• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.565-570
• /
• 2000

In order to make a quiet zone, one can consider methods to generate a secondary sound field that cancels a primary sound field. Active noise control (ANC) is one of the kinds. This paper mainly deals with the issues on determining the optimal positions of control sources and sensors for making a desired quiet zone. The issues address the reason why the positions are important, how the positions are optimized, and what the measure on the optimal positions is in an uncertain sound field. It is also shown that a power control is applicable to a specific uncertain sound field. In addition, this paper shows that a control material method, which passively changes a boundary condition, is essentially found to be on the same road of ANC.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.580-585
• /
• 2003

The present study addresses experimental results to investigate the details of the near field flow structures produced in the under-expanded, dual, coaxial, swirling, jet. The sonic/supersonic swirling jets are emitted from the sonic inner nozzle and the outer annular nozzle produce the co-swirling and counter swirling against the primary swirling jet, respectively. The interactions between both the secondary annular swirling and primary inner supersonic swirling jets are quantified by the pitot impact and static pressure measurements and visualized by using the Schliern optical method. The experiment is performed for different swirl intensity and pressure ratio. The results obtained show that the secondary co-swirling jet significantly changes the inner under-expanded swirling jet, such as the recirculation zone, pressure distribution, through strong interactions between both the swirling jets and the effects of the secondary counter-swirling jet is similar to the secondary co-swirl jet case.

• Applied Microscopy
• /
• v.16 no.2
• /
• pp.14-24
• /
• 1986

The interrelation of secondary defects, intermediate S' phase and aging condition in Al-2.0 wt% Cu-1.1 wt% Mg alloy is studied by transmission electron microscope. The results obtained in this study are as follows. 1. High density of dislocation loops, helices and stacking faults are observed in this specimen with aging treatment. 2. The number of dislocation loops and the width of loop free zone (LFZ) are increased with aging time. 3. The intermediate S' phase precipitates and grows on the dislocations and secondary defects. 4. The misfit dislocations are formed around intermediate S' phase. 5. It is thought that the helices appear to be produced by the climb of screw dislocations, while the dislocation loops appear to be formed both by condensation of vacancies into collapsed discs and by interaction of helices with screw of opposite sign.

• Journal of Environmental Science International
• /
• v.11 no.6
• /
• pp.543-551
• /
• 2002

A Numerical simulation on the thermal flow performance was carried out to propose the incinerator type for the domestic refuses and to investigate the design factor and operating conditions. The SSTI(Standard Stoker Type Incinerator) proposed in this study was modified from the type with central f)ow. It has the characteristics of good mixing between refuse and hot combustion gas in primary combustion chamber and between unburned gas inflowing and secondary air jet in secondary chamber. By predictive results, the SSTI was no recirculation zone in secondary chamber so that mixing time was increased with high residence time. It has good characteristics of combustion and low emission. Parametric screening studies have been understood with phenomenon of combustion in incinerator.

• 한국연소학회:학술대회논문집
• /
• 2005.10a
• /
• pp.148-155
• /
• 2005

In this study, Development of 300,000kcal/hr high velocity Injection burner with fuel multi-stage was performed using experiments. The characteristics of NOx emission in multi fuel/air staged combustor have been experimentally studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is largest access air combustion and the secondary flame is complete combustion zone, where most of fuel bums. Experiments were performed on an industrial scale in a laboratory furnace and Liquefied Natural Gas(LNG) was used as primary and secondary fuels. Comparison of outlet NOx and outlet Temperature under various air rate and primary/ secondary fuel ratio was performed. The test demonstrated that NOx emission con be reduced by 70% in accordance with operating conditions.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.2
• /
• pp.171-178
• /
• 2003

Wing and secondary cracks are unique types of cracks observed in rock masses subjected to uniaxial and biaxial compressive loading conditions. In this study, morphological features of wing and secondary cracks developed in gypsum specimens are investigated in the macro and micro scales. Along the path of wing crack, microtensile cracks are observed. Microtensile cracks coalesce with pores and show branch phenomenon. From the onset of the wing crack, multiple initiations of microtensile cracks are observed. Microtensile cracks show tortuous propagation paths and relatively constant aperture of the cracks during the propagation. It is shown that microtensile cracks propagate by splitting failure. At the micro scale, microfsults are observed in the path of the secondary cracks. Along the path of the secondary cracks, separation of grains and conglomerate grains, oblique microfaults, and irregular aperture of microfault are observed. These features show that the secondary cracks are produced in shear mode. The measured sizes of fracture process zone across the propagation direction near the tip of wing and secondary cracks range from 10$\mu{m}$ to 20$\mu{m}$ far wing cracks and from 100$\mu{m}$ to 200$\mu{m}$ for secondary cracks, respectively.

