• 대한조선학회지
• /
• 제20권1호
• /
• pp.29-33
• /
• 1983

The loading condition, of a ship, especially a multi-purpose cargo carrier, in service, is often changed. Then, the prediction of natural frequency changes is necessary to provide measures for prevention of ship vibrations. In this paper a simplified method for the above purpose is presented. The bases of the method are analytical solutions for the lateral vibrations of uniform Timoshenko beams carrying a concentrated mass and the Dunkerley's formula. In this method a ship in the standard ballast condition is reduced to a uniform Timoshenko beam having same system parameters as those of the midship section. To investigate the validity of the proposed method, numerical calculations are carried out for a 46,000 DWT bulk carrier and compared with detailed calculations based on the finite difference method. Even in cases those the cargoes in a hold, length of which is about 13% of the ship's length, are reduced to a concentrated mass, the proposed method gives results of several percent differences from the detailed calculations up to the six-noded mode.

• KSBB Journal
• /
• 제10권4호
• /
• pp.358-369
• /
• 1995

A mathematical model using local thermodynamic equilibrium isotherms for adsorption in encapsulated adsorbent is proposed in order to optimize the design parameters in situ bioproduct separation process. The model accurately follows the experimental data on the adsorption of berberine, secondary metabolite produced in Thaictrum rugosum plant cell culture. The adsorption rate on encapsulated adsorbent is compared with that on alginate-entrapped adsorbent. The result shows that the higher loading capacity in encapsulated adsorbent is mainly due to the increase in the maximum solid phase concentration. Based on the adsorption rate and loading capacity, the encapsulated adsorbent would be more useful than the entrapped adsorbent when used in situ bioproduct separation process. Design parameters in situ bioproduct separation process, such as the size of the capsule, membrane thickness, the ratio of capsule volume to bulk volume, the ratio of single capsule volume to total capsule volume and the adsorbent content in the capsule, are evaluated by using the model. The ratio of single capsule volume to total capsule volume is the most effective parameter for adsorption of berberine on encapsulated adsorbent.

• 한국토양비료학회지
• /
• 제49권3호
• /
• pp.235-241
• /
• 2016

The soil does not only serve as a medium for plant growth but also for engineering construction purposes. It is very weak in tension, very strong in compression and fails only by shearing. The behaviour of the soil under any form of loading and the interactions of the earth materials during and after any engineering construction work has a major influence on the success, economy and the safety of the work. Soils and their management have therefore become a broad social concern. A limitless variety of soil materials are encountered in both agronomy and engineering problems, varying from hard, dense, large pieces of rock through gravel, sand, silt and clay to organic deposits of soft compressible peat. All these materials may occur over a range of physical properties, such as water contents, texture, bulk density and strength of soils. Therefore, to deal properly with soils and soil materials in any case requires knowledge and understanding of these physical properties. The desired value of bulk density varies with the degree of stability required in construction. Bulk density is also used as an indicator of problems of root penetration,soil aeration and also water infiltration. This property is also used in foundation engineering problems. While not conforming to standard test procedures, this work attempts to add to the basic information on such important soil parameters as water content, bulk density.

• 산업기술연구
• /
• 제30권B호
• /
• pp.17-23
• /
• 2010

Since the propagation of a short fatigue crack is directly related to the large crack which causes the fracture of bulk specimen, the detailed study on the propagation of the short crack is essential to prevent the fatigue fracture. However, a number of recent studies have demonstrated that the short crack can grow at a low applied stress level which are predicted from the threshold condition of large crack. In present study, the threshold condition for the propagation of short fatigue crack is examined with respect to the micro-structure and cyclic loading history. Specimens employed in this study were decarburized eutectoid steels which have various decarburized ferrite volume fraction. Rotating bending fatigue test was carried out on these specimens with the special emphasis on the "critical non-propagating crack length" It is found that the reduction of the endurance limit of their particular micro-structures can be due to the increase of the length of critical non-propagating crack, and the quantitative relationship between the threshold stress ${\sigma}_{wo}$ and the critical non-propagating crack length $L_c$ can be written as ${\sigma}_{wo}{^m}{\cdot}L_c=C$ where m,C is constant. Further experiments were carried out on cyclic loading history on the length of critical non-propagating crack. It shown that the length of critical non-propagating crack is closely related to cyclic loading history.

