• Journal of Preventive Medicine and Public Health
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• v.45 no.6
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• pp.344-352
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• 2012

Mercury is a toxic and non-essential metal in the human body. Mercury is ubiquitously distributed in the environment, present in natural products, and exists extensively in items encountered in daily life. There are three forms of mercury, i.e., elemental (or metallic) mercury, inorganic mercury compounds, and organic mercury compounds. This review examines the toxicity of elemental mercury and inorganic mercury compounds. Inorganic mercury compounds are water soluble with a bioavailability of 7% to 15% after ingestion; they are also irritants and cause gastrointestinal symptoms. Upon entering the body, inorganic mercury compounds are accumulated mainly in the kidneys and produce kidney damage. In contrast, human exposure to elemental mercury is mainly by inhalation, followed by rapid absorption and distribution in all major organs. Elemental mercury from ingestion is poorly absorbed with a bioavailability of less than 0.01%. The primary target organs of elemental mercury are the brain and kidney. Elemental mercury is lipid soluble and can cross the blood-brain barrier, while inorganic mercury compounds are not lipid soluble, rendering them unable to cross the blood-brain barrier. Elemental mercury may also enter the brain from the nasal cavity through the olfactory pathway. The blood mercury is a useful biomarker after short-term and high-level exposure, whereas the urine mercury is the ideal biomarker for long-term exposure to both elemental and inorganic mercury, and also as a good indicator of body burden. This review discusses the common sources of mercury exposure, skin lightening products containing mercury and mercury release from dental amalgam filling, two issues that happen in daily life, bear significant public health importance, and yet undergo extensive debate on their safety.

• Preventive Nutrition and Food Science
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• v.15 no.3
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• pp.213-220
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• 2010

To examine the potential of Terminalia chebula as a whitening agent, we measured antioxidant activity using DPPH$\cdot$, ABTS${\cdot}^+$ assays and ferric-reducing antioxidant power (FRAP) assays, and depigmenting activity using B16F10 melanoma cells. The intracellular reactive oxygen species (ROS) level was monitored by $H_2DCFDA$ fluorescence labeling, and melanin contents in B16F10 melanoma cells by 960 $J/m^2$ dose of UVA-induced oxidative stress. The radical-scavenging activities of T. chebula extract (TCE) were measured in terms of $EC_{50}$ values using DPPH$\cdot$, ABTS${\cdot}^+$ assays and FRAP value were 280.0 ${\mu}g/mL$, 42.2 ${\mu}g/mL$ and 113.1 ${\mu}mol$ $FeSO_4{\cdot}7H_2O/g$, respectively. We found that ROS and melanin concentrations were reduced by TCE treatments of 25 ${\mu}g/mL$ under UVA-induced oxidative stress. Tyrosinase activity and melanin contents in $\alpha$-melanocyte stimulating hormone (MSH)-induced melanoma cells both decreased dose-dependently in the treatment groups. TCE similarly reduced melanogenesis in B16F10 melanoma cells stimulated by $\alpha$-MSH as compared to arbutin as a positive control. T. chebula may prove to be a useful therapeutic agent for hyperpigmentation and an effective component in skin whitening and.or lightening cosmetics.

• Bulletin of the Korean Space Science Society
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• 2009.04a
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• pp.54.3-55
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• 2009

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.6
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• pp.506-511
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• 2017

LED lighting, which many companies are pursuing commercialization, is a representative green energy technology. However, the LED lighting for broadcasting image should have high output and easy portability compared with general LED lighting devices for street lamps, advertisement or transportation devices. Therefore, while shooting a broadcast image if you use LEDs as a substitute light source for halogen lamps and fluorescent lamps that are large in size and uncomfortable to handle it is expected that the lightening of the equipment will activate the broadcasting image lighting equipment industry. After considering the mass production of the LED module board and the SMT production size of the chip mounter, the board size was determined considering the overall size of the product by model. In this paper, four 20W LED boards are arranged vertically in order to produce an 80W board. In other words, by sharing LED module board size by model, high power LED lighting equipments of 120W and 200W can be selected as an increase in the number of boards.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4171-4177
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• 2013

Outer tie rod is lighter than other, but there is the trend item weight and the number is increasing due to vehicle performance improvement. Thus, to improve vehicle fuel efficiency, weight lightening is essential. Therefore, this research performed the finite element analysis to investigate the structural performance of the outer tie rod for an electrical vehicle. This study was performed as the preliminary study for a lightweight design of the outer tie rod. The weight of outer tie rod was optimized by adopting the steel material and applying the trial and error method. The strengths due to durability and buckling should be considered in the structural design of an outer tie rod. Furthermore, the meta model-based optimization was applied to obtain its lightweight design, leading to 9 % weigh reduction.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.513-518
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• 2012

