Volume 39, Issue 9, Pages 763-864(30 July 2002)
Research Article
Embedded turbulence model in numerical methods for hyperbolic conservation laws
NASA Astrophysics Data System (ADS)
Drikakis, D.
2002-07-01
The paper describes the use of numerical methods for hyperbolic conservation laws as an embedded turbulence modelling approach. Different Godunov-type schemes are utilized in computations of Burgers' turbulence and a two-dimensional mixing layer. The schemes include a total variation diminishing, characteristic-based scheme which is developed in this paper using the flux limiter approach. The embedded turbulence modelling property of the above methods is demonstrated through coarsely resolved large eddy simulations with and without subgrid scale models. Copyright
Cross-cultural adaptation of VISA-P score for patellar tendinopathy in Turkish population.
Çelebi, Mehmet Mesut; Köse, Serdal Kenan; Akkaya, Zehra; Zergeroglu, Ali Murat
2016-01-01
VISA-P questionnaire assesses to severity of symptoms and treatment effects in athletes with patellar tendinopathy. The purpose of this study was to translated VISA-P questionnaire into Turkish language and to determine its validity and reliability. The English version of VISA-P questionnaire was translated into Turkish according to the internationally recommended guidelines. Test-retest reliability was determined on 89 participants with time interval 24 h. To determine validity of Turkish VISA-P, 31 (17 male, 14 female) healthy students, 34 (20 male, 14 female) patients with patellar tendinopathy (diagnosed by physical examination and ultrasonography) and 24 (16 male, 8 female) volleyball players (at risk populations) were completed VISA-P-Tr. Internal consistency was determined with Cronbach's alpha. Intraclass correlation coefficients (ICCs) were calculated to analyse test-retest reliability. To assessment of discrimination, VISA-P-Tr scores compared all groups using the Mann-Whitney-U test. The VISA-P-Tr questionnaire showed good test-retest reliability (The Cronbach's alpha was 0.79 and 0.78 respectively and ICC was 0.96). The VISA-P-Tr score (mean ± SD) were 93.7 ± 8.9 and 94.0 ± 8.1 for healthy students, 81.1 ± 13.7 and 80.7 ± 13.4 for volleyball players, 58.8 ± 12.1 and 58.5 ± 11.0 for athletes with patellar tendinopathy. The translated Turkish version of VISA-P has good internal consistency and good reliability and validity. Therefore VISA-P-Tr is useful to evaluate symptoms and follow the treatment effect in athletes with patellar tendinopathy.
Risk Factors for Low Back Pain and Spine Surgery: A Retrospective Cohort Study in Soldiers.
Kardouni, Joseph R; Shing, Tracie L; Rhon, Daniel I
2016-11-01
Musculoskeletal low back pain (LBP) is commonly treated symptomatically, with practice guidelines advocating reserving surgery for cases that fail conservative care. This study examined medical comorbidities and demographic variables as risk factors for chronic/recurrent LBP, spinal surgery, and time to surgery. A 2015 retrospective cohort study was conducted in U.S. Army soldiers (N=1,092,420) from 2002 to 2011. Soldiers with medical encounters for LBP were identified using ICD-9 codes. Surgical treatment for LBP was identified according to Current Procedural Terminology codes. Comorbid medical conditions (psychological disorders, sleep disorders, tobacco use, alcohol use, obesity) and demographic variables were examined as risk factors for chronic/recurrent LBP within 1 year of the incident encounter, surgery for LBP, and time to surgery. Of 383,586 patients with incident LBP, 104,169 (27%) were treated for chronic/recurrent LBP and 7,446 (1.9%) had surgery. Comorbid variables showed increased risk of chronic/recurrent LBP ranging from 26% to 52%. Tobacco use increased risk for surgery by 33% (risk ratio, 1.33; 95% CI=1.24, 1.44). Comorbid variables showed 10%-42% shorter time to surgery (psychological disorders, time ratio [TR]=0.90, 95% CI=0.83, 0.98; sleep disorders, TR=0.68, 95% CI=0.60, 0.78; obesity, TR=0.88, 95% CI=0.79, 0.98; tobacco use, TR=0.58, 95% CI=0.54, 0.63; alcohol use, TR=0.85, 95% CI=0.70, 1.05). Women showed 20% increased risk of chronic/recurrent LBP than men but 42% less risk of surgery. In the presence of comorbidities associated with mental health, sleep, obesity, tobacco use, and alcohol use, LBP shows increased risk of becoming chronic/recurrent and faster time to surgery. Published by Elsevier Inc.
