• Korean Journal of Veterinary Research
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• v.29 no.4
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• pp.417-424
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• 1989

This study was conducted in order to observe the changes in cellular association of seminiferous tubules from 4 to 22 weeks of age and to obtain the cycle and relative duration of seminiferous epithelia from 24 weeks of age in male ducks. Fifety-five male ducks were used in the experiment and divided into 11 groups, consisting of 5 male ducks each, with 2 weeks intervals from 4 to 24 weeks of age. The results were summarized as follows: 1. The body and testes weight showed most rapid increase during 4 to 6 weeks and 18 to 22 weeks of age, respectively. The seminiferous tubules were obruptly enlarged in diameter of tubules during 18 to 22 weeks of age. 2. Gonocytes were seen from 4 to 6 weeks of age, however they were not observed as from 8 weeks of age. Both type Ap spermatogonia and type Ad spermatogonia occured from 8 to 12 weeks of age, while spermatocytes and spermatids were beginning to appear at 16 weeks and 18 weeks of age, respectively. Spermatozoa were first observed at 20 weeks of age. Full spermatogenic activity was completed at the age of 20 weeks. 3. Average paired weight of the testes in male ducks was 78g at 24 weeks of age and its ratio to the body weight was approximately 2.5 percent. 4. Average diameter of seminiferous epithelium at 22 weeks of age was $232{\mu}m$, and average numbers of Sertoli cell, spermatogonia, spermatocyte, spermatids and spermatozoa in the cross section of seminiferous epithelium were 15.30, 59.08, 41.78, 71.11 and 165.30, respectively. Spermatogonia and spermatids were classified into 2 and 4 types, respectively. 5. The cycle of the seminiferous epithelium could be divided into 5 stages at 24 weeks of age. The relative frequencies of stages from I to V were 13.5%, 25.0%, 22.3%, 20.6% and 18.7% respectively. Thus, establishment of spermatogenesis in male ducks were beginning to appear at 20 weeks of age.

• Journal of Korean Society on Water Environment
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• v.18 no.4
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• pp.379-386
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• 2002

In this study, estimation model for iron compound originated from upflow, anaerobic fixed bed reactor, which treats sewage domestic wastewater, was developed. The estimation model was formulated by a mathematical expression which was based on the mass balance. Below the HRT of 60 minute, sulfide concentration combining with iron $FeS_2$ is the highest because the maximum sulfate consumption rate $V_{maxS}$ and half-saturation constant of sulfate $K_{mS}$ exert an important effect on the estimation model as temperature was increased. But increment of $FeS_2$ concentration is weakened above the HRT of 60 minutes and represent the lowest value at the HRT of 108 minutes. It implies that liquid phase distribution ratio of sulfide ${\alpha}r$ becomes lower as temperature was increased. While phosphorus concentration combining with iron $Fe_3(PO_4)_3$ is increased as HRT and temperature are increased, which is affected by phosphorus removal rate constant $k_p$. As the result of estimating the iron concentrations of corrosion by the model, the concentration of iron corrosion is higher than any other at the HRT of 108 minute and $20^{\circ}C$. The predicted values were compared with measured ones at different HRT(13.5, 27, 54, 108 min) and temperature(20, 25, $30^{\circ}C$). The experimental data could be fitted with the simulated curves. Therefore, the mathematical expression could be applicable to design full-scale wastewater treatment plants.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.2
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• pp.91-95
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• 1984

This paper describes to analyze regression relation between the ratio mean draft to freeboard and KM/dm, KB/dm and GM/B, respectively with the 43 Korean fishing vessels (7 Danish seiners; 1l Stowers; 14 Poler and liners; 6 Trawlers; 5 Purse seiners) and the 1 Cargo boat in order to obtain the stability factors of the Korean fishing vessels conveniently. The obtained results are as follows; 1. The stability factors by fishing vessels have a tendency to the larger f/dm, the larger KM/dm and KG/dm, and KB/dm and GM/B are constant. 2. It is found out that M and G differ from the kinds of the fishing vessels because KM/dm is the largest in poler and liners and KG/dm in Danish seiner, respectively. 3. It is confirmed that the stability factors of the fishing vessels which the inclining experiment carry out the wholly in the light and the full loaded condition are the same as the inclining experiment uniformly.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.51-59
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• 2017

