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Auswahl der wissenschaftlichen Literatur zum Thema „D1 cooling“
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Zeitschriftenartikel zum Thema "D1 cooling"
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Maximenko, Serguei I., Jaime A. Freitas, N. Y. Garces, E. R. Glaser und Mark A. Fanton. „Evolution of D1-Defect Center in 4H-SiC during High Temperature Annealing“. Materials Science Forum 600-603 (September 2008): 429–32. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.429.
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The behavior of the D1 center in semi-insulating 4H-SiC substrates revealed by low-temperature photoluminescence was investigated after post-growth high temperature anneals between 1400 and 2400oC. The influence of different post-anneal cooling rates was also studied. The optical signature of D1 was observed up to 2400oC with intensity maxima at 1700 and 2200oC. We propose that the peak at 1700°C can be related to the formation and subsequent dissociation of SiC native defects. It was found that changes in the post-annealing cooling rate drastically influence the behavior of the D1 center and the concentrations of the VC, VSi, VC-VSi and VC-CSi lattice defects.
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Zharov, M. V. „Analysis of features of heat transfer processes during crystallization of aluminum alloy granules in aqueous and water-vapor media“. Materials Science, Nr. 8 (2023): 3–13. http://dx.doi.org/10.31044/1684-579x-2023-0-8-3-13.
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The result analysis of the created mathematical model application of a detailed change in the temperature field and analysis of phase transitions during cooling and crystallization of a melt drop under cooling conditions in an aqueous and water-vapor medium have been carried out. The presented mathematical model allows one not only to determine the temperature fields in the body of a drop or a granule, but also determines the speed of movement of a drop in the coolant at any given time, determines the intensity of heat removal, the cooling rate and the rate of crystallization of the melt at different points in the volume. All this, in the end, makes possible to predict the size of dendrites, properties and phase composition of material of the obtained granules. The mathematical model was tested in the process of granulation of high-doped aluminum alloys (alloys D1 and D16 of the Al—Cu—Mg system, alloys B95 and B96C of the Al—Zn—Mg—Cu system) obtained by the centrifugal melt spraying method and the drip method during cooling in an aqueous medium. The crystallization rate in full-scale samples was measured on the basis of the method of analysis of the dendritic parameter of the material structure. The mathematical model showed a high degree of convergence between the results of simulation modeling and the results of real experiments for obtaining granules. In particular, the model showed fairly accurate results for the formation of granules at ultra-high crystallization rates, in the absence of a «steam jacket», namely, a steam layer arising between the body of the granule and the coolant that prevents the intensity of heat removal, and is an obstacle to increasing the crystallization rate due to a lower thermal conductivity of water vapor.
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Douzi, Wafa, Xavier Guillot, Delphine Bon, François Seguin, Nadège Boildieu, Daniel Wendling, Nicolas Tordi, Olivier Dupuy und Benoit Dugué. „1H-NMR-Based Analysis for Exploring Knee Synovial Fluid Metabolite Changes after Local Cryotherapy in Knee Arthritis Patients“. Metabolites 10, Nr. 11 (13.11.2020): 460. http://dx.doi.org/10.3390/metabo10110460.
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Rehabilitation using cryotherapy has widely been used in inflammatory diseases to relieve pain and decrease the disease activity. The aim of this study was to explore the metabolite changes in inflammatory knee-joint synovial fluids following local cryotherapy treatment (ice or cold CO2). We used proton nuclear magnetic resonance (1H NMR) spectroscopy to assess the metabolite patterns in synovial fluid (SF) in patients with knee arthritis (n = 46) before (D0) and after (D1, 24 h later) two applications of local cryotherapy. Spectra from aqueous samples and organic extracts were obtained with an 11.75 Tesla spectrometer. The metabolite concentrations within the SF were compared between D1 and D0 using multiple comparisons with the application of a false discovery rate (FDR) adjusted at 10% for each metabolite. A total of 32 metabolites/chemical structures were identified including amino acids, organic acids, fatty acids or sugars. Pyruvate, alanine, citrate, threonine was significantly higher at D1 vs D0 (p < 0.05). Tyrosine concentration significantly decreases after cryotherapy application (p < 0.001). We did not observe any effect of gender and cooling technique on metabolite concentrations between D0 and D1 (p > 0.05). The present study provides new insight into a short-term effect of cold stimulus in synovial fluid from patients with knee arthritis. Our observations suggest that the increased level of metabolites involved in energy metabolism may explain the underlying molecular pathways that mediate the antioxidant and anti-inflammatory capacities of cryotherapy.
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Singh, Balkar, Sehijpal Singh, Vivek Aggarwal und Gurpreet Singh. „Modeling and Optimization of Turning Hastelloy C-276 under Sustainable Machining Environments“. Solid State Phenomena 356 (18.03.2024): 21–31. http://dx.doi.org/10.4028/p-bj6vjw.
