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  • 1
    Electronic Resource
    Electronic Resource
    Effect of pH on the Chemistry of the Barium Titanium Citrate Gel and Its Thermal Decomposition Behavior (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this investigation, X-ray diffractometry and 13C NMR spectroscopy were used to characterize the effect of pH on the formation of gel and its thermal decomposition by the Pechini process. It was found that the major effect of pH was to destroy the esterification between citric acid (CA) and ethylene glycol, which in turn could influence Ba species and the formation of a mixed-metal CA complex. It was also found that barium carbonate was derived from the Ba species and was not related to the instability of Ba2Ti2O5CO3, but Ba2Ti2O5CO3 was formed by the thermal decomposition of a mixed-metal CA complex. Moreover, BaTiO3 formed via two routes, the reaction of BaCO3 with Ti species and thermal decomposition of Ba2Ti2O5CO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01038.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of Molar Ratio of Citric Acid to Cations and of pH Value on the Formation and Thermal-Decomposition Behavior of Barium Titanium Citrate (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Several experiments were conducted to examine the effects of the molar ratio of citric acid to cations and of the pH value on the chemistry of a solution prepared by the Pechini method. Two types of precipitates, barium titanium citrate (BTC) and barium citrate, developed, depending on the experimental conditions. Characterization of BTC by FT-IR spectroscopy and solid-state 13C-NMR spectroscopy indicated that barium and titanium ions were chelated simultaneously by the central deprotonated alcoholic ligands and by dissociated carboxylic acid groups with a unidentate type of three citric acid molecules. The possible coordinated structure of BTC was proposed. The thermal decomposition behavior of BTC was investigated by powder X-ray diffractometry, FT-IR spectroscopy, and solid-state 13C-NMR spectroscopy. During decomposition, the nature of bonding between carboxylate groups and cations changed in the order unidentate → bridging → ionic, and carbonate species were detected at 500°C. A small amount of BaCO3 and the intermediate oxycarbonate coexisted at 550°-600°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01931.x
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  • 3
    Electronic Resource
    Electronic Resource
    Evolution of the formation of barium titanate in the citrate process: the effect of the pH and the molar ratio of barium ion and citric acid (1998)
    Springer
    Journal of materials science 33 (1998), S. 3721-3727 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this investigation, several experiments were conducted to study the effects of the molar ratio of barium ion and citric acid and the pH value on the formation of BaTiO3 by the citrate process. It was found that the molar ratio of barium ion and citric acid and the pH value could affect the chelation of carboxylate groups and Ba/Ti ions at temperatures below 450 °C but they seemed not to influence the formation of BaTiO3. The development of an oxycarbonate intermediate during the thermal decomposition of (Ba,Ti) gel was confirmed, which was suggested to possess a structure of BaTiO3, whereby CO−23 was located inside the layer structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004636219542
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  • 4
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    Nanorod epitaxial lateral overgrowth of a-plane GaN with low dislocation density (2009)
    American Institute of Physics
    Details
    Publication Date: 2009-06-22
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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  • 5
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    Interannual Variation of the Cold-Season Rainfall Center in the South China Sea (2016)
    American Meteorological Society
    Details
    Publication Date: 2016-10-10
    Description: During 15 November–31 December, a cold-season rainfall center appears in the southern part of the South China Sea (SCS) north of northwestern Borneo, and juxtaposed along the southwest-northeast direction with rainfall centers for the Malay Peninsula and the Philippines. This SCS rainfall center also coincides geographically with the SCS surface trough. An effort is made to explore the formation mechanism of this rainfall center. It is primarily formed by the second intensification of heavy rainfall/flood (HRF) cold surge vortex (CSV) through its interaction with a cold surge flow over the SCS trough. Both the SCS rainfall center and the SCS surface trough are located at the easterly flow north of the near-Equator trough. Modulated by the interannual variation of the cyclonic shear flow along the near-Equator trough in concert with the El-Niño-Southern Oscillation (ENSO) cycle, the SCS rainfall center undergoes an interannual variation. The impact of this ENSO cycle is accomplished through the regulation of CSV(HRF) trajectories originating from the Philippines vicinity and Borneo, and propagating to different destinations. Rain-producing efficiency determined by the interannual variation of the divergent circulation accompanies the cyclonic shear flow around the near-Equator trough in response to this ENSO cycle.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 6
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    Interannual Variation of Summer Rainfall in the Taipei Basin (2016)
    American Meteorological Society
    Details
    Publication Date: 2016-08-01
