• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.2
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• pp.81-86
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• 2008

ZnO nanowires were synthesized by the thermal evaporation method and their growth mechanisms were confirmed by the characterization of the structural features depending on the growth conditions. The increase of vaporization temperature accelerates the growth rate and morphologies of ZnO nanowires were drastically changed at the temperature over 1000$^{\circ}C$, because of changed $CO/CO_2$ partial pressure. Au particles play their role on growth of ZnO nanowire as catalyst at growth temperature over 700$^{\circ}C$. The synthesized ZnO nanowires exhibit blue emission at 380 nm.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.14 no.1
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• pp.40-46
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• 2003

Background and Objectives : The vocal fold granuloma has been associated with vocal abuse, gastroesophageal reflux, endotracheal intubation and habitual throat clearing etc.. Granuloma is benign growth of hypertrophic granulation tissue. It is usually located on the posterior third of vocal fold, in one or both vocal process of the arytenoid cartilage In spite of the voice therapy, steroid therapy, anti-reflex therapy and surgical procedure. The distinct advantage and uniform success rate of each methods have not been generally shown. Authors report that localized injection of botulinum toxin type A (BOTOX$^{\circledR}$) is the promising method both as an initial treatment and as an alternative treatment in patients who do not respond to standard therapy or who are poor surgical candidates. Materials and Method : We carried out a retrospective study of 9 patients with the diagnosis of vocal fold granuloma on the videostroboscopic examination from Jan 2000 to Mar 2003. The botulinum toxin type A was injected into one or both thyroarytenoid muscle or lateral cricoarytenoid muscle under the electromyography. The average dosage ranges from 6U to 8U per injection. Results : Unilateral vocal fold granuloma in 7 patients had been resolved completely within 2-3 months after first injection : 5 patients received th\ulcorner GER medical therapy in addition to the Botulinum toxin injections, 2 patients was resolved completely who had shown recurrence after $CO_2$ laser vaporization. 2 patients who had shown recurrence after $1^st$ injection were also completely resolved within 6 months after further injections. Conclusion : We expect that localized injection of Botulinum toxin type A can provide an alternative treatment for the refractory cases to the traditional forms of therapy and avoid the recurrence in conjunction with proper medical and voice therapy against GER and vocal abuse.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.9
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• pp.745-751
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• 2012

Hybrid rocket shows interesting characteristics of complicated mixing layers developed by interactions between turbulent oxidizer flow and mass flow from surface due to fuel vaporization. In this study, compressible LES with a ring structure attached at the entrance of the combustor are performed. According to one recent report, adding a ring structure in the middle of the combustor helps increasing regression rate. From the numerical results, it is seen that vortex structures near the wall becomes stronger due to the interaction with surface mass injection, and the local heat flux increases due to the vortices. This phenomenon is obviously related to the generation of dimple structures which are seen in the number of experiments. Also, the ring structure at the entrance induces strong vortex flow which enhances heat transfer to the wall surface and mixing between fuel and oxidizer as well as reaction efficiency.

• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.85-92
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• 1984

The aim of this study was to examine the influence of the speed of grinding and coolants on mercury vaporization during amalgam removal. Forty amalgam filled stone dies were stored at $37^{\circ}C$ and 100% relative humidity for 7 days prior to the beginning of the mercury vapor experiment and were divided into 4 different groups; In Group I; Used by high speed without coolant & evacuator during amalgam removal. In Group II; Used by high speed with coolant & evacuator during amalgam removal. In Group III; Used by low speed without coolant & evacuator during amalgam removal. In Group IV; Used by low speed with coolant & evacuator during amalgam removal. The amalgam specimens were removed in a 30-second time period and mercury vapor was collected with membrane filter at 27mm from the site of removal and 45 degree above there. Samples in Group II, IV were removed with coolant spray at a flow rate of 30 ml/min with high-velocity evacuator. Mercury vapor collected membrane filter was analysed by Atomic Absorption Spectrophotometer using cold vapor method. The results were as follows; 1. The mercury vapor levels were obtained all of the Groups. 2. The mercury vapor levels of the Group II, IV (with coolant & evacuator) were less than that of the Group I, III (without coolant & evacuator). 3. The highest mercury vapor level recorded during amalgam removal procedure was Group I (used by high speed without coolant & evacuator) and its record was $0.78{\pm}0.09\;mg/m^3$, which exceed the T.L.V. by 15 times. 4. The mercury vapor level of the Group IV (used by low speed with coolant & evacuator) was more than that of the Group II (used by high speed with coolant & evacuator), but its difference was not significant, statistically. (p > 0.05)

