• Korean Journal of Cognitive Science
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• v.33 no.1
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• pp.1-22
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• 2022

Lavie's perceptual load theory (Lavie, 1995) proposes that the influence of distractors would be blocked as the load gets higher. Studies of perceptual load have usually adopted the flanker task, developed by Eriksen and Eriksen (1974), which measures reaction time on the target flanked by distractors. In the post-cueing forced task, participants should report the identity of the target cued later, and negative repetition effect (NRE) has often been observed. NRE means the effect that the accuracy of identification is worse when the target is flanked by the same nontargets than when flanked by different nontargets. This study has tried to check whether perceptual load has an effect on identification rate and NRE. Experiment 1 manipulated the similarity between targets and a distractor, and observed a tendency of NRE, but not the effect of perceptual load. Experiment 2 used 4, 2 (in two kinds of diagonal arrangement), or none distractors of the same identity to burden more perceptual load. NRE was significant and perceptual load showed significance but not a linear trend. Experiment 3 checked again whether NRE would be varied according to two levels of perceptual load strengthened by positional variability of load stimuli, but did not find the effect of perceptual load. It is concluded that perceptual load might have a limited effect on the early stage of perceptual processing due to divided attentional processing of the targets briefly exposed. Implications of this study were discussed.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.501-508
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• 2010

A swirl chamber type diesel engine attachable to 18 kW agricultural tractors was improved to reduce exhaust emissions. Compression ratio and throat area ratio of the combustion chamber were varied to determine optimum combustion conditions. Tests were composed of full load and 8-mode emission tests. Compression ratio was fixed as 21, but the swirl chamber volume was increased by 3.8%. Output power, torque, specific fuel consumption, exhaust gas temperature, and smoke level were not considerably different for compression ratios of 21.5 (reference condition) and 21 (test condition), while NOx, HC, CO and PM levels for the compression ratio of 21 were decreased by 11%, 46%, 28%, 11%, respectively, from those for the compression ratio of 21.5. The tests were also conducted with a compression ratio of 22 and 4.3% increased chamber volume. Output power, torque, exhaust gas temperature and smoke level were greater, while specific fuel consumption was less for the compression ratio of 22 than those for the compression ratio of 21.5. Increase of compression ratio decreased HC and CO levels by 24%, 39%, but increased NOx and PM levels by 24%, 39%. Based on these results, a compression ratio of 21 was selected as an optimum value. Then, full load tests with the selected compression ratio of 21 were carried out for different throat ratios of 1.0%, 1.1%, 1.2%. Output power and torque were greatest and smoke was lowest when throat area ratio was 1.1%, which satisfied the target values of specific fuel consumption (less than 272 g/$kW{\cdot}h$) and exhaust gas temperature (less than $550^{\circ}C$). Therefore, a throat area ratio of 1.1% was selected as an optimum value.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1443-1451
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• 2020

The objective of this study is to design a robust power control system for a small pressurized water reactor (PWR) to achieve stable power operations under conditions of external disturbances and internal model uncertainties. For this purpose, the multiple-input multiple-output transfer function models of the reactor core at five power levels are derived from point reactor kinetics equations and the Mann's thermodynamic model. Using the transfer function models, five local reactor power controllers are designed using an H infinity (H_∞) mixed sensitivity method to minimize the core power disturbance under various uncertainties at the five power levels, respectively. Then a multimodel approach with triangular membership functions is employed to integrate the five local controllers into a multimodel robust control system that is applicable for the entire power range. The performance of the robust power system is assessed against 10% of full power (FP) step load increase transients with coolant inlet temperature disturbances at different power levels and large-scope, rapid ramp load change transient. The simulation results show that the robust control system could maintain satisfactory control performance and good robustness of the reactor under external disturbances and internal model uncertainties, demonstrating the effective of the robust power control design.

