• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.40 no.4
• /
• pp.393-400
• /
• 2020

Axial and lateral behavior of helical piles is generally influenced by number, diameter, helix pitch, and locations of helices. In this study, axial and horizontal behavior of helical piles with three helices was investigated varying helices' locations, diameter, and pitch. Especially, due to the spiral shapes of helices, the effect of lateral load directions at pile heads on their lateral behavior was investigated. Axial load test of small-scale helical pile was conducted in laboratory, and its results were compared with numerical analysis results of the same model for cross check of validity of both results. Furthermore, diverse numerical analyses were performed for different shapes of helical piles. Consequently, it was found that, for the given analysis conditions, the helix diameter was the most influential factor on the horizontal and vertical behavior of helical piles.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.35 no.2
• /
• pp.377-386
• /
• 2015

The helical pile is a manufactured steel pile consisting of one or more helix-shaped bearing plates affixed to a central shaft. This pile is installed by rotating the shaft into the ground to support structural loads. Advantages of the helical pile are no need for boring or grout process, and ability to install a pile foundation with relatively light devices. In this study, an optimized design method for helical piles is proposed to minimize the material cost with consideration of the load bearing capacity obtained by the cylindrical shear method. The harmony search meta-heuristic algorithm was adopted for optimization process. The optimized design was verified by comparing with the 2009 International building code. It is noted that the optimization for the configuration of helical piles along with material cost proves to be an out-performed tool in designing helical pile foundation with economic feasibility.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.29 no.1
• /
• pp.21-32
• /
• 1999

Purpose: To evaluate the effect of variable scanning protocols of computed tomography for evaluation of pre-implant site of the mandible through the comparison of the reformatted cross-sectional images of helical CT scans obtained with various imaging parameters versus those of conventional CT scans. Materials and Methods: A dry mandible was imaged using conventional nonoverlapped CT scans with 1 mm slice thickness and helical CT scans with 1 mm slice thickness and pitches of 1.0, 1.5. 2.0, 2.5 and 3.0. All helical images were reconstructed at reconstruction interval of 1 mm. DentaScan reformatted images were obtained to allow standardized visualization of cross-sectional images of the mandible. The reformatted images were reviewed and measured separately by 4 dental radiologists. The image qualities of continuity of cortical outline. trabecular bone structure and visibility of the mandibular canal were evaluated and the distance between anatomic structures were measured by 4 dental radiologists. Results: On image qualities of continuity of cortical outline. trabecular bone structure and visibility of the mandibular canal and in horizontal measurement. there was no statistically significant difference among conventional and helical scans with pitches of 1.0. 1.5 and 2.0. In vertical measurement. there was no statistically significant difference among the conventional and all imaging parameters of helical CT scans with pitches of 1.0, 1.5, 2.0, 2.5 and 3.0. Conclusion: The images of helical CT scans with 1 mm slice thickness and pitches of 1.0, 1.5 and 2.0 are as good as those of conventional CT scans with 1 mm slice thickness for evaluation of predental implant site of the mandible. Considering the radiation dose and patient comfort, helical CT scans with 1 mm slice thickness and pitch of 2.0 is recommended for evaluation of pre-implant site of the mandible.

• Journal of the Korean Wood Science and Technology
• /
• v.15 no.2
• /
• pp.79-89
• /
• 1987

This study was executed to examine helical structure and other feature, of Taxus cuspidata S. et Z. and Larix gmelinii var. principis-ruprechtii Pilger through photomicroscopic and scanning electron microscopic observation, and the obtained result, were summarized as follows: 1. Tracheid transition from springwood to summerwood was abrupt, mel slightly gradual in Taxus cuspidata S. et Z. and summerwood width of Larix gmelinii var. principis-ruprechtii Pilger was wider than that of Taxus cuspidata S. et Z. 2. Normal vertical and horizontal resin canals and surrounding thick epithelial cells were present in Larix gmelinii var. principis-ruprechtii Pilger but not present in Taxus cuspidata S. et Z. 3. Instead of helical thickening, helical chicks were observed only in summerwood trachieds of Larix gmelinii var. principis-ruprechtii Pilger. However, helical thickenings forming S, Z., and horizontal helix perpendicular to long axis of tracheid were observed in springood and summerwood tracheids of Taxus cuspidata S. et Z. and these helical thickenings were considered as analogous to the innermost layer of secondary wall. 4. Uniseriate and fusiform rays were appeared on tangential surface of Larix gmelinii var. principis-ruprechtii Pilger but oly uniserate ray was observed on tangential surface ot Taxus cuspidata S. et Z. The fusiform rays of Larix gmelinii var. principis-ruprechtii Pilger usually contained one horizontal resin canal bot occasionally two horizontal resin canals were contained in a fusiform ray. 5. Trabeculae and crassulae were observed in the tracheids of Larix gmelimii var. principis-ruprechtii Pilger but not observed in the tracheids of Taxus cuspidata S. et Z.

• Imaging Science in Dentistry
• /
• v.34 no.3
• /
• pp.151-157
• /
• 2004

Purpose : To evaluate the quantitative accuracy of three-dimensional (3D) images by means of comparing distance measurements on the 3D images with direct measurements of dry human skull according to slice thickness and scanning modes. Materials and Mathods : An observer directly measured the distance of 21 line items between 12 orthodontic landmarks on the skull surface using a digital vernier caliper and each was repeated five times. The dry human skull was scanned with a Helical CT with various slice thickness (3, 5, 7 mm) and acquisition modes (Conventional and Helical). The same observer measured corresponding distance of the same items on reconstructed 3D images with the internal program of V-works 4.0/sup TM/(Cybermed Inc., Seoul, Korea). The quantitative accuracy of distance measurements were statistically evaluated with Wilcoxons' two-sample test. Results: 11 line items in Conventional 3 mm, 8 in Helical 3mm, 11 in Conventional 5mm, 10 in Helical 5mm, 5 in Conventional 7mm and 9 in Helical 7mm showed no statistically significant difference. Average difference between direct measurements and measurements on 3D CT images was within 2mm in 19 line items of Conventional 3mm, 20 of Helical 3mm, 15 of Conventional 5mm, 18 of Helical 5mm, II of Conventional 7mm and 16 of Helical 7mm. Conclusion: Considering image quality and patient's exposure time, scanning protocol of Helical 5mm is recommended for 3D image analysis of the skull in CT.

