• Journal of the Korean Chemical Society
• /
• v.21 no.4
• /
• pp.276-283
• /
• 1977

Reduction of dichromate at a platinum cathode in acid solution was studied by cyclic voltammetry and controlled potential electrolysis. Cathodic polarization curve consisted of three waves in unbuffered solution of potassium dichromate having initial pH ranges 1.5∼4.0, with sodium sulfate as the supporting electrolyte. Relative heights of the first and the second waves were, respectively, a function of chromium (Ⅵ) concentration and activity of hydrogen ion, but that of the third wave was not proportional to both of them. The current of the first two peaks were proportional to the sweep rate of potential (${\nu}$), while that of the last peak vs. ${\nu}^{1/2}$ was linear at the sweep rate of less than 50mV/sec. By the controlled potential electrolysis, the reduction of chromium (Ⅵ) was almost completely suppressed at potentials more negative than the last peak and at initial pH's above ca. 2.3 of unbuffered solution. Therefore, these peaks represented, respectively, $Cr_2O_7^{2-}{\to}Cr^{3+},\;2H^+{\to}H_2$ and the formation of a cathodic film.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.13 no.2
• /
• pp.1-18
• /
• 2017

Metal fatigue is an important aging mechanism that material characteristics can be deteriorated when even a small load is applied repeatedly. An accurate fatigue evaluation is very important for component structural integrity and reliability. In the design stage of a nuclear power plant, the fatigue evaluations of the Class 1 components have to be performed. However, operating experience shows that the design evaluation can be very conservative due to conservatism in the transient severity and number of occurrence. Therefore, the fatigue monitoring system has been considered as a practical mean to ensure safe operation of the nuclear power plants. The fatigue monitoring system can quantify accumulated fatigue damage up to date for various plant conditions. The purpose of this paper is to describe the fatigue monitoring procedure and to introduce the fatigue monitoring program developed by the authors. The feasibility of the fatigue monitoring program is demonstrated by comparing with the actual operating data and finite element analysis results.

• Journal of Industrial Technology
• /
• v.4
• /
• pp.29-35
• /
• 1984

Buckling is a significant behavior to be considered whenever we design steel structures. In the case of H-shape beams, the lateral buckling occured by bending moment must be considered. Because of the lateral buckling of H-shape beams, the bending strength of the beams are determined by the lateral buckling stress instead of the allowable bending stress. Lateral buckling stress equation, consisting of two terms, i. e. ${\sigma}_{cr}({\nu},{\omega})={\sqrt{[{\sigma}_{cr}({\nu})]^2+[{\sigma}_{cr}({\omega})]^2}}$ has been using, but for the practical purpose of use the following equations are using two, i. e. ${\sigma}_{cr}({\nu})={\frac{0.65E}{{\ell}_h/A_f}}$, ${\sigma}_{cr}({\omega})={\frac{{\pi}^2E}{({\ell}_b/i_b)^2}}$. When we use the above equations, the results are different according to the shape of beam section, and they a re rather complex. In this study lateral buckling stress equation is derived, and the proposed formula$({\sigma}_{cr}(t))$ is compared with above mentioned two basic and practical equations. To verify the proposed formula experimentaly, 16H-shape beams which have different slender ratios arc tested by applying pure bending momet. Through the experiments the buckling behavior of H-shape beams is clarified, and the results shows that the proposed formula$({\sigma}_{cr}(t))$ is accurate enough for practical purpose.

• Microbiology and Biotechnology Letters
• /
• v.25 no.6
• /
• pp.580-585
• /
• 1997

We selected two mutants namely strain D5 and Nu23 by mutagenesis of anthracycline producing Streptomyces: the former is an $\varepsilon$-rhodomycinone overproducing mutant selected from Streptomyces sp. C5, a baumycin producer and the latter, a blocked mutant of early pathway for doxorubicin biosynthesis obtained from Streptomyces peucetius ATCC 27952, a doxorubicin producer. The mutant strain Nu23 does not produce anthracycline metabolites but retains the most of enzyme activities converting aklavinone to doxorubicin and the mutant strain D5 produced $\varepsilon$-rhodomycinone at a level of 150 $\mu$g/ml. These strains were grown separately in NDYE medium and each was mixed at day 3 by equal volume of culture broth but the quantity of doxorubicin produced was far below an estimation based on the level of $\varepsilon$-rhodomycinone normaly produced by the strain D5. On the other hand doxorubicin was reached at maximum level after 4 days in the mixed culture condition which was composed of culture broth of strain D5 grown for 6 day and that of strain Nu23 grown for 3 day. It was turned out that the growth of mutant strain D5 was inhibited by the accumulation of daunorubicin and doxorubicin in mixed culture broth, which cause the limitation of $\varepsilon$-rhodomycinone.

