• Journal of the Korean Ceramic Society
• /
• v.34 no.9
• /
• pp.927-934
• /
• 1997

Static and cyclic fatigue tests were carried out for alumina specimen to study the statistical analyses (normal, lognormal and Weibull distribution) of fatigue lifetime data and nominal initial crack length data. Fatigue lifetime data followed Weibull distribution better than normal or lognormal distribution, for the shape parameter of the notched specimen was larger than that of the unnotched specimen. The nominal initial crack length data obtained from fatigue lifetime followed the lognormal and Weibull distribution better than normal distribution, for the coefficient of variation of the unnotched specimen was larger than that of the notched specimen, and shape parameter of unnotched specimen was smaller than that of the notched specimen.

• Korean Journal of Child Studies
• /
• v.21 no.1
• /
• pp.35-44
• /
• 2000

This study examined the development of phonological awareness of 3-, 5-, and 7-year-old children, 20 subjects at each age level. The 3-year-olds were given 2 phoneme detection tasks and the 5- and 7-year-olds were given 5 phoneme detection tasks. In each task, the children first heard a target syllable together with 2 other syllables and were asked to tell which of the 2 syllables sounded similar to the target. Children were able to detect relatively large segments ($Consonant_1+Vowel$ or $Vowel+Consonant_2$: $C_1V$ or $VC_2$) at the age of 3 and gradually progressed to smaller sound segments(e.g., phonemes). This study indicated the Korean children detect $C_1V$ segments better than $VC_2$ segments and detect the initial consonant better than the middle vowel and the final consonant.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.10 no.3
• /
• pp.130-134
• /
• 1985

In two-dimensional discrete cosine transform(DCT) coding, the measurements of the distributions of the transform coefficients are important because a better approximation yields a smaller mean square distorition. This paper presents the results of distribution tests which indicate that the statistics of the AC coefficients are well approximated to a generalized Gaussian distribution whose shape parameter is 0.6. Furthermore, from a simulation of the DCT coding, it was shown that the above approximation yields a higher experimental SNR and a better agreement between theory and simulation than the Gaussian or Laplacian assumptions.

• Journal of Korean Institute of Industrial Engineers
• /
• v.41 no.1
• /
• pp.59-63
• /
• 2015

A design guideline about legible and preferred Korean character sizes is necessary to provide better visual information in a group-view display. The present study examined the legible and preferred Korean character sizes by an experiment employing eight background-font colors and four representative font types (Gulim, Ming, Gothic, and Batang). Forty subjects (male : 20 and female : 20) in their 20s were recruited for the experiment. The legible and preferred sizes were determined based on the method of limits, one of psychological approaches. The results showed that the legible and preferred sizes increased as the contrast between background and font colors decreased. In addition, the legible and preferred sizes for Gulim were significantly smaller than those of the other font types. It is expected that the present study may contribute to providing better visual information in a group view display.

• Journal of Electrochemical Science and Technology
• /
• v.13 no.1
• /
• pp.120-127
• /
• 2022

Molybdenum disulfide (MoS₂) has been widely used as a catalyst for the bifunctional activities of hydrogen and oxygen evolution reactions (HER and OER). Here, we investigated size dependent HER and OER performance of MoS₂. The smallest size (90 nm) of MoS₂ exhibits the lowest overpotential of -0.28 V at -10 mAcm^-2 and 1.52 V at 300 mAcm^-2 with the smallest Tafel slopes of 151 and 176 mVdec^-1 for HER and OER, respectively, compared to bigger sizes (2 ㎛ and 6 ㎛) of MoS₂. The better HER and OER performance is attributed to high electrochemical active surface area (6 × 10^-4 cm²) with edge sites and low charge transfer resistance (18.1 Ω), confirming that the smaller MoS₂ nanosheets have the better catalytic behavior.

• Journal of the Semiconductor & Display Technology
• /
• v.10 no.2
• /
• pp.65-71
• /
• 2011

Properties of each layer in DSSC were investigated to improve solar cell characterstics. Also in this study, low costsolar simulator system is fabricated and used. Efficiency of DSSC is better in the case of thinner semiconductive layer, because thick semiconductive layer is acted as resistor. Sc-doped ZnO thin films showed better electrical property by proper donor doping effect. Among the dyes, DSSC containing N719 showed higher efficiency, because N719 have smaller electron affinity and shallow band gap.

