• 대한예방한의학회지
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• 제18권1호
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• pp.125-138
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• 2014

Objective : Polycan, exopolymers purified from Aureobasidium pullulans SM-2001 and calcium gluconate have been showed favorable inhibitory effects on the periodontitis and related alveolar bone losses through antioxidant and anti-inflammatory activities, respectively. In the present study, we intended to observe the possible synergic effects of mixed formula consisted of Polycan and calcium gluconate on ligation-induced experimental periodontitis and related alveolar bone losses in rats, and to select the fittest compositions for further developing as effective agents to ameliorate periodontal diseases. Method : Experiments were conducted as two separated two tests - first is synergic effects of Polycan and calcium gluconate 1:1, 1:9 and 9:1 mixtures, and second is 1:99, 2:98, 4:96, 8:92 and 1:9 mixtures. Experimental periodontal diseases were induced by ligature placed around the cervix of upper left incisior teeth of rats. One day after ligation placements, 200mg/kg of each single or mixed formulas of Polycan or/and calcium gluconate were orally administered for 10 days. The changes on the alveolar bone loss index and maxillary bone mineral density (BMD) were observed for detecting alveolar bone losses, and for anti-inflammatory effects, myeloperoxidase (MPO) activities and proinflammatory cytokine (tumor necrosis factor; TNF-${\alpha}$) contents were also evaluated in gingival tissues around ligature placed incisior teeth. The results of mixtures were compared with those of singe Polycan and calcium gluconate treated rat. Results : Each single or mixed formulas of Polycan or/and calcium gluconate favorably and significantly inhibited the inflammatory changes. The inhibitory effects of mixed formula consisted of Polycan and calcium gluconate 1:9 showed against periodontitis and related alveolar bone losses as compared with those of each Polycan and calcium gluconate single formula (p<0.05). In second experiment, Polycan and calcium gluconate 2:98, 4:96, 8:92 and 1:9 mixed formulas also showed significant increased anti-inflammatory and inhibitory effects against alveolar bone losses as compared with those of each single formula. Among them, Polycan and calcium gluconate 2:98 showed the highest efficacy against to ligation-induced experimental periodontitis and related alveolar bone losses. Conclusion : The results obtained in this study suggest that appropriated mixtures of Polycan and calcium gluconate showed synergic inhibitory effects against ligation-induced experimental periodontitis and related alveolar bone losses in rats. Moreover, Polycan and calcium gluconate 2:98 showed the highest efficacies in this experiment, suggesting the fittest composition for further developing as effective agents to ameliorate periodontal diseases.

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.52-58
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• 1999

The leakage and rotordynamic coefficients of see-through type gas labyrinth seals are determined using a two-control-volume-model analysis with Moody's wall-friction-factor formula which is defined with a large range of Reynolds number and relative roughness. Jet flow theory are used for the calculation of the recirculation velocity in the cavity. For the reaction force from the labyrinth seal, linearized zeroth-order and the first-order perturbation equations are developed for small motion about a centered position. The leakage and rotordynamic coefficient results of the present analysis are compared with Scharrer's theoretical analysis using Blasius' wall-friction-factor formula and Pelletti's experimental results. The comparison shows that the present analysis using Moody's wall-friction-factor formula and Scharrer's theoretical analysis using Blasius' wall-friction-factor formula give the same results for a smooth seal surface and the range of Reynolds number less than $10^5$.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.132-142
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• 1999

In this paper, a new formula for primary and secondary thrust of metal belt CVT is proposed considering variation of band tension, block compression and active arc for each of the primary and secondary pulleys. For the secondary thrust, effective friction coefficient is introduced considering the effect of flange deflection. Nondimensional primary and secondary thrust of the metal belt CVT by the new formula agree well with the experimental results except for low torque range, $0\;<\;{\lambda}\;<\;0.2$ at speed ration i = 1.0. The new formula can be used in design of the primary and secondary thrusts control system for the metal belt CVT.

• Journal of Radiation Protection and Research
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• 제19권1호
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• pp.37-50
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• 1994

X-선과 감마선의 에너지에 따른 선질특성과 선량 및 필름의 사진농도와의 관계를 이용한 필름배지선량계의 선량환산식을 실험적으로 체계화 하였고, 시간경과에 따른 잠상퇴행 특성과 방사선의 입사방향에 따른 방향특성을 실험적으로 조사하여 보정계수를 산출하였다. 본 연구에서 구한 선량환산식은 필름배지선량계의 기술기준인 성능판정 기준을 잘 만족시키는 것으로 나타났다.

