• Wind and Structures
• /
• v.6 no.5
• /
• pp.347-356
• /
• 2003

Experimental studies on drag reduction of a circular cylinder of diameter D were conducted in the subcritical flow regime at Reynolds numbers in the range $4{\times}10^4{\leq}Re{\leq}10^5$. To shield the cylinder rear surface from the pressure deficit of the unsteady vortex generation in the near wake, two shield plates were attached downstream of the separation points to form a cavity at the base region. The chord of the shield plates, L, ranged from 0.22 to 1.52 D and the cavity width, G, was in the range from 0 to 0.96 D. It is concluded that significant drag reductions from that of a plain cylinder may be achieved by proper sizing of the shield plates and the base cavity. The study shows that using a pair of shield plates at G/D of 0.86 and angular position ${\theta}$ of ${\pm}121^{\circ}$ results in a configuration with percentage drag reduction of 40% for L/D of 0.5, and 55% for L/D of 1.0.

• Restorative Dentistry and Endodontics
• /
• v.24 no.1
• /
• pp.136-146
• /
• 1999

The purpose of this study was to estimate the changes of marginal adaptation to the cavity floor of light-cured glass ionomer cement base after application of a composite restoration. Eighty non-carious extracted human molars were used in the present study. Circular cavities were prepared on the center of the exposed dentin surface to 0.5mm, 1.0mm, 1.5mm, 2.0mm in depth and the prepared cavities were pretreated with Dentin conditioner and filled with Fuji II LC(GC Int. Co., Japan). They randomly assigned into 3 groups according to the difference in application of a composite restoration; Group 1(control group): only glass ionomer base, Group 2: The application of a composite restoration surrounded by dentin with class I cavity over glass ionomer base after conventional dentin bonding to the exposed dentin and glass ionomer base, Group 3: The application of composite restoration not-surrounded by dentin over glass ionomer base after conventional dentin bonding to the exposed dentin and glass ionomer base. To examine the interface between cavity floor and light-cured glass ionomer cement base, each groups were sectioned vertically through the center of restorations with diamond saw and the gap size(${\mu}m$) of interface measured by SEM. The results were analyzed by using One Way ANOVA. The results were as follows: 1. Good adaptation between glass ionomer cement base and cavity floor was showed in specimens with 0.5mm, 1.0mm depth base of control group. But in specimens with 1.5mm, 2.0mm depth base of control group, the gap was measured about $15{\mu}m$, $40{\mu}m$ respectively. 2. Gap size in group 2 was significantly higher than that in control group(P<0.05). 3. Gap size in group 3 was significantly higher than that in control group and group 2(P<0.05). 4. It was possible to observe the good adaptation between glass ionomer cement base and dentin which was intermediated with 4-10${\mu}m$ hybrid layer in specimens with 0.5mm, 1.0mm depth base of control group. Cohesive fracture within cement base was observed in all specimens which had the gap between glass ionomer cement base & dentin. 5. It was possible to observe the gap formation between cement base and bonding agent and between composite resin and dentin in all specimens of group 2.

• Restorative Dentistry and Endodontics
• /
• v.33 no.6
• /
• pp.570-579
• /
• 2008

The purpose of this study was to investigate the distribution of tensile stress of canal obturated maxillary second premolar with access cavity and notch-shaped class V cavity restored with composite resin using a 3D finite element analysis. The tested groups were classified as 8 situations by only access cavity or access cavity with notch-shaped class V cavity (S or N), loading condition (L1 or L2), and with or without glass ionomer cement base (R1 or R2). A static load of 500 N was applied at buccal and palatal cusps. Notch-shaped cavity and access cavity were filled microhybrid composite resin (Z100) with or without GIC base (Fuji II LC). The tensile stresses presented in the buccal cervical area, palatal cervical area and occlusal surface were analyzed using ANSYS. Tensile stress distributions were similar regardless of base. When the load was applied on the buccal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth with class Ⅴ cavity were slightly higher than that of the tooth without class V cavity. When the load was applied the palatal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth without class V cavity were slightly higher than that of the tooth with class V cavity.

• Journal of the korean Society of Automotive Engineers
• /
• v.14 no.4
• /
• pp.90-96
• /
• 1992

The effect of base cavities on the drag of a simplified tractor-trailor model for Re=4.1*10$^{5}$ is investigated experimentally. Three different types of base cavities are studied in this work. They are solid-wall, slitted-wall, and slotted-wall cavities. Slotted-wall cavity is found to be most effective for drag reduction. A maximum of 11% reduction in the zero-yaw drag coefficient is achieved with the slotted wall cavity.

• Proceedings of the KAIS Fall Conference
• /
• 2010.11a
• /
• pp.305-308
• /
• 2010

본 연구에서는 사출 성형에서 Cavity내의 압력을 측정하여 사출 성형기에서의 설정한 변수 즉, 사출 압력에 따라 Cavity내의 압력이 사출 공정동안 어떠한 추이를 나타내는지 관찰하였다. 이를 CAE 해석과 비교 분석하여 결과에 따른 점도 함수와의 관계를 알아보았다. 우선 Cavity의 압력을 측정하기 위하여 Cavity 내에 압력센서를 설치하고, 이를 시간에 따른 압력측정 결과를 보기 위하여 압력센서 시스템을 제작 하였다. 실제 사출성형하면서 Cavity 내 압력을 측정하고 CAE 해석 결과의 압력 변화와 비교한다. 이때 일반적으로 CAE 해석과 실험결과가 일치하지 않으므로 새로운 점도 곡선을 추정하여 CAE 소프트웨어 D/B(Data Base) 파일에 입력하여 다시 해석하고 실험 결과와 비교하여 압력변화가 일치할 때까지 반복해서 수행한다. 이때 점도는 Power Law로 가정하여 D/B 파일에서 K와 n값을 조절할 수 있고 일반적으로 n값은 Base Resin과 동일하므로 K값의 변화만을 고려하여 압력변화를 해석한다.