In this paper, we propose a gray code order of antenna index permutations for differential spatial modulation (DSM). To facilitate the implementation, the well-known Trotter-Johnson ranking and unranking algorithms are adopted, which result in similar computational complexity to the existing DSM that uses the lexicographic order. The signal-to-noise ratio gain achieved by the proposed gray code order over the lexicographic order is also analyzed and verified via simulations. Based on the gray coding framework, we further propose a diversity-enhancing scheme named intersected gray (I-gray) code order, where the permutations of active antenna indices are selected directly from the odd (or even) positions of the full permutations in the gray code order. From analysis and simulations, it is shown that the I-gray code order can harvest an additional transmit diversity order with respect to the gray code order.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.6
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• pp.9-16
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• 2000

The perception of flicker on the computer display devices depends upon the temporal waveform of the phosphor decay characteristic, the frame rate, and the display size. The lowest frequency at which flicker is not perceived is called the critical fusion frequency or critical frequency. Critical fusion frequency is evaluated by the display illuminance and the modulation (m) defined as the ratio of the amplitude of first harmonic frequency to the DC of the waveform. In this paper, we analyze the relationship bet ween the critical fusion frequency, relating to the decay characteristic of the phosphors and luminance on the monitor, and the frame frequency. Also under considering the viewing angle, we presented the frame frequency that is less sensitive to the full size of the display device.

• The Korean Journal of Community Living Science
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• v.21 no.3
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• pp.285-298
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• 2010

This study aims to analyze teachers job satisfaction according to the working environment of teachers working in child-care centers and to investigate which variables of the working environment relate to job satisfaction of child-care teachers. The main results of this study were as follows. First, married teachers are more satisfied with the job itself, supervision, and colleague relations compared to teachers who are not married. Teachers with certificates are more satisfied with the job itself compared to teachers without certificates. Second, teachers's job satisfaction is significantly correlated with their salary, welfare, and colleague relations. Also teachers' job satisfaction is correlated with responsibility in the case that teachers have a good relation with their principal and child-care parents. Third, the results of this study show that teachers consider substitute teachers, vacation systems, day care systems, compliant with the ratio of teacher and children, job security, order of legal status as important. With regard to external compensation, teachers want salary increase, payment on overtime labor, flexible work-time, use of both full-time and part-time teachers, expansion of educational materials, increase on purchasing cost for textbooks and materials. To improve the quality of child-care teachers' working environment as well as their satisfaction, practical policies need to be implemented.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.221-229
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• 2012

Steel ribs such as H-beam or lattice girder are often reinforced to secure the stability of NATM tunnel when the ground is in the bad condition. When designing, however, steel ribs are not often taken into consideration on the numerical analysis when they are regarded as temporary tunnel supports until shotcrete shows its best performance or if they are, there are various modeling methods. This study shows behavior and loading capacity of steel ribs and shotcrete through the strength test on the bending, pressure and full-scaled. Also, we conducted and analyzed the experiment of composite member consisting of shotcrete and steel ribs under the same condition. Through the result, we can find the fact that shotcrete and steel ribs do not work as one unit because of slipping on the boundary. Also, when numerical analyzing, it was concluded that steel ribs cover all bending moment and shotcrete and steel ribs share with axial force according to the compressive strength.

