• Physical Therapy Rehabilitation Science
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• v.3 no.2
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• pp.112-118
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• 2014

Objective: The purpose of this study was to investigate the effects of an exercise with and without neuromuscular electrical stimulation (NMES) of the quadriceps femoris muscle, on strength, pain, and weight distribution in patients with knee instability post surgery. Design: Randomized controlled trial. Methods: Twenty patients in the early stage of rehabilitation after knee surgery were recruited as subjects and were randomly divided into either experimental group (exercise combined with NMES) (n=10) or control group (n=10). Both groups received strength training of the lower limb for 20 min/day, 5 days/week for 4 weeks. The experimental group used NMES for unilateral quadriceps femoris training with incremental increases in the intensity of isometric contraction over 4 weeks. Outcome measurements were assessed using the digital manual muscle testing, 30-chair stand test (30CST), numeric pain rating scale (NPRS) and weight distribution using the foot analyzer before and after 4 weeks of training. Results: After the 4-week intervention, knee extensor strength increased significantly in the experimental group post intervention (p<0.05), and there was a significant improvement in the experimental group compared with the control group (p<0.05). The 30CST and NPRS scores improved significantly in the experimental group compared to the control group (p<0.05), and there was a significant difference between the two groups (p<0.05). Weight distribution was significantly improved in the experimental group compared with the control group, (p<0.05), but there was no significant difference in improvement between the two groups. Conclusions: This study showed that NMES combined with strengthening exercises of the lower limbs is effective in improving lower limb pain and strength in patients with instability after knee surgery.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.59-63
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• 2007

We propose a controller design analysis for a cross-coupling control system, which is essential for achieving high contouring accuracy in multi-axis CNC systems. The proposed analysis combines three axial controllers for each individual feed drive system together with a cross-coupling controller at the beginning of the design stage in an integrated manner. These two types of controllers used to be separately designed and analyzed since they have different control objectives. The proposed scheme is based on a mathematical formulation of a three-dimensional contour error model and includes a stability analysis for the overall control system and a performance analysis in terms of contouring and tracking accuracy at steady state. A computer simulation was used to demonstrate the validity of the proposed methodology. The performance variation was investigated under different operating conditions and controller gains, and a design range was elicited that met the given performance specifications. The results provide basic guidelines in systematic and comprehensive controller designs for multi-axis CNC systems. A cross-coupling control system was also implemented on a PC-based three-axis CNC testbed, and the experimental results confirmed the usefulness of the proposed control system in terms of contouring accuracy.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.715-730
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• 2023

Broad studies have addressed the issue of structural element damage identification, however, rubber bearing, as a key component of load transmission between the superstructure and substructure, is essential to the operational safety of a bridge, which should be paid more attention to its health condition. However, regarding the limitations of the traditional bearing damage detection methods as well as few studies have been conducted on this topic, in this paper, inspired by the model updating-based structural damage identification, a two-stage bearing damage identification method has been proposed. In the first stage, we deduce a novel bearing damage localization indicator, called element relative MSE, to accurately determine the bearing damage location. In the second one, the prior knowledge of bearing damage localization is combined with sailfish optimization (SFO) to perform the bearing damage estimation. In order to validate the feasibility, a numerical example of a 5-span continuous beam is introduced, also the noise robustness has been investigated. Meanwhile, the effectiveness and engineering applicability are further verified based on an experimental simply supported beam and actual engineering of the I-40 Bridge. The obtained results are good, which indicate that the proposed method is not only suitable for simple structures but also can accurately locate the bearing damage site and identify its severity for complex structure. To summarize, the proposed method provides a good guideline for the issue of bridge bearing detection, which could be used to reduce the difficulty of the traditional bearing failure detection approach, further saving labor costs and economic expenses.

