• Journal of radiological science and technology
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• v.36 no.2
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• pp.149-155
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• 2013

The Korean Thyroid Association recommends fine-needle aspiration biopsy (FNAB) for nodules more than 0.5 cm in diameter. But nodules, smaller than 0.5 cm have been found in papillary carcinomas of the thyroid (PTC) at the health promotion center at SMC. We wanted to evaluate the ultrasonographic findings according to size of nodule in proven PTCs by FNAB, especially less than 0.5 cm. All nodules were classified into three groups by their longest diameter : less than 0.5 cm, more than 0.5 cm but less than 1 cm, and more than 1 cm. Sonographic findings suggesting malignancy were analyzed according to their size groups. Of 288 malignant nodules, 21.5 % (62/288) were less than 0.5 cm, 54.9 % (158/288) were more than 0.5 cm but less than 1 cm, 23.6 % (68/288) exceeded 1 cm. A taller-than-wide shape was observed in 90.3 % (56/62) of nodules less than 0.5 cm, and 48.5 % (33/68) of nodules exceeding 1 cm (p<0.001). There were no well-defined smooth nodules among nodules less than 0.5 cm, and spiculated or irregular margin nodules increased as the size increased (p=0.024). Nodules of size less than 0.5 cm did not showed hyper or isoechogenicity. Hypoechogenicity was greater than the marked hypoechogenicity in each group (p=0.034). Micro- or macro-calcifications were not founded in 77.4 % (48/62) of the nodule group sized less than 0.5 cm. From the small size of the group, micro- or macrocalcifications were observed 21.0 % (13/62), 48.1 % (76/158), 64.7 % (44/68), so the number of nodules containing micro- or macro-calcification increased as size increased (p<0.001). PTCs less than 0.5 cm in size on ultrasonography had taller than-wide shape, spiculated or irregular and ill-defined margins, and exhibited hypo and markedly hypoechogenicity, but microor macro-calcifications were not common. These ultrasonographic features of nodules less than 0.5 cm can be useful in reporting and guiding FNABs or follow-up exams.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.6
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• pp.41-51
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• 2001

Group signature schemes allow a group member to sign messages anonymously on behalf of the group. In case of dispute, only a designated group manager can reveal the identity of the member. During last decade, group signature schemes have been intensively investigated in the literature and applied to various applications. However, there has been no scheme properly handling the situation that a group member wants to leave a group or is excluded by a group manager. As noted in[3], the complexity of member deletion stands in the way of real world applications of group signatures and the member deletion problem has been a pressing open problem. In this paper we propose an efficient group signature scheme that allows member deletion. The length of the group public key and the size of signatures all independent of the size of the group and the security of the scheme relies on the RSA assumption. In addition, the method of tracing all signatures of a specific member is introduced.

• KIPS Transactions on Software and Data Engineering
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• v.8 no.12
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• pp.473-482
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• 2019

There have already been studies analyzing the trajectories of objects from data streams of moving objects. Among those studies, there are also studies to discover groups of objects that move together, called companion groups. Most studies to discover companion groups use existing clustering techniques to find groups of objects close to each other. However, these clustering-based methods are often difficult to find the right companion groups because the number of clusters is unpredictable in advance or the shape or size of clusters is hard to control. In this study, we propose a new method that discovers companion groups based on the distance specified by the user. The proposed method does not apply the existing clustering techniques but periodically determines the groups of objects close to each other, by using a technique that efficiently finds the groups of objects that exist within the user-specified distance. Furthermore, unlike the existing methods that return only companion groups and their trajectories, the proposed method also returns their appearance and disappearance time. Through various experiments, we show that the proposed method can detect companion groups correctly and very efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7B
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• pp.422-430
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• 2007

WDM-PON has been receiving much attention as a key technology to FTTH. As the cost of WDM-PON heavily depends on the number of transceivers implemented at ONU, one of its shortcomings comes from the fixed provision of wavelength resource, which is tightly coupled with costly transceivers. In this paper, we propose a cost-effective WDM-PON architecture for dynamic resource provision. The proposed architecture is based on hierarchical grouping of multiple ONUs into a logical group and hierarchical sharing the resource. For high utilization of dynamic resource, the dynamic resource allocation algorithm is also proposed. We analyze the system efficiency in term of dynamism of system resource and system cost. We also verify that the proposed resource allocation algorithm achieves a high dynamism on resource allocation, and at the same time maintains the fairness between ONUs.