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Due to their numerous applications in the aerospace, chemical, and nuclear power industries, environmentally responsible superalloy machining is a major problem in the current production environment. Additionally, Ni-based superalloys are regarded as difficult to manufacture because of their great strength under hot and chemically reactive settings. Therefore, it is necessary to machine these materials using adequate cooling and lubricating solutions. Current study has been based on the optimisation and modelling of turning Hastelloy C-276 under dry, flood, and least lubrication system. A Taguchi L-9 arrangement was used as plan of experiment and modeling was enabled through ANOVA, regression analysis and Taguchi optimization. The results depicted optimal parameters for surface roughness and temperature at v2-f1-d1-CE3 and v1-f2-d1-CE3. Likewise, for CRC and shear angle the best combination was observed at v3-f3-d2-CE2. From ANOVA analysis, the benefaction of C.E, depth of cut and feed rate on S.R been listed as 46.70%, 40.44% and 10.66%. Likewise, for temperature cutting speed has benefaction of (53.09%), cooling environment (23.94%), depth of cut (6.10%) and feed rate 5.49% . In similar fashion, CRC and Shear angle were influenced by feed rate and cutting speed having contribution of 62.89% and 5.15% respectively. Furthermore, minimum standard error between the fitted and observed values for S.R., temperature, CRC, and shear angle were calculated as 0.0149, 7.66, 0.267, and 1.80 units. Finally, the marginal reduction of cutting temperature and surface roughness through utilization of MQL implies the sustainable machining conditions.
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Mishra, Purna Chandra, Dipti Kanta Das und Susant Kumar Sahu. „Comparative Performance In Hard Turning Of AISI 1015 Steel With Carbide Insert Using Orthogonal Array Design And Grey Relational Analysis Under Spray Impingement Cooling And Dry Environment“. International Journal of Manufacturing, Materials, and Mechanical Engineering 4, Nr. 3 (Juli 2014): 1–32. http://dx.doi.org/10.4018/ijmmme.2014070101.
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This study investigates the effects of cutting parameters on surface roughness (Ra), cutting temperature (T0C) at the chip tool interface and the material removal rate (MRR mm3/min) during hard machining of AISI 1015 (43 HRC) steel using carbide insert under dry and spray impingement cooling environment. A combined technique using orthogonal array and analysis of variance (ANOVA) was employed to investigate the contribution of spindle speed, feed rate, depth of cut and air pressure on responses. Utilization of IR camera is been effective to calculate the temperature at the interface of workpiece and the tool. It is observed that with spray impingement cooling, cutting performance improves compared to dry cutting. The predicted multi response optimization setting (N3-f1-d1-P2) ensures minimization of surface roughness, cutting temperature and maximization of material removal rate. Finally optimal result was validated by confirmatory test and the improvement in grey relational grade was found to be 0.288.
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Yeargin, Susan, Amy L. McKenzie, Lindsey E. Eberman, J. Derek Kingsley, David J. Dziedzicki und Patrick Yoder. „Physiological and Perceived Effects of Forearm or Head Cooling During Simulated Firefighting Activity and Rehabilitation“. Journal of Athletic Training 51, Nr. 11 (01.11.2016): 927–35. http://dx.doi.org/10.4085/1062-6050-51.10.09.
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Context: Cooling devices aim to protect firefighters by attenuating a rise in body temperature. Devices for head cooling (HC) while firefighting and forearm cooling (FC) during rehabilitation (RHB) intervals are commonly marketed, but research regarding their efficacy is limited. Objective: To investigate the physiological and perceived effects of HC and FC during firefighting drills and RHB. Design: Randomized controlled clinical trial. Setting: Firefighter training center. Patients or Other Participants: Twenty-seven male career firefighters (age = 39 ± 7 years; height = 169 ± 7 cm; weight = 95.4 ± 16.8 kg). Intervention(s): Firefighters were randomly assigned to 1 condition: HC (n = 9), in which participants completed drills wearing a cold gel pack inside their helmet; FC (n = 8), in which participants sat on a collapsible chair with water-immersion arm troughs during RHB; or control (n = 10), in which participants used no cooling devices. Firefighters completed four 15-minute drills (D1−D4) wearing full bunker gear and breathing apparatus. Participants had a 15-min RHB after D2 (RHB1) and D4 (RHB2). Main Outcome Measure(s): Change (Δ) in gastrointestinal temperature (TGI), heart rate (HR), physiological strain index, and perceived thermal sensation. Results: The TGI increased similarly in the HC and control groups, respectively (D1: 0.57°C ± 0.41°C, 0.73°C ± 0.30°C; D2: 0.92°C ± 0.28°C, 0.85°C ± 0.27°C; D3: −0.37°C ± 0.34°C, −0.01°C ± 0.72°C; D4: 0.25°C ± 0.42°C, 0.57°C ± 0.26°C; P > .05). The ΔHR, Δ physiological strain index, and Δ thermal sensation were similar between the HC and control groups during drills (P > .05). The FC group demonstrated a decreased TGI compared with the control group after RHB1 (−1.61°C ± 0.35°C versus −0.23°C ± 0.34°C; P < .001) and RHB2 (−1.40°C ± 0.38°C versus −0.38°C ± 0.24°C; P < .001). The physiological strain index score decreased in the FC group compared with the control group after RHB1 (−7.9 ± 1.3 versus −2.6 ± 1.7; P < .001) and RHB2 (−7.9 ± 1.6 versus −3.6 ± 1.1; P < .001), but no differences between groups were demonstrated for ΔHR or Δ thermal sensation (P > .05). Conclusions: The HC did not attenuate rises in physiological or perceptual variables during firefighting drills. The FC effectively reduced TGI and the physiological strain index score but not HR or thermal sensation during RHB. Clinicians and firefighters should not recommend the use of HC during firefighting but can consider using FC during RHB intervals in the field.
