• Structural Engineering and Mechanics
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• v.4 no.5
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• pp.569-586
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• 1996

A new three-dimensional 8-node solid element with rotational degrees of freedom is presented. The proposed element is established by adding rotational degrees of freedom to the basic 8-node solid element. Thus the element has three translations and three rotational degrees of freedom per node. The corner rotations are introduced by transforming the hierarchical mid-edge displacements which are parabolic shape along an edge. The derivation of the element is based on the mixed variational principles in which the rotations are introduced as independent variables. Several types of non-conforming modes are selectively added to the displacement fields to obtain a series of improved elements. The resulting elements do not have the spurious zero energy modes and Poisson's ratio locking and pass patch test. Numerical examples show that presented non-conforming solid elements with rotational degrees of freedom show good performance even in the highly distorted meshes.

• Journal of the Semiconductor & Display Technology
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• v.6 no.1 s.18
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• pp.37-41
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• 2007

Recently PZT is used in ultra precision mechanism field. PZT has a small motion range although it has a high resolution. Many methods, such as inchworm, impact driving, etc., have been applied for the expansion of the motion range.? In this study, the new actuating mechanism for rotational motion with two PZT actuators is proposed. The ultra precision rotational actuator which is made by proposed mechanism is able to operate both coarse and fine motion. The design parameters of the proposed mechanism are considered to improve the performance of the system. The rotational stage which is applied by the proposed mechanism is fabricated. The resolution and velocity for fabricated rotational stage are measured by laser interferometer.

• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.813-820
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• 2001

Solutions of inviscid rotational flows near the corners of an arbitrary angle and within a triangle of arbitrary shapes are presented. The corner-flow solutions has a rotational component as a particular solution. The addition of irrotatoinal components yields a general solution, which is indeterminate unless the far-field condition is imposed. When the corner angle is less than 90$^{\circ}$the flow asymptotically becomes rotational. For the corner angle larger than 90$^{\circ}$it tends to become irrotational. The general solution for the corner flow is then applied to rotational flows within a triangle (Method I). The error level depends on the geometry, and a parameter space is presented by which we can estimate the error level of solutions. On the other hand, Method II employing three separate coordinate systems is developed. The error level given by Method II is moderate but less dependent on the geometry.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.43-48
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• 2007

It is important to measure the rotational accuracy of lathe spindle as it affects to the qualities of all machines machined by the lathe using in industries. The bad rotational accuracy of lathe spindle are caused mainly by wearness of the spindle in using and quality of spindle when machining and using low level bearings. It occurs especially in case of lathes because the cutting force acting to work-piece act on one side to the spindle not to both sides symmetrically. Therefore in this study, constructing experimental apparatus for measuring of rotational accuracy by using eddy current type gap sensors AEC5706PS and sensors, s-06LN, data acquisition board DT9834(USB type) and software for data acquisition, DT Measure Foundry ver. 4.0.7 etc., error data acquired in the rotational accuracy test of lathe spindle are analysed in plots and statistical treatments.

• Journal of International Academy of Physical Therapy Research
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• v.9 no.4
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• pp.1676-1682
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• 2018

The purpose of this study was to investigate the short-term effects of lumbar rotational mobilization under the single-leg standing (SLS) position. Fifteen healthy individuals were recruited, and randomized to agroup of trunk rotational exercise (TRE) and lumbar rotational mobilization (LRM). Trunk twist rotational exercise was performed to the TRE group, and mobilization was applied to the LRM group on the lumbar spine. Velocity of the center of pressure (VCOP) and center of pressure (COP) for each participant were measured through SLS. COPs were not significantly increased or decreased after treatment in both groups. VCOPs also did not change considerably except on the right side when the eye was closed. There was no significant difference between COPs and VCOPs in two groups. This study suggests that trunk rotation exercise and lumbar rotation mobilization would have similar effects on balance ability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3184-3189
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• 2010

To develop gasoline engine fuel pump, it is needed to measure the rotational speed of the pump. In general, because gasoline fuel pump is submerged in the fuel tank, it is difficult to measure the rotational speed directly. Currently, there are two popular methods measuring the rotational speed. One of them is using a piezoelectric accelerometer, and the other is using a current sensor. Originally, a piezoelectric accelerometer had been applied to measure the frequency of the motor vibration. A current sensor is measuring current frequency of the commutator slot. In this study, both the piezoelectric accelerometer and the current sensor have been applied on the fuel pump to calculate the rotational speed at the same time. As a result, the current sensor delivered highly accurate rotational speed information compared with that of the piezoelectric accelerometer. Especially, low rotational speed region, the current sensor shows very robust measuring characteristics. To measure the rotational speed within 1% error, the piezoelectric accelerometer needs to be set with less then 0.5Hz datum storage interval, and the current sensor needs to be set with less then 2.0Hz datum storage interval.

