• Membrane Journal
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• v.7 no.2
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• pp.84-94
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• 1997

The performances of both module sets made by different methods for helical module were compared. All experiments were conducted simultaneously at the same transmembrane pressure and energy cosumption per membrane area. The effects of Dean vortices for reducing concentration polarization and fouling were low for the first module set. The increase of 115% for permeate flux improvement(permeate flux difference ${\times}100$/pemeate flux of linear module) was measured. The second module set was more effective in reducing concentration polarization and fouling.

• Journal of computational fluids engineering
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• v.13 no.1
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• pp.21-27
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• 2008

A numerical study for laminar flow in the entrance region of helical tubes for uniform inlet velocity conditions is carried out by means of the finite volume method to investigate the effects of Reynolds number, pitch and curvature ratio on the flow development. This results cover a curvature ratio range of 1/10$\sim$1/320, a pitch range of 0.0$\sim$3.2, and a Reynolds number range of 125$\sim$2000. It has been found that the curvature ratio does significantly effect on the angle of flow development, but the pitch and Reynolds number do not. The characteristic angle $\phi_c(=\phi/\sqrt{\delta})$, or the non-dimensional length $\overline{l}(=l\sqrt{\delta}cos(atan\lambda)/d)$ can be used to represent the flow development for uniform inlet velocity conditions. In uniform inlet velocity conditions, the growth of boundary layer delays the flow development attributed to centrifugal force, and in which conditions the amplitude of flow oscillations is smaller than that in parabolic inlet velocity conditions. If the pitch increases or if the curvature ratio or Reynolds number decreases, the minimum friction factor and the fully developed average friction factor normalized with the friction factor of a straight tube and the flow oscillations decrease.

• Journal of International Academy of Physical Therapy Research
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• v.10 no.2
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• pp.1797-1802
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• 2019

Background: Breathing is the essential step of Pilates exercise and can be used to activate core muscles. Although the effects of breathing exercise on pain, breathing muscles, and cervical posture have been extensively studied, little is known about the impact of Pilates breathing on spinal posture and alignment. Purpose: To determine the effect of 3D-Pilates breathing exercise on spinal curvature and alignment of healthy adults during corrected to normal alignment. Design: One group pre-post test design Methods: Eighteen participants were given a 3D-pilates breathing exercise twice a week (20 minutes per session) for three weeks and warmed up for 10 minutes before each exercise session. To examine spinal curvature and alignment of each subject, this study used radiation free rasterstereography (Formetric III, Germany). Paired t-test and Wilcoxon signed rank test were performed to determine the difference between pre and post exercise. Results: There were statistically significant differences in height (p<.001), kyphosis angle (p<.05), trunk imbalance (p<.05), kyphotic apex (p<.01), cervical fleche (p<.05), pelvic tilt (p<.01), and lateral deviation (p<.05) between before and after 3D Pilates breathing exercise. However, there was no significant difference in lordosis angle. Conclusions: The study results indicated that three week 3D-pilates breathing exercise program could be presented as an effective rehabilitation method for improving spinal curvature and alignment.

• Journal of Biosystems Engineering
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• v.13 no.2
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• pp.18-27
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• 1988

The basic model of impeller was developed for the theoretical analysis of performance. The developed model was tested with two different blade radius of curvature based on the pumping efficiency under the operating conditions in Korea. And the pump performance of the impeller was also tested for the various speeds. The results obtained are summarized as follows; 1. There was no significant effect on the different blade radius of curvatures on the discharge and pump efficiency. 2. Head and power requirement was increased in proportion to the blade radius of curvature. 3. In the mathematical approach of the blade radius of curvature, the method of involute curve was more recommendable as compared with the method of circular arc curve. 4. The pump efficiency of the model impeller developed based on the theoretical analysis increased about 10% more than that of the existing impeller.

• Journal of the Korean Chemical Society
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• v.16 no.6
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• pp.341-348
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• 1972

The significance of the curvature dependency correction of surface tension is studied in calculating the pore volume distribution of porous adsorbent from nitrogen adsorption isotherm. That is, Kelvin radii are calculated with curvature dependent surface tension values calculated by Chang et al, and then with these Kelvin radii, pore volume distributions of three porous adsorbents, silica alumina (steam deactivated), silica gel (Davidson 59), and silica gel (Mallinc-krodt Standard Luminescent), are calculated. The results are compared with those obtained by the previous method in which surface tension is taken as constant and also with the others. obtained by the modelless method proposed by Brunauer et al. The maximum point of the distribution curve shift to the larger pore radius, when the curvature dependency is considered. Furthermore, the relative pressure at which capillary condensation commences is by far the lower than that accepted previously. This effect becomes significant as the pore radius approaches to the micropore range.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.4
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• pp.289-295
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• 2009

