• Korean Journal of Materials Research
• /
• v.7 no.2
• /
• pp.152-156
• /
• 1997

In this paper, I meritioned ,I study on thc rnechanochernic;~l effec ts of grountl iljckite To investigate the mechanochemical effects of ground tlickite 1,y planet,~r\- mill. a structul-ill i~nalvsis of dickite prepared with different grinding time has been made 11y X-ray diffraction and ilifierenti,~l tl~i.~-ni;~i analysis. 'l'he $SiO_{4}$ hecira was unchanged bl- milling and remained ;is the local ordering unit s t t - ~ c ~ u ~ - c ~ s in the ground dickitc samples I ) v analyzing the radial distribution function. On the other hand, with an increi~se of the grinding time a decrease of coordination number and atomic distance bet\vccn aluminum and oxygen hi1c.r l~een octurreil, and Li~~antitativcl\. coniirrned them This result corresponded to the local c,hange around aliimi~iuni I>V tliftercntii~l t1ii:rm;il ani~lysis. Therefore, the mechanochemical phenomina of ground tiickite werc3 h e to the local c~l~mge around aluminum \IT. the prolonged grinding.

• Journal of the Korean earth science society
• /
• v.26 no.3
• /
• pp.283-296
• /
• 2005

The effect of ozone and surface temperature on the ozone band at $9.7{\mu}m$ has been investigated from radiative transfer theory together with observations in order to derive empirical methods for remotely sensing ground-ozone concentration. Simultaneous observations of satellite (MODIS Aqua; ECT 13:30) and ground-ozone at 79 stations have been used over the Seoul Metropolitan Area (SMA; 125.7-127.2 E, 37.2-37.7 N) during four ozone-warning days in the year 2003. Cloud effect on the band in the methods was filtered out based on synoptic observations. Upwelling radiance values at $9.6{\mu}m$ which have been estimated at the given ozone concentration of 327-391 DU depend on surface temperature (Ts) showing $5.52\~5.78Wm^{-2}sr^{-1}\;at\;Ts = 290 K,\;and\;9.00\~9.57Wm^{-2}sr^{-1}$ Ts = 325K. Thus, the partitioned contributions of ozone and temperature to intensity of ozone absorption band are $0.26Wm^{-1}sr^{-1}/64\;DU\;and\;0.31 Wm^{-2}sr^{-1}/35K$, respectively. Here the intensity which has been used to remotely detect ground-ozone concentration from infrared satellite measurement is defined as the difference in brightness temperature between $11{\mu} m\;and\;9.7{\mu}m (i.e.,\; T_{11-9.7})$. The methods in this study have been applied to estimate ground-ozone from MODIS data in cases that there are significant correlations between the band intensity and ground-ozone. The values of estimated ozone significantly correlate (0.49-0.63) with ground observations at a significance level of $1\%$. For the improved methods, further study may be required to use tropospheric ozone rather than ground-ozone, considering the variation stratospheric ozone.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2000.11b
• /
• pp.43-48
• /
• 2000

This paper introduces MPEG-2 AAC codec system fur digital audio broadcasting. This system consists of encoder and decoder, and this system provides MPEG-2 system multiplexing and demultiplexing functions. Four DSPs are adopted fur encoder and three DSPs fur decoder. Each DSP processes system control, I/O control, and audio signal processing, multiplexing and demultiplexing. This paper also discusses about some near future estimations related to DAB system and services. And at the end of this paper describes about future development plans.

• Journal of Korean Society of Water and Wastewater
• /
• v.22 no.2
• /
• pp.179-182
• /
• 2008

The KIDEA process, occurred in single reactor, is operated by three consequential steps, i.e., aerobic, settling, and discharge while introducing wastewater into the bottom of reactor continuously. It could accomplish biological oxidation (BOD), nitrification, denitrification (T-N), phosphate removal (T-P), and solid separation (SS) through the operational mode mentioned. Especially, this system has removed the T-P by wasting certain amount of sludge at the end of aeration phase during 5~10 minutes and not returned the activated sludge into the reactor, that is, no RAS (Return Activated Sludge). All running mode and instrumentation were controlled by the PLC equipment automatically. In this study, therefore, we have evaluated T-P removal efficiency and moisture content (MC) performance under the different excess sludge wasting mode. T-P track study and MC with TS concentration were analyzed during aerobic and settling phase. It has revealed that there was no significant difference of released T-P concentration between the first case which waste the sludge at the end of aerobic phase (0.2mg/L) and the second case which waste the sludge at 40 min of settling phase (0.25mg/L). Also, dewatering duration and MC have decreased 1.7% when TS concentration was increased from 0.31% to 0.5% during aerobic condition. Hence, it has concluded the system performance was less influenced by the operation time change of PLC program.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.104-106
• /
• 2003

다층의 산화물 박막으로 이루어진 coated conductor의 제조를 위하여 각층의 증착조건이 최적화되어야 한다. 가공/열처리를 통하여 2축배향성을 가지는 Ni 금속 기판위에 $Y_2O_3$, YSZ, $CeO_2$ 등의 산화물 완충층을 증착한 후 초전도층인 YBCO를 증착하였다. 12도와 8도의 in-plane fwhm (full width at half maximum)과 out-of-plane fwhm을 가지는 Ni 기판을 이용하여 13도와 4.5도의 in-plane 및 out-of-plane fwhm을 가지는 YBCO coated conductor를 제조하였다. 임계온도 (Tc), 임계전류 (Ic), 및 임계전류밀도 (Jc) 는 각각 84K, 3.3A, 및 $310,000\;A/cm^2$ 이었다.

