• Journal of the Korea Institute of Building Construction
• /
• v.18 no.4
• /
• pp.321-327
• /
• 2018

Blast furnace slag has been actively used as a substitute for cement in the construction field with high value-added through resource recycling research. However, most of the slag cannot find a clear recycling purpose. This is because some slags contain unstable materials and are used for road-use asphalt and embankment, which are low value-added materials. Electric arc furnace reduction slag(ERS) has been reported to contain a large amount of unstable free CaO due to deoxidation and component adjustment. In this study, free CaO of ERS which is generated in Korean steelmakers is quantitatively evaluated by using ethylene glycol method. As a result of free CaO quantitative evaluation of ERS, it was confirmed that there is a big difference according to the location of each field. In addition, ERS generally existed in powder form as undifferentiated characteristics, but it was confirmed that free CaO content was different due to hydration product in aggregate form due to water treatment. In addition, free CaO is an amorphous material and its crystallization characteristics are different due to the influence of temperature when it is cooled. ERS requires a long-term aging period as it contains a lot of free CaO.

• Korean journal of communication and information
• /
• v.46
• /
• pp.387-419
• /
• 2009

The concept of strategic group is defined as an aggregate of corporations utilizing similar strategies with similar resources. It becomes a kinds of contact point in the middle of corporation and industry between the industrial organization theory and the strategic management theory. This study tried to apply the strategic group model, which has been a main theory in the management studies, to program providing industry in Korea. This study shed lights upon research problems such as number of strategic groups, differences of strategic variables among the groups, finally differential performances according to strategic groups. 40 commercial broadcasting companies were analyzed to find answers. 9 strategic groups were drawn as a result of cluster analysis. Major variables which contribute to making groups were operating efficiency(4.05), pricing(3.83), size(number of system operator, 3.56), reliance on license revenue(2.58), horizontal integration(number of sister networks, 2.16) in order. An analysis of variance between performance variables has shown statistical significance regarding total net revenue per subscriber, however, insignificances statistically in regards to ratio of operating profit to net sales, cash Abstracts 687 flow ratio. Some studies in the past insisted that history variable played an important role to classifying strategic groups. However, this study found that the history didn't exert significant influence on either the group classification itself or performance.

• Journal of the Korea Concrete Institute
• /
• v.26 no.6
• /
• pp.731-739
• /
• 2014

This paper describes the evaluation of the impact performance of steel fiber-reinforced concrete based on high-velocity impact experiments using hard spherical balls. In this experimental study, panel specimens with panel thickness to ball diameter (h/d) ratios of 3.5 or less were tested with variables of steel fiber volume fraction, panel thickness, impact velocity, and aggregate size. Test results were compared with each other to evaluate the impact resistance. The results showed that the percentage of weight and surface loss decreased as the steel volume fraction increased. However, the penetration depth increased with up to steel fiber volume fraction of 1.5%. Particularly the results of specimens with 20 mm aggregates showed poorer performance than those with 8 mm aggregates. The results also confirmed that the impact performance prediction formulas are conservative with (h/d) ratios of 3.5 or less. Despite the conservative predictions, the modified NDRC formula and ACE formula predict the impact performance more consistently than the Hughes formula.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.8 no.3
• /
• pp.51-58
• /
• 2008

Development of a new design guide which is based on empirical-mechanistic concept for pavement design is in action. It is called AASHTO 2002 Design Guide in USA and the KPRP(Korean Pavement Research Project) in Korea. The material characteristic of hot mix asphalt is a key role in the design guide. Therefore it is urgent to get a proper materials database, especially the dynamic modulus of hot mix asphalt. In this research, dynamic modulus test, which is based on aged asphalt binder, has been carried out and proposed the predicted equation of dynamic modulus. Nine different hot mix asphalt with three different asphalt binder have been used for the dynamic modulus test. Short-term aging, which is covers the time for the production of asphalt plant, transportation, lay-down, and compaction, can be simulated at $135^{\circ}C$ with 2 hour curing. Long-term aging has been carried out for a performance period of asphalt pavement. The dynamic modulus of asphalt pavement increases with aging time. As the nominal aggregate size increases, the change of dynamic modulus is not big.

