• 품질경영학회지
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• 제16권2호
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• pp.82-91
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• 1988

This study is concerned with the development of the economic sampling inspection plan when it is possible to carry out a nondestructive screening inspection for the rejected lots by substitutive characteristics closely related to the original quality characteristic. It is assumed that the probabilities of those errors depend linearly on the fraction defective of the process. The inspection policies considered are as follows: take a random sample of size n from the lot of size N and perform a destructive test on the sample. If the number of the defective items is not greater than a critical number C, accept the lot. Expected cost functions are obtained when the process average can be considered to follow a beta distribution and the way of finding the optimal values of (n, c) is to be explored.

• Journal of the Korean Wood Science and Technology
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• 제45권4호
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• pp.471-481
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• 2017

As the molecular weight (MW) of urea-formaldehyde (UF) resins had a great impact on their properties, this work was conducted to study effect of analytical parameters of gel permeation chromatography (GPC) on the MW measurement of UF resins. GPC parameters such as flow rate, column, detector temperature, and sample injection temperature were selected to compare number-average molecular weight (Mn), weight-average molecular weight (Mw), molecular weight distribution (MWD) and polydispersity index (PDI) of two UF resins with different viscosities. As expected, UF resin with higher viscosity resulted in greater Mn and Mw than those of low viscosity UF resin. When the flow rate increased, both Mn and Mw of UF resins decreased and MWD became narrower. By contrast, both Mn and Mw increased and MWD became wide when the column, detector, and sample injection temperature increased. The column, detector, and sample injection temperature of $50^{\circ}C$ at a flow rate of $0.5m{\ell}/min$ resulted in the highest MW and broadest MWD for the GPC analysis. These results suggest that the apparent molecular size or a hydrodynamic radius of UF resin molecules dissolved in the mobile phase affect to Mn, Mw and MWD.

• 소성∙가공
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• 제27권4호
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• pp.211-221
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• 2018

To estimate the recycling feasibility of high melt-indexed polycarbonate, 3.5 inch LGP, tensile, flexural and impact specimens were injection-molded and the LGP was shredded into scraps. The scraps were injection-molded again and this process was repeated for 4 times. Properties of the sample, i.e., optical properties, mechanical properties and number average molecular weight were measured at each cycle. Based on the results, as the number of reprocessing increased, transmittance decreased at low wavelength and color coordinate was changed systematically to yellow. Yellow index increased more than twofold during 4 recycling processes. On the other hand, the number average molecular weight decreased during recycling processes. Flexural and impact strength showed no tendency according to the number of recycling, but tensile strength decreased sharply after the third recycling process. Based on these properties, it was concluded that the number of recycling for high melt-indexed polycarbonate allowed in this study was one.

• 한국치위생학회지
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• 제22권4호
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• pp.241-247
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• 2022

Objectives: This study aimed to determine the Missing Teeth (MT; mean number of missing permanent teeth) index experienced by year for adults between the ages of 19 and 64. Methods: This study was conducted by analyzing the raw data of participants in the 4th to 8th periods of the National Health and Nutrition Examination Survey (NHANES). For the statistical program, IBM SPSS / WIN 26 was used and an independent sample t-test was performed. Results: The average number of MT by year showed a decreasing trend. In 2007, 2008, 2010 and 2011, the average number of MT by sex was higher among females, and this was statistically significant (p<0.05). However, in 2019, males had a higher average number of MT than females, which was statistically significant (p<0.05). Conclusions: Males had a higher average number of MT than females in Korea, so it is considered that oral health programs or oral hygiene management according to sex are necessary.

• Journal of Acupuncture Research
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• 제27권2호
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• pp.115-121
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• 2010

Objectives : Based on a national sample survey, we present an analysis of the current situation in the use of moxibustion therapeutics by qualified medical practitioners in Korea. Methods : The survey population of 11,737 hospitals is stratified by administrative regions, and 331 of them are randomly selected from the list of hospitals. The same number of Korean medical doctors is interviewed under the computer-assisted telephone interviewing(CATI) system. The bound on the error of estimation is ${\pm}\;5.0%$ point. Results : Of the 331 Korean medical doctors surveyed, 69% have used moxibustion therapy for remedial treatment. About half of those doctors have employed the therapy for their patients over 30%. The average number of acupuncture points per treatment using the therapy mostly ranges 1 between 5. The percent of practitioners, who have the number of average minutes less than 20 in treatment, is 74%. The number of practitioners who primarily use modified moxibustion is 4 times as many as that of those using traditional moxibustion. Conclusions : Considering the survey results, if the laser heater, alternative to conventional moxibustion, which not only gives high thermal effect but also reduces both the users inconvenience and side effects, are developed, it may benefit more patients as well as Korean medical doctors.

• Journal of Microbiology
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• 제37권1호
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• pp.1-9
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• 1999

The Biolog redox technology was carried out for evaluation of acidification effect on microbial communities at each stage of pH gradient microcosm. While the number of heterotrophic bacterial population and activities of extracellular enzyme decreased as the pH decreased, the number of total bacteria in the microcosm was not affected. The average color development of sample at each pH-gradient showed a sigmoidal curve, and at higher pH, more overall color development appeared in Biolog plates. Average color development value in Biolog plates was stabilized at 50 hours as an optimum incubation time. The color production in the Biolog plates was caused by cell density at above pH 5.0, but by cell activity below pH 4.0. Principal component analysis of color responses revealed distinctive patterns among the pH-gradient microcosm samples.

