• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.04a
• /
• pp.117-123
• /
• 2003

This paper deals with pressure ripple and noise reduction characteristics for a hydrostatic transmission(HST) consisting of a variable axial piston pump connected in an open loop to a fixed displacement axial piston motor. Pressure ripples in HST is major source of vibration, which can lead to fatigue failure of components and cause noise. In order to reduce the pressure ripple, an annular tube type hydraulic filter proposes to absorb pressure ripples with the high frequencies components to achieve better noise attenuation in HST. The basic principle tube is applied to propagation of pressure wave, reflection, absorption in cross section of discontinuity and resonance in the hydraulic pipeline. It is experimently confirmed that a hydraulic filter is absorbed to be about 30∼40dB of pressure ripple with high frequencies. These results will assist in modeling and design of noise reduction in hydraulic control systems, and here, should provide a means of designing a quieter HST.

• Korean Journal of Human Ecology
• /
• v.17 no.5
• /
• pp.963-973
• /
• 2008

Clothing pressure is closely connected with the degree of comfort of an athlete's tight-fitting garments. Therefore, the construction of sports garments is very important to the wearer's athletic performance. In this study, the fundamental relationship between the reduction rates of stretch fabrics and clothing pressure was explored with the aim of improving clothing comfort and obtaining a systematic pattern reduction for women's tight-fitting bodysuits. A women's bodysuit pattern was obtained by the draping method using a dressform. The basic pattern was divided into four parts and changed into reduced pattems according to the amount of fabric stretch determined by ASTM D2594. Clothing pressure was measured using an air-pack-type pressure sensor (model AMI 3037-2) at 20 locations (shoulder, 9 locations; bust, 5; and armhole, 6). Among the 15 garments tested, the mean pressure of the A1 bodysuit was 4.60 $gf/cm^2$, and that of the C5 bodysuit was 22.98 $gf/cm^2$. The mean pressures of the bodysuits with reduction rates of 10% and 20% were below 10 $gf/cm^2$, while those of suits with reduction rates of 30%,40%, and 50% (except C5) were below 20 $gf/cm^2$. The pressure at the shoulder was 9.50$\sim$32.24 $gf/cm^2$, which was higher than that at the bust (3.34$\sim$24.56 $gf/cm^2$) and the armhole (0.95$\sim$12.15 $gf/cm^2$). The mean pressures of the 15 bodysuits were divided into five groups using analysis of variance (ANOVA), and were found to be significantly different (p<0.001). Regression analysis afforded the following expression: mean pressure ($gf/cm^2$) = 1.607 + 0.369[reduction rate (%)].

• Journal of the Korean Institute of Gas
• /
• v.19 no.6
• /
• pp.72-79
• /
• 2015

Electricity can be generated when the natural gas passes through a turbo-expander pressure reduction system at natural gas pressure reduction stations. Efficiency of the turbo-expander depends on the ratio of the natural gas flow rates to the design flow rate of the turbo-expander. Therefore, the optimal conditions for the operation of the pressure reduction system can be determined by controlling the natural gas flow rates. In this study, we have calculated the electric energy generation depending on the natural gas flow rates at the two low-pressure reduction stations when the pressure of the natural gas is reduced from 17.5 bar to 8.5 bar and have found the optimal conditions for the turbo-expander pressure reduction system through the comparison with the calculation results. The turbo-expander generates the electric power efficiently for the high natural gas flow rates which variations are slight. The determined design flow rate of the turbo-expander has the highest coverage of the natural gas flow rates. The electricity generation is calculated as much as 9 MW(B station) and 12 MW(D station) at each pressure reduction station.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.03a
• /
• pp.411-418
• /
• 2001

The last 30 years have been significant worldwide growth in the use of EPS as a lightweight fill material. This paper analyzes the compressible inclusion function of EPS which can results in reduction of static earth pressure by accomodating the movement of retained soil. A series of model tests was conducted to evaluate the reduction of static earth pressure using EPS inclusion and determine the optimum stiffness of EPS, Also, field test was conducted to evaluate the reduction of static earth pressure using EPS inclusion. Based on field test it is found that the magnitude of static earth pressure was reduced about 20% compared with theoretical active earth pressure.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.3
• /
• pp.33-38
• /
• 2002

This paper deals with pressure ripple attenuation far separated-type Hydrostatic Transmission (HST) consisting ova variable axial piston pump connected in an open loop to a fried displacement axial piston motor. Pressure ripples in HST is major source of vibration which can lead to fatigue failure of components and cause noise. In order to reduce the pressure ripple, an annular tube tripe hydraulic filter is proposed to attenuate pressure ripples with the high frequencies components to achieve better noise reduction in HST. The basic principle of a hydraulic filter is allied to propagation of pressure wave, reflection, absorption in cross section of discontinuity and resonance in the hydraulic pipeline. It is experimentally shown that the hydraulic filter attenuates about 30∼40dB of pressure ripple with high frequencies. These results will assist in modeling and design of noise reduction in hydraulic control systems, and provide a means of designing a quieter HST.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.299-302
• /
• 1997

The pressure ripples are inevitabilitily generated by a fluctuation of flow rate caused pump mechanism, which occur noises, vibrations, and affect a control performance in tluid pipeline. The method for reduction of pressure ripples has been normally used a accumulator which is installed near the pump generating the pressure ripples. This paper introduces the parallel pipeline as a method to reduce pressure ripples in tluid pipeline, and confirms the usefulness of it in reducing the pressure ripples as compared with the fluid pipeline with a accumulator using AMESim(Advanced Modeling Environment for Simulations) Software.