• Steel and Composite Structures
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• v.48 no.3
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• pp.321-333
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• 2023

This paper proposes a comprehensive investigation on lateral stiffness of corner-supported steel modular frame using splice connection. A full-scale modular frame with two stacked steel modules under lateral load is tested. Ductile pattern in the transfer of lateral load is found in the final failure mode. Two types of lateral stiffness, including tangent stiffness and secant stiffness, are defined from the load-displacement due to the observed nonlinearity. The difference between these two types of stiffness is found around 20%. The comparisons between the experimental lateral stiffness and the predictions of classical methods are also conducted. The D-value method using hypothesis of independent case is a conservative option for predicting lateral stiffness, which is more recommended than method of contraflexural bending moment. Analyses on two classical short-rod models, including fix-rod model and pin-rod model, are further conducted. Results indicate that fix-rod model is more recommended than pin-rod model to simplify splice connection for simulation on lateral stiffness of modular frame in elastic design stage.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2823-2828
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• 2007

Numerical simulation on the two-stage centrifugal compressor with Low Solidity Vaned Diffuser LSVD) for HFC-134a Turbo-chiller was performed using a commercial code. The comparative study with experimental results from other compressor was also investigated to testify the simulation schemes. The numerical analysis was separately simulated for each stage of the compressor and the effect of impeller-diffuser flow interaction was considered. Setting angle of the diffuser vane changed in the range of 15 deg. and the effects on its variation were discussed in detail including the flow analysis in the passage of the compressor. The vane setting angle obtained from the preliminary design was slightly adjusted to the optimal value by the performance enhancement in terms of pressure recovery and flow characteristics.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.4
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• pp.5-12
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• 2001

This paper presents the simulation methodology of the interior noise of vehicle using the frequency response function based hybrid modeling of the system which consists of multi-subsystem models obtained by the test or analysis. The complex systems such as a trimmed body of high modal density and a powertrain were modeled by using experimental data, and a sub-frame of a vehicle of low modal density was modeled by finite element data. Modeling of the whole system was executed and validated in the two stages. The first stave is combining the trimmed body and the sub-frame, and the second stage is attaching the powertrain, which is a exciting source, to the combined model of the first stage. The input force to the system was modeled as an equivalent force in the virtual space, which was obtained from impedance method using the FRFs of the powertrain and the responses. The interior noise predicted by the proposed method was very close to the direct measurement, which showed feasibility of the proposed modeling procedure. Since the methodology is easily applied to both the transfer path analysis of structure-borne noise and the analysis of noise contribution of a sub-system, it is expected to be a strong tool for design change of a vehicle in the earlier stare.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.11-15
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• 2012

A rotordynamic analysis is performed for a 7 ton class turbopump applied to the third stage LRE(Liquid Rocket Engine) of the KSLV(Korea Space Launch Vehicle). Based on the heritage of the developed experimental 30 ton class turbopump and developing 75 ton class turbopump for the KSLV first and second stage LRE, the 7 ton class turbopump is designed as an one-axis rotor turbopump. Two rotor systems comprised of one oxidizer pump assembly and the other fuel pump-turbine assembly are connected each other using a spline shaft and operating at a design speed. Through the rotordynamic analysis, it is investigated that the turbopump acquires sufficient separate margin of critical speed as a sub-critical rotor.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.73-79
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• 2003

The characteristics of NOx emission in multi fuel/air staged combustor have been experimentally studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is act as a pilot flame for the secondary combustion stage combustion zone, where most of fuel burns. Experiments were performed on a semi-industrial scale (thermal input 0.233 ㎿) in a laboratory furnace and Liquefied Petroleum Gas(LPG) was used as primary and secondary fuels. The study included parametric study to identify the optimum operating conditions which are primary/secondary fuel ratio, primary/secondary air ratio, primary swirl intensity and secondary swirl intensity for reducing NOx emission. The test demonstrated that NOx emission can be reduced by >70% in accordance with operating conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.06a
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• pp.87-95
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• 1996

The stamping process consists of two stages : First, the blank is held by the blank holder and then it is further formed into the die cavity by punch stroke. In actual stamping process, the accurate prediction of binder wrap is an indispensable step in sheet metal forming analysis because the initial plastic buckling induced by improper die design is directly related with fatal defect at the final stage. In the present work, an approach including the gravity effect of blank material and proper consideration of contact and friction is proposed. Computations are carried out for some actual auto-body parts using 3D FEM code to investigate the validity of the proposed methodology. Comparisons with experimental results show that the suggested scheme can be effectively applied to the precise prediction of binder wrap for arbitrarily curved die faces in which gravity and contact effect must be taken into account.