• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권8호
• /
• pp.3911-3924
• /
• 2016

Compared to the classical cryptography, lattice-based cryptography is more secure, flexible and simple, and it is believed to be secure against quantum computers. In this paper, an efficient signature scheme is proposed from the ring learning with errors (R-LWE), which avoids sampling from discrete Gaussians and has the characteristics of the much simpler description etc. Then, the scheme is implemented in C/C++ and makes a comparison with the RSA signature scheme in detail. Additionally, a linearly homomorphic signature scheme without trapdoor is proposed from the R-LWE assumption. The security of the above two schemes are reducible to the worst-case hardness of shortest vectors on ideal lattices. The security analyses indicate the proposed schemes are unforgeable under chosen message attack model, and the efficiency analyses also show that the above schemes are much more efficient than other correlative signature schemes.

• 한국염색가공학회지
• /
• 제16권1호
• /
• pp.59-64
• /
• 2004

As a simulation of solvent-assisted dyeing, the solvent effects on the structure of polyethylene terephthalate(PET) film treated by dimethylformamide(DMF) were investigated. The effects were evaluated by the atomic force microscopy(AFM) topographical changes and FT-IR spectrum analysis. PET films treated with DMF at $70^{\circ}C$ for several different treatment time(20, 40, and 60 min). AFM topography showed that, with increasing treatment time by DMF, PET surfaces became smooth due to the swelling phenomenon and the rigid structure changed into flexible state which was contributed to increase the surface area of PET films. FT-IR spectrum analysis showed that DMF and molecular chains of PET interacted each other via their polar carbonyl groups and that DMF also affected the out-of-plane bending vibration mode of phenyl ring of PET.

• International Journal of Precision Engineering and Manufacturing
• /
• 제6권4호
• /
• pp.31-36
• /
• 2005

This paper describes a research work on the die design for the deep drawing & ironing(D. D. I) of high pressure gas cylinder. D. D. I die set is large-sized die used in horizontal press, which is usually composed of a drawing, and an ironing die. Design method of D. D. I die set is very different from that of conventional cold forging die set. Outer diameter of the die set is fixed because of press specification and that of the insert should be as small as possible for saving material cost. In this study, D. D. I die set has been designed to consider those characteristics, and the feasibility of the designed die has been verified by FE-analysis. In addition, the automated system of die design has been developed in AutoCAD R14 by formulating the applied methods to the regular rules.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
• /
• pp.64-69
• /
• 1997

정격속도 100,000RPM용 원심분리기(centrifuge) 로터베어링계에 대해 회전체동역학 해석이 수행된다. 시스템은 원심분리기 로터, 유연축, 모터 로터와 축, 그리고 모터축 지지용 두 개의 구름베어링으로 구성된다. 설계목표는 정격속도가 위험속도(critical speed)에 대해 충분한 분리여유를 갖고, 위험속도에서 로터의 양호한 불균형응답특성을 이루어 내는 것이다. 후자의 요구조건은, 시스템이 다수의 위험속도를 통과하며 정격속도 주위에서 충분한 분리 여유를 갖지 않을 수도 있기 때문에 특히 중요하다. 시스템에 초유연축(extra-flexible shaft)을 도입함으로써, 비록 1차 위험속도에서 만족스럽지 못한 큰 불균형응답을 가질지라도 고차 위험속도에서 만족스런 작은 불균형응답을 보인다. 1차 위험속도에서 로터의 큰 변위를 억제하기 위해서 범퍼링(bumper ring) 또는 안내베어링(guide bearing)을 유연축의 적절한 위치에 설치할 필요가 있다. 비록 유연축계라 할지라도 정격속도와 가까운 4차 이상의 고차 위험속도를 정확히 규명하기 위해서는 모터의 동역학을 전체시스템에 결합하여야 함을 볼 수 있다. 해석은 유한요소법(finite element method)에 의해 수행된다.

