증발 냉각 시 물/전기의 거래관계

Alissa Cooperman,John Dieckmann,James Brodrick,윤린 (번역자) 대한설비공학회 2012 설비저널 Vol.41 No.7

Anisotropy of the Electrical Conductivity of the Fayalite, Fe2SiO4, Investigated by Spin Dimer Analysis

이기학,이지영,Rüdiger Dieckmann 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.2

Many properties of inorganic compounds are sensitive to changes in the point-defect concentrations. In minerals, such changes are influenced by temperature, pressure, and chemical impurities. Olivines form an important class of minerals and are magnesium-rich solid solutions consisting of the orthosilicates forsterite Mg2SiO4 and the fayalite Fe2SiO4. Orthosilicates have an orthorhombic crystal structure and exhibit anisotropic electronic and ionic transport properties. We examined the anisotropy of the electrical conductivity of Fe2SiO4 under the assumption that the electronic conduction in Fe2SiO4 occurs via a small polaron hopping mechanism. The anisotropic electrical conductivity is well explained by the electron transfer integrals obtained from the spin dimer analysis based on tight-binding calculations. The latter analysis is expected to provide insight into the anisotropic electrical conductivities of other magnetic insulators of transition metal oxides.

Anisotropy of the Electrical Conductivity of the Fayalite, Fe₂SiO₄, Investigated by Spin Dimer Analysis

Lee, Kee Hag,Lee, Jeeyoung,Dieckmann, Rudiger Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.2

Many properties of inorganic compounds are sensitive to changes in the point-defect concentrations. In minerals, such changes are influenced by temperature, pressure, and chemical impurities. Olivines form an important class of minerals and are magnesium-rich solid solutions consisting of the orthosilicates forsterite $Mg_2SiO_4$ and the fayalite $Fe_2SiO_4$. Orthosilicates have an orthorhombic crystal structure and exhibit anisotropic electronic and ionic transport properties. We examined the anisotropy of the electrical conductivity of $Fe_2SiO_4$ under the assumption that the electronic conduction in $Fe_2SiO_4$ occurs via a small polaron hopping mechanism. The anisotropic electrical conductivity is well explained by the electron transfer integrals obtained from the spin dimer analysis based on tight-binding calculations. The latter analysis is expected to provide insight into the anisotropic electrical conductivities of other magnetic insulators of transition metal oxides.

The development of an optoelectronic on-line carbon dioxide partial pressure probe

Rainer Buchholz,Dirk ltzek,Torsten Steinau,Michael Dieckmann 동서대학교부설연구소 1997 연구소 논문집 Vol.2 No.-

In this work a prototype for an optoelectronic on-line carbon dioxide partial pressure probe was developed. The mechanical arranngement of the optival and optoelectronical compounds was as well as simple, resulting in no changes due to the signal induced by the temperature effects. The resolution for the field of biotechnology with a measuring range from 0 to 100 mbar is at the moment 1.1 mbar with an accuracy of +/- 3 mbar. For the fie이 of beverage industries with a measuring range from 0to 4 bar the resolution is 4 mvar with an accuracy of =/- 25 mbar. The 90% response time by the application of a fibre with a diameter of 1000 microns and a silicone membrance with a thickness of 300 microns is about 8 min. Possibilities were shown to decrease the response time.

9.6 GHz and 34 GHz electron paramagnetic resonance studies of chromium-doped forsterite

Budil,David E. Park, Dong Gon Burlitch,James M. Geray, Roland F. Dieckmann, Rudiger Freed,Jack H. 숙명여자대학교 자연과학연구소 1994 자연과학논문집 Vol.- No.5

Chromium-doped forsterite single crystals grown under conditions that produce a high Cr4+/Cr3+ ratio were examined by electron paramagnetic resonance (EPR) at 9.6 and 34 GHz. The crystals were grown in 2-3 atm of oxygen by the floating-zone method starting from polycrystalline chromium-doped forsterite power synthesized via a sol-gel method. Three crystals with chromium concentrations of 110, 300, and 390 ppm were studied. At 34 GHz, transitions are observed for the laser-active tetrahedral Cr4+ species that are not observable at 9.6 GHz, which improve the resolution and accuracy with which the magnetic parameters can be measured by EPR. In addition, peaks for a non-Kramers species appear at 34 GHz that were not observed at 9.6 GHz. These peaks are not analyzed in detail, but are tentatively ascribed to Cr4+ in the octahedral substitution sites of the crystal. At the highest chromium concentration, the Cr3+ spectra show evidence of direct interaction with Cr4+. A global least-squares fit of the combined 9.6 and 34 GHz data for the 300 ppm crystal gives D=64.26 ±0.18 GHz, E=-4.619 ±0.009 GHz, gx=1.955 ±0.009, g3= 2.005±0.040, g2=1.965 ±0.006, and places the magnetic z axis in the ab plane at an angle of 43.8±0.3°from the b crystallographic axis (in Pbnm). A method for accurately measuring the Cr4+/Cr4+ ratio using EPR line intensities is given. The EPR linewidth of the Cr4+ center exhibits a strong orientation dependence that is well-modeled by including site variations in the D and E zero-field splittings and in the orientation of the z magnetic axis. The linewidth analysis reveals a high degree of correlation between the distributions in D and E, and a somewhat weaker correlation between E and the z axis orientation. These results are interpreted to suggest that the tetrahedral Cr4+ sites vary mainly in the degree of compression of the tetrahedral cage along the a crystallographic axis. The Cr4+ EPR linewidths increase significantly at higher chromium concentration, but maintain the same qualitative orientation dependence. The EPR data indicate that the major contribution to inhomogeneity in the tetrahedral site, which may be related to the tunable range of the Cr4+ laser center, is distortion induced by chromium substitution into the crystal lattice rather than direct chromium-chromium interactions.

