• Tribology and Lubricants
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• v.22 no.2
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• pp.79-86
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• 2006

As the gerotor set with ideal profile meshes too tight, the reduction in the size of the rotor is generally adopted for a smooth operation. In this paper, a method of the profile modification for providing clearances was proposed. The meshing properties of the gerotor were analyzed and the non-boundary section of the inner rotor was identified, which denoted that the adjacent chambers were in the same pressure state. Clearances were imposed on the non-boundary section of the inner rotor, and then the profile of that section was modified as a composite curve of arcs. The other sections of the inner rotor were also interpolated as arcs. Thus, the whole profile of the inner rotor was designed as a composite curve of arcs.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.99-103
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• 2011

Many parameters influence the frictional behavior of steel sheet during stamping. The contact pressure between a die and a sheet during stamping is one of them. Thus, this parameter is investigated for high strength steel (HSS) sheets, which are widely used for auto body panels due to their potential for weight reduction. Since HSS extend the limits of contact pressure for mild steel, the effect of this parameter on friction cannot be ignored. To investigate the influence of contact pressure on the frictional behavior of steel sheets, a flat type of friction test was conducted on three different steel sheets under various contact pressures. For bare steel sheets, the curve representing the relationship between contact pressure and friction coefficient exhibits a U shape. Coated steel sheets show a similar tendency except at low contact pressure. For these materials, when the contact pressure is very low, the friction coefficient slightly increases with pressure before it starts to decrease. The test results show that the effect of contact pressure on frictional behavior of steel sheet is not negligible even for contact pressures that are lower than the strength of HSS sheet.

• Journal of Computing Science and Engineering
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• v.2 no.2
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• pp.180-199
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• 2008

Technology has had a tremendous impact on our daily lives. Recently, technology and its impact on aging has become an expanding field of inquiry. A major reason for this interest is that the use of technology can help older people who experience deteriorating health to live independently. In this paper we give a brief review of the in-home monitoring technologies for the elderly. In the pilot study, we analyze the possibility of employing the data generated by a continuous, unobtrusive nursing home monitoring system for predicting elevated(abnormal)pulse pressure(PP) in elderly(PP=systolic blood pressure-diastolic blood pressure). Our sensor data capture external information(behavioral) about the resident that is subsequently reflected in the predicted PP. By continuously predicting the possibility of elevated pulse pressure we may alert the nursing staff when some predefined threshold is exceeded. This approach may provide additional blood pressure monitoring for the elderly persons susceptible to blood pressure variations during the time between two nursing visits. We conducted a retrospective pilot study on two residents of the TigerPlace aging in place facility with age over 70, that had blood pressure measured between 100 and 300 times during a period of two years. The pilot study suggested that abnormal pulse pressure can be reasonably well estimated (an area under ROC curve of about 0.75) using apartment bed and motion sensors.

• Journal of Korean Academy of Nursing
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• v.42 no.5
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• pp.730-737
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• 2012

Purpose: This study was done to identify the time interval to pressure ulcer and to determine the optimal time interval for position change depending on pressure ulcer risk in patients using foam mattress in intensive care units. Methods: The Braden scale score, occurrence of pressure ulcers and position change intervals were assessed with 56 patients admitted to an intensive care unit from April to November, 2011. The time to pressure ulcer occurrence by Braden scale risk group was analyzed with Kaplan-Meier survival analysis and log rank test. Then, the optimal time interval for position change was calculated with ROC curve. Results: The median time to pressure ulcer occurrence was 5 hours at mild or moderate risk, 3.5 hours at high risk and 3 hours at very high risk on the Braden scale. The optimal time interval for position change was 3 hours at mild and moderate risk, 2 hours at high and very high risk of Braden scale. Conclusion: When foam mattresses are used a slight extension of the time interval for position change can be considered for the patients with mild or moderate pressure ulcer risk but not for patients with high or very high pressure ulcer risk by Braden scale.

• Tunnel and Underground Space
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• v.6 no.3
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• pp.209-222
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• 1996

