• Journal of the korean academy of Pediatric Dentistry
• /
• v.31 no.3
• /
• pp.439-447
• /
• 2004

The aim of this study is to survey the frequency of mutans streptococci species and biotypes isolated from dental plaque in Korean children and the relationship between species and biotypes of mutans streptococci and dft index. Dental plaques were collected from the anterior and molar teeth of upper and lower jaws in the subjects, aged below 12 years old. A dental examination was performed for dft (decayed, filled, total) with the WHO caries diagnostic criteria. The mutans streptococci from the sample were cultured selectively on mitis salivarius-bacitracine (MSB) agar plate. For biotyping of mutans streptococci, biochemical test was performed. From the culture, bacterial genomic DNA was prepared for using of PCR template for the identification of mutans streptococci at the species-level. Forty strains of mutans streptococci were isolated from dental plagues of 40 patients. The biotype I (45%) and biotype IV (32.5%) were most frequently detected. The prevalence of S. mutans and S. sobrinus was 69% and 31%, respectively. There was no positive relationship between species and biotypes of mutans streptococci and dft index. Our results revealed that biotype I and S. mutans were frequently detected in Korean children and support that dental caries incidents by many causative factors not only bacterial factor.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.5 no.1
• /
• pp.43-53
• /
• 1985

This study proposes a reliability based design criteria for the steel bridge (H-beam, plate-girder and composite-beam), which is most common type of steel bridge, and also proposes the theoretical bases of nominal safety factors as well as load and rasistance factors based on the reliability theory. Major 2nd moment reliability analysis and design theories including both Cornell's MFOSM (Mean First Order 2nd Moment) Methods and Lind-Hasofer's AFOSM(Advanced First Order 2nd Moment) Methods are summarized and compared, and it has been found that Lind-Hasofer's approximate and an approximate Log-normal type reliability formula are well suited for the proposed reliability study. A target reliability index (${\beta}_0=3.5$) is selected as an optimal value considering our practice based on the calibration with the safety pravisions of the current steel bridge design code. Galambo's theory is used for the derivation of the algorithm for the evaluation of uncertainties associated with resistences by LRFD Format and SGST Format, whereas the magnitude of the uncertainties associated with load effects are chosen primarily by considering our level of practice. It may be concluded that the proposed LRFD reliability based design provisions for the steel highway bridge give more rational design than the current standard code for steel highway bridge.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.2
• /
• pp.145-152
• /
• 2010

This study evaluated the fatigue degradation in a SUS316L specimen using the nonlinear ultrasonic method. The nonlinearity of the ultrasonic wave was estimated by a relative nonlinear parameter defined as the ratio of the amplitudes for the fundamental wave to the second harmonic wave. In the experiment, a measurement system with contact transducers was constructed; reliable measurements were assured by keeping measurement conditions consistent and reducing extra harmonics generated in the measurement system. Two types of SUS316L specimen were used in experiments; a rotating bar fatigue specimen and a tensile fatigue specimen. The fatigue condition used was high cycle fatigue. The former specimen had a cylindrical shape and was used to observe the change in the nonlinear parameter after fatigue accumulation in a specimen. The latter was a plate-shaped specimen and was used to confirm the change in the nonlinear parameter at the position where the fatigue stress was concentrated. The measured nonlinear parameter showed a strong correlation to the damage level in both fatigue tests.

• Food Science of Animal Resources
• /
• v.24 no.1
• /
• pp.29-36
• /
• 2004

Changes in quality characteristics and shelf-life of two types of grill sausage manufactured by using pork hind leg and re-pasteurized after packaging were investigated during storage at 5$^{\circ}C$ and 10$^{\circ}C$ up to 30 days. The total aerobic plate counts(APC) of N rnberger style grill sausage(NGS) and vegetable added grill sausage(VGS) were initially 3.08 and 3.57 log$\sub$10/CFU/$\textrm{cm}^2$, respectively, and gradually increased during storage time. After 30 days, the APC of NGS stored at 5$^{\circ}C$ and 10$^{\circ}C$ maintained relatively low at the levels of 5.32 and 6.58 log$\sub$10/CFU/$\textrm{cm}^2$, respectively. However, the APC of VGS exceeded the level of 8 log$\sub$10/CFU/$\textrm{cm}^2$ after 30 days at 5$^{\circ}C$ and after 20 days at 10$^{\circ}C$. pH was decreased with storage period, however it tended to increase after 30 days. The values of TBA and VBN for both sausages tended to increase with storage time, and this trend was pronounced at 5$^{\circ}C$ rather than at 10$^{\circ}C$. The purge loss was apparently increased in the VGS compared to the NGS sample as the storage period extended. According to the sensory evaluation, the marketing values of grill sausages stored at 5$^{\circ}C$ and 10$^{\circ}C$ were maintained until day 20 for NGS and day 14 for VGS, respectively.

