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Journal articles on the topic "ACCESS-CM2"
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Aqasha Raechan Anam, Alif Putra Cakra, Wildan Auliya Azka Wardoyo, Sopia Mince Asary, and Rista Hernandi Virgianto. "Pemetaan Tipe Iklim Oldeman Tahun 2022-2100 Berdasarkan Skenario SSP5-8.5 Model ACCESS-CM2." JIPFRI (Jurnal Inovasi Pendidikan Fisika dan Riset Ilmiah) 7, no. 1 (2023): 20–27. http://dx.doi.org/10.30599/jipfri.v7i1.2046.
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Climate change is part of the most serious problem for the life of the world community today. One sector that is highly vulnerable to the impacts of climate change is the agricultural sector. One method that can be used is to see a picture of the future climate by making climate projections based on certain scenarios. The data used in this study are monthly rainfall data at 4 observation points of BMKG stations as well as Historical and Projection model data from the SSP5-8.5 ACCES-CM2 model scenario at 36 points in the West Java region taken from Copernicus ECMWF at https://cds.climate.copernicus.eu/. The results showed that a comparison of Oldeman's classification based on the 2 projection data used showed differences, namely for SSP2-4.5 data it was more categorical in class D while for SSP5-8.5 data the classification was in class C except for the period 2071-2100 for SSP2-4.5 data showing classification in class B. It can be said that in the West Java region rice can be planted once based on SSP2-4.5 data and twice based on SSP5-8.5 data.
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Trębacz, Piotr, Jan Frymus, Mateusz Pawlik, et al. "Comparison of the Ventral Approach to the Canine Hip Joint Using Gelpi Retractors and an Elastic O-Ring Wound Retractor." Animals 13, no. 22 (2023): 3582. http://dx.doi.org/10.3390/ani13223582.
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This study included 10 fresh adult cadavers of large breed dogs (6 males and 4 females). Their weight ranged from 25 to 45 kg (mean ± SD: 33.9 ± 6.2 kg). The breeds represented were crossbreed dogs (n = 5), German shepherds (n = 2), Bernese mountain dogs (n = 1), American Staffordshire terriers (n = 1), and Gordon setters (n = 1). Access to the target area and identification of the femoral head and neck was achieved with two Gelpi retractors inserted orthogonally and with the O-WR in all procedures. In each dog, the approach to the hip joint was made on the left and right sides. There was no significant difference in the area of the surgical wound bed between the two sides using either the Gelpi retractors (−0.52 ± 1.87 cm2; CI 95%: −1.86, 0.81 cm2; p = 0.398) or the O-WR (−0.27 ± 2.34 cm2; CI 95%: −1.94, 1.41 cm2; p = 0.729). The area of the surgical wound bed was 6.28 ± 1.72 cm2 (2.72–9.70 cm2) for the Gelpi retractors and 6.34 ± 1.81 cm2 (4.13–10.77 cm2) for the O-WR, and the difference between the Gelpi retractors and the O-WR was not significant (−0.06 ± 1.72 cm2; CI 95%: −0.86, 0.74 cm2; p = 0.879)
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Hartawan, I. Putu, Muhamad Zaky Ibnu Malik, Laifhan Setyo Qhairaan, Ken Wiralino, Irfani Zahira Rustiawan, and Dimas Harya Wisanggeni. "Koreksi Bias Data Hujan Proyeksi Coupled Model Intercomparison Project Phase 6 (Cmip6) Di Kota Bima." Cerdika: Jurnal Ilmiah Indonesia 5, no. 1 (2025): 57–66. https://doi.org/10.59141/cerdika.v5i1.2438.
