• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.24-33
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• 2012

The present work has suggested the design methods of the bolt body for making the anti-releasing bolts and provided the changed properties of the bolt body after explosion. To prove this work, two models of the anti-releasing bolts, M10 and M20, are produced and the expansion properties of each model are experimentally obtained. This study verify that the expansion of the bolt body is reproducible and the expansion rate could be controlled by the combination of the design factors and the anti-releasing characteristics could be quantified. It also could provide the data that would be needed to make the bolts with the anti-releasing effect.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.157-173
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• 2014

In this study, how social media PR marketing affect corporate brand expansion was studied. this study consist of 5 chapters; needs and purposes in 1st, concept& characteristics, development processes, needs of social media and merits&demerits as marketing tool in 2nd. concept& characteristics and merits&demerits of corporate brand expansion in 3rd. examples of social media marketing in domestic&foreign and current statuses in 4th. In final, conclusion of the effect of social media PR marketing on corporate brand expansion were presented in each chapter.

• 전기의세계
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• v.30 no.7
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• pp.441-447
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• 1981

As a preceeding work for the study on dielectric characterstics of a kind of low density polyethylene introduced morphological change by mechanical method, glass transition temperature which is regarded as a macroscopic aspect for relaxation of molecular chain segments has been observed by means of temperature dependent dilatometric measurement. The origina specimen clearly shows two knees which correspond to two peaks (.gamma. and .betha. peak) in the intenal friction measurement, suggesting the existence of separated glass transition temperatures at 150.deg.k and 260.deg.k respectively. On the specimen irradiated to 100 Mrad both glass transition temperatures tend to shift towards high temperature sides because of crosslinking by irradiation. furthemore an evidence can be seen that radiation effect, even in amorphous phase, is also slelctive depending on slight morphological differences. The specimen extended to four times in length shows a peculiar nature such as negative linear thermal expansion coefficient increasing with temperature between 220.deg.k and ambient temperature and that this fact is interpreted by considering that c axis of the lattice aligns along the extended direction by drawing, further c axis inherently possesses the characteristics of negative linear thermal expansion coefficient. For the observations that the relatively small positive linear expansion on the specimen extended to ca. two times as well as the part below 220.deg.k of the specimen extended to four times, it is considered for the reason of the facts that the incompletely oriented region indicated as the middle part of Peterlin's model tends to restore partially to orginal arrangement-a kind of phase transition-as increasing with temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.4
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• pp.380-387
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• 1994

An experimental study was performed to investigate the characteristics of refrigerant flow rate control and superheat in an evaporator with an electronic expansion valve(EEV). The EEV used in this study was devised using a needle valve coupled with a stepping motor controlled by a personal computer. A Pill control equation was used to control the superheat of the evaporator and to set the superheat to $5^{\circ}C$. In order to determine an optimum running condition for the system, Pill parameters were varied for the wide range of values. The running condition of an air conditioning system with a PI control was reasonably stable compared with that of the Pill control. Experimental results for the PI control using parameter values, $K_p=1.5$, $T_i=400(sec)$ and $T_s=6(sec)$ show that the superheat reached its target value. When external disturbances were introduced to the system, the superheat target value was reached within about 3 minutes. When the EEV was applied to the air conditioning system driven by an inverter, room temperature control was excellent.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1031-1036
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• 2009

This study is intended to identify how quick disconnect coupling which connects with refrigerant piping of air-conditioner using R-22 refrigerant has effect on characteristics of flux. in the case where the air-conditioner installs utilizes quick disconnect coupling, COP has an effect on the quantity of cooling load because of changing flow rate and physical properties of refrigerant which flow into an entrance of expansion valve from coupling. Variation of flow rate can be regulated by changing expansion-contraction angle; $\alpha$ of an entrance and an exit of coupling. In this study, quick disconnect coupling is presented flow of coupling by using FLUENT as heat flow program. To have an effect on the expansion entrance valve, and by changing expansion-contraction angle; $\alpha$ of an entrance and an exit

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.3
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• pp.384-393
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• 2002

