• Korean Journal of Environmental Biology
• /
• v.22 no.1
• /
• pp.75-82
• /
• 2004

Surface and bottom sea water samples were harvested from the 5 stations in the marine ranching ground of Tongyeong coastal water from year 2000 to 2002. Cell number of heterotrophic bacteria was determined by using the plate counting method to explore the variation of the cell population of heterotrophic bacteria. Sea water samples collected in summer (in July and August) contained much larger number of heterotrophic bacteria than those harvested in spring, autumn and winter. Heterotrophic bacteria were usually more abundant in surface sea than in bottom sea water. However the reverse was true for sea water collected in December 2001 and February 2002 due to suspended solids accumulating more abundantly in seabed area because of the slower convective current of the sea water in winter. Number of heterotrophic bacteria did not have a strong relationship with frequency of typhoon indicating that the path and powerfulness of the typhoon, localized torrential downpour and temperature variation accompanying the typhoon should be considered all together at the same time as well as the frequency of typhoon to explain clearly the variation of cell number of heterotrophic bacteria. The dominant species isolated from the marine ranching ground of Tongyeong were identified to be Pseudomonas fluorescens, Pseudomonas stutzeri, Acinetobacter lwoffii and Sphingomonas paucimobilis.

• Fisheries and Aquatic Sciences
• /
• v.20 no.8
• /
• pp.16.1-16.8
• /
• 2017

The exportation of cultured olive flounder (Paralichthys olivaceus) in Korea has been recently decreasing due to the infections with a myxozoan parasite Kudoa septempunctata, and there is a strong demand for strict food safety management because the food poisoning associated with consumption of raw olive flounder harbouring K. septempunctata has been frequently reported in Japan. The life cycle and infection dynamics of K. septempunctata in aquatic environment are currently unknown, which hamper establishment of effective control methods. We investigated sea water and marine invertebrates collected from olive flounder farms for detecting K. septempunctata by DNA-based analysis, to elucidate infection dynamics of K. septempunctata in aquaculture farms. In addition, live marine polychaetes were collected and maintained in well plates to find any possible actinosporean state of K. septempunctata. The level of K. septempunctata DNA in rearing water fluctuated during the sampling period but the DNA was not detected in summer (June-July in farm A and August in farm B). K. septempunctata DNA was also detected in the polychaetes Naineris laevigata intestinal samples, showing decreased pattern of 40 to 0%. No actinosporean stage of K. septempunctata was observed in the polychaetes by microscopy. The absence of K. septempunctata DNA in rearing water of fish farm and the polychaetes N. laevigata intestinal samples during late spring and early summer indicate that the infection may not occur during this period. N. laevigata was suspected as the possible alternate invertebrate host of K. septempunctata, but the actinosporean stage was not found by well plate method and further studies will be necessary. This research provides important baseline information for understanding the infection dynamics of K. septempunctata in olive flounder farms and further establishment of control strategies.

• The Journal of the Acoustical Society of Korea
• /
• v.28 no.1E
• /
• pp.9-15
• /
• 2009

In this paper, FSTL (Field Sound Transmission Loss) measured in a mock-up simulating ship cabins is studied. A mock-up is built by using 6 mm steel plate, and two identical cabins are made where 25 mm or 50 mm sandwich panel is used to construct wall and ceiling inside the steel structure. Various wall panels and ceilings are tested, where effects of wall and ceiling panel thickness, and presence of a unit toilet on FSTL are investigated. It is found that the effect of unit toilet on FSTL is at most 1 dB. From the comparison of FSTL for panels of the same thickness of 50 mm, it is observed that panel having inside air cavity of 10 mm shows higher STL than that of the panel without air cavity. Comparison of FSTL for panels of 50 mm and 25 mm thickness shows that dependency on surface density predicted by mass law is not observed. The sandwich panels act as a mass-spring system, which shows a resonant mode that cannot be explained by the mass law. It is also found that STL from laboratory test is higher than FSTL by 5- 10 dB, which can be explained by flanking structure-borne noise transmission path such as ceiling, floor and corridor-facing wall.