Shut-in pressure, reopenting pressure and fracture orientation are very important parameters to be evaluated precisely in in-situ stress measurement by hydraulic fracturing. Graphical methods on pressure-time curves have been conventionally used, even though these are seriously dependent on subjectivity of interpreters. So there have been many demands on new method to objectivity in determining parameters. We have developed integrated hydrofracturing data processing program (HYDFRAC), based on nonlinear regression analysis and can be invoked under the Window graphical user interface. HYDFRAC consiste of three routines, that is shut-in pressure routine, reopening pressure routine, and fracture delineation routine. Each of routines include independent modules according to parameter determination methods. Its application to field tests ensured both objectivity and facility in determining of hydraulic fracturing parameters. Determining shut-in pressures at each pressurization cycles, we adopted the exponential pressure-decay method(EPD method), the bilinear pressure-decay-rate method (PDR method), and the tangent intersection method in order to find the pressurization-cyclic tendency of shut-in pressures. The estimated pressure by PDR method exists in the range of the upper and lower values by EPD method, and lies near to the upper value more than the lower. Being the pressurization cycle increased, the range of upper and lower limits come to be stabilized gradually. By graphical superposition method and bilinear pressure-accumulated volume method, reopening pressures were determined. Vertical and inclined fracture attitudes were determined by applying the directional statistics and sinusoidal curve fitting, respectively. The results of evaluation of hydrofracturing parameters showed that statistical methods could enhance the objectivity better than graphical methods.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.5
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• pp.371-383
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• 2023

Artillery gun tube experiences very high pressure according to the blast of propellant charge. Therfore, it is essential to guarantee the structural safety of the gun tube. On the other hand, weight reduction of gun tube is also a crucial design factor since the agility of artillery vehicle directly leads to its survivability. In this line of thought, this work proposed an efficient design procedure which utilizes the convex combination of breech pressure and projectile base pressure time histories. Its efficiency is verified by comparing with other procedures. Other procedures utilize different computed max pressure rather than the convex combination design pressure. Additionally, a transient analysis is carried out considering the projectile movement and the corresponding pressure distribution through the newly developed ABAQUS user-subroutine. The analysis confirms the structural safety of the lightweight gun tube designed by the proposed method.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.293-299
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• 2003

In this paper, the correlation of Pressure drop about the Newtonian and non-Newtonian fluid was investigated experimentally for vibrating intravascular lung assist device (VIVLAD) and we determined correlation equation to make a prediction about Pressure drop for designing VIVLAD. Design conditions to predict the pressure drop of the modules were studied through an experimental modeling before inserting the artificial lung assist device into as venous. Experiments were performed by distilled water, glycerol/water mixed solution(40% glycerol) of Newtonian fluids. and the bovine blood of non-Newtonian fluids. These fluids were flowed outside and parallel of hollow fiber membranes. Also we measured pressure drop according to the number of the fiber membranes which ware inserted into the inside diameter of shell of 3 cm, and developed the prediction equations by curve fitting method based on correlation between the experimental pressure drop and the frontal area or the packing density of device. The result showed that the Pressure drop and the friction factor of the water/glycerol mixed solution were similar to that of bovine blood. It was showed that the water/glycerol mixed solution (40% glycerol) could be used for measuring the pressure drop and the friction factor instead of the bovine blood. Also, we could estimate the prediction equation of pressure drop and friction factor as the function of Packing density at the number of hollow fibers. We obtained the reliance of the prediction equations because the pressure drop and the friction factor measured from the experiments were similar to that from the prediction equation. These results may be used to further usefulness for the design of VIVLAD.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.2
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• pp.45-54
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• 1985

Recently, the problem of exhaust gas pollution is increasingly being aggravated by the active use of the Diesel engine. For the fuel-injection system which affects the composition of exhaust gas from the Bosch type single-hole nozzle in the Diesel engine, a mathematical model was set up to study pressure variations in the high pressure pipe, the injection rate, and the needle lift. The fundamental equations of the mathematical model have been solved by the Newton Raphson Method applying the Finite Diffrence Method. The effective stroke of the injection pump plunger due to a change in engine rpm was calculated by the measurement of Control Rack, Pinion, and Plunger sizes and by the use of Characteristic Curve of Governor. The computed results for the pressure variations in the high pressure pipe and needle lift at 800 rpm and 1000 rpm are in good agreement with experimental ones in general. By a developed program, the effects of other various parameters will by calculated for the performance of the fuel-injection system.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.89-92
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• 2001

A rigid-viscoplastic finite element code for superplastic forming processes has been developed The material is assumed to be isotropic and a modified Coulomb friction law is adopted to explain contact between tool and sheet. This code uses the triangular element based on the membrane approximation and a hierarchical contact searching method is implemented The optimum pressure-time relationships for target strain rate are calculated by several pressure control algorithms. By the analysis, optimum pressure-time curves and deformation behavior are predicted.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.1
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• pp.83-91
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• 2000

The purpose of this study is to estimate quantitatively lateral pressure of super-workable fresh concrete applied to form-work of prototype structures, such as tall wall, retaining wall and beam. As a result of this experiment, a function applicable to design a form work system and to predict lateral pressure curve is formulated . Super-workable concrete may be used for the structures reinforced with dense re-bar like box culvert to place concrete at a time, and this study for lateral pressure of super-workable concrete may be useful for form design.