• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.39-46
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• 2015

In this paper, a gas sensor using a modified $90^{\circ}$ hybrid coupler structure with conducting polymer which operates at 2.4 GHz is represented. Conducting polymers are used to the gas sensing material in proposed sensors. The conducting polymer varies its electrical property, such as work function and conductivity corresponding to the certain gas. To verify this variation of electrical property of conducting polymer at microwave frequencies, the conducting polymer is incorporated with the $90^{\circ}$ hybrid coupler structure, and this proposed sensor operates as reflection type variable attenuator and variable phase shifter. The conducting polymer is employed as impedence-variable transmission lines that cause a impedance mismatching between the general transmission line and conducting polymer. The experiment was conducted with 100 ppm ethanol gas at temperature of $28^{\circ}C$ and relative humidity of 85 %. As a result, the amplitude deviation of $S_{21}$ is 0.13 dB and the frequency satisfying ${\angle}S_{21}=360^{\circ}$ is shifted about 2.875 MHz.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.163-176
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• 2012

Effective porosity has been measured for cement specimen as a function of vacuum time and pressure in the vacuum saturation process. Six cement specimen are used; three of them are made of the same ratio of cement and sand, the other three are 100% cement mortar, of which average porosity is about 25% and 40%, respectively. Using the 6 samples, measured effective porosities are compared and examined with 5 different vacuum pressures (2, 4, 6, 8, 10 torr) and times (20, 40, 60, 80, 100 minute), respectively. Comparing measured effective porosity from experiments when vacuum time varies from 100 minute to 20 minute with 20 minute step and vacuum pressure is fixed to 10, 6, and 2 torr, average deviation decreases as 0.6, 0.5, and 0.2% respectively. Comparing measured effective porosity from experiments when vacuum pressure varies from 2 torr to 10 torr with 2 torr step and vacuum time is fixed to 100, 60, and 20 minute, average deviation increases as vacuum time decreases. These results can be a background of suggested method of ISRM that describes the vacuum time longer than 60 minute and vacuum pressure higher than 6 torr. In this study, only qualitative discussion can be possible for the effects on the effective porosity by decreasing 20 minute vacuuming time at the same pressure or by decreasing 2 torr of vacuum pressure at the same vacuum time. This is because the sample could not reached to perfectly dried condition even though the sample were dried at $105^{\circ}C$ and following the ISRM suggested method, so that initial water content could not be the same at each experiment.

• Korean Journal of Agricultural Science
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• v.13 no.2
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• pp.255-264
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• 1986

The objectives of this study were to examine the viscoelastic behaviour of stem samples of rice in force-relaxation and rheological model to represent its relaxation behaviour, and to study the effects of rate of deformation and initial deformation on the relaxation time. The results were as follows; 1. In the process of loading and unloading, there is any plastic deformation so called elasto-plastic hysterisis. 2. Loading and unloading of stem of rice for several cycles has also shown the reduction of plastic or residual deformation and work hardening. 3. The relaxation behaviour of stem of rice in compression may be described by a generalized Maxwell model consisting of three Maxwell units in parallel. The rheological equation of such a model is given as $$F(t)=C_1e^{{-t/{\tau}}_1}+C_2e^{{-t/{\tau}}_2}+C_3e^{{-t/{\tau}}_3}$$ 4. Force relaxation always increased with increasing rates of deformation and initial deformation.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.9-18
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• 1986