Simulation of Wild Pig Control via Hunting and Contraceptives
2013-10-01
in reproductive cycles, attrition, social group- ing and dynamics, diet and feeding, and movement. ERDC/CERL TR-13-21 5 Figure 1. Model...conditions. ERDC/CERL TR-13-21 19 6 References Adkins, R. N., and L. A. Harveson. 2006. Summer diets of feral hogs in the Davis Mountains, Texas...based control of, feral pigs in the Mediterranean climatic region of south-western Australia. Wildlife Research. 34:125-139. Wyckoff, A. C., S. E
Structural Improvements of Flexible Pavements Using Geosynthetics for Base Course Reinforcement
2009-10-01
as a function of cumulative ESALs measured in an unloaded condition....................................................................... 71 Figure...74 Figure 71 . Comparison of microstrains predicted by the FE model and measured by the...TR-09-11 71 0 1 2 3 4 5 6 7 x 10 6 110 120 130 140 150 160 170 180 190 200 Cumulative ESALs S tr es s (k P a) 100 mm AC 300 mm Base 150 mm AC 300
1980-11-01
Systems: A Raytheon Project History", RADC-TR-77-188, Final Technical Report, June 1977. 4. IBM Federal Systems Division, "Statistical Prediction of...147, June 1979. 4. W. D. Brooks, R. W. Motley, "Analysis of Discrete Software Reliability Models", IBM Corp., RADC-TR-80-84, RADC, New York, April 1980...J. C. King of IBM (Reference 9) and Lori A. Clark (Reference 10) of the University of Massachusetts. Programs, so exercised must be augmented so they
Process Tailoring and the Software Capability Maturity Model(sm).
1995-11-01
A Discipline For Software Engineering, Addison-Wesley, 1995; Humphrey . This book summarizes the costs and benefits of a Personal Software Process ( PSP ...1994. [Humphrey95] Humphrey , Watts S . A Discipline For Software Engineering. Reading, MA: Addison-Wesley Publishing Company, 1995. CMUISEI-94-TR-24 43...practiced and institutionalized. 8 CMU/SEI-94-TR-24 . Leveraging mo n o s I cDocument" IRevise & Analyze Organizational LessonsApproach ’"- Define Processes
van Ravenswaay Claasen, H H; Eggermont, A M; Nooyen, Y A; Warnaar, S O; Fieuren, G J
1994-02-01
The bispecific antibodies (bs-mAbs) OV-TL 3/CD3 and OC/TR (MOv18/CD3) efficiently mediate ovarian tumor cell lysis by cytotoxic T cells and activated peripheral blood lymphocytes (PBL) in vitro. OV-TL 3/CD3 and OC/TR are reactive with tumor-associated antigens on ovarian carcinoma cells (OA3 and CA-MOv18, respectively), and CD3 on activated PBL, bridging both cells and simultaneously inducing activation of the effector cells. In a comparative study we investigated the therapeutic efficacy of OV-TL 3/CD3 and OC/TR by targeting activated PBL with the bs-mAbs against intraperitoneally growing NIH:OVCAR-3 human ovarian carcinoma cells. As they have good tumor localization characteristics, HPLC-purified bispecific F(ab')2 fragments were used to target highly active PHA and IL-2-stimulated PBL effector cells. The efficacy of OV-TL 3/CD3 was compared to OC/TR with respect to tumor-associated antigen (TAA) binding on NIH:OVCAR-3 ascites cells and NIH:OVCAR-3 tumor cell lysis in vitro. In this report we show that ip ovarian cancer-bearing nude mice treated with IL-2 and activated PBL coated with bispecific F(ab')2 had a significantly longer survival than the untreated mice. No significant difference in survival was found between the OC/TR or OV-TL 3/CD3 bispecific antibody, although MOv18 expression was higher on NIH:OVCAR-3 ascites cells and PBL targeted with OC/TR induced slightly higher tumor cell lysis in vitro. Thus, the therapeutic efficacy of these bs-mAbs in vivo could not be predicted by TAA expression or bs-mAb-mediated tumor cell lysis in vitro.