• Journal of Oral Medicine and Pain
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• v.22 no.2
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• pp.207-217
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• 1997

This study was performed for Investigation of the magnitude of mandibular positional change in maximum mouth opening. protrusion, lateral excursion, gum and peanut chewing with BioPAK system(Bioresearch Inc. USA) which can analyze mandibular rotational torque movements. For this study 17 female patients with Temporomandibular joint(TMJ) closed lock and 18 female control without any Temporomandibular disorders(TMDs) signs and premature occlusal contact were included. The obtained results were as follows : 1. In maximum mouth opening, the mandibular rotational angle and distance of patients were significantly greater than those of control group in horizontal plane(P<0.05). 2. In protrusion, the mandibular rotational angle and distance of patients were significantly greater than those of control group in frontal and horizontal plane(P<0.01, P<0.05). 3. The mandibular rotational angle and 야stance in lateral excursion to affected side of patients were significantly greater than those in lateral excursion to non-affected side in frontal plane(P<0.05). 4. The mandibular rotational angle in gum chewing to affected side of patients was significantly greater than that in gum chewing to non-affected side in frontal plane. 5. The mandibular rotational angle and distance in peanut chewing to affected side of patients were significantly greater than those in peanut chewing to non-affected side in frontal and horizontal plane. 6. The mandibular rotational angle and distance in peanut chewing to affected side of patients were greater than those in gum chewing, and was the same result in control group in frontal and horizontal plane.

• Restorative Dentistry and Endodontics
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• v.35 no.4
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• pp.246-256
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• 2010

The purpose of this study was to evaluate a rotational stability of endodontic electronic motors by comparing the changes of rotational speed, depending on the number of usages and with/without static load. Twelve new endodontic electronic motors were used in this study. Non contact type digital tachometer was used for measuring the rotational speed of handpiece. True RMS Multimeter was used for measuring the voltages and the electric currents. All measurements were recorded every 10 seconds during 10 minutes and repeated 9 times. Five repetition was done per each electronic motor. To statistical analysis, student t-test, repeated measures and Scheffe's post-hoc tests were performed. In the same motor group, there was no significant difference in all measurements. In all groups, there was no significant difference in the amount of rotational speed changes depending on the number of usages and with/without static load. In the limitation of this study, the results showed that all kinds of endodontic electronic motors in this study had an established rotational stability. Therefore they could be safely used in root canal treatment with a reliable maintenance of rotational speed, regardless of the number of usages and with/without load.

• The Journal of Advanced Prosthodontics
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• v.13 no.6
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• pp.343-350
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• 2021

PURPOSE. The success of an implant-prosthetic rehabilitation is influenced by good implant health and an excellent implant-prosthetic coupling. The stability of implant-prosthetic connection is influenced by the rotational tolerance between anti-rotational features on the implant and those on the prosthetic component. The aim of this study is to investigate the rotational tolerance of a conical connection implant system and its titanium abutment counterpart, in various conditions. MATERIAL AND METHODS. 10 preparable titanium abutments, having zero-degree angulation (MegaGen, Daegu, Korea) with an internal 5-degree conical connection, and 10 implants (MegaGen, Daegu, Korea) were used. Rotational tolerance between the connection of implant and titanium abutments was measured through the use of a tridimensional optics measuring system (Quick Scope QS250Z, Mitutoyo, Kawasaki, Japan) in the as-received condition (Time 0), after securing with a titanium screw tightening at 35 Ncm (Time 1), after tightening 4 times at 35 Ncm (Time 2), after tightening one more time at 45 Ncm (Time 3), and after tightening another 4 times at 45 Ncm (Time 4). RESULTS. The group "Time 0" had the lowest values of rotational freedom (0.22 ± 0.76 degrees), followed by the group Time 1 (0.46 ± 0.83 degrees), the group Time 2 (1.01 ± 0.20 degrees), the group Time 3 (1.30 ± 0.85 degrees), and the group Time 4 (1.49 ± 0.17 degrees). CONCLUSION. The rotational tolerance of a conical connection is low in the "as received" condition but increases with repetitive tightening and with application of a torque greater than 35 Ncm.

• Earthquakes and Structures
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• v.22 no.1
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• pp.1-13
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• 2022

When a building suffers damages under moderate to severe loading condition, its physical properties such as damping and stiffness parameters will change. There are different practical methods besides various numerical procedures that have successfully detected a range of these changes. Almost all the previous proposed methods used to work with translational components of mode shapes, probably because extracting these components is more common in vibrational tests. This study set out to investigate the influence of using both rotational and translational components of mode shapes, in detecting damages in 3-D steel structures elements. Three different sets of measured components of mode shapes are examined: translational, rotational, and also rotational/translational components in all joints. In order to validate our assumptions two different steel frames with three damage scenarios are considered. An iterative model updating program is developed in the MATLAB software that uses the OpenSees as its finite element analysis engine. Extensive analysis shows that employing rotational components results in more precise prediction of damage location and its intensity. Since measuring rotational components of mode shapes still is not very convenient, modal dynamic expansion technique is applied to generate rotational components from measured translational ones. The findings indicated that the developed model updating program is really efficient in damage detection even with generated data and considering noise effects. Moreover, methods which use rotational components of mode shapes can predict damage's location and its intensity more precisely than the ones which only work with translational data.