• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.582-585
• /
• 2004

Most of hard disk drives currently employ fluid dynamic bearing (FDB) for their rotor support. Stiffness of the FDB is affected by many design factors such as bearing clearance, fluid viscosity, and rotational speed. For the high rotating speed HDDs stiffness of the rotor is normally high enough to accomodate load disturbances. However small form factor HDDs that are to be operated in low power consumption are often designed with low stiffness rotors. Although the low stiffness rotor clearly benefits low power operation, it could damage the entire motor structure or head disk interface even by a light mechanical load disturbance such as shock or vibration. In addition, since a single channel HDD does not provide gram load equilibrium in axial direction the rotor could be tilted and make a hard contact to stator. A non-symmetric groove pattern could successfully compensate the tilted rotor angle during operation.

• Transactions of the Society of Information Storage Systems
• /
• v.2 no.2
• /
• pp.130-137
• /
• 2006

The HDD(hard disk drive) using Load/unload(L/UL) technology includes the benefits which are increased areal density, reduced power consumption and improved shock resistance than those of contact-start-stop(CSS). It has been widely used in portable hard disk drive and will become the key technology for developing the small form factor hard disk drive. The main objects of L/UL are no slider-disk contact or no media damage. For realizing those, we must consider many design parameters in L/UL system. In this paper, we focus on lift-off force. The 'lift-off' force, defined as the minimum air bearing force, is another very important indicator of unloading performance. A large amplitude of lift-off force increases the ramp force, the unloading time, the slider oscillation and contact-possibility. To minimize 'lift-off' force we optimizes the slider and suspension using the integrated optimization frame, which automatically integrates the analysis with the optimization and effectively implements the repetitive works between them. In particular, this study is carried out the optimal design considering the process of modes tracking through the entire optimization processes. As a result, we yield the equation which can easily find a lift-off force and structural optimization for suspension.

• Korean Institute of Interior Design Journal
• /
• v.23 no.6
• /
• pp.178-186
• /
• 2014

Recently, a lower levels space has turned into a mediating space where people can experience urban spaces directly and it has revitalized communication between the city and company and also it has changed itself newly. In addition, this space which is connecting interior and exterior spaces of company's buildings can attract people living in the downtown as shock-absorbing and transitional space and it is getting more important part in urban context these days. Through case studies of corporate office space planning characteristics derived lower levels and to provide direction for the lower levels of the corporate office space planning purposes of the present study. Therefore, I establish the concept of the public good corporate office space and transition space, the concept of transition through the first Theoretical Methods. I investigate the properties of the transition area is used as the target for completion of the current construction culture destination since 2000, winning the corporate office, I have been talking about the characteristics of the corporate office along the lower part of the last PPS assessment criteria to apply to the building. PPS by applying an assessment factor can be derived for building enterprise case studies and analysis of the results the following conclusions about the use of publicity and transition space. First, lower levels of corporate office space had been applied to the use and activity in a very important project characteristics. Second, corporate office space, lower levels of access and linkages are important. Finally, in terms of public characteristics transition space is a important characteristic for low-rise space of headquarter buildings.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.6
• /
• pp.586-594
• /
• 2009

This paper is the study on random, sinusoidal and shock vibration responses for the STSAT-3(science and technology satellite-3) proto-model which is the first small size all-composite satellite in Korea. The structure system of the STSAT-3 forms box type structure by joining several hybrid sandwich panels comprised of honeycomb core and carbon fiber reinforced laminated composite skins on both side. Mode shape, stress, displacement and acceleration responses are obtained on both the frequency domain and time domain by means of a commercial FEA software MSC/NASTRAN. From these analysis results, failure, safety factor and design validity are assessed. These results can be successfully applicable as reference data when a new satellite is developed as well as giving out an excellent criteria in satellite vibration treatment design.

• Nuclear Engineering and Technology
• /
• v.52 no.8
• /
• pp.1871-1880
• /
• 2020

Round robin analyses for vessel failure probabilities due to PTS events are proposed for plant-specific analyses of all types of reactors developed in Korea. Four organizations, that are responsible for regulation, operation, research and design of the nuclear power plant in Korea, participated in the round robin analysis. The vessel failure probabilities from the probabilistic fracture mechanics analyses are calculated to assure the structural integrity of the reactor pressure vessel during transients that are expected to initiate PTS events. The failure probabilities due to various parameters are compared with each other. All results are obtained based on several assumptions about material properties, flaw distribution data, and transient data such as pressure, temperature, and heat transfer coefficient. The realistic input data can be used to obtain more realistic failure probabilities. The various results presented in this study will be helpful not only for benchmark calculations, result comparisons, and verification of PFM codes developed but also as a contribution to knowledge management for the future generation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.5
• /
• pp.487-494
• /
• 2011

The safety valve used in LNG/LNG-FPSO ships plays an important role in maintaining a fixed level of pressure by emitting LNG gas out of the pipes in the LNG piping system. The discharge coefficient is regarded as the most important factor in the valve performance. To satisfy the ship's classification, the discharge coefficient of the safety valve must usually be over 0.8. Despite the importance of understanding the flow phenomena inside the safety valve, the valve design is usually based on experience and experiments. We carried out a computational fluid dynamics (CFD) investigation using the ANSYS-CFX software. We observed the flow phenomena inside the valve and measured the discharge coefficients according to changes in the valve lift, which is the distance between the exit of the nozzle and the lower part of the disc plate. We verified our CFD results for the discharge coefficients using available experimental data.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.21 no.2
• /
• pp.64-70
• /
• 2007