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Perubahan iklim global telah memengaruhi pola curah hujan, khususnya di wilayah tropis, termasuk Kota Bima. Model proyeksi iklim seperti Coupled Model Intercomparison Project Phase 6 (CMIP6) menyediakan data penting untuk memprediksi perubahan iklim, namun sering kali mengandung bias yang signifikan. Penelitian ini bertujuan untuk melakukan koreksi bias pada data proyeksi curah hujan CMIP6 menggunakan lima model dalam skenario SSP5-8.5, yaitu CMCC-CM2-SR5, CESM2-WACCM, ACCESS-CM2, CESM2, dan AWI-CM-1-1-MR, dengan mengintegrasikan data historis dari Global Precipitation Climatology Centre (GPCC) dan data lokal dari BMKG. Hasil penelitian menunjukkan bahwa data historis GPCC memiliki korelasi yang sangat kuat dengan data BMKG, dengan nilai koefisien korelasi sebesar 0,97 dan RMSE sebesar 34,41 mm. Hasil koreksi bias data proyeksi menunjukkan bahwa empat model (CESM2-WACCM, ACCESS-CM2, CESM2, dan AWI-CM-1-1-MR) memiliki pola tren yang serupa berdasarkan analisis Weibull plotting. Sementara itu, model CMCC-CM2-SR5 menunjukkan penyimpangan pola yang signifikan. Implikasi penelitian ini adalah meningkatkan akurasi proyeksi curah hujan untuk mendukung perencanaan mitigasi risiko bencana dan pengelolaan sumber daya air di Kota Bima. Penelitian ini juga membuka peluang untuk pengembangan metode koreksi bias yang lebih efisien dengan mengintegrasikan teknologi pembelajaran mesin dan data lokal yang lebih rinci.
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Muhanna, Nidal, Harley Chan, Jimmy Qiu, et al. "Volumetric Analysis of Endoscopic and Maxillary Swing Surgical Approaches for Nasopharyngectomy." Journal of Neurological Surgery Part B: Skull Base 79, no. 05 (2018): 466–74. http://dx.doi.org/10.1055/s-0037-1617432.
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Objectives/Hypothesis The endoscopic endonasal approach (EEA) for nasopharyngectomy is an alternative to the maxillary swing approach (MSA) for selected recurrent nasopharyngeal carcinomas (NPC). We compare the access between these approaches. Methods Three cadaver specimens were used to compare access volumes of the EEA and MSA. Exposure volumes were calculated using image guidance registration to cone beam computed tomography and tracking of accessible tissue with volumetric quantification. The area of exposure to the carotid artery was measured. Results The MSA provided higher volumes for access volume compared with the EEA (66.6 vs 39.1 cm3, p = 0.009). The working area was larger in the MSA (80.2 vs 56.9 cm2, p = 0.06). The exposure to the carotid artery was higher in the MSA (1.88 vs 1.62 cm2, p = 0.04). The MSA provided larger volume of exposure for tumors of the parapharyngeal space with exposure below the palate. Conclusions This study suggests that the MSA for nasopharyngectomy provides a larger volume of exposure. However, much of the increased exposure relates to exposure of the parapharyngeal space below the palate. The EEA provides adequate access to superior anatomical structures.
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Kataria, Vikas, Benjamin Berte, Yves Vandekerckhove, Rene Tavernier, and Mattias Duytschaever. "Modified Transseptal Puncture Technique in Challenging Septa: A Randomized Comparison to Conventional Technique." BioMed Research International 2017 (2017): 1–5. http://dx.doi.org/10.1155/2017/2351925.
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Background. Transseptal puncture (TSP) can be challenging. We compared safety and efficacy of a modified TSP technique (“mosquito” technique, MOSQ-TSP) to conventional TSP (CONV-TSP). Method. Patients undergoing AF ablation in whom first attempt of TSP did not result in left atrial (LA) pressure (failure to cross, FTC) were randomized to MOSQ-TSP (i.e., puncture of the fossa via a wafer-thin inner stylet) or CONV-TSP (i.e., additional punctures at different positions). Primary endpoint was LA access. Secondary endpoints were safety, time, fluoroscopic dose (dose-area product, DAP), and number of additional punctures from FTC to final LA access. Result. Of 384 patients, 68 had FTC (MOSQ-TSP, n=34 versus CONV-TSP, n=34). No complications were reported. In MOSQ-TSP, primary endpoint was 100% (versus 73.5%, p<0.002), median time to LA access was 72 s [from 37 to 384 s] (versus 326 s [from 75 s to 1936 s], p<0.002), mean DAP to LA access was 1778±2315 mGy/cm2 (versus 9347±10690 mGy/cm2, p<0.002), and median number of additional punctures was 2 [1 to 3] (versus 0, p<0.002). Conclusion. In AF patients in whom the first attempt of TSP fails, the “mosquito” technique allows effective, safe, and time sparing LA access. This approach might facilitate TSP in elastic, aneurysmatic, or fibrosed septa.