NASA Astrophysics Data System (ADS)
Huang, Xian; Betha, Raghu; Tan, Li Yun; Balasubramanian, Rajasekhar
2016-01-01
Smoke-haze episodes, caused by uncontrolled peat and forest fires, occur almost every year in the South-East Asian region with increased concentrations of PM2.5 (airborne particulate matter (PM) with diameter ≤ 2.5 μm). Particulate-bound trace elements (TrElems), especially carcinogenic and toxic elements, were measured during smoke haze as well as non-haze periods in 2014 as they are considered to be indicators of potential health effects. The bioaccessibilities of 13 TrElems were investigated using two types of simulated lung fluids (SLFs), Gamble's solution and artificial lysosomal fluid (ALF), instead of the commonly used leaching agent (water). The dissolution kinetics was also examined for these TrElems. Many TrElems showed higher solubility in SLFs, and were more soluble in ALF compared to the Gamble's solution. Cu, Mn and Cd were observed to be the most soluble trace elements in ALF, while in Gamble's solution the most soluble trace elements were Cu, Mn and Zn. The dissolution rates were highly variable among the elements. Health risk assessment was conducted based on the measured concentrations of TrElems and their corresponding toxicities for three possible scenarios involving interactions between carcinogenic and toxic TrElems and SLFs, using the United States Environmental Protection Agency (USEPA) human health risk assessment model. The cumulative cancer risks exceeded the acceptable level (1 in a million i.e. 1 × 10-6). However, the estimation of health quotient (HQ) indicated no significant chronic toxic health effects. The risk assessment results revealed that the assessment of bioaccessibility of particulate-bound TrElems using water as the leaching agent may underestimate the health risk.
Declining survival of black brant from subarctic and arctic breeding areas
Leach, Alan G.; Ward, David H.; Sedinger, James S.; Lindberg, Mark S.; Boyd, W. Sean; Hupp, Jerry W.; Ritchie, Robert J.
2017-01-01
Since the mid 1990s, the number of black brant (Branta bernicla nigricans; brant) nests on the Yukon‐Kuskokwim Delta (YKD), Alaska, USA, the historically predominant breeding area of brant, has declined steadily. This has caused researchers and managers to question if arctic breeding populations can compensate for the reduction in brant nests on the YKD. An important component of the assessment of brant population dynamics is having current estimates of first‐year and adult survival. We banded brant at 4 locations in Arctic Alaska and western Canada, and at 1 location in the subarctic, the Tutakoke River (TR) colony on the YKD, 1990–2015. We used joint live and dead mark‐recapture models to estimate first‐year and adult (≥1 yr old) survival of brant. We also used band recovery rates from a Brownie model to assess temporal trends in band recovery rates of adult brant. First‐year survival of brant hatched at TR declined from approximately 0.60 to <0.20 and, although first‐year survival generally was higher for goslings marked in the Arctic, their survival declined from approximately 0.70 in the early 1990s to ≤0.45 in the 2010s. Annual survival of adult females decreased from an average of 0.881 (95% CI = 0.877–0.885) to 0.822 (95% CI = 0.815–0.829) at TR and from 0.851 (95% CI = 0.843–0.860) to 0.821 (95% CI = 0.805–0.836) in the Arctic, from 1990 to 2014. Band recovery rates of adults generally were <1.25% until the last several years of study, when they reached ≤3.5%. Although the current harvest rates may be partially additive to natural mortality, we do not believe that harvest is the main influence on the declines in survival. The general decline in survival rates of brant breeding across a large geographic area may be influenced by a reduction in the quality of migration and wintering ground habitats. We suggest an analysis of seasonal survival of brant to test the hypothesis that declining habitat quality on wintering or spring migration areas is reducing survival. Our results suggest that the number of breeding pairs at TR will continue to decline and also brings into question the ability of arctic breeding populations to grow at a rate necessary to offset the declines on the YKD. Researchers should continue to closely monitor survival and harvest rates of brant, and assess methods currently used to monitor their abundance.
