• Wind and Structures
• /
• v.17 no.6
• /
• pp.629-646
• /
• 2013

One of the most common solutions adopted to reduce vibrations of skyscrapers due to wind or earthquake action is to add external damping devices to these structures, such as a TMD (Tuned Mass Damper) or TLCD (Tuned Liquid Column Damper). It is well known that a TLCD device introduces on the structure a nonlinear damping force whose effect decreases when the amplitude of its motion increases. The main objective of this paper is to describe a Hardware-in-the-Loop test able to validate the effectiveness of the TLCD by simulating the real behavior of a tower subjected to the combined action of wind and a TLCD, considering also the nonlinear effects associated with the damping device behavior. Within this test procedure a scaled TLCD physical model represents the hardware component while the building dynamics are reproduced using a numerical model based on a modal approach. Thanks to the Politecnico di Milano wind tunnel, wind forces acting on the building were calculated from the pressure distributions measured on a scale model. In addition, in the first part of the paper, a new method for evaluating the dissipating characteristics of a TLCD based on an energy approach is presented. This new methodology allows direct linking of the TLCD to be directly linked to the increased damping acting on the structure, facilitating the preliminary design of these devices.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.8
• /
• pp.1021-1029
• /
• 2001

Rapid prototyping(RP) is a novel technology to create 3D products directly from CAD system. This study proposes a new RP method which uses the PZT ceramic plate to make a Drop-On-Demand liquid jet from the nozzle. The characteristic of drop formation in the new system is investigated both numerically and experimentally. The optimal drop for 3-D Printing can be obtained by the proper amplitude and frequency of the applied voltage. Also the process of the drop formation is analyzed using the pressure wave theory and verified by numerical simulation. First, the pressure wave generated by the deformation of the Piezo-plate at the nozzle is analyzed by solving the 2D axisymmetric wave equation via Finite Element Method. Finally, the drop formation process is simulated using a commercial software, FLOW 3D considering the pressure at the nozzle obtained by solving the wave equation as the boundary condition.

• Journal of the Korean Society for Precision Engineering
• /
• v.8 no.3
• /
• pp.82-92
• /
• 1991

A study on the manufacturing of High Precision Linear Scalr using He-Ne Laser interference Of late, along with the advancement of precision machining technology, the requirement of super precision measurement increases as time goes on, and the accuracy of standard scale which is a basis of precision measurement has been cognized as a criterion of industrial development in a nationl. In this paper, we described on technology by which we could carve scale lines thru optical method under the condition of laboratory by using the coherence of He-Ne two-mode stabilized laser and in turn, put it to practical use as linear scale for the measurement of length. Hence in this research in the case of setting scale interval to 20 ${\mu}m$, we employed super precision scale-carving device associated with Ar laser and acousto optic modulator in lieu of flashing lamp scale-carving device, and we obtained as experimental result superior linear scales carved within the accuracy of ${\pm}$0.3${\mu}m$.

• Proceedings of the SAREK Conference
• /
• 2005.11a
• /
• pp.433-438
• /
• 2005

An AHX(Accumulator Heat eXchanger) consists of a commercial accumulator and an inner heat exchanger located inside of the accumulator. The AHX is used in multi air-conditioners to assure the liquid-phase refrigerant entering into the expansion device. This purpose is achieved by heat transfer between the refrigerant leaving the evaporator and the refrigerant leaving the condenser. In this study, the effects of AHX on the performance of a refrigeration system using H-22 were measured and the test results were analyzed. The operating characteristics of the refrigeration system with the installation of AHX were quite different from those without the installation of AHX. Therefore, it is required to find an optimum refrigerant charging amount and optimum operating conditions, when AHX is installed in the refrigeration system with an fixed area expansion device such as a capillary tube.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.12
• /
• pp.984-991
• /
• 2006

The applications of multi air-conditioners into multiplex and high-rise buildings have been increased by replacing central air-conditioning systems. The pipe length and altitude difference between the indoor and outdoor units can be increased based on installation conditions, which may increase the possibility of flash gas generation at the expansion device inlet. The flash gas generation causes rapid reduction of refrigerant flow rate passing through the expansion device, yielding lower system efficiency. Accumulator heat exchangers have been widely used in multi air-conditioners in order to minimize flash gas generation and obtain system reliability. However, the studies on the heat transfer characteristics and pressure drops of accumulator heat exchangers are very limited in open literature. In this study, the heat transfer rates and pressure drops of accumulator heat exchangers were measured with refrigerant flow rate and operating conditions by using R-22. The heat transfer rate increased with the increase of refrigerant flow rate, while subcooling decreased. The heat transfer rate enhanced with the reduction of inlet superheat and subcooling due to the increased temperature difference between the accumulator and inner heat exchanger.

