• Toxicological Research
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• v.22 no.3
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• pp.253-266
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• 2006

Bone is a dynamic tissue that is constantly being remodelled. Resolution of bone and formation of new bone are closely linked, so that bone mass remains constant. With age, this process becomes unlinked with an imbalance in bore resorption and formation that results in a net loss of bone. Especially, osteoporosis is a disease characterized by low bone mass with age. One form of aging-related primary osteoporosis is postulated with the reduction of circulating estrogen, rapid bone loss occurs as a result of enhanced bore remodelling with an excess of resorption over bore formation. The oxidative stress is also involved in the pathogenesis of osteoporosis. Oxidative stress by cytokines, such as IL-a and TNF-${\alpha}$, inhibits osteoblast function in vitro and stimulates osteoblast apoptosis resulting in an imbalance in bore remodelling. The present article reviews the current perspectives on the interaction between bone remodelling and factors such as estrogen and oxidative stress, providing an interpretation of bone diseases in a view of molecular mechanisms.

• Journal of Astronomy and Space Sciences
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• v.1 no.1
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• pp.23-34
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• 1984

A bubble trapped in the liquid manifold of INTELSAT IV F-7 spacecraft caused a mass imbalance between the System 1 propellant tanks and a wobble half angle of 0.38 degree to 0.48 degree. A maneuver on May 14, 1980 passed the bubble through the axial jet and allowed propellant to redistribute. A 0.2 rpm change in sin rate was observed with an exponential decay time constant of 6 minutes. In this paper, moment of inertia, tank geometry and hydrodynamic models are derived to match the observed spin rate data. The values of the total mass of propellant considered were 16, 19 and 20 kgs with corresponding mass imbalances of 14.3, 15 and 15.1 Kgs, respectively. The result shows excellent agreement with observed spin rate data but it was necessary to assume a greater mass of hydrazine in the tanks than propellant accounting indicated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.444-447
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• 2008

Recently, the need of thin-walled injection molding and enhancement of its productivity is greatly increased. In this study, we designed and manufactured a injection molding system, which can mold a part with the thickness of $500{\mu}m$ and 8 cavity. And processing technique for the multi-cavity injection molding system, which is capable of mass productivity on the plastic parts, was considered. The problems of unbalance/imbalance on the molding process for the multi-cavity mold were predicted by numerical analysis using plastic injection molding commercial code. In addition, controllable system of melt front filling was introduced for a balanced filling using the mold temperature sensor on injection mold. It was shown that balanced filling with the suggested injection molding system was possible for $500{\mu}m$ plastic parts with 8 cavity layout.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.42-46
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• 2006

For mass production, usually injection mold has multi-cavity which is filled through geometrical balanced runner system. Despite geometrical balanced runner system, filling imbalances between cavity to cavity have always been observed. These filling imbalances are one of the most significant factors to affect quality of plastic parts. Filling imbalances are results from non-symmetrical shear rate distribution within melt when it flows through tile runner system. It has been possible to decrease filling imbalance by optimizing processing conditions, but it has not completely eliminated this phenomenon during injection molding processing. This paper presents a solution for these filling imbalances by using Runner Core pin (RC pin). The Runner Core pin which is developed in this study creates a symmetrical shear distribution within runner. As a result of using Runner Core pin, a remarkable improvement in reducing filling imbalances was confirmed.

• Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.13-16
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• 2008

The line of sight(LOS) is affected by the vibration of spacecraft. It is necessary to predict the effect of disturbance on LOS stability. Reaction wheel assembly is anticipated to be the largest disturbance source on spacecraft. The disturbance which is occurred mainly due to the mass imbalance is analyzed with harmonic numbers. The accuracy and stability are verified by probability density function with dynamic equation of the satellite motion.

