• Journal of Korean Neurosurgical Society
• /
• v.43 no.2
• /
• pp.119-122
• /
• 2008

The crossing laminar screw fixation might be the most recently developed approach among various fixation techniques for C2. The new construct has stability comparable to transarticular or transpedicular screw fixation without risk of vertebral artery injury. Quantitative anatomical studies about C2 vertebra suggest significant variation in the thickness of C2 lamina as well as cross sectional area of junction of lamina and spinous process. We present an elderly patient who underwent an occipito-cervical stabilization incorporating crossed C2 laminar screw fixation. We preoperatively recognized that she had low profiles of C2 lamina, and thus made a modification of trajectory for the inferiorly crossing screw. We introduce a simple modification of crossing C2 laminar screw technique to improve stability in patients with low laminar profiles.

• Transactions of the Korean hydrogen and new energy society
• /
• v.27 no.6
• /
• pp.737-746
• /
• 2016

This article describes a comparison on laminar burning velocity measured by Bunsen and spherical flame methods of synthetic natural gas (SNG) with various composition of hydrogen. In this study, the laminar burning velocity measurements were employed by Bunsen burner and cylindrical constant combustor at which flame images were captured by Schlieren system. These results were also compared with numerical based on CHEMKIN package with GRI 3.0, USC-II and UC Sandiego mechanism. In case of spherical flames, the suitable flame radius range and theoretical models were verified using the well-known previous results in methane/air flames. As an experimental condition, hydrogen content of SNG was adjusted 0% to 11%. Equivalence ratios of Bunsen flames were adjusted from 0.8 to 1.6. On the other hand, those of spherical flames were adjusted from 0.6 to 1.4, relatively. From results of this study, the both laminar burning velocities measured in Bunsen and spherical flame methods were resulted in similar tendency. As the hydrogen content increased, the laminar burning velocity also increased collectively. Laminar burning velocity of measured SNG-air flames was best coincided with GRI 3.0 mechanism by comparison of reaction mechanisms.

• Journal of Biomedical Engineering Research
• /
• v.17 no.4
• /
• pp.515-524
• /
• 1996

The flow characteristics of developing unsteady laminar flow in a square-sectional $180^{\circ}$ curved duct are experimentally investigated by using laser doppler velocimerty (LDV) system with data acquisition and processing system of rotating machinery resolver(RMR) and PHASE software. The major flow characteristics of developing laminar pulsating flows are presented by mean velocity profilel velocity distribution of secondary flow, wall shear stress distributions, entrance lengths according to dimensionless angular frequency($\omega^+$), velocity amplitude ratio($A^1$), and time-averaged Dean number($De_ta$). The velocity profiles and wall shear stress distribution of laminar pulsating flow with dimensionlessangular frequency show the flow characteristics of the quasi-steady laminar flow in a curved duct. The developing region of laminar pulsatile flows in a square-sectional $180^{\circ}$ curved duct is extended to the curved duct angle of approximately $120^{\circ}$ under the present experimental condition.

• Advances in Energy Research
• /
• v.4 no.3
• /
• pp.213-221
• /
• 2016

The main purpose of this work is to test the validation of use of a four step reaction mechanism to simulate the laminar speed of hydrogen enriched methane flame. The laminar velocities of hydrogen-methane-air mixtures are very important in designing and predicting the progress of combustion and performance of combustion systems where hydrogen is used as fuel. In this work, laminar flame velocities of different composition of hydrogen-methane-air mixtures (from 0% to 40% hydrogen) have been calculated for variable equivalence ratios (from 0.5 to 1.5) using the flame propagation module (FSC) of the chemical kinetics software Chemkin 4.02. Our results were tested against an extended database of laminar flame speed measurements from the literature and good agreements were obtained especially for fuel lean and stoichiometric mixtures for the whole range of hydrogen blends. However, in the case of fuel rich mixtures, a slight overprediction (about 10%) is observed. Note that this overprediction decreases significantly with increasing hydrogen content. This research demonstrates that reduced chemical kinetics mechanisms can well reproduce the laminar burning velocity of methane-hydrogen-air mixtures at lean and stoichiometric mixture flame for hydrogen content in the fuel up to 40%. The use of such reduced mechanisms in complex combustion device can reduce the available computational resources and cost because the number of species is reduced.

• Journal of Korean Neurosurgical Society
• /
• v.56 no.1
• /
• pp.5-10
• /
• 2014