• Economic and Environmental Geology
• /
• v.5 no.3
• /
• pp.133-144
• /
• 1972

The mine of our present concern is situated at Shim-ri, Gusan-myon, Changwon-gun, Kyongsang-namdo, with lattitude $128^{\circ}35^{\prime}{\sim}36^{\prime}N$ and longitude $35^{\circ}03^{\prime}{\sim}04^{\prime}E$. This mine has not been noticed until the intermittent geological survey for the ore deposits were initiated from September, 1967 till 1970. The main mineralized zones, No.1 and No.2 zones, were studied by the diamond drilling of 9 holes down to the total depth of 1,140m, and found to have ore reserves of Cu 1.99% ore, estimated to reach around $358,000{\frac{M}{T}}$ (proved $117,000{\frac{M}{T}}$, indicated $241,000{\frac{M}{T}}$), which triggered the new exploitation of this mine. Geological composition of the district near the mine is mainly from the andesite belonging to the Silla Series of Kyongsang System and the distribution is broadly spread. Ore deposits are the hydrothermal one, filling the shear zone formed alongside the andesite main joint. There are two stripes of copper bearing mineralized zone which are about 40~70 meters apart and parallel to each other, in addition to which two others are expected. The strike of the main mineralized zone lies at $N15^{\circ}{\sim}20^{\circ}W$, the dip at $60^{\circ}{\sim}70^{\circ}NE$. The principal components of the ore mineral are chalcopyrite, bornite and as secondary, cuprite, tenorite, azurite and malachite. Pyrite, magnetite, specular hematite, very little of galena, sphalerite, quartz, epidote, zoisite, chlorite and calcite are found as gangue mineral. Confirmed by the drilling, the main mineralized zone, No.1 zone, has the length of 320m, average width of 1.62m, Ag 26g/t, Cu 1.84% and the average width of the ore zone except the narrow barren andesite horse interposed in the mineralized zone is 1.32m with Ag 32g/t and Cu 2.26%. The mineralized zone No.2 is 340m long, 1.00m wide with Ag 30g/t and Cu 2.15%. Neglecting the barren andesite horse the width is 0.73m with Ag 42g/t and Cu 2.94%.

• Journal of Ecology and Environment
• /
• v.34 no.3
• /
• pp.259-267
• /
• 2011

A pollen analytical study of sediment sequences collected from Yongneup moor (sampling point: $38^{\circ}$12'57.4" N, $120^{\circ}$7'30.2" E) was conducted to understand the vegetation history in the mountainous region of the central Korean peninsula. Carbon dating was carried out to measure five successive samples obtained from the bottom at a depth of 180 cm to the surface. The Yongneup moor sediment revealed four main local pollen zones; that is, four past vegetation phases as follows: Local pollen zone I: Quercus-Pinus zone; estimated age, 5,900-4,800 calibrated years (cal) before present (BP); vegetation type, cool-temperate central/montane deciduous broad-leaved forest. Local pollen zone II: Pinus-Abies-Quercus zone; estimated age, 4,800-3,400 cal BP; vegetation type, cool-temperate northern/alti-montane mixed coniferous and deciduous broad-leaved forest. Local pollen zone III: Quercus-Pinus-Abies zone; estimated age, 3,400-400 cal BP; vegetation type: cool-temperate central/montane deciduous broad-leaved forest. Local pollen zone IV: Pinus-Quercus zone; estimated age, 400-present cal BP; vegetation type, cool-temperate central/montane mixed deciduous broad-leaved and coniferous forest. It was confirmed that subalpine coniferous forests had expanded to the mountainous region of the central Korean peninsula during the period from 4,800-3,400 cal BP and thereafter deciduous forests dominated by Q. mongolica were established. Notably, secondary forests dominated by P. densiflora developed in the lower part of the mountainous region of the central Korean peninsula about 400 cal BP due to human interference.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.2 no.2
• /
• pp.77-82
• /
• 1992

When a crystal is grown by FZ process, the melt zone is located at between the solid of upper and lower side and is kept by the solid-liquid interface tension. On the surface of the melt zone, a surface tension gradient is occured by the difference of temperature and solute concentration, it is the driving force of marangoni flow. The crystal even in the steady state growth can become imperfect for the dislocation distribution and the solute concentration in the peripheral region of the crystal are higher than those in the inner part and the probability of the formation of the defects such as voids, bubble penetration, secondary phase creation and crack is high near the solid-liquid interface. This is because the solid -liquid interface becomes irregular because of the local variation of temperature in that region due to marangoni convection.

• Nuclear Engineering and Technology
• /
• v.44 no.5
• /
• pp.491-500
• /
• 2012

The dissimilar metal joints welded between Ni-based alloy, Alloy 690 and low alloy steel, A533 Gr. B with Alloy 152 filler metal were characterized by using optical microscope, scanning electron microscope, transmission electron microscope, secondary ion mass spectrometry and 3-dimensional atom probe tomography. It was found that in the weld root region, the weld was divided into several regions including unmixed zone in Ni-base alloy, fusion boundary, and heat-affected zone in the low alloy steel. The result of nanostructural and nanochemical analyses in this study showed the non-homogeneous distribution of elements with higher Fe but lower Mn, Ni and Cr in A533 Gr. B compared with Alloy 152, and the precipitation of carbides near the fusion boundary.