• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2B
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• pp.36-43
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• 2005

This paper suggests a method to effectively apply an application model of fuzzy-neural network to the optimal load distribution algorithm, considering the complication and non-linearity of the web server environment. We use the clustering web server in the linux system and it consists of a load balancer that distributes the network loads and some of real servers that processes the load and responses to the client. The previous works considered only with the scrappy decision information such as the connections. That is, since the distribution algorithm depends on the input of the whole network throughput, it was proved inefficient in terms of performance improvement of the web server. With the proposed algorithm, it monitors the whole states of both network input and output. Then, it infers CPU and memory states of each real server and effectively distributes the requests of the clients. In this paper, the proposed model is compared with the previous method through simulations and we analysis the results to develop the optimal and intelligent load balancing model.

• Design & Manufacturing
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• v.11 no.2
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• pp.1-8
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• 2017

In this study, we applied microcellular foaming injection molding process to improve the performance of system air-conditioner drain fan which had been produced by injection molding process and studied the optimization of process conditions through 6-sigma process and response surface method (RSM) to reduce weight and deformation of products. Additive type, melt temperature, mold temperature, and injection screw shape were selected as the factor affecting the weight and deformation of the products by carrying out analysis of trivial many through ANOVA and design of experiment (DOE) method. Among the effect factor, we set the addictive type to Long G/F and screw shape to foaming screw which had the highest level of weight reduction and deformation reduction. The amount of foaming agent gas was set at 60 ml, which was the limit beyond which the weight of product did not decrease any more. For melt temperature and mold temperature, we studied the conditions where both weight and deformation were minimized using the RSM. As a result, we set the melt temperature to $250^{\circ}C$, fixed mold temperature to $20^{\circ}C$, and moving mold temperature to $40^{\circ}C$. The improvement effect was analyzed by appling the selected optimal conditions to the production process using the microcellular foaming injection molding. The results showed that the mean weight of product was measured to be 1,420g which was 19% lower than that measured in the current process. The standard deviations of the weights were found to be similar to those in the current process and it showed a low dispersion. The mean deformation was measured to be 0.9237mm, which represented a 57% reduction compared to the mean deformation in the current process, and the standard deviation decreased from 0.3298mm to 0.1398mm. Moreover, we analyzed the process capability for deformation, and the results showed that the short-term process capability increased from 2.73 to 6.60 which was even higher than targeted level of 6.0.

• The KIPS Transactions:PartA
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• v.13A no.4 s.101
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• pp.343-350
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• 2006

In this paper, wireless internet proxy server clusters are used for the wireless internet because their caching, distillation, and clustering functions are helpful to overcome the limitations and needs of the wireless internet. A wireless Internet proxy server cluster needs a systematic scalability, simple communication structure, cooperative caching, and serving Hot Spot requests. In our former research, we proposed the CD-A structure which can be scalable in a systematic way and has a simple communication structure but it has no cooperative caching. A hash based load balancing can be used to solve the problem, but it can not deal with Hot Spot request problem. In this paper, we proposed a shared storage based wireless internet proxy server cluster which has a systematic scalability, simple communication structure, cooperative caching, and serving Hot Spot requests. The proposed method shares one cache directory and it has advantages: advantages of the existing CD-A structure, cooperative caching, and serving Hot Spot requests. We performed experiments using 16 PCs and experimental results show high performance improvement of the proposed system compared to the existing systems in Hot Spot requests.

• Journal of the Korean Institute of Gas
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• v.14 no.6
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• pp.15-20
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• 2010

Compressed Natural Gas (CNG) buses have been supplied since the year 2000 in order to resolve severe atmospheric pollution in metropolitan area and contributed on the improvement of urban atmospheric environment. However, it is indispensible to take an adequate measure to guarantee the safety of CNG vehicles because of the possibility of huge fire accident. A receptacle, connecting device between high pressure fuel supply tank and fuel line, plays an important role in CNG supply system. In recent, leakage of CNG from receptacles has been reported. So, the concern about the security and reliability of receptacles has been arisen. Therefore, a lot of efforts to prevent leakage are invested among researchers and the durability of this component should be guaranteed despite repeated operation. This research has performed durability tests of a CNG receptacle regarding the repeated usage, extreme chattering, and continuous full flow test. Although a receptacle used for CNG vehicle satisfies validation requirements in the test results, it has been found that failure in the function of leakage prevention in a receptacle could take place in the case of prolonged exposure to high supply pressure in common quick charging environment on site.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.69-76
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• 2008

Three failure cases of CNG composite vessels were reported since after January 2005. The 1st and 2nd accidents were indebted to vessel defect and installation mistake. The 3rd was caused by gas leak at pipe connections. In this paper various aspects were studied based on information of the three failure analysis, which must be improved for better safety of the CNG bus system. Overpressure region caused by vessel explosion was theoretically predicted and also assessed by PHAST program. Explosion of 120 l vessel under 20 MPa is equivalent to 1.2 kg TNT explosion. The predicted value by PHAST was more serious than theoretical one. However, actual consequence of explosion was much less than both of the predicted consequences. Since the CNG vessel was designed by the performance based design methodology, it is difficult to verify whether the required process and tests were properly conducted or not after production. If material toughness is not enough, the vessel should be weak in brittle fracture at early in the morning of winter season since the metal temperature can be lower than the transition temperature. If autofrettage pressure is not correct, fatigue failure due to tensile stress during repeated charging is possible. One positive aspect is that fire did not ocurred after vessel failure. This may be indebted to fast diffusion of natural gas which hindered starting fire.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.546-555
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• 2019

The purpose of this study was to improve the performance of the bogie-type crematory, which is the mainstream of domestic crematory equipment. A field scale technology was investigated via increasing the volume by changing the shape of the furnace and reducing the cremation time and saving the energy usage through the optimization of burner combustion control. First, the optimized structural design through thermal flow analysis increases the volume of the main combustion chamber by about 70%, which increases the residence time of the combustion flue gas. A designed pilot crematory was then installed and the combustion behavior was tested under various operating conditions and the optimum operating plan was derived from for each furnace shape. Based on the results, the practically applicable crematory was designed and installed at Y crematorium in the P City. Optimal combustion conditions could be derived through operating the demonstration crematory furnace. The crematory time and fuel consumption could be minimized by increasing the energy efficiency by increasing the residence time of high temperature combustion flue gas. In other words, the crematory time and fuel consumption were 38 min and $21.8Nm^3$, respectively which were shortened by 44.1 and 54.4% lower than that of the existing crematory, respectively.