• Journal of the Korean Ceramic Society
• /
• v.36 no.1
• /
• pp.36-42
• /
• 1999

Stacking faults in SiC whiskers grown by three different growth mechanisms; vapor-solid(VS), two-stage growth(TS), and vapor-liquid-solid (VLS) mechanism in the carbothermal reduction system were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The content of stacking faults in SiC whiskers increased with decreasing the diameter of whiskers, i.e., the small diameter whiskers (<1 $\mu\textrm{m}$) grown by the VS, TS, and VLS mechanisms have heavy stacking faults whereas the large diameter whiskers(>2$\mu\textrm{m}$) grown by the VLS mechanism have little stacking faults. Heavy stacking faults of small diameter whiskers was probably due to the high specific lateral surface area of small diameter whiskers.

• International conference on construction engineering and project management
• /
• 2022.06a
• /
• pp.67-73
• /
• 2022

Construction bid documents contain various errors or discrepancies giving rise to uncertainties. The errors/discrepancies/ambiguities in the bid document, if not identified and clarified before the bid, may cause dispute and conflict between the contracting parties. Given the fact that bid document is a major resource in estimating construction costs, inaccurate information in bid document can result in over/under estimating. Thus, any questions from bidders related to the errors in the bid document should be clarified by employers before bid submission. This study aims to examine the pre-bid queries, i.e., pre-bid request for information (RFI), from state DoTs of the United States to investigate error types most frequently encountered in bid documents. For the study, around 200 pre-bids RFI were collected from state DoTs and were classified into several error types (e.g., coordination error, errors in drawings). The analysis of the data showed that errors in bill of quantities is the most frequent error in the bid documents followed by errors in drawing. The study findings addressed uncertainty types in construction bid documents that should be checked during a bid process, and, in a broader sense, it will contribute to advancing the construction management body of knowledge by clarifying and classifying bid risk factors at an early stage of construction projects.

• Journal of Chest Surgery
• /
• v.29 no.7
• /
• pp.734-740
• /
• 1996

The relative importance of various factors influencing the prognosis and survival in the treatment of thymoma is still controversial. Sixty ave patients operated on for thymoma from Jan. 1981 to Dec. 1994 were evaluated, 28 patients (43.1 %) with myasthenia gravis and 37 patients (56.9%) without. Masaoka staging revealed stage I disease in 28 patie ts(4).1%) , stage ll in 1) patients(20.0%), stage 111 In 22 patients(33.8%), stage IVa in 1 patients(1.5%), and stage IVb in 1 patient(1.5%). There was no operative mortality. A complete resection was performed in 48 patients (73.8%) patients, associated in 10 patients (15.4%) with postoperative adjuvant treatment(radiotherapy 5; chemotherapy 1: radio- and chemotherapy 4). Thymomas were found to be predominantly of the epithelial type in 16 patients(24.6%), predominantly Iymphocytic type in 18 patients(27.7%), and mlxed in 22 patients (33.9%). The overall 5- and 10-year survival rates were 87% and 82%, respectively, Factors indicating a poor prognosis included local invasion, incomplete excision, thymic carcinoma, advanced staging and myasthenia gravis. The de- gree of tumor invasion turned out to be the main prognostic factor, and treatment should be planned ac- cordingly. The prognosis is best predicted by the stage of the tumor as determined intraoperatively and is poorer in patie ts with incomplete resection than in those with complete resection of the thynoma. No recurrence developed In patients with stage I disease.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.12
• /
• pp.1119-1125
• /
• 2010

Most of the sludge pre-treatment methods to improve the anaerobic digestibility of sludge are not practied in the fields with low economical efficiency. The venturi cavitation system (VCS) adopting hydrodynamic cavitation is simple and requires low energy. This research was conducted to investigate the optimum design and operating conditions of the VCS. The experimental results indicated that the optimum number of venturi in series was three, and the suction mode operation of the pump yielded 1.6 times higher pre-treatment efficiency per unit energy consumption than the discharge mode. The combination of venturies with different throat sizes did not affect the pre-treatment efficiency. Also, the parallel installation of the three in series venture unit yielded 30% higher pre-treatment efficiency per unit energy consumption than the single unit. Under parallel conditions, the solubilization efficiency was 5.6 mg ${\Delta}SCOD/g$ TS/kWh, which is higher than the previously reported value.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.6
• /
• pp.1789-1793
• /
• 2014

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the reactions of 5-nitro-8-quinolyl nicotinate (4) and 5-nitro-8-quinolyl isonicotinate (5) with alkali metal ethoxides (EtOM; M = K, Na and Li) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plots of $k_{obsd}$ vs. [EtOM] curve slightly upward for the reactions with EtOK and EtONa but are linear for the reactions with EtOLi and for those with EtOK in the presence of 18-crown-6-ether. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constants for the reactions with the dissociated $EtO^-$ and ion-paired EtOM, respectively) has revealed that the reactivity increases in the order $EtO^-{\approx}EtOLi$ < EtOK < EtONa for the reactions of 4 and EtOLi < $EtO^-$ < EtOK < EtONa for the reactions of 5. Comparison of the kinetic results for the reactions of 4 and 5 with those reported previously for the corresponding reactions of 5-nitro-8-quinolyl benzoate (2) and picolinate (3) has revealed that the esters possessing a pyridine ring (i.e., 3-5) are significantly more reactive than the benzoate ester 2 due to the presence of the electronegative N atom (e.g., 2 << 3 < 4 < 5). It has been concluded that $M^+$ ion catalyzes the reactions of 3-5 by increasing the electrophilicity of the reaction center through a five-membered cyclic transition state (TS) for the reaction of 3 and via a four-membered cyclic TS for the reactions of 4 and 5.