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.222-222
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• 2012

Metal oxide gas sensors based on semiconductor type have attracted a great deal of attention due to their low cost, flexible production and simple usability. However, most works have been focused on n-type oxides, while the characteristics of p-type oxide gas sensors have been barely studied. An investigation on p-type oxides is very important in that the use of them makes possible the novel sensors such as p-n diode and tandem devices. Monoclinic cupric oxide (CuO) is p-type semiconductor with narrow band gap (~1.2 eV). This is composed of abundant, nontoxic elements on earth, and thus low-cost, environment-friendly devices can be realized. However, gas sensing properties of neat CuO were rarely explored and the mechanism still remains unclear. In this work, the neat CuO layers with highly ordered mesoporous structures were prepared by a template-free, one-pot solution-based method using novel ink solutions, formulated with copper formate tetrahydrate, hexylamine and ethyl cellulose. The shear viscosity of the formulated solutions was 5.79 Pa s at a shear rate of 1 s-1. The solutions were coated on SiO2/Si substrates by spin-coating (ink) and calcined for 1 h at the temperature of $200{\sim}600^{\circ}C$ in air. The surface and cross-sectional morphologies of the formed CuO layers were observed by a focused ion beam scanning electron microscopy (FIB-SEM) and porosity was determined by image analysis using simple computer-programming. XRD analysis showed phase evolutions of the layers, depending on the calcination temperature, and thermal decompositions of the neat precursor and the formulated ink were investigated by TGA and DSC. As a result, the formation of the porous structures was attributed to the vaporization of ethyl cellulose contained in the solutions. Mesoporous CuO, formed with the ink solution, consisted of grains and pores with nano-meter size. All of them were strongly dependent on calcination temperature. Sensing properties toward H2 and C2H5OH gases were examined as a function of operating temperature. High and fast responses toward H2 and C2H5OH gases were discussed in terms of crystallinity, nonstoichiometry and morphological factors such as porosity, grain size and surface-to-volume ratio. To our knowledge, the responses toward H2 and C2H5OH gases of these CuO gas sensors are comparable to previously reported values.

• Clean Technology
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• v.9 no.4
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• pp.189-196
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• 2003

ZnO-CuO mixed sorbents for desulfurization in hot gas cleaning process Were prepared and investigation on their characteristics was performed in this study. The rate of sulfidation increased as the amount of copper oxide in the composite sorbent was raised. TPO experiments were carried out to investigate the characteristics of the regeneration of the sorbents with severa1 different ratios of Zno to CuO. Copper sulfate was formed at temperatures above $400^{\circ}C$, while it was decomposed by pyrolysis above $700^{\circ}C$. $SO_2$ slippage due to $CuSO_4$ was observed in the sorbent regenerated at temperatures above $600^{\circ}C$. However, it was not observed when regenerated above $700^{\circ}C$. It was confirmed in the ZnO-CuO mixed sorbent system that CuO suppressed the vaporization of ZnO on the one hand and Zno minimized the $SO_2$ slippage due to CuO on the other hand.

• Applied Chemistry for Engineering
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• v.31 no.4
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• pp.443-451
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• 2020

In this study, the physico-chemical properties and pyrolysis kinetics of livestock mature solid fuel were investigated to know its feasibility as a fuel. Ultimate and proximate analysis results showed that livestock mature solid fuel has high contents of volatile matter (64.94%), carbon (44.35%), and hydrogen (5.54%). The low heating value of livestock mature solid fuel (3880 kcal/kg) was also higher than the standard requirement of solid fuel (3000 kcal/kg). Thermogravimetic analysis results indicated that livestock mature solid fuel has three decomposition temperature regions. The first temperature zone (130~330 ℃) was consisted with the vaporization of extracts and the decomposition of hemicellulose and cellulose. The second (330~480 ℃) and third (550~800 ℃) temperature regions were derived from the decomposition of lignin and additional decomposition of carbonaceous materials, respectively. The activation energy derived from model free kinetic analysis results including Friedman, Flynn-Wall-Ozawa (FWO), and Kissinger-Akahira-Sunose (KAS) methods for the pyrolysis of livestock mature solid fuel was in the range of 173.98 to 525.79 kJ/mol with a conversion rate of 0.1 to 0.9. In particular, the activation energy increased largely at the higher conversion than 0.6. The kinetic analysis using a curve-fitting method suggested that livestock mature solid fuel was decomposed via a multi-step reaction which can be divided into five decomposition steps.