• Bulletin of the Korean Chemical Society
• /
• 제6권3호
• /
• pp.135-138
• /
• 1985

A new flexible $N_2O_2$-type tetradentate ligand, ethylene-diamine-N,N'-di-${\alpha}$-butyric acid (eddb), has been synthesized, and a series of cobalt (III) complexes of eddb, $[Co(edda)(L)]^{n+}$ (L = $Cl_2$, $(H_2O)_2$, $Cl\;H_2O$, and $Co^2_3$), have been prepared. Only s-cis isomers have been yielded during the preparation of complexes. Ring strain is cited as the primary cause for the preference for the s-cis geometric configuration.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 추계학술대회 논문집
• /
• pp.815-829
• /
• 2008

Debris flows are a natural hazard which looks like a combination of flood, land and rock slide. Large rainfall in July 2006 produced several large scale debris flows and many small debris flows that resulted in loss of life and considerable property and railway damage, as was widely reported in the national media. The hazard "debris flow" is still insufficiently researched. Furthermore debris flows are very hard to predict. Flexible Ring net barriers are multi-functional mitigation devices commonly applied to rock fall or floating wood protection in floods, snow avalanches and also mud flows or granular debris flows, if properly dimensioned for the process or processes for which they are intended. Overtopping of the barriers by debris flows and sediment transport is possible, supporting the design concept that a series of barriers may be used to stop volumes of debris larger than are possible using only one barrier. The future for these barrier concepts looks promising because these barriers represent the state of art for such applications and are superior to many other available options.

• 로봇학회논문지
• /
• 제16권1호
• /
• pp.12-16
• /
• 2021

Attempts are being made to provide various tactile feedbacks to user. In particular, a variety of soft actuators are being inserted into the tactile feedback device to give a more flexible, soft and strong stimulation. In this study, a basic study was performed to utilize a hydraulically amplified self-healing electrostatic (HASEL) actuator as a tactile feedback actuator. The HASEL actuator showed great displacement and force with a simple circuit configuration. In particular, by making the actuator in a circular shape, the angle was reduced and the electrode was arranged in a ring shape to maximize the displacement of the central part. As a result, the HASEL actuator showed a displacement difference according to the input waveform. In addition, in order to use it safely as an actuator for tactile feedback, we covered the surface with silicone and confirmed that the actuator works well. Using these actuators, it will be possible to manufacture a lightweight, portable tactile feedback device.

• 한국전산구조공학회논문집
• /
• 제15권1호
• /
• pp.147-154
• /
• 2002

수직방향 가속도를 받는 원통형 액체 저장탱크는 내부유체의 슬로싱(sloshing)에 의한 동하중에 의하여 구조 및 제어성능 안정성에 심각한 영향을 받을 수 있다. 더욱이 유체의 슬로싱 진동수가 제어계 혹은 탱크구조물의 고유진동수 근처에 있게되면 발사체에 큰 동하중과 모멘트를 유발하게 된다. 이와 같은 유체의 동적 효과를 억제하기 위하여 일반적으로 링형 탄성체 배플(baffle)을 채용하고 있다. 본 논문에서는 배플의 개수와 내경을 변수로 설정하여 배플의 동적억제효과를 평가 및 분석하기 위한 수치해석을 수행한다. 배플내경에 따른 파라메트릭 해석과, 탱크높이 및 유체높이를 각각 균등 분할하여 설치된 배들에 대한 동억제 효과를 분석한다. 유체와 구조물 사이의 정확하고 효과적인 연계해석을 위하여 ALE(arbitrary Lagrangin-Eulerian) 수치해석 기법을 적용한다.

