• 대한치과교정학회지
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• 제25권5호
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• pp.587-592
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• 1995

교정력에 의한 치아이동시 발생하는 골침착과 흡수의 골재형성 과정을 교정력의 크기와 적용기간에 따라 비교해 보고자 하였다. 성견 6마리를 대조군 1마리와 실험군 5마리로 나누어 실험군에서는 하악 제 1,2소구치 사이에 open coil spring을 장착해서 좌측에는 강한 힘(250-300g), 우측에는 약한 힘(50-75g)이 가해지도록 하여 12시간, 24시간, 3일, 1주, 2주에 각각 희생시켰다. 분리된 조직편에 대해 연X선 촬영을 하여 분석한 결과 다음과 같은 결과를 얻었다. 1. 견인측에서의 신생골 형성은 7일째부터 관찰되기 시작하여 14일째에는 광범위한 부위에서 방사선 불투과상을 관찰할 수 있었으나 힘의 크기에 따른 비교는 불가능하였다. 2. 압박측에서의 치조골 흡수는 3일째에 치조백선의 파괴로 나타나기 시작하여 7일째, 14일째에 걸쳐 증가되는 양상을 보였다.

• ALGAE
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• 제20권2호
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• pp.151-155
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• 2005

To obtain basic data, we investigated the effect of blade length on transplants, the transplanting method of Laminaria japonica for creating L. japonica resources and the number of transplanting plates with surviving L. japonica. The survival rate of L. japonica, blade length of transplants and drag force of transplanting plates were also researched. The number of transplanting plates with surviving L. japonica, the survival rate and blade length of 20 cm long-initial transplants were greater than those of 1.5, 5 and 10 cm long-initial transplants in an outdoor aquarium. At the depth of 4 m in the coastal waters, the number of transplanting plates with surviving transplants, the survival rate and the blade length of 30 cm long-initial transplants were higher than those of 10 and 20 cm longinitial transplants. The drag force is calculated by cording up sporophytes of L. japonica into the transplanting plates under water. The drag force in the case of a 2.18 kg-weight transplanting plate and in a current speed of 0.5 m${\cdot}s^{-1}$ for considering stability of the plate was 631.50 g to a concrete substratum on the seabed, 703.92 g to a shingle substratum, 788.00 g to a sand substratum, and 1018.30 g to a silt substratum. If we consider the stability and economic efficiency of the transplanting plate, the proper weight of the plate per one individual of 18.11 cm in blade width and 190.20 cm in total blade length is regarded as 508.2 g when it is calculated with the concrete substratum that shows the lowest drag force.

• Journal of Biosystems Engineering
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• 제9권1호
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• pp.11-21
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• 1984

This study was intended to analyze the dynamic force system which induced the shattering of paddy grains. A model to predict the shattering of paddy grains was developed, and physical quantities, such as mass distribution and rigidity of rice plant, needed for evaluating the minimum shattering forces were also measured. Under the assumption that rice plant right before harvesting is a vibratory system, the mathematical model of the vibratory system was developed and solved with the varied conditions of forcing functions. The results of the study were summarized as follows: 1. The shattering of grain occurred at the abscission layer of grain by the bending moments resulted from the impact force due to the collision of panicles of rice plant. 2. The vibratory model developed for milyang 23 rice variety was analyzed to give the natural frequencies of 7-9 Hz, which were closely related with the excitation frequencies of 4-10 Hz caused by various machine parts besides engine. Thus, avoiding the resonance should be taken into consideration in the design of the harvesting machinery. 3. It was analyzed to predict the lowest frequency that could develop the shattering when the excitation force was applied to the lower end of stem. The lowest frequency for the Milyang 23 rice variety ranged from 8.33 Hz to 11.66 Hz as the amplitude varied from 1 cm to 2.5 cm. 4. The degree of shattering depended upon the magnitude of the impact force and its application point. For Milyang 23 rice variety, the minimum impact force developing the shattering was $5g_f$ when it was applied at 1 cm above the lower end of stern and $1g_f$ when applied at 5 cm above the lower end of stem. 5. The minimum colliding velocity of the panicle, when it was on the ground that would just develop the shattering, was given as follows, $$V=\sqrt{\frac{K_t}{m_g}{\cdot}{{\phi}^2}}$$ where V : The colliding velocity of the panicle against ground to cause the shatteering of rice grain. (cm/sec) $K_t$ : The minimum spring constant for bending at the abscission layer of grain. (dyne-cm/rad) ${\phi}$ : The minimum shattering angle of grain (rad) $m_g$ : The maximum mass of grain. (g).