• 한국정밀공학회지
• /
• 제16권10호
• /
• pp.164-171
• /
• 1999

An optimum blank design technology is required for near-net of net-shape cold forming using sheets. Originally, the backward tracing scheme has been developed for preform design in bulk forming, and applied to several forming processes successfully. Its key concept is to trace backward from the final desirable configuration to an intermediate preform of initial blocker. A program for initial blank design in sheet forming which contains the capabilities of forward loading simulation by the finite element method and backward tracing simulation, has been developed and proved the effectiveness by applying to a square cup stamping process. In the blank design of square cup stamping, the backward tracing program can produce an optimum blank configuration which forms a sound net-shape cup product without machining after forming. Another general application appears in the blank design of a cup stamping with protruding flanges, one of typical automobile components. The blank configurations derived by backward tracing simulation have been confirmed by a series of loading simulations. The approach or decision of an initial blank configuration presented in this study will be a milestone in fields of sheet forming process design.

• 한국철도학회논문집
• /
• 제11권1호
• /
• pp.54-60
• /
• 2008

다층 탄성모델에 근거한 철도노반 설계는 열차의 반복 윤하중에 의한 궤도 하부 구조의 거동을 반영하는 응력 의존적인 회복탄성계수$(E_R)$가 각 층의 중요한 입력물성치가 된다. 그러나 반복하중을 가하는 기존의 회복탄성계수 시험법은 비용이 고가이고 시험장비와 숙련도에 따라 결과의 일관성이 떨어지는 단점이 있어 실질적인 적용에 어려움이이었다. 본 연구에서는 이를 극복하기 위해 동적물성치를 이용한 대체 회복탄성계수 시험법을 적용하여 철도노반의 회복탄성계수를 결정하였다. 강화노반에 주로 사용되는 쇄석의 회복탄성계수는 측정된 동적물성치와 열차 운행 중 경험하는 강화노반의 응력을 고려하여 결정되었고, 체적응력과 축차응력의 거듭제곱 형태로 예측모델을 나타내었다. 쇄석의 회복탄성계수는 체적응력이 증가함에 따라 전체적으로 증가하는 경향을 보였고 축차응력이 증감함에 따라 감소하였다. 상 하부노반의 주재료인 SM계열 토사 재료에 대하여 회복탄성계수를 평가하였고, 축차응력만을 이용한 거듭제곱 형태의 예측모델과 상관성이 매우 높게 나타났다.

• 구강회복응용과학지
• /
• 제22권4호
• /
• pp.329-340
• /
• 2006

Statement of problem: Damping of the peak force transmitted to implants has been reported by in vitro studies using impact forces on resin-veneered superstructures. Theoretical assumptions suggest that use of acrylic resin for the occlusal surfaces of a prosthesis would protect the connection between implant and bone. Therefore, the relationship between prosthesis materials and the force transmitted through the implant system also needs to be investigated under conditions that resemble the intraoral mechanical environment. Purpose: The purpose of this study was to analyze the fracture strength and modes of temporary prosthesis when a flange or occlusally extended structure were connected on the top of the abutment. Material and method: Modified abutments of winged and bulk design were made by casting the desired wax pattern which is made on the UCLA type plastic cylinder. Temporary crowns were made using templates on the modified abutments, and its fracture toughness and strain were compared to the traditional temporary prosthesis. To evaluate the effect of aging, 5.000 times of thermocycling were performed, and their result was compared to the 24hours specimen result. Results: The following conclusions were drawn from this study: 1. In the fracture toughness test, temporary crown's fracture line located next to the screw hole while modified designs with metal support showed fracture line on the metal and its propagation along the metal-resin interface. 2. Wing and bulk structure didn't show significant difference in the fracture toughness (p>0.05), but wing structure showed stress concentration on the screw hole area compared to bulk structure which showed even stress distribution. 3. In the fracture toughness test after thermocycling, wing and bulk structure showed increased or similar results in metal supported area while off-metal area and temporary crown showed decreased results. 4. In the strain measurement after thermocycling, its value increased in the temporary and bulk structure. However, wing structure showed decreased value in the loading point while increased value in the screw hole area. Conclusion: Wing type design showed compatible result to the bulk type that its application with composite resin prosthesis to the implant dentistry is considered promising.

