• Restorative Dentistry and Endodontics
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• 제24권1호
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• pp.26-39
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• 1999

Bis-GMA, the representative monomer of bonding resin, contributes to the rigidity of bonding layer. Hydrophilic monomer contributes to the permeability into dentin substrates while weaken the bonding layer due to its small molecular weight. The degree of conversion also contributes to the ultimate strength of the bonding layer. This study was performed for the correlation analysis of monomer ratio and dentin bonding strength via degree of conversion. 7 experimental bonding resins were prepared with Bis-GMA, ratio from 20% to 80% by 10% increment, and hydrophilic HEMA monomer. Their degree of conversion and shear bond strength to dentin were compared with Scotchbond Multi-Purpose adhesive, and the fractured surfaces were examined microscopically. The results were as follows; 1. The degree of conversion increased when, the ratio of Bis-GMA increased from 20% to 70%, whereas it decreased when the ratio of Bis-GMA was 80%. 2. Shear bond strengths of the experimental bonding resins of 80%, 70%, 60% ratio of Bis-GMA were significantly higher than those of the experimental bonding resin of 50% ratio of Bis-GMA and Scotchbond Multi-Purpose adhesive. Lower shear bond strengths were obtained with the experimental bonding resins of 40%, 30%, 20% ratio of Bis-GMA (p<0.05). 3. Adhesive fractures were associated with the bonding resins of the lower bond strength, while cohesive fractures within the bonding resin layer were associated with the bonding resins of higher bond strength. Bonding resins with shear bond strength higher than 18MPa showed some cohesive fractures within the composite resin or within the dentin. 4. Correlations between Bis-GMA ratio and the degree of conversion (r=0.826), between Bis-GMA ratio and shear bond strength (r=0.853), and between the degree of conversion and shear bond strength (r=0.786) were significant (p<0.05).

• Asian-Australasian Journal of Animal Sciences
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• 제24권12호
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• pp.1757-1762
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• 2011

Aflatoxins are natural contaminants of poultry feeds and feed ingredients and cause liver damage, immunosuppression, reduction in performance and mortality in broilers. A number of studies have been carried out to study the effects of aflatoxin on feed conversion ratio in broilers. The results on feed conversion ratio of 10 research articles in broilers fed with aflatoxin from first day of age to six weeks of age were compiled and were subjected to meta-analysis. Chi-square test and $Tau^2$ (heterogeneity co-efficient) were applied to test for significance of heterogeneity of studies. To integrate results, fixed effect model by Inverse Variance method (IV method) was used when heterogeneity was insignificant and otherwise random effect model by DerSimonian and Laird Method (DL method) was used. The results of meta-analysis showed that the adverse effect of aflatoxin on feed conversion ratio at the end of first week was negligible, second week was medium and third to six weeks was very large.

• 전력전자학회논문지
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• 제17권1호
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• pp.34-40
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• 2012

In this paper, voltage clamped tapped-inductor boost converter with high voltage conversion ratio is proposed. The conventional tapped-inductor boost converter has a serious drawback such as high voltage stresses across all power semiconductors due to the high resonant voltage caused by the leakage inductor of tapped inductor. Therefore, the dissipative snubber is essential for absorbing this resonant voltage, which could degrade the overall power conversion efficiency. To overcome these drawbacks, the proposed converter employs a voltage clamping capacitor instead of the dissipative snubber. Therefore, the voltage stresses of all power semiconductors are not only clamped as the output voltage but the power conversion efficiency can also be considerably improved. Moreover, since the energy stored in the clamp capacitor is transferred to the output side together with the input energy, the proposed converter can achieve the higher voltage conversion ratio than the conventional tapped-inductor boost converter. Therefore, the proposed converter is expected to be well suited to various applications demanding the high efficiency and high voltage conversion ratio. To confirm the validity of the proposed circuit, the theoretical analysis and experimental results of the proposed converter are presented.

• 대한화학회지
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• 제21권6호
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• pp.440-444
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• 1977

$CS_2$/KOH catalysis를 이용해서 ${\varepsilon}$-caprolactam의 음이온중합을 시키고 percent conversion과 점도를 측정하였다. $80^{\circ}C,\;105^{\circ}C$의 비교적 낮은 온도에서는 $CS_2$/KOH mole ratio가 0.5일때 percent conversion이 가장 높았으며 또 KOH의 당량에 비례하여 percent conversion도 증가하였다. 그러나 $130^{\circ}C,\;155^{\circ}C$로 중합온도를 상승함에 따라 $CS_2$/KOH mole ratio와 KOH양에는 크게 관계없이 높은 percent conversion을 얻을 수 있었다. 그리고 30分 정도의 짧은 중합시간으로도 $80{\%}$ 이상의 높은 percent conversion을 얻을 수 있었다.