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Effiong, Enobong, G. C. Iheanacho, G. V. Awari, and K. S. Iheagwam. "Microbiological Assessment of Smartphone Surfaces Obtained from Final Year Students at Hezekiah University Umudi, Nkwerre, Imo State, Nigeria." Journal of Life and Bio Sciences Research 5, no. 02 (2024): 18–23. http://dx.doi.org/10.38094/jlbsr502118.
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Smartphones of students in tertiary institutions have been described as an understudied and under-explored microcosm by leading public health experts. The microbial quality of smartphone surfaces has been a constant reason for several scientific discussions. Two hundred students were initially targeted for the study, ten students in the final year class at the Hezekiah University Umudi permitted access to their phones during the sampling. The study carried by swabbing the surface of their phones with a normal saline-moistened swab stick using a square quadrant. The content was dislodged and diluted using a 10-fold serial dilution technique. The samples were evaluated for total heterotrophic count, coliform, fungal and Staphylococcal count. The bacterial isolates were tentatively identified using biochemical reactions. The total heterotrophic count of the samples obtained from the male students ranged from Log 2.82 CFU/cm2 to Log 3.21 CFU/cm2 while the total coliform count was observed to range from Log 1.3 CFU/cm2 to Log 1.6 CFU/cm2. The total heterotrophic count ranged from Log 2.82 CFU/cm2 to Log 3.21 CFU/cm2 for male students and from Log 1.6 CFU/cm2 to Log 2.73 CFU/cm2 for female students. The isolates obtained from the study were Acinetobacter sp., Escherichia coli, Proteus sp., Klebsiella sp., Pseudomonas sp. and Staphylococcus sp. There is a need for the University to educate students on the need to routinely use alcohol-based wipes to clean the surfaces of their phones as a precautionary measure to limit diseases associated with the use of mobile phones.
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Kumari, Sonali, Vikram Singh, and Shakti Suryavanshi. "Future Prediction of Consecutive Dry Days (CDD) in Rapti River Basin Using Model ACCESS-CM2 Climate Projection." International Journal of Environment and Climate Change 14, no. 7 (2024): 343–55. http://dx.doi.org/10.9734/ijecc/2024/v14i74275.
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The Rapti River basin in India is a region increasingly vulnerable to extreme precipitation events, which pose significant challenges to water resource management and flood mitigation. This study investigates the extreme precipitation patterns in the Rapti River Basin, India, by analyzing historical and projected data using advanced climate models and indices. Utilizing the Expert Team on Climate Change Detection and Indices (ETCCDI) framework, we focus on Consecutive Dry Days (CDD). The study evaluates the trends under different global warming scenarios of 1.5˚C, 2˚C, and 3˚C, employing ACCESS-CM2 Model. The findings reveal significant variations in the trends and magnitudes of CDD across the different warming levels. At 1.5˚C, CDD shows a decreasing trend. At 2˚C, models project a continued decrease in CDD. At 3˚C, mixed trends are observed with notable increases in CDD, highlighting the potential for prolonged wet periods and increased flood risks. The study underscores the impact of climate change on the hydrological behavior of the Rapti River Basin, emphasizing the need for adaptive water resource management strategies. It provides valuable insights into the future precipitation trends in the Rapti River Basin, guiding the development of strategies to enhance resilience against climate-induced hydrological changes.
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Ali, Hossam Mohsen Hassan Hussein, Sameh Mohamed Abdel-Wahab, Amr Mahmoud Abdel-Samad, and Ahmed El-Shimy. "Unilateral versus Bilateral Femoral Arterial Access for Uterine Artery Embolization." Open Access Macedonian Journal of Medical Sciences 10, B (2022): 1432–39. http://dx.doi.org/10.3889/oamjms.2022.9828.
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Background: Uterine fibroids are the most common benign tumors in women. Their clinical presentation includes menorrhagia, metrorrhagia, lower abdominal pain and infertility. Treatment of uterine fibroids includes medical management, surgical resection known as myomectomy as well as minimally invasive options like uterine artery embolization. Uterine artery embolization can be done via unilateral or bilateral femoral arterial access. We aim to define the differences between unilateral and bilateral femoral access in concern to radiation dose, procedure time , fluoroscopy time as well as the number of angiographic images.
