• Journal of ILASS-Korea
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• v.27 no.4
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• pp.181-187
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• 2022

For carbon neutrality, direct-injection hydrogen engines are attracting attention as a future power source. It is essential to estimate the transient injection rate of hydrogen for the optimization of hydrogen injection in direct injection engines. However, conventional injection rate measurement techniques for liquid fuels based on the injection-induced fuel pressure change in a test section are difficult to be applied to gaseous fuels due to the compressibility of the gas and the sealing issue of the components. In this study, a momentum flux measurement technique is introduced to obtain the transient injection rate of gaseous fuels using a force sensor. The injection rate calculation models associated with the momentum flux measurement technique are presented first. Then, the volumetric injection rates are estimated based on the momentum flux data and the calculation models and compared with those measured by a volumetric flow rate meter. The results showed that the momentum flux measurement can detect the injection start and end timings and the transient and steady regimes of the fuel injection. However, the estimated volumetric injection rates showed a large difference from the measured injection rates. An alternative method is suggested that corrects the estimated injection rate results based on the measured mean volumetric flow rates.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.6
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• pp.173-183
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• 2020

The paper investigates the determinants of foreign direct investment (FDI) in Vietnam in 2000-2019 period. This study uses difference Generalized Methods of Moments (GMM) and Pooled Mean Group (PMG) to analyse panel data officially provided by General Statistical Office of Vietnam. The results show that market size impacts positively significant on FDI attraction: 1% -1.45% (PMG) and 1% -1.25% (GMM). Besides, some other factors have positive influences as labor force, macroeconomic policy, macroeconomic stability and skilled labor. Meantime, the trade openness negatively affects FDI inflows in the short-term, while not being statistically significant in the long-term. Moreover, economic shocks often have a negative impact on FDI inflows. The findings of this study lead to the following recommendations. First, authorities should pay special attention to encourage economic growth rate in Vietnam to expand market size because this is the first priority of foreign investors. Second, authorities need to continue increasing the rate of skilled labor, especially highly qualified management force, engineers and well-skilled workers. Third, the authorities should adjust trade openness to boost the role of its determinant in attracting FDI inflows. Fourth, macroeconomic stability needs to be governed by international standards in order to secure the belief of foreign investors in the long-term.

• Progress in Superconductivity and Cryogenics
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• v.19 no.1
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• pp.9-12
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• 2017

Recently, DNA vaccination is attracting attentions as a new therapeutic method for lifestyle diseases and autoimmune diseases. However, its clinical applications are limited because a safe and efficient gene transfer method has not been established yet. In this study, a new method of gene transfer was proposed which utilizes the jet injection and the magnetic transfection. The jet injection is a method to inject medical liquid by momentary high pressure without needle. The injected liquid diffuses in the bio tissue and the endocytosis is considered to be improved by the diffusion. The magnetic transfection is a method to deliver the conjugates of plasmid DNA and magnetic particles to the desired site by external magnetic field. It is expected that jet injection of the conjugates causes slight membrane disruptions and the traction of the conjugates by magnetic field induces the efficient gene transfer. In conclusion, the possibility of improvement of the gene expression by the combination of jet injection and magnetic transfection was confirmed.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.345-350
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• 2001

Dynamic behavior of high speed train is very important because the high speed train should be safe and satisfied with the ride comfort. An eddy current brake system is mounted on trailer bogie and wheelset. The eddy current braking force longitudinally exerts on the articulated trailer bogie and the attraction force vertically exerts on the wheelset. Because a frame of eddy current brake system is flexible, these forces generate the vertical vibration at middle point of the frame. Also, the vibration change the vertical clearance between an electromagnet and top of rail which affect the magnitude of braking and attracting forces. Therefore, the dynamic behavior of the eddy current braking system must be predicted for design the dynamic characteristic of its mounting system when normally operate on rail which have irregularity. Vampire program is used for prediction of the dynamic behavior of an eddy current braking system. Five design variables and five performance index are considered for optimization through D-optimal experimental design in this paper. Also model center is used to search the optimal point for sum of performance index with variational matric method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.473-477
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• 2009

In general, the softer the stiffness of a linear vibration isolator the better the performance of isolation can be achieved. However, the stiffness of the isolator cannot be made too soft because it needs a sufficient stiffness to hold the load. This is the most critical limitation of a linear vibration isolator. Recently, a HSLDS (High-Static-Low-Dynamic-Stiffness) magnetic vibration isolator was proposed to overcome this fundamental limitation. The suggested isolator utilizes two pairs of attracting magnets that that introduces negative stiffness. Previously, this new type of vibration isolator was merely introduced and showed a possibility of practical use. In this paper, detailed dynamics of the HSLDS magnetic isolator are studied using computer simulations. Then, the isolation performance is examined for various design parameters to aid the practical use.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.371-378
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• 2000

In this study an adaptive node generation procedure in the Element-free Galerkin (EFG) method using bubble-meshing technique is proposed. Based on the error function that obtained by projected error estimation method, the initial node arrangement is defined along the background cell that is used in the numerical integration. To obtain the smooth nodal configuration, the nodal configuration are regenerated by bubble-meshing technique. This bubble meshing technique was originally developed to generate a set of well-shaped triangles and tetrahedra. Its basic idea is packing circles or spheres, called bubble, into the specified area or space naturally using some dynamic equations with attracting and repelling force. To demonstrate the performance of proposed scheme, the convergence behaviors are investigated for several problems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.1
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• pp.92-97
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• 2010

In general, the softer the stiffness of a linear vibration isolator the better the performance of isolation can be achieved. However, the stiffness of the isolator cannot be made too soft because it needs a sufficient stiffness to hold the load. This is the most critical limitation of a linear vibration isolator. Recently, a HSLDS(high-static-low-dynamic-stiffness) magnetic vibration isolator was proposed to overcome this fundamental limitation. The suggested isolator utilizes two pairs of attracting magnets that introduces negative stiffness. Previously, this new type of vibration isolator was merely introduced and showed a possibility of practical use. In this paper, detailed dynamics of the HSLDS magnetic isolator are studied using computer simulations. Then, the isolation performance is examined for various design parameters to aid the practical use.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.382-385
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• 2003

In this paper, the solenoid for high-voltage circuit breaker which is composed of bobbin, solenoid coil, stationary core and plunger was studied. The solenoid is made of a soft magnetic iron bar with a large number of coil windings. when an electric current passes through this, this stationary core becomes the strong magnet used for hydraulic and pneumatic valve of a solenoid operated valve. For the performance evaluation of the solenoid for high-voltage circuit breaker, electromagnetic characteristics and dynamic characteristics were analyzed. And, the parameters which is related to performance improvement were investigated.

• Smart Media Journal
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• v.5 no.2
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• pp.51-58
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• 2016

Recently, the unmanned aerial vehicle Drone technology is attracting new interest around the world. The versatilities in science, military, marketing, sports, and entertainment fields are the driving force of the drone fever. Thus, the potential power of future industrial is expected as the application range is extensive. In this paper, we design and propose the prototype of unmanned aerial vehicle-based bigdata processing system.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.425-427
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• 1994

A manipulator which can separate dielectric particles (biological cells) was fabricated on a silicon wafer using polyimide and n-type electroplating. It consists of 1024 electrode arrays ($60{\mu}m{\times}60{\mu}m$) and spacing insulator. Positive dielectrophoresis is used for attracting particles. We have the solution of 3-D laplace equation about this device and calculate the force acting on the particles. The solution has spatial periodicity in the x, y directions and decays exponentially in the z direction.