• Journal of Periodontal and Implant Science
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• v.38 no.sup2
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• pp.385-394
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• 2008

Purpose: The aim of this study was to evaluate the factors affecting healing patterns of surgically created circumferential gap defects around implants in dogs. Materials and Methods: In four mongrel dogs, all mandibular premolars were extracted. After 8 weeks of healing periods, implants were submerged. According to the surface treatment, turned surface was designated as a group A and rough surface as a group B. In each dog, surgical defects on the left side were made with a customized tapered step drill and on the right with a customized paralleled drill. Groups were also divided according to the width of the coronal gaps: 1.0mm, 1.5mm, or 2.0mm. The dogs were sacrificed following 8 weeks and the specimens were analyzed histologically and histomorphometrically. Results: During the postoperative period, healing was uneventful and implants were well-maintained. As the size of the coronal gap was increased, the amount of bone-to-implant contact was decreased. The bone healing was greater in rough surface implants compared to the turned ones. About the defect morphology, tapered shape showed much bone healing and direct bone to implant contact even in the smooth surface implants. Conclusion: Healing of the circumferential defect around dental implant is influenced by the implant surface, defect width and the morphology of the defect. When using rough surface implants, circumferential gap defects within 2 mm do not need any kinds of regenerative procedures and the healing appeared to be faster in the tapered defect morphology than the paralleled one.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.337-345
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• 1999

The purpose of this study was to compare the shape of root canal after instrumentation with some engine driven NiTi files. Thirty narrow and curved canals(15-35 degree) of mesial canals of extracted human mandibular first molars were divided into three groups. Group 1: After radicular access with Gates Glidden drill, apical shaping using step back method with Flexo file Group 2: After radicular access with Gates Glidden drill, apical shaping with Profile .04 Group 3: Canal shaping with GT file and Profile .04. Using modified Bramante technique, the root was sectioned at 2 mm from apical foramen, height of curvature, 2 mm from canal orifice. Canal centering ratio, amount of transport, amount of dentin removed, shape of canal were measured and statistical analysis is done using SPSS Program V 7.5. The results were as follows: 1. Canal centering ratio of group 3 was the lowest at coronal part, but there was no statistical difference. Centering ratio of group 2 was the lowest at curve part, and there was statistical difference between group 1(P<0.05). Centering ratio of group 2 was the lowest at apical part, but there was no statistic difference. 2. Amount of transport of group 3 was the lowest at coronal part, but there was no statistical difference. Amount of transport of group 2 was the lowest at curve part, and there was statistical difference between group 1(P<0.05). Amount of transport of group 3 was the lowest at apical part, and there was statistical difference between group 1 and group 2, group 1 and group 3(P<0.05). 3. Amount of dentin removed of group 3 was the lowest at coronal part, bur there was no statistical difference. Amount of dentin removed of group 2 was the lowest at curve part, but there was no statistical difference. Amount of dentin removed or group 2 was the lowest at apical part, and there was statistical difference between group 1 and group 2, group 1 and group 3(P<0.05). 4. The shape of the canals after instrumentation varied among the groups. The majority of canals at coronal and curve part for group 1 were round in shape(7 in 10), those at apical part were oval(8 in 10). The majority of canals at coronal part for group 2 were round in shape(7 in 10) and there was no difference in the number of shape at other part. There was no difference in the number of shape at every part for group 3. As above results, NiTi rotary instrumentation showed a trend to remain more centered in the canal than SS file instrumentation. At using NiTi file, coronal shaping with Gates Glidden drill was not statistically different from shaping with GT file. But shaping with GT file showed tapered canals, so it may be said that shaping with GT file is a safe and valuable instrumentation method.

• The Journal of Advanced Prosthodontics
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• v.9 no.4
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• pp.315-320
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• 2017

PURPOSE. The aim of this investigation was to analyze the dimensions of clinical crowns and to classify the crown and the gingival type in the anterior teeth in Korean young adults. MATERIALS AND METHODS. Casts were obtained from 50 subjects ranging in age from 24 to 32. Measurements of length and width were made on the casts using a pair of digital calipers on the entire dentition. Crown thickness and papilla height were also measured and MDW/CL (mesiodistal width to clinical length) and CW/CL (cervical width to clinical length) ratios of the maxillary anterior teeth were calculated. The K-clustering method was used for CW/CL to classify the anterior tooth shape into three groups (tapered, ovoid, and square), and one-way analysis of variance and Duncan's post-hoc comparison were used to evaluate statistical significance between the groups. Pearson's correlation analysis was performed between tooth shape and papillary height (PH) to demonstrate the correlation between tooth shape and gingival morphological characteristics. RESULTS. The average length of the maxillary central incisors was 9.89 mm; the mesio-distal width was 8.54 mm; and the ratio of width/length was 0.86 in Korean young adults. The average bucco-palatal thickness of the central incisor was 3.14 mm at the incisal 1/3 aspect. Ovoid type was the most common tooth shape (48%), followed by square type (29%) and taper type (23%) in the central incisors of Korean young adults. Tooth shape and gingival type were correlated with each other. CONCLUSION. New reference data were established for tooth size in Korean young adults and the data show several patterns of tooth shape and gingival type. Clinicians should diagnose and treat based on these characteristics for better results in the Korean population.

• Journal of Korean Association for Spatial Structures
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• v.10 no.2
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• pp.105-115
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• 2010

Recently, High-rise building are irregular-shaped to be city landmarks and function as vertical cities to enable the efficient use of land. 3T (Twisted, Tilted & Tapered) designs are being suggested for irregular buildings and studies to develop new structural system have been actively made to satisfy slender shape ratio. In diagrid system, not only gravity load but also lateral load is delivered based on the triangular shape of diagrid, so most of columns are eliminated. Because shearing force is delivered by the axial behavior (tensile/compressive) of diagrid to minimize shearing deformation, the system is more applicable to irregular buildings than existing system where shearing force is delivered by the columns. In this study, the process of selecting connection details and the structural safety of the selected details are verified using the finite element analysis with focus given to the construction overview of the Cyclone Tower. However, the relersed methods of stress concentration are suggested and the performance of stress concentration relieves that it's suggested for the appropriate cap plate thickness and extended length.