2009-09-01
To characterise the training environment in ICM across Europe, with a particular focus on factors influencing competency-based training. A cross-sectional web-based survey completed by the national coordinator for the CoBaTrICE (Competency-Based Training in Intensive Care medicinE) programme in each of 28 European countries. Since the last survey in 2004, 50% of EU countries have modified their training programmes. Seven have already adopted the CoBaTrICE programme since its completion in 2006. Multidisciplinary access to ICM training ('supraspeciality' model) is available in 57%, most commonly as a 2-year training programme. National examinations are held by 26 (93%); in 24 (86%) this is a mandatory exit exam; ten use the European Diploma of Intensive Care (EDIC). A formal national system for quality assurance of ICM training exists in only 18 (64%) countries. National standards for approving hospitals as training centres vary widely. In 29% there is no designated specialist with responsibility for training at the local level. Time for teaching was cited as inadequate by 93% of respondents; only 21% of trainers receive contractual recognition for their work. In 39% there is no protected teaching time for trainees. Half of countries surveyed have no formal system for workplace-based assessment of competence of trainees. There is considerable diversity in pedagogic structures, processes and quality assurance of ICM across Europe. National training organisations should develop common standards for quality assurance, health systems need to invest in educator support, and the EU should facilitate harmonisation by recognising ICM as a multidisciplinary speciality.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Opitz, Robert; Lutz, Ilka; Nguyen, Ngoc-Ha
2006-04-01
Amphibian metamorphosis represents a unique biological model to study thyroid hormone (TH) action in vivo. In this study, we examined the utility of thyroid hormone receptors {alpha} (TR{alpha}) and {beta}A (TR{beta}A) mRNA expression patterns in Xenopus laevis tadpoles as molecular markers indicating modulation of TH action. During spontaneous metamorphosis, only moderate changes were evident for TR{alpha} gene expression whereas a marked up-regulation of TR{beta}A mRNA occurred in hind limbs (prometamorphosis), head (late prometamorphosis), and tail tissue (metamorphic climax). Treatment of premetamorphic tadpoles with 1 nM 3,5,3'-triiodothyronine (T3) caused a rapid induction of TR{beta}A mRNA in head and tail tissue withinmore » 6 to 12 h which was maintained for at least 72 h after initiation of T3 treatment. Developmental stage had a strong influence on the responsiveness of tadpole tissues to induce TR{beta}A mRNA during 24 h treatment with thyroxine (0, 1, 5, 10 nM T4) or T3 (0, 1, 5, 10 nM). Premetamorphic tadpoles were highly sensitive in their response to T4 and T3 treatments, whereas sensitivity to TH was decreased in early prometamorphic tadpoles and strongly diminished in late prometamorphic tadpoles. To examine the utility of TR{beta}A gene expression analysis for detection of agonistic and antagonistic effects on T3 action, mRNA expression was assessed in premetamorphic tadpoles after 48 h of treatment with the synthetic agonist GC-1 (0, 10, 50, 250 nM), the synthetic antagonist NH-3 (0, 40, 200, 1000 nM), and binary combinations of NH-3 (0, 40, 200, 1000 nM) and T3 (1 nM). All tested concentrations of GC-1 as well as the highest concentration of NH-3 caused an up-regulation of TR{beta}A expression. Co-treatment with NH-3 and T3 revealed strong antagonistic effects by NH-3 on T3-induced TR{beta}A mRNA up-regulation. Results of this study suggest that TR{beta}A mRNA expression analysis could serve as a sensitive molecular testing approach to study effects of environmental compounds on the thyroid system in X. laevis tadpoles.« less
NASA Astrophysics Data System (ADS)
Bhattarai, Nishan; Mallick, Kaniska; Brunsell, Nathaniel A.; Sun, Ge; Jain, Meha
2018-04-01
