• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.576-582
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• 2015

The efficiencies of thermal power system using fossil fuel depend on heat exchangers which extract energy from the exhaust gas before it is expelled to the atmosphere. To increase heat transfer efficiency it is very important to maintain the surface of heat exchanger as clean condition. The accepted skill of cleaning of fouled surface of heat exchanger is soot blowing. A high pressure jet of air is forced through the flat surface of plate to remove the deposit of fouling. There is, however, little knowledge of the fundamental principles of how the jet behave on the surface and how the jet actually removes the deposit. Therefore, the study focuses on the measuring of cleaning area and cleaning dwell time after accumulating the simulated deposit on the flat surface. The deposit test rig was built for the study and simulated deposit material is used after measuring the physical property of the each material by shearing stress test. Much data was obtained for the analysis by the parameters change such as the different jet speed, different inner pressure and variable distance of the jet from the test rig surface. The experimental data was compared with the theoretical equation and most of the data matches well except some extreme cases.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.174-178
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• 2007

The cleaning process to remove small particles, ions, and other polluted sources is one of the major parts in the recent semiconductor industry because it can cause fatal errors on the quality of the final products. According to the other reports, the major factors of bath's fluid motion are the cleaning method, nozzle, the geometry (of bath, guide and wafer), and the position (of guide and wafer). So to enhance cleaning efficiency in the bath, these factors must be controlled. The purpose of this study is to analyze and visualize fluid motion in the cleaning bath as basic data for designing the nozzle system and finding the process control parameters. For that, we used the general CFD code FLUENT.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.248-254
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• 2012

In the situation of expanding domestic solar power supply business long-term performance modeling of a proposed solar-cooling and cleaning system to increase electromotive force and light transmission is carried out to test the effectiveness of the system. To test the effectiveness of the system, the data which comparing the solar power planet installing the system to not installing at the same time is used. A difference between the utilization factor of each comparison group were recorded. Approximately from one year to two years Field Test was performed, Result of apply to cooling/cleaning technology, Each of plant by From least 7 percent up to 16 percent utilization factor increased, and the cooling / cleaning is output through improved as a result of the determined.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.32 no.1
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• pp.41-52
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• 2022

Objectives: This study intends to review the impact on cleaning workers and suggest directions for improvement by reviewing the legal and institutional ways in which Article 86 Nos. 7 and 16 of the Enforcement Decree of the Occupational Safety and Health Act work on the maintenance and promotion of cleaning workers' health. Methods: The following laws and systems were reviewed and considered: First, the occupational safety and health legislation obligated or required to be applied to protect the health of cleaning workers; Second, the status of control of chemicals or mixtures used at cleaning sites through the Consumer Chemicals Product and Biocide Safety Control Act; Third, Control of consumer products according to foreign material safety data sheet related laws. Results: Legal and institutional measures necessary to protect the health of cleaning workers include the legal control of harmful substances to be controlled, work environment monitoring, and special health examinations. The application of the Consumer Chemicals Product and Biocide Safety Control Act does not satisfy the legal and practical level of health maintenance and promotion required by the Occupational Safety and Health Act, and the communication of chemical information is insufficient. Overseas, there are restrictions on the use of consumer products in the workplace without material safety data sheets. Conclusions: It is necessary to improve the system to ensure the health of workers handling consumer chemical products. The remaining laws and regulations exempted from the obligation to prepare material safety data sheets should be additionally reviewed.

• Applied Chemistry for Engineering
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• v.25 no.5
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• pp.548-551
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• 2014

In order to reduce toxicity on the human body, four new cleaning agents (1-4) containing ester and ether functionalities have been invented. The synthesized cleaning agents's physical properties, biodegradabilities, and $LD_{50}$ values, which were conducted by Korea Testing Certification Institute by using standard method, showed excellent values. A specimen for cleaning ability was prepared by cutting in $60{\times}40mm$ size of stainless steel plate. The surface of the above specimens was treated with four different kinds of contaminants, such as cutting oil, anti-rust oil, drawing oil, and lubricating oil. Contaminated specimens were then immersed in compounds (1-4) for 1 to 5 minutes to dissolve oil in the cleaning agent. The data indicate that all compounds (1-4) exhibit good cleaning ability toward four contaminant oils. It is also confirmed that these compounds can be applicable to various industrial cleaning fields as nontoxic and biodegradable cleaning agents because of their excellent biodegradabilities and $LD_{50}$ values.