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권4호
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• pp.169-174
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• 2002

This paper presents a high-resolution capactive microaccelerometer using branched finger electrodes with high-amplitude sense voltage. From the fabricated microacceleromcter, the total noise is obtained as 9 $\mu\textrm{g}$/√Hz at the sense voltage of 16.5V, while the conventional microaccelerometers have shown the noire level of 25~800 $\mu\textrm{g}$/√Hz. We reduce the mechanical noise level of the microaccelerometer by increasing the proof-class based on deep RIE process of an SOI wafer. We reduce the electrical noise level by increasing the amplitude of AC sense voltage. The nonlinearity problem caused by the high-amplitude sense volage has been solved by a new electrode design of branched finger type, resulting in self force-balancing effects for the enhanced linearity and bandwidth. The fabricated microaccelerometer shows the electrical noise of 2.4 $\mu\textrm{g}$/√Hz at the sense voltage of 16.5V, which is an order of magnitude reduction of the electrical noise of 24.3 $\mu\textrm{g}$/√Hz measured at 0.9V. For the sense voltage higher than 2V, the electrical noise of the microaccelerometer is lower than the voltage-independent mechanical noise of 11 $\mu\textrm{g}$/√Hz. Total noise, composed of the electrical noise and the mechanical noire, has been measured as 9 $\mu\textrm{g}$/√Hz at the sense voltage of 16.5V, which is 31% of the total noise of 28.6 $\mu\textrm{g}$/√Hz at the sense voltage 0.9V. The self force-balancing effect in the blanched finger electrodes increases the stiffness of the microaccelerometer from 1.1N/m to 1.61N/m as the sense voltage increases from 0V to 17.8V, thereby generating additional stiffness at the rate of 0.0016$\pm$0.0008 N/m/V$^2$.

• Applied Biological Chemistry
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• 제43권3호
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• pp.179-183
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• 2000

감귤의 성숙과 저장 중에 일어나는 연화(softening)가 품질에 미치는 영향을 검토하기 위하여 궁천조생 온주밀감을 $3^{\circ}C$, 85% RH에서 저장하면서 저장 중 경도, 펙틴분해효소의 활성 등의 변화를 측정하였다. 저장기간이 경과함에 따라 부폐율은 저장 90일에 18.8%이었으며, 그 이후 급속히 증가하였다. 저장기간에 따른 중량감소는 24.5%까지 계속하여 완만하게 증가하였다. 경도는 2mm probe에서 538.9 g-force에서 336.9 g-force까지로 저장 중에 조금씩 감소하는 경향이었다. 수분 함량은 저장기간에 따라 과피에서 71.8%에서 72.6%까지로, 과육에서 90.3%에서 88.3%까지로 각각 약간 감소하였다. 성숙 중 경도는 1,176.8g-force에서 503.6 g-force로 급속히 감소하였고, 수분 함량은 과피와 과육이 각각 75.3%에서 74.9%로, 91.8%에서 90.7%로 약간 감소하였다. 세포벽 분해효소인 exo-polygalacturonase의 경우 저장 90일까지 과피에서는 326.0 units/100 g에서 534.9 units/100 g까지로, 과육에서는 63.1 units/100 g에서 81.0 units/100 g까지로 증가를 하다가 그 후 저장 150일까지 각각 394.0 units/100 g, 38.0units/100 g으로 감소하는 경향이었다. Pectinesterase 활성은 저장 60일까지 과피에서는 $14.4\;{\mu}mol$에서 $38.8\;{\mu}mol$까지로 증가하다가, 그 이후에 $6.0\;{\mu}mol$로 크게 감소하는 경향이었다. 과육에서는 저장 60일까지 $26.0\;{\mu}mol$에서 $39.0\;{\mu}mol$까지로 증가를 하다가 $8.2\;{\mu}mol$ 크게 감소하는 경향이었다.

