• Journal of Korean Society of Transportation
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• v.24 no.3 s.89
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• pp.17-27
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• 2006

Car following model is a theory that examines changes of condition and interrelationship of acceleration deceleration. headway, velocity and so on closely based on the hypothesis that the Posterior vehicle always follows the preceding vehicle. Car following mode) which is one of the research fields of microscopic traffic flow was first introduced in 1950s and was in active progress in 1960s. However, due to the limitation of data gathering the research depression was prominent for quite a while and then soon was able to tune back on track with development in global positioning system using satellite and generalization of computer use. Recently, there has been many research studies using reception materials of global Positioning system(GPS). Introducing GPS technology to traffic has made real time tracking of a vehicle position possible. Position information is sequential in terms of time and simultaneous measurement of several vehicles in continuous driving is also practicable. Above research was focused on judging whether it is feasible to overcome the following model research by adopting the GPS reception device that was restrictively proceeded due to the limitation of data gathering. For practical judgment, we measured the accuracy and confidence level of the GPS reception devices material by carrying out a practical experiment. Car following model is also being applied in simulations of traffic flow analysis, but due to the difficulty of estimating parameters the basis of the above result. it is our goal to produce an accurate calibration of car following model's parameters that is suitable in this domestic actuality.

• Journal of Chest Surgery
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• v.31 no.10
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• pp.945-951
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• 1998

Background: Although profound hypothermia with total circulatory arrest(TCA) is a valuable maneuver in cardiac surgery, its applications have been limited due to serious complications, especially cerebral damage. In this study, the possible role of creatinine kinase-BB(CK-BB), an index enzyme of ischemic cerebral damage, was assayed as a parameter for the assessment of the cerebral complications after TCA. Hemoglobin(Hb), ionized calcium(Ca++), and blood glucose levels were also assessed as clinical parameters involved in cerebral damage. Materials and methods: Among patients with congenital heart disease, 18 patients who had been operated on with TCA were randomly selected and divided into two groups: 6 with acyanotic and 12 with cyanotic heart disease. Arterial blood from each patient was collected before and after TCA at scheduled times(15 min., 30 min, 1, 2, 4, 8, and 12hr). The levels of CK-BB, Hb, Ca++, and blood glucose were assessed in each sample. Results: As a whole, correlation between CK-BB level and blood sampling time after TCA was not statistically significant. Also, the difference in the level of CK-BB after TCA was not significant between the acyanotic and cyanotic groups. The levels of Hb and CK-BB correlated significantly. Conclusions: The results, which showed no correlation between the alterations in CK-BB level and the TCA duration, suggest that the single assay of the CK-BB level is not a representative measurement for the assessment of cerebral damage after TCA. Also, the cyanotic congenital heart disease group is not more vulnerable to cerebral damage induced by TCA.

• The Korean Journal of Pain
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• v.9 no.2
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• pp.340-343
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• 1996

Background: In our hospital, stellate ganglion block(SGB) has been performed for the prevention and treatment of vasospasm after microscopic reimplantation of finger(s). If brachial plexus block(BPB) has the same effect of sympathetic block on the upper extremity as SGB, it may be preferable to the SGB because it povides postoperative analgesia and is administered continuously. So we measured and compared the change of skin temperature on the forearm as the parameter of sympathetic blockade after SGB and BPB. Methods: The forty-two patients, belonged to ASA class 1~2, were received BPB for hand surgery. The skin temperature was measured before and after BPB on the forearm with patient monitor(LN 6199, YSI 400 Series Temperature Probe, Hellige, Germany). After 24 hours, ipsilateral SGB was performed and skin temperature was recorded before and after SGB. Results: The increase of skin temperature after procedures was $1.1{\pm}0.5^{\circ}C$(from $34.5{\pm}0.7^{\circ}C$ to $35.6{\pm}0.5^{\circ}C$) in BPB and $0.6{\pm}0.3^{\circ}C$(from $34.9{\pm}0.5^{\circ}C$ to $35.5{\pm}0.5^{\circ}C$) in SGB. The changes of skin temperature in both blocks were statistically significant(p<0.01), and the skin temperatures after each procedure were revealed no significant difference(p$\simeq$0.62). Conclusion: We thought that BPB produced sympathetic blockade on the upper extremity as much as SGB. Moreover, it provides postoperative pain relief and may be employed as continuous BPB could be used for hand surgery with many advantages.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.3
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• pp.321-331
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• 2008

