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Language use in the EFL classroom : A literature review on the advantages and disadvantages of teachers’ choices of instructional language in the EFL classroomWeijnblad, Malin January 2017 (has links)
This literature review investigates what previous research has found regarding target language use in the Elementary EFL classroom, and what different views there might be on communicating in English during English lessons. The study is conducted with Stephen Krashen’s (1982) Second Language Acquisition Theory as theoretical perspective. Findings show that one important reason for target language use in the EFL classroom is increasing the target language exposure to provide opportunities for the pupils to develop their language proficiency, while first language is used to instruct, translate, scaffold, explain, and facilitate and confirm learning, to discipline and criticise, and to give feedback and positive reinforcement. The results from the five reviewed studies in this thesis imply that both target language and first language have their place in the EFL classroom, and that the teachers’ choice of which language to use is highly individual. They also indicate that vocabulary acquisition and communicative skills call for different language approaches, and that different language theories apply to different teaching situations. Another conclusion from this review is that further research on teachers’ choices of instructional language is needed, as are further investigations of pupils’ preferences and in what situations they benefit from target language and first language respectively.
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Angular Velocity Estimation and State Tracking for Mobile Spinning TargetHuang, Jun-hao 09 August 2010 (has links)
Spinning targets are usually observed in videos. The targets may sometimes appear as mobile targets at the same time. The targets become mobile spinning targets. Tracking a single point on a target is easier than tracking the whole target. We use a characteristic point on the target to estimate the interested parameters, such as angular velocity, virtual rotation center and moving velocity. Among these parameters, virtual rotation center does not spin, therefore it can be used to represent the position of the target. Traditionally, extended Kalman filter (EKF), unscented Kalman filter (UKF) and particle filter (PF) are choices for solving the nonlinear problems, but some problems exist. Linearization errors cause that EKF cannot accurately estimate the angular velocity. UKF and PF have high computational complexity. In the thesis, we give angular velocity an initial value. So we can establish a linear dynamic system model to displace the nonlinear model. Then, a new structure is proposed to avoid errors caused by initial value of angular velocity. In the structure, angular velocity is estimated individually and used to correct the initial value by feedback. We try to use fast Fourier transform to estimate angular velocity. But the convergence time of this method is affected by the value of angular velocity, and the direction of angular velocity can not be estimated directly. Therefore, Kalman filter (KF) with pseudo measurement is proposed to estimate the value of angular velocity. The estimator is accurate and has low computational complexity. Once angular velocity is estimated, we can easily predict the virtual rotation center from geometric relationship. In video system, measurements may be quantized and targets may sometimes be obstacled. We fix the measurement equation and use KF to mitigate quantization error. When measurements for the target is missing, the previous state is used to predict the current state. Finally, computer simulations are conducted to verify the effectiveless of the proposed method. The method can work in environments where measurement noise or quantization error exists. The methods can also be applied to different kinds of mobile spinning targets.
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Target Erosion Pattern Control and Performance Enhancement of DC Magnetron Sputtering Systems by Structural AdjustmentYeh, Hsiao-chun 02 August 2011 (has links)
In the process of sputtering, what a system operator concerns are the sputtering rate, target utilization, and substrates uniformity. All of them are influenced by variables such as electromagnetic environment, chamber temperature, and pressure. In thin film manufacturing, targets bombarded by ions will sputter atoms to the substrates in order to make thin films; therefore, when a certain target zone is extensively bombarded by ions, target surface will become thinner. In general, when certain part of the target is penetrated, it is no longer usable while utilization rate only from 30 to 50 percent. It causes considerable waste and relatively higher costs. As a result, the objective of this study is to enhance target utilization and the sputtering rate through appropriate adjustment in the structure of the existing DC Magnetron Sputtering System (MSS). Since, the magnetic field distribution in the chamber will be appropriately adjusted inside the DC MSS with extra iron annulus and active compensation magnetizations being added. However, in order to get the better structural refinement of DC MSS it needs a thorough design and management based on Taguchi Method. Then, based on such structural adjustment, electron trajectories on top surface of targets can be conveniently controlled, and target erosion patterns and the number of ions bombarding the target will be indirectly controlled. It will, as a result, achieve the objective of this study by enhancing not only the target utilization efficiency but the sputtering rate.
