• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.284-292
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• 2014

This paper presents a characteristic evaluation of commercial gallium nitride (GaN) transistors having two different gate-lengths of $0.4-{\mu}m$ and $0.25-{\mu}m$ in the design of a class-S power amplifier (PA). Class-S PA is operated by a random pulse-width input signal from band-pass delta-sigma modulation and has to deal with harmonics that consider quantization noise. Although a transistor having a short gate-length has an advantage of efficient operation at higher frequency for harmonics of the pulse signal, several problems can arise, such as the cost and export license of a $0.25-{\mu}m$ transistor. The possibility of using a $0.4-{\mu}m$ transistor on a class-S PA at 955 MHz is evaluated by comparing the frequency characteristics of GaN transistors having two different gate-lengths and extracting the intrinsic parameters as a shape of the simplified switch-based model. In addition, the effectiveness of the switch model is evaluated by currentmode class-D (CMCD) simulation. Finally, device characteristics are compared in terms of current-mode class-S PA. The analyses of the CMCD PA reveal that although the efficiency of $0.4-{\mu}m$ transistor decreases more as the operating frequency increases from 955 MHz to 3,500 MHz due to the efficiency limitation at the higher frequency region, it shows similar power and efficiency of 41.6 dBm and 49%, respectively, at 955 MHz when compared to the $0.25-{\mu}m$ transistor.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.11
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• pp.483-488
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• 2013

Users can access their data anywhere, at any time by using outsourced storage. But they cannot know how service provider manage the data. Even user cannot know when data damaged. To solve these problems, the outsourced storage auditing schemes has been proposed. Most proposed schemes are based on Homomorphic Verifiable Tags. But it has computational efficiency limitation because data used to exponent. In this paper, we propose a novel approach to outsourced storage auditing scheme using coefficient matrix. In the proposed scheme, data used to auditing by coefficient matrix form. Auditing procedures are proceed as solving the linear simultaneous equation. The auditor can audit easily by solving the equation using solution vector. The auditor can audit the n size data using sqrt(n) size data through out proposed scheme.

• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.621-628
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• 2003

Stud shear connectors are the most commonly used shear connectors: up to 22mm studs are usually used in steel-concrete composite structures. To expand the current design codes for stud connectors, large studs with a diameter of more than 25mm should be investigated. Through push-out tests on large stud shear connectors that transcend the limitation of current design codes, fatigue behavior was investigated and comparisons with design equations performed. The shear stiffness of the connectors in elastic range was evaluated through shear tests on 25mm, 27mm, and 30mm studs and compared with those from static tests. The fatigue behavior of large studs was discussed in terms of residual slip and load-slip curves. The initiation of fatigue cracks in the welding part could be detected through the history of displacement range. Test results showed that the design fatigue endurance of S-N curves in current design codes could be applied to large stud shear connector.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.4
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• pp.667-680
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• 2024

If the software is not updated after the vulnerability is disclosed, it can continue to be attacked. As a result, the importance of N-day detection is increasing as attacks that exploit vulnerabilities increase. However, there is a problem that it is difficult to find specific version information in the published vulnerability database, or that the wrong version or software is outputted. There is also a limitation in that the connection between the published vulnerability databases is not good. In order to overcome these limitations, this paper proposes a method of building information including comprehensive vulnerability information such as CVE, CPE, and Exploit Database into an integrated database. Furthermore, by developing a website for searching for vulnerabilities based on an integrated database built as a result of this study, it is effective in detecting and utilizing vulnerabilities in specific software versions and Windows operating systems.

• Clean Technology
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• v.11 no.3
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• pp.117-122
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• 2005

N-vinyl caprolactam (NVCL), a kind of N-vinyl amide monomer, must be dissolved in continuous phase ($scCO_2$) for dispersion polymerization in supercritical carbon dioxide. Phase behavior of $CO_2$+NVCL is very important and necessary for determining initial polymerization condition and for monomer extraction from final polymer. There is the limitation of experimental method for obtaining pure properties of the monomer because of the possibility of polymerization. And N-methyl caprolactam (NMCL) is the useful solvent for the gas treating process. In the viewpoint of molecular thermodynamics, NVCL and NMCL have same functional group i.e. ${\varepsilon}$-caprolactam. In the case of NVCL, hydrogen of amide group is substituted with vinyl group and for NMCL, hydrogen of amide group is substituted with methyl group. We suggested modified group contribution method for this ${\varepsilon}$-caprolactam derivatives. This new group contribution parameter was applied to correlate $CO_2$ + N-vinyl caprolactam or N-methyl caprolactam system.

• Korean Journal of Environmental Agriculture
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• v.38 no.3
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• pp.119-123
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• 2019

BACKGROUND: Estimation of soil nitrogen supply is essential to manage nitrogen fertilization in arable land. In Korea, nitrogen fertilization is recommended based on the soil organic matter content because it is difficult to assess nitrogen (N) mineralization of upland soils directly. In this study, the relationship between soil organic matter (SOM) content and N mineralization was investigated to explore the limitation of using SOM in predicting soil N mineralization. METHODS AND RESULTS: Soil samples from the 0 to 10 cm depth were collected from 18 individual pepper cultivated fields in Tae-an and Chung-yang provinces before fertilization. N mineralization in the soils was quantified using incubation for 70 days at $30^{\circ}C$. The mineralizable soil N (MSN) was positively correlated with SOM, and the relation equation between MSN and SOM was '$MSN(kg\;10a^{-1})=0.2933{\ast}SOM(g\;kg^{-1})+0.0897$ ($r^2=0.6224$, p<0.001)'. However, the differences of N mineralization among the soils with the similar concentrations of soil organic matter were about 3 to 4.6 times, suggesting that the other soil factors such as total N concentration or EC should affect N mineralization. CONCLUSION: We concluded that SOM alone could not reflect the capacity of soil to supply N that is used for recommendation of N fertilization rate. Therefore, other soil properties should be considered to improve N fertilization management in arable land for sustainable agriculture.