• Journal of the Korean Statistical Society
• /
• v.7 no.1
• /
• pp.3-10
• /
• 1978

Let $X_i,...,X_n$ be a random sample from a distribution with cumulants $K_1, K_2,...$. The statistic $t = \frac{\sqrt{x}(\bar{X}-K_1)}{S}$ has the well-known 'student' distribution with $\nu = n-1$ degrees of freedom if the $X_i$ are normally distributed (i.e., $K_i = 0$ for $i \geq 3$). An Edgeworth series expansion for the distribution of t when the $X_i$ are not normally distributed is obtained. The form of this expansion is Prob $(t

• Journal of Integrative Natural Science
• /
• v.1 no.2
• /
• pp.79-83
• /
• 2008

As a new standard for performance measurement, NEMA NU2-2001 was presented recently. In this study, I investigated the spatial resolution, sensitivity, scatter fraction, and noise equivalent count ratio (NECR) in order to know the information of physical characteristics and system performance of GE discovery ST using this new standard. Bismuth germinate crystals ($6{\times}6$ array, $6.3mm{\times}6.3mm{\times}30mm$) were used in discovery ST (energy window:375-650 keV, coincidence window:11.7 nsec). To measure the sensitivity, five aluminum sleeves (Data Spectrum Corp., Chapel Hill, NC., USA, thickness:1.25 mm)-NEMA sensitivity phantom- filled with F-18 solution were used. Successive measurements in 2D and 3D acquisition mode were made with a line source at the center of transaxial field of view and 10 cm off from the center until the count was over 500,000. Spatial resolution was estimated using a point source (F-18, 0.1 mCi) at different locations in the FOV. Scatter fraction and NECR was tested using a NEMA scatter phantom. Dynamic data were acquired for 7 half-lives using F-18 solution. And true to background ratio was averaged at last three frames when the random rate was as small as ignorable for the calculation of scatter fraction. We anticipate this overall evaluated results could be used for the quality assurance and optimized image acquisition for clinical research.

• Journal of Korean Philosophical Society
• /
• v.126
• /
• pp.263-293
• /
• 2013

Die vorliegende Abhandlung beachtet die methodologische $N{\ddot{u}}tzlichkeit$ der Dialektik $f{\ddot{u}}r$ die philosophische $Wissenschaftst{\ddot{a}}tigkeit$ des Aristoteles in einer besonderen Aufmerksamkeit auf den Begriff "${\delta}{\iota}{\alpha}{\pi}o{\rho}{\varepsilon}{\iota}{\nu}$". Bei Aristoteles bedeutet "${\delta}{\iota}{\alpha}{\pi}o{\rho}{\varepsilon}{\iota}{\nu}$" 'das durchaus $gr{\ddot{u}}ndliche$ Untersuchen einer Aporie', und eine solche Untersuchungsweise folgt der Dialektik. Deshalb beabsichtige ich zuerst, durch eine Begriffsanalyse und - interpretation von "${\delta}{\iota}{\alpha}{\pi}o{\rho}{\varepsilon}{\iota}{\nu}$" die dialektische Aporetik zu bestimmen als eine Argumentationsmethode nicht nur in einer dialogischen, sondern auch in einer nicht-dialogischen Situation. Besonders will ich einen methodologischen Grund $daf{\ddot{u}}r$ suchen, dass ein allein Forschender in der nicht-dialogischen Situation die dialektische Aporetik verwendet, indem ich einen Text von "De caelo" II 13, 294b 6~13 interpretiere. $N{\ddot{a}}mlich$ betont Aristoteles in Bezug auf den Durchgang der $Wissenschaftst{\ddot{a}}tigkeit$ eine Forderung der selbstkritischen Haltung, die der allein Forschende sich selbst seine Untersuchung in $R{\ddot{u}}cksicht$ auf die anderen Untersuchungen und auch auf die vorhersehbaren Hypothesen ${\ddot{u}}berpr{\ddot{u}}fen$ und verifizieren, um die aus seiner Untersuchung zu entdeckenden Aporien auf die dialektische Weise zu $l{\ddot{o}}sen$. Und diese Position von Aristoteles kann der wichtige Grund $daf{\ddot{u}}r$ sein, den fachsprachlichen Sinn von "${\delta}{\iota}{\alpha}{\pi}o{\rho}{\varepsilon}{\iota}{\nu}$" als auch den wissenschaftlichen Sinn der dialektischen Untersuchung der Aporie richtig verstehen und $erkl{\ddot{a}}ren$ zu $k{\ddot{o}}nnen$. Zuletzt bin ich in der Absicht, die dialektische Aporetik und ihre Funktion in drei Modeln zu formulieren und einige Beispiele $f{\ddot{u}}r$ jedes Model vorzustellen, um zu zeigen, auf welche Art und Weise Aristoteles die dialektische Aporetik $f{\ddot{u}}r$ den Lauf seiner Theoriebildung in der Tat anwendet. Durch solchen Versuch $w{\ddot{u}}nsche$ ich, dass meine Untersuchung ${\ddot{u}}ber$ die dialektische Aporetik etwas besseres $Verst{\ddot{a}}ndnis$ $f{\ddot{u}}r$ die wissenschaftliche Bedeutung der aristotelischen Dialektik anbieten $k{\ddot{o}}nnte$, und auch dass diese Studie als bedeutsame Basisdaten zu einer noch tieferen Forschung und $Verst{\ddot{a}}ndigung$ ${\ddot{u}}ber$ die philosophische Haltung und Methode des Aristoteles betrachtet werden $k{\ddot{o}}nnte$.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.44.1-44.1
• /
• 2015