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Development of a Pilot Study Simulation to Investigate the Impact of Target Costing on Team Dynamics and Design AestheticsGottipati, Udaya Naidu 2010 August 1900 (has links)
Target costing is widely accepted across the automobile manufacturing industries such as the Toyota Corporation followed by other manufacturing companies such as Nissan, Chrysler, Boeing, Sony, etc. However, its use in the construction industry has been limited. The application of target costing in the construction industry has been referred to as Target Value Design (TVD), which forms an important fragment of the whole lean delivery system, Integrated Project Delivery. For the purpose of studying the team dynamics and the impact of cost on aesthetics, this research is split in to the following two parts.
1. Conducting simple experiments /simulations with students, such as designing and building a product to target cost to explore the impact of cost on the design of the product and the team dynamics.
2. Exploring the challenges faced by the teams while working on TVD through literature review and Focus Group Interviews with construction industry professionals with experience in the TVD process.
Similar to other lean simulations like the airplane game and the dice game, aimed at demonstrating the impact of lean, this simulation of designing a two feet (2’) tall wine glass holder with materials such as paper, Styrofoam plates, cups etc. is an attempt to understand the challenges of designing to target cost process. The simulation conducted is to mirror the real world TVD process. Results of the experiment conclude that cost does not have a negative influence on the design. There is no correlation between the high costs and better design, that is, the most expensive solutions are not always the best solutions. However, correlation existed between the target cost and the design aesthetics. Indeed, cost as a constraint aided the team in focusing on the design and developing solutions within the project constraints. The results of the experiment are similar to the practice of the TVD in reality as case studies and interviews arrive at similar conclusions. Finally, the experiment depicted that collaborating and working in a team might result in arguments but generates competitive design solutions without affecting the team dynamics. The research is of significance to construction industry professionals and owners to investigate the challenges and implications of implementing target costing in designing to target cost.
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Non-destructive evaluation of RbCl and Rb targets in Sr-82 productionBach, H. T., Hunter, H. T., Summa, D. A., Stull, C. J., Olivas, E. R., Connors, M. A., Reass, D. A., Moddrell, C., Nortier, F. M., John, K. D. 19 May 2015 (has links) (PDF)
Introduction
Sr-82 is produced for PET cardiac imaging at the Isotope Production Facility (IPF) with 100-MeV proton beams. During irradiation, the target material (RbCl, Rb) and Inconel capsule are ex-posed for extended periods to intense radiation, thermally and mechanically induced stresses, and chemicals. The structural integrity of the Inconel capsules is of crucial importance to containing the target starting materials and produced Sr-82. Unexpected failure capsules severely affects the reliability of the isotope supply chain and increases in radioactive emission and wastes, maintenance cost, and personnel radia-tion exposure. Knowledge of the structural integrity of a target before irradiation plays an important role in that defects may be identified and rejected prior to irradiation. In the cases of where a breach occurs, the location of the breach can be correlated with the inspected data.
Material and Methods
RbCl target failure: IPF has a successful irradiation history of RbCl targets at 230 A proton beam current since the facility commissioning in 2004. In 2013 run cycle, three targets irradiated in the medium energy B slot (35–65 MeV) [1] failed unexpectedly. The failure mode was the formation and propagation of cracks at the cor-ner radius along the edge of the target (FIGS. 1a-b). The common failure location was in the rear window relative to the beam direction and at the top of the target. These targets failed relatively early in the course of irradiation and typically after several cycles of beam loss and recovery.
Possible failure mechanisms: A calculated von-Mises stress analysis at room temperature of an Inconel capsule under a static pressure load at 4 MPa shows a stress concentration at the corner radius and deformation of the window (FIG. 2).
Additionally, a beam loss and recovery process causes the capsule windows to fatique especially at the corner due to a thermal and pressure cyclic loading. Furthermore, there is a thermal stress within the window due a temperature gradient resulting from nonuniform heating by the donut-shaped IPF beam [2]. Finally, Cl vapor in the void region or Rb liquid at the top of the target where the highest temperature of target material (RbCl or Rb) is expected may have contribution to a stress-corrosion cracking. An individual or a combination of these mechanisms aggrevate target failure if defects (voids, cracks, or thinning) exist. When the applied stress exceeds the ultimate tensile strength of Inconel, the target is likely to fail at these locations.