MNDO and STO-3G calculations were performed to determine relative stabilities of rotamers for ${\alpha}$-substituted acetones, $CH_2XCOCH_3$, X = F, Cl, OH, SH, and $NH_2$. It was found that rotamers corresponding to gauche forms are preferred for all the ${\alpha}$-substituents except for X = F and NH$_2$, for which the cis forms were the preferred ones. The stability of gauche form was dictated by the stabilizing two-orbital-two-electron interaction ${\sigma}_{cx}$-${\pi}_{co}^*$, operating uniquely in the gauche form due to the substantial vicinal overlap and energy gap narrowing between ${\sigma}_{cx}$ and ${\pi}_{co}^*$ orbitals. The energy gap narrowing was caused by the lowering of ${\pi}_{co}^*$ level due to the hyperconjugative ${\sigma}_{cx}^*$-${\pi}_{co}^*$ interactions; the red shift in the n-${\pi}^*$ transition was another effect of the relatively large ${\sigma}_{cx}^*$-${\pi}_{co}^*$ splitting. Various ${\sigma}-{\pi}$ interactions in the gauche form were found to be stronger in the third-row hetero atom system, X = Cl and SH. Interactions between nonbonding orbital on N, $n_N$ and vicinal C-C ${\sigma}$ bond were shown to be stronger in the trans than in the cis orientation.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.363-377
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• 2002

The purpose of this study was to improve the problems of the voltaic cell described in the science textbooks of secondary schools. For this purpose, the contents of science textbooks which are related to the voltaic cell were analyzed and the problems which were not explained clearly by theorems were tried to be explained by experiments, and lastly sug-gestions were made toward the improvements regarding the voltaic cell in the science textbooks. The findings are that there are problems on the ways of ensuring whether the voltaic cell operates properly as a chemical battery, on the explanation of why the hydrogen bubbles form at the zinc electrode, on the cell potential, on the unification of the electrode terminology used, and on the mention of the current. Solutions to the problems except the cell potential were suggested. According to the experiment, the theoretical potential was calculated by considering the potentials of redox reactions at the two electrodes of the cell and by taking into account the characteristics of the electrodes such as the work function, ionization energy, stan-dard reduction potential, and electronegativity.The cell potential of the voltaic cell is explained by several factors. In the improved version of the textbook's introduction section to the voltaic cell, it is necessary to describe the voltaic cell his-torically.For the conceptual section, it should be explained in terms of the Daniel cell.

• Korean Journal of Plant Tissue Culture
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• v.26 no.2
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• pp.115-119
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• 1999

The single node cuttings of sweet potato (cv. Mokpo #29) plantlets maintained in vitro were cultured with (MF+) or without membrane filter (MF-) under photomixotrophic (PM), hetrotrophic (HT) and autotrophic (AT) conditions. Shoot length was the greatest (11.9cm) in 3$0^{\circ}C$ (HT) treatment and it was the shortest (3.4 cm) in $25^{\circ}C$ (PM) treatment. Nodal explants cultured in 3$0^{\circ}C$ treatment looked more vigorous than those of $25^{\circ}C$ in appearance, and node number was the greatest (10.5 per plantlet) among the treatments. But plantlets grew in 3$0^{\circ}C$ (HT) treatment were observed all overgrown. The size in leaf area was about 2 times greater and shoot length was about 2 times shorter in PM than in HT condition. Percent dry matter of shoots was 5.9% (HT) and 7.4% (PM) in $25^{\circ}C$ treatment and 6.1% (HT) and 7.4% (PM) in 3$0^{\circ}C$ treatment. Plantlets cultured in the MF+ treatments were less succulent than those cultured in the MF- treatment. Vitrified plantlets were examinated 14.8% (both $25^{\circ}C$ and 3$0^{\circ}C$) in PM condition and 22.2% ($25^{\circ}C$) and 31.5% (3$0^{\circ}C$) in HT condition. Sucrose was necessary for the survival of in vitro plantlets. In the sucrose-free medium, explants cultured in the MF- had turned yellow and were dead after 30 days of culture. But explants cultured in the MF+ were alive and produced plantlets with shoot and root (AT). On the other hand, the survival of explants on the MS basal medium (sucrose-free and hormone-free) depended entirely upon the MF attachment.

