• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.5
• /
• pp.49-59
• /
• 2008

The effects of design parameters on the pellet transport rate in the ejector system which is widely used in the production processes of automotive parts were investigated experimentally. The primary nozzle geometry, the area ratio (R) of nozzle exit cross-sectional area to mixing chamber cross-sectional area and the distance (S) from primary nozzle exit to mixing chamber entrance were considered as the design parameters. The area ratios of the primary nozzle were varied from R=0.10 to R=0.25, 0.30, 0.40 and 0.55. The primary nozzle was positioned at the non-dimensional distance (S/D) of 1.30, 1.87, 2.44, 3.00 and 3.75, normalized using the mixing chamber diameter (D). The design parameters were determined to run with high efficiency by measuring the pellets transport rate. The geometry and the area ratio (R) of the primary nozzle had an effect on the pellet transport rate of the ejector system, and the area ratio of R=0.3 was carefully selected after taking the minimum fluidization velocity and transport rate of applied pellets into account. The higher pellet transport rate with the variation of the distance (S/D) was observed at S/D of 2.44.

• Journal of the Korean Society of Physical Medicine
• /
• v.5 no.2
• /
• pp.233-243
• /
• 2010

Purpose : This study aimed to examine the effects of sling exercise therapy on the relief of low back pain and the cross-sectional area change of lumbar muscles by CT analysis for chronic low back pain patients. Methods : Forty-one patients with diagnosis of chronic low back pain was divided sling exercise therapy group(SEG) 19 subjects and conservative physical therapy group(CPG) 22 subjects. we randomized and treated them(subjects) for 12 weeks. As using visual analogue scale(VAS), we evaluated recovery accuracy of pain, and for investigating cross-section area change of lumbar muscles for before and after treatment we used computed tomography(CT). Results : This study were summarized as follows : 1) As treatment period, in each compared testing on VAS of SEG and CPG, the both group was significantly different(p<.05). 2) Compared testing on VAS of between-subject groups(SEG and CPG) were not significantly different(p>.05). 3) At SEG of before and after treatment, in compared testing on cross-section area size of lumbar muscles, All muscles of psoas major, quadratus lumborum, erector spinae and multifidus were significantly different(p<.05). At CPG, psoas major was significantly different(p<.05). But other muscles were not significantly different(p>.05). Conclusion : From this result, both sling exercise therapy and the conservative physical therapy are effect on decrease of pain for chronic low back pain patients. but Increasing of the cross-section area being proportioned with muscular strengthening of low back muscle is noticeable difference in SEG. Therefore, sling exercise therapy have affect both decreasing of pain for chronic low back pain patients and lumbar muscles strengthening.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.09a
• /
• pp.9-16
• /
• 2000

Applicability of the cross shaped drain in a soft clay ground is examined using the laboratory discharge capacity test, column consolidation test and 3-D numerical flow analysis. The equivalent diameter of the tested drains is back-calculated from the laboratory experiment and compared with those calculated from the formula suggested in the literature. The effective range of the cross shaped drain about the discharge capacity and coefficient of permeability is analyzed. The results of numerical analysis show that the cross shaped drain which has a cross-sectional area twice of the band shaped drain can reduce the consolidation time by 30% from that for the band shaped drain in a soft clay ground that K is over 1${\times}$10$\^$-7/cm/sec

• International Journal of Aeronautical and Space Sciences
• /
• v.17 no.3
• /
• pp.409-422
• /
• 2016

A parametric study based on an unsteady mathematical model of a pyrotechnically actuated device was performed for design optimization. The model simulates time histories for the chamber pressure, temperature, mass transfer and pin motion. It is validated through a comparison with experimentally measured pressure and pin displacement. Parametric analyses were conducted to observe the detailed effects of the design parameters using a validated performance analysis code. The detailed effects of the design variables on the performance were evaluated using the one-at-a-time (OAT) method, while the scatter plot method was used to evaluate relative sensitivity. Finally, the design optimization was conducted by employing a genetic algorithm (GA). Six major design parameters for the GA were chosen based on the results of the sensitivity analysis. A fitness function was suggested, which included the following targets: minimum explosive mass for the uniform ignition (small deviation), light casing weight, short operational time, allowable pyrotechnic shock force and finally the designated pin kinetic energy. The propellant mass and cross-sectional area were the first and the second most sensitive parameters, which significantly affected the pin's kinetic energy. Even though the peak chamber pressure decreased, the pin kinetic energy maintained its designated value because the widened pin cross-sectional area induced enough force at low pressure.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.45 no.4
• /
• pp.237-240
• /
• 2000

This experiment was conducted to evaluate the effect of split application of nitrogen(N) on development of vascular bundle(VB) and yield components of rice. Two cultivars were used in this study; IR58, an indica type and Shinunbongbyeim a japonica type. The number and total cross sectional area of the VB in the peduncle and leaf blade were more and bigger in N split application than 100 percent basal fertilizer. Nitrogen split application at necknode differentiation stage increased the number and size of the VB. Nitrogen split application resulted in increased panicle number with application of N before transplanting and at tillering stage; increased spikelets number with N application at necknode differentiation stage; and increased spikelet fertility and 1000 grain weight with N application at necknode differentiation and heading stages. Grain yield increased 7-10% in N split as compared to all basal application. The total cross sectional area of VB in peduncle closely correlated with the number of spikelets per panicle. Nitrogen management can have an impact on spikelet differentiation through more and bigger VB and increase grain yield potential.