Non-destructive evaluation methods: Digital radiographic images were generated using a Philips 450 x-ray source set to 150–190 keV and a Varian panel detector. Ultrasonic (UT) amplitude and time-of-flight (TOF) images were generated with a spherically-focused transducer operated at 50 MHz.
Results
Inconel capsule halves: Radiographic images of the front and rear parts of 7 RbCl A targets (~65-95 MeV) and 7 RbCl B targets prior to target assembly (FIG. 3). For target A halves (left two columns), there is some variation in thickness between the front and rear parts. Other than thickness variation, no other defects (inclusions, voids, cracks) was detected. For target B halves (right two columns), all rear parts exhibit thinning around their edges, whereas the front parts appear more uniform.
UT TOF images were performed on 4 target A halves (155, 156, 157, and 159) and 7 target B halves (154-160). The rear window of 155A appears to thin out (~12.5%) near the rim on the right half. The front of 159A shows a similar thinning (~ 15%) near the rim on the left half. Although there is a thinning along the edges, all parts except 159A front have an average thickness within the stated specification (TABLE 1).
Similarly to radiographic data, UT TOF data con-firm a thinning towards the edges of the window on most of target B parts. Only images of 155B are illustrated in FIG. 4. Significant thinning (15%) is observed on 154B (front & rear), and the rear windows of 155B, 157B, 158B, and 159B. Although there is a thinning, all parts have an average thickness within the stated specification (0.0120” ± 0.0005”) except for the rear windows of 154B and 155B. No inclusions or voids are apparent in any of the parts.
RbCl filled targets: For comparison purpose, three B (130, 135, 147) and two A (137, 147) filled targets were evaluated. Radiographic data show no defects in the Inconel capsules while the RbCl pucks have numerous features (cracks, voids). The images of targets 130B and 135B illustrate the basic conditions of the RbCl pucks (FIG. 5).
UT TOF images of targets 130B and 135B rear and front windows are illustrated in FIG. 6. Average thicknesses of 0.011–0.014” for both rear and front windows of all 5 targets are within the stated specification. However, there is thinning around the edge of the target 135B front window.
Rb empty capsule: Radiograph of an unfilled Inconel capsule with and the fill tube is shown in FIG. 7. The predrilled 1-mm OD pinhole on the front window can be easily detected with the instrument’s detection limits of 30-μm pinhole and 5-μm crack. There is no other visible defect or thickness variation. This target was filled with Rb to characterize the reaction released Rb through the pinhole with water and its effects on equipment.
Rb metal filled targets: Radiographs of two Rb metal filled targets show the front and side views of Rb distribution and fill tube (FIG. 8). Voids are visible throughout the Rb and small amount of Rb remaining in the fill tube. TOF results indicate the average thicknesses of 0.0201–0.0214” for both rear and front windows of 2 targets. Except the 2B front window, all thicknesses are within stated specification (0.020” ± 0.0005).
UT TOF images for the rear and front of each target capsule are shown in FIG. 9. Moiré pat-terns are likely caused by a combination of stress arising in the manufacturing/filling process and some degree of measurement artifact. Target 1B windows exhibit uniform thickness across the bulk of the diameter, with the front window being slightly thinner overall than the rear. There is slight thinning observed near the edges on both windows. Thinning is more pronounced on the left side of the rear window than the right side of the front window. Target 2B shows a more pronounced distortion particularly on the rear window. The rear window appears to have a slightly thinner concentric region approximately one-quarter of diameter in. The front window displays good uniformity, with slight thinning along the inner edge of the left. Both targets 1B and 2B were successfully irradiated up to 230 A for 2 hours. Higher beam current and longer irradiation of Rb targets is underway.
Conclusion
Radiographic and ultrasonic methods were used in non-destructive evaluation of pre-assembly Inconel parts and fully assembled RbCl and Rb targets. These studies show the potential to identify defective parts and/or targets prior to irradiation, to provide useful information for improving target manufacturing process, and to enable better decision-making in managing risks of target failure. The results also have target quality assurance potential, enable comparison of target features and document data for future interpretation of target failure. The benefits of non-destructive evaluation include improved target reliability, reduced target failure rate, reduced revenue loss and increased productivity of Sr-82.
