• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.251-257
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• 2011

This paper deals with the statistical properties of parameters B and q in the creep crack growth rate (CCGR) law, da/dt=B$(C^*)^q$, in Mod. 9Cr-1Mo (ASME Gr.91) steel which is considered a candidate materials for fabricating next generation nuclear reactors. The CCGR data were obtained by creep crack growth (CCG) tests performed on 1/2-inch compact tension (CT) specimens under an applied load of 5000N at a temperature of $600^{\circ}C$. The CCG behavior was analyzed statistically using the empirical equation between CCGR, da/dt and the creep fracture mechanics parameter, $C^*$. The B and q values were determined for each specimen by the least-squares fitting method. The probability distribution functions for B and q were investigated using normal, log-normal, and Weibull distributions. As far as this study is considered, it can be appeared that B and q followed the log-normal and Weibull distributions. Moreover, a strong positive linear correlation was found between B and q.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.179-193
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• 1997

We use B band CCD images to investigate the surface brightness distributions and dynamical properties of 29 Galactic globular clusters. Model fits suggest that 22 clusters show King type surface brightness profiles, while 7 clusters are characterized by power law cusp profiles. For the King type clusters, concentration parameters $(c=log(r_{t}/r_{c}))$ range from 1.20 to 2.10, and core radii are 0.4 to 1.9 pc. The mean value of power law slopes of 7 cuspy clusters was estimated as ${alpha}=1.011{\pm}0.065$. Total masses of King type globular clusters are in the range of $1.7{ imes}10^4M_{odot}$ to $1.0{\times}106M_{\odot}$ with a mean of $1.7{\times}10^5M_{\odot}$. A significant positive correlation between mass and mass-to-light ratio of King type globular clusters has been confirmed with a Pearson's correlation coefficient r = 0.52 and a confidence level of 99%. Our data also confirm a linear relation between total mass and absolute magnitude of King type globular clusters.

• The Korean Journal of Air & Space Law and Policy
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• v.28 no.1
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• pp.115-157
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• 2013

Some contracting States of the Convention on International Civil Aviation (commonly known as the Chicago Convention) issue FAOC(Foreign AOC and/or Operations Specifications) and conduct various safety audits for the foreign operators. These FAOC and safety audits on the foreign operators are being expanded to other parts of the world. While this trend is the strengthening measure of aviation safety resulting in the reduction of aircraft accident, it is the source of concern from the legal as well as economic perspectives. FAOC of the USA doubly burdens the other contracting States to the Chicago Convention because it is the requirement other than that prescribed by the Chicago Convention of which provisions are faithfully observed by almost all the contracting States. The Chicago Convention in its Article 33 stipulates that each contracting State recognize the validity of the certificates of airworthiness and licenses issued by other contracting States as long as they meet the minimum standards of the ICAO. Consequently, it is submitted that the unilateral action of the USA, China, Mongolia, Australia, and the Philippines issuing the FOAC to the aircraft of other States is against the Convention. It is worry some that this breach of international law is likely to be followed by the European Union which is believed to be in preparation for its own unilateral application. The ICAO established by the Chicago Convention to be in charge of safe and orderly development of the international civil aviation has been in hard work to both upgrade and emphasize the safe operation of aircraft. As the result of these endeavors, it prepared a new Annex 19 to the Chicago Convention with the title of "Safety Management" and with the applicable date 14 November 2013. It is this Annex and other ICAO documents relevant to the safety that the contracting States to the Chicago Convention have to observe. Otherwise, it is the economical burden due to probable delay in issuing the FOAC and bureaucracies combined with many different paperworks and regulations depending on where the aircraft is flown. It is exactly to avoid this type of confusion and waste that the Chicago Convention aimed at when it was adopted in 1944. The State of the operator shall establish a system for both the certification and the continued surveillance of the operator in accordance with ICAO SARPs to ensure that the required standards of operations are maintained. Certainly the operator shall meet and maintain the requirements established by the States in which it operate. The authority of a State stops where the authority of another State intervenes or where the former has yielded its power by an international agreement for the sake of international cooperation. Hence, it is not within the realm of the State to issue FAOC towards foreign operators for the reason that these foreign operators are flying in and out of the State. Furthermore, there are other safety audits such as ICAO USOAP, IATA IOSA, FAA IASA, and EU SAFA that assure the safe operation of the aircraft, but within the limit of their power and in compliance with the ICAO SARPs. If the safety level of any operator is not satisfactory, the operator could be banned to operate in the contracting States with watchful eyes until the ICAO SARPs are met. This time-honoured practice has been applied without any serious problems. Besides, we have the new Annex 19 to strengthen and upgrade with easy reference for contracting States. We don't have no reason to introduce additional burden to the States by unilateral actions of some States. These actions have to be corrected. On the other hand, when it comes to the carriage of the Personal or Pilot Log Book, the Korean regulation requiring it is in contrast with other relevant provisions of USA, USOAP, IOSA, and SAFA. The Chicago Convention requires in its Articles 29 and 34 only the carriage of the Journey Log Book and some other certificates, but do not mention the Personal Log Book at all. Paragraph 5.1.1.1 of Annex 1 to the Chicago Convention even makes it clear that the carriage in the aircraft of the Personal Log Book is not required on international flights. The unique Korean regulation in this regards giving the unnecessary burden to the national flag air carriers has to be lifted at once.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.299-306
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• 2015

The quality for the domestic pavement is evaluated based on flexural strength at the age of 28 days in accordance with KS regulation. Most specimens of the flexural tensile strength used currently are relatively large ones with a dimension of $150{\times}150{\times}550mm$. Accordingly, it is difficult to treat the specimens, and the utilization of a curing tank is low. In this paper, the study tried to resolve the problem by specimen size specified in the code. For this purpose, a flexural strength test was conducted according to the log scale within the specimen size specified by the KS. And, based on the results of this experiment, a comparative analysis was conducted using the prediction formula of Size Effect Law (SEL) proposed by Bazant to examine the correlation between specimen sizes, so as to use the result as basic data for the reduction of the specimen size in the quality evaluation of concrete pavement.