• Korean Journal of Veterinary Service
• /
• v.33 no.1
• /
• pp.45-50
• /
• 2010

Mycoplasma gallisepticum (MG) is major cause of chronic respiratory disease in chickens. M. synoviae (MS) most frequently occurs a subclinical upper respiratory infection but may result in airsacculitis and synovitis in chickens and turkeys. Both mycoplasmas induce economic losses by triggering chronic respiratory signs, airsacculitis and decreased egg production. For prevention of the infections, live attenuated andinactivated vaccines are commercially used for prevention of MG but not MS in Korea. Serum plate agglutination (SPA) and enzyme-linked immunosorbent assay (ELISA) have been commonly used for serological diagnosis for MG and MS. Recently, it is believed that MS spread in chickens is very seriously in Korea and respiratory infection with MS causes substantial loss in poultry farms. In this study, we investigated the serological prevalence of MG and MS in unvaccinated chickens between 2008 and 2009. The overall seroprevalence of MG was 24% of 2,094 for individual chickens and 24% of 189 farms. The overall seroprevalence of MS was 36% in 2,095 chickens and 39% in 198 farms. The results show that seropositive ratio of MS is higher than MG. The geographical prevalence of MG has been estimated in following sequence; Gangwon, Jeolla, Gyeonggi, Gyeongsang, and Chungcheong. The geographical prevalence of MS has been estimated as follows; Gangwon, Gyeonggi, Gyeongsang, Chungcheong, and Jeolla. Seasonal seroprevalencewas also examined, and it found that seroprevalence in spring, fall and winter was higher than that in summer in MG, but not in MS. No significant difference was shown in seroprevalence according to breed. Future study about pathogenicity of MS isolates would be needed and economical losses by MS outbreaks should be analyzed. Moreover, we compared sero-positivity obtained with SPA and ELISA. The kappa value of MG between SPA and ELISA was 0.8061 and the kappa value of MS between SPA and ELISA was 0.7649.

• Food Science of Animal Resources
• /
• v.36 no.5
• /
• pp.594-600
• /
• 2016

This study aimed to examine the microbial contamination levels in livestock products at retail stores. Beef, pork, and chicken samples from raw materials and final products were obtained between January and December 2015. All homogenized meat samples (25 g) were tested for the aerobic plate count (APC), coliform count (CC), and Escherichia coli count (E. coli). The highest APCs in meat samples, by month, at retail shops were obtained in September, followed by July, May, and October (p<0.001). However, APC was the highest in summer and the lowest in winter (p<0.001). Average APCs for beef, pork, and chicken samples were 2.90, 3.19, and 3.79 Log CFU/g, respectively (p<0.05). A comparison between different months revealed that, CC levels in meat samples ranged from 0 to 1.13 CFU/g, and the highest CC was obtained in August (p<0.001). By season, the highest CC was found in the summer, followed by autumn, and spring (p<0.001). All meat samples were negative for E. coli. The average log₁₀APC and CC for all samples was 3.10 and 0.37 Log CFU/g, respectively. Furthermore, there was a direct correlation between the season and coliform presence (p<0.001). There was also a positive correlation between the APC and CC (r = 0.517, p<0.001). The microbiological APCs for livestock products were in most cases below 10⁶ CFU/g.

• Journal of Institute of Control, Robotics and Systems
• /
• v.22 no.11
• /
• pp.912-918
• /
• 2016

This paper presents various strategies for humanoid vehicle driving and egress tasks. For driving, a tele-operating system that controls a robot based on a human operator's commands is built. In addition, an autonomous assistant module is developed for the operator. Normal position control can result in severe damage to robots when they egress from vehicles. To prevent this problem, another approach that mixes various joint control techniques is adopted in this study. Additionally, a footplate is newly designed and attached to the vehicle floor for the ground landing phase of the egress task. The attached plate enables the robot to step down onto the ground in a safe manner. For stable locomotion, a balance controller is designed for the humanoid. For the design of the controller, the robot is modeled using an inverted pendulum that consists of a spring and a damper. Then, a state feedback controller (with pole placement and a state observer) is built based on the simplified model. Many approaches that are presented in this paper were successfully applied to a full-sized humanoid, DRC-HUBO+, in the DARPA Robotics Challenge Finals, which were held in the United States in 2015.