• The Journal of Advanced Prosthodontics
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• v.4 no.4
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• pp.192-196
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• 2012

PURPOSE. The purpose of this study was to evaluate the effect of provisional cement removal by different dentin cleaning protocols (dental explorer, pumice, cleaning bur, Er:YAG laser) on the shear bond strength between ceramic and dentin. MATERIALS AND METHODS. In total, 36 caries-free unrestored human third molars were selected as tooth specimens. Provisional restorations were fabricated and cemented with eugenol-free provisional cement. Then, disc-shaped ceramic specimens were fabricated and randomly assigned to four groups of dentin cleaning protocols (n = 9). Group 1 (control): Provisional cements were mechanically removed with a dental explorer. Group 2: The dentin surfaces were treated with a cleaning brush with pumice Group 3: The dentin surfaces were treated with a cleaning bur. Group 4: The provisional cements were removed by an Er:YAG laser. Self-adhesive luting cement was used to bond ceramic discs to dentin surfaces. Shear bond strength (SBS) was measured using a universal testing machine at a 0.05 mm/min crosshead speed. The data were analyzed using a Kolmogorov Smirnov, One-way ANOVA and Tukey HSD tests to perform multiple comparisons (${\alpha}$=0.05). RESULTS. The dentin cleaning methods did not significantly affect the SBS of ceramic discs to dentin as follows: dental explorer, pumice, cleaning bur, and Er:YAG laser. CONCLUSION. The use of different cleaning protocols did not affect the SBS between dentin and ceramic surfaces.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.11
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• pp.599-609
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• 2007

Due to the restrictions of Flash memory such as overwrite limitation and write/erase operational unit differences, block cleaning is required in Flash memory based file systems and known as a key factor on the performance of file systems. In this paper, we identify three parameters, namely utilization, invalidity and uniformity, and analyze how the parameters affect the cost of block cleaning. The analysis show that as uniformity degrades, the cost of block cleaning increases drastically. To overcome this problem, we design a new modification-aware(MODA) page allocation scheme that strives to keep uniformity high by separating frequently-updating data from infrequently-updating data. Real implementation experiments conducted on an embedded system show that the MODA scheme can actually enhance uniformity of Flash memory, which consequently leads to reduce the cost of block cleaning with an average of 123%, compared to the traditional sequential allocation scheme that is used in YAFFS.

• Journal of KIISE
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• v.43 no.6
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• pp.627-635
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• 2016

When many processes issue write operations alternately on Log-structured File System (LFS), the created files can be fragmented on the file system layer although LFS sequentially allocates new blocks of each process. Unfortunately, this file fragmentation degrades read performance because it increases the number of block I/Os. Additionally, read-ahead operations which increase the number of data to request at a time exacerbates the performance degradation. In this paper, we suggest a new cleaning method on LFS that minimizes file fragmentation. During a cleaning process of LFS, our method sorts valid data blocks by inode numbers before copying the valid blocks to a new segment. This sorting re-locates fragmented blocks contiguously. Our cleaning method experimentally eliminates 60% of file fragmentation as compared to file fragmentation before cleaning. Consequently, our cleaning method improves sequential read throughput by 21% when read-ahead is applied.

• The KIPS Transactions:PartA
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• v.13A no.5 s.102
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• pp.387-398
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• 2006

In this paper, we propose a new page allocation scheme for flash memory file system. The proposed scheme allocates pages by exploiting the concept of Purity, which is defined as the fraction of blocks where valid Pages and invalid Pages are coexisted. The Pity determines the cost of block cleaning, that is, the portion of pages to be copied and blocks to be erased for block cleaning. To enhance the purity, the scheme classifies hot-modified data and cold-modified data and allocates them into different blocks. The hot/cold classification is based on both static properties such as attribute of data and dynamic properties such as the frequency of modifications. We have implemented the proposed scheme in YAFFS and evaluated its performance on the embedded board equipped with 400MHz XScale CPU, 64MB SDRAM, and 64MB NAND flash memory. Performance measurements have shown that the proposed scheme can reduce block cleaning time by up to 15.4 seconds with an average of 7.8 seconds compared to the typical YAFFS. Also, the enhancement becomes bigger as the utilization of flash memory increases.

• Korean Journal of Occupational Health Nursing
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• v.24 no.3
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• pp.183-193
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• 2015

Purpose: The purpose of this study was to describe cleaning workers' working experiences in Korea. Methods: The data were collected in two focus-group interviews with 9 cleaning workers. The phenomenological analytic method suggested by Colaizzi was used to analyze the data. Results: Five theme clusters and thirteen themes emerged from the analysis. The first theme clusters, 'Dead-end choice' included Limits of elderly women workers, Financial difficulties, Lowered self-esteem. The second theme clusters, 'Facing with discriminatory working environments' included Fear and unfair working conditions. The third theme clusters, 'Potential health problems' included Physical overload, Repeated exposure to hazardous substances and Emotional labor. The fourth theme clusters, 'Excluded from protection of the law' included Gloomy reality and Sexual harassment. The fifth theme clusters, 'Desire to get out of social isolation' included Efforts to maintain the status, Desire to live confidently and Desire to change social recognition. Conclusion: The findings of the study provide understanding on cleaning workers' working experiences to explain by their vision and language and should ensure proper working conditions and environment to live a better life.