• Wind and Structures
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• v.32 no.4
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• pp.309-319
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• 2021

The vortex-drift pattern over a girder surface, actually demonstrating the complex fluid-structure interactions between the structure and surrounding flow, is strongly correlated with the VIVs but has still not been elucidated and may be useful for modeling VIVs. The complex fluid-structure interactions between the structure and surrounding flow are considerably simplified in constructing a vortex model to describe the vortex-drift pattern characterized by the ratio of the vortex-drift velocity to the oncoming flow velocity, considering the aerodynamic work. A spring-suspended sectional model (SSSM) is used to measure the pressure in wind tunnel tests, and the aerodynamic parameters for a typical streamlined closed-box girder are obtained from the spatial distribution of the phase lags between the distributed aerodynamic forces at each pressure point and the vortex-excited forces (VEFs). The results show that the ratio of the vortex-drift velocity to the oncoming flow velocity is inversely proportional to the vibration amplitude in the lock-in region and therefore attributed to the "lock-in" phenomena of the VIVs. Installing spoilers on handrails can destroy the regular vortex-drift pattern along the girder surface and thus suppress vertical VIVs.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.173-176
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• 2007

The characteristics of the tool system give many effects into the costs and qualities for the finished components. This study proposes a new method for manufacturing of high manufacturing productivity, production process reduction and low cost through back pressure forming. The Lock-up hub is manufactured through many processes, such as upsetting($1^{st}$ Forming), piercing, direct extrusion($2^{nd}$ Forming), final sizing process($3^{rd}$ Forming). In this study, process design for closed-die forging of a Lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of Lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• Journal of Oral Medicine and Pain
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• v.16 no.1
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• pp.113-120
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• 1991

The authors examined the patterns and various ranges of mandibular movements in TMJ lock closed patients in the frontal, sagittal and horizontal plane pre-end post-treatment. And the author obtained the following results. 1. In the frontal plane, the patterns and ranges of mandibular movement of the patients were very irregular and small before treatment. But after the treatment, the patterns were similar to the typical shield shape of the normal subjects. And the velocity of opening and closing was improved after the treatment. 2. In the sagittal plane, the mean amount of maximum mouth opening was 27.0±4.0mm before treatment and 44.0±5.4mm after treatment. And there was statistically significant improvement(p<0.005). The patterns of the movement were very irregular and small before treatment, but were similar to the shape of "Posselt's envelope of motion" after the treatment. The velocity of opening and closing was improved after the treatment 3. In the horizontal plane, the mean amount of maximum laterotrusion was 8l2±2.5mm in the affected side and 6.7±2.2mm in the non-affected side before treatment. There was a significant difference between the sides(p<0.05). After the treatment, the mean was 10.4±2.6mm in the affected side and 8.9±2.3mm in the non-affected side and there was no significant difference between the sides(p>0.05). There was no significant difference in the mean amount of maximum protrusion between the before and aftertreatment(p>0.05), but the patterns of the movements were improved.

• 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.

• Wind and Structures
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• v.5 no.6
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• pp.527-542
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• 2002

Wind-excited vibrations of slender structures can induce fatigue damage and cause structural failure without exceeding ultimate limit state. Unfortunately, the growing importance of this problem is coupled with an evident lack of simple calculation criteria. This paper proposes a mathematical method for evaluating the crosswind fatigue of slender vertical structures, which represents the dual formulation of a parallel method that the authors recently developed with regard to alongwind vibrations. It takes into account the probability distribution of the mean wind velocity at the structural site. The aerodynamic crosswind actions on the stationary structure are caused by the vortex shedding and by the lateral turbulence, both schematised by spectral models. The structural response in the small displacement regime is expressed in closed form by considering only the contribution of the first vibration mode. The stress cycle counting is based on a probabilistic method for narrow-band processes and leads to analytical formulae of the stress cycles histogram, of the accumulated damage and of the fatigue life. The extension of this procedure to take into account aeroelastic vibrations due to lock-in is carried out by means of ESDU method. The examples point out the great importance of vortex shedding and especially of lock-in concerning fatigue.

• Wind and Structures
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• v.25 no.4
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• pp.397-413
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• 2017

When bridges are constructed with lower heights from the ground, the formed channel between the deck and the ground will inevitably hinder or accelerate the air flow. This in turn will have an impact on the aerodynamic forces on the deck, which may result in unexpected wind-induced responses of bridges. This phenomenon can be referred to "ground effects." So far, no systematic studies into ground effects on the wind-induced responses of closed box girders have been performed. In this paper, wind tunnel tests have been adopted to study the ground effects on the aerodynamic force coefficients and the wind-induced responses of a closed box girder. In correlation with the heights from the ground in two ground roughness, the aerodynamic force coefficients, the Strouhal number ($S_t$), the vortex-induced vibration (VIV) lock-in phenomena over a range of wind velocities, the VIV maximum amplitudes, the system torsional damping ratio, the flutter derivatives, the critical flutter wind speeds and their variation laws correlated with the heights from the ground of a closed box girder have been presented through wind tunnel tests. The outcomes show that the ground effects make the vortex-induced phenomena occur in advance and adversely affect the flutter stability.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.2
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• pp.152-156
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• 2013