• Interaction and multiscale mechanics
• /
• v.3 no.1
• /
• pp.55-79
• /
• 2010

The effect of soil-structure interaction on a single-storey, two-bay space frame resting on a pile group embedded in the cohesive soil (clay) with flexible cap is examined in this paper. For this purpose, a more rational approach is resorted to using the finite element analysis with realistic assumptions. Initially, a 3-D FEA is carried out independently for the frame on the premise of fixed column bases in which members of the superstructure are discretized using the 20-node isoparametric continuum elements. Later, a model is worked out separately for the pile foundation, by using the beam elements, plate elements and spring elements to model the pile, pile cap and soil, respectively. The stiffness obtained for the foundation is used in the interaction analysis of the frame to quantify the effect of soil-structure interaction on the response of the superstructure. In the parametric study using the substructure approach (uncoupled analysis), the effects of pile spacing, pile configuration, and pile diameter of the pile group on the response of superstructure are evaluated. The responses of the superstructure considered include the displacement at top of the frame and moments in the columns. The effect of soil-structure interaction is found to be quite significant for the type of foundation considered in the study. Fair agreement is observed between the results obtained herein using the simplified models for the pile foundation and those existing in the literature based on a complete three dimensional analysis of the building frame - pile foundation - soil system.

• Proceedings of the KIEE Conference
• /
• 2007.11a
• /
• pp.154-155
• /
• 2007

This paper describes frequency response of two-mass system for gyroscope applications. The two-mass system of the proposed device is adapted to the sensing part of the gyroscope in this research. Two-mass system has two resonant peaks and wide flat region between two resonant peaks. The resonant frequency of driving part is in this flat region. Therefore, frequency tuning is not necessary for mode matching. In the proposed device, resonant frequency is designed as 7183 Hz in driving part. Mass ratio of two masses in sensing part is 0.1 and device size is 6 mm $\times$ 6 mm. The device is fabricated by SiOG process. The fabricated spring width is increased from $4{\mu}m$ to $4.5{\sim}4.7{\mu}m$, and the measured resonant frequency is 8392 Hz in driving mode. We operated the sensing part using parallel plate of proof mass to verify the sensing part. It is confirmed the device has a wide fiat region in frequency response curve and the resonant frequency of the driving part is in the wide flat region of sensing mode.

• Smart Structures and Systems
• /
• v.28 no.6
• /
• pp.745-760
• /
• 2021

Dynamic buckling of structure is one of the failure modes that needs to be considered since it may result in catastrophic failure of the structure in a short period of time. For a thin fiber-reinforced polymer (FRP) plate under compression, buckling is an inherent hazard which will be intensified by the existence of defects like holes, cracks, and delamination. On the other hand, the growth of the delamination is another prime concern for thin FRP plates. In the current paper, reinforcing the plates against buckling is realized by using SMA wires in the form of stitches. A numerical framework is proposed to simulate the dynamic instability emphasizing the effect of the SMA stitches in suppressing delamination growth. The suggested algorithm is more accurate than the other methods when considering the transformation point of the SMA wires and the modeling of the cohesive zone using simple and yet reliable technique. The computational design of the method by producing the line by line orders leads to a simple algorithm for simulating the super-elastic behavior. The Lagoudas constitutive model of the SMA material is implemented in the form of user material subroutines (VUMAT). The normal bilinear spring model is used to reproduce the cohesive zone behavior. The nonlinear finite element formulation is programmed into FORTRAN using the Newmark-beta numerical time-integration approach. The obtained results are compared with the results obtained by the finite element method using ABAQUS/Explicit solver. The obtained results by the proposed algorithm and those by ABAQUS are in good agreement.

• Composites Research
• /
• v.34 no.6
• /
• pp.426-433
• /
• 2021

The carbon fiber reinforced plastic manufacturing process has a problem in that a dimensional error occurs due to thermal deformation such as residual stress, spring-in, and warpage. The main causes of thermal deformation are various, including the shape of the product, the chemical shrinkage, thermal expansion of the resin, and the mold effect according to the material and surface condition of the mold. In this study, a viscoelastic model was applied to the plate model to predict the thermal deformation. The effects of chemical shrinkage and thermal expansion of the resin, which are the main causes of thermal deformation, were analyzed, and the analysis technique of the 3-D viscoelastic model with and without mold was also studied. Then, the L-shaped mold effect was analyzed using the verified 3D viscoelastic model analysis technique. The results show that different residual deformation occurs depending on the surface condition even when the same mold is used.