• 한국가스학회지
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• 제19권6호
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• pp.40-46
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• 2015

이론공연비방식 엔진은 삼원촉매를 이용하여 유해배기가스를 매우 효과적으로 저감시킬 수 있는 장점을 가지고 있다. 삼원촉매는 높은 정화효율을 보이는 공연비범위가 좁기 때문에 엔진에서의 공연비 제어가 매우 중요하다. 본 연구에서는 삼원촉매 성능을 평가하기 위하여 다양한 운전영역에서 삼원촉매의 전환효율을 비교 분석하였다. 최적의 전환효율을 보이는 당량비를 확인하기 위하여 당량비 제어값 변화에 의한 전환효율을 살펴보았다. 실험결과 당량비 제어를 통하여 각 운전조건에서 NMHC, CH4, CO 및 NOx의 전환효율이 95%이상 나타내는 최적 운전조건을 찾을 수 있었다. 동등한 배기가스 온도 조건에서는 출력이 증가할수록 최적당량비가 선형적으로 증가하는 경향을 보였다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권4호
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• pp.156-163
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• 2001

In this paper an optimal switching angle control of a switched reluctance motor (SRM) drive system is investigated for achieving maximum energy conversion ratio. A new magnetizing method is proposed with a low switching frequency. The proposed algorithm maximizes the positive energy conversion region, which is directly related to the mechanical output, and reduces the reactive power region with the same field energy region. As a consequence, a torque ripple is also sufficiently reduced compared with that of the conventional switching angle magnetizing method. Experimental results show that the proposed scheme provides a high efficiency and a low ripple drive.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.117-123
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• 2004

The burning characteristics of interacting coal particles in a convective flow are numerically investigated at various Reynolds numbers. The transient combustion of 2-dimensionally arranged particles, both the fixed particle distances of 5 radii to 20 radii horizontally and 3 radii to 24 radii vertically, is studied. The results obtained from the present numerical analysis reveal that the transient flame configuration and retardation of particle temperature augmentation with the horizontal or vertical particle spacing substantially influence devolatilization process and carbon conversion ratio of interacting particles. Volatile release and carbon conversion ratio of the second particle with decreasing horizontal and vertical particle spacing decrease gradually, whereas those of the first particle with decreasing vertical particle spacing increases due to flow acceleration. When the vertical particle spacing is smaller than $6R_{o}$, volatile release and carbon conversion ratio of the second particle decrease greatly due to reduction of flame penetration depth.

• 한국운동역학회지
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• 제25권1호
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• pp.39-47
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• 2015

Objective : The purpose of this study was to investigate the velocity conversion coefficient and invariance for the optimal phase ratio on the performance of the women's triple jump. Methods : Three-dimensional kinematic data were obtained from the three finalists of the women's triple jumper competition at the 2011 Daegu IAAF World Championships. Computer simulations were performed using the biomechanical model of the triple jump to optimize the phase ratio for the longest actual distance for all athletes with altered velocity conversion coefficients. Results : Top elite triple jumpers showed better technical consistency at the phase ratio. Also, no consistent relationship was observed between the loss in horizontal velocity and the gain in vertical velocity across supporting the three phase. In addition, regardless of the magnitude A1, all athletes were optimized with jump-dominated technique. Finally, as the magnitude of A1 increased, the athletes showed better performance. The obtained overall distance jumped showed the longest actual distance when the optimal phase ratio was transferred from hop-dominated to jump-dominated(the step ratio was 30%~31%), and when the optimal phase ratio was transferred from balanced to jump-dominated(the step ratio was 27%~29%). Conclusion : Future studies need to be conducted in order to explore the active landing motion and the inclination angle of the body with the velocity conversion coefficient simultaneously at each supporting phase.

• 한국소음진동공학회논문집
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• 제20권3호
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• pp.296-307
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• 2010

This paper deals with the energy transmission ratio of the elastic waves transmitting through a solid wall. Based on the displacement of the reflected and transmitted waves relative to the incident waves, the energy transmission ratio of the wave was obtained by multiplying the vibration velocity and stresses. Numerical calculation provided with the transmission ratio and refraction angle corresponding to the incidence angle, and it showed the mode conversion from the incident longitudinal wave to the transmitted transverse wave in particular incidence angle range. The paper established a procedure to find the incidence angle of the maximum energy transmission ratio and confirmed it by experiment.

• 한국해양공학회지
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• 제4권1호
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• pp.43-48
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• 1990

The results of previous works on the wave energy conversion do not seem to be satisfactory due to irregularity, and the non-linear hydrodynamic effect which is inevitably featured due to the structural complexity of the ocean wave energy conversion device. These may cause the difficulty estimating the extracted wave power. In this paper a study on estimating the extracted wave power and its ratio. The present authors have developed another method estimating the extracted wave power using the three dimensional source distribution method, which was turned out to be an improved one. It has been observed that the present results may be used for the control of the wave energy conversion device and the optimal design has been derived from the several case studies.