    Description: The Taipei basin, located in northern Taiwan, is formed at the intersection of the Tanshui River valley (~30 km) and the Keelung River valley (~60 km). Summer is the dry season in northern Taiwan, but the maximum rainfall in the Taipei basin occurs during 15 June–31 August. The majority of summer rainfall in this basin is produced by afternoon thunderstorms. Thus, the water supply, air/land traffic, and pollution for this basin can be profoundly affected by interannual variations of thunderstorm days and rainfall. Because the mechanism for these interannual variations is still unknown, a systematic analysis is made of thunderstorm days and rainfall for the past two decades (1993–2013). These two variables are found to correlate opposite interannual variations of sea surface temperature anomalies over the National Oceanic and Atmospheric Administration Niño-3.4 region. Occurrence days for afternoon thunderstorms and rainfall amounts in the Taipei basin double during the cold El Niño–Southern Oscillation (ENSO) phase relative to the warm phase. During the latter phase, a stronger cold/drier monsoon southwesterly flow caused by the Pacific–Japan Oscillation weakens the thunderstorm activity in the Taipei basin through the land–sea breeze. In contrast, the opposite condition occurs during the cold ENSO phase. The water vapor flux over the East/Southeast Asian monsoon region converges more toward Taiwan to maintain rainfall over the Taipei basin during the cold ENSO phase than during the warm ENSO phase.
    Print ISSN: 1558-8424
    Electronic ISSN: 1558-8432
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 7
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    A Forecast Advisory for Afternoon Thunderstorm Occurrence in the Taipei Basin during Summer Developed from Diagnostic Analysis* (2016)
    American Meteorological Society
    Details
    Publication Date: 2016-03-15
    Description: Summer is a dry season in northern Taiwan. By contrast, the Taipei basin, located in this region, has its maximum rainfall during summer (15 June–31 August), when 78% of this rainfall is contributed by afternoon thunderstorms. This thunderstorm activity occurs during only 20 days in summer. Because of the pronounced impacts on the well-being of three million people in the basin and the relative infrequency of occurrence, forecasting thunderstorm events is an important operational issue in the Taipei basin. The basin’s small size (30 km × 60 km), with two river exits and limited thunderstorm occurrence days, makes the development of a thunderstorm activity forecast model for this basin a great challenge. Synoptic analysis reveals a thunderstorm day may develop from morning synoptic conditions free of clouds/rain, with a NW–SE-oriented dipole located south of Taiwan and southwesterlies straddling the low and high of this dipole. The surface meteorological conditions along the two river valleys exhibit distinct diurnal variations of pressure, temperature, dewpoint depression, relative humidity, and land–sea breezes. The primary features of the synoptic conditions and timings of the diurnal cycles for the four surface variables are utilized to develop a two-step hybrid forecast advisory for thunderstorm occurrence. Step 1 validates the 24-h forecasts for the 0000 UTC (0800 LST) synoptic conditions and timings for diurnal variations for the first five surface variables on thunderstorm days. Step 2 validates the same synoptic and surface meteorological conditions (including sea-breeze onset time) observed on the thunderstorm day. The feasibility of the proposed forecast advisory is successfully demonstrated by these validations.
    Print ISSN: 0882-8156
    Electronic ISSN: 1520-0434
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 8
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    Genesis and Development of Spring Rainstorms in Northern Southeast Asia: Southwest China–Northern Indochina and the Northern South China Sea (2017)
    American Meteorological Society
    Details
    Publication Date: 2017-12-01
    Description: During May and June, the monsoon rainfall in northern Southeast Asia is primarily produced by rainstorms. At the mature stage, these storms, coupled with a midtropospheric subsynoptic-scale trough, produce rainfall ≥50 mm (6 h)−1and exhibit a cyclonic surface vortex. With a scale ~ O(102) km, rainstorms during the period of 1979–2016 are identified with station and satellite observations, along with assimilation data. Several dynamic processes of rainstorm geneses are disclosed by an extensive analysis. 1) Maximum occurrence of rainstorm geneses is located in the midtroposphere of two regions (northern Vietnam–southwestern China and the northern South China Sea), but eventually penetrates downward to the surface. 2) The environment favorable for rainstorm genesis is a southwest–northeast-oriented narrow trough formed by the confluence of the midtropospheric northeasterly around the eastern Tibetan Plateau and the lower-tropospheric monsoon southwesterlies. Because the criterion for Charney–Stern instability is met by the shear flow of this narrow trough, rainstorms are likely initiated by this instability. 3) The majority of rainstorm geneses occurs during the evening over the land and the morning at sea. This timing preference is caused by the modulation of the clockwise rotation of the East Asia continent circulation in response to the diurnal variation of the land–sea thermal contrast. These new findings from this study offer not only a new perspective for the genesis mechanism of the late spring–early summer rainstorms in northern Southeast Asia, but also a new initiative to develop medium-range forecasts for these rainstorms.
