuffling-based masking method was used, and double-key-based encryption of the masking information was used to prevent restoration by others. In order to reuse the original image, the original image could be restored through a security key. Through this, we were able to secure security for high personal information areas and improve usability through original image restoration. The research results of this paper are expected to contribute to industrial use of data without personal information leakage and to reducing the cost of personal information protection in industrial fields using video through de-identification of personal information areas included in video data.

• Annals of Hepato-Biliary-Pancreatic Surgery
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• v.28 no.2
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• pp.125-133
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• 2024

Undifferentiated carcinoma with osteoclast-like giant cells (UC-OGCs) of the pancreas is a rare neoplasm that accounts for less than 1% of all pancreatic malignancies. The aim of this study was to review the literature regarding UC-OGC, and to highlight its biological behavior, clinicopathologic characteristics, prognosis, and therapeutic options. A systematic review of the literature in PubMed/Medline and Scopus databases was performed (last search October 31st, 2023) for articles concerning pancreatic UC-OGC in the adult population. Fifty-seven studies met the inclusion criteria, involving 69 patients with a male-to-female ratio of 1.1:1 and a mean age of 62.96. Main symptoms included abdominal pain (33.3%), jaundice (14.5%), weight loss (8.7%), while fourteen patients (20.3%) were asymptomatic. Surgical resection was performed in 88.4% of cases. Survival rates at one, three, and five years were 58%, 44.7%, and 37.3% respectively. Sex, age, size (cut-off of 4 cm), location, and adjuvant treatment did not significantly affect patient survival. UC-OGC of the pancreas is a rare subtype of undifferentiated pancreatic carcinoma with a better prognosis than conventional pancreatic ductal adenocarcinoma or undifferentiated carcinoma without giant cells. The establishment of a dedicated patient registry is imperative to further delineate the optimal treatment for this uncommon clinical entity.