• Journal of the Korean Society for Railway
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• v.14 no.3
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• pp.262-270
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• 2011

Track support stiffness which affected track maintenance and riding comfort had a big effect on the track and train. Also, track support stiffness of the track design which was based on theory differs from track support stiffness of the track generated on the field. Track support stiffness was generated by several factors such as dynamic wheel loads, vertical displacement of track, and stress at rail bottom on the field test. With the results of the field test was compared with theoretical value. This paper analyzed that track support stiffness of ballast depended on condition of ballast, and support stiffness of concrete track also depended on the characteristic of track structures such as, normal elastic fastening system, rail floating system and sleeper floating system. However, on the ballast and concrete track, the designed track support stiffness was underestimated less than the measured track support stiffness. When the track condition was estimated on service line, it would not consider the track condition on the field. Therefore, this study proposed the various track type and the range of track support stiffness based on the experimental test.

• Journal of the Korean GEO-environmental Society
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• v.19 no.9
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• pp.13-19
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• 2018

Recently, there have been various problems aroused on the domestic infrastructures as the domestic cities become old. Accordingly, the national concerns grow on the urban railway and the related structures, which brings the national interests are brought on the research on the maintenance and rehabilitation of the old infrastructures. The underground structure of urban railway are checked with the strain gages or fiber brag grating (FBG) sensors on the railway. However, these methods are known to have resolution limitations on the investigations of the specified abnormal section. Therefore, the applicability of the Brillouin Optical Correlation Domain Analysis (BOCDA) based distributed fiber optic sensor system on the railway was evaluated in this study. The constructed BOCDA fiber optic sensor system shows high resolution of 10, 20, 50, 100 cm and capability of continuous monitoring on overall or specified section within 2 km range. The applicability evaluation was performed on the 250 m distribution of fiber optic sensors abandoned railway for continuous monitoring. The applicability of the system on the specified area was evaluated with wheel load testing. As a result, data loss tends to increase with the reduction of spatial resolution from 1.0 m to 0.1 m. Even though the measuring speed is reduced with lower spatial resolution, data accuracy increases on the location and deformation. The system can be applicable to various structures if the proper distribution method is invented later.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.831-838
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• 2006

An experimental/analytic study has been conducted to understand the adverse effects of low vehicle speed, high axle load and high tire pressure on the performance of asphalt pavements. Of 33 asphalt sections at KHC test road, two sections having different base layer thickness (180 mm versus 280 mm) are adopted for rollover tests. During the test, a standard three-axle dump truck maintains a steady state condition as moving along the wheel path of a passing lane, and lateral offsets and real travel speed are measured with a laser-based wandering system. Test results suggest that vehicle speed affects both longitudinal and transverse strains at the bottom of asphalt layer (290 mm and 390 mm below the surface), and even slightly influences the measured vertical stresses at the top of subbase and subgrade due to the dynamic effect of rolling vehicle. Since the anisotropic nature of asphalt-aggregate mixtures, the difference between longitudinal and transverse strains appears prominent throughout the measurements. As the thickness of asphalt pavement increases, the measured lateral strains become larger than its corresponding longitudinal strains. Over the limited testing conditions, it is concluded that higher axle weight and higher tire pressures induce more strains and vertical stresses, leading to a premature deterioration of pavements. Finally, a layered elastic analysis overestimates the maximum strains measured under the 1st axle load, while underestimating the maximum vertical stress in both pavement sections.

• Journal of Conservation Science
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• v.32 no.2
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• pp.273-291
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• 2016