 Methods: A total of 48 patients were divided into two groups equally; one with a unilateral femoral access and the other group with a bilateral femoral arterial access.
 Results: The age of the patients ranged between 25 to 40 years, embolization was done with calibrated spheres. Bilateral procedures compared to the unilateral ones had less fluoroscopy times (8.6 minutes vs 24.3 mins) , less total procedure time (28.4 minutes vs 54.4 minutes) and less dose area product (155 Gy cm2 vs 340.5 Gy cm2) as well as less mean number of angiographic images (93.8 vs 176.5) with no significant difference in puncture site complications.
 Conclusion: Fluoroscopy times, procedure times, number of angiographic images as well as radiation dose were significantly lower in the bilateral approach with no significant difference in the rates of puncture site complications between the two approaches.
 Keywords: Uterine Artery Embolization, uterine fibroids, unilateral versus bilateral access.
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Cragg, James, Danielle Lowry, Jonathan Hopkins, et al. "Safety and Outcomes of Ipsilateral Antegrade Angioplasty for Femoropopliteal Disease." Vascular and Endovascular Surgery 52, no. 2 (2017): 93–97. http://dx.doi.org/10.1177/1538574417739762.
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Purpose: Previous reports have suggested higher periprocedural complications after ipsilateral antegrade femoral arterial access (AA). We looked at a contemporary series comparing complication rates between AA and contralateral retrograde femoral arterial access (RA) for femoropopliteal angioplasty. Method: A prospective review of all cases between 2010 and 2015 in a United Kingdom tertiary vascular center. Demographical and procedural data were obtained for those undergoing percutaneous femoropopliteal angioplasty. The primary outcome looked at periprocedural complications including retroperitoneal hematoma, pseudoaneurysm, hematoma requiring transfusion, arteriovenous fistulation, and surgical intervention. Secondary outcomes included contrast and radiation doses in addition to procedural failure leading to major amputation. Results: A total of 556 (66% male) patients underwent femoropopliteal angioplasty, 461 (82%) via AA. Groups were of comparable age, sex, comorbidity, and symptomatology. AA patients had a lower body mass index, 26 versus 29 ( P = .005). No significant difference was seen in periprocedural (15.8% AA vs 11.6% RA; P = 0.292) or access site complications (3.7% AA vs 1.1% RA; P = 0.186). There was less need for a closure device, 40.3% AA vs 73% RA ( P < .01), less contrast, 94 mL AA: 114 mL RA ( P < .001), and less radiation, 3487 cGy cm2 AA: 9697 cGy cm2 RA ( P < .001). Arterial access was also associated with greater technical success of 83.8%: 73.3% RA ( P = .002). Conclusions: Arterial access is associated with higher technical success and reduced contrast/radiation doses with no significant difference in complications compared to RA contrary to previous reports.
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Ghose, Tapan, Ranjan Kachru, Jaideep Dey, et al. "Safety and Feasibility of Ultrasound-Guided Access for Coronary Interventions through Distal Left Radial Route." Journal of Interventional Cardiology 2022 (March 25, 2022): 1–10. http://dx.doi.org/10.1155/2022/2141524.
