• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.605-609
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• 1996

Continuous sliding mode control is applied to turning process for cutting force regulation. The highest feedrate compatible with the allowable cutting force is applied in rough cutting process such that maximum productivity is ensured and tool breakage is avoided. The programmed feedrate is overridden after the control algorithm is carried out. However, most CNC lathe manufacturers offer limited number of data bits far feedrate override, thus resulting in nonlinear behavior of the machine tools. Such nonlinearity brings “quantized” effect, and the optimal faedrate is rounded off before being fed into the CNC system. To compensate for this problem, continuous sliding mode control is applied. Conventional switching control law at a sliding surface is replaced by a smooth control interpolation in a selected boundary layer to avoid the excitation of high-frequency dynamics. Simulation results are presented in comparison with those obtained by applying adaptive control.

• 대한치과교정학회지
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• 제49권5호
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• pp.299-309
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• 2019

Objective: This study aimed to investigate the effect of pre-applied orthodontic force on the regeneration of periodontal ligament (PDL) tissues and the underlying mechanisms in tooth replantation. Methods: Orthodontic force (50 cN) was applied to the left maxillary first molars of 7-week-old male Sprague-Dawley rats (n = 32); the right maxillary first molars were left untreated to serve as the control group. After 7 days, the first molars on both sides were fully luxated and were immediately replanted in their original sockets. To verify the effects of the pre-applied orthodontic force, we assessed gene expression by using microarray analysis and real-time reverse transcription polymerase chain reaction (RT-PCR), cell proliferation by using proliferating cell nuclear antigen (PCNA) immunofluorescence staining, and morphological changes by using histological analysis. Results: Application of orthodontic force for 7 days led to the proliferation of PDL tissues, as verified on microarray analysis and PCNA staining. Histological analysis after replantation revealed less root resorption, a better arrangement of PDL fibers, and earlier regeneration of periodontal tissues in the experimental group than in the control group. For the key genes involved in periodontal tissue remodeling, including CXCL2, CCL4, CCL7, MMP3, PCNA, OPG, and RUNX2, quantitative RT-PCR confirmed that messenger RNA levels were higher at 1 or 2 weeks in the experimental group. Conclusions: These results suggest that the application of orthodontic force prior to tooth replantation enhanced the proliferation and activities of PDL cells and may lead to higher success rates with fewer complications.

• 대한수학회논문집
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• 제18권1호
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• pp.133-149
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• 2003

Local stability of steady states of an epidemic model is considered. An age structured S-I-R epidemic model with separable inter-cohort force of infection with external force is considered. Stability result for the nontrivial steady states is obtained.

• 대한기계학회논문집A
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• 제25권8호
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• pp.1173-1182
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• 2001

Recent noticeable advances of CNC machine tools have considerably improved productivity and precision in manufacturing processes. However, in the respect of productivity some defects still remain because selection of machining conditions entirely depends on the experiences of programmers. Usually, machining conditions such as feed rate and spindle speed have been selected conservatively by considering the worst cases, and it has brought the loss of machining efficiency. Thus, the improvement of cutting force controller has been done to regulate cutting force constantly and to maximize feedrate simultaneously in case that machining conditions change variously. In this study, sliding mode control with boundary layer is applied to milling process for cutting force regulation and in a commercial CNC machining center data transfer between PC and PMC (programmable machine controller) of CNC machine is done using a standard interface method. And in the cutting force measurement, an indirect cutting force measuring system using current signal of AC servo is adopted in order not to use high-priced equipment like tool dynamometer. The purpose of this study is to maximize the productivity in milling process, thus its results can be applied to cases such as rough cutting process.

• 한국CDE학회논문집
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• 제7권1호
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• pp.27-33
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• 2002

MDO(Multidisciplinary Design Optimization) methodology is a new technology to solve a complicate design problem with a large number of design variables and constraints. The design of a dental implant system is a typical complicate problem, and so it requires the MDO methodology. Actually, several analyses such as rigid body dynamic analysis and structural stress analysis etc. should be carried out in the MDO methodology application to the design of a dental implant system. In this paper, as a first step of MDO methodology application to the design of a dental implant system, the impact force which is applied on the tooth in masticating is calculated through the rigid body dynamic analysis of upper and lower jaw-bones. This analysis is done using ADAMS. The impact force calculated through the rigid body dynamic analysis can be used for the structural stress analysis of a dental implant system which is needed for the design of a dental implant system. In addition, the rigid body dynamic analysis results also show that the impact time decreases as the impact force increases, the largest impact force occurs on the front tooth, and the impact force is almost normal to the tooth surface with a slight tangential force.