• Korean Journal of Applied Biomechanics
• /
• v.25 no.3
• /
• pp.311-322
• /
• 2015

Objective : The purpose of this study was to investigate the effects of landing height and knee joint muscle fatigue on the movement of the lower extremity during cutting after landing. Method : Subjects included 29 adults (age: $20.83{\pm}1.56years$, height: $172.42{\pm}9.51cm$, weight: $65.07{\pm}10.18kg$). The subjects were asked to stand on their dominant lower limb on jump stands that were 30 and 40 cm in height and jump from each stand to land with the dominant lower limb on a force plate making a side step cutting move at a $45^{\circ}$ angle with the non-dominant lower limb. The fatigue level at 30% of the knee extension peak torque using an isokinetic dynamometer. Results : The results showed that the difference of landing height increased maximum range of motion and angular velocity of hip, knee, and ankle joints in the sagittal plane, and in the angular velocity of motion of the hip joint in the sagittal plane. The maximum range of motion of the knee joint in the sagittal plane and the frontal plane decreased on landing from both heights after the fatigue exercise. The angular velocity of the hip joint in the sagittal plane, and the maximum range of motion of the hip joint in the transverse plane decreased for both landing heights after the fatigue exercise. The angular velocity of the hip joint in the frontal plane decreased for the 30 cm landing height after the fatigue exercise. On the other hand, the angular velocity and maximum range of motion of the ankle joint in the sagittal plane for both landing heights, and the angular velocity and maximum range of motion of the ankle joint in the frontal plane increased on landing from the 40 cm height after the fatigue exercise. Conclusion : Different landing heights of 30 and 40 cm and 30% fatigue of peak torque of knee extensor found a forefoot and stiff landing strategy, when cutting after landing. These results might be due to decline in the shock absorption capability of the knee joint and the movement capability related to cutting while increasing the contribution of the ankle joint, which may cause increased ankle joint injuries.

• Journal of Food Hygiene and Safety
• /
• v.26 no.2
• /
• pp.154-159
• /
• 2011

Inadequate food handling and poor hand hygiene playa major role in the occurrence of foodborne diseases. The objective of this study was to find out if the level of microbial contamination on the hands of food preparers varies by time during their working period. This study focused on the contamination of aerobic plate count, total and fecal coliforms, Escherichia coli, Staphylococcus aureus, and Salmonella spp. Sampling from left hand and right hand of twenty food preparers was done with glove-juice method at every two hours during their work. Microbiological testing was conducted according to the Food Code of Korea. The microbiological load on the hands was changed over time. Samples taken from their hands before work and at 8 hours showed higher levels of bacteria than those taken at 2, 4, and 6 hours during work and/or after work (p < 0.05). The contamination levels of microorganisms were consistently higher in right hand than in left hand. Poor hand hygiene practices were indicated by the positive results for total and fecal coli forms, E. coli, S. aureus, and Salmonella spp. on the hands of some food preparers. This study indicates food preparers' hands can be a vehicle of pathogen during their work. The results of this study emphasize the importance of hand hygiene education and training targeting the food preparers.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.4
• /
• pp.337-346
• /
• 2014