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Talarico, F. M., E. Stump, B. F. Gootee, K. A. Foland, R. Palmeri, W. R. Van Schmus, P. K. Brand und C. A. Ricci. „First evidence of a “Barrovian”-type metamorphic regime in the Ross orogen of the Byrd Glacier area, central Transantarctic Mountains“. Antarctic Science 19, Nr. 4 (02.08.2007): 451–70. http://dx.doi.org/10.1017/s0954102007000594.
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AbstractThe Selborne Group comprises two metamorphic rock units, the muscovite±dolomite bearing Madison Marble and the biotite-muscovite±quartz-calcite Contortion Schist, which contains thick lenses of variably deformed metabasalts and metaconglomerates. Petrological and structural data indicate a polyphase metamorphic evolution including: i) an early stage of upper greenschist regional metamorphism (P = ~0.15–0.3 GPa; T = ~380–450°C), ii) prograde metamorphism during D1 up to amphibolite facies peak conditions (P = 0.58–0.8 GPa, T = ~560–645°C), iii) syn-D2 unloading-cooling retrograde metamorphism, iv) a post-D2 contact metamorphic overprint at variable T between 450 and 550°C and ~0.2 GPa connected to the emplacement of granitic plutons and felsic dyke swarms. Geochronological data constrain the polyphase syn-D1/D2 evolution between ~ 510 and 492 Ma. A similar metamorphic path, including a medium P stage but at lower T conditions, is documented in greenschist facies metabasalts within the Byrd Group in the Mount Dick area. The metamorphic pattern and close lithostratigraphic matching between Selborne Group and Byrd Group sharply contrast with the high-grade Horney Formation that is exposed north of the Byrd Glacier and corroborate the hypothesis that the Byrd Glacier discontinuity marks a first-order crustal tectonic boundary crossing the Ross orogen.
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Schulz, Bernhard. „Mineral chemistry, geothermobarometry and pre-Alpine high-pressure metamorphism of eclogitic amphibolites and mica schists from the Schobergruppe, Austroalpine basement, Eastern Alps“. Mineralogical Magazine 57, Nr. 387 (Juni 1993): 189–202. http://dx.doi.org/10.1180/minmag.1993.057.387.01.
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AbstractAlternating eclogitic amphibolites, mica schists and orthogneisses in the Schobergruppe to the south of the Tauern Window suffered a post-Upper-Ordovician progressive deformation D1-D2which produced parallel planar-linear structures in all the rocks. Zoned garnets, preferentially oriented zoned clinopyroxenes (Jd 35-42%) and albite (An 7-9%) give evidence of high-pressure metamorphism (550-650°C 14-16 kbar) of the metabasites. Ca-amphiboles crystallized during subsequent decompression. In a kyanite-staurolite-garnet mica schist 300 metres below the metabasites, garnetbearing assemblages grew synchronous with the development of foliations S1and S2. Garnets are zoned with increasing XMgand decreasing-increasing-rcdecreasing Xcafrom cores to rims. Albitic plagioclase (An 1-3%) and micas are enclosed in garnet cores and rims, are in contact with garnet, and occur with garnet in microlithons. When these minerals are used for geothermobarometry, a prograde P-T evolution (460 to 680°C with coeval pressure variations which reach high-pressure conditions can be estimated. This suggests that garnet-plagioclase geobarometry with albitic plagioclase works in the relevant P-T field. Similar garnet zonation trends and a similarly shaped P-T path from mica schists of an adjacent region with late-Variscan cooling ages, points to an eady-Variscan age of the syn-D1-D2high-pressure and subsequent amphibolite-facies metamorphism.
