• 한국수학교육학회지시리즈B:순수및응용수학
• /
• 제23권1호
• /
• pp.1-12
• /
• 2016

This paper shows that the solutions to the perturbed differential system $y^{\prime}=f(t, y)+\int_{to}^{t}g(s,y(s),Ty(s))ds+h(t,y(t))$ have asymptotic property and uniform Lipschitz stability. To show these properties, we impose conditions on the perturbed part $\int_{to}^{t}g(s,y(s),Ty(s))ds+h(t,y(t))$, and on the fundamental matrix of the unperturbed system y' = f(t, y).

• Design & Manufacturing
• /
• 제14권3호
• /
• pp.31-36
• /
• 2020

In injection molding processes, the property of molten resin should be characterized accurately. Among several properties, the PvT state is the most important one, since it affects the shrinkage, warpage, molded weight, and the part density. Thus, the PvT data is crucial to the simulation of the injection molding process. This work shows how such a measurement can be performed for a semi-crystalline and amorphous polymers. The PvT measurement has been conducted using a capillary rheometer using a suitable accessory that blocks the capillary. The results have shown that the PvT data can be obtained using such a rheometer and then the PvT coefficients of the Tait equation can be reached.

• 대한수학회논문집
• /
• 제32권3호
• /
• pp.661-676
• /
• 2017

Let T be a bounded linear operator acting on a complex Hilbert space ${\mathfrak{H}}$. In this paper we introduce the class, denoted ${\mathcal{Q}}(A(k),m)$, of operators satisfying $T^{m{\ast}}(T^{\ast}{\mid}T{\mid}^{2k}T)^{1/(k+1)}T^m{\geq}T^{{\ast}m}{\mid}T{\mid}^2T^m$, where m is a positive integer and k is a positive real number and we prove basic structural properties of these operators. Using these results, we prove that if P is the Riesz idempotent for isolated point ${\lambda}$ of the spectrum of $T{\in}{\mathcal{Q}}(A(k),m)$, then P is self-adjoint, and we give a necessary and sufficient condition for $T{\otimes}S$ to be in ${\mathcal{Q}}(A(k),m)$ when T and S are both non-zero operators. Moreover, we characterize the quasinilpotent part $H_0(T-{\lambda})$ of class A(k) operator.

• 한국자기공명학회논문지
• /
• 제11권1호
• /
• pp.30-41
• /
• 2007

The backbone molecular dynamics of the C-terminal part of the mouse Cdt1 protein (tCdt1, residues 420-557) was studied by high field NMR spectroscopy. The Secondary structure of this protein was suggested by analyzing of chemical shift of backbone atoms with programs TALOS and PECAN, together with NOE connectivities from 3D $^{15}N-HSQC-NOESY$ data. Measurement of dynamic parameters $T_1,\;T_2$ and NOE and limited proteolysis experiment provided information for domain organization of tCdt1(420-557). Analysis of the experimental data showed that the C-terminal part of the tCdt1 has well folded domain for residues 455-553. The residues 420-453 including ${\alpha}-helix$ (432-441) are flexible and probably belong to other functional domain in intact full length Cdt1 protein.

• Journal of Radiation Protection and Research
• /
• 제46권4호
• /
• pp.178-183
• /
• 2021

Background: This study was carried out to provide environmental transfer parameter values to estimate activity concentrations of these radionuclides in agricultural crops when direct contamination occurred. Materials and Methods: Mass interception fractions (F_Bs) and weathering half-lives (T_ws) of ¹³¹I and radiocesium were calculated using openly available monitoring data obtained after the Fukushima Daiichi Nuclear Power Plant accident. F_B is the ratio between the initial radioactivity concentration of a radionuclide retained by the edible part of the plant (Bq·kg^-1 fresh weight [FW]) and the amount of deposited radionuclide in that area (Bq·m^-2). T_w values can be calculated using activity concentrations of crops decreased with time after the initial contamination. Results and Discussion: Calculated F_B and T_w values for ¹³¹I and radiocesium were mostly obtained for leafy vegetables. The analytical results showed that there was no difference of F_Bs between ¹³¹I and radiocesium by t-test; geometric mean values for leafy vegetables cultivated under outdoor conditions were 0.058 and 0.12 m²·kg^-1 FW, respectively. Geometric mean T_w value of ¹³¹I in leafy vegetables grown under outdoor conditions was 8.6 days, and that of radiocesium was 6.6 days; there was no significant difference between T_w values of these radionuclides by Wilcoxon rank sum test. Conclusion: There was no difference between ¹³¹I and radiocesium for F_Bs and T_ws. By using these factors, we would be able to carry out a rough estimation of the activity concentrations of ¹³¹I and radiocesium in the edible part of leafy crops when a nuclear accident occurred.

