• Progress in Medical Physics
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• v.8 no.2
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• pp.45-57
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• 1997

It is mandatory to measure accurately the dose distribution and the total absorbed dose of fast neutron for putting it to the clinical use. At present the methods of measurement of fast neutron are proposed largely by American Associations of Physicists in Medicine, European Clinical Neutron Dosimetry Group, and International Commission on Radiation Units and Measurements. The complexity of measurement, however, induces the methodological differences between them. In our study, therefore, we tried to establish a unique technique of measurement by means of measuring the emitted doses and the dose distribution of fast neutron beam from neutron therapy machine, and to invent a standard method of measurement adequate to our situation. For measuring the absorbed doses and the dose distribution of fast neutron beam, we used IC-17 and IC-18 ion chambers manufactured by A-150 plastic(tissue-equivalent material), IC-17M ion chamber manufactured by magnesium, TE gas and Ar gas, and RDM 2A electrometer. The magnitude of gamma-contamination intermingled with fast neutron beam was about 13％ at 5cm depth of standard irradiated field, and increased as the depth was increased. At the central axis the maximum dose depth and 50％ dose depth were 1.32cm and 14.8cm, respectively. The surface dose rate was 41.6-54.1％ throughout the entire irradiated fields and increased as the irradiated fields were increased. Beam profile was that the horn effect of about 7.5％ appeared at 2.5cm depth and the flattest at 10cm depth.

• Journal of Ecology and Environment
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• v.41 no.9
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• pp.271-280
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• 2017

Background: Soil microorganisms play key roles in nutrient cycling and are distributed throughout the soil profile. Currently, there is little information about the characteristics of the microbial communities along the soil depth because most studies focus on microorganisms inhabiting the soil surface. To better understand the functions and composition of microbial communities and the biogeochemical factors that shape them at different soil depths, we analyzed microbial activities and bacterial and fungal community composition in soils up to a 120 cm depth at a fallow field located in central Korea. To examine the vertical difference of microbial activities and community composition, ${\beta}$-1,4-glucosidase, cellobiohydrolase, ${\beta}$-1,4-xylosidase, ${\beta}$-1,4-N-acetylglucosaminidase, and acid phosphatase activities were analyzed and barcoded pyrosequencing of 16S rRNA genes (bacteria) and internal transcribed spacer region (fungi) was conducted. Results: The activity of all the soil enzymes analyzed, along with soil C concentration, declined with soil depth. For example, acid phosphatase activity was $125.9({\pm}5.7({\pm}1SE))$, $30.9({\pm}0.9)$, $15.7({\pm}0.6)$, $6.7({\pm}0.9)$, and $3.3({\pm}0.3)nmol\;g^{-1}\;h^{-1}$ at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively. Among the bacterial groups, the abundance of Proteobacteria (38.5, 23.2, 23.3, 26.1, and 17.5% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) and Firmicutes (12.8, 11.3, 8.6, 4.3, and 0.4% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) decreased with soil depth. On the other hand, the abundance of Ascomycota (51.2, 48.6, 65.7, 46.1, and 45.7% at 15, 30, 60, 90, and 120 cm depths, respectively), a dominant fungal group at this site, showed no clear trend along the soil profile. Conclusions: Our results show that soil C availability can determine soil enzyme activity at different soil depths and that bacterial communities have a clear trend along the soil depth at this study site. These metagenomics studies, along with other studies on microbial functions, are expected to enhance our understanding on the complexity of soil microbial communities and their relationship with biogeochemical factors.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.482-488
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• 2012

To fabricate a precise micro metal mold, the electrochemical etching process has been researched. We investigated the electrochemical etching process numerically and experimentally to determine the etching tendency of the process, focusing on the current density, which is a major parameter of the process. The finite element method, a kind of numerical analysis, was used to determine the current density distribution on the workpiece. Stainless steel(SS304) substrate with various sized square and circular array patterns as an anode and copper(Cu) plate as a cathode were used for the electrochemical experiments. A mixture of $H_2SO_4$, $H_3PO_4$, and DIW was used as an electrolyte. In this paper, comparison of the results from the experiment and the numerical simulation is presented, including the current density distribution and line profile from the simulation, and the etching profile and surface morphology from the experiment. Etching profile and surface morphology were characterized using a 3D-profiler and FE-SEM measurement. From a comparison of the data, it was confirmed that the current density distribution and the line profile of the simulation were similar to the surface morphology and the etching profile of the experiment, respectively. The current density is more concentrated at the vertex of the square pattern and circumference of the circular pattern. And, the depth of the etched area is proportional to the current density.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.6
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• pp.1175-1180
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• 2022

