• Journal of Welding and Joining
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• v.27 no.1
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• pp.71-78
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• 2009

In the circumferential welding of pipe, welding phenomenon changes with the position of pipe. Especially in the overhead position, back bead of vertical-up position would be sunk. To investigate the size of back bead and keyhole with the change of the flow rate of pilot and shield gas at each position, bead-on plate welds were conducted on 6mm thickness SS400 with inclined-up position. When the rest of welding conditions remained constant, the width of back bead was increased as the flow rate of pilot gas was increased. And back bead tended to convex as the flow rate of shield gas was increased.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.1
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• pp.10-19
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• 1990

A fault tolerant control system, in which a digital back-up controller system is added on the existing analog control system, is developed for enhancing reliability of boiler control system in power plant. The digital back-up controller system(DBCS) has a multi-processor structure with capabilities of fault diagnosis, back-up control, self test, and graphic monitoring. Specifically, switching mechanism composed of expandable modules is designed so that back-up controller takes over any faulty control loops and the number of back-up control loops is determined as that of simultaneous faults. A process simulator that simulates the boiler analog control system is developed for safety test and performance evaluation prior to real plant application. DBCS is installed at the Ulsan thermal power plant, and fault tolerant control performance is assured under the faults that some controller modules are pulled out.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.915-916
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• 2007

There are many equipments for the Short Circuit Test, for example Short Circuit Generator, Induction Motor, Sequence Timer, Exciter, CLR, Back Up Breaker, Making Switch and TRV etc. Especially Back up Breaker and Making Switch are very important equipments to test the short circuit test. A role of a Back up Breaker is to break high-voltage and high-current for short circuit test and a Making Switch should be operated always same speed/time and kept electrical-mechanical characteristics to make the voltage and current of short circuit test. This study introduces to the short circuit test also to kinds, principal movements and compare them of Back up Breaker and Making Switch.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.173-176
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• 2007

The characteristics of the tool system give many effects into the costs and qualities for the finished components. This study proposes a new method for manufacturing of high manufacturing productivity, production process reduction and low cost through back pressure forming. The Lock-up hub is manufactured through many processes, such as upsetting($1^{st}$ Forming), piercing, direct extrusion($2^{nd}$ Forming), final sizing process($3^{rd}$ Forming). In this study, process design for closed-die forging of a Lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of Lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• Safety and Health at Work
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• v.5 no.1
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• pp.13-16
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• 2014

Background: This study assesses influences of baseline psychological risk factors on prevalence of low back pain (LBP) at baseline and follow-up among nurses. Methods: A prospective longitudinal study was performed at two phases, baseline and 1-year follow-up among 246 nurses of university hospitals in Shahroud, Iran. A standardized Cultural and Psychosocial Influences on Disability questionnaire was used for data collection. Logistic regression was performed for analysis. Results: At the baseline of the study, 58.9% of nurses reported back pain in the previous 12 months. Age (p = 0.001), belief that work causes pain (p = 0.022), and somatization tendency (p = 0.002) significantly increased risk of LBP. At 1-year follow-up, prevalence of LBP was 45.7% and expectation of back pain at baseline (p = 0.016) significantly increased risk of LBP in this phase (p < 0.05). Conclusion: Results indicate that risk factors for prevalence of back pain at baseline and 1-year follow-up are different. At baseline, the risk factors are age, belief that work causes pain, and somatization tendency, and at follow-up, expectation of pain is the major risk factor.

• Steel and Composite Structures
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• v.42 no.4
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• pp.513-538
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• 2022

This paper reports on experiments addressing the buckling and collapse behavior of an innovative built-up cold-formed steel (CFS) columns. The built-up column consists of four individual CFS lipped channels, two of them placed back-to-back at the web using two self-drilling screw fasteners at specified spacing along the column length, while the other two channels were connected flange-to-flange using one self-drilling screw fastener at specified spacing along the column length. In total, 12 experimental tests are reported, covering a wide range of column lengths from stub to slender columns. The initial geometric imperfections and material properties were determined for all test specimens. The effect of screw spacing, load-versus axial shortening behaviour and buckling modes for different lengths and screw spacing were investigated. Nonlinear finite element (FE) models were also developed, which included material nonlinearities and initial geometric imperfections. The FE models were validated against the experimental results, both in terms of axial capacity and failure modes of built-up CFS columns. Furthermore, using the validated FE models, a parametric study was conducted which comprises 324 models to investigate the effect of screw fastener spacing, thicknesses and wide range of lengths on axial capacity of back-to-back and flange-to-flange built-up CFS channel sections. Using both the experimental and FE results, it is shown that design in accordance with the American Iron and Steel Institute (AISI) and Australia/New Zealand (AS/NZS) standards is slightly conservative by 6% on average, while determining the axial capacity of back-to-back and flange-to-flange built-up CFS channel sections.