• The KIPS Transactions:PartD
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• v.19D no.1
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• pp.1-14
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• 2012

As the size of the data warehouse is large, the selection of indices on the data warehouse affects the efficiency of the query processing of the data warehouse. Indices induce the lower query processing cost, but they occupy the large storage areas and induce the index maintenance cost which are accompanied by database updates. The bitmap join indices are well applied when we optimize the star join queries which join a fact table and many dimension tables and the selection on dimension tables in data warehouses. Though the bitmap join indices with the binary representations induce the lower storage cost, the task to select the indexing attributes among the huge candidate attributes which are generated is difficult. The processes of index selection are to reduce the number of candidate attributes to be indexed and then select the indexing attributes. In this paper on bitmap join index selection problem we reduce the number of candidate attributes by the data mining techniques. Compared to the existing techniques which reduce the number of candidate attributes by the frequencies of attributes we consider the frequencies of attributes and the size of dimension tables and the size of the tuples of the dimension tables and the page size of disk. We use the mining of the frequent itemsets as mining techniques and reduce the great number of candidate attributes. We make the bitmap join indices which have the least costs and the least storage area adapted to storage constraints by using the cost functions applied to the bitmap join indices of the candidate attributes. We compare the existing techniques and ours and analyze them in order to evaluate the efficiencies of ours.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.149-159
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• 2006

This research is a development of useful S/W program for real industry about optimal product scheduling in real plant for manufacturing polymer products. For this, we used a fine model with total amount of losses in weight(ton) as an objective for optimal scheduling and a genetic algorithm for optimization in this factory they manufacture three different products. Major products are A and B but the product which can be process in the period of products change over. They also sells them as a chap product in market. The major products have several types of packing process-bulk, pack for domestic market, pack for export. The demands of product with each packing type are increased, and frequently they failed keep the deadline for sail. Based on realistic production situation, we composed a fine modeling for optimal scheduling. And we also develop a S/W program for optimal scheduling which can be used by non-specialist in scheduling problem. We used a modified genetic algorithm and it gave us a better solution in process. We can have a result of reducing the total amount of losses in weight by half compared with the losses when existing production schedule.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.1
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• pp.9-16
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• 2017

As a preliminary study of enter or leaving traffic patterns of the Korea main port, port Management Information System (Port-MIS) data was used to check the volume of vessels entering and leaving the port of Busan, and three consecutive days from each seasons were selected for study. Selected 12-day General Information Center on Maritime Safety & Security (GICOMS) data was also used to analyze the traffic pattern in the main traffic lane of Busan port for dangerous goods carrier. Also, the distance between dangerous goods carriers and Oryukdo breakwater of east breakwater in the main traffic lane was analyzed. Collision probability was estimated using the cumulative probability distribution function of the normal distribution for the maritime traffic safety audit scheme based on the assumption that a ship's trajectory has a normal distribution for a section of the route. However, in case of entry or leaving thorough the Oryukdo breakwater and entry thorough the east breakwater, ship's sailing trajectories were revealed not to follow a normal distribution via regularity testing using a KS-test and SW-test. Especially in the north port, the tendency of the right side of the ship to pass was remarkable. It is desirable to develop a traffic model suitable for the characteristics of the port rather than to apply general traffic theories, and to apply this model to a maritime traffic safety diagnosis, so further research is needed.

• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.137-147
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• 2008

Fault rupture directivity of the Odaesan earthquake, which was inferred to be the main cause of the high PGAvalue (> 0.1 g) unusually observed at the near-source region, was analyzed by using the data from the nearby (R < 100 km) dense seismic stations. The Boatwright's method (2007) was adopted for this purpose in which the azimuth and takeoff angle of the unilateral rupture directivity function could be estimated based on the relative peak ground-motions of seismic stations resulting from the nature of the rupture directivity. In this study, the approximate values of the relative peak ground-motions was derived from the difference between the log residuals of the point-source spectral model (Boore, 2003) for the main and secondary events based on the Random Vibration Theory. In this derivation, the spectral difference for a frequency range between the source corner frequencies of main and secondary events was considered to reflect only the effect of the fault directivity. The inversion result of the model parameters for the fault directivity function showed that the fault-plane of NWW-SEE direction dipping steeply to the North with high rupture velocity near upward in SE direction is responsible for the observed high level of ground-motion at the near-source region.