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 9
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    Interannual Variation of the Summer Rainfall Center in the South China Sea (2017)
    American Meteorological Society
    Details
    Publication Date: 2017-09-01
    Description: A northwest–southeast-oriented summer monsoon trough exists between northern Indochina and northwestern Borneo. Ahead of this the South China Sea (SCS) trough is located at a convergent center west of the Philippines, which provides an environment favorable for rain-producing synoptic systems to produce rainfall over this center and form the SCS summer rainfall center. Revealed from the x–t diagram for rainfall, this rainfall center is developed by multiple-scale processes involved with the SCS trough (TR), tropical depression (TY), interaction of the SCS trough with the easterly wave/tropical depression (EI), and easterly wave (EW). It is found that 56% of this rainfall center is produced by the SCS trough, while 41% is generated by the other three synoptic systems combined. Apparently, the formation of the SCS summer monsoon rainfall center is contributed to by these four rain-producing synoptic systems from the SCS and the Philippines Sea. The Southeast Asian summer monsoon undergoes an interannual variation and exhibits an east–west-oriented cyclonic (anticyclonic) anomalous circulation centered at the western tropical Pacific east of the Luzon Strait. This circulation change is reflected by the deepening (filling) of the SCS summer monsoon trough, when the monsoon westerlies south of 15°N intensify (weaken). This interannual variation of the monsoon westerlies leads to the interannual variation of the SCS summer monsoon rainfall center to follow the Pacific–Japan oscillation of rainfall. The rainfall amount produced over this rainfall center during the weak monsoon season is about two-thirds of that produced during the strong monsoon season. The rain-production ratio between TR and TY + EI + EW is 60:38 during the strong monsoon season and 47:49 during the weak monsoon season.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 10
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    Impact of the Summer Monsoon Westerlies on the South China Sea Tropical Cyclone Genesis in May (2017)
    American Meteorological Society
    Details
    Publication Date: 2017-04-17
    Description: After the onset of the Southeast Asian summer monsoon in mid-May, the South China Sea (SCS) trough is deepened by the intensified monsoon westerlies to facilitate the development of a synoptic cyclonic shear flow. This shear flow forms an environment favorable for the SCS tropical storm (TS)/typhoon (TY) genesis triggered by the surge of this monsoon circulation. This genesis mechanism has not been well documented. Seventeen named SCS TS/TY geneses in May over 1979–2016 occurred under the following environmental conditions/processes: 1) with its maximum located south of 15°N, the intensified monsoon westerlies are extended eastward beyond 120°E, 2) the synoptic SCS cyclonic shear flow is developed by the tropical easterlies fed by a northeast Asian cold surge (or a North Pacific cold-air outbreak) and the intensified monsoon westerlies, and 3) SCS TS/TY genesis is triggered by the surge of monsoon flow. The accuracy of the monthly mean forecasts is limited. However, it is found that SCS TS/TY genesis only occurs after the existence of persistent, strong, monsoon westerlies lasting for at least 5 days. Forecasts from the National Centers for Environmental Prediction Global Forecast System (2004–16) and the Global Ensemble Forecast System (1985–2003) cover these 15 SCS TS/TY geneses. The requirements for SCS TS/TY genesis in May described above are met by the 5-day-mean Southeast Asian summer monsoon circulation. Based on a statistical analysis of 5-day forecasts for these TS/TY geneses, a four-step forecast advisory is introduced. The forecasts for SCS TS/TY genesis can be made 3 days prior to occurrence.
    Print ISSN: 0882-8156
    Electronic ISSN: 1520-0434
    Topics: Geography , Physics
    Published by American Meteorological Society
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