Recent studies have highlighted the need for improved characterizations of aerodynamic conductance and temperature (gA and T0) in thermal remote-sensing-based surface energy balance (SEB) models to reduce uncertainties in regional-scale evapotranspiration (ET) mapping. By integrating radiometric surface temperature (TR) into the Penman-Monteith (PM) equation and finding analytical solutions of gA and T0, this need was recently addressed by the Surface Temperature Initiated Closure (STIC) model. However, previous implementations of STIC were confined to the ecosystem-scale using flux tower observations of infrared temperature. This study demonstrates the first regional-scale implementation of the most recent version of the STIC model (STIC1.2) that integrates the Moderate Resolution Imaging Spectroradiometer (MODIS) derived TR and ancillary land surface variables in conjunction with NLDAS (North American Land Data Assimilation System) atmospheric variables into a combined structure of the PM and Shuttleworth-Wallace (SW) framework for estimating ET at 1 km × 1 km spatial resolution. Evaluation of STIC1.2 at 13 core AmeriFlux sites covering a broad spectrum of climates and biomes across an aridity gradient in the conterminous US suggests that STIC1.2 can provide spatially explicit ET maps with reliable accuracies from dry to wet extremes. When observed ET from one wet, one dry, and one normal precipitation year from all sites were combined, STIC1.2 explained 66 % of the variability in observed 8-day cumulative ET with a root mean square error (RMSE) of 7.4 mm/8-day, mean absolute error (MAE) of 5 mm/8-day, and percent bias (PBIAS) of -4 %. These error statistics showed relatively better accuracies than a widely used but previous version of the SEB-based Surface Energy Balance System (SEBS) model, which utilized a simple NDVI-based parameterization of surface roughness (zOM), and the PM-based MOD16 ET. SEBS was found to overestimate (PBIAS = 28 %) and MOD16 was found to underestimate ET (PBIAS = -26 %). The performance of STIC1.2 was better in forest and grassland ecosystems as compared to cropland (20 % underestimation) and woody savanna (40 % overestimation). Model inter-comparison suggested that ET differences between the models are robustly correlated with gA and associated roughness length estimation uncertainties which are intrinsically connected to TR uncertainties, vapor pressure deficit (DA), and vegetation cover. A consistent performance of STIC1.2 in a broad range of hydrological and biome categories, as well as the capacity to capture spatio-temporal ET signatures across an aridity gradient, points to the potential for this simplified analytical model for near-real-time ET mapping from regional to continental scales.
1983-10-01
POSSA’P(fOPTI,TDP) * [23] E20:TOP4-T [27] POSS4T(TOP.T,TDP);TP-TOP-(NVL xTI);TOP-,LI~xTT *[28] t125:T’VN1)/-l;IS [30] -(rN=1)/ L53 [31] (P50 C1;TIS; [IV...8217ST4RTI’fl rrVE OF pTjg srvuL4TrovJ=’ [2] TO4-] [3) ’’Tr4E rNC1RE4~VT~’ L4 Tr-] * [5] ’OURA2To’v OP 5rYu&4rrOv=’ 16] TV-T0. TD -1 *[7] PosrT[O’V OF
Deppisch, Nina; Ruf, Peter; Eißler, Nina; Lindhofer, Horst; Mocikat, Ralph
2017-01-01
Combinatorial approaches of immunotherapy hold great promise for the treatment of malignant disease. Here, we examined the potential of combining an immune checkpoint inhibitor and trifunctional bispecific antibodies (trAbs) in a preclinical melanoma mouse model using surrogate antibodies of Ipilimumab and Catumaxomab, both of which have already been approved for clinical use. The specific binding arms of trAbs redirect T cells to tumor cells and trigger direct cytotoxicity, while the Fc region activates accessory cells eventually giving rise to a long-lasting immunologic memory. We show here that T cells redirected to tumor cells by trAbs strongly upregulate CTLA-4 expression in vitro and in vivo. This suggested that blocking of CTLA-4 in combination with trAb treatment enhances T-cell activation in a tumor-selective manner. However, when mice were challenged with melanoma cells and subsequently treated with antibodies, there was only a moderate beneficial effect of the combinatorial approach in vivo with regard to direct tumor destruction in comparison to trAb therapy alone. By contrast, a significantly improved vaccination effect was obtained by CTLA-4 blocking during trAb-dependent immunization. This resulted in enhanced rejection of melanoma cells given after pre-immunization. The improved immunologic memory induced by the combinatorial approach correlated with an increased humoral antitumor response as measured in the sera and an expansion of CD4+ memory T cells found in the spleens. PMID:27966460
Deppisch, Nina; Ruf, Peter; Eißler, Nina; Lindhofer, Horst; Mocikat, Ralph
2017-01-17