• The Journal of Sustainable Design and Educational Environment Research
• /
• v.3 no.1
• /
• pp.1-14
• /
• 2003

This study attempts to review the present situations of rural schools in South Korea, to analyze problems regarding the educational environments for their students, and to present direction for improving toward better educational environments. All the data and information are based on using avaiable documents and personal macro observation and insights. The sharp decrease of rural population for recent decades has made lots of public schools unexceptionall much smaller by school number and students' number. Nearly five thousands of rural small schools have already been abolished and the rest are also endangered to be dosed. In order to tackIe such problem, the Government has been trying to provide rural students with better educational environment, but failed to attract them to stay in rural schools. Most of rural school students have poorer family environment, underprivilged school learning environment, and less civilized community environment. Those normal parents living in rural areas are likely to send their kids to urban schools for prior opportunities to enter better quality of higher level of schools and then the remained attending rural schools are those who live with grand parents or whose parents are very disadvantaged. The rural school teachers are teaching much less number of students compared to urban teachers, but their students are less achieved learners. Notwithstanding their abudant natural community learning environments, the rural school students are less making use of those resources and less benefited from more civilized life due to their underdeveloped community conditions. In order to improve such educational environments, incentives for young couples to safely reside in rural communities, incentives for better qualified teachers to preferably work for rural schools, better learning facilities for rural school students and for better vocational experiences, lifelong learning opportunities for all community people, and increased public support to rural development for rural people not to worry about their rural lives, need to be guarantyed.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.34 no.3
• /
• pp.25-31
• /
• 2002

The purpose of this study was to analyze how the fiber properties and mixing ratio of softwood and hardwood pulp affect on roundness of printed image. Softwood pulp and hardwood pulp were refined to 400 and 600ml CSF by Valley beater and handsheets of 70 g/$m^2$ basis weight were made at different mixing ratios of hardwood and softwood pulp. The roundness, dot area, and shape of the printed dot were measured by Image Analyzer. The depths and shapes of the acridine orange penetration into paper were measured by CLSM. With higher mixing ratio of hardwood pulp, the paper showed higher air-permeability and better formation, especially at lower freeness. The roundness of the printed image became better and the dot size became smaller when the amount of hardwood pulp increased. Penetration depth of acridine orange by CLSM became greater and roundness increased to real circle when the amount of hardwood pulp increased. It was thought that higher mixing ratio of hardwood fibers resulted in efficient penetration by better formation with uniform micro-pore distribution and it increased roundness. It was thought that fiber properties and mixing ratio affected the structure of paper and the shape of the printed dot. This study showed that the measurement of depth of the liquid penetration into paper without destruction and contact was feasible. Moreover, this method showed that the shape of the liquid penetration was measurable.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.5
• /
• pp.563-569
• /
• 2015

For some low-frequency applications such as power-related circuits, NEM relays have been known to show better performance than MOSFETs. For example, in a step-down charge pump circuit, the NEM relays showed much smaller layout area and better energy efficiency than MOSFETs. However, severe process variations of NEM relays hinder them from being widely used in various low-frequency applications. To mitigate the process-variation problems of NEM relays, in this paper, a new NEM-relay charge pump circuit with the self-adjustment is proposed. By self-adjusting a pulse amplitude voltage according to process variations, the power consumption can be saved by 4.6%, compared to the conventional scheme without the self-adjustment. This power saving can also be helpful in improving the power efficiency of the proposed scheme. From the circuit simulation of NEM-relay charge pump circuit, the efficiency of the proposed scheme is improved better by 4.1% than the conventional.

• International Journal of Quality Innovation
• /
• v.10 no.1
• /
• pp.115-126
• /
• 2009

Video transmission effectiveness in the Ad Hoc network is becoming important recently, if different routing protocols are applied. Some researchers conclude that the reactive protocols are better for file transfer protocol (FTP) and constant bit rate (CBR) or hypertext transfer protocol (HTTP) transmission in an Ad Hoc wireless network but the performance report of video transmission is not much. This study adopts Qualnet (Network Simulator) as a simulation tool for environmental designing and performance testing, and employs an experimental design with eight groups. Our experiment shows that: (1) The performance of AODV (reactive) protocol is better than DSDV, ZRP and DSR when the transmission load has only one video stream; (2) Proactive (DSDV) and Hybrid protocols (ZRP) are better for a smaller Ad Hoc network when it transmits a video stream with some applications (VoIP, FTP and CBR). We conclude that packet loss rate is sensitive to the quality of video transmission and it has negative relationship with Peak Signal-to-Noise Ratio (PSNR) value. In addition, our experiment also shows that PSNR is a simple Metric for the performance evaluation of video transmission.