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Aims. Left distal transradial arterial approach (ldTRA) is a new interventional route that spares right radial artery (RRA) for use in haemodialysis and as bypass graft. Vasant Kunj Left dIstal Transradial ArtEry approach (VKLITE) study aimed to assess the feasibility and safety of ldTRA access during coronary angiography (CAG) and percutaneous coronary intervention (PCI). Methods and Results. Between April 2018 and June 2020, 108 patients were enrolled and underwent CAG ± PCI via ultrasound guided ldTRA. Arterial puncture, CAG, and PCI were successful in 96.3% (104/108), 92.1% (93/101), and 94.1% (32/34) patients, respectively. Access site crossover rate was 14/108 (13.0%). Mean puncture, procedure, and haemostasis time (minutes) were 6.7 ± 7.1, 55.7 ± 32.8, and 23.1 ± 11.9. Median total fluoroscopic time was 6.6 minutes (IQR-14.2), and median total radiation dose was 39.2 Gy-cm2 (IQR-97.0). Local haematoma occurred in 11 patients (10.2%) with major haematoma in 1.9%, all recovering within three weeks. Mean pain score was 2.4 ± 2.3, and patient satisfaction score was 9.0 ± 1.3. LdTRA access compared with RRA access (n = 121) showed significantly increased mean procedure time (55.7 ± 32.8 vs. 43.9 ± 26.0 minutes, p = 0.01) and median total fluoroscopic time (6.6 [IQR-14.2] vs. 4.7 [IQR-8.2] minutes, p = 0.02), with similar median total radiation dose (39.2 [IQR-97.0] vs. 43.8 [IQR-54.5] Gy-cm2, p = 0.56). No radial artery loss, dissection, pseudoaneurysm, arteriovenous fistula, or nerve injury was noted. Conclusions. LdTRA access is feasible with few complications during CAG/PCI. Patient comfort and satisfaction makes it a desirable route for coronary interventions.
Conference papers on the topic "ACCESS-CM2"
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Bao, Guangyu, Xiaomin Chen, and Ramesh K. Agarwal. "Optimization of Anastomotic Geometry for Vascular Access Fistula." In ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-26130.
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Arteriovenous fistula (AVF) is one type of vascular access which is a surgically created vein used to remove and return blood during hemodialysis [1]. It is a long-term treatment for kidney failure. Although clinical treatment and technology have both achieved great improvements in recent years, the vascular access for hemodialysis still has significant early failure rates after the insertion of AVF in patients [2]. Studies have shown that stenosis in the vascular access circuit is the single major cause for access morbidity. Majority of efforts to understand the mechanisms of stenosis formation, and its prevention and management have largely focused on understanding and managing this complication based on the pathophysiology, tissue histology and molecular biology; however these efforts have not resulted in significant progress to date. We believe that the major impact in this area will come from continued and accurate understanding of the hemodynamics, and by development of techniques of intervention to modulate factors such as flow rates, pressures and compliance of the circuit. The goal of this paper is to study anastomotic models of AV access using Computational Fluid Dynamics (CFD) and optimize them to minimize the wall shear stress (WSS). In order to achieve this goal, the commercial CFD software FLUENT [3] is employed in conjunction with a single objective genetic algorithm [4]. Computations for two types of AVF currently in use in clinical practice are performed. AVF with 25° angle/3–4mm diameter and 90° angle/3–5mm diameter are selected to conduct the optimization. A single-objective genetic algorithm is employed in the optimization process and a k-kl-ω turbulence model is employed in CFD simulations; this model can accurately compute transitional/turbulent flows. In order to optimize for the same flow conditions, a fixed boundary condition is used during the optimization process. Computations for 16 to 20 generations of the selected AVFs are obtained from the genetic algorithm solver. The maximum WSS in the two AVFs considered are 6997.8 and 7750 dynes/cm2; however, the maximum WSS in the shape-optimized AVFs are reduced to 3511.2 and 4293.9 dynes/cm2 respectively, which have decreased by 49.82% and 44.59% respectively. Thus, the probability of the formation of stenosis in AVFs and early failure rates of vascular access are reduced by using the optimized AVFs.
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Bao, Guangyu, Xiaomin Chen, and Ramesh K. Agarwal. "Optimization of Anastomotic Geometry for Vascular Access Fistula." In ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7612.