• Structural Engineering and Mechanics
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• v.65 no.2
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• pp.163-171
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• 2018

Plain concrete is a brittle material with a very low tensile strength compared to compressive strength and critical tensile strain. This study analyzed the dynamic characteristics of high-performance fiber-reinforced cementitious composites based on slurry-infiltrated fiber concrete (SIFCON-based HPFRCC), which maximizes the steel-fiber volume fraction and uses high-strength mortar to increase resistance to loads, such as explosion and impact, with a very short acting time. For major experimental variables, three levels of fiber aspect ratio and five levels of fiber volume fraction between 6.0% and 8.0% were considered, and the flexural strength and toughness characteristics were analyzed according to these variables. Furthermore, three levels of the aspect ratio of used steel fibers were considered. The highest flexural strength of 65.0 MPa was shown at the fiber aspect ratio of 80 and the fiber volume fraction of 7.0%, and the flexural strength and toughness increased proportionally to the fiber volume fraction. The test results according to fiber aspect ratio and fiber volume fraction revealed that after the initial crack, the load of the SIFCON-based HPFRCC continuously increased because of the high fiber volume fraction. In addition, sufficient residual strength was achieved after the maximum strength; this achievement will bring about positive effects on the brittle fracture of structures when an unexpected load, such as explosion or impact, is applied.

• Magazine of the Korea Concrete Institute
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• v.5 no.4
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• pp.179-187
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• 1993

In thls study, cylindrical concrete specimens wth varlous strength levels were tested to lnves tlgate the fatigue behavlor of high strength concrete. Selected test variables welp cornpresslve strength with 4 levels(26 MIPa, 54 MPa, 82 MPa. 103 MPa) and maximum \tress wlth 4 levels (75% 80%, 85%, 95%). A total of 160 specimens(${\phi}100{\times}200mm$) were cdsted fol the test. l'he fatigue llfe was decreased for the hlgher strength concreate. R model fol S N, relationship con sidering the effect of compressive strength, was proposed. In addition, this model included the stram rate effect whlch was modified for the strength level. It was found that the ~rrecoverable stram of normal strength concretc3 was greater than that of high strength concrete However the strain ~ncrease per cycle of load was great for the highcr strength concrete.

• Journal of Environmental Health Sciences
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• v.26 no.2
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• pp.97-107
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• 2000

PCBs [Polychlorinated biphenyls] are halogenated aromatic compounds with the empirical formula C12H10-nCln(n=1~10), and are a mixture of possible 209 different chlorinated congeners. PCBs were widely used as dielectric fluids for capacitors, transformers, plasticizers, lubricant inks, and paint additives. once released into the environment, PCBs persist for years because they are so resistant to degradation. In addition to their high degree of lipophilicity. In 1970s, the worldwide production of PCBs seem to be still in use. The environmental load of PCBs was prohibited since 1983 in Korea. In spite of these actions, many PCBs seem to be still in use. The environmental load of PCBs will continue to be recycled through air, land, water, and the biosphere for decades to come. This study was conducted to measure the concentrations of PCBs I the serum samples of 112 women by GC/MSD(Hewlett Packard 5897 Gas Chromatography-Mass Chromatography Detector) and CG/ECD(Hewlett Packard 5890 series-II gas chromatography-Electron capture detector, U.S.A). The main results of this study were as follows; The mean and standard deviation of serum PCBs were 3.613, 0.759 ppb, respectively and median of it was 3.828 ppb. The correlation coefficients of the concentrations of 13 PCB congeners ranged from 0.7913 to 0..9985 and were significantly correlated between each items(p=0.0001). The PCB concentrations were positively associated with age(simple linear regression; R2=0.86, =0.08023, p<0.001) and with total lipids in serums(simple linear regression; R=0.7058, =0.00486, p<0.001). The age adjusted model (Y=$\beta$0+$\beta$1age+$\beta$2X) was applied for possible predictors of PCBs levels in serum. For BMI(Body Mass Index), major residential area, and fish, meat, and dairy consumption, there was no association with PCBs levels, Also there was negative association for the number of pregnancy and lactation period with PCBs levels.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.105-112
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• 2011

We propose an adaptive load balancing scheme to transport real-time video streams efficiently in this paper. The playback buffer level of a video requesting client is high or low temporarily in mobile environment. This scheme attempts to allocate more network bandwidth to serve a video request with the lower buffer level preferentially. In this scheme, the amount of network bandwidth is dynamically allocated to the requesting clients according to their playback buffer levels in a distributed mobile system. In order to improve the quality of service and real-time performance of individual video playback, the proposed load balancing scheme tries to maximize the number of frames that are transported successfully to the client prior to their playback times. Fair services can also be provided to all the concurrent clients by making their playback situation more adaptive. The performance of this load balancing scheme is compared with that of other static load balancing scheme through extensive simulation experiments, resulting in the higher ratio of frames transmitted successfully within given deadlines.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.155-165
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• 2014