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Hermansyah, Hermansyah, Novian Sutami und Miksusanti Miksusanti. „AMPLIFIKASI PCR DOMAIN D1/D2 28S rDNA MENGGUNAKAN PRIMER ITS1 DAN ITS4 SAMPEL DNA DARI Candida tropicalis YANG DIISOLASI DENGAN METODE PENDINGINAN“. Indonesian Journal of Pure and Applied Chemistry 1, Nr. 1 (23.07.2018): 1. http://dx.doi.org/10.26418/indonesian.v1i1.26037.
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The purpose of this research was to isolated DNA from the yeast C. tropicalis with freeze thawing method -200 C conducted on 3 colonies of C. tropicalis. Each colony threated variations of cooling, 3x15 minutes, 3x25 minutes and 3x35 minutes, to break the cell walls. Subsequently all the samples amplified with 3 variations of PCR cycles, 15 cycles, 25 cycles and 35 cycles, after all of the samples isolated by freeze thawing method -200 C. Its was known that sample A15 has the smallest concentration of DNA yeast C. tropicalis, ie 50 µg/mL, while sample C35 had the largest concentration of DNA yeast C. tropicalis, ie 225 µg/mL. The result of the research indicated that the best condition can be reached in 3x35 minutes. On 35th cycle has clearer C. tropicalis DNA bands than the 25th and 15th PCR cycle. C. tropicalis DNA bands at 35th cycles there were 7 DNA bands were detected and bright bands on a long 35 minutes cooling. In the 25th and the 15th cycle, there was no DNA bands were detected in all samples. Based on the results obtained, the amplification process must be carried out at least 35 times cycles so that the C. tropicalis DNA bands can be detected.
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Balogun, Kayode B., Griffin Nicholls, Olujide Sokunbi und Kara R. Stewart. „PSV-9 Effects of Natural Honey Inclusion in Dilution and Freezing Extenders on Frozen-thawed Semen Quality in Boars“. Journal of Animal Science 99, Supplement_1 (01.05.2021): 211. http://dx.doi.org/10.1093/jas/skab054.346.
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Abstract Improvements in the post-thaw quality of frozen semen could allow increased utilization of this technology in the swine industry. The objective of this study was to investigate the effects of natural honey inclusion in semen extender and freezing media on motility, mobility, and morphology of cryopreserved boar sperm. Ejaculates from 6 terminal cross-bred boars were collected using the gloved-hand technique for 3 weeks and used in a 2 x 3 factorial study design. Following collection, semen samples were incubated overnight in dilution extender with and without natural honey (D0: Androhep Plus; D1: Androhep Plus + 0.25% honey). The following day, the semen samples were cooled to 4 C in LEY cooling extender then frozen in freezing media containing 93% cooling extender + 6% glycerol + 1% Equex-STM Paste (F1), or freezing media with natural honey replacing 50% of the glycerol (F2) or 50% of the Equex-STM paste (F3). Semen samples were frozen using a controlled-rate freezer and stored in liquid nitrogen. Two straws per treatment for each boar were thawed and semen quality assessed. The inclusion of natural honey in dilution extender had no effect on post-thaw motility (P=0.733), progressive motility (P=0.562), or other mobility parameters (0.995≤P≥0.081). However, D1 had a higher percentage of normal acrosomes (P=0.001) and morphologically normal cells (P< 0.001) resulting from lower tail abnormalities compared to D0 (P=0.006). Post-thaw motility (P< 0.001) and progressive motility (P< 0.001) were increased in F3 compared to both F2 and F1. F1 had reduced normal acrosomes (P=0.009) and morphologically normal cells (P< 0.001) resulting from higher tail abnormalities (P< 0.001). In conclusion, the inclusion of natural honey, at 0.25%, in dilution extender helps maintain normal sperm and acrosome morphology, and replacing 50% Equex-STM Paste with honey in freezing extender improves post-thaw sperm motility and progressive motility of frozen-thawed boar semen.
Dissertationen zum Thema "D1 cooling"
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Dash, Gentle. „Simultaneous D1 laser cooling of Bose-Fermi Lithium isotopes“. Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLE039.