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Arteriovenous fistula (AVF) is one type of vascular access which is a surgically created vein used to remove and return blood during hemodialysis [1]. It is a long-term treatment for kidney failure. Although clinical treatment and technology have both achieved great improvements in recent years, the vascular access for hemodialysis still has significant early failure rates after the insertion of AVF in patients [2]. Studies have shown that stenosis in the vascular access circuit is the single major cause for access morbidity. Majority of efforts to understand the mechanisms of stenosis formation, and its prevention and management have largely focused on understanding and managing this complication based on the pathophysiology, tissue histology and molecular biology; however these efforts have not resulted in significant progress to date. We believe that the major impact in this area will come from continued and accurate understanding of the hemodynamics, and by development of techniques of intervention to modulate factors such as flow rates, pressures and compliance of the circuit. The goal of this paper is to study anastomotic models of AV access using Computational Fluid Dynamics (CFD) and optimize them to minimize the wall shear stress (WSS). In order to achieve this goal, the commercial CFD software FLUENT [3] is employed in conjunction with a single objective genetic algorithm [4]. Computations for two types of AVF currently in use in clinical practice are performed. AVF with 25° angle/3–4mm diameter and 90° angle/3–5mm diameter are selected to conduct the optimization. A single-objective genetic algorithm is employed in the optimization process and a k-kl-ω turbulence model is employed in CFD simulations; this model can accurately compute transitional/turbulent flows. In order to optimize for the same flow conditions, a fixed boundary condition is used during the optimization process. Computations for 16 to 20 generations of the selected AVFs are obtained from the genetic algorithm solver. The maximum WSS in the two AVFs considered are 6997.8 and 7750 dynes/cm2; however, the maximum WSS in the shape-optimized AVFs are reduced to 3511.2 and 4293.9 dynes/cm2 respectively, which have decreased by 49.82% and 44.59% respectively. Thus, the probability of the formation of stenosis in AVFs and early failure rates of vascular access are reduced by using the optimized AVFs.
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Rodriguez, G. A., R. M. Hart, A. J. Sievers, and Z. Schlesinger. "Far-IR intensity dependence of the cyclotron resonance of a 2-D electron gas." In OSA Annual Meeting. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oam.1987.tud3.
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A transversely excited atmospheric CO2 laser pumped far-IR laser has been used to prove the cyclotron resonance line shape of a 2-D electron gas at GaAs/AlGaAs interface for intensities up to 1 MW/cm2. Samples with densities between 0.9 and 4.5 × 1011 electrons/cm2 at 1.7 K as determined by Shubnikov-de Haas resistivity measurements have been studied. The present work focuses on extending the range of frequencies beyond that reported previously.1 The sample is mounted in the Faraday configuration inside a 10-T superconducting solenoid in an optical access cryostat. At far-IR frequencies between 8 and 120 cm−1 the cyclotron resonance line shape is obtained by measuring the transmission as a function of the magnetic field. At high intensity the cyclotron resonance line shape broadens in a way consistent with carrier heating. The onset intensity for this nonlinear behavior increases with increasing frequency.
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Korn, G., C. Y. Chien, J. S. Coe, et al. "Highly efficient second harmonic generation of ultra-intense Nd:glass laser pulses." In International Conference on Ultrafast Phenomena. Optica Publishing Group, 1994. http://dx.doi.org/10.1364/up.1994.md.16.
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The technique of chirped pulse amplification (CPA) [1] has been successfully used to generate peak laser powers well beyond the terawatt region [2-4], These subpicosecond laser pulses when focused can produce intensities exceeding 1018 W/cm2, thus giving access to new regimes of laser-matter interaction. Second harmonic generation (SHG) in nonlinear crystals is important because it extends the available wavelength range and significantly improves the contrast ratio. This is an important issue for high density laser-plasma experiments in which the fs-laser radiation should interact with the solid rather than with a pre-formed plasma.
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Jung, Ki Wook, Hyoungsoon Lee, Chirag Kharangate, et al. "Experimental Investigation of Single-Phase Cooling in Embedded Microchannels: 3D Manifold Heat Exchanger With R-245fa." In ASME 2019 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ipack2019-6400.