• Korean Journal of Soil Science and Fertilizer
• /
• v.32 no.4
• /
• pp.327-332
• /
• 1999

Manganese (Mn) oxides in soils have been a research subject since they react with nutrients and contaminants and Mn itself is an essential element for plant growth. Birnessite was synthesized in the presence of iron (Fe) in the precipitating solution. Influence of Fe, one of common elements in soils, on crytallinity, morphology, and chemical reactivity of birnessite was examined using X-ray diffraction (XRD), electron microscope, canon exchange capacity (CEC), and chromium (Cr) oxidation capacity. With increasing Fe concentration in the precipitating solution, crystallinity and crystal size decreased. Hexagonal plates of the birnessites formed at low Fe concentration were dominant and replaced more and more by aggregate of small particles with increasing the Fe concentration. There is no significant change in CEC with changing the Fe concentration. Chromium oxidation capacity of the birnessite increased with increasing the Fe concentration. Iron in the precipitating solution poisoned crystal growth by adsorption on the surface and increased nucleation. Since Fe is a common constituent under pedogenic environment and Fe and Mn oxides often coexist in Mn oxide nodules, the birnessite with small particle, low crystallinity, and high chemical reactivity is the form which is more likely to be formed in soils. The high CEC ($140cmol_ckg^{-1}$) and oxidation capacity of birnessite indicate that birnessite can be used in environment and agriculture.

• Journal of Korea Port Economic Association
• /
• v.33 no.3
• /
• pp.35-52
• /
• 2017

Interest and demand in heavy cargo logistics is increasing and becoming more diverse as economic scales have expanded and manufacturing activity has increased. Although cargo moves via maritime and/or land transportation, there is currently insufficient research on the actual condition of heavy cargo logistics. The purpose of this study is to carry out an in-depth analysis of heavy cargo laws, systems, logistics patterns, and current transportation status. By proposing measures to solve existing problems, this study aims to make an important and ongoing contribution to the scarcely studied field of heavy cargo logistics. The result of regression analysis on the main seven factors show that transportation frequency and law/system structure have a positive effect on working conditions. Furthermore, the result of correlation analysis on the main seven factors show that the cargo weight variable is highly positively correlated with cargo size. Also, the working conditions variable is highly positively correlated with the law/system structure. Detailed proposal measures to solve existing problems are summarized as follows. First, it is necessary to establish a clear concept of heavy cargo as numerous existing definitions differ. Second, laws and provisions relating to maritime and land transportation of heavy cargo need to be established and consolidated as current applicable legislation is insufficient. Third, the classification system for heavy cargo transportation needs improvement. Fourth, it is necessary to improve transportation performance statistics and the aggregate criteria system. Finally, the management system of heavy cargo also needs improvement.

• Journal of Korea Technology Innovation Society
• /
• v.10 no.3
• /
• pp.509-530
• /
• 2007

This paper examined the relationship between innovation and firm performance by integrating industry competitive context and firm-level knowledge constructs. After controlling for firm site, age, and the presence of a union, cross-section analysis of survey data from 1,419 medium sized manufacturing firms yielded following findings. The first was the expected positive relationship between firm-level innovation and firm knowledge and also industry dynamism, as measured by the intensity of industry-level R&D. This results indicate that industries with greater aggregate levels of R&D intensity are home to higher rates of firm-level innovative activity and managers must increase their numbers of technical staff and the level of training. But the interaction between firm knowledge and industry dynamism was non-significant. Second, innovation was not significantly related to firm performance, as measured by revenue growth. This relationship was not moderated by industry dynamism and firm level knowledge. In high and low technology sectors, the relationship between innovation and performance was non-significant, consistent with the full-sample analysis. The results suggest that the effects of firm-level knowledge assets and investments in training don't work in different ways in different industry settings. This research used three control variables to analyze innovation and firm performance. Firm age was negatively associated with firm performance and did not significantly predict innovation. Firm size was positively associated with innovation and performance in the low-technology sector. The presence of a labor union was not a significant with respect to innovation.