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Development of a forced-convection gas target for improved thermal performanceUittenbosch, T., Buckley, K., Schaffer, P., Hoehr, C. 19 May 2015 (has links) (PDF)
Introduction
The internal pressure experienced by a gas tar-get during irradiation is dependent on the beam energy deposited in the target, the beam cur-rent, and the thermal behaviour of the target. [1] The maximum beam energy deposited is a function of the cyclotron capabilities and the gas inventory within the target. The maximum beam current is limited by the pressure produced in the target and the ability of the target assembly to remain intact. This is also a function of the thermal behaviour of the target, which is difficult to predict a priori since it is dependent on such things as convection currents that occur during irradiation. We conducted bench tests with model gas targets with and without forced convection currents to observe the effect on thermal behaviour. Based on those results we constructed a prototype gas target, suitable for irradiation, with an internal fan assembly that is rotated via external magnets.
Material and Methods
Bench tests were conducted with cylindrical and conical target bodies of aluminum. A nickel-chromium heater wire was inserted into the gas volume through the normal beam entrance port (FIGURE 1) to heat the gas while water cooling was applied to the target body. The voltage and current of the heater coil was monitored along with the pressure inside the target and the water inlet and outlet temperature. In the case of tests with a driven fan blade either the voltage applied to the electric motor was monitored or the fan speed itself was recorded. By assuming the ideal gas law, the pressure gives the average bulk temperature and a global heat transfer coefficient can be calculated between the target gas and the cooling water. [2]
A cylindrical target body was constructed that incorporated a fan blade driven by an external motor. This assembly used a simple o-ring seal on the rotating shaft. This seal was not robust enough for any tests under beam conditions. A prototype design suitable for in-beam operation employs a propeller mounted on a rotating disc housing two samarium cobalt magnets and spinning on two micro-bearings which are constructed to operate in high temperature environments. The micro-bearings are mounted on a pin projecting from a plate welded to the back of the gas target to allow assembly of the fan mechanism prior to attachment to the body (FIGURE 2).
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Further exploration of C-11 HP target on PETtraceDick, D. W., Erdahl, C. E., Bender, B. R. 19 May 2015 (has links) (PDF)
Introduction
At WTTC 14 we presented data on the target yields of our GE PETtrace C-11 HP target in comparison to the target yields we had been getting on the MC17 prior to its decommissioning1. Discussion with other attendees alerted us to the fact that the target may be too “thin”, allowing the beam to spread out and interact with the walls, which could result in a lower target yield. Additionally, a GE service engineer indicated that we could be striking the top of the target with some of the beam, due both to target thinning and the “banana” effect from the magnetic fringe fields. Experiments were carried out to determine the potential magnitude of this effect and the efficacy of potential solutions.
Material and Methods
All experiments were performed on a GE PET-trace cyclotron. The first set of experiments was performed on the C-11 HP target in its natural mounting state (no aids). The change is gas pressure as a function of beam current was measured, from 5 to 70 microamps for three different gas fill pressures: 210, 230 and 250 PSI. The second set of experiments was performed after mechanically lifting the back end of the target with a box, changing the target angle from 23.9 degrees past horizontal to 25.2 degrees past horizontal. While this change in angle does not seem drastic, it did pick up all the slack in the target mount due the sagging of the target from its longer length than other GE targets. The change in gas pressure as a function of beam current was measured, from 5 to 80 microamps for four different gas fill pressures: 190, 210, 230 and 250 PSI. (Note that the box is a temporary solution and the target will sag over time without a more permanent solution for supporting the back end of the target.)
Results and Conclusion
The graphical results of pressure rise as a function of beam current are shown in FIGURE 1. Note that measurements were stopped when the pressure approached 470 PSI, based on advice from GE engineers. There is some flattening out for the 190-PSI data, even with the increase in angle as an attempt to counteract the banana effect (note that GE’s recommended fill pressure is 187 PSI). Increases in the fill pressure helped in keeping the target thick, but with the tradeoff that less beam can be put onto the target before reaching the maximum specified pressure. Final-ly, using a lifting mechanism to raise the back of the target also helped to prevent thinning, as seen in the r-squared values for the linear fit, shown in TABLE 1. The data presented indicate that a shorter target that can withstand higher pressures could be beneficial for the PETtrace cyclotron, allowing the beam to fully stop before striking the walls, be it through target thinning or the “banana” effect while still allowing the user to run high beam currents.