9.6 GHz and 34 GHz electron paramagnetic resonance studies of chromium-doped forsterite

Budil,David E.,Park, Dong Gon,Burlitch,James M.,Geray, Roland F.,Dieckmann, Rudiger,Freed,Jack H. 숙명여자대학교 자연과학연구소 1994 자연과학논문집 Vol.- No.5

Chromium-doped forsterite single crystals grown under conditions that produce a high Cr4+/Cr3+ ratio were examined by electron paramagnetic resonance (EPR) at 9.6 and 34 GHz. The crystals were grown in 2-3 atm of oxygen by the floating-zone method starting from polycrystalline chromium-doped forsterite power synthesized via a sol-gel method. Three crystals with chromium concentrations of 110, 300, and 390 ppm were studied. At 34 GHz, transitions are observed for the laser-active tetrahedral Cr4+ species that are not observable at 9.6 GHz, which improve the resolution and accuracy with which the magnetic parameters can be measured by EPR. In addition, peaks for a non-Kramers species appear at 34 GHz that were not observed at 9.6 GHz. These peaks are not analyzed in detail, but are tentatively ascribed to Cr4+ in the octahedral substitution sites of the crystal. At the highest chromium concentration, the Cr3+ spectra show evidence of direct interaction with Cr4+. A global least-squares fit of the combined 9.6 and 34 GHz data for the 300 ppm crystal gives D=64.26 ±0.18 GHz, E=-4.619 ±0.009 GHz, gx=1.955 ±0.009, g3= 2.005±0.040, g2=1.965 ±0.006, and places the magnetic z axis in the ab plane at an angle of 43.8±0.3°from the b crystallographic axis (in Pbnm). A method for accurately measuring the Cr4+/Cr4+ ratio using EPR line intensities is given. The EPR linewidth of the Cr4+ center exhibits a strong orientation dependence that is well-modeled by including site variations in the D and E zero-field splittings and in the orientation of the z magnetic axis. The linewidth analysis reveals a high degree of correlation between the distributions in D and E, and a somewhat weaker correlation between E and the z axis orientation. These results are interpreted to suggest that the tetrahedral Cr4+ sites vary mainly in the degree of compression of the tetrahedral cage along the a crystallographic axis. The Cr4+ EPR linewidths increase significantly at higher chromium concentration, but maintain the same qualitative orientation dependence. The EPR data indicate that the major contribution to inhomogeneity in the tetrahedral site, which may be related to the tunable range of the Cr4+ laser center, is distortion induced by chromium substitution into the crystal lattice rather than direct chromium-chromium interactions.

Modeling applied to drifting in aquatic insects

Tuyen Van Nguyen,Rupert Mazzucco,Dong-Hwan Kim,Ulf Dieckmann,Tae-Soo Chon 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.05

Stream and river habitats are characterized by a uni-directional water flow. Organisms colonizing such habitats are faced with the constraint of continuous downstream flow. Some ecologists find it puzzling that upstream is colonized by insect communities although the insects are continuously faced with downstream flow. The obvious solution to the puzzle is that there exist compensatory strategies, three of which have gained some notoriety in recent years: 1) diffusive random movement and density-dependent regulation of population size; 2) daily directed movement during larvae stage; 3) the compensation of larval drift by adult upstream flight. We have adapted an eco-evolutionary individual-based model (IBM) to accommodate typical life events of aquatic insects, such as birth, death, diffusion, and drifting. The probabilities of these events, which occur on the individual level, depend on both biological (e.g., local competition, upstream flight by adult insects) and environmental (e.g., unidirectional flow) constraints. The evolution of selected traits, namely, adapted water velocity, drifting time and distance, and upward flight distance, was investigated through simulation. We find that, while the three strategies are generally able to sustain upstream populations, the exact compensation of drift loss allowed by upstream flight makes the third strategy less “asteful” a population of upstream flight strategists to outcompete diffusive movement strategists. We also report branching of adapted traits in drifting during the course of evolution. Individuals with high current velocity preferences either spend short (several seconds) or long (an hour) duration in water flow, while the individuals with low current-velocity preference only spend middle range (half an hour) of duration in water flow.