• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.989-994
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• 1995

Rigid porous carbon fiber composites with the uniform pore size distribution were prepared by vacuum forming from water slurries containing carbonized PAN fibers, a phenolic resin and ceramic binders. The composites were designed to use for highly efficient carbon fiber filters for particulate filtration and gas adsorption. As the as-received carbon fibers of 1mm in length were milled to an approximate average length of 300${\mu}{\textrm}{m}$, modulus of rupture (MOR) of the composite filter was increased from 1MPa to the value larger than 5 MPa. Modulus of rupture (MOR) for the composite filter fabricated using the milled carbon fiber was increased from 5 MPa to 10 MPa as the carbonization temperature of the PAN fiber was raised from 90$0^{\circ}C$ to 140$0^{\circ}C$. The air permeability and an average pore size of the composite filter were increased from 40 to 270cc/min.$\textrm{cm}^2$ and from 35 to 80${\mu}{\textrm}{m}$, respectively, as the apparent porosity increased from 80 to 95%. It was shown that the MOR of the carbon fiber composite filter was dependent primarily on the average length of carbon fiber, carbonization temperature and the type of bonding materials.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.127-132
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• 2001

We describe the pulse forming of pulsed $CO_2$laser using multi-pulse superposition technique. A various pulse length, high duty cycle pulse forming network(PFN) is constructed by time sequence. That is, this study shows a technology that makes it possible to make various pulse shapes by turning on SCRs of three PFN modules consecutively at a desirable delay time with the aid of PIC one-chip microprocessor. The power supply for this experiment consists of three PFN modules. Each PFN module uses a capacitor, a pulse forming inductor, a SCR, a High voltage pulse transformer, and a bridge rectifier on each transformer secondary. The PFN modules operate at low voltage and drive the primary of HV pulse transformer. The secondary of the transformer has a full-wave rectifier, which passes the pulse energy to the load in a continuous sequence. We investigated laser pulse shape and duration as various trigger time intervals of SCRs among three PFN modules. As a result, we can obtain laser beam with various pulse shapes and durations from about 250 $mutextrm{s}$ to 600 $mutextrm{s}$.

• Design & Manufacturing
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• v.2 no.5
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• pp.5-10
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• 2008

Recently, ultra precision and light-weight micro products are needed in various industries. Injection molding products with metal insert material is often satisfied with light-weight and precision simultaneously. The researches on macro-size insert deformation have been performed but, a research on micro-size insert is meager. In this paper, the injection molding product with $300{\mu}m$ thin foil insert is designed and insert injection molding process is performed. Finally, the deformation of thin foil insert is analyzed according to insert feature and gate length.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.722-727
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• 1996

A simple compost windrow-forming car and a compost tuner were developed at the aim of low cost manure management systems. The developed compost windrow- forming car is possible windrows formation at a short time. In order to be pulverized and mixed by upper and lower beaters at the windrow-forming, the condition of air and the mixing of materials to play a major role in composting is filled. This car can also utilized for a manure spreader by folding the windrow-forming cover. The developed compost turner is a type equipped with tractor rear-right side. Main specifications are 2.5m working width, overall length 3.3m and 45degrees conveyer inclination angle, 2 beaters for mixing and pulverization are equipped in front parts. Windrows of 2.5m width and 1.5m height are turned at the speed of 4.5-5.1m/min. In accordance with the above, by combining the compost windrow-forming car and the compost turner, a simple composting system for each farmer could be constructed by the low c st.

• Korean Journal of Ichthyology
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• v.27 no.3
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• pp.189-198
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• 2015

This research has been launched in order to observe the osteological development of sevenband grouper, Epinephelus septemfasciatus larvae and juveniles and will be used for the basic data of phylogenetically systematics research. We got some samples of larvae and juveniles from a adult fish which belongs to the sea cage in Geomun-do, Yeosu-si, Jeolla-namdo province, and we have watched them. The average of breeding water temperature was $21.5{\sim}24.5^{\circ}C$ (average $23.0{\pm}1.5^{\circ}C$). In yolk-sac larvae just after hatching, ossification was not observed at all, and when the average total length reached 2.66 mm, the premaxillary and maxillary forming the upper jaw, dentary forming the lower jaw, and parasphenoid forming the skull base were ossified. In addition, the preopercle and opercle forming the opercular region began to be ossified. The caudal skeleton supporting the caudal fin is built with the caudal complex consisting of the malleus and incus. Until the average total length reached 2.59 mm, ossification did not occur at all and the urostyle bent at 45-degree angle. As to the ossification of the pterygiophore, when the average total length was 6.12 mm, the first interhemal spine began to be ossified in articulation with two spines of the anal fin, and the synapse also began to be ossified in articulation with two spines of the dorsal fin. When the average total length was 21.9 mm, individuals with completed ossification of the interhemal spines and synaptic clefts began to appear.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1853-1860
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• 1992