• 한국자동차공학회논문집
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• 제24권1호
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• pp.16-23
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• 2016

The EWB(electronic wedge brake) is one in which the braking force is developed in a wedge and caliper system and applied to a disk and wedge mechanism. The advantage of the wedge structure is that it produces self-reinforcing effect and hence, utilizes minimal motor power, resulting in reduced gear and current. The extent of use of clamping force sensors and protection from failure of the EWB system directly depends on the level of vehicle mass production. This study investigated the mathematical equations, simulation modeling, and failsafe control algorithm for the clamping force sensor of the EWB and validated the simulations. As this EWB system modeling can be applied to motor inductance, resistance, screw inertia, stiffness, and wedge mass and angle, this study could improve the accuracy of simulation of the EWB. The simulation results demonstrated the braking force, motor speed, and current of the EWB system when the driver desired to the step and pulse the brake force inputs. Moreover, this paper demonstrated that the proposed failsafe control algorithm accurately detects faults in the clamping force sensor, if any.

• Molecules and Cells
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• 제37권8호
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• pp.592-597
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• 2014

The cell membrane provides critical cellular functions that rely on its elaborate structure and organization. The structure of turtle membranes is an important part of an ongoing study of erythrocyte membranes. Using a combination of atomic force microscopy and single-molecule force spectroscopy, we characterized the turtle erythrocyte membrane structure with molecular resolution in a quasi-native state. High-resolution images both leaflets of turtle erythrocyte membranes revealed a smooth outer membrane leaflet and a protein covered inner membrane leaflet. This asymmetry was verified by single-molecule force spectroscopy, which detects numerous exposed amino groups of membrane proteins in the inner membrane leaflet but much fewer in the outer leaflet. The asymmetric membrane structure of turtle erythrocytes is consistent with the semi-mosaic model of human, chicken and fish erythrocyte membrane structure, making the semi-mosaic model more widely applicable. From the perspective of biological evolution, this result may support the universality of the semi-mosaic model.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권2호
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• pp.147-152
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• 1999

Semiconductor piezoresistive type vibration sensor was fabricated by using semiconductor process and micromachining technology. To measure the micro electromagnetic force between coil and magnet, fabricated vibration sensor was used. Toapply micro electromagnetic force produced from the micro exciter, small-sized NdFeB permanent magnet was attached on the mass of the fabricated vibration sensor. The measured electromagnetic force are about 5~180dyne when the applied sinusoidal current of 1KHz in the range of 1.5~8mA. The measurement of micro electromagnetic forcewas performed by changing the distance between coil and magnet. Output characteristics of micro electromagnetic force according to the applied coil current were linear. Furthermore, output results were used to get the transfer constant that is important to decide the efficiency and the performance of the coil and magnet.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2723-2731
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• 2000

Ultrasonic motors(USM) has been emerging as one type actuators, which possess many advantages such as high torque, low weight, compact size and no magnetic field generation. In spite of these features, there are several problems to be solved, which are temperature rise in case of long term operation, non -linearity, and hysteresis. Among these, hysteresis cause the most serious problem in force/torque control applications. To cope with this paper we propose a new PWM driving method which can be applied to force/torque control applications. To cope with this problem, in this paper we propose a new PWM driving method which can applied to force/torque control of USM. To verify the proposed method, an experimental setup was built and several experiments were performed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.972-977
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• 2009

For the improvement of a train speed in the conventional line from overhead system point of view, it is necessary to approach not only in the aspect of the increasement of tension for catenary but the application of a pre-sag. A certain tension acting on a dropper is removed when it is slack by the pantograph passing. Right after the pantograph passes, the dynamic force caused by the mass of contact wire acts on the dropper. If the pre-sag is applied to the catenary, the static force on the dropper is increased. For the assurance of the safety for the dropper, it is necessary to predict the dynamic force. The purpose of this study is to predict and analyze the force on the dropper according to the applied pre-sag.