• Journal of Digital Convergence
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• v.17 no.3
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• pp.463-471
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• 2019

The purpose of this study was to investigate the effect of muscle imbalance on motion of back squat. The isokinetic muscle strength of the 8 subjects was recorded for the knee flexion/extension by the cybex 770 dynamometer. Each subject performed 3 back squats with the long barbell with an intensity of 25% body weight(BW), 50%BW, 100%BW, 125%BW. During the back squat through the recorded kinematic data the subjects' maximum flexion and extension knee angle, center of mass displacement and V-COP were calculated for evaluation of the stability of the movement. For the statistical analysis independent t-test was used. Knee flexion angle and COM displacement are dominated by the reciprocal muscle ratio. V-COP factor was dominated by bilateral extension deficit. Based on the results we can know that as the intensity of the squat increased to a level control was difficult because the muscles' imbalance influenced the movement.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.233-239
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• 2022

The injection molding process is a process in which thermoplastic resin is heated and made into a fluid state, injected under pressure into the cavity of a mold, and then cooled in the mold to produce a product identical to the shape of the cavity of the mold. It is a process that enables mass production and complex shapes, and various factors such as resin temperature, mold temperature, injection speed, and pressure affect product quality. In the data collected at the manufacturing site, there is a lot of data related to good products, but there is little data related to defective products, resulting in serious data imbalance. In order to efficiently solve this data imbalance, undersampling, oversampling, and composite sampling are usally applied. In this study, oversampling techniques such as random oversampling (ROS), minority class oversampling (SMOTE), ADASYN(Adaptive Synthetic Sampling), etc., which amplify data of the minority class by the majority class, and complex sampling using both undersampling and oversampling, are applied. For composite sampling, SMOTE+ENN and SMOTE+Tomek were used. Artificial neural network techniques is used to predict product quality. Especially, MLP and RNN are applied as artificial neural network techniques, and optimization of various parameters for MLP and RNN is required. In this study, we proposed an SA technique that optimizes the choice of the sampling method, the ratio of minority classes for sampling method, the batch size and the number of hidden layer units for parameters of MLP and RNN. The existing sampling methods and the proposed SA method were compared using accuracy, precision, recall, and F1 Score to prove the superiority of the proposed method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.557-563
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• 2001

Small capacity gas absorption systems for cooling and heating have been favorably considered to reduce the seasonal imbalance of electrical loads and LNG consumption recently. A multifunctional plate-fin heat exchanger was adopted as an absorber and the performance was tested and analyzed to reduce the size and weight of the absorption heat pump. The test was performed using breadboard type ammonia absorption machine. The performance was compared with the plate type absorber and there was little difference in heat and mass transfer characteristics. The heat and mass transfer performance was a function of poor solution and vapor flow rates and the mass transfer was dependent on vapor flow rate more than heat transfer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.175-181
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• 2016

This occurs when the unbalanced rotating body is inconsistent with the mass center line axis geometric center line. Wheelsets are assembled by a single axle with two wheels and a rotating body of a running railway vehicle. Owing to non-uniformity of the wheel material, the wear, and error of the wheel and axle assembly may cause an imbalance. Wheelsets will suffer the effects of vibrations due to the unbalanced mass, which becomes more pronounced due to the thin and high-speed rotation compared to the shaft diameter This can affect the driving safety and the running behavior of a rail car during high-speed running. Therefore, this study examined this unbalanced wheel using a railway vehicle multibody dynamics analysis tool to assess the impact of the dynamic VI-Rail movement of high-speed railway vehicles. Increasing the extent of wheel imbalance on the analysis confirmed that the critical speed of a railway vehicle bogie is reduced and the high-speed traveling dropped below the vehicle dynamic behaviour. Therefore, the adverse effects of the amount of a wheel imbalance on travel highlight the need for management of wheel imbalances. In addition, the static and dynamic management needs of a wheel imbalance need to be presented to the national rail vehicles operating agency.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1277-1282
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• 2003

The purpose of the present paper is to investigate the noise and vibration characteristics of externally pressurized air proceeding bearings with a circular slot restrictor. To do this, the nonlinear transient analysis including rotor imbalance was performed for a rotor-bearing system. The effects of radial clearance and the width of the bearing and mass eccentricity of the rotor on the noise and vibration characteristics of the bearing are also examined. The results show that the noise and vibration of the rotor-bearing system first increase up to critical speed of the system, and then decrease up to instability threshold speed of the system as the rotational speed of the rotor increases, and the noise of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the width of the bearing.