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Abstract High performance and economically viable thermal cooling solutions must be developed to reduce weight and volume, allowing for a wide-spread utilization of hybrid electric vehicles. The traditional embedded microchannel cooling heat sinks suffer from high pressure drop due to small channel dimensions and long flow paths in 2D-plane. Utilizing direct “embedded cooling” strategy in combination with top access 3D-manifold strategy reduces the pressure drop by nearly an order of magnitude. In addition, it provides more temperature uniformity across large area chips and it is less prone to flow instability in two-phase boiling heat transfer. Here, we present the experimental results for single-phase thermofluidic performance of an embedded silicon microchannel cold-plate bonded to a 3D manifold for heat fluxes up to 300 W/cm2 using single-phase R-245fa. The heat exchanger consists of a 52 mm2 heated area with 25 parallel 75 × 150 μm2 microchannels, where the fluid is distributed by a 3D-manifold with 4 micro-conduits of 700 × 250 μm2. Heat is applied to the silicon heat sink using electrical Joule-heating in a metal serpentine bridge and the heated surface temperature is monitored in real-time by Infra-red (IR) camera and electrical resistance thermometry. The experimental results for maximum and average temperatures of the chip, pressure drop, thermal resistance, average heat transfer coefficient for flow rates of 0.1, 0.2. 0.3 and 0.37 lit/min and heat fluxes from 25 to 300 W/cm2 are reported. The proposed Embedded Microchannels-3D Manifold Cooler, or EMMC, device is capable of removing 300 W/cm2 at maximum temperature 80 °C with pressure drop of less than 30 kPa, where the flow rate, inlet temperature and pressures are 0.37 lit/min, 25 °C and 350 kPa, respectively. The experimental uncertainties of the test results are estimated, and the uncertainties are the highest for heat fluxes &lt; 50 W/cm2 due to difficulty in precisely measuring the fluid temperature at the inlet and outlet of the micro-cooler.
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Ansari, S., T. Cader, N. Stoddard, et al. "Spray Cooling Thermal Management of a Semiconductor Chip Undergoing Probing, Diagnostics, and Failure Analysis." In ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35206.
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With the proliferation of flip chip packaging and multiple metal layer technology in advanced semiconductor integrated circuits (IC’s), traditional front-side probing and failure analysis tools are no longer viable. Full transistor level access from the substrate side (i.e., backside) of the chip is now required to fully realize such investigative work. Silicon is transmissive in the near-IR above its bandgap (≅ 1,000nm to 1,100nm). As a result, transistor level access can be achieved by optical means. To enable such optical access, it is necessary to first remove all heat dissipating devices such as finned heat sinks and integrated heat spreaders placed in contact with the silicon substrate. For most applications, the silicon is then mechanically thinned down to approximately 100μm, and a microscope objective is used to “probe” the chip optically for diagnostics and failure analysis. During such diagnostics and failure analysis, the device under test (DUT) is electrically exercised typically “at speed”, which translates into high power dissipation levels. A thermal management system that can be physically and optomechanically integrated with state-of-the-art diagnostics and failure analysis systems, and can dissipate significant power levels is required to maintain the DUT’s temperature equilibrium and avoid thermal runaway, that could irreversibly damage the DUT. One possible and efficient solution is provided by spraying a dielectric coolant directly onto the chip. In the present study, a test chip was used in conjunction with an exact model of a novel microscope objective that is in full contact with the device. The test chip was powered in increments from 0 to 82W/cm2, and the device level temperature was measured by several temperature sensors embedded in the chip. A spray head was designed to deliver conditioned coolant to the test chip’s surface, while simultaneously accommodating the obstruction of the microscope objective and allowing full optical access to the entire chip surface. Thermal performance results for the cooling system are provided for uniform heat flux levels of 30, 52, and 82W/cm2, with the optical probe located in the worst-case center of the test chip. For all heat fluxes studied, the maximum device level temperature did not exceed 60°C, the across-chip temperature differential was approximately 31°C, and surface temperature fluctuations were seen to have a standard deviation of less than ±1°C. The results are discussed in-depth, and are put in perspective of industry needs.
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Schneider, C., R. Hampel, A. Traichel, A. Hurtado, S. Meissner, and E. Koch. "Experimental Investigation of Nucleate Boiling on Capillary Tubes Under PWR Specific Subcooling and Flow Parameters." In 2012 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icone20-power2012-54640.
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During full power operation of Pressurized Water Reactors (PWR), heat transfer phenomena of subcooled nucleate boiling may occur on the surface of the fuel rods. Despite high subcooling, this behavior results from the high heat flux up to 100 W/cm2 where vapor bubbles condensate when they are detached from the rod surface. In case of an accident with disturbance of cooling during transition from bubble to film boiling the critical heat flux (CHF) can be reached. This paper outlines the experimental investigation of heat transfer during subcooled flow boiling on a capillary tube. To investigate the heat transfer processes under these boiling conditions, a test facility for flow boiling with access for optical measuring methods was constructed. The temperature is measured with a thermocouple inside the tube while boiling bubbles are generated on the outside. For different subcooling and flow velocity the heat flux is increased in a range from zero up to approximately 115 W/cm2. The major aims of these investigations are to generate a database for modeling of these dependencies in computational fluid dynamic (CFD) codes and enhance the knowledge of phenomenological effects of subcooled flow boiling. This provides a contribution for the prediction of the critical heat flux with simulation codes.