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Development and Applications of Tracking of Pellet StreamsPyszniak, Andrzej January 2014 (has links)
The development of a system for optical tracking of frozen hydrogen microsphere targets (pellets) was done. It is intended for the upcoming hadron physics experiment PANDA at FAIR, Darmstadt, Germany. Knowledge of the interaction position, obtained with this system, will improve background rejection, precision of particle track reconstruction and will also help distinguish between primary and secondary vertices. Investigations of pellet detection conditions and pellet stream parameters were performed at Uppsala Pellet Test Station located at The Svedberg Laboratory. Various illumination and detection conditions were checked and optimized. The gained knowledge has been used to develop Monte Carlo procedures simulating experiments with pellets. Then simulations of pellet tracking were carried out including the constraints from the PANDA setup. The performance of the tracking was checked for various pellet stream and pellet detection conditions. Two procedures of pellet track reconstruction were developed – a fast procedure and a high efficiency procedure. The studies were done for one tracking section (just below pellet generator) and for two sections (the second just above pellet dump) and showed that the resolution of the tracking system can be better than 100 μm (sigma) in each direction and that the interaction point will be reconstructed for 70-95% of hadronic events, for suitable pellet stream and detection conditions. Usage of pellet tracking information in the hadronic data analysis was discussed, concerning the data taking, particle track reconstruction together with the PANDA micro vertex detector, hadronic event classification and treatment of the various classes. Test measurements with the WASA setup at FZJ, Jülich, Germany were done to check how the information about the number of pellets in the accelerator beam region can be used in the hadronic data analysis. Instantaneous rates of WASA "elastic" triggers were used for classification of hadronic events as coming from pellets or from a background. The study clearly showed that one can distinguish between the two event classes. The study gave experience in using two different systems synchronized with each other – the experiment's DAQ and another system that works with a much longer time scale – similar to the pellet tracking system. / Ett system för optisk spårning av frysta mikrosfärer av väte (pelletar) har utvecklats för användning i det kommande hadronfysikexperimentet PANDA vid FAIR, Darmstadt i Tyskland. Kunskapen om positionen för växelverkan som fås med hjälp av detta system kommer att förbättra möjligheten att diskriminera mot bakgrund, att öka precisionen i partikelspårsrekonstruktionen och kommer också att hjälpa till att skilja mellan primära och sekundära växelverkanspunkter. Undersökningar av pelletdetektionsmöjligheter och pelletströmmens egenskaper har gjorts vid Uppsala Pellet Test Station vid The Svedberglaboratoriet. Olika belysnings och detektionsvillkor har testats och optimerats. Den erhållna kunskapen har använts för att utveckla en Monte-Carlo procedur för att kunna simulera de olika experimenten med pelletar. Därefter genomfördes simuleringar av förväntade pelletspårningsprestanda för PANDA uppställningen. Prestanda och upplösning av spårningen kontrollerades för olika pelletsström och detektionsförhållanden. Två procedurer för spårrekonstruktion utvecklades för studien – en snabbare och en med högsta möjliga effektivitet. Den kommer att kunna användas i dataanalysen när fullskalig pelletspårning används ihop med ett partikeldetektorsystem. Studien gjordes för två fall, dels för en spårningssektion (placerad just under pelletgeneratorn) och dels med ytterligare en sektion (placerad just ovanför pelletdumpen). Studien visade att positionsupplösningen som förväntas från spårningssystemet är bättre än 100 μm (sigma) i varje riktning och att växelverkanspunkten kan rekonstrueras för 70-95% av de hadroniska händelserna, för lämpliga pelletströms- och detektionsvillkor. Användningen