In this paper the measurement method of cable's curvature using fiber optic microbend effect and its experimental results are presented. The novel structure of fiber optic microbender, which can generate microbend effect on the optical fiber in the case of both directional bending of cable, was designed. Through the experiment using suggested sensing system, the increasing trend of attenuated optical power was found out under the range from $0.1\;cm^{-1}$ to $0.4\;cm^{-1}$ of curvature. To the multi and distributed measurement, using OTDR, the scattered optical pulses at the bending points are measured and compared with the result which was measured by optical power meter.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.75-81
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• 2001

In this paper we analyzed the localization error of near-field detection algorithm in the sea. The near-field detection algorithms using triangulation and wavefront curvature basically assume a signal in two dimension of bearing and range. But the assumption causes localization error because there is three dimension of bearing, range, and depth in the sea. Even through three dimensional effect is considered, the localization error is occurred if multipath propagation in the sea is ignored. To analyze the localization error in the sea, we simulate the near-field localization using acoustic propagation model and focused beamforming considering wavefront curvature. The simulation results indicate that localization error always occurs in the sea and the error varied with sound velocity profile, water depth, bottom slope, source range, etc.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.803-811
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• 2002

Current composite steel and concrete bridges are designed using full-interaction theory assuming there is no relative slip, between the steel and concrete components along their interface, because of the complexities of partial-interaction analysis techniques. However, in the assessment of existing composite bridges this simplification may not be warranted as it is often necesary to extract the correct capacity and endurance from the structure. This may only be achieved using partial-interaction theory which tuly reflects the behaviour of the structure. In this paper, Parametric analyses have been carried out in order to confirm the partial-interaction curvatures with deflection effect using the finite element method. Therefore, the model is considered for simply supported steel and concrete composite bridges with a uniform distribution of connectors subjected to a single concentrated load. For the case studies, this study applicate a parameters such as the number and space of stud shear connector and elastic modulus of concrete slabs. From this study, it is known that partial-interaction effect was in the increase to the increasing the deflection of composite bridges, and stiffness and strength of slab concrete considering the occurrence of crack effect seriously to the partial-interaction behavior.

• Korean Journal of Applied Biomechanics
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• v.30 no.1
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• pp.93-101
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• 2020

Objective: The purpose of this study was to differences of foot plantar pressure balance and lung capacity according to cervical posture in adults. Method: The subjects consisted of 33 adults in their 20s and 50s who use M centers in B-gu and H-gu, B-City, and they measured foot plantar pressure balance and lung capacity according to cervical posture (cervical normal curvature posture, cervical flexural posture) in adults. Results: In this study, the difference of foot plantar pressure balance according to cervical posture were analyzed. In the difference between left and right foot pressure balance. It was 1.50% increased in the cervical flexural posture than in the cervical normal curvature posture, and a statistically significant difference was observed. In the difference between the anterior and posterior foot pressure balance. It was 4.28% increased in the cervical flexural posture than in the cervical normal curvature posture, and a statistically significant difference was observed. The difference of lung capacity according to cervical posture were analyzed. In the PEF, It was 58.63 l/min decreased in the cervical flexural posture than in the cervical normal curvature posture, and a statistically significant difference was observed. In the FEV1, It was 0.15 ℓ decreased in the cervical flexural posture than in the cervical normal curvature posture, and a statistically significant difference was observed. Conclusion: The results of this study suggest that had a positive effect on differences of foot plantar pressure balance and lung capacity at cervical normal curvature posture in adults. In future research, itis believed that research on the elderly who have collapsed the normal curvature posture due to aging, as well as teenagers whose normal curvature posture due to the use of smartphones, will contribute to the balance of foot pressure and improvement of the right cervical habits. In future studies, it is also believed that it will be necessary to measure lung capacity after performing exercise according to the cervical posture, thereby providing sufficient oxygen during exercise to enhance the persistence and efficiency of the movement.

• Proceedings of the Korean Geotechical Society Conference
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• 1988.06c
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• pp.71-123
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• 1988

The aim of this paper is to examine the end bearing capacity of a pile in cohesionless soils. The ode of failure of soil due to pile installation is assumed from experimental observation of actual soil deformation. A new solution is proposed complying with the assumed mode of failure by employing the theory of cavity expansion. The effect of curvature of failure envelope is studied in relation to tile proposed solution. The influence of a curved failure envelope becomes larger with increasing degree of curvature and the level of confining stress. This effect in some cases or reduce the end bearing capacity by tore the 80 percent compared with that given by a straight failure envelope. For practical application of tile proposed solution, the method of determining the average volume change in the plastic zone is re-evaluated. The proposed solution is confirmed by comparing the theoretical values with experimental results obtained from model pile tests in a calibration chamber. The comparison shows that the proposed solution provides a reasonable prediction of end bearing capacity for both weak and strong grained soils.