• Journal of Electrochemical Science and Technology
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• 제2권3호
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• pp.131-135
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• 2011

It is, in general, believed that during the activation process, the proton conductivity increases due to wetting effect and the electrochemical resistance reduction, resulting in an increase in the fuel cell performance with time. However, until now, very scant information is available on the understanding of activation processes. In this study, dominant variables that effect on the performance increase of membrane electrode assemblies (MEAs) during the activation process were investigated. Wetting, pore restructuring and active metal utilization were analyzed systematically. Unexpectedly, the changes for both ohmic and reaction resistance characterized by the electrochemical impedance spectroscopy (EIS) after initial wetting process were much smaller when considering the degree of cell performance increases. However, the EIS spectra represents that the pore opening of electrode turns into gas transportable structure more easily. The increase in the performance with activation cycles was also investigated in a view of active metals. Though the particle size was grown, the number of effective active sites might be exposed more. The impurity removal and catalytic activity enhancement measured by cyclic voltammetry (CV) could be a strong evident. The results and analysis revealed that, not merely wetting of membrane but also restructuring of electrodeand catalytic activity increase are important factors for the fast and efficient activation of the polymer electrolyte fuel cells.

• 한국식품위생안전성학회지
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• 제12권4호
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• pp.328-332
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• 1997

In order to investigate the trace metals in Korean foods, the contents of Magnesium, Zinc, Manganese, Molybdenum and Selenium are studied in this paper. As show in the Table 1; a total of 250 samples of 25 species were analyzed by neutron activation analysis. The results obtained were as follows; 1. The overall ranges and mean (mg/100 g) were; Mg, 12.212∼151.346(55.164); Zn, 0.045∼38.180 (2.473); Mn, 0.003∼0.796 (0.225);Mo, ND∼0.035 (0.007); Se, ND∼0.069 (0.016). 2. The levels of all metals except Mo in shell fishes were high and the level of Mo in spices was higher than that in other foods. 3. The levels of Zn and Mo in oyster were higher than another spcies.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2581-2584
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• 2020

Boron has been considered to play a nutritionally important role in humans and animals, but its biochemical functions are not clearly understood. Though there are signs that boron affects the mineral and hormone metabolisms, there is no comprehensive epidemiological evidence establishing a relationship between a boron intake and osteoporosis due to the excretion of calcium in the bones. In this study, we investigated the influence of boron intake on the calcium excretion of old female mice in the menopause. The concentrations of calcium in backbone, thigh bone, blood, kidney, liver, and spleen were investigated by using instrumental neutron activation analysis.

• 분석과학
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• 제18권6호
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• pp.520-528
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• 2005

Two biological Certified Reference Materials (CRMs), KRISS 108-04-001 (oyster tissue) and 108-05-001 (water dropwort stem), were prepared by Korea Research Institute of Standards and Science (KRISS)during FY '01. The certified values of these materials had been determined by Isotope Dilution Mass Spectrometry (IDMS) for six elements (Cd, Cr, Cu, Fe, Pb and Zn). Additional analytical works are now progressing to certify the concentrations of a number of the environmental and nutrimental elements in these CRMs. The certified values in a CRM are usually determined by using a single primary method with confirmation by other method(s) or using two independent critically-evaluated methods. Instrumental Neutron Activation Analysis (INAA) plays an important role in the determination of certified values as it can eliminate the possibility of common error sources resulting from sample dissolution. In this study INAA procedure was used in determination of 23 elements in these two biological CRMs to acquire the concentration information and the results were compared with KRISS certified values.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1349-1354
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• 2018

Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) is widely used for the determination of trace elements in geological samples in Iran. In this paper, we have calculated the detection limits of neutron activation analysis (NAA) for some of the common elements in such samples utilizing the ORIGEN and MCNP codes and verified the simulations using the experimental results of three soil standard reference materials, namely, G02.SRM, G18.SRM, and G28.SRM. The results show that while the detection limit of ICP-AES method is usually in the mg/kg range, it is represented to the ${\mu}g/kg$ range for most of the elements of interest using the NAA method, and the simulations can be verified in a tolerance range of 20%.

• Bulletin of the Korean Chemical Society
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• 제7권5호
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• pp.347-353
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• 1986

Fisher's discriminant method has been applied to the problem of the classification of Korean potsherds, using their elemental composition as analyzed by neutron activation analysis. A combination of analytical data by means of statistical linear discriminant analysis has resulted in removal of redundant variables, optimal linear combination of meaningful variables and formulation of classification rules.