A model has been constructed in this study for the investigation of physical characteristics of the Gyeonggi Bay and Han River estuary. MIKE 21 HD (HyDrodynamics) has been used for the uncertainty analysis of the tide of the Gyeonngi Bay and Han River estuary. A total of 15 model experiments have been performed for the hydrodynamic parts and the analysis of results have been made in terms of RMSD (Root-mean square deviation) which has been frequently employed in the suitability analysis of hydrological data since the introduction by NERC(1975), U.K. A smaller value of RMSD indicates the more suitability of a parameter to the model. Analysis of the hydrodynamic results has shown that RMSD of the mean tidal range has the largest value of 0.1148 at Yeomha channel while has the smallest value of 0.0400 at Yeonphyong-do, indicating that the uncertainty in the mean tidal range on near-shore side is larger than that of offshore side. Experiment with reduced water depth by 10% has produced a most significant increase in RMSD. It is therefore implied that the model response changes more sensitively to water depth rather than grid sizes, open boundary forcing and river discharge.

• Journal of the Korean earth science society
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• v.31 no.6
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• pp.608-624
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• 2010

Morphological surveys of southern Gyeonggi Bay in the Yellow Sea were conducted for2 years (2006 and 2007) by using multibeam echosounder for investigating the morphological features of bedforms. The subaqueous dunes are shown in various shapes (A~F type) and continuous spectrum of heights and lengths of transverse-to-current dunes on the wide range of sedimentary types. The height-length power-law correlation of dunes is $H_{mean}=0.0393L^{0.8984}$ (r=0.66). The comparison between Flemming (1988)'s correlation and height-length correlation of this study indicates that the subaqueous dunes in the study area are equilibrated in the present hydrological and sedimentary environment. The major controlling factors to thedevelopment and maintenance of subaqueous dunes are both strong tidal currents and the abundant availability of sand. Marine sand mining, artificial impact, changes from the original shape to an irregular shape of the subaqueous dunes with a shorter wavelength and lower height, which has influence on the development and maintenance of bedform because it causes a decrease of the availability of sediment. Water depth and sedimentary characteristics, and othercontrolling factors seem to play limited roles in the development and maintenance of subaqueous dunes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.259-272
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• 2019

Steel-concrete single-leaf blast-resistant doors are protective structures consisting of a steel box and reinforced concrete slab. By the domestic blast-resistant doors, the structure is not designed efficiently because few studies have examined the effects of variables, such as the blast pressure, rebar ratio, and steel plate thickness on the structural behavior. In this study, the structural behavior of the doors was analyzed using the FE method, and the support rotation and ductility ratio used to classify the structural performance were reviewed. The results showed that the deflection changes more significantly when the plate thickness increases than when the rebar spacing is a variable. This is because the strain energy absorbed by the door is reduced considerably when the plate thickness increases, and as a result, the maximum deflection becomes smaller. According to a comparison of the calculated values of the support rotation and the ductility ratio, the structural performance of the doors could be classified based on the support rotation of one degree and ductility ratio of three. On the other hand, more explosion tests and analytical studies will be needed to classify the damage level.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.12
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• pp.660-673
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• 2001

