• 한국생산제조학회지
• /
• 제20권4호
• /
• pp.419-426
• /
• 2011

In this study, an experimental and theoretical program were carried out to determine the cutting forces and chip formation at different cutting speeds using a 0.4mm nose radius ceramic insert and -7 rake angle for non heat-treated AISI 4140 (27HRc) and heat-treated AISI 4140 (45 HRc) steel. The results obtained were compared to show the hardness differences between the materials. The secondary deformation zone thicknesses when comparing the two materials show different physical structure but similar size. These results were also discussed in light of the heat treatment and the effects it had on the machining characteristics of the material. In addition, the Oxley Machining Theory was used to predict the cutting forces for these materials and a comparison made. The predicted cutting performances were verified experimentally and showed good agreement with experimental data.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
• /
• pp.156-161
• /
• 2005

Two and Three dimensional numerical simulations have been carried out to understand the combustion characteristics of LNG-fueled gas turbine combustor for power generation. Focus of the study was given to the influences of different fuel composition of imported and domestic natural gases with the flow conditions selected from the gas turbine operation data. Reacting flow characteristics of the swirl stabilized natural gas combustor were understood from the comparison of the two-dimensional and three-dimensional results. The thermal influences of different natural gases were very small and the fuel composition and flow rate were considered to be tuned well.

• 한국미생물·생명공학회지
• /
• 제23권2호
• /
• pp.209-213
• /
• 1995

During the screening of inhibitors of melanin biosynthesis from microbial secondary metabolites, a fungal strain MR-93 which was capable of producing high level of an inhibitor was selected from plant leaf. Based on taxonomic studies, the fungus could be classified as a strain of Trichoderma sp.. The active compound (MR-93D) was purified from the culture broth by Diaion HP-20 column chromatography, ethylacetate extraction, Sephadex LH-20 column chromatography and HPLC. The inhibitor was identified as 4-hydroxy-8-isocyano-l-oxaspiro[4-4]cyclonon-8-en-2- one by spectroscopic methods of UV, $^{1}$H-NMR, ESIMS and IR. MR-93D showed a strong tyrosinase inhibitory activity with 0.03 $\mu$g/m of IC$_{50}$ value. It also inhibited melanin biosynthesis with 35 mm inhibition zone at 30 $\mu$g/paper disc in Streptomyces bikiniensis, a bacterium used as an indicator organism in this work.

• Journal of Plant Biology
• /
• 제11권3호
• /
• pp.8-17
• /
• 1968

A grafting method, cleft grafting of ordinary dormant scion into an inverted radicle of a germinated seed was tested with good success for chestnut as well as for walnut trees. It was seen that verticilate roots which were produced from the cut and of radicle after grafting made a complete union with scion and made healthy development to produce a successful graft. The radicle before secondary rootlets emerged from its rooting zone was proved to be best stock for inverted radicle grafting. The dormant but was also used for grafting scion with success in this method. Though green house grafting gives higher survival, field grafting was also feasible by this method. Those early growing geason after grafting, the later development of root system and the shoot of the graft were to be studied in the future.

• 대한전기학회논문지
• /
• 제36권3호
• /
• pp.153-162
• /
• 1987

The purpose of this paper is to analysis and develop theoretically the characteristics of tubular linear induction motor, which is a special industrial motor that generates directly thrust force from electrical power. The Poisson equation about vector potential which is created by the application of Maxwell electromagnetic equation with the speed considered, results in modified Bessel equation by the assumption that is applied to each region of the experimental motor. Vector potential, magnetic flux density, secondary current, and thrust force according to its region respectively were found out by substituting boundary condition for this equation and rearranging. Besides, a attendant materials, that is, thermal characteristic, which is one of the characteristics under the operation of experimental motor each part's magnetic flux distribution characteristics within active zone, the required time for reciprocating motion, and variation of power factor vs. a slip were found.

• 한국소음진동공학회논문집
• /
• 제13권7호
• /
• pp.499-507
• /
• 2003

This paper presents a method for active noise control (ANC) in a duct by using a ring-tyPe smart foam. The ring-type smart foam consists of an elastic porous material of lining shape and a PVDF film embedded In the material. The PVDF element acts as a secondary sound source to reduce the noise. Active noise control using a ring-type smart foam is only effective locally because of the way to excite radially. To enlarge the quiet zone, the duct Is lined with additional acoustic foam between the smart foam and the error microphone. When cancellation path ks optimized by the LMS/RLS algorithm, the computation power is reduced while control performance Is maintained. The filtered-x LMS algorithm is used to minimize the error signal.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2003년도 추계학술발표회
• /
• pp.83-86
• /
• 2003

Soil Aquifer Treatment (SAT) is a technique in which secondary- or tertiary-treated wastewater is infiltrated through unsaturated soil and stored in the saturated zone. In SAT, contaminants are removed by physical and biochemical reactions taking place in soils. In this study, a numerical model was developed to predict changes in water quality during SAT operations. The contaminant species considered in the model were ammonium, nitrate, dissolved organic carbon, and dissolved oxygen. The model was calibrated against experimental data obtained from one dimensional soil column tests conducted for 84 days. The calibrated model will be used to find out optimum conditions for the pilot- and regional-scale SAT operations to be scheduled for the next phase of this project.

• Journal of Chest Surgery
• /
• 제22권1호
• /
• pp.10-15
• /
• 1989

Excision of bullous emphysema or decortication of chronic empyema commonly results in a prolonged air leakage. Prolonged air leakage requires prolonged intercostal drainage, delays recovery, and can be followed complications such as pneumothorax, atelectasis, incomplete expansion of remained lung, secondary infection. To minimize these complications free muscle grafts can be used like a patch to close the opening of visceral pleura and reinforce suture lines without undue tension. From a preliminary study using the latissimus dorsi muscle as a free muscle graft in the rabbit pleural space, viable muscle fibers that seems the result of the process of regeneration can be consistently identified around the degenerating muscle fibers. Voluminous connective tissues and numerous blood vessels are also observed in the peripheral zone. Further studies in that free muscle graft will be sutured with visceral pleura and lung parenchyme will hopefully provide additional information before clinical application.

• Journal of Welding and Joining
• /
• 제16권4호
• /
• pp.83-91
• /
• 1998

Cracking problems which high temperature plant components suffer during long-term service, occur very often at welded locations. The crack occurs due to accumulated creep damage near fusion line or at heat affected zone (HAZ). However, most of the studies on creep crack growth behavior have been performed with matrix metal not wit welded metal due to the difficulty of interpreting the test results. In this study, creep crack growth rates were measured with C(T) specimens whose cracks were formed along the fusion line or HAZ. The measured crack growth rates were characterized by {TEX}$C_{t}${/TEX}-parameter derived for elastic-primary-secondary creeping material. Since contribution of primary creep was significant for the tested 1Cr-0.5Mo steel, its effect was carefully studied. Effects of crack tip plasticity and material aging were also discussed.

• 대한안전경영과학회지
• /
• 제4권2호
• /
• pp.223-235
• /
• 2002

This paper presents some indirect physical evidences indicating that reduced friction occurs in an economical cryogenic machining process, in which LN2 is applied selectively in well-controlled jets to the localized cutting zone. These evidences include cutting force components, tool wear rate and chip morphology. LN2 reduced the tool wear rate to a great extent and elongated the tool life up to four times compared to emulsion cooling. The friction reduction was further reflected in larger shear angle and less secondary deformation in the chip microstructures. This study also found that the effectiveness of LN2 lubrication depends on the approach how LN2 is applied.