• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.10
• /
• pp.907-911
• /
• 2016

This paper provides the compressive failure strength value of composite laminate developed by using regression analysis method. Composite material in this document is a Carbon/Epoxy unidirection(UD) tape prepreg(Cycom G40-800/5276-1) cured at $350^{\circ}F(177^{\circ}C$). The operating temperature is -$-60^{\circ}F{\sim}+200^{\circ}F$($-55^{\circ}C{\sim}+95^{\circ}C$). A total of 56 compression tests were conducted on specimens from eight (8) distinct laminates that were laid up by standard angle layers ($0^{\circ}$, $+45^{\circ}$, $-45^{\circ}$ and $90^{\circ}$). The ASTM-D-6484 standard was used for test method. The regression analysis was performed with the response variable being the laminate ultimate fracture strength and the regressor variables being two ply orientations ($0^{\circ}$ and ${\pm}45^{\circ}$).

• The Journal of the Korea Contents Association
• /
• v.11 no.2
• /
• pp.22-30
• /
• 2011

In the IT convergence environment changed with not only the quality but also the material abundance, it is the most crucial factor for the strategy of personalized recommendation services to investigate the context information. In this paper, we proposed the recommendation using the service ontology based context awareness modeling. The proposed method establishes a data acquisition model based on the OSGi framework and develops a context information model based on ontology in order to perform the device environment between different kinds of systems. In addition, the context information will be extracted and classified for implementing the recommendation system used for the context information model. This study develops the ontology based context awareness model using the context information and applies it to the recommendation of the collaborative filtering. The context awareness model reflects the information that selects services according to the context using the Naive Bayes classifier and provides it to users. To evaluate the performance of the proposed method, we conducted sample T-tests so as to verify usefulness. This evaluation found that the difference of satisfaction by service was statistically meaningful, and showed high satisfaction.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.10
• /
• pp.125-130
• /
• 2017

Automotive materials and plant modules need to be prepared for freezing parts to operate in extreme areas such as Eastern Europe, Russia, and Canada. However, the only thing that has been done for ultra-qualifying materials for extremely low operating materials is that only the effects at low temperatures are conducted at room temperature, and the effects at low temperatures are only identified at low speeds. Therefore, this study examined the low-temperature characteristics of materials by conducting comparative tests on the mechanical properties of the room at the temperature and temperature of TP304 and TP316 materials, which are the most common materials.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.1
• /
• pp.146-153
• /
• 1996

A SCARA type direct drive robot which can be used in the assembly operation was designed and manufactured. Graphite fiber epoxy composite material was used in the fabrication of the robot arm structure in order to improve the speed of the robot arm with a high damping effect. For model-based control and sensitivity analysis of system parameters, the dynamic model of robot arm and drive servo amplifier parameters such as equivalent gains of PWM driver and velocity gains of servo system were estimated from frequency response tests. The complete dynamic model for overall robot system was used in the simulation of the open-loop control. The simulation results agreed reasonably well to the experimental results. The feedforward control using the dynamic models improved the trajectory tracking performance, decreasing the tracking error by factor of three compared with PID control. This study found that the inverse dynamic model of the robot arm including the drive servo system showed better performances than the case of arm dynamic model only.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1823-1826
• /
• 2002

The purpose of this experiment was to develope Triggered Vacuum Switch (TVS) for the high voltage and high current. The TVS has an array of rods of alternate polarity in which a fixed gap spacing is maintained between the rods. The cross section of each rod has trapezoidal shape. It consists of electrode, ceramic chamber, getter and trigger. Currently, triggered vacuum switch (TVS) with seal-off has been designed and fabricated at PAL. An experimentation and trigger devices for TVS were designed for testing characteristics of electricity. For making the prototype of TVS, it is developed of fabrication process and fined of electrode material. The fabrication of the TVS is a lot of process which have manufacturing of part, chemical clean, ceramic brazing and metal welding. The fabricated TVS is tested of leak for vacuum, hold-off voltage and conditioning of trigger system. The TVS has pinch-off after it is removed of gas in the TVS and activated of getter in degassing furnace. The prototype TVS tested about 20 kV, 75 kA, 83 ${\mu}s$ with 100 kJ capacitor bank and inductance 5 ${\mu}H$. This paper describes the results of tests and the characteristics of the switch.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.8 no.4
• /
• pp.87-96
• /
• 2004