In Video-on-Demand (VoD) servers, disk throughput is an important system design parameter because it is directly related to the number of user requests that can be served simultaneously. In this paper, we propose an efficient periodic request grouping scheme for disk array-based VoD servers that reduces the disk seek time, thus improving the disk throughput of VoD disk arrays. To reduce the disk seek time, the proposed scheme groups the periodic requests that access data blocks stored in adjacent regions into one, and arranges these groups in a pre-determined order (e.g., in left-symmetric or right-symmetric fashion). Our simulation result shows that the proposed scheme reduces the average disk bandwidth required by a single video stream and can serve more user requests than existing schemes. For a data block size of 192KB, the number of simultaneously served user requests is increased by 8% while the average waiting time for a user request is decreased by 20%. We also propose an adaptation technique that conforms the proposed scheme to the user preference changes for video streams.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4277-4283
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• 2012

Slip coefficient, whose value is dependent on the condition of contact surface at the friction joint of high tension bolt, is determined by slip load. Because contact area affects slip load, contact area that varies with bolt hole size is also related to the slip coefficient. In this study, we manufactured 32 specimens and performed bending and tension tests in order to examine changes in slip coefficient and load with material type, bolt diameter, and size of bolt hole. Slip load of specimens with oversize bolt hole had strength that was more than 80% higher than the slip load of specimens with standard bolt hole, and it also exceeded the design slip strength. In addition, we observed significant correlation between net-section ratio and slip ratio of specimens with oversize and standard bolt hole. However, some differences between the specimens are thought to have been caused by reduction in initial axial force of high tension bolt, which is an important parameter of slip coefficient. It is self-evident that increased bolt hole size would lead to decrease in design strength as it reduces both slip coefficient and bolt axial force. Nevertheless, we suggest that some flexibility in regulation of bolt hole, as long as it does not threaten the structural stability, may be a positive factor in terms of workability and efficiency.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.105-114
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• 2016

With approximately 20 million transportation card data entries of the metropolitan districts being generated per day, application of the data to management and policy interventions is becoming an issue of interest. The research herein attempts a model of the possibility of dynamic demand change predictions and its purpose is thereby to construct a Dynamic Passengers Trip Assignment Model. The model and algorithm created are targeted at city rail lines operated by seven different transport facilities with the exclusion of travel by bus, as passenger movements by this mode can be minutely disaggregated through card tagging. The model created has been constructed in continuous time as is fitting to the big data characteristic of transport card data, while passenger path choice behavior is effectively represented using a perception parameter as a function of increasing number of transfers. Running the model on 800 pairs of metropolitan city rail data has proven its capability in determining dynamic demand at any moment in time, in line with the typical advantages expected of a continuous time-based model. Comparison against data measured by the eye of existing rail operating facilities to assess changes in congestion intensity shows that the model closely approximates the values and trends of the existing data with high levels of confidence. Future research efforts should be directed toward continued examination into construction of an integrated bus-city rail system model.

• Journal of the Korean Society of Food Culture
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• v.3 no.3
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• pp.309-317
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• 1988

The effects of $CaCl_2$, K-sorbate, and fermented fish sauces and blanching on the texture of Chinese cabbage of Kimchi were evaluated. The addition of salt-fermented shrimp or salt-fermented anchovy accelerated the pH reduction, acidity increase and reducing sugar consumption, but K-sorbate, Ca-chloride and blanching suppressed the ripening process of Kimchi. The latter retarded the softening rate of Chinese cabbage during Kimchi fermentation, as demonstrated by the cutting force, compression force, recovered height and work ratio. The sensory evaluation confirmed the results of instrumental texture measurments. The instrumental measurements, i.e. pH, acidity cutting thickness, cutting force and compression test parameters, showed acidity acidity was calculated as % lactic acid attributes, i.e. the preferences for taste, appearance and texture, and the level of crispiness, hardness, chewiness and fibrousness. The pH of Kimchi was appeared to be an important quality parameter, whiih had significant correlations with the taste, appearance, chewiness, hardness, fibrousness and crispiness.