• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.269-278
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• 2011

We investigate the heat-transfer and pressure-drop characteristics of fin-and-tube heat exchangers with a copper plate or copper spiral fins. Twenty-four samples with different fin pitches and tube rows were tested. For both configurations, the effect of the fin pitch on the j factor is negligible, and the f factor increases with the fin pitch. The effect of the tube row depends on the configuration. For plate fin-and-tube heat exchangers, the j factor decreases as the row number increases; the reverse is true for spiral exchangers. We explain this by considering the flow pattern. The j factor for plate fin-and-tube heat exchangers is larger than that for spiral exchangers, and the difference decreases as the row number increases. The f factor of the plate fin-and-tube heat exchanger is also larger. We compare our results with existing predictions of correlations.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.83-90
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• 2011

Removal of dissolved uranium by D. baculatum, a sulfate-reducing bacterium, and effects of trace metals such as manganese, copper, nickel, and cobalt were investigated. Total concentrations of dissolved uranium and trace metals were used by $50\;{\mu}M$ and $200\;{\mu}M$, respectively. Most dissolved uranium decreased up to a non-detectable level (< 10 ppb) MS during the experiments. Most of the heavy metals did nearly not affect the bioremoval rates and amounts of uranium, but copper restrained microbial activity. However, it is found that dissolved uranium rapidly decreased after 2 weeks, showing that the bacteria can overcome the copper toxicity and remove the uranium. It is observed that nickel and cobalt were readily coprecipitated with biogenic mackinawite.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.442-448
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• 2021

Flow field is an important parameter for polymer electrolyte membrane fuel cell (PEMFC) performance to have an effect on the reactant supply, heat and water diffusion, and contact resistance. In this study, PEMFC performance was investigated using Cu foam flow field at the cathode of 25 cm² unit cell. Polarization curve and electrochemical impedance spectroscopy were performed at different pressure and relative humidity conditions. The Cu foam showed lower cell performance than that of serpentine type due to its high ohmic resistance, but lower activation and concentration loss due to the even reactant distribution of porous structure. Cu foam has the advantage of effective water transport because of its hydrophobicity. However, it showed low membrane hydration at low humidity condition. The metal foam flow field could improve fuel cell performance with a uniform pressure distribution and effective water management, so future research on the properties of metal foam should be conducted to reduce electrical resistance of bipolar plate.

• Food Science of Animal Resources
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• v.28 no.1
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• pp.27-31
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• 2008

This study investigated the effects of copper and zinc sources on growth performance, nutrient digestibility, carcass traits and meat characteristics in finishing pigs. Dietary treatments included 1) inorganic copper ($CuSO_4{\cdot}5H_2O$ 30ppm), 2) organic copper (Cu-methionine, 30 ppm), 3) inorganic zinc (ZnO, 80 ppm) and 4) organic zinc (Zn-methionine, 80 ppm). ZnO treatment improved the ADFI (average daily feed intake) compared to Cu-met and Zn-met treatments (p<0.05) during 5 weeks of treatment. However, during the entire experimental period, the ADG (average daily gain), ADFI and F:G ratio (feed conversion ratio) were not significantly different among the treatments (p>0.05). DM and N digestibility were not significantly different among the treatments after 5 weeks (p>0.05). At the end of the experiment, DM and N digestibility were decreased with Zn-met treatment relative to the other three treatments. The pH value of meat from $CuSO_4$ treated pigs was greater than Zn-met and ZnO treated pigs (p<0.05). Sensory evaluation was carried out for randomly selected (n = 16) paired loin samples. Meat color levels were increased (p<0.05) with Cu treatments compared to Zn treatments. $CuSO_4$ decreased the marbling of meat relative to the other treatments (p<0.05). The firmness was greater with ZnO treatment compared to Cu-met and ZnO treatments (p<0.05). These results indicate that inorganic Zn can improve growth performance, however, inorganic Cu and Zn are as effective as organic Cu and Zn at improving nutrient digestibility, carcass traits and meat quality. This form of organic additive can be friendlier to the environment than inorganic supplements.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.1
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• pp.51-55
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• 1998

The experiment was conducted to elucidate the growth response of rice seedling to heavy metals, copper and zinc. The copper and zinc concentration in rice seedling was 50mg/l and 100mg/l, respectively. Germination. chlorophyll and organic compounds were investigated in seedling of rice with or without heavy metals. Root growth and germination were inhibited at 50mg/l Cu and at 100mg/l compared to control and such reduction in growth was more remarkable at 100mg/l Zn than at 50mg/l Cu. Chlorophyll content was slightly reduced at both 50mg/l Cu and 100mg/l Zn. Malic acid was remarkably increased at 50mg/l Cu compared with that at Zn 100mg/l regardless of rice cultivars. The content of organic acids such as succinic, citric, and malic acid and free proline was increased with treatment of copper and zinc.