• 한국항해항만학회지
• /
• 제39권6호
• /
• pp.473-478
• /
• 2015

본 논문에서는 어선원 및 일반인들이 해상에서 조난을 당하였을 경우 구조를 위해 조난신호 및 위치정보를 송신할 수 있으면서, 팽창식 구명조끼에 장착이 가능한 유연한 다중대역 안테나를 제안한다. 이 안테나는 VHF-DSC 대역(156MHz), COSPAS-SARSAT 대역(406MHz) 및 GPS대역(1,575MHz) 에서 동작하는 3중대역 안테나이다. GPS대역은 사각형 슬롯 링(square slot-ring) 형태의 평판 구조로 구현하였고, COSPAS-SARSAT 대역과 VHF-DSC 대역은 모노폴 구조로 구현을 하였다. 또한 기판은 구명조끼 장착을 위한 유연성 확보를 위해 0.2mm 두께를 가지는 FR4-epoxy 기판을 사용하였다. 제작된 안테나는 최종적으로 사람이 구명조끼를 장착한 상태에서 VHF-DSC, COSPAS-SARSAT, GPS 대역에서 각각 -8.8dB, -20.4dB, -10.7dB의 반사손실 특성을 나타내었다.

• 한국미생물생명공학회:학술대회논문집
• /
• 한국미생물생명공학회 2002년도 학술발표대회
• /
• pp.18-25
• /
• 2002

The pikromycin biosynthetic system in Streptomyces venezuleae is unique for its ability to produce two groups of antibiotics that include the 12-membered ring macrolides methymycin and neomethymycin, and the 14-membered ring macrolides narbomycin and pikromycin. The metabolic pathway also contains two post polyketide-modification enzymes, a glycosyltransferase and P450 hydroxylase that have unusually broad substrate specificities. In order to explore further the substrate flexibility of these enzymes a series of hybrid polyketide synthases were constructed and their metabolic products characterized. The plasmid-based replacement of the multifunctional protein subunits of the pikromycin PKS in S. venezuelae by the corresponding subunits from heterologous modular PKSs resulted in recombinant strains that produce both 12- and 14-membered ring macrolactones with predicted structural alterations. In all cases, novel macrolactones were produced and further modified by the DesVII glycosyltransferase and PikC hydroxylase leading to biologically active macrolide structures. These results demonstrate that hybrid PKSs in S. venezuelae can produce a multiplicity of new macrolactones that are modified further by the highly flexible DesVII glycosyltransferase and PikC hydroxylase tailoring enzymes. This work demonstrates the unique capacity of the S. venezuelae pikromycin pathway to expand the toolbox of combinatorial biosynthesis and to accelerate the creation of novel biologically active natural products. The polyketide backbone of rifamycin B is assembled through successive condensation and ${\beta}$-carbonyl processing of the extender units by the modular rifamycin PKS. The eighth module, in the RifD protein, contains nonfunctional DH domain and functional KR domain, which specify the reduction of the ${\beta}$-carbonyl group resulting in the C-21 bydroxyl of rifamycin B. A four amino acid substitution and one amino acid deletion were introduced in the putative NADPH binding motif in the proposed KR domain encoded by rifD. This strategy of mutation was based on the amino acid sequences of the corresponding motif of the KR domain of module 3 in the RifA protein, which is believed dysfunctional, so as to introduce a minimum alteration and retain the reading frame intact, yet ensure loss of function. The resulting strain produces linear polyketides, from tetraketide to octaketide, which are also produced by a rifD disrupted mutant as a consequence of premature termination of polyketide assembly. Much of the structural diversity within the polyketide superfamily of natural products is due to the ability of PKSs to vary the reduction level of every other alternate carbon atom in the backbone. Thus, the ability to introduce heterologous reductive segments such as ketoreductase (KR), dehydratase (DH), and enoylreductase (ER) into modules that naturally lack these activities would increase the power of the combinatorial biosynthetic toolbox. The dehydratase domain of module 7 of the rifamycin PKS, which is predicted to be nonfunctional in view of the sequence of the apparent active site, was replaced with its functional homolog from module 7 of rapamycin-producing polyketide synthase. The resulting mutant strain behaved like a rifC disrupted mutant, i.e., it accumulated the heptaketide intermediate and its precursors. This result points out a major difficulty we have encountered with all the Amycolatopsis mediterranei strain containing hybrid polyketide synthases: all the engineered strains prepared so far accumulate a plethora of products derived from the polyketide chain assembly intermediates as major products instead of just analogs of rifamycin B or its ansamycin precursors.