• Bulletin of the Korean Chemical Society
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• 제32권spc8호
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• pp.3051-3056
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• 2011

We calculate the free energy surfaces for two small proteins and a protein-RNA complex system by using a lattice model approach. In particular, we employ the Munoz-Eaton model, which is a native-structure based statistical mechanical model for studying protein folding problem. The model can provide very useful insights into the folding mechanisms by allowing one to calculate the free energy surfaces efficiently. We first calculate the free energy surfaces of ubiquitin and BBL, using both approximate and recently developed exact solutions of the model. Ubiquitin exhibits a typical two-state folding behavior, while BBL downhill folding in our study. We then extend the method to study of a protein-RNA complex. In particular, we focus on PAZ-siRNA complex. In order to elucidate the interplay between folding and binding kinetics for this system we perform comparative studies of PAZ only, PAZ-siRNA complex and two mutated complexes. We find that folding and binding are strongly coupled with each other and the bound PAZ is more stable than the unbound PAZ. Our results also suggest that the binding sites of the siRNA may serve act as a nucleus in the folding process.

• 한국산학기술학회논문지
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• 제19권8호
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• pp.1-7
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• 2018

본 접이식 태양광 발전 시스템은 독립형 시스템의 하나로, 태양광 패널이 부착되어 있는 구조물이다. 이를 지지하는 부분과 이동의 용이함을 위해 접히는 부분으로 구성되어 있다. 태양광 패널의 발전효율을 최대화 하여 전기를 생산하기 위해서는 태양광 패널의 효율도 중요하지만 가장 중요한 것은 구조물 안정성이다. 본 연구에서 개발하고자 하는 접이식 태양광 발전 구조물은 격오지에서도 독립으로 전기를 생산할 수 있는 시스템으로 이동과 설치가 용이한 접이식 방식의 구조물이다. 이러한 구조물은 야외에 설치되므로 풍하중, 적설하중 등이 작용한다. 본 논문에서는 접이식 태양광 발전 구조물에 가장 영향이 큰 풍하중을 MeshFree 유한요소법을 사용하여 구하였다. 일반적으로 구조물의 형상은 복잡하고 큰 설계안 때문에 Mesh를 수행할 때 시간이 오래 걸린다는 단점을 가지고 있다. 이러한 기존 Mesh의 문제점을 해결하기 위해 최근 MeshFree가 개발되어 사용되고 있다. MeshFree는 기존 해석 시 요구되는 Mesh 작업을 간소화함으로써, 사용자가 보다 쉽게 해석 할 수 있는 프로그램이다. 또한, 사계절 남중고도에 따라 일반적으로 많이 설치되는 각도인 $15^{\circ}$, $30^{\circ}$의 각도로 설계하여 해석하였다. 해석결과 풍하중은 지면과의 경사각이 클수록 커지는 것을 알 수 있었다. 또한, 풍하중실험을 통해 신뢰성을 확보하였다.

• 소성∙가공
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• 제19권2호
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• pp.88-94
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• 2010

The next generation of diesel engine can operate at high injection pressure up to 1,800bar. The common rail pipe must have higher internal strength because it is directly influenced by the high-pressure fuel. Folding defects in the Common rail pipe can not ensure the structural safety. Therefore, Preform design and fatigue-life analysis are very important for preventing the head of the common rail pipe from folding in the heading process and for predicting fatigue life according to the amount of folding. In this study, a closed form equation to predict fatigue life was suggested by Goodman theory and pressure vessels theory in ASME Code in order to develop an optimization technique of the heading process and verified its reliability through fatigue-structural coupled field analysis. The results calculated by the theory were in good agreement with those obtained by the finite element analysis.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권5호
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• pp.473-481
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• 2013