• 한국항만학회지
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• 제11권2호
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• pp.257-271
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• 1997

The calculation of earthwork plays a major role in plan or design of many civil engineering projects and thus it has become very important to advanced the accuracy of earthwork calculation. The purpose of this paper is to calculate the excavation volume of terrain using a proposal area formular in eathwork volume determination for reclamation of the harbor. A proposal area formular by first and third equation is compared with end area, middle area, prismoidal formula by trapezoidal, simpson formular to excavation volume for an experimental terrian $1\sim12$. As a result of this study, algorithm of a proposal area formula by prismoidal formula should provide a better accuracy than end area, middle area, prismoidal formula by trapezoidal formular, simpson formular.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.80-83
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• 2008

The characteristics of the spread of a forest fire are generally related to the attributes of combustibles, geographical features, and meteorological conditions, such as wind conditions. The most common methodology used to create a prediction model for the spread of forest fires, based on the numerical analysis of the development stages of a forest fire, is an analysis of heat energy transmission by the stage of heat transmission. When a forest fire breaks out, the analysis of the transmission velocity of heat energy is quantifiable by the spread velocity of flame movement through a physical and chemical analysis at every stage of the fire development from flame production and heat transmission to its termination. In this study, the formula used for the 1-dimensional surface forest fire behavior prediction model, derived from a numerical analysis of the surface flame spread rate of solid combustibles, is introduced. The formula for the 1-dimensional surface forest fire behavior prediction model is the estimated equation of the flame spread velocity, depending on the condition of wind velocity on the ground. Experimental and theoretical equations on flame duration, flame height, flame temperature, ignition temperature of surface fuels, etc., has been applied to the device of this formula. As a result of a comparison between the ROS(rate of spread) from this formula and ROSs from various equations of other models or experimental values, a trend suggesting an increasing curved line of the exponent function under 3m/s or less wind velocity condition was identified. As a result of a comparison between experimental values and numerically analyzed values for fallen pine tree leaves, the flame spread velocity reveals has a error of less than 20%.

• Design & Manufacturing
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• 제17권4호
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• pp.1-7
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• 2023

In the fabrication of curved multi-display glass for automotive use, the surface roughness of the mold is a critical quality factor. However, the difficulty in detecting micro-cutting signals in a micro-machining environment and the absence of a standardized model for predicting micro-cutting forces make it challenging to intuitively infer the correlation between cutting variables and actual surface roughness under machining conditions. Consequently, current practices heavily rely on machining condition optimization through the utilization of cutting models and experimental research for force prediction. To overcome these limitations, this study employs a surface roughness prediction formula instead of a cutting force prediction model and converts the surface roughness prediction formula into experimental data. Additionally, to account for changes in surface roughness during machining runtime, the theory of position variables has been introduced. By leveraging artificial neural network technology, the accuracy of the surface roughness prediction formula model has improved by 98%. Through the application of artificial neural network technology, the surface roughness prediction formula model, with enhanced accuracy, is anticipated to reliably perform the derivation of optimal machining conditions and the prediction of surface roughness in various machining environments at the analytical stage.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.138-144
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• 2004

Pneumatic damping through a orifice type duct for OWC type wave energy device is studied experimentally. Forced oscillation tests are made to measure chamber pressure and velocity of air flaw through orifice. Pneumatic damping coefficient are deducted from the experimental research, and discussion are made far the influence of frequency, heave amplitude, and orifice size. Finally two formula are proposed for the estimation of non-dimensional pneumatic damping coefficient by regression analysis. The proposed formula proves to be a reliable method far practical application.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
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• pp.321-326
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• 1998

Shear failure of reinforced concrete beams is serious problem due to sudden brittle failure and many experimental results proved that size effect in shear behavior is an important feature of reinforced concrete members. For this reason, the structural safety of the reinforced concrete beams for shear has been checked by applying empirical design formula, which includes the size-effect, derived from experimental data. However, as the sizes of reinforced concrete members become extremely large, experiments sometimes become very difficult so that the formula or the experimental data could not be obtained and size-effect analyses of shear behavior become significant. In this study, size-effect analysis of shear behavior in reinforced concrete beams is performed by modeling tension stiffening/shear stiffening on reinforced concrete and the tension softening/shear softening on plain concrete. Then, the influences of models in the size-effect analyses of shear behavior in reinforced concrete beams are analyzed.

• 한국해안해양공학회지
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• 제15권3호
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• pp.186-189
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• 2003

방파제 피복석의 중량 산정을 위하여 여러 가지 경험식들이 개발되어져 왔다 Hudson 식은 많은 결함이 있음에도 불구하고, 형태가 간결하기 때문에 가장 널리 사용되고 있다. van der Meer 식은 가끔 크로스체크 용으로 사용되고 있지만, 식의 복잡성과 관련 변수들의 불확실성 때문에 아주 널리 사용되지는 않고 있다 한편 최근에 유(2003)는 'action slope'라는 새로운 무차원수를 사용하여 형태가 간결한 식을(이후 Yoo 식이라고 부름) 제안하였다. 본 연구에서는, 해안공학 기술자들에게 이 공식들의 사용에 대한 판단 기준을 제공하기 위하여, van der Meer가 1987년과 1988년에 보고한 실험 자료와 비교하여 이들의 정밀도를 평가하였다. 검토 결과, van der Meer 식이 가장 높은 정밀도를 보였으며, Hudson 식은 정밀도가 매우 낮아서 사용에 신중을 기해야 하는 것으로 나타났다. 한편, van der Meer 식보다 정밀도가 약간 낮기는 하지만 형태가 간결한 Yoo 식은 안전율을 약간 높게 잡으면 실무에 사용해도 무방한 것으로 판단된다.