The effects of hole expansion angle and the arrangement of nozzles on a film cooling system for a turbine-blade-shaped surface were experimentally investigated. Liquid crystal with flue-temperature correlation and an image processing system were employed to evaluate surface temperature. Distributions of cooling effectiveness were then presented to figure out the change of heat transfer characteristics with different geometric conditions of cooling-holes. It was found thats the averaged cooling efficiency on the suction surface was maximum with 10 degree of the cooling hole expansion angle. It was also shown that the averaged cooling efficiency on the pressure surface and the averaged cooling efficiency for dual array case were not affected by the hole expansion angle.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.350-353
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• 2001

This study proposes a new method for the transmission system expansion planning using the fuzzy integer programming. It presents stepwise cost characteristics analysis which is a practical condition of an actual systems. A branch and bound method which includes the network flow method and the maximum flow-minimum cut set theorem has been used in order to proceed the stepwise cost characteristics analysis. Uncertainties of the permission of the construction cost and not strict reserve rate and load forecasting of expansion planning have been included and also processed using fuzzy set theory in this study. In order to proceed the latter analysis, the solving procedure is illustrated in detail by branch and bound method which includes the network flow method and maximum flow-minimum cut set theorem. Finally, case studies on 21-bus test system show that the algorithm proposed is efficiently applicable to the practical expansion planning of transmission systems in future.

• Journal of Korea Foundry Society
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• v.5 no.2
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• pp.85-96
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• 1985

In order to investigate the effect of particle size and distribution of silica sand on the characteristics of investment, W/P ratio, setting time, temperature change during setting, setting expansion, thermal expansion and compressive strength of the investments were measured. In this experiment, magnesia clinker and mono ammonium phosphate were used as binder, and particle size and distribution of silica sand were classified for convinence into 10 categories. The main results obtained from this investigation were summerized as follows. 1. W/P ratio decreased with increase of particle size and evenness in distribution of sand grain. 2. Setting time decreased with increase of evenness in distribution of sand grain, and temperature during setting increased with evenness in distribution of sand grain. 3. Setting expansion decreased with increase of particle size, while it increased with evenness in distribution of sand grain. 4. Thermal expansion decreased with increase of particle size. 5. Compressive strength increased with increase of particle size and evenness in distribution of sand grain. From above results, G.F.N. 250 sand which contains 30% of 50-100 mesh could be recommended for investment casting.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.75-83
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• 2018

This paper described a results of dynamic stability by using wheel tracking test and unconfined compression test, in order to evaluate behavior characteristics on the developed pocketable expansion material for emergency restoration of ground cavity. The wheel tracking test result showed that the settlement increment ratio of the recovered ground by the expansion material was decreased compared to the sandy ground in high load condition. That is, it was confirmed that the expansion material was able to restrain the settlement due to the material stiffness, and the same results were obtained for the dynamic stability evaluation results. From the results of unconfined compression test, the pocketable expansion material was found to be able to fully support load on the restored cavity.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.3
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• pp.197-203
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• 2022

Urban space expansion is an important symbol of the urbanization process and has always been an important topic in urban studies. In addition, for sustainable city management, it is important to identify factors that can influence, such as the driving force and direction of urban space expansion, from the stage of establishing an urban development plan. To understand these factors, by observing the expansion process of a specific city, it is possible to sufficiently observe how the urban spatial dimension changes. Through a series of processes, the spatial growth characteristics of the city are analyzed, and the influence and results of important factors are analyzed. For this purpose, this paper examines the changes in the city's outer boundary and land use structure through monitoring data on urban areas of 14 cities in Hunan Province, China from 2000 to 2016. Temporal and spatial regularity according to the urban space expansion of these cities were analyzed, and a preliminary assessment was made on whether the urban space expansion is coordinated with the urban population growth. The assessment result showed: (1) The urban space of most cities has been extended rapidly in 2000-2015 however, the rate and the intensity of urban space expanding has been declining. (2) The construction of the industrial park is the core driving force of the urban space expanding, and the change of the urban space structure is manifested as enclave city expansion because that the industrial park is usually far away from the city center. (3) The population agglomeration is another driving force of the urban space expanding. At this time, the urban space expanding is like boundary extension. (4) Except Changsha city, all of the cities has a high urbanization-area-growth elastic coefficient. It means that most of the cities should enhance the land use degree.