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Cette thèse porte sur la construction d’une expérience de nouvelle génération sur un mélange de gaz quantiques bosons-fermions. Nous implémentons un refroidissement sub-Doppler D1 simultané sur les isotopes ⁶Li et ⁷Li de l’atome de lithium. Nous opérons une mélasse D1 sur la transition |Fg = 2⟩ → |Fe = 1⟩ du ⁷Li et la transition |Fg = 3/2⟩ → |Fe = 3/2⟩ du ⁶Li qui présentent des états noirs. En utilisant une nouvelle séquence pulsée, nous refroidissons les deux isotopes à partir d’une température de piège magnéto-optique (MOT) de ∼ 1 mK à moins de 100 µKen 3 ms. Nous discutons de l’optimisation de la séquence de refroidissement pulsé. Nous fournissons également une description détaillée de la machine en nous concentrant en particulier sur le système de diode lasers, la conception des bobines de champ magnétique et le nouveau contrôle informatique de l’expérience. Les densités dans l’espace des phases obtenues, de ∼ 2 × 10⁻⁶ pour les deux isotopes, sont adaptées au chargement direct d’un piège dipolaire fortement désaccordé avec∼ 7×10⁵ atomes où un refroidissement par évaporation jusqu’à la double dégénérescence quantique pourrait être effectué. Nos résultats ouvrent la voie à l’étude des propriétés quantiques des mélanges Bose-Fermi à très basse températureThis thesis reports on the construction of a new generation Bose-Fermi quantum gas experiment. We implement simultaneous D1 sub-Doppler cooling on ⁶Liand ⁷Li isotopes. We operate D1 molasses on ⁷Li |Fg = 2⟩ → |Fe = 1⟩ and on ⁶Li |Fg = 3/2⟩ → |Fe = 3/2⟩ which display dark states. Using a novel pulsed sequence we cool both isotopes from a magneto optical trap (MOT) temperature of ∼ 1 mKto less than 100 µK in 3 ms. We discuss the optimization of the pulsed cooling sequence. We also provide a detailed description of the machine focusing in particular on the all-diode laser system, the magnetic field coil design and the new computer control system. The obtained phase space densities of ∼ 2 × 10⁻⁶ are suitable for directly loading a far detuned optical dipole trap with ∼ 7 × 10⁵ atoms where evaporative cooling to dual quantum degeneracy could be performed. Our results pave the way towards the study of Bose-Fermi quantum many-body physics at low temperature
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Sievers, Franz. „Ultracold Fermi mixtures and simultaneous sub-Doppler laser cooling of fermionic 6Li and 40K“. Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066221/document.
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Ce travail rend compte de nouvelles techniques développées pour l'étude expérimentale de gaz ultrafroids de lithium et de potassium fermioniques. Les améliorations de notre expérience 6Li-40K y sont décrites et caractérisées. Nous présentons un laser solide de grande finesse capable d'émettre 5W de puissance à 671 nm. Nous utilisons cette source laser dans le contexte d'une nouvelle technique de refroidissement sub-Doppler, reposant sur la transition atomique D1 des atomes alcalins, pour refroidir des atomes de lithium. Cette melasse D1 nous permet de refroidir simultanément les atomes de 6Li et de 40K à des températures bien inférieures à la limite Doppler, tout en manipulant des grands nombres d'atomes à des densités importantes. Nous avons mesuré une densité dans l'espace des phases après l'étape de mélasse de l'ordre de 10-4 à la fois pour le 6Li et le 40K. Le refroidissement laser D1 ouvre la voie à une évaporation rapide vers la dégénérescence quantique dans un piège magnétique ou optique. Nous présentons le refroidissement évaporatif d'atomes de 40K. L'évaporation débute dans une piège magnétique pluggé et continue dans un piège dipolaire optique. A l'issue de l'évaporation, nous obtenons un mélange de spins dégénéré, avec plus de 7x105 atomes dans chacun des deux états de spin et une température T/TF<0.34This thesis reports on novel techniques for experimental studies of ultracold, fermionic lithium and potassium quantum gases. The new parts of our 6Li-40K apparatus are described and characterised. We present a narrow-linewidth, all-solid-state laser source, emitting 5W at 671 nm. We employ the laser source in the context of a novel sub-Doppler cooling mechanism, operating on the D1 atomic transition of alkali atoms, for laser cooling of lithium. This D1 molasses allows us to simultaneously cool a mixture of 6Li and 40K atoms to deep sub-Doppler temperatures, while retaining large atom numbers and high atomic densities. The measured phase space densities after the molasses phase are on the order of 10-4 for both 6Li and 40K. The D1 laser cooling paves the way for fast evaporation to quantum degeneracy in magnetic and optical traps. We present the evaporative cooling of 40K atoms. The evaporation starts in an optically plugged magnetic quadrupole trap and continues in an optical dipole trap. At the end of the evaporation, we obtain a quantum degenerate spin-mixture of 40K atoms, with more than 7x105 atoms in each of the two spin states and T/TF<0.34
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Neto, Julio Flemming. „Co-desaceleração de dois alcalinos via laser e aumento de eficiência e novas formas de aprisionamento em armadilhas magneto-ópticas“. Universidade de São Paulo, 1995. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-26052014-163530/.