Combinatorial approaches of immunotherapy hold great promise for the treatment of malignant disease. Here, we examined the potential of combining an immune checkpoint inhibitor and trifunctional bispecific antibodies (trAbs) in a preclinical melanoma mouse model using surrogate antibodies of Ipilimumab and Catumaxomab, both of which have already been approved for clinical use. The specific binding arms of trAbs redirect T cells to tumor cells and trigger direct cytotoxicity, while the Fc region activates accessory cells eventually giving rise to a long-lasting immunologic memory. We show here that T cells redirected to tumor cells by trAbs strongly upregulate CTLA-4 expression in vitro and in vivo. This suggested that blocking of CTLA-4 in combination with trAb treatment enhances T-cell activation in a tumor-selective manner. However, when mice were challenged with melanoma cells and subsequently treated with antibodies, there was only a moderate beneficial effect of the combinatorial approach in vivo with regard to direct tumor destruction in comparison to trAb therapy alone. By contrast, a significantly improved vaccination effect was obtained by CTLA-4 blocking during trAb-dependent immunization. This resulted in enhanced rejection of melanoma cells given after pre-immunization. The improved immunologic memory induced by the combinatorial approach correlated with an increased humoral antitumor response as measured in the sera and an expansion of CD4+ memory T cells found in the spleens.
Kandasamy, Palani; Moitra, Ranabir; Mukherjee, Souti
2015-01-01
Experiments were conducted to determine the respiration rate of tomato at 10, 20 and 30 °C using closed respiration system. Oxygen depletion and carbon dioxide accumulation in the system containing tomato was monitored. Respiration rate was found to decrease with increasing CO2 and decreasing O2 concentration. Michaelis-Menten type model based on enzyme kinetics was evaluated using experimental data generated for predicting the respiration rate. The model parameters that obtained from the respiration rate at different O2 and CO2 concentration levels were used to fit the model against the storage temperatures. The fitting was fair (R2 = 0.923 to 0.970) when the respiration rate was expressed as O2 concentation. Since inhibition constant for CO2 concentration tended towards negetive, the model was modified as a function of O2 concentration only. The modified model was fitted to the experimental data and showed good agreement (R2 = 0.998) with experimentally estimated respiration rate.
NASA Astrophysics Data System (ADS)
Ebbing, J.; Goerigk, L.; Nasuti, A.; Roberts, D.; Korja, T. J.; Smirnov, M.
2014-12-01
The deep geology of northern Trøndelag is somewhat speculative as the Central Scandinavian Caledonides are intersected by the Møre-Trøndelag Fault Complex (MTFC) and only a few depth-penetrating geophysical profiles exist. Here, we correlate the mapped geological units and faults between a seismic-reflection profile and a MT profile. The seismic-reflection data were acquired in 5 segments over the period 1986-1990. The westernmost section of the seismic profile is dominated by a complex pattern of reflections and diffractions. This type of pattern is typical of polydeformed terranes with a mixture of contrasting felsic and mafic lithologies. The two steeply-dipping strands of the MTFC (Hitra-Snåsa and Verran faults) that transect the profile do not show any distinctive signature in the seismic data. The MT data were acquired in 2007 from the Swedish border to the Norwegian coast. The conductivity profile shows some distinct vertical changes as well as changes from the near-surface to shallow depths. The strands of the MTFC show especially a distinctive change in conductivity. The two profiles are almost parallel but separated by 100 km. To correlate the structures seen on both profiles, we have applied lineament analysis and 3D modelling of the gravity and magnetic field. The tilt derivative of the magnetic and isostatic gravity anomaly clearly allows us to identify and link the main geological boundaries between the profiles and to trace the strands of the MTFC from one profile to the other. This trend analysis indicates that at least the Verran Fault visibly modifies the pattern of seismic reflections. However, the main change in crustal lithology occurs farther to the west, almost at the coast where the Tarva Fault intersects the MT profile. This integrated analysis shows the benefit of combining gravity and magnetic interpretations with MT and seismic data to enable us to understand the near-surface geology and structure in more detail.