Some ceramic artifacts representing time-wise from comb pattern pottery in the Neolithic Age to white porcelain in Joseon Dynasty were selected from 7 sites in the north and south area of Charyeong Mountain Range in order to making techniques interpretation and development process of ancient ceramics through physicochemical and mineralogical quantitative analysis. Studied pottery samples in the Prehistoric times showed trace of ring piling in soft-type, and pottery in the Three Kingdoms Period had both soft and hard-type but kettle-ware and storage-ware were made with ring piling, but table-ware was made by wheel spinning. Different from pottery after the Three Kingdom Period when refinement of source clay was high, pottery in the Neolithic Age and in the Bronze Age exhibited highly mineral content in sandy source clay, which showed a lot of larger temper than source clay. Groundmass of celadon and white porcelain almost did not reveal primary minerals but had high content of minerals by high temperature firing. Ceramic samples showed some different in major and minor elements according to sites irrespective of times. Geochemical behaviors are very similar indicating similar basic characteristics of source clay. However, loss-on-ignition showed 0.01 to 12.59wt.% range with a large deviation but it rapidly decreased moving from the Prehistoric times to the Three Kingdom Period. They have correlation with the weight loss due to firings, according to burning degree of source clay and detection of high temperature minerals, estimated firing temperatures are classified into 5 groups. Pottery in the Neolithic Age and in the Bronze Age belongs from 750 to $850^{\circ}C$ group; pottery in the Three Kingdom Period are variously found in 750 to $1,100^{\circ}C$ range of firing temperature; and it is believed celadon and white porcelain were baked in high temperature of 1,150 to $1,250^{\circ}C$. It seems difference between refinement of source clay and firing temperature based on production times resulted from change in raw material supply and firing method pursuant to development of production skill. However, there was difference in production methods even at the same period and it is thought that they were utilized according to use purpose and needs instead of evolved development simply to one direction.

• Journal of Distribution Science
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• v.9 no.1
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• pp.29-38
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• 2011

Since a distribution market was opened in 1993 after the conclusion of the Uruguay Round (UR), various new businesses emerged in the Korean retail industry, such as convenience shops, supermarkets, specialty stores, non-store marketing methods, and cyber shopping malls, in addition to traditional markets and department stores. Competition among these retail businesses has intensified. According to the National Statistical Office (NSO), the growth rate of the total retail industry has shown a 32% increase in the past 5 years. While department stores, supermarkets, specialty stores, and other non-store retailing venues have shown signs of stagnation at a growth rate of 20-30%, which is similar to the growth rate of the entire retail industry, convenience shops and non-store marketing have shown 60-70% growth over the same period. By comparison, the growth rate of cyber shopping malls has nearly tripled. When applying development aspects of retail businesses through the competition to the retail life cycle, mom-and-pop stores and traditional markets have already entered the decline phase as specialty stores reach their maturity phase and demonstrate their limit of growth. Department stores are now in the latter part of the growth phase, which is still considered to have some growth potential. Big super markets are still in the early part of their growth stage although they were introduced 20 years ago. Meanwhile, retail businesses such as convenience stores, supermarkets, mail order houses, and warehouse stores are entering the middle growth phase and are expected to continue with their quantitative growth. At a time when most retail businesses in Korea are in a state of development or in the full growth stage, what kind of new innovative retailing will appear and develop? Moreover, what growth engine will drive it? This study analyzes the appearance of innovative retailing and its development process by establishing a discussable consumer's choice model through the interlocking mutual behavior of differentiated competitiveness and consumers' choice based on an awareness of this issue. The analysis of the results of this study can be summarized as follows. First, if a new vacuum zone emerges at the retail market level, innovative retailing such as low price/low service or high price/high service will emerge simultaneously. Second, if the number of new businesses in the vacuum zone increases, this will create competitiveness among the businesses, and each retailer will develop raising of level. Third, if a new business that raises the level develops, competition between the new and the existing retailer will occur, and an assimilation process between the existing retailing and the new retailing will be unfolded. Fourth, each retailing will promote distribution innovations in order to break the frontier of the existing distribution technology, and other retailing will follow the innovator. On the basis of an analysis of the abovementioned results, this study presents the following three suggestions. First, responding to the consumer's decision-making process on the attributes of retail shops that promote differentiation in strategies, this study established a consumer's choice model that can be discussed in relation to changes in market share. Second, this study provided an analysis of the emerging and developmental processes of innovative retail businesses using a more precise logical structure on the basis of the consumer's choice model described in this study. Third, the development process of retail businesses discussed in this study presented retailing solutions regarding management aspects on how to compose a strong retail mix that can help retail businesses gain competitive advantages in the market.

