Last 7 days
Bookmark and Share    
Full Text
See detailConstructive design of an aluminum microchannel evaporator for a solar hybrid module
Schneider, Lars Marvin; Rullof, Johannes UL

Poster (2016)

This poster summarizes the findings of the scientific report with the following content: As part of the PVT-direkt project, a constructive evaporator design was developed. First, the findings of the ... [more ▼]

This poster summarizes the findings of the scientific report with the following content: As part of the PVT-direkt project, a constructive evaporator design was developed. First, the findings of the current project, the necessary manufacturing fundamentals and the problem of lubricating oil return are presented. Designing the aluminum evaporator was based on a comprehensive three-phase structure. This is first aimed at identifying relevant material properties and their availability. A thorough literature review was carried out to evaluate the findings with respect to the refrigerant distribution and the oil recirculation. Following a constructive evaporator design was developed with respect to the identified standard temperature drop caused by pressure losses to ensure the oil return in comparable evaporator concepts. From the results of a simulation of the evaporation process, the temperature distribution was analyzed in connection with the created design model. Due to the complexity of simulating the refrigerant distribution, this simulation was not carried out – only their general influence is involved. All of this resulted in two evaporator concepts - a harp and a meander model – which were ultimately evaluated and converted into manufacturing drawings. Therefore, this document provides the manufacturing specifications for the prototype to be produced. [less ▲]

Detailed reference viewed: 7 (0 UL)
Full Text
See detailExperimental studies of the technical feasibility of a lamination process for PVT-direct modules
Hilger, Lukas; Roßbach, Nils; Wirth, Florian et al

Poster (2016)

The PVT-direct module covers the technical connection of solar PV technology and solarthermal systems. The structure is similar to conventional PV modules apart from the backsheet which is replaced by an ... [more ▼]

The PVT-direct module covers the technical connection of solar PV technology and solarthermal systems. The structure is similar to conventional PV modules apart from the backsheet which is replaced by an aluminum backside plate. Along with compressor, gas cooler for heat rejection and expansion valve the PVT-direct module acts as an evaporator in a heat-pump cycle. The module is characterized by a direct CO2 evaporation in small microchannels which are brazed on the aluminum backside plate. The combination of both photovoltaic and thermal components in one module leads to high demands in terms of the choice of materials and the production process itself. In this context, further investigations on the technical feasibility of a lamination process for solar PVT-direct modules are necessary in order to guarantee an intended market maturity. The development of a suitable lamination process and its parameters form the major part of this work. The lamination schedule depends on the performance and structure of the used encapsulating material as well as the laminator itself. The lamination process is adjusted through experimental studies until satisfactory results are achieved. It can be characterized by the maximum lamination temperature and the total process time along with the heating/cooling ramp. The additional aluminum backside plate including headers and microchannels can have a significant impact on the PVT-direct module during lamination process. Therefore, measurement methods which indicate the state of the module after the lamination are required. On the one hand, the quality of the adhesion between the different parts of the module is an important factor for long-term resistance of the system. The cross linking of the encapsulating material and of the adhesion layer is verified by DSC-Measuring. On the other hand - due to a changed design of the PVT direct module and mechanical stress distribution during the lamination process - the mechanical condition of the cells inside of the laminate is checked. This can be evaluated by Electroluminescence-Measuring in order to ensure the absence of cracks and fraction of the PV-cells. Current tasks involve the distortion of the laminated modules due to different thermal expansion coefficients of glass and aluminum as well as the occurrence of blisters in the laminate. These issues and the lamination of a module in standard measures will be addressed in the ongoing process of the project. [less ▲]

Detailed reference viewed: 11 (1 UL)
Full Text
See detailBoah, siehst du schlau aus! Intelligenzdiagnostik auf einen Blick – funktioniert das?
Baudson, Tanja UL

Article for general public (2016)

Detailed reference viewed: 4 (2 UL)
Full Text
See detailDistributed Processing of Generalized Graph-Pattern Queries in SPARQL 1.1
Gurajada, Sairam; Theobald, Martin UL

in CoRR (2016), abs/1609.05293

Detailed reference viewed: 5 (0 UL)
Full Text
See detailLearning Tuple Probabilities
Dylla, Maximilian; Theobald, Martin UL

in CoRR (2016), abs/1609.05103

Detailed reference viewed: 8 (2 UL)
Full Text
Peer Reviewed
See detailJ-NERD: Joint Named Entity Recognition and Disambiguation with Rich Linguistic Features
Nguyen, Dat Ba; Theobald, Martin UL; Weikum, Gerhard

in TACL (2016), 4

Detailed reference viewed: 5 (1 UL)
Full Text
Peer Reviewed
See detailDistributed Set Reachability
Gurajada, Sairam; Theobald, Martin UL

in Proceedings of the 2016 International Conference on Management of Data, SIGMOD Conference 2016, San Francisco, CA, USA, June 26 - July 01, 2016 (2016)