A voltage drop in the electrical circuit must be unavoidable. The voltage drop in the electrical circuit means a loss of heat. The heat lost would change the characteristics of the insulator and thus, the insulating performance would be towered resulting in electric leakage, electric shock, power failure, fire and other accidents. Hence, an optimized design against the voltage drop in the electrical circuit must be an important factor determining safety and economy of electrical facilities. This study analyzed the effects of voltage drop on the electrical circuit for such low-voltage electrical facilities requiring the public safety foremost and subject to multi-distributed random loads as street lamps, buildings and subway stations, and thereupon, developed an optimized voltage drop computation program to enhance safety and economy of those electrical facilities.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
• /
• v.30 no.1
• /
• pp.74-86
• /
• 2017

Objectives : This study aimed to assess the scientific evidence for the use of Hwanglyeonhaedok-tang, a traditional herbal formula, in the treatment of rhinitis, and prepare the basis for the investigational new drug application by analyzing the experimental studies. Methods : Ten electronic databases were searched up to December, 2016 without language limitation. Experimental studies on the anti-inflammatory and anti-allergic effects of Hwanglyeonhaedok-tang against rhinitis were included. We extracted data about study design, characteristics of intervention, outcomes, and pharmacological effects from the included studies and summarized them. Results : Eight hundred and thirty-three potentially relevant studies were identified, of which 18 experimental studies met our inclusion criteria. Of 18 included studies, 5 had conducted cell viability test, and all studies had reported that Hwanglyeonhaedok-tang was non-cytotoxic. Hwanglyeonhaedok-tang exhibits anti-inflammatory effect by regulating the inflammation-related cytokines including nitric oxide(NO), prostaglandin $E_2(PGE_2)$, interleukin-6(IL-6), and tumor necrosis $factor-{\alpha}(TNF-{\alpha})$ in vitro and in vivo. Hwanglyeonhaedok-tang exhibits anti-allergic effect by suppressing eosinophil, and histamine levels. Hwanglyeonhaedok-tang helps in the recovery of nasal mucous membrane by supressing goblet cells, heat shock protein 70, and substance P. Conclusions : This study suggests that Hwanglyeonhaedok-tang has the potential to be developed as therapeutic agent for rhinitis. Further experimental and clinical studies needed to be performed to prove the safety and efficacy.

• Design & Manufacturing
• /
• v.16 no.2
• /
• pp.33-38
• /
• 2022

Currently, Korea is an aging society, and it is expected to enter a super-aging society in about 4 years. Accordingly, many X-ray technologies are being developed. In X-rays, 99% of X-rays are converted into heat energy and 1% into light energy (X-rays). 99% of the thermal energy raises the temperature of the anode and its surroundings, and the cooling system is an important factor as overheating can affect the deterioration of X-ray quality and shortened lifespan. There is a method of forced air cooling using natural convection. Therefore, in this study, when X-rays were taken 5 times, Flow analysis was performed on heat removal according to temperature rise and cooling time for the heat generated at the anode of the X-ray tube (input power 60kW, 75kW, 90kW). Based on one-shot, the most rapid temperature rise section increased by more than 57% to 0.03 seconds, A constant temperature rises from 0.03 seconds to 0.1 seconds, It is judged that the temperature rises by about 8.2% or more at one time. After one-shot cooling, the cooling drops sharply from about 60% to 0.03 seconds, It is judged that the temperature has cooled by more than 86% compared to the temperature before shooting. One-shot is cooled by more than 86% with cooling time after 0.1 seconds, As the input power of the anode increases, the cooling temperature gradually increases. Since the tungsten of the anode target inside the X-ray tube may be damaged by thermal shock caused by a rapid temperature rise, an improvement method for removing thermal energy is required when using a high-input power supply.

• Smart Media Journal
• /
• v.11 no.5
• /
• pp.75-81
• /
• 2022

In order to respond to carbon neutrality and climate change in agriculture, agricultural machinery, which has been developed centered on internal combustion engines, needs to be converted to an electric-based technology that does not emit greenhouse gases. In this study, simulations for electric UTV suspension design were performed to reduce vibration and shock of electric UTV for agricultural use and to improve driving stability and control performance of the vehicle. The simulation was performed by dividing the tolerance load of the vehicle body and the loaded load state. The range of motion of the suspension spring of UTV is within 30% of the range of motion under condition B under tolerance, the displacement of the UTV suspension with full load is reduced from 264mm to 121mm, and the damping speed is 260mm/s to 300mm/s that it can be seen that the range of motion is within 60%. Suspension design of electric UTV for multi-purpose agricultural work is a very important factor for maintaining agricultural work ability in towing work such as tillage as well as driving and terrain adaptation. The results of this study can be usefully used to determine the spring parameters with the appropriate damping range so that the electric UTV can be used for various agricultural tasks.