• Applied Biological Chemistry
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• v.50 no.2
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• pp.101-106
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• 2007

Twenty-two strains of nematophagous fungi were isolated from 100 soil samples. Nematophagous fungi were classified into three categories; 3-dimensional adhesive nets (A group), 2-dimensional adhesive nets (B group) and constricting ring (C group). Nine strains were selected and identified on the basis of morphological characteristics (hypha, conidiophore, form and size of conidia, number of conidia, node of conidophore, number and location of septa, size and color of chlamydospore) and ITS (internal transcribed spacer) region of rDNA sequences. As the results, the isolated were identified as belonging to the species of Monacrosporium thaumasium (Kan-2, Kan-4, Kan-11), Arthrobotrys oligospora (Kan-9, Kan-13, Kan-20, Kan-21), A. musiformis (Kan-12), and A. dactyloides (Kan-22).

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.509-511
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• 2019

Hydrazine derivatives used in fine chemicals, pharmaceuticals and cosmetics can be synthesized by reduction reaction from diazonium derivatives. The reduction method using $SnCl_2$ facilitates the reaction conversion, but the use of $SnCl_2$ is limited when residual heavy metals are issued in the final product. For the conversion of protected (2-hydroxyphenyl)diazonium derivatives into its hydrazine derivatives in Ramalin preparation process, the reduction method was developed by using $NaHSO_3$. In this study, the effect of steric hindrance according to the protected 2-hydroxygroupinphenyldiazonium derivatives was found, and linear C1~C5 alkyl groups for the hydroxy protection were preferable during the diazonium reduction reaction. Considering the economical efficiency and industrial production for the preparation of Ramalin, a variety of protecting groups were investigated. As a result, 2-(allyloxyphenyl)hydrazine was obtained with 85% yield and 99.7% purity when the hydroxy protecting group was used as an allyl group that could be easily deprotected.

• Journal of Environmental Health Sciences
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• v.31 no.4 s.85
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• pp.316-321
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• 2005

4개 업종(축전지제조업, 광명단 제조업, 2차 제련업, 라디에타 제조업)에서 근무하는 총 100명의 근로자를 대상으로 8단계다단충돌기(eight stages personal cascade imparter)에 의한 입자 크기 별 납농도를 측정하였다 크기 별 납 농도는 총납(PbA), 흡입성납(IPM-PbA), 흉곽성납(TPM-PbA), 호흡성납(RPM-PbA), $1{\mu}m$ 미만의 납$(Pb_{1\mu})$ 그리고 $1{\mu}m$ 이상의 소화성납$(Pb_{ing})$이었다. 동일한 근로자(100명)를 대상으로 혈액에서 납농도를 측정하였다. 혈액 중 납은 원자흡광광도계(atomic absorption spectrometry)의 Zeeman effect graphite furnace를 이용하여 분석하였다. 총 납의 노출농도는 노출기준$(50\;ug/m^3)$을 크게 초과하였다. 평균 호흡성 납 노출농도$(115.7\;ug/m^3)$ 총 납의 노출기준을 훨씬 초과하였다. $1{\mu}m$미만의 납$(Pb_{1\mu})$ 노출농도의 범위는 0.7에서 $(492.2\;ug/m^3)$이나 되었다. 근로자의 $46\%$가 혈액 중 납 농도 40 ug/dL을 초과하였다. 60 ug/dL을 초과한 경우도 $13\%$나 되었다. 입자 크기가 큰 납인 총납, 흡입성 납 그리고 호흡성 납 농도는 혈액 중 납 농도와 유의한 상관을 보였다(p<0.0001). 그러나 가장 높은 상관은 $1{\mu}m$미만의 납$(Pb_{1\mu})$ 혈액 중 납과의 관계였다. T-test에서 $50ug/m^3$이상의 호흡성 납을 나타낸 근로자 그룹과 $50ug/m^3$ 이하의 근로자 그룹간에의 혈액 중 납 농도는 유의한 차이가 있는 것으로 나타났다(p=0.000). 이러한 연구결과는 입자크기 구분이 없는 현재의 총납에 의한 노출기준과 측정방법은 미세 납 먼지에 노출되는 근로자의 납흡수를 보호하는데 한계점이 있다는 것을 의미한다. 향후 납 입자크기는 물론 근로자의 개인적인 위생과 작업내용 등을 변수로 납 흡수에 영향을 미치는 종합적인 요인을 찾아내는 연구를 진행할 필요가 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.804-813
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• 2020