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Nós demonstramos, pela primeira vez, o resfriamento via laser de um feixe atômico duplo. Ao se carregar um forno a 650oC com uma liga de Li179Na obtêm-se uma destilação efusiva que produz um feixe com fluxos idênticos de Li e de Na. Este feixe formado por duas espécies é desacelerado pela técnica Zeeman utilizando-se dessintonias iguais a Li = -850 MHz e Na = +150 MHz das respectivas transições atômicas 2S1/2 F = 2 2P3/2 F = 3. Em um segundo experimento, mostramos uma nova armadilha magneto-óptica bicromática, em cela de vapor. Obtivemos um incremento de ~10 vezes no número de átomos resfriados utilizando uma armadilha de Na do tipo I circundada por uma armadilha do tipo II, que não se superpõe à primeira. Isto ocorre quando temos o laser de captura a 12 MHz para o vermelho da transição 32S1/2 F = 2 32P3/2 F = 2. Em um terceiro experimento, observamos a primeira armadilha magneto-óptica para alcalinos operando na transição 2S1/2 2P1/2 (linha D1). Para o caso escolhido de átomos de sódio, obtêm-se quatro armadilhas diferentes dentro desta linha D1, contendo de 105 a 107 átomos resfriados. Para duas delas, é necessário inverter-se o sinal das polarizações circulares usuais dos lasers de resfriamento, devido aos desvios Zeeman negativos dos níveis hiperfinos inferioresWe demonstrate, for the first time, a laser cooling of a double atomic beam. By loading an oven at 650oC with a Li179Na alloy we get an effusive distillation producing a beam with equal fluxes of Li and Na. This two-species beam was laser cooled by Zeeman technique with Li = -850 MHz and Na = +150 MHz detunings from the corresponding 2S1/2 F = 2 2P3/2 F = 3 atomic transitions. In a second experiment, we show a new two-color vapor-cell magneto-optical trap. By surrounding type-I Na trap with a non-overlaping type-II trap we achieve a ~10-fold improvement in the number of cooled atoms. This is achieved when the capture laser is detuned 12 MHz to the red of the 32S1/2 F = 2 32P3/2 F = 2 transition. In a third experiment, we observe the first alkaline magneto-optical trap operating on 2S1/2 2P1/2 transition (D1 line). For the choosen sodium atoms, we have four different traps within D1 line, with 105 to 107 cooled atoms. For two of them, one has to revert the usual sign of circular polarizations of the cooling lasers, due to negative Zeeman shift of the lower hyperfine levels
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Kretzschmar, Norman. „Experiments with Ultracold Fermi Gases : quantum Degeneracy of Potassium-40 and All-solid-state Laser Sources for Lithium“. Thesis, Paris, Ecole normale supérieure, 2015. http://www.theses.fr/2015ENSU0012/document.
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Cette thèse présente de nouvelles techniques pour l'étude expérimentale des gaz quantique ultrafroids d'atomes fermioniques de lithium et de potassium. Dans la première partie de cette thèse, nous décrivons la conception et la caractérisation des nouveaux composants de notre dispositif expérimental capable de piéger et refroidir simultanément des atomes de $^6$Li et de $^{40}$K à des températures ultrabasses. Nous rendons compte d'une nouvelle technique de refroidissement sub-Doppler, reposant sur la transition de la raie D$_1$ des atomes alcalins, pour refroidir des atomes de lithium et de potassium par laser. Après cette étape de mélasse, nous avons mesuré une densité dans l'espace des phases de l'ordre de $10^{-4}$ à la fois pour le $^6$Li et le $^{40}$K. Nous présentons le refroidissement par évaporation forcée d'atomes de $^{40}$K qui commence dans un piège magnétique quadripolaire pluggé et continue dans un piège optique dipolaire. Dans ce contexte, nous rendons compte de la production d'un gaz quantique de Fermi dégénéré de $1.5\times10^5$ atomes de $^{40}$K dans un piège dipolaire croisé avec $T/T_{_F} = 0.17$, ce qui ouvre la voie à l'étude des superfluides de $^{40}$K en interaction forte. Dans la deuxième partie de cette thèse, nous présentons une source laser à état solide, de faible largeur spectrale et capable d'émettre 5.2 W de puissance autour de 671 nm, dans la gamme des longueurs d'onde des transitions de la raie D du lithium. La source repose sur un laser en anneau pompé par diode, émettant sur la transition à 1342 nm de Nd:YVO$_4$, capable de produire 6.5 W de lumière dans un faisceau monomode limité par la diffraction. Nous rendons compte de trois différentes approches pour la génération de seconde harmonique du faisceau de sortie, à savoir en utilisant une cavité amplificatrice comprenant un cristal ppKTP, par doublage de fréquence intracavité et par un structure de guide d'onde de ppZnO:LNThis thesis presents novel techniques for the experimental study of ultracold quantum gases of fermionic lithium and potassium atoms. In the first part of this thesis, we describe the design and characterization of the new components of our experimental apparatus capable of trapping and cooling simultaneously $^6$Li and $^{40}$K atoms to ultracold temperatures. We report on a novel sub-Doppler cooling mechanism, operating on the D$_1$ line transition of alkali atoms, for laser cooling of lithium and potassium. The measured phase space densities after this molasses phase are on the order of $10^{-4}$ for both $^6$Li and $^{40}$K. We present the forced evaporative cooling of $^{40}$K atoms, starting in an optically plugged magnetic quadrupole trap and continuing in an optical dipole trap. In this context, we report on the production of a quantum degenerate Fermi gas of $1.5\times10^5$ atoms $^{40}$K in a crossed dipole trap with $T/T_{_F} = 0.17$, paving the way for the study of strongly interacting superfluids of $^{40}$K. In the second part of this thesis, we present a narrow-linewidth, all-solid-state laser source, emitting 5.2 W in the vicinity of the lithium D-line transitions at 671 nm. The source is based on a diode-end-pumped unidirectional ring laser operating on the 1342 nm transition of Nd:YVO$_4$, capable of producing 6.5 W of single-mode light delivered in a diffraction-limited beam. We report on three different approaches for second-haromonic generation of its output beam, namely by employing an enhancement cavity containing a ppKTP crystal, intracavity frequency doubling and a ppZnO:LN waveguide structure
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Suchet, Daniel Léo. „Simulating the dynamics of harmonically trapped Weyl particles with cold atoms Simultaneous sub-Doppler laser cooling of fermionic 6Li and 40K on the D1 line : Theory and experiment Analog simulation of Weyl particles with cold atoms“. Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066262.