This study aimed to understand the mode characteristics of a droplet subject to periodic forced vibration and the detachment of a droplet placed on a plate surface. An surface was coated with Teflon to clearly observe the behavior of a droplet. The contact angle between the droplet and surface and the hysteresis were found to be approximately $115^{\circ}C$ and within $25^{\circ}C$, respectively. The coating process was performed in a clean room that had an environment with a low level of contaminants and impurities such as air dust, detergents, and particles. To predict the resonance frequency of a droplet, theoretical and experimental approaches were applied. Two high-speed cameras were configured to acquire side and top views and thus capture different characteristics of a droplet: the mode shape, the detachment, the separated secondary droplet, and the waggling motion. A comparison of the theoretical and experimental results shows no more than 18 discrepancies when predicting the resonance frequency. These differences seem to be caused by contact line friction, nonlinear wall adhesion, and the uncertainty of the experiment. For lower energy inputs, the contact line of the droplet was pinned and the oscillation pattern was axisymmetric. However, the contact line of the droplet was de-pinned as the oscillation became more vigorous with increased energy input. The size of each lobe at the resonance frequency is somewhat larger than that at the neighboring frequency. A droplet in mode 2, one of the primary mode frequencies, exhibits vertical periodic movement as well as detachment and secondary ejection from the main droplet.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.15 no.3
• /
• pp.185-190
• /
• 1982

In utilization of small size red muscled fishes like mackerel, sardine, and filefish, mechanical dressing is usually required. The removal of dark muscle is also necessary to improve qualify of the product, which could hardly be done by mechanical process. As a method of separating dark muscle, specific gravity method using sugar solution was investigated in this study. And the effects of the level of specific gravity, the size and density of meat particles, and stability of meat particle float on the separation of dark muscle were discussed. From the results, effective specific gravity, in case of sucrose solution, ranged 1.067 to 1.072 for mackerel, 1.062 to 1.070 for sardine, and 1.072 to 1.077 for filefish, respectively. The maximum separation of more than $90\%$ was obtained at specific gravity of 1.075, 1.070, and 1.075 in cases of mackerel, sardine and filefish, respectively. The size of meat particles which were ground with 0.2cm orifice plate was adequate to yield $90\%$ separation or above. The meat particle float in the glucose solution began to precipitate within 5 minutes after separation while 25 minutes in case of sucrose solution. Lipids were also fairly removed by the dark muscle separation process.

• The korean journal of orthodontics
• /
• v.26 no.3
• /
• pp.291-299
• /
• 1996

Orthodontic force is a mechanical stress controlling both of tooth movement and skeletal growth. The mechanical stress stimulate bone cells that may exert some influence on bone remodeling. The purpose of this study was to evaluate the difference in cellular activity depending on mechanical stresses such as compressive and tensile force by determining the alkaline phosphatase(ALP) activity. A clonal osteogenic cell line MC3T3-E1 was seeded into a 24-well plate($2{\times}10^4/well$). At the confluent phase, a continuous compressive hydrostatic pressure($25g/cm^2$, $300g/cm^2$) and continuous tensile hydrostatic pressure($-25g/cm^2$, $-300g/cm^2$) were applied for 4, 6, 10, 14, 18, 20 days respectively by a diaphgragm pump. At the end of the stimulation period, cell layers were prepared for ALP activity assay. The ALP activity of the compressive group increased more than that of the tensile group at same force magnitude, whereas the cells responded to a similar pattern regardless of the type of mechanical stress The ALP activity of the compressive and tensile group turned into the level of the control group as the length of time increased. These results indicated that a mechanical stress may be more effective on cellular activity during active cellular proliferation and differentiation periods. The time to achieve maximum ALP activity was delayed as the mechanical stress increased in both the compressive and the tensile group. Accordingly, the magnitude of the stress rather than the type of mechanical stress may have more influence on cellular activity.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.3
• /
• pp.165-172
• /
• 2016

An experimental study of the thermal-hydraulic characteristics of passive safety systems (PSSs) was conducted using a system-integrated modular advanced reactor-integral test loop (SMART-ITL). The present passive safety injection system for the SMART-ITL consists of one train with the core makeup tank (CMT), the safety injection tank, and the automatic depressurization system. The objective of this study is to investigate the injection effect of the PSS on the small-break loss-of-coolant accident (SBLOCA) scenario for a 0.4 inch line break in the safety-injection system (SIS). The steady-state condition was maintained for 746 seconds before the break. When the major parameters of the target value and test results were compared, most of the thermal-hydraulic parameters agreed closely with each other. The water level of the reactor pressure vessel (RPV) was maintained higher than that of the fuel assembly plate during the transient, for the present CMT and safety injection tank (SIT) flow rate conditions. It can be seen that the capability of an emergency core cooling system is sufficient during the transient with SMART passive SISs.