• 대한치과교정학회지
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• 제31권3호
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• pp.311-323
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• 2001

편측성 II급 부정교합의 치료 시 다양한 mechanics가 사용되어지는데 그중 한가지가 asymmetric face-bow를 가진 head gear이다. 이 asymmetric head gear의 편측 효과에 대해 다양한 연구결과를 보고하고 있는데 이에 저자는 편측성 II급 부정교합의 상악 치열 모델링과 임상에서 자주 사용되는 Power arm asymmetric face-bow를 모델링하고, 견인력을 달리하여 유한 요소법을 통해 치근막에서 발생되는 응력의 분포와 그에 따른 각 방향의 반력, 그리고 그로 인한 변위를 관찰하여 역계를 이해하고 치료효과를 예견하고자 실험을 고안하였다. 발치나 교정치료의 경험이 없는 25세 남자 정상 교합자를 대상으로 컴퓨터 단층 촬영을 시행하여 얻은 방사선필름을 기초로 하여 유한 요소 상악 모델과 치주인대 모델을 제작하고 그후 다시 좌측 제 1 대구치가 근심 편위되어있는 편측성 상악 II급 부정교합 모델로 제작하고, RMO 사의 Face-bow (Penta-$^{TM}$/Medium size)를 기본 모델로 0.045 inch 직경의 inner-bow와 0.072 inch 직경의 outer-bow를 가지는 asymmetric face-bow를 우측을 25mm 짧게 하여 모델링한 후, 좌우측 제 1 대구치에 각각, 250g, 300g, 350g 씩 견인력을 부여하여 다음과 같은 결론을 얻었다. 1. 양쪽 제1 대구치가 받는 힘의 총합은 견인력이 증가함에 따라 증가하는 경향을 보였는데 대체로 근심위치된 치아가 정상 위치한 치아보다 더 많은 힘을 받는 것으로 나타났으며, 두치아 모두 윈심으로의 힘을 받으며, 원심으로 이동하는 양상을 보여주었다. 2. 측방력은 두 치아 모두 협측으로의 힘을 받는 것으로 나타났는데, 힘의 성분을 분석하여 보면 견인력이 증가함에 따라 X축으로의 힘이 근심 위치된 치아에서 점점 작아지며, 정상 위치한 치아에서 점점 증가하여 측방력의 성분이 힘을 많이 받는 쪽에서 적게 받는 쪽으로 이동하는 양상을 보여주었다. 3. 원심으로의 이동과 동시에 회전과 경사이동 양상을 보여주었는데 견인력의 증가시 함께 증가하는 양상을 보였고, 힘을 많이 받는 쪽, 즉 근심 위치된 치아가 더 많은 회전과 경사이동을 보였으며 적은 양이나마 정상 위치된 치아에 서도 같은 양상의 변위를 보였다.

• Restorative Dentistry and Endodontics
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• 제26권5호
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• pp.418-435
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• 2001

Root canal preparation process is of utmost importance in successful treatment of root canal. Also, one of the most important purpose of the root canal preparation is to enlarge the root canal three dimensionally without changing the curvature of the root canal However as the curvature of the root canal increases, there are many difficulties involved in formation of optimum root canal. Therefore in order to solve the above mentioned problems, new developments in methods of root canal preparation and equipments for such purposes were made. Recently, vigorous studies about newly introduced engine-driven nickel-ti-tanium rotary file are conducted. As shown in research results to dates, it is well established that the use of nickel-titanium file is better suited for curved root canal than stainless steel file in maintaining the curvature or root canal and reducing the deformation of root canal. However it is also acknowledged that there are a few discrepancies in research results according to protocol, due to failure to remove variables in experiments. In addition, although it is recommended by the manufacturer that the GT rotary file should maintain a low rotational speed of 150~350rpm and 'light pressure' as light as not to break the lead of a pencil, academic studies about the vertical force which is not yet standardized are not sufficiently explored. Therefore, this research devised and utilized a special research equipment to standardize the appropriate range of vertical force for GT rotary file through experiments by breaking of the lead of a pencil as expressed by the manufacturer and to accurately measure factors involved through repeating and recreating the environment of root canal preparation. Forming nine experimental groups by varying the vertical forces (150g. 220g, 300g) and rpm (150rpm, 250rpm, 350rpm), the effects of changing vertical forces and rpm on working efficiency were measured in terms of time expended in root canal preparation by crown-down method using a transparent resin block with 35 degree curvature and GT rotary file (z-test). The following research using this special research equipment that involved nine experimental groups and varying the vertical force for root canal preparation from 300g which is within the normal vertical force range to 700g and 1000g which fall outside the normal rpm range. The results were as follows : 1. Analysis of the experiment results revealed that the time spent in root canal preparation decreased as the vertical forces and rpm increased (p<0.05). Also, the effects of rpm were greater than those of the vertical forces within the normal vertical force range ($\beta$-weight test). 2. Observation of the deformation of GT rotary file revealed that deformation increases in a direct correlation with the vertical force increase and in a reverse correlation with the rpm decrease. In the case of the vertical forces close to the normal range, the probability of GT rotary file deformation were quite different depending on the rpm changes. In the case of greater vertical forces, the occurrences of deformation of the file were more frequent regardless of the rpm changes. 3. Deformation and breakage of file were also commonly observed in the expended time measurement experiments and GT rotary file deformation experiments in which low speed rpm (150rpm) was used and at the curved portion of the resin block.