av pelletspårningsinformationen i analysen av hadroniska händelsedata diskuterades m.a.p. datainsamling, m.a.p. partikelspårsrekonstruktion ihop med PANDA's mikrovertexdetektor och m.a.p. klassificering av händelser. Det gjordes testmätningar med WASA-uppställningen vid FZJ, Jülich i Tyskland för att se hur informationen om antalet pelletar i acceleratorstrålområdet kan användas i experimentets dataanalys. Den momentana frekvensen av elastiska spridningshändelser användes för en grov klassificering av händelsers ursprung såsom varande antingen från en pellet eller från någon källa till bakgrund. Studien visade klart att man kan skilja de båda klasserna åt. Studien gav också erfarenhet av hur man kan använda två synkroniserade datasystem – experimentets datainsamlingssystem och ett annat system som arbetar med en mycket längre tidsskala – liknande pelletspårningssystemets. / Wykonane zostały prace nad rozwojem systemu pozwalającego na optyczne śledzenie zamarzniętych wodorowych mikrokulek (pelletów). System przeznaczony jest do zastosowania w planowanym eksperymencie z dziedziny fizyki hadronowej, PANDA (FAIR, Darmstadt, Niemcy). Wiedza o położeniu punktu interakcji, uzyskana dzięki temu systemowi, poprawi redukcję tła, precyzję rekonstrukcji torów cząstek, a także pomoże w rozróżnianiu pierwotnych i wtórnych wierzchołków interakcji. Na Uppsalskiej Stacji Pelletowej (Uppsala Pellet Test Station) umieszczonej w Laboratorium The Svedberga, przeprowadzone zostały badania warunków detekcji pelletów i parametrów strumienia pelletowego. Różne warunki oświetlenia oraz detekcji pelletów zostały sprawdzone i zoptymalizowane. Uzyskana wiedza została użyta do stworzenia procedur Monte Carlo symulujących eksperymenty z pelletami. W następnym kroku przeprowadzone zostały symulacje śledzenia pelletów biorące pod uwagę więzy narzucone przez konstrukcję systemu PANDA. Wydajność systemu sprawdzona została dla różnych warunków strumienia pelletowego i detekcji pelletów. Stworzone zostały dwie procedury rekonstrukcji torów pelletowych -- procedura szybka i procedura wysokoefektywna. Badania przeprowadzone zostały dla jednej sekcji śledzącej (bezpośrednio poniżej generatora pelletów) oraz dla dwóch sekcji (druga bezpośrednio nad miejscem zbierania pelletów) i pokazały, że rozdzielczość systemu śledzenia może być lepsza niż 100 μm (sigma) w każdym z kierunków oraz że punkt interakcji będzie zrekonstruowany dla 70-95\% zdarzeń hadronowych, dla odpowiednich warunków strumienia pelletów i warunków detekcji. Użycie informacji ze śledzenia pelletów w analizie danych hadronowych zostało przedyskutowane uwzględniając proces zbierania danych, rekonstrukcję torów cząstek we współpracy z mikrodetektorem wierzchołków systemu PANDA, klasyfikację zdarzeń hadronowych oraz sposób traktowania różnych klas zdarzeń. Pomiary testowe z użyciem detektora WASA (FZJ, Jülich, Niemcy) zostały dokonane w celu sprawdzenia jak informacja o liczbie pelletów w obszarze wiązki może zostać użyta w analizie danych hadronowych. Chwilowe częstotliwości "elastycznych" triggerów systemu WASA zostały użyte w celu klasyfikacji zdarzeń hadronowych jako pochodzących z interakcji wiązka-pellet lub wiązka-tło. Badania wykazały iż możliwe jest rozróżnienie między tymi dwoma klasami zdarzeń. Uzyskano również doświadczenie w używaniu dwóch różnych systemów zsynchronizowanych ze sobą – eksperymentalnego systemu zbierania danych oraz innego systemu, działającego w znacznie dłuższej skali czasowej – podobnie do systemu śledzenia pelletów.
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Weiterentwicklung des Detektorsystems am QCLAM-Spektrometer des S-DALINAC und Untersuchung der Reaktionen 48 Ca(e, e') und 58 Ni(e, e') unter 180°Reitz, Bodo. Unknown Date (has links)
Techn. Universiẗat, Diss., 2000--Darmstadt.
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Untersuchungen zu den Reaktionen 233U(nth, f) und 235U(nth, f) Winkelkorrelationen zwischen den in der ternären Spaltung emittierten Teilchen und quaternäre Spaltung /Jesinger, Peter. Unknown Date (has links) (PDF)
Universiẗat, Diss., 2001--Tübingen.
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