The plane-strain stamping process is analyzed by a forming energy minimization method in order to obtain forming load, slip length and strain distribution in each step of punch stroke. All the developed programs are integrated into total CAD/CAE SYSTEM for the purpose of the practical usage in die design. The computed strain distribution and the amount of draw-in are compared with those of the actually developed panel It is found that there is a good agreement between theoretical and experimental results.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.6
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• pp.48-59
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• 1990

A finite element program was developed using line elements for simulating the stretch/draw forming operation of an arbitrarily-shaped plane-strain section. An implicit, incremental, updated Lagrangian formulation is employed, introducing a minimum plastic work path assumption for each time step. Geometric and material nonlinearities are also considered within each time step. The finite element equation is based on the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The membrane approximation is adopted under the plane stress assumption. The sheet material is assumed to obey a rigid-viscoplastic constitutive law. The developed program was tested in the die-tryout of typical automotive inner panels. In order to determine a single friction coefficient and boundary length, FEM results and measurements of thinning for a stretched section of final die were compared. After finding analysis parameters, the sheet forming operations of original and final die designs were simulated. Excellent agreement between measured and computed thickness strains was obtained and the developed program was able to identify die designs which were rejected during die tryout.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.4
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• pp.58-68
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• 1994

An equilibrium approach is suggested as an effective tool for the analysis of sheet metal forming processes on the basis of force balance together with geometric relations and plasticity theroy. In computing a force balance equation, it is required to define a geometric curve approximating the shape of the sheet metal at any step of deformation from the geometric interaction between the die and the deforming sheet. Then the geometic informations for contacting and non-contacting sections of the sheet metal such as the number and length of both non-contact region, contact angle, and die radius of contact section are known from the geometric forming curve and utilized for optimization by force balance equation. In computation, the sheet material is assumed to be of normal amisotropy and rigid-phastic workhardening. It has been shown that there are good agreements between the equilibrium approach and FEM computation for the benchmark test example and auto-body panels whose sections can be assumed in plane-strain state. The proposed equilibrium approach can thus be used as a robust computational method in estimating the forming defects and forming severity rather quickly in the die design stage.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.2
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• pp.57-64
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• 2008

In general, the entire of paper mulberry bark, which is not cut into pieces with an appropriate length, have been used in the pulping. This kind of pulping method couldn't accomplish the improvement of beating and sheet forming efficiency. For this reason, we investigated the effects of the cutting length of paper mulberry bast fiber on pulping and Hanji (Korean traditional paper) properties, in order to develop high quality Hanji manufacturing process. The cutting length variation of paper mulberry white bast did not great effects on pulp yields. The pulp yields based on pulping methods were sulfomethylated pulping av. 57.4%, alkali-hydrogen peroxide pulping av. 55.4%, and alkaline pulping av. 53.5% respectively. The optical properties such as brightness, opacity, scattering coefficient, and absorption coefficient were slightly improved by the increase of paper mulberry white bast cutting length. The increase of paper mulberry white bast cutting length resulted in poor sheet formation. Physical properties such as breaking length, TEA, tear index, burst index, and folding endurance were slightly improved by the increase of cutting length. The modified pulping processes, which used sulfomethylated method and alkali-hydrogen peroxide method, showed better pulp and sheet properties than conventional alkaline pulping.

• Communications for Statistical Applications and Methods
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• v.18 no.3
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• pp.301-317
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• 2011

Statistical and probabilistic behaviors of fibers forming fiber webs of all kinds are of great significance in the determination of the uniformity and physical properties of the webs commonly found in many industrial products such as filters, membranes and non-woven fabrics. However, in studying the spatial geometry of the webs the observations must be theoretically as well as experimentally confined within a specified unit area. This paper provides a general theory and framework for computer simulation for quantifying the fiber segments bounded by the unit area in consideration of the "edge effects" resulting from the truncated length segments within the boundary. The probability density function and the first and second moments of the length segments found within the counting region were derived by properly defining the seeding region and counting region.