• 한국결정성장학회지
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• 제12권4호
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• pp.190-195
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• 2002

NaX seed결정(10~20 $\mu$m)을 $3.5Na_2$O : $Al_2O $: $2.1SiO_2$ : $1000H_2$O 용액에 0.5~2.0g 첨가한 후 연속결정화법으로 50 $\mu$m의 균일한 결정을 성장시켰다. 연속결정화법에 의한 결정성장을 시험하기 위하여, 모액을 7일, 5일, 3일, 2일과 1일 간격으로 공급하였다. Seed 첨가의 결과는 첨가하지 않은 용액과 비교하여 보다 균일하고 큰 결정들을 얻었다. 합성용액에 seed의 첨가는 반응물과 물리적인 접촉 면적을 초래하여 합성 겔의 핵성장 없이 seed 결정의 결정성장을 확인할 수 있다.

• 대한조선학회논문집
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• 제57권1호
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• pp.23-34
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• 2020

This paper covers the development of prediction techniques for ice load on ice-breakers operating in continuous ice-breaking under level ice conditions using particle-based continuum mechanics. Ice is assumed to be a linear elastic material until the fracture occurs. The maximum normal stress theory is used for the criterion of fracture. The location of the crack can be expressed using a local scalar function consisting of the gradient of the first principal stress and the corresponding eigen-vector. This expression is used to determine the relative position of particle pair to the new crack. The Hertz contact model is introduced to consider the collisions between ice fragments and the collisions between hull and ice fragments. In order to verify the developed technique, the simulation results for the three-point bending problems of ice-specimen and the continuous ice-breaking problem around a wedge-type model ship with bow angle of 20° are compared with the experimental results carrying out at Korea Research Institute of Ships and Ocean Engineering (KRISO).

• 유통과학연구
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• 제11권8호
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• pp.25-30
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• 2013

Purpose - Foodservices have grown to over 60% of the franchise industry. However, despite reaching this high level, the foodservice franchise industry is experiencing severe ups and downs. While factors such as expansion by franchises and the entry of large multinational firms are causing this imbalance, the more serious problem faced by franchisees is the lack of know-how and correct operating procedures. Franchise headquarters should advise franchisees on important matters such as food ingredients, interior design, tableware, and fixtures. However, even though franchise headquarters have the ability to impart such management know-how, this is often a neglected area. Research design, data and methodology - This study was conducted in an industrial environment to present suitable competitive alternatives for foodservice franchises. Empirical analysis was conducted using a sample of 232 people with experience in targeting customers. The main purpose of this study is not to identify and analyze the factors affecting customer satisfaction. Customers of the Food Service Industry to invite contacts until departure for the service flow by identifying the expectations and allow this area by analyzing the resulting measures to enhance the competitiveness has presented. Results - Actual results contact factors affecting the quality of service on customer satisfaction was a significant influence. However, the end of this analysis, the actual customer satisfaction directly affects the quality of service that is only important factor can commit mistakes. Relatively large impact on customer satisfaction, which is relatively independent of the quality factor should be a review of zone of tolerance. In this study, eating phase relative to contact the service customer satisfaction was the most influential. The results, however, zone of tolerance for an area in the waiting and ordering dissatisfaction factors are appearing. And in the course of these services outside the zone of tolerance area is unsatisfactory evaluation is being done. Conclusions - After all, Foodservice, the contact service management for zone of tolerance the top priority should be can be seen. Foodservice contact first in the case of service quality factors caused by the continuous flow of services, so this step-by-step identification needs to be clearer. This, of course, to distinguish between the actual per unit of activity appears to be more difficult to follow, for it seems to need a lot of future complementary. Next is the assessment of customer service quality. Customers remember the experience for the services of a real contact through the assessment and service evaluation clearly emerge as the expected level can be difficult. However, this situation is controlled by the test method cannot be avoided unless there is no limit to the number of leave. Despite these limitations, the next step to contact a service evaluation and analysis have to continue to refine and thereby franchisees for the operation of the store in terms of practical know-how required to provide to the office believe.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.966-970
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.

• 상하수도학회지
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• 제26권2호
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• pp.219-228
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• 2012

Problems due to the taste and odor in drinking water are common in treatment facilities around the world. Taste and odor are perceived by the public as the primary indicators of the safely and acceptability of drinking water, and are mainly caused by the presence of two semi-volatile compounds-2-methylisoborneol(2-MIB) and geosmin. Conventional treatment processes in water treatment plants, such as coagulation, sedimentation and chlorination have been found to be ineffective for the removal of 2-MIB and geosmin. Pulse UV system is a new UV irradiation system that is a non-mercury lamp-based alternative to currently used continuous wave systems for water disinfection. This study shows pulse UV system to be effective in treatment of these two compounds. Geosmin removal efficiency of UV process alone achieved approximately 70% at 10sec contact time. 2-MIB removal efficiency of UV only process achieved approximately 60% at 10sec contact time. The addition of $H_{2}O_{2}$ 7mg/L increased geosmin and 2-MIB removal efficiency upto approximately 94% and 91%, respectively.