• Journal of the Korean Dietetic Association
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• v.7 no.3
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• pp.282-294
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• 2001

n accordance with the National Health Promotion Act of 1995, newly designed National Health and Nutrition Survey was carried out in winter of 1998. Although this survey amended most of the problems noted in previous Nutrition Surveys, it still had a limitation in reflecting seasonal variation in food intake due to the survey period which was confined to November and December. In order to counterbalance this limitation and estimate the yearly food intake of Korean population, three seasonal nutrition surveys were taken place in spring, summer, and fall of 1999. Seasonal Nutritional survey targeted 15 households each in 60 nationwide primary sampling units(PSUS) which were part of 200 PSUS of 1998 National Health and Nutrition Survey. Therefore, total of 2,700 households were surveyed in 3 seasons. The interviewers visited each household members and carried out face to face interview on household. Daily food intake was monitored using 24 hour recall method. According to the survey results, fruits, beverage and alcohol intake showed large variation with season while processed foods showed almost no variation. And intake of vegetables and fruits were influenced by their own harvesting time and had impact on the list of foods consumed most. With the result of the 1998 NHNS, this study made it possible to estimate the yearly average food intake of Korean population. The result of this survey is expected to be used in planning food supply and setting tolerance level of contaminants of each foods at the government level.

• Journal of the Society of Disaster Information
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• v.9 no.4
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• pp.429-438
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• 2013

In this study, compare and analyze for high-rise evacuation safety design criteria improvement about internal high-rise building egress safety rule. To the result, high-rise evacuation safety design criteria improvement data can be summarized as follows. First, should compute the evacuation capacity about the number of persons and when more than 2 exits are requested, over 50% of evacuation capacity must be satisfied even approaching to 1 exit is unable. Second, 2 ways of evacuation can be made smoothly by the stair or exit separation-distance standard regulation. Third, regulate the length limitation of dead-end corridor or passageway and it should give grades in limitation of whether the spring-cooler has been installed. Fourth, must secure the evacuation way and do the evacuee guidance when it's safety area and elevator or stair. Also needs to provide extra safety area to secure horizontal direction Escape Safety except fire escaping floor.

• Journal of KIISE
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• v.43 no.8
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• pp.841-847
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• 2016

As network technology advances, a larger number of devices are connected through the Internet. Recently, cloud storage services are gaining popularity, as they are convenient to access anytime and anywhere. Among cloud storage services, object storage is the representative one due to their characteristics of low cost, high availability, and high durability. One limitation of object storage services is that they can access data on the cloud only through the HTTP-based RESTful APIs. In our work, we resolve this limitation with the in-memory file system which provides a POSIX interface to the file system users and communicates with cloud object storages with RESTful APIs. In particular, our flush mechanism is compatible with existing file systems, as it is based on the swap mechanism of the Linux kernel. Our in-memory file system backed by cloud storage reduces the performance overheads and shows a better performance than S3QL by 57% in write operations. It also shows a comparable performance to tmpfs in read operations.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.12
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• pp.7657-7661
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• 2013

Background: This study concerns uptake and results of colorectal cancer (CRC) screening of government servant as part of the Health Screening Program that was conducted in Brunei Darussalam in 2009. Materials and Methods: Government servants above the age of 40 or with family history of CRC were screened with a single fecal occult blood test (FIT, immunohistochemistry). Among 11,576 eligible subjects, 7,360 (66.9%) returned their specimen. Subjects with positive family history of CRC (n=329) or polyps (n=135) were advised to attend clinics to arrange screening. All the subjects with positive FIT (n=142, 1.9%) were referred to the endoscopy unit for counselling for screening colonoscopy. Results: Overall only 17.7% of eligible subjects attended for screening; 54.9% (n=79/142) of positive FIT, 8.8% (n=29/329) of positive family history of CRC and none with history of polyps (n=0/135). Of these, only 54 patients (50.5%) agreed for colonoscopy, 52 (48.6%) declined as they were asymptomatic, and one was not offered (0.9%) due to his very young age. On screening colonoscopy, 12.9% (n=7) had advanced lesions including a sigmoid carcinoma in situ and six advanced polyps. The other findings included non advanced polyps (n=21), diverticular (n=11) and hemorrhoids (n=26). One patient who missed his screening colonoscopy appointment re-presented two years later and was diagnosed with advanced right sided CRC. All the advanced lesions were detected in patients with positive FIT, giving a yield of 20.5% for advanced lesions including cancers in the 5.1% FIT positive subjects. Conclusions: Our study showed screening for CRC even with a single FIT was effective. However, the uptake rate was poor with just over half of the patients agreeing to screening colonoscopy. Measures to increase public awareness are important. Since one limitation of our study was the relatively small sample size, larger studies should be conduced in future.