• Restorative Dentistry and Endodontics
• /
• v.25 no.3
• /
• pp.321-337
• /
• 2000

Dental caries, one of the most frequent dental disease, become larger because it can be thought as a simple disease. Further more, it can progress to unexpected root canal therapy with fabrication of crown that needs reduction of tooth structure. Base is required in a large caries and ZOE, ZPC, glass ionomer are used frequently as base material. They, with restorative material, can affect the longevity of the restoration. In this study, we assume that the mandibular 1st molar has deep class I cavity. So, installing the 3 base material, 3 kinds of fillings were restored over the base as follows; 1) amalgam only, 2) amalgam with ZPC, 3) amalgam with ZOE, 4) amalgam with GI cement, 5) gold inlay with ZPC, 6) gold inlay with GI cement, 7) composite resin only, 8) composite resin with GI cement. After develop the 3-dimensional model for finite element analysis, we observe the distribution of stress and temperature with force of 500N to apical direction at 3 point on occlusal surface and temperature of 55 degree, 15 degree on entire surface. The analyzed results were as follow : 1. Principal stress produced at the interface of base, dentin, cavity wall was smallest in case of using GI cement as base material under the amalgam. 2. Principal stress produced at the interface of base, dentin, cavity wall was smaller in case of using GI cement as a base material than ZPC under gold inlay. 3. Composite resin-filled tooth showed stress distributed over entire tooth structure. In other words, there was little concentration of stress. 4. ZOE was the most effective base material against hot stimuli under the amalgam and GI cement was the next. In case of gold inlay, GI cement was more effective than ZPC. 5. Composite resin has the small coefficient of thermal conductivity. So, composite resin filling is the most effective insulating material.

• YAKHAK HOEJI
• /
• v.35 no.3
• /
• pp.197-202
• /
• 1991

In order to study drug release from the suppository, three types of hollow suppositories and one conventional suppository were prepared using indomethacin(IDM) as a model drug and Witepsol H-15 as a base. The 4 types of suppository prepared are as follows: type I, conventional suppository containing 50 mg of IDM powder, type II, hollow supository containing 50 mg of IDM powder in the cavity, type III, hollow suppository containing 25 mg of IDM powder in the base and IDM microcapsules (25 mg as IDM powder) in the cavity, and type IV, hollow suppository containing IDM microcapsules (25 mg as IDM powder) in the base and 0.5 ml of 5%(w/v) IDM-PEG 300 solution in the cavity. The drug amount released(%) from type II and I within 24 hrs was 46.7% and 66.9%, respectively. Comparing with the drug amount released from four types of suppository within initial 2 hrs and 24 hrs, that of type IV was high as 32.7% and 76.6%, respectively. IDM-ethycellulose microcapsules passed through 270 mesh sieve and the IDM content was 20.95%.

• Journal of Industrial Technology
• /
• v.27 no.A
• /
• pp.9-14
• /
• 2007

This study was designated to clarify the aspect of the wave propagation around the cavity. The change of traveltime and amplitude of the seismic wave was observed according to the various wave velocities of the cavity. The seismic wave detour or penetrate the cavity depending on the seismic velocity of the in-filled material. Generally, seismic wave detours toward high velocity zone around the cavity, and when the velocity of the cavity material reaches to 80 % of the base rock, the wave penetrates the cavity. The traveltime of the detouring seismic wave is not sensitive to the change of the cavity velocity, but as the velocity of the cavity increases, the fall of the amplitude was reduced. The penetrating wave showed the steeply increasing amplitude due to the reiteration of the detouring wave.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.7 no.3
• /
• pp.294-300
• /
• 1983

The purpose of this study is to investigate the radiant emission characteristics of diffuse equi-lateral trapezoid groove cavity for the case of uniform surface temperature. The theoretically developed results for the apparent emissivity are presented and the values of apparent emissivity for the trapezoid groove cavity were compared with those of the V-groove cavity. In the experimental part of this study, the test models were manufactured from 100x 100x 15mm copper plates on which the equi-lateral trapezoid cavities were grooved. The inclined angles of the groove were 30,45 and 60 degrees and the ratio of groove depth to base surface width varied from 1 to 5 for each inclined angle. As a result of this work, it was found that the trapezoid groove cavity was more general form of V-groove and the apparent emissivity of trapezoid groove cavity was greater than that of V-groove cavity. The resulting equation for the apparent emissivity in the trapezoid groove cavity was valid for the angles greater than 40 degrees.

• Wind and Structures
• /
• v.11 no.5
• /
• pp.377-389
• /
• 2008

An experimental investigation has been conducted to determine the effectiveness of base shield plates in reducing the drag of a rough circular cylinder in a cross flow at Reynolds numbers in the range $3{\times}10^4{\leq}Re{\leq}10.5{\times}10^4$. Three model configurations were investigated and compared: a plane cylinder (PC), a cylinder with a splitter plate (MC1) and a cylinder fitted with base shield plates (MC2). Each configuration was studied in the sub and supercritical flow regimes. The chord of the plates, L, ranged from 0.22 to 1.50D and the cavity width, G, between the plates was in the range from 0 to 0.93D. It is recognized that base shield plates can be employed more effectively than splitter plates to reduce the aerodynamic drag of circular cylinders in both the sub- and supercritical flow regimes. For subcritical flow regime, one can get 53% and 24% drag reductions for the MC2 and MC1 models with L/D=1.0, respectively, compared with the PC model. For supercritical flow regime however, the corresponding drag reductions are 38% and 7%.