Detailed reference viewed: 5 (1 UL)
Full Text
See detailÜberflieger oder Oberfreak? Die Darstellung von Hochbegabten in den Medien.
Baudson, Tanja UL

Article for general public (2015)

Detailed reference viewed: 5 (0 UL)
Full Text
See detailAusgemänndelt! Tilgen sich Männer häufiger durch Dummheit aus dem Genpool als Frauen?
Baudson, Tanja UL

Article for general public (2015)

Detailed reference viewed: 3 (0 UL)
Full Text
Peer Reviewed
See detailStabilization with the Dynamic Cervical Implant: a novel treatment approach following cervical discectomy and decompression.
Matge, Guy; Berthold, Christophe; Gunness, Vimal Raj Nitish et al

in Journal of neurosurgery. Spine (2015), 22(3), 237-45

OBJECT: Although cervical total disc replacement (TDR) has shown equivalence or superiority to anterior cervical discectomy and fusion (ACDF), potential problems include nonphysiological motion ... [more ▼]

OBJECT: Although cervical total disc replacement (TDR) has shown equivalence or superiority to anterior cervical discectomy and fusion (ACDF), potential problems include nonphysiological motion (hypermobility), accelerated degeneration of the facet joints, particulate wear, and compromise of the mechanical integrity of the endplate during device fixation. Dynamic cervical stabilization is a novel motion-preserving concept that facilitates controlled, limited flexion and extension, but prevents axial rotation and lateral bending, thereby reducing motion across the facet joints. Shock absorption of the Dynamic Cervical Implant (DCI) device is intended to protect adjacent levels from accelerated degeneration. METHODS: The authors conducted a prospective evaluation of 53 consecutive patients who underwent DCI stabilization for the treatment of 1-level (n = 42), 2-level (n = 9), and 3-level (n = 2) cervical disc disease with radiculopathy or myelopathy. Forty-seven patients (89%) completed all clinical and radiographic outcomes at a minimum of 24 months. Clinical outcomes consisted of Neck Disability Index (NDI) and visual analog scale (VAS) scores, neurological function at baseline and at latest follow-up, as well as patient satisfaction. Flexion-extension radiography was evaluated for device motion, implant migration, subsidence, and heterotopic ossification. Cervical sagittal alignment (Cobb angle), functional spinal unit (FSU) angle, and range of motion (ROM) at index and adjacent levels were evaluated with WEB 1000 software. RESULTS: The NDI score, VAS neck and arm pain scores, and neurological deficits were significantly reduced at each postoperative time point compared with baseline (p < 0.0001). At 24 months postoperatively, 91% of patients were very satisfied and 9% somewhat satisfied, while 89% would definitely and 11% would probably elect to have the same surgery again. In 47 patients with 58 operated levels, the radiographic assessment showed good motion (5 degrees -12 degrees ) of the device in 57%, reduced motion (2 degrees -5 degrees ) in 34.5%, and little motion (0-2 degrees ) in 8.5%. The Cobb and FSU angles improved, showing a clear tendency for lordosis with the DCI. Motion greater than 2 degrees of the treated segment could be preserved in 91.5%, while 8.5% had a near segmental fusion. Mean ROM at index levels demonstrated satisfying motion preservation with DCI. Mean ROM at upper and lower adjacent levels showed maintenance of adjacent-level kinematics. Heterotopic ossification, including 20% minor and 15% major, had no direct impact on clinical results. There were 2 endplate subsidences detected with an increased segmental lordosis. One asymptomatic anterior device migration required reoperation. Three patients underwent a secondary surgery in another segment during follow-up, twice for a new disc herniation and once for an adjacent degeneration. There was no posterior migration and no device breakage. CONCLUSIONS: Preliminary results indicate that the DCI implanted using a proper surgical technique is safe and facilitates excellent clinical outcomes, maintains index-and adjacent-level ROM in the majority of cases, improves sagittal alignment, and may be suitable for patients with facet arthrosis who would otherwise not be candidates for cervical TDR. Shock absorption together with maintained motion in the DCI may protect adjacent levels from early degeneration in longer follow-up. [less ▲]