Development of Radar Control system for Multi-mode Active Phased Array Radar for atmospheric probing
NASA Astrophysics Data System (ADS)
Yasodha, Polisetti; Jayaraman, Achuthan; Thriveni, A.
2016-07-01
Modern multi-mode active phased array radars require highly efficient radar control system for hassle free real time radar operation. The requirement comes due to the distributed architecture of the active phased array radar, where each antenna element in the array is connected to a dedicated Transmit-Receive (TR) module. Controlling the TR modules, which are generally few hundreds in number, and functioning them in synchronisation, is a huge task during real time radar operation and should be handled with utmost care. Indian MST Radar, located at NARL, Gadanki, which is established during early 90's, as an outcome of the middle atmospheric program, is a remote sensing instrument for probing the atmosphere. This radar has a semi-active array, consisting of 1024 antenna elements, with limited beam steering, possible only along the principle planes. To overcome the limitations and difficulties, the radar is being augmented into fully active phased array, to accomplish beam agility and multi-mode operations. Each antenna element is excited with a dedicated 1 kW TR module, located in the field and enables to position the radar beam within 20° conical volume. A multi-channel receiver makes the radar to operate in various modes like Doppler Beam Swinging (DBS), Spaced Antenna (SA), Frequency Domain Interferometry (FDI) etc. Present work describes the real-time radar control (RC) system for the above described active phased array radar. The radar control system consists of a Spartan 6 FPGA based Timing and Control Signal Generator (TCSG), and a computer containing the software for controlling all the subsystems of the radar during real-time radar operation and also for calibrating the radar. The main function of the TCSG is to generate the control and timing waveforms required for various subsystems of the radar. Important components of the RC system software are (i) TR module configuring software which does programming, controlling and health parameter monitoring of the TR modules, (ii) radar operation software which facilitates experimental parameter setting and operating the radar in different modes, (iii) beam steering software which computes the amplitude co-efficients and phases required for each TR module, for forming the beams selected for radar operation with the desired shape and (iv) Calibration software for calibrating the radar by measuring the differential insertion phase and amplitudes in all 1024 Transmit and Receive paths and correcting them. The TR module configuring software is a major task as it needs to control 1024 TR modules, which are located in the field about 150 m away from the RC system in the control room. Each TR module has a processor identified with a dedicated IP address, along with memory to store the instructions and parameters required for radar operation. A communication link is designed using Gigabit Ethernet (GbE) switches to realise 1 to 1024 way switching network. RC system computer communicates with the each processor using its IP address and establishes connection, via 1 to 1024 port GbE switching network. The experimental parameters data are pre-loaded parallely into all the TR modules along with the phase shifter data required for beam steering using this network. A reference timing pulse is sent to all the TR modules simultaneously, which indicates the start of radar operation. RC system also monitors the status parameters from the TR modules indicating their health during radar operation at regular intervals, via GbE switching network. Beam steering software generates the phase shift required for each TR module for the beams selected for operation. Radar operational software calls the phase shift data required for beam steering and adds it to the calibration phase obtained through calibration software and loads the resultant phase data into TR modules. Timed command/data transfer to/from subsystems and synchronisation of subsystems is essential for proper real-time operation of the active phased array radar and the RC system ensures that the commands/experimental parameter data are properly transferred to all subsystems especially to TR modules. In case of failure of any TR module, it is indicated to the user for further rectification. Realisation of the RC system is at an advanced stage. More details will be presented in the conference.
2006-09-30
DRDC-A, and the NATO Undersea Research Centre, La Spezia Italy (this is ongoing). Under these main topics, accomplishments included: a...associated with clutter from an undersea ridge and mud volcano cluster. RESULTS A constrained comparison of waveguide reverberation theory and...1000 Hz c) 0 10 20 −70 −60 −50 −40 −30 −20 −10 Angle (deg) S ca tte rin g S tr en gt h (d B ) 900 Hz a) Figure 1. Measured (x) seabed a

George Sudarshan