• 한국식품위생안전성학회지
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• 제12권2호
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• pp.125-131
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• 1997

Gulbi, salted and dried yellow corvenia, is a favorite diet food in Korea from the ancient times. A Few studies have dealt with sanitary concerns related to its products, while a number of investigators studied its taste compounds. This study attemps to establish the basic data for ensuring the safety of Gulbi. The contents of nitrate and nitrite were detected 1.2 and <0.1 mg/kg in raw sample, but their contents were detected 3.6~3.9 and 1.2~2.0 mg/kg during its processing and storage of Gulbi, respectively. TMAO contents decreased while betaine, TMA, DMA and formaldehyde increased in yellow corvenia during its processing and storage. Recovery from raw, salted, salt-dried and stored sample spiked with 10$\mu\textrm{g}$/kg for NDBA was 83.2~102.7% average 92.7%). N-nitrosamine such as NDMA, NDEA and NDPA was not detected in raw sample and drastically increased during Gulbi processing and storage. The levels of NDMA, NDEA and NDPA in Gulbi stored for 30 days were about 2.7,4.5 and 5.3 times higher than those in salted sample, respectively. Regardless of cooking methods, NDMA, NDEA and NDPA during cooking when sample were cooked using direct heating methods such as a gas and a briquet fire than when sample were cooked using indirect methods such as an microwave oven and a fried pan. Indirect cooking methods was effective to minimize the N-nitrosamine formation such as NDMA, NDEA and NDPA during cooking of Gulbi.

• 응용통계연구
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• 제33권4호
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• pp.451-466
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• 2020

CCC-r 관리도는 불량률이 매우 낮은 고품질 공정을 관리하는 데 효율적이라고 알려져 있다. 대부분의 공정에서 공정 모수의 값은 알려져 있지 않기 때문에 제1국면에서 이를 추정해야 하는데, 표본의 크기가 충분히 크지 않은 경우 추정 오차가 발생하여 원하는 관리상태에서의 성능을 만족하지 못하는 경우가 발생한다. 뿐만 아니라 제1국면에서 추출하는 표본에 따른 산포로 인하여 관리상태일 때의 성능의 산포 또한 커지게 된다. 이러한 문제를 해결하기 위해 이 논문에서는 관리상태일 때 신호까지의 평균관측개수가 사전에 정한 확률로 목표하는 값보다 큰 값을 갖도록, 붓스트랩 알고리즘을 사용하여 CCC-r 관리도의 관리한계를 조정하는 절차를 제안하였다. 이때 고품질 공정에 적용하기 위하여 최대우도추정량 대신 베이즈추정량을 사용하여 불량률을 추정하였다. 다양한 상황에 대해 모의실험을 수행한 결과, 제안된 절차는 CCC-r 관리도의 관리상태 성능을 크게 향상시킴을 알 수 있었다.

• Journal of Communications and Networks
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• 제12권3호
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• pp.222-230
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• 2010

In this paper, we present a closed-form approximation of the average sum rate of zero-forcing (ZF) beamforming (BF) with semi-orthogonal user selection (SUS). We first derive the survival probability associated with the SUS that absolute square of the channel correlation between two users is less than the orthogonalization level threshold (OLT).With this result, each distribution for the number of surviving users at each iteration of the SUS and the number of streams for transmission is calculated. Secondly, the received signal power of ZF-BF is represented as a function of the elements of the upper triangular matrix from QR decomposition of the channel matrix. Thirdly, we approximate the received signal power of ZF-BF with the SUS as the maximum of scaled chisquare random variables where the scaling factor is approximated as a function of both OLT and the number of users in the system. Putting all the above derivations and order statistics together, the approximated ergodic sum rate of ZF-BF with the SUS is shown in a closed form. The simulation results verify that the approximation tightly matches with the sample average for any OLT and even for a small number of users.

• Geomechanics and Engineering
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• 제30권1호
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• pp.67-73
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• 2022

In this study, the fiber orientation distribution (FOD) is investigated using both micro-CT (computerized tomography) and image analysis of physically cut specimens prepared from Polyvinyl Alcohol (PVA) fiber reinforced cemented Toyoura sand. The micro-CT images of the fiber reinforced cemented sand specimens were visualized in horizontal and vertical sections. Scans were obtained using a frame rate of two frames and an exposure time of 500 milliseconds. The number of images was set to optimize and typically resulted in approximately 3000 images. Then, the angles of the fibers for horizontal sections and in vertical section were calculated using the VGStudio MAX software. The number of fibers intersecting horizontal and vertical sections are counted using these images. A similar approach was used for physically cut specimens. The variation of results of fiber orientation between micro-CT scans and visual count were approximately 4-8%. The micro-CT scans were able to precisely investigate the fiber orientation distribution of fibers in these samples. The results show that 85-90% of the PVA fibers are oriented between ±30° of horizontal, and approximately 95% of fibers have an orientation that lies within ±45° of the horizontal plane. Finally, a comparison of experimental results with the generalized fiber orientation distribution function 𝜌(θ) is presented for isotropic and anisotropic distribution in fiber reinforced cemented Toyoura sand specimens. Experimentally, it can be seen that the average ratio of the number of fibers intersecting the finite area on a vertical plane to number of fibers intersecting the finite area on a horizontal plane (N^V_tot/N^H_tot) cut through a sample varies from 2.08 to 2.12 (an average ratio of 2.10 is obtained in this study). Based up on the analytical predictions, it can be seen that the average N^V_tot/N^H_tot ratio varies from 2.13 to 2.17 for varying n values (an average ratio of 2.15).