Detailed reference viewed: 5 (0 UL)
Full Text
Peer Reviewed
See detailVisualization of the medial forebrain bundle using diffusion tensor imaging.
Hana, Ardian; Hana, Anisa; Dooms, Georges et al

in Frontiers in neuroanatomy (2015), 9

Diffusion tensor imaging is a technique that enables physicians the portrayal of white matter tracts in vivo. We used this technique in order to depict the medial forebrain bundle (MFB) in 15 consecutive ... [more ▼]

Diffusion tensor imaging is a technique that enables physicians the portrayal of white matter tracts in vivo. We used this technique in order to depict the medial forebrain bundle (MFB) in 15 consecutive patients between 2012 and 2015. Men and women of all ages were included. There were six women and nine men. The mean age was 58.6 years (39-77). Nine patients were candidates for an eventual deep brain stimulation. Eight of them suffered from Parkinson's disease and one had multiple sclerosis. The remaining six patients suffered from different lesions which were situated in the frontal lobe. These were 2 metastasis, 2 meningiomas, 1 cerebral bleeding, and 1 glioblastoma. We used a 3DT1-sequence for the navigation. Furthermore T2- and DTI- sequences were performed. The FOV was 200 x 200 mm(2), slice thickness 2 mm, and an acquisition matrix of 96 x 96 yielding nearly isotropic voxels of 2 x 2 x 2 mm. 3-Tesla-MRI was carried out strictly axial using 32 gradient directions and one b0-image. We used Echo-Planar-Imaging (EPI) and ASSET parallel imaging with an acceleration factor of 2. b-value was 800 s/mm(2). The maximal angle was 50 degrees . Additional scanning time was < 9 min. We were able to visualize the MFB in 12 of our patients bilaterally and in the remaining three patients we depicted the MFB on one side. It was the contralateral side of the lesion. These were 2 meningiomas and one metastasis. Portrayal of the MFB is possible for everyday routine for neurosurgical interventions. As part of the reward circuitry it might be of substantial importance for neurosurgeons during deep brain stimulation in patients with psychiatric disorders. Surgery in this part of the brain should always take the preservation of this white matter tract into account. [less ▲]

Detailed reference viewed: 8 (1 UL)
Full Text
Peer Reviewed
See detailDiffusion tensor imaging--arcuate fasciculus and the importance for the neurosurgeon.
Hana, Ardian; Dooms, Georges; Boecher-Schwarz, Hans et al

in Clinical neurology and neurosurgery (2015), 132

OBJECTIVE: Tumors in eloquent areas of the brain like Broca or Wernicke might have disastrous consequences for patients. We intended to visualize the arcuate fasciculus (AF) and to demonstrate his ... [more ▼]

OBJECTIVE: Tumors in eloquent areas of the brain like Broca or Wernicke might have disastrous consequences for patients. We intended to visualize the arcuate fasciculus (AF) and to demonstrate his relation with the corticospinal tract and the visual pathway using diffusion tensor imaging (DTI). METHODS: We depicted between 2012 and 2014 the AF in 71 patients. Men and women of all ages were included. Eleven patients had postoperative controls also. We used a 3DT1-sequence for the navigation. Furthermore T2- and DTI-sequences were performed. The FOV was 200 x 200 mm(2), slice thickness 2mm, and an acquisition matrix of 96 x 96 yielding nearly isotropic voxels of 2 x 2 x 2 mm. 3-Tesla-MRI was carried out strictly axial using 32 gradient directions and one b0-image. We used Echo-Planar-Imaging (EPI) and ASSET parallel imaging with an acceleration factor of 2. b-Value was 800 s/mm(2). Additional scanning time was less than 9 min. RESULTS: AF was portrayed in 63 patients bilaterally. In one glioblastoma patient it was impossible to visualize the left AF and in seven other patients we could not portray the right one. The lesions affected AF by disrupting or displacing the fibers. CONCLUSIONS: DTI might be a useful tool to portray AF. It is time-saving and can be used to preserve morbidity in patients with lesions in eloquent brain areas. It might give deeper insights of the white matter and the reorganization of AF-fibers postoperatively. [less ▲]

Detailed reference viewed: 6 (0 UL)