This paper finds that Korean zero-leverage firms are not homogeneous. By conducting both univariate and multivariate logit regression analysis, this paper finds that Korean zero-leverage firms have zero leverage as either a consequence of financial constraints or because of a strategic decision to mitigate under-investment incentives and preserve financial flexibility. There are two distinct groups of unlevered firms with different levels of constraints as measured by their dividend policy, namely dividend payers and non-payers. Importantly, this paper finds new evidence that these two groups have different motives for selecting a zero leverage policy. Firms in the first group (non-payers) have zero leverage, mainly due to financial constraints. They rely heavily on their internal funds and consequently invest in fewer growth opportunities than their levered counterparts. Firms in the second group (payers) deliberately avoid debts and preserve financial flexibility to mitigate investment distortions, as predicted by the under-investment and financial flexibility hypotheses.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.5
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• pp.3-15
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• 2003

The secure group communication enables the members, which belong to the same group, to communicate each other in a secure and secret manner. To do so, it is the most important that a group key is securely distributed among them and also group membership is efficiently managed. In detail, the generation, the distribution and the refreshment of a group key would be highly regarded in terms of low communication and computation complexity. In this paper, we show you a new protocol to generate a group key which will be safely shared within a group, utilizing the 2-party Diffie-Hellman key exchange protocol and the complete binary tree. Our protocol has less complexity of computation per group member by substituting many parts of exponentiation computations for multiplications. Consequently, each group member needs constant computations of exponentiation and multiplication regardless of the group size in the protocol and then it has less complexity of the computation than that of any other protocols.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.407-413
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• 2022

This study demonstrates a method for synthesis of amine functionalized and easily size controllable silica nanoparticles through biomimetic polyamine complex. First, we generate a polyamine nanocomplex composed of polyallylamine hydrochloride (PAH) and phosphate ion (pi) to synthesize silica nanoparticles. The size of polyamine nanocomplex is reversibly adjusted within the range of about 50 to 300 nm according to the pH conditions. Amine groups of the PAH in the nanocomplex catalyzes the condensation reaction of silicic acid. As a results, silica nanoparticles are synthesized based on nanocomplex in a very short time. Finally, we synthesize silica nanoparticles with various sizes according to the pH conditions. In the process of synthesizing silica nanoparticles, polyamine chains that act as catalysts are incorporated into the inside and surface of the particles, subsequently, amine groups are exposed on the surface of silica nanoparticles. As a results, the synthesis and surface modification of silica nanoparticles are performed simultaneously, and the silica nanoparticles introduced with amine groups can be easily synthesized by adjusting the sizes of the silica nanoparticles. Finally, we demonstrate the synthesis of functional silica nanoparticles in a short time under milder conditions than the conventional synthetic method. Furthermore, this method can be applicable to bioengineering and materials fields.