A fractional folding analog-to-digital converter (ADC) with a novel arithmetic digital encoding technique is discussed. In order to reduce the asymmetry errors of the boundary conditions for the conventional folding ADC, a structure using an odd number of folding blocks and fractional folding rate is proposed. To implement the fractional technique, a new arithmetic digital encoding technique composed of a memory and an adder is described. Further, the coding errors generated by device mismatching and other external factors are minimized, since an iterating offset self-calibration technique is adopted with a digital error correction logic. A prototype 8-bit 1GS/s ADC has been fabricated using an 1.2V 0.13 um 1-poly 6-metal CMOS process. The effective chip area is $2.1mm^2$(ADC core : $1.4mm^2$, calibration engine : $0.7mm^2$), and the power consumption is 88 mW. The measured SNDR is 46.22 dB at the conversion rate of 1 GS/s. Both values of INL and DNL are within 1 LSB.

• Applied Biological Chemistry
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• 제47권1호
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• pp.33-40
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• 2004

Ubiquitin 폴딩 반응의 초기에 나타나는 transient 폴딩 intermediate 상태의 열역학적인 특성을 연구하였다. 온도와 화학변성제의 농도를 바꾸어주면서 측정한 폴딩 kinetics의 결과로부터 unfolded 상태와 intermediate 상태의 평형상수 및 자유에너지를 quantitative kinetic modeling을 통하여서 구하였으며 또한 온도에 따른 자유에너지의 변화로부터 unfolded 상태에서 intermediate 상태로 전환될 때의 열역학적 함수인 ${\Delta}H,\;{\Delta}S,\;{\Delta}C_p$를 구하였다. Ubiquitin이 unfolded 상태에서 intermediate 상태가 될 때의 ${\Delta}C_p$는 unfolded 상태에서 native 상태로 되는 과정의 ${\Delta}C_p$의 약 80% 정도 되었다. 이것은 intermediate가 native 상태에 가까운 매우 조밀한 구조를 이루고 있는 ensemble state임을 나타낸다. 상온에서의 ${\Delta}H$는 양의 값을 보였다. 이는 ubiquitin의 unfolded 상태에서 소수성 잔기 주위에 위치한 물 분자의 규칙적인 구조가 intermediate 상태가 될 때 와해되기 때문이라고 여겨진다. 이러한 양의 enthalpy는 자유로워진 물 분자에 의한 전체 계의 entropy의 증가에 의하여서 보상되어 unfolded 상태에서intermediate 상태로의 전환은 음의 자유에너지를 갖게 되며 폴딩 반응의 초기에 관찰되는 것으로 여겨진다.

• 대한전자공학회논문지SD
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• 제48권4호
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• pp.14-23
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• 2011

본 논문에서는 자체보정 벡터 발생기(Self-Calibrated Vector Generator)를 이용한 7-bit 2GSPS folding/interpolation A/D Converter (ADC)를 제안한다. 제안하는 ADC는 2GSPS 의 고속 변환에 적합한 상위 2-bit, 하위 5-bit 인 분할구조로 설계 되었으며, 각각의 folding/interpolation rate는 4와 8로 설정되었다. 최대 1GHz의 높은 입력신호를 처리하기 위해 cascade 구조의 preprocessing block을 적용하였으며, 전압 구동 방식 interpolation 기법을 적용하여 기준전압 생성 시 발생하는 추가적인 전력소모를 최소화하였다. 또한, 새로운 개념의 자체보정 벡터 발생기를 이용하여 device mismatch, 기생 저항 및 커패시턴스 등에 의한 offset error를 최소화하였다. 제안하는 ADC는 1.2V 0.13um 1-poly 7-metal CMOS 공정을 사용하여 설계 되었으며 calibration 회로를 포함한 유효 칩 면적은 2.5$mm^2$ 이다. 측정 결과 입력 주파수 9MHz, sampling 주파수 2GHz에서 39.49dB의 SNDR 특성을 보이며, calibration 회로의 작동결과 약 3dB 정도의 SNDR의 상승을 확인하였다.