• Resources Recycling
• /
• v.30 no.6
• /
• pp.19-27
• /
• 2021

Electrically conductive mortar used in industrial carbon material byproducts was manufactured and analyzed in this study. The contents of the carbon material and mixed water were controlled, and the distance between electrodes was set to 0.42 m and 0.88 m. The carbon material was graphite with a layered structure. The carbon material was used as fine powder and aggregate substitutes according to particle size. The average particle sizes of each materials were 18.4㎛ and 546.1 ㎛ and the electrical conductivities were 62.3 S/m and 32.5 S/m, respectively. To maintain similar mortar flow in each sample, the water content was increased with increasing carbon material, and accordingly, the porosity showed an increasing trend. When electrode distance of the mortar (week 6) was 0.42 m, the voltage-current values were 342 V-1.48 A (S20) and 349 V-1.44 A (S30). For electrode distance of 0.88 m, these values were 513 V-0.98 A (S20) and 500 V-1.01 A (S30). The exothermic properties improved with increasing carbon material content and decreasing electrode distance.

• Journal of Aquaculture
• /
• v.11 no.1
• /
• pp.49-58
• /
• 1998

The spawning behavior and early life history of the Korean aucha perch, Coreoperca herzi were studied. The eggs were spawned in a one-layer mass, hanging from the underside of a largy stone and guarded by one male. According to the considerable size difference os eggs in the individual ovaries, it was concluded that they spawns several times within a spawning season of May~June. The ripe eggs were demersal and adhesive, and their diameter were 2.60~3.04mm with several oil globule of 0.10~0.64mm. Hatching in the tank with $19.0{\pm}1.0^{\circ}C.$ in men water temperature started from the 380 hours after fertilization. Newly-hatched larvae were measured 6.45~7.34mm in total length (TL, mean : 6.85mm), and mouth and anus were open. Melanophores were present on the head, around the yolk, and on the dorsal part of the abdominal region. 3 days old larvae were measured 7.00~7.40mm in TL (mean : 7.25mm), and they fed Daphnia sp. and Brachionus plicatilis actively. 6 days old larvae transformed to postlarval stage and they were 7.94~10.10mm in TL (mean : 9.00mm). As yolk sac were nearly absorbed, the caudal notochord flex at 45. Aggregate numbers of all fin rays were completed at over 16.90~19.80mm in TL (30 days after hatching), at which time the larvae reached the juvenile stage. In fifty days old larvae(24.60~27.10mm in TL) were similar in body form, lateral line and color to adult.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.6
• /
• pp.101-108
• /
• 2003

Small-scale models have been frequently used for experimental evaluation of seismic performance because of limited testing facilities and economic reasons. However, there are not enough studies on similitude law for analogizing prototype structures accurately with small-scale models, although conventional similitude law based on geometry is not well consistent in the inelastic seismic behavior. When fabricating prototype and small-scale model of reinforced concrete structures by using the same material. added mass is demanded from a volumetric change and scale factor could be limited due to size of aggregate. Therefore, it is desirable that different material is used for small-scale models. Thus, a modified similitude law could be derived depending on geometric scale factor and equivalent modulus ratio. In this study, compressive strength tests are conducted to analyze equivalent modulus ratio of micro-concrete to normal-concrete. Equivalent modulus ratios are divided into multi phases, which are based on ultimate strain level. Therefore, an algorithm adaptable to the pseudodynamic test. considering equivalent multi-phase similitude law based on seismic damage levels, is developed. In addition, prior to the experiment. it is verified numerically if the algorithm is applicable to the pseudodynamic test.