• Journal of Korean Society for Quality Management
• /
• v.19 no.2
• /
• pp.138-144
• /
• 1991

In this paper, we suggest the test statistic based on the total time on test (TTT-) transtorm for testing exponentiality against new better than used in convex ordering (NBUC) and its dual, new worse than used in convex ordering (NWUC). The validity of the test is examined by simulation for some alternative distributions when the sample size is n = 10 and n = 20.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.11C
• /
• pp.880-882
• /
• 2008

This paper presents LDPC codes' upper bounds over the waterfall SNR region. The previous researches have focused on the average bound or ensemble bound over the whole SNR region and showed the performance differences for the fixed block size. In this paper, the particular LDPC codes' upper bounds for various block sizes are calculated over the waterfall SNR region and are compared with BP decoding performance. For different block sizes the performance degradation of BP decoding is shown.

• Communications for Statistical Applications and Methods
• /
• v.1 no.1
• /
• pp.41-51
• /
• 1994

We consider nonparametric procedures for the selection and ranking problems. Tukey's generalized lambda distribution is condidered as the distribution for the score function because the distribution can approximate many well-known contionuous distributions. Also we compare these procedures in terms of efficiency, defined by the ratio of a probability of a correct selection divided by the expected selected subset size.

• Carbon letters
• /
• v.3 no.3
• /
• pp.146-151
• /
• 2002

Activated carbon fibers were prepared from the petroleum isotropic pitch and organometallic compounds. The metalsvwere dispersed uniformly in the ACFs. The specific surface area and pore size distributions of metal containing ACFsvwere measured. The mesopores of ACFs were developed by Co, Ni, and Mn metals addition and the catalytic reactivityvof ACFs'SOx removal was increased by adding Ni and Pd metals. It was found that the mesopores did not work forvthe improvement of catalytic reactivity of ACFs' SOx removal with the blank experiment using the metal removedvACFs.

• Communications for Statistical Applications and Methods
• /
• v.15 no.3
• /
• pp.403-409
• /
• 2008

In this paper we show that the peak of the type I error rate of the Oochran-Armitage trend test could be greater than the nominal level when $2\;{\times}\;C$ contingency tables obtained from two multinomial distributions are extremely unbalanced. This result justifies the use of the exact Cochran-Armitage trend test in extremely unbalanced $2\;{\times}\;C$ contingency tables.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.3
• /
• pp.326-334
• /
• 1986

The effects of flow interaction between adjacent sprays in twin-spray system on the spatial distribution of injected liquid (water) and drop size distribution in condensable (steam) environment were carefully observed through experiments. The spatial distribution of injected liquid in twin-spray system appears to be more uniform than the simple superposition of the spatial distributions of liquid obtained from each individual spray. Drop size distribution was obtained by using the immersion sampling technique. It was found that, in the twin-spray, the larger numbers of small drops are collected throughout the spraying region due to the increase of entrainment velocity of ambient steam compared with the case of simple superposition of each individual spray. Moreover, in the overlapped portion of the twin-spray, the drop size distribution was changed also due to the collision between large drops. As a result, the behavior of twin-spray system (and eventually multiple-spray system) can not be predicted precisely by simple superposition of the behaviors of each constituting spray. Hence, for the design of multiple spray system, the effect of flow interaction between sprays should be taken into account seriously.

• Journal of environmental and Sanitary engineering
• /
• v.17 no.2
• /
• pp.11-17
• /
• 2002

Diesel particulate matter (DPM) is known to be one of the major harmful emissions produced by diesel engines. The majority of diesel particles are in the range of smaller than $I{\mu}\textrm{m}$. Because of their tiny volume, ultrafine diesel particles contribute very little to the total mass concentration which is currently regulated for automobile emissions. Diesel particles are known to have deleterious effects upon human health because they penetrate human respiratory tract and have negative effects on the health. The measurement of the number distribution of nanometer size particles (nanoparticles) in the diesel exhaust emission is important in order to evaluate their environmental and health impact, and to develop new types of diesel particulate filters. In this study, we directly sampled particulate matters emitted from a diesel truck mounted on the chassis dynamometer by a flow separator and dilution system, and measured the nanoparticles using two types of differential mobility analyzers combined with a Faraday cup electrometer (FCE) and a condensation particle counter (CPC). The particle size distributions were analyzed by changing engine operation condition, i.e. ratio of engine loading. The total number concentration of particles were increased with the engine loading ratio and the nanoparticles (less than 50nm) were affected by hydrocarbon (HC) concentration in the diesel exhaust.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.12
• /
• pp.2376-2384
• /
• 1992

A theoretical analysis is carried out to predict the characteristics of transient ignition phenomena for the spherical fuel droplets cloud with non-uniform droplet size and number density distribution. Numerical calculations are performed for various cases depending on the combinations of the major parameters such as ambient temperature and initial distributions of droplet size and number density. The results of present study show that the ignition delay decreases for higher ambient temperature and smaller droplet size. Droplets cloud of hollow type with outer concentrated distribution ignites most rapidly.

• Journal of Korean Society for Atmospheric Environment
• /
• v.15 no.5
• /
• pp.575-586
• /
• 1999

The size-resolved number concentrations of aerosols ranging from 0.3 to 25 $mu extrm{m}$ were observed in Seoul and Anmyondo in the west coast of Korea during an Yellow Sand phenomenon in April 1998. Number size distributions of aerosols observed in both places are characterized by decrease in small particles of diameter less than 1${\mu}{\textrm}{m}$ and increase in large size between 1.35 and 10${\mu}{\textrm}{m}$ in heavy dust period. For particles in this size range, there was a good correlation between number concentrations observed in both places during the Yellow Sand episode. On the other hand, the number of small particles less than 0.82${\mu}{\textrm}{m}$ decreased, but the correlation between these particles in both places was enhanced during more intense dust period. The number of coarse particle larger than 10 ${\mu}{\textrm}{m}$ showed a distince diurnal variation without a significant change in amplitude, which was more visible in Seoul. It suggests that these coarse particles were more affected by local sources. Form these results, it was range of 1~10${\mu}{\textrm}{m}$ originated possibly from the dust source regions and the source signature depended on the degree of dust intensity.

• Journal of Ocean Engineering and Technology
• /
• v.24 no.1
• /
• pp.99-105
• /
• 2010

The concentration and size analysis of in-situ suspended particulate material were measured using an optical instrument, LISST-100, in the bottom layer at the three inlets of the Seomjin River Estuary, mouth of Gwangyang bay, and Gwangyang bay-side of the Namhae Bridge. In the Seomjin river estuary and mouth of Gwangyang bay-side of the Namhae Bridge, the in-situ mean grain size of the suspended material changed from a uni-modal distribution with a dominant peak at a coarse fraction to a bi-modal distribution with a secondary peak at the finer particles. Seomjin River. The interactions between suspended particulate concentration and beam attenuation coefficient of suspended particulate matters depended on the supply of finer and coarser particles in the mouth of Gwangyang Bay and Seomjin River. So, interactions reflected difference of the concentration, mean size and sorting of suspended particulate matters. The difference of interaction showed dynamic behaviors to the resuspension and deflocculation processes increased river discharge. This showed that it may be possible to use the interactions between the suspended particle concentration and beam attenuation coefficient to monitor the temporal and spatial distributions of in-situ particles.