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Au cours de ma thèse, j'ai travaillé à la construction de l'expérience Fermix, consacrée à l'étude d'un mélange de fermions (6Li-40K) à très basses températures où les effets quantiques sont prédominants. Nous présentons ici deux résultats principaux. Premièrement, nous avons développé une nouvelle méthode de refroidissement sub-Doppler qui tire parti de l'existence d'états noirs dans la raie optique D1. Cette mélasse grise permet d'atteindre une densité de l'espace des phases de 10⁻⁴, la valeur la plus élevée rapportée dans la littérature pour le refroidissement laser simultané des deux espèces. Grâce à cette étape, nous avons pu réaliser un gaz fortement dégénéré de 3x10⁵ atomes de 40K, répartis dans deux états de spins, à une température de 62 nK, soit 17% de la température de Fermi. D'autre part, nous introduisons une transformation canonique pour montrer l'équivalence formelle entre le comportement de particules ultra-relativistes sans interactions (particules de Weyl) dans un potentiel harmonique et celui de fermions froids confinés dans un piège quadrupolaire. Nous étudions expérimentalement, numériquement et théoriquement la relaxation de tels systèmes vers un état stationnaire, non-Botlzmanien, caractérisé par des températures effectives fortement anisotropes. Cette analogie permet également d'interpréter des propriétés caractéristiques des particules relativistes. Ainsi, nous montrons que le paradoxe de Klein est analogue aux pertes Majorana. Pour finir, nous proposons une étude théorique des interactions médiées à longue distance par un système en dimensions mixtesDuring my PhD, I contributed to the design and construction of the Fermix experiment, dedicated to the study of a 6Li-40K fermionic mixture at ultra low temperatures. Our main results are twofold. First, we developed a new sub-Doppler laser cooling scheme, taking advantage of the existence of dark states in the D1 line of alkali atoms. This so-called \emph{grey molasses} allows for a phase space density up to 10⁻⁴, the highest value reported for the simultaneous laser cooling of those two species. The improvement due to this cooling step enabled the production of a quantum degenerate 40K gas in a dipole trap, with 3x10⁵ atoms in two spin states at 62 nK, corresponding to 17% of the Fermi temperature. Second, introducing a canonical mapping, we showed that non-interacting ultra-relativistic particles (Weyl fermions) in a harmonic trap can be simulated by cold fermions confined in a quadrupole potential. We study experimentally, numerically and theoretically the relaxation of these systems towards a steady state which can not be described by a Boltzman distribution, but rather presents strongly anisotropic effective temperatures. This analogy also allows us to translate fundamental properties of relativistic particles in the language of cold atoms. In particular, we demonstrate that the Klein paradox is equivalent to Majorana losses. Finally, we present a theoretical study of the long range interactions between particles confined in two 2D layers immersed in a 3D atomic cloud
Bücher zum Thema "D1 cooling"
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Refrigeration, International Institute of, Hrsg. Cold chain refrigeration equipment by design: Proceedings of meetings of commissions B1, B2, D1, D2/3 (November 15-18, 1993). Paris: The Institute, 1993.
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Wang, Xue-yi, Jian Pu, Rui-ming Yuan und Jian-hua Wang. „Combined Influence of Surface Deposition and Hole-Blockage on Film-Cooling Performances“. In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56902.
