• Journal of Biosystems Engineering
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• v.25 no.1
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• pp.39-46
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• 2000

This work was conducted to study the operating characteristics of a grinding system designed to obtain fine rice husk ash powder. To find better utilizing of rice husk, a valuable by-product from rice production, once the rice husk was incinerated and the thermal energy was recovered from the furnace, the ash was fed and pulverized in the grinding system resulting a fine powder to be used as a supplementary adding material to the portland cement manufacturing . The rice husk ash grinding system consisted of a high speed centrifugal fan for the preliminary coarse milling and a dry-type stirred ball mill for the subsequent fine grinding . Total grinding time 9 5, 15, 30, 45 min), impeller speed (250, 500, 750 rpm) , and mixed ratio (4.8, 7.9, 14.9) were three operating factors examined for the performance of a stirred ball mill used for the fine grinding of ash. With the stirred ball mill used in this study, the minimum attianable mean diameter of rice husk ash powder appeared to be 2 ${\mu}{\textrm}{m}$. During the find grinding, the difference in specific surface area of powder showed an increase and the grinding energy efficiency decreased with the increase in total grinding time, impeller speed ,and mixed ratio. For the operating conditions employed , the resulting mean diameter of fine ash powder, specific energy input, and grinding energy efficiency were in the range of 1.79 --16.04${\mu}{\textrm}{m}$, 0.072-5.226kWh/kg, an d1.11-12.15$m^2$/Wh, respectively. Grinding time of 30 min , impeller speed of 750 rpm, and mixed ratio of 4.8 were chosen as the best operating conditions of the stirred ball mill for fine grinding . At these conditions, mean particle diameter of the fine ash, grinding energy efficiency, grinding throughtput, and specific energy input were 2.73${\mu}{\textrm}{m}$, 3.95$m^2$/Wh, 0.25kg/h, and 1.22kWh/kg, respectively.

• Electrical & Electronic Materials
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• v.12 no.11
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• pp.1-14
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• 1999

• The Korean Journal of Cytopathology
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• v.7 no.2
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• pp.111-121
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• 1996

Fine needle aspiration cytology(FNAC) is preferred because of simplicity, safety, and reliability in the evaluation of patients with thyroid nodule or hyperplasia. However, there are a few limitations such as false-negative or false-positive cases and non-diagnostic material. To evaluate the usefulness of FNAC in thyroid lesions, we reviewed 704 FNAC cases of thyroid nodules from 1988 to 1994 at Soonchunhyang University Hospital. The results are as follows. 1. Among 704 FNAC cases of thyroid gland, 571(81.1%) cases were benign, 12(1.7%) were suspicious, 71(10.1%) were malignancy, and 50(7.1%) were material insufficiency. The cytologic diagnoses of the benign lesions included 168 cases of follicular neoplasm, 139 cases of adenomatous goiter, 162 cases of follicular lesion such as follicular neoplasm or adenomatous goiter, 61 cases of Hashimoto's thyroiditis, 13 cases of subacute thyroiditis, and 28 cases of colloidal nodule or benign nodule. The malignant lesions included 68 cases of papillary carcinona, two medullary carcinomas and a case of metastatic colon cancer. 2. The average number of cytologic smear slides was $4.12{\pm}1.81$ in material insufficiency and $5.63{\pm}1.79$ in diagnostic cases. This difference was statistically significant(p<0.00001). 3. Histological assessment of 150 cases revealed 2 false negative and 1 false positive cases. The false negative cases were a case of marked sclerosis in papillary carcinoma and an occult case of papillary carcinoma. The false positive case resulted from pseudo-ground glass nuclei due to marked dry artifact. 4. Comparison between the FNAC and the histologic diagnosis revealed that FNAC had a sensitivity of 93.5%, a specificity of 99.2%, a false negative rate of 6.6%, a false positive rate of 0.8%, and an overall diagnostic accuracy of 98.0%. Therefore, FNAC of thyroid gland is a very reliable diagnostic method with excellent accuracy rate.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.3
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• pp.9-12
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• 2013

The pavement is generally used on the highways, local loads, roads for bicycle riding and neighborhood living facility such as parking lot, plaza, park and sports facilities. However, the pavement material that is usually used on the most of roads is impermeable asphalt-concrete and cement-concrete. If the pavement material is impermeable, many problems can be happened on the drainage facilities in the rainy season. Additionally, a lot of rainwater on the pavement surface cannot permeate to the underground and flows to the sewage ditch, stream and river, etc. If a lot of rainwater flows at once, the floods can be out along the streams and rivers. So, underground water can be exhausted. Micro organisms cannot live in the underground. Recently, many studies has been conducted to exploit the permeable concrete that has high performance permeability. However, it is required to develop the permeable concrete which has high strength and durability. In this study, permeable and strength tests were performed to investigate the permeable characteristics of porous concrete according to fine aggregate content and substitution ratio of blast furnace slag. In this test, crushed stones with 10~20 mm and sand with 5~10 mm were used as a coarse aggregate and a fine aggregate respectively. The substitution ratio of blast furnace slag to cement weight is 0 %, 15 %, and 30 %. The ratio of fine aggregate to total aggregate is 0 %, 18 %, and 35 %. As a result, permeability coefficient was decreased according to fine aggregate ratio of total aggregate. Compressive strength was also decreased according to substitution ratio of blast furnace slag.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.101-108
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• 2015