This paper presents a fast-lock dual-loop successive approximation register-controlled duty-cycle corrector (SARDCC) circuit using a mixed (binary+sequential) search algorithm. A wider duty-cycle correction range, higher operating frequency, and higher duty-cycle correction accuracy have been achieved by utilizing the dual-loop architecture and the binary search SAR that achieves the fast duty-cycle correcting property. By transforming the binary search SAR into a sequential search counter after the first DCC lock-in, the proposed dual-loop SARDCC keeps the closed-loop characteristic and tracks variations in process, voltage, and temperature (PVT). The measured duty cycle error is less than ${\pm}0.86%$ for a wide input duty-cycle range of 15-85 % over a wide frequency range of 0.5-2.0 GHz. The proposed dual-loop SARDCC is fabricated in a 0.18-${\mu}m$, 1.8-V CMOS process and occupies an active area of $0.075mm^2$.

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.291-306
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• 1995

Mandibular movement is composed of border movement and functional movement. Border movement such as maximal mouth opening, hinge opening ad lateral eccentric movement has good reproducibility, but functional movement such as chewing, swallowing and speech has also reproducibility. Especially for chewing movement, individual reproducibility has been confirmed by many studies. Study of chewing pattern is still in controversy. In new approach for raising the diagnostic value, numeric parameters and morphologic characteristics could be used for evaluation of chewing pattern. This study was performed to investigate the differences between chewing pattern in controls and in patients with temporomandibular disorders. Sixty-three patients with temporomandibular disorders participated in this study, and they were divided into unilaterally affected subjects or bilaterally affected subjects. Then unilaterally affected subjects were classified into closed lock group, disk displacement with reduction group, and degenerative joint disease group. For recording of chewing pattern, subjects were asked to chew one piece of presoftened chewing gum on both sides, and the chewing movement was recorded with the Electrognatho- Graphy(Bio-Research Associates Inc., U.S.A.). Tooth contact pattern for occlusal stability (Total left-right statistics )was also recorded with T-Scan(Tekscan Co., U.S.A.). The dta related to chewing pattern and total left-right statistics were statistically analyzed by SAS/stat program. The obtained results were as follows : 1. In patient group, mean value of A-P distance and the ratio of A-P distance to vertical distance were larger than control group, but the value of lateral distance in affected side and the closing velocity in unaffected side were smaller than that of control group, respectively. 2. In case of unilateral affected patients, chewing pattern of other side had tendency to restricted movement and slow velocity in closed lock group or degenerative joint disease group than control group or disk displacement with reduction group. 3. In bilateral degenerative joint disease patients, contralateral side had tendency to large range of motion and slow chewing velocity than preferred chewing side. 4. The patients with restricted mouth opening below than 35mm had higher value of total left-right statistics than patient group mouth opening above 35mm. Also closed lock group had higher total left-right statistics than disk displacement with reduction group, degenerative joint disease group and control group. 5. There was some difference in morphologic characteristics of chewing pattern between in control group and in affected side of unilateral patient group, but no difference between control group and unaffected side of unilateral patient group. 6. There were positive correlations between vertical distance and A-P distance, between vertical distance and chewing velocity, between A-P distance and chewing velocity, and between opening velocity and closing velocity in unilateral affected patients.

• Journal of Oral Medicine and Pain
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• v.37 no.4
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• pp.221-225
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• 2012

Disc dislocation without reduction, as known as closed lock, is a clinical condition in which the disc is dislocated from the condyle and does not return to normal position during condylar movement When the condition of disc dislocation without reduction is acute, the initial therapy should include an attempt to reduce or recapture the disc by manual manipulation. When patients report a history of being locked for 1 week or less, manual manipulation is usually successful. In patients with a longer history, success rate tends to decrease rapidly. If the disc has been successfully recaptured, placing an anterior positioning appliance is recommended to prevent clenching on the posterior teeth, which would likely redislocated the disc. But it is hard to make an appliance immediately in the clinic because it takes too much time. And making an appliance using self-curing acrylic resin is not very popular because of its discomfort by odor and working time. Also, if the patient has resin allergy or is under orthodontic treatment, or if it is impossible to control behavior of the patient, it has been restricted to make an appliance immediately. Therefore, to supplement this disadvantages, we tried to confirm about successful short term use of temporary anterior positioning splint made by using putty impression material after manual manipulation in this study.

• Transactions of Materials Processing
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• v.17 no.2
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• pp.124-129
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• 2008

Net shape forging technologies give many effects into the costs and qualities for the finished products. So, the studies to reduce the additional machining amount are very important in forging industry. Specially, there are two main topics in cold forging industry, such as, tool life and precision forging. In this study, new forging technique was proposed to eliminate the machining process for fixing up the length and improve the lead accuracy of gear. The luck-up hub is manufactured through many processes, such as upsetting, piercing and direct extrusion. The gear is formed in direct extrusion process; however, lead accuracy of the gear is over allowance limit. Therefore, the additional sizing process must be added. In this study, process design for closed-die forging of a lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.