Recently, automobile parts have been required to have high strength and toughness to allow for weight lightening or improved stability. But, traditional micro-alloyed steel cannot be applied in automobile parts. In this study, we considered the influence of quenching temperature and cooling rate for specimens fabricated by vacuum induction furnace. Directly quenched micro-alloyed steel for hot forging can be controlled according to its micro structure and the heat-treatment process. Low carbon steel, as well as alloying elements for improvement of strength and toughness, was used to obtain optimized conditions. After hot forging at $1,200^{\circ}C$, the ideal mechanical properties (tensile strength ${\geq}$ 1,000 MPa, Charpy impact value ${\geq}\;100\;J/cm^2$) can be achieved by using optimized conditions (quenching temperature : 925 to $1,050^{\circ}C$, cooling rate : ${\geq}\;5^{\circ}C/sec$). The difference of impact value according to cooling rate can be influenced by the microstructure. A fine lath martensite micro structure is formed at a cooling rate of over $5^{\circ}C/sec$. On the other hand, the second phase of the M-A constituent microstructure is the cause of crack initiation under the cooling rate of $5^{\circ}C/sec$.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.7-14
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• 2019

The type III vessel, which is used to store high-pressure hydrogen gas, is made by wrapping the vessel's liner with carbon fiber composite materials for strength performance and lightening. The liner seals the internal gas and the composite resists the internal pressure. The properties of the fiber composite material depends on the angle and thickness of the fiber. Thus, engineers should consider these various design variables. However, it significantly increases the design cost due to the trial and error under designing based on experience or experiments. And, for aluminum liners, fatigue loads due to using and charging could give a huge impact on the performance of the structure. However, fatigue failure does not necessarily occur in the position under the highest load in use. Therefore, for hydrogen storage vessel, fatigue evaluation according to design patterns is essential because stress distribution varies depend on composite layer patterns. This study performed an optimization analysis and evaluated a high-pressure hydrogen storage vessel to minimize these trial and error and improve the reliability of the structure, while simultaneously conducting fatigue assessment of all patterns derived from the optimization analysis process. The results of this study are thought to be useful in the strength improvement and life design of composite reinforced high-pressure storage vessels.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.5
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• pp.941-946
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• 2021

This paper is a study on the design and implementation of a rehabilitation wearable robotic hand that reduces weight and volume by using a 3D printer and a motor. Rehabilitation wearable robots are important not only for the effect of rehabilitation but also for ease of use. However, most of the currently researched and developed rehabilitation exoskeleton robots are heavy in volume and weight, or they have to be used in place. Therefore, a wearable robot that is easy to wear and does not burden the user is required, so a lightweight electric rehabilitation wearable robot hand is proposed. A 3D printer was used to reduce the weight and volume and to make it easier to wear. In addition, to increase portability, the structure was simplified by adopting an electric method rather than a pneumatic method. Finally, the effectiveness was examined through the experiment of the lightweight electric rehabilitation wearable robot hand.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.5
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• pp.135-141
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• 2021

As a trend of lightening automobiles and electronic products, several studies are currently underway to replace parts of metals with resins. In particular, heterojunctions between metals and resins are now under the spotlight. This study aims to evaluate the variation in bonding strength with process conditions when the polybutylene terephthalate (PBT) polymer is bonded to a specimen of the lightweight 6061 aluminum alloy (AL6061). Conditions of the bonding surface of the AL6061 specimen, the temperature of the injection mold, and the content of the glass fiber were considered to be process variables. Bonded specimens were manufactured for different values of these variables. Bonding strength tests were then performed on these specimens and variations were analyzed in their characteristics corresponding to those of the process conditions. Fractures in these specimens were assessed using scanning electron microscopy (SEM) to assess the fracture surface. This was then used to analyze the fracture shape and determine whether anodizing the specimen led to the development of cracks on the joint surface. Results of the above test indicated that while the surface condition of the specimen and the temperature of the injection mold significantly influenced the strength of bonding, the content of the glass fiber did not.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.3
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• pp.299-310
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• 2019

Increase of combat capability through the lightweighting of vehicles has been internationally issued. One of the methods for lightening is applying high hardness armor(HHA) steel which is outstanding ballistic performance and protection performance compared to weight. Development of HHA steel is currently completed in America, United Kingdom, Australia and Germany. It is used for not only combat vehicle, but also various combat device. Korea is developing new material of HHA steel according to this trend. When such HHA steel is applied to structure, welding process is used for connection of the structure. Cracks from hydrogen embrittlement and cold cracking are easily generated in welds of HHA steel and it greatly affects the strength of all structure. Decrease of strength from welding defect is critical to combat capability. Therefore, welding process optimization is important for performing the role of structure. In this study, international welding technology is reviewed through scientific research paper and patent.