• Journal of Korean Society of Water and Wastewater
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• v.11 no.3
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• pp.67-78
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• 1997

The objective of study was to examine to transient response of hydraulic shock loading in activated sludge process for treatment of municipal sewage. The general experiment approach was to operate the system under steady-state(pre-shock), then to apply step changes during 24hours in fourfold hydraulic shock loading at the same organic loading. Performance was assessed in both the transient state and the new steady-state(post-shock). Three bench scale activated sludge reactors were operated to investigate the effect of fourfold hydraulic shock loading on TSS and COD removal efficiency. In activated sludge reactors operated with 13hours and 7hours of HRT, effluent quality of all reactors was not changed for few effects, and also showed no foaming and no sludge bulking. Those results are the same as sludge withdrawn reactors. The effect of fourfold hydraulic shock loading on the activated sludge reactors operated with 3hours of HRT was most severe. The effluent quality was deteriorated significantly and generate foaming in reactors. Less than 24hours after the fourfold shock loading applied, the activated sludge system seemed to attain a new steady-state condition as show by effluent.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.937-943
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• 2023

In this study, the mast cover of submarine was reverse engineered and structural analysis was performed. In order to print with the 3D printer, the modeling was reduced to 1/5 size by applying geometric similarity. From the structural analysis results, it was found that the maximum value of equivalent stress generated in the mast cover was 180.9 MPa. This stress value occurs on the inner surface in the major axis. As a result of applying the load condition at a diving depth of 600 m, the mast cover is in a completely elastic state. The 1/5 size model printed on FDM 3D printer with PLA filament was the same as the reverse engineered modeling and it was printed in a perfect shape with no apparent defects. The 1/5 size model printed on PBF 3D printer with SUS316L powder was perfectly manufactured with no apparent defects.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.379-387
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• 2011

Research and development of LP EGR system for the performance improvement and emission reduction on diesel engine is proceeding at a good pace. LP EGR system seems to be helpful method to further reduce$NO_x$ emissions while maintaining PM emissions at a low level because the boost pressure is unchanged while varying EGR rate. This study is experimentally conducted on a 2.0L common rail DI engine at the medium load condition (2000 rpm, BMEP 1.0 MPa, boost pressure 181.3 kPa) that difficult to use large amount of EGR gas because of deteriorations of performance and fuel consumption. And we investigated the characteristics of performance and fuel consumption while varying EGR systems. The overall results using LP EGR system equipped with ETC identified benefits on reduction of PM and improvement of fuel consumption and thermal efficiency while keep the $NO_x$ level compared to HP EGR and LP EGR with back pressure valve.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.6
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• pp.723-731
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• 2020

The design of offshore plants should reflect the various requirements of the owner and the classification society. For a topside module mounted on an of shore structure, the design process is very demanding because of the large spatial constraints and the many requirements related to marine environmental conditions and safety such as the movement of the structure. In this study, the load acting on the hydraulic power unit, which is one of the main equipment in the topside module, was calculated according to the DNVGL rule; the structural safety was evaluated according to each load condition and the structural reliability of the developed product was improved. For structural analysis, MSC software was used, and structural analysis was performed under five load conditions to review structural safety for various movements. The results show that the maximum stress occurred during pitching toward the stern (Load Case 5). The stress level was approximately 85 % of the allowable stress, and the maximum deformation was approximately 5 % of the allowable value. The structural safety was confirmed, and no intermember interference occurred.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.122-130
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• 2016

This study is a numerical study using commercial simulation program GT-Power on 1.5MW diesel engine for power generation. Performance comparison has done for diesel operation with dual fuel operation for different engine load(50%, 75%, 100%) using the target engine model with additional gas injection system. Effect of using Hi-sene, which is actually being used in island area, instead of diesel was also studied. As a result, under 60% natural gas with diesel condition, BSFC was increased by 32% without modifying system. There was almost no change for natural gas/Hi-sene condition compared with natural gas/diesel condition. Decrease of burned fuel fraction was the main reason of these phenomena. After optimizing system, BSFC was improved by 2%.

• PNF and Movement
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• v.7 no.4
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• pp.31-36
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• 2009

Many daily activities require people to complete a motor task while walking. Substantial gait decrements during simultaneous attention to a variety of cognitive tasks have been shown by a group of severely injured neurological patients of mixed etiology. And previous studies have shown that the attentional load of a walking-associated task increased with its level of difficulty. The purpose of this study was to analyze subjects' gait changes are affected by the effects of arithmetic task difficulty and performance level. Participants performed a walking task alone, three different Arithmetic tasks while seated, and among them, two kinds of the simillar Arithmetic tasks in combination with walking. Reaction time and accuracy were recorded for two of the Arithmetic tasks. The mean values of the gait were measured using a Timed Up and Go test among 11 with post-stroke patients while walking with and without forward counting (WFC) and backward counting(WBC).There was significant Arithmetic Task Difficulty level between the 10-forward counting task condition(FC) and the 10-backward counting task condition(BC)(p=0.008). The mean values of T.U.G time were significantly higher under backward counting dual-task condition than during a simple walking task(p=0.009) and WFC(p=0.009). The change in T.U.G time during WFC was higher when compared with the change during a simple walking, but there was no significant difference (p=0.246). This study suggesting that a high interference could be linked with a high level of difficulty, whereas adaptive task enabled participants to perfectly share their attention between two concurrent tasks. Future research should determine whether dual task training can reduce gait decrements in dual task situations in people after stroke. And the dual-task-based exercise program is feasible and beneficial for improving walking ability in subjects with stroke.