• 대한치과교정학회지
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• 제24권1호
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• pp.37-62
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• 1994

This study was undertaken to investigate the three dimensional vascular changes of periodontal ligament following orthodontic tooth movement. Experimental tooth movement was carried out in 96 Sprague-Dawley rats with the weight of 250g. They were divided into four experimental groups (each 24 rats). The left maxillary first molar was moved mesially with 25g force in group I, and with 75g force in group II. Each three animals were sacrificed after 1, 6, 12, 24 hours, and 3, 7, 14, 21 days. In group III, 25g mesial force was applied for 3 days, and in group IV, 75g mesial force was applied for 3 days. Then the appliances were removed, and each three animals were sacrificed after 1, 6, 12, 24 hours, and 3, 7, 14, 21 days from removal of appliance. The contralateral molars were used for control group. Casting media was injected via left ventricle and polymerized in warm water. After corrosion of surrounding soft tissue, three dimensional vascular changes were examined using scanning electron microscopy. The findings of this study were as follows: 1. Pressure side of group I and II showed degenerative vascular changes such as vascular compression, reduction of vasculature, leakage of casting media. But, regenerative changes were dominant after 7 days of tooth movement. Although the degenerative vascular changes were more severe in group II, which was exposed to heavy force, the timing of these changes was not different between two groups. 2. Periodontal vasculature was reestablished by the growth of new capillaries and their differentiation and union from the remaining periodontal vessels and vessels of alveolar bone marrow. Although vascular regeneration was more rapid in group I, which was exposed to light force, the vasculature was not fully normalized in both groups even after 21 days. 3. There was no remarkable changes in tension side of group I and II, but looping of capillary, new capillary growth, dilation of vessels, redirection of vessels in the direction of tensile force were occurred. 4. In pressure side of group III and IV, in which appliance was removed after 3 days of orthodontic force, bone resorption was continued even after removal of appliance. Regeneration of vasculature was initiated after 1-6 hours, and it was more rapid in group III than group IV. In both groups, the vasculature was not fully normalized even after 21 days. 5. After removal of appliance, tension side of group III and IV showed vascular compression and loss of vasculature.

• 대한치과보철학회지
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• 제35권1호
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• pp.118-129
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• 1997

The purpose of this study was to evaluate the shock absorbing effect of 4 restorative materials and intramobile connector. The damping effect of four restorative materials used to veneer test crown rigidly connected to IMZ implant and subjected to an impact force was measured. These materials included a gold alloy(stabilor G) : a noble metal ceramic alloy(Degudent H) : porcelain(Duceram) : composite resin(Dentacolor). In addition, this study compared damping effect of same restoretive materials after using polyoxymethylene intramobile connector(POM IMC). The result of this study suggest that : In case of using metal IMC 1. Veneered composite resin(group IV) reduced the impact force by 75%, when compared to an equivalent thickness of porcelain(group III). Group IV reduced the impact force by 87% and 89%, respectively, when compared to Stabilor G(group I) and Degudent H(group II). 2. The impact force recorded was higher for the alloy with the higher elastic modulus.(Stabilor G, group I, Young's modulus 107 Gpa, versus Degudent H, Group II, Young's modulus 95 Gpa) 3. It took the longest time for composite resin veneered group(IV) to reach to peak force when compared group I, II, III. In case of using POM IMC 4. The mean impact force recorded were reduced by 79%(group I), 78%(group II), 69%(group III), 84%(group IV), respectively, when compared to using metal IMC. 5. The time required to reach the peak force were increased by 78%(group I, II) 87%(group III), 34%(group IV), respectively, when compared to using metal IMC>.

• 수산해양기술연구
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• 제20권1호
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• pp.1-5
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• 1984

고기가 자망에 이망될 숙건하에 그물면에 작용하는 붕어(Carassius carassius)의 유영력을 시험수조에서 strain gauge를 써서 즉정한 결과는 다음과 같다. 1. 순간최대유영력 및 지속최대유영력과의 체중과의 관계는 F 하(M) =1.45W, F 하(s) =0.29W 이다. 2. 순관최대유영력 및 지속최대유영력과의 체중과의 관계는 F 하(M) =0.11L 상(2.63), F 하(S) =0.15L 상(1.77)이다. 3. 붕어의 유체저항계수는 C 하(s) ≒0.287이다.