• Journal of Powder Materials
• /
• v.31 no.2
• /
• pp.163-168
• /
• 2024

As the demand for lithium-ion batteries for electric vehicles is increasing, it is important to recover valuable metals from waste lithium-ion batteries. In this study, the effects of gas flow rate and hydrogen partial pressure on hydrogen reduction of NCM-based lithium-ion battery cathode materials were investigated. As the gas flow rate and hydrogen partial pressure increased, the weight loss rate increased significantly from the beginning of the reaction due to the reduction of NiO and CoO by hydrogen. At 700 ℃ and hydrogen partial pressure above 0.5 atm, Ni and Li₂O were produced by hydrogen reduction. From the reduction product and Li recovery rate, the hydrogen reduction of NCM-based cathode materials was significantly affected by hydrogen partial pressure. The Li compounds recovered from the solution after water leaching of the reduction products were LiOH, LiOH·H₂O, and Li₂CO₃, with about 0.02 wt% Al as an impurity.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.06a
• /
• pp.21-31
• /
• 2001

The last 30 years have been significant worldwide growth in the use of EPS as a lightweight fill material. A new construction method was introduced, which reduces earth pressure acting on culvert and conduit by placing a thin layer of EPS. This paper analyzes the compressible inclusion function of EPS and geogrid which can results in reduction of earth pressure by arching that is the behaviour of soil-structure system involving redistribution of soil stress around the structure. Field test was conducted to evaluate the reduction of vertical earth pressure using EPS and geogrid inclusion. Based on field test it is found that the magnitude of reduced vertical earth pressure was about 24~50% compared to conventional method.

• Korean Journal of Community Nutrition
• /
• v.18 no.6
• /
• pp.626-643
• /
• 2013

This study was performed to evaluate the differences in blood pressure, sodium intake and dietary behavior changes according to the extent of session attendance on sodium reduction education program for pre-hypertensive adults in a public health center. Sodium reduction education program consisted of 8 sessions for 8 weeks. Fifty three patients who completed the pre and post nutritional assessments were classified into 2 groups according to the session attendance rate. Nineteen participants who attended the education program 3 times or less (${\leq}3$) were categorized into the less attendance (LA) group and 34 participants attended 4 times or more (${\geq}4$) into the more attendance (MA) group. Blood pressure, anthropometric measurements, serum lipid profile, nutrient intakes including sodium, nutrition knowledge and dietary behavior score were assessed before and after the nutrition education program. Mean sodium intakes (p<0.001), systolic/diastolic blood pressure (p<0.001), and weight (p<0.001) were significantly decreased in the MA group after sodium reduction education program. Compared to the MA group, mean sodium intakes, systolic/diastolic blood pressure were not significantly changed after the education program even with significantly increased nutrition knowledge (p<0.05) and dietary behavior score (p<0.01) in the LA group. It appears that pre-hypertensive adults need to attend the sodium reduction education program for at least 4 times or more to gain beneficial effects from the intervention. Positive feedback of healthcare team or offering more cooking classes may be needed to raise the attendance rate in the sodium reduction education program.

• Advances in pediatric surgery
• /
• v.3 no.2
• /
• pp.126-132
• /
• 1997

Reduction of intussusception using air or oxygen has wide acceptance as an alternative to conventional hydrostatic reduction. This study was undertaken to evaluate the results and complications of air pressure enema in 948 pediatric intussusception. One hundred and twenty nine cases were operated on at the Department of Surgery, Masan Samsung Hospital from 1985 to 1996 because of air reduction failure. The success rate was 86.4 %. Twenty-one patients(2.2 %) showed perforation during air reduction. Risk prone factors of perforation were; age less than 3 months(42.9 % vs 11.1 %), duration of symptoms greater than 48 hours (66.7 % vs 33.3 %), and presence of pathologic leading point(28.6 % vs 3.7 %). Vomitting and spontaneous rectal bleeding revealed higher prediction to the complication. In nineteen cases, bowel infarction, coagulated necrosis and hemorrhage suggested that the cause of perforation was due to the preexisting strangulation. In conclusion, when doing an air pressure enema reduction, care must be taken if the patient is of a young age or the symptoms are of long duration.