• 한국가스학회:학술대회논문집
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• 한국가스학회 1997년도 추계학술발표회 논문집
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• pp.78-85
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• 1997

Indentation and small punch tests are very powerful methods to monitor the materials reliability since they are very simple, easy and almost non-destructive. First, recently-developed continuous indentation test can provide the more material properties such as hardness, elastic modulus, yield strength, work-hardening exponent, etc., than the conventional hardness test. In our study, the true stress-strain curve was derived from the indentation load-depth curve for spherical indentation. In detail, the strain was able to be obtained from plastic depth/contact radius ratio, and the flow stress was from mean contact pressure through the analysis of elastic-plastic indentation stress field. Secondly, the small punch test was studied to evaluate the fracture toughness and defomation properties such as elastic modulus and yield strength. Like the indentation test, this test can be applied without severe damage of the target structure.

• Environmental Engineering Research
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• 제16권4호
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• pp.231-236
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• 2011

Biological nitrogen removal, using a continuous flow packed-bed reactor (CPBR) in a consecutive nitrification and denitrification process, was evaluated. An apparent decline in the nitrification efficiency coincided with the steady increase in $NH_4{^+}$-N load. Sustained nitrification efficiency was found to be higher at longer empty bed contact times (EBCTs). The relationship between the rate of alkalinity consumption and $NH_4{^+}$-N utilization ratio followed zero-order reaction kinetics. The heterotrophic denitrification rate at a carbon-tonitrogen (C/N) ratio of >4 was found to be >74%. This rate was higher by a factor of 8.5 or 8.9 for $NO_3{^-}$-N/volatile solids (VS)/day or $NO_3{^-}-N/m^3$ ceramic media/day, respectively, relative to the rates measured at a C/N ratio of 1.1. Autotrophic denitrification efficiencies were 80-90%. It corresponds to an average denitrification rate of 0.96 kg $NO_3{^-}-N/m^3$ ceramic media/day and a relevant average denitrification rate of 0.28 g $NO_3{^-}$-N/g VS/day, were also obtained. Results presented here also constitute the usability of an innovative porous sulfur ceramic media. This enhanced the dissolution rate of elemental sulfur via a higher contact surface area.

• 한국물환경학회지
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• 제25권5호
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• pp.758-763
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• 2009

This study presents the optimal conditions of zero-valent iron (ZVI) pretreatment for color removal from real dye wastewater. Removal of color by ZVI was strongly subject to the acidity of the wastewater buffering the pH increased after ZVI reduction. The real dye wastewater did not contain a sufficient amount of acidity and thus it was necessary to supplement acid to the dye wastewater before treatment. In continuous operation of iron column, the empty bed contact time (EBCT) and initial pH were varied to find the optimal conditions. A non-linear regression model fitted well the experimental result predicting that the optimal EBCT and pH for 80% removal efficiency was present in the range of 57~90 and 5~5.9, respectively. Color of column effluents could be further removed in the following biological oxidation step and the biodegradability of wastewater was also enhanced after iron pretreatment.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.612-615
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• 1996

In the continuous casting process, molten metal contacts the mold wall and the molten metal surface is subject to the mold oscillation. The mold oscillation results in the oscillation marks on the surface of solidified steel, which has undesirable effects on the quality of slabs. In order to reduce the oscillation marks by achieving soft contact of molten metal with the mold surface, alternating magnetic field is applied to the surface of molten metal. However, if the magnetic field strength becomes too strong, the melt flow induced by the magnetic field. causes the instability of the molten metal surface, which has also the bad influence on the slab quality. Therefore, it is very important to choose the optimal position of the inductor coil and the optimal level of electric power to minimize the surface defects. In the present work, as a first step toward the optimization problem of the process, numerical studies are performed to investigate the effects of coil position and the electric power level on the meniscus shape and the flow field. As numerical tools, the boundary integral equation method(BIEM) is used for the magnetic field analysis and the finite difference method (FDM) with orthogonal grid generation is used for the flow analysis.

• 한국가시화정보학회지
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• 제12권2호
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• pp.23-29
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• 2014

Although many studies have been done on an open-end capillary, the invasion into a closed end capillary is still novel in its investigation. In this research we have explored the fluid invasion in closed-end capillaries where the shape of the meniscus and the height of invasion were accompanied by gas compression inside the capillary. Theoretically, the one dimensional momentum balance equation shows the fluid oscillation. In the experiments, we have found the different phenomena, either the fluid oscillation with low frequency or no oscillation. This discrepancy is mostly caused by two factors. First, a continuous decrease of the advancing contact angle due to decreasing invasion velocity as increasing pressure inside the closed-end capillary reduces the invasion velocities. Second, the high shear stress within the entrance length region was generated by the plug like velocity profile.