Objective : When the pedicle screw insertion technique is failed or not applicable, C7 intralaminar screw insertion method has been used as an alternative or salvage fixation method recently. However, profound understanding of anatomy is required for safe application of the bilaterally crossing laminar screw at C7 in clinic. In this cadaveric study, we evaluated the anatomic feasibility of the bilateral crossing intralaminar screw insertion and especially focused on determination of proper screw entry point. Methods : The C7 vertebrae from 18 adult specimens were studied. Morphometric measurements of the mid-laminar height, the minimum laminar thickness, the maximal screw length, and spino-laminar angle were performed and cross-sectioned vertically at the screw entry point (spino-laminar junction). The sectioned surface was equally divided into 3 parts and maximal thickness and surface area of the parts were measured. All measurements were obtained bilaterally. Results : The mean mid-laminar height was 13.7 mm, mean minimal laminar thickness was 6.6 mm, mean maximal screw length was 24.6 mm, and mean spinolaminar angle was $50.8{\pm}4.7^{\circ}$. Based on the measured laminar thickness, the feasibility of 3.5 mm diameter intralaminar screw application was 83.3% (30 sides laminae out of total 36) when assuming a tolerance of 1 mm on each side. Cross-sectional measurement results showed that the mean maximal thickness of upper, middle, and lower thirds was 5.0 mm, 7.5 mm, and 7.3 mm, respectively, and mean surface area for each part was $21.2mm^2$, $46.8mm^2$, and $34.7mm^2$, respectively. Fourteen (38.9%) sides of laminae would be feasible for 3.5 mm intralaminar screw insertion when upper thirds of C7 spino-laminar junction is the screw entry point. In case of middle and lower thirds of C7 spino-laminar junction, 32 (88.9%) and 28 (77.8%) sides of laminae were feasible for 3.5 mm screw insertion, respectively. Conclusion : The vertical cross-sectioned area of middle thirds at C7 spinolaminar junction was the largest area and 3.5 mm screw can be accommodated with 77.8 % of feasibility when lower thirds were the screw entry point. Thus, selection of middle and lower thirds for each side of screw entry point in spino-laminar junction would be the safest way to place bilateral crossing laminar screw within the entire lamina. This anatomic study result will help surgeons to place the screw safely and accurately.

• 한국연소학회:학술대회논문집
• /
• 2015.12a
• /
• pp.77-78
• /
• 2015

Laminar burning velocities have been predicted by constant volume combustion chamber, counter flow burner and others. In this study, the measured flame propagation velocities in an assembled annular stepwise diverging tube were plotted with respect to equivalence ratio, length scale, and velocity scale. Three dimensional approach to understand the flame propagation velocity including laminar burning velocity is investigated, and the surface provides the correlation among quenching distance, propagation velocity, and equivalence ratio.

• 한국연소학회:학술대회논문집
• /
• 2013.06a
• /
• pp.103-105
• /
• 2013

Spherically expanding flames are used to measure flame speeds, which are derived the corresponding laminar flame speeds at zero stretch. Dimethyl Ether-Air mixtures at high pressure are studied over an extensive range of equivalence ratios. The classical shadowgraph technique is used to detect the reaction zone. In analytical methodology the optimization process using least mean squares is performed to extract the laminar flame speeds. Laminar flame speeds are compared with results reported in the literature.

• Journal of Korean Neurosurgical Society
• /
• v.50 no.1
• /
• pp.11-16
• /
• 2011

Objective : The purpose of the present study was to determine the incidence of dural tears and predictable factors suggesting dural tears in patients who had lumbar burst fractures with vertical laminar fractures. Methods : A retrospective review was done on thirty-one patients who underwent operative treatment for lumbar burst fractures with vertical laminar fractures between January 2003 and December 2008. All patients were divided into two groups according to existence of dural tears, which were surgically confirmed; 21 patients with dural tears and 10 patients without dural tears. Clinical and radiographic findings were analyzed for their association with dural tears. Results : Among a total of 31 patients, dural tears were detected in 21 (67%) patients. A preoperative neurological deficits and mean separation distances of the edges in laminar fractures were found to be the reliable factors of dural tears (p=0.001 and 0.002, respectively). Decreased ratio of the central canal diameter and interpedicular distance were also the reliable factors suggesting dural tears (p=0.006 and 0.015, respectively). However, dural tears showed no significant association with age, sex, level of injury, absence of a posterior fat pad signal, the angle of retropulsed segment, or site of laminar fracture. Conclusion : Our study of lumbar burst fracture combined laminar fracture revealed that dural tears should be ruled out in cases of a preoperative neurological deficits, wide separation of the laminar fracture, severe canal encroachment, and wider interpedicular distance.

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.5
• /
• pp.509-518
• /
• 2005

Liquid film thickness in laminar film condensation for flow over a flat plate generally is so thin that both fluid acceleration and thermal convection within the liquid film can be neglected. An integral solution method is proposed to solve the conjugate problems of laminar film condensation and heat conduction in a solid wall. It is found that approximate solutions of the governing equations involve four physical parameters to describe the conjugate heat transfer problem for laminar film condensation. It is shown that the effects of interfacial shear. mass transfer and local heat transfer are strongly dependent on the thermo-physical properties of the working fluids and the Jacob number.

• Journal of computational fluids engineering
• /
• v.7 no.3
• /
• pp.53-59
• /
• 2002

A two-dimensional laminar flow through a channel with a pair of symmetric vertical fins is investigated. At far up- and down-stream from the fins, the plane Poiseuille flow exists in the channel. The Stokes flow for this channel is first investigated analytically and then the other laminar flows by numerical method. For analytic method, the method of eigen function expansion and collocation method are employed. In numerical solution for laminar flows, finite difference method(FDM) is used to obtain vorticity and stream function. From the results, the streamline patterns are shown and the additional pressure drop due to the attached fins and the force exerted on the fin are calculated. It is clear that the force depends on the length of fins and Reynolds number. When the Reynolds number exceeds a critical value, the flow becomes asymmetric. This critical Reynolds number Re/sub c/ depends on the length of the fins.