• Tribology and Lubricants
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• 제14권3호
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• pp.7-16
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• 1998

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose powder (average particle size: 17.77 $\mu$m) was investigated at room temperature with electric fields up to 2.5 KV/mm. For development of anhydrous ER suspensions using at wide temperature range, we aimed to know the effect of activation of phosphoric ester cellulose particles on the ER activities. As a first step, the anhydrous ER suspensions mixing with the phosphoric ester cellulose particles which were treated with 2M phosporic acid and 4M urea were measured. After activating the anhydrous ER suspensions at 12$0^{\circ}C$, not only the analysis of dispersing cellulose particles which were reacted by phosphoric ester but also the electrorheological characteristics of ER suspensions such as dielectric constant, current density, electrical conductivity and rheological properties were studied. From the experimental results, the activation of phosphoric ester cellulose particles had an influence on the ER properties of anhydrous ER suspensions. As the activation time went by, the size and number of dispersing particles, the electrical properties and the initial apparent viscosity $(η_0)$ of ER suspensions were increased till the activation time passed 5 hours. Also, it was possible, the electrorheological effect $($\tau$/$\tau$_0)$ of ER fluids was grown by the activation of phosphoric ester cellulose particles.

• 대한물리의학회지
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• 제9권3호
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• pp.271-278
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• 2014

PURPOSE: This study researched the effects of different types of high heels on the muscles surrounding the cervical spine, the thoracic spine, and the lumbar spine by analyzing muscle activation of the paraspinal muscles during walking while wearing high heels. The high heels were all of the same height: 8cm. METHODS: The 28 subjects in this experiment were females in their 20s with a foot size of 225-230mm. To measure the muscle activation of the paraspinal muscles, EMG electrodes were attached on the paraspinal muscles around C6, T7, and L5. The muscle activation during walking while wearing 8cm high wedge heels, setback heels, and french heels was measured. The measurements were performed 3 times each and the mean value of the result was used for analysis. Two kinds of velocity were used in this study. One of the velocity was 2.5 m/s. The other was 3.5 m/s. RESULTS: The muscle activation of paraspinal muscles increased significantly according to increase of walking velocity. But there was no significant difference according to the heel types. CONCLUSION: In view of the results, the height of heels and the velocity of walking are more convincing variables than the width of the heels on the muscle activation of paraspinal muscles. So wearing high heels is not recommended for those who have pain or functional problem of cervical and lumbar vertebrae.

• The Korean Journal of Physiology and Pharmacology
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• 제7권5호
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• pp.255-259
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• 2003

Dendritic cells (DCs) play a critical role in various immune responses involving $CD4^+$ T cells and have been used to generate anti-tumor immunity. Chemotherapy induces severe side effects including immunosuppression in patients with cancer. Although immunosuppression has been studied, the effects of anticancer drugs on DCs are not fully determined. In this study, we demonstrated that CD40 activation strongly protected DCs from 5-fluorouracil (5-FU) or mitomycin C-induced apoptosis. DCspecific surface markers, including CD11c and major histocompatibility complex (MHC) class II, were used for identifying DCs. CD 40 activation with anti-CD40 mAb significantly enhanced the viability of DCs treated with 5-FU or mitomycin C, assayed by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide). Fluorescence staining and analysis clearly confirmed the enhancing effect of anti-CD40 mAb on the viability of DCs, suggesting that CD40 activation may transduce critical signals for the viability of DCs. Annexin V staining assay showed that CD40 significantly protected DCs from 5-FU or mitomycin C-induced apoptosis. Taken together, this study shows that CD40 activation with anti-CD40 mAb has strong anti-apoptosis effect on DCs, suggesting that CD40 activation may overcome the immunosuppression, especially downregulation of number and function of DCs in chemotherapy-treated cancer patients.

• ETRI Journal
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• 제38권5호
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• pp.885-895
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• 2016

The lowest power mode (passive-standby mode) was proposed for reducing the power consumption of set-top boxes in a standby state when not receiving content. However, low-power set-top boxes equipped with the lowest power mode have been rarely commercialized because of their low-quality user experience. In the lowest power mode, they deactivates almost all of operational modules and processes, and thus require dozens of seconds for activation latency (that is, the latency for activating all modules of the set-top boxes in a standby state). They are not even updated in a standby state because they deactivate their network interfaces in a standby state. This paper proposes an adaptive standby mode scheduling method for improving the user experience of such boxes. Set-top boxes using the proposed method can analyze the activation pattern and find the frequently used time period (that is, when the set-top boxes are frequently activated). They prepare for their activation during this frequently used time period, thereby reducing the activation latency and enabling their update in a standby state.