The quantities of heavy weight waste glass have been progressively increased because of the rapid industrialization and the change of quality of life. And, the most of them are not recycled. The heavy weight waste glass have been treated by illegal dumping or being buried in landfills. Meanwhile, in order to ensure the safety of nuclear power plant structure, the excellent construction materials are socially required for shielding performance. Concrete is the most widely used construction material, the huge amounts of natural resources are required to make concrete. So, it is needed to investigate the possibility of recycling of heavy weight waste glass as concrete material ingredient. In this study, the heavy weight waste glass was evaluated for the applicability as fine aggregate of shielding concrete. From the results, when heavy weight waste glass was replaced as fine aggregate of mortar, shielding performance can be improved due to increasing in unit weight of mortar. It showed that the strength decreased according to mixing of heavy weight waste glass, Non-Washed heavy weight waste glass is more advantageous in the strength development than Washed case.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.502-502
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• 2007

Current thin film process using memory device fabrication process use expensive processes such as manufacturing of photo mask, coating of photo resist, exposure, development, and etching. However, direct printing technology has the merits about simple and cost effective processes because inks are directly injective without mask. And also, this technology has the advantage about fabrication of fine pattern line on various substrates such as PCB, FCPB, glass, polymer and so on. In this work, we have fabricated the fine and thick metal pattern line for the electronic circuit board using metal ink contains Ag nano-particles. Metal lines are fabricated by two types of printing methods. One is a conventional printing method which is able to quick fabrication of fine pattern line, but has various difficulties about thick and high resolution DPI(Dot per Inch) pattern lines because of bulge and piling up phenomenon. Another(Second) methods is sequential printing method which has a various merits of fabrication for fine, thick and high resolution pattern lines without bulge. In this work, conductivities of metal pattern line are investigated with respect to printing methods and pattern thickness. As a result, conductivity of thick pattern is about several un.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.321-326
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• 2022

In this study, cogeneration power plants that use biomass as a raw material to convert them into energy have recently received a lot of attention worldwide and are gradually increasing in South Korea. Therefore, in order to confirm the possibility of using the generated floor material as a fine aggregate for concrete, properties and stability evaluation experiments were performed. Compared to standard sand, the compressive strength of wood chip aggregate was improved by 11 % to 111 %, the length change rate was 89 %, and the waste processing test results met all criteria for hazardous substances. All of these are satisfied, and it is judged that the floor materials by the cogeneration power plant can be used as a fine aggregate for concrete.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.557-564
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• 2023

Nuclear materials such as uranium are used as fuel for nuclear power generation, but there is a high possibility that they will be used for non-peaceful purposes, so international inspections and regulations are being conducted. Isotope analysis data of fine particulate obtained from nuclear facilities can provide important information on the origin and concentration method of nuclear material, so it is widely used in the field of nuclear safety and nuclear forensics. In this study we describe the analytical method that can directly identify nuclear particles and measure their isotopic ratios for fine samples using a large-geometry secondary ion mass spectrometer and introduce its preliminary results. Using the U-200 standard material, the location of fine particles was identified and the results consistent with the standard value were obtained through microbeam analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1080-1083
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• 2001

Ultrafine NiO/YSZ composite powders were prepared by using a glycine nitrate process for anode material of solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ composite powders were examined with controlling pH of a precursor solution and the content of glycine. The characteristics of synthesized composite powders were examined with X-ray diffractometer, a BET method with N$_2$absorption, scanning and transmission electron microscopy. The strongly acid precursor solution increased the specific surface area of the synthesized composite powders. This is suggested to be caused by the increased binding of metal ions and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of NH$_3$$\^$+/. After sintering and reducing treatment of NiO/YSZ composite powders synthesized by GNP, the Ni/YSZ pellet showed ideal micro-structure very fine Ni parties of 3-5${\mu}$m were distributed uniformly and fine pores around Ni metal particles were formed, thes, leading to an increase of the triple phase boundary among gas Ni and YSZ.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.7
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• pp.923-932
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• 2001

A series of experiments were conducted to generate fine liquid(water) drops through the electrohydrodynamic atomization process. The atomization mode depended on flow rate and DC voltage input. For water, having electric conductivity larger than 10(sup)-7S/m, the spindle mode turned out to be the only mode to generate uniform-size drops within the range of 30-450 microns that have wide applications. Within this mode, both the uniformity and the fineness of drops were improved at an optimum voltage input for a given flow rate. This optimum voltage increased with increasing of the liquid flow rate. Another important parameter considered was the nozzle material with different electric conductivity and liquid wettability. A stainless-steel nozzle (the material with high electric conductivity and high liquid wettability) and a silica nozzle (the electrically non-conducting material with low liquid wettability) were tested and compared; and more uniform drops could be obtained with the silica nozzle.