This study measured and compared the variation of ventilation rate and fan energy consumption according to various control strategies after installing wireless sensor-based pilot ventilation system in order to verify the applicability of demand-controlled ventilation (DCV) strategy that was efficient ventilation control strategy for underground parking lot. The underground parking lot pilot ventilation system controlled the ventilation rate by directly or indirectly tracking the traffic load in real-time after sensing data, using vehicle detection sensors and carbon monoxide (CO) and carbon dioxide ($CO_2$) sensor. The ventilation system has operated for 9 hours per a day. It responded real-time data every 10 minutes, providing ventilation rate in conformance with the input traffic load or contaminant level at that time. A ventilation rate of pilot ventilation system can be controlled at 8 levels. The reason is that a ventilation unit consists of 8 high-speed nozzle jet fans. This study proposed vehicle detection sensor based demand-controlled ventilation (VDS-DCV) strategy that would accurately trace direct traffic load and CO sensor based demand-controlled ventilation (CO-DCV) strategy that would indirectly estimate traffic load through the concentration of contaminants. In order to apply DCV strategy based on real-time traffic load, the minimum required ventilation rate per a single vehicle was applied. It was derived through the design ventilation rate and total parking capacity in the underground parking lot. This is because current ventilation standard established per unit floor area or unit volume of the space made it difficult to apply DCV strategy according to the real-time variation of traffic load. According to the results in this study, two DCV strategies in the underground parking lot are considered to be a good alternative approach that satisfies both energy saving and healthy indoor environment in comparison with the conventional control strategies.

• Journal of Korean Association for Spatial Structures
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• v.23 no.2
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• pp.19-28
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• 2023

Timber structures are susceptible to moisture, contamination, and pest infestation, which can compromise their integrity and pose a significant fire hazard. Despite these drawbacks, timber's lightweight properties, eco-friendliness, and alignment with current architectural trends emphasizing sustainability make it an attractive option for construction. Moreover, timber structures offer economic benefits and provide a natural aesthetic that regulates building temperature and humidity. In recent years, timber domes have gained popularity due to their high recyclability, lightness, and improved fire resistance. Researchers are exploring hybrid timber and steel domes to enhance stability and rigidity. However, shallow dome structures still face challenges related to structural instability. This study investigates stability problems associated with timber domes, the behavior of timber and steel hybrid domes, and the impact of timber member positioning on dome stability and critical load levels. The paper analyzes unstable buckling in single-layer lattice domes using an incremental analysis method. The critical buckling load of the domes is examined based on the arrangement of timber members in the inclined and horizontal directions. The analysis shows that nodal snapping is observed in the case of a concentrated load, whereas snap-back is also observed in the case of a uniform load. Furthermore, the use of inclined timber and horizontal steel members in the lattice dome design provides adequate stability.

• BMB Reports
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• v.48 no.4
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• pp.209-216
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• 2015

Stress is now recognized as a universal premorbid factor associated with many risk factors of various chronic diseases. Acute stress may induce an individual's adaptive response to environmental demands. However, chronic, excessive stress causes cumulative negative impacts on health outcomes through "allostatic load". Thus, monitoring the quantified levels of long-term stress mediators would provide a timely opportunity for prevention or earlier intervention of stressrelated chronic illnesses. Although either acute or chronic stress could be quantified through measurement of changes in physiological parameters such as heart rate, blood pressure, and levels of various metabolic hormones, it is still elusive to interpret whether the changes in circulating levels of stress mediators such as cortisol can reflect the acute, chronic, or diurnal variations. Both serum and salivary cortisol levels reveal acute changes at a single point in time, but the overall long-term systemic cortisol exposure is difficult to evaluate due to circadian variations and its protein-binding capacity. Scalp hair has a fairy predictable growth rate of approximately 1 cm/month, and the most 1 cm segment approximates the last month's cortisol production as the mean value. The analysis of cortisol in hair is a highly promising technique for the retrospective assessment of chronic stress. [BMB Reports 2015; 48(4): 209-216]