• Journal of the Korean Society of Physical Medicine
• /
• v.5 no.4
• /
• pp.615-621
• /
• 2010

Purpose : The purpose of this study was to compare chronic LBP patients and asymptomatic subjects on measures of multifidus size (cross-sectional area;CSA, thickness) and symmetry (proportional difference of relatively larger side to smaller side). Methods : Data were obtained from 12 asymptomatic subjects without a prior history of LBP (8 females, 4 males), and a retrospective audit was undertaken of records from 12 chronic low back pain patients (8 females, 4 males). CSA and Thickness of the lumbar multifidus muscles was measured from axial T1-weighted magnetic resonance images(MRI). Results : The results of the analysis showed that chronic LBP patients had significantly smaller multifidus CSA and thickness than asymptomatic subjects at L4-5 vertebral levels(p<.05). The asymmetry between sides was seen at L4- L5 vertebral level in patients with chronic low back pain presentations(p<.05). Conclusions : MRI provided a quantitative measure of change between asymptomatic subjects and chronic low back pain patients of multifidus muscle. MRI identified significant differences in cross-sectional area and thickness and helps to evaluate clinically and plan the treatment modalities of LBP.

• Journal of Chest Surgery
• /
• v.26 no.5
• /
• pp.343-348
• /
• 1993

Growth of suture line and anastomosis is required for long-term success after the tracheal and bronchial surgery in infant and pediatric patient. We used various suture materials in these cases, but the results were differ. To select the adequate suture material in tracheal surgery, we tried next. Tracheal anastomoses were performed in 150 Sprague Dawley rats, aged 4 to 8 [mean 5.8] weeks and weight 62 to 106[mean 83.6] gram, to compare polydioxanone[PDS] 7-0, polyglactin 910[Vicryl]7-0, and polypropylene [prolene] 8-0 suture materials. In 150 rats, only 29[20%] were lived over 300 days, and the weight was 250 to 320[mean 289.5]gram. Cross sectional area of the anastomoses and two or three tracheal rings below anastomosis site were measured under microscope, and calculated and compared as Hsieh`s equition. Cross-sectional area,anastomosis site/normal site 100, were 89.4 $\pm$ 5.34% in PDS group[n=9], 75.7 $\pm$ 6.06% in Vicrylgroup [n = 10], and 80.8$\pm$ 4.06% in Prolene group[n = 10]. Histopathologic studies were done for all autopsies or put in death around 300 days postoperatively. PDS absorblion was not seen 16 weeks after suture but disappeared over 24 weeks slide. Vicryl absorbtion was noted postoperative 8 to 16 weeks, with marked tissue reaction. Prolene showed least tissue reaction, but the suture material was persisted with regional fibrotic capsule.Causes of death were respiratory failure in 76 cases, tracheal rupture in 22 cases, hemorrhage, biting, starvation and etc. in 23 cases. With the brief review of literatures, we report the results.

• Journal of Korea Foundry Society
• /
• v.26 no.2
• /
• pp.85-91
• /
• 2006

Inclusions in Ti investment castings are generally known to have detrimental effects on the performance of the castings. However, actual inclusions are infrequent and hard to be located. As a result, it is extremely difficult to obtain sufficient amount of fatigue test specimens of titanium investment castings having inclusions in the gage section. Thus, in-depth research of the adverse influence of inclusions is also hindered. To address this problem, a new casting methodology of specimens containing hard alpha inclusions was developed in this study. To guarantee successful introduction of an inclusion and casting, a carefully designed mold with 8 legs and a special tool were employed. After solidification, castings were cut, and X-ray radiography determined that the inclusions were successfully incorporated into the castings. The castings were further prepared to obtain multiple test specimens and they were fatigue-tested consecutively. Fractography analysis confirmed that fatigue cracks initiated at the hard alpha inclusion. In a nonlinear regression model, the fatigue life can be modeled as an exponential function with a negative exponent of the cross-sectional area of an inclusion. The fatigue life of Ti specimens containing inclusions is inversely proportional to the cross-sectional area of an inclusion.

• Computers and Concrete
• /
• v.9 no.6
• /
• pp.469-486
• /
• 2012

This paper presents Neuro-Fuzzy (NF) based empirical modelling of torsional strength of RC beams for the first time in literature. The proposed model is based on fuzzy rules. The experimental database used for NF modelling is collected from the literature consisting of 76 RC beam tests. The input variables in the developed rule based on NF model are cross-sectional area of beams, dimensions of closed stirrups, spacing of stirrups, cross-sectional area of one-leg of closed stirrup, yield strength of stirrup and longitudinal reinforcement, steel ratio of stirrups, steel ratio of longitudinal reinforcement and concrete compressive strength. According to the selected variables, the formulated NFs were trained by using 60 of the 76 sample beams. Then, the method was tested with the other 16 sample beams. The accuracy rates were found to be about 96% for total set. The performance of accuracy of proposed NF model is furthermore compared with existing design codes by using the same database and found to be by far more accurate. The use of NF provided an alternative way for estimating the torsional strength of RC beams. The outcomes of this study are quite satisfactory which may serve NF approach to be widely used in further applications in the field of reinforced concrete structures.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.403-408
• /
• 2003

The objective of this study is to understand the variables affected the confinement for the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The structural performance of T-shaped walls was advanced by the transverse reinforcement which restrained the concrete subjected to compressive stress. If the arrangement of transverse reinforcement was not suitable for the confinement, T-shaped walls happened the brittle failure by web crushing or bucking of vertical reinforcement at the compression zone. It is necessary to confine transverse reinforcement in order to prevent the these failure. But the location of neutral axis and the magnitude of ultimate strain vary according to the section shape, a ratio of axial load, a ratio of wall cross sectional area to the floor-plan area, an aspect ratio and the reinforcement ratio. Therefore, the objective of this research is to grasp the location of neutral axis and the range which needs for the confinement of transverse reinforcement through the results of the sectional analysis which varies the ratio of axial load and the ratio of vertical reinforcement.