• 사물인터넷융복합논문지
• /
• 제6권4호
• /
• pp.21-26
• /
• 2020

자율주행 시스템은 빅데이타를 기반으로 하여 딥러닝 시스템을 기반으로 하고 있으며, 사용되는 데이타는 다양한 센서를 이용하여 수집된다. 그런 센서에 있어서 소형화와 고성능화는 자율주행 시스템 뿐만 아니라 IoT 기반의 다양한 제품에서도 요구되고 있다. 특히, 소형화는 센서의 소형화 뿐만 아니라 센서를 설치하기 위한 기구의 소형화도 동시에 요구하고 있다. 그런 점에서 금속 기구는 센서를 고정하기 위한 가장 좋은 방법을 제시해 주고 있다. 하지만, 소형 센서를 위한 금속 기구 형상을 가공하는 것이 어렵거나, 제작 비용이 높아질 수 있다. 이를 위한 대안으로 본 연구에서는 금속 필라멘트를 기반으로 한 FDM (Fused deposition modeling) 공정을 제시하고, 금속 FDM의 기초가 되는 공정에 대한 연구를 진행하였다. 금속 FDM 공정을 통해서 얻어지는 금속 부품은 탈지-소결의 후 과정을 통해서 만들어진다. 본 연구에서는 출력 시 설정 변수인 내부 채움 비율(Infill rate) 과 소결 공정 후 밀도 사이에 관계를 조사하였다. 이는 내부 채움 비율과 후 처리 이후 얻어지는 시편의 밀도가 다를 수 있음을 기반으로 하고 있으며, 금속 FDM 공정 이후 얻어지는 출력물의 밀도를 높이기 위한 기초 연구로 의미가 크다고 할 수 있다.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
• /
• pp.290-297
• /
• 2002

This paper presents analysis results for the effect of power control strategies on the part load performance of gas turbine based power generation systems utilizing exhaust heat of the gas turbine such as cumbined cycle power plants and regenerative gas turbines. For the combined cycle, part load efficiency variations were compared among different single shaft gas turbines representing various technology levels. Power control strategies considered were fuel only control and IGV control. It has been observed that gas turbines with higher design performances exhibit superior part load performances. Improvement of part load efficiency by adopting air flow modulation was analyzed and it is concluded that since the average combined cycle performance is affected by the range of IGV control as well as its temperature control principle, a control strategy appropriate for the load characteristics of the individual plant should be adopted. For the regenerative gas turbine, it is likewise concluded that maintaining exhaust temperature as high as possible by air flow rate modulation is required to increase part load efficiency.

• 한국유체기계학회 논문집
• /
• 제6권3호
• /
• pp.28-35
• /
• 2003

This paper presents analysis results for the effect of power control strategies on the part load performance of gas turbine based power generation systems utilizing exhaust heat of the gas turbine such as combined cycle power plants and regenerative gas turbines. For the combined cycle, part load efficiency variations were compared among different single shaft gas turbines representing various technology levels. Power control strategies considered were fuel only control and IGV control. It has been observed that gas turbines with higher design performances exhibit superior part load performances. Improvement of part load efficiency of the combined cycle by adopting air flow modulation was analyzed and it was concluded that since the average combined cycle performance is affected by the range of IGV control as well as its temperature control principle, a control strategy appropriate for the load characteristics of the individual plant should be adopted. For the regenerative gas turbine, it is likewise concluded that maintaining exhaust temperature as high as possible by air flow rate modulation is required to increase part load efficiency.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권4호
• /
• pp.1944-1956
• /
• 2016

The Digital Video Broadcasting-Common Scrambling Algorithm is an ETSI-designated algorithm designed for protecting MPEG-2 signal streams, and it is universally used. Its structure is a typical hybrid symmetric cipher which contains stream part and block part within a symmetric cipher, although the entropy is 64 bits, there haven't any effective cryptanalytic results up to now. This paper studies the security level of CSA against impossible differential cryptanalysis, a 20-round impossible differential for the block cipher part is proposed and a flaw in the cipher structure is revealed. When we attack the block cipher part alone, to recover 16 bits of the initial key, the data complexity of the attack is O(2^44.5), computational complexity is O(2^22.7) and memory complexity is O(2^10.5) when we attack CSA-BC reduced to 21 rounds. According to the structure flaw, an attack on CSA with block cipher part reduced to 21 rounds is proposed, the computational complexity is O(2^21.7), data complexity is O(2^43.5) and memory complexity is O(2^10.5), we can recover 8 bits of the key accordingly. Taking both the block cipher part and stream cipher part of CSA into consideration, it is currently the best result on CSA which is accessible as far as we know.

• 한국방사선학회논문지
• /
• 제11권7호
• /
• pp.619-625
• /
• 2017

본 연구는 조영제 주입 전 복부 검사 시 필수적으로 적용되고 있는 HASTE, HASTE(f/s), FFE(in, out)를 중심으로 두 기기에 대한 복부장기의 신호 대 잡음비(SNR; Signal to Noise Ratio)와 대조도 대 잡음비(CNR; Contrast to Noise Ratio)를 정량적으로 평가함으로서 최적의 장비선택을 알아보고자 하였다. 데이터분석은 1.5T 와 3.0T 자기공명영상기기(Philips medical system, Netherland)를 이용하여 검사한 복부영상을 무작위로 선정하여 분석을 하였다. 정량적 분석결과 간(Liver), 신장(Kidney), 비장(Spleen)에서는 1.5와 비교했을 때 3.0T가 SNR, CNR 값이 높게 나타났고(p<0.05), 위(Stomach), 복부지방(Abdominal Fat), 췌장(Pancreas)에서는 1.5T 가 높은 결과를 얻었다(p<0.05). 결론적으로 두기기별 장기에 대한 정량적 평가를 했을 때 인체의 바같 부분 조직은 전반적으로 3.0T 가 높게 나타났고 가스를 포함하여 자화율의 차이를 많이 발생시키는 안쪽부분의 장기는 1.5T 가 높은 결과를 얻었다. 이러한 결과는 환자상태에 따라 조영제를 사용하지 못하고 MRI 검사를 하는 경우 정확한 진단학적 정보를 제공하는데 가이드라인이 될 것이다.