• Journal of the Korean Society for Railway
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• v.18 no.6
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• pp.543-551
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• 2015

Quick-hardening track (QHT) is a construction method which is used to change from old ballast track to concrete track. Sufficient time for construction is important, as the construction should be done during operational breaks at night. Most of the time is spent on exchanging the ballast layer. If it is possible to apply the ballast non-exchange type of quick-hardening track, it would be more effective to reduce the construction time and costs. In this paper, pouring materials with high permeability are suggested and a construction method involving a layer separation pouring process considering the void condition is introduced in order to develop ballast non-exchange type of QHT. The separate pouring method can secure the required strength because optimized materials are poured into the upper layer and the lower layer for each void ratio condition. To ensure this process, a rheology analysis was conducted on the design of the pouring materials according to aggregate size, the aggregate distribution, the void ratio, the void size, the tortuosity and the permeability. A polymer series was used as the pouring material of the lower layer to secure the void filling capacity and for adhesion to the fine-grained layer. In addition, magnesium-phosphate ceramic (MPC) was used as the pouring material of the upper layer to secure the void-filling capacity and for adhesion of the coarse-grained layer. As a result of a mechanics test of the materials, satisfactory performance corresponding to existing quick-hardening track was noted.

• Journal of the Korea Society of Computer and Information
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• v.19 no.11
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• pp.115-126
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• 2014

In order to improvement of the perceptive of health state and the motivation, this study suggests the ways and design forms which provide PHR information customizing individual attributes as well as guidelines through a decision support system and services which integrate medical information visualization. Expression methods using the color, form, position in order to visualization based on images improved performance of information awareness by changing radar chart from existing information which provide only numerical figure. The methods providing a graphic figure which seems like beads of blood which shows the result of blood tests would also arise patient's attention. They gives the patient's information which is able to compare their health status and normal status and visualizes the records as a human figure in order to perceiving their status as well. The visualization showing the position of human body figures marks in inspection elements located in position of relevant organs. The method also uses icons represent examination results so they improve attention of the results and shorten recognize times.

• Journal of the Korean Society for Library and Information Science
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• v.53 no.4
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• pp.5-22
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• 2019

The purpose of this study is to analyze the factors that hinder the role recognition and role performance of teacher librarians and suggest some improvement methods. For this purpose, a questionnaire was conducted among 41 persons who participated in the first-level qualification training for teachers librarians at K University Secondary Teacher Training Institute in 2019.The results showed that there was a difference between the expected role and the execution role of the teacher librarians. In other words, teacher librarians recognize that they should teach information literacy as instructors and operate library-based instruction and cooperative classes as teaching partners. However, the most frequently played roles are reading education and library use education. They recognizes the cause as institutional limitations, such as the absence of a national level curriculum and the ambiguity of the role of specialists in school libraries. And it is perceived as a real problem such as the lack of partnership and recognition of their peers. Among the variables of teacher librarians, the higher their educational level, the more they perceived their peers as teachers. Based on this, some suggestions for strengthening the role of the teacher librarians' instructor and teaching partner were proposed in terms of including cross-curricular subjects of information literacy education, analyzing jobs and establishing scholarship system for school libraries.

• Ocean policy research
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• v.33 no.2
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• pp.83-119
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• 2018

Under the Korean Marine Environment Management Act (hereunder, the KMEMA), the duty to arrange spill clean-up equipments, including spill clean-up vessels, required by the article 67 of the KMEMA is in essence the provision of public goods since it is a precautionary or preventive measure for the efficient performance of oil spill cleaning up. Also the obligation to control marine pollution and the duty to arrange of anti-pollution measures imposed on polluters is the obligation imposed by the public law in accordance with "the Polluter-Pays Principle". Therefore, the execution of such obligations shall be accompanied by the minimum legal and institutional arrangements. On the other hand, judging whether to form the roles of the public and private sectors in providing public goods is basically a matter of policy decision. However, even if the private sector is allowed to participate in the provision of public goods, it is imperative that a minimum requirement be provided to secure the public interest. Although major countries allows polluters to conclude a preliminary contract with a civil anti-pollution management company, these civilian institutions are in principle constituted by the owners of oil storage facilities. Additionally it is worth noting that it operates as a non-profit organization. In particular, if the practitioner performs pollution control for commercial purposes, their profitability may depend on the size of the pollution, the period spent on pollution control, the size of the equipment and manpower mobilized in the pollution control, and so on. Considering the above problems, caution should be taken to allow marine environmental management companies to be un-limitedly entrusted with the responsibility of arranging measures such as pollution control. In order to allow the marine environmental management contractor to be entrusted for the assignment of duty to protect the marine environment, the marine environment management business should be expanded so that the marine pollutant management capacity satisfies the statutory control capacity. For this purpose, it is necessary to manage and supervise the maintenance and improvement of the control capability of the marine environment management business. It is also necessary to discuss the introduction of the grading system for the control ability of the civil control companies alike in major countries.