• Journal of the Korean GEO-environmental Society
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• v.6 no.1
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• pp.53-62
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• 2005

This paper estimates the long-term settlement of Kimpo metropolitan landfill based on measured settlement data from 180 landfill monitors accumulated over a period of 12 years. Comparison of domestic and international settlement records indicate that the domestic compression rate is slightly lower due to greater portion of organic component. Several existing settlement models are used to compare with the observed behavior and also to estimate long-term settlement. The hyperbolic, Gibson & Lo, Bjarngard & Edgers and Power Creep Law models compare well with the measured settlement of the Kimpo metropolitan landfill. The settlement models are further used to estimate long-term settlement. Bjarngard & Edgers and Power Creep Law models result in higher estimates of the long-term settlement compared to the hyperbolic and Gibson & Lo models. Further comparisons indicate that other models, including Sowers and log models, are inapproriate for predicting the long-term settlement of the Kimpo metropolitan landfill.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2737-2742
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• 2007

Strong wind flow around a building complex was numerically studied by LES. The original motivation of this work stemmed from the efforts to develop a risk assessment technique for windstorm hazards. Lagrangian-averaged scale-invariant dynamic subgrid-scale model was used for turbulence modeling, and a log-law-based wall model was employed on all the solid surfaces including the ground and the surface of buildings to replace the no-slip condition. The shape of buildings was implemented on the Cartesian grid system by an immersed boundary method. Key flow quantities for the risk assessment such as mean and RMS values of pressure on the surface of the selected buildings are presented. In addition, characteristics of the velocity field at some selected locations vital to safety of human beings is also reported.

• Journal of the Korean Mathematical Society
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• v.54 no.3
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• pp.835-845
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• 2017

The $GCF_{\epsilon}$ expansion is a new class of continued fractions induced by the transformation $T_{\epsilon}:(0, 1]{\rightarrow}(0, 1]$: $T_{\epsilon}(x)={\frac{-1+(k+1)x}{1+k-k{\epsilon}x}}$ for $x{\in}(1/(k+1),1/k]$. Under the algorithm $T_{\epsilon}$, every $x{\in}(0,1]$ corresponds to an increasing digits sequences $\{k_n,n{\geq}1\}$. Their basic properties, including the ergodic properties, law of large number and central limit theorem have been discussed in [4], [5] and [7]. In this paper, we study the large deviation for the $GCF_{\epsilon}$ expansion and show that: $\{{\frac{1}{n}}{\log}k_n,n{\geq}1\}$ satisfies the different large deviation principles when the parameter ${\epsilon}$ changes in [-1, 1], which generalizes a result of L. J. Zhu [9] who considered a case when ${\epsilon}(k){\equiv}0$ (i.e., Engel series).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1271-1278
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• 2004

In order to measure non-intrusively velocity profile in liquid metal flow, a modified electromagnetic flowmeter was designed, which was based on electromagnetic tomography technique. Under the assumption that flow is fully-developed, axisymmetric and rectilinear, the velocity profile was reconstructed after the flowmeter equation, the first kind of Fredholm integration equation, was linearized. In reconstruction process Tikhonov regularization method with regularization parameter was used. The reconstructed velocity profile had the nearly same as turbulent flow profile which was approximately represented as log law. In addition, flowmeter output fur a fixed magnet rotation angle was linearly proportional to flow rate. When magnet rotation angle was 54$^{\circ}$, axisymmetric weight function was nearly uniform so that the flowmeter gives a constant signal for any fully-developed, axisymmetric and rectilinear profile with a constant flow rate.

• Journal of the Korean Society of Visualization
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• v.14 no.1
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• pp.46-50
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• 2016

Direct numerical simulations (DNSs) of turbulent pipe flows with temporal deceleration were performed to examine response of the turbulent flows to the deceleration. The simulations were started with a fully-developed turbulent pipe flow at the Reynolds number, $Re_D=24380$, based on the pipe radius and the laminar centerline velocity, and three different constant temporal decelerations were applied to the initial flow with varying dU/dt = -0.001274, -0.00625 and -0.025. It was shown that the mean flows were greatly affected by temporal decelerations with downward shift of log law, and turbulent intensities were increased in particular in the outer layer, compared to steady flows at a similar Reynolds number. The analysis of Reynolds shear stress showed that second- and fourth-quadrant Reynolds shear stresses were increased with the decelerations, and the increase of the turbulence was attributed to enhancement of outer turbulent vortical structures by the temporal decelerations.

• Journal of Korean Institute of Industrial Engineers
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• v.19 no.2
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• pp.15-21
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• 1993

This paper considers the optimal design of accelerated life test in which the stress is linearly increased. It discusses the special case when the life distribution under constant stress follows an exponential distribution and the accelerated equation satisfies the inverse power law. It is assumed that cumulative damage is linear, that is, the remaining life of test units depends only on the current cumulative fraction failed and current stress(cumulative exposure model). The optimization criterion is the asymptotic variance of the maximum likelihood estimator of the log mean life at a design stress. The optimal increasing rate is obtained to minimize the asymptotic variance. Table of sensitivity analysis is given for the prior estimators of model parameters.