• KSBB Journal
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• v.10 no.5
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• pp.561-567
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• 1995

Using superoxide dismutase (SOD)-deficient mutants of Saccharomyces cerevisiae, the oxygen toxicity induced by paraquat was studied. In aerobic culture condition, yeasts lacking MnSOD (milochondrial SOD) showed more significant growth retardation than CuZnSOD (cytoplasmic SOD)-deficient yeasts. However, not so big differences in growth pattern of those mutants compared with wild type were observed under anaerobic condition. When exposed to paraquat, the growth of yeasts lacking CuZnSOD was severely affected by higher than 0.01mM of paraquat in culture medium. By the analysis of several cellular components ivolved in free radical generating and scavenging system, it was found that, under aerobic condition, the content of lipid peroxides in cell membrane as well as cellular activity of glutathion peroxidase of CuZnSOD-deficient mutants was increased in the presence of paraquat, although significant decrease of catalase activity was observed in those stratns. In MnSOD-deficient yeast, however, increment in cellular activity of glutathion peroxldase and catalase by paraquat was observed without any deterioration of membrane lipid. It implies that the lack of mitochondrial SOD could be compensated by both of glutathion peroxldase and catalase, but that only glutathion peroxidase might act for CuZnSOD in cytoplasm. In contrast, all of SOD-deficient mutants showed a significant decrease in catalase activity, but slight increase in the activities of glutathion peroxidase, when cultivated anaerobically in the medium containing paraquat. Nevertheless, any significant changes of lipid peroxides in cell membranes were not observed during anaerobic cultivation of SOD-deficient mutants. It suggests that a little amount of free radicals generated by paraquat under anaerobic condition could be sufficiently overcome by glutathion peroxidase but not by catalase.

• Korean journal of applied entomology
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• v.29 no.4
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• pp.257-268
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• 1990

The regional characteristics in the occurrence of the rice stem borer, Chilo suppressalis (Walker), in Korea, were examined by analyzing the light trap data obtained from 39 locations during the years of 1965-1988, and some ecological significance of the overwintering larval populations collected from the four locations where some of the typical ecological-race have been known, the results obtained are as follows; The total number of the moths have decreased greatly throughout the nation since 1970. The decrease in the total number of moths related with those in the spring moth but not in the summer moths, and suggested that the changes in the rice production systems have effected significantly on the second generation of the insect. The variations between the regions had been gret in 1960's, decreasing phase in 1970's and increasing phase in loast decade. The overall average of 50% emergence dates have shifted earlier in both moths, and the changes were different considerably with the regions as wheel as in generations. When the overwintered larvae were incubated at $25^{\circ}C$ and RH of 90%, the average mortalities were 21.07% for Suweon, 43.06% for Iri, 63.51% for Jinju, 27.04% for Gwangju. When the overwintered larvae were incubated at $25^{\circ}C$ and RH of 90%, the average mortalities were different with the body weight; 45.44% for the larvae of less than 39 mg, 37.61% for 40-49 mg, 37.28% for 50-59 mg, 30.17% for greater than 60 mg. When the overwintered larvae wee incubated at $25^{\circ}C$, post-diapause larval development periods of body weight classes were 18.6$\pm$1.2 days for the larvae of less than 39 mg, 20.4$\pm$3.3 days for 40-49 mg, 21.4$\pm$3.2 days for 50-59 mg, 21.8$\pm$3.2 days for grater than 60 mg, and only the larvae of less than 39 mg, body weight class less than 39 mg was found statistically different in post-diapause larval development periods. From these results, the changes in the cultural practice of the rice have effected on the ecological pattern of the rice stem borer, and the effects seemed to be different with the generations, and with the regions where the different ecological races are distributing.

• Journal of Biosystems Engineering
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• v.3 no.1
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• pp.1-19
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• 1978