As a special concrete, which is a mixture of soil, cement and water, has strength like regular concrete for pavement, soil cement has been used in various field such as pavement and soft soil improvement. The objective of this study was to investigate the characteristic of unconfined compressive strength and time dependent behavior of soil cement that is made from decomposed granite soil or coluvial and inorganic solidification liquid. The results showed that the unconfined compressive strength appears to increase as the amount of cement and curing time increase In addition, the strength seems to decrease with increase of the potion of fine particles(No 200 sieve). The result of XRD indicated that there is Vermiculite, the product of reaction, in the soil cement. The dynamic properties of material, such as shear complex compliance, shear complex modulus, and phase angle could be calculated from the hysteresis loop obtained from the Haversine Creep Tests. Finally, creep behavior was able to be predicted from these dynamic properties.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.6
• /
• pp.113-123
• /
• 2012

The technology developed for the decrease of applying loads and self-weight of a structure is to improve conventional Foam Cement Banking Method (FCB) by applying mixed slurry of bottom ash, cement and foams. Since the foam-mixed concrete, which is a major material of the Bottom ash-mixed Light weight concrete Banking method (BLB) developed, contains mineral admixture such as cement, the behavior shows time-dependent deformation and deterioration of durability due to environmental exposure. Thus, this study is subject to figure out the characteristics of long-termed behavior and durability of the developed method by carrying out experiments for schemed parameters, which are considered to be factors affecting mainly on concrete's characteristics from mechanical analysis. As results of tests, it was found that the developed concrete offers higher resistance than conventional foamed concrete in terms of long-termed behaviors associated with drying shrinkage and creep, and durability problems of freeze-thaw and carbonation processes, especially with addition of bottom ash.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.1
• /
• pp.69-75
• /
• 2012

The study was conducted to determine the effects of adding pig blood as an admixture to both mortar and concrete. The mortar tests included the determination of its unit weight, flow and its compressive strength. Moreover, the concrete test includes the determination of air content, slump, bleeding, setting time compressive strength and freeze-thaw resistance of the material. As the test result, the utilization of pig blood, as an additive to both mortar and concrete mixtures causes air entrainment. The mortar flow increased and both the unit weight and the compressive strength of mortar decreased. As the blood replacement rate increases, the air content decreases over time, the setting and amount of bleeding showed a tendency to decline and reduced compressive strength, and the freeze-thaw resistance of the concrete increased.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.2
• /
• pp.33-40
• /
• 1988

In this study, effects of the density of soil and the confining pressure applied to the soil sample on the elastic moduli of subgrade soils are experimentally analyzed. Through investigation of subgrade materials of domestic expressways, five typical types of subgrade soils are selected for the experiments. A series of unconsolidated undrained triaxial tests is performed on samples prepared with various water contents and densities at the confining pressures of 1.02, 2.04, and $3.06kg/cm^2$. Initial tangent modulus is inferred from the unloading-reloading portion of the stress strain curve obtained during an individual loading-unloading-reloading test. As a result of the analysis, it is found that the effect of the confining pressure on the elastic modulus of subgrade material is well consistent with the equation proposed by Janbu, and that the elastic modulus can be related to the dry unit weight expressing the Janbu constants as exponentiial functions of it. It is also found that the water content has little effect on the elastic modulus for the samples with the degree of saturation less than 70%.

• Composites Research
• /
• v.12 no.1
• /
• pp.68-75
• /
• 1999

This study has observed that the dynamic behavior of Metal Matrix Composites (MMCs) in low velocity impact varies with impact velocity. MMCs with 15 fiber volume percent were fabricated by using the squeeze casting method. The AC8A was used as the matrix, and the alumina and the carbon were used as reinforcements. The tensile and vibration tests conducted yielded the yielded the tensile stress and elastic modulus of MMCs The low pass filter and instrumented impact test machine was adopted to study dynamic behaviors of MMCs corresponding to impact velocity. Stable impact signals were obtained by using the low pass filter. Impact corresponding to impact velocity. Stable impact signals were obtained by using the low pass filter. Impact energy of unreinforced alloy and MM s increased as the impact velocity increased. The increase of crack propagation energy was especially prominent, but the dynamic toughness of each material did not change much. To show the relation between crack initiation energy and dynamic fracture toughness, a simple model was proposed by using the strain energy and stress distribution at notch. The model revealed that crack initiation energy is proportional to the square of dynamic fracture toughness and inversely proportional to elastic modulus.