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Commercial aero-engines may operate in dust-laden environments, such as taking off and landing on desert ground or flying through volcano dust cloud, and foreign particles frequently deposit at hot surface and film hole-exits, which results in partial blockage of film holes, clog of cooling air, reduction in cooling effect, and could induce catastrophic damage. This problem has not been well solved up to now. This paper presents an experimental investigation on two surface deposition models (deposition limited to upstream of hole with a peak height of 1.5 diameter of hole called D1.5, and downstream forming a trench with a peak height of 1.0 diameter of hole, called D1) and two blockage models (leading edge of hole LB, and trailing edge TB), as well as two combined models D1.5-LB, and D1-TB. The experiments are conducted in a low speed water tunnel using Planar Laser Induced Fluorescence (PLIF) technique. Through this experiment, the following interesting phenomena, which were not reported in previous literatures, are reveled: 1) The effect of blockage ratio at leading edge on cooling performance of combined D1.5-LB is opposite to individual LB, i.e. in the case of combined D1.5-LB, a higher blockage ratio corresponds to a lower cooling effectiveness; whereas, for individual LB, the cooling effectiveness increases with the blockage ratios in the tested range. 2) At all blowing ratios, the cooling performances of combined D1.5-LB are better than that of perfect model D0-B0 (without deposition and blockage). At all blockage ratios tested in this experiment, in the case of combined D1.5-LB, a higher blowing ratio corresponds to a higher cooling effectiveness and a lager film coverage length. 3) At lower blockage ratios of 0.1 and 0.3, the overall-averaged cooling effectiveness of combined D1-TB is higher than that of perfect model D0-B0. At large blockage ratio 0.5, the blockage effect is dominant, and the averaged cooling effectiveness of combined model D1-TB is lower than that of D0-B0. In the case of individual deposition model D1-B0, although the lateral-averaged film cooling effectiveness is augmented, the area of film cooling is reduced.
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Gevorgian, G. A., K. E. Kahramanian, R. B. Kostanian und E. V. Kosheverskii. „Crystalline Air Cooled CW Laser“. In The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/cleo_europe.1996.cwf40.
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In order to reduce the weight-size dimensions of the lasers and apply their atmospheric low temperetures, it is often needed to use air cooled lasers, instead of traditional water cooled ones. It is known [1], that the heat exchange ratio when cooled diffusely by air, is approximately by two orders of magnitude lower than that for the liquid cooling Therefore, creation of air cooled CW lasers with pump power up to 3kW is one of the actual problems of modern laser techniques. The main problem in creation of similar lasers is to obtain high heat transmission ratios in cooling channels, which will ensure for the lasers working temperature regimes to be near the ones when cooled by liquids. For obtaining such high ratios of heat transmission the authors of this paper succeeded in developing of the turbulence of the flow in the channels with straight flow of the air with Reynolds number R e 0.875 = d 2 − d 1 v P m a x ( d 2 − d 1 ) 2 g k L ρ where d2-d1- is the hydraulic diameter of cooling channel, v-the kinematic viscosity of the air, Pmax-the maximal input pressure of the channel, g-free falling acceleration, k-hydraulic resistance ratio, L-the cooling channel's length, ρ- the air density. The principle of cooling is based on achieving an equality between the times of diffuse propagation of heated air molecule from the cooled object in the plane, perpendicular to the air flow and its running time from the channel's entrance along all its length. Inserting the number Re in the formula for calculating the heat exchange ratio [1] α = λ d 2 − d 1 { … } R e 0.875 P r n , we get its value for cooling channels of various dimensions and configurations, where λ- is the air heat conductivity, Pr - the Prandtl's number, n = 0.4 + 0.5 2 P r + 1 and figure brackets contain tabulated values of this formula and also constructive-technical parameters of the cooled channel very slightly influencing the heat exchange ratio's value.
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Ali, Ehtesham, Hwabhin Kwon, Je-Hyun Lee und Heesung Park. „Analysis of Melting and Solidification Behavior in DED Laser Welding of Inconel 901“. In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82851.
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Abstract In this study, a transient simulation of laser welding is carried out using Directed energy deposition (DED) method for the 4mm thick Inconel 901 plate. Experimental and numerical simulation method are used to investigate the thermal behavior and solidification characteristics. Five different cases are investigated using COMSOL Multiphysics® software. The parameters used in this study are the laser power ranging from 550 W to 750 W and the laser scanning speed ranging from 6.67 to 10.0 mm/s. The cooling time between the melting and solidification process is evaluated in the region under the top surface of substrate for different laser power and laser scanning speed. Among the cases studied, D5 shows the highest temperature variation under top the surface of the substrate, followed by D2, D3, D4, and D1 has the lowest temperature due to lower laser power. The temperature variation under the top surface of substrate is also calculated for different conditions of laser assisted DED processes. The numerical simulation results are compared with the experimental results which are in good agreement and well validated. The obtained conclusions in this paper demonstrated that this numerical study of thermal behavior could provide a better understanding of the melting and solidification process inside the molten pool using laser assisted DED processes.