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Pugsley, Deborah Nassif, and Lutz Hüwel. "Rayleigh and Raman Diagnostic of Laser Generated Plasmas." In Laser Applications to Chemical and Environmental Analysis. Optica Publishing Group, 1996. http://dx.doi.org/10.1364/lacea.1996.lwd.13.
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Laser-produced plasmas have long attracted the attention of researchers because of their unusual properties coupled with ease of generation. With laser power densities above approximately 1013 W/cm2 high electron densities and temperatures can be achieved and here x-ray lasers and laser fusion are important applications. At lower intensities, among other applications plasma etching and spectrochemical analysis make use of laser plasmas. We have found1 that for laser power densities of about 1010 W/cm2 the temperatures in the aftermath of Q-switched laser sparks in air (or other gases) can be several thousand degree Kelvin, even at times as late as 100 μs after ignition. Obviously, the plasma must eventually decay and approach ambient temperature. At least in principle, this opens the possibility to access conditions relevant for combustion and other high temperature chemical processes-even if only on a small spatial scale and during short time intervals. To study the feasibility of such high rep rate generation of temperatures in the range from say 300 to 3000 K we have investigated the spatial and temporal structure of Nd:YAG laser generated sparks in air and other gases during their final stages of decay, i.e. when their temperature and pressure approaches that of the surrounding gas.
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Hsu, W. F., and A. A. Sawchuk. "High accuracy address decoding scheme for 2-D optical-memory devices." In OSA Annual Meeting. Optica Publishing Group, 1993. http://dx.doi.org/10.1364/oam.1993.mzz.3.
Full textAbstract:
Optical data storage has advantages over electronic memory in data capacity and access bandwidth. The high bandwidth of optical storage is mainly due to the large access unit (page), perhaps 128 × 128 to IK × IK bits at each read/write cycle [1]. Work is in progress on developing 2-D cell-oriented optoelectronic (OE) devices for short-term optical data storage or buffering, having a typical density of 1 Mbit/cm2 [2]. In this paper, an electrically controlled, optical addressing scheme for random access to a 2-D OE array is presented. The address decoding scheme employs micro laser sources, volume holograms, and a smart pixel array. Approximately 4 log 2 J binary patterns are recorded in a volume hologram acting as an optical addressing system. The reconstruction beams from the laser sources regenerate half of the recorded patterns, which overlap at the image plane. Using a thresholding operation implemented by smart pixel devices, a designated storage position can be identified. In this scheme, coding technology is used to achieve a high relative ratio of the first two high intensity levels. The relative intensity ratio is constant and independent of the OE storage size. Using this scheme, the optical buffer can thus tolerate larger noise and non-uniformities.
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Estler, R. C., E. C. Apel, and N. S. Nogar. "Laser Etching and Evaporation of CaF2 Studied by Mass Spectrometry." In Microphysics of Surfaces, Beams, and Adsorbates. Optica Publishing Group, 1987. http://dx.doi.org/10.1364/msba.1987.wc10.
Full textAbstract:
In this work we describe the interaction of relatively high-fluence laser pulses (ϕ≥10 J/cm2) with polished CaF2 substrates. Both electron impact- and laser ionization-mass spectrometry have been used to probe the material spalled by the fundamental(1.06μ) and harmonic (355 nm and 266 nm) outputs from a Q-switched Nd:YAG laser. Primary ions produced in the source region of a quadrupole mass spectrometer were detected by turning off the eletron impact ionizer, while survey electron impact mass spectra were typically acquired at an energy of 75 eV. A time-of-flight mass spectrometer was modified to permit optical access by both the etching and interrogation laser beams1. This latter apparatus was used to measure velocity distributions, and to provide optical spectroscopic identification of the ion precursors.