STI has been studied a lot as a process technology for wide area planarization according to miniaturization and high integration of semiconductor devices. In this study, as methods for improving the STI profile, wet etching of pad oxide using hydrofluorine solution and dry etching of O₂+CF₄ after STI dry etching were proposed. This process technology showed improvement in profile imbalance and leakage current between patterns according to device density compared to the conventional method. In addition, as a result of measuring the HLD thickness after CMP for a device having the same STI depth and HLD deposition, the measured value was different depending on the device density. It was confirmed that this was due to the difference in the thickness of the nitride film according to the device density after CMP and the selectivity of the slurry.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.107-115
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• 2009

The labyrinth weir can be applied to increase the overflow rate, maintain constant water depth and improve water quality. This weir can be defined that the plane shape of overflow part is not straight line and is a kind of weir having overflow length increased by changing its plane shape. There are relatively few studies related to effect of maintaining the water depth which has been used to consider for various functions as hydraulic facilities and design conditions of labyrinth weirs. Thus, it is needed to conduct studies related to the maintenance of water depth by the labyrinth weir. This study was to provide fundamental data which may become a facilitator for more accurate and proper design of hydraulic facilities related to the maintenance of water depth. The ranges of constant water depth ($H_t/P=0.08\sim0.27$) were provided for the triangle type labyrinth weir, and the effect of maintaining water depth was analyzed using hydraulic laboratory experiments and 3D-numerical simulations(Flow-3D).

• Journal of the Korean Institute of Navigation
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• v.13 no.3
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• pp.45-65
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• 1989

Various typhoon data near Yongil Bay, Korea from 1961 to 1985 were collected with some critria and analyzed with the help of the computer. Introducing the pressure profile models and predicting the typhoon wind and wave fields, the 100-year design wave parameters were calculated. Additionally, the wave data at the southeast coast of Korea were statistically analyzed. The deep water wave climate of this bay indicated that Typhoon Brenda, 1985 had wave characteristics of 100-year return period, Typhoon model and storm surge model studies were made for this typhoon. These, including other design parameters, were introduced into the calculation of total design water depth.

• Tribology and Lubricants
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• v.20 no.5
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• pp.259-265
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• 2004

The sealing performance of O-rings is affected by working conditions such as applied pressure, operation temperature, pre-compressed ratio and material properties. In this paper, a pressurized and compressed elastomeric bi-polymer O-ring in which is inserted into a rectangular groove is analyzed by non-linear MARC finite element program based on the Taguchi experimental method. O-rings with 9 different profile models are analyzed for design parameters that are related to the diameter ratio between outer diameter and inner one of bi-polymer O-ring, compressive ratio, groove angle and groove depth. The calculated FEM results showed that the affection ratio of design parameter dlD, which may control sealing pressure of O-rings, is the most influential parameter among the groove angle, groove depth and compression ratio.

• Journal of the Korean Magnetics Society
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• v.20 no.4
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• pp.160-166
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• 2010

X-ray resonant magnetic scattering (XRMS) allows us to extract magnetic depth profiles in magnetic multilayers and magnetization distribution in magnetic nanostructures in element-specific manner using x-ray reflectivity and diffraction. XRMS is explained with a brief introduction and examples of magnetic structures and magnetic switching mechanism in magnetic multilayers and nanostructures.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.119-124
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• 2002

Generally, Portland cement concrete(PCC) pavements have the advantage of durability and superior surface friction when compared to most dense-graded asphalt. However, It is known that PCC pavements create more noise than asphaltic surfaces due to the noise from interaction of tire and pavement surface. Recently exposed aggregate concrete(EAC) pavement was sugested to reduce traffic noise. So in this paper, we considered several materials and mixture proportions for proper depth of exposed aggregate which was measured by the sand patching test, and then according to those relationships, we tried to find out dosage of retarding agents and optimum mixture proportions for expecting good effects to noise reduction. It were also evaluated sound level at every conditions of surface texture as like depth of aggregate exposed, profile peak, distance of aggregate and types of aggregate.

• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.24-32
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• 2006

Compaction is becoming a greater concern in crop production and the environment because it can have deleterious effects on growing conditions that are difficult to remediate. Because compaction can vary considerably from point to point within a field, and also from depth to depth within the soil profile, it is important to consider quantification and management of the spatial and vertical variability in soil compaction when developing an overall site-specific crop management plan. In this paper, the importance of soil compaction, techniques for quantification of its variability, and the concept of site-specific tillage are examined. Methods and systems to detect within-field variation in soil strength as a surrogate measure of soil compaction and related soil properties are also compared and discussed. Quantification of variability in soil compaction and site-specific compaction management was motivated recently, and sensors and control systems are still under development. Future study will need to address a number of issues related to understanding and applying the sensor measurements.