• Transactions of the Korean hydrogen and new energy society
• /
• v.23 no.4
• /
• pp.404-411
• /
• 2012

This research numerically analyses the effects of the damping device on the operation characteristics of a free piston linear engine. In this paper, the free piston linear engine uses spring as a damping device. The investigated parameter is spring hardness which is varied at 0.5, 1, 2.9, and 14.7 N/mm. The effects of spring hardness on the dynamic characteristic, thermodynamic characteristic and electric power of the engine are investigated. Beside, the equivalent ratio is also changed to provide more information for this study. The simulation results show that, by increasing spring hardness from 0.5 to 14.7 N/mm, all of parameters related to dynamic characteristic such as piston velocity, acceleration, displacement, and frequency increase accordingly. Beside, the peak pressure in the cylinder and electric power are also increased when increasing spring hardness. The tendency is also observed at varied equivalent ratios.

• Journal of the Korea Society of Computer and Information
• /
• v.12 no.1 s.45
• /
• pp.25-32
• /
• 2007

In this paper, the abstract layer for motion capture system is designed and implemented to meet the various hardware and different capturing method. The abstract layer can offer the unified programming by providing device independent API(Application Programming Interface). The device drivers of the optical system and mechanical system are emulated to verify the designed abstract layer. The optical system employs the AOA Ole while the mechanical system uses BVH file. An application program is written to call the abstract layer functions to drive both optical and mechanical drivers and receive the frame data, simulated motion data, that are displayed sequentially on the computer screen by utilizing Direct3D.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.82-82
• /
• 2007

The chemical mechanical polishing (CMP) process has been widely used to obtain global planarization of multilevel interconnection process for ultra large scale. integrated circuit applications. Especially, the application of copper CMP has become an integral part of several semiconductor device and materials manufacturers. However, the low-k materials at 65nm and below device structures because of fragile property, requires low down-pressure mechanical polishing for maintaining the structural integrity of under layer during their fabrication. In this paper, we studied electrochemical mechanical polishing (ECMP) as a new planarization technology that uses electrolyte chemistry instead of abrasive slurry for copper CMP process. The current-voltage (I-V) curves were employed we investigated that how this chemical affect the process of voltage induced material removal in ECMP of Copper. This work was supported by grant No. (R01-2006-000-11275-0) from the Basic Research Program of the Korea Science.

• Journal of the Korean Society of Industry Convergence
• /
• v.22 no.6
• /
• pp.767-773
• /
• 2019

The thermal diffusion performance of the electronic device is a factor for evaluating the stability of the electronic device. Therefore, many of research have been conducted to improve the thermal characteristics of thermal interface materials, which are materials for thermal diffusion of electronic products. In this study, nano thermal grease was prepared by blending graphene, silver and copper nano powders into a thermal grease, a type of thermal interface materials, and the heat transfer rate was measured and compared for the purpose of investigating the improved thermal properties. As a result, the thermal properties were good in the order of graphene, silver and copper, which is thought to be due to the different thermal properties of the nano powder itself.

• Journal of the Korean Society for Heat Treatment
• /
• v.22 no.4
• /
• pp.203-209
• /
• 2009

Dual mass flywheel is the newly developed flywheel system which reduces the noise and vibration and make a better and comfortable ride of cars by adding inertia mass and damping device. However, verification of performance for this system should be carried out since this system is under developing status in our country. Especially, the durability for each part of this system should be guaranteed. Durable properties of driver plate which is the key component of dual mass flywheel were first investigated both in the raw (SCM435 in JIS) and heat-treated material. In addition, fatigue life analysis of driver plate was preformed in the real condition and the results were verified by comparison with the results of rig test.