Power tiller is a major unit of agricultural machinery being used on farms in Korea. About 180.000 units are introduced by 1977 and the demand for power tiller is continuously increasing as the farm mechanization progress. Major farming operations done by power tiller are the tillage, pumping, spraying, threshing, and hauling by exchanging the corresponding implements. In addition to their use on a relatively mild slope ground at present, it is also expected that many of power tillers could be operated on much inclined land to be developed by upland enlargement programmed. Therefore, research should be undertaken to solve many problems related to an effective untilization of power tillers on slope ground. The major objective of this study was to find out the travelling and tractive characteristics of power tillers being operated on general slope ground.In order to find out the critical travelling velocity and stability limit of slope ground for the side sliding and the dynamic side overturn of the tiller and tiller-trailer system, the mathematical model was developed based on a simplified physical model. The results analyzed through the model may be summarized as follows; (1) In case of no collision with an obstacle on ground, the equation of the dynamic side overturn developed was: $$\sum_n^{i=1}W_ia_s(cos\alpha cos\phi-{\frac {C_1V^2sin\phi}{gRcos\beta})-I_{AB}\frac {v^2}{Rr}}=0$$ In case of collision with an obstacle on ground, the equation was: $$\sum_n^{i=1}W_ia_s\{cos\alpha(1-sin\phi_1)-{\frac {C_1V^2sin\phi}{gRcos\beta}\}-\frac {1}{2}I_{TP} \( {\frac {2kV_2} {d_1+d_2}\)-I_{AB}{\frac{V^2}{Rr}} \( \frac {\pi}{2}-\frac {\pi}{180}\phi_2 \} = 0 $$ (2) As the angle of steering direction was increased, the critical travelling veloc\ulcornerities of side sliding and dynamic side overturn were decreased. (3) The critical travelling velocity was influenced by both the side slope angle .and the direct angle. In case of no collision with an obstacle, the critical velocity $V_c$ was 2.76-4.83m/sec at $\alpha=0^\circ$, $\beta=20^\circ$ ; and in case of collision with an obstacle, the critical velocity $V_{cc}$ was 1.39-1.5m/sec at $\alpha=0^\circ$, $\beta=20^\circ$ (4) In case of no collision with an obstacle, the dynamic side overturn was stimu\ulcornerlated by the carrying load but in case of collision with an obstacle, the danger of the dynamic side overturn was decreased by the carrying load. (5) When the system travels downward with the first set of high speed the limit {)f slope angle of side sliding was $\beta=5^\circ-10^\circ$ and when travels upward with the first set of high speed, the limit of angle of side sliding was $\beta=10^\circ-17.4^\circ$ (6) In case of running downward with the first set of high speed and collision with an obstacle, the limit of slope angle of the dynamic side overturn was = $12^\circ-17^\circ$ and in case of running upward with the first set of high speed and collision <>f upper wheels with an obstacle, the limit of slope angle of dynamic side overturn collision of upper wheels against an obstacle was $\beta=22^\circ-33^\circ$ at $\alpha=0^\circ -17.4^\circ$, respectively. (7) In case of running up and downward with the first set of high speed and no collision with an obstacle, the limit of slope angle of dynamic side overturn was $\beta=30^\circ-35^\circ$ (8) When the power tiller without implement attached travels up and down on the general slope ground with first set of high speed, the limit of slope angle of dynamic side overturn was $\beta=32^\circ-39^\circ$ in case of no collision with an obstacle, and $\beta=11^\circ-22^\circ$ in case of collision with an obstacle, respectively.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.107-115
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• 2018