• Mass Spectrometry Letters
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• v.7 no.1
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• pp.21-25
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• 2016

Dual-channel nano-electrospray has recently become an ionization technique of great promise especially in biological mass spectrometry. This unique approach takes advantage of the mixing processes that occurs during electrospray. Understanding in more detail the fundamental principles influencing spray formation further study of the origins of the mixing processes: (1) in a Taylor cone region, (2) in charged droplets or (3) in both environments. The dual-channel emitters were made from borosilicate theta-shape glass tubes (O.D. 1.2 mm) and had a tip diameters of less than 4 μm. Electrical contact was achived by deposition of a thin film of an appropriate metal onto the surface of the emitter. The experimental investigation of the Taylor cone formation in a dual-channel electrospray emitter has been carried out by injection of polystyrene beads (diameter 3 μm) at very low concentrations into one of the channels of the non-tapered theta-glass tubes. High-speed camera experiments were set up to visualize the mixing processes in Taylor cone regions for dual-channel emitters. Mass spectra from dual nano-electrospray are presented.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.43-50
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• 1992

The purpose of this study is to ascertain the robustness of p-version model with hierarchic intergrals of Legendre shape functions in various applications including plane stress/strain, axisymmetric and shell problems. The most important symptoms of accuracy failure in modern finite elements are spurious mechanisms and a phenomenon known as locking which are exhibited for incompressible materials and irregular shapes which contain aspect ratios(R/t, a/b), tapered ratio(d/b), and skewness. The condition numbers and energy norms are used to estimate numerical errors, convergence characteristics and algorithmic efficiencies for verifying the aforementioned symptoms of accuracy failure. Numerical results from p-version models are compared with those from NASTRAN, SAP90, and Cheung's hybrid elements.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.114-121
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• 1997

Helical anchors are foundation structure that designed to resist uplift loads are installed by applying in load to shaft while rotating it into the ground. These can be a cost effective means of proving tension anchorage for foundation where soil conditions permit their installation because of ease of installation. At present time, tapered helical anchors are commonly used to carry uplift loads. The uplift capacity includes the following factors : the height of overburden above the top helix, the resistant along a cylinder, the weight of the soil in the cylinder and suction force. In order to make clear behavior characteristics of helical anchors with pullout, model tests were conducted with respect to various embedment depth, space of helix, shape of helix. Based on the experimental study, the following conclusions are drawn. 1) The uplift capacity of multi helical anchors increase with embedment ratio of anchors The increase is smooth after critical uplift capacity. 2) Critical breakout factors and critical embedment ratio of multi helical anchor exist 7∼8, 4∼6 respectively. 3) Variation of uplift capacity with helix spaces show down after S/D=5. 4) Critical breakout factors of helical anchor in the laboratory test are similar to Das's theory.

• Transactions of Materials Processing
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• v.21 no.5
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• pp.312-318
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• 2012

With an increasing trend toward miniaturization, electrical discharge machining(EDM) has been receiving a lot of attention as a suitable production technology for micro-parts, since it enables the machining of hard conductive materials with a high degree of repeatability and without alteration to the material. When a micro-hole is fabricated by EDM, however, the diameter of the inlet hole is larger than that of the outlet region due to the additional discharge effect caused by the eroded particles. In this paper, a shot blasting surface treatment, in which an abrasive material is accelerated through a pressurized nozzle and directed at the surface of a part, is suggested as an effective method to reduce the tapered shape of EDM micro-hole. In addition, the influence of process parameters such as spark-on time and electrode diameter on the machining performance was investigated. It is shown quantitatively that the difference in diameter between the inlet and outlet holes decreases with the shot blasting treatment and with decreasing spark-on time.

• Laser Solutions
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• v.18 no.3
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• pp.1-5
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• 2015

A 3D printer based on laser powder deposition (LPD), also known as DED (direct energy deposition), has been developed for fabricating metal parts. The printer uses a ytterbium fiber laser (1070nm, 1kW) and is equipped with an Ar purge chamber, a three-dimensional translation stage and a powder feeding system composed of a powder chamber and delivery nozzles. To demonstrate the performance of the printer, a tapered cylinder of 320mm in height has been fabricated successfully using Ti-6Al-4V powders. The process parameters including the laser output power, the scan speed, and the powder feeding rate have been optimized. A 3D printed test specimen shows mechanical properties (yield strength, ultimate tensile strength, and elongation) exceeding the criteria to employed in a variety of Ti alloy applications.

• International Journal of High-Rise Buildings
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• v.9 no.3
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• pp.283-300
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• 2020

The Lakhta Center is a Multifunction Complex Development (MFCD) consisting of 1) an 86 story office tower rising 462 m above the ground to provide high-end offices for Gazprom Neft and Gazprom Group affiliates 2) a Multi-Function Building (MFB) that includes, a scientific/educational center, a sport center, a children's technopark, a planetarium, a multi-transformable hall, an exhibition center, shops, restaurants, and other public facilities 3) a Stylobate 4) "The Arch, which forms the main entrance to the tower, restaurants, and cafes 5) underground parking and 6) a wide range of large public plazas. While each of the MFCD buildings is technically challenging in its own right, the focus of the paper is to present the development and integration of the structural and foundation systems of the bowed, tapered, and twisted shape of the tower into the fabric of the tallest Tower in Europe.