• Wind and Structures
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• 제1권4호
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• pp.317-336
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• 1998

In this paper the appraisal of a folding dome structure under the influence of wind loading is discussed. The foldable structure considered is constructed from an assembly of interconnected elements, together with a flexible membrane, all of which are initially store in a compact form and on deployment expand, like an umbrella, into a dome structure. Loading on the dome was obtained from a wind tunnel analysis of the pressure distribution over the roof of a 1:10 scale model of the structure. The critical loading obtained from the wind tunnel investigation was used, together with individual member and material tests, to form a series of numerical non-linear finite element models which were, in turn, used to investigate the forces within the structure. The numerical analysis was used to determine the critical wind loading that the structure can sustain, as well as providing a method by which to investigate the failure modes of the structure. In order to enhance the load carrying capacity of the dome it was found that both the strength and stiffness of the structural nodes needed to be enhanced and in addition, changes were necessary to substantially increase the stiffness of the individual member and caps.

• 한국생물정보학회:학술대회논문집
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• 한국생물정보시스템생물학회 2000년도 International Symposium on Bioinformatics
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• pp.86-87
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• 2000

Protein folding is a fundamental problem in structural bioinformatics and so numerous studies have been devoted to the subject. As the most common regular secondary conformation in proteins, helix has been an important ingredient of the protein folding problem. In particular, alanine based polypeptides are widely studied to identify the helix folding process in that the aianine amino acid is known to have one of the highest helix propensities. In principle, intrinsic helix propensities can be obtained from gas-phase measurements where solvent effect is absent. Hudgins et al. studied alanine-based peptides in vacuo using high-resolution ion mobility measurement technique. It was reported that introduction of a single Iysine at the C terminus resulted in the formation of very stable, monomeric polyalanine helices. We also have investigated helix formation in vacuo with different terminal charge conditions; we have found a new type of helix motif, To the best of our knowledge, this type of helix conformation has not been characterized before and we name it as I-helix.

• 대한전자공학회논문지SD
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• 제47권3호
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• pp.18-27
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• 2010

본 논문에서는 offset self-calibration 기법을 적용한 7-bit 1GSPS folding-interpolation A/D 변환기를 제안한다. 제안하는 A/D 변환기는 folding rate 2, interpolation rate 8의 1+6 구조로 고속 동작에 적합하게 설계되었다. 또한 offset self-calibration 회로를 설계하여 공정 mismatch, 기생 저항, 기생 캐패시턴스 등에 의한 offset-voltage의 변화를 감소시켜 A/D 변환기의 성능 특성을 향상 시켰다. 제안하는 A/D 변환기는 1.2V 65nm 1-poly 6-metal CMOS 공정을 사용하여 설계 되었으며 유효 칩 면적은 $0.87mm^2$, 1.2V 전원전압에서 약 110mW의 전력소모를 나타내었다. 측정 결과 샘플링 주파수 800MHz, 입력 주파수 250MHz에서 39.1dB의 SNDR 특성을 보여주었으며, offset self-calibration 회로를 사용 하지 않은 A/D 변환기에 비해 SNDR이 약 3 dB 향상되었다.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• 제23권1호
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• pp.12-17
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• 1995

Space explorations by spacecraft have detected the solar wind and the interplanetary magnetic field (IMF), whose existences had been suggested to explain the narrow comet plasma tail formation before the space age. Thereafter, a global magnetic structure seperating the opposite polarity regions of IMF in the heliosphere was discovered (Wilcox and Ness, 1965). It is called helispheric current sheet (HCS). Comets have been proved as the useful heliospheric probes. Recently, another capability of comet as a probe of HCS was suggested by Yi (1994). In the process of comet plasma tail disconnection events (EDs) showing the ray folding and main tail severance between the folding rays (Brandt, 1982), the folding rays preceding DE might be the visualization of HCS draped around comet, In order to test this new idea, the association of comet Halley 16 DEs with comet crossings of HCS confirmed by spacecraft observations at the time of comet Halley apparition 1985~1986 was investigated.