• 펄프종이기술
• /
• 제43권4호
• /
• pp.23-30
• /
• 2011

Fillers have been used for papermaking in order to enhance the optical properties, to improve sheet formation, printability and dimensional stability and to reduce the furnish cost. However, filler particles in paper interfere with fiber-fiber bonding, resulting in decreased paper strength. In order to increase filler content in paper without sacrificing too much paper strength, dual addition technology of fillers was investigated. As a first step, the effects of thick stock addition of fillers on paper properties and papermaking process were elucidated. It was shown that thick stock addition of fillers could increase paper strength at a given filler content. No significant adverse effects on formation, drainage and filler retention were observed. However, bulk of paper was reduced with thick stock addition of fillers, which shall be resolved with regulating other factors such as the mixing ratio of pulps and type of fillers.

• 한국전기전자재료학회논문지
• /
• 제15권12호
• /
• pp.1060-1064
• /
• 2002

We have studied the effect of crystallization temperature, composition and film thickness, which are the fundamental processing parameters of lead zirconate titanate(PZT) thin film fabrication, in the respect of the piezoelectric properties by our pneumatic loading method(PLM). A great deal of research has been done in the field of characterization for piezoelectric thin films after the first report on the measurement for the piezoelectric coefficient of thin films in 1990. Even though the piezoelectric properties of thin films are very critical factors in the micro-electro mechanical system(MEMS) and thin film sensor devices, a few reports for the piezoelectric characterization are provided for the last decade unlikely the bulk piezoelectric devices. We have found that the piezoelectric properties of thin films are improved as the increase of crystallization temperature up to 750$\^{C}$ and this behavior can be also explained by the analysis of dielectric polarization hysteresis loop, X-ray diffraction and scanning electron microscopy. The effect of Zr/Ti composition has been also studied. This gives us the fact that the maximum piezoelectricity is found near Morphotropic Phase Boundary(MPB) as bulk PZT system does.

• 대한조선학회논문집
• /
• 제32권2호
• /
• pp.103-107
• /
• 1995

선체거더의 종진동 현상은 60년대에 이미 조사된 바 있으나 기존 선박들에서는 종방향 기진력이 작았기 때문에 선체 종진동 현상이 거의 나타나지 않았다. 그러나 80년대 중반이후의 대형 저속디젤엔진 추진선에서는 추진축계 비틂 공진점에서 연성되어 작용하는 축계 종방향 기진력에 의하여 선체전체의 종진동이 유발될 수도 있다. 본 연구에서는 73,000톤 산적화물선에서 감지된 선체거더의 종진동 현상을 실선계측 및 해상기진기 실험 그리고 유한요소 해석방법으로 분석하였다. 분석결과 이러한 선체 종진동 현상은 Over-critical 축계 시스템을 갖춘 선박에서만 축계 종방향 기진력에 의해 나타날 수가 있으며 그 중에서도 주기관의 연속 사용금지구역(barred range)이 설정되지 않은 선박의 경우엔 하중조건에 따라 저속 입출항 운항시 선루를 포함한 선체에 심한 중진동이 발생될 수 있슴이 판명되었다.