• Clean Technology
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• v.27 no.1
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• pp.17-23
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• 2021

Black polymer spacers are currently used for physically separating aligned camera lenses in camera modules of mobile phones. However, the mechanical properties of polymer spacers have their limits, especially in the current trend of using more lenses in thinner camera modules. Thus, copper (Cu) becomes a good candidate for those polymer spacers because of its superior mechanical properties and its inherent blackness due to its black surfaced oxides, such as copper (II) oxide (cupric oxide, CuO). The latter property is critical in quality control because the closer the color of a spacer is to black, the less light interference and flaring phenomena can occur. A standard Cu blackening process and its operational conditions were proposed in this study through a comprehensive analysis of previous research and patents. The Cu blackening process is composed of cleaning, deoxidizing, activating, blackening and sealing. The effects of operational parameters, such as the temperature of each unit process and the activator concentration, were then investigated by measuring the blackness of the Cu strips with a colorimeter. The proposed operational conditions were determined by whether the blackness of Cu strips was within the on-spec. value used in the field.

• Korean Journal of Environmental Biology
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• v.28 no.2
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• pp.64-68
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• 2010

The mosquito, Aedes albopictus is important vector of humen phatogen such as dengue fever. And Aedes albopictus has widly distribution in oriental regions. This study was conducted to investigate the biological effects of cooper on the development of the Asian tiger mosquitoes, Aedes albopictus (Skuse). Aedes albopictus was affected with pupation ratios, mortalities, and wing lengths of the 3th and 4th instars by exposure to different concentration $CuCl_2$ (0.0, 2.5, 25.0 and 50.0 ppm) for 24 h and 48 h depending on dose and exposure period. The lowest $LC_{50}$ (median lethal concentration) value of $CuCl_2$ was 18.1 ppm at the 3rd instars for 48 h exposure. The pupation ratio of the larvae exposed at 50.0 ppm for 48 h was 14% which was much lower than those exposed to other treatment groups Changes of adult wing length showed significant decreased by Cu treatment. In conclusion, the most prominent effects of high concentration and longer exposure period were to reduce in the survival and pupation rates of larvae and wing length of Ae. albopictus.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.139-146
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• 2014

In this research, we quantified the environmental load while using and not using secondary resources. During the process of primary processed product of metal resources (copper, aluminum), we applied LCA technique and analyzed by dividing into 8 environmental impact categories that affect the environment. Furthermore, we analyzed the greenhouse gas that occur during the process of primary processed product domestically and globally according to the changes of each metal resource's recycling rate. Consequently, when producing 1 ton of copper using secondary resources, the environmental effects were found to be 6.09E + 01 person-yr/f.u. and 7.23E + 01 person-yr/f.u. Additionally, as the recycling rate increased both globally and domestically, the amount of greenhouse gas decreased. Producing 1 ton of Aluminum using secondary resources, the environmental effects were found to be 2.34E + 02 person-yr/f.u. and 3.01E + 02 person-yr/f.u. Moreover, as the recycling rate domestically decreased, the amount of greenhouse gas increased, however the globally was decreased.

• Investigative Magnetic Resonance Imaging
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• v.13 no.2
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• pp.171-176
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• 2009

Purpose : To investigate the effect of coating material in RF coil, which is one of main parts in MRI machine, on the Q-factor and SNR(signal-to-noise ratio) in MR images. Materials and Methods : RF coils with inner diameter of 1.7 mm were made by using copper wires coated with polyester, polyurethane, polyimide, polyamideimide, and polyester-imide, and by using copper wires in which coating materials had been removed. Q-factors of the RF coils were measured by network analyzer, and SNR values in the spin-echo MR images obtained by 600 MHz (14.1 T, Bruker DMX600) micro-imaging system for the coated and uncoated cases. Results : The measured SNRs were almost same for the RF coils with coat-removed copper wires, however SNRs and Q-factors were different for the coated cases depending on the coating material. They were maximized in the polyurethane-coated case in which the SNR was > 30% greater than polyester-coated case. Conclusion : We made solenoid-type RF coils which were easily used for MR micro-imaging in Bruker MRI probe. There was a significant coating-material dependence in the measured Q values and SNRs for the home-made RF coils. The study demonstrated that the choice of coating material of RF coil may be a critical factor in the MRI sensitivity based on SNR value.

• Korean Journal of Psychosomatic Medicine
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• v.30 no.2
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• pp.137-144
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• 2022

Objectives : This study was designed to investigate the effect of sleep quality on depression symptoms and the mediating effect of interpretation bias and anxiety symptoms in psychiatric patients. Methods : Data accumulated for outpatients and inpatients in the Department of Mental Health Medicine at Hanyang University Guri Hospital were used. The measurement tools were Pittsburgh Sleep Quality Index (PSQI), Ambiguous/Unambiguous Situations Diary-Extended Version (AUSD-EX), Beck Anxiety Inventory (BAI), Beck Depression Inventory-II (BDI-II). Correlation analysis and bootstrapping analysis were conducted using SPSS 25.0 and SPSS Macro based on 162 patient data. Results : As a result of the study, the double mediating effect of interpretation bias for Ambiguity and anxiety symptoms was significant in the relationship between sleep quality and depression symptoms. Conclusions : In this study, it was confirmed that low sleep quality sequentially affects anxiety and depression symptoms through interpretation bias for ambiguity. Based on this, it is expected that the development of other psychiatric symptoms can be prevented by preferentially performing therapeutic intervention on preceding symptoms.