• Journal of the Korean Society of Radiology
• /
• v.7 no.4
• /
• pp.307-311
• /
• 2013

This study examined the change of artifact volume by analyzing the level of image change associated with the setting of threshold through 3D imaging in scan parameter(slice thickness and helical pitch) and 3D image reconstruction to explore whether the presence of pathology was fully distinguished when CT was taken by lower dose than the existent dose to reduce exposure. Furthermore, this study attempted to investigate Scan Parameter acceptable in CT to reduce exposure dose. For materials and methods, silicon was used to produce samples. Five spherical samples were produced at 10-millimeter intervals(50, 40, 30, 20, and 10 mm) in diameter and were fixed at 120 Kvp of tube voltage and 50 mA of tube current. Varied slab thickness((1.0, 2.0, 3.0, 5.0, and 7.0mm) and Helical Pitch(1.5, 2.0, 3.0) were scanned. The image at an interval of 1.0, 2.0, 3.0, 5.0, and 7.0mm was transmitted to the workstation. Threshold(-200, -50, 50 ~ 1,000) was changed using the volume rendering technique, 3D image was reconstructed, and artifact volume was measured. In conclusion, 1.5 of Helical Pitch showed the least change of volume and 3.0 of helical pitch showed the greatest reduction of volume change. The experiment suggested that as slice thickness was increased, artifact volume was decreased more than actual measurement. Furthermore, in the 3D image reconstruction, when the range of threshold was set as -200 ~1,000, artifact volume was changed the least. Based on the results, it is expected to have an effect of reducing exposure dose.

• Advances in aircraft and spacecraft science
• /
• v.5 no.1
• /
• pp.73-105
• /
• 2018

A particular type of constant speed helical trajectory, with variable ascension rate, is proposed. Such trajectories are candidates of choice as motion primitives in automatic airplane trajectory planning; they can also be used by airplanes taking off or landing in limited space. The equations of motion for airplanes flying on such trajectories are exactly solvable. Their solution is presented, together with an analysis of the restrictions imposed on the geometrical parameters of the helical paths by the dynamical abilities of an airplane. The physical quantities taken into account are the airplane load factor, its lift coefficient, and the thrust its engines can produce. Formulas are provided for determining all the parameters of trajectories that would be flyable by a particular airplane, the final altitude reached, and the duration of the trajectory. It is shown how to construct speed interval tables, which would appreciably reduce the calculations to be done on board the airplane. Trajectories are characterized by their angle of inclination, their radius, and the rate of change of their inclination. Sample calculations are shown for the Cessna 182, a Silver Fox like unmanned aerial vehicle, and the F-16 Fighting Falcon.

• Korean Journal of Optics and Photonics
• /
• v.25 no.6
• /
• pp.311-314
• /
• 2014

In this paper, we design a helical fin structure for the heat sink for a high-power LED lighting module, and analyze its thermal properties. By means of the helical fin structure, we can obtain about 14% larger surface area for the limited volume and it can decrease the LED chip temperature by about 12%. Because this helical fin heat sink has 15% less total volume than a conventional one, we can also expect to reduce the production cost due to these structural properties.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.11
• /
• pp.1428-1436
• /
• 2000

The absorption of vapor involves simultaneous heat and mass transfer in the vapor/liquid system. In this paper, a numerical study for vapor absorption process into LIBr-H$_2$O solution film flowing over helical absorber has been carried out. Axisymmetric cylindrical coordinate system was adopted to model the helical tube and the transport equations were solved by the finite volume method. The effects of operating conditions, such as the cooling water temperature. the system pressure, the film Reynolds number and the solution inlet concentration have been investigated in view of the absorption mass flux and the total absorption mass flux and the total absorption rate. The results for the temperature and concentration profiles, as well as the local absorption mass flux at the helical absorber are presented. It is shown that solution inlet concentration affected other than operation conditions for a mass flux.

• BMB Reports
• /
• v.30 no.6
• /
• pp.426-430
• /
• 1997

The helical periodicity of the triple-stranded $(dT)_n{\cdot}(dA)_n{\cdot}(dT)_n$ sequence was determined by measuring gel-mobilities of bent DNA fragments containing the sequence. In the bent DNA fragments, a $GA_{22}G$ $CT_{22}C$ sequence was located between two bent DNA loci composed of six $A_{6}{\cdot}T_{6}$ repeats. and the DNA length between the bent DNA loci was varied by 1 base pair over a full helical turn. The gel mobility of each bent DNA fragment reflected the overall extent of DNA bending and varied with the DNA length between the two bent loci. Mobilities of the bent DNA fragments in 5% polyacrylamide gel were measured after preincubating the DNA fragments both in the presence and absence of $CT_{22}C$ oligonucleotide. By comparing the bent DNA fragments containing an intermolecular triplex structure with those of a genuine duplex structure in the gel mobilities, the helical periodicity of the $T_n{\cdot}A_n{\cdot}T_n$ triplex DNA was determined to be $11.5({\pm}0.3)bp/turn$.