• Smart Structures and Systems
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• v.19 no.5
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• pp.487-497
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• 2017

Semi-active devices use the building's own motion to produce resistive forces and are thus strictly dissipative and require little power. Devices that independently control the binary open/closed valve state can enable novel device hysteresis loops that were not previously possible. However, some device hysteresis loops cannot be obtained without active analog valve control allowing slower, controlled release of stored energy, and is presents an ongoing limitation in obtaining the full range of possibilities offered by these devices. This in silico study develops a proportional-derivative feedback control law using a validated nonlinear device model to track an ideal diamond-shaped force-displacement response profile using active analog valve control. It is validated by comparison to the ideal shape for both sinusoidal and random seismic input motions. Structural application specific spectral analysis compares the performance for the non-linear, actively controlled case to those obtained with an ideal, linear model to validate that the potential performance will be retained when considering realistic nonlinear behaviour and the designed valve control approach. Results show tracking of the device force-displacement loop to within 3-5% of the desired ideal curve. Valve delay, rather than control law design, is the primary limiting factor, and analysis indicates a ratio of valve delay to structural period must be 1/10 or smaller to ensure adequate tracking, relating valve performance to structural period and overall device performance under control. Overall, the results show that active analog feedback control of energy release in these devices can significantly increase the range of resetable, valve-controlled semi-active device performance and hysteresis loops, in turn increasing their performance envelop and application space.

• Wind and Structures
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• v.25 no.2
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• pp.195-214
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• 2017

Full-scale wind characteristics based on the field measurements is an essential element in structural wind engineering. Statistical analysis of the wind characteristics at Sutong Cable-stayed Bridge (SCB) site is conducted in this study with the recorded long-term wind data from structural health monitoring system (SHMS) between 2008 and 2015. Both the mean and turbulent wind characteristics and power spectra are comprehensively investigated and compared with those in the current codes of practice, such as the measured wind rose diagram, monthly maximum mean wind speed, turbulence intensity, integral length scale. Measurement results based on the monitoring data show that winds surrounding the SCB site are substantially influenced by the southeast monsoon in summer and strong northern wind in winter. The measured turbulence intensity is slightly higher than the recommended values in specifications, while the measured ratio of lateral to longitudinal turbulence intensity is slightly lower. An approximately linear relationship between the measured turbulence intensities and gust factors is obtained. The mean value of the turbulence integral length scale is smaller than that of typical typhoon events. In addition, it is found that the Kaimal spectrum is suitable to be adopted as the power spectrum for longitudinal wind component at the SCB site. This contribution would provide important wind characteristic references for the wind performance evaluation of SCB and other civil infrastructures in adjacent regions.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.3
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• pp.407-413
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• 2011

Effect of dietary protein and lipid levels on compensatory growth of juvenile olive flounder (Paralichthys olivaceus) was determined in suboptimal temperature ($13.4{\pm}1.42^{\circ}C$). Five hundred forty fish averaging 79.2 g were randomly distributed into 27 of 300 L flow-through tanks (20 fish/tank). Nine treatments were prepared in triplicate: fish were hand-fed with control (C) diet for 10 weeks (10WF-C); four fish groups were starved for 1 week and then fed with C, high protein (HP), high lipid (HL) and combined high protein and high lipid (HPL) diets for 9 weeks, referred to as 9WF-C, 9WF-HP, 9WF-HL, 9WF-HPL, respectively; and other four fish groups were starved for 2 weeks and then fed with C, HP, HL and HPL diets for 8 weeks, referred to as 8WF-C, 8WF-HP, 8WF-HL and 8WF-HPL, respectively. Weight gain and specific growth rate of fish in 9WF-HP, 9WF-HPL, 8WF-HP and 8WF-HPL treatments were higher than those of fish in 9WF-HL and 8WF-HL treatments. Feed efficiency of fish in 8WF-HP treatment was higher than that of fish in 9WF-C, 9WF-HL and 8WF-HL treatments. Protein efficiency ratio of fish in 10WF-C, 8WF-C, 8WF-HP and 8WF-HPL treatments was higher that that of fish in 9WF-HL and 8WF-HL treatments. Juvenile olive flounder subjected to 2-week feed deprivation could achieve full compensatory growth with dietary supplementation of protein or combined high protein and high lipid.