• Particle and aerosol research
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• v.7 no.1
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• pp.9-19
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• 2011

The effects of different transient loading conditions on xylene removability and bacterial activity were evaluated in the polyurethane (PU) biofilter inoculated with Rhodococcus sp. EH831: BF1 (the control) was operated under continuous and constant loading ($200{\pm}50ppm$); BF2 under continuous and constant loading after a 2-week long-term shutdown; BF3 under discontinuous (8 h on/16 h off on weekdays and a 2 day-shutdown at weekends); and constant loading BF4 under discontinuous and high loading ($700{\pm}300ppm$); and BF5 under continuous and fluctuating loading (high loading for 8 h and low loading ($75{\pm}25ppm$) for 16 h on weekdays and low loading at weekends). Xylene removal efficiencies in the BF1, BF2, BF3, and BF5 were ranged 83-89%, indicating that 2-week long-term shutdown, intermittent or fluctuant loading condition did not significantly influence the biofilter performance. However, discontinuous and high load condition (BF4) caused to deteriorate xylene removability to 52%. Rhodococcus sp. EH831 could be maintained at $10^9{\sim}10^{10}CFU/g-dry$ PU under 5 kinds of loading conditions. The result of polymerase chain reaction-terminal-restriction fragment length polymorphism showed that there was no significant change in bacterial community structures by different loading conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.8 s.99
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• pp.815-824
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• 2005

In this paper, we proposed a new DGS(Defected Ground Structure) Doherty amplifier for IMT-2000 band. Originally, active load-pull analysis of a Doherty amplifier assumes ideal harmonic termination condition. However, there have been no papers considering this ideal harmonic termination condition. We obtained excellent improvements of efficiency, gain, maximum output power as well as superior size reduction of a Doherly amplifier by satisfying the overlooked assumption of ideal harmonic termination through the adaptation of DGS at the output transmission line of carrier and peaking amplifier that is essential for Doherty operation. The amount of both the 2nd and the 3rd harmonic rejection of the proposed DGS Doherty amplifier over the conventional one are 44.92 dB and over 23.77 dB, respectively. The acquired improvement in Pl dB, gain, drain efficiency, and ACPR to WCDMA 1FA signal were 0.42 dB, 0.33 dB, $6.4\%$ and 5.4 dBc, respectively. Moreover, electrical length of $90{\circ}$ is reduced at each of the DGS carrier amplifier path and DGS peaking amplifier path, therefore the whole amplifier circuit size is considerably reduced.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.7
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• pp.635-641
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• 2016

In order to drive a hybrid propulsion device which combines an engine and an electric propulsion unit, battery packs that contain dozens of unit cells consisting of a lithium-based battery are used to maintain the power source. Therefore, it is necessary to more strictly manage a number of battery cells at any given time. In order to manage battery cells, generally voltage, current, and temperature data under load condition are monitored from a personal computer. Other important elements required to analyze the condition of the battery are the internal resistances that are used to judge its state-of-health (SOH) and the open-circuit voltage (OCV) that is used to check the battery charging state. However, in principle, the internal resistances cannot be measured during operation because the parallel equivalent circuit is composed of internal loss resistances and capacitance. In most energy storage systems, battery management system (BMS) operations are carried out by using data such as voltage, current, and temperature. However, during operation, in the case of unexpected battery cell failure, the output voltage of the power supply can be changed and propulsion of the hybrid vehicle and vessel can be difficult. This paper covers the implementation of a high safety battery management system (HSBMS) that can estimate the OCV while the device is being driven. If a battery cell fails unexpectedly, a DC power supply with lithium iron phosphate can keep providing the load with a constant output voltage using the remainder of the batteries, and it is also possible to estimate the internal resistance.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.2
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• pp.232-242
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• 2003

Statement of problem : Fiber-reinforced posts have lower modulus of elasticity than titanium post or cast post-core. With this similar elasticity to that of dentin, fiber-reinforced posts have been known to have a tendency to reduce the risk of root fracture. However, there were few studies on the teeth restored with fiber-reinforced posts under the condition of reduced periodontal support. Purpose : The purpose of this study was to evaluate the fracture strength and failure mode of endodontically treated teeth restored with fiber-reinforced posts and titanium posts under the condition of reduced periodontal support. Material and method : Extracted human maxillary incisor roots were divided into 3 groups (group 1 carbon fiber post, group 2 : glass fiber post, and group 3 : titanium alloy post). After coronectomy and endodontic treatment, teeth were restored with each post systems and resin core according to the manufacturer's recommendation. Then, teeth with simulated periodontal ligament were embedded in the acrylic resin blocks at the level of 4 mm below the cemento-enamel junction. Each specimen was exposed to $10^5$ load cycles with average 30 N force in $36.5^{\circ}C$ water using a computer-controlled chewing simulator. Loads were applied at $45^{\circ}$ angle to the long axis of the teeth. After cyclic loading, teeth were subjected a compressive load until failure at a crosshead speed of 0.5 mm/min. Fracture strength (N) and failure mode were examined. The fracture strength was analyzed with one-way ANOVA and the Scheffe adjustment at the 95% significance level. Results and conclusion : The results were as follows. 1. There was no statistically significant difference in the mean fracture strength among the groups (P<.05). 2. Carbon fiber post and glass fiber post group showed less root fracture tendency than control group. 3. All specimens with root fractures showed fracture lines above the level of acrylic resin block, except for only one specimen in group 3.