• Journal of Korea Soil Environment Society
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• v.3 no.2
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• pp.101-114
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• 1998

Soil vapor extraction (SVE) is known to be an effective process to remove the contaminants from the soils by enhancing the vaporization of organic compounds using forced vapor flows or applying vacuum through soils. Experiments are carried out to investigate the effects of the organic contaminants, types of soils, and water contents on the removal efficiency with operating time. In the study, simulated soils include the glass bead which has no micropore, sand and molecular sieve which has a large volume of micropores. As model organic pollutants, toluene, methyl ethyl ketone, and trichloroethylene are selected. Desorption experiments are conducted by flowing nitrogen gas. Under the experimental conditions, it is found that there are linear relationships between logarithm of removal efficiency and logarithm of number of pore volumes. The number of pore volumes are defined as the total amount of air flow through the soil column divided by the pore volume of soil column. For three organic compounds studied, the removal rate is slow for no water content, while the number of pore volumes for removal of organic compounds are notably reduced for water contents up to 37%. For the removal of dense organic compound, such as trichloroethylene, a large number of pore volumes are needed. Also, the effects of the characteristics of simulated soils on the removal efficiency of organic compounds are studied. After the characterization of soil surface, porosity of soil columns and types of contaminants, the results could provide a basis for the design of SVE process.

• Clean Technology
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• v.20 no.4
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• pp.383-389
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• 2014

$CO_2$ absorption processes have a good potential for large scale capture of $CO_2$ but a large amount of absorbing solution has to be regenerated, undesirably increasing the consumption of energy such as sensible heat and latent heat of vaporization. In this study, a cooling crystallization process which would separate the $CO_2$-rich potassium bicarbonate crystals from $CO_2$-lean water was developed to reduce the energy penalty. Sterically hindered alkanolamine additives were used to enhance the $CO_2$ removal efficiency and their antisolvent effect on the crystallization was found in a continuous cooling crystallizer. The production yields of crystals were increased in the sequence of 2-amino-2-methyl-1-propanol (AMP) < 2-amino-2-methyl-1,3-propanediol (AMPD) < 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), which are related to the number of hydroxyl groups in the additive molecules. Using $^{13}carbon$ nuclear magnetic resonance, the additives favored the formation of bicarbonate ions by steric hindrance effect and increased the supersaturation of $KHCO_3$. It is shown that the additives increase the mean size of crystals and crystal growth rate by increasing supersaturation. The additives are promising for enhancing the $CO_2$ removal efficiency and reducing the regeneration energy cost of $CO_2$ absorbing solution by promoting $KHCO_3$ crystallization.

• The Korean Journal of Pesticide Science
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• v.20 no.4
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• pp.305-311
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• 2016

In cultivation environment, various pesticides are used and some of them could be volatilized into the air. This could affect farmer's health and also cause environmental pollution. This study was carried out to investigate the volatilization of pesticides, and use the reference data for preventing farmer's pesticide intoxication and securing worker safety. The experiment was conducted in a greenhouse using a lysimeter which was of $1m^2$ area and 1.5 m depth filled with upland soil. The pesticides treated in lysimeter soil were ethoprophos (5.0% GR), diazinon (34.0% EC), alachlor (43.7% EC), metolachlor (40.0% EC), chlorpyrifos (2.0% GR), pendimethalin (31.7% EC), carbaryl (50.0% WP), napropamide (50% WP), tebuconazole (25.0% WP) and imidacloprid (2.0% GR). Each pesticide was treated at a concentration of 770.5 mg based on A.I (%). The recovery of pesticide ranged from 77.4 to 99.3%. The volatilized pesticides in air were collected by personal air sampler with PUF tube at 4 l/min flow rate. In addition, temperature and humidity were measured. The collected samples were extracted using acetone in a soxhlet apparatus for 8 hours. The extracted pesticides were resoluted with acetonitrile and diluted 5 times. It was analyzed with LC-MS/MS. For 720 hours experiment, the largest vaporization amount of each pesticide in air was ethoprophos $15.24{\mu}g/m^3$, diazinon $5.14{\mu}g/m^3$, pendimethalin $2.70{\mu}g/m^3$, chlorpyrifos $1.76{\mu}g/m^3$, alachlor $1.40{\mu}g/m^3$, metolachlor $1.12{\mu}g/m^3$, carbaryl $0.27{\mu}g/m^3$, napropamide $0.22{\mu}g/m^3$, tebuconazole $0.11{\mu}g/m^3$ and imidacloprid $0.05{\mu}g/m^3$. The R value (coefficient of correlation) between volatilization and vapor pressure of pesticides is higher than 0.99. Therefore, there is high correlation between volatilization and vapor pressure of pesticides.