We present joint constraints on the number of effective neutrino species $N_{eff}$ and the sum of neutrino masses ${\Sigma}m_{\nu}$, based on a technique which exploits the full information contained in the one-dimensional Lyman-${\alpha}$ forest flux power spectrum, complemented by additional cosmological probes. In particular, we obtain $N_{eff}=2.91{\pm}0.22$ (95% CL) and ${\Sigma}m_{\nu}$ < 0.15 eV (95% CL) when we combine BOSS Lyman-${\alpha}$ forest data with CMB (Planck+ACT+SPT+WMAP polarization) measurements, and $N_{eff}=2.88{\pm}0.20$ (95% CL) and ${Sigma}m_{\nu}$ < 0.14 eV (95% CL) when we further add baryon acoustic oscillations. Our results tend to favor the normal hierarchy scenario for the masses of the active neutrino species, provide strong evidence for the Cosmic Neutrino Background from $N_{eff}{\approx}3$($N_{eff}=0$ is rejected at more than $14{\sigma}$), and rule out the possibility of a sterile neutrino thermalized with active neutrinos (i.e., $N_{eff}=4$) - or more generally any decoupled relativistic relic with $${\Delta}N_{eff}{\sim_=}1$$ - at a significance of over $5{\sigma}$, the strongest bound to date, implying that there is no need for exotic neutrino physics in the concordance ${\Lambda}CDM$ model.

• Aerospace Engineering and Technology
• /
• v.2 no.2
• /
• pp.142-150
• /
• 2003

Turbulent flows and related heat transfer in a square heated duct is investigated by a turbulence model and a large eddy simulation. The cooling channel of calorimeter is modeled to the square duct. The nonlinear k-ε-fμ model of Park et al. [3] is slightly modified and their explicit heat flux model is employed. The Reynolds number is varied in the range 4000≤Reｂ≤20000. The heat transfer is closely linked to the secondary flows which driven by the turbulent motion. Its magnitude is 1~3% of the mean streamwise velocity. The relation of Nu~Re0.8Pr0.34 is validated by comparing with the predicted Nu of k-ε-fμ model. Finally, the coherent structures and thermal fluctuations are scrutinized.

• Nuclear Engineering and Technology
• /
• v.54 no.12
• /
• pp.4499-4513
• /
• 2022

Spent fuel behavior of dry storage was simulated in a continuous state from steady-state operation by modifying FRAPCON-4.0 to incorporate spent fuel-specific fuel behavior models. Spent fuel behavior of a typical PWR was compared with that of NuScale Power Module (NPM^TM). Current PWR discharge burnup (60 MWd/kgU) gives a sufficient margin to the hoop stress limit of 90 MPa. Most hydrogen precipitation occurs in the first 50 years of dry storage, thereby no extra phenomenological safety factor is identified for extended dry storage up to 100 years. Regulation for spent fuel management can be significantly alleviated for LWR-based SMRs. Hydride embrittlement safety criterion is irrelevant to NuScale spent fuels; they have sufficiently lower plenum pressure and hydrogen contents compared to those of PWRs. Cladding creep out during dry storage reduces the subchannel area with burnup. The most deformed cladding outer diameter after 100 years of dry storage is found to be 9.64 mm for discharge burnup of 70 MWd/kgU. It may deteriorate heat transfer of dry storage by increasing flow resistance and decreasing the view factor of radiative heat transfer. Self-regulated by decreasing rod internal pressure with opening gap, cladding creep out closely reaches the saturated point after ~50 years of dry storage.