PURPOSES : As the population of the mobility handicapped, who are classified as the disabled, the elderly, pregnant women, children, etc., has increased, the voices for guaranteeing their rights have been increasing as well. Thus, the design manuals for roads and sidewalks for the mobility handicapped were developed by the local government, such as the Ministry of Land, Transport, and Tourism, in Seoul City. However, according to the 2013 survey results of the Seoul Metropolitan City, the mobility handicapped still feel uncomfortable with the sidewalks, and particularly request for the improvement of the step and slope of the sidewalk curb. Therefore, in this study, we conducted an empirical experimental study to determine the slope of the sidewalk curb and height of the steps considering the mobility handicapped and analyzed whether there is a statistically significant difference. METHODS : The methodology of this study is an empirical experimental one. In the study, five non-disabled people, 10 wheelchair users, and 10 eye patch and stick users walked about 2-3 min on the sidewalk plates of the sloped type (0%, 5%, 6.3%, 8.3%) and stepped type (0 cm, 1 cm, 3 cm, 6 cm), and their human physiological responses, such as the skin temperature, volume of perspiration on forehead and chest, and heart rate, were measured and recorded. After combining the data, we conducted a nonparametric test, ANOVA, or t-test to determine whether there was a statistically significant difference according to each slope and step type. RESULTS : It was found that for the non-disabled, there was no significant difference in human physiological responses according to the slope and steps of the sidewalk. It can be said that the non-disabled do not feel much physiological discomfort while walking. In the case of the sloped sidewalk plate, the heart rate of the wheel chair users increased when the slope was 6.3%. In the case of the eye patch and stick users, the volume of perspiration on the chest increased at a slope of 5.0%. In general, it is judged that a sidewalk with a slope that is less than 5% does not cause a change in the physiological response. In the case of a stepped sidewalk plate, when 0 cm, 1 cm, and 3 cm were compared for wheelchair users, the amount of forehead perspiration increased from 1 cm. Meanwhile, in the case of the eye patch and stick users, when 0 cm and 6 cm were compared, the amount of perspiration on the forehead and chest as well as the heart rate all increased at 6 cm. Taken together, in the case of wheelchair users, a difference was shown when the height of the step of the sidewalk plate was 1 cm, suggesting that installing it at 0 cm does not cause any physiological discomfort. Moreover, in the case of the eye patch and stick users, when comparing only 0 cm and 6 cm, 0 cm was considered to be suitable, as there was a difference in physiological response at 6 cm. CONCLUSIONS : In this study, we set the human physiological responses such as chest skin temperature, amount of perspiration, and heart rate as evaluation items, and our study was considered to be a meaningful experiment that targeted wheelchair users as well as eye patch and stick users. The validity of the evaluation items was confirmed, as the results of human physiological responses were significant. As for the sidewalk design, according to the experiment result, it is considered that differential application should be implemented according to the type of mobility handicap, rather than uniformly applying a sidewalk step of 2 cm and sidewalk slope of 1/25, which are the current legal standards.

• Restorative Dentistry and Endodontics
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• v.27 no.2
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• pp.142-149
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• 2002

Low-viscosity composite resins may produce better sealed margins than stiffer compositions (KempScholte and Davidson, 1988: Crim, 1989). Plowable composites have been recommended for use in Class V cavities but it is also controversial because of its high rates of shrinkage. On the other hand, in the study comparing elastic moduli and leakage, the microfill had the least leakage (Rundle et at. 1997) Furthermore, in the 1996 survey of the Reality Editorial Team, microfills were the clear choice for abfraction lesions. The purpose of this study was to evaluate the microleakage of 6 compostite resins (2 hybrids, 2 microfills, and 2 flowable composites) with and without load cycling. Notch-shaped Class V cavities were prepared on buccal surface of 180 extracted human upper premolars on cementum margin. The teeth were randomly divided into non-load cycling group (group 1) and load cycling group (group 2) of 90 teeth each. The experimental teeth of each group were randomly divided into 6 subgroups of 15 samples. All preparations were etched, and Single bond was applied. Preparations were restored with the following materials (n=15) : hybrid composite resin [Z250(3M Dental Products Inc. St. Paul, USA), Denfil(Vericom, Ahnyang, Korea)], microfill [Heliomolar RO(Vivadent, Schaan, Liechtenstein), Micronew(Bisco Inc. Schaumburg, IL, USA)], and flowable composite［AeliteFlo(Bisco Inc. Schaumburg, IL, USA), Revolution(Kerr Corp. Orange, CA, USA)]. Teeth of group 2 were subjected to occlusal load (100N for 50,000 cycles) using chewing simulator(MTS 858 Mini Bionix II system, MTS Systems Corp. Minn. USA). All samples were coated with nail polish 1mm short of the restoration, placed in 2％ methylene blue for 24 hours, and sectioned with a diamond wheel. Enamel and dentin/cementum margins were analyzed for microleakage on a sclale of 0 (no leakage) to 3 (3/3 of wall). Results were statistically analyzed by Kruscal-Wallis One way analysis, Mann-Whitney U-test, and Student-Newmann-Keuls method. (p = 0.05) Results : 1. There was significantly less microleage in enamel margins than dentinal margins of all groups (p＜0.05) 2. There was no significant between six composite resin in enamel margin of group 1. 3. In dentin margin of group 1, flowable composite had more microleakage than others but not of significant differences. 4. there was no significant difference between six composite resin in enamel margin of group 2. 5. In dentin margin of group 2, the microleakage were R＞A =H=M＞D＞Z. But there was no significant differences. 6. In enamel margins, load cycling did not affect the marginal microleakage in significant degree. 7. In enamel margins, load cycling did affect the marginal microleakage only in Revolution. (p＜0.05).