• Journal of Korean Physical Therapy Science
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• v.9 no.2
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• pp.27-36
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• 2002

The purpose of this study was to examine the effects of graded low back exercise program with patient education about low back pain care on abdominal strength, endurance and flexibility of waist of chronic low back pain patents. For this study 13 patients aged 40 to 60 were selected as subjects, who suffered from low back pain and got diagnosed by physician. The exercise program and the education were executed for total 6 weeks, posture education were executed with physical exercises over first 1 to 4 weeks period and over 5 to 6 weeks the exercises were executed. The effect of the exercises and the education were evaluated through weights, WHR, fat(%), flexibility by sit-and-reach and trunk extension test, strength by sit-up test and back sit-up test. Weights were, decreased after physical exercise and education, but there was no statistical significance. Wasit hip ratio(WHR) and fat(%) were decreased after physical exercise and education, but there were no statistical significances. Sit-and-reach was significantly increased from $13.68{\pm}5.59cm$ to $19.45{\pm}3.81cm$ after education and physical exercise(P<0.05). Trunk extension was significantly increased from $30.31{\pm}11.34cm$ to $40.88{\pm}6.16cm$ after education and physical exercise(P<0.05). Sit-up and Back sit-up were increased after physical exercise and education, but there were no statistical significances. These results suggest that graded low back exercise program with patient education about low back pain care increase the abdominal strength, endurance and the flexibility of waist in low back pain patients.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.129.1-129.1
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• 2010

Since the commencement of the fuel cell business in 2007, POSCO POWER has been the major supplier of the MCFC (Molten Carbonate Fuel Cell), which is the most commercialized stationary fuel cell system in the world. With its quite, yet active movement, more than 20MW MCFC systems have been installed and are operating in Korea. While trying to localize the components and set up a firm supply chain in Korea to provide more reliable and cost-competitive products to its customers, POSCO POWER is also devoting itself to developing new MCFC application products. One such product is a back-up power system, in which a back-up algorithm is embedded to the present system so that the product can work as a back-up generator in case of grid failure. The technology to enhance load following capability of a stack module is also being developed with the back-up algorithm. Another example is a building application, the goal being to make the present Sub-MW product suitable for urban area. For this, downsizing and modularization are the main R&D scope. The project for developing ship service fuel cell for APU application will launch soon as well. In the project, a system which can operate in marine environment, and reforming technology for liquid logistic fuel will be developed.

• Steel and Composite Structures
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• v.29 no.1
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• pp.23-37
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• 2018

In this paper, seismic provisions related to built-up special concentrically braced frames (BSCBFs) are investigated under cyclic loading using non-linear finite element analysis of a single-bay single-story frame. These braces, which contain double angle and double channel brace sections, are considered in two types of single diagonal and X-braced frames. The results of this study show that current seismic provisions such as observing the 0.4 ratio for slenderness ratio of individual elements between stitch connectors are conservative in BSCBFs, and can be increased according to the type of braces. Furthermore, such increments will lead to decreasing or remaining the current middle protected zone requirements of each BSCBFs. Failure results of BSCBFs, which are related to the plastic equivalent strain growth of members and ductility capacity of the models, show that the behaviors of double channel back-to-back diagonal braces are more desirable than those of similar face-to-face ones. Also, for double angle diagonal braces, results show that the failure of back-to-back BSCBFs occurs faster in comparison with face-to-face similar braces. In X-braced frames, cyclic and failure behaviors of built-up face-to-face models are more desirable than similar back-to-back braces in general.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.107-115
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• 1999

Hydrocarbon emission from spark ignition engines deeply relates with fuel evaporation mechanism. Therefore, fuel evaporation on the back of the intake valve is very important to understand fuel evaporation mechanism during engine warm up period. Intake valve heat transfer model was build up to estimate the amount of fuel evaporation on the intake valve back . Intake valve temperature was measured intake valve temperature is increased rapidly during few seconds right after engine start up and it takes an important role on fuel evaporation. The liquid fuel evaporation rate on the intake valve back proportionally increases as valve temperature increases, however its contribution slightly decreases as intake port wall temperature increases. The fuel evaporation rate on the valve back is about 40∼60% during engine warm-up period and it becomes about 20∼30% as intake port wall temperature increases. The estimation model also makes possible model also makes possible to review the effect of valve design parameters such as the valve mass and seat area on fuel evaporation rate through intake valve heat transfer.